■Hiiveftity Courses

for Electronics & Electrical Engineering

www.elektor.com

FEBRUARY 2008

£ 3.90

electronics worldwide

DIY: CAN Bus Explorer

DIY: LED Ringflasher for macro photography
Disassembled: Philips LivingColors

R08

02

9

770268

45113

sts

\. /

ON-LINE 1
•ALL PRICING IN
POUND STERLING
•MINIMUM ORDER
ONLY £10

1 0A 1 2VDC Motor Speed Controller

KC-5225 £7.95 + post & packing
Ideal for controlling 12V DC motors in cars such as fuel
injection pumps, water/air intercoolers and water
injection systems. You can also use it for headlight
dimming and for running 12V DC motors in 24V vehicles.
The circuit incorporates a soft start feature to reduce
inrush currents, especially on 12V
incandescent lamps.

Includes PCB and all
electronic
components.

Clock Watcher’s Clock

KC-5404 £41 .75 + post & packing
KC-5416 £55.25 + post & packing
This amazing clock uses an AVR driven circuit, and
produces a dazzling display with 60 LEDs around the
perimeter. It looks amazing, but can't be properly explained
here. We have filmed it in action so you can see for yourself
on our website www.jaycarelectronics.com. Kit supplied
with double sided

silkscreened plated through
hole PCB and all board
components as well as the
special clock housing!
Available in Red or Blue
Red KC-5404

Blue KC-5416

St

Bm

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W

Smart Fuel Mixture Display for
Fuel Injected Cars

KC-5374 £8.95 + post and packing
This kit features auto dimming for night driving,
emergency lean-out alarm, and better circuit protection.
Another great feature is the 'dancing' display which
operates when the ECU is operating in closed loop. Kit
supplied with PCB and all electronic components with
clear English instructions.

* Car must be fitted with air flow and
EGO sensors (standard on
all EFI systems) for
full functionality.

45 Second Voice Recorder Module

KC-5454 £1 1 .75+ post & packing
This kit can be set up to record two, four or eight different
messages for random-access playback, or a single
message for ‘tape mode' playback. It provides clean,
glitch-free line-level audio output suitable for feeding to an
amplifier or PA system. It can be powered from any source
of 9-1 4V DC. Supplied with silk screened and solder
masked PCB and all
electronic components.

Audio Playback Adaptor for CD-ROM Drives

KC-5459 £19.00 + post & packing

Put those old CD-ROM drives to good use as CD players using
this nifty adaptor kit. The adaptor accepts signals from common
TV remote controls and operates the audio functions of the drive
as easily as you would control a normal CD player. Kit features a
double sided PCB, pre-programmed micro controller, and IDC
connectors for the display panel. Supplied with solder masked
and screen printed PCB and all required electronic components.

Build-Yourself
Electronic Project Kits

Looking for a particular KIT?

Checkout Jaycar’s extensive range.

We have kits and electronic projects for use in:

• Audio & Video

• Car & Automotive

• Computer

• Learning & Educational

• Lighting

• Power

• Test & Meters

• General Electronics Projects r 430+ pages

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Post and Packing Charges

Order Value

Cost

Order Value

Cost

£200 - £499.99
£500+

£10 - £49.99 £5

£50 - £99.99 £10

£100 - £199.99 £20

Max weight 121b (5kg). Heavier parcels POA
Minimum order £10.

£30

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Note: Products are despatched from Australia, so local
customs duty and taxes may apply.

How to order:

Phone: Call Australian Eastern Standard Time Mon-Fri
on 0800 032 7241

Email: techstore@jaycarelectronics.co.uk
Post: PO BOX 6424, Silverwater NSW 1811. Australia
Expect 10-14 days for air parcel delivery

Check out the Jaycar range in your FREE Catalogue - logon to

www.jaycarelectronics.co.uk/elektor

or check out the range at

www.jaycarelectronics.co.uk

0800 032 7241

(Monday - Friday 09.00 to 17.30 GMT + 10 hours only)
For those who want to write: 100 Silverwater Rd
Silverwater NSW 2128 Sydney AUSTRALIA

Handy Helpers

Fujiya 175mm Screw Removing Pliers

TH-2330 £7.00+ post and

packing

Remove screws even with
completely stripped heads. Simply
grab the screw head with these
Japanese made pliers and turn.

Beautiful.

• 175mm long

• Soft grip handle

i

Waterproof (IP67) LED
Lighting Modules

Each £5.75 + post and packing
Endless possibilities - backlighting signs, strip lighting in
stairwells & passageways, boats, garages etc. Supplied as
10x3 LEDs module, 10 modules, with 500mm flying leads
for termination. Each module is spaced at approximately
110mm between centres. Simply connect up a 12VDC
600mA supply and away you go.

Two types available
ZD-0490 White
ZD-0492 Blue

Low Voltage Battery Warning

KG -9000 £3.00 + post and packing
This circuit monitors any battery
voltage between 3-15 volts.

Whenever the voltage falls
below a predetermined
value a Red LED lamp
lights up to alert you.

Uses a tiny amount of
power from the battery
being monitored. Use it for
monitoring all sorts of battery
systems and avoiding battery damage.

Light-Sensitive Switch 240VAC 1 0A

AA-0326 £3.00 + post and packing
Turn a mains powered device on or off
according to the ambient light level. Ideal
for garden lighting or security
applications. The controller is weather
resistant and includes a
mounting bracket. Approx
80mm high.

B

PC Oscilloscopes <& Analyzers

DSO Test Instrument Software for BitScope Mixed Signal Oscilloscopes

'- 101*4 -.I — -

WhQf |

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. -

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4 Channel BitScope

Digital Storage Oscilloscope

Up to 4 analog channels using industry standard
probes or POD connected analog inputs.

Mixed Signal Oscilloscope

Capture and display up to 4 analog and 8 logic
channels with sophisticated cross-triggers.

Spectrum Analyzer

Integrated real-time spectrum analyzer for each
analog channel with concurrent waveform display.

Logic Analyzer

8 logic, External Trigger and special purpose
inputs to capture digital signals down to 25nS.

Data Recorder

Record anything DSO can capture. Supports
live data replay and display export.

Networking

Flexible network connectivity supporting
multi-scope operation, remote monitoring and
data acquisition.

Data Export

Export data with DSO using portable CSV files or
use libraries to build custom BitScope solutions.

2 Channel BitScope

Pocket Analyzer

BitScope DSO Software for Windows and Linux

BitScope DSO is fast and intuitive multi-channel test and measurement software for your
PC or notebook. Whether it's a digital scope, spectrum analyzer, mixed signal scope,
logic analyzer, waveform generator or data recorder, BitScope DSO supports them all.

Capture deep buffer one-shots or display waveforms live just like an analog scope.
Comprehensive test instrument integration means you can view the same data in
different ways simultaneously at the click of a button.

DSO may even be used stand-alone to share data with colleagues, students or
customers. Waveforms may be exported as portable image files or live captures replayed
on other PCs as if a BitScope was locally connected.

BitScope DSO supports all current BitScope models, auto-configures when it connects
and can manage multiple BitScopes concurrently. No manual setup is normally required.
Data export is available for use with third party software tools and BitScope's networked
data acquisition capabilities are fully supported.

www . bitscope .com

2/2008 - elektor

3

Theme
of the month

With trade magazines it is custo-
mary for the editorial planning for
the year to be based on themes or
points of focus set for each issue.
However the theme planning is
not just a crucial bit of informa-
tion to the magazine editors — it
also offers guidance to press and
PR agencies, advertisers and,
importantly, potential authors who
will typically use the list to report
a relevant article to... the editor!
Elektor's theme plan for 2008 is
available for all & sundry to see
at www.elektor.com if you click on
the Service tab.

For sure, a number of our themes
can be accessed from so many
angles that they can be relied
on to fill the magazine pages on
their own strength. The January
2008 issue had a strong focus on
energy, energy savings and the
environment. For this month, LEDs
and LED technology form the plot,
unmistakably. Immediately after
releasing our theme plan, articles
and projects using LEDs poured in
to the extent that they could easily
have filled the pages of an Elektor
issue exclusively on LEDs.

LEDs are hot (and / cool / ) as we've
noticed from the response to
relevant news items on our News
& New Products pages and in the
Elektor E-weekly. Not a week goes
by without 'breaking news' of a
yet brighter or more efficient LED,
or a stunning application.

The light emitting diode has come
a long way since its introduction
in the mid 1 970s. Today the full
spectrum from infrared right up to
ultra-violet is readily available, and
white LEDs (a class of their own)
get brighter and whiter all the time.
Efficiency-wise LEDs have long
since surpassed halogen lamps
and they now look poised to match
low-energy CFLs. In the automotive
industry, to talk of a LED array as a
replacement for xenon lights is no
longer utopian. Not forgetting TFT
backlighting (till now the exclusive
domain of incandescent lamps)
where LEDs will be seen soon
— literally!

Jan Buiting
Editor

leKlo r

electronics worldwide

Due to the fact
that we received
two circuit
designs for
television mood
lighting and they
both fit with the
theme of this issue,
we initiated a unique
Elektor project: in this issue
we present two completely dif-
ferent designs that produce nearly
the same effect. Our French contribu-
tor Alex Vercey took the analogue approach, while Steffen Schutte
from Germany went the 'microcontroller way'. See, compare,
experience for yourself!

BEng., MEng.,
perhaps a PhD.?

Here's a 3-step primer on the
subject: first get oriented; then
hear opinions and finally, de-
cide where to hang out.

So you were thinking of study-
ing for an Electronics and
Electrical Engineering degree
or similar qualification at a UK
university or other higher level
educational establishment?

30 What University

CONTENTS

CAN Explorer

P ‘“ CANBUS R3 M

|! S

n *

1

“ * p s- - k

IC 3

m

^ *5V

^ R5 «— «B nir-

Tjj

IC1 M

r - C Q t! SJ f 5 ^

Implementing
the CAN bus
network is

C 2 Q - e

: L I

:

df ZO&6

' , '■> ' x o g g r; g o

© ■•!> 3 9 O V O G Ij G
£■ I <i

060201-1

PARALLEL PORT ^elektor

not a trivia
undertaking.

This low-cost
solution is a
CAN board
which sits bet-
ween the CAN
bus and a
PC. Using the

versatile (free) software it can monitor activity on the network
and test the functioning of other nodes.

50 LED Ringflash

With macro-photography, if
lighting conditions are not ideal,
it will be necessary to resort to
the use of flash, with the attendant
risk of shadows. The solution is a
ringflash - and while we're about
it, why not one using LEDs?

Power to the LEDs

In two short picture stories
we tell not only how LEDs
are designed and produced
(basically!), but also look at
what Philips Lumileds Lighting
Systems are pursuing technically in
a bid at making a versatile high-power
LED for mass production.

Volume 34
February 2008
no. 374

projects

16 Surround Light

24 TV Light

38 CAN Explorer

42 RGB LED Mood Lighting

50 LED Ringflash

56 E-blocks: Thermometer /
Thermostat

60 LEDBUS System

Design Tip:

1 MHz frequency counters
using AT89C2051

74 Frost Detector

technology

66 Power to the LEDs
Philips LivingColors
Vista versus LPT

info & market

6 Colophon
8 Mailbox

News & New Products
What University
80 ElektorSHOP
Sneak Preview

infotainment

76 Hexadoku

77 Retronics: Programmable
Disco Lights Array (1984)

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.

assent-

LtacLronlcH noih

Volume 34, Number 374, February 2008 ISSN 0268/4519

Elektor Electronics 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,
Ernst Krempelsauer, Jens Nickel, Guy Raedersdorf.

Design stc Antoine Authier, Ton Giesberts, Paul Goossens,
Luc Lemmens, 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

Customer Services: Anouska van Ginkel

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

6

elektor - 2/2008

PIC Microcontro Hers

Silent alarm, RGB fader, poetry box.

night buzzer and more!

PIC Mi crocontrolle r

lektor

This hands-on book covers a series of exciting and
fun projects with PIC microcontrollers. You can built
more than 50 projects for your own use. The clear
explanations, schematics, and pictures of each
project on a breadboard make this a fun activity.
You can also use it as a study guide. The technical
background information in each project explains why
the project is set up the way it is, including the use of
datasheets. This way you'll learn a lot about the
project and the microcontroller being used. Even after
you've built all the projects it will still be a valuable
reference guide to keep next to your PC. All software
used in this book can be downloaded for free,
including all of the source code, a program editor,
and the JAL open source programming language.

446 pages • ISBN 978-0-905705-70-5 • £27.00 • US$ 54.00

Elektor

Regus Brentford
1 000 Great West Road
Brentford

TW8 9HH
United Kingdom

Tel. +44 20 8261 4509

Order quickly and safe through WWW.elektor.COIn/shop

or use the Order Form near the end of the magazine

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.brady@husonmedia.com
Internet: www.husonmedia.com
Advertising rates and terms available on request.

International Advertising Frank van de Raadt, address as Head Office

Email: advertenties@elektor.nl

Advertising rates and terms available on request.

Copyright Notice

The circuits described in this magazine are for domestic use only. All drawings, photographs,
printed circuit board layouts, programmed integrated circuits, disks, CD-ROMs, software carri-
ers and article texts published in our books and magazines (other than third-party advertise-
ments) are copyright Segment, b.v. and may not be reproduced or transmitted in any form
or by any means, including photocopying, scanning an recording, in whole or in part without

prior written permission from the Publishers. Such written permission must also be obtained
before any part of this publication is stored in a retrieval system of any nature. Patent protec-
tion may exist 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 Publishers to alter
the text and design, and to use the contents in other Segment publications and activities. The
Publishers cannot guarantee to return any material submitted to them.

Disclaimer

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

© Elektor International Media B.V. 2008

Printed in the Netherlands

2/2008 - elektor

7

INFO & MARKET

MAILBOX

Alternative and original uses for the LED driver board

(September 2007 issue) (2)

12-V converter using the PR4401

Many thanks for the nice lamp driver, al-
though the 1C is almost too good for a piddly
little lamp. I had a different problem in my
lab: my digital multimeter (Conrad BT-555)
uses an expensive 1 2-V photo battery. It
needs a new one every few weeks, and after
replacing the battery twice you have paid
for the instrument twice over. I thus needed to
build a voltage converter to generate 1 2 V
from a 1 .2-V source (a NiCd or NiMH cell).

To do so, I fitted a 1 2-V zener diode to the
board that came with the September 2007 is-
sue of Elektor. Naturally, you can use a diode
with a different zener voltage if you need a
different output voltage. The 1 .2-V recharge-
able cell came from a 9-V battery (GF22),
which consists of a flat stack of six cells. All of
this fits perfectly in the multimeter. Now I can
use the multimeter with renewed pleasure!
John Dyer

Hi Jan — I am considering installing it in a
book reading lamp with a white LED, and a
plastic diffuser sheet from a broken phone
LCD panel.

I found the diffuser plastic works really well
in providing a more even light distribution. It
removes the contrasting rings of light dark cast
from the led and there is very little loss of inten-
sity. I tested the diffuser with a commercial LED
torch and it makes the torch more usable.

I believe the diffuser plastic is very similar to
what Luminit manufacture using holographic
technology.

www.luminitco.com/index.html

Peter Wintu ich (Australia)

MAKE A JOULE THIEF

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Residual charge converter

When I saw the Elektor LED driver circuit, I
was immediately reminded of the following
website: www.emanator.demon.co.uk/
bigclive/joule.htm

As you can see, an even simpler solution is
possible. In theory you could also omit the 1-
kQ resistor by winding the coil with resistance
wire.

Ron Keller man

Dejd vu

This was a sort of deja vu experience. I
discovered a three-lead LED driver around two
years ago. The circuit (of which I found two
versions) is used in an aluminium pocket torch
with a single AAA cell, and it starts working
at around 0.7 V. If you forget to switch off the
torch, it keeps working down to below 0.2 V.
This should also be possible with your 1C. This
means it could also be used with a single-cell
solar module, which could then be used to
recharge a mobile phone.

I also found another type of circuit in an
aluminium torch from China. It consists of six
discrete components and drives six white LEDs
from a voltage of around 0.7 V or more. This
circuit board is not much larger, since the tran-
sistors are in SOT23 packages.

Frederic Stephens

The PR4401 is not the best choice for a solar
charger with only one solar cell. This would
need a somewhat lower minimum input voltage ,
and the maximum output current would have to
somewhat higher. The TPS61200 from TI is one
possible recommendation , although it is some-
what limited by its 3x3 QFN package.

What can I write about?

Hi Jan — I was a regular read-
er & subscriber to Elektor India
Magazine until it was stopped
a couple of years ago. I was
wondering if I could contribute
technical articles & projects for
publication in your magazine.

If so, please reply.
Venkateswaran
Gopalakrishnan (India)

As opposed to a number of
our competitors on the market ,
Elektor is open to contributions
from external authors and de-
signers. Mind you , we do have
challenging requirements for ar-
ticles and projects. Please have
a look at our Author Guidelines
and the Elektor Publishing Plan
for 2008. Both documents are
available for anyone to view
at www.elektor.com under the
' Service ' tab.

Be a good sport

Dear Jan — I have been
secretly wishing for many
years that Elektor would feel
the need to cast its eye over
sports and the application of
electronics in aiding training
and competition. I have been
eagerly waiting for you to
run an issue on just electronic
projects for sports. I loved the
Robotics issue (July/August
2007), and something along
those lines would be excellent.

I and many sports coaches
I am sure would love to see
electronic projects that could
be built at a reasonable cost.
Projects based on the follow-
ing ideas I am certain would
be a great success.

- Automated electronic timer
that stores times and can be
downloaded into Excel.

- An accelerometer belt that is
worn by a sprinter and stores/
calculates ground contact times.

- The use of super bright LED
pace makers that set the pace
around a track and bleep
when the athlete passes them.

- A cheap alternative to a
force plate that measures jump
height and ground contact
time and calculates power.

M. Newman (UK)

Really fine ideas which I am
happy to copy into the electro-

8

elektor - 2/2008

USB Data Acquisition Card

November 2007, p. 16-20, ref. 070148-1

In the circuit diagram, the USB+ and USB- pins on K2 should
be swapped. The PCB track layout shown in the article should
also be corrected. PCBs supplied through the Elektor Shop
have the correct USB signal routing and are not affected.
Although different values are indicated in the circuit diagram
and the parts list, both 27 Q and 33 Q resistors may be used
in positions R3 and R4.

nics design community! Please
get in touch with Elektor to dis-
cuss your proposals.

Sound card for
SDR receiver

Which sound card is recommen-
ded for the SDR receiver descri-
bed in the May 2007 issue?

You gave the minimum specifi-
cations for the sound card in a
later issue, but when I search
for sound cards on websites
I find very little information
about these specifications, so
I would like to have a brand
and type if possible.

Francis McGee

There are many different sound
cards available , and we were
not able to test all of them for use
with the SDR radio. For this rea-
son , we wrote an article on how
to test your own sound card. You
can download this article free of
charge from the Elektor website
via the following link:
www.elektor.com/magazines/
2007/june/sdr-soundcard-tes-
ter.91895.lynkx

Incidentally most of the better
modern sound cards are suitable
for SDR reception.

USB interference
with SDR

The circuit described in the
May 2007 issue had poor
reception characteristics.

The cause of this was strong
interference on the USB bus.
Unfortunately, PC switch-mode
power supplies are not a good
source of power for sensitive
analogue circuits. The only

remedy is a filter. With the
SDR project, this means that
capacitor C9 (4.7 |jF) must be
replaced by a 470 |jF / 1 0 V
type. This yields a remarkable
improvement.

Using an external power sup-
ply for the circuit, as suggested
by Burkhard Kainka, was not
as satisfactory as replacing
the capacitor, and in any case
using the USB bus for power is
more attractive.

Helmut DH6KR

I have tested the circuit with the
larger-value capacitor. It visibly
cleans up the interference , but
there is still some
noise below
around 30 Hz. I
suspect that every
PC has a different
interference spec-
trum. With mine ,
I obtained better
results with the
voltage regulator.
Incidentally some
readers have at-
tempted to use
the frequency
range around
0 Hz directly. This
yields poor results
because signals such as an AM
carrier dry up ' in that region.
I set the lower frequency limit
relatively high to reduce USB
interference feedthrough. This is
why you should use an IF of 10
to 15 kHz , since no USB interfe-
rence is present there.

Burkhard Kainka

Macs and microcontrollers

I have purchased an AVR USB
board, and I would like to
learn how to program it. I am
highly encouraged

by the easily understandable
articles in your magazine, but I
have a small problem.

I have a new Apple Macbook
with the Leopard operating
system, and after long (really
long) searching I have not
found a single program that I
can use to program the board.
There are a few sites on the
Internet with complicated
instructions describing how this
might be arranged, but most
of them are rather difficult to
understand. Is there any sort of
software that I could use?

If not, perhaps it would be a
good idea to publish an article
on how to do this. By that I
mean something truly under-
standable, not the confusion
propagated on the Internet.
Peter Pantott (Germany)

the answer in your hand: the
Macbook.

Simply use Bootcamp to install
Windows XP (in addition to
the Mac OS) in a small disk
partition. For your purposes ,

6 GB should be more than
enough. With your Mac
configured this way you have
full access to everything there is.

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.

With regard to micro-
controllers we can only
advise to not even try to
find suitable software ,
because it practically
does not exist.

The good news is that
you already
have

2/2008 - elektor

9

INFO & MARKET

NEWS & NEW PRODUCTS

Multiroom Sonocontrol Audio Transmitter

Until now, if you wanted to en-
joy music from your iPod® without
headphones, you had to either
connect the handy MP3 player to
the hi-fi system - a complicated
feat - or place it in a special dock-
ing station.

Thanks to the new technology from
sonostream, the music lover no long-
er has to let go of his iPod and can
select his favourite tracks on-the-go,
as usual. The hi-fi system plays them
immediately with the best sound.
The iPod can be placed onto the
small exact-fitting Sonocontrol Au-
dio Transmitter with one click, and it
is transformed into a handy remote
control for every hi-fi system.

There are special versions of the
transmitter for all common iPod
models (Nano G23, Classic
60/80, iPod Touch, iPhone). All of
the player's functions can be con-

trolled as usual: display, menu, and
information always at a glance,
sonostream 's transmitter-receiver
system enables an interference-
free and absolute loss-free digital
radio transmission from the player
to the stereo system and to active
speakers. With further receivers or
sonostream active speakers in oth-
er rooms, the system becomes a
wireless multi-room system, allow-
ing you to directly activate or shut
off individual listening zones using
the transmitter.

Especially practical: To charge it,
the iPod and the audio transmitter,
that already has its own recharge-
able battery, are placed onto the
docking station together so that
you no longer have the bothersome
switching back and forth. Accord-
ingly, the iPod can remain docked
onto the transmitter for synchroni-

sation on the computer, because
the signals are looped through.

www.sonovision-digital.com

(070904-X)

VB400 and VBC Save on KWh and Energy Costs

IEPC claims to make lighting con-
trol pay with its VB400 and Vari-
Ballast Control (VBC.) These light-
ing controls reportedly save cus-
tomers money from the very first
month of use, and with up to 25 to

70 percent savings in lighting en-
ergy every month, the lighting con-
trols make existing HID and both
T5 / T8 lighting systems pay.

The VB400 lighting control system
is meant to replace outdated, inef-

ficient, un-controlled high-bay and
low-bay HID lighting fixtures. The
Vari-Ballast Control (VBC) enables
the use of T5 and T8 florescent
ballasts. Both lighting control sys-
tems can be used with any manu-
facturer, wattage, bulb type and
input voltage.

To save energy, many facilities
managers of high-bay lighting
structures switch an existing HID
lighting system for a less bright,
non-controllable fluorescent light-
ing system. The VB400 and the
VBC offer more efficient, controlla-
ble and more cost-effective alterna-
tives. IEPC provides either solution
T5/T8 or HID.

With traditional ballasts, the fix-
tures are spaced closely together
due to inefficiencies in magnetic
ballast technology. With lEPC's

PIC programmer for design licensing

With firmware beginning to domi-
nate the development costs and
value of electronic products, the
question of how to manage it and
trade it securely is becoming in-
creasingly important. FlexiPanel
Ltd tackles this issue head-on with
the release of its TEAclipper range
of encrypted PIC programmers.
From just £ 20 (€ 30) and the
size of thumbnail, they are a wel-
come break from the cumbersome

gang programmers of the past.
They are plugged into the target
circuit board and program the PIC
in seconds.

