curve tracer on USB

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Free CAD

design tools
online

LED Lighting

FPGA

for

model coaches

programming

inC

VISIT 2000 SERIES 3000 SERIES

PicoScope 5000 Series

25G MHz bandwidth
1 GS/i real-time sample rate
12G mega sample record length

yj The No Compromise
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Technology

to check out our tu II line of PC- baaed instruments or tall 01 480 396 395 for information and a product catalogue

Capacitive Touch Sensing
In a Flexible, Single-chip Solution

Capacitive touch interfaces provide an excellent way to add low-cost, reliable
and stylish buttons into your design. Microchip Technology's mTouch™ Sensing
Solution includes comprehensive development kits and a free diagnostic tool
to make implementation easy and fast. Our free source code can be seamlessly
integrated with your existing firmware on a single PIC® microcontroller -
eliminating the need for additional controllers.

THE mTouch SENSING SOLUTION FEATURES:

• FREE license libraries and source code

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GET STARTED IN 3 EASY STEPS

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The Microchip name and logo, the Microchip logo, MPLAB and PIC are registered trademarks of Microchip Technology Incorporated in the USA and other countries. mTouch and PICDEM are trademarks of Microchip
Technology Incorporated in the USA and other countries. All other trademarks are property oftheir respective companies.© 2008, Microchip Technology Incorporated. All Rights Reserved. ME211Eng/08.08

Microcontrollers Digital Signal Analog Serial

Controllers EEPROMs

Cooking and
grilling with Elektor

Our technical staff in the Elektor lab
always do their best to make a seri-
ous impression, working all the time
with complicated electronic designs
and test equipment. However,
sometimes their sense of fun gets
the upper hand, and then there's no
telling what might happen. This time
the action revolved around a can of
frankfurters left standing in a corner
for half a year already, waiting for
some sort of special preparation.

And when we say special, we mean
special.

Needless to say, cooking and grill-
ing with Elektor always goes hand in
hand with a certain electric tension
(literally) and suitable sensation. The
plan was to apply an ac voltage
directly to the frankfurter so it could
be cooked almost instantaneously.
Our lab staff are keen on special
effects, so they decided it would be
nice to stick a few LEDs in the frank-
furter, with the idea that they would
light up when the frankfurter was
cooked through. This led to a fairly
animated discussion of whether they
would actually light up. Apparently
it's not that easy to apply Ohm's law
and Kirchoff's rules to a frankfurter.
Finally, the time came for action.

The can of frankfurters was opened,
a heavy-duty adjustable, double
isolated transformer was brought
out of storage, forks were borrowed
from the canteen so the current
could penetrate deep into the
frankfurter, and a good crowd of
people gathered around to watch
the events first-hand. Interestingly
enough, our lab manager, Antoine
Authier, took up a position behind a
low cabinet that provided strategic
cover. The French naturally know
how to deal with food, and he
probably thought the frankfurter
might suddenly catch fire.

...Tension rising ... of 40 V, the
frankfurter still resolutely maintains
its resistance. . . the first wonder
occurs at 70 V: the LEDs light up!
...the voltage rises even higher... at
80 V, the first plume of smoke comes
from the frankfurter , and it's done!
The LEDs made a positive contribu-
tion to the cooking session. After
some experimenting, we found that
the best results can be expected
at 80 V. The only other thing we
should mention is that Jan Visser ate
the frankfurters and is still in good
health (as far as we know). And of
course: never try this at home!

Wisse Hettinga

International Editor

leKio r

electronics worldwide

This practical instrument can be used to measure and record the cha-
racteristic curves of NPN and PNP bipolar transistors, N- and P-chan-
nel JFETs, and N- and P-channel MOSFETs. The circuit is based on an
R8C/1 3 microcontroller, which transfers the measurement data to a
Windows application program via USB.

3

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Several electronic component
manufacturers now offer design
tools online or for free download.
We registered on a dozen or so
websites to see just what's being
offered and what it's like.

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KlfU r - * t T, -K +

CONTENTS

Volume 35
February 2009
no. 386

The lighting controller described in this
article is a combination of an SMD LED
strip and a PIC1 2F683 for compatibility with
the Marklin system. The LEDs allow easy adaptation to
different colours while three different lengths of the board enable the
project to fit all common coach types.

69 Mini VHF FM Receiver

These days tiny FM radios are often integrated in many portable
devices such as mobile phones and
MP3 players. But why not
make a simple receiver
ourselves? There are
currently several nice
ICs available
that contain a
(nearly) complete
receiver.

projects

24 Transistor Curve Tracer

Microcontrollers
for Dummies...

4 ' Tri-State Timer

53 BASCOM-AVR Course (6)
(final)

56 Model Coach Lighting

65 Mini VHF FM Receiver

Opacity Measurement
by PC

74 Design Tips:

No varicap? Try a Schottky
diode

Three-from-four fan control

technology

1 8 Free CAD

38 From 1 7x4

to Channel Routing

46 An Eye for Distance

60 Prog ramming FPGAs in C

64 C Sharp (1 )

info & market

6 Colophon

8 Mailbox

News & New Products

52 Decibit 2.4 GHz RF

Transceiver Development
Kit (review)

68 Electromagnetic

Compatibility (EMC) page

80 ElektorSHOP

Sneak Preview

infotainment

76 Hexadoku

77 Retronics:

Elektor Digisplay (1976-77)

ELECTRONICS WORLDWIDE

elektor international media

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 beginner to diehard, from student to lecturer. Information, education, inspiration and entertainment.

Analogue and digital; practical and theoretical; software and hardware.

Volume 35, Number 386, February 2009 ISSN 1 757-0875

Elektor aims at inspiring people to master electronics at any personal level by
presenting construction projects and spotting developments in electronics and
information technology.

Publishers: Elektor International Media, Regus Brentford,

1000 Great West Road, Brentford TW8 9HH, England. Tel. (+44) 208 261
4509, fax: (+44) 208 261 4447 www.elektor.com

The magazine is available from newsagents, bookshops and electronics retail
outlets, or on subscription.

Elektor is published 1 1 times a year with a double issue for July & August.

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

International Editor:

Wisse Hettinga (w.hettinga@elektor.nl)

Editor: Jan Buiting (editor@elektor.com)

International editorial staff: Harry Baggen, Thijs Beckers,
Eduardo Corral, Ernst Krempelsauer, Jens Nickel, Clemens Valens.

Design stc Antoine Authier (Head), Ton Giesberts,

Luc Lemmens, Daniel Rodrigues, Jan Visser, Christian Vossen

Editorial secretariat: Hedwig Hennekens (secretariaat@elektor.nl)
Graphic design / DT Giel Dols, Mart Schroijen

Managing Director / Publisher: Paul Snakkers
Marketing Carlo van Nistelrooy

Subscriptions: Elektor International Media,

Regus Brentford, 1000 Great West Road, Brentford TW8 9HH, England.
Tel. (+44) 208 261 4509, fax: (+44) 208 261 4447
Internet: www.elektor.com/subs

6

elektor - 2/2009

CapSense Express
Evaluation Kits

f \

CapSense Buttons Evaluation Kit

This kit contains the CY321 8-CAPEXP1
evaluation board, a retractable USB mini
cable (A to mini B), a PSoC CY3240-I2
bridge board and an AA battery.

Also included is the kit CD which contains

your perfect guides to better
switches and slider devices

PsOC programmer, .NET Framework 2.0,
PSoC Express 3, CapSense Express
Extension Pack and the CapSense Express
documentation.

£27.50 • US $39.95

If ever there was a chance to get into PSoC and
cap sense at a sensible price, it's right now.

By special arrangement with Cypress, Elektor offers
two entry-level CapSense Express development kits
to enable readers to get acquainted with capacitive
sensing technology in a time efficient way.

Both kits represent excellent educational
value for all of you wishing to
eradicate, once and for all,
the weaknesses and failures of
mechanical switches and slider pots.

CapSense Sliders Evaluation Kit

Contents as CapSense Buttons Evaluation
Kit, except CY321 8-CAPEXP2 evaluation
board included in this kit.

Art.# 080875-92 • £27.50 • US $39.95

v J

Further information and ordering

lektor

SHOP

Email: subscriptions@elektor.com

Rates and terms are given on the Subscription Order Form.

Head Office: Elektor International Media b.v.

P.0. Box 1 1 NL-61 1 4-ZG Susteren The Netherlands
Telephone: (+31 ) 46 4389444, Fax: (+31 ) 46 43701 61

Distribution: Seymour, 2 East Poultry Street, London EC1A, England
Telephone:+44 207 429 4073

UK Advertising Huson International Media, Cambridge House,
Gogmore Lone, Chertsey, Surrey KT1 6 9AP, England.

Telephone: +44 1932 564999, Fax: +44 1932 564998

Email: p.brody@husonmedia.com
Internet: www.husonmedia.com
Advertising rates and terms available on request.

Copyright Notice

The circuits described in this magazine are for domestic use only. All drawings, photo-
graphs, printed circuit board 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 transmitted in any form or by any means, including photocopy-
ing, scanning an recording, in whole or in part without prior written permission 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 ex-
ist in respect of circuits, devices, components etc. described in this magazine. The
Publisher does not accept responsibility for failing to identify such patent(s) or other
protection. The submission of designs or articles implies permission to the Publisher
to alter the text and design, and to use the contents in other Elektor International
Media publications and activities. The Publisher cannot guarantee to return any mate-
rial submitted to them.

Disclaimer

Prices and descriptions of publication-related items subject to change.
Errors and omissions excluded.

© Elektor International Media b.v. 2009

Printed in the Netherlands

2/2009 - elektor

7

INFO & MARKET

MAILBOX

PLDM LED Driver —

DIY and commercial

Dear Editor — I noticed the
December 2008 issue's LED
bike lamps and clever related
step-down current regulator
trick: to reduce feedback
votage loss — it's been filed!
However with the 60 lux Busch
and Muller Cyo available (and
legal) with efficient optics, one
might as well leave DIY LED
bike lamps as extra auxiliary
lamps.

I discovered a "£9.74 Nite
Ize L.E.D. Upgrade for C & D
Cells [LRB-07-PR]" pre-focus
bulb with 3-watt LED and
electronics: a rectifier and cap
would allow easy conversion
of lamps: presumably you
would need to ensure heatsin-
king via a metal bulb holder
connection to, for example,
foil.

It seems to work for 2 to 6
cells so must have a buck-boost
converter.

Also, LED domestic bulbs are
made by a Phillips division
called Lemnis, see
www.lemnislighting.com/pha-
rox_led_bulb.html
Alan Bradley (UK)

That's brilliant (pun intended ),
thanks Alan for letting us know
this commercial alternative.

Hi from the USA

The following testimonial about
the early days of Elektor was
received from our correspondent
Ed Dell of Audio Amateur Inc.,
forwarding an email from Dick
Campbell.

"If you are of a certain age
or traveled in Europe you will
remember the wonderful mag-
azine, "Elektor". I subscribed

back when it was translated
into English (from the original
Dutch) in the UK and shipped
to the USA. Then my finances
changed and I had to drop
the subscription. Later when I
tried to find them again the UK
publisher had disappeared.

I still have the issues I bought
back then and still make
reference to them from time
to time. Besides the
great construction
articles they

also have very clear explana-
tions of how the circuitry in the
articles work. In particular their
explanation of how a pseudo
random noise generator works
is the very best and clear-
est I have ever found. I have
passed that explanation onto
one of the best DSP engineers

around and he found it useful.
"It is now available in the USA
— see www.elektor.com/
USA/ for subscription info."

I saw them at the AES in San
Francisco and somehow did
not stop and subscribe. Thanks
for the reminder, I have just
sent in my subscription.

"This is a remarkable maga-
zine for DIY or just plain
inspirational projects in many
areas of electronics."

They also make quality bare
circuit boards available at
reasonable prices for their
projects which makes them
very easy to build.

Ray A. Rayburn (USA)

Wiring up (3)

Dear Editor, regarding Phil
Pumphrey's letter in Mailbox,
October 2008, what he needs
is something called a DRO
(digital readout). There are
many websites on the subject
and many homebrew contrap-
tions, including a few ones
based on hacked mic even the
optical ones. Just ask Google
about 'homemade / home-
brew dro'.

Please tell Phil that I'll be
happy to be of assistance;
you may give him my e-mail
address.

Jorge L. (Spain)

Thank you Jorge for your kind
offer, we'll do the necessary to
get you in touch with Phil.

Electrobike — kit supplier

Hi Jan — last November's
issue had an interesting article
on an electrobike retrofit con-
version kit, reportedly sourced
via EBay. Unfortunately I
was unable to find the kit
described. Can you help me,
please?

Herbert Polzer (Germany)

The prototype was bought
from Wilkotec's e-boy shop at
http://stores/ebay.de.E-bikeTec
which was olive and kicking at
the time of publishing. Wilkotec
also have their own online shop
ot www.wilkotec.de. Other sup-

pliers of e-bike wheels and kits
may be found on ebay.com.

Electrobike —
need to know

Dear Elektor — after reading
this great article, some ques-
tions remain, if I may.

1 . did you fit new spokes,
reposition the front wheel or
convert a children's bike?

2. Any findings on the esti-
mated range?

2. How much should I expect
to pay for a battery pack?

Joachim Herbert
(Germany)

For the test we had a mountain
bike ovoiloble with 26-inch
wheels. However, owing to on
error somewhere in the supply
chain, the electrobike wheel we
received was a 24-inch type (for
sure, 26-inch and 28-inch versi-
ons are available).

Three series connected 12 V
7.2 Ah batteries represent 30 to
40 minutes worth of bike riding
without any pedal assistance.
However if the motor is used
as a support only, a range of
40-50 kms is not exceptional,
depending of course on the ter-
rain and the load. A set of 12-
Ah batteries almost doubles the
range.

For the experiment we used CSB
batteries from the 'EVX' range,
which ore specially designed
for electric wheel powering and

8

elektor - 2/2009

cyclic charging. A 12 V 7.2 Ah
battery costs about 45 €, or
60 € for a 12 Ah type.

Jan Visser (Elektor labs)

New Elektor videos on
YouTube

Recently added videos on Elek-
tor's YouTube channel include
the Messaging Spin Top from
the December 2008 issue , and
a filmed report of Elektor's Live!
event held in the Netherlands on
22 November 2008. An over-
view of current Elektor videos is
found at

www.youtube.com/elektorim

where 'im stands for Internatio-
nal Media. Once on the chan-
nel you'll be able to watch
short films on the Profiler milling
machine , Microdrones , the Elek-
tor SMT oven , Ball & Beam , For-
mant , study trips to China and

o few items from the Retronics
series. New films will be added
to the 'channel' os they become
ovoiloble.

Selecting 'videos' on YouTube
and then searching for 'elektor'
will return all videos somehow
linked to the word 'elektor'. It
should be noted that many of
these videos ore unrelated to
our magazine , or to electronics
in general.

Vinculum not secure?

Dear Editor — I'd like to thank
you for the article 'ATmega
meets Vinculum' ( Elektor
November 2008, Ed.), which
should keep me busy solder-
ing and programming for a
few winter evenings. I was
surprised however to read the
notice on having to remove the
USB stick when the Vinculum
is switched on or off. As I see
it, the Vinculum is not ready
for its expected application.
After all, it should be perfectly
possible to switch an electronic
device on or off without suf-
fering data loss. I may have
missed something and would
be grateful for your advice.

Very likely another error was
present at the time the doto loss
occurred. Whatever the cause ,
one thing to ovoid at all times
is supply removal during a write
process. Windows even has a
special function for this: remove
hardware securely.

Burkhard Kainka

Elektor magazine's Messaging Spin Top

A Messaging

i r » j

A -

•JW;

LED Sp'

M I

Elektor Decerinber'ZOOS
www.elektor.com

Electronic Transformers

Dear Elektor — as a staunch
reader since issue # 1 I'd like
to provide some information
that's supplemental to your
article 'Electronic Transformers
Revealed and Explained' in
the December 2008 issue.
These 'transformers' are
actually switch-mode power
supplies or, more accurately,
'power auto oscillators' and
most of them are based on
application note AN528 from
STmicroelectronics. Even if
bipolar transistors have been
replaced by MOSFETs in
recent models, the principle
remains the same. The applica-
tion note provides a detailed
operation of these supplies,
and has good educational
value.

Interesting as that may be, if
we look at the schematics in
detail, it's apparent that these

the load, which will benefit the
life expectancy of the bulbs
(effectively preventing the
high inrush current when the
filament is cold). It is also
much more agreeable in the
bathroom, particularly in the
morning when harsh lights
normally greet you there.
Electronics enthusiasts may
reap another benefit from
these cheap supplies by simply
rectifying and smoothing the
output voltage, and so make a
cheap, powerful, 0 to 15 volts
adjustable supply.

Be sure to observe electrical
safety, as the potentiometer
terminals are connected to the
rectified AC mains voltage. A
potentiometer with a plastic
spindle must be used, prefer-
ably in combination with an
ABS enclosure.

Alain Caillard (France)

supplies may be modified to
act as dimmers. The oscilla-
tor is triggered by a diac using
an RC network. If a potentiom-
eter with value 10 R is inserted
in series with R, a dimmer is
created with a range close to
0 - 100 %.

Sure, you have to know a bit
about electronics but I would
expect Elektor readers to be
able to locate the resistor (if
necessary, consult the appli-
cation note), and lift up one
of its legs. The resistor value
is usually between 100 k£l
and 220 k£l, depending on
the model and the associated
capacitor. Do not remove the
resistor completely, as it will
act as a protection if the pot is
set to zero. In the absence of
the fixed resistor, a resistance
below the original value could
well cause the supply to go up
in smoke.

An even more exciting modi-
fication is to link the potenti-
ometer to a switch. This setup
allows a smooth switch-on of

Electronic Transformer for
a 12V Halogen Lamp,
Fichera, P. and Scollo, R.,
AN528/0999, STMicroelec-
tronics, 1 999.
www.st.com/stonline/prod-
ucts/literature/an/3707.pdf

Mai I Box Terms

• Publication of reader's orrespondence
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 MailBox

correspondence to:

editor@elektor.com or
Elektor, The Editor,
1 000 Great West Road,
Brentford TW8 9HH, England.

2/2009 - elektor

9

ADVERTISEMENT

3 NlikroElektronika

DEVELOPMENT TOOLS I COMPILERS I BOOKS

Now you need a...

By Dusan Mihajlovic

Do you want your new device to have a simple and intuitive
interface? If the answer is YES, then a graphic LCD display with
touch panel is the best choice because together they create a
Touchscreen (Glcd + Touch Panel = Touchscreen). In that way,
with a small number of electronic components you will be able
to create an attractive and easy to use device.

Mikroelektronika Hardware Department

In this case, the voltage is read on the left contact
of the X surface.

Connecting to microcontroller

What is a touch panel? A touch panel is a thin,
self-adhesive transparent panel placed over the
screen of a graphic LCD. It is very sensitive to
pressure so that even a soft touch causes some
changes on output signal. There are a few types
of touch panel. The simplest one is the resistive
touch panel which will be discussed here.

Principle of operation

A resistive touch panel consists of two transpar-
ent rigid foils, forming a "sandwich" structure,
that have resistive layers on their inner sides. The
resistance of these layers usually does not ex-
ceed 1 Kohm. The opposite sides of the foils have
contacts available for use through a flat cable.
The process of determining coordinates of the
point in which the touch panel is pressed can be
broken up into two steps. The first one is the de-
termination of the X coordinate and the second
one is the determination of the Y coordinate of
the point. In order to determine the X coordinate,
it is necessary to connect the left contact on the
X surface to ground and the right contact to the
power supply. This enables a voltage divider to
be obtained by pressing the touch panel. The val-

ue of the divider is read on the bottom contact of
theY surface. Voltage can be in the range ofOVto
the power supply and depends on the X coordi-
nate. If the point is closer to the left contact of the
X surface, the voltage will be closer to OV. In order
to determine the Y coordinate, it is necessary to
connect the bottom contact on the Y surface to
ground, and the upper contact to power supply.

Flat cable
detail

In order to connect a touch panel to the micro-
controller it is necessary to create a circuit for
touch panel control. By means of this circuit, the
microcontroller connects appropriate contacts of
the touch panel to ground and the power supply
(as described above) in order to determine the X

vcc

X surface

Determination of Y coordinate

Figure 1. Touch panel internal structure

Advertisement article of MikroElektronika www.mikroe.com

mikroC® and mikroC PRO® are registered trademarks of MikroElektronika. All rights reserved.

NOTE:

... 4~n*jJlc SOFTWARE AND HARDWARE SOLUTIONS FOR EMBEDDED WORLD WWW.mikroe.COm

+5VO-

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TOUCHSCREEN

10E

22pF,

GLCD

Schematic 1. Connecting Touchscreen

and Y coordinates (Refer to Schematic 1 ). The bottom contact of the Y sur-
face and left contact of the X surface are connected to the microcontroller's
A/D converter. The X and Y coordinates are determined by measuring voltage
on these contacts, respectively. The software consists of writing a menu on
graphic LCD, turning the circuit for touch panel control on/off (driving touch
panel) and reading the values of A/D converter which actually represent the
X and Y coordinates of the point.

Once the coordinates are determined, it is possible to decide what we want
the microcontroller to do. For the purpose of illustration, let us examine
Example 1. It explains how to turn on/off two digital microcontroller pins,
connected to LED diodes A and B, using a display and a touch panel.

Flat cable on-board connector
before...

...and after connecting touch
panel.

Considering that the touch panel surface is slightly larger than the surface
of the graphic LCD, in case you want greater accuracy when determining
the coordinates, it is necessary to perform the software calibration of the
touch panel.

Functions used in the program

ADC_Read() Read analog value
Delay_ms() Delay

Gicd_box() Draw filled box*

Glcd_circle() Draw circle

Glcd_Dot() Draw dot

Glcd_Fill() Delete/fill display*

Glcd_H_Line() Draw horizontal line
Glcd_lmage() Import image

Glcd_lnit() LCD display initialization*

Glcd_Line() Draw line
Glcd_Read_Data() Read data from LCD

Glcd_Rectangle() Draw rectangle*

Glcd_Set_Font() Select font*

Glcd_Set_Page()

Glcd_Set_Side()

Glcd_Set_X()

Glcd_V_line()

Glcd_Write_Char()

Glcd_Write_Data()

Select page
Select side of display
Determine X coordinate
Draw vertical line
Write character
Write data

| Glcd_Write_Text() Write text*

* Glcd library functions used in the program

mikroC PRO for AVR® library editor with ready to use libraries such as:
Ethernet, CAN, SD/MMC etc.

Code for this example written for AVR® microcontrollers in C, Basic and
Pascal as well as the programs written for PIC® and dsPIC® microcontrollers
can be found on our web site www.mikroe.com/en/article/

Examine 1j_ Program to demonstrate touchscreen operation

// Glcd module connections

char GLCD_DataPort at PORTC;

sbit GLCD_CS1 at P0RTD.B2;
sbit GLCD_CS2 at P0RTD.B3;
sbit GLCD_RS at P0RTD.B4;
sbit GLCD_RW at P0RTD.B5;
sbit GLCD_EN at P0RTD.B6;
sbit GLCD_RST at P0RTD.B7;

sbit DRIVE_A at P0RTA.B2;
sbit DRIVE_B at P0RTA.B3;

char GLCD_DataPort_Direction at DDRC;

sbit GLCD_CS1_Direction at DDRD.B2;
sbit GLCD_CS2_Direction at DDRD.B3;
sbitGLCD_RS_Direction at DDRD.B4;
sbit GLCD_RW_Direction atDDRD.B5;
sbitGLCD_EN_Direction atDDRD.B6;
sbit GLCD_RST_Direction at DDRD.B7;

// End Glcd module connections

sbit DRIVE_A_Direction at DDRA.B2; //Touch Panel module connections
sbit DRIVE_B_Direction at DDRA.B3; // End Touch Panel module connections

long x_coord, y_coord, x_coord1 28, y_coord64;

// scaled x-y position

unsigned int GetX() {

DRIVE_A = 1;
DRIVE_B = 0;
Delay_ms(5);
return ADC_Read(0);

}

unsigned int GetY() {

DRIVE_A = 0;
DRIVE_B = 1;
Delay_ms(5);
return ADC_Read(1);

}

//reading X

// DRIVEA = 1 (LEFT drive on, RIGHT drive on, TOP drive off)
// DRIVEB = 0 (BOTTOM drive off)

// READ-X (BOTTOM)

//reading Y

// DRIVEA = 0 (LEFT drive off, RIGHT drive off, TOP drive on)
// DRIVEB = 1 (BOTTOM drive on)

// READ-X (LEFT)

void main() {

DRIVE_A_Direction = 1;
DRIVE_B_Direction = 1;
PORTB.BO = 0;

DDRB.BO = 1;

P0RTB.B1 =0;

DDRB.B1 = 1;

GlcdJnitO;

Glcd_Fill(0);

Glcd_Set_Font(font5x7, 5, 7, 32);
Glcd_Fill(0);

// Set DRIVE_A pin as output
// Set DRIVE_B pin as output

// Set PBO pin as output (Default value 0)

// Set PB1 pin as output (Default value 0)

// Initialize GLCD
//Clear GLCD
// Choose font,

Glcd_Write_Text("TOUCHPANEL EXAMPLE", 10,0, 1);
Glcd_Write_Text("MIKROELEKTRONIKA", 17,7,1);

Glcd_Rectangle(8, 16,60,48,1);
Glcd_Rectangle(68,1 6,1 20,48,1 );
Glcd_Box(1 0,1 8,58,46,1 );

Glcd_Box(70,1 8,1 18,46,1 );
Glcd_Write_Text("BUTTON 1 ",1 4,3,0);
Glcd_Write_Text("PB0 OFF", 14, 4,0);
Glcd_Write_Text("BUTTON2"74,3,0);
Glcd_Write_Text("PB1 OFF", 74, 4,0);

while (1) {

x_coord = GetX();
y_coord = GetY();

x_coord 1 28 = (x_coord * 1 28) / 1 024;
y_coord64 = 64 -((y_coord *64) / 1 024);

//Display Buttons on GLCD:

// read X-Y and convert it to 1 28x64 space

//if BUTTON 1 is selected

if ((x_coord1 28 >= 10) && (x_coord128 <=58) && (y_coord64 >= 18) && (y_coord64 <= 46)) {
if(PORTB.B0 == 0) {

PORTB.BO = 1;

Glcd_Write_Text("PB0 ON ",1 4,4,0);

}

else {

PORTB.BO = 0;

Glcd_Write_Text("PB0 OFF", 1 4,4,0);

}

}

//if BUTTON2 is selected

if ((x_coord1 28 >= 70) && (x_coord1 28 <= 1 1 8) && (y_coord64 >= 1 8) && (y_coord64 <= 46)) {
if(PORTB.B1 == 0) {

PORTB.B1 =1;

Glcd_Write_Text("PB1 ON "74,4,0);

}

else{

PORTB.B1 =0;

Glcd_Write_Text("PB1 OFF", 74, 4,0);

}

}

}

Delay_ms(100);

Atmel®, logo and combinations thereof, AVR® and others are registered trademarks or trademarks of AtmelCorporation or its subsidiaries.
Other terms and product names may be trademarks of others.

Saturday, February 21, 2009, from 10:00 am to 3.30 pm.

Masterclass Hiqh-End Valve Amplifiers

Birmingham City University, Technology Innovation Centre.
Presenter: Menno van der Veen , MSc.

Introducing Jeremy,
the ultimate 3D 1C customer

The future success of the semicon-
ductor industry will depend on how
successful it is in implementing 3D
1C technology to meet the demands

Donabedian sees Jeremy (and the
next generation of electronics con-
sumers) as ready to buy a host of
integrated applications that will

In this Masterclass Menno van der Veen will examine the predictability and
perceptibility of the specifications of valve amplifiers. Covered are models that allow
the characteristics of valve amplifiers to be explored up to the limits of the audible
domain from 20 Hz to 20 kHz. This then leads to the minimum stability requirements
that the amplifier has to satisfy. The coupling between output valves and output
transformer are also modelled. This gives new insight into a unique type of distortion:
Dynamic Damping Factor Distortion (DDFD). Negative feedback is often used in
amplifiers. What is the optimum and what are the audible consequences? The correct
amplification of micro details is explained, based on new research, and new models
about this are presented.

The course fee is £ 160, including handout, certificate and lunch. Elektor subscribers
are entitled to a 5% discount. Register now, seating capacity is strictly limited.

Further information and registration at www.elektor.com/events

April 3-1 2, 2009.

Study trip: Visit China with Elektor

Tour host: Margriet Debeij ( with
assistance from local guides and
interpreters).

Elektor's third study trip to China is
planned for 3-12 April 2009. And you
can join us! During this 1 0-day trip we
will visit the China Electronics Fair in
Shenzhen, a professional industrial
electronics fair with an area of no
less than 60,000 m 2 . We will also pay
at least one visit to the well-known
'electronics high street' in Shanghai.

As the name suggests, this street
is entirely dedicated to electronics
shops, each vying to be the largest.

In addition, a variety of interesting
company visits are on the itinerary
(with a tour of the production
department). We are also organising
a business conference where you
can obtain a wealth of information
about doing business (and how not
to do business) in China. We put all
the do's and don'ts in a tidy list for
you. Naturally, there's also time for
culture. We will visit the Bund, French
Confession and the Shanghai TV tower.
There's also a Shanghai sightseeing
tour planned.

As with the first and second 'Elektor
goes to China' tours, this edition will
again be blogged using the Elektor
website.

Further information at www.elektor.
com/china-trip

of a 17-year-old consumer named
Jeremy, according to Ziptronix
CEO Dan Donabedian. In a pres-
entation at the fifth annual The
future success of the semiconductor
industry will depend on how suc-
cessful it is in implementing 3D 1C
technology to meet the demands of
a 1 7-year-old consumer named Jer-
emy, according to Ziptronix CEO
Dan Donabedian. In a presenta-
tion at the fifth annual 3D Architec-
tures for Semiconductor Integration
and Packaging conference today
in Burlingame, CA, Donabedian
described the role his company's
revolutionary bonding technology
will play in the emerging 3D 1C
supply chain.

