Fireflies

Easy experimenting with
Artificial Intelligence

+ Super Robots

Myths, promises, threats

+ Sceptre

The software library

Unilab

A switch-mode 0-30 V / 3 A
bench supply

+ OBD Analyser NC
gets Bluetoothed

Measuring Tweezers

Special tools for measuring
SMD components

WWW

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Pop it off the stack

Contrary to what some readers seem to
think or even fear, assembling Elektor
as a monthly journal is hardly ever a
problem in terms of articles in stock.
Indeed I've a small stack of articles
worth 50 odd pages I can easily slot into
any edition — no problem, it seems,
but thafs in terms of pages only. The
trouble comes with the various factors
exerting force on the content. Let me
list a few, not necessarily in order of
importance: the theme of the month,
the enthusiasm of a lab worker about
his XYZ widget, advertising pages sold
and arriving at 11.59, announcements
printed on the Coming Attractions page,
Anglo-American electronics culture
issues, embedded systems shows, cover
design, competitors' coverage of the
subject, author contracts, Items sold in
our web shop, articles to be supplied for
translation to licence partners. Each of
these factors (there are many more) can
clash with just about any of the others,
so the conflict matrix Is potentially large,
while the only dead certs I look at every
month are: 88 pages to fill and the edi-
tion to arrive at subscribers on [date#i]
sort of punctually and in bookshops on
[date#2+5], punctually.

While this paints a grim situation,
nothing untoward happened these past
399 editions and in fact it's the wide
diversity of subjects and articles that
brings relief rather than complication.
The edition at hand is a fine example of
variegated articles at many levels and
covering the ever increasing areas and
niches modem electronics seems to
diverge into. We look at robotics both
high brow {Super Robots, page 16) and
down to earth (Fun with Fireflies, page
58) with the latter article a small gem
by presenting a hands-on approach to
the concepts of artificial Intelligence and
robot swarms.

Our efforts at removing widespread
fears of working with SMD parts conti-
nues unabated with Measuring Tweezers
(page 22) in which five of those nifty
tools are examined to see if they are
worth the investment. Another can
of worms called microcontroller vs,
conventional electronics can remain
largely dosed this month with both
'sides' served almost equally in terms
of pages. Tell me If you think otherwise
and I wilt put your message on the stack
of things to do to keep everybody happy
in 88 pages,

jan Suiting

Editor, Elektor UK & US editions

6

8

10

22

44

Colophon

Corporate information
on Elektor magazine.

Mailbox

Monthly pick of Letters to the Editor

News & New Products

A monthly roundup of all the latest in
electronics land.

Super Robots

Myths, promises and the 'here and now',
with a focus on swarm theories
applied to robotics.

Measuring Tweezers

five SMD measuring tweezers compared
and put through their paces.

Unilab

A construction project for a switch-mode
0-30 V / 3 A benchtop power supply.

Grasping the Sceptre

Continuing on from last month we discuss
the software library developed for the
Elektor Sceptre ARM platform.

A Fast Charger

Here's how to turn a low-cost computer
S MRS into a battery charger — and not
just for the Elektor E-Wheelie.

Latest from the Elektor Lab

On guests in the lab and fighting
corrosion with protective sprays.

The making of the dsPIC board

A look behind the scenes of project
production in the Elektor lab.

C0 2 meter under test

A road test of our C 0 2 meter.

How does it perform In a car?

4

nfin

CONTENTS

Volume 36
April 2010
no. 400

16 Super Robots

With time, things that were once considered phantastleal quite often get to be
‘realised’. How close are we to realising the kinds of robots and intelligent com-
puter systems depicted in films such as HAL in Kubrick's 2007 A Space Odyssey ,
or the lifelike child in At, or the kinds of robots in i Robot?

22 Measuring Tweezers

SMD parts are a pain to deal with —you can hardly tell different types of passive
components apart, and the markings are not especially clean Now, with special
SMD measuring tweezers, you can quickly check what type of component you
have and measure its value. We tried out five such devices in our lab.

26 Unilab

This switch-mode 0-30 V / 3 A dual power supply is especially handy when you
need more than one supply voltage. Naturally, both supplies are galvanically
isolated, so they can also be connected in series for higher voltages or in paral-
lel (connected via diodes) to provide more current

54 Bluetooth for OBD-2

Elektor 1 s hand-held OBD Analyser NG has an open-source operating system
and a biFilt-in expansion port. Both enable a Bluetooth module to be integrated
with ease. Now at the other end of an RF link you can view engine parameters
and faults on a netbook or notebook PC!

48 Small is Beautiful: MinimodiS

Introducing the successor of the Elektor
ATMiS: pushbuttons, LCD, USB, I2C,
ISP/SP1 and an ATmega32,
all on a compact board.

54 Bluetooth for OBD-2

Th is is what you need to extend your
GBD-2 Analyser NG with wireless
communication to a laptop,
netbook or notebook PC,

58 Fun with Fireflies

Learn about the basics of robot swarms
and artificial intelligence with these
little creatures,

64 BurnorTurn?

Got a dead hard disk lying around? Why
not convert it to a motor and
make it do something useful?

67 Beep, beep ... Sesame

A keypad operated door lock
with a musical talent.

70 5 V Power Controller

Convert "anything* between 2 V and 8 V
into a stable and reliable 5 V source
for microcontroller projects,

75 Design Tips

A voltage booster for Arduino
UV light box

76 Hexadoku

Our monthly puzzle with an electronics
touch.

77 Retro nics: C4WIIVI

24cm ATV Transmitter (1994)

Regular feature on electronics odd &
ancient*.

84 Coming Attractions

Next month in Elektor magazine.

elektor 03-2010

5

elektor

international media bv

Elektor International Media provides a multimedia and interactive platform for everyone interested
in electronics. From professionals passionate about their work to enthusiasts with professional
ambitions. From beginnerto diehard, from student to lecturer, information, education, inspiration
and entertainment. Analogue and digital; practical and theoretical; software and hardware.

Jektor

Apir

Fireflies

Easy experimenting with
Artificial Intelligence

+ Super Robots

Myths 4 promises, threats

+ Sceptre

The software library

i

J

Unilab

A switch -mode 0- 30 V / 3 A
bench supply

+ OB D Analyser IMG

gets Bluetoothed

Measuring Tweezers

Special tools for measuring
5MD components

ANALOGUE • DIGITAL jynH
MICROCONTROLLERS & EMBEDDED
AUDIO • TEST & MEASUREMENT

Volume 36, Number 400, April 2010 ISSNT757-0875

Elektor asms at Inspiring people to master electronics at any
personal level by presenting construction projects and spotting
developments in electronics and information technology,

Elektor International Media, Bogus Brentford.

1000 Cl eat West Road, Brentford TW8 gHH, England.

Tel. (+44)208 2&t 4509. fax: (+44)208 261 4447
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Elektor is published n times a year with a double issue for July & August

aii— __ _

Elektor is also published in French, Spanish, American
English, German and Dutch. Together with franchised
editions the magazine is on circulation in more than 50
countries.

International Editor,

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Jan Bolting (edStor@elektor.com)

Harry Bag gen, Thijs Beckers,

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Antoine Authier (Head), Ton Giesberts,

Luc Lemmens. Daniel Rodrigues, Jan Visser. Christian Vos sen

Edo one] secretarial:

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Tsi ' -44 20 8 2 G 1 4509 . fa x: (+4 4) 20 & 261 4447
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6

04-2010 elektor

Elektor Tools for
PCB Productio

(ZZ^> PCB-DIY All the Way

It’s clear that a good set of tools is required for
PCB production and SMD component stuffing.
With the Elektor stencil machine you get the solder
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Further information and ordering at

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^ r

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Copyright Notice

The circuiLs described in Lhis magazine are for domestic Lise
only. All drawings, photographs, printed circuit hoard layouts,
programmed integrated circuits, disks, CD-ROMs, software
carriers and article texts published in our books and magazines
{other than third-party advertisements) are copyright Elektor
International Media b.v, and may not be reproduced or transmit-
ted In any form or by any means, including photocopying, scan-
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mission from the Publisher. Such written permission must also be
Obtained before any part of this publication is stored in a retrieval

system of any nature. Patent protection may exist in respect of
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The Publisher does not accept responsibility hir failing to identifv
such patent(s) or other protection. The submission of designs or
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Disclaimer

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elektor 04-2010

1

MAILBOX

OTOOra - 1;'

LEDs as photosensors — busted?

‘LEDs double as photosensors’, Analogue Design Tips,
Elektor January 2010 ( 0703S6-] )

A number or readers responded to this Design
Tip , some confirming its operation and hap-
pily experimenting , others suspecting that it
was an early April Fools joke : Thomas Scherer
one of our regular contributors put the circuit
through its paces and reported on the results of
his measurements as follows:

Dear Jan — I checked out a number of LEDs
fn my collection. The interesting conclu-
sion is that some of them work, some
don't, and some are excellent In my tests,
the blue LEDs gave the worst results. With
the other colours, I measured anything
from 0.5 V to nothing. Even some of the
white LEDs generated around 120 mV, The
best results were obtained with red, green
or yellow LEDs with clear, colourless pack-
ages. They yielded an amazing 1 .2 to 3 .3 V,
LEDs with clear coloured packages were
also somewhat better than those with dif-
fuse coloured packages. Otherwise 1 could
not draw any systematic conclusions; it
appears to depend on the manufacturer.
Even a pair of LEDs that must be 30 years
old still produced 60 mV, My test condi-
tions were: illumination with a 20-W
fluorescent lamp (daylight colour) at a
distance of 50 cm.

Modern wireless technology

The 2,4 GHz Bandaiyser, E
lektor February 2010 (090985-!)

Dear Editor — i am pleased to see that you
are featuring more and more projects
related to modern wireless technology
(ISM, ZigBee, WLAM, etc.) in your maga-
zine. You published an article in the Febru-
ary issue on a 2.4-GHz scanner. It's a bit
of a pity that the wireless receiver module
used in this project (type CYWM6935) has
already been discontinued by the manu-
facturer. As you also designed the scanner
described in this article around an Atmel
AVR microcontroller as the main control
unit (and you regularly use this microcon-
troller in other projects as well), I would
like to suggest that you consider a project
using the new (and thus highly current)
Atmel ATmegal28RFA1 microcontroller.

This device features a 2.4-GHz transceiver
module integrated on the same chip as the
microcontroller. As I personally use Atmel
microcontrollers frequently and by prefer-
ence, I look forward with great anticipa-
tion to an Elektor project featuring this
new device, so that I can learn something
about how to use it.

Rodrigo Supper

The problem with product discontinuation is
unfortunately sometimes unavoidable because
it cannot be foreseen . However in most case s
the components remain available from distribu-
tors and retailers for a relatively long time. The
other side of the coin is that with new ICs you
sometimes have to wait a long time after the
product announcement before real products
become available: the elapsed time between
the first design samples and the actual avail -
ability of regular production devices is often sev-

eral months. There have also been cases where
fully developed projects could not be published
because regular production of the devices con-
cerned was simply cancelled in economically
uncertain times. In such cases, all you're left with
is a few prototypes and your expenses.

I agree that the ATmega microcontroller plus
wireless transceiver combo could form the
basis for an interesting project ; Accordingly ,
I have forwarded your suggestion to my col-
leagues in the Elektor Jab with my worm
recommendation.

Hands off my loudspeakers

’Power Cut Alert*, Christmas Holidays Circuits,
Elektor December 2009

Dear Jan — I recently completed a project
for converting my loudspeakers into an
active loudspeaker system. It cost a lot
of time, effort and money. As my loud-
speakers were stolen once already, I also
thought about how I could prevent this in
the future.

The aim was to protect the loudspeakers
reliably and unobtrusively without using
an additional cable. As the loudspeaker
system is driven by a balanced signaljt
would be possible to use the "phantom
supply' principle to apply a DC voltage to
the loudspeaker signal line and monitor
this voltage. With this arrangement, an
alarm will be generated if the XLR connec-
tor fo r the ioudspea ker is d iscon nected ,
The drawback of this approach is that the
loudspeakers and the amplifier outputs
must be isolated from the phantom
voltage. This would require using (large)
capacitors to couple the audio signal in
and out while blocking the DC voltage.
This is not especially practical, and cer-
tainly not desirable.

Another option would be to use motion

□1

00 E r u

H i

D [1 £

G

8

04-2010 elektor

MAILBOX

sensors, but this would certainly create
problems with our industrious house
cleaner, who has no fear of dusting off the
loudspeaker enclosures. In the December
2009 issue of Elektor, f found a circuit
under the heading 'Power cut alert’ that is
designed to monitor the AC mains voltage.
Even though my application is quite differ-
ent, this circuit is also suitable for provid-
ing property protection, and I certainly
regard my expensive loudspeakers as
property worth protecting. Of course, the
same technique could also be used with
other valuable Items.

I have now built and tested the circuit, and
it works perfectly. As soon as the AC power
cable of the active speakers is unplugged,
the alarm goes off.

I n order to disable the alarm if necessary, 1
mounted a Cinch socket in an inconspicuous
location on the loudspeaker connector pane!
and connected it to the emitter and collector
of the BC547 transistor. To disable the alarm,
it's only necessary to plug in a shorted Cinch
plug , but burglars won’t know this (or at
least I assume that burglars do not make a
habit of reading Elektor!),

The only drawback of this circuit is that
the battery needs to be replaced from
time to time. However, the battery could
be replaced by a small power supply with
a transformer and rectifier that charge
a large electrolytic capacitor and keep it
charged as long as the mains voltage is
available. If mains power is lost, the charge
in the capacitor will allow the piezoelectric
alarm to operate as long as necessary. Of
course, the capacitor charge won’t last for
several hours, but it will last long enough
to cause the burglars to flee,

G, Luyt (Netherlands)

Compensation method

'Two black boxes", Retro nics, March 2010

Hi Jan — 1 always find the Retro nics articles
fascinating. For the article In the March
2010 issue (Two black boxes’), you actu-
ally didn't need to go so far back in time
to find a description of the compensation

method. It was described in the 1 980 edi-
tion of the Radio and Electronic Laboratory
Handbook by M.G. Scroggle, who was very
well known at that time.

For more information, see:
http://phy3ab.nuaa.edu.cn/edit/Upload-
File/20091 151 7446235.pdf

CJ, War ners

Thank you very much for your response. The arti-
cle in the PDF document does indeed describe
the compensation method in detail I wasn't
able to find a modern description of this principle
because / didn't think of using ' potentiometric ’
as a search term. This illustrates once again that
you can't find everything on the internet if you
don't know the right search terms.

Incidentally what especially struck me when
I was in the attic of De
Slegte (in Utrecht) with
that book in my hands
was that the schematic
diagram (Figures in my
article) was virtually a
construction drawing for
my compensator. Per-
haps the accompanying
photo makes this more
apparent. The circular
selector switches are
arranged differently, but
you can probably imagine
how excited / was with the
similarity.

The original version of my
article included a longer quote , / hod to omit
it due to lack of space , but it may be nice to
present the full version of the quote here ,
which is written in an old-fashioned style that
is a (ways fun to read:

let A B be a wire with large resistance (Figure
4). A constant element with high electromo-
tive force E is connected between the extremi-
ties A and B, The two elements El and E2 to
be compared are connected (as shown in the
schematic drawing) to point A and to a pin 5,
from which a lead proceeds further by means of
a moveable contact. If one now determines the
two points PI and P2 at which no current flows
through the galvanometer branch circuit with

El and E2, respectively the foi lowing expres-
sion hoids true:

E1/E2 = resistance of API / res/stance of AP2

With an extended wire of uniform thickness, the
ratio of the resistances can s imply be taken to
he the ratio of the lengths. If one imagines this
extended wire to he replaced by a resistor substi-
tution box , for each change in the resistance 4 C
it will be necessary to relocate the contact C to a
different point in the resistor substitution box , hut
in such case it will generally prove impossible to
maintain the resistance of A Bata constant value.
However ; if A B is replaced by two identical resis-
tor substitution boxes connected in series, and C
is taken to be the point at which these two boxes
are connected together, one can adjust resistance
AC to any desired value less than A B while
maintaining a fixed resist-
ance between A and B.
This only requires that
the shorting plugs
removed from the
one box he plugged
into the same positions
in the other box, which
a/though if may in itself
appear simple, often gives
rise to errors. Conse-
qu en tly, ins t rumen ts ha ve
been devised in which
the mutual changes to
the resistances are effected
entireiy automatically so
that a constant resistance is
always present between the two end points , An
instrument of this sort is called a compensator,
if one examines the current flow in Figure 5, it is
immediately apparent that no matter how the
knobs are adjusted , the same resistance is always
present between the +B and-B terminals, namely
14,999.9 while by contrast the resistance
between points +0 and - Dean be set to any value
from 0.1 to 14,999.9 il. The numerical markings
next to the knobs directly indicate the value of this
resistance .’

Tm sure you'll agree with me that this text does
full justice to the ingenuity of the automatic
compensator

Rolf BEijleven

MailBox Terms

* Publication of reader's correspondence is at the
discretion of the Editor.

* Viewpoints expressed by correspondents are not
necessarily those of the Editor or Publisher,

• Correspondence may be translated or edited for
length, clarity and style.

•When replying to Mailbox correspondence,
please quote Issue number,

• Please send your Mail Box correspondence to:

editor@elektor.com or

Elektor. The Editor,
tooo Great West Road,
Brentford TW 8 gHH, England,

elektor 04-2010

9

NEWS & NEW PRODUCTS

Nl Multisim n simplifies circuit simulation for
teaching and design

National Instruments introduces Multisim 11 , the latest version of its circuit simulation
software, with specialized editions for both hands-on learning and professional circuit
design. The easy-to-use Multisim software delivers a graphical approach that abstracts
the complexities of traditional circuit simulation, helping educators, students and engi-
neers employ advanced circuit analysis technology.

The academic edition of Multisim 1 1 incorporates specialized teaching features and
is complemented by
circuits textbooks and
courseware. This inte-
grated system helps
educators engage
stu d e n t s a nd re i nf o rc e
circuit theory with an
interactive, hands-on
approach to investi-
gating circuit behavior.

Widely implemented
throughout academia,
technical colleges and
four-year universities
choose Multisim for
its interactive com-
ponents, simulation-
driven instruments
and integration to real-
world analog and dig-
ital measurements.

Multisim 1 1 Profes-
sional helps engineers optimize circuit designs, minimize errors and reduce prototype
iterations. When combined with the new Nl Ulti board 1 1 layout and routing software,
Multisim provides engineers a cost-effective, end-to-end prototyping platform, its inte-
gration with Nl LahVIEW measurement software also helps engineers define custom
analyses to improve design validation.

Key benefits of Multisim 1 1 include the following:

Multisim tt Academic

Simplify digital circuits teaching by exporting raw VHDL from a programmable logic
device (PLD) schematic

Guide hands-on electronics experiments with new educator-requested AC single-
frequency analysis

Correlate simulated data with real-world measurements by integrating with the Nl
Electronic Laboratory Virtual Instrumentation Suite (Nl ELVIS) educational prototyp-
ing platform

Multisim ti Professional

Simulate better with SPICE parser improvements, updated BSIM models, support for
advanced parameters and enhanced digital simulation accuracy
Prototype easier and ensure design synchronization and transparency with enhanced
forward/backward annotation from the Multisim schematic to an Ultiboard layout
Improve design communication with on-page connectors and a new WYSIWYG net
naming system

Readers can learn more and watch videos about Multisim 1 1 by visiting the web page
below.

www.m.com/multisim/upgrade [100106-I)

CPS receivers with or
without antenna

The PM 8 -648 CPS module from Parallax
provides high performance with a SiRFstar-
III chipset and integrated patch antenna.
See the Parallax CPS Comparison Chart
to evaluate this model side-by-side with
the very similar PMB-68S and the low cost
PMB-248.

The PMB-648 CPS features 20 parallel sat-
ellite-tracking channels for fast acquisition
of NMEA0183 v2.2 data for robotics naviga-
tion, telemetry, or experimentation. There
is a built-in patch antenna; rechargeable
battery for memory and RTC backup; cable
for power, TTL and RS-232 connections.

Features:

high sensitivity
* SiRFstarlll chipset

20 parallel satellite tracking channels for
fast acquisition and ^acquisition
built-in rechargeable battery for memory
and RTC backup

supports NMEA01 83 V2.2 data protocol
includes cable for power, TTL and RS-232
connections

The new PM8-688 CPS module has a SiRFs-
tarlll chipset and integrated patch antenna
plus an MMCX connector for the company's
external GPS antenna. The PMB-688 retails
at $39.99.

wwAf.Parallax.com (100106-!!)

10

04-2010 elektor

NEWS & NEW PRODUCTS

Haptic piezo controller

Maxim Integrated Products introduces the
MAXT1835 fully integrated, programma-
ble HPC (haptic piezo controller) for single-
layer and multilayer piezo actuators. The
MAX1 1835 is a novel haptic solution that
provides customers with an enhanced, true
M touch” experience with touch screens.
Consumers are accustomed to ‘feeling*
the button press on keyboards, keypads,
and many modern devices* Touch screens
and capacitive sensors provide an interac-
tive user interface, but the user cannot feel
the touch because there is no mechanical
button. The MAX1 1835 adds the feeling of
mechanical feedback to touch screens and
capacitive buttons* The product can be used
with any touch-screen or touch-button con-
troller. However, as part of its new TacTouch
concept, Maxim provides design-in sup-
port and reference designs guaranteeing
an optimal touch experience and simplified
design-in when combined with the compa-
ny's touch-screen controllers.

Texas Instruments and Circuit Cellar launch
DesignStellaris 2010 Design Contest

Texas Instruments and Circuit
Cellar' invite you to compete
against other top embedded
engineers around the world In
the Texas Instruments Design-
Steilaris 2010 Design Contest!
The sky is the limit when you're
designing with an ARM-based
Texas Instruments Stelfaris
microcontroller featuring the
SafeRTOS real-time kernel inte-
grated into on-chip ROM* By
entering a project you could win
a share of SI 0,000 in cash prizes

and recognition in Circuit Cellar magazine!

Texas Instruments has generously supplied everything you need to get started! The
Stelfaris EKK-LM3S9B96 Evaluation Kit includes: an evaluation board with an 80 MHz
LM359B96 MCU featuring Ethernet MAOPHY, CAN, USB OTG, and SafeRTOS in ROM; a
time-limited copy of the Kell RealView Microcontroller Development Kit, cables, docu-
mentation, and SteJIarisWare software.

So how do you get started? Easy. First, to learn more, visit link # 1 below. Then request
your complimentary sample kit using link # 2.

Tl has generously provided all the essentials you need to get started!

Because Circuit Cellar s primary role is publishing a print magazine about hands-on
embedded systems projects, every DesignStellaris 2010 contest entrant is viewed as a
potential author. Industry leaders pay attention to these contests. Circuit Cellar maga-
zine is proud to report that a considerable number of past contest entrants say that
the publicity from their participation benefited both their careers and manufacturing
ambitions.

As of December 1 , 2009, Circuit Cellar is an Elektor International Media publication.

1 * wwwxircuitcel Icir.com/dcsignstellaris2010;' index.htm I

2. www.circu1tcellar.com/designstcllans2010/kit.html (100106-! If)

oesteisiii

Stellaris" ™

^ T C

H-jtAs iwrreunQrts )

CIRCUIT
CELLARI

Target applications are any consumer or
industrial equipment that has touch-screen
displays or traditionally has mechanical but-
tons. Typical examples include cell phones,
MIDs (mobile Internet devices}, MP3 play-
ers, portable media players, digital photo
frames, multifunction printers, digital still/
video cameras, and POS (point-of-sale)
terminals*

The MAX1 1835 drives both single-layer and
multilayer piezo actuators over a wide 5V to
250V voltage range. The wide output volt-
age range not only lets designers choose
between these two types of piezo actua-
tors, but also guarantees a future-proof
solution for alternative actuator technolo-
gies. By integrating a user-programmable
haptic pattern generator, programmable
boost converter, and high-voltage, high
capacitive load driver, the MAX1 1835 gen-
erates a user- configurable, slew-rate-li un-

ited, boosted voltage output
The MAX1 1835 has sufficient on-chip
memory to simultaneously store multi-
ple user-defined haptic waveforms, which
are downloaded at power-up through the
serial I2C interface* During operation, only
a haptic trigger pulse is required from the
system or application processor to play out
the waveform. Unlike other driver ICs, no
high-speed waveform pattern needs to be
sent during operation. This simplifies code
design on the system or application proc-
essor, reduces software load, and improves
haptic response time. Obtaining low latency
(from the instant of touch detection to hap-
tic response) is crucial to effectively mimic
the real-world feeling of a button press.

www.maximHc.com/IVlAX11835 (100106-IV)

Configure a custom
power supply in under
five minutes

ACAL Technology announce the immediate
availability of the Extelsys powerKit which
allows designers to use the world's small-
est power supplies to configure a plug-and-
play custom power module in under five
minutes.

Each powerKit contains an application-spe-
dfit Xgen powerPac chassis module, and
seven different Xgen powerMod dc output
modules which can be inserted, removed or
exchanged to create a custom power-sup-
ply. These provide a range of output volt-
ages, from 1.5V to 58V, with a maximum
current of up to 50A. The kits are presented

elektor 04-2010

11

NEWS & NEW PRODUCTS

in a rugged case and include two pairs of
serial, and two pairs of parallel, links as well
as power and signal connectors, documen-
tation, screwdriver and a voltage adjust-
ment tool.

The Xgen series of power sources provides
additional flexibility with a number of user-
configurable functions. These include local
and remote adjustment, adjustable straight-
line or foldback current limit and output
inhibit/enable functions. powerMods can
be configured in parallel for higher-current
applications and in series for operation at
higher voltages. High-efficiency conversion
techniques allow Xgen series power sources
to achieve minimal power losses, whilst
advanced packaging reduces their size to cre-
ate the industry’s smallest power supplies.
The powerKit has been optimised for stand-
ard, medical, high -temperature and low-
noise applications. The standard and medi-
cal versions are available with power ratings
of 1 340W or 7 SOW, with 6 and 4 powerMod
siots respectively; the powerKit for high-
temperature applications has a 6GQW rating
and six slots; whilst the low-noise powerKit
is rated for 1 200 W and offers six slots.

www. a ca 1 1 e ch no I ogy . com / u k / exce I sy si

( 100106 -V)

Customizable high-speed
USB2.0 module

QuickUSB from Saelig Company is a unique
and customizable quick and easy USB2.0
connectivity solution. This compact 2 ,T x1 1 '
circuit board implements a bus-powered Hi-
speed USB 2.0 endpointterminating in a sin-
gle SO- pin target interface connector. With
the companion QuickUSB Customizer soft-
ware, you can tailor the QuickUSB Module
to give your product a custom-developed
took and feel with a user-defined *My Prod-

uct' string descriptor, a unique RID (Product
ID), and a user- defined serial number to cre-
ate uniquely identifiable products.

Today, any product that connects to a PC
must have a Hi-Speed USB 2.0 connec-
tion, and a number of generic solutions are
available. But when you finally have your
USB interface working, USB device must
be assigned product ID (PID) and a ven-
dor ID (VID). VIDs are assigned by the USB
Implementors Forum at approx. $2,000.
None of these generic solutions allows you
to easily make a product that enumerates
on a PC with your company and product
identification.

QuickUSB gives you the ability to include

a complex, high-performance computer
interface Into you r product quickly and
easily. No-one will even know it's Quick-
USB inside. QuickUSB is a functional mod-
ule that includes built-in firmware, a device
driver and software that works on Windows
98SE, ME, 2K, XP, Vista and Windows 7. !t
includes drivers and software applications
that work right out of the box. The Quick'
USB Library supplied supports all the popu-
lar programming languages and works v\ :r
any language that can call a DLL. QuickC 5 =
Is supported on Linux too (MacOS X supp c n
will be available soon).

QuickUSB module provides: an 8 or 16- - :
High Speed Parallel Port for really fast cat:
transfer, from DSPs or FPGA based circi. :s
up to three general- purpose 8-bit para a
I/O ports; two RS-232 ports; one I2C pr:.
with multiplexer; one soft 5P3 port or F Re-
configuration port. These interfaces g . a
the designer the ability to convert exist - :
products to USB 2.0 or create new des cm
from scratch, fn both cases, the soft,. a
supplied with the modules eliminates a~
need to understand the workings of USB 2. ’
while making it really easy to access the d r -
ferent interfaces from the PC, This is a com -
plete implementation of USB 2.0 that uses

full speed potential unlike other options that
are "compatible” with USB 2.0 but use much
slower USB 1.1 data transfer. With QuickUSB,
96 MBps bursts on parallel port and 20 MBps
continuous data are possible.

These software libraries include the USB
2.0 drivers, application DLL and examples
of using the software in most commonly
used programming languages, includ-
ing Visual Basic, C++ and Delphi, The DLL
includes functions to read and write individ-
ual bytes or data blocks from each interface,
and all the set up details needed to provide
flexibility e.g. LSB or MSB first on SPI port,
input or output on each I/O pin or baud rate
on serial port.

QuickUSB modules are available now from
Saelig Co, Inc, Pittsford \Y, USA at SI 49
each.

wfww.saelig.com ( 100106 - VI)

New high frequency
LCR Meters

GW Instek pr-: emt : : new high frequency
LCR Meters tra LC7-S 1 1 OG and the LCR-
8105G. —:‘v atest members of the GW
Instek ra~ge, :~ese high frequency LCR
mete -3 ree ca a aped to satisfy the grow-
ing -ees’ : '"equency component and

mcc. e aaactf^ sation.

- : ; - : . :-.e opment of telecommu-

" :a: _ ~ a: “ " ; ;gy. the need for accurate

- :_a _ : component and module
mrecteica: - s essential. The LCR-8OO0G

- - e accuracy, versatility and high

-i. a .v ide range of component

— i:: _ - e — e - ‘s: including DC resistance

: _'e“e":s and voltage/current moni-
; : - - : I : ^ -orient characteristics can be
a a number of circuit models
= - ; :e3i ‘■ecjencles to emulate real circuit
: : ea: :r ensuring accurate verification
a - : ;n J aantly reduced trial and error
■ — a Customised program sequences can

- m : :ec . sing the Multi-Step function.

12

04-2010 elektor

NEWS & NEW PRODUCTS

Each program sequence supports up to
30 test steps set with separate parameters
and test limits. This allows normally tedious
test routines to be automatically stepped
through with the press of a button. To easily
verify components, the Graph Mode plots
component response over a wide range of
frequency or voltage sweeps. Both GP1B and
R5-232C interfaces are standard to display
test results on a PC or for remote control,

www, q wi nstek.com (i o 01 o 6 - VI I }

Australia’s youngest
engineers to innovate
using Altium Designer

Altium is adding a local element to its FIRST
Robotics Competition (FRC) sponsorship,
supporting the first Australian team to enter
the worldwide competition.

The FRC is an annual robot design com-
petition organized by FIRST, a not-for-
profit organization dedicated to fostering
a greater understanding and appreciation
of science and technology. Designed to
inspire young people to innovate, the FRC
challenges teams of students to develop a
robot in six- weeks using a standard kit of
parts and a common set of rules. The com-
petition attracts thousands of students and
is televised by stations around the world.
This year Altium is sponsoring the Australian
FRC team as well as providing all 1 ,800 FRC
teams with a 1 2-month licence of Its elec-
tronics design software, Altium Designer.
This gives young engineers real-life experi-
ence with the same electronics design tool
used by organisations that include NASA,
Cessna, Cochlear and the Volkswagen Group
of America,

Alti urn’s extended support also sees engi-
neers from Altium’s research and develop-
ment team mentor the students.