TEAclippers were developed for
businesses needing to ensure their
subcontract manufacturers don't
rip off their products and engineers
who want to license their electron-
ic designs. They have a limited-
download feature which ensures
that only a fixed number of cop-

ies may be made, and they store
their firmware securely on-board
for easy archiving of different ver-
sions. Customization features al-
low serial numbers, random num-
bers and configuration settings to
be individually set each time a PIC
is programmed.

www.flexipanel.com

(070996-1)

lighting controls, the layout can
be expanded due to higher watt-
age output, a power factor cor-
rection of nearly 1 00 percent and
the ability to precisely control the
lumens/fixture output. Also, tradi-
tional HID ballasts have a Watt
Stopper, which can only regulate
up to eight lights at a time. The
VB400 and the VBC allow control
of a single lamp, part of an area
or an entire area with thousands of
lamps from one computer.

The VB400, VB400N and the Vari-
Ballast controls are available im-
mediately through a pilot program
with IEPC.

www.iepc.cc

(070904-XI)

10

elektor - 2/2008

First Technology Transfer courses

Andrew Eliasz and Jim Davies
founded First Technology Trans-
fer (FTT) in the early 1 990s with
a view to providing special-
ist, innovative, advanced and
highly tailored technical train-
ing and consultancy to organi-
sations developing both tradi-
tional IT and embedded sys-
tems applications. Since then, it
has built around the core of the
company a network of consult-
ants and technologists who col-
lectively provide FTT with access
to extensive expertise across the
complete spectrum of IT and soft-
ware engineering disciplines.

These consultants have had es-
tablished careers within their
own sectors and have seen
many projects through the full
life cycle. This diversity ena-
bles FTT to put together experi-
enced multidisciplinary teams to
provide mentoring, consultancy
and training in a wide range of
projects ranging from real time
process control and laborato-
ry automation through to net-

worked and distributed database
projects.

FTT's expertise and training curric-
ulum encompasses the following
disciplines:

• Programming languages

• Embedded Linux and Unix

• Small microcontrollers

• Networking

• IPV6

• Microchip/CMX approved
courses

• Service oriented architecture

• UML and 00 analysis

• Windows programming

• Open source databases

• Bioinformatics

It is an inevitable fact that the use
of real-time software running in

embedded devices is going to
become more and more per-
vasive in our society. However,
unfortunately, the number of
experienced engineers in this
area is very limited, and there
is substantial demand for suita-
bly trained staff to meet these re-
quirements. FTT's vision, shared
by it's sister company — Robotiq
(focussed on educational robot-
ics) is to encourage the young
(and not so young) people to
become more actively involved
with technology and engineer-
ing by providing them with the
training and support to equip
them with the necessary skills to
fulfil their ambitions.

All of FTT courses include a sig-
nificant component of hands-
on work. These courses can be
provided either on-site at the
client location or at FTT's fully
equipped training centre in Car-
shalton, Surrey.

http://www.ftt.co.uk

( 070996 - 11 )

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2/2008 - elektor

11

INFO & MARKET

NEWS & NEW PRODUCTS

New PSoC® evaluation kit

Cypress Semiconductor Corp. re-
cently introduced a new evaluation
kit for its fast-growing PSoC mixed-
signal arrays. The new CY3209
ExpressEVK includes four different
PSoC devices and gives designers
an easy to use platform to try a
multitude of designs.

The CY3209 ExpressEVK includes
four sections, each of which contains
a separate PSoC device. The sections
can all be networked together eas-
ily via l 2 C interfaces to test numerous
combinations of functions using the
PSoC Express(tm) visual embedded
design tool. The new kit offers hard-
ware, software and design examples

to help designers implement a variety
of functions, including:

• PSoC CapSense 1 ™ 1 capacitive
touch interfaces

• Wireless communication

• "Drag and drop" USB
programming

• LCD and LED control

• Accelerometer, tilt or drop
sensing

• Voltage monitoring

Details of the kit are at www.cy-
press.com/CY3209-ExpressEVK
and it is available for purchase
on the Cypress Online Store and
through authorized distributor part-

ners, including Future, Arrow, Av-
net, Digikey, Mouser, P&S, and
MSC. It costs $ 129.99.

www.cypress.com

(070996-IV)

0.9V Boost LED Driver PR4403 for Solar Lamps

The new PR4403 from PREMA
Semiconductor GmbH drives and
controls white LEDs out of one sin-
gle battery charged by solar cells.
It uses the connected solar cells to
detect daylight.

LED solar lamps operate with au-
tomatic LED control depending on
the ambient light level. The battery
is charged by solar cells. Normally
this requires several components like
Schottky diodes, capacitors, resistors,

two or three rechargeable battery
cells and a photo resistor. In contrast
to this standard solution the PR4403
saves several components, as it is
able to drive the current for the white
LED out of a single rechargeable bat-
tery cell. Also the expensive photo re-
sistor is no longer needed.

A supply voltage of down to 0.9V
is sufficient for the 1C to drive a cur-
rent of up to 40mA independent of
the input voltage. The value of the
external inductor defines the LED
current. Instead of the photo resis-
tor, the solar cell is directly con-
nected to the 1C for daylight level
detection, and an optional resistor
sets the light threshold. Depending
on the voltage at this connection,
the integrated step-up converter is
switched on or off. During daytime
the driver is shut-down and the so-
lar cell charges the battery via the

external Schottky diode. With de-
creasing ambient light the voltage
at the solar cell drops, the 1C is ac-
tivated and drives the LED current
out of the battery cell.

Deep discharge of the battery cell
is prevented as the PR4403 shuts
off the driver when the supply volt-
age drops to less than 850 mV.
Therefore PREMA's PR4403 saves
cost for LED solar lamps as it re-
duces the number of components.
Applications for the PR4403 are
solar garden lamps as well as
house number lights, decoration
lights and road markers powered
by solar cells.

Samples in S08 package are
available upon request.

www.prema.com / pdf / pr4403.pdf

(070996-V)

New MAX HZ CPLDs for portable applications

Altera Corporation announced the
new, zero-power MAX® IIZ CPLD
designed specifically to address
the power, package and price con-
straints of the portable applications
market. Offering a resource advan-
tage of up to six times the density
and three times the I/Os compared
to competing traditional macrocell-
based CPLDs, MAX IIZ devices al-
low designers to meet changing
functional requirements at the same
or lower power while saving board
space. Adding zero-power and ultra-
small packages to the most popular
CPLD series in the industry, the MAX

IIZ devices deliver the many benefits
of CPLDs — including flexibility, fast-
er time to market, and board-level
integration — to handsets and other
portable applications.

MAX IIZ devices are available in
densities of 240 and 570 logic ele-
ments (LEs). The devices are avail-
able in ultra-small MBGA packages
with up to 160 I/Os. This increased
logic density and greater I/O count
allow greater integration of exist-
ing functions from other devices,
substantially reducing board space
and power consumption while low-
ering overall system costs.

(070996-VII)

www.altera.com /b / maxiiz
www.altera.com /b / maxiiz-portable

12

elektor - 2/2008

mikroElektronika

DEVELOPMENT TOOLS | COMPILERS | BOOKS

EasyPIC

with hardware
In-Circuit Debugger

For only

$119.00

USD

M CRQCHIP

PIC

n^ipi rpfjiFJT

BOARD

The system supports 8-, 14-, 18-, 20-, 28- and 40- pin PIC micro-
controllers (it comes with the PIC16F877A). The mikrolCD (In-
circuit Debugger) enables very efficient debugging and fast pro-
totype developing. Examples in C, BASIC and Pascal language
are provided with the board. EasyPIC5 comes with printed docu-
mentation which includes: EasyPIC5 Manual, PICFIash with
mikrolCD Manual, mikrolCD Manual.

EasyPIC5 Add-On Boards

Various range of additional daughter-boards for EasyPIC5 development board

Digital POT - MCP41010
SPI Interfaced digital poten-
tiometer.

SmartMP3 Board -

VSIOOIk MP3 decoder with
SPI Interface.

Serial 7-seg Display 2
Board - MAX7219 SPI Inter-
faced, LED Display Drivers
with 8 Common-Cathode
LED Displays

LightToFreq Board -

TSL230BR programmable
light-to-frequency converter.

EasyConnect Board - Con-
nects your peripherals easily
and fast using connectors.

CAN-1 Board - Interfaces
CAN via MCP2551 .

CANSPI Board - Makes
CAN network with SPI inter-
face.

RS485 Board - Connects
devices into RS-485 network

Serial Ethernet - Make
ethernet network with SPI
Interface (ENC28J60).

lrDA2 Board - Irda2 serves
as wireless RS232 commu-
nication between two MCU’s.

Port Expander Board -

MCP23S17 is the 16-bit port
expander with SPI interface.

CF Board - Easy way to use
Compact flash in your
design.

MMC/SD Board - Easy way
to use MMC and SD cards in
your design.

EEPROM Board - Serial
EEPROM board via I2C
interface.

RTC Board - PCF8583 RTC
with battery backup.

SmartADAPT MINI - Config-
ures 8 output pins by moving
jumpers on-board.

SmartADAPT 2 - Configures
16 output pins by moving
jumpers on-board.

ADC Board - 12-bit analog-
to-digital converter (ADC)
with 4 inputs.

DAC Board - 12-bit digital-
to-analog converter (DAC)
with SPI.

Keypad 4x4 Board - Adds
keypad to your application.

Accel. Board - Accel, is an
electronic device that meas-
ures acceleration forces .

LIN Board - MCP201 LIN
Transceiver up to 20K baud
rate

AudioAMP Board - LM386
power amplifier designed for
use in low voltage consumer
applications.

ini

HWTDWAfH
i: iin HiVihi:-
LJC23SD

Lfl HOARD
PniXJVMUCK

UIVU

DEVELJOPMOJT PfiFpLlfihWJCE

SYSTEM

MvCLO'

FiTl^Tl

KC>T

World-Class Development Tool

A state-of-the-art very fast USB 2.0 programmer
including mikrolCD (In-circuit Debugger) on-
board with simplified driver installation.

The Best Just got Better

Following the tradition of its predecessor
EasyPIC4 as one of the best PIC development
systems on the market, the EasyPIC5 has more
new features for the same price.

Train for the future

EasyPIC5 was designed to allow students or
engineers to easily exercise and explore the
capabilities of the PIC microcontrollers.

Designed to suit your needs

Your development time can be
considerably reduced, resulting in an early proto-
type design and fast time-to-market for your end
product.

mikroElektronika Compilers

Pascal, Basic and C Compilers for PIC microcontrollers

Supporting an impressive range of PIC microcon-
trollers, an easy-to-use IDE, several hundreds of
ready-to-use functions and many integrated tools
makes Mikro Elektronika compilers one of the best
choices on the market today. Besides mikrolCD,
mikroElektronika compilers offer a statistical mod-
ule, simulator, bitmap generator for graphic dis-
plays, 7-segment display conversion tool, ASCII
table, HTML code export, communication tools for
SD/MMC, UDP (Ethernet) and USB, EEPROM
editor, programming mode management, etc.

Touch screen controller with connector
is available on-board.

Please visit our web page for more info http://www.mikroe.com

SOFTWARE AND HARDWARE SOLUTIONS FOR EMBEDDED WORLD

2/2008 - elektor

13

INFO & MARKET

NEWS & NEW PRODUCTS

Technology Highway at Nepcon UK

Powered By

g \ v 71 S / li /M V 7

J

NEC2008

(o •

29TH APRIL - 1ST MAY 2008* NEC www,nepeon.co.uk

{r

THE UK EVENT FOR THE ELECTRONICS INDUSTRY

Nepcon UK invites exhibitors to
step on board the 'Technology
Highway' - where AOI and X-
Ray Inspection will be firmly in
the headlights for the 2008 event.
From the entrance to the Nepcon
event and running right through the
hall, this hands-on feature will be
visible to visitors from the moment
they step onto the show floor.

The Technology Highway will pro-
vide an exclusive opportunity to
view a whole range of AOI and X-
Ray equipment used across the pro-
duction line. As visitors make their
way along the Highway they will
be able to see equipment in action

and quiz technical operators from
participating companies — with
stands adjacent to the Highway
— on issues which affect their in-
dividual manufacturing process.
Towards the end of the highway
populated boards will be tested
by both low and high volume sys-
tems, with real time data being col-
lected from the inspection process.
This invaluable information will be
made available to visitors to assist
them in their purchasing decisions
according to their budget.

The Technology Highway will be
the central feature at the UK's na-
tional electronics manufacturing

event, providing participating ex-
hibitors with a unique occasion
to display equipment and to dem-
onstrate capabilities to key indus-
try buyers, alongside competitor
products.

A 'Technology Highway Inspec-
tion Guide' featuring information
on participants' products will be
made available prior to the show,
and handed out to visitors during

the 2008 exhibition. For more in-
formation on how to take part in
the Technology Highway, call the
Nepcon team on +44 (0)20 8910
7706.

Nepcon will take place 29th April
- 1st May 2008 at the Birming-
ham NEC in Hall 20.

www.nepcon.co.uk

(070996-VI)

CAN for long-wire and low speed industrial apps

AMI Semiconductor (AMIS) has an-
nounced an ASSP family for long-
wire and low baud rate Controller
Area Network (CAN) applications.
Designers now can use a qualified
and proven CAN transceiver for
very long wires and/or low baud
rates, enabling the use of CAN-en-
abled equipment in industrial ap-
plications requiring line lengths in
excess of 500 meters.

Available in 3.3 V and 5 V inter-
face variants, the new ASSP family
includes a device with a functional-
ity that automatically adapts com-
munication rates to the observed
line speed. In addition, all of AMI
Semiconductor's CAN
transceivers have exceptional over-
voltage protection on the CAN bus
of +/-45 V (common mode).

The CAN protocol requires an in-
frame response which, for long

wires, is achieved by reducing
transmission speed. However, at
low speeds (below 60 kbaud),
a timeout system limits CAN use
and hence line length. To support

long-wire CAN communications in
industrial applications, AMIS has
extended its CAN product line by
providing versions with adapted
time-out function for all of its long-

wire CAN transceiver products.
The AMIS long-wire CAN trans-
ceiver ASSPs target end applica-
tions with wired communication in
physically long or distributed sys-
tems. Examples of these systems
include elevators, security moni-
toring systems, in-building com-
munication, building control, proc-
ess control, machine control, and
HVAC systems.

There are five members of the long-
wire high-speed CAN transceiver
family: AMIS-42670 (5V), AMIS-
42671 (3.3V, auto-baud rate),
AMIS-42673 (3.3V), AMIS-42675
(low power) and AMIS-42770
(CAN repeater).

www.amis.com

(070996-VIII)

LEDs for railway applications

Historically LEDs have been per-
ceived as difficult to use, requiring
a range of power supplies, drivers,
resistors, soldered connections,
making them tricky to market in
railway applications. CML-IT's new
Connect&Glo© program is de-
signed to make solid state lighting
easy, and is changing this percep-
tion. The company is offering a sys-
tem of linking LED lighting units that
anyone can connect together, just
as easily as ordinary light bulbs.

LED lighting modules from CML-IT
allow the environmentally friendly

replacement of inefficient incandes-
cent lighting and offer increased
performance, increased life of
approximately 50,000 h against
3,000 h for traditional incandes-
cent lights, reduced maintenance
and up to 80% reduction in energy
consumption. When total life costs
of lighting systems are considered,
modern LED-based lights nowadays
already come at a comparable cost
to traditional incandescent lights.

Part of the Connect&Glo© pro-
gram and specifically targeted at
train interiors is the Acsentio series

of LED accent lights. Easy to fit and
install, the lights feature an internal
heat management system enabling
them to run at relatively low tem-
peratures. Acsentio offers subtle
shades of light and are available in
blue, red, green, yellow and white
as part of a complete LED-based in-
terior lighting system for commuter
and underground trains.

Also part of the Connect&Glo©
program from CML-IT are LEDules,
a behind-the-scenes system of LEDs
mounted on PCBs in a whole variety
of shapes and sizes and designed

to allow designers to mount lighting
into whatever shape is available.
LEDules feature 1 , 3, 4, 8, 9 or 1 4
watt power and a consistent unit-to-
unit colour temperature. Available
colours are cool white, warm white,
blue, cyan, green, amber and red.
A new RGB version (featuring red,
green and blue LEDs) enabling
subtle colour changing for 'mood'
lighting applications has also been
added to the range.

www.cml-it.com

(070996-IX)

14

elektor - 2/2008

The No Compromise
o PC Oscilloscopes

250 MHz bandwidth
1 GS j>. real-time sample rate
123 mega sample record length

O With da is-Eeading bandwidth* sampling rate, memory depth aod an Array of Advanced high-end features, the
PicoScope 5000 PC Oscilloscopes give you the features and performance you need without any compromise.

The P'-co Scope 3000 Ser et of oscilloscopes from Pico TechnoFogy

Advanced Triggers

In addition to the si andard triggers the PicoScope 5000 series comes as
standard with pulse width, window, dropout, delay, and logic level triggering.

250 MHi Spectrum Analyser
High-speed USB 2*0 Connection
Automatic Measurement!

Arbitrary Waveform Generator

Dcfme your own waveforms or select from 0
predefined signals with the 12 bit, 12 5 MS/s

■irbilr.iry w^vr'forrn gi , *n , r .liar,

Waveform Playback Tool

Pic.dk ope sofvwiu'o now
allows you to go back, review,.
W and analyse up to 1000 capture?
vrirhln In waveform play bade wot.

Technology

in: ludi-V j^i j niT.il ptFpOS^ and h^h resoluilofl hkhMs: Wi|h 12 bll
resolution and 11b accuracy, the lOMHi RicoScupc 3*121 is able to detect
changet as small m 0.024^ (244ppm) - making it ihr ideal 4-chflnftti
oscilloscope for analog dc-s- jjn and analysis. The MjjJwt
speed B bit imsdds m the FkcoScopc 3000
senes u ra i sampi r r. -. :- u j 1 :■

20GM5/S and up to 1 M5/s record le^Lhs
for p^eneral purpose nod portable
applications.

. The PicoScopc 2000 series oscilloscopes
offer single and dual channel units

Thai offer highly ^

portable/ tow cost solutions Jo general purpose testing The
award winn ng 2 SM I \? handheld PscoScope 210^ fits ft R

comfortably Imo die palm of your hand yet tnil indudct m J

the powerful Fcalurcs Found in larger osc bioscopes.

www.picotech.com/scope452

to check out our full iin^ of PC-based instruments or call 01480 396 395 for information and a product catalogue

SURROUND LIGHT SYSTEMS

Due to the fact that we received two circuit designs for television mood lighting and they both fit with
the theme of this issue, we initiated a unique Elektor project: in this issue we present two completely
different designs that produce nearly the same effect. Our French contributor Alex Vercey took the
analogue approach, while Steffen Schulte from Germany went the 'microcontroller way 7 .

16

elektor - 2/2008

The analogue approach

Surround

Alex Vercey, alex.vercey@wanadoo.fr

When Philips launched the Ambilight system
for its television sets in 2004, the author
immediately had the idea of
building a similar system
for PCs. The result
is described
here.

The operating principle of both de-
signs consists of measuring the aver-
age colour of an image and using col-
our LEDs to emit the same colour in
order to ‘paint’ an impression of the
image on the background behind the
screen. This generates a more intense
experience, creates a visual point of
reference, and produces refined mood
lighting.

The target audience for this product
consists of dedicated film fans and vo-
racious gamers.

Technical considerations

In its product, Philips uses a spectrum
analyser integrated in the video matrix
processor. This method is only used
with LCD and plasma displays. The
control logic of non-scanned displays of
this sort allows digital analysis of the
signal based on the individual regions
of the internal display driver matrix.
Philips originally used a system with
small neon tubes and an acrylic reflec-
tor to diffuse the light. However, LEDs
are used in the latest models. The sys-

tem uses three basic col-
ours controlled by pulse-width
modulated (PWM) signals with a res-
olution of only four bits.

The design described here operates on
a different principle, with the objective
of achieving better reproducibility. In
addition, the system described here
can also be used with a PC or a raster-
scan monitor (an ‘old-fashioned’ CRT
monitor).

The system described in this arti-
cle is the PC version of the Surround
Light design. The television version is
more complex, primarily due to safety
considerations rather than technical
issues.

The Surround Light system consists of
a three-colour LED lamp driven by ana-
logue signals, which allows all possible
colour combinations (14 billion) to be
generated from the three basic colours.
For comparison, the software-control-
led version uses an ADC and PWM sig-
nal with 16-bit resolution, which yields
65,536 possible colours.

Three identical circuits are used for
the LED drivers (one for each colour).

However, different calibration curves
are used for the individual colours to
adapt the visually perceived colours to
the spectrum of the LEDs used in the
system.

As specified by the CCIR VGA stand-
ard, the maximum amplitude of a PC
video signal (700 mV) corresponds to
a full white image. This was confirmed
by measurements made using a Geo-
force FX7300 card. There is also an op-
tion for isolation of the input signal.

As a minor detail, this system (un-
like the Philips system) does not sup-
port generation of different colours on
the left and right sides of the monitor,
since this would require a much more
complicated colour analyser.

LEDs are active semiconductor de-
vices with a non-linear response to an
electrical signal, and they are current
driven instead of voltage driven. This
means that the brightness of a LED
cannot be controlled by adjusting the
supply voltage.

In theory, it would be possible to vary
the intensity of a LED by very accu-
rately adjusting the voltage across the

2/2008 - elektor

17

SURROUND LIGHT SYSTEMS

LED, but this approach has a very small
tolerance and essentially requires indi-
vidual calibration of each type of LED
in order to obtain good results.

For this reason, current control is used
here, which allows any desired type of
LED to be used with an assured output
control range of 0 to 100%.

Protection

The LEDs used in the prototype be-
came hot when stationary white are-

as were present in the image (such as
during word processing, working with
text windows, or Web browsing), and
in such situations mood lighting is any-
how not especially meaningful.

For this reason, the whiteness of the
image is measured and after a suitable
delay the brightness of the LEDs is re-
duced by decreasing the drive current
supplied by the MOSFET.

Each colour is measured, and if white
is detected a timeout is initiated us-
ing a capacitor charging circuit and
a reference voltage, and a protection

circuit is triggered at the end of a de-
fined time. This is a distinctly analogue
approach.

This timeout is only necessary to avoid
restrictions on the system when a sta-
tionary white image is displayed.

The timeout is approximately 20 sec-
onds, which is long enough to ignore
‘white’ sequences in films.

The discharge time (after the screen is
no longer white and the Surround Light
can thus return to normal operation) is
the same to keep things simple, and it

avoids flickering when changing win-
dows in an office application.

Block diagram

The block diagram in Figure 1 is rel-
atively complex. This arises from the
processing of the video signal, which
is received in VGA or X-XGA format.
The signal first passes through a buff-
er. It is then amplified using a precise-
ly defined gain. The resulting signal is
clipped in a block that uses a diode.
After this, the signal is fed to a resis-

tor network to limit the rising edges of
the signal with high-resolution video
(1600 x 1200).

An RC network integrates the signal
to obtain the average voltage (the col-
our signal resulting from this process),
which is fed to an adjustable voltage
divider.

The LEDs are driven by a voltage-to-
current converter with a MOSFET
power stage.

Finally, the protection circuit responds
to detection of a stationary image and
the output level of the voltage regula-
tor. If the supply drops too low or the
regulator malfunctions, the LED drive
current is reduced to prevent damage
due to an unstable supply voltage or
an inappropriate image. The overall
transfer function of the system can be
described with the following formula:

(V inp ut - 2 x 18.49 - 1.2 V) - 9.33

Schematic diagram

The schematic diagram in Figure 2
shows the functional elements of the
block diagram in more detail. Let’s ex-
amine the technical aspects of some of
them more closely.