According to Donabedian's presen-
tation, one of the crucial elements
for successful implementation of 3D
1C technology is a reliable, econom-
ical, low temperature oxide bond-
ing process that will enable true
3D integration of semiconductors.
"A high throughput bonding proc-
ess that achieves true metal-to-metal
interconnect without requiring high
temperature or compression has
long been seen as the 'missing link'
in the 3D 1C supply chain that is
now taking shape in the semicon-
ductor industry," he explained.

"Ziptronix technology will be one
of the key factors in making 3D 1C
integration a mainstream semicon-
ductor technology."

be enabled by 3D 1C technology,
including:

• Mobile phones with high res-
olution digital cameras and
increased functionality

• Ultramobile, low power, light-
weight PCs

• Interactive handheld gam-
ing devices with projection
capabilities

• Embedded pico-projectors in a
variety of portable multimedia
devices

• Advanced automotive sen-
sors (lane change/collision
warning)

• Sophisticated medical imaging
systems

The Ziptronix processes can be
implemented throughout the present
semiconductor supply chain - by
the OEMs/IDMs; by fabless and
'fab-lite' companies; by the major
foundries; by semiconductor tool
manufacturers and EDA vendors;
and by the OSAT houses.

www.ziptronix.com

(080965-VIII)

elektor - 2/2009

i~\ r~\ r~\ r\ r~\

A N T E X

LJLJLJ LJL J

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am t(

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A large range of replacement tips are available for most irons,
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Our now website has all of our runs, and soldering spares and
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Why not give antes.co.uk a try!

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Tel: ^ 44(0)1822 613565
fax: +44(0}1S22 61759S
Email: salesdSantex.co.uk
Web: www.antex.co.uk

n

Elektor SMT Oven

^ Multi-purpose and indispensable
to professional and enthusiast

Selected, tested & certified by Elektor
Including Elektor-produced user manual
Fully menu controlled

Ideal for R&D laboratories, schools, small companies and.
electronics enthusiasts

Product support from Elektor Customer Services

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Art. # 080663-91 • Price: £962.00 • € 1195.00 • US $1665.00 (Excl. VAT)

Main technical specifications

Line voltage: 230 V AC / 1 650 W
Line frequency: 50-60 Hz

Size: 418x372x250 mm (16. 5 x 14. 6 x 10 inch)
Weight: 1 6.7 kg (net)

Effective PCB area: 280 x 280 mm (11 x 1 1 inch)

Further information and ordering at www.elektor.com/smtoven

k

2/2009 - elektor

13

INFO & MARKET

NEWS & NEW PRODUCTS

Elektor USA on newsstand distribution

Following a three-month introduc-
tion period and the rapid growth
of its subscriber base, Elektor USA
is now progressing to newsstand
sales, allowing 'folks' to browse
a copy before buying. Starting
with this February 2009 issue,
the magazine is stocked by Bor-
ders bookshops in selected cities
in the USA. This may be followed
by other store chains.

Elektor USA joins the successful
English, Dutch, Spanish, French,

German, Italian, Portuguese and
Brazilian editions centrally produ-
ced by Elektor International Media,
with websites to match.

American and Canadian readers
originally subscribed to the Euro-
pean Elektor can now subscribe
on-line using the specially created
USA landing page, which con-
tains an offer they will find hard to
refuse. The expanded Elektor USA
website is expected to come online
around 1 February 2009.

electronics worldwide

wwM.eiek1ar.6Dni OCTOBER 2008

US tr.Ofr'CjradA

Elektor International

is coming to North America

www.elektor-usa.com

MontaVista: big endian support for ARM1 1 family

MontaVista® Software, Inc.
announced that MontaVista
Linux now provides support for
the ARM1 176JZ-S™ and ARM-
1 176JZF-S™ processors, including
the first ever 'big endian' support
option for the ARM1 1™ family in
a Linux environment. By suppor-
ting these ARM1 1 family proces-
sors, MontaVista gives consumer
device manufacturers a commer-

cial-quality Linux implementation
along with tools to reduce time-to-
market and development costs for
custom SoC designs.

MontaVista provides a commercial
quality Linux platform for mobile
device manufacturers. Its broad
hardware support, dedication to
quality, and full support has made
it the undisputed leader in the

mobile Linux market. Its advanced
power management, fast startup,
and advanced connectivity provide
the features mobile device manuf-
actures require. In addition to pow-
ering a majority of today's Linux
handsets, MontaVista Linux is the
only Linux to demonstrate support
of and integration with all major
Linux mobile software stacks, is
the only mobile Linux certified as

being ready for IPv6, provides sup-
port for new mobile device proces-
sors from Freescale® Semiconduc-
tor, Intel®, Texas Instruments and
others and was awarded "Best
Software Innovation of the Year"
for 2007 by EDN.

www.mvista.com

(081040-IX)

BIGAVR-2 Board

MikroElektronika recently
introduced a new develop-
ment tool for AVR® microcon-
trollers. The new BIGAVR®2
supports 8, 64-pin and 100-
pin AVR (TQFP package) AVR®
and gives designers an easy
to use platform to try a multi-
tude of designs. The BIGAVR®2
comes complete with everything
you need to learn, experiment,
design and program with AVR®.
The BIGAVR®2 includes a Touch-
Panel controller, so you can eas-
ily add additional input to proto-
type devices.

Like its predecessor, BIGAVR®2
has an ultra fast on-board USB
2.0 programmer. The new

board delivers an extensive list of
features, including:

• TouchPanel controller

• Buttons for changing states of
all pins

• LEDs for displaying states of all
pins

• Support for Character LCD

• Support for Graphic LCD

• JTAG connector

• RS232 communication

• Support for PS/2

• 4.096 Vref for ADC

• Selectable USB or external
power supply

• MMC/SD Card Slot

• I DC 1 0 connectors for further
expansion

• Pull up/pull down selection of

each pin

Every feature of the board is sup-
ported by examples written in mik-
roC PRO, mikroPascal and mikro-
Basic compilers for AVR®.

The BIGAVR®2 Board is available

for purchase on the mikroelek-
tronika website and through
authorized distributors.

www.mikroe.com

(081040-V)

CapSense (tm) proximity sensing achieves 25 cm detection range

Cypress Semiconductor Corp.
announced that its proximity detec-
tion solution enables a best-in-class
proximity detection range of 25
cm. Proximity sensing enables new

usage models where direct touch
is not required, instead detecting
a finger or another object as it
approaches the device. The solu-
tion allows for enhanced industrial

designs that only expose inter-
faces or buttons when necessary
and provides incremental power
savings by activating an interface
only when needed.

To simplify use of this proximity
sensing functionality, Cypress also
announced a free online tutorial
that shows how to develop prox-
imity sensing detectors without

[continued on page 16 ]

14

elektor - 2/2009

QUASAR

electro nics

Quasar Electronics Limited

PO Box 6935, Bishops Stortford
United Kingdom

CM23 4WP,

Tel: 0870 246 1826
Fax: 0870 460 1045

E-mail: sales@quasarelectronics.conj
Web: www.QuasarElectronics.com

08717

Postage & Packing Options (Up to 0.5

3-7 Day
Europe

Delivery - £3.95; UK Mainland
(EU) - £6.95; Rtjst of World - £
SOrder online for reduced price UK Pc

We accept all major credit/debit cards
to Quasar Electronics. Prices include
Please visit our online shop now for
projects, modules and publications.

<g gross weight): UK Standard
Next Day Delivery - £8.95;
f).95 (up to 0.5Kg)

stage!

. Make cheques/PO’s payable
17.5% VAT.

cjetails of over 500 kits,
iscounts for bulk quantities.

fcs?

-----

I

177 168

The Electronic Kit Specialists Since 1993

Motor DHvers/Controllei's

Here are just a few of our controller and
driver modules for AC, DC, Unipolar/Bipolar
stepper motors and servo motors. See
website for full range and Pdetails.

Controllers & Loggers

Here are just a few of the controller and
data acquisition and control units we have
See website for
for all units: Ord

full details. S
er Code PSU

uitable PSU
445 £8.95

Computer Controlled / Standalone Unipo-
lar Stepper Motor Driver

Drives any 5-35Vdc 5, 6 or
8-lead unipolar stepper
motor rated up to 6 Amps.

Provides speed and direc-
tion control. Operates in stand-alone or PC-
controlled mode for CNC use. Connect up to
six 3179 driver boards to a single parallel
port. Board supply: 9Vdc. PCB: 80x50mm.
Kit Order Code: 3179KT - £12.95
Assembled Order Code: AS3179 - £19.95

Computer Controlled Bi-Polar Stepper
Motor Driver

Drive any 5-50Vdc, 5 Amp
bi-polar stepper motor using
externally supplied 5V lev-
els for STEP and DIREC-
TION control. Opto-isolated
inputs make it ideal for CNC applications
using a PC running suitable software. Board
supply: 8-30Vdc. PCB: 75x85mm.

Kit Order Code: 3158KT - £17.95
Assembled Order Code: AS3158 - £27.95

Bi-Directional DC Motor Controller (v2)

Controls the speed of
most common DC
motors (rated up to
32Vdc, 10A) in both
the forward and re-
verse direction. The
range of control is from fully OFF to fully ON
in both directions. The direction and speed
are controlled using a single potentiometer.
Screw terminal block for connections.

Kit Order Code: 3166v2KT - £17.95
Assembled Order Code: AS3166v2 - £27.95

DC Motor Speed Controller (100V/7.5A)

Control the speed of
almost any common
DC motor rated up to
100V/7.5A. Pulse width
modulation output for
maximum motor torque
at all speeds. Supply: 5-15Vdc. Box supplied.
Dimensions (mm): 60Wx100Lx60H.

Kit Order Code: 3067KT - £13.95
Assembled Order Code: AS3067 - £21.95

I lost items are available in
r assembled and ready for

kit form (KT suffix)
use (AS prefix).

8-Ch Serial Isolated I/O Relay Module

Computer controlled 8-
channel relay board. 5A
mains rated relay outputs. 4
isolated digital inputs. Useful
in a variety of control and
^sensing applications. Con-
trolled via serial port for programming (using
our new Windows interface, terminal emula-
tor or batch files). Includes plastic case
130x100x30mm. Power Supply:
12Vdc/500mA.

Kit Order Code: 3108KT - £54.95
Assembled Order Code: AS3108 - £64.95

Computer Temperature Data Logger

4-channel temperature log-
ger for serial port. °C or °F.
Continuously logs up to 4
separate sensors located
200m+ from board. Wide
Fange or tree software applications for stor-
ing/using data. PCB just 45x45mm. Powered
by PC. Includes one DS1820 sensor.

Kit Order Code: 3145KT - £17.95
Assembled Order Code: AS3145 - £24.95
Additional DS1820 Sensors - £3.95 each

Rolling Code 4-Channel UHF Remote

State-of-the-Art. High security.

4 channels. Momentary or
latching relay output. Range
up to 40m. Up to 15 Tx’s can
be learnt by one Rx (kit in-
cludes one Tx but more avail-
able separately). 4 indicator LED ’s. Rx: PCB
77x85mm, 12Vdc/6mA (standby). Two and
Ten channel versions also available.

Kit Order Code: 3180KT - £44.95
Assembled Order Code: AS3180 - £54.95

DTMF Telephone Relay Switcher

Call your phone num-
ber using a DTMF
phone from anywhere
in the world and re-
motely turn on/off any
of the 4 relays as de-
sired. User settable Security Password, Anti-
Tamper, Rings to Answer, Auto Hang-up and
Lockout. Includes plastic case. Not BT ap-
proved. 130x110x30mm. Power: 12Vdc.

Kit Order Code: 3140KT - £54.95
Assembled Order Code: AS3140 - £69.95

Infrared RC Relay Board

Individually control 12 on-
board relays with included
infrared remote control unit.

Toggle or momentary. 15m+
range. 112x122mm. Supply: 12Vdc/0.5A
Kit Order Code: 3142KT - £47.95
Assembled Order Code: AS3142 - £59.95

PIC & ATMEL Programmers

We have a wide range of low
ATMEL Programmers. Comply
documentation available from

Programmer Ac
40-pin Wide ZIF
18Vdc Power su
Leads: Parallel
(LDC441) £3.95 /

cessories:

socket (ZIF40W) £14.95
pply (PSU010) £18.95
(LDC136) £3.95 /Serial
USB (LDC644) £2.95

cost PIC and
te range and
bur web site

NEW! USB & Serial Port PIC Programmer

USB/Serial connection. Header
cable for ICSP. Free Windows
iXP software. Wide range of
supported PICs - see website for
\T complete listing. ZIF Socket/USB
lead not included. Supply: 16-18Vdc.

Kit Order Code: 3149EKT - £39.95
Assembled Order Code: AS3149E - £49.95

NEW! USB 'All-Flash' PIC Programmer

USB PIC programmer for all
‘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 - £44.95

“PICALL” PIC Programmer

“PICALL” will program virtu-
ally all 8 to 40 pin serial-
mode AND parallel-mode
(PIC16C5x family) pro-
grammed PIC micro control-
lers. Free fully functional software. Blank chip
auto detect for super fast bulk programming.
Parallel port connection. Supply: 16-18Vdc.
Assembled Order Code: AS31 17 - £24.95

ATMEL 89xxxx Programmer

Uses serial port and any
standard terminal comms
program. Program/ Read/

Verify Code Data, Write
Fuse/Lock Bits, Erase and
Blank Check. 4 LED’s display the status. ZIF
sockets not included. Supply: 16-18Vdc.

Kit Order Code: 3123KT - £24.95
Assembled Order Code: AS3123 - £34.95

■I

Th im i i t m

li'tm ftp

Tl d M nip

tfs*

www. QuasarElectronics. coin

i

s

ecure Online O

rdering Facilit

ies • Full Proc

Juct Listing, D

escriptions &

Photos • Kit [

)ocumentatior

l & Software C

downloads

INFO & MARKET

NEWS & NEW PRODUCTS

writing or debugging a single
line of C or Assembly code using
Cypress's PSoC Designer ,tm| embed-
ded design tool. The 30-minute
interactive video entitled "Building
a Proximity Detector Using PSoC
Designer" is available at the web-
site below.

The new video includes an intro-
duction to proximity sensing with
a demonstration of the detection
range of the CapSense solution,
and it features Cypress member of

technical staff Dave Van Ess pre-
senting the design of a proxim-
ity sensing interface using PSoC
Designer software via the PSoC
FirstTouch (tm| Starter Kit. The USB
thumbdrive kit can also be used
for touch-sensing, temperature-sen-
sing and light sensing-designs. The
CY3270 PSoC FirstTouch Starter
kit is available for US$ 29.95.
The follow-on CY3271 PSoC First-
Touch Starter Kit with CyFi (tm| low-
power RF enables proximity sens-

ing as well, and is available for
US$ 69.95 (all prices plus P&P).
CapSense Sliders and CapSense
Buttons evaluation kits are avail-
able from Elektor at a special dis-
counted price.

www.cypress.com / proximitysensing
www.cypress.com /ProximityDemo
www.cypress.com /FirstTouch

(081040-1)

New EDP modules from RS: Bluetooth and WiFi

hosting a WiFi SD
card, such as the Spectec
802. 1 1 b card, the module
allows communication rates of
up to 1 1 Mbit/s over distances
of up to 150 m. The modules pro-

and

visual

media, home
monitoring data or Inter-
net connectivity.

Following Elektor's review of the RS
Components Embedded Develop-
ment Platform (EDP) in the Decem-
ber 2008 issue, RS Components
have released two new modules
for the system.

The new Bluetooth Application
Module (EDP -AM-BT54) allows
you to replace cable communica-
tion in a variety of applications,
with ease. The module combines a
PIC1 8LF6722 microcontroller and
FlexiPanel's LinkMatik Bluetooth
radio, allowing designs to synchro-
nise with any Bluetooth enabled

device within a 100 m range and
allow data rates of up to 2. 1 Mbit/
s. The module is fully FCC / CE /
1C certified and operates in the
globally unlicensed Industrial, Sci-
entific & Medical (ISM) 2.4 GHz
short-range radio frequency band-
width, therefore reducing the need
for licensing and certification of
your final design.

The new WiFi Application
Module (EDP-AM-WFSD) pro-
vides a solution for designs requir-
ing higher throughput over larger
distances than Bluetooth. Through

vides a robust and highly secure
wireless medium for applications
such as the transmission of audio

http: / / rswww.com /edp

(081040-VI)

Compact, high-performance digital amplifier with IIS digital audio signal input

ses a significant processing load.
In the R2J15116FP, in contrast,
processing for the volume control
and the parametric equalizer*2 for

generate a more varied and hig-
her quality sound environment for
video applications.

The R2J151 16FP employs a feed-

mil

^ENESAS

R2J15116

FP

TTmTTTmT

Renesas Technology Europe
recently announced the
R2J15116FP, a compact, high-
performance digital amplifier sup-
porting IIS* 1 digital audio signal
input with a built-in 24-bit audio
DSP. It is intended for use in thin
flat-screen TVs employing LCD or
plasma display panels.

The device, contained in a com-
pact 7x7 mm package, accepts
IIS digital audio signal input, per-
forms signal processing using
a built-in 24-bit audio DSP, and
amplifies the result with a digital
amplifier to deliver stereo output to
two speakers at up to 15 watts per
channel. Typically, thin flat-screen
TVs require detailed tuning of their
audio systems for different markets
and screen sizes. This processing
is usually performed in the prece-
ding stage of this digital amplifier
by the main DSP, which mainly
handles tasks such as surround pro-
cessing and decoding. This impo-

optimizing the speaker characteri-
stics is done by the built-in audio
DSP. This reduces the load on the
main DSP and makes it possible to

back circuit to stabilize the output
level when the power supply volt-
age fluctuates, an approach with
a proven track record in products

employing analog input. In addi-
tion to the volume control and
seven-band parametric equalizer,
there is a two-band tone con-
trol, a loudness function useful
for low- and high-range expan-
sion compensation, a power lim-
iter function that allows setting of
a user-defined maximum output
level, and a dynamic range con-
trol (DRC) function that lowers the
signal amplitude without distortion
at high volume levels and raises it
at low volume levels. Settings for
all of these functions can be made
flexibly from the MCU via the l 2 C
bus.

The R2J151 16FP uses a compact
48-pin HTQFP package, requires
no heat sink, and delivers maxi-
mum stereo output of 15 watts per
channel.

http://eu.renesas.com/

(081040-11)

16

elektor - 2/2009

Renewable Energy Education set

Horizon announces its
new and comprehensive
Renewable Energy Edu-
cation set, the latest and
final development in its
line of clean energy sci-
ence sets designed for
discovery and inventive-
ness in classrooms, sci-
ence fairs, or at home.

Similar to a futuristic
chemistry set, this new
kit is Horizon's most
comprehensive science
kit covering all aspects
of wind, solar, water and hydro-
gen elements in a modular form
for numerous experiments. The
kit explores clean energy from

I

4

wind or solar power, hydrogen
energy storage, and distributed
power generation using fuel cells.
The kit includes a miniature wind

turbine, a solar cell, an electro-
lyzer, a fuel cell, water-based
hydrogen and oxygen storage
tanks, a small electric motor and

an LED light module. All
items are set on modular
base with interconnect-
able wiring and tubing.
The Renewable Energy
Education set introduces
fuel cell, solar cell and
wind turbine technol-
ogy to students, aspiring
scientists, teachers and
engineers investigating
clean energy concepts
and technologies.

This new set is part of
Horizon's extensive line
of clean energy science
education kits.

www.horizonfuelcell.com

(081040-VII)

Gumstix: open source, Linux compatible, lowest cost ARM platform

At only 17x58x4.2 mm in size,
the Overo™ Earth motherboard
from Gumstix gives open source
innovators access to the industry's
highest performance, generally
available ARM® based platform
in the tiniest, lowest cost Linux com-
puter available based on the Texas
instruments (Tl) OMAP 3503 appli-
cations processor. With Overo
Earth, the open source community
can freely innovate in a vast range
of application areas using this tiny
computer.

Nearly 40 percent smaller than
existing Gumstix motherboards,
the Overo Earth motherboard runs
Linux kernel 2.6.27 or higher. Linux
developers can also take advan-
tage of the 256 MB low power

Leveraging the laptop-like perfor-
mance of the OMAP3503 proces-
sor, the Overo Earth motherboard
takes advantage of the 600 MHz
ARM Cortex™-A8 processor and
integrated peripherals. This Cor-
tex-A8 processor achieves an addi-
tional 4x performance improve-
ment over the 300 MHz ARM9
through its superscalar architec-
ture, which allows implementa-
tion of instruction-level parallelism
within a single processor.

The Overo Earth motherboard is
now available for purchase for
US$ 149 (plus P&P).

www.gumstix.com

(081040-III)

DDR RAM, 256 MB NAND flash,
on-board microSD
adapter, 24-pin
flex ribbon
connec-
tor for
camera
con-
trol
sig-
nals

and two
70-pin AVX 5602
14 connectors for
a wide range
of functional
options in
expansion board
design. The power con-
sumption of the Overo Earth

motherboard is typically less than
1 watt.

Overo Earth is plug compat-
ible with future Overo
products to be
based on Tl's
OMAP35x
applications
processors,
such as
the super-
scalar

OMAP3530
which fea-
tures the ARM,
high-performance digital signa
processor (DSP), PowerVR SGX T
graphics engine licensed by Imagi-
nation Technologies and multimedi-
arich accelerators.

Tet' 01635 40347

an-n. m m ™

iLlfl

re

■ 1 1 f i pi Lfii m m

Milted

com

Advertisement

2/2009 - elektor

17

online design tools

Clemens Valens

Clemens Valens (Elektor France Editorial)

Several electronic component manufacturers now offer design tools online or for free
download. We registered - often an obligatory step - on a dozen or so websites to see just
what's being offered and what it's like.

Analog Devices www.analog.com

The Analog Devices website offers a whole range of
interactive design tools, with names that all start with
ADIsim. For example, there's ADIsimPower, a simula-
tor for power supplies - or DC-DC convertors, to be more
precise. Analog Devices also offers a resistance bridge
calculator, an aid for dimensioning photodiode amplifi-
ers, and a tool for calculating analogue filters.

There are also tools on free download, like SRD Design
Studio, a tool for simulating short range radio systems,
and Multisim for Analog Devices, a monster at
183 MB (v 10.0.0).

After running this program, we downloaded the Get-
ting Started project, which is not actually mentioned
anywhere, but can be found at the bottom of the direc-
tory where the program has been installed. This example
shows a single-digit digital counter using the output of an
amplifier amplifying a 1 kHz signal as its clock. Click-
ing the Run button at the top right of the screen starts
the simulation. Double-clicking on the oscilloscope icon
opens a window displaying a two-channel digital oscil-
loscope. It's all very pretty.

Apart from some models of certain common components,

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Multisim only handles Analog Devices components, and
it's not possible to modify them or create new ones.

_ ffx

AVX www.avx.com

AVX offers several tools for selecting its capacitors. We
tried SpiCALCI 3.0, a tool for dimensioning capacitors
for switch-mode power supplies. Unfortunately the pro-
gram does not offer a help function so a good awareness
is required of the various capacitors in the AVX product
range. After selecting a capacitor type, working volt-
age, dielectric, etc. the program displays the capacitor's
resonance frequency and dissipation at a user selected
temperature. A graph can be produced showing imped-
ance response and ESR.

18

elektor - 2/2009

Epcos www.epcos.com

This passive components manufacturer offers several
tools, including AlCap for dimensioning aluminium elec-
trolytic capacitors, and the Ferrite Magnetic Design
Tool, used for evaluating Epcos magnetic materials and
for performing certain calculations pertaining to induct-
ances and coils.

Fairchild www.fairchildsemi.com

FETBench is Fairchild's online design tool, and com-
prises three parts:

- Device Analysis lets you evaluate a component with
customized graphs;

- Application Analysis is a switch-mode power sup-
ply simulator;

- Thermal Analysis lets you specify a board and posi-
tion active components from Fairchild on it. Then the tool
shows a coloured diagram with the temperature distribu-
tion across the surface of the board.

But there's even better from Fairchild: SPM Tool, a very
fine piece of software that is not only able to simulate
motor drivers, but also contains all the theory of motors
in the form of interactive animations. Not to be missed!
Before you can download the software, you are asked
for a username and password. These are the same ones
you used when you signed on.

The same goes for PFC Toolkit, a tool for exploring
phase correction techniques.

Linear Technology www.linear.com

LTSpice IV is the current name of the SPICE simulator
from Linear Technology, originally launched a few years
ago as SwitcherCAD, principally for simulating switch-
mode power supplies. Users soon found that the tool is in
fact a souped-up SPICE that lends itself perfectly to other
simulations. LTSpice is fairly easy and intuitive to use.
You can quickly draw a circuit diagram and simulate
it equally swiftly. OK, so maybe the graphics aren't the
best in the world - but this is a very powerful tool and is
regularly updated.

Apart from LTSpice, the site also offers FilterCAD and
BodeCAD and a number of tools for evaluating certain
Linear Technology components.

2/2009 - elektor

19

TECHNOLOGY

CAD

Maxim www.maxim-ic.com

Maxim does not offer any very sophisticated online
design tools, but there are twenty or so useful calcula-
tors available. Some of them are dedicated to a spe-
cific Maxim component, but not all of them, and there
are several you may find useful. The interesting thing is
that Maxim gives references and detailed explanations
that let you delve into the theory applied practically in
the calculator.

The Power-Supply Cookbook lets you download,
for each regulator in the Maxim catalogue, a PDF file
containing a circuit diagram and component list for
several configurations of the chip. It is also possible to
download all the files in one go, in the form of a 9 MB
PDF, which does save time. It's a bit like the old data-
books, with loads of ideas for circuits.

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Microchip www.microchip.com

Mindi is the analogue simulator from Microchip based
around (X)SPICE and developed by SIMetrix. Mindi is
supplied with lots of component models - we counted
around 4,500 - which makes entering the circuit very
convenient. After selecting a component, you can mod-
ify its parameters, which in most cases comes down to
choosing one of the models provided.

Another free design tool from Microchip is FilterLab2,
which lets you simulate Chebychev, Butterworth, and Bes-
sel type filters. In a quite user-friendly environment, you
can choose your filter, and the software plots the char-
acteristic curves. It also offers an implementation of the
filter, based on Sallen & Key or MFB (multiple feedback)
sections. Several ways of designing the filter are offered.
Once you are satisfied with the theoretical performance
of the filter, you have immediately available a circuit dia-
gram and a SPICE model.

Murata www.murata.com

Five design tools are available for download from
Murata, for capacitors, EMC filters, and thermistors. We
tried out the Murata EMI Filter Selection Simula-
tor (version 3.6.0). This tool lets you dimension EMC
filters for transmission lines. Several configurations are
supported and users can set the circuit parameters in
detail. Once these parameters have been entered, a click
on the Start Simulation button is all it takes to have access
to the results in the form of diagrams. In short, a fine,
easy-to-use tool.

National Semiconductor www.national.com

National Semiconductor has been offering its WEBENGH
simulator for some years now, originally for simulating
power supplies, but now the tool also helps with design-
ing filters, phase-locked loops, LED drivers and even
audio amplifiers. In less than ten minutes, for example,
we were able to design and simulate an ADC with anti-
aliasing filter. Remember to enable pop-ops, otherwise
you won't see all the results of the simulations.

20

elektor - 2/2009

NXP www.nxp.com

SimPort brings together the online simulators from NXP,
developed, like Mindi from Microchip, by SIMetrix/SIM-
PLIS. In fact, there are just two: Active Datasheet and
Buck Designer. Before it is possible to use them, you
need to register, just like everywhere else. Nothing so
special about that, you may say - but you do need to
have good eyesight! If you're not yet registered, you need

to follow the link at the top right of the page which lets
you choose between the two simulators. In Active Datash-
eet, you can select a MOSFET from NXP and generate for
yourself the curves that are usually found on a data sheet.
The difference from a data sheet is that here its up to you
to specify the values for which the curves are generated.
Buck Designer is a tool for simulating a step-down con-
verter The tool offers you a block diagram and a detailed
circuit diagram, and generates diagrams where you can
enlarge certain zones and measure certain parameters.

2/2009 - elektor

21

TECHNOLOGY

CAD

STMicroelectronics www.st.com

Tools from ST, online and to download. For the online
tools, an audio amplifier simulator and a switch-mode
PSU simulator, you need to install the Java runtime envi-
ronment (JRE) first. Then the tools will work... more or
less, at least, on my test computer.

On the other hand, ST Lighting Designer is a Flash
tool for dimensioning fluorescent lighting that is worth
going out of your way for. A designer must have spent
a lot of time on the graphics interface - you'll either like
it or you won't - and the tool works wonderfully well.
Once you have realized that it's not possible to have a
solution with all the options enabled, the tool outputs the
circuit, the components list, and some graphs. You can
then fine-tune loads of parameters.

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Texas Instruments www.ti.com

TINA-TI is the free simulator for downloading from Texas
Instruments and is able to use SPICE models. TINA-TI is
one part of TINA, a complete CAD tool with circuit entry,
PCB design, and simulator.

SwitcherPro is Texas Instruments' switch-mode PSU
simulator. For some months now, this simulator has also
been available online. As usual, you have to register
before you can use it. Once you are connected to the
simulator, it can be run in two ways: from a component
or from specifications.

Vishay www.vishay.com

ThermaSim is a thermal simulator for PCBs. It's not
terribly intuitive to use, but after a bit of effort you can
manage to get the tool to accept your parameters, and it
wi ii th en send the results by e-mail - rather original, but
not very quick. And then when the message does even-
tually arrive, you find that there was a problem and the
simulation has failed. "Please correct and start again",
the e-mail reads. Sure, of course...