'The FIRST Robotics Competition provides

a wonderful opportunity for young engi-
neering minds to experience science and
technology in a fun and competitive envi-
ronment," said Matt Schwaiger, Senior
Vice President of Global Customer Success.
"We are proud to be fostering the talents of
these students and providing them with all
the tools and support they need to excel in
the FIRST Robotics Competition."

The FRC Championship will be held April 1 5-
1 7, 201 0 in Atlanta’s Georgia Dome.
"Australia doesn’t produce enough of its own
engineers and we can't afford to wait until kids
are at HSC level before we start trying to get
them interested,” said Australian team coordi-
nator, Associate Professor Mike Heimlich.
"This program is designed to get kids
excited about engineering, science and
technology by giving them the opportunity
to see what a fun and creative process work-
ing in this field can be,”

VAVw.altium.com (iooio6-Vllf)

Three C/V
characterization
capabilities in one chassis

Keithley Instruments' Model 4225-PMU Ultra
Fast l-V Module is the latest addition to the
growing range of instrumentation options
for the Model 42QQ-SC5 Semiconductor
Characterization System, It integrates ultra-
fast voltage waveform generation and cur-
rent/voltage measurement capabilities into
the Model 4200-SCS’s already powerful test
environment to deliver the industry's broad-
est dynamic range of voltage, current, and
rise/fall/pulse times, expanding the system’s
materials, device, and process characteriza-
tion potential dramatically. Just as important,
the Model 4225-PMU makes ultra-fast l-V
sourcing and measurement as easy as mak-
ing DC measurements. Its wide program-
mable sourcing and measurement ranges,
pulse widths, and rise times make It well-
suited for applications that demand both
ultra-fast voltage outputs and synchronized
measurement— from nanometer CMOS to
flash memory.

Unlike previous solutions, which required up
to three different test stands to characterize
a device, material, or process thoroughly,
the Model 4225-PMU's broad dynamic
range allows characterizing the full range
of materials, devices, and processes with a
single set of instrumentation. Now, labs can

configure one flexible system to handle all
three measurement types: precision DC l-V
(Model 4200-SMU), AC impedance (Model
4210-CVU C-V Instrument), and ultra-fast I-
V or transient l-V (Model 4225-PMU),

Each 4225-PMU module provides two
channels of integrated sourcing and meas-
urement but takes up only one slot in the
nine-slot chassis. Each chassis can accom-
modate up to four modules for a maximum
of eight ultra-fast source/measure channels.
Each channel combines high speed voltage
outputs (with pulse widths ranging from
60 nanoseconds to DC) with simultaneous
current and voltage measurements. The
module provides high speed voltage puls-
ing with simultaneous current and voltage
measurement, at acquisition rates of up
to 200 megasamples/second (MS/s) with
14-bit ana log -to-drgital converters (A/Ds),
using two A/Ds per channel (four A/Ds per
card). Users can choose from two voltage
source ranges (±1 0 volts or ± 40 volts into
1 megohm) and four current measurement
ranges (800 milliamps, 200 mllliamps, 10

milliamps, 100 microamps).

Each Model 4225-PMU can be equipped with
up to two optional Model 4225-RPM Remote
Amplifier/Switches, which provide four addi-
tional low current ranges. They also reduce
cable capacitance effects and support auto-
matic switching between the Model 4225-
PMU, the Model 421 Q-CVU, and other SMUs
installed in the chassis. The Model 4220-PGU
Pulse Generator Unit, which offers a voltage-
sourcing-only alternative to the Model 4225-
PMU, is also available,

http:// keit h I ey . a c ro ba t . com / P7740274 2 j

(1001 06- IX)

13

elektor 04-2010

NEWS & NEW PRODUCTS

World’s smallest motor now even smaller

Last year Elettor
reported on the small-
est hand-made mini-
ature electric motor,
with an E-weekly item
in April 2009 editon
and an article with
a drive circuit in the

Features of the new

diameter 13 mm
length 03 mm
volume 0,9 mm3

weights mg November 2009 edition of Elektor. With this

speed 500-1 0,000 rpm motor, Elektor reader jos d'Haens booked a

world record and managed to obtain an official
certificate from Guinness World Records, natu-
rally accompanied by a notice In the well-known Guinness book.

Now, thanks to improved and refined production methods and production tooling, jos
d'Haens has succeeded in further reducing the size of the motor, which was already
good for a world record last year, so much that its volume could be reduced from
1 + 9 mm 2 to 0.9 mm 1 (or more precisely, 1 30 x 0.65 = 0.863 mm 5 ), which breaks the
'psychological barrier' of 1 mm 3 . In order to achieve this, a small CNC machine tool was
developed for drilling the holes in the motor end plates (hole diameters 03 mm and
0.1 mm). Thanks to improved polishing of the shaft and rhodium plating of the bear-
ings t it was possible to increase the speed to the range of 10,000 to 12,000 rpm.

In the meantime, a new control circuit has also been developed as an alternative to the
original combination of a 555 1C and a 401 8 1C. Now a programmed ATtinyl 3 micro-
controller handles this task. This makes driving the motor a good deal easier, but the

original method is still preferable for high speeds because it allows the frequency to
be ramped up more gradually.

This is an impressive achievement, which is bound to be rewarded by a new certificate
from Guinness World Records. Here at Elektor we have no doubt that Jos has plans for
even further miniaturisation.

The photo shows the motor next to a 50-eurocent coin for comparison.

(iooioG-X)

World’s First 4 Channel /
30 GHz solution enables
56 Gb/s IQ Modulated
QPSK analysis

LeCroy Corporation has extended the
power of its Wave Master® 830 Zi 30 GHz
real-time oscilloscope by providing a sim-
ple and fast method to combine two oscil-
loscopes and provide 4 channels at 30 GHz.
This solution Is ideal for measurement and
analysis of 28 to 56 Cb/s IQ modulated sig-
nals where ultra-high real-time bandwidth
and four channels is required, or for cap-
ture and detailed analysis of other leading
edge technologies. The solution is enabled
with the Zi-8CH -SYNCH Oscilloscope Syn-

chronization Kit, which is compatible with
all WaveMaster 8 Zi models, so It may be
used to create four channel data captures
from 20 GHz to 30 GHz or eight channel
data captures from 4 GHz to 16 GHz.

The oscilloscope synchronization kit is com-
prised of a small hardware module that
plugs into one of the two oscilloscopes.
Once attached, it identifies that oscilloscope
as the ‘Master 1 for display and control pur-
poses. A variety of other cables for trigger
synchronization, dock sharing, and data
transfer are connected between the "Mas-
ter" and a ‘Slave 1 oscilloscope. Triggering of
both oscilloscopes may be performed in a
pseudo-auto trigger mode, or by applica-
tion of a customer trigger signal. Upon suc-
cessful trigger, all waveforms from both the

‘Master’ and the 'Slave 1 oscilloscope are dis-
played on the ‘Master’ oscilloscope grid for
easy viewing, debug and analysis. The com-
plete setup time is no less than 5 minutes
prior to deskewing channels.

The LeCroy WaveMaster 830 Zi oscillo-
scope was launched on January 5, 2009 as
the second product line developed from
LeCroy T s next-generation “Apollo' chipset.
The scope features a real-time band-
width of 30 GHz and a sampling rate of 80
Gigasamples/second on two channels. The
complete acquisition system used in the
Alcatel-Lucent experiment used two Wave-
Master 830 ZI oscilloscopes for a total of 4
channels at 30 GHz.

www.lecroyxo.uk (iooio6-XI)

Multi-Instrument 3.2
released

Virtlns have realeased Multi-Instrument 3.2
a nd offer it for d ownload at for 2 1 days 1 fu I ly
functional free trial. The free trial period is
valid even if you have tried previous ver-
sions of the software on the same compu-
ter before.

If you are our existing customer, you areeli-
g i ble for free u pg ra ding to the same license
level you own. Both softkey and hard key
upgrade links are available a the Virtins
website.

fl Q-iOiiCQ' %
' 0.GQ1263 V
9a.7i3&40 '.16

04-2010 elektor

NEWS & NEW PRODUCTS

New features in Version 3.2 include and
added DDP Viewer, the ability to run the
program as an ActiveX automation Server,
the Hot Panel Setting Toolbar, added func-
tions to Lock / Unlock Panel setting under
Help submenu, functions to Hide j Show
various Toolbars In Dislay Setting Dia-
log, “Start Frequency” option for X axis
in Spectrum Analyzer and Spectrum 30
Plot, and more.

vwwv.virtins.com (iooio6-X!V)

Speed, performance and
low cost combined in
spectrum analyzer

Anritsu has developed the MS2830A Spec-
trum Analyzer which is an addition to the
expandable M5269xA product line and sup-
ports high measurement speeds and supe-
rior performance at a low cost. As a result
this helps improve efficiency of R&D and
production, cutting measurement time,
improving yield, and reducing power con-
sumption to cut C02 emissions.

The new instrument supports frequency
ranges from 3.6 to 13.5 GHz, providing
superior RF specifications for average noise
level of-1 53 dBm (1 GHz, without preampli-
fier), third-order inter-modulation distortion
(TO I) of +15 dBm, a nd total level accu racy of
±0,3 dB (typical). Easily customized expand-
ability from the minimum configuration to
an all-in-one advanced TRx tester helps keep
down costs to only what Is needed, and is
available from less than TO l< .

The measurement speeds for basic spec-
trum analyzer functions, such as sweep-
ing, frequency switching, peak search,
display and reading of measurements put
the MS2830A at the top of its class, while
the Vector Signal Analysis option supports
even faster measurement of band widths up

to 31 ,25 MHz. The instantaneous averaging
of modulation signals and noise dispersion
measurement significantly out perform all
conventional sweep spectrum analyzers.
The MS2830A is caopable of measuring
average noise levels of -153 dBm (1 GHz,
without preamplifier), third-order inter-
modulation distortion (TOI) of +1 5 dBm,
and has a total level accuracy of ±0.3 dB
(typical), yet at a low cost of below 1 QK€.
The IV152S3QA can be customized from basic
configuration to comprehensive all-in-one
tester to meet customer’s current needs at
minimum cost or to minimize future expan-
sion costs. This provides the convenience of

a modular based system, but with the per-
formance and convenience of a dedicated
test instrument.

The MS283GA consumes 45% less power
than current models, cutting electricity
costs and saving CO, emissions.

The IVtS269xAand MS2830A measurement
software are fully compatible. Using the
MS269xA for R&D and the MS2830A for
manufacturing reduces production start-up
times and makes it easy to transfer control
software from R&D to manufacturing.

www. anritsu, com (100106-Xll)

Fast signal plotting and chart creation
under Windows

LightningChart Pro from the Finnish company Arctlon is especially designed for profes-
sional data acquisition software, PC-based oscilloscopes and signal analysers, scientific
research, medical and other real-time measurement and signal monitoring applica-
tions, Optimized for high-speed sampled signal data handling with innovative CPU
overhead saving techniques, it is able to handle huge point counts, where all other
chart/ graph controls get delayed, frozen or crashed.

By utilizing great power of modern display adapters, the screen resolution can be very
high even with the most demanding real-time measurements. There are numerous
horizontal scrolling modes available, providing an ideal and smooth scrolling effect
for every scenario. The data handling capacity is up to hundreds of millions of new
data points / sec.

LightningChart Pro allows using many different series types, signal tracking cursors
and signal markers. Data handling capacity and performance is excellent also in signal
review and analysis applications. For that purpose, it has also built-in customisable scroll
bars, with 64-bit value range for direct usage as sample indexing in long high speed
measurements. Appearance Is fully customisable providing very modern user interface.
For easy properties setup, charthasa built-in Chart editor window.

wvwv.arctton.com (100106-XIH)

eloktor 04-2010

15

ROBOTICS AND ARTIFICIAL INTELLIGENCE

Super Robots

Myths, promises, threats and

the ‘here and now’

By Andrew Eliasz (First Technology Transfer Ltd., United Kingdom)

Artificial Intelligence and ‘Intelligent Robots’ are topics that fire the imagination. Generally, imagination runs
ahead of what can be achieved, yet, with time, things that were once considered phantastica! quite often get
to be ‘realised’. How close are we to realising the kinds of robots and intelligent computer systems depicted in
films such as HAL in Kubrick’s 2001 A Space Odyssey , or the lifelike child in Al, or the kinds of robots in I Robot?

A common theme in many science fiction books and films involv-
ing robots is based on the fear, that lies deep in many of us, that
robots created 'to serve mankind" may turn on it and either destroy
or enslave it* This may have something to do with the fact that we
live in a culture where getting rich and acquiring power is seen by
many as the only goal in life* The potential of achieving such things
with the aid of powerful Al software and versatile ’smart’ robots
appeals to such people, but there is always the fear +f what if they
acquire our values and turn out to be better than us”.

It is quite possible that one of the many current developments in
Artificial Intelligence and Robotics whose significance has not yet
been realized may turn out to be a key 21 st Century technology.
Maybe some of the topics covered here will inspire some of the next
generation of Elektor projects, or be the start of an illustrious engi-
neering career. Let’s hope that these future developments serve a
socially useful purpose.

Learn from nature

At the outset it is worth noting that simple mechanisms can some-
times give rise to very complex behaviour, as, for example, dem-
onstrated by fractal and chaotic systems, or the complex behav-
iours demonstrated by social insects such as ants, termites or honey
bees. Leaving aside deep philosophical discussions as to the nature
of intelligence we may list pertinent questions like

■ what kinds of intelligent systems can we buitd now or in the
near future?

* what kinds of mechanisms can be constructed for moving
around and manipulating the environment without direct
(human) intervention?

■ what can we team from studying how biological systems have
evolved and the strategies that have developed for allow-
ing organisms and systems to flourish, and how might these
insights be applied?

Food for thought! Back on earth, the Ingredients’ at our disposal are

* sensors

* transducers capable of providing motion or manipulation
capabilities

* analogue and digital electronics components

- software (either compiled directly into silicon, or executed via a
processor or processors)

* sources of computer inspiration from biology

* patterns for constructing artificial life models in hardware

* competitions and challenges designed to stimulate research
and progress

* patterns and protocols for learning and communication

This is a multi-disciplinary brew that should attract not only special-
ists but also technophiles, interdisciplinarians and ‘broad thinkers’,
and the results should by n ow surpass 'a utonomous robots’ of which
there are plenty a roun d already (Figure 1 ) . A good sta rting point for
those interested in the Inspirational role of biology in computing
is Nancy Forbes 1 book P on, among others, attempts to construct
information processing systems that use biological systems.
Techniques based on this work and ideas that have been applied to
various aspects of robotics such as path planning, image processing,
locomotion control and data fusion include neural networks, genetic
algorithms and artificial immune systems. Areas that are still in their
very early stages include DNA computing, self-assembly and nan-
otechnology and amorphous computing (based on models of cell
colonies or swarms of bees — systems that demonstrate self-organ-
ising capabilities). A fascinating and reasonably up to date collection
of descriptions of actual robots and robot models inspired by exam-
ples from living organisms has been put together by Adamatzkyand
Komosrnski 1^1, Here can be found such marvels as

* the stiquito, a hexapod insectoid robot that uses heat activated
nitinof wires for locomotion, and a description of attempts to
construct and study a colony of such Insectoids;

* using neural networks and delayed reward protocols to learn
legged locomotion such as how to hop over rough terrain, or,
how to ru n if you re a fou r legged robot

* a swimming and walking robotic salamander (the one
described here uses PICT 6 and PI Cl 8 microcontrollers and 12 1
for interprocessor communication, although a CAN bus based
version is planned.)

* a gorilla robot that can walk on two legs, or use all four limbs for
locomotion, or climb ladders and swing from branch to branch

16

04-2010 elektor

ROBOTICS AND ARTIFICIAL INTELLIGENCE

"How do you spot a ‘rogue’ robot?” (from the film “ I Robot")

(a form of motion is called “brachiation")

* the use of genetic algorithms to optimise the design of the
walking mechanisms of legged robots

• the use of FPGA devices to implement the perception, and navi-
gation systems for roving robots by means of a reward based
conditioning strategy (you might think of it as applying Pavlo-
vian conditioning to the developing of robot behaviour)

♦ the use of microbial fuel cells to power robots

* using slime moulds as a mechanism for controlling robot behav-
iour by interfacing a slime mould 'chip 1 to a microcontroller

The approaches just described are still a long way from being widely
applied but do demonstrate the potential and excitement associ-
ated with this area of robotics research. Currently it seems unlikely
that robots will contain purely biological systems inspired software
or make heavy use of biological sensors and biological control sys-
tems. Development of biological systems inspired software is com-
putationally very intensive and time consuming, and hence can only
be applied to fairly specific problems.

Kismet and the human(oid) factor

Learning and language capabilities are likely to become more and
more important for a whole range of robot applications e.g. com-
panion robots, exploratory robots, “smart” household appliances
(think of e.g. a much improved ROOMBA that can be ta ught and
instructed by voice).

Smartness should include the ability to communicate e.g. robot-
human communication, robot-robot communication. Devising soft-
ware endowing robots with language and learning capabilities (e.g.
being able to tefl a robot to perform some task or take note of some
feature in its environment) is a very complex task, even if we are
considering a language restricted to a fairly narrow domain.

Think how you might build and program a robot that could respond
appropriately to an instruction such as “pick up those socks and
put them in the laundry basket". If you don't believe me then dip
into a copy of Language and teaming for Robots i 3 J, an apparently
introductory book till you try to implement the code it outlines.
Yet , considerable progress has been made in realising such socia-
ble machines. An impressive example of what could be achieved

Figure 1 . It’s too easy to call a robot autonomous 1 if biological aspects are not, or insufficiently, included in the design.

elektor 04-2010

17

ROBOTICS AND ARTIFICIAL INTELLIGENCE

Figure 2. Kismet in action (stills do not do it justice).

using 1990's technology was MIT's Kismet HI, “an expressive robotic
creature with perceptual and motor modalities tailored to natural
human communication channels” (Figure 2 ). The computing power
underlying Kismet is fairly substantial involving four Motorola 63322
embedded systems running a specialised variant of Lisp; nine net-
worked workstations running QNX (a Unix like RTQS): networked
Linux and Microsoft Windows machines.

The videos of Kismet interacting with real live humans are very
impressive. The resources consumed in developing Kismet prob-

Figure 3. Nao footballers at the RoboCup 2009 Final,
fortunately Aldebaran has an IDE for "Choreographing"

NAO robot movement.

ably ran Into several millions of dollars even allowing for the fact
that bright MIT PhD students are a cheap source of labour (the hard-
ware alone cost around S25K). Software maintenance costs would
be huge if Kismet were to be deployed in the real world. It should
not come as a surprise that the Kismet project is no longer being
actively pursued.

Sociable robots

Progress in the practical realisation of sociable as well as team player
robots requires the availability of standardised platforms with
standardised application development frameworks at prices in the
1GK-20K range. An example of one such robot is Nao l s l, a human-
oid robot that has been used in the development of Robot Soccer
teams (Figure 3). its underlying development environment Is Gos-
tai’s URBL For those with more limited budgets it is worth noting
that URBI has also been ported to Lego Mindstorms INIXT.

Socially capable robots can be found in helping children and adults
with learning and social interaction difficulties, such as those suf-
fering from autism. The robot dolls and faces developed for this
work are far less complex and sophisticated than Kismet, for exam-
ple, but have proven to be remarkably effective. These robot dolls
and toys, because of their relative simplicity make possible less
overwhelming social experiences and are very forgiving of social
faux pas. One such cute simplified robot is called Keepon (Fig-
ure 4), and it has proven to be remarkably successful in helping
children with communication disorders.

From concept to silicon

As with software engineering, so also with robotics and Ai there
is the dream of a "magic silver bullet” that will banish complexi-
ties and make building super robot systems almost effortless. Many
people take software for granted and it is not all that uncommon to
hear statements such as “it can't be that difficult it s only a piece of
software”, or "what do you mean by claiming that designing and
writing software Involves considerable creativity , Unlike power-
ful, well organised and politically well connected professions such
as the legal or medical professions the engineering and software
engineering professions are not held in great esteem. Very few
users of mobile phones, for example are even remotely aware of the
complexity of the software that makes these almost indispensible
“gadgets” work, not only the image and voice processing, but also
the underlying operating system and the need to make the soft-
ware extremely reliable. The blue screen of death is not an option
for mobile telephony software. Yet, the software for autonomous
robots must be even more reliable, especially where robot malfunc-
tion may result in serious damage or injury.

The problem with software is that it "contains bugs”, and the more
complex the software the larger the number of bugs. It would be
extremely rash to claim that any computer system was completely
bug free. It must also be pointed out the processors too may con-
tain bugs that may necessitate workarounds when implementing
software that will run on these processors. For some, so called hard
realtime' applications it is a bug if the software does not respond to
certain events within a specified time of the event occurring, or if

18

04-2010 ciektor

ROBOTICS AND ARTIFICIAL INTELLIGENCE

Swarm robotics and Ad Hoc smart networks

An 1 -Swarm nome.

A "swarm" of Symbrion Robots*

For robots to co-operate socially they need to communicate in some
way. They can either all communicate via some central communica-
tions hub t or, they can make use of self "Organising wireless networ-
king technology of the kind used in Ad Hoc networks*

Quite a few of the robots being developed in this context have
turned out to be surprisingly complex. Current swarms are relati-
vely small in number ( 10 *s to 100 ’s of robots). The J -SWARM project
aims to deploy a swarm of a thousand or more tiny (they will fit into
a 3 mm sided cube) robots [7], Some fascinating projects on swarm
behaviour include

* Symbrion -Replicator, which is also exploring the use of Artificial
Immune System techniques for controlling swarm behaviour [ 8 ]
and developed from the I -SWARM project and the open S WARM -
ROBOT project [9]

• the S-Bot project developed attheEPFLin Lausanne (Switzerland)

[ 10 ]

The Symbrion bots and the 5-Bots contain quite powerful proces-
sor hardware needed to run the complex software that makes them
work so well. The processors being researched for the various Sym-
brion bots include ARM7, ARM Cortex 1 1 , XScale PXA270 (ARM 1 0)
and Blackfin. The S-Bot has a 400 MHz XScale CPU, 64 MB Flash.

32 MB RAM and 1 2 distributed PIC microcontrollers for low level l/Q
and sensor handling.

Development of applications using these swarm robots requires use
of simulators to explore various scenarios before trying them out on
the real robots*

1

WiFi r

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DC/DC

3x PIC processor

XScale Linux
400 MHz
64M RAM

(CompactFlash)

PIC processor

3x PIC processor

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HT-

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2x servo gripper
and arm motor

U omnidirectional camera

4x microphone

temperature sensors
C gripper sensor

elevation motor
rotation motor
gripper motor

PC Bus

Lithium Ion Battery 10 Wh

PIC processor

2D traction sensor

PIC processor

8x RGB LEDs
<i C light sensors

PIC processor

PIC processor

< 15x proximity sensors

r 4x ground proximity
^ sensors

2x PIC processor

S>

t

differential tree Is

100013- T1

Block diagram of an S-Bot.

elektor 04-2010

19

ROBOTICS AND ARTIFICIAL INTELLIGENCE

Figure 4. ‘Keepers' can help children with communication

disorders.

and it is partly in response to the annoyances of having to grapple
with dosed source frameworks that powerful open source frame-
works are being developed. A good example is the ROS framework
— which works with e.g, the PR2 robot (Figures), and an example of

Figure 5. WillowGarage's PR2 Robot

a framework that is moving from closed to open source in the URBI
framework — which works with e.g. the MAO robot.

The best robot — no such thing

There are many tradeoffs to consider when building robot systems.
In the case of software the selection of algorithms and frameworks
may need to take into account issues such as scalability and speed,
and obtaining the ‘best’ solution or simply a ‘good enough 1 solu-
tion. For instance if we look at image processing software there is
a great deal of difference between software that can distinguish
between balloons of different colours, perform numberplate rec-
ognition, or recognise facial gestures. Similarly, with voice recogni-
tion there is a whole range of difficulty levels e.g, recognising a few
dozen words, processing whole sentences, or being able to hold a
rational and interesting conversation.

For autonomous mobile robots the locomotion and navigation plat-
form is an essential subsystem. At the simplest level there are line
following and maze traversing robots. At a higher level there are
robots that need to be able to explore, learn about and navigate in
their environment, like the robots entered into the Trinity College
Fire Fighting Robot competition. At a still more advanced level there
are robots such as NASA’s Mars Explorer, or the robots that compete
in the DARPA autonomous vehicle event.

Sensors and subsystems found in autonomous robots, typically
include

• touch / contact / bump sensors

• sonar or laser-based ranging sensors

• digital compass and GPS

• LEO / photodiode sensors for e.g. line following

• odometry subsystem (e.g, using optical encoders)

• CCD cameras

• iR imaging sensors

• Radar subsystem

The inputs from all these various subsystems and sensors need to
be co-ordinated and acted upon appropriately. The more input data
and the faster the input data rate the more complex the software
needed to handle it.

For systems with relatively few sensors and performing relatively
simple tasks an approach based on Finite Statemachines (FSMs),
or their more complex relations Extended FSMs, Hierarchical Finite
FSMs and Statecharts may be sufficient State Machines can be mod-
elled using UML Case Tools and quite a few of these Case Tools are
capable of generating code from the state machine design. IAR h s
Visual State tool is a good example of a tool aimed at embedded
systems developers that concentrates on the use of Statecharts
for embedded systems design. For more complex systems there
are many options to choose from i 6 ) to carry out subtasks such as
transformation, feature extraction, pattern recognition, sensor data
fusion.

Here you’ll find techniques such as digital signal processing, statisti-
cal and syntactic pattern recognition e.g. using Bayesian networks
or Hidden Markov Models (HMM), discriminant functions. Classifica-
tion And Regression Trees (CART), Neural Networks, Genetic Algo-
rithms, Artificial Immune Systems (AIS) as well as various hybrid

20

04-2010 elektor

approaches based on combinations of the above techniques (e.g,
using a Genetic Algorithm to evolve a Neural Network}. These tech-
niques can be deployed in an ‘adaptive" or ‘non adaptive 1 Le. fixed
manner.

Developing software for robotics systems has many interrelations
with developing simulation* computer game, entertainment system
and "electronic trading" system software. Simulation can be used
to explore robot capabilities before the robot has been constructed,
or to explore various deployment scenarios before robot deploy-
ment in the field. It is perfectly reasonable to devise robots that exist
purely as software running on powerful computers, or a network
of such computers connected via the web. Examples of such hots
include chatterbots, game playing bots and e-trading bots.

By providing these bots with access to semantic web resources such
as knowledge rich 'ontology 1 based repositories (e.g, by exposing
these resources as web services) it is apparent how the capabilities
of robot systems can be extended. Adding in smart sensor based Ad
Hoc networks it is easy to envisage entire ‘communities' of robots
with varied self organising capabilities. If we further add in the pos-
sibility of interfacing robots with biological systems {e,g. arrays of
electrodes implanted into e.g. animal brains, or arrays of surface
electrodes picking up signals associated with neural activity) it is
possible to envisage all kinds of applications of which prosthetic
limbs and exoskeletons are but a starting point. Adding in the dis-
coveries from stem cell research, molecular biology and genetic
engineering suggest the development of e.g, computers with bio-
logical extensions. The ethical issues with developing and deploying
such technologies are many and complex.

(100013)

Internet Links and References

[1] Forbes. Nancy; "Imitation of Life, How Biology is Inspiring
Computing", MIT Press, ISBN 0-262-06241-0 (Pbk) (2005).

[2] Adamatzky, Andrew; Komosinsky, Maciej; "Artificial Life
Models in Hardware*. Springer. ISBN 978-1 -84882-529- 1 ,
(2009),

|31 Crangle. Colleen; Suppes, Patrick: "Language and Learning for
Robots", CSLJ Publications, ISBN 1-881526-19-4, (1994)

f4| www.ai . m it.edu/projects/humanofd -robotics-group/kismet/

kismet.html

[5] www.aldebaran-robotics.com/en

[6] Duda, Richard, 0; Hart, Peter. E; Stork. David, G; “Pattern In-
terscience. ISBN 0-471-05699-3 (2001)

[7] http://robJpr.kit.edu/engfish/research.php

[8] www.symbrfon.eu/

[91 www. s wa rm robot.org/

[1 OJ http://lis.epfl.ch/research/projects/SwarmBots/index.php

The new PicoScope 4000 Series
high-resolution oscilloscopes

a>

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The PicoScope 4224 and 4424 High Resolution
Oscilloscopes have true 12-bit resolution inputs
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elektor 04-2010

21

SMD MEASURING TWEEZERS

Measuring Tweezers

By Harry Baggen (Elektor Netherlands Editorial)

SMDs are nice and compact, but their small dimensions also have some drawbacks. You can hardly tell
different types of passive components apart, and the markings are not especially clear. With special SMD
measuring tweezers, you can quickly check what type of component you have and measure its value. We
tried out five such devices in our lab.

SMDs have several advantages compared with conventional leaded
components. For example, they take up much less space on the
PCB, which allows the entire circuit to be made a good deal smaller.
Thanks to the small component dimensions, the signal paths can
also be shorter, which results in less interference and allows opera-
tion at higher frequencies or dock rates. However, there are also
some disadvantages. Especially with relatively large ICs, manual
PCB assembly is rather difficult. You quickly reach the point where
you need an SMD oven If you want to do a good job of assembling
boards with SMDs, Another disadvantage becomes apparent in
prototype assembly or when you need to repair a board fitted with
SMDs: component overlay markings are usually minimal due to the
tiny dimensions. For this reason, SMD boar ds from the Elektor Shop
often do not have any component overlay at all, and in such cases
we print the boa rd layout at somewhat larger scale in the ma gazine.
The differences in the external appearance of resistors, inductors
and capacitors are also often so small that you have to guess at what
type of component you're looking at.

Manufacturers of measuring instruments have also recognised this prob-
lem, and they have developed special devices to deal with it Now we can
hear you thinking: things actually aren’t all that bad; you can manage
fairly well with a multimeter and suitable (small) probe tips. That's true,
of course, but with special measuring equipment it's a whole lot easier
to make measurements on passive SMD components.

For this review article, we surveyed the market to see what types
of measuring tweezers are available. By this we mean RC and RLC
meters equipped w'ith special tweezers for use with SMDs. Some
of these instruments have all of the circuitry and the display built
into the base of the tweezers, resulting in a more or less conven-
ient instrument (more about this later) that you can use to meas-
ure component values and (in some cases) determine what type
of component you're measuring, all without having to direct your
gaze somewhere else. There are also ‘normal’ multimeters where
the meter (with the display) is a separate unit and SMD measure-
ment capability is provide by special tweezers equipped with a cable
that can be connected to the meter.

Five candidates

The instruments in this practical test differ considerably in their basic
design and price. First we have two measuring tweezers, priced at
less than £35 (€40), that are suitable for measuring resistors and
capacitors. One of these instruments can also measure DC voltage.
Our third example of ‘pure’ measuring tweezers is the Smart Tweez-
ers instrument, a clever device for making R, L t Cand voltage meas-
urements that features a significantly higher price tag — nearly £260
(€300). This is the only instrument in the group that is also suitable
for lefties, since it has a configurable display orientation. In addi-
tion, we have two meters with a fairly conventional design. The Peak

Brand i Second Source

Model

Price (approx, rrp)

Suppller(s)

Agilent

vwwv.agilent.com

U1732B

U17S2ASMD tweezers

around £200 (€230) exd. VAT
tweezers around £25 (€30) exd. VAT

Agilent webshop or authorized
distributors worldwide.