Video input and clipping (A)

The input impedance is 10 kQ to 22 kQ,
depending on the fitted resistors. This
value provides a good match to the am-
plifier input, avoids overloading the
output of the graphic card, and avoids
distortion of the video signals due to
excessively low parallel impedance.
The input circuit attenuates the signal
by 50% because the serial and parallel
resistors have the same value.
Jumpers are fitted at the input. They
can be replaced by serial capacitors
if clamping is necessary. Clamping is
optional because it is not compatible
with the video signal, but it may be
necessary in some cases.

The gain (kl) is determined by the col-
our threshold value, which is set to
1210 mV by two 1N4148 diodes con-
nected in series (this approach was
chosen because it provides a stable
threshold value). This value must cor-
respond to 15% of the nominal signal
voltage. This is the key to the entire
design, and maintaining a threshold
level of 15% of the dynamic range of the
signal is essential for good results. We
can now calculate the gain as follows:
1210 mV across the series-connected
diodes = 15% of (350 mV x kl)

This yields a value of 18.49 for kl.

This must be increased to compensate

070491 - 12

Figure 1. Block diagram of the Surround Light. Although the block diagram of the analogue version of this system looks much more
complicated than its digital counterpart, the circuit is a lot smaller than you might expect.

18

elektor - 2/2008

K5 RIO

Figure 2. Schematic diagram of the Surround Light. You can easily see the various functions of the block diagram here.

2/2008 - elektor

19

SURROUND LIGHT SYSTEMS

Table 1 . Power dissipation of the driver transistors at various LED voltages.

Minimum

Average

Maximum

LED

voltage

Power

LED

voltage

Power

LED

voltage

Power

Red LED

2.31 V

1.254 W

2.95 V

870 mW

3.51 V

534 mW

Green LED

2.79 V

966 mW

3.42 V

588 mW

4.23 V

102 mW

Blue LED

2.79 V

966 mW

3.42 V

588 mW

4.23 V

102 mW

for the loss over the diodes that pro-
vide the threshold value.

The SENSE lines are connected to the
watchdog circuit, which monitors the
average input voltage to see whether
it rises above 600 mV. If it exceeds this
value too long, the LEDs are placed in
the protected mode.

Signal integration and converter ad-
justment (B)

The signal must be integrated before
it is fed to the input of the voltage-to-
current converter. The integration time
constant is matched to the timing of
the line pulses. The raster line puls-
es cause relatively weak modulation
of the current, which is nevertheless
sufficient to reduce the average pow-
er dissipation of the LEDs. (The LEDs
used here are not suitable for pulse-
mode operation.)

The time required to charge to 2/3 of
the maximum level is 650 [is with com-
ponent values of 10 kQ and 100 nF,
which is sufficient to eliminate the line
sync pulses from the VGA signal.

The corresponding discharge time is
100 [is due to the presence of R53 in
the voltage divider formed by R14 and
R53. This value produces only a small
delay in determining the colour (due to
the total capacitance of the measuring
chain), so the system has a sufficiently
short response time.

Drive circuits for the LUXEON K2
LEDs (C)

As already mentioned, the LEDs are
operated under current control. The
LEDs are powered from the 5-V sup-

ply voltage with an average current of
less than 700 mA (or 2.1 A peak if you
ignore the breaks during the video sig-
nal flyback intervals).

The individual LEDs are driven by
emitter followers (T1-T3) that form cur-
rent sources in combination with the
opamps in IC2.

The value of resistor R22 is small
enough to supply sufficient current to
T1 and large enough to limit the cur-
rent from the opamp if no load (LED)
is connected. The voltage rises to the
maximum value when the output of the
amplifier is open-circuited.

The LED current is sensed by resistors
R25, R26 and R33 in the emitter circuit
of the transistor, which also conduct
the base current. The sensed value is

j'led = J c + 2 B’ so j b mus t be kept as
small as possible to avoid adverse-
ly affecting current sensing: (i Bmax =

J Cmax Vnn) = 700-60 = 11 mA max,
or 1.57%).

The transistor type used here is de-
signed for operation with a small V CE ,
so it does not lose much of the 5 V even
when in saturation. This ensures that
there is sufficient voltage available for
the LED.

The design value of the sense voltage
is around 500 mV at the rated current,
which yields a power dissipation of
350 mW in the resistors. A larger re-
sistance would yield somewhat better
accuracy, but it would also increase
the power dissipation.

The transistors are thermally coupled
to a copper plane on the PCB with an
area of approximately 7 cm 2 to improve
cooling.

The nominal dissipation depends
on two parameters: the actual cur-
rent through the LED and the voltage
across the LED.

With regard to thermal dissipation at
25 °C, the manufacturer’s data sheet
indicates that the power is approxi-
mately 500 mW per transistor at maxi-
mum brightness (with an average volt-
age of 3.75 V at 650 mA). The thermal
coefficient of the transistor is 6.25 K/W,
which would yield a temperature rise
of 3.5 °C with an ideal heat sink.

The thermal resistance from the PCB to
the air is not known, so the maximum
temperature rise is not known precise-
ly. An estimate based on the copper
area on the PCB and the total volume
of copper yields a value of 45 °C/W,
which yields a maximum temperature
rise of 24.5 °C (plus 3.5 °C due to the
thermal resistance of the package), or
0 amb + 24.5 °C.

Transistor derating and possible effects
from the power dissipation of adjacent
devices have been ignored here.

Power dissipation

Each transistor dissipates a power P
proportional to the current level:

P = (5 V — V LED — V SEN ) x i
The power dissipation of the driver
transistors at various LED voltages is
shown in Table 1 for a LED current of
600 mA, a supply voltage of exactly 5 V,
and V SEN = 500 mV.

Protection circuit

The circuit is protected against station-
ary images on the monitor. There is not
much point in mood lighting for office
applications, so the current is reduced
in such situations to minimise power
dissipation and increase the useful life
of the LEDs.

The protection circuit is triggered
when a very bright image is present
for longer than a defined time. When
this occurs, the current through the

LED specifications

LUXEON K2

Basic colour

Royal Blue

Green

Red

Blue

Red-Orange

Max. continuous current [mA]

1 500

1 500

700

1 500

700

Continuous voltage [V]

3.85

3.85

3.4

3.85

3.4

Effective continuous voltage [V]

3.2 V @350 mA

3.2 V @310 mA

2.56 V @230 mA

3.5 V @280 mA

2.7 V @190 mA

Wavelength [nm]

455

530

630

470

617

Luminous flux [lumen]

250 mW/rad.

130

75

46

100

Total included angle [°]

160

140

140

140

140

With the LUXEON configuration , Red-Orange is preferable to Red and Blue is preferable to Royal Blue.

20

elektor - 2/2008

XX Xx XX

Figure 3. The component layout of the main circuit board...

LEDs is reduced by a factor of 10 and
the power dissipation remains below
1 W (with a 5-V supply voltage).

Detection

The image is considered to be very
bright if all three colours have high

levels at the same time. A circuit with
three transistors measures these high
levels approximately, since the detec-

COMPONENTS LIST

Resistors

R1 -R6,R1 4,R1 5 / R20 / R39 / R52 / R61 / R62 / R65 / R
66,R67 = lOkD (SMD 1206)

R7 / R8 / R9 / R1 3,R1 7,R1 8,R1 9,R3 1 ,R49,R50,R5
1,R57 = 3kD9 (SMD 1206)

R1 0,R1 1 ,R1 2 = 68kD (SMD 1 206)

R1 6,R53,R56 = 1 l<D (SMD 1206)

R2 1 / R32 / R43 / R45 / R47 / R54 / R60 = 4kD7
(SMD 1 206)

R22 / R23 / R24 / R36 / R40 / R41 / R42 / R58 = 1 kD
(SMD 1 206)

R25 / R27 / R29 = 6D8 (SMD 2512)
R26,R28,R30,R33,R44,R46 = 1D8 (0207)
R34 = 220I<D(SMD 1206)

R35 = 1MD (SMD 1206)

R37,R59 = 680D (SMD 1206)

R38 = 47kD (SMD 1206)

R63 = 2kD2 (SMD 1206)

R64 = 6kD8 (SMD 1206)

R68 = ID (SMD 1206)

R48,R55,R69 = 75D (SMD 1206)

PI = lOkD
P2 = 1 kQ

Capacitors

Cl-C4 / C7-C12 / C14 / C15 = lOOnF
(SMD 1206)

C22 = lOnF (SMD 1206)

C21,C23 = InF (SMD 1206)

C16 = 470pF (SMD 1206)

C5,C1 3,0 7-C20 = 1 OO/iF 25V
C6 = 1 0jL/F 25 V

Inductors

LI = 47/Jh (Wurth 12x12)

L2-L5 = choke, 91 D @ 100 MHz
(SMD 1 808)

Semiconductors

01-08,011-014,021,022 = LL4148 (SMD
SOD-80)

D9,D1 0,D1 6,D20 = BZX84C5V6 (SMD
SOT-23)

D17,D18,D19 = LED, 3mm, red
D23= RS3K (SMD SMC)

D15,D24 = 30BQ040 (SMD SMC)

T1,T2,T3 = MJD44H1 1 (SMD DPAK-N)
T4,T5,T6 = FDS6630 (SMD SO-8)

T7-T1 2,T1 4 = BC817 SMD SOT-23)

T1 3 = BC807 (SMD SOT-23)

IC1 ,IC2 = LM324 (SMD SOU)

IC3 = LM2592 (SMD SOT-263)

D25 = Luxeon LED, red (LXK2-PD1 2-R00)
D26 = Luxeon LED, green (LXK2-PM1 4-U00)
D27 = Luxeon LED, blue (LXK2-PB1 4-N00)

Miscellaneous

51 = single-pole on/off switch (Farnell #
9575502)

52 = 4-way DIP switch

K1 = 4-way SIL pinheader
K2,K3 = 5-way DIN socket
K4 = DC supply socket, PCB mount
K5 = VGA socket, PCB mount
K6 = SCART socket, PCB mount
FI = fuse, 1A slow, with PCB mount holder
Enclosure, e.g. Vero # 1 6-3638089
PCBs # 070491-1 and 070491-2, see Ele-
ktor Shop section or www.elektor.com

2/2008 - elektor

21

SURROUND LIGHT SYSTEMS

Figure 4. ...and the LED circuit board.

tion circuit is not thermally stabilised
in order to keep the circuit simple.

A digital signal indicates whether a
bright image has been detected.

A diode connected across the base-
emitter junction of each detection tran-
sistor protects the transistor if there
are problems with the video signal
(such as a negative signal level due to
poor clamping).

Timeout delay

The timeout delay is implemented very
simply using an RC network with a bi-
nary comparator. The threshold level of

Our first prototype. All connections are at the rear.

the delay circuit can be adjusted using
trimpot RV1, but the actual time delay
is not adjustable. The switch-on delay
is much shorter than the switch-off de-
lay. In other words, if moving imagery
appears on the screen again, the LEDs
will start operating again relatively
quickly. This rapid return to normal
operation is only necessary to prevent
flickering when switching between
windows on the PC.

Diode D4 prevents C5 from discharging
via IC2d if the IC is not powered, in or-
der to avoid damage to the IC.

Current limiting

The current flowing through the LEDs
is limited by modifying the operation
of the drive circuits. During normal op-
eration the current limiter is not active,
and it holds the MOSFETs in the ful-
ly conducting state with low source-
drain resistance (-R DS on)- This increases
the current level due to the relatively
low resistances connected in parallel
across the current-sense resistors.
When current limit protection is acti-
vated, the MOSFETs are switched off
and the full LED current flows though
a larger resistance (R29), so the nomi-
nal voltage across the sense resistor is
obtained at a lower current level.
When current limiting is active, the
current level is set by R29 alone, while
in normal operation it is set by R29 and
the parallel combination of R30 and
R46 via the MOSFET (to use a simpli-

fied analysis).

If desired, the two parallel resistors can
be replaced by a single resistor rated
at 0.82 Q / 1 W. For the sake of conven-
ience, the author used two 1.8-Q resis-
tors in parallel to obtain an equivalent
resistance of 0.9 Q, but a single resis-
tor rated at 0.82 Q/1W would work
just as well. The current is 600 mA
at 500 mV, which is not especially
worrisome.

A Tyco RL733A R82 would be perfect
for this application.

Supply voltage protection

If the supply voltage for the LEDs ris-
es too high, protection is triggered by
a circuit that detects an overvoltage
condition on the 5-V supply line. This
would cause excessive dissipation in
the supply circuitry, which is not good
for the circuit. The temperature must
also be kept below 60 °C everywhere in
the circuit to avoid the risk of burns.
The detection threshold voltage is
V Dz 20 +1.2V = 6.8V
The supply voltage protection circuit
(built around T12 and T13) generates a
signal that causes the MOSFETs to be
switched off using the same arrange-
ment as for current limiting with a sta-
tionary image. Resistors R58 and R58
provide a path for the leakage current
of the Zener diode next to the voltage
sense transistor.

Photo of the printed circuit board with three LEDs. This requires
a bit of mechanical assembly skill.

22

elektor - 2/2008

Use of the LUXEON K2 LED

The principal model employs a system with three discrete LEDs type LUXEON K2 Power.

The mounting of the LEDs on aluminium pads is identical to the previous model because the
metal part on the board has been designed for compatibility with both systems.

Only the LED current is changed to fall within a range of 300 to 700 mA (per LED), with the
Philips LUXEON chip capable of carrying this current and outputting very bright light at no less
than 3 x 75 lumens.

Chromatic rebalancing may be viable by trial and error. The initial values are those resulting
from tests with the triple LED (PROLIGHT).

Characteristics of PROLIGHT power LEDs

Total included angle:

Power:

Current :

Wavelength:

Luminosity:

140°

red = 2.2 V blue = 3.55 V

350 mA max. for each colour
red = 625 nm green = 530 nm

red = 30 lumen green = 30 lumen

green = 3.55 V

blue = 470 nm
blue = 1 0 lumen

Supply voltages

The circuit has three types of on-board
supply voltages, all derived from the
main supply voltage obtained via pow-
er connector K4:

• Stabilised reference voltages

• A filtered supply voltage for the
opamps

• A high-power supply voltage for the
LEDs

The stabilised voltages are generat-
ed locally using Zener diodes. Most
of them are reference voltages for the
comparators. The main -I- 12 V sup-
ply voltage comes from an AC mains
adapter, or it can be taken directly from
the PC. This voltage is stabilised ex-
ternally, and the circuit includes a fuse
(FU3) and a diode (D23) for reverse-po-
larity protection.

The LEDs are powered from a much
lower voltage in order to minimise the
power dissipation in the control tran-
sistors, which operate in their linear re-
gion in this design. A switch-mode reg-
ulator is used to provide this voltage in
the circuit described here, and it gen-
erates an accurately stabilised voltage
from the + 12-V supply voltage. This re-
duces the amount of current that has to
be transported by the supply cable and
makes it easier to handle. If the circuit
is built into the PC, a convenient alter-
native is to use the 5-V supply voltage
from the PC power supply.

The switch-mode regulator is built
around a National Semiconductor
LM2592 using a standard design. Ac-
cording to the manufacturer’s data, the
efficiency is nearly 80%.

A standby mode is implemented by
monitoring the voltage on T14 and D26.
The regulator shuts down if the voltage
on the + 12 V line is less than 6 V. The
5-V supply voltage is thus not present
if the 12-V supply voltage is absent or
is too low to ensure correct operation.

Indicator LEDs

The circuit has three indicator LEDs:

• The ‘Power OK’ LED (D17) indicates
that both supply voltages (12 V and
5 V) are present.

• The ‘Over-Video’ LED (D18) indicates
that the video level is too high and the
timeout has been actuated.

• The ‘Protection’ LED (D19) indicates
that current limiting is in effect. It is
lit when the MOSFETs are conducting.
There are two possible causes for this:
either temporary protection due to an
excessive bright image or a power sup-
ply problem.

Mechanical assembly

After all this discussion of theory, it’s
time to turn our attention to something
more interesting.

We designed two PCBs for this project:
the main circuit board (Figure 3) and
the LED circuit board (Figure 4). The
figures show only the component lay-
outs; the copper track layouts can be
downloaded from the Elektor web-
site. You can also order the two PCBs
from the Elektor Shop (order numbers
070491-1 and 070491-2).

Start by assembling the main circuit
board. Solder the components in the
following order: resistors, inductors,
capacitors, diodes, transistors, ICs,
and finally the MOSFETs.

Using a multimeter, check to ensure
that the supply voltage lines are not
shorted anywhere, and check for conti-
nuity between the supply sources and
the positive supply voltage pins of IC1
and IC2.

After fitting all the components, check
everything again for short circuits and
incorrect or incorrectly fitted compo-
nents. Ensure that that the MOSFETs
make good thermal contact with the
associated copper surfaces. This also
applies to the LM2592.

Now it’s time to assemble the LED
board as shown in the photo in Fig-
ure 5. To provide proper cooling of the
LEDs, the LED board is secured to a
heat sink using a DIY clamp fixture.

• Cut a piece of aluminium with the
same thickness as the PCB (1.2 mm) to
dimensions of 20 x 7 mm such that it
fits in the slot in the LED circuit board
(see photo).

• Prepare the heat sink by drilling and

tapping holes for securing the LED cir-
cuit board with the aluminium strip in
between.

• Pre-assemble the board without ap-
plying any pressure to the heatsink
surfaces of the LEDs and solder the
LEDs to their solder pads.

• Loosely fit the assembly to the heat
sink using screws of the right size. You
can optionally place mica insulators
under the LEDs. The mating surfaces
of the components and the heat sink
can be coated with thermal paste (this
is recommended) to improve the ther-
mal contact. Apply only a thin coating,
as otherwise it will be ineffective.
After the LEDs with their mica insula-
tors are properly fitted, carefully tight-
en the screws until they are moderate-
ly tight (to avoid damaging the LEDs).
Take care to avoid applying any force to
the LEDs during this operation. Also be
careful with the diffuser lenses, which
are very fragile.

- Solder four wires (three for the colours
and one for +5 V) to the four solder
pads, and then solder the other ends
to a DIN 5 plug according to the sche-
matic diagram shown in Figure 2.

Set-up and adjustment

• Fit the Surround Light board in an
open plastic box to avoid electrical
contact between the circuit board and
any conductive surfaces.

• Set trimpots RV1 and RV2 to their
midrange points.

• Connect the LED board via the
connector.

• Place the LED board behind the PC
monitor.

2/2008 - elektor

23

SURROUND LIGHT SYSTEMS

• Switch on the Surround Light supply
voltage.

• Connect a cable from the monitor
(VGA) to the Surround Light.

You will need a VGA splitter for con-
nection to the PC.

Now you have to adjust trimpots RV1
and RV2.

• Configure the PC to display a bright
white image on the screen, measure
the currents through the sense resis-
tors (maximum 700 mA), and ensure
that the protection circuit is not acti-
vated (12 V on pin 14 of IC1 - if neces-
sary, turn RV1 back until protection is

no longer active).

• Again display a white image on the
monitor (a picture or Word document)
to adjust the protection circuit for office
applications.

• Using a hair dryer, heat the Surround
Light circuit board to around 35-40 °C
and turn RV1 while measuring the volt-
age on pin 13 of IC1.

• Adjust until you reach the switching
point of the comparator (from 0 V to 12
V, or until the ‘Protection’ LED lights
up).

Verify that the comparator output
switches when the screen display

changes from a picture to the window
of a word-processing program.

Now you’re all set to go. We wish you
many pleasant hours with the Surround
Light in your free time (or at work!).

( 070491 - 1 )

Web Links

LM2592 data sheet:

http://cache.national.com/ds/LM/LM2592HV.

pdf

TV Surround
Light

Steffen Schutte

A while ago the author saw a
demonstration of a Philips
television system equipped
with the Ambilight
system. This lights up
the background with colours
that are dynamically matched to the image
content. The author thought it would be an excellent idea to
create a similar DIY system for mood lighting. No sooner said than done, as
can be seen from the TV Light project described here - a system that is very similar to the now
legendary Ambilight system.

Before starting on this project, the au-
thor ploughed through a whole stack
of specifications for different video sig-
nals. It shouldn’t be all that difficult, he

thought - after all, there are only a few
types of connections: the well-known
Cinch (RCA) sockets and the SCART
connector. All you have to do is to find

out which type of signal is being used
in order to decide how to design a
circuit for TV background lighting as
quickly, simply and inexpensively as

24

elektor - 2/2008

possible.

He gradually realised that the SCART
standard is only a point of reference for
all sorts of signals that are necessary
for connecting various kinds of video
equipment to a television set. To avoid
any misunderstanding, note that the
circuit described here can only be used
with equipment that supplies RGB sig-
nals, in combination with a fully wired
SCART cable.

Due to the complexity of the composite
video signal, it is not possible to use a
direct connection to the yellow Cinch
socket that provides this signal, which
is also present on pin 19 of the SCART
connector. For someone in the author’s
situation (i.e. not an expert in the com-
plicated theory of signal processing),
working with RGB signals is a lot eas-
ier - and it makes explaining the ins
and outs of the circuit easier. See refer-
ence [1] for a summary description of
video standards.

First

considerations

Before delving
in to the details
of the design, we
need to consid-
er what types of
LEDs to use for this
project.

A bit of searching on
the Internet turns up two
usable types of LEDs:

1. SuperFlux LEDs [2] at ap-
proximately 70 p (euro 1.20)
each;

2. LED arrays (light bars with
nine SMD LEDs) at around
£15 (euro 24) per bar.

The SuperFlux LEDS have a luminous
intensity of 10,000 mcd and thus pro-
duce sufficient light (a maximum of six
per section is needed), but they have
the disadvantage that the colour mix-
ing is not homogeneous.

A bit of browsing on the Internet to
find a solution to this problem yielded a
few tips and tricks, such as using bak-
ing paper and hot-melt glue, but they
reduce the brightness too much. The
LED light bars with SMD LEDs provide
a better approach, but they are more
expensive. They operate from a 12-V
supply voltage (with a common an-
ode) and provide a fully homogeneous
colour palette, and they produce even
more light than the SuperFlux LEDs.

Block diagram

The block diagram in Figure 1 shows
that the circuit uses four input signals
taken from the SCART connector of a
DVD player or the VGA connector of a
graphics card in a PC. These four sig-
nals - red (R), green (G), blue (B), and
composite video (C) - are fed to the cir-
cuit via two connectors. All of the sig-
nals received via these two connectors
are processed the same way.

The first three signals contain the
colour information for each scan line,
while the fourth signal (C) is only used
for horizontal and vertical synchronisa-
tion. This means we can use an IC that
is very often used for this purpose: the
LM1881 [3].

As the three colour signals are ana-
logue signals, we have to start by con-
verting them to the digital domain.
This requires a set of A/D converters,
and here we used the Analog Devices
type ADC 1175 [4]. This IC is designed
specifically for digitising video signals

to drive the nine LED sections of the
system, consisting of one section for
each colour (R, G and B) for each of
the three parts of the image. That’s all
there is to be said about the block dia-
gram, so it’s time to turn our attention
to the next topic: the detailed design.

Schematic diagram

The schematic diagram in Figure 2 is
actually just a more detailed version of
the block diagram in Figure 1. If you
glance at the author’s first prototype
shown in the photo, you can recognise
the main features of the block diagram
in Figure 1. From left to right and top
to bottom, you can see the three ana-
logue to digital conversion modules us-
ing the ADC1175 (IC7-IC9). This A/D
converter operates at 20 MHz and has
a resolution of 8 bits.

After building the initial prototype us-
ing several circuit boards interconnect-
ed by a rat’s nest of cables, we could

070487-12

Figure 1. Block diagram of the TV Light. The digital approach to this ambient lighting system boasts two microcontrollers.

and can operate at clock rates up to
20 MHz. As the duration of a television
scan line is 56 jlls, this would in theo-
ry make a resolution of more than 1000
pixels per line possible (or more pre-
cisely, 1120 pixels).

A Microchip PIC18F4550 microcontrol-
ler clocked by the sync signal from the
LM1881 processes the digital data and
uses integration to compute the aver-
age values of the colours in the left, up-
per, and right parts of the image on the
screen These values are passed direct-
ly to a second microcontroller, in this
case a Microchip PIC15F628, which in
turn generates the PWM signals used

test the circuit to determine whether
it worked the way the author intend-
ed. When everything proved to work
properly, we designed a ‘clean’ circuit
board layout that held most of the cir-
cuitry. The A/D converters were placed
on three separate modules, which
were connected to the PIC18F4550 by
lengths of 10-way flat cable.