Apart from ThermaSim, Vishay also offers several basic
calculators, like for example the TN-507 calculator for
strain gauges.

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22

elektor - 2/2009

Wiirth Elektronik www.we-online.com

Two tools are available from the Wurth website: WE
Inductor Selector 1.0 and WE Flex Designer 2.0.

The latter is used to select a transformer for flyback-type
switch-mode power supplies. The tool isn't exactly pretty
to look at, at least on the test PC, since all the buttons
and boxes were displaced, however a single click on the
Calculate button is all it takes to generate a transformer
reference number.

Cjk-alili

And finally...

It's 2009, and all the component manufacturers are offer-
ing free design tools... All of them? Well, not quite... some
manufacturers are still holding out against this trend. On
the Infineon, Hitachi, Freescale, Toshiba, and NEC web-
sites, for example, we found nothing at all that was worth
mentioning here.

Despite the number of design tools available on the Web,
we may well be asking ourselves just how useful they are.
Sure, some of them are well done, some of them are good
to look at — but is there really any need for so many switch-
mode PSU simulators?

( 080874 - 1 )

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a *ll tf’l

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Microcontrollers, robotics, sensors, and electronics accessories for the engineer, hobbyist, and student.

Milford Instruments

(+44) 1 977 683665
http://www.milinst.com

www.parallax. com

2/2009 - elektor

23

TEST EQUIPMENT

Rainer Schuster (Germany)

This practical instrument can be used to measure and record the characteristic curves of NPN and PNP
bipolar transistors, N- and P-channel JFETs, and N- and P-channel MOSFETs. The circuit is based on an
R8C/13 microcontroller, which transfers the measurement data to a Windows application program via USB.

Quick Project Specs

• R8C/1 3 microcontroller control module

• PC link via USB port

• User-friendly PC program with Help function (runs under Windows 2000 and XP)

• Curve data can be exported to and imported from Excel

• Checking transistor matching

• Records characteristic curves of NPN and PNP transistors, N-channel and P-channel MOS-
FETs, and N-channel and P-channel JFETs

• Plotted curves can be printed out or embedded in other applications

Curve tracers have a long history in
Elektor. The first article on this sub-
ject appeared in the 1979 Summer
Circuits issue, followed by an article
in June 1980, one in October 1988,
and another one in December 1989.
However, none of these circuits had
a computer interface, and except for
the circuit published in the Decem-
ber 1989 issue, they were limited to
NPN transistors.

This situation changed with the project
published in the May 1990 issue, which
provided a control interface for connec-
tion to the Centronics port of an Atari
computer. A version for use with a PC
followed in September 1993. The circuit
was upgraded in April 1998, includ-
ing control software running under
Windows 95.

Now, more than 10 years on it’s time
for a new curve tracer with features
that definitely outclass all the previ-
ous versions.

Curve tracer operating principle

The operating principle of curve tracers
has not changed much since the first
article appeared in Elektor. The basic
idea is to generate a time-dependent
collector current by combining a ramp-
shaped collector-emitter voltage with a
base current that is increased either in
discrete steps or continuously. The col-
lector voltage is plotted on the X axis,
and the collector current is plotted on the
Y axis. The block diagram in Figure 1 is
based on this operating principle.

Control module

The curve tracer described here is
built around an R8C/13 microcontrol-
ler, which is linked to a USB to serial
converter (type PL2303). The complete
circuit diagram is shown in Figures 2a
and 2b. It does not require much com-
ment, since the circuitry of the R8C/13
section was described earlier in the

February 2006 issue [1] and the USB
controller is wired as described in the
March 2006 issue [2]. All of this is fitted
on a PCB measuring only 80 x 35 mm.
Power is supplied via the USB port.
Various I/O port pins, +V and ground
are fed out to a 20-way socket header
so the microcontroller module can also
be used for other tasks.

The microcontroller can be reset when-
ever desired by means of Reset push-
button SI. A set of eighteen 470-Q
resistors limit the output currents of
the I/O pins to approximately 10 mA
in order to protect the board against
the potentially fatal consequences of a
connection error.

When jumper JP1 is fitted, program
code can be downloaded into the
microcontroller via the USB port. One
way to do this is to use the Renesas
Flash Development Toolkit, which can
be downloaded free of charge from the
Web address for this project [3]. The
previously mentioned Elektor articles
and the R8C topic on the Elektor forum
[4] provide adequate information about
generating the software, downloading
the hex file to the microcontroller, and
installing the USB driver on the PC.

Circuit description

Generating the base current or gate-
source voltage

Timer Y is operated in PWM mode to
drive the base or gate of the transis-
tor under test (TUT). See the descrip-
tion of the firmware for more details.
The pulse rate is 2 kHz, and the pulse

24

elektor - 2/2009

width can be set over a range of 0 to
100%. A Butterworth low-pass filter
built around IC5a converts this sig-
nal into a variable DC voltage, which
is amplified by a factor of 2 in IC5b
to provide a voltage at the output of
IC5b with an adjustment range of 0 to
+ 10 V. The linearity of the output volt-
age can be seen clearly in the oscillo-
scope images (Figure 3).

The output voltage is inverted by IC8a
to generate the base current for PNP
transistors or the gate voltage for P-
channel MOSFETs and N-channel
JFETs. Switches SI and S2 (INI and
IN2) of analogue switch IC7 connect
either a positive voltage or a negative
voltage to the base or the gate of the
TUT (see the firmware description for
the associated truth table).

Switches S3 and S4 (IN3 and IN4) of
IC7 are used to select the desired cur-
rent range (0-10 jl/A, 0-100 /JA , or 0-

1 mA). The 0-1 mA range is always
used with the ‘FET’ setting to set the
gate voltage.

Generating the collector-emitter or
drain-source voltage

Timer Z of the R8C/13 is also operated
in PWM mode with a fixed pulse rate
of 2 kHz. A Butterworth low-pass fil-
ter built around IC6 converts the pulse
width into an analogue voltage and
amplifies the voltage by a factor of

2 to again provide an output voltage
with a range of 0 to +10 V. The volt-
age is inverted by IC8b to generate
the collector-emitter voltage for PNP
transistors or the drain-source voltage

for P-channel MOSFETs and P-channel
JFETls. Switching between positive and
negative voltages is provided by ana-
logue switch IC9. The current gain is
provided by IC10 in combination with
a transistor output stage formed by Tl-
T4. Resistors R34 and R35 limit the out-
put current to approximately ±0.5 A.

Measuring the characteristics

The configured base current is not

measured, but instead calculated by
the software from the configured base-
emitter voltage and the selected base
current range.

In order to measure the configured col-
lector-emitter voltage, it is first recti-
fied by IC11 because it can be either
positive or negative. After being
divided by a factor of 2 by R42/R43, the
rectified voltage is fed to the microcon-
troller A/D converter input ADO. The

2/2009 - elektor

25

TEST EQUIPMENT

C11

C7

h i i mi

100n

10|_i

25V

R7 R6 R5 R12

D1

R9

LL4148

R31

in

^Tooi

n s

Ui

PI .7

8

/

PI .6

9

/

10 _

11

PI .3

12

/

PI .2

13

/

P1.1

14

/

P1.0

15

/

P4.5

16

/

P3.3

17

s

R8

+5V

1

Tr29 | R30

1 0

19

VCC AVCC/VREF
P37/TXD1 0/RXDI P00/AN7/TXD1 1

RESET

P17/INT1/CNTR0
P16/CLK0
P15/RXD0
P14/TXD0
P13/KI3
P12/KI2
P11/KI1
PIO/KIO
P45/INT0
P33/INT3/TCIN
CNVSS

R8C/13

P01/AN6
P02/AN5
P03/AN4
MODE
P04/AN3
P05/AN2
P06/AN1
P07/AN0
P30/TXOUT
P31/TZOUT
P32/INT2/CNTR1
IVCC

VSS

AVSS

XOUT/P47

XIN/P46

C3

22p

XI

I I

20MHz

32

31 P0.1

30 P0.2

29 P0.3

28

27 P0.4

26 P0.5

25 P0.6

24 P0.7

_22

20 P3.1

18 P3.2

23

Cl

21

1 22p

JP1

C12

22p

080068-12

Figure 2. Schematic diagram of the microcontroller module (a) and control circuitry (b).

measurement range of 0 to ±10 V for
the collector-emitter voltage thus cor-
responds to a range of 0-5 V at the A/D
converter input. Diode D5 prevents the
A/D input voltage from rising above
5 V in the event of a fault and protects
the input from negative voltages.

The collector or drain current flows
through R49 and generates a positive
voltage at the output of IC12b. The
output voltage ratio is 1 mV/mA. IC13
amplifies the voltage by a factor of 10
to yield a ratio of 10 mV/mA at the A/D
converter input (ADI). The voltage and
the A/D input is 4 V at the maximum
collector or drain current of 400 mA.
Here again, diode D8 prevents the A/
D input voltage from rising above 5 V
in the event of a fault and protects the
input from negative voltages.

Table

1: Pin assignments

of K1.

Pin

Signal

Pin

Signal

1

PI. 7

1 1

P3.0

2

GND

12

P3.1

3

PI. 3

13

P0.7

4

PI. 6

14

P0.6

5

Pl.l

15

P0.4

6

PI. 2

16

P0.5

7

P4.5

17

P0.2

8

P1.0

18

P0.3

9

P3.2

19

+ 5V

10

P3.3

20

P0.1

Power supply

The curve tracer is powered by an on-
board PCB -mount transformer with
two secondary windings, each rated
at 15 V / 0.5 A. The rectified DC volt-
ages of approximately ±20 V are fed to
IC2 and IC3, which produce regulated
voltages of ±15 V to power all of the
analogue circuitry with the exception
of the output stages. LEDs D10 and
Dll indicate the presence of the sup-
ply voltages.

The ±12 V supply voltages for the out-
put stages are provided by IC1 and
IC4, which require heat sinks. Here
LEDs D9 and D12 indicate the pres-
ence of the supply voltages.

R8C firmware

The microcontroller firmware was writ-
ten in C using the Renesas High-per-
formance Embedded Workshop. The
details of the development environ-
ment fall outside the scope of this arti-
cle. It has been described in the R8C
articles in previous issues of Elektor

[1] [2] [4] . HEW can also be downloaded
from the project Web address [3].

Program flow

Initialisation

Timers Y and Z are first initialised as
PWM timers with a pulse rate of 2 kHz.
Timer X is used to execute wait loops.
The UART1 interface is initialised to
9600 baud, 8 data bits, 1 stop bit, and
no parity. The interrupt for this inter-
face is enabled with a priority of 6. The
following default values are then set:

• Maximum collector or drain current:
100 mA

• Transistor type: NPN

• Base current range: 10 /dA

• Number of curves: 5

Configuring the base current range

The base current range is set using I/O
pins PI. 2 and PI. 3 as follows:

PI. 2 PI. 3 Base current range

1 1 10 /dA

0 1 100 ji/A

1 0 1mA

Configuring the transistor type

The polarity of the base current or gate
voltage and the collector-emitter or
drain-source voltage are set using 1/
O pins P1.0, Pl.l, PI. 6 and PI. 7 (see

Table 2).

Main program loop

The main program loop constantly
polls the UART1 serial interface to see

26

elektor - 2/2009

Table 2: Transistor type setting.

P1.0

Pl.l

PI. 6

PI. 7

Base or gate
polarity

Collector or
drain polarity

Transistor type

0

1

0

1

+

+

NPN transistor or
N-channel MOSFET

0

1

1

0

+

—

P-channel JFET

1

0

0

1

—

+

N-channel JFET

1

0

1

0

—

—

PNP transistor or P-
channel MOSFET

whether any characters have been
received. This interface is connected
to the PC via the USB to serial adapter
(PL2303). The protocol described
below has been implemented for data
transmission.

Each command consists of a com-
mand code (a letter in the range A to
Z) optionally followed by one or more
parameters, which are always writ-
ten as ASCII character strings sepa-
rated by commas. The defined com-
mand string terminators are CR (0x13)
and LF (0x10). This protocol applies to
transmissions in both directions (from
the PC to the curve tracer module and
from the curve tracer module to the
PC), although the curve tracer module
does not send commands to the PC

on its own initiative. It can only send
replies in response to requests from
the PC. The commands are summa-
rised in Table 3.

Initiation of curve measurement

The curve measurement process starts

with the configuration of the output
parameters.

For bipolar transistors, the base cur-
rent range is set to 10 /J A and the
base-emitter voltage (U BE ) is set to 0.
For MOSFETs, the base current range
is set to 1 mA and the gate-source

2/2009 - elektor

27

TEST EQUIPMENT

Figure 3. Pulse width and IC5b output voltage at pulse width ratios of 10% (a), 50% (b), and 90% (c).

voltage (U GS ) is set to 0. For JFETs, U GS
is set to the maximum level, which is
+ 10 V for P-channel JFETs or -10 V for
N-channel JFETs. The collector-emit-
ter voltage ( U CE ) or drain-source volt-
age ( U DS ) is set to the maximum value
( + 10 V or -10 V), and curve tracing is
started.

The base current (J B ) or gate-source
voltage ( U GS ) is increased until the
maximum collector or drain current is
reached. With bipolar transistors, the
base current range is also incremented
if the maximum collector current has
not been reached. With JFETs, U GS is
reduced until the maximum drain cur-
rent is reached.

If the maximum collector or drain cur-
rent is not reached with the maxi-

mum value of I B or U GS , curve tracing
is terminated and the error message
‘Ml < CFO <LF>’ is sent to the PC. The
message ‘M2<CR><LF>’ is sent if the
maximum collector or drain current is
reached with a very low value of I B or
U GS , which can occur with a shorted
transistor. This message is also sent if
too many curves are set with the “K”
command. After the base current or
gate-source voltage corresponding to
the maximum collector or drain current
has been calculated, the delta (incre-
ment value) is calculated from the base
current and the number of curves to
be measured (delta = J B( ma x) divided
by number of curves). The previously
mentioned error message is also sent
if the increment is zero.

The actual measuring process begins
if no error has been detected. For each
value of I B or U GS , the collector-emit-
ter or drain-source voltage is swept
from 0 to 10 V while the associated col-
lector or drain current is measured. The
results are sent to the PC in the follow-
ing format:

P < curve_no. >,< IB >,< Range > <CR>
<LF>

N<UCE>,<IC> <CR> <LF>

curve_no.: the number of the curve
presently being measured;

IB: xbase current or gate-source volt-
age (0-10 V);

Range: base current range; 0 = 10 fjA ,
1 = 100 /JA, 2 = 1 mA;

28

elektor - 2/2009

Table 3: Commands.

Command

letter

Parameter

Meaning

Response from curve tracer module

A

-

Query l D of curve tracer module

Note 1)

B

0 - 255

Pulse width for l B or U GS ; range 0-1 0 V

—

C

0 - 255

Pulse width for U CE or U DS ; range 0-1 0 V

—

D

0 = 1 0 pA

1 = 1 00 pA

2 = 1 mA

Base current range

—

E

0 = Positive

1 = Negative

Polarity of l B or U GS

—

F

0 = Positive

1 = Negative

Polarity of U CE or U DS

—

G

—

Query current value of U CE or U DS

GO - 1024

Voltage [V] = parameter value divided by 100

H

—

Query current value of l c or l D

HO - 1024

Current [mA] = parameter value divided by 2

1

0-1024

Maximum collector or drain current

Current [mA] = parameter value divided by 2

—

J

1 = NPN

2 = PNP

3 = N-MOSFET

4 = P-MOSFET

5 = N-JFET

6 = P-JFET

Transistor type setting

—

K

0 -10

Number of curves (see text)

—

L

—

Start curve measurement

See text

1 ) The curve tracer module responds by sending its ID code: A + Curve Tracer VX.X + <CR> <LF>' (X.X = current version number). After this, the
curve tracer module sends the current settings of the following configuration parameters:

- Maximum collector current (default = 100 mA)

- Transistor type (default = NPN)

- Number of curves (default = 5)

Wo dhxci

UCE: collector-emitter voltage; range
0-1024 (0-10.24 V);

IC: collector or drain current; range 0-
1024 (0-512 mA).

The base current is calculated as
follows:

Range = 10 juA: base current =
IB x 0.025 I/UA];

Range = 100 jliA: base cur-
rent = (IB - 14) -5- 2.3 [JUA] if
IB > 14; otherwise base cur-
rent = 0;

Range = 1 mA: base current
= (IB - 16) - 2.6 x 10 [ji/A] if
IB > 16; otherwise base cur-
rent = 0.

After all the values have
been transferred, the
curve tracer module sends
‘0<CR> <LF>’ to the PC,
which can then process the
data and display the curves.

Downloading the firmware

The Renesas High-perform-
ance Embedded Workshop
generates a Motorola (!) hex

file (Curve_Tracer.mot), which can
be downloaded via the USB interface
with the aid of the Flash Development
Toolkit [3].

To enable downloading, fit jumper JP1
on the microcontroller board and press
the Reset button. After the firmware has
been downloaded, remove the jumper
and press the Reset button again.

Application program

Trtmitlor curve tracer VI.?

ft* (yrt nrk>

T] (Twin'eruHk' fScS4?f

w

tn

a?

03

04

as

07

CB

IN

10

UC5(V]

M« cnlretm ruienr |nA]

Ciort recoidng

S«re et tetaence

Tiarmtw M*
fS NPN

r PNP

r nmosht

r pmosfet

r NJFET

r pjfet

Status: connected to Curve Tracer VI .1

Figure 4. Example characteristic curve chart.

The application program provides the
user interface for the curve tracer mod-
ule and is written in Visual Basic 6.0.
All program components were pack-
aged using the VB6 Packaging Wizard.
They can be installed in any desired
folder by running the Setup.exe pro-
gram. The application pro-
gram can run under Win-
dows 2000, XR and Vista. All
DLL files and ActiveX compo-
nents are registered during
installation, except for the
Prolific driver for the USB to
serial converter. This driver
must be installed by running
PL -2303 Driver Installer.exe.
The Curve_Tracer.exe pro-
gram can be started after
the curve tracer module is
connected to a USB port of
the PC.

Functions

The window shown in Fig-
ure 4 appears after the pro-
gram starts up and estab-
lishes a connection to the

2/2009 - elektor

29

Figure 5. Layout of the microcontroller PCB.

Figure 6. Layout of the main PCB.

COMPONENT LIST

Controller board # 080068-2
Resistors

R1 = 1 kQ5, SMD 0603
R2,R3 = 270 ., SMD 0603
R4,R1 0,R1 1 ,R1 4-R28 = 470^ SMD 0603
R5 / R6 / R7 = 220kf2, SMD 0603
R8,R9,R1 2 / R29 / R30 / R31 = 4kf27, SMD
0603

R13 = IkQ, SMD 0603

Capacitors

Cl ,C2,C4,C8,C9,C1 1 ,C 1 3 = lOOnF,

SMD 0603

C3,C1 2 = 22 pF, SMD 0603
C5,C6 = lOpF, SMD 0603
C7,C 1 0 = 1 OyL/F 25V, SMD case A

Semiconductors

D1 = LL4148

D2 = LED, 3mm, low-current
IC1 = PL2303X

curve tracer module. The follow-
ing functions are available in this
window:

• Recording the characteristic curves
of NPN and PNP transistors, N-chan-
nel and P-channel MOSFETs, and N-
channel and P-channel JFETs.

• Exporting curve data to Excel and
importing curve data from Excel.

• Checking transistor matching.

• Printing curve charts or embedding
them in other applications.

The program has an extensive Help
function, so the operation of the pro-
gram is not described in detail here.

Construction

As can be seen from the schematic
diagrams, the hardware is divided
between two PCBs. The small micro-
controller board (Figure 5) holds the
R8C/13 and the PL2303, along with the
associated components (Figure 2a).
The main board (Figure 6) contains
the rest of the hardware (Figure 2b),
including the transformer.

All of the components on the microcon-
troller board are SMDs, so a reasonable
amount of soldering experience is nec-
essary for assembly. The main board is
more roomy, and all of the components
have leads or pins. The two 12-V volt-
age regulators, as well as power tran-
sistors T3 and T4, are fitted with heat
sinks. Here you must take care that the
heat sinks of the two transistors do not

30

elektor - 2/2009

IC2 = R5F21134FP (R8C/13)

Miscellaneous

K2 = USB-B socket

K1 = 20-way (2x10) DIL pinheader

SI = pushbutton, 6mm, SMD

XI = 20 MHz quartz crystal, SMD

X2 = 1 2 MHz quartz crystal, SMD

JP1 = 2-way SIL pinheader with jumper

FI = 100 mA Polyfuse

COMPONENT LIST

Main board # 080068-1
Resistors

R1 -R1 8,R24-R33,R37,R38,R41 -
R45,R48,R51,R52,R53 = lOkD
R19,R20,R22 = 4kQ7
R21 = 931 kQ
R23 = 88kf27
R34,R35 = 1Q5
R36 = 100D

R39,R40,R46,R47 = 20kD
R49 = IQ 1W
R50 = 90kf29

Capacitors

Cl ,C2 = 2200jL/F 35V radial
C3-C6,C1 1 ,C1 2,C1 4-C1 7, Cl 9-C35 =
lOOnF, lead pitch 2.5mm
C7-C10 = 10jL/F 25V radial
Cl 3, Cl 8 = 47nF, lead pitch 2.5mm
C36,C37 = 22nF, lead pitch 2.5mm

Semiconductors

D1-D4,D6,D7 = 1N4148
D5,D8 = 5.6 V 500 mW zener diode
D9-D12 = LED, low-current, 3 mm
B1 = VM1 8, bridge rectifier 1 A / 1 00 V,
DIP4

T1,T2 = BC547A
T3 = BD139
T4 = BD140
IC1 = 7812
IC2 = 7815

IC3 = 7915

IC4 = 7912

IC5,IC6,IC8,IC1 1 ,IC1 2 = TL082P

IC7,IC9 = DG441DJ

IC10, IC13 = TL081P

Miscellaneous

K1 = 20-way DIL socket

K2 = 3-way PCB terminal block, lead pitch
2.5mm

FI =100 mAT (slow) glass fuse, with
holder

TR1 = mains transformer, secondary 2x
1 5V / 1 4VA

4 heatsinks type FK218/SA32 (21 K/W)

Microcontroller and PC Software: free
download 080068-11.zip at [3].

PCBs 080068-1 and 080068-2, avail-
able from the Elektor Shop.

Controller board also with components fit-
ted, Elektor Shop # 080068-91 .

touch. It’s a good idea to use a piece of
insulating material here.

The microcontroller board plugs into a
20-pin DIL socket on the main board.
The assembled board set can be fitted
in a suitable enclosure, such as the

Bopla type E450 FVL. Various types
of transistor sockets can be fitted to
the enclosure to provide connections
for the transistors, although a set of
three short leads terminated in alliga-
tor clips is also a workable solution.

( 080068 - 1 )

Internet Links

[1] www.elektor. com/0501 79-2

[2] www.elektor.com/0501 79-3

[3] www.elektor.com/080068

[4] www.elektor.com/forum, go to R8C topic.

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2/2009 - elektor

31

MICROCONTROLLERS

Microcontrollers fo

... Arduino (or the enlightened

Clemens Valens (Elektor France Editorial)

Apparently Arduino is an Italian name - but when you search on the Internet, you mainly
find dozens of references relating to electronics and programming. What's more, these
references are often in relation to art. Electronics and art - now there's an interesting
subject that's worth delving into! So just what exactly is Arduino?

At first sight, Arduino [1] is a small microcontroller board
with a USB port (Figure 1) that comes in several models.
There are even 'daisy'-shaped boards (Lilypads) intended
for wearable applications, i.e. to be incorporated into gar-
ments. The Arduino board is programmed in a language
very similar to C using Open Source tools available for
Windows, Mac, and Linux. The hardware is also Open and
anyone can make their own Arduino - the circuit diagrams
and PCB photo masks are available free over the Internet.
Arduinos are used a great deal by artists who need elec-
tronics in their creations.

Figure 1.

A Diecimila Arduino board.
The new Duemilanove
board is almost identical.
These boards are cheap
and easy to find.

When you look at it a bit more closely, an Arduino is not
exactly a microcontroller board. In fact, an Arduino is quite
simply an 8-bit microcontroller from Atmel - an ATmega8
for the earliest Arduinos and now more likely to be an
ATmegal68. This microcontroller is loaded with a 'boot-
loader' program that lets you load an application into the
controller via a serial port, without overwriting the boot-
loader. Since modern computers no longer have serial
ports, a USB port is often used. All this becomes an Arduino
when you decide to dedicate certain pins of the controller

to certain functions, since this allows the Arduino develop-
ment environment to be used for writing and compiling
application before loading them onto the controller.

The applications, called 'sketches', are written in a lan-
guage that closely resembles C. Hardly surprising - it is
C, but with some additional functions. All of the functions
presented as the language for Arduino form a Hardware
Abstraction Layer that lets you program the controller with-
out needing to delve into the innards of the processor. The
language has everything you need for most applications.
Broadly speaking, there are functions for digital and ana-
logue inputs/outputs, a few basic mathematical functions,
time management functions (delays) and a few function for
serial port communication - asynchronous (UART) and syn-
chronous (SPI).

The digital I/O functions let you manipulate the logic levels
of the pins, to read and write them. There is also a special
function that makes it possible to measure the duration of
a pulse. Using the analogue I/O functions, it is possible to
read voltages and generate PWM signals. Lots of appli-
cations don't require anything more than this, and this is
exactly where Arduino's strength lies. There's no need to
go ferreting around in the registers and the controller data
sheet to make a PWM output or a counter work — the 'dirty
work' has already been done.

If these functions aren't enough, it's perfectly possible to pro-
gram on a lower level and, just as in standard C, you can
also add libraries with their own functions. But do watch
out - if you go off into the darker depths of the Arduino
programming language, you risk losing compatibility with
the rest of Arduino community.

The Arduino community? Already, Arduino is a microcon-
troller, as well as a development environment and a pro-
gramming language - now it's a community too? Yes! In
fact, Arduino is more of a philosophy, the aim of which is
to popularize technology to make it accessible to artists.
Arduino is a logical sequel to Processing [2] and Wiring [3]
projects. Processing is a multimedia programming language
and Wiring is a development environment for artistic elec-
tronics But now we're starting to get away from our original

32

elektor - 2/2009

point; refer to the box about the origins of Arduino if
you want to find out more.

the name Freeduino for home-made
Arduino boards. But after all, it's only
a name, so let's call ours Elektorino.

Elektorino

Simple, free programming is something we're interested in.
What's more, the electronics involved seem to be simple
- so what could be more logical than to produce our own
Arduino-compatible system? Well, that's just what we're
going to do!

Our starting point is the basic Arduino Serial board. The
office computer I use all the time still has a serial port, but
for the unlucky owners of a computer that doesn't, we're
going to use the USB-TTL cable [4]. In any event, we're
going to be needing a TTL interface of some kind, as our
own Arduino will only have a TTL serial port.

Our processor is going to be an ATmegal 68, which we'll
be running at 16 MHz, to avoid getting caught out. For
even though the controller is perfectly capable of operat-
ing at up to 20 MHz, the standard bootloader assumes a
speed of 1 6 MHz. This can of course be modified if you
are prepared to go delving into the bootloader - but for the
moment we just want an Arduino board that works.

To finish off our Arduino, all we need do is add an LED, a
reset push-button, a few resistors and capacitors, and two
connectors: one for the serial port and the other for pro-
gramming the bootloader. We need the latter to be able to
program our Arduino for the first time, when the controller
is still blank. Later, when the application is finished and the
bootloader is no longer needed, this connector can be used
for programming the controller directly from the application,
which saves memory.

The LED has several functions. Given that the LED is present
on several types of Arduino, lots of sketches use it. So does
the bootloader, which flashes it at start-up.

Here's the circuit diagram of our finished Arduino (Fig-
ure 2). Thanks to the simplicity of the circuit, we can build
it on prototyping board.

Unfortunately, we are not allowed to call our fine project
Arduino - only boards approved by the Arduino community
have the right to that name. This is why a second move-
ment Freeduino [5] was created, which allows free use of

Implementation

Before you can load a sketch into the Elektorino, you need
to load the bootloader. This is where things get more com-
plicated, as there are two official Arduino bootloaders, the
only apparent difference between them being the way the
sketch is run after loading. This is achieved by way of a
controller reset, which the Arduino environment can handle
if the board has been equipped for it, and if it has the right

J2 +5V +5V

Figure 2.

The circuit of the
Elektorino. Not at
all complicated. The
connectors for the pins are
not necessary, they are
mainly used as a reference.

2/2009 - elektor

33

MICROCONTROLLERS

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Figure 3.
The Arduino development
environment.

bootloader. We haven't made any provision for this, and so
we need the basic bootloader for the so-called NG (New
Generation) boards.

But there is also another option: a third bootloader called
ADABOOT [6]. This bootloader, an improved version of the
official bootoaders, handles the reset and run delays differ-
ently. Initially, I worked for a bit with the NG bootloader,
before replacing it with ADABOOT. Both worked perfectly
well, but in the end I adopted ADABOOT, because it flashes
the LED while the sketch is loading and because it is more
convenient.

See the box to find out how to load the bootloader into the
controller.

Hello world!

Once you have succeeded in loading the bootloader, it's
time to see if Elektorino manages to communicate with the
Arduino environment and if it is possible to load a sketch.
So let's install Arduino. I've only done it under Windows
XP, and that was extremely easy. All I had to do was down-
load a large zipped file and unzip it somewhere onto the
hard drive.

After running the Arduino environment (arduino.exe), you
find yourself with a window like the one shown in Fig-
ure 3. Go into the Tools menu, then Board, and select the
Arduino board being used. Of course, our one isn't listed,
but an NG board using an ATmega 1 68 will do.

You also have to select the serial port to be used for pro-
gramming the microcontroller. Go into the Tools menu, then
Serial port and select the correct port. If you want to use a
USB serial port, check first that the drivers are present.