Siborg

www.siho rg .com /s m arttweezers

Smart Tweezers

£260 (€295) and up. exd. VAT

Siborg webshop.

Peak Electronics
www. peake lee. co.uk

LCR4G with PEAK-5 MD03
accessory (SMD tweezers)

£79 irtcl. VAT (€81 exd. VAT)

Tweezers £20 (€23)

Peak webshop or authorized
distributors.

Voltcraft

Extec

RC- 1 00 SMD tester

Ex tec Tweezers

£20 ind. VAT

Conrad Electronics:
www1.uk.tonrad.com, # 121434
-S9.

Extec Tweezers

Voltcraft

Tenna

SMD-200 RCD meter
fenna Component Tester

£30 (€35) (ind. VAT)

Conrad Electronics:
www 1 . Lik.co n rad , com ,

# 1 23007 - 89.

Tenna: Parnell # 1749431

22

04-2010 elektor

SMD MEASURING TWEEZERS

Atfas LCR40 is a small, intelligent LCR meter priced at around £80
(€1 0G), with a tweezers probe available as an accessory. The final
member of the group is the Agilent U1 7328, an RLC meter with a
large display and priced at around £200 (€230), An accessory SMD
tweezers probe is also available for this instrument.

Voltcraft RC-ioo / Extec SMD tester

This is a lightweight RC meter in tweezers form, powered by two
LR44 button cells. The reasonably large 3 3 / d -digit display Is easy
to read. The 'Function’ button (which also acts as an on/off but-

instrument does not recognise the component type automatically,
so you need to know whether you are dealing with a resistor ora
capacitor. There is a Relative' button for making relative measure-
ments (measuring the difference between one component value
and another one).

Voltcraft SMD-20 0 / Tenna Component Tester

This meter has the same basic design as the RC-100, but with a
somewhat different case design and a different colour (grey Instead
of dark yellow). It is also powered by two LR44 button cells, and it

ton) selects the measurement mode: resistance, capacitance,
or diode. The meter has autoranging capability (which cannot
be disabled) for resistance and capacitance measurements. The
resistance ranges extend to 40 Mil, while the capacitance ranges
extend to 200 pF, The forwa rd voltage of the diode is displayed
in diode mode. Power is switched off automatically after 1 5 min-
utes of non-use.

The RC-100 is reasonably adequate for measuring SMDs. The tips
of the tweezers are fairly wide and rounded off, which makes it
difficult to make good contact with the contact surfaces of SMDs,
especially if they are already soldered on a board. Although the
autoranging function is handy, it takes several seconds for the
instrument to find the right range. With high capacitance values,
you have to wait qu ite a wh i le before the rl g ht va I ue a ppea rs . The

also has a 3 3 / 4 -digit display. However, it differs in operation. After
being switched on with the 'Function' button, the meter enters
scan mode where ft automatically determines what type of com-
ponent it is connected to (resistor, inductor or capacitor) and then
displays the component value (or the forward voltage if the com-
ponent is a diode). You can manually select a component type by
repeatedly pressing the ‘Function’ button, and you can use the sepa-
rate “Range' button to disable autoranging and select a particular
range. The resistance ranges extend to 60 MO, while the capaci-
tance ranges extend to 60 pF. Power is switched off automatically
after 1 0 minutes of non-use.

As a special feature, the SMD-200 allows the tweezers portion to be
unplugged and replaced by a cable (included) with an adapter and
probe tips. In this configuration, the device can be used as a replace-

eleklor 04-2010

23

SMD MEASURING TWEEZERS

ment for a regular multimeter, and tt enables you to measure DC
and AC voltages up to 600 V.

The SMD-2GQ is somewhat more satisfactory than the R0-1 00 for
measuring SMDs* thanks to its automatic component detection*
which is certainly convenient. The tips of the tweezers are very simi-
lar to those of the RC-100, which means they aren't great. The autor-
anging function is reasonably fast and certainly usable in practice.
According to the user guide, the auto-scan function does not work
properly with capacitors larger than 6 (iF. However, in practice we
had no trouble measuring values exceeding 1 00 pF without need-
ing to change to manual operation,

Siborg Smart Tweezers

This is the most luxurious SMD tester in the group, with prices start-
ing at around £270 (€300). You may not see the difference right
away, but the secret is in the details. The probe arms extending from
the case, which has a good ergonomic design, are excellent; the tips
are finished very precisely and mate well. You can even fit differ-
ent types of tips (available as accessories). The meter body holds
the circuitry and a graphic display (with 4-digit resolution for the
main value) and three LR44 button cells; a version with a recharge-
able battery and charging station is also available. The measuring

have the knack it's pretty smooth. The probe tips make good con-
tact and can be positioned precisely. With resistors, capacitors and
inductors, the component is identified almost immediately and the
measured value is displayed along with extra information at the top
of the display, such as the measuring frequency and (with inductors
and capacitors) either the internal resistance or the dissipation fac-
tor or £> (quality) factor {user selectable). This way you can imme-
diately get an idea of the quality of the component. Four different
measuring frequencies can be selected: 1 00 Hz, 1 20 Hz, 1 kHz and
10 kHz, When a diode is measured, a diode symbol is displayed if
it is OK. The voltage trace mode is a nice extra feature, but it's not
especially convenient because it must be selected separately in a
submenu and you also have to change the setting of a small switch.
However, that*s the only shortcoming of what is otherwise a very
handy little meter, which unfortunately is rather pricey.

Peak Atlas LCR40

The LCR40 is housed in a small enclosure with a two-line display that
shows the value of the measured component with 4-digit resolu-
tion. It is powered by a 1 2-V alkaline battery. A short, permanently
attached cable with two small probe tips provides the connection
to the component to be measured. You can also connect an acces-

tweezers are activated and operated by a sort of thumbwheel with
a built-in pushbutton. There is a fairly extensive menu that can be
used to select all sorts of manual modes and other settings, but by
default the Smart Tweezers are configured for automatic LCR detec-
tion. You can also switch manually to diode measurement, voltage
measurement* or even a trace mode in which the screen shows a
sort of osci lloscope display for slowly changing voltages. The meas-
uring ranges (manual or autoranging ) extend to 10MQ, 5000 pF.
and 1 000 mH. The voltage range is limited to S V. A cap is included
for protecting the probe tips. The meter switches off automatically
after a user-configurable time (default: 30 seconds).

Making measurements with the Smart Tweezers Is a piece of cake.
The thumbwheel control takes a while to get used to, but once you

sory cable with SMD tweezers (SMD03) in place of the dips. The
meter switches off automatically around 1 5 seconds after a meas-
urement is made.

This instrument automatically detects resistors, capacitors and
inductors* and it has autoranging capability (which cannot be disa-
bled). Operation is especially simple, with only two buttons avail-
able. The ‘On/Test* button switches on the instrument and starts
the measurement process. The value appears on the display five
seconds later; this delay can be eliminated by pressing the button
a second time. Only the component value is shown with resistors,
but with capacitors and inductors you can also display the measur-
ing frequency selected automatically by the instrument (1 , 1 5 or
200 kHz, depending on the component value, or DC with relatively

24

04-201 q elektor

SMD MEASURING TWEEZERS

Other options

If you don’t want to right away buy a separate meter For measuring
SMDs, you can always buy a tweezers accessory, which are available
from mail order suppliers, including Mouser, Famell and DigiKey, The
accompanying cable and banana plugs typically allow the add-on to
be connected to a normal multimeter. Many multimeters nowadays
can also measure capacitance, so this arrangement at least enables

you to measure resistors and capacitors.

it is also possible to put build your own SMD tweezers, for example
from a few pieces of PCB material. You can find a detailed construc-
tion description for this on the Maxim Integrated Products website at

vrww.maxinvic.com/app-notes/index.mvp/id/4459

high-value electrolytic capacitors). The internal resistance of induc-
tors is also measured, and you can use this to calculate the Q fac-
tor. The LCR40 is suitable for resistors up to 2 MO, capacitors up to
1 0,000 uF, and inductors up to 1 0,000 mH,

There’s not much more to say about the LCR40. It is easy to use,
produces accurate measurements, and automatically detects the
component type. One drawback is the fact that you have to press
the button each time you want to make a new measurement, which
is dearly intended to achieve long battery life. The tweezers acces-
sory is easy to use, and the right-angle metal tips provide a good
grip on small SMD components.

Agilent U1732B

This is the only instrument in the group with a conventional form
factor. It is approximately the same size as a typical multimeter. The
meter has an especially large, clear display that shows the primary
measured value (4’/^ digits) along with several other items, such as
the selected component type, the measuring frequency, dissipation

has an optical port for connection to a PC using an accessory cable.
It has several built-in terminals for fast measurement of leaded com-
ponents, and several short cables with alligator dips are included,
Agilent can also supply a special SMD tweezers accessory for this
meter, equipped with three connectors (+, - and shield).

Although this is a fairly large instrument, the U1732B is convenient
in use. The connecting cable is fairly long, but the build-in shield
makes it reasonably thick, with the result that it sometimes gets in
the way. The measuring tweezers are solidly built and have nicely
finished gold-plated tips, but they are certainly not petite. The tips
are also fairly large, and they have such a smooth finish that the
SMDs sometimes pop out. The meter works quite well, is very accu-
rate, and provides a lot of information. There are a variety of extra
features that we did not try out for this practical test, such as testing
components within specific tolerance ranges and measuring com-
ponents in series or parallel mode. This may not be the most suit-
able instrument for use as a special SMD meter, but it is otherwise
an excellent instrument with such a low price that it should actually
be standard equipment in every electronics lab.

factor, 0 factor or phase angle (user selectable), and a few other
settings. It also has backlighting, which can be switched on manu-
ally. This instrument does not automatically detect the component
type; you must first press a button to select what you want to meas-
ure (inductance, capacitance or resistance). However, it does have
autoranging (which can be disabled). The measuring ranges extend
to 10 M£2, 1 0,000 uF, and 1000 H. The basic accuracy is a respect-
able 0.5% in the resistance ranges and 0.7% in the inductance and
capacitance ranges. It takes several seconds to make a measure-
ment. There is a button for changing the standard measuring fre-
quency (1 kHz) to 100 Hz, 120 Hz or TO kHz. With capacitors and
inductors, you can choose to have the dissipation factor, Q factor or
phase angle shown in addition to the component value. The meter

Conclusion

For electronics entusiasts who occasionally need to measure SMDs,
the inexpensive measuring tweezers are doubtless usable but fairly
limited, and their mechanical construction is not so great. The Peak
LCR meter is a good deal better; it is fast and accurate and has serv-
iceable tweezers. Unfortunately, you have to press the button for
each measurement and the display switches off rather quickly.

The best choice For SMD measurements is unquestionably the Smart
Tweezers; you only need to grasp a component with its pointed tips
and it shows you the component type and value, including the dissi-
pation factor or Q factor. However, it is rather expensive, so it is prob-
ably only attractive for people who work with SMDs on a daily basis.
The Agilent U1 732B is a robust and accurate LCR meter with quite
a few features, and it is more than worth its price for electronics
enthusiasts and professionals who need to make LCR measurements
fairly often. Although the SMD tweezers accessory has very nice
mechanical construction, it is not especially suitable for making
measurements on such tiny components. In addition, the U 17328
does not have automatic component detection, which makes it less
suitable for quickly sorting out loose SMDs.

The main question is how you intend to use such an instrument.
The Smar t Tweezers are especially handy for working exclusively
with SMDs, but the drawbackofinstruments of this sort is that they
are poorly suited to measuring leaded components. If you are look-
ing for a general-purpose solution, the relatively inexpensive Peak
LCR40 or the somewhat more expensive but vastly more versatile
Agilent U1 732B is a much better choice.

( 091038 )

elektor 04-2010

25

POWER SUPPLIES

UniLab

By Sebastian Richter and Stephan Pohl
(Germany)

A power supply with adjustable output voltage and current limiting is part of the basic equipment of every
electronics lab. However, the increased complexity of a switch-mode design scares away many potential
builders, even though it actually isn’t all that complicated if you use a suitable combination of well-known
technologies. The circuit described here is suitable for a building a single or dual power supply.

The Idea of developing a switch -mode labo-
ratory power supply arose in the electron-
ics enthusiasts group M l of the Institute
for Power Electronics and Electrical Drives
(ISEA) P) at RWTH University in Aachen,
Germany. Conceived as a starter project for
novice electronics designers, it manages
without a microcontroller and can be imple-
mented at low expense.

This power supply is based on an integrated
switching regulatorto keep the component
count within reasonable limits. The func-
tional units of this 1C include voltage regula-
tion, switching signal generation, and inte-
grated power switch. This means that only a
few external components are necessary.
Thanks to the compact construction, it is
easy to bu i Id a dual power supply in a single
end osu re. A d ua I power supply is especia lly
handy when you need more than one sup-
ply voltage. Naturally, both supplies are gal-

vanically isolated, so they can also be con-
nected in series to achieve higher voltages
or used In parallel (connected via diodes) to
provide more current.

Architectures

A conventional power supply architecture
has a mains transformer followed by a rec-
tifier and a linear regulator that controls the
output voltage. At high power levels with a
large difference between the input and out-
put voltages, a linear regulator dissipates a
lot of power as heat and needs a large heat
sink. This high power dissipation makes
the power supply inefficient, and it means
that the transformer must provide the dis-
sipated power as well as the useful power.
This makes the transformer unnecessarily
heavy and expensive.

Another option, which results in signifi-
cantly lower power dissipation and thereby

improved efficiency, is to use a switch-
ing regulator instead of a linear regulator.
Although secondary-side switch-mode
power supplies are somewhat more com-
plicated than power supplies with linear
regulators, they have only slightly higher
component counts thanks to the availabil-
ity of integrated circuits. The higher effi-
ciency allows a more compact design, and
in particular a distinctly smaller heat sink.
Although the mains transformer cannot
be eliminated, it is smaller than with a lin-
ear regulator because the higher efficiency
means that transformer does not have to
provide as much power that is dissipated
as heat.

By contrast, a primary-side switch-mode
power supply rectifies the mains voltage
straight away without a mains transformer
and filters the rectified voltage to obtain a
high DC voltage (325 V). This Is then con-

26

04-2010 elektor

POWER SUPPLIES

Features

* Adjustable secondary-side switch-mode power supply {buck converter)

* Output voltage 0-30 V (typical) {25 V minimum)

* Adjustable current limiting up to 3 A

* Maximum output power 90 W

* Compact PCB layout

* Switching frequency 52 kHz

* Parts kit available from the ElektorShop

verted into a low AC voltage by the com-
bination of a suitable converter (such as a
full-bridge circuit) operating at a high fre-
quency (in the kilohertz range) and a small
high-frequency transformer. This voltage
is in turn rectified to obtain a low DC volt-
age, A galvanically isolated sensing cir-
cuit feeds this voltage back to the regula-
tor section of the converter, which in turn
maintains the desired output voltage. The
major advantages of this technology are the
very small transformer (depending on the
switching frequency) and high efficiency
(90% or better is possible). However, this
form of low-voltage generation requires
a very high component count and a com-
plex design, and due to the high input volt-
age it can be hazardous in the construction
and test phases. In addition, the inductive
components in particular must often be
custom-made.

Consequently, we decided to use the sec-
ondary-side switch mode option for this
project, which is intended to be suitable for
novices. It utilises a step-down (buck) con-
verter topology Dl.

Switching regulator

Many ICs are available to simplify the con-
struction of buck converters* The National
Semiconductor LM2576 used here is a mem-
ber of the Simple Switcher family HI and has
already become almost a classic example of
its type* Along with a power switch, it con-
tains the functional units for generating the
pulse-width modulated drive signal and reg-
ulating the output quantity. Figure 1 shows
a block diagram of the internal structure of
the LM2 576 as well as the standard configu-
ration for output voltage regulation.

The regulator operates by comparing the
voltage on pin 4 of IC1 with an internal 1.23-
V reference voltage. The difference signal is
amplified and compared with a sawtooth
waveform. The sawtooth signal goes to
zero at the start of each switching cycle,
and the power switch is switched off at the
same time. When the instantaneous value
of the sawtooth signal exceeds the value of
the amplified difference signal, the power
switch is switched on and remains on until
the start of the next switching cycle. As a
result, the output voltage (V [JUt in the sche-

matic diagram shown in Figure 2) is regu-
lated such that the voltage on pin 4 of IC1 ,
which is taken from the junction of voltage
divider PI /R 12, is 1*23 V* If PI Is adjusted
to a higher resistance, the voltage on pin 4
drops. This causes the switch to remain on
longer, and the output voltage increases to
the point that the voltage on pin 4 is again
1.23 V. In the opposite direction, reduc-
ing the resistance of PI causes the switch
to remain off longer, which causes the out-
put voltage to drop. However, it is not pos-
sible to reduce V out below 1 .23 V with the
standard circuit. If PI is set to 0 O, the out-
put voltage is connected directly to pin 4 via
R14. R1 4 is included in the circuit to prevent
the output of IC3b from being connected
directly to the power supply output when
PI is set to its minimum value {0 i>).

A negative auxiliary voltage is generated
to allow V out to be adjusted down to 0 V,
On the positive half-cycles of the input AC
voltage, D2 conducts and charges C2* On

the negative half-cycles, D2 is cut off and
D3 conducts whenever 02 is charged to a
higher voltage than 03. Capacitor 02 dis-
charges into 03, causing 03 to be charged to
a voltage that is negative relative to ground.
This voltage Is stabilised by an LM377 linear
regulator (102), and it can be adjusted with
P3 so that the reference ground potential
(PGND) for IC1 is negative relative to the
power supply ground by the amount of
the reference voltage* This means that the
voltage on pin 3 of 101 is -1 .23 V. This off-
set only affects the regulator circuit in IC1 ,
while the output voltage V (UJt remains refer-
enced to CND, This trick makes It possible to
adjust v out down to 0 V*

With this buck converter topology, output
capacitor 05 can be ‘actively' charged by
switching on the power switch, with the
result that V 0Mt rises. However, 05 can only
be discharged 'passively' by the connected
load whife the power switch is off. It Esthete-

Figure 1. Block diagram and basic circuit of the switching regulator.

elektor 04-2010

27

POWER SUPPLIES

fore a good idea to provide a minimum load,
here consisting of R4 and R5, to allow the
output voltage to quickly reach the set level
even when no external load is connected.

Current limiting

Adjustable current limiting is often very
helpful in a lab environment in order to pro-
tect the connected circuitry. For this pur-
pose, the circuit detects the voltage across
sense resistor R8 t which is proportional to
the output current. lC3a amplifies this sig-
nal by a factor of approximately 4 t and C6
attenuates high-frequency noise, P4 is used
to compensate for the offset of the current
sensing circuit (including the offset of Oa),
Ob is wired as an adjustable non invert-
ing amplifi er, with D6 and D7 at the output
allowing only positive output currents. As a
result, Oh can increase the voltage on R1 2
but not reduce it. If Ob increases the volt-

age on pin 4 of 1C 1 above the val ue resulting
from the setting of PI , the current limiter
causes the power switch to switch off ear-
lier. This reduces the value of V out and thus
limits the output current to the maximum
level set by P2,

If the current is less than the set maximum
value, the anode of D6 (and D7 as well) is
negative relative to the cathode, which
causes the diodes to be cut off. In this state,
the switch-off point of the power switch is
determined solely by the voltage regulator.
D6 is connected in series with D7 to prevent
reverse -voltage breakdown of the LED, since
the maximum allowable reverse voltage of
the LED is only around 5 V.

The upper limit of the adjustable current
range can be preset with P5. The lower limit
is determined by the maximum gain of Ob.
The desired current limit level (maximum
current) can be set within these limits by

adjusting P2. As an LED, D7 provide a visual
indication when current limiting is active.

Construction and initial use

The transformer should be rated for at
least 1 .2 times the nominal output power
of the power supply, which means at least
90 watts or so for a single power supply.
The secondary voltage should not be higher
than 25 V, since the maximum voltage that
1C1 and IC2 can handle is 42 V. With a 25-
V transformer, you still have some safety
margin even with 1 0% overvoltage on the
AC mains. If you want to build a dual power
supply, you can use a toroidal transformer
with twice the power rating and two sec-
ondary windings as an alternative to two
separate transformers. For sense resistor R6,
you can use a length of inexpensive resist-
ance wire instead of a Teal' sense resistor.
With the specified resistance wire, a length

♦

Figure 2, Power supply schematic diagram. A negative auxiliary voltage allows the output voltage to be adjusted down to 0 V.

28

04-2010 elektor

POWER SUPPLIES

COMPONENT LIST

Figure 3. The double-sided circuit board allows very compact

power supply construction*

Resistors

f default: 250 m W 1 %)

R1 ,R2 = 8200
R3 = 2400
R4,R5 = 560ft 1W

R6 = 0.05ft 5W (Vishay Dale type LVR-
G5K0500FE73 or 1 ,73ft/m resistance wire,
see text)

R7.R8 - 1 2kft
R9 = 47 kO
RIO = 39kft
R11 = 160kH
R12.R13 - 1 kft
R14 = 100Q
R15 “ TOOkft
Rl6 = iokn

PI = 25kft potentiometer, linear
P2 = 250kft potentiometer, linear
P3 " 50 ft trim pot, multiturn, vertical
P4 = 1 0kft trimpot, multiturn, vertical
R5 = 50kft trimpot, multiturn, vertical
P6 = 1 kft trimpot, multiturn, vertical
P7 = 2000 trimpot. multiturn, vertical

Capacitors

Cl * 10.000pF50V radial
C2,C3 - 220pF 63V radial
C4 - 1 OQpF 63 V radial
C5 = 22O0pF 63V* radial
C6 = 680pF ceramic
C7 - lOOnF ceramic

Inductors

LI = 330pH 4.5A (mu Rata Power Solution
type 1433445C) or 330 pH 3 A (Wurth type
744137)

Semiconductors

B 1 = 800V 6A bridge rectifier (e.g. Vishay type
CSIB6S0)

D1 = 1 N5822 (Schottky diode, 40V 3A)

D2»D3 = 1 N4007
D4 = zener diode 22 V 1 W
D5 - zercer diode 18V 1W
D6 = 1N4148

D7 “ LED, 3mm* red* low current (2mA)
ftl - LM2576T-AD) (National Semiconductor)
(see text)

IC2 = LM337LZ
IC3 = LM358AIM

Miscellaneous

TR 1 = power transformer, seconda ry 25V 3 . 2 A

(see text)

Heatsink forICl (TO-220 <9,9K/W. e.g, Fischer
Elektronik type SK 1 29 25.4 SIS)

K1 ,K2 = 2-pin PCB terminal block, lead pitch
5mm

K3 = 6-pin DIL pinheader, lead pitch 2.54mm
(OH”)

PCB, order code 090786-1

Kit of parts, contains all components except
power transformer. Order code 090786-71*
see Elektor Shop section or www, elektor,
com/090786.

090786-i v2
Cc>Elektor

elektor 04-2010

29

POWER SUPPLIES

About the authors

Sebastian Richter completed his studies in Electrical Engineering at RWTH Aachen University in 2005 and was awarded the degree of Diplom-
Ingenieur (equivalent to an MSc). Since then he has been working as a research assistant at ISEA in the field of power electronics. He is also
actively involved in teaching and is one of the co-founders of the Institute's electronics enthusiasts group.

Stephan Pohl completed his studies in Electrical Engineering at RWTH Aachen University in 2008 and was awarded the degree of Diplom-lng-
enieur. Since then lie has been working as a hardware designer at PicoLAS GmbH, where he is involved in the development of current sources
for laser diodes. During his studies, he served as an advisor forthe electronics enthusiasts group at ISEA, in which role he was primarily in-

votved in teaching students analogue circuit technology.

of wire equal to the distance between the
through-plated lead holes will have a resist-
ance of approximately 50 m Cl. Any small dif-
ference can be compensated by adjusting
P5.

With regard to parts selection, it is impor-
tant to use a genuine National Semiconduc-
tor LM2576-ADJ, since problems may arise
with 'type-equivalent" components from
unknown manufacturers.

Before assembling the circuit board (Fig-
ure 3), you should preset mufti-turn trim-
pots P3 and P4 for minimum resistance
(for this purpose, connect the wiper to the
appropriate potentiometer terminal as
indicated by the PCB layout). After assem-
bling the board, you should again check
the polarisation of the electrolytic capaci-
tors (Cl > C2, C3 and C5) and setting PI and
P2 to mid travel before switching the circuit
on for the first time.

If the circuit is working properly, it should be
possible to adjust the output voltage from
approximately 0 V to around 25 V after it
is switched on. To precisely adjust the zero
point, rotate PI (preferably a multiturn
potentiometer) to its minimum resistance
and connect a load. Now you can adjust P3
to set the output voltage to exactly 0 V.

To calibrate the current sensing circuit, meas-
ure the voltage across the series connection
of R1 5 and P6 (between (IC3a pin 1 and
K3 pin 6) with no external load connected.
Adjust P4 until this voltage is set to zero.

If you now connect a low-resistance load
to the output and turn P2 to its upper limit,
you can adjust P5 to set the upper limit of
the adjustable current limit range (do not
exceed 3 A),

A proper lab power supply also has volt-
age and current displays. Voltage divid-
ers R15/P7 (voltage) and R16/P6 (current)
are provided for this purpose. Potentiom-
eters P3 and P4 are used to set the zero
points for the output voltage and current.

while P6 and P7 are used to calibrate the
built-in instruments. For this purpose, set
the power supply output to a point near
the upper end of Its voltage or current
range and calibrate the built-in instru-
ments by comparing the displayed values

with reference values measured using a
multimeters.

If you want to build a dual lab power supply
with two UniLab boards, a tailor-made dis-
play unit with a backlit four-line LCD mod-
ule is being developed in the Elektor lab. It

continuously shows the voltage and current
of the two outputs. Along with this display
unit, Elektor provisionally plans to publish
an article on a suitable enclosure and a front
panel design in a future edition,

(090786)

figure 4. A tailored display unit with a backlit four-line LCD module is being developed in
the Elektor lab for building a dual lab power supply with two UniLab boards.

Links and Reference Documents

[ 1 1 Bragard. Michael and Richter. Sebastian: 'LED Top with Special Effects'. Elektor December 2008
(download from www.elektor.com/080678)

[2] www.isea .rwth-aachen.de/en

13] Sanchez Moreno, Sergio: ‘Cool Power 1 , Elektor June 2008 (download from www.elektor.com/080l 98)
[4] LM2576 data sheet (download from www.natlonal.com/ds/LM/LM2576.pdf}

30

04-2010 elektor

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efektor 04-2010

31

SCEPTRE

Grasping the Sceptre

By Clemens Valens (Elektor France Editor}

jutf

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\ fast prototyping
)!atform is no use without
echnical support. However well-designed
he hardware, however comprehensive the

software, if no-one explains howto actually use it

all, it won’t be as easy to use as you'd like. So having described the hardware last month, here now are the
explanations and details of the Sceptre software. Let your reign begin!

Before getting into the details of program-
ming the Sceptre, let's start by reminding
ourselves of a few of the basic principles
of programming in C. Oh yes, most of the
Sceptre is programmed in C — for the time
being, at least, as there are plans afoot for a
C++ layer. We're not aiming here to go into
detail about C itself, but rather, about the

mechanism for converting a program writ-
ten in C into executable code for the micro-
controller. It's important to understand
how all this works so as to be better able to
program any microcontroller-based system,
including the Sceptre, of course.

Figure 1 gives a flow diagram that shows
which tool is used at which moment and

with what type of data. At the top, we find
the application In C, which may be made up
of several files. At the bottom, the execut-
able to be programmed Into the microcon-
troller. So what goes on in between?

First of all, the compiler 'translates’ (com-
piles) the source code In C to turn it into
source code in assembler language. The

32

04-2010 elektor

SCEPTRE

Figure 1 , Flow diagram for the compilation chain.

compiler can issue warnings and flag up
errors. Always take care to resolve any
warnings, if you possibly can. Errors are of
the typo* or 'undefined object 1 variety, and
must be corrected , or else you won't be able
to goon.

It’s the assembler that converts the source
code into assembler language, creating
from it what are called 'objects 1 . At this
point, it's possible to add other functions
written directly in assembler. This will often
be the case for a special file commonly
named CRT (from C Runtime) or Startup,
which contains the very low level system
initialization. In this file, the interrupt and
reset vectors and stack are initialized, along
with the memory and the p re-initialized var-
iables, it's also from this file that we call the
main function of a program in C.

The linker Incorporates all the objects pro-
duced by the assembler into the executable.
It also adds the objects archived in libraries
that the application is going to need. The
libraries contain functions that don't change
very often, like printf, but which can be re-
used over and over again. If this tool fails
to find certain objects, It will return 'unre-
solved externa l'-sty I e errors.

The linker requires a map of the memory
in order to organize the objects and create
links between them. With the help of this
map (or table), it determines the function
addresses and writes them into the various
calls and jumps in the program. That’s why
it’s called a linker’.

It's up to the user to provide this memory
map (also called a linker script’), since It
depends of course on the hardware.

The end product of the linker is an execut-
able file that can be programmed into the
microcontroller.

What we've just been describing Is the 'com-
pilation chain’. The previous instalment
explained that we've opted for WinARM l 2 \
as our compilation chain. You can refer back
to part 1 for details on installing WinARM.
Apart from the functions for controlling the
board, the Sceptre’s software distribution PI
contains the elements needed for the com-
pilation chain, such as a Startup file and a
memory table(, ID fife).

The compilation chain is launched using the
make command, a very powerful program
(included in WinARM, of course); make runs
a script usually named makefile. A makefile
contains all the commands and options for
producing an executable from the source
Hies and libraries. Make is so powerful that
a makefile can be extremely complex and
incomprehensible. So the best thing to do
It to take a makefile that works and adapt it
to your own project. Naturally, the Sceptre
distribution also contains a makefile.

The Sceptre library

Since the Sceptre offers a certain number
of on-board peripherals, it’s only logical
to bring all their drivers together into one
library to make them easier to use and save

100017-12

Figure 2. The Sceptre library, its contents,
and its place in a project.

a little compiling time, since they don't
have to be re-compiled every time. At the
time of writing, the library already con-
tains the drivers for the USB, the SD mem-
ory card reader, the Bluetooth module, the
UARTSt the counters, the real-time clock
(RTC), ADC, DACs, PWM, the thermometer,
and the accelerometer (Figure 2). Certain
functions for Initializing the micro are also
included in the library, along with part of
the newlib interface (see boxaboutnewlib).
Not surprisingly, the library is called sceptre
(.a), in order to use it, you need to include
the file sceptre. h in your project and tell the
linker where it can find the library.

The Sceptre library offers functions that
make it easier to use a peripheral. For exam-
ple, to set up a Bluetooth connection, all
you have to do is call the blue toot ^con-
nect function after the module has been
initialized. To read the accelerometer, there
is the accelerome t er_read function,
while thermometer read Jets you read
the thermometer. It's easy, too, to turn
the Sceptre into a USB key thanks to usb_

Tnass_storage_irL.it and usb_mas5 stor-

age tick. Files on the SD card are manipu-
lated using f_open t f close, f_read and
fwrite (similar to fopen, f close, freed
and f write in Hbc) and to write to serial
port 0, there is printf . You see, a lot of the
work has already been done — and it's not
finished yet! Take a look at the documenta-
tion in the doc\html folder, starting from
the mdex.htmf Hie.

elektor 04-2010

33

SCEPTRE

Flash Magic

Toab

33

T animal,

I

Ffle ISP OfJfoiW

ea Q A3*

Figure 3. Here's how to run the Flash Magic
terminal and configure it. The speed of the
terminal’s serial port can be different from
that of the programming mode.