To make the final version of the circuit
more suitable for DIY construction, we
put everything on a single printed cir-
cuit board for the Elektor version to
eliminate the need for complicated in-
terconnections. The input signals are
received via a SCART connector (K2)

2/2008 - elektor

25

SURROUND LIGHT SYSTEMS

Figure 2. Schematic diagram of the TV Light. You can easily see the various functions of the block diagram here.

26

elektor - 2/2008

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Figure 3. PCB layout for the TV Light circuit (reduced scale). Note that two positions are provided for components IC7 to IC9.

or VGA connector (K3).

Now let’s work through the schematic
diagram from left to right and top to
bottom. The system clock is provided
by IC4, a type ICS502 [5]. This IC con-

tains a PLL circuit that oscillates at
20 MHz thanks to crystal XI. The ‘in-
ter-PIC ’ traffic is handled by five signal
lines comprising a clock line and a line
for each of the four data bits. There are

also 18 clock signals for the nine LEDs.
The final clock pulse is held at a high
level for a slightly longer interval to en-
sure proper synchronisation.

The LM1881 (IC6) does exactly what

COMPONENTS LIST

Resistors

R1 ,R5-R20,R22-R29,R40,R42-R47,R54,R59,R
63,R68,R72,R77 = 100D
R2,R3 = 22Q
R4,R21,R30,R39, = 4kD7
R31 -R38,R41 = 180D
R48 = 680Q
R49,R52,R61 ,R70 = 75D
R50 = 620D
R51 = 680kQ
R53,R62,R71 = 3kQ6
R55 / R64 / R73 = 1 20Q
R56,R65,R74 = lOkD
R57 / R66 / R75 = 8kD2
R58,R67,R76 = 220D
R60 / R69 / R78 = 47D

Capacitors

C3 = 470nF

C4,C5,C7,C8,C1 0-C1 4,C21 ,C22,C23,C30,
C31,C32 = lOOnF

C9 = 560pF
C1,C20,C29 = lOOpF
C2,C1 5-C1 9 / C24-C28 / C33-C36 = 10jL/F
25V

C6 = 220a/F 25V

Semiconductors

D1-D4 = LL4148

D5 = LL4007 (SOD- 106)

D6 = LED, 5mm, red
T3,T6,T9 = BC857
T1 ,T2,T4,T5,T7,T8 = BC847
IC1 = PIC1 8F4550-I/F) programmed, Elektor
Shop # 070487-41

IC2 = PIC1 6F628-20I/8 programmed, Ele-
ktor Shop # 070487-42

IC3 = ICS502 (S08)

IC4 = 7805

IC5 = 74AC00N (DIPT 4)

IC6 = LM1881 (DIP8)

IC7,IC8,IC9 = ADC1 175
IC10-IC18 = CNY17-1
XI = 20 MHz

Miscellaneous

SI ,S2,S3 = 2-way SIL pinheader
(pushbutton)

54 = 4-way DIP switch

55 = single-pole on/off switch (Farnell #
9575502)

K1 = DC supply socket, PCB mount
K2 = SCART socket
K3 = VGA socket

JP1 ,JP2 = 2-way SIL pinheader with jumper
K4,K5 = 5-way SIL pinheader
K6 = USB-B socket
K7 = connector (optional)

K8,K9,K10 = 5-way DIN socket
PTC = Current protection (PTC660 or wire
link)

Enclosure, e.g. Vero # 16-3638089
PCB # 070487-1 , see Elektor Shop section
or www.elektor.com

Project software; PIC source and hex files in
archive # 070487-1 1 .zip, free download
from www.elektor.com

2/2008 - elektor

27

SURROUND LIGHT SYSTEMS

Reset button
pressed

070487 - 13

Figure 4. Summary of the functional modes of the TV Light.

it is designed to do: extract the sync
signal from the composite video signal.
The signal provided by this IC goes
straight to the first PIC (IC 1), which is
the ‘brain’ of this complex design.

The four-way DIP switch (S4) can be
used to connect termination resistors
to the signal lines of the input connec-
tors (SC ART and VGA). They have the
same effect here as in the Surround
Light circuit described elsewhere
in this issue. When the switches are
open, the inputs have a relatively high
impedance. When they are closed, the
input impedance is 75 Q.

The supply voltage for the circuit is pro-
vide by a 7805T (IC3) using a conven-
tional circuit design that hardly needs
any comment. LED D6 on the front side
indicates that the supply voltage is
present. Switch S5 can be used to se-
lect one of two supply voltage sources.
This allows the supply voltage to be
taken from a USB port if the TV Light
is used in combination with a PC. The
supply current is drawn via a thermis-
tor that interrupts the supply voltage if
the current becomes too large.

The red, green and blue LED light bars
are connected to the system via 5-way
DIN connectors (K8-K10). This method
ensures reliable connections. Optocou-
plers IC10-IC18 provide galvanic isola-
tion between the circuit and the LED
light bars.

PCB

If you look at the PCB layout in Fig-
ure 3 (designed using Layo 1 PCB),
you can see right away that it uses
quite a few SMD components. Due to

possible availability problems with
the ADC 1175, the board is designed to
accommodate two different SMD ver-
sions: JM and TC. The locations on the
PCB for the smaller version (TC) are
marked with an ‘A’ .

As this circuit operates using high-fre-
quency signals, a large ground plane
extending over the entire board is pro-
vided on the component side. Ground
plane areas are also placed beneath
the connectors on the other side.

Assembly

Successful completion of this project re-
quires a certain amount of experience
in handling SMD devices. For readers
with relatively little experience, we of-
fer a PCB with all of these components
pre-assembled (order number 070487-
91), so all you have to do is solder the
connectors and operator control com-
ponents. Preprogrammed PIC micro-
controllers are also available from the
Elektor Shop (070487-41 and -42).
With the exception of a few ICs and
connectors, all of the components are
SMD types. It is thus important to al-
ways check everything that has to be
done at each stage of assembly. Pay
particular attention to correct orienta-
tion of the SMD ICs, since unsoldering
incorrectly fitted IC can cause damage
to the tracks on the PCB. Soldering the
smaller version of the A/D converter re-
quires special care to avoid producing
shorts that will subsequently have to
be eliminated.

A pair of pushbutton switches must
be connected to the points marked ‘SI’
and ‘S2’. They should be fitted to the
rear panel of the enclosure between
the 12-V power supply connector (Jl)
and the DIN connector for the red,
green and blue LED light bars. These
two buttons, which are labelled ‘Re-
set’ (SI) and ‘Mode/Bootload’ (S2), are
used to select the operating mode of
the unit. This is described in more de-
tail below under the ‘Operating modes’
heading.

Note: jumpers JP1 and JP2 must be fit-
ted (closed) if the LEDs are powered
via supply voltage connector Kl.

Operating modes

The PIC that generates the PWM sig-
nals (IC2) can be programmed using an
ordinary programmer. The second PIC
(the 18F4550) can be programmed us-
ing a USB cable, which is very practical
if you want to develop your own soft-
ware for the TV Light. The circuit can

remain switched on during program-
ming, and you can program the PIC us-
ing a laptop computer next to the tel-
evision set. Naturally, a boot loader has
to be installed first. This is explained
further on in this article.

The first button (SI, Reset) is used to
restart the unit, while the second but-
ton (S2, Mode/Bootload) is used to se-
lect the operating mode after a restart.
You can press the second button dur-
ing a restart to activate the USB boot
loader so you can reprogram the TV
Light circuit, or press it in normal oper-
ating mode to switch between 4:3 and
16:9 image aspect ratios.

The various operating modes are sum-
marised in Figure 4 with associated
comments.

To enter boot loader mode, hold the
Mode button pressed while you switch
on power or press the Reset button.
When you have finished programming
the TV Light via the USB port, press
the Reset button again (this time with-
out pressing the Mode button). In re-
sponse, the TV Light will initialise vari-
ous parts of the circuit and then exe-
cute a test program that switches all
the LEDs on and then switches off the
nine outputs in sequence. This gives
you an opportunity to check that the
LEDs are positioned properly around
the television set. This test is also very
convenient for initial testing of the cir-
cuit after you have assembled the PCB,
especially because it does not require
any A/D conversion or input signals.
After the first test is completed, the
TV Light switches to Light Show mode
with RGB colours. In this mode it runs
through a rainbow cycle with all nine
LED light bars, which is repeated eve-
ry 45 seconds. This low speed lets you
get a good idea of the various colours.
To exit this RGB mode, simply press
the Mode button briefly. This causes
the TV Light to switch immediately to
the normal operating mode, in which
the input signals are sampled and
processed.

With films displayed in wide-screen
format (16:9), it is not advisable to an-
alyse the upper 10 percent of the im-
age. To avoid this, simply press the
Mode button once again. In response,
the program will search for the first
non-black line (note that here ‘black’
is not exactly zero, but instead a very
low value from the A/D converter). The
first non-black line is the uppermost
line that is used for colour analysis
(corresponding to the variable Start-
Line in the code segment detectTop of
the source code).

28

elektor - 2/2008

An example of the LED light bars used in this project.

Development tips and tricks

We are often asked to shed a bit more
light on the design and development
processes of our authors. Some of
the interesting aspects are described
here.

RGB generator (PIC16F628A-I/P)

It is recommended to disable the
brown-out reset while you are pro-
gramming the PIC16F628.

After a bit of experimenting, it proved
to be better to take the supply power
for the LED light bars from a separate
power supply.

It is advisable to use the I/P version
of the PIC16F628A in this circuit be-
cause the PWM signals generated by
a standard 16F628A produce flicker-

not noticeable to the naked eye. If you
want to recompile the loader routine,
you need the full version of the C18
compiler (or an educational version for
a trial period) due to the optimisation
performed by the compiler.

The configuration bits [6] are used to
program the loader.

We hope you have a lot of fun with
your TV Light!

( 070487 - 1 )

TV Light control logic (PIC18F4550)

Almost all pins of the PIC are used
here. As the Microchip loader routine
normally uses RB4, the author rec-
ompiled the code to use RBO instead.
This means that one of the colours has
a resolution of only 7 bits, but this is

ing effects. The
author does not
know the exact
reason for this,
but the I/P ver-
sion is intended for
industrial applica-
tions and is probably
less sensitive to elect
cal noise - and this circuit
generates lots of noise.

Photo of the author's initial prototype. It is somewhat larger than the final version described in this article.

Web Links

[1] www.mediaprofis.net

[2] SuperFlux LEDs datasheet:
www.lumileds.com/pdfs/DS05.pdf

[3] LM1881 datasheet:

http://cache.national.com/ds/LM/LMl 881 .
pdf

[4] ADC1 1 75 datasheet:

http://cache.national.com/ds/DC/DCl 1 75.
pdf

[5] ICS502 datasheet:

www.idt.com/products/getDoc.
cfm?doclD= 1 6325487

[6] www.burger-web.com/Projects/PIC-

1 8F4550USB/en_PICl 8UsbBoard.htm. en

2/2008 - elektor

29

INFO & MARKET

UNIVERSITIES GUIDE

What University

Steve Gold

So you were thinking of studying for an Electronics and Electrical Engineering degree or
similar qualification at a UK university or other higher level educational establishment?
BEng., MEng., perhaps a PhD.? Here at Elektor, we decided to take the pain out of asking the
obvious not so obvious questions with our 3-step primer on the subject: (1) get oriented; (2)
hear opinions and (V9) where to hang out.

1 . www and what / where / who?

Studying at a university or higher educational establishment
offering degree-level (or similar) courses in electronics and
electrical engineering has never been easier in the United
Kingdom.

The availability of low-cost loans (indexed to inflation and
repayable only when obtaining employment with an annual
income of more than £ 25,000, means that the age-related
barriers to study are no longer there.

Students on these courses can now be (and are) of almost
any age and from almost any country, although students
from outside the European Union are generally charged
higher fees.

We looked at six degree educational establishments in
some depth and spoke to their Electronics and Electrical

Engineering course staff.

Whilst the establishments varied in funding and size, their
main attribute — in common with all the colleges and uni-
versities we spoke to when researching this feature — was
high levels of enthusiasm and, despite government cutbacks,
healthy funding in the Electronics and Electrical Engineer-
ing departments.

It's also worth noting that the main table, which shows
the UK establishments offering BEng (Bachelor of Engineer-
ing) and MEng (Master of Engineering) degree courses in
Electronics and Electrical Engineering, and the places avail-
able. The data is based on 2006/2007 figures from HESA
(www.hesa.ac.uk ) and are the latest available at the time
of writing.

30

elektor - 2/2008

Universities in England, Scotland, Wales and Northern Ireland
offering courses in Electronics & Electrical Engineering

England

website

places

Anglia Ruskin University

www.anglia.ac.uk

215

Aston University

www.aston.ac.uk

135

The University of Bath

www.bath.ac.uk

230

University of Bedfordshire

www.beds.ac.uk

5

The University of Birmingham

www.bham.ac.uk

400

The University of Bolton

www.bolton.ac.uk

255

Bournemouth University

www.bournemouth.co.uk

30

The University of Bradford

www.bradford.ac.uk

195

The University of Brighton

www.brighton.ac.uk

90

The University of Bristol

www.bristol.ac.uk

285

Brunei University

www.brunel.ac.uk

275

Buckinghamshire Chilterns University College

www.bcuc.ac.uk

5

University of Central England in Birmingham

www.bcu.ac.uk

820

The University of Central Lancashire

www.uclan.ac.uk

125

City University

www.city.ac.uk

465

Coventry University

www.coventry.ac.uk

190

Cranfield University

www.cranfield.ac.uk

5

De Montfort University (Leicester)

www.dmu.ac.uk

105

University of Derby

www.derby.ac.uk

275

The University of East Anglia

www.uea.ac.uk

5

The University of East London

www.uel.co.uk

190

The University of Essex

www.essex.ac.uk

135

The University of Exeter

www. exete r. a c . u k

45

The University of Greenwich

www.gre.ac.uk

270

University of Hertfordshire

www.herts.ac.uk

420

The University of Huddersfield

www.hud.ac.uk

370

The University of Hull

www.hull.ac.uk

95

Imperial College of Science, Technology & Medicine (London)

www.imperial.co.uk

505

The University of Kent

www.kent.ac.uk

170

King's College London

www. kcl.ac.uk

175

The University of Lancaster

www.lancs.ac.uk

40

Leeds Metropolitan University

www.leedsmet.ac.uk

25

The University of Leeds

www.leeds.ac.uk

260

The University of Leicester

www.leicester.ac.uk

1 10

Liverpool John Moores University

www.ljmu.ac.uk

260

The University of Liverpool

www.liv.ac.uk

255

London Metropolitan University

www.londonmet.ac.uk

240

London South Bank University

www.lsbu.ac.uk

225

Loughborough University

www.lboro.ac.uk

420

The Manchester Metropolitan University

www.mmu.ac.uk

250

The University of Manchester

www.manchester.ac.uk

465

The University of Newcastle-upon-Tyne

www.ncl.ac.uk

170

The University of Northumbria at Newcastle

www.northumbria.ac.uk

45

The Nottingham Trent University

www.ntu.ac.uk

65

The University of Nottingham

www.nottingham.ac.uk

380

Oxford Brookes University

www.brookes.ac.uk

180

The University of Plymouth

www.plymouth.ac.uk

155

The University of Portsmouth

www.port.ac.uk

515

Queen Mary and Westfield College of London

www.qmul.ac.uk

210

Ravensbourne College of Design and Communication

www. rave.ac.uk

85

The University of Reading

www.reading.ac.uk

280

The University of Salford

www.salford.ac.uk

30

Sheffield Hallam University

www.shu.ac.uk

265

The University of Sheffield

www.shef.ac.uk

365

Southampton Solent University

www.solent.ac.uk

60

The University of Southampton

www. soes . soto n . a c . u k

380

Staffordshire University

www.staff.ac.uk

80

The University of Sunderland

www.sunderland.ac.uk

60

(continued overleaf)

2/2008 - elektor

31

INFO & MARKET

UNIVERSITIES GUIDE

The University of Surrey

www.surrey.ac.uk

355

The University of Sussex

www.sussex.ac.uk

120

The University of Teesside

www.tees.ac.uk

240

Thames Valley University

www.tvu.ac.uk

5

University College London

www.ucl.ac.uk

170

The University of Warwick

www.warwick.ac.uk

215

University of the West of England, Bristol

www.uwe.ac.uk

170

The University of Westminster

www.wmin.ac.uk

235

The University of Wolverhampton

www.wlv.ac.uk

15

The University of York

www.york.ac.uk

335

Wales

University of Wales, Aberystwyth

www.wales.ac.uk

65

University of Wales, Bangor

www.bangor.ac.uk

70

Cardiff University

www.cf.ac.uk

230

University of Wales Institute, Cardiff

www.uwic.ac.uk

75

University of Glamorgan

www.glam.ac.uk

200

The North-East Wales Institute of Higher Education

www.newi.ac.uk

55

Swansea Institute of Higher Education

www.sihe.ac.uk

20

University of Wales, Swansea

www.swan.ac.uk

145

Scotland

1740

The University of Aberdeen

www.abdn.ac.uk

no

University of Abertay Dundee

www.abertay.ac.uk

35

Bell College (Note 1 )

www.paisley.ac.uk

5

The University of Dundee

www.dundee.ac.uk

60

The University of Edinburgh

www.ed.ac.uk

285

Glasgow Caledonian University

www.gcal.ac.uk

185

The University of Glasgow

www.gla.ac.uk

195

Heriot-Watt University

www.hw.ac.uk

185

Napier University

www.napier.ac.uk

70

The University of Paisley 1

www.paisley.ac.uk

25

The Robert Gordon University

www. rgu.ac.uk

275

The University of Strathclyde

www.strath.ac.uk

305

UHI Millennium Institute

www.uhi.ac.uk

5

Northern Ireland

335

The Queen's University of Belfast

www.qub.ac.uk

245

University of Ulster

www.ulster.ac.uk

90

1 University of Paisley merged with Bell College in 2007.

Considerable changes are taking place at many universi-
ties during the current academic year, with many campuses
merging or changing their roles. Please check the relevant
websites for more information. For less official stuff the por-
tal website www.whatuni.com is also a good starting point.

Birmingham University

www.eece.bham.ac.uk

Electronic , Electrical & Computer Engineering

The University of Birmingham, Birmingham B15 2TT. Tel.

0121 414-5630.

The EE & CE Department is research-led and has 28 aca-
demic staff and 15 support staff who look after over 500
undergraduate students, around 60 MS c Students and a
similar number of students studying for their doctorate.
Turnover on research is £ 2 million per year, and in the
last government Research Assessment Exercise the Depart-
ment attained a grade 5 listing, as well as 24/24 marks
on Teaching Quality Assessment

Th e £ 2 million funding derives from a variety of sources

including government and industry as well as the Euro-
pean Union.

Brunei University

www.brunel.ac.uk

School of Engineering and Design

Brunei University, Uxbridge, Middlesex UB8 3PH. Tel.

01895 274000

Brunei is a world-class university based in Uxbridge, West
London and just over 40 years old. There are several elec-
tronics and Electrical Engineering courses available includ-
ing the new Electronic and Computer Engineering M Eng;
Electronic and Electrical Engineering (Communications Sys-
tems) BEng; Electronic and Electrical Engineering (Control
Systems) BEng; Electronic and Electrical Engineering (Power
Electronics Systems) BEng; Electronic and Electrical Engi-
neering BEng &MEng; and Electronic and Microelectronics
Engineering BEng.

The Electronics and Electrical Engineering (Communications
Systems) BEng. course, for example, is a three year full-time

32

elektor - 2/2008

course, of four years 'thick' sandwich (block study) course
that seeks to deliver well-rounded engineers with a high
level of analytical and engineering design skills.

Students are said to develop a sound knowledge of all as-
pects of Electronic and Electrical Engineering and related
areas. The course is accredited by the Institution of Engi-
neering and Technology (IET).

City University London

www.city.ac.uk

School of Engineering & Mathematical Sciences

City University, Northampton Square, London EC IV OHB.

Tel. 020 7040-8130.

The School of Engineering has entered a new dynamic
phase following the University's decision in 1999 to invest
heavily in the School, its restructuring in 2001 into a de-
partment-less School headed by a new Dean and its merger
with the Department of Mathematics to form the School of
Engineering and Mathematical Sciences.

Research in the School of Engineering and Mathematical
Sciences has a basic and applied component and has a
strong interdisciplinary character and it is characterised
by close links with industry and awareness of its location
in London.

London Electronics College

www.lec.org.uk

20 Penywern Road, London SW 5 9SU. Tel. 020
7373-8721.

The London Electronics College is a centre of adult learning
providing technical training dating back to 1 892.

This unique college attracts a wide range of students from
all backgrounds, notable international and ethnic. The col-
lege says that small classes and a friendly environment help
make learning enjoyable and rewarding.

The college is very close to the exhibition centre in Earls
Court and 20 minutes walk from Olympia. The area is well
served by buses, tubes and rail.

University of Manchester

School of Electrical and Electronic Engineering
www.manchester.ac.uk

Oxford Road, Manchester Ml 3 9PL. Tel. 0161
306-6000.

Established in 1924, the school has six research groups:

1 . Microwave and Communication Systems (MACS) The
MACS group considers a wide range of advanced topics
applicable to communications and radar; from highly mo-
bile wireless networks, propagation, microwave and mil-
limetric components, through to digital signal processing,
coding and signal analysis.

2. Control Systems (CS) — has an international reputa-
tion for its pioneering research in systems theory includ-
ing the development of frequency domain design tools for
multivariable systems, self-tuning and adaptive control and
the use of symbolic algebra in the development of control
algorithms.

3. Sensing, Imaging and Signal Processing (SISP) — pur-
sues collaborative and cross-disciplinary research that ex-
ploits the complementary expertise in sensing, imaging and
signal processing that is brought together in the group.

4. Electrical Energy and Power Systems (EEPS) — is at the

forefront of research and teaching in the field of electric
power engineering in the United Kingdom and internation-
ally with its 1 0 permanent academic members of staff and
its 30+ researchers.

5. Power Conversion — The efficient conversion & control
of electrical energy is a vital infrastructure technology that
underpins much of what we take for granted in an industr-
ialised country; electricity generation & distribution, land,
sea & air transport, computer & communications systems,
& countless industrial processes.

6. Microelectronics and Nanostructures (M&N) — Research
activities cover a range of topics concerned with the funda-
mental materials and physics issues surrounding advanced
semiconductor devices, novel high speed electronic and op-
toelectronic devices, and advanced sensors and systems.

Robert Gordon University

School of Engineering
www.rgu.ac.uk

Schoolhill, Aberdeen AB10 1 FR. Tel. 01224 62000

Robert Gordon University's
Garthdee library
with its techno-futuristic
architecture.

The University has developed an international reputation
for providing high quality education from Undergraduate
to PhD level.

In 2006 The Times newspaper named RGU as the top uni-
versity for graduate employment. The uni says that all its
electronics and electrical engineer courses are designed in
close co-operation with industry, with collaborative work
with professional bodies, industrial organisations, govern-
ment departments and research institutes.

Many courses are designed with a part-time study option
and a number of courses are available through the Univer-
sity's virtual campus, a remote university computer system.

Sheffield University

Department of Electronic & Electrical Engineering
www.shef.ac.uk/eee

Mappin Street, Sheffield SI 3JD. Tel. 01 14-222-5355

Sheffield Uni's E&EE Department is respected internationally
for its many important contributions in the field of Electronic
and Electrical Engineering.

The Department currently has 35 academic staff (including
12 professors), 8 academic-related staff, 29 research staff,
81 PhD students, 54 MSc students and approximately 360
undergraduate students.

The Department's reputation in both teaching and research
has been confirmed by the highest possible award in the
Teaching Quality Assessment (24/24 points) and a five star
award in the HEFCE Research Assessment Exercise.

2/2008 - elektor

33

INFO & MARKET

UNIVERSITIES GUIDE

London Electronics College
(LEC) classroom.

Malcolm Spalding of LEC
has reason to disagree with
the proposed statement.