The Arduino environment comes with a small sketch, Blink,
for checking that the board is working, and we can use this,
since we have fitted the LED. The procedure is simple:

- Load the sketch; it's in File > Sketchbook > Examples >
Digital > Blink.

- Compile the sketch by clicking the Verify/Compile button;
this only takes a few seconds and (usually) ends with a suc-
cess message.

- Load the sketch into Elektorino; first press the Reset button
briefly, then click Upload to set the program loading. If all
is well and if you are using ADABOOT, after a short delay
you'll see the LED start to flash randomly — this is normal,
it shows the transfer is taking place. After around five sec-
onds (depending on the size of the sketch), the program
is loaded and the controller is rebooted (the exact way in
which the program is run depends on the bootloader). If
the LED now flashes at a frequency of 1 Hz, everything has
gone alright. Elektorino is working! If nothing happens, try
resetting Elektorino.

Loading the bootloader...

...is not as hard as all that, as long as you have all the information you need. To save you hours on the Net, we've summed it up
for you here in a few lines.

First of all, you need a programmer. There are several possibilities, for example, the one published in the 2008 double issue [7],
or another 'SK200 compatible' programmer, easy to build using the circuit available on the PonyProg website [8]. On the Arduino
website [1 ] yet another parallel port programmer is mentioned which is very simple and can be used directly from the Arduino en-
vironment. I tried it out, and managed to scramble one controller with it... so I went back to an SK200 one I already had.

Next, choose your bootloader. I recommend ADABOOT [6], but the NG version available on the Arduino website works perfectly
well too.

Loading the bootloader into the controller can be done, for example, using AVRDUDE [9], supplied with the Arduino environ-
ment. AVRDUDE is a typical UNIX tool - it's basically a FreeBSD tool - with lots of incomprehensible options. Because it's very
easy to make a mistake, here are the commands that work well (copy the bootloader into the directory that contains the AVRDUDE
executable):

avrdude -p ml68 -c pony-stk200 -V -e -U lock:w: 0x3F:m -U hfuse : w: OxDF :m -U lfuse : w: OxFF :m -U efuse : w: 0x0 :m
avrdude -p ml68 -c pony-stk200 -V -D -U f lash : w : ATmegaBOOT_168_ng . hex
avrdude -p ml68 -c pony-stk200 -V -U lock: w: 0x0F:m

If you use another programmer, replace pony-stk200 with the appropriate value. Also check the name of your bootloader.

There are three commands that, broadly speaking, unlock the memory, load the program, set the fuses, and finally lock the me-
mory. Refer to the AVRDUDE instructions if you want to know exactly what is going on (sensitive souls are advised to refrain!). Loc-
king the memory is used to avoid overwriting the bootloader accidentally when loading a sketch.

A good website about the AVR is called Lady Ada [10].

34

elektor - 2/2009

A real application

It's all very well to have an Arduino development environ-
ment that works wonderfully well, but without a real appli-
cation, it's not very interesting. I already had ten motorized
slider pots, and it was high time to put them to good use.
Why not with Elektorino? Elektorino has analogue inputs
and PWM outputs — everything we need to drive a motor.
So I'm going to suggest a driver for motorized faders. Note
that this circuit can be used with any ATmegal 68-based
Arduino board.

The fader in question (Figure 4) consists of a slider pot,
a small motor, and an assembly of a few rollers, springs,
and a piece of cord that enables the motor to move the
slider in both directions. This assembly allows the motor to
freewheel when the slider is unable to move - at each end
of its travel, for example. Apart from the 10K B marked on
the fader, I didn't have any technical data on it, but a few
experiments showed that the motor turned at a suitable
speed when powered from 1 2 V. In this case, its consump-
tion was around 200 mA.

The B marked on the fader might lead us to think it's a log
model (as is often the case), but after checking, my faders
turned out to be linear ones.

As a motor driver, I chose a cleverly-modified double H
bridge with just two control lines and three states: anti-
clockwise, clockwise, and braking - just what we need
(Figure 5). Usually, two controls allow four states, but in
this circuit, states 00 and 1 1 are the same. A 5 V regulator
has been slipped into the circuit so as to be able to power
the whole controller assembly and motor from 1 2 V. The
transistor are all NPN types, and those forming the bridge
must be capable of carrying 200 mA happily. In my proto-
type, I used BD1 39s.

The potentiometer is wired as a simple potential divider. By
measuring the voltage on the wiper, we know where it is
(just so long as it's a linear pot).

The motor driver controls must be connected to digital out-
puts capable of supplying a PWM signal. An Arduino
based around an ATmegal 68 has six, an ATmega8 only
three. The pot wiper itself can be connected to any of the
analogue inputs - in our case, inO.

The sketch

Now that we have connected a motor driver to Elektorino
(Figure 6), it's time to deal with the software. You'll see,
the final sketch will be amazingly simple, thanks to the
power of the Arduino.

A basic sketch consists of two functions: setup/) and loop/),
which are called by the layer of a lower level. In setup,
called once at runtime, we put everything that relates to ini-
tializing the system - for example, the inputs/outputs and
the serial port speed.

99.9% of embedded programs probably spend their whole
lives in a loop. This is why in Arduino this loop is already
implemented in the form of the loop function. This loop
function is called periodically and may be regarded as
Arduino's main. It's important to realize that, even though
it looks like a special function, loop is just like any other
function in C. So its local variables are reset each time it is
called and variables that are required to keep their values
between different occasions loop is called must be declared
globally (or as static, for those familiar with C.)

The setup in our sketch doesn't contain anything very much.
The Arduino pins are inputs by default, so only the two
outputs need to be initialized. We're going to be using the

Figure 4.

A motorized fader of
unknown make.

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Figure 5.

The modified double H
bridge and its three states.
The labels refer to the
pin designations, not the
terminals on the controller.

Figure 6.

The Elektorino prototype:
the ATmegal 68 is on the
left and the double H
bridge to drive the motor
on the right.

serial port to drive our circuit, and for this it needs to be
initialized. Thanks to the simplification offered by Arduino,
all we have to do is enter the communication speed - in
our case, 9,600 baud.

2/2009 - elektor

35

MICROCONTROLLERS

Processing, Wiring, and Arduino

Processing [2] is a language and an Open Source programming environment for programming images, animations, and inter-
actions. The project, an initiative from Ben Fry and Casey Reas, is based on ideas developed by the Aesthetics and Computation
Group of the MIT Media Lab. Processing was created in order to teach the fundamentals of programming in a visual context and
to serve as a sketchbook or professional software production tool. Processing runs under GNU/Linux, Mac OS X, and Windows.

Several books have already been written on Processing.

Just like Arduino, Wiring [3] is a programming environment with microcontroller board for exploring electronic arts, teaching pro-
gramming, and quick prototyping. Wiring, programmed in Processing, is an initiative by Hernando Barragan and was designed at
the Interaction Design Institute Ivrea (IDII) in Italy.

Arduino [1] is a fast, Open Source electronic prototyping platform. Arduino is aimed at artists, stylists, enthusiasts, and anyo-
ne interested in creating objects or interactive environments. Created by Massimo Banzi, Gianluca Martino, David Cuartielles,
and David Mellis, Arduino uses a programming language based on 'Processing'. Arduino may be regarded as a simplification of
'Wiring'.

Moving the pot wiper is done in loop. The principle is very
simple: if the voltage measured on the input pin is different
from the voltage required, the slider must be moved in the
direction which will reduce this difference. In real life, it's
a bit more complicated than that. To start with, there's the

The STK200 compatible programmer used by the author. There are also simpler
programmers - it's a matter of personal preference.

D8

problem of direction, but more significant still is the problem
of inertia. Once the slider is moving, it takes a little time for
it to come to a complete halt. So it's easy to overshoot the
required position if braking occurs too late. In the event of
an overshoot, the slider has to be brought back, with the
same risk of overshooting again, and so on. The system

may even begin to oscillate.

To avoid these problems, we have used a Proportional Dif-
ferential (P-D) regulator. In this type of regulator, the system
reaches its final value without overshoot by continuously
adjusting the correction signal according to the difference
remaining to be corrected. So at the start of an adjustment,
when the error is greatest, a strong correction signal is
applied. Then, once the difference starts to reduce, the cor-
rection signal reduces too and the system slows down.

The correction signal consists of two parts: a signal propor-
tional to the error (P) and a signal proportional to the error
reduction (D). With a properly adjusted system of this sort,
the slider can be moved quickly without overshooting the
target value.

In the sketch (Listing 1) we can see the P-D regulator in the
loop function. First, we measure the voltage at the wiper.
The target value is subtracted from the measured value to
obtain the error to be corrected. From this value, we calcu-
late the two components P and D of the correction signal.
The P component is the error multiplied by the constant K p ;
the D component is obtained by multiplying the difference
between the current value and the previous error by the con-
stant /C d . The values for these constants were determined by
experimentation, and you can modify them to see how the
affect the adjustment. It's highly instructive.

The two components P and D are combined and the result
is adapted to the range of usable values. The pot slider
doesn't move for values below 50, and the maximum value
for the PWM signal is 255.

Then we look to see if the error is small enough for us to be
able to stop the motor. This comparison has to be performed
for both slider directions. We leave a small margin for error,
since perfection is perhaps a little over-ambitious.

When the error is small enough, we prevent further correc-
tions so as to free up the slider; we make the assumption
that the system is never going to overshoot the target value.

AVR ISP via USB

If you use the FT232R chip as a USB interface and if you have access to all its pins, it is possible to use this chip to load the boot-
loader into the microcontroller without even needing a special ISP programmer! The FT232R chip has a bus called a CBUS with
a bit function that lets you manipulate the associated pins individually. A certain Mr Suz from Japan has written a small piece of
software that exploits this possibility and which can be downloaded free. Its avrdude-serjtag tool only works under Windows and
its website is unfortunately in Japanese (suz-avr.sblo.jp/article/4438871 .html). However, on his site one of his compatriots kindly
explains in detail in English howto program an Arduino using this tool. See reference [1 1] for details.

36

elektor - 2/2009

In this way, it's possible to move the slider manually, with-
out the system's trying to move it back into place. (Who's
the strongest?)

Once the slider has been released, the system starts to out-
put the slider position periodically (10 Hz) via the serial
port. The serial port input is also scanned and as soon as
four characters have been received, they are transferred as
a target value for the slider and the PD regulator is re-acti-
vated to move it to its new position. No format checking
is performed for the value received, the system requires an
ASCII four-digit value between 0000 and 1023. To mini-
mize errors, the target value obtained is limited between 3
and 1020, which minimizes problems of continuous activa-
tion at the ends of the travel.

The serial port is not used while the motor is operating, as
this might produce interference, resulting in inaccurate posi-
tions or even oscillation. I've not taken the trouble to find
out why: I'll leave that for you to do!

( 080931 - 1 )

References and Resources

[1 ] http://arduino.cc

[2] www.processing.org

[3] http://wiring.org.co

[4] www.elektor.fr/usb-ttl

[5] www.freeduino.org

[6] http://nearspacevermont.org/TheShoppe/freeduino/ADA-
BOOT.shtml

[7] SimpleProg - ISP for AVR, Elektor, July/August 2008

[8] www.lancos.com/prog.html

[9] www.bsdhome.com/avrdude

[10] www.ladyada.net/learn/avr/index.html

[11] www. geocities.

jp/arduino_diecimila/bootloader/index_en.html

Getting Started with Arduino, Banzi, Massimo, O'Reilly, 2008

Making Things Talk, Igoe, Tom, O'Reilly, 2007

The Duemilanove Arduino board is available from several sour-
ces including FunGizmos (US), LittleBird (Australia), SKPang (UK),
Tinker (Italy), Make Magazine (Makershed.com).

Listing 1 “ Easy-peasy!

void loopO
{

int error;
int val ;
int spd ;

float spd_p, spd_d;

// read wiper voltage,
val = analogRead ( slider) ;

// Calculate error,
error = val - target;

// Calculate proportional component P.

// Two directions - so use absolute value.
spd_p = abs (error ) *Kp ;

// Calculate differential component D.
spd_d = ( last_error-error ) *Kd;
last_error = error;

// Now mix P and D.
spd = int ( spd_p+spd_d) ;

//Do not exceed limits,
spd = constrain ( spd, 0 , 255 ) ;

// Compensate friction,
if (spd<50) spd += 50;

if (error<-l && stop==0)

{

// To maximum value ("left") .
digitalWrite (motor2 , LOW) ;
analogWrite (motorl, spd) ;

}

else if (error>l && stop==0)

{

// To minimum value ("right") .
digitalWrite (motorl , LOW) ;
analogWrite (motor2 , spd) ;

}

else

{

/ / Shut down motor
digitalWrite (motorl , LOW) ;
digitalWrite (motor2 , LOW) ;
stop = 1;

// Transmit cursor position.

Serial . println (val ) ;
de 1 ay ( 1 0 0 ) ;

// 4 characters form a new target value,
if (Serial . available () >=4 )

{

target = Serial . read ( )

- 'O'; // Thousand.

target = Serial . read ( ) - 'O'

+ target *10; // Hundred.

target = Serial . read ( ) -

v 0' + target*10; // Ten.

target = Serial . read ( ) -

'O' + target *10; // One.

constrain (target , 1 , 1022 ) ;

/ / Start motor
stop = 0;

}

}

}

2/2009 - elektor

37

TECHNOLOGY

SATELLITE TV

Marc Neujahr (Germany)

Direct reception of satellite broadcasts
is still not a reality — we need to fit
a dish and receiver before viewing can
begin. However, with the help of a little
hardware it is now possible to supply
programmes to over 100 subscribers
using just one dish. Another novel system
allows eight receivers to view different
programmes over a single coax cable!

It was back in the mid 1 990's that domestic reception
of satellite TV programmes first became economically
viable. The satellite signal path is line-of-sight and
highly directional so it does not suffer so much from the
obstacles to propagation that sometimes afflict terrestrial
TV broadcasts. The picture and sound quality were a
revelation at the time but some of the limitations of this
type of reception also became apparent: How could you
record one programme while watching another? How
could a second TV be added to the system? How could
programmes be distributed to many users in apartments
without producing an unsightly forest of dishes?

The technology is a little more mature now and many sys-
tems have since been developed which directly address
these problems.

A typical domestic installation consists of a dish pointed
at the satellite of interest with an LNB (see Glossary at
the end of the article) fitted at the dish focus sending a
frequency down-converted band of signals to a receiver
(tuner). Adjacent channels are transmitted with alternate
polarisation to help reduce interference. This set up effec-
tively produces a horizontal and vertical receive band
of frequencies, the basic LNB cannot receive both bands

simultaneously so switching between vertically or horizon-
tally polarised signals is achieved by changing the supply
voltage from the receiver to the LNB from 14 to 1 8-V.
When the satellite bandwidth (10.7 to 1 1 .7-GHz) was
increased with the introduction of the high band (1 1 .7 to
1 2. 7-GHz) the number of satellite receive bands went up
to four: (horizontal Low-Band, vertical Low-Band, horizon-
tal High-Band, vertical High-Band). The high band is used
almost exclusively for digital transmissions and is often
referred to as the digital band but this is not strictly correct.
The receiver superimposes a 22-kHz signal on the LNB
coax to make it switch from low to high band reception.
Using the basic LNB only one of the bands can be down-
converted (to prevent unacceptable losses in the coax)
and sent to the tuner at any one time so a single coax
cable is required between each LNB and receiver. Band
selection takes place inside the LNB or in more complex
systems in a Multiswitch unit.

Switched LNBs and Multiswitch units

One solution to the problem of using two TVs in the sys-
tem is to fit a second complete system so that both receiv-

38

elektor - 2/2009

Illustration: courtesy GTN GmbH

ers work independently. More recent advances in design
have produced LNBs with multiple outputs, these are sup-
plied with single, twin (known as a 'twin output'), quad
or octal outputs supplying signals for one, two four or
eight set-top tuners. Each tuner can independently select
its own band from the LNB by putting the appropriate
control voltage on its coax. This system requires a single
coax for each tuner so up to eight cables are run from
the LNB to wall mounted satellite signal outlets. The term
'uni' when applied to an LNB indicates that it can receive
all four bands transmitted by the satellite.

This type of installation gives several users independent
control over programmes transmitted by one satellite
but when more than eight subscribers want to select
programmes from more than one satellite and also incor-
porate terrestrial/cable TV feeds it is necessary to install
a Multiswitch unit. This is used with a special Quattro
LNB which does not need to be switched between bands
and simply outputs the four satellite bands simultaneously
to the Multiswitch via four lengths of coax. The Quattro
LNB is not to be confused with the quad LNB mentioned
above. Conventional 'uni' LNBs can also be used here
and in this case the Multiswitch fixes the receive band

Figure 1.

The ECS 1708 from
GTN GmbH Is a
cascadeable Multiswitch
capable of distributing
16 satellite bands (plus
a terrestrial TV input)
to eight subscribers.

for each LNB by generating the necessary tone and/or
voltage level. The Multiswitch unit now has access to the
complete satellite signal spectrum so it can switch any
selected channel through to any of the 1 6 user outputs.
Sometimes when a Multiswitch installation cannot receive
all programmes the problem can be traced back to a
fault in the control signals to the LNBs.

Looking for something bigger?

Conventional Multiswitch installations are suitable for up
to 1 6 subscribers and some of the larger units provide
inputs for up to 16 bands which allow four Quattro LNBs
to be fitted to the same dish, each focussed on different
satellites. This type of installation provides a large num-
ber of transponders from a single dish and should help to
reduce the urban 'dish clutter' often seen in inner cities.

Figure 2.

Visual inspection of
an SMD populated
Multiswitch PCB.
(photo: GTN GmbH).

2/2009 - elektor

39

TECHNOLOGY

SATELLITE TV

Figure 3.
Cascaded Multiswitches
distribute the signals
from four satellites (16
satellite bands plus 1
terrestrial) to more
than 1 00 subscribers
on the left and right
of the diagram while
input bands are bussed
through to the next
cascaded Multiswitch
unit.

Figure 4.
The Unicable system
employs channel
routing: The Unicable
LNB takes the
programme of interest
from the satellite
signal and converts it
to a specific satellite
IF which will only
be detected by the
requesting receiver.
Programmes for up to
eight receivers can be
routed onto the same
coax, (illustration:
STMicroelectronics)

More recent Multiswitch units provide an additional input
for a terrestrial UHF TV signal so that this signal can also
be switched to the subscriber and sent over the same
coax feed. The system can be expanded beyond 1 6
subscribers by using cascadeable Multiswitch units Fig-
ure- 1). Th is installation allows up to 100 subscribers to
be serviced by just one dish and would be suitable for a
small block of apartments or subscribers in a neighbour-
hood. One advantage of this type of installation is that
it is quite simple to expand a relatively simple one-satel-
lite system up to a four-satellite system just by swapping
the Multiswitch/LNB units, the existing subscriber coax
cabling need not be disturbed or expanded.

As can be seen in Figure-3 all the received signal bands

Web links

ST7LNB LNB microcontroller:

http://mcu.st.com/ mcu/
inchtml.php?fdir=pages&fnam=st7lnb

Channel Router Chip:

www.st.com/stonline/ products/literature/bd/1 0465.htm

DiSEqC:

www.eutelsat.com/ satellites/ pdf/Diseqc/
Reference%20docs/bus_spec.pdf

are bussed to the inputs of all the cascaded Multiswitch
units, signal buffering and amplification may be neces-
sary to compensate for signal attenuation and correct ter-
minating resistors should be used at the end of the bus.

DiSEqC switching

Using switched quad LNBs together with a DiSEqC switch
it is possible to produce a relatively small system suitable
for four tuners which can receive programmes from four
satellites.

DiSEqC commands are generated when a receiver
requests a programme to route the receiver input through
to the correct LNB via the DiSEqC switch, selection of the
correct band is performed with 14/1 8-V voltage level
shifting and the 22-kHz tone switching which is routed
through the switch to the correct LNB. These switches are
available with two, four and more recently eight inputs.
Satellite equipment suppliers offer so called '1 7 by 4'
(17x4) -Multiswitch units which actually comprise of
four individual 4-to-l DiSEqC switches fitted in the unit
together with a feed from a terrestrial TV signal. Power
for the switch is taken directly from the receiver and
routed through to the selected LNB via the coax cable so
there is no requirement for an external power supply. This
method of power distribution can sometimes be a source
of interference to other subscribers when the supply load-
ing is switched during channel selection.

The single cable solution

With the advent of digital satellite signal there have been
a number of 'single cable' solutions to the problem of
distributing the broadcasts especially for satellite receiver
owners interested in one language only. Germany, for
example, has one of the highest uptakes of satellite TV
equipment in Europe (approx. 40% of households) and
there are many satellite programmes available in this
language.

One such system uses a special LNB which selects spe-
cific parts of the received bands carrying programmes of
interest to German speakers and packs them all together
on a single coax.

A potential disadvantage of this approach is if for any
reason one of the TV stations changes their transponder
it may no longer be possible to receive that programme
without fitting a new LNB!

Channel Routers

The 1C manufacturer STMicroelectronics has produced
its own solution to the single-cable system and not

40

elektor - 2/2009

surprisingly it involves microcontrollers and integrated
circuit wizardry. The system is known as 'linkable' and
employs an 8-bit microcontroller type ST7LNB integrated
into an LNB. The single coax output supplies programme
feeds for up to eight receivers, each with a fully indepen-
dent program signal.

In this set up each satellite receiver or recorder has a
fixed receive frequency in the SAT IF band and informa-
tion about each receivers programme channel selection
is sent to the controller in the LNB where the requested
channel is selected and down-converted to the unique IF
band for that particular receiver (Figure-4) programme
signals for up to eight receivers are then sent along the
coax. The LNB is in fact a highly integrated Quattro LNB
together with a mini channel-router and microcontroller.
The system uses the existing DiSEqC control protocol
together with some application specific additional com-
mands and can easily be expanded to cater for signals
from more satellites.

This system can currently supply eight independent sig-
nals over a single daisy-chained coax which should be
sufficient for an average home installation. Single receiv-
ers can be replaced by twin receivers without the need
for any additional cabling. The price of a Unicable LNB
is currently around £1 00-150 (145-2 1 0 euros) which is
a little more expensive than a small Multiswitch together
with a suitable LNB but the cabling costs are much lower.

( 060228 - 1 )

Glossary

LNB: Low No ise Block (down converter). Satellite sig-
nals are focussed into this unit by the dish. It converts the
received 10.7 to 12.7-GHz signal into a 950 to 2150-MHz
signal and sends it to the receiver over one or more coax
cables.

Sat IF: Satellite receiver intermediate frequency. The fre-
quency range from 950 to 2150 MHz sent from the LNB to
the satellite tuner.

Twin Receiver: Receiver containing two independent tun-
ers allowing the simultaneous reception of two programmes
(one for the TV and the other for a video recorder).

DiSEqC: Digital Satellite Equipment Control. A standard
produced by Philips and Eutelsat in 1994 defining a control
method between the LNB or Multiswitch and the receiver,
(see web links and the DiSEqC moniter article in this maga-
zine).

Transponder: Receive channel from a satellite. Analogue
satellite TV used one channel per transponder but several
compressed digital TV signals can now be packed into one
transponder using a single wideband carrier.

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2/2009 - elektor

41

CLOCKS

Markus Bindhammer (Germany)

Inspired by a binary clock he
saw at a mathematics museum
the author of this design went
one step further and came up
with a more mathematically
challenging timepiece...

This unusual large format digital clock in
the photo shows the time in binary and
is exhibited at the German Museum of
Mathematics ‘Mathematikum’ in the town
of Giessen, Germany [1], The museum is
the brainchild of Prof. Beutelsbacher and
has been described as the first ‘hands-on’
mathematical museum in the world. The
clock inspired Marco Freitag to design
the PIC16C54 based binary clock fea-
tured earlier in this magazine [1]. After a
visit to the museum the author was moti-
vated to experiment with this alternative
format for time representation which re-
quires a little more concentration to read
compared to the average clock.

The Trit

We are familiar with the role of the ‘bit’
in binary systems so it is probably not
surprising to discover that in trinary
systems we use the trit which is a con-
traction of the words ‘trinary digit’. The
basis of the trinary system (a.k.a. ter-
nary or base three) is 3. The positional
power of any number expressed in tri-
nary (starting from the least significant
position) is given by:

3° = 1; 3 1 = 3; 3 2 = 9; 3 3 = 27; etc.

The only numbers allowed to represent
a value are 0, 1 and 2. To indicate that a
value is written in trinary it is append-
ed with a subscripted 3, for example

1210 3 = 48 d

(1x27 + 2x9 + 1x3 + 0x1).

In order to display any value in trinary
it is necessary to use a device which
can have three visible states. Bi-colour
LEDs have been chosen here to repre-

sent ‘0’ (both LEDs off), ‘1’ (green LED
on) and ‘2’ (red LED on).

The table (Figure 1) shows the decimal
values of a clock reading together with
its representation in trinary and the cor-
responding LED colours used for the dis-
play. It can be seen that for the hours (0
to 23) we need three bi-colour LEDs and
the minutes (0 to 59) require four. It is
also necessary to use a corresponding
number of counters to count the seconds
and minutes. The counters go from 0 to
2 while the third output resets the coun-
ter to zero and acts as a carry-out to in-
crement the next in the chain. The AND
gate IC11.B detects when the hour count
reaches 24 and resets the hours while

IC11.D does the same to the minute
counters when they reach 60 and also
increment the hour counter.

Counting the time

Reading the time on this clock can be
a little challenging but in contrast the
circuit diagram is quite simple to fol-
low. In principle it shouldn’t be too dif-
ficult to read the time providing you
can count up to three. . .

All of the timing and counting for the
clock is not hidden away somewhere
inside a microcontroller memory but
instead is done the old fashioned way
by wiring the hardware counters and

42

elektor - 2/2009

logic shown on the circuit diagram in
Figure 2. A division ratio 2 15 (32768) is
necessary to provide a 1 Hz signal from
the 32.768 kHz watch crystal XI. The 14
stage binary counter IC10 can manage
2 14 which gives a 2 Hz clock output from
pin 3. Resistor R39 has a relatively high
value and this helps reduce loading on
the crystal. A small watch crystal like
this can dissipate a maximum power of
around 1 jl/W (nominally 0.1 jl/W).

The D-type flip-flop IC12A is config-
ured as a divide-by-two to produce a
1 Hz output while IC8 and IC9 provide
a divide -by- 10 and divide -by- six func-
tion to generate minute pulses. IC12.
B drives the second pulses to LED D4
which alternates between red and
green. The use of 5-stage Johnson
counters (which can count up to 10) for
IC1 to IC7 may seem a bit like overkill
since they never need to count above
three but these devices are less prob-
lematic to interface than some of the

trinary

decimal

trinary

decimal

trinary

decimal

0000

0

0

2

1

0

21

1

1

2

0

42

000

i

1

0

2

1 1

1

22

1

1

2 1

1

43

o

o

o

2

2

0

2

1

2

23

1

1

2

2

44

00

1

0

3

0

2

2

0

24

1

2

00

45

00

1 1

1

4

0

2

2 1

1

25

1

2

0

1

46

00

1

2

5

0

2

2

2

26

1

2

0

2

47

00

2

0

6

1

000

27

1

2

1

0

48

00

2 1

1

7

1

00

1

28

1

2

1 1

1

49

00

2

2

8

1

o

o

2

29

1

2

1

2

50

0

1

00

9

1

0

1

0

30

1

2

2

0

51

0

1

0

1

10

1

0

1 1

1

31

1

2

2 1

1

52

0

1

o:

2

11

1

0

1

2

32

1

2

2

2

53

0

1

i

0

12

1

0

2

0

33

2

000

54

0

1

1 1

1

13

1

0

2 1

1

34

2

00

1

55

0

1

i

2

14

1

0

2

2

35

2

o

o

2

56

0

1

2

0

15

1

1

00

36

2

0

1

0

57

0

1

2 1

1

16

1

1

0

1

37

2

0

1 1

1

58

0

1

2

2

17

1

1

0

2

38

2

0

1

2

59

0

2

00

18

1

1

1

0

39

2

0

2

0

60

0

2

0

1

19

1

1

1 1

1

40

0

2

o:

2

20

1

1

1

2

41

Figure 1. Time represented in trinary together with the decimal equivalent.
The colours indicate the bi-colour LED display.

IC10

+5V

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IC11 =4081
IC12 = 4013
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Figure 2. The circuit diagram shows a classic hardwired hardware approach.

2/2009 - elektor

43

CLOCKS

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44

elektor - 2/2009

other CMOS digital chips and produce
a simpler circuit. With reference to the
table LEDs D1 to D3 display the hours,
D5 to D8 the minutes and D4 pulses at
second intervals.

Setting the time

The PCB layout shown in Figure 3 is
rather reminiscent of a digital clock de-
sign from around 30 years ago when
TTL technology was king. Thanks to
CMOS circuitry and the LED outputs
used in this design it consumes far
less energy. The operating current de-
pends on the number of LEDs illumi-
nated which in turn is governed by
the time of day. The prototype board
shown in Figure 4 draws between 22
and 88 mA. This current level would
give a relatively short battery life but
should be no problem for a low power
5 V, 100 mA mains adapter. The five
volt supply does not need to be too
precise; the circuit will function happi-
ly at any voltage between 4.5 and 6 V.
To set the clock it is necessary to pull
out the jumpers JP1 and JP2 from
their RUN positions to the SET H (set
hour) position and then SET MIN (set

minute). The hours and the minutes
will increment at second intervals un-
til the correct value is achieved where-
upon the jumpers are returned to their
original position. The jumpers can be
replaced by slide or toggle switches to
make time setting easier.

With the component values given the
accuracy of the crystal in the prototype
was measured at +43 ppm which is
within the quoted crystal tolerance.
The crystal ran below its nominal value
but those of you who have the means
to measure the frequency accurately
(or who have enough patience) can im-
prove the accuracy by adjusting (trim-
ming) the values of Cl and C2 slightly
to change the capacitive loading on the
crystal. Increasing the capacitance will
slow the frequency.