Figure 4. ft works! The Sceptre start-up
messages on an RS-232 terminal 1 .

You can extend, modify, and correct the
library, as you have access to everything.
Each time you modify something in this
library, you'll need to re-compile it This
can be done at a command-fine prompt by
running the make command in the distri-
bution's core directory (perform a ‘clean 1
first so as to be sure you are starting out
from zero):

C : \sceptre\core>make clean
C ; \sceptre\core>make

For ARM7 experts, here's an interesting
bit of information: the library can be com-
piled in ARM mode or in thumb interworks
(iw) mode. In ARM mode, the Sceptre is a
true 32-bit system, but the executables are
larger. In thumb-iw mode, the executables
are smaller, but also slower, as the processor
works in a 16-bit-compatible mode. With
51 2 kB of program memory, there's plenty
of room to store a program in ARM mode,

but programming the microcontroller will
take longer. By default, the library is com-
piled in ARM mode; to compile it in thumb-
iw mode, use:

C : \sceptre\core>make clean
C : \sceptre\core>make
ARM_MODE = thumb

That way, you'll get the sceptre-iw.a
library.

Always check that the application and the
library are using the same mode!

The Sceptre library includes other libraries
found on the Internet, in particular Ipcusb
HI and fatfs l 5 E The former provides the
USB driven the latter is a FAT file system
making it possible to read and write Win-
dows, Linux, or MAC-compatible SD cards.
When you compile the Sceptre library,
you may see a number of warnings dur-
ing compilation of files from the external
libraries. Ignore them, there's nothing
terribly serious, these libraries work pep
fectly. Given that these libraries are main-
tained independently of Sceptre, we avoid
modifying them.

Getting stuck in-*

The Sceptre distribution contains a test
application named app_pre!oad. This pro-
gram is pre-loaded on the Sceptre boards
available from our website lb and lets you
check easily that the whole board is work-
ing properly. To use it, you need to con-
nect the Sceptre’s USB port (JP4 and JP5 on
pins 1 and 2) to a computer with the FTDI
drivers installed (see previous article 1 1 1 ).
Run an RS-232 terminal program on the
computer — for example. Flash Magic bl-
and configure the correct serial port for a
speed of 1 1 5,200 baud, eight data bits, no
parity, and one stop bit (see Figure 3). Dis-
able the hardware flow control Press the
board's Reset button. Now you should see
a screen similar to the one in Figure 4*

After a few seconds, the application
attempts to open an SD card to write a few
tittle files with information about the system
to it, then, for 30 seconds or so, it saves in
two other hies the data read from the ther-

mometer and accelerometer (wave the
board about a bit!) By writing a file named
test_bt.pls to the SD card, containing a
name in ASCII (1 6 characters max., with no
spaces or you request the Bluetooth test
and the module starts up. Lastly, the Scep-
tre becomes a 'USB key' that also sends the
thermometer and accelerometer data to
serial port 0 . It is now possible to hot-con-
nect the Sceptre's USB pin header so as to
access the 'USB key 1 : remove JP5, then JP4,
refit JP4 on pins 2 and 3, and finish by fit-
ting JP5 on pins 2 and 3. It's also possible to
change the USB key mode into serial port
mode, but nine times out of ten, this will
entail re- booting the board.

If you connect an LED with its anode to pin
1 of K7 and its cathode to GND via a 330 Q
(or so) resistor, it will flash at a frequency
of 1 Hz ♦

With the Bluetooth module enabled, It
ought to be possible to connect to a compu-
ter and send data. The Sceptre sends every-
thing It receives on UART0 to the Bluetooth
module and vice-versa.

The test application is compiled via a com-
mand-line prompt in the app^preload
directory:

C : \sceptre\app_preload>make
clean

C : \sceptre\app_preload>make

The test application's makefile compiles
the application and if necessary the Scep-
tre library too.

If everything works properly, make will end
without any errors and creates a preload*
hex file. This is the file you'll have to pro-
gram Into the microcontroller, using for
example Ipc21isp (included in WinARM)
or Flash Magic (see previous article [1])*
The latter detects automatically if the HEX
file lt T s supposed to use has been modified
{what's more, it displays the date and time
the file was last saved), so all you have to
do is dick on the Start button to begin the
flashing. The flashing will take longer or
less time, depending on the file size. Unless
you're keeping an eye on the programming,

34

□ 4-2010 elektor

SCEPTRE

you may not spot the Flash Magic success
message, as it goes oft about 30 seconds
after the end of flashing.

Flashing the microcontroller using Ipc21 isp
is done using the command (if you're using
COM4):

Ipc21isp -control preload. hex
com4 38400 12000

The -control option indicates that it’s
Ipc21isp that puts the board into program-
ming mode and will restart it once program-
ming is over.

Two indicators alongside the USB socket
show if a data transfer has in fact taken
place.

We recommend taking the test application
as a starting point for your own project.
Thanks to its makefile, you don't need to

compile the library separately* Create a
directory for your project alongside the
app_preload directory so as to ensure that
all the paths remain correct* Consult the
main.c file to find out how to use the Scep-
tre library.

You can use any text editor to write a pro-
gram, just so long as the source code
doesn't contain any formatting codes or
page formatting (nothing but ASCII, in other
words!) The Programmer's Notepad (PN)
i 6 l editor supplied with WinARM is a good
choice (see box).

Add your C files into your project’s make-
file (not into the library one!) below the tine
‘SRC - mainx\ like this (note the k +=’!):

SRC - main.c
SRC += my_f ile * c

You can add as many files as you tike. To

change the name of your executable, mod-
ify the line:

TARGET =t preload

by entering the name you want.

To be continued. ..

The Sceptre library is still not complete. Cer-
tain parts are almost finished, others have
barely been started, and new functions are
going to be added as you go along. In the
coming months, well be presenting exten-
sions and applications for the Sceptre which
will all offer new possibilities. Updates will
be announced on l 7 i,

(1000174)

Proarammer’s Notepad 2

The WinARM distribution also includes Programmer's Notepad 2,
a special text editor for programmers. This tool can be found in the
WinARM\pn directory and is initially configured for WinARM. There
is now a more recent version PL Alt you need do to Install this version
is to delete everything in the WtnARMlpn directory except for the
tools sub-directory containing the macros for WinARM. Next, down-
load the Portable Edition and unzip it into the WinARM \pn directory.

Use the command Tools-> [WinARIVLC] make all - CTRL-F7 to

co m p i I e y ou r p rog ra m .

PN picks up the messages issued by the tools called by make and
displays them in the Output window. Do look at the messages care-
fully, as there may be warnings or errors to he corrected. Sometimes

a tool stops because of an error that’s nothing to do with your pro-
gram, but which indicates a Windows problem (noticed in particular
with Windows Vista), if this happens to you, it’s better to cal! make
manually from the command line prompt.

print!, fopen, ...

libc, newlib, syscalls, and BSP

GNU C includes the libc library containing a very large number of
functions that make programming in C easier Certain of these func-
tions depend on the hardware, particularly the functions that manip-
ulate files and data streams* Normally, it’s
the operating system (OS) that makes the
link between the hardware and libc, but
where the OS doesn't do it, it’s up to you
the user to do it yourself (only if you want
to make use of these functions, of course).

This is why a version of libc for embedded
systems has been introduced, with the
name of newlib. This new !ibrary offers an
interface named syscalls which lets you
graft a board support package (BSP) onto
the library in order to adapt it to the hard-
ware. If now you are only using standard C
functions in your application, ail you have
to do is modify the BSP to make it all work
on another platform.

100017-13

elektor 04-2010

35

SCEPTRE

For the Sceptre, we’ve incorporated some of the syscalls in order to
allow use of printf, fopen, etc. Among others, printf is a very handy
function for debugging and lets you send character strings to Scep-
tre's serial port 0.

Documentinq usinq Doxvqen

It's important to document software, but this is not always easy and
one soon forgets to update the documentation following a modifi-
cation* Tools exist that let you automatically extract the comments
(KEMs) from a piece of software so they can he presented in a usable
form. Doxygen is one of these tools, and by no means the least.
What's more, Doxygen is free and open-source, and so Ideally suited
for our project,

Int accelerom(?ter_read ( fkat r fn_dst )

Read the accelerometer

Para meters:

Address to wnte data to.

Returns:

The number of bvtes read an success, -1 otherwise.

Definition at line 51 of file occelern meter, c,

To make the most of Doxygen' s capacities, you need to respect cer-
tain layout rules for source files* Like any self-respecting software,
Doxygen offers a plethora of options that you'll probably never use,
but already with just a handful of commands, it's possible to do
some good things. So remember to format your comments like this:

/ * +

* ©file

* Description of file,

*/

A Doxygen comment starts with / ’ * and ends with * / — the other
asterisks are optional, it’s also possible to enter a Doxygen comment
on a single line using ///.

An "^ffle 1 block is obligatory, in order for Doxygen to take account
of the file. Use the block below for commenting on a function.

/ * *

* Short function description*

* ©pa ram cparameter name> cparameter
description

* ©return description of value returned^

*/

Doxygen extracts all these blocks of comments and creates from
them a collection ol HTML pages (among others) with the links to
the definitions, sources* types* etc* — IV s very impressive. Take a
look, for example, at the Sceptre documentation included in the
distribution.

And here’s another very handy Doxygen command; @todo

Doxygen creates a special page with each todo found. With a func-
tion like that, you'll never forget anything again!

In the world of microcontrollers, it's very important to use vari-
able types that correspond to the hardware. The size of the types
depends on the hardware, and the fact that a character uses eight
bits on platform A by no means implies that it will use as many on
platform EL So to avoid such difficulties* you define dear types like
uint8_t (unsigned 3-bit integer) or int32_t (signed 32-bit integer).
Unfortunately, everyone does this a bit after their own fashion, and
the result, when you glean your code a bit from everywhere, is that
you often find yourself with several definitions of the same type (and
not necessarily identical) like BYTE, BOOL, or DWORD, which the
compiler doesn’t like one bit So we strongly recommend you to only
use the types defined in sysinth* supplied with the GNU tools* This
file contains type definitions specially designed for programming mi-
crocontrollers, Do this* and everyone will be grateful to you for it.

Internet Links

I VI www.elektorxom/090559

HI

so u reef o rge.net/projects/lpcusb

Pi www.siwawi.arubi.

[5]

elm-chan.org/fsw/ff/OOindex_e.html

u ni-kl.de/avr_projecls/ a rm_projec ts/ #wmarm

t&l

www, pnotepad.org

PI w w w.ele kto r.com / 1 0 0 0 1 7

id

elektorembedded.blogspot.com

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elektor 04-2010

37

READERS CIRCUITS

A Fast Charger

By Uwe Hofmann, Gunter Ceroid and Dr. Thomas Scherer (Germany)

Here’s how three ElektorWheelie fans came up with an idea for a fully automatic fast charger to keep the
batteries in prime condition. This low-cost design uses an off-the-shelf switch-mode power supply coupled
to an intelligent controller and can be easily adapted to charge other types of cell.

In 2009 we published the complete con-
struction details of the ElektorWheelie |1J ,
a single-axle, self balancing, electric pow-
ered personal transporter. 31 was through
the German forum that the three authors

made contact. Before long they had agreed
that a fast charger for the ElektorWheelie 1 s
two lead acid batteries would make a useful
addition to the project. The idea was to add
an external controller to an existing low-cost

industry standard 1 2 V 60 W switch -mode
power supply (SMPS} shown in Figure 1 . It
needed a little more investigation to make
sure it was up to the job. The SMPS must
supply a voltage of 14.4 to 14.8V for the

Figure 2 . The SMPS output voltage is sensed
by a TL431 (SHR1 ) shunt regulator.

Figure I.Thc SMPS used here. These types of power supplies are
now widely available and are quite cheap.

Figure 2a. A flying lead is soldered to R21 in the SMPS so that its
output voltage can be controlled by the external add-on board.

04-2010 elektor

READERS CIRCUITS

final charging phase and must also remain
stable with an output of less than 10 V.

Lifting the lid revealed a fairly typical layout
using a switched primary winding. The sec-
ondary voltage level is sensed by aTL431 Hl
three pin adjustable shunt regulator (SHR1
in Figure 2). This type of regulator is also
known as an l adju stable zener diode' ; the
zener voltage is defined by a simple volt-
age divider network (see Figure 3). The
regulator senses the secondary voltage
and adjusts the switching controller on the
primary side via an optocoupler. The out-
put voltage adjustment preset can be seen
in Figures 2 and 3. This basic operating
configuration is standard and used in hun-
dreds of other 5MPS designs so you are not
restricted to the model specified here.

In order to convert this basic 5MPS into an
'intelligent’ battery charger we need to add
a microcontroller to measure current (via a
series ‘sense’ resistor) and control the volt-
age using the TL431 fitted in the SMPS,

Tweaking the supply

As shown in Figure 3 a connection to the
TL43 1 5 s reference pin is necessary so that an
external voltage can control the SMPS’s out-
put voltage. From the resistor values used
in the SMPS it was calculated that a control
voltage of 0 to 5 V connected via a 1 0 Kfl
resistor would produce an output voltage
range from 9.5 V to 1 5.5 V.

Resistor R21 on the SMPS circuit hoard has
one end connected to pin 1 of the TL431.
This is a convenient point to solder the wire
which will feed in our external control volt-
age (see Figure 2a). A test with a 10 k resis-
tor connected to 5 V gave an output voltage

Figure 3.

The circuit diagram.

from the SMPS of 9.5 V. The upper voltage
level however hit a wail at 1 4.7 V even with
the 10 kn resistor grounded. This is not
going to be quite enough to fully charge a
12 V lead acid battery. It seems as though
there is some additional voltage limiting
measure built into the circuit for safety,

A closer look revealed the culprit; under-
neath the transformer Is a 1 3 V Zener diode
wired in series with the input LED of an
optocoupler. Its output is connected to the
switch-mode controller 1C to limit the out-
put voltage. The solution was to add a sil-
icon diode type 1N4148 in series with the
zener to lift the threshold, the maximum
output voltage increased to 15.4V (see
Figure 4),

The circuit

With the aid of a microcontroller and a few
additional components we can build a fully
automatic charging station (Figure 5). For
processing power you can use an ATtiny24 <
it has everything required already built-in:
an ADC input to measure levels of current
and voltage, a PWIV1 output with 16-bit
resolution to generate the 0 to 5 V control
voltage and some digital outputs to switch
the charging supply and control an RGB LED
to display one of seven distinct colours to
indicate the charger's status. A crystal is
not needed if the interna! 8 MHz oscillator is
used. A low reference voltage (1 .1 V) allows
the use of a low impedance current sense
resistor and reduces energy dissipation.

A 5 V voltage regulator supplies power to
the controller and LED. The power MGSFET
T2 disconnects the output when an error
is detected. Power Schottky diode D1 pre-
vents a potentially destructive current flow-

Features

► For fast chargeable 12 V lead acid
batteries.

- 3.5 hour fast charge.

* Protected against short-circuit and
reverse polarity connection,

* Optimised charging curve,

* Based on a modified low-cost industry
standard SMPS.

* High efficiency from 76 %,

* Dead battery detection.

* The firmware supports g Ah
cells, other cell capacities can be
accommodated.

* Suitable for lead-acid and LiPo
rechargeable cells.

ing through the parasitic diode ofT2 if a bat-
tery is connected in reverse to the charger.
The two paralleled Schottky diodes con-
nected to the port pins PA1 and 2 likewise
protect these inputs against accidental bat-
tery reversal.

IC1 calculates the charge current by measur-
ing the voltage drop across R9. A 2 W resis-
tor will suffice for current up to 3.6 A, The
10-bil A/D converter and 1.1 V reference
voltage allow a measurement resolution of
around 10 mA,

The output voltage is measured by R1 0 t R12
and PI. The maximum voltage drop across

Figure 4. Hidden under the transformer is
an over-voltage protection zener diode and
optocoupler. An additional silicon diode
in series with the zener diode raises the
maximum output voltage by 0.7 V.

eiektor 04-2010

39

READERS CIRCUITS

Table 1 . Operating modes

Mode

Description

Voltage

Current

LED

1

No Battery

< 1 V

-

white

2

Deep discharge

1 tolO.V

-

yellow

1 3 1

Pre-charge

5 0 to 1 2 V

1/20 C

cyan

4

Start fast charge

>12 V

increasing

violet

5

Fasi charge

12 to 14.6 V

max. 3/1 0 C

blue

6

float charge

13.8 V

max. 1 /50 C

green

| 7

Error

-

-

red

8

TO (time-out)

-

-

blink

Table 3 . Using standard components

Component

Description

IC1

ATtiny24 r Dill 4

IC2

78105 ,

D1

SB540

D2

1N4148

D4.D5

SB140

ri

RC547

, t2

IRF540

Table 2 . Error modes

Mode

Description

when...

LED

A

Overvoltage

> 1 5 V

red

B

TO pre-charge

Mode 3 >1 h

blink cyan

C

TO start charge

Mode 4 > 1 0 s

blink violet

D

TO fast charge

Mode 5 > 4 h

blink blue

R9 is 036 V which leaves 0.74 V of the of the
1.1V reference voltage to measure the volt-
age. This means that the measuring resolu-
tion of a 1 5.5 V level (at maximum current) is
not 1 5 mV but more like 22 mV* Correction for
the scaling change is performed in firmware.

The controller produces a 1 0-bit PWM sig-
nal of a few kiloher tz filtered by the low
pass filter formed by R3 and C2. The result-
ing smoothed DC level in the range from 0
to 5 V is connected to the reference pin of
the TL431 in the SMPS via resistor R2. R3

FDD&614

Figure 5. Two ICs plus a few discrete components converts the SMPS into an efficient

battery charger.

and R2 together make 9.5 kO in total. The
SMPS now outputs a controllable voltage
level in the range from 9.5 V to 1 5.4 V. R2
can be changed to alter the voltage range
if necessary.

Operational Modes
The following describes charging a 12 V
9 Ah (1 C = 9 A) lead add battery. The operat-
ing and failure modes are fisted in Tables 1
and 2.

* After switch on the controller measures
the voltage on the output and switches
to mode 1 if no battery is connected.

The SMPS output voltage will be set to
less than 10 V.

* With a battery connected the control-
ler measures its voltage. A value of less
than 10V indicates the battery is either in
deep discharge or one of its cells ts defec-
tive. The charger switches to mode 2.

* A battery voltage in the range from 10 V
to 1 2 V, will initiate a pre-charge phase
supplying a charge current of 1 /20 C (=
450 mA). After one hour if the battery is
still ‘bad' the controller indicates failure
modeC

* Should the battery voltage rise above

a 1 2 V threshold the controller initiates
mode 4 where the current ramps up to
reach 3/10 C(= 21 A) in a few seconds,

* This charge level is maintained in mode
5 for a maximum of four hours. When
the battery voltage reaches 14.6 V a
constant-voltage charge phase begins
which gradually reduces the charge cur-
rent with rising cell voltage.

* When the charge current falls to 1 /5G C
= 1 80 mA it enters float charge mode,
supplying a maximum current of 1 /50 C
and a maximum voltage of 13.8 V until
the battery is removed.

Construction

Thanks to the miniaturisation expertise of
Uwe Hofmann we have managed to cram

40

04-2010 elektor

READERS CIRCUITS

Figure 6, 3D simulation of the mini PCB
topside rendered using Target 3001 .
The double-stded board is not through-
hole plated.

Figure 7, 3D simulation of the mini PCB Figure 8. Prototype of the twin fast

underside rendered using Target 3001 . chargers laid bare (rough draught) for the
Ensure that the diode and MOSFET are ElektorWheelie with 2x1 2 V outputs,

correctly fitted.

everything onto a PCB measuring just 3 x
3,7 cm (Figure 6), the circuit could almost
be fitted in the SMPS case. The disadvan-
tage is that SMD components are used but
all of the components specified can be eas-
ily hand soldered if necessary. All the PCB
files are available so those of you with the
facilities can make the board yourself. The
PCB requires some through-contacts to be
soldered by hand to connect between the
two layers. The PCB and the circuit diagram
in Target-3001 format, the PCB layout in EPS
format and the firmware source code {also
the hex file) can be freely downloaded from
the article's web page
When soldering the components to the PCB
by hand first start on the underside with T2

COMPONENT LIST

Resistors
(SMD 1206)

R1 ,R7 = 18k£2
R2 = 6.8k ft
R3 = 2.7kft
R4 = 470ft
R5=1.5kft
R6 = Ikft
R8 = 12kft
R9 = 0.1ft 2W
R1 0 - 27kft
R11 = 1.2kft

PI = 500ft, multiturn preset

and D5 (Figure 7) these are quite bulky and
the board becomes hot when they are sol-
dered in place. Afterwards solder the top-
side components. When a soldering oven is
used bake the top side components, leaving
the few remaining underside components to
be hand soldered. Finally solder the connec-
tor and preset carefully into place, the plas-
tic on these components cannot withstand
high temperatures for too long. The board is
double sided but not through-hole plated so
there are a few pads which require a small
length of wire soldered through to make
connections between the two layers.

The RGB LED must be a common anode type
with four pins. Diffuse 5 mm LEDs manufac-

Ca pad tors

(SMD 1206)

C1.C2 = ipF 25V, electrolytic or multilayer
C3,C4 = lOGnF
C5,C6 = 10nF

Semiconductors

D1 - 5QWQ03FN, Schottky. SMD T0252AA

D2 - LL4148, SMD MINIMELF

D3 - 4-pin RGB LED. 5mm, common anode *

II = BC846, SMD SOT23

T2 = FDD5614, SMD TQ252AA

tCI = ATtiny24, SMD SOM

IC2 = LM78L05A, SMD SOS

tured by A-BRIGHT are suitable r T
Although a neat job is produced it is not
absolutely necessary to use the PCB, The
circuit is quite straightforward and can be
built using conventional leaded compo-
nents on a small square of prototyping perf-
board. Table 3 lists the necessary leaded
components.

Adaptations

The circuit as It stands has been designed
to fast charge a 1 2 V lead acid battery with
a capacity of up to 12 Ah, The firmware
assumes that a 9 Ah (as specified for the Ele-
ktorWheelie) will be charged. The Elektor-
Wheelie uses two batteries so two separate
fast chargers connected in series (Figure 8)

Miscellaneous

K 1 = 3-pin PCB plug, lead pitch 2.54mm (0.1")
K2 = 2-pin PCB plug, lead pitch 2.54mm (0.1 M )
K3 = 6-pin double row pinheader
SMPS 12V, 5A ’

Silicon diode for SMPS, e,g, 1 N4 1 48 '

PCB *

Firmware' for 1C 1
' see text

elekfcor 04-2010

4 1

READERS CIRCUITS

Test and calibration

Ontf the add-on controller board is fully populated connect a bench top power supply

(minimum voltage range: 8 to 1 4 V @ 1 A) to pins 1 and 3 of connector KI . Now carry out

the following calibration procedure:

• Mode i: First set the bench power supply output to 8 V and then switch it on. The add-
on board LED showing white indicates that the circuit is functioning correctly.

■ Mode 2: Link V- from Ki with V+ from K2 . 1 his effectively bypasses T2 and Di, The
output on K2 will be 8 V and the LED will show yellow.

• Mode 3: Set the bench supply output to exactly 10 V. Pi can now be adjusted to the
point at which the LED switches from yellow to cyan.

■ Mode 4 & B: Increase the voltage slowly, when the voltage gets to 12 V the LED turns to
violet, 10 slater the LED will begins blinking violet indicating that the current ramp up
to 3/10 C was not achieved in 10 s.

• Mode 5: Set the bench top supply to 13,5 V and connect a load to pass a current of 0.2
to 0.3 A (e.g, two 100 Q/4W resistors connected in parallel). Switch the bench supply
quickly off and then on. the LED will show blue.

• Mode 6: Reduce the output loading so that 100 to 150 mA current flows {remove one of
the 100 ii load resistors). This is now the end of the fast charge phase and the charger
switches to float charge. The LED changes to green. Remove the wire linking V+ on
connectors Ki and K2 and then remove the load resistor, load current now' Tails below
the minimum threshold for a connected battery and the controller switches to mode 1.

Now with the calibration almost complete we can dispense with the bench top supply and
connect the SMPS plus and minus to connector KI . The flying lead from the SMPS connects
to the 'PWM 1 position on KI. AL switch on the LED should show white.

Turn the output voltage adjust preset on the SMPS until a value of 9.5 to 9.9 V is reached.
Fnsure that the LFD on the SMPS does not start flickering, The charger is now ready for use.

T he voltage drop across R 9 gives the charging current.

Table 4* values for LiPo cells

Mode Description

1 | No battery

2 Deep discharge

3 Pre-charge

4 Start fast charge

5 Fast charge

6 Float charge

A Overvoltage

- SMPS rating

RIO

3 cell

<1 V
< 9 V
9 to 1 1 V
>11 V
12.6 V
12V
>13 V
12V
27 kn

4 cel l

< 1 V

< 12 V
13 to 14.1 V

>14.3 V

16.8 V

16 V
>17.2 V
15V
36 ki7

Current

1/10 c

Increasing

1C

_J/ 50 C
4 A

The Authors

Uwe Hofmann is a technician working at Miniatur-Wunderland in Hamburg. Germany w

Gunter Ceroid Is a self-employed radio and TV technician & l

Dr, Thomas Scherer works as a technical author and designs laboratory equipment,

42

will be required to enable the batteries to
be charged independently. The pin assign-
ments of the charger plug are the same as
that used in the previous ‘Power Charger*

article fd,

The circuit can easily be adapted to cater for
other rechargeable batteries. It is however
important to choose a SMPS capable of sup-
plying sufficient current. The supply's nomi-
nal output voltage should correspond with
the battery’s nominal voltage* The SMPS
we used here exhibited a certain degree of
‘ hunting 1 if we tried to adjust the output to
less than 9.5 V. This condition is not danger-
ous but caused the LED to pulse. The add-
on controller board described here is suit-
able for use with SMPSs with outputs In the
range from 8 V to 20 V.

To use the fast charger for any voltage other
than 1 2 V it will be necessary to change the
value of the voltage divider formed by RIO
and R 1 1 . In addition some constants defined
in the firmware need changing. This last part
is easy; the source code is well documented
and written in BASCOJVL Thanks to the pro-
gram size it is possible to recompile the
software using the size- restricted free demo
version of the BA 5 COM environment*

The fast charger is also suitable for use with
4 Ah LiPo cells popular with model builders.
With a charge current of 4 A = 1 Cthe LiPo
cells will be fully charged in a little over an
hour* Table 4 gives values for each mode of
the charging process.

(090858}

Internet Links

i 1 ) www.elektor.com/090248

[ 2 www. e I e ktor. d e / w 1 1 eel fe- forum

| 4 j www.falrchildsemi.com/ds/
TL% 2 FTL 431 .pdf

[ 5 j www.elektor, com /0908 5 8

[6 ] www. a -brig h t com , t w/ f u I Iclamp/AL-
513 RGBW-A-Q 04 .pdf

[ 7 1 www, elektor.com/090582

[ 8 ] www .miniatur-wunderland.de

[ 9 ] www.gerold-online.de/cms

04-2010 elektor

Guests in the tab

February was chilly but we were pleased to extend a warm wel-
come to some visitors who dropped by to see us, Remco Krul of
National Instruments brought the latest release of Multisim with
him (see News; www.ni.com/inultisim). Our February article
'Blinded by the Light 1 also prompted a visit from Gerard Grashof
of Fluke (www.fluke.com). Armed with a '434 Power Quality Ana-
lyzer 1 he was able to give us more insights into power factor meas-
urement of LED lamps. More on this in our next edition!

Rob Staals (photo) of JTAG Technologies (www.jtag.com) was
spreading

bly testing. In V

the old days M V’ | llfflfj "V g W '
an assem- ) ? ,11

bled PCB was ?

tested in a

fixture using a ^

to contact -

ity of today's

multi-layer boards using hlgh-density LGA and BGA chip outlines
means that some signals cannot be probed. This is a real headache
for board testers. The answer is boundary scanning. In essence
each signal pin of each chip has a dual function; In test mode they
are configured as a cell in a ‘boundary scan' shift register passing
through every chip on the PCB. Test patterns can be shifted into
place and latched into the chips to generate outputs. Individual
PCB tracks can be tested and shorted/open circuits pads identi-
fied. After testing, all the chips revert to normal mode and the test
circuitry effectively becomes invisible. In addition to the register
cells the manufacturers need four extra pins on each 1C for control
and passage of the serial data. Most manufacturers (but not all)
now offer JTAG interface capability option for their chips, Rob’s
Company supplies the fixtures and software for boundary scan
board testing. With the circuit net list the software automatically
tests all connections. Memory modules can be tested by simulat-
ing the signals of a boundary-scan enabled microcontroller.

Corrosion fighter spray

by Jens Nickel

Last month we took a look at the problem of
dusty pots and wafer switches. This provoked
an email from a long time Eiektor reader
(from issue 1 1) praising the article he went on
to outline a problem he had himself. A tele-
phone socket fitted In the wall of an outdoor
enclosure often had a layer of condensation
on the plastic faceplate. Despite a good level
of ventilation, over the years the humidity has
resulted in leakage currents and oxidation of
the plug contacts, corrosion of the conducting
tracks, terminal block and to some extent the
incoming telephone wire pair.

His question is how can he rectify the prob-
lem? Should the telephone outlet and plug
assembly be covered with a layer of non-con-
ducting silicon grease or petroleum jelly? Or
would a dose of 'Kontakt 61 T contact coating
do the trick?

We hesitate to recommend either of these
options; besides the mess there is a very real
chance that the plug contacts will get smeared
with grease when the phone is unplugged
and poor/intermittent contact will add to the
problem.

5 k ht mnS Scfiulz gcgen Ntte**: WET.PROTECT !ilr aMe

A fairly recent development of a spray coating
is Ideally suited to this situation. The company
at www.wet-protect.com advertises a range
of sprays which claim to protect electrical cir-
cuits from the effects of water ingress and
condensation. The spray leaves a permanent
water repellent protective film over the sur-
face. A promotional video shows a treated hair
dryer operating under water! (Don’t try this

WET

PROTECT

one at home). Similar products may be avail-
able from other suppliers, let us know which
ones you’ve found to actually work — highest
odds among products for model building and
ship repair. In the meantime Graupner distrib-
ute rebadged cans of WET. PROTECT. Graupner
products are stocked by model shops through-
out the world.

eiektor 04-3010

ELabslnside@Elektor

* Got a question for the designer of an Eiektor circuit?

* Any contributions or comments on the E-Labs Inside stones?

■ Suggestions of boards or electronic software that you think would
be interesting to review?

* Discovered anything new that you want to tell us about?

Don't hesitate; we look forward to your feedback sent to
elabsinside@elektor.com, please include [e-labsj in the subject line.

LT)

GG

<

UJ

E-LABS INSIDE

making

the dsPIC board

By Jens Nickel

project in its own right Elektor developer Daniel Rodrigues got
down to work on the project

We usually receive many more projects than we have space to
print. So first we make a preliminary selection at an editorial
meeting, bringing together both editors and lab technicians.
This whittles the total down to about ten high-quality projects
every month. These go on the ‘waiting fist" of interesting cir-
cuits , which forms the basis on which the individual editions of
Elektor are planned, taking into account the Publishing Plan,
The editorial meeting takes place about four months ahead of
the planned publication date for the magazine, and projects
that make it this far then go off to the labs.