2. Opinions: how far would you agree or disagree with the statement
"electronics as a science, a study, a pastime and professional activity is

migrating fast to India, China and the Far East 7'

This is not so, says Dr. Geoff Baines, an admissions tu-
tor with Manchester University's School of Electri-
cal and Electronic Engineering, who says that, whilst
a number of UK call centre jobs have been flowing steadily
overseas to the Indian sub-continent in the last five years,
students from around the world are now flowing into UK
universities as never before.

"Around 40 per cent of our electronic and engineering
students are from outside the European Union, despite the
fact that their fees are around the £ 1 2,900 a year mark,
compared to £ 3,145 a year for UK and European Union
students," he told Elektor.

And, he added, overseas students' fees are paid from a
wide range of sources, including parental contributions,
bank loans, foreign government and similar scholarships
and company sponsorships,

"In addition, once the international students have finished
their courses, not all of them return to their country of origin.
Many choose to stay in the UK and get a job or go on for
post-graduate training," he said.

"This task has been made a lot easier by the fact that the
UK government allows students to go on to get a relevant
job for up to 12 months without having to get a work per-
mit," he added.

Coupled with the fact that applying for a work permit on the
employer's side, particularly in the electronics and electrical
engineering industry, is now a lot easier than it used to be,
Baines says that a sizeable minority of non-European Union
students go on to settle in the UK.

"There's always been a shortage of graduates in the elec-

tronics and electrical engineering fields, so getting a work
permit is easy enough, provided you fill in the required
forms", he explained.

Over at the London Electronics College, Malcolm
Spalding, the college's Principal, also dismisses any sug-
gestion that electronics and engineering jobs are drifting
overseas.

He should know, as the college has been providing techni-
cal training since 1 892, when it was first established.

"We trained Harold Bridge, the radio operator of the Titan-
ic, as well as his counterpart, Harold Cottam, on the Car-
pathian, the first boat to arrive as the Titanic was sinking
after it hit an iceberg. Our students go on to a wide range
of positions in the UK, as well as abroad," he told Elektor.
According to Spalding, since the college is located close
to the exhibition centre in London's Earls Court on the west
side of London, it attracts a sizeable number of international
students from all over the world.

"These students then go on to hold high-ranking positions
in the electronics industry. Today the courses range from
BTECs through to HNC/HNDs and we have around 160
students aged 1 9 years or older studying for a wide range
of courses".

Unlike the traditional universities teaching electronics and
electronic engineering courses, Spalding says that the av-
erage age of students at the London Electronics College is
36 years.

Course fees at the college are well below those of a tra-
ditional university at £ 600 per course per year and, says
Spalding, anyone on benefits — any form of government
benefits — can attend the college for their first course, free
of all tuition fees.

International (non-European Union) fees come in at around
£ 5, 1 00 — again well below that of a traditional university,
which is why, says Spalding, the college has around 70 of
its students from ethnic minorities.

"Around 50 per cent of our students are from London, with
the majority of the remainder coming from overseas," said
Spalding, adding that his educational team stay in contact
with their students after they have left the college.

"I'd say that around half of them go into further education
with the remainder going into regular employment, both
here and when they return to their home country."

Up in Scotland, at the Robert Gordon University in

Aberdeen, which describes itself as a professional's uni-
versity, having attained the distinction of being the top
Scottish university for graduate employment, Dr Chris-
topher Macleod, a Lecturer in Electronic Engineering,
says there is some truth in the claim that electronics jobs
are flowing abroad.

"Companies like Hewlett-Packard, Intel and Motorola are
doing some of the production overseas, but the design and
development is still largely here in the UK, as well as the
US," he said.

Macleod, who is a course leader in Artificial Intelligence
and Robotics with the university, as well as being lead-
er of the university's artificial neural networks research
group, says that, in some ways a move towards India
may suit the UK.

34

elektor - 2/2008

"This is because we have strong historical links in India —
and arguably better than with the US, even if we do speak
the same language — and there will be good opportunities
for companies to expand on this," he said.

If anything, he told Elektor, the UK needs to view this as an
opportunity and develop these links, rather than see them
as a threat.

Interestingly, Macleod says that, as a pastime, electronics
has been dead among the young for many years.

"When I started lecturing 20 years ago, if you asked a
class of 50 how many of them were hobbyists, most stu-
dents would have put up their hands, Now I ask the same
question and only one or two do," he said.

According to Macleod, there are many reasons for this, es-
pecially — and somewhat paradoxically — when it comes
to the field of new technology.

"Why spend hours building a crystal (radio) set when you
can experience the wonders of the Internet," he said, add-

ing that at least some of the blame for this has to lay at the
door of hobbies like amateur radio.

"If you pick up a copy of RodCom (the journal of the Ra-
dio Society of Great Britain) or Practical Wireless (now it
is full of arguments about the use of morse code and the
technical aspects of the hobby have been brushed aside,"
he explained.

"In many ways, the hobbies have no relevance for kids
any more in what has become a mobile phone, Internet
and iPod-enabled 21st Century. The hobbies have failed to
keep up with modern times and integrate new technology
as part of the pastime," he said.

Against this backdrop, Macleod predicts that these aspects
of the hobby of electronics and radio amateurs, will be
populated by an increasingly ageing membership ('old far-
tdonrT, as he calls it), so further alienating the younger ele-
ments of society.

3. Atmospheric soundings from Mc^lhchester

Manchester -
bridge at the Lowry.

With no less than three universities — the University of Sal-
ford, the University of Manchester and Manchester Metro-
politan University — Manchester is truly a student city.
Electronics and Electrical Engineering courses are available
at all three universities, who are also inextricably linked
with each other historically.

According to Abigail Ridgway, a student studying Infor-
mation Systems at Manchester Metropolitan University for
two years, and who transferred to the university's Crewe
campus for final year, Manchester is a great place to study
and live.

"I lived in the student halls during my stay in Manchester,
which was great for my social life, as the halls are so cen-
tral" she said, adding that the only issue she had with her
stay was the cost of living in Manchester from a student's
perspective.

The cost of living in the halls of residence, she says, was
not that cheap, even though the halls provided excellent
self-catering facilities, but it was the cost of leisure pursuits
that she found heavy on her pocket.

"Entertainment in Manchester, as in all large cities, is al-
ways going to be an expensive option. Going out in the
evening, especially to one of the city's clubs, can be expen-
sive," she explained.

When it came to choosing between stay in the halls of resi-
dence and renting private property, Abigail says she was
only given minimal information by the university authorities
to help her choose.

"I think we were given a leaflet on the accommodation
choices and that was about it. I was, however, able to log
into one of the many student forums on the Internet and
read about other student's experiences with choosing where
to live", she said.

2/2008 - elektor

35

INFO & MARKET

UNIVERSITIES GUIDE

Manchester University's
Whitworth Hall.

The Internet forums for the various universities, she went on
to say, has helped students immensely, since it allows stu-
dents from different years share their information informally,
even to the extent of allowing people to post their views
between universities.

Manchester Metropolitan University is slightly unusual for
a UK university in being split across five campuses in Man-
chester and a further two in nearby Alsager and Crewe.
Abigail moved to the Crewe campus for her final year as it
allowed her to move out of the halls of residence in order to
save on her living expenses, which, she says, are the most
troublesome part of university life.

Her advice to prospective students wanting to study an Elec-
tronics and Engineering course at a UK university — or, for
that matter any course at university — is to check whether
they want to stay in the halls of residence or take up private
accommodation.

"Renting privately can be cheaper than living in the halls,
especially if you live in shared accommodation", she told

(left) Manchester's
night life and general
atmosphere are well
geared to students,
(right) Cryogenic research
at EEPS Manchester.

Elektor, adding that the cost of phoning home and to/from
friends is another cost.

"In the halls we had phones of our own, but they all took
phonecards, which proved to be expensive. In private rent-
ed accommodation, you can share the cost of a phone line
with others and, if you have a mobile phone, that can help
you reduce the cost of staying in touch with your friends
and family", she said.

Manchester nightlife has changed immensely in the last few
years, with the relaxation in UK licensing laws allowing
bars and clubs to stay open much later than previously, and
sometimes on a 24-hour basis.

This hasn't triggered a drinking culture, however, as
many students are now choosing to go out for a drink
or club much later than they would have done just a few
years ago.

Clubs in Manchester now numbers into several dozen, with
the top four clubs — Sonkeys in Radium Street, Mint Lounge
in Oldham Street, Twisted Elegonce@Ampersond in Long-

36

elektor - 2/2008

(left) Programming
microprocessors at EEPS
Manchester....

(right) ... requires total
memory clearing at certain
times.

worth Street and Funkodemia in Central Street — attracting
regular visitors.

Although entrance fees at these clubs can easily run to £ 20
or £ 30, competition between the clubs for new customers
is ferocious, meaning that discount schemes for students
and/or regular visitors all help to cut the costs.

And, of course, the fact that the University halls of residence
in Manchester are quite centrally located means that late
night revellers can travel home by night bus or even walk,
rather than taking a cab, which all helps to keep entertain-
ment costs to sensible levels.

"The central location of the halls whilst I was there meant
that, even if had to share a cab between us, the cost was
relatively inexpensive", said Abigail, adding that the sheer
variety of culture in Manchester is a great plus point for liv-
ing and studying there.

The culture scene in Manchester has also improved im-
mensely in recent years, with a number of museums and
other 'cultural sites' available during extended opening
hours free of charge.

One key site that students should check out immediately on
arrival in Manchester is the Urbis Centre in Cathedral Gar-
dens in the heart of Manchester.

Urbis is an exhibition centre focusing on city life with en-
trance to exhibitions, which cover photography, design,
architecture, music, contemporary art and other topics, free
of charge.

The centre, which has become a cultural icon in its own
right has free interactive exhibits, a range of family activi-
ties, a shop and a cafe bar.

The interactive exhibits allow visitors to take a ride through
different cities around the world, create your own identity
card or go global to discover a 3D satellite view of any
city on the planet.

And, of course, because everything is centrally located in
Manchester, as Abigail says, students can generally walk
home to their halls of residence or private accommodation,
if they miss their night bus.

( 071019 - 1 )

Urbis Centre -
a must-visit for everyone
arriving in Manchester.

2/2008 - elektor

37

BUS SYSTEMS

Fredi Kruger

The CAN bus network is usually
associated with vehicle systems or
industrial automation but it can also be used
in many other situations including home automation.

Implementing the network is not a trivial undertaking. This
low-cost solution is a CAN board which sits between the CAN bus
and a PC. Using the versatile (free) software it can monitor activity on
the network and test the functioning of other nodes.

CAN Explorer

Versatile
PC-CAN Interface

Although originally conceived (by
Bosch) to provide a network linking to-
gether electronic vehicle subsystems,
the CAN bus was later adopted by com-
panies specialising in industrial control
systems. A quick trawl of the Internet
indicates that the CAN bus has many
devotees who have used it in a number
of interesting applications [1]. Among
the advantages of this network are its
excellent error detection, good interfer-
ence rejection and a wide range of low-
cost components. Following links [2a]
and [2b] will fill in some of the back-
ground information on this network
standard. The available node hardware
extends from so-called Stand-Alone-
Controllers up to microcontrollers with
integrated CAN controllers.

One of the difficulties in a network is
to establish communication, so that
information can be sent reliably be-
tween different system components.
The level of difficulty is further mul-
tiplied if it is necessary to build the
whole network from scratch and man-
age bidirectional data on the network.
This article presents a CAN bus-to-PC

interface card which together with the
use of free software can not only moni-
tor traffic on an existing CAN network
but also send and receive CAN-format
messages and monitor the functioning
of other nodes on the network. Use of
these features gives the user a good
insight into the workings and capabili-
ties of the CAN bus.

Simple, low-cost and versatile

The CAN controller chip MCP2515
from Microchip is relatively low-priced
while the PC software is available free-
of-charge from Microchip [3]. The soft-
ware allows direct access to the CAN
controller’s registers to configure the
controller for specific applications.
CAN bus messages can also be sent
and received and a configurable filter/
mask allows the user to set-up and test
for message acceptance.

The board interfaces to the PC using
the parallel printer port which nowa-
days (unless your printer is very old)
is hardly ever used. This port offers
good communication speed and low-

cost interface hardware (with regard
to Windows Vista problems, see the
LabTalk article elsewhere in this mag-
azine). The parallel printer port must
be configured in software for bidirec-
tional data flow.

In order for the hardware to run the
software from Microchip it is neces-
sary that the circuit diagram (Fig-
ure 1) corresponds closely to the CAN
bus board described by Microchip
on their web site [3]. Two 74HCT245
bus transceivers (IC1, IC2) are used to
buffer signals between the printer port
and the MCP2515 CAN controller chip
(IC3). Communication to the chip takes
place using the serial SPI interface
with the necessary signals produced/
received by the PC software via par-
allel port pins. The additional signals
are used to poll/control the status of
other signals of the CAN controller. An
MCP2551 (IC4) is used as the CAN bus
driver/receiver but alternatives like the
PCA82C521 are also suitable.

The PCB for this project, no. 060201 -
1 can be ordered through Elektor’s
business partner ThePCBShop. Jump-

38

elektor - 2/2008

Figure l.Bus transceivers 1C land IC2 buffer signals between the printer port and the CAN controller chip (IC3). IC4 is a CAN bus driver.

er JP1 can be used to connect a 120
Ohm terminating resistor across the
network cable if this board is the end
node. This is recommended to reduce
signal reflections in the cable. Physi-
cal connection to the CAN bus is made
via a PCB mounted 9-way sub-D con-
nector (K2). Pin assignments are giv-
en on the circuit diagram and spare
pins are used to allow the board to be
powered from the bus connector with
either 12 V or 5 V (use JP2 to select).
Alternatively a separate mains adapt-
er input is provided (K3) to power the
board. The bridge rectifier (Bl) ensures
that a mains adapter (‘wall wart’) pro-
ducing a low-voltage AC or DC output
(with a plug wiring of either polarity)
can be used without problem.

Fitting it all together

The resistors and capacitors can be
fitted first, followed by the other com-
ponents according to their size. Make
sure that the correct polarity is ob-
served for the electrolytic capacitors
(C7; CIO), LED (Dl), rectifier (Bl), and

do pay attention to the correct orien-
tation of the ICs on the board. Once
you are happy that the layout is cor-
rect and you have not made any un-
intentional solder bridges between
pads and tracks, it is time to connect
the power supply (8 V to 12 V) to con-
nector K3. LED Dl should now light.
With the board connected to the par-

allel printer port of a PC and with the
software (described below) running
the hardware will automatically be
recognised as an ‘Eval-Board’.

Software

Software for the project can be down-
loaded free-of-charge from the Micro-

Figure 2. Following software installation and a few mouse clicks, these options are available.

2/2008 - elektor

39

BUS SYSTEMS

16.0C69

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pitch

04, 05 = 22pF

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JP1 = 2-way pinheader with jumper

LIST

07 = 470a/F 25V (radial)

JP2 = 3-way pinheader with jumper

CIO = 47yL/F 25V (radial)

K1 = 25-way sub-D plug, right-angled pins,

PCB mount

Resistors

Semiconductors

K2 = 9- way sub-D plug, right-angled pins,

R1 ,R2,R3 = 10kn

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PCB mount

R4 = 1 20Q

D1 = LED, 3mm, 2mA

K3 = mains adaptor socket (HEBW25),

R5 = 1 k£2

101,102 = 74HCT245

right-angled pins

IC3 = MCP2515 (SOIC)

XI = 1 6MHz quartz crystal (HC49U)

Capacitors

IC4 = MCP2551SN (SOIC)

PCB, no. 060201-1 from

01,02,03,06,08,09 = lOOnF, 5mm lead

IC5 = 7805 (TO220)

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Figure 3. Using / MCP2515 Register View' gives access to all of the MCP2515 registers.

chip web site [3]. It is based on the
CANking software produced by the
company Kvaser [4] with a driver add-
ed specifically for the MCP2515. The
software is compatible with all ver-
sions of Microsoft PC operating sys-
tems from Windows 95 upwards. To
enable access to the port, a copy of dl-
portio.sys will also need to be saved
to the C:\Windows\system32\drivers
folder on the PC. It is free and can be
downloaded from [5].

Once the Microchip software has been
downloaded, installed and running the
user is presented with the menu op-
tions shown in Figure 2. On some PCs
the dlportio.sys driver does not run au-
tomatically and an error message ap-
pears on the screen. In this case the
driver will need to be started manually.
It is also necessary to select the cor-
rect address for the printer port; fur-
ther information to help resolve these
problems can be found in the accompa-
nying file CANHelp.pdf which is avail-

40

elektor - 2/2008

able from the Elektor website [6].
Selecting ‘MCP2515 Register View’
gives you access to all the internal reg-
isters of the MCP2515. A new window
pops up for each of the selected func-
tions (Figure 3). Selecting ‘MCP2515
Evaluation Board’ / ‘MCP2515 Basic’
switches the software into bus-moni-
toring mode and bus activity is dis-
played (Figure 4). More detailed in-
formation of the software is available
from the Microchip website [3].

( 060201 - 1 )

Web Links

[1 ] http://caraca.sourceforge.net
[2a] http://www.computer-solutions.co.uk/info/
E m bed ded_tuto ria I s/ca n_tutorial.htm
[2b] http://en. wikipedia.

org/wiki/Controller_Area_Networl<

[3] http://www.microchip.com/stellent/

idcplg?ldcService=SS_GET_PAGE&nodel
d= 1 406&dDocName = en531 891

[4] www. kva s e r. co m

[5] www.driverlinx.com/download/dlportio.

htm

[6] www.elektor.com/canbusE

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Figure 4. Choosing 'MCP2515 Evaluation Board 7 / 'MCP2515 Basic' (see Figure 2) switches the software into bus monitor mode
showing all bus traffic.

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2/2008 - elektor

41

TECHNOLOGY

LED LIGHTING

Ambience courtesy of an MSP430

Dirk Gehrke and Christian Hernitschek

High-brightness LEDs are being used more and more widely in lighting applications.
Here we present a simple 'mood light' using just a few components. Each of three
LEDs is provided with a constant current using a switching regulator, and
brightness control is performed by an MSP430 microcontroller generating
three PWM signals. The printed circuit board could be fitted inside a table
lamp with a frosted glass envelope or could be used with an LED spotlight
for indirect lighting.

Whatever their power, LEDs are now
normally driven using a constant cur-
rent source. This is because their light
output, measured in lumen (lm), is pro-
portional to the current flow.

All LED manufacturers therefore spec-
ify parameters such as light output
(sometimes expressed as optical ef-
ficiency), viewing angle and wave-
length as functions of forward current
I F rather than of forward voltage V F as
might be expected. We therefore use
suitable constant current regulators in
our circuit.

Constant current
for high-brightness LEDs

The majority of switching regulators on
the market are configured as constant
voltage sources rather than as constant
current sources. A small and easy-to-
understand modification to the circuit
is required to convert a constant volt-
age regulator to constant current op-
eration. Instead of the voltage divider
normally used to set the output voltage
we use a current sense resistor, across
which the voltage drop is regulated.

Figure 1 illustrates the circuit
in simplified form.

Dimming LEDs

There are essentially two ways to dim
LEDs. The first, and simplest, way is
analogue control, where the current
flowing through the LED is controlled
directly: a lower current gives a low-
er brightness. Unfortunately there are
two severe disadvantages to this meth-
od. First, the brightness of the LED is
not exactly proportional to the current,

Caution! High-
brightness LEDs!

Never look directly into the LEDs!

Very bright LEDs are not just uncomfort-
able to look at; they can actually be dan-
gerous to the eyes as they can damage
the retina. We therefore recommend oper-
ating the board with the LEDs pointing at
a white wall to give indirect illumination.

V 0 ut = Vfb R2 + R1

Figure 1. A switching regulator can be configured as a voltage source or as a current source.

42

elektor - 2/2008

and second, the wave-
length (and hence colour)
of the emitted light shifts
as the current is varied away
from the nominal value for the
LED in question. These two phenom-
ena are seldom desirable.

The slightly more complicated control
method uses a constant current source
configured to deliver the nominal op-
erating current for the LED. An addi-
tional circuit can then quickly switch
the LED on and off with a given mark-

space ratio, on average emitting less
light. This is perceived as a reduc-
tion in light intensity. By adjusting the
mark-space ratio we can easily adjust
the perceived brightness of the LED.
This method is known as pulsewidth
modulation (or PWM).

Dimming using PWM

We will look at ways of implementing
PWM control using the TPS62260 as an
example. The TPS62260 is a synchro-
nous step-down converter with inte-

Figure 2. Three ways to implement the dimmer function.

grated switching element, operating at
a typical clock frequency of 2.25 MHz.
In the circuit of Figure 2 we show in
black the possibility of connecting the
PWM signal directly to the EN (ena-
ble) pin. The whole switching regula-
tor circuit is started up and shut down
in sympathy with the PWM signal. Ex-
periments in our laboratory indicate
that in this configuration we can use
a PWM frequency of up to 100 Hz. The
advantage of this arrangement is its
simplicity: no additional components
are required. It is also the most en-
ergy-efficient implementation, as the
switching regulator draws very lit-
tle quiescent current when disabled.
Its disadvantage is that the reaction
of the LED to a high level on the en-
able pin is delayed. This is because
the switching regulator has a ‘soft-
start’ function: when the device is en-
abled the output current is gradually
ramped up until it reaches the nominal
LED current. In some applications this
ramp can be problematic as the wave-
length of the light emitted by the LED
varies as the current builds up from its
minimum value to the normal operat-
ing level. For example, in a DLP projec-

2/2008 - elektor

43

TECHNOLOGY

LED LIGHTING

+3V3

©

+3V3

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R5

C3

+3V3

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10

ENCODER

R1

11

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24

4

3

R4

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23

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NMI/RST

U1 TEST

P2.0/ACLK/CA2

PI .7/TA2/TDO/TDI

P2.1/INCLK/CA3

P1.6/TA1/TDI/TCLK

P2.2/CAOUT/TAO/CA4 PI .5/TAO/TMS

P2.3/TA1/CA0

P1.4/SMCLK/TCK

P2.4/TA2/CA1

PI .3/TA2

P2.5/CA5

PI .2/TA1

XIN/P2.6/CA6

P1.1/TA0

XOUT/P2.7/CA7

PI .0/TACLK

MSP430F2131 IRGE

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22

21

20

18

17

16

15

14

13

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070892 - 13

Figure 3. Control part of the circuit, based on an MSP430 microcontroller, with JTAG connection (JP1), eZ430 connector (JP2) and
rotary encoder (Rl).

tor or in the LED backlight for an LCD
television panel, such variation might
not be acceptable. For this demonstra-
tion project, however, the effect is not
noticeable to the eye.

In the second variant (shown in red in
Figure 2) the PWM signal is coupled
into the error amplifier input of the
TPS62260 via a small-signal diode. In
this circuit a positive voltage in excess

of 600 mV applied to the control input
will over-drive the error amplifier in-
put and thus switch off the LED. Since
this circuit does not use the enable in-
put it does not suffer from the start-up
delays associated with the soft-start
function of the regulator, and the LED
is switched on and off very rapidly.
The shift in output wavelength due to
the current ramp mentioned above is
therefore negligibly small in this con-
figuration. Furthermore, we found in
the laboratory that the PWM frequency
could be raised to 5 kHz.

The third possibility is shown in blue in
Figure 2. Here the PWM signal is used
to control a MOSFET wired across the
LED. The MOSFET shorts out the LED
and allows it to be switched on and off
even more rapidly. The regulator is op-
erating in constant current mode, and
this current will flow either through
the LED or through the MOSFET. Dis-
advantages of this approach include
the additional cost of the MOSFET and
poor energy efficiency: up to 180 mW of
power can be dissipated continuously
in the 2 Q current sense resistor. Its ad-
vantage is the high switching frequen-
cy: in experiments we saw successful
operation of the TPS62260 in this con-

NET-DIMM

_LED2

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C32

t

TP31

R12, R22, R32 = 2Q
R12, R22, R32 = 1Q69

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TS4148RY

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Figure 4. Circuit section consisting of three switching regulators configured as constant current sources and a 3.3 V stabilised supply built using discrete components.