(060030e)

Literature and Links:

[1] The German Museum of Mathematics:
www.mathematikum.de

[2] Marco Freitag: 'Binary Clock',

Elektor Electronics July/August 2006

COMPONENTS LIST

Resistors

R1-R8 = 220 Q
R9-R26 = 1 kD8
R27-R37 = lOOkD
R38 = 4MD7
R39 = 270kQ

Capacitors

Cl = 27pF
C2 = lOOpF
C3 = 100/+ 25V radial
C4-C15 = lOOnF

Semiconductors

D1-D8 = bicolour LED, red/green,
common cathode (e.g. Conrad Elec-
tronics # 1 85000)

D9- D22 = 1N4148
T1-T18 = BC547B
IC1-IC9 = 4017
IC10 = 4060
IC11 = 4081
IC1 2 = 4013

Miscellaneous

JP1,JP2 = 3-way SIL pinheader with
jumper, or miniature changeover
switch

XI = 32.768kHz quartz crystal
7 wire links

PCB, ref. 060030-1 from
www.thepcbshop.com

See your design in print!

Elektor Electronics (Publishing)
are looking for

Freelance Technical Authors/Designers

If you have

# an innovative or otherwise original design you would like to see in print

in Europe's largest magazine on practical electronics

# above average skills in designing electronic circuits

# experience in writing electronics-related software

# basic skills in complementing your design with an explanatory text

# a PC, email and Internet access for efficient communication with our in-house design staff;

then do not hesitate to contact us for exciting opportunities in getting your designs published on a regular basis.

Elektor Electronics
Jan Suiting, Editor

P.O. Box II, NL-6II4-ZG Susteren, The Netherlands, Fax: (+31) 46 4370161
Email: editor@elektor.com

2/2009 - elektor

45

MICROCONTROLLERS

Udo Jursz and Wolfgang Rudolph (Germany)

People don't come with built-in rulers, but if we need to know how far away an object is, we can
estimate the distance (and we do it all the time). However, how can a robot determine the distance to
an object and do so with sufficient accuracy?

In this article, we examine the various methods that can be used and describe a distance measuring
system that uses an infrared sensor and the ATM18.

Our ability to estimate distances accu-
rately depends on many factors, such as
how well we can see the remote object
and whether we know the size of the
object and other objects in its vicinity
In any case, our estimates are approx-
imations and rarely exact. However, a
moderately accurate estimate is usually
sufficient for finding our way around in
our surroundings. Things are different
with a robot, for example when it has
to adjust its speed and acceleration
while approaching an object located 80
to 150 centimetres away.

We started by taking a closer look at
various methods for determining the
distance to an object. The following
three methods are apparently the most
important:

1. Propagation time and relative phase
measurements using radio signals

2. Optical measurements (including
laser measurements)

3. Measurements using ultrasonic
signals

With regard to the last of these meth-
ods, we would like to make a small
digression here to the animal world.
As you know, bats use various sonar
techniques with fixed frequencies and

varying frequencies that yield a con-
stant reflected frequency from station-
ary objects. The results are calculated
so fast that these small aerobatic art-
ists can navigate through narrow caves
in full darkness with incredible virtu-
osity, and they can locate and capture
insects in full flight. Although artificial
ultrasonic measuring devices employ
methods that are similar to those found
in the animal world, our technology
falls far short of the capabilities of nat-
ural sonar systems.

Every method has its advantages and
disadvantages. Ultrasound is very sen-
sitive to reflections and the physical
properties of the atmosphere. Measure-
ments based on the propagation time
of radio signals require lightning-fast
signal processing circuitry.

Optical triangulation [1] is a commonly
used method for measuring distances
with light.

Angle measurement

Optical triangulation is based on meas-
uring the angle between emitted and
reflected light beams instead of the
propagation time of a light signal. Pro-
fessional equipment uses laser diodes

for this purpose in order to obtain high
accuracy, but a normal LED can be
used for relatively short distances if
high accuracy is not necessary.

The operating principle of optical trian-
gulation is shown in Figure 1. The LED
at the left end of the sensor acts as the
emitter. A precision lens forms the
light emitted by the LED into a narrow
beam that is reflected from the target
object. A portion of the reflected light
enters the lens of the receiver section
of the sensor (at the right in the figure).
The angle of the reflected light beam
depends on the distance between the
sensor and the target object. A ‘posi-
tion-sensitive detector’ (PSD), or in
other words a linear-array CCD IC, is
located behind the receiver lens. The
receiver lens focuses the reflected
light beam into a spot that illuminates
as few of the light-sensitive cells of
the CCD array as possible, so that its
position can be determined. If the dis-
tance to the target object changes, the
angle a of the received light beam also
changes, and a different part of the
light sensor is illuminated (Figure 2).
This clearly illustrates the operating
principle: when the distance changes,
the spot of light on the PSD (which

46

elektor - 2/2009

results from the reflected light beam)
moves to a different position. The inte-
grated signal processing circuit of the
sensor can thus generate a signal volt-
age that depends on the angle a and
thus on the distance. Unfortunately, the
relationship between the signal value
and the distance is not linear, since it is
based on a trigonometric function.

The essential requirements for using
this method are that the distance
between the emitter diode and the
receiver array of the sensor is known, as
well as the angle a. The signal process-
ing circuit obtains the latter value indi-
rectly from the position of the light spot
on the PSD. Using this information, the
sensor’s integrated signal processing
circuit generates a signal that is avail-
able at the sensor output. Another con-
sideration is that this method is only
suitable for short distances (up to a
few metres) because the sensitivity
depends on the distance between the
emitter and receiver sections, which are
both contained in a small package.

If you want to determine the distance
from the voltage generated by the sen-
sor, you have to do some calculations.
The following trigonometric formulas
can be used to determine the distance
x - x 0 from the measured distance

tan d =

x' — x

!

0

/

-> tan a =

Xg

D

x = D • tan {a + d) = D •

tan£r + tanJ
1 — tan^r* tanJ

x = D •

~y v _ V* ^

A 0 I A A 0

D ^ f

-y ^ ^

•A-q .A .A q

~d'~T

Figure 1. Distance measurement using optical triangulation.

Figure 2. The distance x - x 0 can be determined from the measured distance x' - x 0 ' by using trigonometry.

2/2009 - elektor

47

MICROCONTROLLERS

Figure 3. Sharp infrared distance sensor.

0 20 40 60 80 100 120 140

Distance to reflective object L (cm) >

080847 - 14

Figure 4. The relationship between output voltage and distance is non-linear.

Figure 5. The sensor needs an additional SMD electrolytic capacitor for decoupling.

From the final formula for calculating
the value of x, it should in any case be
clear that our little 8-bit microcontrol-
ler has far too little processing power
for continual measurement of the dis-
tance to any given object. There are
other methods that can be used to
determine the distance from the sen-
sor output voltage without using a
lot of processing power, but we don’t
want to get bogged down in theoreti-
cal aspects here. What matters now is
putting the theory into practice!

IRDMS in practice

The focus of this project is using infra-
red distance sensors made by the Jap-
anese manufacturer Sharp [2]. They go
by the moniker ‘IRDMS’, which stands
for ‘infrared distance measurement
sensor’. There are two different sorts
of IRDMS sensors. One sort has dig-
ital outputs with an internal compara-
tor set for a specific distance [3], while
the other sort has analogue outputs.
Here we use only sensors with ana-
logue outputs. Several sensors suitable
for different distance ranges are listed
in Table 1. For our experiments, we
selected the GP2Y0A02YK0F, which is
intended to be used with distances of
20 to 150 cm. However, any other type
listed in Table 1 can also be used, so
you can select the type that best suits
your particular application.

As you can see from Figure 4, the sen-
sor output signal is highly non-linear.
The distance cannot be derived directly
from the signal without linearisation.
However, this is not necessary for our
initial experiments.

In theory, all you have to do to obtain
a sensor signal with a range of up to
approximately 2.7 V is to connect a
5-V supply voltage to the sensor. The
IR diode operates in pulse mode and
emits short, powerful flashes, which
create a high peak load on the power
supply. It is thus recommended to con-
nect an electrolytic decoupling capac-
itor close to the sensor. Incidentally,
the emitted light is in the near infra-
red range and is just barely visible to
the naked eye in a dark environment,
but it is readily visible on the monitor
of a digital camera.

The internal linear array CCD has
approximately 100 active pixels. As
a result, the level of the output sig-
nal changes in steps of approximately
20 mV. A small ripple voltage with
around the same amplitude is super-
imposed on the output signal, so a low-
pass filter is a good idea. The 10-bit A/

48

elektor - 2/2009

D converter of the Mega88 has a reso-
lution of around 5 mV with the exter-
nal 5-V reference voltage, which in
theory is adequate for this application.
However, the C code developed for
this project selects the microcontrol-
ler’s internal 1.1 -V reference voltage,
which yields a resolution of approxi-
mately 1 mV. Caution: make sure that
REF jumper JP2 is not fitted.

A voltage divider consisting of a 5.6-kQ
resistor and a 4.7-kQ resistor must be
connected ahead of the input to match
the signal to the measuring range.
With this arrangement, the measuring
range of the microcontroller extends
to 2.4 V. A 1 -jL/F capacitor connected
across one leg of the voltage divider
lets it act as a low-pass filter as well.
The additional hardware is quite mini-
mal. Aside from the two resistors for
the voltage divider, you only need
two capacitors. First you have to sol-
der a capacitor with a value of 10 to
100 /jF as close as possible to the sen-
sor. It’s beyond us why Sharp didn’t

Table 1

Sharp IR distance sensors with analogue out-
puts, suitable for various distance ranges.

Type designation

Range [cm]

GP2D1 20XJ00F

4-30

GP2D1 2J0000F

10-80

GP2D1 5J0000F

10-80

GP2Y0A02YK0F

20-150

GP2Y0A71 OKOF

1 00-500

simply include this on the PCB in the
sensor package. Figure 5 shows this
‘user enhancement’ implemented
with an SMD capacitor fitted directly
to the PCB.. If you don’t want to mon-
key with the sensor PCB, you can fit a
small electrolytic capacitor externally,
which means soldering it to the pins
- but keep the leads as short as pos-
sible. Then you have to put together
the combined voltage divider and low-
pass filter, which as previously men-
tioned consists of a 6.8-kQ resistor
and a 4.7-kQ resistor (preferably with
a tolerance of 1% or better). Then sol-
der a 1-/JF capacitor across the 4.7-kQ
resistor (see Figure 6). Connect the
junction of the voltage divider to the
AD 6 input. The full circuit on the pro-
totyping board is shown in Figure 7.
Connect buttons SI, S2 and S3 to PB3,
PB4 and PB5, and connect the PCO
and PCI outputs to any desired inputs
(one each) of the ULN 2003 so they can
be used to drive the associated LEDs
(these connections are not shown in

Figure 6. Two resistors and an electrolytic capacitor form a combined voltage divider and low-pass filter for the sensor signal.

si

GP2012 / GP2Y0A02

GND

+5V

10|J...100|J
(close to sensor)

080847 - 15

Figure 7. All connections at a glance.

Figure 8. Displayed sensor values.

2/2009 - elektor

49

MICROCONTROLLERS

Listing 1

Distance calculation in Bascom

Sub Calculate_s
D = Getadc ( 6 )

' U = D/1023 * (4 . 7 + 5 .6) /4 . 7

'U = D * 5
U = D * 1 . 1
U = U * 10.3
U = U / 4 . 7
U = U / 1023
'Print U

' 0.008271

+ 939.6 x Us

' s =

' 1 - 3.398 x Us +

17.339 x Us x Us
If U > 0.4 Then
SI = 930.6 * U

51 = SI + 0.008271
S3 = U * U

S3 = 17.339 * S3

52 = 3.398 * U
S2 = 1 - S2

S2 = S2 + S3
S = SI / S2
Else
S = 0
End If
Print S
End Sub

End

the photos).

Software

The C software for this project
(ATM18_IRDMS_GP2xxx, download-
able from www.elektor.com) is quite
straightforward in use. Two limit val-
ues are defined, and the program moni-
tors these values and uses the LEDs to
indicate the switching points. If the LC
display is connected, three values are
displayed: the output of the A/D con-
verter (ADC: xxx), the upper limit (UL:
xxxx), and the lower limit (LL: xxxx)
(see Figure 8).

You can press SI (left button) to set
lower limit to the current sensor value,
or press S3 (right button) to set the
upper limit to the current sensor value.
If you press the middle button (S2), the
upper limit and lower limit are set to
the default values.

After the limit values have been set,
you can move almost any desired
object around in the acquisition range,
and the voltage generated by the sen-
sor will be shown on the display. If the
either of the limit values is reached, the
corresponding LED on the prototyp-
ing board lights up. A possible appli-
cation for this arrangement would be

controlling a robot so that it never gets
trapped in a corner and avoids obsta-
cles. Of course, the distance parameter
values could also be adjusted dynami-
cally by the software according to the
speed of motion.

For developing your own applications,
we can provide a small tip here. You
can determine the distance with rea-
sonably good accuracy by using the
following simple formula:

0.00827 1 -1- 939.6 X U s

1)1 — —

1 - 3.398 XU S + 17.339 xU s xUs

Here Us is the sensor signal voltage,
which ranges from 2.5 V at a distance
of 20 cm to 0.45 V at a distance of
150 cm.

Naturally, this can be calculated much
faster than the previously stated for-
mulas. It can also be used in a Bascom-
based solution.

If you need to make distance meas-
urements in an application and con-
vert them to physical units, you natu-
rally want to use the fastest possible
method, which means using a look-up
table. This involves creating a table of
sensor output voltages for the entire
distance range and having the soft-
ware read values from this table.
However, the implementation
described here provides an adequate
starting point for enabling a mobile
object to decide which action to take,
similar to the way a bat navigates with
its ultrasonic localisation system. If an
obstacle is looming, the motors can
be stopped, and if the object keeps on
coming, they can be put into reverse.
That’s something even a bat can’t do!

Lamp control in Bascom

The Bascom program (downloadable
from www.elektor.com) uses the sen-
sor for a simple lamp control instead
of displaying the measured distance
to an object. The lamp in question is
a desk lamp, which is controlled via
all bits of Port B. One option is to use

the ULN2003 driver IC on the board to
drive a relay.

In use, the distance sensor is aimed
at the work station. If someone
approaches the desk, the lamp goes
on automatically. If they leave the
work station, the lamp is switched
off after a delay of 100 seconds. The
movements of the person working at
the desk are also monitored. With nor-
mal desk work, people constantly move
around by more than 3 cm. If motion is
no longer observed, the person being
monitored has probably fallen asleep.
In this case, the desk lamp is switched
off in the interest of a good office nap.
However, it switches back on immedi-
ately if the boss comes by and wakes
his employee.

The function Calculate_s (Listing 1)
makes a measurement and converts
the result into the distance s in cen-
timetres. The calculation must be
performed in individual steps in Bas-
com; writing the full expression in a
single line with lots of parentheses
won’t work here. The voltage meas-
urement code takes into account the
voltage divider (6.8 kQ / 4.7 kQ) and
the internal reference voltage (1.1 V).
The calculated distance is also sent
to the PC via a 9600-baud link. Expe-
rience shows that the accuracy of the
distance measurement is relatively
good, with an error of around 10%. If no
object is present in the visible range, a
value of zero is output. The lines for an
alternative sensor connection without
a voltage divider, which requires using
the 5-V supply voltage as the reference
voltage, have been commented out.

( 080847 - 1 )

References and links

[1] Contactless Distance Measurement,
Elektor Electronics, April 2002

[2] www.sharpsma.com

[3] Distance Measurement using Infrared,
Elektor Electronics, July/August 2002

The ATM18 project at Computer:club 2

ATM18 is a joint project of Elektor and Computer:club 2 (www.cczwei.de) in collaboration with
Udo Jursz, Chief Designer of www.microdrones.de. The latest developments and applications
of the Elektor ATM1 8 are presented by Computenclub 2 member Wolfgang Rudolph in the
CC 2 -tv programme broadcast on the German NRW-TV channel. The IR distance sensor and
ATM1 8-AVR board combination described here was featured in instalment 25 of CC 2 -tv.

CC 2 -tv is broadcast live by NRW-TV via the cable television network in North Rhine-Westphalia
and as a LiveStream programme via the Internet (www.nrw.tv/home/cc2). CC 2 -tv is also avail-
able as a podcast from www.cczwei.de and - a few days later - from sevenload.de.

50

elektor - 2/2009

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w

2/2009 - elektor

51

INFO & MARKET

REVIEW

Decibit 2.4 GHz RF Transceiver
Development Kit

Jan Buiting (Elektor UK/USA Editorial)

Decibit DDK contents

• CD-ROM: programmer, AVRasm2,
WinAVR, example code files, USB driver

• USB programmer

• USB cable

• 2 DCBT-24AX modules

• 1 DCBT-24R6 Tiny RC

• 2 Handheld Testers

• 6 AA batteries

1 printed datasheet

I never considered a battery holder for
three AA batteries or a CD-ROM bulky
components until I opened the DDK v. 2.1
RF development kit from Decibit. For sure,
it’s because of the tiny (25 X 10 mm) RF
transceiver modules with even tinier ICs
on them (like 5x5 mm and 4x4 mm).
Decibit rely on proven technology:
Atmel’s ATMegal68 microcontroller in
combination with an nRF24L01 trans-
ceiver chip from Nordic Semiconductor
together from the IC complement of a
series of intelligent 2.4 GHz (ISM band)
transmitter/receiver (TX/RX) modules
with ISP connectivity and, remarkably,
the ability to run AVR firmware created
by you, the user.

Plug & Play but AVRasm too

The DDK kit, advertised at US$ 69 at
the time of writing (December 2008)
has great educational value as there
is so much to discover and develop for
different levels of users. Schools, for
example, may follow the plug and play
approach: install CD on PC; plug mod-
ule on USB programmer and run the
batch file. Next, insert the programmed
modules in HHTs (hand held test-
ers), press a button on one HHT and
observe the LEDs on the other located
at the far end of the classroom.

More advanced users should explore
the examples demonstrating differ-
ent RF data transfer methods and per-
haps expand or modify the example
code chunks supplied. These cover
one-way and two-way RF links using

Shockburst protocols, with or without
ACK(knowledge). There is even a ping-
pong demo allowing you to check the
TX/RX range by walking around (I was
able to cover distances up to about
50 m in and around my home). You can
see (well, kind of) the data send/resend
actions on the HHT LEDs.

Development tools

The USB compatible programmer unit
contained in the kit is a gem as it allows
you to develop your own code for blow-
ing into the ATmega on the modules.
The ingredients: Decibit’ s own pro-
gramming software; AVRasm2 from
Atmel, the WinAVR C/C + + Compiler
and a USB driver. If you can make an
ATmega write “hello world”, you’re
equally okay to talk to the Nordic TX/RX
on the Decibit module as if it was just

another peripheral device like an LCD.
For example, CALL_label is sufficient to
do a data transfer. The abilities of this
system go far beyond those of com-
monly found ‘passive’ transceiver mod-
ules listening to AT-style commands
— the Decibit DCBT-24 modules can
be controlled right down (or should we
say ‘up’?) to AVR assembly code level
which makes them highly interesting to
developers designing RF remote control
applications ‘the embedded way’.

Modules: you choose

• DCBT-24N (low-power ultra small
size TX/RX);

• DCBT-24B (low-power TX/RX w.
external antenna connection);

• DCBT-24C (80 mW power amplified
TX/RX with SMA antenna connector);

• DCBT-24R6 (6-button key for remote
control).

For the TX/RX modules, several hard-
ware/software versions are available,
which customers can specify using
the extensive ordering information
system.

According to Decibit, ETSI and FCC
approvals are pending for the DCBT-24
products. Also, RF modules with more
pins will be released in the future,
or versions based on the latest AVR
technology like XMEGA. For now, the
ATmegal68 does a fine job already.

( 080868 - 1 )

www.decibit.com

52

elektor - 2/2009

MICROCONTROLLERS

BASCOM AVR Course

( 4 )

A DDS generator using the
ATmega32

Burkhard Kainka (Germany)

The first five instalments of this course have already covered many programming techniques
with an emphasis on practical applications. This final instalment builds on this theme giving
a detailed insight into all the software routines needed to make a simple DDS generator. We
also have an offer for you, see the final page of this article!

To get a good overview of some of the possibilities of the
BASCOM language and the ATmega controllers it is worth
looking through the BASCOM AVR help pages, particularly
all the Config options (Figure 1). Some of the topics we
have already covered in this course and in other ATM-1 8
projects include:

• COM-interface, hardware and software

• Ports, input, input pull-ups, output

• A/D converter

• Timer and counter

• Timer interrupts

• PWM outputs

• RC5 input

• l 2 C master

• Servo impulse

• One-wire bus (elsewhere in this edition)

There is of course much more internal and external hard-
ware that can be used. The ATmega family share the same
basic core but more specialised applications call for a care-
ful study of the datasheets to find the version best suited to
the task.

This month we build an AF generator using the principles of
DDS to produce the signal. The microcontroller interfaces to
an LCD which is driven from the port pins.

The DDS generator produces a sine wave signal from a
digital PWM output. Two pushbuttons increment or decre-
ment the output frequency in steps of 10 Hz. The output
frequency is shown on an LCD and also sent to the COM
interface port. For this test a Me ga32 type controller has
been used, it has many I/O pins and is a popular choice.
It would be simple to make changes to allow the program
to run on other controllers from the ATmega family.

The principle

The block diagram in Figure 2 gives an overview of the
external components connected to the microcontroller. The
PWM signal is output from pin OC1 B, and passes through

$ BASCOM AVR H«lp

E

H.V

El Ark

Horn*

&

l*rnl

Ccftfertt ijjdex Search ! avw/lej

2) CONFIG
SI CONFIG lWIPf
SI CONFIG ACI
SI CONFIG ADC
SI CONFIG ATEMU
SI CONFIG BCCARD
SI CONFIG CLOCK
SI CONFIG CLOCKDIV
SI CONFIG COM1
SI CONFIG COM2
SI CONFIG COMk
21 CONFIG OATF
21 CONFIG OCF77
2) CONFIG OFAOUfJC.F
21 CONFIG Hi TAG
21 CONFIG I2COFI AY
2] CONFIG I2CSI AVF
21 CONFIG INPUT
2] CONFIG INTk
2] CONFIG GRAPHl CD

ff-

Uplims

CONFIG

IfiC Etfi mui M£22

DIRECTIVE

( UNI IG ! WIKI

:0NFIG ACI

CONTIG ATCMU

CONFIG BCCAKD

CO NF IG CLO CK DIV

CONI 1G COM I

CONFIG COM2 also COM3. COM4
CONFIG DATE

CONFIG DCr 77

CONFIG UfcBOUNCfc

CONFIG GRAPHLCD

CONFIG HITAG

CONI 1G I2CDILAY

:ONFIG I2CSLAVE

com |C, IN lk

NO

YFS

RE-

USABLE

NO

YES

NO

NO

NO

YU

YES

NO

NO

NO

NO

NO

NO

NO

NO

Yl

Figure 1.

Bascom help for the config
options.

a low-pass filter to produce a sine wave. The filter design is
very simple but for test purposes is sufficient. A better solu-

Figure 2.

Block diagram of the DDS
generator.

2/2009 - elektor

53

MICROCONTROLLERS

Figure 3.
The LCD setup page.

Listing 1

Initialising and writing to the LCD

Config Lcdpin = Pin , Db4 = Portb . 4 ,
Db5 = Portb . 5 , Db6 = Portb . 6 ,

Db7 = Portb . 7 , E = Portb . 3 , Rs =
Portb . 2

Config Led = 16 * 2

Initlcd

Cls

Led "DDS"

Listing 2

Sine wave lookup table and frequency selection

For N = 1 To 256
A = N - 1
A = A * 3 . 1415
A = A / 128
B = Sin(a)

B = B * 120
B = B + 128
Table (n) = Int (b)

Next N

Freq = 10
Do

Locate 2 , 1
Led Freq
Led " Hz

If Pind.6 = 0 Then
Freq = Freq + 10
Print Freq
End If

If Pind.7 = 0 Then
Freq = Freq - 10
Print Freq
End If
Waitms 10
A = Freq
'43200/65535
B = A / 0 . 65918

F = Int (b)

Loop

tion would use a (many-poled) filter with a much steeper
response and a cut-off frequency of around 15 kHz. A sim-
ple piezo buzzer can be directly connected to the output
without the need for any filter at all.

LC display

Whenever a design calls for an LCD to display lines of char-
acters it can be achieved using six port pins for the drive
signals. The LCD usually works in 4-bit mode with each data
byte split into two before being sent to the display. Two
control signals, E and RS, are also needed. In addition to
these six signals we need three for the power supply and
contrast setting.

The port pin assignments can be defined in the Menu
Options/Compiler/LCD (Figure 3). A better method is to
make the assignments in the source file (Config Lcdpin).
Th is ensures that it runs successfully on different systems. It
is also necessary to define the type of LCD used (Config Led
= 16*2). When the system is first switched on one line of
the LCD will be dark and the other light. After the display is
initialised (Initlcd) the dark line becomes light. Characters
(Led "Text") or a variable (LCD Freq) can now be sent to
the display. After each character is written to the display
the position is automatically incremented ready for the next
character, but the second line does not automatically follow
from the first. Writing to the second line it is necessary to
define the position (Locate 2 , 5). The entire screen can be
cleared at any time using the Cls command.

The example given in Listing 1 writes the text / DDS / to
the first line. The frequency value is sent to the second line
of the display (Listing 2) followed by the units 'Hz'. The
displayed frequency value will not always have the same
number of characters so it is necessary to include enough
spaces to ensure that all characters previously displayed
will be overwritten by the new value.

Sine table and frequency selection

A sine function lookup table must be written into memory
for use by the DDS generator. The table size is 256 bytes.
These represent the analogue values of the wave which are
sent to the PWM output to produce the sine wave.

At start up the generator has an output frequency Freq =
10 Hz (Listing 2). The two pushbuttons PD6 and PD7
increment and decrement the output frequency in 1 0 Hz
steps. The output frequency value is written to the two line
display and each time the frequency is changed the new
value is sent to the PC. Operation without an LCD is there-
fore possible. The generator can be used for example to
tune an instrument; the standard ' K note (440 Hz pro-
duced on a tuning fork can be selected without problem.
The frequency in Hz is scaled to give the variable F. Every
change of F immediately affects the output frequency. This
is made possible by the use of an interrupt routine.

Timer and DDS

The sine wave generator uses the DDS (Direct Digital Syn-
thesis) principle with values of a sine waveform stored (as
bytes) in a lookup table. A phase accumulator (the variable
Accu) is increased by the value of the variable F to point
to the next value in the lookup table. Only the high byte of
the 1 6-bit Accu is used as a pointer to the table. When F
has the value 1 it will therefore take 256 timer interrupts
before the next value in the table is used and produces an
output sine wave with a frequency of 0.6591 8 Hz. This is
the resolution of the frequency generator. As the value of F

54

elektor - 2/2009

increases the pointer steps through the table more quickly.
When its value reaches 256 the pointer will start to jump
over individual values but the output will still be sinusoidal.
At the highest frequency of 1 0 kHz only around four val-
ues are used to produce a complete sine wave cycle. The
lowpass filter ensures that a good approximation to a sine
wave will still appear at the output.

The program uses two timers. Timer 1 generates the 8-
bit PWM signal. In this setup the PWM frequency is
1 1 059200 Hz / 256 = 43200 Hz. The 8-bit Timer 0 with-
out any prescaler overflows at a rate of 43.2 kHz. This is
therefore the rate at which the interrupt service routine is
called, a new value is fetched from the lookup table and
written to the PWM register before the next interrupt occurs
(Listing 3).

Without any prescaler an 8-bit timer will interrupt every
256 clock cycles. Between interrupts the controller must
not only execute all the instructions in the interrupt service
routine, but also push all the working registers onto a stack
and lastly pop them off again. In some cases the timing
could be a little tight. It is important to be sure that there will
be enough time to carry out all the activities. The simplest
way to indicate how long the controller spends servicing
the interrupt is to get it to set a port pin (Port.O = 1) as it
enters the ISR and reset it (Portb.O = 0) when it exits. With
an oscilloscope probe on the pin we can now observe the
mark/space ratio directly to see how much time is avail-
able. In the example here the pin is high for less than 50%
of the time. The main routine can only execute its tasks
when this waveform is low. Using a simple software delay
like Delayms will produce noticeably longer delay times
than expected.

Two lines are 'commented out' in the interrupt routine.
When these comment characters are removed the signal
generator now has a sweep function. The frequency is
incremented each time an interrupt occurs, the generator
now sweeps from 0 to 1 0 kHz approximately three times
per second. The oscilloscope display (Figure 4) shows the
resulting output waveform after the low-pass filter. A piezo
buzzer connected to the output will produce a characteris-
tic twittering sound.

( 080866 - 1 )

Downloads and more info

Go to the project page at www.elektor.com/080866 for more in-
formation and the program downloads. We welcome your feed-
back in the Elektor forum.

BASCOM-AVR Reader Offer

Exclusive to Elektor readers, the download version of MCS
BASCOM-AVR is now available at £ 55.00 (€ 69.00), a discount
of more than 20% compared to the normal price of £ 71 .00
(€ 89.00). As a bonus, pdf copies of all six BASCOM-AVR
course instalments that appeared in Elektor are included with the
download. The offer is valid from 19 January 2009 through
9 February 2009. Further details at www.elektor.com/bascom-
avr. US readers please check US$ prices on website.

Listing 3 The DDS

Config Timerl = Pwm , Prescale = 1 , Pwm =
8 ,

Compare A Pwm = Clear Down ,

Compare B Pwm = Clear Down
Config TimerO = Timer , Prescale = 1
On OvfO TimO_isr
Enable TimerO
Enable Interrupts
Pwmla = 127
Pwmlb = 0

TimO_isr :

'Timer 43.2 kHz at 11.0592 MHz
Portb .0=1
Accu = Accu + F
N = High (accu)

Pwmlb = Table (n)

'F = F + 1

'If F > 15000 Then F = 1
Portb .0=0
Return

Figure 4.