It starts with a prototype

A printed circuit board is not essential for a project, but does
make it much more attractive. An assembled and function-
ing printed circuit board from the author gives us confidence
that the project can be made to work, but nevertheless we
reroute all boards in our labs in order to comply with our house
style and to generate component mounting plans. Usually our
in-house developer will ask the author(s) to send in his pro-
totype, and in this case it was not long before Daniel had a

O 0 0 P O O O olSO
d O 0 p p p ^ o -o o o o o o Q P O o C' o o o o o a -o *a

Ti L 'Mn

■ ■

filler

The 'dsPIC board', a processor hoard with a range of interfaces,
was originally conceived by two authors from the French-speak-
ing part of Switzerland, and so communications were handled
by the staff of Elektor’s French edition. We had not previously
used the dsPOO, a powerful PtC-family microcontroller with

rather impressive processor board on his bench {see photo).
The authors also sent in their CAD files, by good fortune pre-
pared using Altium Designer, the same package as we use in
our labs. We can also accept Eagle PCB and schematic files, as
well as Ultiboard or Multisim files.

DSP functions. The authors had already designed a printed cir-

cuit board, developed a few working example applications, and
produced comprehensive documentation. The editorial meet-
ing approved the project without hesitation.

A few months passed before publication plans crystallised for
this compact board. During that time the authors, working at
the celebrated Ecole Poly technique in Lausanne, sent us updates
and extensions to his project, including an elegant expansion

After a quick scan of the circuit diagram Daniel started to check
the availability of the components used. If a component seems
hard to obtain we will try to find a more readily-available sub-
stitute, although this is not always possible in the case of some
special-purpose devices. In the case of the dsPIC board Daniel
had little cause for concern: “I changed the fuses," he reports,
“because holders for the fuses the author had used were not

hoard for controlling a solar heating installation. This made the
project a perfect fit for the May 2010 issue, whose theme was
to be 'green electronics’ (see Publishing Plan at www.elektor,
com). At the planning meeting for that issue, at the beginning
of January, the team quickly came to the conclusion that we
should publish the two circuit boards as two separate articles,
since the processor board might be interesting to readers as a

easy to find.” To bring the design into line with our standards,
SMDs in an 0603 package were replaced by 0805 types. This
makes the project a little easier for constructors. “In some cir-
cuits we have to replace everything: voltage regulator, micro-
controller, display, the lot," says Daniel When substituting
components, there are often also corresponding changes to
be made to firmware as well

44

04-2010 elektor

Once Daniel has put together the parts list for the board, he
passes it to Jan Visser in the next-door office, jan knows the
catalogues of mail order giants such as Farnell, Conrad Elec-
tronics and DigiKey backwards: "it usually takes three days to
a week to get all the parts in/' he explains. Of course our lab
also boasts an extensive stock of standard SMD and in particular
leaded components. We also keep about forty different types
of microcontroller, and the Elektor Shop sells a wide range of
pre-programmed devices.

The Eiektor PCB

Meanwhile, Daniel has been working on the printed circuit
board. Since Altium CAD files had already been prepared, the
work was quicker than usual. First the components are posi-
tioned on the blank board, using the footprints provided by the
author. Tve tried to keep roughly to the component placements

the author used,"' Daniel says. For our double-sided board lay-
out we made sure all connectors were mounted on the same
side of the board. As can be seen from the screenshots (author's
layout on the left, ours on the right) we have also removed alf
the 90 ° corners from the tracks, replacing them with 45 ° turns.
For the original layout the author had made vias using the leads
of components — common practice for prototypes but not suit-
able for professional manufacture. So these were changed, and
then finally the dimensions of the board (already a little larger
than the original) were rounded up to a whole number of centi-
metres. We don't often work to standard sizes such as the Euro-
card format unless the requirements of a particular enclosure
dictate otherwise.

The finished board design is then sent for manufacture to our
partners Eurocircuits, just across the border in Mechelen, Bel-
gium, This gives a little time for our engineers to work on other
projects before components and circuit board come together
in the lab. By the middle of February there area good dozen cir-
cuits in the pipeline for the summer double issue.

Daniel is making progress with the second board, and has some
questions for the authors. In particular he is concerned about
the type of flow sensor the author is using in his solar installa-
tion. Fie has also noticed an oddball connector used to supply
power to the temperature sensors.

To the author for testing

As soon as the two boards have been made and populated they
undergo a range of tests. “'For this project we just checked for
shorts and other obvious problems/ 1 Daniel explains. For func-
tional testing the board is sent to the authors, who can try it
out in conjunction with the other expansion boards they made,
They can also replace the boards in their solar installation with
our versions fora practical test

“Doing those tests here would have been difficult," Daniel
remarks, "because we don't have the necessary sensors and

magnetic valves to hand,” He also notes that authors will often
have much more experience and skill in using special-purpose
devices like the dsPIC microcontroller, pointing out that it would
take a long time just to write suitable test routines to exercise
all the pins and interfaces on the microcontroller,

What tf the authors find that Elektor board doesn't work? Daniel
grins, “Then we just have to work quickly/' Like time and tide,
publication deadlines wait for no man. Find out what happens
in the next instalment!

(091079)

We receive a steady stream of questions from readers who
have designed interesting circuits. How do we decide which
projects make it into the magazine? What do we require
from the author? Flow is the work divided between author
and the Elektor labs? Here we complement our 'Author
Guidelines' (which can be found tucked away on our website
under 'Service') with our 'Making of E-Labs Inside pages.

elektor 04-2010

45

E-LABS INSIDE

Meter under test

By Jens Nickel

Back in January we mentioned that we were working on the
design of a newC0 2 meter. This one is specifically designed for
use in cars where the confined space can quickly lead to a build
up of C0 2 concentration in the air. Its effects are well known:
headache* sickness and poor concentration.

We chose a C0 2 sensor which uses the principle of infrared
absorption. The alternative is a laboratory-grade cell but these
are not so practical; they require a couple of hours before pro-
ducing an offset-corrected measurement. The sensor used
for this design is ready to go within one minute* true to the
plug'n'play philosophy we can just plug the C0 2 meter in (to

It's a tough job..*

One cold February morning we assembled in the car park*
we would be using my (aging) VW Golf to put the C0 2 meter
through its paces. The plan was a short journey through the
countryside and then around 20 miles of motorway driving.
Before starting we calibrated the meter using some local fresh
air to give a reading of 400 ppm.

In the first few miles we switched the car ventilation system
to recycle so that no fresh air would be drawn in. As expected
the meter reading began to rise* after just five minutes it had
already exceeded 1 000 ppm and was still rising steeply. At eight
minutes we had reached 1 740 ppm but the rise was now less
steep (we guessed this was probably due to air leakage around
the door seals). At this level you don't need a meter to tell you
that the C0 2 concentration is high* you are increasingly aware
of the stuffy* fuggy atmosphere and feel a growing urge to
open a window. After another ten minutes the C0 2 level had
plateaued at around 1900 ppm* again we guessed that leakage
around the doors had achieved equilibrium with the expelled
CO z . 1 900 ppm is a surprisingly high reading after just 1 5 min-
utes driving.

Prototype***

The sensor is produced by ZyAura of Taiwan, It features a high
level of integration including an SPI interface* This allowed us
to get the first prototype up and running relatively quickly. The
module repeatedly sends data packets over this interface indi-
cating the C0 2 concentration and air temperature. Alf that's
necessary is a microcontroller (e,g. an ATmega) to extract and
display the data, A small alphanumeric display using HD4478Q
compatible commands is all that's necessary for display pur-
poses. Chris Vossen was able to produce the necessary firmware
relatively quickly using pre-programmed software building
blocks {in the form of C functions). From the hardware point
of view the prototype only needed a small square of prototyp-
ing board, a couple of chips for the power supply and a suit-
able enclosure (not forgetting ventilation holes to allow for air
circulation).

.,.but someone has to do it

We were all feeling uncomfortable so everyone was in agree-
ment with the next stage of the test... we needed air. We
switched the ventilation controls to draw in fresh air and turned
the fan on. Depending on the fan setting we recorded readings
between 1 1 00 and a more bearable S00 ppm.

For the last part of the test we would really be stretching our
powers of endurance to the limit; travelling at 70 mph with
an outside temperature hovering around zero centigrade we
switched the ventilation fan to maximum and wound down the
windows. The C0 2 concentration quickly dropped to just over
600 ppm.

Result: The sensor has a really fast reaction time and its good
resolution means that you quickly get an indication whet her C0 2
concentration is stable* decreasing or increasing. This informa-
tion can be critical when several people are gathered together
in a confined space. The head of our lab Antoine Authier had
also discovered that you don't need a full car to get high levels
of C0 2 ; he had recorded in-car levels of 1 300 ppm and above
during his dally 50 minute commute through rush hour traffic.
This little box of tricks is going to be very useful, If alt goes well
we will reveal all in the May 2010 edition of Elektor,

(ogogSi)

... and test

Once we had the prototype sorted it was dear that we would
need to devise a rigorous and punishing series of trials to fully
test the design (would you expect any less?).

We had previously made preliminary lab tests on the circuit and
our chief designer Antoine Authier had already tested the meter
in his own car. The time was now right to make a more system-
atic trial using a real-world test environment; I went in search
for some willing lab rats.,.

By the end of the day I had assembled our team; Chris volun-
teered to shout out the readings f rom the passenger seat* Anto-
ine would make notes and our graphic designer Mart Schroijen
wou Id be responsible for ta kl ng some photos.

46

04-2010 elektor

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Programmer Accessories:

40-pin Wide ZIF socket (ZIF4GW) £14.95
ISVdc Power supply (PSU120) £19.95
Leads: Serial (LDC441) £3,95 / USB
(LD0644) £2.95

USB & Serial Port PIC Programmer

USB/$erial connection. Header cable for
ICSP. Free Windows XP software. Wide
range of supported PICs - see website for
complete listing. ZIF Socket/USB lead not
included. Supply; 16-1 8Vdc.

Kit Order Code: 3149EKT - £49.95
Assembled Order Code: AS3149E - £59.95

USB All-Flash' PIC Programmer

USB PIC programmer for ail
'Flash' devices. No external
power supply making it truly
portable. Supplied with box and
Windows Software. ZIF Socket
and USB lead not included.

Assembled Order Code: AS3128 - £49.95

See website for full range of PIC & ATMEL
Programmers and development tools.

No.1

a KITS

Secure Online Ordering Facilities * Full Product Listing, Descriptions & Photos • Kit Documentation & Software Downloads

MICROCONTROLLERS

By Wolfgang Rudolph and Dr DetievTtetje (Germany)

Minimodi8 is a very compact general-purpose microcontroller module. It includes frequently requiied
peripheral components, such as pushbuttons and an LC display, as well as several interfaces (USB, PC and
ISP/SPI), You only have to assemble the peripheral circuitry necessary for your specific application and
connect it to the Minimoch8. This way you can build a complete device with entry and display capability in

almost no time.

This tiny microprocessor module immedi-
ately invites comparison /The KIM-1 compu-
ter Id was a sensation when it was launched
in 1976. For US$245, you got a real compu-
ter with a 6502 microprocessor running at
a 1-MHz clock rate. Of course, the KIM was
supplied 'naked': no case, no power supply,
and no interfaces {see Figure 1), Neverthe-
less, the first boards cost around £1 50 at
that time and were hard to come by almost
everywhere outside of the USA.

In terms of processing power, the Mini-
modlS is leagues ahead of the KIM.
Although the Minimod 1 3 lacks some of the
features of the distant ancestor of today’s

PCs, such as the system monitor program
and an abundance of I/O ports, it offers
many excellent technical features and is
distinctly more compact than the KIM-1.
The inset provides a brief summary of the
integrated features, including pushbuttons,
an LC display, a 64-KB EEPROM, and three
interfaces: USB, PC and ISP/SPI.

Integrated boot loader

The Minimod 18 board measures 80 by 25
millimetres (Figure 2), which makes it
only half as large as the already pleas-
antly small ATM 18 board. It is fitted with
an ATmega328P-AU microcontroller in a
TQFP32 package The only essential dif-

ference between this microcontroller and
the ATmegaSS is its considerably more gen-
erous memory capacity, so it is fully com-
patible with our AT Ml 8 projects. This also
allows us to sacrifice a bit of the flash mem-
ory space for an integrated boot loader.

A boot loader is a small program located at
the top of flash memory. If the microcon-
troller is configured appropriately, it starts
this program first. After starting up, the
boot loader can establish a link to an exter-
nal device, receive data, and store the data
in flash memory orEEPROM. This eliminates
the need for accessory hardware in the form
of a programmer. The Minimod 18, which

48

04-2010 elektor

MICROCONTROLLERS

can be ordered from the Eiektor Shop,
comes pre-programmed with an adapted
version of USBaspLoader, This means that
newcomers no longer have to procure addi-
tional programming hardware.

USBaspLoader emulates the very popular
and widely used USBasp programmer UI
and is thus compatible with a large number
of PC programs, including the widely used
program AVR-Dude, which is conveniently
included with the GCC compiler (WinAVR),
Alt you need is a USB cable, since the Mini-
modi 8 has a built-in USB port. The USB
port is connected to the same pins as the
'Passepartout' project featured in Eiektor
March 2010, Just like it, the MinimodlS
board is powered directly from the USB
port.

If you hold the left button pressed while
applying power to the board (plugging in
the USB cable), the Minimodi 8 enters pro-
gramming mode and can write data to the
flash memory and internal EEPRGM. You
have to launch AVR-Dude for this purpose.
For example: to copy the contents of the file
‘hello. hex 1 to flash memory, enter 'avrdude
-c usbasp -p m328p -U fIash;w;heflo,hex* in
the command line (see Figure 3), Press the
right button to exit programming mode and

Features

Microcontroller:

* Atm el ATmega328P-AU AVR RISC
microcontroller

* 32 KB flash memory

* 1 KB EE PROM

* 2 KB RAM

* SADCinputs

* 3 timers and 6 PWM channels

* 20 MHz dock

* IK, 5PI, and U5ART interfaces

* Supply voltage 1 .8-5.5 V

Board:

■ USB socket

- Power supply over USB possible

■ 16 MHz crystal

* 64 KB EEPRDM with \K interface

■ EADIP5Q82-HNLED LCD module

{2x8 alphanumeric with LED backlight)

* Contrast adjustment trim pot

■ 2 buttons

* Connector for SPi/ISP

* Connector for \ 2 C and ADC

Figure 1. KIM-1 was one of the first hobby computers that did not require any soldering by

the user (photo: University of Stuttgart [7]).

COMPONENT LIST

Resistors

R1 ,R2,R5 = 2.2kQ (0603)

R3,R4 = 680 (0603)

R6 = l Oka (0603)

PI = 10kH Trimmer (TC33)

Capacitors (0603)

C1,C2 = 22pF
C3-C6 - lOOnF

Inductors

LI =10 pH (0603)

Semiconductors

Dl,D2^3.6V(SOT23)

IC1 = AT24C5 1 2 (SQ-08M)

!C2 - ATmega328-AU (TQFP32-08), program-
med, Eiektor order# 090773-41

Miscellaneous
LCD =

E AD I PS O 8 2- H N LE D

K1 - 1-pin pin header,
right angled
l<2 = USB-B socket
K3 = 6-pin pinheader,
angled

51 ,S2 = PCB mount
pushbutton

XI = 1 6 MHz quar tz cry-
stal (ABM3)

PCB. order #080950-1
from Eiektor Shop
or

ready populated and
tested module with
preinstalled bootloa-
der, Eiektor Shop or-
der# 090773-91*

Figure 2. The compact PCB can easily be fitted in your own

equipment.

eiektor 04-2010

49

MICROCONTROLLERS

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urduile : input File liellra.lwx contains r i 5 (l byte-.
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imrrtLLilp t mf Emmie i S‘i*st. Lr Oli
nurdiiilE iIufie . 1 li.iriK (mu .

Figure 3. The microcontroller can be programmed in practically no time

with the free AVR-Dude PC program.

Figure 4. The alphanumeric display module has LED backlighting.

start the application program (the down-
loaded program). This is all you need in
most cases. However, the system does not
atlow you to change the fuse settings (which
control the baste operation of the microcon-
troller) in programming mode. This is actu-
ally an advantage for novices, since it's pos-
sible to make costly mistakes with the fuse
settings. Under certain conditions, you can
even render the Minimodi 8 totally unpro-
g ram triable. 8y contrast, nothing can go
wrong when you use the boot loader.

if direct programming is nevertheless nec-
essary for some reason, such as replacing
the boot loader with a new version, you
will have to use an external programmer.
It can be connected to six-way connector

K3. Before you do this, you must alter the
configuration of the solder bridge on the
back of the board to make the Reset pin
available in place of the Slave Select (SS)
pin and transform the SPI interface into an
ISP interface. This gives you full control over
the configuration and programming of the
microcontroller.

Display

A DIPS0B2-HNLED module from Electronic
Assembly HI is used for the display. This is a
very high-contrast, backlit module with two
lines of eight characters each (Figure 4).
Unlike the two-wire LCD module of the
ATM 1 8 board, it is connected in the conven-
tional manner with a 4-hlt bus, which allows
the optimised library functions of BASCOM

or corresponding modules for other compil-
ers can be used. This only requires adjusting
the pin assignments. The same holds true
for programs written for the ATM1 8 board
If you want to run them on the Minimodi 8
board. On the Minimodi 8 board, PD4-PD7
and PCI -PC3 are used for the Enable, R/W
and RS signals (see the schematic diagram
in Figure 5). The display contrast can be
adjusted using trim pot PI .

USB interface

As already mentioned, the USB-B port can
also be used to power the Mini-modi 8
board. The port circuitry follows the rec-
ommendations of the V-USB project HI in
order to allows USB driver 'USB Jreiber'
to be used. This driver is also used for the
boot loader. The Minimodi 8 board Is also
very suitable for implementing many other
applications that simulate a USB device in
software, such as a PC keyboard or other
device.

The module can be powered either via the
USB port or via pin 2 of SPI/1SP connector
K3. The module draws around 60 mA, most
of which us used to backlight the LC display.
If you use the Minimodi 8 board without a
PC, it can be powered from a 5-V AC mains
adapter with a USB connector. These AC
adapters are available at very reasonable
prices.

Other interfaces

A standard SPI interface, which is supported
by the Atmel hardware, is provided for driv-
ing external peripherals. You can alter the
configuration of solder jumper]! to convert
it to a programming Interface (ISP port). The
pins can also be used individually for digital
I/O signals. Pins PB3, PB4 and PBS are con-
nected to pins 4, 1 and 3 of connector K3,

The three A/D converter inputs (ADC6,
ADC7 and ADCO/PCQ) are available on pins
3, 4 and 5 of connector K1 . This gives the
Mini mod 1 S access to the worl d of ana logue
electronics. A PWM output of the microcon-
troller (PD3) is also available on pin 6 of con-
nector K1 Jt can alternatively be used as an
interrupt input {INTI ).

The connectors can be used independently
(one 6-way and one 10-way) for connect-

5 °

04-2010 elektor

MICROCONTROLLERS

f

LCDt

^ \

EADIPSQ82-HNLED

J

QQOQQQQQ

090773 11

f igure 5. Various ATmega microcontroller signals are available via connectors.

Eng your own peripheral circuitry using flat
cables. However, it is also possible to fit the
additional hardware on a single PCS with
a 2- row by 10-way socket header, which
can be mated directly with the MinimodlS
board.

The AREF input, which supports the use of
an external voltage reference, Is also fed
out to pin 1 of connector K1, There is no
jumper for connecting the reference volt-
age line to V cc as on the ATM 18 board, since
the ATmega has internal capability for using
the supply voltage (AVCC) as the reference
voltage.

The Minimodi 8 board has two pushbutton
switches (SI and S2) that use the Internal

pull-up resistors of the ATmega microcon-
troller, SI (left) Is connected to PB1 . while
S2 (right) is connected to PBG.

The 64-KB onboard EEPROM (IC1 ) provides
sufficient storage space for using the Mini-
modi 8 as a data logger, among other pos-
sibilities. The 24C51 2 EEPROM is connected
over an PC bus and can be accessed directly
from BASCOM. With GCC, you can simply
use the included PC library.

The entire circuit design corresponds to
Atmel's recommendations. An external 1 6-
MHz crystal is provided for dock generation,
a 1 Q-kn pull-up resistor is connected to the
Reset input, and a 100-nF film capacitor is
provided for supply decoupling. The AREF

input also has an external 1 00-nF film capac-
itor. and AVCC is decoupled from the V cc rail
by a 10-pH inductor and a film capacitor.

The first program

The controller in the LCD module is com-
patible with the widely used HD44780 con-
troller, The Internet offers C programmers
a variety of libraries for driving LCD mod-
ules, which only require configuring the
right pin assignments. For maximum com-
patibility, the R/W input of the LCD mod-
ule is connected to PC3. This allows polling
of the controller’s Busy flag, which many
libraries in fact do. However, BASCOM does
not make any use of this input; instead, It
assumes that this pin is tied to ground. Con-

elektor 04-2010

Si

MICROCONTROLLERS

'Hello World" listing

$regf ile - „m328pdef . dat "
$crystal ” 16000000
$baud - 19200
Shwstack = 32

$swstack = 10

$framesize = 40

$initmicro

Config Lcdpin = Pin , Db4
PortdL 6 , Db7 = Portd , 7
Config Led. - 16 * 2

Cls

Led „Hello"

Loweriine
Led „ World"

End

initmicro :

Ddrc .3=1
Porte, 3 - 0
Return

1 specify the used micro
' used crystal frequency
' use baud rate
' default use 32 for the
'hardware stack
1 default use 10 for the
'SW stack

1 default use 40 for the
' frame space

1 run subroutine _init_miero
Portd . 4 , Db5 = Portd. 5 , Db6
E = Porte. 1 , Rs = Parte. 2
'configure led screen,

'8*2 not available

'end program

'LCD i R/W low

ATmega microcontroller
pin utilisation

PB0&PB1: Buttons 1 & 2
PB2-PB5: ISP/SPI interface

PC0: ADG0 / digital I/O

PCI; LCD E

PC2: LCD RS

PC3: LCD RW

PC 4 & PCS ; PC I n ter face

(external EEPRGM)

PCS: Reset

PD0“PD2: US8/RS232 interface
PD3: PWM/INT1 /digital I/O

PD4-PD7: LCD D4-D7

AVCC. AREF t ADC6, and ACD7 are used
for A/D conversion

sequently, it is necessary to pull PC3 low
before starting to configure the LCD mod-
ule. This is done by l $initmicro' in BASCQM.
The example program shown in the L Hetlo
World 1 listing illustrates how to access the
LC display with BASCOM. This program can
be downloaded from the project page for
this article [6].

W hat’s next?

This general-purpose miniature module
is a perfect starting point for developing
your own applications. All you have to do
is assemble your own circuit on a bit of pro-
totyping board, download your program

code to the Minimodi 8 via the USB port,
and then mate the boards. Now you 1 re
ready to go!

However, we aren’t leaving you entirely on
your own. Two applications for the Mini-
modi 8 are already underdevelopment, and
they should be published in Elektor the near
future. One is a general-purpose battery
charger that only requires assembling the
power circuitry on another PCB. The other
is a weather station with a data logger and
wireless sensors. Here the Minimodi 8 can
also show the acquired data on the display.
On top of this, you can run most of the pre-
viously published ATM 1 8 projects on the

Minimodl 8 board. This usually requires
only minor adaptations to accommodate
the hardware differences (available pins and
LCD module drive).

Incidentally, we don’t plan to toss the
ATM 18 board on the scrap heap. We will
continue to use it in future projects,

(090773-I)

Internet Links

|1 j http://en.wikipedia.ofg/wiki/KIM-1

[2] www.atmeLcom/dyn/resources/prod_documents/8 161S.pdf
[3 1 www.obdev.at/products/vusb/usbasploader.html

1 4] http://www.lcd-module,com/eng/pdf/doma/dips082e.pdf

[5] http: / / vus b . wi k i dot xo m

[6] http://www.elektor.com/090773

1 7 j http: //com pu termuseu m.in format! k.u nLstuttgart.de

04-2010 elektor
52

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The upgraded Elektor-PLUS subscription!

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'

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subscription you get exclusive access
to wwvwelektor-ptusxom where the
three latest editions of Elektor magazine
are available in the form of pdf files
fix. the current issue and the two pre-
ceding ones). With a simple click you
download the complete issue (front to
back!) or any single article,
www.elektor-plusxom aiso sup-
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Or use the subscription order form near the end of the magazine.

AUTOMOTIVE ELECTRONICS

Bluetooth for OBD-2

By Folker Stange and Erwin Reuss (Germany)

The hand-held OBD Analyser NG Featured in the
September 2009 edition of Elektor has an open-source
operating system and a built-in expansion port. Both
enable a Bluetooth module to be integrated with ease.
Now at the other end of an RF link you can view engine
parameters and faults on a netbook or notebook PC!

The OBD Analyser NG Ml diagnostics tool
uses an AT90CAN1 28 controller with 1 28 KB
flash memory- This is more than enough for
hand-held use but if you were planning to
implement a trouble-code database you
would soon start to feel that memory space
was becoming a little cramped- Likewise
its simple display is ideal for quick diagno-
sis of simple problems but does not allow
more complex graphical representations
of sensor readings. Nowadays the majority
of netbook or notebook computers come
equipped with a Bluetooth interface and

54

04-2010 elektor

if yours does not have one a low-cost
Bluetooth dongle can easily be added.
With this in mind, what's to stop us
from adding a Bluetooth Interface to
the popular OBD analyser NG and (with
the right software) turning it into a far
more useful and sophisticated engine
dataanalyser?

The Bluetooth module
The BTM-222 module is the central
player in the expansion of the OBD
analyser NG- Regular readers will rec-

ognise It from the role it played as an add-
on to our ATM18 microcontroller board
described in the December 2009 edition
of Elektor. In its application here the Blue-
tooth module and decoupling capacitors
are mounted onto a small carrier board
soldered to the analyser’s expansion port
using pinheader strips. Printing the quar-
ter-wave antenna directly on to the PCB
simplifies construction and assembly of
the expansion board Into the case of the
OBD analyser.

The BTM-222 is a class 1 type of mod-

AUTOMOTIVE ELECTRONICS

Figure 1 . The complete Bluetooth expansion circuit requires little more than the BTM-222

Bluetooth module and a voltage regulator.

Table 1 . Bluetooth Class vs, range

Class

Max, Power

JmW]

Max, Power
|dBm]

Range (unobstructed)
[m]

Class 1 1

100

20

approx, 100

Class 2

2.5

4

approx. 50

Class 3 '

1

0

approx. 1 0

Features

• Bluetooth Class i (range up to 100 m)

* Antenna printed on the PCB

* RF data rate of 19200 Baud

• Low cost Bluetooth module

- 28 mm x 38 mm PCB ,

ule which specifies a maximum transmit-
ter power of 100 mW (20 dBm}, giving a
range of a rou nd 1 00 m (300 ft) . I n order to
achieve an RF link over this distance it is nec-
essary for the Bluetooth transceiver in the
notebook or netbook to also be Class 1 . A
Class 2 or 3 module wifi result in a reduced
operating range (see Table 1)* If your PC has
low-power or no Bluetooth capability then a
Bluetooth USB stick (make sure it's Class 1}
can be added at very little cost.

The circuit and construction

The circuit (Figure 1 ) consists of just a Blue-
tooth RF module (IC1 ) } a voltage regulator
(1C2) and two rows of pinheaders (jl and J2).
IC2 converts the 5 V supply to 3,3 V required
by the Bluetooth module. The pinheaders
carry the 5 V supply and three control sig-
nals, Port pin PF5 from the analyser's micro-
controller is used here to switch the power
regulator on the BTM-222 under software
control, PF6 and PF7 carry the serial data
communication between the BTM222 and
a software DART in the OBD analyser.
Assembling the expansion board and fit-
ting it to the analyser is relatively simple.
The PCB (Figure 2} is supplied with the
voltage regulator and supply decoupling
capacitors already fitted so It Is only nec-
essary to mount the BTM-222, Do this in
the same way that you would solder a large
SMD 1C but just solder the Rx 3 Tx, antenna,
supply voltage and ground pins to their
PCB pads, just five pins of the Q8D ana-
lyser's expansion port are required by the
expansion module (see photos). All of the
20 pins however pass through the expan-
sion board (Figure 3) to facilitate any future
developments.

Get your motor running

Before we can begin communications with
the Bluetooth module we need to check
that the OBD analyser NG is running the

latest firmware version (available from the
Elektor website 1 2 I). The firmware support-
ing Bluetooth operation is the file named
HandheldOpen_121 in the zipped folder
09091 8-1 1, This latest firmware version has
been shipped with the OBD analyser NG kit

Capacitors

C1,C2 = IjxFSMD

Semiconductors

IC1 = BTM-222 Bluetooth radio module
IC2 - TS5205CX 533 (SMD SOT23)

Miscellaneous

JTJ2 * 10 -pin pinheader
Kit of parts, contains partly populated
PCB and all components. Elektor Shop #
090918-7 ! . see www.elektor.com / 0909 18

since January 2010. Those of you who took
delivery before this date will need an ISP
programmer (e.g. either ffi or I 4 1), See the
'Firmware update’ text box for details of
how to transfer the latest firmware version
to the controller.

Figure 2. The Bluetooth PCB uses a length
of PCB track as a 'printed 1 antenna.

COMPONENT LIST

elektor 04-2010

55

AUTOMOTIVE ELECTRONICS

Updating the Firmware

Check the OBD analyser NC main menu options, if the Bluetooth mode is not available (all versions below build 121} then you need to down-
load the latest firmware version from the Elektor Website i 2 l. You will require an ISP programmer with a 10 -pin connector to fit the Atmel AVR
controller family of devices (see 1*1 or Ml for example). This is connected to programmer socket SV1 on the component side of the PCS. If the
programmer provides a supply voltage on pin 2 of SV1 the analyser should be unplugged from the vehicle's OBD connector for program-
ming. In this case fit jumper]3 (behind pin 2 on SV1 }. The downloaded software ZIP folder can now be unpacked to a directory and the soft-
ware run. Firmware update will take just a few seconds.

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PC software for the OBD Analyser NG

So far we have dealt with the 0 BD a nalyser NG 's
hardware expansion. The only thing missing is diag-
nostic software running on the laptop to interpret
and display engine data. The moDiag program Nl
performs this function and is available as three dif-
ferent versions offering increased levels of sophisti-
cation. MoDiag is optimised for OBD interfaces us-
ing ACV and DIAMEX chip sets and therefore ideally
suited for the Elektor OBD analyser NG which uses a
DXM module.

The program stores sensor readings during transit
in Flies with a : \csv extension for later analysis using
spread sheet programs such as MS Excel, Bluetooth
communication removes the need for any in-car
cabling which could potentially distract the driver.

Also interesting is the graphical representation of
the lambda readings which can be used to identify
a worn-out sensor. The ability to combine several
sensor readings on the display gives the laptop a
big advantage* In contrast the hand held OBD ana-

lyser on its own does notallow this flexibility. Similarly a database containing the meanings of all the possible diagnostic trouble codes greatly
speeds up fault identification whereas the hand held unit does not have memory space to accommodate this feature. The moDiag 'profes-
sional’ version can also map a 3D representation of a combination of sensor data.