44

elektor - 2/2008

A brief history of LEDs

The story of the light emitting diode (or LED), or luminescence diode',
starts in earnest in 1962 when General Electric (GE) began to manu-
facture and sell red LEDs on the commercial market. Customers had
to be satisfied with a rather poor light output: an LED of that time had
an output of just 0.1 Im/W, corresponding to an efficiency of barely
0.1 %. The material used was a mixed crystal comprising gallium ar-
senide and gallium phosphide. Since then the market for LEDs has
changed out of all recognition, with many other manufacturers making
advances in LED technology, and light output available for a given cur-
rent has increased steadily.

Efficiency, as well as electrical and thermal robustness, needed to
increase still further before LEDs could be practically used as light
sources in any significant quantity. At the same time, prices have fallen
rapidly, opening up entirely new application areas. Such has been the
result of forty years of research and development.

Today it is possible to buy very bright LEDs at moderate prices which
run at respectable levels of efficiency: for example, the Golden Dragon
range from OSRAM Opto (formerly Infineon), the Rebel LED range
from Lumileds (Philips Semiconductors) and the X-Lamp range from
Cree. There are of course many other manufacturers of high-bright-
ness LEDs, although for reasons of time we were unable to evaluate
them all for this article.

The light output of LEDs available today has risen to 20 Im/W, and
some examples manage as much as 40 Im/W. These values corre-
spond to efficiencies of 5 % and 10 % respectively, rather higher than
the efficiency of a standard commercially-available incandescent bulb,
which offers in the region of 10 Im/W, or an efficiency of around 2 %.
High-brightness LEDs are already more efficient than halogen bulbs
(around 25 Im/W) and will probably also soon be outperforming en-
ergy-efficient bulbs (around 60 Im/W).

figuration with PWM frequencies as
high as 50 kHz.

The practical circuit

At the heart of the circuit (Figure 3 and
Figure 4) is an MSP430F2131 micro-
controller. This is programmed to op-
erate as a triple PWM generator and
to read values from the rotary encoder
(Rl). The encoder value is used to in-
dex a look-up table containing mark-

space ratio values for each of the red,
green and blue LEDs. The correspond-
ing PWM signals are then made avail-
able on output pins TA0, TA1 and TA2
at a frequency of approximately 122 Hz.
This is high enough to ensure that the
LEDs do not appear to flicker, as the
eye smoothes out the individual pulses
of light to an average perceived inten-
sity value.

For a practical implementation we
chose the PWM control method shown

in red in Figure 2, which gives a good
compromise between circuit complex-
ity and performance. Each LED, red
(D14), green (D24) and blue (D34) is
supplied with a constant current from
a separate TPS62260 DC/DC convert-
er. The 2 Q resistor sets the nominal
current flowing through the LED at
300 mA. Higher currents (up to 1 A)
can be obtained using a TPS62290, the
TPS62260’s ‘big brother’, which comes
in the same package style.

Clock generation

MSP430 microcontrollers have a choice of integrated clock sources.

In software, the MSP430 can switch between an external crystal-based
oscillator and an internal RC-oscillator. To keep circuit costs down we
have dispensed with external components and used the internal cali-
brated RC oscillator. 'Calibrated' means that the calibration parame-
ters, stored in the MSP430's 'information memory', simply need to

be copied into the relevant control registers in the clock generator
module. Using these calibration parameters gives an overall accu-
racy for the RC oscillator of ±2.5 % over the temperature range from
0 °C to 85 °C. The RC oscillator frequency lies between 7.8 MHz and
8.2 MHz: this frequency is used as the CPU clock frequency and to
drive the counter in the Timer A module.

Implementation of triple PWM

The Timer_A module in the MSP430 consists of a counter block and a
range of capture and compare blocks. The frequency of the generated
PWM signals is determined by the rate at which the counter overflows.
Since the Timer_A counter is 1 6 bits long, the PWM frequency is given
by f PWM = f| N /2 1 6 = 8 M Hz/65536 = 1 22.07 Hz, where f !N is the fre-
quency of the clock input to Timer_A.

= =

2 16 65536

f pwM '■ PWM signal frequency
f t : Timer _ A frequency — input clock

If we repeat this calculation using the minimum and maximum fre-
quencies given above, we obtain the maximum deviation of the PWM
signal frequency from its nominal value. We find that 1 1 9 Hz < f PWM
<125 Hz.

T

PWM

I \9Hz < f PWM <\25 Hz

Generation of the PWM signals themselves is carried out by the 'output
units' which form a part of each capture and compare block. In the
MSP430F2 1 3 1 the Timer_A module has a total of three capture and
compare blocks and therefore three output units. Each capture and
compare block consists of a digital comparator which compares the
current value in the counter with a value specified independently for
each block (TACCR0, TACCR1 , and TACCR2). If the values match then
the comparator output triggers the output unit, setting the correspond-
ing PWM output to a '1 '. The PWM outputs are reset in software. The
overflow of the 1 6-bit counter causes an interrupt; the interrupt service
routine sets all the PWM outputs to zero in turn.

Using software to reset the PWM outputs puts a limit on the available
range of mark-space ratios. Execution of the Timer_A interrupt service
routine takes approximately 1 00 cycles, and so the three colour table
arrays may only contain values in the range from 100 to 65535.

2/2008 - elektor

45

TECHNOLOGY

LED LIGHTING

Rotary encoder

The PWM mark-space ratios can be set manually using a rotary enco-
der (or 'shaft encoder'), which is a device similar in appearance to a
potentiometer. However, instead of containing a resistive track, it em-
ploys two contacts which open and close as the shaft is turned in a 2-
bit Gray code pattern. The internal construction of the encoder is very
simple. A wiper with two contacts sweeps over two conducting rings,
insulated from one another. An insulating material covers the rings in a
pattern such that as the wiper turns it operates as a switch, producing
the two-bit Gray code on the output pins.

The upper figure shows in outline how the encoder is connected to the
microcontroller, and the lower figure shows the output signals when the
shaft is turned steadily in either direction.

Using the two signals A and B we can detect when the shaft is turned,
as well as in which direction. In the timing diagram four states, a, b,
c and d, are shown. These states repeat continuously as the shaft is
turned. If the MSP430 software detects a change from state a to state
b, it knows that the colour table pointer LEDptr needs to be incremen-
ted. Conversely, a change from state b to state a causes the pointer to
be decremented.

If the encoder oscillates between states a and b the pointer will be
alternately incremented and decremented. This can give rise to a flicke-
ring of the LEDs as the settings change to and fro. For this reason (as
well as to reduce the effective resolution of the encoder to a more com-
fortable value for the user) the pointer LEDptr is divided by four before
it is used to access the colour table arrays.

Finally, a note on the wiring of the rotary encoder. In the circuit dia-
gram of Figure 3 the pull-up resistors for each contact are connected to
pin 8 of the MSP430 (P2.2) rather than to VCC. This is not a mistake:
P2.2 is taken high in software and is therefore at 3.3 V, the same volta-

PWM1

PWM2

PWM3

ge as VCC. Of course, the pull-up resistors could be connected directly
to VCC (3.3 V), freeing up P2.2 for other purposes.

COMPONENTS LIST

Resistors

(SMD 0603 unless otherwise stated)

R2 = 330C2
R3,R4,R6 = 1 00kT2
R5 = 47k£2

R1 1 ,R1 3,R21 ,R23,R31 ,R33 = ^0kQ
R12,R22,R32 = 2Q (SMD 1206)

Capacitors

Cl, Cl 1,C13,C21,C23,C31,C33 = 4ji/F7
6.3V; X5R, (SMD 0603)

C2 = lOOnF (SMD 0603)

C3 = 1 OnF (SMD 0603)

C4,C1 2,C22,C32 = 22ji/F (SMD1210)

Semiconductors

D1 = BZX84-C3V3 (SMD SOT23)

D13,D23,D33 = TS4148 RY (SMD 0805)
D14 = 1W LED, Golden Dragon, red
(Osram)*

D23 = 1W LED, Golden Dragon, green
(Osram)*

D33 = = 1W LED, Golden Dragon, blue
(Osram)*

Ul = MSP430F21 31 RGB (Tl)

U1 1 ,1121 ,U31 = TPS62260DRV SMD SON-
6 (Tl)

Inductors

LI 1 ,L2 1 ,L3 1 = 2jL/H2, 1.1 A, 110 mQ, SMD
2x2.5 mm (MIPSA2520D2R2, FDK)

Miscellaneous

R1 = rotary encoder, Bourns 3315-001

JP1 = 1 4-way boxheader

JP2 = 6-way connector (Samtec

TMS-106-XX-X-S-RA)

TP1 1 ,TP1 2,TP1 3,TP21 ,TP22,TP23,TP31 ,TP32
,TP33 = test pin, e.g. Keystone 5001
Heatsink, Fischer SK 477 100
Heat conducting self-adhesive tape, Fischer
WLFT 404 R25
PCB, order code 070892-2**

*LED alternatives:

Lumiled REBEL LED using PCB 070892-1**
CREE XLAMP LED using PCB 070892-3**

** Artwork download and PCB ordering at
www. e I e kto r. co m

Colour table

The colour look-up table takes the form of an array stored in the
MSP430. The array is arranged so that it can at any time be extended
with additional pulse width modulation values for the red, green and
blue LEDs. Whenever the rotary encoder is turned new red, green and
blue values are read from the array and used to generate the three

PWM output signals. Currently 252 values are stored, which can be
changed if desired. A decimal value of 100 switches the LED off, and a
value of 65535 produces a mark-space ratio of 100 %.

When the 5 V supply is applied the MSP430 goes into a demonstration
mode where the values stored in the array are read and output in se-
quence in an infinite loop. As soon as the rotary encoder is turned the
sequence stops and a particular fixed colour value can be selected.

46

elektor - 2/2008

The PWM signal is coupled in using a
small-signal diode (D13, D23 and D33).
When the PWM signal is high it over-
rides the normal error signal input of
the corresponding switching regulator,
which has a threshold voltage level of
600 mV. This means that a high level
on the PWM signal forces the LED to
extinguish. When the PWM signal sub-
sequently goes low the regulator starts
up again and the LED lights.

The whole circuit is powered from a
regulated 5 V 1 A DC mains adaptor.
A simple voltage stabiliser built using
a resistor and a Zener diode reduces
the 5 V level to 3.3 V for the MSP430
microcontroller.

The circuit can be built on the printed
circuit board shown in Figure 5. There
are three versions of the circuit board
differing only in the footprint and con-
nection arrangement of the LEDs. This
allows various types of LED to be used.
The LED options available are listed in
the parts list.

Heat map

Operating temperature is an impor-
tant parameter in the performance of
a high-power LED. It strongly affects
operating life, forward voltage, output
wavelength and even the brightness
of the device. The higher the operat-
ing temperature of the LED, the short-
er will be its expected lifetime. For
this reason the dimensions of our ex-
perimental printed circuit board have
been chosen to allow a type SK477100
heatsink (made by Fischer Elektronik)
to be fixed to the reverse of the board
using double-sided adhesive thermal
transfer material. Running at full pow-
er, this reduces the temperature of the
LEDs from 61 °C (without heatsink) to
54 °C (with heatsink). The heatsink
also helps to spread the dissipation of
heat over the area of the printed cir-
cuit board.

To make an example thermal image we
populated the board with LEDs from
Cree. Figure 6 shows the results viv-
idly, illustrating the temperature of the
LEDs without heatsink (on the left) and
with heatsink (on the right).

Software

The source code for the MSP430 soft-
ware for this application is available
for download from the Elektor web-
site. The code begins by including the

Figure 5. Printed circuit board for building the circuits of Figure 3 and Figure 4. Three variants are available for download, supporting
different types of LED.

2/2008 - elektor

47

TECHNOLOGY

LED LIGHTING

i -63

-60

-56

-52

-48

-44

-40

-36

-32

-28

-24

°c

Figure 6. Thermal image of the circuit board, populated with LEDs from Cree. Left: without heatsink; right: with attached heatsink.

‘MSP430F21x2.h’ header file, which
contains definitions of all the con-
trol register names and of the control
bits available in the MSP430. Next the

length of the colour table is defined.
Notice here that the value of ‘LEDTa-
bLength’ is actually set to four times
the length of the table. Then follows

About the authors

Dipl. Ing. (FH) Dirk Gehrke

Dirk Gehrke was born in Munster in Germa-
ny and studied communications technology
at Dortmund University of Applied Sciences
and Arts. He started working for Texas Instru-
ments in 1998 as a Field Application Engi-
neer (FAE) in Britain, France and the United
States. From 2000 he worked in Freising,
Germany, as an FAE for power management
products, and in January 2006 he became
Business Development Manager for ana-
logue products in EMEA (Europe, the Mid-
dle East and Africa). Contact: http://www.
ti.com/europe/csc.

Dipl. Ing. (FH) Christian Hernitscheck

Christian Hernitscheck studied electronic
engineering at the Landshut University of
Applied Sciences in Germany, specialising in
microelectronics. Since 1998 he has worked
as an FAE for Texas Instruments covering the
whole of Europe, focussing on the MSP430
microcontroller product line. Contact: http://
www.ti.com/europe/csc.

the colour table itself, with a separate
array for each individual LED. Pointer
‘LEDptr’ is used to read the relevant
PWM mark-space ratio settings for
each of the three outputs from the in-
dividual colour table arrays: see also
the text box ‘Colour table’.

The microcontroller is initialised at the
beginning of the function ‘main()\ The
watchdog timer is disabled, the cali-
bration values for the adjustable sys-
tem clock are loaded, the Timer_A
module is configured and the multi-
plexed inputs and outputs are suitably
initialised. The main loop consists of
two ‘while’ blocks. In the first ‘while’
block the colour table pointer LEDp-
tr is incremented, which results in a
continuous change in the PWM mark-
space ratios and thus in the generat-
ed colour. The overall timing of these
colour changes is governed using two
nested ‘for’ loops. The first ‘while’ loop
runs until the rotary encoder reports a
change on one of its outputs. The sec-
ond ‘while’ block, written as an infinite
loop, then takes control: it increments
or decrements the colour table pointer
according to the direction in which the
rotary encoder is turned.

A bright future

The printed circuit board allows addi-
tional functionality to be implement-
ed. For example, there is a socket for a
Texas Instruments eZ430-RF2500 radio
module. The eZ430-RF2500 kit is sup-
plied with two radio modules. One of
these can be fitted with a rotary encod-
er (using the test pins on the microcon-
troller in the radio module), creating a
radio link to the LED board.

The circuit board described here is pri-
marily intended for experimentation
and evaluation purposes. Since the
MSP430 source code is made available,
it is possible to modify it for a range of
other projects. The switching regula-
tors can also find use in other applica-
tions: have fun!

( 070892 - 1 )

48

elektor - 2/2008

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49

PHOTOGRAPHY

The availability of increasingly high-performance digital cameras and falling prices has encouraged
a good many people to take an interest in photography, and macro-photography too. If lighting
conditions are not ideal, it will be necessary to resort to the use of flash, with the attendant risk of
shadows. The solution is a ringflash - and while we're about it, why not one using LEDs?

The author found himself confronted
with the challenge of constructing
a flash specially designed for mac-
ro-photography. That needed some
thinking about, out of which came a
list of. . .

Requirements

Not a mere wish-list, but a specifica-
tion of what the operational device has
to do:

O build a flash unit suitable for taking
macro photos;

O produce a soft light (no risk of hard
shadows);

Ouse sufficiently powerful white LEDs
(20,000 mcd);

O arrange the LEDs in a circle (to avoid
shadows);

O put as many LEDs on the ring as pos-
sible (32 if possible);

O have control over the duration of the
flash, independently of the camera’s
shutter speed;

Obe able to take, for example, photos
of the splash of a water droplet.

It’s all very well spelling out what
you want on paper, but meeting these
specifications means you have to solve
certain...

Problems

The first hurdle we face is powering
the LEDs. Although there aren’t too
many options to choose from - parallel
or series - the implications of these are
more restrictive (see Table 1).

Solutions in the form of
a circuit diagram

Rarely have circuits published in Ele-
ktor been any simpler than our ring-
flash. To keep it both compact and sim-
ple, there’s only one option: a micro-
controller. It is used to:

O detect when the camera fires the

50

elektor - 2/2008

Photo : Huib Theunissen

flash;

O display the chosen flash duration via
LEDs;

O switch the ringflash.

The author opted for series connection
of the LEDs, and rather than re-invent
the wheel, chose to use an electronic
flash board cannibalised from a dispos-
able camera - this was in fact the only
readily- available electronics capable of
supplying a voltage significantly in ex-
cess of the 64 V actually needed.

The circuit (Figure 1) of this electron-
ics board from Kodak can be found on
numerous websites, including the one
listed at [1]. It’s important to note that
this is only a typical circuit — the vari-
ous models of disposable camera may
well have different electronics, but the
principle remains the same.

Using this type of board has undoubt-
ed advantages: it comes ready-built,
works very well, and is easy to get
hold of. You can always ask your local
photographer to let you have a dispos-
able camera that’s been opened for de-

veloping the film. If not, you could al-
ways go out and buy one.

Once the electronics from the dispos-
able camera are available, all that re-
mains is to separate off the part that’s
going to be useful for this project, i.e.
everything upstream of capacitor C2.
The high voltage will be taken from
across the terminals of C2 (take care
to discharge the electronics properly
before you start - if capacitor C2 dis-
charges to your fingers, you’ll get a
nasty jolt).

Let’s move on to the electronics of the
flash control board shown in Figure 2.
The heart and brain of the ringflash
takes the form of a PIC16F628 from the
Microchip stable [2].

The PIC16F628’s port B inputs have in-
ternal pull-ups.

Line RBO is used to detect triggering.
Line RB3 is used to trigger the MOS-
FET, an IRFBF20 [3] switched at 5 V
and having a V (BD)DSS (drain-source
breakdown voltage) of 900 V; this
line is intended for setting the flash

Table 1. Parallel or series

- that's the question

Configuration

Current

Voltage

Dropper resistor

Parallel

High

32 x 40 mA
= 1.28 A

Low

~ 2 V

Either all LEDs in parallel 1 resistor

Q: Will all the LEDs give good brightness?

Or each LED has its own dropper
means a large number of resistors

Series

Low

~ 40 mA

High
>32x2
...>64 V

1 single resistor

2/2008 - elektor

51

PHOTOGRAPHY

V+ Flash (300V)

Figure 1. Typical circuit of disposable camera flash electronics (source: Kodak).

duration.

Line RB4 is simply used to select a pre-
defined switching time. By default, the
first position corresponds to a duration
equal to that of the camera itself (to
within a few PIC instructions).

Display of the selection is achieved by

way of a 4051 CMOS analogue multi-
plexer/demultiplexer IC, whose out-
puts drive a series of eight LEDs, all
the cathodes of which are connected to
ground. Provision is made for eight du-
rations, encoded on lines RA0-RA2.
The flash can be tested using minia-

ture pushbutton SI, while S2 is used
to set the flash duration. Each time S2
is pressed, the duration increments, in-
dicated by lighting of the next LED in
the bargraph.

Connector K2 has been provided to
allow the microcontroller to be pro-
grammed if necessary.

The block shown adjacent to the V+
Flash (300 V) and 0 Flash (300 V) points
represents the recycled capacitor mod-
ule mentioned throughout this article.
This high voltage module connects be-
tween PCI and PC2 (GND) points. Pay
attention to the polarity of the capaci-
tor module when connecting it to the
control board.

The system uses a dual power system:
one 9 V battery for the PIC -based con-
trol electronics, and a separate 1.5 V
battery for the flash electronics - this
cell can easily supply the over 2.5 A
needed when capacitor C2 (160ji/F/
350 V) starts charging. The PSU is con-
ventional: the 9 V supplied by the bat-
tery is smoothed and reduced to +5 V
by the 78L05 regulator IC3. LED D10
is used to indicate the supply voltage
is present.

And to end with, the most important
module in this project, the ring fitted

K2

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RB6

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high voltage generator

-0 0 Flash (300V)

At

D2

13

14

15

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12

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330n

+5V

Q

C4

1u

16V

C5

lOOn

DIO

¥

GND

070612-11

Figure 2. Circuit of the home-brew electronics: the ringflash control board.

52

elektor - 2/2008

with the 32 LEDs and their current
limiting resistor connects to the main
board via a 3.5 mm mono jack.

Construction

This involves two stages: constructing
the electronics, and the ring.

The ‘electronics’ stage itself breaks
down into two steps:

1) ‘cannibalising’ the flash board. As
the photo in Figure 3 shows, this sub-
unit doesn’t look particularly impres-
sive. On certain models, the miniature
neon is replaced by an LED. You will
need, by some means or another, to
prepare this module by replacing the
pushbutton (which controls charging
of the capacitor) by a switch. The al-
ternative solution suggested by the
author is to use a dual reed relay (in
order to avoid pressing the switch
inadvertedly).

Once you have the flash charger, it’s
time to move on to constructing the
control board, the component overlay
for which is given in Figure 4.

The components should be fitted in the
usual order, starting with the smaller
components: jumpers, resistors, capac-
itors, diodes (watching out for their po-
larity), and then the larger components:
pushbuttons, transistor, switches, crys-
tal, ICs. The two DIL ICs should be fit-
ted in sockets (good quality ones). The
actual position of the LEDs and switch-
es S1-S3 depends on how you plan on
housing the circuit. We strongly recom-
mended putting everything into one
case, to which the ring of LEDs will
be connected (the inset ‘Constructing
the ring’ explains how to build it). That
way there’s no risk of getting a shock
if you make a false move. If you opt for
this solution, you’ll need to mount the
various indicator LEDs on the case,
along with the on/off switch and push-
buttons SI and S2.

The free end of the link cable going to
the flash socket on the camera con-
nects to the PC 3 and GND in the vicin-
ity of SI. Note that some cosmetic mod-
ifications have been made between the
prototype shown in the photo (Figure 4)
and the final version of the PCB.

Operation in practice

The way the capacitor module works
may vary from one disposable camera
to another. On some, you have to keep
the button pressed until the LED lights
to show the capacitor is fully charged;
on others (like the one we’ve used)
you only have to press the button mo-

Figure 3. Photo of the active part of the flash recycled from a disposable camera.

Figure 4. Photo of the prototype's control board.

COMPONENTS LIST

Resistors

R1 = lOkD
R2 = 1MQ
R3,R4 = 330D

Capacitors

Cl ,C2 = 22pF
C3 = 330nF
C4 = 1 a/F
C5 = lOOnF

Semiconductors

D1 = BAT42

D2-D10 = LED, 3mm, red
T1 = IRFBF20

IC1 = PIC16F628, programmed, Elektor
Shop # 070612-41

IC2 = 4051
IC3 = 78L05

Miscellaneous

XI = 4MHz quartz crystal
S1,S2 = miniature switch, PCB mount
S3 = on/off switch
K2 = 6-way SIL pinheader
K1 = 3.5mm jack socket
6 solder pins
PCB, ref. 070612-1 from
www.thepcbshop.com
Project software, PIC source and hex. files,
free download # 07061 2-1 1 -UK. zip from
www. e I e kto r. co m

LED ring parts

Semiconductors

32 LEDs, 5mm, white, HLMP-CW1 1 -XI 000
(Avago; from Farnell)

Miscellaneous

Ring support, home made (see inset "Con-
structing the ring")

2/2008 - elektor

53

PHOTOGRAPHY

Constructing the ring

There are several options for constructing the ring to hold the 32 LEDs. The author chose to
turn up a special plastic ring in Ertalon® on a lathe. But not everyone has such a tool, so
we set out to find another solution. A visit to a number of builders' merchants enabled us to
get our hands on a 110 mm/80 mm soil pipe adaptor (seen in the background of the pho-
to in Figure 5) which seems almost to have been designed especially for our purpose! We're

going to cut off the top part at a height of around 1 7 mm. Once the ring has been nicely
trimmed and sanded, it's time to drill the holes for fitting the LEDs. We start by marking a
circle mid-way between the inner and outer circumferences of the ring. To make this job
easier, you can divide the ring into four 90° sectors, which will each hold 8 LEDs. The cen-
tres of the LEDs are spaced by 9.8 mm. Once the 32 points have been accurately marked
around the circle, all that remains is to drill the 32 holes (5 mm dia.) for the LEDs. The LEDs
can be fixed using a dab of hot-melt glue, and interconnected, anode of one to cathode of
the next, as far as the last pair, whose respective anodes and cathodes will be left free to
connect to the cable that plugs into jack K1 .

mentarily and then wait for the LED to
light showing the capacitor is charged
ready.