Oscilloscope display of the
swept output signal.

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2/2009 - elektor

55

_ 1 _ ii 1^,/M f P i jjj- ^ ~t. ’ ■>; y m 4| mj’,'

One area that many model train enthusiasts have never been totally happy with is the lighting of
coaches. Until now. The lighting controller described in this article is a combination of an SMD LED strip
and a PIC12F683 for compatibility with the Marklin system. The LEDs allow easy adaptation to different
colours while three different lengths of the board enable the project to fit all common coach types. The
controller can be assigned an address without removing it from the coach. •

Being able to turn the lighting on and
off in a model railway coach used to
be a challenge, as a separate decoder
in the coach was at times not easy
to conceal, and when installed, the
address for the decoder was not easy
to set or change. This challenge led the
author to develop a solution that would
address the following list of criteria:

• Cost effective with regard to buying
commercial units.

• Easily adaptable to various colours.

• Switching individual coach lighting
on and off.

• Controlling the intensity of lighting
in individual coaches.

• Turning coach marker (‘tail’) lights
on and off.

• Changing addresses of the decod-
ers without having to open the
coaches.

• Having a single feed for power link-
ing coaches.

• Eliminating flicker due to the unbal-
anced Marklin track signal.

• Different length units to fit all com-
mon coach types.

The result has been the building of a
coach lighting strip with an on-board
controller. The board uses a PIC12F683
8-pin microcontroller to decode the
incoming Marklin signals and con-
trol the intensity of the LED lighting.
This microcontroller contains a PWM
(pulsewidth modulator) and it can be

obtained for a very reasonable price,
keeping the cost of the unit low.

LEDs, colours & board sizes

In principle, any colour SMD LEDs
may be used. When purchasing LEDs
ensure that they are rated at least
100 mcd (milli-candelas) with a view-
ing angle of at least 110 degrees.
White LEDs in a 0805 package with
140 mcd output and a viewing angle
of 140 degrees work very well. For yel-
lowish) lighting, LEDs in a 1206 pack-
age are also a good choice. Experiment
with a number of different LEDs until
you find the ones that you think pro-
vide the colour that you like best.

The board is available in three lengths
to accommodate different model coach
lengths. The short board has a length
of 110 mm and has four illuminating
LEDs. The medium board has a length
of 190 mm and accommodates eight
LEDs. Finally, the long board is 230 mm
in length and has 10 LEDs. All boards
are single-sided and surface mount
components are used throughout.

The circuit

As shown in Figure 1 , the Marklin
system supply voltage arrives via the
rails on the bridge diodes D1-D4 via
PCI (Marklin RED) and PC5 (Marklin
Brown). The output of the bridge is
clamped by a 27-volt zener diode, D2,

to protect the regulator from exces-
sive voltage spikes that may occur on
the track layout. The 22 /jF capacitor
C3 acts as a reservoir device to pre-
vent the microcontroller from resetting
owing to short periods of power loss.
This power configuration also elimi-
nates the flickering of the LEDs due
to the unbalanced Marklin track sig-
nal. The 16-19 V raw DC output from
the bridge is fed to the 5 volt regulator
IC1 that in turn feeds the PIC micro-
controller and the TLE4913 Hall effect
switch, IC3.

The Hall switch pulls its output Low
if a magnet is detected in its vicinity.
Using software, this condition is used
to enter the board address setup pro-
cedure discussed further on.

Output GP2 from the PIC microcon-
troller then drives an MMBF170 sur-
face mount FET (T2) to turn the coach
illumination LEDs on and off via PWM.
A second output (GP4) and a second
FET (Tl) control two external LEDs
that form the left and right tail lights
on the coach. The tail lights should
be connected between terminals A’
(anode) and ‘C’ (cathode) and pro-
vided with their own current limiting
resistor (2.2 kQ is suggested). If you do
not need tail lights, Tl and R9 may be
omitted from the board.

It should be noted that the circuit dia-
gram shown in Figure 1 is generic for
the project. Three options exist for the
construction — you decide.

56

elektor - 2/2009

Quick project specs

• Marklin compatible

The short board uses LEDs D6, D8,
DIO and D15 only.

The medium board uses LEDs D6, D8,
DIO, D15, D7, D9, Dll and D13 only.
The long board uses all LEDs shown,
i.e. D6, D8, DIO, D15, D7, D9, Dll,
D13, D12 and D14.

The PIC micro

We’re sorry if this sounds patronising
to microcontroller boffins but the PIC
12F683 device used in this project is
(1) an SMD device and (2) has to be
programmed before it has any func-
tionality: so, either you buy it ready-
programmed from the Elektor Shop
(order code 080689-41) or you obtain a
blank device from your favourite sup-
plier and do the programming yourself
using your own programming system
and the software that’s supplied free
of charge through the Elektor website
(archive file 080689-11. zip). Assembly
language and hex files are provided.
The project software was developed
using Microchip MPLAB IDE v3.14.

Construction

The boards all employ SMD compo-
nents and those of not you not used to
handling these tiny parts (or recover-
ing them from mom’s vacuum cleaner
all the time) may want to seek help
from fellow modellers in a club or
on the Elektor forums, also when it

comes to ordering parts and boards,
using the motto: Strength in Numbers!
Elektor does its part by supplying

bundle discounts for the PCBs and the
microcontroller, see the Shop section
of our website.

IC1

UA78L05ACL

-j 2 ^. £3* Cl

27V

500mW

22u

35V

PIC12F683

*see text

tail lights (optional)

Figure 1. Circuit diagram of the coach lighting controller:
basically, it's no more than a PIC micro and a series of LEDs under PWM control.

2/2009 - elektor

57

MODEL RAILWAY

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Figure 2. The control board comes in three sizes: long (a),
medium (b) and short (c) to suit most model coach sizes. Full-
size PCB artwork for all three board versions is available free
of charge from the Elektor website.

The component mounting plans for
the board are given in Figure 2a (long
board), 2b (medium board) and 2c
(short board). All three board sizes are
available individually and ready-made
from the Elektor Shop (order codes
080689-1, -2, -3).

In the Elektor labs, it was proved that
populating these boards is feasible
with a steady hand, a fine tipped solder
iron and nothing in the way of special
SMD soldering tools. This is probably
due to the fact that the parts are small
but generously spaced on the board.
You should start, however, by mount-
ing the programmed microcontroller.

A few more remarks. The length and
spacing of the copper pads for the
LEDs allow a wide range of devices to
be used including ‘0805’ and ‘1206’.

Be sure to know, verify again, and dis-
cuss with your friends, the polarity of
the electrolytic capacitor C3 before fit-
ting it on the board with absolute cer-
tainty. The electrolytics on our proto-
type boards had their positive ( + )
terminal marked with a red bar. C3
may be increased if you require the
coach lights to stay on longer in the
absence of power on the rails. You
may even consider replacing C3 with
a ‘Goldcap’.

Regarding the SMD diodes, when in
doubt, do a polarity measurement or
seek advice from your supplier.

It is recommended to test the board
before mounting it in a coach. This
is easily done by providing a tempo-
rary wired connection to the rails. Our
thanks are due to Mr. Henk Prince for
testing the three prototype boards in
his privately owned Marklin layout.

Mounting it in the coach

The light strip should be attached to
the inside roof of the carriage using
Prestic adhesive or double sided tape.
Ground (Marklin Brown) should be con-
nected to ground pickup springs on a
set of the coach’s wheels and routed
to PC 5 of the lighting board. The cen-
tre shoe pickup Red wire should be
connected to PCI on the lighting strip
or from the conductive coupler on the
end of the coach. PC2 should
carry current from
the oppo-

site

end of the coach
to the opposite end con-
ductive coupler to feed positive
supply voltage to the following coach.

Setting up the board address

Having digested that in a Marklin sys-
tem each device — whether locomo-
tive, semaphore or turnouts — has its
unique, individual device address, it’s
no surprise that the coach lighting con-
trol is just another device to be incor-

COMPONENT LIST

Resistors

(all SMD 0805 except R8)

R1 ,R2 = 1 kQ

R3 = 2kD2

R4 =270kD

R5 = 47kD

R6,R7,R9 = lOkD

R8 = on (wire link) (SMD 1 206)

Capacitors

Cl ,C2,C4 = 1 OOnF (SMD 0805)

C3 = 22/L/F 35V tantalum (in D or X case)

Semiconductors

01,03,04,05 = BAS16
D2 = 27V 500mW zener diode in SOD-
80C case, e.g. BZV55C27

D6-D1 4 = white or yellow SMD LED, min.

1 OOmcd, min. 1 1 0 degrees (see text)

T1 ,T2 = PMBF1 70 (or equivalent for BS1 70
in SOT-23 case)

IC1 = 78L05 (SOT-89-3 case, e.g.
L78L05ABUTR)

IC2 = PIC1 2F683-E/SN or-l/SN, pro-
grammed, Elektor Shop # 080689-41
IC3 = TLE4913 (Hall sensor)

Miscellaneous

PCB, long version (I = 230mm), Elektor
Shop # 080689-1*

PCB, medium version (I = 190mm), Elektor
Shop # 080689-2*

PCB, short version (I = 1 10mm), Elektor
Shop # 080689-3*

* select length to fit coach size.

58

elektor - 2/2009

porated in the system. The board is Figure 3. The three boards, ready for installing into model

configured as follows, assuming it’s railway coaches,

working correctly, connected up and
installed in a coach.

1. Place coach on rails.

2. Reset the Marklin control unit: Press

and hold the stop and go
buttons until con-
trol unit

resets.

3. Enter address of engine, e.g. 06.

4. Hold a magnet over the end of the

coach until the coach lights blink.

5. Remove magnet, then wait till light

stops flashing.

6. Turn on engine lights using F0.

7. Adjust speed dial to adjust desired

illumination level of lights.

7. Turn on FI to save illumination
level.

8. The coach light will blink a few
times to indicate acceptance of
the level.

The decoder is now programmed to
address 06. Lights can now be turned
on and off with the F0 buttons. If you

have connected marker lights, then
they can be operated using the F3 but-
tons. FI has no function after setting
the illumination level during program-
ming setup.

Model railway fans, please send us
your photographs of coaches fitted
with the controller described here!

( 080689 - 1 )

Programmer

settings

Device: PIC12F683 SOIC-8
Oscillator internal RC, no clock
Watchdog: enabled
Power Up Timer: enabled
CPD: disabled
Brown out: enabled
SBOREN: disabled
MCLR pin: enabled

Internal External Switch Over: disabled
Fail-Safe Clock Monitor: enabled

About the author

Graham Guthrie worked as an IBM cus-
tomer Engineer for 31 years on mainframes
and entered early retirement at the end of
1999.

After retiring he took up model trains as a
hobby to keep himself occupied. Graham
now makes various decoders and control-
lers for the local model train fraternity in his
spare time.

He is also involved in helping others in the
hobby with computer automation of their
layouts.

Email: grahamg7@telkomsa.net

2/2009 - elektor

59

TECHNOLOGY

PROGRAMMING

Programming FPGA

C-to-Hardware synthesis using Alt

Volker Brandstetter (Altium Germany)

FPGAs are normally programmed in special-purpose programming languages such as VHDL,
which unfortunately can be hard to learn. Now, however, it is possible to program hardware
in good old-fashioned C! Compared with conventional sequential execution of a program in
a microcontroller, the results are considerably faster. We look at how C code can be compiled
into hardware, using the Altium Designer development suite as an example.

FPGAs are hardware devices whose internal structure is
determined by software. Compared with sequential pro-
gram execution in a microcontroller, an FPGA can offer
a considerable increase in speed; compared with ASICs
FPGAs are more flexible and overall design costs for small
to medium quantities are much lower.

Traditionally FPGAs (and ASICs) have been designed by
specifying the structure and function of the circuits inside
the device at the register transfer level (RTL) via a hardware
description language such as Verilog or VHDL. Once the
design has been simulated and verified the RTL description
is converted into GDSII data for mask making (in the case
of ASICs) or into binary configuration files (in the case of
FPGAs).

The RTL development approach allows the hardware
designer to work with the final silicon implementation in
mind, and hence to optimise the circuit for speed or for
power. Sometimes, however, these factors can be less
important than low development costs or short develop-
ment time.

In these respects the RTL approach has a number of
disadvantages:

• Development is carried out at a low level of abstrac-
tion. A program that might run to 100 lines in a high-
level language might easily balloon into a 1 000-line RTL
description.

• There are limited opportunities for code re-use as the RTL
description specifies the structure of a system explicitly.

• When using an RTL description optimisation is usually
carried out at the sub-system level; optimisation at a
higher level can often have a greater impact on cost and
performance.

C with benefits

Now we shall look at how so-called C-to-Hardware synthe-
sis can address these disadvantages. Parts of a C program,
that normally would be run on a microcontroller, can be
transformed into FPGA hardware using the development
suite, with an immediate performance gain.

One powerful development suite offering such a feature
is Altium Designer from Australian software maker Altium
(http://www.altium.com/ products/altiumdesigner). The
company also sells development boards which offer such a
wide range of peripherals and expansion possibilities that
they can be used directly for hardware prototyping. An
example is the NanoBoard (see text box), which was used
to test the sample applications described in this article.

The C-to-Hardware synthesis feature of the design suite
allows designers to develop FPGA-based prototypes with-
out having to learn Verilog or VHDL. C is used as the hard-
ware description language, supported by a comprehensive
IP library of ready-made FPGA modules including soft proc-
essor cores (microcontrollers implemented within the FPGA),
memory controllers and various peripherals.

The C-to-Hardware synthesis process in Altium Designer con-
verts an ISO C/C++ program into synthesisable RTL code.
The compiler generates the circuit on the basis of a list of
functional units (such as adders, ALUs, MACs, dividers and
so on) and their characteristics. In doing so it endeavours
to obtain the highest possible performance, for example
by constructing functional units in such a way that they can
be run in parallel.

The advantages of C-to-Hardware synthesis come to the
fore when a processor core is integrated into the FPGA.
C code can then either be executed on the processor or
be converted into RTL code. The embedded compiler and
C-to-Hardware synthesis are closely integrated in Altium
Designer. Which functions are executed by the processor
and which in hardware can be selected with just a couple
of clicks of the mouse.

60

elektor - 2/2009

The twofold way

In principle there are two ways of using the C-to-Hardware
compiler.

1 . The first use is in developing functional circuit blocks in
C. In this case the compiler is used to convert individual
C functions into hardware. A so-called 'C Code Symbol'
makes it easy to integrate the function into the design. The
result of the compilation process is an FPGA block that can
be used as a module alongside other circuit blocks written
in VHDL or Verilog, or ready-synthesised IP modules, con-
nected via its defined inputs and outputs (Figure 1).

The C-to-Hardware compiler can convert the C function into
a purely combinatorial circuit or into a multi-cycle circuit.
This choice is made by setting the relevant property on the
C Code Symbol (Figure 2).

In the case of combinatorial blocks only the parameters
to the C function appear as inputs and outputs on the C
Code Symbol. For multi-cycle circuits Altium Designer adds
in the extra signals (such as clock and reset) that need to
be connected.

2. The second use is in increasing the speed of a proc-
essor-based system. Here the C source code for selected
software functions is converted into hardware in such a
way that they can still be 'called' from the main embed-
ded program, which is now running in a processor imple-
mented in the FPGA. The C-to-Hardware compiler is used
in conjunction with the embedded software compiler which
is also part of the design suite. Implementing speed-critical
functions in hardware can result in enormous increases in
speed (Figure 3).

Faster in parallel

Operations that are described as occurring sequentially
in C but which could be run in parallel in hardware are
converted into suitable RTL code by the compiler. For many
algorithms, such as those used in image and signal process-
ing, the parallel use of the available FPGA resources not
only relieves the processor of computational burden but also
provides a performance improvement.

The so-called Application Specific Processor block (or ASP
block functions here as an interface between the opera-
tions being carried out in hardware and the remainder of
the C program still running on the processor. When a hard-
ware function is called from the embedded program, the
processor passes the values of the function parameters to
the ASP, which then initiates the function. When the hard-

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2/2009 - elektor

61

TECHNOLOGY

PROGRAMMING

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ASP to indicate where the values of the function param-
eters are stored.

The ASP block is easily configured via a dialogue box (Fig-
ure 4). A list (upper right) allows the designer to specify
which global variables are implemented in ASP block RAM.
Access to this memory, internal to the ASP, is many times
faster than access to memory which is also directly visible
to the processor. A further list (lower right) lets the designer
select which C functions are implemented in hardware and
which in software.

Rotating 3D cube

Now we shall see how these ideas fit together using a dem-
onstration example where we show a three-dimensional
rotating cube on the NanoBoard's TFT display.

To enter the example system design into Altium we use the
'OpenBus' editor. The components needed to construct the
system are selected from a list and then placed and con-
nected together; all this can be done without needing to
worry about the nitty-gritty of implementation.

The C source code is then entered using the integrated edi-
tor. Altium Designer includes a compiler, linker and debug-
ger for the TSK3000 (a 32 bit RISC processor) as well as a
range of other 8 bit and 32 bit processors.

When the individual components have been created and
connected together the system can be configured using the
corresponding forms. This includes the ASP configuration
form described earlier as well as (for example) facilities
for setting the address ranges occupied by various periph-
erals and the quantities of internal and external memory
available to the processor (Figure 5). The memory map
is displayed graphically, and any change made is auto-
matically propagated to the embedded software project.
This is one of the advantages of an integrated development
environment.

62

elektor - 2/2009

The C program can be
tested and verified in
real time using the Nano-
Board. The resources avail-
able on the NanoBoard
and the interfaces to the
FPGA daughter board are
selected using special sym-
bols from a supplied library,
and connected to the FPGA
circuit in the overall circuit
diagram (Figure 6). For
our 3D cube examp e we
need to represent the TFT
panel, the clock and reset
signals, a LED display and
two SRAMs. The document
describing the FPGA cir-
cuit is wired into the sche-
matic in a hierarchical fash-
ion using an automatically
generated symbol to rep-
resent it. It is connected to
the resources of the Nano-
Board in the overall circuit
diagram.

Chocks away!

When the system specification is complete the build process
can be initiated (Figure 7 shows the so-called 'cockpit'). The
build process takes place in four steps. First, the C-to-Hard-
ware synthesis step takes the selected functions and compiles
the corresponding C source code. The subsequent steps (RTL
synthesis, placement and routing) then create a binary con-
figuration file suitable for programming the FPGA. The C
program can be debugged by the design software using the
so-called 'soft JTAG chain' while the program is running in
the processor core implemented in the FPGA.

In our example the buttons arranged below the TFT panel
allow the user to choose whether or not the C functions syn-
thesised into hardware are used to compute the individual
frames of the 3D cube display (Figure 8).

A test shows that the processor working on its own can man-
age to compute around 2.7 frames per second. Using the
ASP (that is, with the speed-critical functions implemented
in hardware , the system runs around ten times faster, at
approximate y 28 frames per second.

( 080625 - 1 )

NanoBoard

Alongside the Altium Designer development soft-
ware, which provides an environment for circuit
design, the development of embedded software
and the design of FPGA-based systems, Alti-
um also offers a reconfigurable hardware plat-
form called the 'NanoBoard' (http://www.altium.
com/products/thenanoboard).

A selection of plug-in peripheral boards supports a
wide range of I/O and other hardware functions.
Using swappable daughter boards various FPGAs
and processors can be tested in the early stages of
prototype system development.

Figure 7.

Altium Designer's Devices
View, the 'cockpit' for
the build and real-time
verification process.

Figure 8.

Using C-to-Hardware
synthesis can give a factor
of ten increase in speed!

2/2009 - elektor

63

TECHNOLOGY

PC PROGRAMMING

Sharp

PC programs using .NET and C#
Part 1

Veikko Krypczyk (Germany)

Electronics people often need to write short PC programs, for instance to evaluate test and
measurement data. Windows PC users will find the .NET Framework particularly handy for
this task. It works with various languages, eliminates most of the burden of programming
and doesn't cost a penny — not even the development environment. Here's a basic
introduction to the C# language and its many advantages.

Today's electronics enthusiasts increasingly need to be soft-
ware developers as well. An obvious situation is program-
ming microcontrollers. Frequently the need arises for a short
program written from scratch, perhaps for outputting con-
trol data to an interface card or for displaying measure-
ment data on screen. Alternatively, an existing program
may need to be adapted or expanded.

Software development is to a large extent bound up with
the target platform and the operating system. In this series
of articles we shall be looking at the development of pro-
grams running under Microsoft Windows XP and Vista. The
underlying foundation is a runtime library that goes by the
name of .NET Framework (pronounced 'dotnet'), which is
supplied with Vista and is offered gratis as a retrofit for XP.
Anyone using older versions of Windows need not go away
empty-handed, as the support pages of Microsoft may offer
a solution. Finally, it's well worth mentioning that an Open
Source version of the .NET Framework has appeared in the
meantime and this so-called 'Mono' framework [1] even
runs on Linux computers!

Classes as programming modules

The introduction of the .NET Framework brought a signifi-
cant change to software development for Windows. Greatly
simplified, we're talking about a powerful library of Base
Classes, offering a wide variety of 'oven ready' approaches
for setting problems and getting answers, saving program-
mers a mountain of work. In the process the .NET Frame-
work has averted a lot of long-winded discussion about the
'best' programming language. The choice of language has
become a secondary consideration, as the Base Classes
provide this themselves, and a common type system exists.
Regardless of the language of the source code, a program

is always translated into the same 'intermediate' code,
which is subsequently executed by the .NET run-time envi-
ronment (more correctly, it is recompiled when the program
starts). The use of this 'Common Intermediate Language'
brings with it security advantages and also enables pro-
gramming that is substantially independent of the operating
system. Porting across involves no more than changing the
(lean) runtime environment.

Variants of C from Microsoft

For the.NET Framework there are languages like Visual
Basic for .NET (from Microsoft) or Delphi for .NET (from
Embarcadero Technologies). An overview of the languages
compatible with the .NET Framework can be found for
example at [2].

These two languages mentioned have been merely adapted
for .NET (VB.NET is certainly not completely compatible
with classic VB, although VB6 source code is fairly simple
to adapt). On the other hand C# (pronounced 'C Sharp')
has been developed by Microsoft from scratch specifically
for the task. The complexity of the C and C++ languages,
with their heavy learning curves, finds no place in C#. For
example, pointer arithmetic (relished by few programmers)
has fallen by the wayside. On the other hand, plenty of
effective and user-friendly concepts from other languages
have been incorporated. And another thing in favour of
this variant of C: there exists an extremely compact .NET
Framework for programming microcontrollers, which even
includes a gratis compiler, in fact for C# [3]!

Understandably this two-part mini series cannot be a com-
plete training course on C# but it may well encourage read-
ers like you to get deeper involved with C#. In this first

64

elektor - 2/2009

Some language concepts of G#

Some of the language elements in C# may be familiar from
other programming languages. All syntax questions can be
resolved using the online help pages at [6].

1 . C# treats upper and lower case letters as different, so the
variable 'total' would be handled differently from the vari-
able 'Total'.

2. Single-line comments are started with //, whereas /*...*/
indicates a comment with several lines of text.

3. Important fundamental data types include: byte, int, float,
double, decimal and string.

4. Variables are declared and initialised by prefixing the data
type:

int Total = 5;

string text ="one character string";

5. Basic operators: +, -, *, /

6. The flowing loops exist: for, while, do and foreach. The last-
named iterates for example Objects assembled in listings
(Collections).

7. Selection instructions are: If, else if, else and switch (...)
case.

8. User-defined data types are declared with the keyword
'struct' (user-defined Classes are introduced with Class):
struct Dataset

{

int Alter;
string Name;

}

part we shall develop a small program with the help of the
Visual Studio development environment, which is free to
download. The second part will take us into object orienta-
tion, the foundation of the.NET Framework and 'made with
C#'. Our practical example from the realm of 2-D graphics
will create an application that should be particularly inter-
esting for electronically-minded people.

Debug I Debugging using the green arrowhead on the
symbol tool bar, see Figure 2). Initially the application
contains just an empty window. Nevertheless the neces-
sary functions of a Windows application are already imple-
mented. So you can for instance shift the window around
the screen, minimise or close the application using the sys-
tem menu.

And off we go!

To get developing, the first thing we need to do is make sure
our computer is set up with everything we need. The only
new item absolutely necessary is a C# compiler for trans-
lating the source code and as a bare minimum an editor
can suffice for compiling the code. Far more practical and
convenient, however, is a dedicated tool for the job, the
Integrated Development Environment or IDE. Here you have
basically two options. The first is a Microsoft offering, its
so-called Express editions of Microsoft Visual Studio, avail-
able as a free download. The functional capability is some-
what restricted compared with the professional versions but
this should not cause any problems on small to medium-
size projects. Express editions are available for each of the
languages C#, Visual Basic for .NET and C++. For Web
development there is a further tool available, Visual Web
Developer Express. For our mini-series Visual C# Express in
the 2008 Version is the correct choice. Information on the
products mention and downloading details are all at [4].

A free Open Source alternative is Sharp Develop [5], which
also enables programming in C# (among other languages).
This option requires you to have the .NET-Framework SDK
(Software Development Kit) already installed.

Your first program

To create our first application, we need to boot up Microsoft
Visual C# 2008 Express Edition. You will be greeted by this
development environment's start page, which among other
things enables you to open the last project you worked on.
To start a new project click on File I New I Project.... Out
of the options offered select 'Windows Forms Application'
(Figure 1). Your second task is to select a name for the
project. After confirming with OK the IDE produces a frame
code for this application. The result is displayed immedi-
ately on your screen. You can confirm that this is already a
complete application by making a first test run (start menu

Figure 1.

Constructing a Windows
application (frame code)
simply using the wizard.

Forml.ts [OeskjTiJ

r 1
O
CT
O

X

Figure 2.

Starting an application
in the development
environment's Debug
mode.

2/2009 - elektor

65

TECHNOLOGY

PC PROGRAMMING

Figure 3.
Editing an Object's
characteristics in the
Properties window
is a breeze.

• three labels for the legend (descriptions);

• a button to start the calculation.

With the help of the IDE the formation proceeds apace. Call
up the Toolbox (Appearance I Toolbox in the active form.
Now you can select the elements of the panel using the
mouse and place them on the form. There are guide lines to
help you get everything neat and tidy. Once an element has
been installed on the panel we can edit its characteristics
(Properties). This is done with ease using the Properties win-
dow (press the F4 function key for the Object highlighted).
For example, we have assigned the tag 'textboxN umber' to
the first text field's Property 'Name' (Figure 3).

Figure 4.

The first (extremely simple)
application in action.

L

Ending the application reverts to the development environ-
ment, enabling us to expand the template with the first ideas
of our own. So here's a simple example of how this can
be done, gathering and adding together two figures to
produce an output of the result in a text field. We'll start
with creating the top-level information panel for the user.
We require:

• three text fields for the figures and the result;

Source code for the Button

Ftaving designed the user panel it's time to start producing
some code. The calculation needs to be performed when
the corresponding button is clicked. A mouse click on this
button while the program is running produces a so-called
click event. It's the programmer's task to assign appropri-
ate source code to events of this kind so that the code is
then executed (in this case the addition of two numbers).
To assist programmers the IDE produces the frame code
automatically for the click event of a button, if the button is
double-clicked during the development process. Inside the
frame code we now enter:

float numberll = float.Parse(textBoxNumberl .Text);
float number2 = float. Parse(textBoxNumberl2. Text);
float result = numberll + number2;
textBoxResult.Text = result.ToString ();

First the values of the text box (the type being a character
string) are read out and converted into a number. This takes
care of the Method 'float.Parse'. The addition follows next
and finally the result is passed to the text box named 'text-
BoxResult'. Described more accurately, the text box then
displays the value of the result if the value 'result.ToString' is

Activating interfaces

Electronics people may be wondering how they would control
the computer interfaces their hardware is connected to. Par-
ticularly when a fundamental security principle of .NET (for
desktop computers) states that interfaces cannot be activated
directly by the application program.

C#- or VB.NET applications tend to access the corresponding
Windows driver and in most cases this must first be installed.
With off-the-shelf hardware (including most test gear) this is
generally supplied by the manufacturer.

Programming a driver tends to be hardware-specific and un-
der Windows C + + would be a good choice. For reasons of
space we cannot go deeper into driver programming here.
However, here is a small example of how an existing driver is
called up. In this case it's for a parallel port interface, which is
used in many hook-ups on account of its simplicity.

This sample application is by Levent Saltuklaroglu [8] and uses
the well-known driver inpout32.dll, which can be downloaded
for free [9]:

using System;

using System. Runtime. InteropServices;

public class PortAccess

{

[Dlllmport ("inpout32.dll", EntryPoint= "Out32")]
public static extern void Output(/nf address, int value);

}

The Using directive incorporates important Base Class librar-
ies. Access to the driver is encapsulated in a user-defined
Class named PortAccess. This is where the 'Output' Method
is defined with two parameters (parallel port address - for
example decimal 888 for LPT1 together with the value to be
output). The parameters within the Class are passed to the
Out32routine of inpout32.dll, which finally places a byte at
the parallel port.

After implementing the Class it is easy to export data from the
C# application program, for example using:

PortAccess.Output(888, 255);

Using the serial interface is even easier. Versions 2.0 onwards
of .NET Framework provide the Class System. lo. Ports. Serial-
port, which allows you to address the serial interface, without
even involving a .dll file. Information on this is in the online
documentation [10].

66

elektor - 2/2009

delivered to its Property 'Text'. As you can see, we can alter
the information panel's Properties both during the develop-
ment process (as we have just seen) and from inside the
program. These are indicated in the code following the
name of the information panel with a dot and the name of
the Property, for example, (textBoxResult.Text).