3E*

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Using either the moDiag ‘expert 1 or ‘professional’ version allows continuous measurements of engine powder and torque to be displayed as a
graph. The current instantaneous value is also shown on the display, The professional version also Includes a special LPC adjustment mode to
optimise an engine set up for LPG operation and includes a large library of trouble code meanings. The 'professional' version is useful for ve-
hicle workshops and includes functions to optimise LPG engine conversion settings and also has an extensive data base to store documenta-
tion, diagnostic reports, data readings and gas conversion details of every customer’s vehicle.

The Bluetooth set up procedure described in the text can be simplified by the use of a small assistant in the moDiag program which independ-
ently searches for the interface and in most cases avoids the need to use the Windows device manager.

moDiag is suitable for PCs running Windows 2G00 r XP. Vista or Windows 7. The standard version of the program is free and available for
download from the Elektor website i2 h

Matthias Tiehen

For operation you will require a Bluetooth-
capable Windows notebook or netbook (as
described above). The first step is to plug the
OBD analyser NIG into the vehicle’s OBD con-
necter. Now select the Bluetooth option (Fig-
ure 4 ) from the menu on the OBD analyser.
When activated the blue backlight tights up*

On the notebook Windows will indicate
that a new Bluetooth device is available. A
serial port should have been found, click on
this and then ‘next’. Now enter a passkey.
In our case we simply use the sequence
1 1 234' and then press Enter. Windows
now activates the newly found Bluetooth

device and displays some GOlVl ports. The
first “detailed 1 COM-Port is the one which
needs to be entered into the application
software (OBD software running on the
notebook) as the communication port. The
application software can be the 'moDlAG 1
DJ software, or similar.

56

04-2010 elektor

AUTOMOTIVE ELECTRONICS

An automatic scan
performed by the applica-
tion software will search and
confirm that the correct port is
identified and listed. Once this com-
munication path is correctly configured
there is nothing else to prevent us running
diagnostics with PC support,

( 09091 S)

[ 1 ] www.elektor.com/090451
[2 1 www.elektor.com/090913

[3j www.elektor.com/030161

| 4 ) www.stang e-di st rihution.de
(click on the Union Flag)

[5], www.modfag.de/engSish/
m oby d i a g_ pro. h t m

Figure 3. The PCB comes with the supply decoupling capacitors Figure 4. The latest firmware now has a Bluetooth option,

and voltage regulator already mounted.

elektor 04-2010

57

HOBBY

Fun with Fireflies

Grass-roots artificial intelligence

By Abraham Vreugdenfiil (The Netherlands) *

Communication is happening everywhere around £

us all the time. Between people, computers
and also in nature we see communication
among creatures. This communication
can have many meanings, like indicating
a source of food by ants and bees,
the search for a suitable partner by
other animals, or human beings
simply being sociable. It is this
communication, between 'fireflies* in
particular, thafs being explored here in a
fun way and on a shoestring budget.

Fireflies flash their lower abdomens in an
attempt to attract members of the opposite
sex. In the dark these flashing fireflies form
a fascinating spectacle. Searching, finding
and communicating, that is the object in
this case. This has strong similarities with all
kinds of electronic applications. But to what
extent can we mould this into a concept for
an electronic firefly?

The direction of the communication
between different, small robotics circuits
forms the basis of this idea* The objective
here is for different robots to seek each
other out and to recognise their response.
For the sensors we use an infrared transmit-
ter and receiver. A ring of eight bi-colour
LEDs functions as the visible ‘memory 1 of
our ‘Firefly" and indicates in which direction
it has recognised a counterpart* The Firefly
looks around with the aid of the servo on
which it sits. All this is driven by a simple-to-
program microcontroller type ATmega88.

Operation

The main objectives of the Firefly are orien-
tation and communication. To do this you
have the ability to communicate using an

infrared (IR) signal. This is done with the
circuit shown in Figure 1 . You use the serial
output of the microcontroller, so that you
can simply use the print x command in the
software program. You then take a separate
output of the processor and use It to gener-
ate a 36-kHz square wave. You connect the
IR transmitter diode between these two
outputs. In this way you generate a serial
RS-232 signal that Is modulated at 36 kHz.
To be able to receive this signal you take a
special IR-receiver, type SFH 5110. The spe-
cial attribute of this receiver is that it has
a 36-kHz filter built in, creating a nice RS-
232 signal that you can connect directly
to the serial input of our microcontroller. If
you use a somewhat slow communication
speed (2400 baud in our case), then you can
establish some very effective communica-
tions between multiple robots.

You can accomplish the orientation if the
Firefly is able to look around. To do this,
the robot is mounted on a modified servo.
A normal servo rotates through an angle of
only 270 degrees, but in this circuit a con-
tinuously rotating servo Is used (see side-
bar ‘Servo modification 1 ). In this way the

Firefly can scan its surroundings with the
IR-receiver. The first time it recognises a
counterpart, a red LED will light up in the
direction of where it found this counter-
part. After it has been detected a second
or third time the relevant bi-colour LED will
light up orange and any subsequent detec-
tions will result in a green glowing LED*
When a counterpart is no longer detected
(perhaps because it has turned away), the
series reverses, so from green to red and
eventually off.

When the robot turns, the ring of LEDs on
the robot also ‘turns 1 , so that those LEDs
pointing in the direction of its counterparts
always remain lit. In this case the 8 bi-col-
our LEDs are connected in a matrix con-
figuration to save I/O pins. Each column is
switched by a transistor type BC547. When
one of the outputs (PD4 through PD7) is
pulled High, then the corresponding transis-
tor will co nduct and one or more of the fou r
outputs PCO through PC3 are pulled High,
so that the corresponding LEDs will light
up* A short time later another transistor is
turned on allowing 4 other LEDs to come on
also. Since this happens quite quickly there

5 *

04-2010 elektor

HOBBY

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Figure 1 . The schematic for the Firefly is quite minima!. There is nevertheless a type of

intelligent communication.

is the impression that all! 6 LEDs are turned
on simultaneously. In the programs slightly
longer delay is used in order to obtain some-
what of a slowly blinking effect, just as with
real fireflies.

When starting up there is the option of
entering the calibration procedure for the
servo. Pushbutton SI is used for this. A 22-
k Q. pull-up resistor ensures that the cor-
responding input of the microcontroller is
High and only goes Low when the button is
pushed. The calibration procedure is started
when the signal at the input of the micro-
controller (PEN ) is Low*

For peripheral devices there are a light
dependent resistor (LO R)„ a piezo trans-
ducer and a voltage divider available. The
LDR in our design is used to simulate ran-
domness, to determine whether the servo
is to turn to the left or to the right. A 1 0-
bit ADC measurement is performed and
the value of the least significant bit (bit 0 )
is used for certain decisions. The least sig-
nificant bit (LSB) changes value frequently,
particularly since this was made dependent
on the ambient light. Very small changes
in light level that are almost impossible to
detect will result in a very rapidly changing
value of the least significant bit. This creates
a primitive but effective pseudo-random
number generator.

To drive the piezo-transducer a resistor of
about 47 Q is required and a small electro-
lytic capacitor of 10 pF, 16 volts w.v. When
you buy the piezo transducer, do make
sure that you get a transducer mounted in

a housing. Without the housing you won't
be able to hear much.

Software

The 'brains' of our Firefly is of course the
software that runs in the ATmegaSB, The
program, RreF/y_vT,bas 1 is a free down-
load from the project web page [, L It basi-
cally consists of a main loop, which repeat-
edly sends the number ‘V by using the
print } command. Subsequently, the Firefly
will turn 45 degrees in a random direction
depending on the servo_dir variables and
a check is made whether a character has
arrived at the serial input using the com-
mand A = ischarwaitmg(). If this is the case
then the variable Target is set.

The 1 6-bit variable with the name Long Jed
contains information about the state of the
eight bi-colour LEDs. The lowest bit is the
green LED! , the second bit is the red LED 1 ,
the third bit the is green LED2, the fourth
bit Is the red LED2, etc. With the call to L_

led_bew(servo_dir_2 , Target) this variable
is continually updated, based on the turn-
ing direction of the servo (servojdirJ) and
if something has been seen (Target). The
interrupt service routine that runs in the
background, continually jumps to the label
Display Jed, Each time in that subroutine the
next four bits of the variable Long_Led are
copied to the correct positions of the eight
bi-colour LEDs.

In the main loop, based on the measurement
of the LDR, a decision is made as to which
direction the servo will turn. If the lowest bit
is a ( T then the servo will turn to the left, if it
is a 'O' then it will turn to the right i nstea d. Al I
this wifi give the appearance that the Firefly-
circuit lives a life of its own.

There is a routine built into the software to
deaf with servo specific tasks. Each type of
servo requires a different amount of time
to turn a specific amount. This is deter-

Proarammina lanauaae

The software for the Firefly is written in BASCOM AVR. This basic-compiler has been especially written for the Atmel AVR series of processors
to which the ATmega 88 also belongs. Programming microcontrollers with BASCOM AVR represents a nice introduction to microcontrollers
and robots. The compiler is well supported, has clear documentation with many examples and the demo version can compile a program
of up to 4K. That's more than enough for many projects, including this one. The registered version has no limits in program size and is fully
supported. In previous issues of Elektor (September 2008 through January 2009. among others) more detail is provided on BASCOM and
you are kindly referred to those pages.

The ATmegaSB is also very suitable for use with a so-called bootloader. That's a piece of software allowing the software to be programmed
without using the ISP cable, but by using the ]R-connection instead. For this purpose you obtain a bootloader from the internet 14 and add
the routine that generates the 3 6-kHz carrier signal. So now you can reprogram the Firefly with a new program using a USB -I R module,
without needing a cable between the Firefly and the computer. Reprogram the Firefly on the fly, so to speak.

elektor 04-2010

59

HOBBY

Figure 2. Take care with the ATmega
fuse bit settings! if you accidentally use
the wrong settings it is possible that the
controller cannot be programmed any
more using ISP.

mined by the subroutine ijkert: This routine
is called when SI is pressed while the Fire-
fly is switched on. At the end of the rou-
tine the values are stored in the EEPROM of
the microcontroller. If you start the Firefly
without pushing then SI the microcontrol-
ler retrieves this information from its FER-
RO IV1. If there are no values stored in the

The prototype may look somewhat
‘unfinished’* but that is why it is called a

prototype.

EEROM then an (erroneous) default value
will be used and the Firefly will not operate
properly.

Programming

With the aid of Bascom AVR and the Sam-
ple Electronics ISP-programmer [2] (easy to
make with the use of a cheap LPT periph-
eral card in the PC and three resistors of
around 300 to 500 O) you can program the
ATmegaSS. The AtmegaSS has been factory
preset to use the built in 8 -MHz oscillator
and the divide-by-8 internal divider for the
dock speed. These settings cause (timing)
problems with the servo controller, so you
have to change a Fuse-bit. The relevant Fuse-
bit is C (see Figure 2). This is by default ena-
bled and in your case it has to be changed to
Disabled. Afterwards the program will run
at 8 MHz instead of the default 1 MHz.

By the way: When you're looking at the
Fuse-bits you will notice that there are many
different settings for all kinds of things. Dif-
ferent clock speeds* internal clock, external
clock, bootloader enable* far too many to
mention. But be careful! If you accidentally
select the bit for external clock* for exam pie,
then the circuit will no longer work and you
will not be able to get it going again with
the ISP programmer. You will then require
a ‘reap programmer capable of pulfing the
reset pin to 1 2 V* which allows the proces-
sor to be brought back to life. Alternatively
you will need to connect an external clock
from another* working processor. All annoy-
ing and a hassle* so take care!

When the software is programmed via the
ISP into the controller* the EEPROM is also
overwritten. Consequently the servo cali-
bration procedure needs to be repeated
every time the ATmega is reprogrammed
via ISP.

Getting started

A printed circuit board was designed for this
project* which is available from the Elektor
Shop as item # 100014-1 . The board con-
tains a few eye-catching features: the ring
of eight bi-colour LEDs* the IR receiver, the
IR transmitter, the connectors for the servo
and the ISP programmer, the two contact
pins for the ping-pong ball bracket and*
of course, the microprocessor. Because

the IR receiver can also sense the IR light
that is transmitted by the IR LED on the
board* you need to make a metal screen of
15x15x15 mm. Any light leaks 1 can be
plugged with correction fluid (like Tipp-ex)
or similar This is easy to use and once it has
dried it blocks all light. Using 1 8 to 20 cm
of spring steel wire (piano wire* 03 mm
diameter), make a bracket to suspend the
ping-pong ball In this ping-pong ball you
melt two small holes to capture the spring
steel wire. At both ends solder a push-on
connector so that the ping-pong ball can
be easily attached and removed. The ball is
mounted directly above the IR LED, so that
it becomes a diffused beacon* visible from
all directions.

The PC8 is attached to the servo. For the
four cells you could use, for example* a 1x4
or 2x2 AAA battery holder. Either can be
attached with a cable tie* Velcro or double-
sided tape to the servo. The optional piezo
transducer may be mounted to the side of
the servo with some double-sided tape.
The servo is attached to a base with its driv-
ing wheel. This base consists of an old 3,5 S1
floppy disk, to emphasize that it is a true
foundation in more ways than one. Drill a 2
to 3 mm hole and screw the disk directly to
the servo wheel. Four rubber furniture felt
pads can help to prevent the floppy disk
from sliding around.

Calibration

Each type and brand of servo is slightly dif-
ferent. As a consequence you have to cali-
brate the servo. This is what the servo cali-
bration program is about. When switch-
ing the Firefly on (with 52), the controller
checks whether 51 is pressed. When SI is
pressed, the servo will turn increasingly
slower When it stops you have to release
SI, Press 51 again. The servo will start to
turn again and slowly reduce its speed until
it reaches standstill. Release SI again. The
first time round is a coarse calibration, the
second* a fine calibration. In this way the
controller has learned' when the servo
stops. Now you have to teach it how fast
the servo turns around. Press 51 again* the
motor will turn again and now release 51
after two full revolutions are completed.
Repeat this once more (the motor will now

6o

04-2010 elektor

HOBBY

COMPONENT LIST

Resistors

R1 .R3.R5.R1 1 = 22 kO
R2.R14,R15,R16,R17-4.7kft
R4 = LDR, e.g. type A906Q, Conrad Electronics
#. 145475
R6 - 470

R7,RS.R9 t R1G,R1 2 - 2200
R13 =470Q

turn the other way} and the controller is able
to calculate the amount of time required for
a 45 degree turn.

Current consumption

The Firefly uses four AAA (LR03) batteries as
its power source because of their versatility.
The eight bbcolour LEDs together with the
IR transmitter, IR transceiver the control-
ler and not forgetting the servo use about
100 mA, The capacity of good alkaline AAA
batteries is typically 900-1150 mAh. This
allows the Firefly to operate for about ten

Capacitors

C1 S C6= IQjiF 16V radial
C2.C3 = 22pF
C4 = 4.7 nF
C5,C7 - lOOnF

Semiconductors

D1 p D2,D3,D4,D5,P6,D7,D8 = bicolour LED.
5mm

D9 = IR LED, 5 mm

T1,T2.T3,T4 = BC547

IC1 - ATmegaSS, programmed

hours on a set of fresh batteries. Recharge-
able AAA cells can also be used, but when
using these make very sure that there are
no short circuits anywhere. With an alkaline
battery the voltage drops quickly when the
cu rrent i s too high, but with a recha rgea ble
batter the voltage remains high, which can
lead to charred, defective components.

Experimenting

The IR communication takes place via the
36-kHz modulation of the RS-232 signal at
2400 baud. This signal can easily be gen-

Miscellaneous

XI = 12MHz quartz crystal
GZ1 = AC buzzer

51 = 5PNO pushbutton, Tyco Electronics type
FSM4]H

52 = SPOT miniature switch. C&Ktype
ET01MD1CBE

K1 = 6-pin (2x3) pmheader

PCB t order # 1 0001 4-1 , see www.elektor.

com/ 1000 14
Servo motor
Ping-Pong ball

erated or detected with, for example, the
US8-IR module that can be obtained from
Conrad Electronics (part number 993137-
89), or an equivalent. With this you can
verify whether the Firefly is transmitting IR
ight and you can also send light, to which
the Firefly will react.

The piezo is not yet used in this program,
but could be utilised, for example, to gener-
ate a certain sound depending on how many
‘counterparts 1 the Firefly has detected.

The resistive divider, comprising two 22-kD

Advermemem

M

D

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Propeller Microcontroller

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with a speech synthesis demonstration written by the Propeller
chip’s inventor, Chip Gracey. Numerous illustrations and example
programs accompany each application. Example source code and
other related resources are available for free download from
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elektor 04-2010

61

HOBBY

Servo modification

A servo operates with an input signal of 1 to 2 ms that is repeated every 20 ms* A signal of 1 ms
means that the servo is rotated completely in one direction, 1 .5 ms means the centre position
and at 2 ms the servo rotates completely to the other direction. Servos normally rotate through
an angle of about 270 degrees, but here we want to it to turn all the way around. We therefore
have to modify the servo.

The modification in principle comprises three things: removing the end-stop so that the me-
chanics can rotate through a full 360 degrees, taking out the potentiometer and replacing it
with two fixed resistors so that the electronics in the servo thinks that the potentiometer is al-
ways in the centre position.

First we disassemble the servo (Photo 1) and with a sharp knife remove the end-stop from the
final gear (Photos 2 and 3). Now we will (partially) remove the potentiometer. There are two
types of potentiometer. With cheaper servos, such as the Hitec-300 that we used here, the shaft
of the potentiometer is the same as the shaft of the final gear in the servo. When we want to
remove the potentiometer we will have a problem with the attachment of the final gear of the
servo. If the servo has a separate bearing for the final gear, then we can simply take out the po-
tentiometer. In the first case we have to modify the potentiometer instead of removing it. Open
the potentiometer (Photo 4) and remove the wiper and that part that rotates inside the poten-
tiometer and hits against the internal ridge with a small drill and a hobby knife (Photo 5), You
don’t need the ‘lid* of the potentiometer (with the carbon track)* so leave that out.

In place of the potentiometer you need to connect two resistors on the servo PCB, First check
the resistance value of the potentiometer (usually 5k H) and take two resistors that together
also have about this same value. Two resistors of 2.2kO or 2,7kn each are suitable in our case.
Connect them to the servo PCB instead of the potentiometer (Photo 6). Make sure that you
connect the resistors in such a way that it appears to the electronics that a potentiometer is
connected and that it is always in the centre position.

Before putting the servo back together, check that that all the parts of the servo are able to ro-
tate around completely. Now you're ready to reassemble the servo (Photo 7) and check once
more that the servo can rotate 360 degrees. The servo is now ready for use.

resistors, is not yet used either. At the node
between these two resistors you should
be able to measure half the power supply
voltage, with a resolution of 1 0 bits (1 024
steps from 0 to 5 volts). You could use this
to measure the condition of the batteries
quite accurately. In theory, the operation
of the servo changes when the battery volt-
age decreases. This changing characteris-
tic could be compensated for, based on the
measured voltage.

The Firefly circuits are all identical. They all
send the same message and all look for the
same information. Whenever ‘something 5
arrives, they recognise that and respond
to it. They could also each have their own
identity or number. In this case each Fire-
fly transmits a different message. The pro-
gram could then be adapted so the Fireflies
will recognise only certain counterparts
before reacting. You are free to experiment
with this circuit and there is no maximum

number of Fireflies that can communicate
with each other. The more the merrier...

(100014-I)

Internet Links

m www.elektor.com/ 100014

(2] http://8051 help.mcseiec.com/index.htm
l7sampleeiectronicslspprogramnier.htm

(3) http://mcselec.com

62

04-2010 elektor

DISTANCE LEARNING COURSE /

| Programming Embedded
PIC Microcontrollers

using Assembly, C and Flowcode

In this course you will learn how to program an embedded
microcontroller. We will start with the absolute basics
and we will go into a lot of detail. You cannot learn about
software without understanding the hardware so we will
also take a close look at the components and schematics.

Special Introductory price

for Elektor subscribers

£40 1 $70 1 €50 DISCOUNT

'l.eiektor.conrldisunceiearnn^

At the end of the course you will be able to design your own
embedded applications and write the appropriate

Contents:

Background
Digital Ports
Serial Communication
(RS232)

Analog Signals
Pulse Width Modulation
Timers/ Counters/lntermpts
Memory
LCD Display
PC Communication
SP1 Communication
USB Communication
Configuration (Fuses)
Answers to the assignments
Appendix

{800 pages)

* CD-ROM including software
and example files

■ Application Board

■ Support at Elektor Forum

• Elektor Certificate

Price: £395.00 / S645.00 / €445.00

Please note: to be able to follow this course, £- blocks
hardware is required which you may already have
fin part). All relevant products are available
individually but also as a set at a discounted price.
Please chec k www.ef ektor.com fd I stan c elearninq
for f urth er i nform ation .

software for it.

Your course package:

* Courseware Ring Binder

ACADEMY

the school of electronics

READERS CIRCUITS

Burn or Turn?

1 * 1 * I _ _

By G, van Zeijts (The Netherlands}

Has your hard drive crashed? Don’t throw it away! You can still use it in many interesting projects. As an
example, the author has used the read/write arm to make an alternative motor that is controlled via the PC.

No doubt some readers wilt have experienced this at some time: the
hard drive in the PC has given up the ghost. This is very irritating,
and even more so when you haven't made a backup of your data.
The silver lining of this cloud is that inside every hard drive is an
interesting part, which well make use of in this article. The online
encyclopaedia Wikipedia refers to this part as an actuator ! 1 c
The actuator moves the read /write arm of the hard drive, on which
the magnetic read and write heads are mounted, to the correct
position. The actuator is controlled via a clever bit of electronics,
which is found inside every hard drive. The actuator itself is nothing
more than a coil inside a very strong magnetic field.

The nice thing is that the arm has quite a long throw and is com-
paratively powerful. This article should motivate the real do-it-your-
selfers amongst us to start experimenting with these actuators, it
shouldn't be the end of the world If you don’t have a broken hard
drive to hand. Since a fair number of hard drives crash you’ll find
that every computer repair shop will have a few in their bin. if you
ask nicely you may even get them free of charge.

Actuator

What exactly does one of these actuators look like? Once you’ve
removed the cover and electronics from the old hard drive you’re

Figure 1 , It makes it easier if we remove part
of the aluminium plate (left) and connect the actuator coil to a

terminal block (right).

left with an aluminium plate with two motors: one to rotate the
platters and one to position the read/write arm. The latter is the
actuator that we Ye after.

To ma ke it easier to work with, we ft rst remove some of the alumin-
ium plate so that Just the actuator remains (see Figure 1 ). Be careful
that you don’t cut through any of the steel parts, since the steel fil-
ings will immediately fly to the magnets. They'll be very difficult to
remove again, since those magnets are really powerful!

At the end of the actuator arm are the read/write heads, but we
have no use for these here. The interesting part for us is the coil that
turns between the magnets. The two connections for this coil are
made with two very thin wires that usually go to a multi-pole con-
nector, We have to find these two connections and provide them
with a separate connector. One possibility is to use a terminal block,
as can be seen on the right in Figure 1 .

The resistance of the coil is usually somewhere between B and
1 2 ohms, which makes it perfect for use with a 5 volt supply. The
motor will obviously provide more power if you put 1 2 volt across
it, but this can only be done for short periods! Otherwise the coil
turns into a smalt heater (with a very limited lifespan)! Reversing the
+ and - causes the actuator to provide a force in the opposite direc-

Figure 2 . The metal plate that moves through
the two photo interrupters tells the PC what the position of the

crankshaft is.

64

04-2010 elektor

READERS CIRCUITS

Figure 3. The outputs of the photointerrupters are connected to

the parallel port of the PC,

Figure 4. Three outputs from the parallel port (and a ground
connection) are required to drive the HD1 motor

tion. When a computer is used to control the actuator any real DIYer
should be able to come up with various ideas to try out

What can I do with it?

An actuator normally doesn’t get much attention, but it should be
ideal to drive ‘something’, considering the relatively large force it
can provide. As an example, you should be able to make a rotat-
ing motor, which works using the same principle as that used in a
car engine. The back and forth motion of the actuator is converted
into a rotary motion by the crankshaft. Since an actuator is used as
the driving element, our project was given a suitable name; the HD
motor, (Hard Disc motor)

In this article we look at two types:

* a single-cylinder motor, driven by 1 actuator (the HD1 motor)

* a four-cylinder motor, driven by four actuators (the HD4 motor)

*

Since the HDI motor is more interesting as far as the control is con-
cerned well look at this in more detail.

The HDi motor

The arm of the actuator has to be connected to a crankshaft. For this
a read/write head from a broken video recorder was used. This part
has very smoothly running bearings and it even has a small flywheel,
which reduces the shocks in the rotating movement.

The actuator is capable of pushing or pulling, depending on the
polarity of the supply voltage applied to the coil. Since there is often
a need to reverse the rotation of DC motors in various devices, ded-
icated ICs have been developed for this purpose. This 1C also has
a function built in for the control of the speed of the motor. The
paragraph on The driver chip' explains the workings of this 3C in
more detail.

In order to determine when the actuator has to push or peril, a
piece of metal has been mounted on the crankshaft, which rotates
through two photo interrupters (see Figure 2), From these the com-
puter can determine the position of the crankshaft and hence out-
put the correct signal for the actuator to push or pull. The speed of
the HDI motor can be controlled via the computer (see the para-
graph The driver chip’). To see if the actuator is pushing or pull-
ing, a red and green LED have been connected in parallel with the
actuator.

Connections to the PC

The connections from the photointerrupters to the computer are
shown in the circuit in Figure 3. All connections are made via the
parallel port. Two inputs are used: one to indicate that the crank-
shaft is in the left position and one for when It Is on the right. The
type of photo! nterr it pter used Isn't important, just about anything
should be suitable, A photointerrupter from an old printeroroutof
a mouse can easily be used here, for example.

Three outputs from the parallel port are used to drive the actuator.
One to make the actuator push , one to make it pull and the last one
is for speed control (enable) (see Figure 4).

The driver chip

The driver chip for controlling the actuator sits between the paral-
lel port and the motor. For this we've chosen an 1C with the part
number TPIC0298 (other numbers such as TLP298 or L298IM are also
used for this 1C). This is a so-called Dual full H-Driver', obtainable
from various sources. Further details on H-Drivers (also called an H-
Brldge) can be found on the Internet, for example on izJ and hi. This
3C was originally designed to control a bi-directional step per- motor,
but it can also be used to drive two DC motors independently and
make them turn in either direction.

The circuit «n Figure 4 shows the !C and the connections between

elektor 04-2010

65

READERS CIRCUITS

Figure 5. The completed HD1 motor.

Admittedly, it’s a sizeable circuit. These days it could be made
much smaller, but this way is more fun.

Figure 6. A Tour-cylinder' version is constructed as a radial engine.

the HD-motor and the computer To drive the HD motor we use only
half of the 1C. Inside the 1C are four electronic switches that are con-
trolled by the logic AND gates in such a way that the actuator pulls
in one state (pin 2 high and pin 3 low) and pushes in the other state
(pin 2 low and pin 3 high).

One computer output is connected to the Enable input of the 1C
and is used to control the speed of the HD motor using PWM (Pulse
Width Modulation). The PWM works in both directions of the actua-
tor and provides a smooth speed control. Four protection diodes
have been added to the circuit to prevent damage to the 1C from
back EM F surges.

Software

The program that drives the motor is written in Visual Basic under
Windows XP and can be freely downloaded from the web page for
this project under number 090120-1 1 .

The program is quite simple and provides the following functions:

* Determine the position of the crankshaft and control the actua-
tor accordingly: “push 1 or ‘pull’

* Select clockwise or counter clockwise rotation

* Control the speed using PWM

* Measure and display the revs in rpm.

* Where necessary, the program includes comments and it can of
course be written in any computer language. It can however be
possible that Windows throws a spanner in the works:

* With Windows Vista Microsoft only permits you to access the
USB ports; the program can therefore not be used under Vista

* With Windows XP it is still possible to access the parallel port
directly (using the dll 'inpout32.dll')

* With Windows 98, 95 and older you can still play to your heart's
content with all ports (parallel, serial, game and sound, using
the dll ‘ports.dlT).

The program available for download will therefore work under Win-
dows versions up to XP, but not under Vista of Windows 7!

The results

The completed HD1 motor (Figure 5) turns at a maximum rate of
about 1 000 rpm using a 5 volt supply and about 1 800 rpm using
1 2 volt. As already mentioned, the latter should only be tried for

very short periods of time. Otherwise the coil will heat up rapidly
due to the current that flows through it. The lowest speed at which
the HD1 motor can run is about 200 rpm.

As an aside: the efficiency of the complete system surrounding the
HD1 motor is about 1%..., considering

* estimated power consumption of the PC: 200 W,
actuator: 12 W.

• estimated mechanical power output: 2 W

More cylinders?

If you feel that a single cylinder is a bit frugal, by ail means add
some morel Once the single cylinder motor worked well the author
thought that it should also be possible to build 4, 6 or 8 cylinder ver-
sions. It ended up as a four-cylinder version, which was christened
the HD4.

Since it is very complicated to make a crankshaft for a four-cylinder
motor the actuators have been placed in such a way that we end
up with a radial motor (see Figure 6 and ^ ! ), The four cylinders in
a radial motor all drive the crankshaft on the same plane. They Ve
been mounted on a square so they each take care of 90 degrees.
This made it possible to mount everything on a single flat wooden
board, as can be seen from the photo.

To determine the position of the crankshaft four photointerrupters
have been added. From these the computer can determine which actu-
ator should be turned on. One thing that differs from the H D 1 motor is
that the actuators are no longer driven by an (expensive) 1C Instead, a
simple Darlington transistor is used per actuator. Because of this, each
actuator can no longer push but only pull. However the four-cylinder
motor can still rotate either clockwise or counter clockwise.

(090120)

Internet Links

[1 j http://en.wikipedia.org/wiki/Actuator
[2 ] http://en . wikiped ia.org/wiki/ H-bridge
[ 3 1 www.discovercircult5.com/ H/hbridge.htm
1 4 j h ftp : // www. el ektor. co m / 09 0 1 2 0
1 5] http: / /en.wikipedia .org/wl kl /Radtal_engine

66

04-2010 el ektor

ACCESS SYSTEMS

Beep, beep... Sesame

A musical electronic lock

By Bernard Chabbert (France)

A motorised gate is jolly useful, just so long as you don't forget
the remote control or the key. Normally, the control system forthis
type of gate makes provision to connect a push-button for opening or
closing it without needing a remote control or key. This button must not be

accessible from outside, whence the need for a more complex system. The code lock suggested here lets
you control up to three such gates using push-buttons after entering a valid secret code

Tec

hnical

* m *

* digital keypad with sound effects

* four codes with up to 15 digits

* three individually-driven floating
contact outputs

* plays the March of the French Foreig n
Legion

* PIC16FS4 microcontroller
- no critical components

There's a digital keypad for entering the
secret code* The device can store up to four
different codes, each with a maximum of
1 5 digits, since each member of the fam-

ily wifi find it easier to remember a code
they've chosen themselves than one that’s
imposed upon them* The holder of code #1
is the only person who can modify all four
codes*

For the security of the system, it's going to
be constructed in two parts, since if every-
thing is in a single external unit, all you'd
need to do to open the gate would be to
break open the case and short a contact.
So the external part will only contain the
keypad and a little speaker to give a sound
when you press a key. Of course, this part
will have to be protected from the rain, with
a little roof or a door* The electronic part will
be Installed somewhere inaccessible from
outside — inside the house, for example*

There is a beep every time you press a key t
regardless of whether it's the right one or
not. If you make a mistake, there is nothing
to tell you th is until you get to the end of the
code. The code (which mustn't start with an
*} must end with a #, Then you choose the
function: operate one of the three relays, or
go into administration mode (see Table 1).
When an incorrect code is entered, it counts
as an error* After four errors, the keypad
stops working for two minutes* There is
another security feature: there must be less
than two seconds between keystrokes, oth-
erwise the current procedure Es abandoned*
The end or abandon of a procedure is indi-
cated by three high-pitched beeps*

If a code is forgotten, only the adminlstra-

elcktor 04-2010

67

ACCESS SYSTEMS

+5V

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Figure 1 . A musical electronic lock doesn't need many components if the microcontroller is

powerful enough.

tor can enter a fresh code. If the administra-
tor’s code ever gets lost — a situation to be
avoided, naturally — there’s a special proce-
dure, which involves opening up the elec-
tronics unit.