In the light of experience

The author has been using this ring-
flash for over six months, and it has
become indispensable for macro work
(see photos in Figure 6).

Practical experience has shown it to
be very worthwhile for macro work at
distances of less than 40 cm from the
camera.

As our spec sheet stipulated, arrang-
ing the LEDs in a ring provides a nicely
diffused light.

However, the 20,000 mcd (each) bright-
ness of the LEDs is not enough to al-
low much stopping down (from // 2.8 to
// 8, for example) to increase the depth
of field.

Even white LEDs tend to be rather blu-
ish in colour. So always remember to do
a white balance before starting macro
work. Or else reduce the blueness later
using a photo retouching programme
(‘to photoshop’ has become a very hip
term of late in the world of mass-distri-
bution magazine publishing. . .).

Since the LEDs are controlled inde-
pendently, it’s preferable to keep the
camera in ‘Manual’ mode and try to
find an acceptable compromise be-
tween f - stop and shutter speed.

As the LEDs brightness is not too pow-
erful (and fortunately not the main ob-
ject of the exercise), it has never in fact
proven necessary to reduce the flash
duration on the camera (works inde-
pendently of the photo shutter).

The author uses a magnet to operate
the reed relay to recharge the flash ca-
pacitor, and has noted that the LED
system uses comparatively little pow-
er. You can fire off around ten or so
l/100 th second flashes before thinking
about recharging the capacitor.

This project offers lots of scope for de-
velopment. In view of the high voltage
generated by the disposable flash mod-
ule, it might be interesting to try using
other LEDs, like the Luxeon 1 watt or
even 3 watt types - photographers are
always after more light, to get as close
as possible to natural daylight. Neither
we nor the author have tried this ap-
proach - we’ll leave that and other pos-
sibilities to our readers’ imaginations.
Happy macro photography! Don’t
hesitate to send us the best of your
masterpieces.

( 070612 - 1 )

54

elektor - 2/2008

Web Links

[1 ] http://www.geocities.com/lemagicien_
2000/elecpage/maxflash/maxflash.html

[2] PIC16F628 datasheet

http://www.datasheetcatalog.com/datasheets
pdf/P/l/C/1 /PIC 1 6F628.shtml

[3] IRFBF20 datasheet

http://www.datasheetcatalog.com/da-

tasheets_pdf/l/R/F/B/IRFBF20.shtml

[4] 4051 datasheet

http://www.fairchildsemi.com/ds/CD/CD-

4051BC.pdf

Figure 5. Our LED ring started life as a pipe connector found in many DIY stores.

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2/2008 - elektor

55

E-BLOCKS

Thermometer /
Thermostat

Let's take the temperature...
and then maintain it

Jean-Paul Brodier

The previous applications we presented for E-blocks
made use of fairly elementary data input/output
modes: switches or photo-electric barriers as inputs,
LEDs as outputs, always involving purely binary
on/off information, often referred to as 'digital'.
Now it's time to go analogue and hey presto
Flowcode and E-blocks again turn out a
perfect combination!

The thermometer described here measures the tempera-
ture as an analogue quantity and displays it in text form on
the liquid crystal display (LCD). The thermostat operates in
a binary manner on one output, to turn a heating device
on or off.

Hardware

The liquid crystal screen used comes in the EB-005-00-
2 E-blocks module, and plugs into the Multi-programmer
board's port B socket. It's powered via a wire from the
display board's +V terminals and the one on the Multi-pro-
grammer board. No negative wire is needed, as the mod-
ule's ground is already connected to the Multi-programmer
via the sub-D socket.

The microcontroller chosen is the PIC16F877. This appli-
cation requires a type that includes an analogue-to-digital
converter (ADC). This one has a resolution of 10 bits with
eight inputs multiplexed onto the pins of port A.

The screen can be included into the circuit by clicking on
the 'LCD' symbol in the left-hand vertical bar. For all com-
ponents added this way, you can click on the arrow on
the top bar to display the Properties menu and modify, for

example, the connection location. By default, the display
is connected to port B. The same thing has to be done for
the thermometer on analogue input ADCO and the control
pot connected to analogue input ADC1 . The display form
chosen is the cursor, but you can also opt for a conventional
button and choose the colours.

The output LED is connected to pin 3 of port A. The pins of
port A can in fact be configured at will between analogue
inputs and binary input/outputs - and if necessary, any
mix of these.

Macro-commands associated with the hardware

The program handles the hardware by way of software li-
braries (available in Flowcode), loaded as and when they
are called by the macro-commands. The Flowcode file 'ther-
mo. fcf' for the project discussed here is available free from
the Elektor website.

Let's start with the LC display. Click on the square (hatched
outline, in the symbol bar), announced by the help bub-
ble as Component Macro, and keeping the mouse button
pressed, drag it to its place in the flowchart. Right-clicking
on Properties lets you choose the component (LCD), the
macro to be executed to initialize it (Init), and to rename
the box.

56

elektor - 2/2008

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Figure 1.

The PC screen shows all the
system components in order
to simulate operation.

The screen interface operates in 4- or 8-bit. To configure it,
we need to send it a sequence of instructions in 4-bit for-
mat, separated by pauses of defined duration. This is the
job of the Init macro-command, which takes account of the
quartz crystal frequency in the microcontroller's configura-
tion screen to set the speed. It automatically sets the format
to 4 bits - handy for saving on input/output pins, and in-
dispensable for the smaller types of controllers.

A call to the PrintString macro for the same component
will display the text that has been set up in parameters.
The string must be enclosed in double quotes, otherwise
the compiler will take the characters as a variable name.
The standard display's character table does not include
accented characters. The compiler accepts them and the
simulator displays them on the computer screen, but they
do not appear on the display, or display wrongly. Using a
series of commands to the display, it is possible to create
up to eight special characters that will be stored in RAM
alongside the ROM.

In our application, the first (top) line of the screen shows the
labels for the numbers that are going to be displayed on the
second line. Three quantities are displayed — two measured,
one calculated. The LCD screen is useful in that it displays
much more information than simple LED numeric displays. But
there's nothing to stop you adapting the display to circum-
stances and to display the relevant data at a given moment
— for example, an alarm and what's causing it.

Loop

After initializing the screen, the program enters the main
loop. The same operations are repeated at intervals of one
second, set by the box Delay.

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Figure 2.

The LCD connection
defaults to port B

We start by clearing the bottom line (line 1) by writing
16 spaces to it, starting from the first position (0). Then
come the measurements, calculations, and displays.

Measurement and scaling

The two quantities measured are the result of the Scaling
macro reading the analogue-to-digital converter - once for
the temperature and once for the control pot. This meas-
urement is followed by scaling. We want to make the
1 ,024 points (1 0 bits) of the measurement correspond to
a range of 1 0 to 30°C, i.e. an amplitude of 20°C and an
offset of 1 0°C. Whence the set of calculations in the Scale
macro:

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2/2008 - elektor

57

E-BLOCKS

Properties: Component Macro

Display name:

I nit LCD

Figure 3.

Each component has
a certain number of
dedicated macro-
commands. The LCD
screen can display one
character at a time, a
string, or a number. It also
accepts cursor movement
commands etc.

Component:

Macro:

AD 0(0]

AD cm

LEDsfOj

AD 0(2]

V

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F'rintA.SCII

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Variables ..

R eturn Value

I 3

OK

Cancel

MEASURED = MEASURED * 20
MEASURED = MEASURED / 102
MEASURED = MEASURED +100

The factors used in the calculation have been chosen in
the ratio 200:1024, to avoid yielding an intermediate re-
sult over 32,767 (the maximum value for an integer in the
FlowCode system). The error introduced by these approxi-
mation factors is just under 4 in 1 ,000, i.e. 0.4% - half the
tolerance of precision components, so perfectly acceptable.
The result is expressed by ten points per degree, so well
have to cheat a bit so as to be able to display the tenths
of degrees.

Display

The driver routines for the LCD only display whole numbers
between -32,768 and +32,767. So it's up to us to organ-

Figure 4.

The home-made display
macro breaks down the
number into digits and
inserts the decimal point.
As the format is fixed, this
is much more economic
than the FlowCode macro,
which has to allow for all
possible eventualities,
with tens of thousands,
thousands, the sign, and
hexadecimal numbers.

ize the data in such a way as to make full use of the resolu-
tion of the converters.

The tens digit is displayed (except of course zero), the units,
the decimal point, and then the tenths of degrees. We use
the maths operations division and modulo (remainder after
division). If the result of the measurement is less than 100
(tenths of a degree) the tens digit is replaced with a space.
If it is 1 00 or more, the figure to be displayed is obtained
by dividing the measured value by 1 00. The remaining dig-
its to be displayed are the remainder after division by 1 00,
obtained using the operation modulo. We do the same for
the units (tens of tenths). The remainder after division by 10
is going to represent the tenths of degrees.

As these calculation and display routines are used three
times over — for the measured temperature, the target tem-
perature, and the difference — they form two macros, Scale
and Display.

Between displays, we perform the measurements, and also
reposition the cursor on the line. The LCD lines (y) and char-
acters (x) are counted from zero. For example, the display
of the Target temperature starts on (y=l ; x=7) i.e. on line 1 ,
character position 7.

Thermostat

The thermostat function consists of actuating a relay if the
measured temperature is lower than the target temperature.
Actuation of the relay is confirmed by the lighting of the LED
connected to port A.

Calculation of the difference

The factor that determines the action of the thermostat is the
difference between the target and measured values. The
absolute value is the result of the subtraction

DIFFERENCE = TEMPERATURE - TARGET

or the opposite if the actual temperature is lower than the
target. The method used is simpler than calculating the ab-
solute value and determining the sign. If the difference be-
tween the measured temperature and the target is negative,
the LED lights to indicate that the relay is activated. Because
of the low frequency of the loop and the division performed
for scaling, there is no risk of relay chatter as a result of
noise from the converters.

The periodic blanking of the bottom line has the added ad-
vantage of showing that the system is working. But if you
find this blinking annoying, it can be eliminated completely,
or made more discreet — for example, by blanking only
four of the characters. In any event, all the characters, in-
cluding spaces, are updated each time round the loop.

The end-of-loop timer (Delay) is programmed with your
choice of seconds or milliseconds. The compiler then looks
after calculating the number of wait cycles or the value for
reloading the counters, according to the clock frequency.

( 070852 - 1 )

Web Link

Update of FlowCode 3 to version v3.2.2.40 (needed for the
thermometer/thermostat program to work properly)

http://www.matrixmultimedia.com/Flowcode3a-X.php

58

elektor - 2/2008

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2/2008 - elektor

59

DRIVING HIGH-POWER LEDS

Programmable control (or LED lighting

Jorg Prim

It is of course possible to drive LEDs using a simple series resistor. However, in a modern efficient
lighting system we would not want to tolerate the wastage of power in these resistors. Also desirable is
a remotely controlled dimming function.

The circuit described here, called ‘LED-
BUS\ fits the bill perfectly. It also al-
lows a practically unlimited number
of LEDs to be controlled and up to ten
lighting programs can be configured,
which can be called up at the press of
a button using a standard infrared re-
mote control. Each lighting program
specifies the desired brightness of each
LED module individually. For example,
one program could make the lights
bright for reading while another could
dim the lights and add a warm red tint
for a more relaxing atmosphere.

In theory

The circuit consists of two printed
circuit boards, the main unit and the
power module (Figure 1). The main
unit can control a number of power

modules over the ‘LEDBUS’, and one
power module can drive from one to six
1 W LEDs, with the LED brightness ad-
justable in 256 steps. The LEDBUS op-
erates like a shift register, and so there
is no addressing in the protocol. Other
parameters besides LED brightness
can also be controlled from the main
unit.

In the example configuration in Fig-
ure 1 the main unit is connected to
a chain of three power modules. The
main unit has an output shift register
and an input shift register, while each
power module has a shift register at
its input and a pass-through output. A
termination connector is therefore re-
quired at the end of the chain so that
the signal can be shifted back to the
main unit.

Normally a shift register would re-

quire a clock signal, a data signal and
a strobe, but in the LEDBUS these
three signals are replaced by a single
wire, with the protocol being decoded
in software.

The transmission of one byte is illus-
trated at the bottom of Figure 1. First
comes the start bit which lasts for half
a bit time. This is followed by a low
level for the same period. Then comes
the command bit and then the data bits
from bit 7 to bit zero: each of these bits
occupies a full bit time. The command
bit indicates whether the accompany-
ing byte is a command (1) or is data (0).
A command is transferred immediately
to the output of the power module so
that all the power modules in a chain
receive a command essentially simul-
taneously. If the byte is data then the
contents of the internal data shift reg-
ister are output. Rather than waiting
for the entire byte to be received the
module starts outputting data immedi-
ately after the start bit is seen, which
means that each power module intro-
duces a delay of one bit time. A more
detailed description is given in the text
box All about bits’.

Circuits

The circuit of the main unit is shown in
Figure 2. An LCD panel with two lines
of twenty characters displays status
information and the selected program,
all functions being accessible via men-
us. An I 2 C connector allows for easy
expansion of the circuit: a mains relay
board is already planned.

The main unit is based on an AT-
mega32 microcontroller; other compo-

Figure 1. Block diagram of the complete system. In this example three power modules are connected to the main unit.

60

elektor - 2/2008

+5V +5V

Figure 2. Circuit of the main unit, centred on an ATmega32.

2/2008 - elektor

61

DRIVING HIGH-POWER LEDS

All about bits

A command byte is divided into two four-bit nibbles. The high nibble specifies one of 16 possible command groups as follows:
0: Group 0: see below

1 : Write register: lower nibble gives register address

2: Read register: lower nibble gives register address

3 to F: not used

Group 0 commands:

0: Clear data shift register

1 : Device select: when the data register is zero the device is deselected; otherwise it is selected

2: Device activate

3: Query selection: data register is set to 1 if the device is selected

4 to E: not used

F: Permanent save

A device (i.e., a power module) is either selected or not. When selected its green LED lights and it takes part in data transfers. If the device is not
selected it does not take part in data transfers on the LEDBUS, and its output is equal to its input. In this state only commands in group 0 are
executed.

Command 02 (device activate) always activates a device. Command 01 (device select), on the other hand, only activates a device if its data shift
register holds a non-zero value. This allows the main unit to select individual devices and exchange data with them without having to clock the
data through every device on the LEDBUS.

Up to 16 registers can be read and written using commands in groups 1 and 2.

0:

Current brightness: brightness changes immediately when this register is written

1:

Brightness change speed: 0 = fast; 1 = slow

2:

Current brightness: brightness changes gradually (at a speed determined by the contents of register 1 ) when this register is
written

3. ..12

Not used

13:

Inversion flag: 0: 0 = off, FF = maximum brightness; 1 : vice versa

14:

Minimum brightness

15:

PWM frequency: 0 = 8 kHz; 1 = 2 kHz; 2 = 500 Hz

In order to get a power module to operate at full brightness, first write FF into the data register. Then use command 1 0 to copy the value into re-
gister 0: the PIC will then switch the module to full brightness.

In order to make a gradual transition to half brightness, write the value 80 into the data register and then send command 1 2. The PWM signal will
then gradually change (at a speed determined by the contents of register 1) until brightness 80 is reached.

The PIC can be configured to make it compatible with different LED driver ICs. If the value in register 1 3 is zero, FF will correspond to the LED
being at full brightness and zero to the LED being off. Since in our circuit T1 inverts the PWM signal, we need to set register 1 3 to 1 .

Register 1 4 sets the minimum brightness. The value varies from module to module, but the LED does not normally start to light until the brightness
value reaches approximately 05. It would be preferable if the LED started to light at a value of 01 , and this can be achieved using a suitable set-
ting of register 1 4. Register 1 5 sets the PWM frequency to 500 Hz, 2 kHz or 8 kHz.

However, in practice there is no need for any mental binary arithmetic, as the main unit controls the power modules in response to simple com-
mands. The settings for each power module can be stored in the PIC's internal EEPROM using command OF so that the modules do not need to be
reconfigured every time power is applied. On reset the PIC loads the values stored in its EEPROM into the 1 6 registers: observe that this also deter-
mines the brightness of the LED at power-on.

nents form the LCD interface, I 2 C bus
and LEDBUS interfaces, and there are
four status LEDs, four buttons, an IR re-
ceiver and a programming interface.
The LCD data bus is connected to
Port A of the microcontroller, and the
R/W, RS and E signals are connected
to port pins PD5, PD6 and PD7. The
backlight can be switched on via tran-

sistor Tl, connected to microcontroller
port pin PD4. PI sets the contrast of
the display.

Pins PC0 (SCL), PCI (SDA) and PC6
of the microcontroller are taken to the
I 2 C connector K6. The connector also
carries the 5 V supply and the unreg-
ulated 12 V supply, so that 12 V re-
lays can easily be used on expansion

boards. PC6 acts as an spare enable
signal. If I 2 C bus expansion is not re-
quired, components K6, R3 and R4 can
be dispensed with. The current version
of the software does not support the
I 2 C bus.

PC2, PC3, PC4 and PC5 drive the sta-
tus LEDs, with D5 being an infrared
LED. The unit can generate RC5 format

62

elektor - 2/2008

K3

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070495 - 12

Figure 3. Circuit of a power module. Here again a microcontroller (a PIC12F683) provides the intelligence.

signals, making it easy to program a
remote control that is capable of ‘learn-
ing’ commands. PBO, PB1, PB3 and PB4
are connected to buttons, which are
not needed for normal operation: they
are used for configuring the RC5 code
parameters and setting the user inter-
face language. All other functions are
carried out using the remote control.
The LEDBUS interface consists of a
MAX491 (IC3) which conforms to the
RS-422 differential signalling standard,
which is relatively immune to interfer-
ence. The LEDBUS also carries the un-

regulated 12 V supply, used to supply
the PICs in the power modules.

The remote control input uses a
TSOP1736, which is connected to PB2
on the microcontroller. The device con-
verts the 36 kHz-modulated infrared
signals into a digital signal. It can be
soldered directly to the printed circuit
board or, if required in a particular ap-
plication, it can be mounted off-board
and connected using a cable. In our
prototype we wired a stereo audio jack
socket to the board, which we could
then hide away in a cupboard with just

the infrared receiver externally visible.
If a 2.5 mm jack socket is used, a Haup-
pauge TV card remote control sensor
can be pressed into service: indeed,
we found that we could connect the
sensor to the TV card and to the main
unit simultaneously (isolating the pow-
er supplies using a diode), and then
use a single remote control to operate
both. Alternatively, a TSOP1736 and
some heat-shrink sleeving will do the
job just as well.

The 10- way ISP connector K4 is com-
patible with the standard Atmel con-

Figure 4. Printed circuit board for the main unit.

Figure 5. Printed circuit board for a power module.

2/2008 - elektor

63

DRIVING HIGH-POWER LEDS

COMPONENTS LIST

Power module 070459-1
Resistors

R1 = 0Q33 1 W (SMD 2515)

R2,R3 = 220Q (SMD 0805)

R4 = 1 OkU (SMD 0805)

Capacitors

Cl ,C2 = lOOnF (SMD 0805)

C3 = 2jllF 2 (SMD1 2 10; dielectric X7R or
X5R)

Semiconductors

D1 = 10BQ100 (Schottky)

D2,D3 = SMD LED (SMD 1206)

T1 = BC850
IC1 = A/A78L05ACD
IC2 = MAX491CSD
IC3 = PIC1 2F683-I/SN, programmed,
Elektor Shop # 070459-41
IC4 = ZXLD1 350ET5CT

Miscellaneous

LI = 68jllH SMD inductor, 10x10; e.g.

Epcos B82464G4683M
K1 = 4-way PCB terminal block, lead
pitch 5mm

K2 = 6-way SIL pinheader
K3,K5 = 6-way mini-DIN socket, PCB
mount

Up to 6 power LEDs; e.g. Luxeon 1W
types (see text)

PCB, ref. 070459-1 from www.thepcb-
shop.com

Project software, free download from
www.elektor.com

COMPONENTS LIST

Central unit 070459-2

Resistors
R1,R2 = 15kU
R3,R4,R6 = 4kQ7
R5 = 33U
R7-R10 = IkQ
R1 1-R14 = lOkU
PI = 1 OkU preset

Capacitors

Cl ,C2,C4,C5,C6 = lOOnF
C3 = IOOjuF 25V radial
C7,C8 = 22pF

Semiconductors

D1 = 1N4001

D3, D4 = LED 3mm; low-current (D2
omitted)

D5 = LD271; IR-LED
T1 = BC337
IC1 = 7805

IC2 = ATmega32-l 6PC (SMD), pro-
grammed, Elektor Shop # 070459-42
IC3 = MAX491CSD

Miscellaneous

S1-S4 = pushbutton, 6x6 mm

XI = 1 6MHz quartz crystal

K4,K6 = 1 0-way boxheader

K5 = 6-way mini-DIN socket, PCB mount

RC-5 receiver, e.g. SFH51 10-36 (on K3)

LCD Module witn 2x20 characters; e.g.

Displaytech 202A (on K2)

PCB, ref. 070459-2 from www.thepcb-
shop.com

Project software and Guide to Operation,
free download from www.elektor.com

nector and hence also with USBprog.
The power module (Figure 3) uses
a Zetex ZXLD1350 (IC4) to drive the
LEDs. This device is a step-down con-
verter with current regulation, with R1
setting the maximum current through
the LEDs. A value of 0.33 Q corre-
sponds to a current of 300 mA. With
a 24 V supply up to six 1 W LEDs can
be driven in series. IC4 is very efficient
and there is no noticeable heat dissipa-
tion. Control commands are processed
by the PIC12F683.

The power module needs its own sep-
arate power supply: only the PIC is
powered from the LEDBUS, via a 78L05
regulator. The microcontroller produces
a PWM signal which is used to con-
trol the driver IC to dim the LED via
Tl. The PIC can generate a PWM sig-
nal with a choice of 256 different mark-
space ratios, giving 256 different LED
brightnesses.

The software for the main unit was

written using AVR Studio 4 and the
free WinAVR C/C + + compiler. Only
the interrupt routine is written in as-
sembler, the higher-level functions be-
ing written in C. The PIC software was
written using the free MPLAB environ-
ment from Microchip (and is download-
ed to the microcontroller using connec-
tor K5). The software uses interrupts
to react to serial, infrared and LEDBUS
signals: the interrupt routines simply
set flags, leaving the actual processing
to the main program loop.

Construction

Figure 4 and Figure 5 show the print-
ed circuit boards for the main unit and
the power module. The latter is chiefly
populated with SMD components: the

LED driver IC is particularly small. A
fine-tipped soldering iron and a good
measure of patience are required to
solder this device successfully. When
using PICkit2 to program the PIC via
K2 pin 1 (marked by a triangle) should
be nearest the corner of the board. If
you are using a ready-programmed
microcontroller, K2 may of course be
dispensed with. Take care to allow
enough space around K1 to connect the
programmer if you need to. You will of
course need to assemble as many cop-
ies of the power module as you need.
The main unit employs only one SMD
(IC3), which requires care in soldering.
The buttons, LEDs, display connector,
and IR receiver (if fitted) are soldered
to the reverse of the board.

After the board has been populated
the ATmega is programmed using USB-
prog or other suitable programmer. All
software files for the project are avail-
able for free download from the Elektor

website (reference 070459-11). Ready-
programmed microcontrollers are also
available for purchase from the Elektor
shop (see parts list).

The power modules are connected in a
chain using 6-pin mini-DIN connectors.
The first cable runs from the main unit
to K3 on the first power module. The
second runs from K5 on the first power
module to K3 on the next, and so on. A
terminator plug (see Figure 7) is fitted
to K5 of the last module in the chain.
The author has prepared a guide to
programming and operation of the
system, which for reasons of space we
cannot print here. It is, however, avail-
able for free download from the Elektor
website.

( 070459 - 1 )

Figure 6. A couple of assembled boards in action.