So that the result of the test box (a floating-point number of
the type Float) can be displayed, it must first be converted
into a character string. To do this in the code we need to
indicate the name of the Variable Result, followed by a
dot and the name of the Method (ToString). To understand
how to set the Properties and application of Methods of
the Object 'textBoxResult' of the Class 'Textb' you do need
some prior experience of object-oriented programming.
Sorry, but it has to be like this, since object orientation is at
the very heart of C# (and VB.NET). It's not only the top-level
elements but all the variables that are objects!

The next steps...

After starting an application, the result should look like Fig-
ure 4. If you feel like it, you could carry on programming
such as a pocket calculator handling all the main types
of calculation, which shouldn't be too difficult to turn into
reality.

If you are now taking a shine to C#, you should find plenty
of technical literature in any decent bookshop, both at
'Dummies' level for newcomers and more advanced tomes
for seasoned users. There are significantly more books
on C# than for VB.NET (and classic VB, which VB.NET is
increasingly supplanting). In developer periodicals and on
the Internet, problem solutions in the .NET world are being
written almost exclusively in C#.

As already mentioned, the .NET programmer doesn't have
to do all the work himself but can serve him/herself in a
gigantic .NET Class library (all Objects are arranged in
'Classes' that determine which type of Properties and Meth-
ods an Object has). There is also online documentation
from Microsoft that you can use as a reference work at [6].
Assistance is also available in an offline version as part of
Visual Studio (warning: this is extremely comprehensive!).
For each Class, the help file shows all the elements (Meth-
ods, Properties, Events) (Figure 5). Frequently, a sample
application is given as well, structured according to the con-
stituent programming language. Since there are frequently
several ways of calling the Methods of a Class (so-called
Overloads), a glance at the documentation is often abso-
lutely necessary. So, for example, the 'Show' Method of the
Class 'MessageBox' for displaying an information window)
includes a total of 20 (!) call conventions. These vary in the
parameters by which the calls must be passed.

When you are inputting source code the 'IntelliSense' fea-
ture of the development environment (Figure 6) can also
be extremely helpful. As an example, when you are enter-
ing the name of an Object in a specific Class, all the Prop-
erties and Methods are indicated interactively.

In the second part of this series we will make a quick inspec-
tion into object-oriented programming. A section on 2-D
vector graphic programming provides a practical task.
Source code for the examples can be found on the Elektor
project page [7].

( 080668 - 1 )

, 3 K

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a comprehensive reference
work for the Base Classes.

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t l tun b uf 11 = 1 log L _ Carve I i

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Figure 6.

Interactive support for
programmers with the help
of 'IntelliSense'.

Internet Links and Further Reading

[1 ] www.mono-project.com/Main_Page

[2] http://dotnetframework.de/dotnet/produkte/sprachen.aspx

(all onward links are in English)

[3] www.elektor.com/080450

[4] http://www.microsoft.com/express/product/default.aspx

[5] www.icsharpcode.net/OpenSource/SD

[6] http://msdn.microsoft.com/en-gb/vcsharp/default.aspx

[7] www.elektor.com/080668

[8] www.codeproject.com/KB/cs/csppleds.aspx

[9] http://logix4u.net/

[10] http://msdn.microsoft.com/en-gb/library/system.io.ports.
serialport.aspx

See also Wikipedia (http://en. wikipedia. org/wiki/C_Sharp_(pro-
grammingjanguage)) for other background on C#. Also the
tutorial on programming in C# at http://www.java2s.com/Tuto-
rial/CSharp/Cata logCSharp.htm

About the author

Veikko Krypczyk studied Business Information Technology. An
enthusiastic programmer, he has been involved with C# and
the .NET Framework for several years. His special interest
is in application programming and the development of 2-D
graphics applications (you can follow up his current project at
http://easy-grafiker.de/cms/index.php and select the English
menu). As an electronics hobbyist he cannot resist picking
up his soldering iron now and again to try out interesting
projects. You can e-mail Veikko at veikko2000@yahoo.de.

2/2009 - elektor

67

INFO & MARKET

EMC GUIDELINES

EMC DIRECTIVE

From 1 January 1996, home-made equip-
ment must take into account emc Directive
89/336/eec (emc = ElectroMagnetic
Compatibility). Basically, the directive
states that no equipment may cause, or
be susceptible to, external interference.
Here, interference means many phenom-
ena, such as electromagnetic fields, static
discharge, mains pollution in the widest
sense of the word.

Legislation

Home-made equipment may be taken into
use only when it is certain that it complies
with the directive. In the United Kingdom, the
dti (Department of Trade and Industry) will,
in general, only take action against offend-
ers when a complaint has been made. If the
equipment appears not to comply with the
directive, the constructor may be sued for
damages.

ce label

Home construc-
tors need not affix
a ce label to their
equipment.

965001 - 1-52

Elektor Electronics
and the Directive

The publishers of Elektor Electronics intend
that designs published in the magazine
comply with the directive. Where neces-
sary, additional guidelines will be given
in the article. However, the publishers are
neither obliged to do so, nor can they be
held liable for any consequences if the con-
structed design does not comply with the
directive. This column gives a number of
measures that can be taken to ensure that
EE-designed equipment complies with the
directive. However, these are needed only in
some designs. Other measures, particularly
in case of audio equipment, are not new and
have been applied for some time.

Why emc?

The important long-term benefit for the user
is that all electrical and electronic equipment
in a domestic, business and industrial envi-
ronment can work harmoniously together.

Radiation

The best known form of emc is radiation that
is emitted spuriously by an apparatus, either
through its case or its cabling. Apart from
limiting such radiation, the directive also
requires that the apparatus does not impart
spurious energy to the mains — not even in
the low-frequency range.

Ferrite through-filters as illustrated are used
for feeding cables through a panel.

Immunity

The requirements regarding immunity
of an equipment to emc are new. Within
certain limits of ambient interference, the
apparatus must be able to continue work-
ing faultlessly. The requirements are fairly
extensive and extend to a wide range of
possible sources of interference.

Computers

Computers form the prime group for appli-
cation of the directive. They, and micropro-
cessors, are notorious sources of interfering
radiation. Moreover, owing to the way in
which their internal instructions are carried
out sequentially, they are also very sensitive
to interference. The notorious crash is but
one manifestation of this.

Enclosures

A home-made computer system can comply
with the emc directive only if it is housed in a
metal enclosure. A minimum requirement is
that the underside and rear of the enclosure
is an l-shaped frame. All cabling must con-
verge on this area or be filtered. If there are
connectors on the front panel, a u-shaped
metal frame should be used.

Even better results are obtained if a 20
mm wide, 1 mm thick copper strip is fixed
along the whole width of the rear wall with
screws at 50 mm intervals. The strip should
have solder tags at regular distances for
use as earthing points.

A closed case is, of course, better
than an l-shaped or u-shaped frame. It is
important that all its seams are immune to
radiation ingress.

Power supplies

In any mains power supply, account should
be taken of incoming and outgoing interfer-
ence. It is good practice to use a standard
mains filter whose metal case is in direct
contact electrical contact with the enclosure
or metal frame. Such a filter is not easily
built at home. It is advisable to buy one with
integral mains entry, fuse holder and on/off
switch. This also benefits electrical safety in
general. Make sure that the primary of the fil-
ter is terminated into its characteristic imped-
ance — normally a series network of a 50 Q, 1
W resistor and a 1 0 nF, 250 V capacitor.

Mains transformers must be provided
with rc-networks at the primary and second-
ary side. Bridge rectifiers must be filtered
by rc-networks. The peak charging current
into the reservoir capacitor must be limited
by the internal resistance of the transformer
or by additional series resistors. It is advis-
able to use a 250 V, 2 W varistor between the
live and neutral mains lines. At the second-
ary side, it is sometimes necessary to use
a transient suppressor, preferably following
the reservoir capacitor.

If the supply is used with digital systems,
a common-mode inductor in the secondary
a.c. lines may prove beneficial for limiting
radiation. For audio applications, an earth
screen between primary and secondary is
advisable. This screen must be linked via a
short wire with the earthing strip.

The supply must be able to cope with
a mains failure lasting four periods and
with mains supply variations of +10% and
- 20 %.

Peripheral equipment and earthing
All cables to and from peripheral appara-
tus, such as measurement sensors, control
relays, must be fed through the metal wall
of the enclosure or frame. The earth lines of
such cables must be connected directly to
the earthing strip at the inside of the enclo-
sure or frame via a wire not longer than 50
mm. When plugs are used, the cable earth,
if any, must be connected to the earth pin or
the metal surround of the connector.

Basically, all non-screened signal lines
must be provided with a filter consisting of
not less than a 30 mm ferrite bead around
the cable or bunch of wires. This bead may
be outside the enclosure (for instance,
around the pc-to-monitor cable).

Leads that may have a resistance
of 150Q must be provided with a 150Q
series resistor at the inside of the connec-
tor shell. If technically feasible, there should
also be a capacitor from this point to earth.
Commercial feed-through t-filters or 71 -filters
may, of course, be used. In all other cases,
screened cable must be used for connec-
tions within the enclosure. Symmetrical lines
must consist of twisted screened cable and
be earthed at both ends.

The earth plane of printed-circuit boards
must be linked as firmly as feasible with the
earthing strip, for instance, via a flexible flat
metal strip or flatcable.

Electrostatic discharge (esd)

All parts of an equipment that can be touched
from outside must preferably be made from
insulating, antistatic material. All parts that
can be touched and enter the enclosure,
such as potentiometer and switch spindles,
must be earthed securely. All inputs and
outputs whose wires or connector pins can
be touched must be provided with an earth
shield, for instance, an earthed metal sur-
round via which any electrostatic discharge
are diverted. This is most conveniently done
by the use of connectors with sunken pins,
such as found in sub-d connectors, and a
metal case.

Audio equipment

Immunity to radiation is the most impor-
tant requirement of audio equipment. It is
advisable to use screened cables through-
out. This is not always possible in case of
loudspeaker cables and these must, there-
fore, be filtered. For this purpose, there are
special high-current t-filters or 71 -filters that
do not affect bass reproduction. Such a fil-
ter must be fitted in each loudspeaker lead
and mounted in the wall of a metal screen-
ing box placed around the loudspeaker
connections.

Low-frequency magnetic fields

Screened cables in the enclosure do not
provide screening against the low-frequen-
cy (< a few kHz) radiation of the mains
transformer. Therefore, these cables must
run as close as possible to the walls of the
enclosure. Moreover, their braid should be
linked at one end to the earthing strip. In
extreme cases, the power supply should
befitted in a self-contained steel enclosure.
Special transformers with a shading ring
that reduce the stray field can lower the
hum even further.

High-frequency fields

High-frequency fields must not be allowed
to penetrate the metal enclosure. All exter-
nal audio cables must be screened and the
screening must be terminated outside the
enclosure. This again necessitates the use
of all-metal connectors. All cable braids
must be linked to the earthing strip inside
the enclosure.

Owing to the skin effect, it is important
to choose an enclosure with a wall thickness
>2 mm to ensure that internal and external
fields are kept separate. Any holes must be
either small (<20 mm) or be covered with a
metal mesh.

Heat sinks

Heat sinks should preferably be inside the
enclosure and be earthed at several points.
Non-earthed heat sinks in switch-mode
power supplies often create problems. If
possible, place an earth screen between

Standard mains filters built into a mains entry
together with an on/off switch. The metal shell
must be in firm contact with the enclosure.

transistor and heat sink. Ventilation holes
must be covered with metal mesh unless
they are smaller than 20 mm. Ventilators
should be fitted inside the case.

Cables

Cables often function as transmit/receive
aerials. This applies equally well to screened
cables. The braid of a coaxial cable must be
terminated into a suitable connector such
that it makes contact along the whole cir-
cumference. The braid may be used as the
return path to obtain r.f. magnetic screen-
ing. For a.f. magnetic screening it is better
to use twisted-pair screened cables. In a rib-
bon (flat) cable, each signal wire should be
flanked, if at all possible, by earthed wires.
The cable should be screened along one
surface or, preferably, all around. Cables
that carry signals >10 kHz that are not fil-
tered in the enclosure, must be provided
with a ferrite bead functioning as a com-
mon-mode inductance.

Printed-circuit boards

Elektor Electronics printed -circuit boards
are provided with coppered fixing holes that
are connected to the earth of the circuit.
This arrangement, in conjunction with metal
spacers, ensures good contact between
the board and the circuit earth. Where this
is important, boards have a special earth
plane that can be connected, where fea-
sible, to the earthing strip via a flatcable.
These boards normally have no other earth-
ing points and their fixing holes are, there-
fore, not coppered.

(960006)

T-filters and k- filters ensure that interference
cannot em te from, or enter, the equipment via
signal lines. They are available in various cur-
rent ratings and for various frequency ranges.

68

elektor - 2/2009

MINI PROJECT

PRO

Ton Giesberts (Elektor Labs), from an i

dea by Karl Odenthal (G

erman

These days tiny FM radios are often integrated in many portable devices such as mobile phones and
MP3 players. But why not make a simple receiver ourselves? There are currently several nice ICs
available that contain a (nearly) complete receiver.

For this project we cast our eye on the
TDA7021T from ST-NXP Wireless (for-
merly a part of Philips Semiconduc-
tors), an IC that is well over 20 years
old, but is still readily available. Good
designs, apparently, have a much
longer life than many modern ICs of
which a new version seems to appear
every few months.

This project is a complete receiver cir-
cuit with excellent receive and sound
qualities. The only disadvantage of
using this IC, from the DIY enthusiast’s
perspective, is the fact that it is only
available in a 16-pin SMD package.
To make the construction easier we
designed a small printed circuit board
for this project. And to ensure that
the completed circuit would be quite

compact, the remainder of the circuit
is also built using SMD parts, most of
them 0805 size. The dimensions of this
tiny PCB are only 3.2 x 2.7 cm! The
circuit contains no difficult coils, only
the VCO requires an air-cored inductor
with only 4 turns.

Inner workings

Figure 1 shows a block diagram of
the internals of the TDA7021T. This is
a (nearly) complete integrated receiver
circuit which has been specifically
designed for portable radios and the
like, requiring only a minimum of exter-
nal components. As a result the final
dimensions of the radio can be kept
very small.

The IC uses a frequency-locked-loop
(FLL) system with an intermediate
frequency of 76 kHz. The selectivity
is obtained with the aid of active RC
filters. The only ‘calibration’ adjust-
ment in the circuit is the resonance
frequency of the oscillator (for the
tuning).

The RF signal enters at pin 12 and is
amplified first, after which it is trans-
formed down by the mixer and passes
through two IF filters. It is subse-
quently limited in amplitude. The IF
limiter also supplies a signal for the
optional signal strength indicator (via
pin 9). The limited FM signal then goes
to the demodulator and the correlator
which decides whether the signal is
tuned in properly. The demodulated

1/2009 - elektor

69

MINI PROJECT

flfM

MUX Ail KF •fKji adVNLh

Figure 1. The internal design of the TDA7021T.

are entirely available. This is also the
reason that it is not recommended to
connect the audio output directly to
the line input of an audio system.

Circuit

The complete circuit for the FM receiver
is shown in Figure 2. The design is vir-
tually identical to the test circuit shown
in the datasheet for the IC, because
this is difficult to improve even a little
without adding a lot of additional elec-
tronics. Now we only need a few resis-
tors and capacitors plus a coil.

In Figure 3 you can see the little PCB
that we designed for this receiver. As
mentioned earlier, SMD parts are used
everywhere to keep the dimensions
as small as possible. Soldering these
small parts requires a bit of practice
however. We have already explained
how to deal with SMD components
on several occasions in earlier issues
of Elektor. For example, have a look at
the articles ‘SMDs? Don’t panic’ in the
January and February 2003 issues.

signal now passes through a loop-filter
and a mute controller and then finally
arrives at the audio output amplifier.
The output of the loop filter also gen-
erates a control signal for the oscillator
(VCO), which together with the exter-
nal resonance network provides the
tuning function.

For mono audio, the output amplifier
delivers enough power (via a resistor)
for a set of small earphones. You can,
however, also connect a decoder to this
output to generate a stereo signal. The
output signal on pin 14 is not limited
in frequency, that is, both the 19-kHz
pilot signal as well as the L-R signal

Practical matters

Moving on to a few practical instruc-
tions for the construction:

The inductor for the VCO is an air-cored
coil with 4 turns. It is best if you use
silver-plated wire for this. The easiest
way is to wind 4 turns on a 4-mm drill
and then stretch the coil slightly until
the ends of the coil line up exactly with
their respective mounting holes in the
PCB. Place the coil a few millimetres
above the board, so that you can easily
adjust it slightly later on (by stretching
or compressing) so that the tuning cir-
cuit correctly covers the entire VHF FM
broadcast band from 88 to 108 MHz.
Tuning is done with trimmer capacitor
C5. This does however require a small
screwdriver and a little patience, but
you generally tend to listen to one and
the same radio station anyway.

If you want, you can optionally (con-
nected with wires as short is possi-
ble) replace the SMD trimmer capac-
itor with a proper tuning capacitor.
Make sure you obtain the correct tun-
ing range. This should be possible by
changing the value of C4 and perhaps
adding a series capacitor for C5.

All connections to the board are made
with 2- way pin headers, to which you
can connect your own choice of con-

K1

V

R3

L2

l

BT1

3V

luH

C11

In

R2

T

C14
47 u
10V

CD

C16

C15

C13

lOOn

3n3

220p

in

CO

CM

C12

R1

CIO

rlli

n

1n5

O

a>

IC1

TDA7021T

C3

lOn

CM

Cl

lOn

C2

lOOn

C6

lOOn

m

C8

820p

C7

1n5

C4

33p'

C5

25p

LI

36nH

080556-11

Figure 2. The complete receiver consists only of the IC and a few passive components.

70

elektor - 1/2009

nectors. For the earphones you could use a stereo 3.5-mm
jack socket, for example (with the L and R terminals con-
nected in parallel). The output of the IC supplies
sufficient power to drive several 32-Q earphones
directly. A 390-Q resistor is connected in series
with the output to prevent a short circuit of the
output and prevent potential problems with
longer screened cables. Because of this,
resistor the output capacitor C14 can be
kept quite small.

There is also a connection (K2) for
a simple signal strength meter.

Via resistor R1 and decoupling
capacitor C9, pin 9 supplies
a DC voltage which is a
measure of the received sig-
nal strength. At 170 /JA the out-
put current is too small to drive an
LED, but you could connect an ‘old
fashioned’ moving coil meter.

For the antenna you can use a simple wire
antenna of about 75 cm long, which is soldered
directly to the PCB.

Considering that the current consumption is only 6.3 mA,
the circuit is eminently suitable to be powered from bat-
teries. We decided to use two penlight (AA) cells here, but

even using a lithium cell for the power supply will give
nearly 20 hours of running time. It is also possible to use a
mains adaptor. But note that the power supply voltage for
the IC has to be between 1.8 and 6 V (most defi-
nitely not higher!).

Finally

This receiver is, to be sure, a
mono implementation, but at
the output (as already men-
tioned) the entire multi-
plexed signal (up to 53 kHz)
is available. By using a
PLL stereo decoder, such
as the TDA7040T, a stereo
signal can be generated in a
straightforward way from the
output signal of the TDA7021T.
We will describe this circuit in a
future mini project.

( 080556 - 1 )

Advertisement

Figure 3. The receiver can be built on this tiny circuit board.

COMPONENT

LIST

Resistors (SMD 0805)

R1 = 8kD2
R2 = 1 OkD
R3 = 390D

Capacitors (SMD 0805)

C1,C3 = lOnF
C2,C6,C9,C16 = lOOnF
C4 = 33pF

C5 = 25pF trimmer (Murata
type TZB4Z250AB1 0R00)
C7,C1 0 = 1 nF5
C8 = 820pF
Cl 1 = InF
Cl 2 = 68pF
Cl 3 = 220pF
Cl 4 = 47jL/F 10V (Nichi-

con UWX1 A470MCL1 GB
5.5mmL chip type)

Cl 5 = 3nF3

Inductors

LI = 36nH (4 turns 0.5mm
silver-plated wire, inside di-
ameter 4mm; length 7mm)

L2 = 1 yuH, SMD case 0805
(fres > 300 MHz)

Semiconductors

IC1 = TDA7021T (SMD in
SOI 6 case)

Miscellaneous

K1 ,K2 = 2-way pinheader

BT1 = 2-way pinheader +
battery holder for 2-4 AA
batteries

Are 5,000 components too many for you?
Just order the 580 your production run actually needs

*iiifl 4 *ii 4 ii«vi«ti|*ivil 91 llt

i

RS Production Packaging
rswww.com/electronics 08457 201201

2/2009 - elektor

71

MODDING & TWEAKING

Opacity Measuremen

Jose Luis Basterra (Spain)

Opacity is a measure of impenetrability of objects or substances to radiation. Here, we are concerned
with light, specifically within the spectrum visible to the human eye. In this month's instalment of the
Modding & Tweaking series, we examine how the PC can do paper opacity measurements for us — all
experimentally and on a budget of course!

The (simplified) relative sensitivity
curve of the human eye shown in Fig-
ure 1 tells us that he eye is more sensi-
tive to green light than to yellow.

In order to be able to measure the vis-
ual opacity we ideally need a photode-
tector whose spectral sensitivity is sim-
ilar to that of the human eye. A com-
monly available photodetector like the
BPW34 has good sensitivity within a
part of the spectrum perceived human
eye, although its response curve is dis-
similar, see Figure 2.

The response also depends on the type
of light with which the object is illumi-
nated. If we use a yellow LED we can
look forward to an emission distribu-
tion roughly as in Figure 3.

The use of a yellow LED as the light
source causes the detector to see the
yellow part of the spectrum only, result-
ing in a better approach of the spectral
response of the human eye. The com-
parison is illustrated by the graphs in
Figure 4 and Figure 5. Possibly, the

Figure 1. Plot human eye sensitivity as a function of
light wavelength and you get a graph like this.

use of mixed yellow and green light is
even better although the results with
yellow only are quite good.

The electronics

The opacity meter is based on fre-
quency variation obtained from an
oscillator that’s controlled by the
intensity of light detected by a BPW34
photodetector. Figure 6 shows the
schematic. The oscillator consists of a
NAND gate from a 4093 package. Its
frequency (10-100 Hz) is determined by
C3 and R3, together with preset PI and
the BPW34 (D3) in the feedback circuit.
The ‘LCO’ (light-controlled oscillator)
output signal is digitized by three more
gates from the same IC. The oscillator
and the LEDs (one yellow, one red) are
powered by a voltage regulator around
a 7809. The red LED is an on/off indi-
cator and helps to position the reader
unit over the paper surface.

The circuit of the PC interface is shown
in Figure 7. The interface with the
computer is by means of the Centron-

Figure 2. The response of the BPW34 within the spectrum
seen by the eye is by no means flat.

ics port and a series of optocouplers;
four in the PC817 chip of which three
are used. The connections between the
circuit and the LPT1 (‘parallel printer’)
port on the computer are as follows:

Circuit terminal

Pin no. on DB25

El

1 (/STR)

E2

2 (DO)

E3

3 (Dl)

GND

25 (GND)

The oscillator output signal enters the
interface at Jl. The circuit charges a
47 ijF tantalum electrolytic capacitor
(Cl) to about 4.5 V, at which level zener
diode D2 starts to pass current, illumi-
nating the LED in optocoupler IC2. This
causes a logic Low at El, signalling to
the program running on the computer
to stop counting. The process com-
prises the following phases.

1. By means of a High level supplied to
input E2, the PC effectively blocks the
arrival of oscillator pulses.

Figure 3. Heavily simplified spectral distribution of
light emitted by a yellow LED.

72

elektor - 2/2009

2. With Cl discharged, output El is
held High i.e. deactivated.

3. Via E2, the software enables the
arrival of oscillator pulses again.

Figure 4. Response obtained from the combination:
BPW34 + yellow LED.

Figure 5. As Figure 4, but for the combination:
BPW34 + human eye.

4. The period it takes for the capacitor
to charge to 4.5 V and pull El Low rep-
resents a time T, which is compared to
a table entry in the program in order to
determine the relative opacity value.

The value so obtained will be a reason-
able approach of the actual opacity in
the majority of cases. The table stored
in the program is calibrated for values
of opacity between 78 and 92%.

Software

This series of articles being free from
rocket science, the very simplest form
of Basic was used for the control pro-
gram. True to the Modding & Tweak-
ing tradition, all readers are invited to
improve the program, come up with
alternatives, perhaps develop code for
Linux, C, 32-bit ARM platforms, what
have you! Here, only the nitty-gritty is
shown to serve as an incentive.

The BASIC program was written to
measure, store and ‘graph’ instanta-
neous and average opacity values of
paper sheets. You can download the
program as file # 080579-11. zip from
the Elektor website.

The address &H378 is the base
address of printer port LPT1 on the

12-15V dc

IC2

- Xo

> o

PI

©

IC1

R1

+9V

-©

R2

C2 ci © Tm Td2

r t I

10n ) __^^red^Jyellow

R3 1M

IC1.A

D3

BPW34

IC1.B IC1.C IC1.D

V 3 ■

5

8

s 10 ,

12

&

&

s 4 ,

&

&

’ 6

’ 9

M3

C3

lOOn

IC1 = 4093

080579- 16

Figure 6. Schematic of the BPW34-controlled oscillator.

PC; &H37A is the control register at
[base + 2]. The first is used to send
commands to the reader interface via
LPT data lines DO and Dl, the second,
for reading the capacitor charge sta-

Figure 7. The PC interface consists mainly of optocouplers
connected to Centronics port pins.

tus using the /STR (inverted strobe)
line (which is bidirectional).

( 080579 - 1 )

Figure 8. Internal view of the opacity reader.

Figure 9. The face of the BPW34 photodetector protrudes from

a small hole.

Figure 10. The PC817 quad optocoupler is by far the largest
part in the PC interface.

2/2009 - elektor

73

DESIGN TIPS

No Varicap? Try a Schottky diode

Martin Ossmann (Germany)

Varactor diodes (Varicaps) along
with many other exotic compo-
nents which are often specified in
HF and RF designs are sometimes
difficult to obtain and in some
cases may even have gone out of
production. Not very encourag-
ing if you had been planning to
build a design that we featured
in an earlier edition of Elektor.
Anyone finding themselves in
this situation may be surprised to
learn that help may be on hand
from an unexpected source...

400

200

a

- 100

o
o

S 60

80

o

CO

a.

(0

O

40

£ 20

o

10

0.1

Tj =

25°

C

0.5 1 5 10

Reverse Voltage, V R [V]

40 60 100

080799 - 12

2

V CTRL R1

O h look \

Any general-purpose silicon di-
ode has capacitive properties
when reverse biased; the deple-
tion region at the PN junction
acts as a dielectric. Increasing
the reverse bias widens the re-
gion, reducing the capacitance.
Power engineers are aware that
high voltage rectifiers can store
high levels of charge at their
depletion region. This property
is not beneficial in rectification
applications but using a little lat-
eral thinking and with the motto
"It's not a bug... it's a feature"
in mind, we can maybe use this
characteristic to substitute a di-
ode for a varactor. The datasheet

of an SB 1 1 00 Schottky power di-
ode indicates that at 4 V reverse
bias the diode has a "total ca-
pacitance" of 1 10 pF, and look-
ing at the curve of this character-
istic it is indeed proportional to
voltage (see Figure 1).

To test the idea a simple LC oscil-
lator was built (Figure 2) around
the crystal oscillator inverter cir-
cuit integrated in an AtMega88
microcontroller. The application
note AN456 Philips/NXP "Using
LC oscillator circuits with Philips
microcontrollers' ' [1] is a useful
reference here. The finished volt-

age-controlled LC oscillator (VCL-
CO) actually works surprisingly
well. The values of effective small
signal capacitance (as measured
on a capacitance meter) are giv-
en in the Table along with the
oscillator output frequency.

The next time you are stumped
for a varicap, instead of pulling
your hair out it would be worth-
while taking a look through your
collection of power diodes, you
may well find something suitable
there.

( 080799 - 1 )

ATmega88

XTAL1

3—i

XTAL2

9

10

Cl

LI

II

II

2|iH

loop

D1

C2

C3

SB1100

22p

22p

080799-11

Internet Link

[1] Philips/NXP Application note
AN456:

www.nxp.com/acrobat_down-

load/applicationnotes/AN456.pdf

Table

V ctr , [V]

Cef, [pF]

F [MHz]

0

125

19.49

1

82

19.70

2

64

20.00

3

54

20.19

4

48

20.34

5

44

20.46

Three-from-four (an control

Rainer Reusch (Germany)

Most PC-motherboards have mul-
tiple connectors for plugging in
the cooling fans. These are in-
creasingly frequently the four-
way connectors. These connec-
tors are mechanically and elec-
trically compatible with the more
common three-way connectors,
which carry the power supply
and tacho signal. On the fourth
connection the motherboard sup-
plies a pulsewidth modulated TTL
signal, which is used to control
the speed of the fan. A separate
potentiometer or a temperature
dependent speed controller to re-
duce the noise of the fan is now
really history. But the availability
of fans with a four-way plug is
still rather limited and these fans
are generally also more expen-
sive. With the small, additional
circuit that is proposed here, it

nevertheless becomes possible
to use these cheap and ubiqui-
tous fans with their three-way
connectors.

The transistor T1 , the Schottky di-

ode, the inductor and the capaci-
tor C2 are, just like the 'old-fash-
ioned' speed control circuit, con-
nected in series with the fan. A
reasonably clean power supply

voltage for the three-wire fan is
generated from this PWM signal
— and with good efficiency, we
may add. The tacho signal gen-
erated by the fan is routed direct-
ly back to the motherboard.
Building the circuit is not difficult.
The capacitors must have a volt-
age rating of at least 16 V and
the inductor has to be able to
handle a minimum of 200 mA.
Obtaining the right four-way plug
with the necessary crimp contacts
could be a bit of a problem how-
ever. As an alternative you could
use the sockets that are designed
to mate with the common pin-
headers (2.54 mm pitch). If you
decide to use these you will have
to be careful and make sure you
do not plug the connector in the
wrong way around!