Circuit

The circuit of the project {Figure 1} is
remarkably simple: there’s no keyboard

decoder, no debounce circuit. The PIC16F84
microcontroller takes care of all that. None
of the components is critical. The RC oscil-
lator formed by PI and C5 is set to around
1 MHz, which means 250,000 instructions
per second. RBI to 3 output a voltage to
scan the keypad in a matrix of three col-
umns and four rows. This voltage is input
to RB4 to 7, For example, if we press the 5

key, RB5 receives a pulse. Touching any key
wakes up the microcontroller, which is nor-
mally in standby. In this standby condition,
the oscillator is stopped and the power con-
sumption is practically zero.

Following entry of a valid code, key 1 oper-
ates RE1 for 2 s via output RBQ, key 2 oper-
ates RE2 via output RA3, and key 3 operates
RE3 via output RA2, R8, and T2. This output
is designed for a low- voltage electric strike,
powered from its own transformer.

RAO and RA1 output the beeps. This device
produces a kind of ‘twang’ (a bit like a
plucked string), which is kinder on the ear
than the usual basic ‘beep’. Before giving
the l twang\ capacitor C6 is charged for
80 ms via RAO (via R7.T1 t and R6). RA1 then
drives the speaker (via R9 and T3) for an
80 ms beep. If you prefer the basic beep, all
you have to do is omit R7, T1 , and C6, and
connect the speaker directly to R6, instead
oftoTI collector.

RA4 is used for the special procedure in the
event of losing the administratorcode (code
#1 ): fit a jumper to K4 and press * and # at
the same time, then remove the jumper.
Turn off the power when fitting and remov-
ing the jumper. Code #1 Is now just #, like
the very first time you use it after program-
ming the microcontroller.

March of the
French Foreign Legion

The program generates four beeps at dif-
ferent pitches that can follow each other
at intervals of 80 ms. If the oscillator Is
adjusted correctly, these will be the four
notes G rt (784 Hz) C 6 ( 1 047 Hz) , E, ( 1 3 1 9 Hz),
and C (1568 Hz). These are the same four
notes a bugle makes, and are all you need to
play the bugfe part of a military march. So
why not do just that? We’ve included this in
the program, since there was some room to
spare in the program memory, tf you press
7 after entering a code, the speaker plays
the ‘March of the French Foreign Legion 1
for about a minute. This can be used to
set the oscillator using an oscilloscope,
for those who have one. Set PI to obtain
a 250 kHz squarewave on test point PCI
while the tune’s playing. Without a scope,
the oscillator can be set by comparing the

Tablet.

After entering a valid code followed by #, eight functions are possible: To activate a relay,
enter a code, then #, then 1 , 2, 3, or 8. This table summarises all the functions available.

Function

Description

1

Activate relay RET for 2 s

2

Activate relay RE2 for 2 s

3

Activate relay RET for 2 s

4

Modify one of the four codes:

enter code 1 without pausing for snore than 2 s, then # 4, then the new code,
then # followed by the number of the code (1-4).

The new code is only stored if the procedure is completed without errors, and
you’li hear beeps if it has worked correctly.

5

Disable beeps

6

Enable beeps

7

Set oscillator frequency

S

Activate relay RET for 5 s

68

04-2010 eiektor

ACCESS SYSTEMS

COMPONENT LIST

Resistors

Rl “ 22kQ
R2-R5 = 10kQ
R6 = 56S2
R7 - 3.3ka
R8, R9 = 2.2ka

Capacitors

Cl = 470juF25V, radial
C2 = 2 2 li F 1 6 V, radial
C3, C4 = IQQnF
C5 = TOOpF

C6 - 330pF 16 V. radial

Semiconductors

61 = W06M bridge rectifier,
800mA
D1 = 1N40Q1
D2 .03,04 - 1 M4148
IC1 =7805

IC2 = PICT 6F84-4/P, pro-
grammed, Elektor #

Figure 2, How to wire up the PCB.

beeps with a tuning fork or a musical instru-
ment playing C, or just so the tune sounds
nice, neither too fast nor too slow. With-
out the music playing, the microcontroller
is in standby, the oscillator is stopped, and
there's nothing to see on the scope.

The beeps can be disabled by pressing 5
after entering a valid code, or enabled by
pressing 6, The beeps are enabled by default
when power is applied.

Powering

No provision has been made for a trans-
former. There are plenty of them availa-
ble commercially or in second-hand shops
(plug -top power adaptor, which obviates
introducing 230 V mains into your project),
just so long as they provide a round 1 2 volts
and 1 50 mA , either AC (bridge rectifier
B1 will take care of rectifying It) or DC (B1
means you don't have to worry about the
connection polarity).

Relay #3

The contacts of the little 8-pin DEL relays RET
and RE2 (0.2 A) are not intended for the cur-
rent needed to operate an electric strike for
a door, which often requires 2 A @ 1 5 V AC
This needs a heavier-duty relay, RE3, which
Is a 1 2 V relay powered from 1 2-1 5 V (V+
tapped off before the regulator 1C 1). As the
microcontroller can t drive this sort of relay
directly, it is operated via T2.

Warning: under no circumstances is this cir-
cuit a ble to supply the power for an electric
strike! The contacts of RE3 are simply used
to feed the electric strike from the power
provided by Its own transformer. If you're
not using an electric strike, you can omit R8,
D1, REB.and T2.

Software

The program is written in Microchip PIC
assembler language. It’s not very difficult,
as there are only 35 possible instructions.
But the program does use over 600 of them,
with copious comments. It's assembled
using MPASMWIN (included with MPLAB
1 >) which converts it to a hex file that can be
loaded directly into the PIC using a suitable
program and a programming device. The
PCB doesn't make any provision for in-situ
programming (ICSP).

081143-41
T1 ,T3 = BC337
T2 = BC547

Miscellaneous

PI = 10kn horizontal multiturn trimpot
RE1 ,RE2 - 5V SPNO relay, 500£2 coil, Meder
type D1P05-1 A72-12D
RE3 = 12V DPDT relay. Tyco type
V23057-B002-A201

K1,K2,K3,K6 = 2-pin PCB screw terminal

You can download the source program. Its
flow diagram, and the hex file free from l 2 l

Construction and testing

You shouldn’t encounter any difficulties
building this project (Figure 2). Relays RE1
and RE2 look symmetrical but in reality they
aren't, due to the integrated diode: for RE3,
follow the holes on the PCB, Where there
are no holes, you'll need to cut off the pins
that aren't required. Take care to get the
microcontroller the right way round, as a
wrongly-fitted PIC will be ruined for good!
Connect up the keypad and speaker using a
10-core cable (including one forthe ground
link). This may not be used If the case is plas-
tic, but it must be there — it Is connected
to the negative power rail and to the cable
screen.

Once you have finished construction and
wiring up. apply power to the circuit. You'll
hear three high-pitched beeps to tell you
that the system is initialising. If you don't
hear them, the circuit isn't working prop-
erly! Turn off the power at once and investi-
gate the cause.

If you did hear the three beeps, press the
key sequence # 1, Each press is followed

block, lead pitch 0.2 inch (5,08 mm)
l<4 - 2-pin pinheader, lead pitch 0,1 inch
(2.54 mm), with jumper
K5 = 1 0-pin pinheader, 1 0 contacts, lead
pitch 0.1 inch (2.54 mm)

Loudspeaker, 50H impedance
Numerical keypad, 4x3
PCB, order code 08 1 1 43-1 , see Elektor S hop
section or www.elektor.com / OS 1 1 43

by a beep and relay RE1 is activated for 2 s
(easy enough to check with an ohmmeter}.
You’ll also hear a beep indicating a correct
code, a little 5-beep jingle that indicates the
process has ended correctly, and! to end, the
three high-pitched beeps that indicate the
initialization of the microcontroller, after
which it goes Into standby.

Next, try out all the procedures in Table 1
before your final installation.

Go on, have fun, you’ve earned it — press
#7.

Don’t forget to store at least secret code

# 1 ,

(081143)

internet Links

[il www. microchi p.com / mpla b

[2] www.elektor.com/QSn43

[3 1 http:/ / pagesperso-orange.fr/

Bernard. chabbert /

elektor 04-2010

69

POWER SUPPLIES

By Daniei Goss (Germany)

These days many components and microcontrollers are designed for low-voltage operation and can be
powered directly from a battery. For various reasons, however, it is often necessary to power them from
35V supply. Designing a high-efficiency supply is time-consuming, and so he we present a universal
solution in the form of our 5 V power controller.

Features

- Input voltage range 2 V to 8 V {for example from two AA cells or two lithium-ion or lithium-
polymer cells)

* Power 35V circuit drawing up to 150 mA using two AA cells

* Especially designed for 5 V microcontroller circuits

* Efficiency: 75 % at 2 V and >76 % from 3 V to 8 V input voltage

* Standard, readily available components

- All connections on 2.54 mm pitch headers

■ Soft-off function under processor control

■ Power on button can also be used as general input button

* Low current consumption in soft-off standby

if a circuit can run on a wide range of power
supply voltages it is easy to power it directly
from a (rechargeable) battery. However, if
we want to use components like LCD panels
or sensors, it is often the case that a tight-
tolerance supply is required. Many micro-
controller application circuits still use a 5 V
supply, and so there is a clear need for this
versatile supply, capable of producing a
stable 5 V at its output with an input volt-
age anywhere from 2 V to 8 V.

This means that the circuit can be pow-
ered from two AA cells (2 V to 2 *4 V). two
lithium-ion or lithium-polymer cells (about
7*2 V), or anything in between. The maxi-
mum output current of 1 50 mA should be

enough for most battery-operated circuits.
Logic level control inputs allow the circuit to
be started up, as well as to enter and exit a
standby mode.

The Idea

In view of its voltage range and easy avail-
ability we selected the Linear Technology
LT13Q2, normally used as a boost-type
switching converter. Here, however, we use
it in a SEPIC (single-ended primary inductor
converter) topology [1 1, effectively turning
the device into a buck-boost converter |2J ,
This gives a wider input voltage range, as
the converter operates in either step-up
mode (with an input voltage below 5 V)
or step-down mode {with an Input volt-

age above 5 V) as appropriate. As a bonus
we also get DC isolation between input and
output when the circuit is disabled.

The circuit (Figure 1) is constructed on a
small printed circuit board using surface-
mount components (Figure 2). The pins
on the board are on a 2.54 mm pitch (Fig-
ure 3) and so it can easily be mounted on
prototyping board for experimentation. The
battery is connected at K1 , and the output
is present on K3. K2 is a test jumper. The
minimum allowable input voitage of 2 V at
K1 means that in practice two AA cells can
be discharged to 1 V each before the circuit
fails to operate.

Pin 1 on K3 carries the regulated 5 V out-
put* The other pins are BattSense, PowerOn,
PowerHold and ground, BattSense allows a
microcontroller with an analogue-to-digital
converter to monitor the battery voltage,
The other pins function as follows.

If PowerOn is taken to ground the switching
converter starts up and delivers 5 V at the
output. The microcontroller can now take
PowerHold to 5 V to keep the converter run-
ning, if PowerOn is now released the circuit
will continue to run as T1 remains turned on.
The microcontroller can power itself down
by taking PowerHold low* We will look at
how to connect the circuit to a microcon-
troller, as well as other applications, in the
last part of this article*

7 t>

04-2010 clektor

POWER SUPPLIES

Figure 1 . Circuit diagram of the 5 V power controller using the Linear Technology LT 1302.

Function

Figure 4 shows a block diagram of the
LT1 302, which is essential to understanding
how the circuit works. Readers who would
like to analyse the circuit in more detail are
recommended to look at the free LTSplce i ]?
simulation program.

The free download accompanying this arti-
cle |4i includes a few illustrative oscilloscope
traces from the simulator.,

COMPONENT LIST

Resistors

(all SMD 0805, 1%)

R1,R2.R4 = 10kO
R3 - ion (see text)

R5 = 100kn
R6 = 560kQ
R7 = 680kfi

Capacitors

Cl ,C6,C7 = 100pF 25V SMD(e,g. Fame!! #
1735335)

C2.C8 = 1 0OnF 100V SMD (e.g. Reichett.de #
SMD-1 81 2 100N, see text)

C3 = 1 liF 25V SMD tantalum 0805 {e.g. Farnell
#1135280)

C4 = 1 0nF 1 00V SMD (e.g. Reichelt.de # SMD-
1812 10N, see text)

C5 = 220pF 35V SMD (e.g. Farnell #9695877)

In boost mode (step-up) operation a boost
cycle starts with the switching transistor
integrated into !C1 (Q4 in Figure 2) conduct-
ing to ground, causing a current to flow in
LI . C5 then discharges via L2, and the cur-
rent in L2 increases. Figure 5 shows the cur-
rent flows in LI and L2 when the transistor
is conducting. The currents are in opposite
directions but of approximately the same
magnitude. Now IC1 turns the transistor off,
C5 is no longer con nected to g round via Q4,

Inductors

LI .12 « 33mH, 2A, 0. 1 2Q SMD (e.g. Farnell #

} 6 1 2699, Reichelt.de # L-PISM 33u)

L3 = 27juH, 0.8A T 0,260, SMD (e.g. Farnell #

\ 539570)

Semiconductors

(all SMD)

D1 ,D2 - GAT 54$ (SOT-23. STM i c roe lectron its)

D3 = MBR5340 (SMC, ON Semiconductor)

T1 = BSS138N (SOT-23. Infineon)

!C1 =111302(50 -8, Linear Technology)

Miscellaneous

K1JC2 * 2-pin pin header

K3 = 5-pin pinheader

PCB #090719, see Elektoi Shopoj www.ele-
ktor.com/0907T9

PCB artwork download from www.elektor,
com/0907 1 9

but to the input supply voltage further offset
by the back e.m.f. of LI . L2 also tries to main-
tain its current flow. In conjunction with C5,
this causes a positive voltage to appear on
D3 that is greater than the supply voltage to
1C1 (which is the input voltage to the circuit).
Figure 6 shows the current flows when the
transistor is not conducting.

C5 and L2 thus together charge reservoir
capacitor C6, This continues for around

Figure 2, The printed circuit board
is entirely populated with surface-
mount devices. Because of the high
temperatures used in reflow soldering
with lead-free solder C2. C4, C8 and
the headers are fitted manually.

elektor 04-2010

71

POWER SUPPLIES

Lab Notes

By Ton Giesberts

Here in the Elektor labs we made a few minor changes to the aut
hor s original circuit Resistor R1 and dual diode D1 were added to
protect the gate of T1 , and we felt that it would be a good idea to
use pins on the board with a 0.1 -inch pitch to make it easier to use
the circuit in prototypes. The fixing holes are noton this grid to allow
the hoard to be slightly smaller. In any case, if the board is plugged
or soldered into a prototyping board no fixing screws will be needed.

from 3.5 V to 6,5 V. At higher input voltages the efficiency gradually
falls off to 76,2 % at 8 V.

The main advantage of the buck-boost principle is the wide range of
acceptable input voltages. The disadvantage is the lower efficiency
compared to the standard configuration of the LT ] 302 as a pure
boost mode converter, where a maxim urn efficiency of 87 % can be
achieved with a 3 V input and a 5 V output.

Three of the surface-mount
components are 1 8 1 2-outline
film capacitors. These are MKT-
type devices with a low equi-
valent series resistance (ESR)
and better dielectric properties
than, for example, 0805-outline
ceramic capacitors, However,
it is doubtful whether the film
capacitors can withstand reflow
soldering with lead-free solder
paste: Wima's 1812 film capaci-
tors are rated up to 2 20 °C T and
the datasheet gives 21 0 Q C as
the maximum temperature for the core of the capacitor. The melting
point of polyester is around 245 °C

For our prototype we soldered all the components except for the
headers and capacitors C2, C4 and C8 in the Elektor SMD oven using
lead-free solder, with the temperature reaching 260 °C C2. C4. CS
and the headers were soldered by hand.

We measured the efficiency of the circuit with an output current of a
little over 150 mA. using a 33 ft load resistor and fitting the test jum-
per at K2. The efficiency depends on the input voltage, from a mini-
mum of 74.8 % at 2 V to a maximum of nearly 77 % at input voltages

The LT1 302 data sheet suggests
that for input voltages over 5 V
it is worth adding extra decou-
pling on the 1C f s power supply
consisting of a 10 ft resistor (mi-
nimum 2 ft) and a 1 pF tantalum
capacitor. For our experiments
we used a 0 ft resistor for R3 and
a 100 nF 0805-outline capaci-
tor for C3. At input voltages in
the 2 V range the voltage drop
across R3 can mean that the
supply voltage to the LT 1 302
falls too low. If, for example, the
circuit is powered from two A A cells, R3 can be bridged and a tanta-
lum electrolytic used for C3,

When the SHDN signal is low the quiescent current varies from
around 0,4 mA to 1 mA with input voltages from 2 V to 8 V. The 1C
itself draws just 0.2 mA t and the rest is down to the current through
pull-up resistor R2 when SHDN is low. The minimum shutdown
voltage is 1 .8 V and the minimum bias current for the pin is 20 pA,
and for this reason a value of 10 kft was chosen for R2. In practice a
rather higher value will work perfectly well, which will improve the
efficiency of the circuit at higher input voltages. When II is off (gate
taken to ground) the circuit draws just 10 pA.

4.5 us, at which point IC1 turns Q4 on again.
C5 Is discharged again via 12 and a current
again begins to flow in LI . This alternating
pattern continues until the voltage on FB
(pin 4 of IC1 ) reaches 1 .245 V. When this
happens, the LT1 302 switches off its inter-
na! 220 kHz oscillator. Since current can
no longer flow into C5, the output voltage
starts to fall. When the voltage on FB falls
below 1 ,24 V the oscillator starts up again.
After four cycles or so the threshold volt-
age is again reached and the oscillator stops
once more.

In buck mode (step-down) operation, at
higher input voltages, one switching cycle

is typically enough to bring the voltage on
FB over the 1 .245 V threshold, and so the
oscillator stops immediately. As the input is
isolated from the output via C5, no further
current can flow and the output voltage
starts to fall. As soon as the voltage on FB
falls below 1 .24 V another cycle starts.

As a result of the way the converter works,
the output voltage has rather a lot of ripple.
To smooth out this ripple, C6 is followed by
a filter comprising 13, C7 and C8, To ensure
accurate regulation, the voltage divider
used to generate the voltage on FB (R5, R6
and R7) is rather complex, R6 is responsible
For 55 % of the feedback voltage and ensures

a rapid response, while R7 helps compen-
sate for the voltage drop across 13,

A low level on the shutdown input (SHDN,
pin 3) activates the LT1302; if the pin is
pulled high (via R2) the device will remain
in a standby state, T1 pulls SHDN low if
the connected microcontroller drives its
input high.

R3 and C3 together provide a supply to the
LT 1 302 relatively free of voltage variation
and spikes.

Use with a microcontroller

The example circuit in Figure 7 shows how
the circuit can be connected to an ATtiny24

7 Z

04-2010 elektor

POWER SUPPLIES

SfNSS V* SW

Figure 4. Block diagram of the LT1302.

Q4 switches the current through external inductors.

Figure 3, The headers are on a 2.54 mm (.1
inch) pitch and so the board can easily be
mounted on an ordinary prototyping board.

microcontroller. The PowerOn and Power-
Hold pins on K3 of the 5 V power controller
board are connected to the microcontroller.

It is important not to leave Power Hold open
circuit, as then II will not turn completely
off and the overall current consumption of

the circuit will increase unnecessarily.
Pushbutton SI can be read by the micro-
controller as an ordinary input, using R1 as

ms AVR 8' Bit Main PCB Board.',

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elektor 04-2010

73

POWER SUPPLIES

Figure 5, The pattern of current flow in LI Figure 6, Pattern of current flow when the
and 12 when the transistor is conducting. transistor is not conducting.

*sv

FOwwOrt

PtjtWHlrfff

Figure 7. Example connection to a
microcontroller.

a pull-up resistor, Schottky diode D2 in the
power supply circuit isolates it from the
pull-up, and so the button can be used as
a 'power on’ button for the supply. When
the button is pressed the supply starts
up and delivers 5 V to the microcontrol-
ler. The microcontroller starts running its
program, which can then take Power No Id
high, FET T1 in the supply circuit now con-
ducts and keeps the circuit active even if
the button is released. The microcontrol-
ler can subsequently switch off the power
supply, for example after the user selects
a certain menu item or after a certain
period of inactivity, by taking PowerHold
low. The whole circuit, including R1 and
hence also the PowerHold signal, goes to
ground potential, T1 turns off fully, and
the current consumption of the power
supply circuit drops to less than 20 jiA,
The circuit can of course be used just to
power individual parts of a larger circuit.
In this case again the PowerHold signal is

driven by the microcontroller in order to
enable and disable the 5 V supply.

Since the microcontrollerwill not be able to
drive the PowerHold signal high while it is
being programmed, we have provided an
option to enable the supply permanently
by fitting a jumper to K2, This allows for
programming, debugging and testing of
the system, including the supply itself,
without needing to make any software
modifications.

if the BattSense pin is to be connected to
an analogue-to-digital converter in the
microcontroller, the input used should be
as high impedance as possible. This pin is
never isolated from the battery, even in
standby mode, and this means that atten-
tion must be paid to the current flowing
through the voltage divider. Since the volt-
age is present when the supply is off, it can
be used to power a wake-up circuit or as
a back-up supply to retain memory con-

tents, although it is important to note that
the voltage is neither regulated nor filtered.
To make an accurate measurement of bat-
tery voltage, a 100 nF smoothing capacitor
can be added to the voltage divider: this will
buffer the divider from glitches arising from
the sample-and-hold capacitor at the input
to the analogue-to-digital converter, allow-
ing higher resistancesto be used in the volt-
age divider. Observe also that the battery
voltage will be present on the microcon-
troller input even if the rest of the circuit is
unpowered. Normally this will not cause any
difficulty because of the high impedance of
the voltage divider.

( 090719 )

About the author

Daniel Goss is a qualified information technology and systems inte-
gration specialist. He works as an IT consultant designing technical
and security solutions with the largest IT services supplier in Ger-
many. In his spare time he designs electronic circuits, mostly based
around AVR microcontrollers, and writes Windows programs in C++
and in C#.

E-mail address: flashback@flashsystems.de

Home page with software and more projects: http://www.flas hsys-
tems.de {in German}

Internet Links

1 1 j http://en.wikipedia.org/wikl/SEPIC_converter
(description of the SEPIC principle)

\ 2 ] www.maxim-k.com/app-notes/index.mvp/id/ 1 05 1
(application note)

[3] www.linear.com/designtools/software/

(free download of LTSpice)

[41 www.elektor.com/09071 9

(project pages with Free downloads)

74

04-2010 elektor

DESIGN TIPS

A voltage booster using Arduino

By Clemens Valens (Eiektor France Editorial)

If your project needs a higher voltage rail than is already available
in the circuit, you can use an off-the-shelf step-up device. But when
you want a variable output voltage, it's less easy to find a ready-
made 1C. However, it's not complicated to build such a circuit your-
self, especially if you have a microcontroller board that’s as easy to
program as the Arduino. And this also lets you experiment with the
circuit so you can get a better understanding of how it works.

No surprises in the circuit— a largely conventional boost convertor. The
MOSFET is driven by a pulse width modulated (PWM) signal from the
uC„ and the output voltage is measured by one of the pCs analogue
inputs. The driver adjusts the PWM signal according to the difference
between the output voltage measured and the voltage wanted.

We don’t have enough space hereto go into details about how this
circuit works, but it’s worth mentioning a few points of special inter-
est. The small capacitor across the diode improves the efficiency of
the circuit. The load is represented by R3. The components used
make it possible to supply over 1 A (current limited bytheMSS126GT
683 M IB inductor from Colic raft), but maximum efficiency (89^) is
at around 95 mA (at an output voltage of 1 0 V), To avoid damaging
the controller's analogue input (<5 V), the output voltage may not
exceed 24 V. For higher voltages, the values of resistors R1 and R 2
would need to be changed.

The MOSFET is driven by the pC, which is nothing but a little Arduino
board. The Ardulno’s default PWM signal frequency is around
500 Hz — too low for this application, which needs a frequency at
least 1 00 times higher. So we can’t use the PWM functions offered
by Arduino. But that’s no problem, as the Arduino can also be pro-

Arduino \

DIGITAL .Flftl 11 y-

62.SkH7

ANALOG_FliTcTy
Arduino

V*T1

IRF644

+4V3...+24V
-@v +

fU

ItHJu jV

090S49- It

grarnmed in assembler, allowing a maximum frequency of 62.5 kHz
(the pC runs at 1 6 MHz). To sample the output voltage, a frequency
of 1 00 Hz is acceptable, which means we can use Arduino's standard
timers and analogue functions. The Arduino serial port is very handy
— we can use it for sending the output voltage set point (5-24 V)
and for collecting certain information about the operation.

Thanks to the Arduino environment, it only took about half an hour
to program. You can download the software from !| .

[ 1 1 www. eiektor. com/0908 94

(090894-1)

UV light box

By Cert Baars (The Netherlands)

Fabricating printed circuit boards is not something that every elec-
tronics hobbyist does for themselves. It is, however, not realty that
difficult, The most important necessities are a PCB layout, a printer
(or perhaps a copier), a light box, photo -sensitive PCB material,
chemicals and an etching tray. It is often the light box that presents
the most difficulties.

The PCB layout can be copied (using a copier) from an existing
design or you can design it yourself using a computer and suitable
software. The layout needs to be printed onto a transparency (make
sure that the transparency is suitable for use in laser or inkjet print-
ers). The necessary chemicals (sodium hydroxide for the develop-
ing and iron(lll)-chlonde or copper-chloride for the etching) are not
difficult to obtain. It is not necessary either to etch using a foam-
etching box, but this does etch much quicker. Etching can simply
be done in a plastic tray, and etching with iron(lll)-chloride will be a
little faster if the etchant is at about 40 °C
As already mentioned, exposing the PCB is often the most diffi-
cult part. In the past, the PCB with the layout in an exposing frame
would sometimes be placed in the bright sun and it is also possible
to expose the PCB using UV lamps. To make a real 1 light box yourself

is not nearly as difficult as most people assume.

The required items are a housing with a sheet of glass, UV fluo-
rescent tubes and perhaps a timer. The latter is not really neces-
sary when a clock or watch Es available. It therefore comes down to
obtaining the UV fluorescent tubes with starters and ballast and a
housing with a sheet of glass.

There is a cheap solution for this. For the housing you can use a dis-
carded sheet scanner with all the innards removed. The fluorescent
tubes could come from a face tanning machine, for example. In the
prototype' made by the author the frame complete with the fluo-
rescent tubes was cut out. This could then be placed in its entirety
into the housing for the scanner. The accompanying starters and
ballast fitted elsewhere in the old scanner housing and after con-
necting ail the wires everything immediately worked as it should.
Because the layout has to be in good contact with the PCB to pre-
vent shadowing, a sturdy piece of cardboard the same size as the
glass was attached to the inside of the lid of the scanner. It is neces-
sary to apply some pressure on the lid during the exposure, but a
few books or fat catalogues on top of the fid is already sufficient. The
exposure time for the best results with this construction appears to
be about 2-3 minutes.

(090088)

eiektor 04-2010

75

INFOTAINMENT

Hexadoku

V

'i'

i an

Here's another fresh Hexadoku for everyone with a soft spot for puzzle solving. Our records indicate that
Hexadoku has become popular with spouses of Elektor readers, too, and that’s a good sign. The more
correct entries, the better! Send the hexadecimal numbers in the grey boxes to us and you automatically
enter the prize draw for four Elektor Shop vouchers. Have fun!

The instructions for this puzzle are straightforward. Fully geared to
electronics fans and programmers, the Hexadoku puzzle employs
the hexadecimal range 0 through F, in the diagram composed of
16 x 16 boxes, enter numbers such that all hexadecimal numbers
0 through F (that's 0-9 and A-F) occur once only in each row, once

Solve Hexadoku and win!

Correct solutions received from the entire Elektor readership automa-
tically enter a prize draw for one Elektor Shop voucher worth £ 80.00
and three Elektor Shop Vouchers worth £ 40,00 each, which should
encourage all Elektor readers to participate.

in each column and in each of the 4><4 boxes (marked by the thicker
black lines). A number of dues are given in the puzzle and these
determine the start situation. Correct entries received enter a draw
for a main prize and three lesser prizes. All you need to do is send us
the numbers in the grey boxes.

Before May 1,2010, send your solution (the nu mbers i n the g rey
boxes) by email, fax or post to

Elektor Hexadoku - 1 000, Great West Road - Brentford TW8 9HH
United Kingdom.

Fax (+44) 208 2614447 Email: hexadoku@elektorxom

Prize winners

The solution of the February 2010 Hexadoku is:95CD4.

The £80.00 voucher has been awarded to: Alex Murphy (USA),

The £40.00 vouchers have been awarded to: Edwin Velner (The Netherlands), Kaz Tchorzewski (UK)

and Ludwing Sanchez Carrillo (Colombia).

Congratulations everybody!

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The competition is not open to employees of Elektor International Media, its business partners diid/or associated publishing houses.

76

04-2010 elektor

RETR0N1CS

G4WIM

24cm ATV Transmitter (1994)

By Jan Suiting, PEiCSI (Elektor UK/US Editorial)

I n the ea rly 1 990s, activity in the 23 cm amateu r rad io ba nd ( 1 250-
1300 MHz) soared due to the arrival on the market of wideband
RF power amp lifier mod tiles that a I lowed easy generation of tra ns-
mitter power levels in the watts range. Most of these units were
Motorola and Mitsubishi made and originally designed as drop-in
power amps in base stations of 800/900 MHz cellphone networks
which were rolled out at a terrific pace at that time. In the years
before the modular RF power amp, hams on 23 cm had a choice of
( 1 ) being happy with a few milliwatts, ( 2 ) juggling with expensive
transistors, or (3) going through immense trouble to build a high
power amplifier using tubes (usually 2C39s).

The 23 cm radio amateur band got its name from the section with
most activity; 1 296-1 298 MHz where phone, CW (moonbounce)
and SSB reigned. However In most 1ARU zones the band extends
down to 1250 MHz offering plenty of space for "new* operating
modes so wide they cannot be accommodated in any of the lower
bands like 70 cms. 24 cms were "new pastures green" for amateur
television (ATV) users. Finally these guys had a chance of using wide-
band FM for their TV transmissions. Luckily, at the same time, ana-
logue satellite TV receivers like the Amstrad were widely available,
first at low prices and then free out of skips and trash cans. Then
Mitsubishi stopped being fussy about supplying their M67xxxx RF
power modules as one offs. A techie hotbed was
created and the popular-
ity of FM ATV of 24 cms
was boosted further by
many repeater stations
installed at elevated posi-
tions, all built, operated,
maintained and paid for by
kind souls.

In February 1994 Tim For-
tester G4WIM published a
classic in the history of Ele-
ktor: a compact PLL control-
led ATV transmitter with 1,5
watts output power for use
at 24 cms (1 250-1 270 MHz).

The double sided high-qual-
ity board and kit of hard-to-get
parts supplied by Tim himself all
added to an excellent repeatabil-
ity factor. The project deservedly
became popular and got built, cop-
ied, extended, bashed, tweaked and
improved by hams all over the world
(what do you mean 'open-source’?).

Including Dutch radio amateur Geert Jan de
Groot PEI HZG who kindly supplied his ATVTX

and spurred me on to write this instalment.

Geert Jan's modifications to the original G4W3M/E!ektor design
include an add-on board for 3-channel selection (instead of
2), PLL rewiring for operation at his favourite frequencies
(1279/1265/1252 MHz) and combining "power on/off with the IX
power level switch. A further switch allows the sound subcarrier
to be switched off (useful for measurements). As recommended in
the 1 994 article, the transmitter was built into a diecast enclosure
with the heatsin k secu red to the bottom panel to help the M677 1 5
module keep its cook

In the 24 cm band, whether using ATV or any other mode, every-
thing depends on your antenna and its height. Low-loss coax cables
rule, as well as parabolic dishes, G3JVL loop yagis and other direc-
tional antennas preferably mounted at the top of a high mast.

The G4W1M transmitter being such a compact design, 12 -volt
powered and having enough output power to carry camera signals
over a few miles to a base station, portable operation was within
easy reach and "portacam ATV' was often used to amuse the gen-
eral public at special events. With this in mind, and to keep the sta-
tion cost down, Geert Jan built a double-quad antenna from 5/8-
snch PVC conduit and a matching T junction box. A piece of dou-
ble sided unetched circuit board acts as the reflector and a length

of stiff copper-plated wire was bent into the well-
known "quad 1 shape mounted at the front of the
conduit. The yellow conduit can slide in the T
piece — note the black marking to indicate
the optimum distance between the quad
and the reflector.

Tim Forrester G4W1M also published an IMBFM
transceiver in Elektor September 1992. At the time
of writing he is still active as a radio amateur.

( 090882 )

Retronics is a monthly column covering vintage electronics including legendary Elektor design s. Contributions, suggestions and
requests are welcomed: please send an email to editorQPelektoncom

elektor 04-2010

77

ELEKTO

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Real Time Systems

• Assembler C, C++ (ail levels)

• 8, 16 and 32 bit microcontrollers

• Microchip, ARM, Renesas, II, Freescafe

• CMX, uCQSli, FreeRTOS, Linux operating
systems

• Ethernet, CAN, USB r TCP/IP, Zigbee, Bluetooth
programming

FLEXIPANEL LTD

www.flexipanel.com

TEAclippers - the smallest
PIC programmers in the world,
from £20 each:

• Per-copy firmware sales

• Firmware programming & archiving

• In-the-field firmware updates

• Protection from design theft by subcontractors

Instruments

A Rohde&Schwarz Company

0 Oscilloscopes
0 Power Supplies
0 Radio Frequency

Measuring instruments
Programmable
Measuring Instruments

0

Great Value in
Test & Measurement

www.hamegxom

78

04-2010 eiektor

products and services directory

FUTURE TECHNOLOGY DEVICES

http :// www.ftd ECh f p . co m

FTDI designs and sells
USB-UART and USB-FIFO
interface i.c.’s.

Complete with PC drivers,
these devices simplify the task of designing or
upgrading peripherals to USB

HEX WAX LTD

www.hexwak.com

Worfd leaders in Driver-Free USB JCs:

* USB-UART/SPI/I2C bridges

* TEAleaf-USB authentication dongles

* expand 10- USB I/O USB expander

* USB-RleSys flash drive with SPI interface

* USB-DAQ data logging flash drive

RFID COMPONENTS

h ttp/w w w. a pdang i ia, org * u k

For DIY, OEM's & Experimenters
• EM41QQ Cards ,99 p (Prices inc vat)

• Keyfobs £1.09

• R/W Keyfobs £1,65

• RFID Coils £2.95

• RFID PCB
with RS232 port

• RFID IC's EM4095 - U2270B

* microRFID module (similar to Core 1012)

* Free Reader download - Technical pages
Order online 24 hrs - Tel: 01244 520684

MQP ELECTRONICS

www.mqp.com

* Low cost USB Bus Analysers

* High, Full or Low speed captures

* Graphical analysis and filtering

* Automatic speed detection

* Bus powered from high speed PC

* Capture buttons and feature connector

* Optional analysis classes

ROBOT ELECTRONICS

http://www.robot-electranfes.co.iik

Advanced Sensors and Electronics for Robotics

• Ultrasonic Range Finders

• Compass modules

• Infra-Red Thermal sensors

• Motor Controllers

• Vision Systems

• Wireless Telemetry Links

• Embedded Controllers

USB INSTRUMENTS

http://www.usb-instrumenfs.com

USB Instruments specialises
in PC based instrumentation
products and software such
as Oscilloscopes, Data
Loggers, Logic Analaysers
which interface to your PC via USB,

WWW.

elektor.

com

ROBOTIQ

http://www.robotiq,co,uk

Build your own Robot!

Fun for the whole family!

Now, available in time for X-mas

* Arduino Starter Kits *NEW!3*

* Lego NXT Mindstorms

* Affordable Embedded Linux Boards

* Vex Robotics (kits and components)

* FOB Robots (kits and components)

email: sal es@robotiq, co.uk Tel: 020 S669 0769

V1RT1NS TECHNOLOGY

www.virtins,com

PC and Pocket PC based
virtual instrument such
as sound card real time
oscilloscope, spectrum
analyzer, signal generator,
multimeter, sound meter,
distortion analyzer, LCR meter.
Free to download and try.

SHOWCASE YOUR CO

Elektor Electronics has a feature to help
customers promote their business,

Showcase - a permanent feature of the
magazine where you will be able to showcase
your products and services.

For just £242 + VAT (£22 per issue for
eleven issues) Elektor will publish your
company name, website address and a
30- word description
For £363 + VAT for the year (£33 per
issue for eleven issues) we will publish
the above plus run a 3cm deep full colour

image - e.g. a product shot, a screen shot
from your site, a company logo - your
choice

Places arc limited and spaces will go on
a strictly first come, first served basis,
So-please fax back your order today I

— -|

1 wish to promote my company, please book my space:

• Text insertion onl_\ for £242 + VAT * Text and photo for £363 + VAT

NAME- ORGANISATION-

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WEB ADDRESS

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J

elektor 04-2010

79

SHOP BOOKS, CD-ROMs, DVDs, KITS & MODULES

Going Strong

A world of electronics
from a single shop!

articles included

n^ore tnan

Elektor

Design

Guides

Application

Notes

Driver

limited Period Offer

for Subscribers’.

£5 DISCOUNT

www.elektor.com|L

Elektor

Designer’s

Companion

Tools I

OpticTJ

Sensors^

Thermal'

'Controller

S&e the light on Solid State lighting

DVD LED Toolbox

This DVD-ROM contains carefully-sorted comprehensive technical documentation about and
around LEDs. For standard models, and fora selection of LED modules, this Toolbox gathers to-
gether data sheets from all the manufacturers, application notes, design guides, white papers and
soon. It offers several hundred drivers for powering and controlling LEDs in different configura-
tions, along with ready -to -use modules (power supply units, D MX controllers, dimmers, etc.). In
addition to optical systems, light detectors, hardware, etc., this DVD also addresses the main
shortcoming of power LEDs: heating. This DVD contains several Elektor articles (more than 100 }
on the subject of LEDs.

ISBN 978 90-5381-245-7 - £28.50 * US$46.00

Embedded USB Know How

USB Toolbox

This CD-ROM contains technical data
about the USB interface. It also includes a
large collection of data sheets for specific
USB components from a wide range of
manufacturers. There are two ways to in-
corporate a USB interface in a microcon-
troller circuit: add a USB controller to an
existing circuit, or use a microcontroller
with an integrated USB i interface. Both op-
tions are available on this CD-ROM. Includ-
ed on this CD-ROM areUSB Basic Facts,
several useful design tools for hardware
and software, and all Elektor articles on
the subject of USB,

ISBN 978-90-5381-21 2-9
£19,90 * US $32, 10

Software Tools & Hardware Tips

Ethernet Toolbox

This CD-ROM includes a collection of data
sheets for dedicated Ethernet interface I Cs
from many different manufacturers. It pro-
vides a wealth of information about con-
nectors and components for the physical
layer (PHY) and specific software tools for
use with the Ethernet (Software). To help
you learn about the Ethernet interfaces,
we have compiled a collection of all articles
on this topic that have appeared in Elektor
and complemented them with additional
documentation and links to introductory
articles on Ethernet interfaces. The docu-
ments are PDF fifes.

ISBN 978-90-5381-214-3
£19,50 * US $31 ,50

8o

04-2010 elektor

Prices and item descriptions subject to change. E, & O.E

A whole year of Etektor magazine
onto a single disk

DVD Elektor 2009

The year volume DVD/ CD- ROMs are
among the most popular items in Elek-
tor’s product range. This DVD-ROM con-
tains ail editorial articles published in
Volume 2009 of the English, American,
Spanish, Dutch, French and German edi-
tion s of Elektor Using the supplied Adobe
Reader program, articles are presented in
the same layout as originally found in the
magazine. An extensive search machine is
available to locate keywords in any arti-
cle. With this DVD you can also produce
hard copy of PCB layouts at printer reso-
lution, adapt PCB layouts using your
favourite graphics program, zoom in / out
on selected PCB areas and export circuit
diagrams and illustrations to other pro-
grams.

ISBN 97 8 '90 -53 81 *251-8
El 7.50 - US $28*30

1 1 0 issues, more than 2,100 articles

DVD Elektor
1990 through 1999

This DVD-ROM contains the full range of
1990-1999 volumes (all 1 1 0 issues) of
Elektor Electronics magazine (PDF). The
more than 2,100 separate articles have
been classified chronologically by their
dates of pu bl ica tio n ( mo nth / yea r) t b ut a re
also listed alphabetically by topic,
A comprehensive index enables you to
search the entire DVD.

ISBN 978*0-905 705-76-7
£69.00 » US$111.30

Look into the electronics of eco-power

Practical Eco-Electrical
Home Power Electronics

This book Is a sequel to Your own Eco -
Electrical Home Power System and goes
deeper into the electronics of photovol-
taic a nd thermal solar technologies, wind
power conversion, inverter circuits, and
loads such as electronic lighting. Power
electronics circuit theory is presented
while analyzing commercial circuits,
including little-known converters and
subtleties such as snubbers and leakage
inductance. The book also offers in-depth
coverage of power system strategizing
for optimal efficiency and utility, inclu-
ding a 170 V DC bus, commercial solar
charger design with detailed circuit
explanations, wind generator electric
machine electromechanical theory, wind
converter design requirements and the
series -L zero-current-switching converter
and power supplies found inside loads
connected to home power systems and
their potential problems and conse-
quences for inverters.

192 pages * (SBN 978 0-905705-83-5
£2490 * U5 $40.20

r ^

More information on the
Elektor Website:

www.elektor.com

Elektor

Reg us Brentford
1 000 Great West Road
Brentford
TW 8 9HH
United Kingdom

Tel.: +44 20 8261 4509
Fax: +44 20 8261 4447
Fmail: I ps@elektor.com

r

Home electric power

Your own Eco-Electrical
Home Power System

This book provides the semi-technical,
power-conscious homeowner a place to
begin in the quest for home electric power.
Both the essential principles and detailed
information on howto build or maintain a
home electric system off the utility grid
are presented in an easy-going style. This
booklet will help you to safeg yard or de-
velop your own home electricity supply. It
conta in sstep - by -stepcalculations, practi-
cal details, examples and much more.

96 pages * ISBN 978-0-905705-82-8
E 76-50 * US $26.70

Several case studies included

PIC Cookbook for

Virtual Instrumentation

The software simulation of gauges, con-
trol-knobs, meters and indicators which
behave just like real hardware components
on a PCs screen is known as virtual instru-
mentation. In this book, the Delphi pro-
gram is used to create these mimics and PIC
based external sensors are connected via a
USB/RS232 converter com muni cation link
to a PC Case studies of virtual instruments
are detailed including a compass, an oscillo-
scope, a digital and analogue thermometer
and virtual displays for cars and aircraft.

264 pages * ISSN 97 8 0-9 05795 -84- 2
£29.50 - U5 $47,60

elektor 04-2010

81

SHOP BOOKS, CD-ROMs, DVDs, KITS & MODULES

Learn more about C# programming and .NET

C# 2008and.NET
programming

This book is ai med at Eng ineers and Scien-
tists who want to learn about the , N ET en-
vironmentand C# programming or who
have an interest in interfacing hardware to
a PC. The book covers the Visual Studio
2008 development environment, the .NET
framework and C# programming language
from data types and program flow to more
advanced concepts including object ori-
ented programming.

240 pages * ISBN 978-0-905705-8 1-1
£20.50 * US 547.60

COMPUTE PRACTICAL
MEASUREMENT SYSTEMS

w mh -i" i

Circuit design and programming

Complete practical measure-
ment systems using a PC

This book covers both hardware and soft-
ware aspects of designing typical embed-
ded systems based on person a komputers
running the Windows operating system.
it f s use of modern techniques in detailed,
numerous examples has been designed
to s h o w c I ea rfy h ow strai g h tfo r wa rd i t ca n
be to create the interfaces between digital
and analog electronics, programming and
Web-design. Readers are encouraged by
examples to program with ease: the book
p rovides c lea r g u idel i n es a s to th e appro p ri-
ate programming techniques “on the fly".

292 pages * ISBN 978 0-905705-79-S
£28,50 * US 546.00

v y

(March 2010)

Theexternal appearanceof this small mo-
dule with an LC display almost belies what
it has inside: a complete stereo preampli-
fier and final amplifier with I R remote con-
trol. adjustable tone, volume and signal
levels, and an output power of 2 x 20 W
(Class D), all with a single 1 2-V supply vol-
tage. This ma kes it perfect for use in a car,
boat or motor home.

PCBs, SMD-populated, and all other
components

nAmp Contro

(February 2010)

A variety of remote control devices for
Winamp and other PC-based media pla-
yers have been available for a good wh I le.
All of these systems have one thing in
common, which is that they are limited to
buttons or keys or use virtual progress
bars on the computer monitor. If you want
to have a complete hardware interface
unit with the same level of sophistication
as the virtual Winamp design, you need a
physical progress bar. In this project a
small ATmega microcontroller uses the
USB interface to provide a bidirectional
link between the Winamp software and a
hardware studio fader, which acts as a
c □ m b i n ed I nd i ca to r a n d entry de v ice*

Kit of parts, including PCB

(December 2009)

EEektoCs Software Defined Radio (SDR) is
deservedly popular. The performance of
a receiver depends to a large extent on its
i nput filters, A selective input circuit i im-
proves anten na matching and imm unity
to i nterference from other strong signals.
This preselector allows the use of up to
f o u r f i I te rs , tu n ed u nd er soft wa re con tro 1
using varicap diodes. A tuned loop anten-
na is also described that lets you use our
SDR without an outdoor antenna.

Kit of parts, contains partly populated
hoard , coil formers, ferrite rod with coils

(September 2009)

The compact GBD2 Analyser in the June
2007 issue w r as an enormous success -
not surprisi ng for an affordable handheld
onboard diagnostics device with auto-
matic protocol recognition and error
codes explained in plain language. Now
enhanced with a graphical display. Cortex
M3 processor and an Open Source user
interface, the next generation of Elek tor's
standalone analysersets new standards
for a DIY OBD2 project. The key advan-
tage of this OBD2 Analyser NC is that it's
self-contained and can plug into any
OBD diagnostic port.

Kit of parts including DXM Module, PCB
5/11 D-p refitted, case, mounting materials
and cable

82 Prices and item descriptions subject to change. E. Sr O.E

04-2010 elektor

April 201 0 (No. 400) £ USS

Uni Lab

090786-1 Printed circuit board * 16,00. 26.00

090786-71 .... PCS and all components, less power transformer www.elektor.com

Small is Beautiful: Minimodi 8

09077 3-4 1 „„ Pro gra mm e d co n trol ler wi th Bootloader

pre-programmed 2 1.80. ......36.00

090773-91 .... PCB, populated and tested with Bootloader

pie -p rogram med 56.00 .90 .00

Bluetooth forQBD-2

090918-71 PCB with SMOs fitted. BTM222 Bluetooth module..,.. 26.70. 43.00

Fun with Fireflies

100014-1 Printed circuit board 1 1.00., .....18.00

100014-41 .,.. Prog ram med cont ro 1 1 er. 1 1 .00, ..,.,.18.00

Beep. beep... Sesame

081 143-41 ....Programmed controller.... 15.50 25.00

5 V Power Controller

09071 9- 1 ...... Printed circuit board 8.90 1 4,50

March 2010 (No. 399)

Reign with the Sceptre

090559-91 .... PC8, populated and tested, test software loaded „.. www.elektor.com

Modulo 0

090563-71 .... PCB, SMD- populated, and all other components 69.90 1 1 2.80

February 2010 (No. 393}

Battery Checker

071 131-41 ...,ATmega32-16PU. programmed,... 17,80 ,.28.80

071 131-71 .... Kit of parts, extl. enclosure.... 124,00 200-00

Winamp Controller

0 —1 0 531 1 Is 1 1 o 1 p arts . . . . . , . . . . . . . ........ , ....... ...... . ..... . .... . J . 0 0 ..... 1 1 3 . 6 L*

The ATM 1 8 Radio Computer

090740-71 .... PCB with Si4734/35 radio 1C ready

mounted and tested iitritritriiiitiiiiiiiiiititriiiiiTiiiiMirrimr 27.50 44.40

January 2010 (No, 397)

USB Magic Eye

090788-1 Printed circuit board ..

090788-41 .... ATtiny23T3-20PU 1 programmed

MIAC for Home Automation

090278-91 .... Populated PCB in enclosure

Dimmer with a Micro

090315-41 PIC12F629A. programmed

0 ete m ber 2 009 ( N o, 396)

Preselector for Elektor SDR

090615-7 1 ... Kit of parts, contains partly populated board

..9.90 16.00

,.9.90 16.00

154.00 248.40

, I * B J I I J B B .1 a I. 7.60 b + 4 12.30

coil formers, ferrite rod with coils,,.,.,

47,00,...

...75.90

Top -of-the- Bill Lights Sequencer

090125-1 ...... PCB, bare (master module)

10,80,,..

...17,50

0901 25-2 PCB, bare (lamp module)

2,30.,..

3,80

090125-41 Controller (PIG 8F255C)

for main PCB, programmed

14.50....

...23.40

090125-42 .... Controller (PIC1 2F508-I/5N)

fo r lam p u n it, prog ram med

2 30

.... 3.80

The Vi kings Are Coming!

080948-71 .... Kit of parts: bare PCB and

bluetooth module BTM222

23.70..,.

.,.38.30

MfnimalisticTIme Switch

090823-41 .... PIC1 2F683-I/5N, programmed

6.50...

...10.50

November 2009 (No. 395)

Solder Station ‘Plus'

090022-41 .... PIC1SIF45 20 .programmed 11,50 18,60

AVR-Max Chess Computer

081101-1 Printed circuit hoard 12.90 20.90

081101-41,.,, Prog ra mm ed co ntroller AT m ega8 8 „ . 1 1 , 50 h+ . . 1 8 .60

081101-71 Kit of parts inch PCB.

programmed control ler and components. 29.90, + „.„48,30

Complete practical measurement using a PC

ISBN! 978-0-905705-79-8.... £28.50 US $46-00

3

C# 2008 and .NET programming

ISBN 978-0-905705-81-1 .... £29.50 US $47.60

Practical

4

5

1

2

3

4

5
1

Eco-Electrical Home Power Electronics

ISBN 978-0-905705-83-5.... £24.90 US$40.20

Your own

Eco-Electrical Home Power System

ISBN 978-0-905705-82-8.... £16.50 US$26.70

DVD Elektor 2009

ISBN 978-90-5381-251 -8.... £1 7.50 US $28.30

DVD Elektor 1990 through 1999

ISBN 978-0-905705-76-7.... £69.00 ...US$11 1 .30

DVD LED Toolbox

ISBN 978-90-5381-245-7.... £28.50 U5 $46.00

Ethernet Toolbox

ISBN 978-90-5381 -21 4-3.... £19.50.... US$31.50

ECO 5

ISBN 978-90-5381-159-7.... £24.90 US$40.20

SDR Preselector

Art. #09061 5-71 £47.00 US$75.90

2

3

4

5

WinAmp Controller

Art. # 090531 -71 £85.00 ... US $ 1 43.60

R32C/111 Starterkit

Art. #080928-91 £27.00 US$43.60

Modulo D

Art. #090563-71 £69.90 ...US $1 1 2.80

Battery Checker

Art. #071 131-71 £124.00 ...US $200.00/

www.elektor.com/shop

or use the Order Form near the end
of the magazine!

Elektor

Regus Brentford

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Fax +44 20 82614447

Email: sates@elektor.com

elektor 04-2010

S3

COMING ATTRACTIONS

NEXT MONTH IN ELEKTOR

dsPIC Development Board

Thb powerful control board with a i6-bit dsPIC3oFGoio offers plenty of application scope
including motor control. The base board has interfaces for USB, RS232, CAN, PC and ICD2,
There are also four DACs and all essentia! signals are bonded out to expansion connectors.
The expansion board described in the same edition has even more connectivity to offer.

Fast Responding C0 2 Meter

A new CO. meter was specially developed by Elektor Labs for use in confined spaces like
cars. Thanks to the use of a sensor based on CCh level detection by Infra red light the meter
lias hardly any warm up time and should be ready to take measurements a minute or so
after switch-on. Measured data are processed by an ATmega MCU that also takes care of
driving a two-line LCD.

Auto Balancer for liPo Battery Packs

With lithium -polymer battery packs it's essential to keep a close watch on the charge
distribution between cells to prevent one of these from being overcharged or deep dis-
charged, Typically, special ICs are used for this purpose but this project shows that stand-
ard components can do the job equally well. A single LM324 and some power Darlington
transistors are sufficient for a battery pack with up to five cells.

Article titles and magazine content s sohjcc i la change; phase check the Magazine tab on www.eiektor.com
Eiektor UK/European edition: an sale April 22, 20 jo . Liektor USA edition: published April 15,

w.elektor.com www.eIektor.com www.elektor.com www.elektor.com www.elektor.com

Elektor on the web

All magazine articles back to volume 2000 are available online in pdf format. The article summary and parts list (if applicable) can be
instantly viewed to help you positively identify an article. Article related items are also shown, including software downloads,, circuit
boards, programmed ICs and corrections and updates if applicable. Complete magazine issues may also be downloaded.

In the Elektor Shop you’ll Find all other products sold by the

publishers, like CD-ROMs, DVDs, kits, modules, equipment,
tools and books. A powerful search function allows you to
search for items and references across the entire website.

Also on the Elektor website:

Electronics news and Elektor announcements

• Readers Forum

PCB, software and e-magazine downloads

• Time limited offers

FAQ, Author Guidelines and Contact

0lektor

Hlnftiiinf Etficp

84

□4-2010 elektor

Description Price each Qty. Total Order Code

DVD Elektor 2009 ffiga £17.50

PIC Cookbook

for Virtual Instrumentation £29.50

Complete practical measurement systems

using a PC £28,50

Practical Eco- Electrical

Home Power Electronics £2a.90

Your own Eco-Electrical

Home Power System eis.so

Sub-totai

Prices and item descriptions subject to change.

The publishers reserve the right to change prices P&P

without prior notification. Prices and item descriptions

shown here supersede those in previous issues. E. & O.E, Total potd

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subscription s* elektor. com

£L04

ORDERING INSTRUCTIONS, P&P CHARGES

All orders, except for subscriptions (for which sec below), must be sent BY POST or FAX to our Brentford address using the Order Form
overleaf. Online ordering: www.elektor.com/shop

Readers in the USA and Canada should send orders, except for subscriptions (for which see below), to the USA address given on the
order form. Please apply to Elektor US for applicable P&P charges. Please allow 4-6 weeks for delivery.

Orders placed on our Brentford office must include P&P charges (Priority or Standard) as follows: Europe: £6,00 (Standard) or £7,00
(Priority) Outside Europe: £9*00 (Standard) or £11 *00 (Priority)

HOW TO PAY

All orders must be accompanied by the full payment, including postage and packing charges as stated above or advised by Customer
Services staff.

Bank transfer into account no* 40209520 held by Elektor Electronics with ABN-AMRO Bank, London.

IB AN: GB35 ABNA 4050 3040 2095 20,

Bit: ABNAGB2L. Currency: sterling (UKP)* Please ensure your full name and address gets communicated to us*

Cheque sent by post, made payable to Elektor Electronics* We can only accept sterling cheques and bank drafts from UK-resident
customers or subscribers. We regret that no cheques can be accepted from customers or subscribers in any other country.

Giro transfer into account no. 34-152-3801, held by Elektor Electronics. Please do not send giro transfer/deposit forms directly to us,
but instead use the National Giro postage paid envelope and send it to your National Giro Centre*

Credit card VISA and MasterCard can be processed by mail, email, web, fax and telephone. Online ordering through our website is
SSL- protected for your security,

COMPONENTS

Components for projects appearing in Elektor are usually available from certain advertisers in this magazine* if difficulties in the supply
of components are envisaged, a source will normally be advised in the article. Note, however, that the source(s) given is (are) not
exclusive.

TERMS OF BUSINESS

Delivery Although every effort will be made to dispatch your order within 2-3 weeks from receipt of your instructions, we can not guaran-
tee this time scale for all orders. Returns Faulty goods or goods sent In error may be returned for replacement or refund, but not before
obtaining our consent. All goods returned should be packed securely in a padded bag or box, enclosing a covering letter stating the
dispatch note number. If the goods are returned because of a mistake on our part, we will refund the return postage. Damaged goods
Claims for damaged goods must be received at our Brentford office within 10-days (UK): 14-days (Europe) or 21 -days (all other countries).
Cancelled orders All cancelled orders will be subject to a 1 0% handling charge with a minimum charge of £5,00, Patents Patent protection
may exist in respect of circuits, devices, components, and so on, described in our books and magazines. Elektor does not accept responsi-
bility or liability for failing to identify such patent or other protection. Copyright All drawings, photographs, articles, printed circuit boards,
programmed integrated circuits, diskettes and software carriers published in our books and magazines (other than in third-party adver-
tisements) are copyright and may not be reproduced or transmitted in any form or by any means, including photocopying and recording,
in whole or in part* without the prior permission of Elektor in writing. Such written permission must also be obtained before any part of
these publications is stored in a retrieval system of any nature. Notwithstanding the above, printed-circuit boards may be produced for
privaLe and personal use without prior permission. Limitation of liability Elektor shall not be liable in contract, tort, or otherwise, for any loss
or damage suffered by the purchaser whatsoever or howsoever arising out of. or in connexion with, the supply of goods or services by Elektor
other than to supply goods as described or, at the option of Elektor, to refund the purchaser any money paid in respect of the goods. Law Any
question relating to the supply of goods and services by Elektor shall be determined in all respects by the laws of England.

January 2010

SUBSCRIPTION RATES FOR ANNUAL
SUBSCRIPTION

Standard Plus

United Kingdom £49,00 £61 .50

Surface Mail

Rest of the World

£63.00

£75.50

Airmail

Rest of the World

£79.00

£91.50

USA

£64*95

See www.elektor.com fusa

Canada

£75*95

for specie! offers

HOW TO PAY

Bank transfer into account no. 40209520 held by Elektor Elec-
tronics* with ABN-AMRO Bank, London. EBAN: GB35 ABNA 4050
3040 2095 20. BIC ABMACB2L Currency: sterling (UKP), Please
ensure your full name and address gets communicated to us*
Cheque sent by post, made payable to Elektor Electronics, We can
only accept sterling cheques and bank drafts from UK-resident cus-
tomers or subscribers. We regret that no cheques can be accepted
from customers or subscribers in any other country.

Giro transfer into account no. 34-1 52-3801 1 held by Elektor Elec-
tronics. Please do not send giro transfer/deposit forms directly to
us, but instead use the National Giro postage paid envelope and
send it to your National Giro Centre.

Credit card VISA and MasterCard can be processed by mail, email,
web, fax and telephone. Online ordering through our website is
SSL-protected for your security.

SUBSCRIPTION CONDITIONS

The standard subscription order period is twelve months.

If a permanent change of address during the subscription
period means that copies have to be despatched by a more
expensive service, no extra charge will be made. Conversely,
no refund will be made, nor expiry date extended, if a change
of address allows the use of a cheaper service*

Student applications, which qualify fora 20 % (twenty per
cent) reduction in current rates, must be supported by
evidence of studentship signed by the head of the college,
school or university faculty.

A standard Student Subscription costs £39.20, a Student
Subscription -PI us costs £51 .70 (UK only).

Please note that new subscriptions take about four weeks
from receipt of order to become effective.

Cancelled subscriptions will be subject to a charge of 25%
(tw r enty-five per cent) of the full subscription price or £7.5G f
whichever is the higher, plus the cost of any issues already
dispatched. Subscriptions cannot be cancelled after they have
run for six months or more.

January 2019

DVD Elektor 2009

i=>

A whole year of Elektor magazi
onto a single disk

aztne

The year volume DVD/CD-ROMs are among the most popular items in
Elector's product range. This DVD-ROM contains all editorial articles
published in Volume 2009 of the English, American, Spanish, Dutch, French
and German editions of Elektor. Using the supplied Adobe Reader program,
articles are presented in the same layout as originally found in the maga-
zine. An extensive search machine is available to locate keywords in any
article. With this DVD you con also produce hard copy of PCS layouts at
printer resolution, adapt PCB layouts using your favourite graphics program,
zoom in / out on selected PCB areas and export circuit diagrams and
illustrations to other programs.

rag®

Annuo'

jobbers

Anno*

joorgnf^g

Anuel

lektor

Elektor

Reg us Brentford
1000 Great West Road
Brentford TWS 9HH
United Kingdom
TeL +44208261 4509

L

Further information and ordering atwww.elektor.com/shop

Index of Advertisers

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78

HexWax Ltd. Showcase

Latic enter. ...

MikroElektronika

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Nufve Networks

Parallax ........

Peak Electronic Design.

Pico.

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Robot Electronics, Showcase.

Ro hotter Showcase

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USB Instruments, Showcase
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www.hexwax.com

79

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3

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61

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31

www.picotech.com/scopBiG63 . .

21

www.quasareIectrofitcs.com . . . .

47

www. robot-electronics, co. uk . . .

. 79

www.robotiq.co.uk

79

f- « B- + 1 *■ + !■■■• + + 0 ■ 1 + #■ I 4 + 1 ii * + p *

, . . . 73. 79

www.usb-instruments.com . .... .

79

vfww.virtins.com. .............

79

- + ■ + § ■ + 1 P “

Advertising space for the issue 20 May 2010
may be reserved not later than 20 April 2010

with Huson International Media * Cambridge House - Gogmore Lane -
Chertsey, Surrey KT16 9AP - England - Telephone 01932 564 999 -
Fax 01 932 564 998 - e-mail ros.elgar@liusonmedia.com to whom all
correspondence, copy instructions and artwork should be addressed,

elektor 04-2010

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