( 080377 - 1 )

74

elektor - 2/2009

STU-UK-1

iscount!

Software buijdt

Secure a head start in electronics
with a Student Subscription!*

*Only available in UK. Ask for the conditions.

[ Advantages to subscribers

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www.elektor.com/subs • Tel. +44 20 8261 4509

INFOTAINMENT

PUZZLE

MaYaHAkM Pu«lewithan
I ivAOVJvixLI electronics touch

This February edition of Hexadoku is again intended to try your patience and perseverance in solving a
puzzle. Fortunately, looking at the vast number of correct solutions we get every month, lots of Elektor
readers not only have a great time with Hexadoku, but also care to enter a prize draw for an E-blocks
Starter Kit Professional and three Elektor Shop vouchers.

The instructions for this puzzle are straightforward.

In the diagram composed of 1 6 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 in each column and in
each of the 4x4 boxes (marked by the thicker black lines). A

SOLVE HEXADOKU AND WIN!

Correct solutions received from the entire Elektor readership
automatically enter a prize draw for an

E-blocks
Starter Kit

Professional

worth £300

and three

Elektor SHOP
Vouchers worth
£40.00 each.

We believe these prizes
should encourage

all our readers to participate!

The competition is not open to employees of Elektor International Media,
its business partners and/or associated publishing houses.

6

F

9

7

5

B

0

5

E

0

1

8

3

6

2

4

9

D

8

F

D

5

A

2

B

7

2

5

4

A

D

0

8

C

6

B

1

3

F

C

6

2

B

1

F

3

E

8

9

7

3

F

E

C

5

A

2

1

4

6

F

E

1

A

8

D

B

7

2

6

B

C

F

D

1

3

1

5

F

6

C

8

4

4

0

3

9

8

6

F

7

D

2

E

8

9

B

8

5

2

F

C

B

9

7

A

D

C

5

1

F

B

2

1

9

A

E

3

6

2

5

A

7

B

D

E

(c) PZZL.com

number of clues are given in the puzzle and these determine the
start situation.

All correct entries received for each month's puzzle go into a
draw for a main prize and three lesser prizes. All you need to
do is send us the numbers in the grey boxes. The puzzle is also
available as a free download from the Elektor website

PARTICIPATE!

Please send your solution (the numbers in the grey boxes) by email to:

hexadoku@elektor.com - Subject: hexadoku 02-2009 (please copy exactly).
Note: new email address as of this month!

Include with your solution: full name and street address.

Alternatively, by fax or post to: Elektor Hexadoku

Regus Brentford - 1 000 Great West Road - Brentford TW8 9HH

United Kingdom - Fax (+44) 208 2614447

The closing date is 1 March 2009.

PRIZE WINNERS

The solution of the December 2008 Hexadoku is: E5071.

The E-blocks Starter Kit Professional goes to:

Nicole Stahlschmidt (Germany).

An Elektor SHOP voucher worth £40.00 goes to:

Pau Sastre (ES), Guido Claes (B) and Helmut Balcke (F).

Congratulations everybody!

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76

elektor - 2/2009

RETRONICS

INFOTAINMENT

Elektor Digisplay (1976-77)

Dirk Dral (The

Netherlands)

While cleaning out the
instrument cabinet in our
company shop, I came
across a Digisplay unit
that I built and used many
years ago with considerable
pleasure.

At that time, I regularly put
together circuits with gates,
timers, counters and read-
outs, and it was a godsend
to be able to tap 14 to 16
signals at once with an 1C
test clip and see the states
of all these signals at the
same time on a screen.

In May 1976 Elektor pub-
lished a circuit for connec-
tion to an oscilloscope that
allowed the values of 16
signals to be read on the
screen in the form of 1 's
and 0's. There was apparently
a lot of demand for this circuit,
since Elektor decided to develop
and sell a PCB design for it (#
EPS 9376) in 1977.

At that time I was planning to
build a new oscilloscope to
replace my vintage 1965 kit
'scope, and I had already bought
a DG 732 CRT for this purpose.
Shortly afterward, Hameg came
out with an attractively priced
oscilloscope kit and I bought
it right away, which meant I
had a DG732 left over. It
thus seemed like a good
idea to build a Digisplay as
a self-contained unit includ-
ing the 'scope tube and fit-
ted with only one control:
an on/off switch. No need
to make things complicated
when I already had some-
thing to sink my teeth into!

The PCB was not espe-
cially difficult, since the cir-
cuit basically consisted of
a 74150 TTL 1C that con-
verted the 16 input signals
into a BCD code. A pair of
gates did duty as an internal
clock generator, and a few
counters, decoders and D/A
converters generated the X
and Y deflection signals for
the 'scope tube.

For the power supply of my

simple oscilloscope, I used a
design published in the Decem-
ber 1 971 issue of Elektuur (Dutch
edition). I designed a circuit
board for this circuit with suitable
trimpots for the adjustments.

The X and Y amplifiers were a
different story, and after a bit of
searching I decided to copy the
amplifiers in the Hameg kit. I
made PCB designs for both cir-
cuits using grid paper overlaid

i i o

i O f

0 * i

1 t (

i

with tracing paper. The actual
artwork was created using a few
drawing pens. After this, every-
thing was exposed on photo-
sensitive PCB stock, etched and
rinsed. Then it was just a matter
of drilling the holes and fitting
the components, and the boards
were ready for use.

The power transformer that I
used had only two secondary

s r *-■.

j fLJfT W I

■tr--.;, .*

i-.

j- jU, V/;-.

• . ■■■

windings: a 250-V wind-
ing that provided 350 VDC
after rectification, and a
6.3-V winding for the fila-
ment current of the 'scope
tube and the power supply
for the main circuit board.
During this process, I also
managed to find a suitable
enclosure: a Philips SQ4
case intended for audio
equipment, which I had left
over from some time earlier,
was the right size to hold the
tube, the power supply, and
the circuit boards. I fitted a
22-way chassis-mount con-
nector on the front panel for
the 1 6 inputs, the four BCD
outputs, and circuit ground.
The tube shield was fash-
ioned from the liner of an
old recessed spotlamp fix-
ture, and the handle/stand
was a cut-down carrying
handle from an old transis-
tor radio. That's recycling at its
best, and you should remember
that many electronics hobbyists
work this way - they never throw
anything away, since they can
always find a use for it.

The exciting part was always
trying out a new project: would
everything work as you expected,
or would it all go up in smoke?
After a few minor adjust-
ments, which didn't involve
any disasters, I could see
the ones and zeros on the
screen. A little miracle,
which I could share with my
family.

I was able to use the Digis-
play several times in prac-
tice to help sort out prob-
lems with various circuits.
However, I think that the
greatest satisfaction lies in
building something like this
yourself, because you learn
something new with each
project and thus expand
your knowledge.

Another moment of satis-
faction, and certainly not
the least one, comes when
you plug it in after 30 years,
switch it on, and it still works
perfectly!

(080926-1)

Retronics is a monthly column covering vintage electronics including legendary Elektor designs. Contributions, suggestions and requests are
welcomed; please send an email to editor@elektor.com

2/2009 - elektor

77

ELEKTOR

SHOWCASE

To book your showcase space contact Huson International Media

Tel. 0044 (0) 1 932 564999

AVIT RESEARCH

www.avitresearch.co.uk

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• USB to I2C

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FTDI designs and sells
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Complete with PC drivers,
these devices simplify the task of designing or
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WWW.

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com

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Website full of Projects and Resources for
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• Tutorial

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Everyone can submit a story as a useful source!
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78

elektor - 2/2009

products and services directory

MQP ELECTRONICS ^

www.mqp.com / p * = :

• Low cost USB Bus Analysers

• High, Full or Low speed captures

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• Thousands of 0BD cables and connectors in
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• Custom cable design and manufacturing

• 0BD breakout boxes and simulators

• Guaranteed lowest prices

• Single quantity orders OK

• Convenient online ordering ^

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Surrey SM5 2HW

email: sales@robotiq.co.uk Tel: 020 8669 0769

SCANT00L.NET

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ScanTool.net offers a complete line
of PC-based scan tools for under £50.

• 1 year unconditional warranty

• 90 day money back guarantee

ROBOT ELECTRONICS

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Advanced Sensors and Electronics for Robotics

• Ultrasonic Range Finders

• Compass modules

• Infra-Red Thermal sensors

• Mntnr flontmllpr^

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• Compatible with a wide range
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• Vision Systems

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USB INSTRUMENTS

http://www.usb-instruments.com

USB Instruments specialises
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products and software such
as Oscilloscopes, Data
Loggers, Logic Analaysers
which interface to your PC via USB.

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PC and Pocket PC based
virtual instrument such
as sound card real time
oscilloscope, spectrum
analyzer, signal generator,
multimeter, sound meter,
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• USB to CAN bus interface

• USB powered

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• Receive, transmit & log.

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• Rugged IP67 version available

® nc :rpmc5

SHOWCASE YOUR COMPANY HERE

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
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2/2009 - elektor

79

BOOKS, CD-ROMs, DVDs, KITS & MODULES

Going Strong

A world of electronics
from a single shop!

45 projects for PIC, AVR and ARM

Microcontroller Systems Engineering

This book is about a state of the art tool, Flowcode, and how you can use Flowcode to develop
microcontroller applications. Flowcode is one of the world's most advanced graphical program-
ming languages for microcontrollers. This book covers 45 exciting and fun projects for beginners
and experts. Each project has a clear description of both hardware and software with pictures
and diagrams, which explain not just how things are done but also why. The book starts very
simply with a tutorial project and step-by-step instructions. As you go along the projects increase
in difficulty and the new concepts are explained. You can use it as a projects book, and build the
projects for your own use. Or you can use it as a study guide to learn more about microcontrol-
ler systems engineering and the PIC, AVR and ARM microcontrollers.

336 pages • ISBN 978-0-905705-75-0 • £29.00 • US $58.00

From LED to graphical LCD

Universal Display Book

for PIC Microcontrollers

This book begins with simple programs to
flash LEDs, and eventually by stages to use
other display indicators such as the 7-seg-
ment and alphanumeric liquid crystal dis-
plays. As the reader progresses through the
book, bigger and upgraded PIC chips are
introduced, with full circuit diagrams and
source code, both in assembler and C. A
tutorial is included using theMPLAB program-
ming environment, together with the PCB
design package and EAGLE schematic to
enable readers to create their own designs.

192 pages • ISBN 978-0-905705-73-6
£23.00 • US $46.00

Silent alarm, poetry box, night buzzer and more

PIC Microcontrollers

This hands-on book covers a series of
exciting and fun projects with PIC micro-
controllers. You can built more than 50
projects for your own use. The clear expla-
nations, schematics, and pictures of each
project on a breadboard make this a fun
activity. The technical background infor-
mation in each project explains why the
project is set up the way it is, including the
use of datasheets. Even after you've built
all the projects it will still be a valuable
reference guide to keep next to your PC.

446 pages • ISBN 978-0-905705-70-5
£27.95 • US $55.90

V J V J

Prices and item descriptions subject to change. E. & O.E

80

elektor - 02/2009

\

5.0, 6.0, VBA, .NET, 2005

Visual Basic for Electronics
Engineering Applications

This book is targeted towards those
people that want to control existing or
self-built hardware from their com-
puter. After familiarizing yourself with
Visual Basic, its development environment
and the toolset it offers are discussed in
detail. Each topic is accompanied by
clear, ready to run code, and where nec-
essary, schematics are provided that will
get your projects up to speed in no time.

476 pages • ISBN 978-0-905705-68-2
£29.95 • US $59.90

Compufor Villen

rViinipLai Pta-riH*

Principles and Practice

Computer Vision

Computer vision is probably the most
exciting branch of image processing, and
the number of applications in robotics,
automation technology and quality control
is constantly increasing. Unfortunately
entering this research area is, as yet, not
simple. Those who are interested must first
go through a lot of books, publications
and software libraries. With this book,
however, the first step is easy. The theore-
tically founded content is understandable
and is supplemented by many examples.

320 pages • ISBN 978-0-905705-71-2
£32.00 • US $64.00

EMBEDDED UHW
CONTROL CENTRE

«h 1 PC

e

A DIY system made from recycled components

Design your own

Embedded Linux

control centre on a PC

This book covers a do-it-your-self system
made from recycled components. The
main system described in this book re-
uses an old PC, a wireless mains outlet
with three switches and one controller,
and a USB webcam. All this is linked to-
gether by Linux. This book will serve up
the basics of setting up a Linux environ-
ment - including a software develop-
ment environment - so it can be used as
a control centre. The book will also guide
you through the necessary setup and
configuration of a Webserver, which will
be the interface to your very own home
control centre. All software needed will
be available for downloading from the
Elektor website.

234 pages • ISBN 978-0-905705-72-9
£24.00 • US $48.00

More information on the
Elektor Website:

www.elektor.com

Elektor

Regus Brentford
1 000 Great West Road
Brentford
TW8 9HH
United Kingdom
Tel.: +44 20 8261 4509
Fax: +44 20 8261 4447
Email: sales@elektor.com

110 issues, more than 2,100 articles

DVD Elektor 1990
through 1999

This DVD-ROM contains the full range of
1 990-1 999 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 publication (month/year), but
are also listed alphabetically by topic. A
comprehensive index enables you to
search the entire DVD. The DVD also con-
tains (free of charge) the entire 'The Ele-
ktor Datasheet Collection 1 . . .5' CD-ROM
series, with the original full datasheets of
semiconductors, memory ICs, microcon-
trollers, and much more.

ISBN 978-0-905705-76-7 • £69.00 • US$109.00

Modern technology for everyone

FPGA Course

FPGAs have established a firm position in
the modern electronics designer's toolkit.
Until recently, these 'super components'
were practically reserved for specialists in
high-tech companies. The nine lessons
on this courseware CD-ROM are a step
by step guide to the world of Field Pro-
grammable Gate Array technology. Sub-
jects covered include not just digital logic
and bus systems but also building an
FPGA Webserver, a 4-channel multimeter
and a USB controller. The CD also con-
tains PCB layout files in pdf format, a
Quartus manual, project software and
various supplementary instructions.

m

ISBN 978-90-5381-225-9 • £14.50 • US$29.00

02/2009 - elektor

81

BOOKS, CD-ROMs, DVDs, KITS & MODULES

More than 68,000 components

ECD 4

The program package consists of eight
databanks covering ICs, germanium and
silicon transistors, FETs, diodes, thyristors,
triacs and optocouplers. A further eleven
applications cover the calculation of,
for example, LED series droppers, zener
diode series resistors, voltage regulators
and AMVs. A colour band decoder is in-
cluded for determining resistor and in-
ductor values. ECD 4 gives instant access
to data on more than 68,000 compo-
nents. All databank applications are fully
interactive, allowing the user to add, edit
and complete component data. This CD-
ROM is a must-have for all electronics
enthusiasts.

ISBN 978-90-538 1-1 59-7 • £17.50 • US$ 35.00

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 interface. Both
options are available on this CD-ROM.
Included on this CD-ROM areUSB Basic
Facts, several useful design tools for hard-
ware and software, and all Elektor articles
on the subject of USB.

ISBN 978-90-5381-212-9 • £19.90 • US $39.80

y

Prices and item descriptions subject to change. E. & O.E

LED Top

with Special Effects

(December 2008)

If you fit a line of LEDs on a circular PCB
and power them on continuously, they
generate rings of light when the board is
spun. If you add a microcontroller, you
can use the same set of LEDs to obtain a
more interesting effect by generating a
Virtual' text display. The article also de-
scribes a simple technique for using the
Earth's magnetic field to generate a syn-
chronisation pulse. The potential appli-
cations extend from rotation counters to
an electronic compass.

Kit of parts incl. SMD-stuffed PCB and
programmed controller

Art-Nr. 080678-71 • £39.00 • US $59.00

Remote control
by Mobile Phone

(November 2008)

Remote control using mobile phones and
SMS (Text Messaging) is in great demand
but many systems on sale suffer from im-
perfections. This ingenious new design
combines powerful capabilities with low
technical overheads. It has programma-
ble AC mains switching outlets plus status
reports by text message and alarm-acti-
vated delivery of GPS data. Remote con-
trol by mobile was never easier, cheaper
or more reliable!

Kit of parts, incl. PCB, programmed
controller and all parts

Elektor SMT Reflow Oven

(October 2008)

The Elektor SMT reflow oven will faithfully
handle most if not all your soldering of
projects using surface mount devices
(SMDs). The oven is particularly suited for
use not just in Colleges, workshops, clubs
and R&D laboratories, but also by the ad-
vanced electronics enthusiast. This pre-
cious workbench tool is at home where
SMD boards have to be produced to a
variety of requirements on size, compo-
nents and soldering materials.

Size: 4 1 8x372x250 mm
(16.5 x 14.6x 10 inch)

Art. # 080663-91 • £962.00 (Exd. VAT) •
US$1665.00 (Exd. VAT)

Communicating with CAN

(October 2008)

The CAN (Controller Area Network) proto-
col was originally developed for use in the
automotive sector. It is now over 20 years
old, but is still frequently used these days.
It was specially designed for use in envi-
ronments where you have a lot of elec-
tromagnetic interference. Despite the fact
that the CAN protocol is a serial protocol,
it can't just be connected to (the serial port
of) a computer. The all-round USB-CAN
adapter described in last month's Elektor
is a compact and simple solution. With the
help of the accompanying software you
can follow all data communications taking
place and carry out operations such as fil-
tering and storage at the flick of a (mouse)
switch.

PCB, partly populated

Art. # 080324-71 • £54.00 • US $99.00

Art. #071 120-71 • £54.90 • US$109.80

82

elektor - 02/2009

■\

February 2009 (No. 386)

Model Coach Lighting Decoder

080689-1 PCB, long (I = 230 mm)

080689-2 PCB, medium (I = 190mm)

080689-3 PCB, short (I = 110mm)

080689-41 .... PIC12F683, programmed

Transistor Curve Tracer

080068-1 Main PCB

080068-91 .... PCB, populated and tested

January 2009 (No. 385)

Radio for Microcontrollers

071125-71 ....868 MHz module

ATM18on the Air

071125-71 ....868 MHz module

Meeting Cost Tinier

080396-41 ....ATmegal 68, programmed

Capacitive Sensing and the Water Cooler

080875-91 ....Touch Sensing Buttons Evaluation kit

080875-92 ....Touch Sensing Slider Evaluation kit

Three-Dimensional Light Source

080355-1 Printed circuit board

Moving up to 32 Bit

080632-91 ....ECRM40 module

December 2008 (No. 384)

PLDM

071 1 29-1 Printed circuit board

Hi-fi Wireless Headset

080647-1 Printed circuit board: Transmitter

080647-2 Printed circuit board: Receiver

LED Top with Special Effects
080678-71 .... Kit of parts incl. SMD-stuffed PCB

and programmed controller

November 2008 (No. 383)

Motorised Volume Pot

071135-41 .... Programmed controller ATMEGA8-16PU

Speed Camera Warning Device

08061 5-1 Printed circuit board

080615-41 ....Programmed controller PIC16F876A-I/SO....
Remote Control by Mobile Phone

080324-1 Printed circuit board

080324-41 .... Programmed controller ATMEGA8-16PU

080324-71 ....Kit of parts

Tracking Hot Spots

080358-1 Printed circuit board

AT meg a meets Vinculum

071152-91 .... VDIP1 module

October 2008 (No. 382)

Communicating with CAN

071 1 20-71 .... PCB, partly populated

Elektor SMT Precision Reflow Oven

080663-91 .... Ready to use oven (230VAC only)

Multi-purpose GPS Receiver

070309-41 .... Programmed controller PIC1 8F2520

ATM18 Relay Board and Port Expander

071 035-72 .... Relay PCB with all components and relays

071 035-95 .... Port Extension PCB, populated with SMD

RF Sweep Frequency Generator / Spectrum Analyser
040360-41 ....Programmed controller ATmega8535

£ US$

7.30 10.95

7.30 10.95

5.80 8.95

6.20 9.50

26.50 42.00

see www.elektor.com

...7.20 9.95

,.7.20 9.95

,.8.50 12.50

27.50 39.95

27.50 39.95

24.90 39.90

32.00 46.50

5.80 9.50

,7.90 15.80

.7.90 15.80

39.00 59.00

..5.90 11.80

15.50 31.00

11.80 23.60

17.80 35.60

..5.90 11.80

54.00 99.00

..9.10 18.20

22.50 45.00

..54.90 109.80

962.00.... 1665.00

..11.60 23.20

..36.90 73.80

..13.40 26.80

..21.80 43.60

Bestsellers

O

od

Universal Display Book

£23.00. US $46.00

ISBN 978-0-905705-73-6..

Embedded Linux Control Centre

ISBN 978-0-905705-72-9 E24.00.....US $48.00

PIC Microcontrollers

ISBN 978-0-905705-70-5 E27.95.....US $55.90

Visual Basic for Electronics Engineering Applications

ISBN 978-0-905705-68-2 E29.90.....US $59.90

Computer Vision

ISBN 978-0-905705-71-2 £32.00. US $64.00

Elektor 1990 through 1999

ISBN 978-0-905705-76-7 £69.00 ...US $109.00

FPGA Course

ISBN 978-90-5381-225-9 £14.50. US $29.00

£17.50. US$35.00

ECD 4

ISBN 978-90-5381-159-7

USB Toolbox

ISBN 978-90-5381-212-9 £19.90. US $39.80

O

r net Toolbox

ISBN 978-90-5381-214-3 £19.50. US $39.00

LED Top with Special Effects

Art. # 080678-71 £39.00.... US $59.00

Elektor SMT-oven

Art. # 080663-91 £882.00 US $1525.00

Evaluation Kit CapSense Buttons

Art. # 080875-91 £27.50 US $39.95

Evaluation Kit CapSense Sliders

Art. # 080875-92 E27.50.....US $39.95

Remote control by Mobile Phone

Art. # 080324-71 £54.00.... US $99.00

Order quickly and securely through

www.elektor.com/shop

or use the Order Form near the end
of the magazine!

September 2008 (No. 381)

DCC Command Station

070989-71 .... Kit of parts incl. programmed ARM module 88.50 177.00

lektor

SHOP

Elektor

Regus Brentford

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Brentford TW8 9HH * United Kingdom

Tel. +44 20 8261 4509

Fax +44 20 8261 4447

Email: sales@elektor.com

02/2009 - elektor

83

INFO & MARKET

SNEAK PREVIEW

4 to 16 — Port Extension for Micros

Ever so often a microcontroller simply doesn't have enough ports to control all functions in your circuit. Our clever port
extension boards provide the solution, requiring no more than 16 (SPI) control lines. The first board sports 16 digital
outputs; more may be obtained by 'cascading' boards. The second, equally simple to drive board gives access to an
HD44780 compatible LCD. The hardware is completed by free software examples for AVR controllers.

i

TinyBrick M16C Module

The Ml 6C display board published in May 2008 got a good response and is now complemented by a small
Ml 6 module with a DIL footprint called 'TinyBrick'. Like the display, TinyBrick is programmable in TinyBasic.
For development purposes we also present a carrier board, and there's more: as an example of a real life application,

we describe a home alarm system capable of sending SMS Text messages.

From R8C to R32C

The article series we published in 2006 on the Elektor 'Tom Thumb' R8C-base mini-
ature microcontroller board was a resounding success and we now take the next
step by presenting R32C, a Renesas micro with 32 bits architecture, floating point
and 50 MHz clock.

As with the R8C13 projects, the hardware consists of a carrier board containing the micro-
controller, and an application board with various interfaces and a prototyping area. Brand new,
we reckon, is the OLED display control developed for this system.

Article titles and magazine contents subject to change, please check 'Magazine' on www.elektor.com

The March 2009 issue comes on sale on Thursday 1 9 February 2009 (UK distribution only).
UK mainland subscribers will receive the issue between 14 and 17 February 2009.

w.elektor.com www.elektor.com www.elektor.com www.elektor.com www.elektorl

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, kits 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

• Surveys and polls

• FAQ, Author Guidelines and Contact

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84

elektor - 2/2009

Description Price each Qty. Total Order Code

Microcontroller Systems Engineering £ 29.00

DVD Elektor 1990 through 1999 £69.00

CapSense Buttons Kit(oso875-9i) j^rgTTl £ 27.50

CapSense Sliders Kit ( 080875 - 92 ) jjjl £27 ' 50

Universal Display Book

for PIC Microcontrollers £ 23.00

LED Top

with Special Effects (oso678-7i) £ 39.00

Free Elektor Catalogue 2009

Sub-total

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 paid

Name

Address + Post code

Tel.

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Date - - Signature

EL02

Yes, I am taking out an annual subscription
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2GB MP3 player*.

I would like:

I I Standard Subscription (11 issues)

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(11 issues plus the Elektor Volume 2008 CD-ROM)

* Offer available to Subscribers who have not held a subscription
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See reverse for rates and conditions.

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Elektor

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United Kingdom

Tel.: +44 20 8261 4509
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www.elektor.com
sales@elektor.com

*USA and Canada residents should use $ prices,
and send the order form to:

Elektor US
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Phone: 603-924-9464
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METHOD OF PAYMENT

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Please send this order form to

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1000 Great West Road
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United Kingdom

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Fax: +44 20 8261 4447
www.elektor.com
subscriptions@elektor.com

ORDERING INSTRUCTIONS, P&P CHARGES

All orders, except for subscriptions (for which see 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)

HOWTO 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. IBAN: GB35 ABNA 4050 3040 2095 20.

BIC: 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
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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 guarantee 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 10% 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 responsibility 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 advertisements) 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 private 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 2009

SUBSCRIPTION RATES FOR ANNUAL
SUBSCRIPTION

Standard Plus

United Kingdom £44.00 £53.00

Surface Mail

Rest of the World

£58.00

£67.00

Airmail

Rest of the World

£74.00

£83.00

USA

£59.95

See www.elektor.com/usa

Canada

£70.95

for special offers

HOWTO PAY

Bank transfer into account no. 40209520 held by Elektor Electronics,
with ABN-AMRO Bank, London. IBAN: GB35 ABNA 4050 3040 2095 20.
BIC: 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.

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 for a 20% (twenty per cent)
reduction in current rates, must be supported by evidence of stu-
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A standard Student Subscription costs £35.00, a Student
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Please note that new subscriptions take about four weeks from
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Cancelled subscriptions will be subject to a charge of 25%
(twenty-five per cent) of the full subscription price or £7.50,
whichever is the higher, plus the cost of any issues already
dispatched. Subsciptions cannot be cancelled after they have
run for six months or more.

January 2009

tQisues , more than 2,100 articles

This OVD- vO vA contains the full range of 1 990-1999 volumes
(all issues) of Elektor Electronics magazine. The more than
2,100 separate articles have been classified chronologically
by their dates of publication (month/year), but are also listed
alphabetically by topic. A comprehensive index enables you
to search the entire DVD. This DVD also contains (free of
charge) the entire 'The Elektor Datasheet Collection 1 ...5'
CD-ROM series, with the original full datasheets of
semiconductors, memory ICs,
microcontrollers, and much more.

ISBN 978-0-905705-76-7 • £69.00 • US $109.00

Elektor

Reg us Brentford
1 000 Great West Road
Brentford TW8 9HH
United Kingdom
Tel. +44 20 8261 4509

L J

Further information and ordering www.elektor.com

«_

Index of Advertisers

Antex Electronics Ltd www.antex.co.uk.

13

Avit Research, Showcase www.avitresearch.co.uk 78

Beijing Draco www.ezpcb.com

31

Beta Layout, Showcase www.pcb-pool.com 51, 78

ByVac, Showcase www.byvac.com

78

C S Technology Ltd, Showcase www.cstech.co.uk 78

Decibit Co. Ltd, Showcase www.decibit.com 78

Designer Systems, Showcase www.designersystems.co.uk 78

EasyDAQ, Showcase www.easydaq.biz

78

Easysync, Showcase www.easysync.co.uk.

78

Elnec, Showcase www.einec.com

78

EMCelettronica Sri, Showcase www.emcelettronica.com 78

Euro circuits www.eurocircuits.com

55

First Technology Transfer Ltd, Showcase . . www.ftt.co.uk 78

FlexiPanel Ltd, Showcase www.flexipanel.com 78

Future Technology Devices, Showcase. . . . www.ftdichip.com 78

General Circuits www.pcbcart.com.

41

Labcenter www.labcenter.com.

88

Lcdmod Kit, Showcase www.lcdmodkit.com

78

London Electronics College, Showcase . . . www.lec.org.uk 78

Microchip www.microchip.com/mtouch 3

MikroElektronika

MQP Electronics, Showcase. .

Netronics, Showcase

Newbury Electronics

Nurve Networks

Parallax

Peak Electronic Design

Pico

Quasar Electronics

Robot Electronics, Showcase.

Robotiq, Showcase

RS Components

ScanTool, Showcase

Showcase

USB Instruments, Showcase .
Virtins Technology, Showcase

www.mikroe.com 10, 11

www.mqp.com 79

www. cananalyser. co.uk 79

www. newburyelectronics. co.uk 17

www.xgamestation.com 17

www. parallax, com 23

www.peakeiec.co.uk 51

www.picotech.com 2

www.quasarelectronics.com 15

www. robot-electronics, co.uk 79

www.robotiq.co.uk 79

www.rswww.com/electronics 71

www.obd2cables.com, www.scantooi.net .... 79
78, 79

www.usb-instruments.com 79

www.virtins.com 79

Advertising space for the issue of 19 March 2009
may be reserved not later than 17 February 2009

with Huson International Media - Cambridge Flouse - Gogmore Lane -
Chertsey, Surrey KT 1 6 9AP - England - Telephone 01 932 564 999 -
Fax 01932 564998 - e-mail: p.brady@husonmedia.com to whom all
correspondence, copy instructions and artwork should be addressed.

2/2009 - elektor

87

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