64

elektor - 2/2008

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electron ics

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Quasar Electronics Limited
PO Box 6935, Bishops Stortford
CM23 4WP, United Kingdom

Tel: 0870 246 1826
Fax: 0870 460 1045
E-mail: sales@quasarelectronics.cor
Web: www.QuasarElectronics.com

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Here are just a few of our controller and
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Here are just a few of the controller and

data acquisition
See website for
for all units: Ord

full details. S
er Code PSU

and control units we have

uitable PSU
445 £8.95

PC / Standalone Unipolar
Stepper Motor Driver

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

Provides speed and direc-
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controlled mode. Up to six 3179 driver boards
can be connected to a single parallel port.
Supply: 9Vdc. PCB: 80x50mm.

Kit Order Code: 3179KT - £12.95
Assembled Order Code: AS3179 - £19.95

Bi-Polar Stepper Motor Driver

Drive any bi-polar stepper
motor using externally sup-
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and direction control. These
usually come from software
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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
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range of control is from fully OFF to fully ON
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Screw terminal block for connections.

Kit Order Code: 3166v2KT - £17.95
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DC Motor Speed Controller (100V/7.5A)

Control the speed of
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Kit Order Code: 3067KT - £13.95
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lost items are available in kit form (KT suffix)
>r assembled ^nd ready for use (AS prefix).

8-Ch Serial Isolated I/O Relay Module

Computer controlled 8-
channel relay board. 5A
mains rated relay out-
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inputs. Useful in a vari-
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programming (using our new Windows inter-
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Kit Order Code: 3108KT - £54.95
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Computer Temperature Data Logger

4-channel temperature log-
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Continuously logs up to 4
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Kit Order Code: 3145KT - £17.95
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Additional DS1820 Sensors - £3.95 each

Rolling Code 4-Channel UHF Remote

State-of-the-Art. High security
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Kit Order Code: 3180KT - £44.95
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DTMF Telephone Relay Switcher

Call your phone num-
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Kit Order Code: 3140KT - £54.95
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Infrared RC Relay Board

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

Toggle or momentary. 15m+ "
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PIC & ATM

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We have a wide flange of low
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NEW! USB 'All-Flash' PIC Programmer

USB PIC programmer for all
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“PICALL” PIC Programmer

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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

www. QuasarElectronics. corn

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

2/2008 - elektor

65

TECHNOLOGY

LIGHT EMITTING DIODES

Power to the

Luxeon Rebel - cool on a ceramic die

Rob Alferink, Philips Lumileds Lighting Systems R&D

LEDs are all the rage lately and the high-power blue and white ones in particular even appeal to
unexpected audiences like youths of the msn & mp3 generation who use them to pimp their scooters
and PCs. In two short picture stories we tell not only how LEDs are designed and produced (basically!),
but also look at what Philips Lumileds Lighting Systems are pursuing technically in a bid at making a
versatile high-power LED for mass production.

LED basics

What's an LED? Electrically, thermally, optically, mechanically?

Basic principle

An LED (light emitting diode) converts
electrical energy into light, with heat
as an unwanted and highly problem-
atic by-product.

The heart of an LED is called ‘die’
(“dai"). A die is composed of several
materials specially selected for certain
physical properties and exhibiting the
so-called semiconductor effect. Its size
is approx, lxl mm.

To prevent overheating, the die for a
high-power LED is secured on a heat-

sink that often doubles as the case. electrical connections.
The die has wires attached to it for the

What basic materials?

For red, orange/red and amber LEDs
the basic semiconductor material is
AlInGaP, where
A1 = aluminium
In = indium
Ga = gallium
P = phosphor

Blue, cyan and green LED dies are pro-
duced using InGaN, where
N = nitrogen

Ball Bond

In a reactor, these materials are ‘sput-
tered’ at a certain mixing ratio onto a
ruby (wafer-) carrier called the sub-

strate. The wafer has a diameter of 2
or 4 inch.

66

elektor - 2/2008

Low power LEI with traditional leads.
No problems with high temperatures,
so no heatsink required.

High power LED; the case/heatsink
and the lens/dome are the largest
parts. "

InGaN technology

Patterns may be created
using lithography. The
positive and negative
electrodes are at one
side.

The LED colour

can be chosen from a wide spectrum.

In practice, this is achieved by combin-
ing several semiconductor materials.

How to make white light led shade of white.

Blue light from an InGaN LED is con-
verted into yellow using a phosphor
layer. The result is a carefully control-

Making it light

An ordinary incandescent bulb can
be powered by DC or AC voltage
source.

An LED can also be powered by a
voltage source if a suitably dimen-
sioned resistor is included. Howev-
er, for more repeatable results and
better control of the LED response,
the preferred method is pure current
sourcing.

Lumiramics

New technologies allow a thin phos-
phor plate to be used instead of a
damped-on powder.

2/2008 - elektor

67

TECHNOLOGY

LIGHT EMITTING DIODES

How the Luxeon Rebel came about

The Luxeon Rebel LED from Philips Lumileds has great potential for all sorts of lighting applications
where energy wasting fluorescent lights and even incandescent lamps are long overdue for replacement
by a smarter, more durable light source. The Rebel has its roots in earlier Luxeon technology.

Standard Luxeon

These devices can be classified by:

1. Power:

• 1 watts

• 3 watts

• (5 watts)

2. Colour:

• red

• orange/red

• amber

• green

• cyan

• blue

• royal blue

3. Radiation pattern:

• Lambertian

• bat wing

• side emitter

'Binning': fine tuning
the device selection

Within the constraints for colour, pow-
er and radiation pattern, LEDs are se-
lected in a high-speed automated in-
dustrial process. The selection is on

• amount of light produced (‘flux’), ex-
pressed in lumen (lm) or milliwatts
(mW). Advanced radiometric measu-
rement is applied.

• wavelength (actually, dominant
wavelength)

• forward voltage

The selection employs ‘bins’ and the
process is called ‘binning’ (nothing to
do with rubbish, hopefully).

A selection example for bin code R2H

Flux (green)

lower (lm)

upper [lm]

^dom 1 (green)

lower [nm]

upper [nm]

V f (green)

[V]

[V]

Q

30.6

39.8

1

520

525

H

3.03

3.27

R

39.87

51.7

2

525

530

J

3.27

3.51

S

67.2

87.4

3

530

535

K

3.51

3.75

T

87.4

1 13.6

4

535

540

L

3.75

3.99

5

540

545

M

6

545

550

N

1 Dominant wavelength (A, dom ) is determined for a colour using its coordinates in an x-y colour plane.

The classification is meaningful for any primary colour except white.

68

elektor - 2/2008

LEDs on a board

Luxeon LEDs can be supplied pre-
mounted on boards with several
shapes. The individual LEDs are ca-
refully selected for equal colour and
brightness. Surprising applications
include open top deepfreeze cabinets
in supermarkets and beverage ven-
ding machines. In both cases the co-
lour has to be controlled accurately for
the best appearance of the foodstuffs
and drinks on display. For sure, the co-
lour produced by the LED lighting was
adjusted from sales results based on

Luxeon DCC Star

questionnaires and interviews with unsuspecting clients!

Luxeon K2 TTFC and K2 Prime TTFC

These two members of the Luxeon

family are marked by

• availability as a Lambertian radiator
only

• highly suitable for higher currents
and temperatures

• suitability for reflow soldering (as op-
posed to standard Luxeon devices)

The basic K2 LED (Luxeon K2 TFFC,

thin film flip chip) sustains a current

of 1.5 amps!

Luxeon Flash products

These are white LEDs invariably. They
come in two main versions:

1. mounted on a carrier = PWF
(F = flash)

2. integrated with a lens = PWM
(M = module)

The next generation:

LEDs on ceramics

The ‘Luxeon Rebel’ LED from Philips
Lumileds is an unusual member of the
Luxeon family in that it is produced on
a ceramic die. Ceramics have a long
history at Philips, and the relevant
manufacturing technologies have been
well documented as a result of exten-
sive research over many years. Certain

ceramics have good heat conducting

properties, which helps to prevent the
LED die from dying (pun intended) ow-
ing to overheating. Heat, by the way, is
the main problem LED manufacturers
are contending with. It’s kind of obvi-
ous since thermal instability and runa-
way not only affect important device
parameters like forward voltage and
life expectancy, but also the colour pro-
duced by the LED (however slightly).

For further reading

Philips Product Datasheet # DS25 on
the Luxeon LED and the associated
Reliability Datasheet # RD25 delve
deep in the technology of Luxeon LED
production and application.

You can find the documents as free
downloads on the web page for this

article at www.elektor.com, courtesy
of Philips Lumileds Lighting Systems.

Further interesting documents
may be found at these urls.

1. General information on Lumileds:

www.lumileds.com/

2. Luxeon K2:

www. lumileds. co m/p rod u cts/
line.cfm?lineld= 1 8

3. Luxeon Rebel:

www.lumileds.com/products/
line.cfm?lineld = 1 9

( 070906 - 1 )

2/2008 - elektor

69

TECHNOLOGY

LIVINGCOLORS

Philips LivingColo

Luc Lemmens

Strange people they are, the editors and technicians at Elektor. And I count myself among
them. They generally show greater enthusiasm for disassembling things than for assembling
them. It is therefore not surprising that I counted five colleagues around the table at my
request to attack a Philips LivingColors unit with a screwdriver. It must be in our DNA.

At first glance the LivingColors — a bit of an unusual name
for a lamp — looks more like a set of speakers from Harman
Kardon for a Mac. A handsome, transparent, spherical hou-
sing which contains a goblet shaped interior that looks more
like a speaker than a heatsink. The lamp, on command, con-
jures up colours on a light wall and colours the room to your
taste. A little bit' to your taste, because to fully appreciate
the effect of this lamp all the other lights in the room have to
be turned right down.

To conjure up all the colours of the rainbow, the lamp is pro-
vided with a number of coloured LEDs (2 x red, 1 x green
and 1 x blue) which, when combined in various intensities
generate the desired colour. It is a very effective demonstra-
tion of chromatics from physics class. Philips has been very
fond of LEDs recently and has produced various household
devices to add colour to your life. The 'singing LED candles'
(because the LED is driven by a music chip) from Philips are
a great success and this LED application is also certain to
find its way to the consumer.

Unpacking and disassembling

In addition to the lamp the LivingColors box also produces a
remote control, a few batteries and, of course, the manual. The
goal of the assembled Elektor posse is to disassemble the thing
in the shortest possible time. The RF boys rip into the remote con-
trol with military precision and the others realise quite quickly
that brute, yet gradual force is best for removing the front panel
of the lamp. In less than a minute we reach the PCB that also
contains the four LEDs.

These LEDs generate quite a bit of heat so their bottom side is
mounted on the goblet shaped fin in the lamp which acts as
the heatsink. An amazing amount of electronics appears to be
necessary to get the whole thing to go. There is obviously the
RF section for the communication link with the remote control,
there are four separate control circuits for driving the LEDs and
then a further circuit that drives these four circuits. At the heart
of this control circuits sits - surprisingly - an MSP430 processor
from Texas Instruments.

70

elektor - 2/2008

Operation

The remote control uses a radio link and makes the lamp a
very unusual toy. Completely in the style of ' everyth ing-with-an-
i-in-front' it has a kind of colour circle on the front. You would
expect that this allows you to move continuously through all
the colours, but that appears not to be so. It all works with ca-
pacitive sensors and you really have to place your fingers in a
particular location to get the desired colour. The RF spectrum
analyser should have given us an indication regarding the sig-
nal from the remote control, but no matter how hard we look-
ed, there was only noise. Not that strange: after some detec-
tive work, i.e. looking very hard at what is written on the tiny
1C, we learned that the remote control operates at 2.4 GHz.
Quick googling of the part number CC2500 shows that it is
a 2.4-GHz transceiver from (again!) Texas Instruments. The
accompanying antenna is a c osed ] /2 X folded dipole formed
with a copper trace on the PCB — says Jan.

The remote control also has the ability to activate a few special
functions. According to the manual we have to hold the remote
control close to the logo on the lamp to make controlling several
lamps possible and the same trick can be used to start the demo
program. Because there are no sensors that allow the position of
the remote control to be determined, we concluded that it works
by signal strength detection in the receiver. By holding the remo-
te control close the receiver an RSSI-ish control circuit produces
a signal that's used to activate the special functions.

Everything revolves of course around the LEDs. These are from
the Luxeon K2 series from Lumileds. On the circuit board, under-

neath the LEDs, there are a large number of vias (plated through
holes), which conduct the heat to the surface on the back of the
PCB that in turn is in contact with the 'cooling tower'. Thermal
conducting paste has been used very sparingly though...

Hacked & Cracked

Up to now this whole exercise has been more of a 'crack'
instead of a 'hack'. Intriguing is the JTAG connection, the foo-
tprint for an SMD connector is on the board but the connector
itself is not fitted. Through this we would have direct access
to the contents of the processor and be able to do nice things
ourselves, but in all likelihood Philips will have blown the JTAG
fuse in this 1C so that the interface is no longer usable (?). So off
the cuff, could the LivingColors lamp be changed into a kind
of Ambilight? Perhaps it is possible to drive the remote control
separately and obtain other visual effects. Could we use the
remote control for other things? Do you have any other ideas
or suggestions?

The LivingColors lamp is currently heavily discounted. If you
want more colour, you can use it to brighten up your home
nicely and there are certainly other decorating applications to
be found. In any case, we were quite surprised at the quality
of the construction — real design, we could say. Now the only
thing left is to collect all the loose parts and see if we can put
the lamp back together gain.

( 070956 - 1 )

2/2008 - elektor

71

TECHNOLOGY

LABTALK

Vista versus LPT

Deathblow for the printer port?

Paul Goossens

Last month in this column we described the problems in our lab con-
cerning the use of Vista. The biggest stumbling block appeared to be
the parallel printer port. This port is eminently suitable when desig-
ning cheap programmers, JTAG-interfaces and the like. With Vista,
the new operating system from Microsoft, it appears to be very diffi-
cult for electronics enthusiasts to use this very useful interface.

That the parallel printer port has been slowly disappearing as a
standard interface is clear. Many new computers are no longer fit-
ted with a Centronics interface. This port was originally intended to
control printers. A long time later, affordable scanners appeared for
home use, which also used this parallel port.

These days it is common for such devices to be fitted with a USB
connection. So it appears logical that the user will not miss the pa-
rallel port.

Internal debate

The debate during an editorial meeting became heated after I sug-
gested this topic for this month's Labtalk.

Many of those present considered the parallel port a relic from
another era. Comments such as "All peripherals have USB!" and
"The parallel port is out of date!" were used as counterargument. But
for an electronics designer this port is darn handy.

(Ab?)use

Electronics engineers have received the parallel port enthusiastically.
The reason was that there now existed a standard interface, which
could be used as a simple l/O-interface. With this interface you could
use a number of status lines and 8 data lines as digital outputs. In
addition there are a few lines available that can be used as digital
inputs. Obviously, the parallel port was not originally invented for
this purpose, but that does not mean that you cannot ab(?)use it for
your own purposes.

During the nineties the parallel port was developed further, resulting
in the EPP/ECP-port. The big step forward was that the data lines
could now be switched between input or outputs as required. This
was very interesting for a number of manufacturers of scanners and
other external devices (such as ZIP-drives), because they were now
able to send data at a much greater speed. Of course, this also in-
creased the usefulness of this port to electronics engineers.

Applications

Many programmers and JTAG interfaces still make use of the paral-
lel port. In many cases you can make a nice programmer with a few
standard ICs that is directly connected to the parallel port. The de-
velopment of a programmer or JTAG -interface with a USB interface
requires considerably more time and especially knowledge.

Here at Elektor as well, we have often used the parallel port to drive

programmers and the like. It would be a shame if these could no
longer be used with Vista.

Driver

As described in last month's article, we encountered some problems
when installing a parallel port PCI expansion card.

Our usual programmer that uses this port to program an innumerable
range of devices could not cope with this port. The Quartus FPGA
software and Altium Designer refused to work as well. No parallel
port found, was the message — despite the fact that the driver was
installed correctly, according to Windows.

After some investigation on the Internet it appeared that the driver
is solely intended to control printers, not to use the parallel port as
digital I/O.

People who bought a PC with a parallel port on the motherboard do
not appear to have these problems. Apparently, Microsoft Vista only
supports the parallel port on this type of PC.

Strategy

Microsoft will (just like the motherboard manufacturers) in the fore-
seeable future cease to support the old interfaces such as the serial
port, parallel port and similar. This is also apparent from two docu-
ments on their website, where they outline their strategy to banish
this old technology to the museum. Microsoft have chosen for the
intermediate solution of continuing to support the parallel port only
if it is integrated on the motherboard.

Solution

It makes absolutely no difference to the processor whether the LPT-port
is on an expansion card or whether it is integrated on the mother-
board. So perhaps it is nevertheless possible to use our expansion
board? The answer appears to be 'YES'.

The solution is to force Windows to use the file parport.sys (by de-
fault this can be found in the Windows folder) as the driver when
installing the expansion board.

After this installation, the problems with Quartus and Altium Designer
were gone. In all likelihood this trick will also work with all kinds of
other software (for example for programming or debugging of con-
trollers) when used with Windows Vista.

I do have to note that the base address of this LPT port is rather unu-
sual, namely EF00-EF07. It is possible that some programs require
that the LPT-port has a standard address. If that is not the case then
you can just continue to use your parallel port with Vista!

( 070854 - 1 )

Web Links

http://download.microsoft.eom/download/l/6/l/161ba512-40e2-4cc9-843a-923143f3456c/

ISAW2.doc

www.microsoft.com/whdc/archive/legacylO.mspx

72

elektor - 2/2008

DESIGN TIPS

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Sagjad Mosavi

Here's a very simple circuit ca-
pable of measuring frequency
up to 1 MHz at 1 Hz accuracy
without an additional divider or
prescaler circuit. The circuit em-
ploys an Atmel microcontroller
type AT89C2051-24XX as the
main part.

The input signal should be a
square wave with maximum
and minimum level of +5 V and
0 V respectively. If you want to
apply non-TLL waveforms you
may use the level converter
around T 7 — it will convert
your signal into to a TTL square
wave as well as protect the
counter from excessive signals
swings.

To be able to measure higher
frequencies, divider (prescal-
er) ICs like the SAB6456 or
SP8704 may be used. If so, the
frequency appearing on display
should be multiplied by the divi-

sion ratio to obtain the exact
frequency in hertz.

If you're not into gigahertz'ing
then TTL dividers like those
good old 74LS93 and 74LS90
with divide ratios like 2, 4, 5, 8
or 10 are a good choice. Such
dividers can be cascaded to ob-
tain higher ratios but the input
frequency must not exceed the
maximum stated for the part in
its datasheets.

The Atmel AT89C2051 is a 20-
pin 8-bit microcontroller with
2 k flash memory, 128 bytes
RAM and two 1 6-bit timer/
counter blocks. It is used here
because of its price/ perfor-
mance tradeoff, compatibility
with MCS-51 products, low pin
count and last but not least...
the author being familiar with its
programming language!

The frequency is measured by
counting the number of rising
edges of the input clock pulse in

one second. The program uses
timer/counterO in 1 6-bit counter
mode for counting the number
of input pulses, and timer/
counterl in 1 6-bit timer mode
to set up the one-second gate
interval. The routine calculating
the frequency stores its result in
register bank 0 from R2 to R7.
The display routine then shows
the results on the 7-segment
common-anode displays. To
suppress trailing zeroes the pro-
gram tests registers for 'zero'
content before displaying. For
the frequency display, each of
the six digits (displays) in the
readout is turned on individually
and all others will be off while
the desired number for that digit
is output on the microcontroller's
PI port for a short time. The
microcontroller then switches
on the relevant digit, which
shows the number. This action
is so fast that you can't see any
display flicker. The displays
are bussed on the P3 port, with

4.7 kQ resistors at the base of
each pnp driver transistor to
limit the current.

Note that you should use
AT89C205 1-24XX in this circuit
because a 24 MHZ crystal is
used.

The AT89C2051 program that's
available for free downloading
with this article (ref. 060028-
1 1 .zip) may be assembled us-
ing any 8051 family assembler
likeASM51 assembler and the
OHS51 linker. The output will
be a .hex file and can be pro-
grammed on the microcontroller
using a suitable programmer.
When building the counter, the
display circuitry is best built on
a separate board for convenient
panel mounting.

The regulated +5 V supply volt-
age may be provided by a type
7805 regulator.

( 060028 - 1 )

2/2008 - elektor

73

PROJECTS MINIPROJECT

Frost Detector

Above or below zero,
that's the question

Ton Giesberts

In rooms without adequate heating but containing sensitive equipment it would be nice to obtain at
least an indication as to whether the temperature has dropped below freezing. You then know that the
heating is inadequate and that the equipment has to be moved somewhere else. This detector, thanks to
its battery powered supply, can be used anywhere in the home.

To know whether it is freezing you only
need to measure the temperature. This
has to be done accurately, of course,
and therefore we need to choose a tem-
perature sensor that we have some
confidence in.

The choice has again been made for
a type that we have already used in
many previous Elektor circuits, the
LM35CZ (-40 to 110 °C). This sensor
is not expensive and generates an
output voltage that is proportional to
the temperature in degrees Celsius
(10 mV/°C).

Sensor

An LM35 is normally powered from a
single-ended power supply and 0 °C
corresponds to an output voltage of 0 V.
It is therefore not possible to measure
negative temperatures with an LM35
in the standard application circuit. It is
however possible to measure negative
temperatures if its output is connected
to a negative supply voltage via a re-
sistor. There needs to be a current of
50 /jA through this resistor (R2 in the
schematic).

We only need to detect the freezing

point with this circuit. That is why the-
re is a comparator after the temperatu-
re sensor, which turns an LED on if the
temperature has dropped below 0 °C
during the course of the night. To ensu-
re that the comparator operates proper-
ly it is necessary that the measurement
value can become slightly more nega-
tive with respect to the input. To sol-
ve this problem, a diode (Dl) has been
connected in series with the ground
connection of the LM35. The voltage
drop across Dl (because of the small
current through the LM35 this is only
0.47 V) acts as 'negative' power supply.
Since the non-inverting input of com-
parator IC2 is connected via R3 to the
anode of Dl it functions as the 0°C -re-
ference level for the comparator.

Comparator

The comparator is a standard opamp
type TLC271, which we configured
for minimal current consumption by
connecting the bias -select input (pin 8)
to the power supply voltage. There is
no need for the detector to be fast and
it will therefore work well with the
opamp operating in its most economi-
cal mode.

LED D3 provides the frost indication.
It is the intention that the LED stays
on once the temperature in the room
drops below freezing or when it has
been below freezing. To realise this, an
asymmetric hysteresis is created with
the aid of R3, R4 and D2. The instant
that the output goes high, the non-in-

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070785- 11

Figure 1. The frost detector circuit consists of a temperature sensor and comparator with LED indicator.

74

elektor - 2/2008

verting input goes more positive via D2
and R4, and the output therefore stays
high. The temperature would now have
to increase to more than about 30° be-
fore the LED will go out by itself. In
practice this probably means that it
is summer and that it is not likely to
freeze anyway. If need be, the hystere-
sis can be increased by increasing the
value of R3.

Capacitor C2 is added to make sure
that the LED remains off (the circuit
is reset) when the power supply is
connected. The non-inverting input
of the opamp is briefly connected to
ground and the output is therefore low.
R1 and SI are only required if the cir-
cuit needs to be reset when the battery
is connected. Instead of SI you could
also use a power supply switch or even
just simply disconnect the battery for
a moment.

Thrifty Power supply

Since the circuit is assumed to be
powered from a battery there was a
conscious effort to minimise the power
consumption. The current consumption
of the prototype, at a power supply vol-
tage ranging from 6 to 9 V, was less
than 120 /JA . When the LED is on, the
current consumption rises to only 1 mA
at 6V and 1.8 mA at 9V, because a low-
current LED is used. In our prototype
we used a green, low-current LED.

If four AA penlight batteries (with a ca-
pacity of about 2 Ah) are used, then the

circuit will run for about two years in
standby mode. When the LED is on this
is considerably shorter, of course (about
two months, this is easily long enough
to run through a severe winter period).
A standard 9-V battery will also last a
single winter, provided you frequently
check whether the LED is on.

Finally, a comment about the TLC-
271CP used here. The version with the
C -suffix is specified for an operating
range from 0 to 70 °C, but will continue
to work at lower temperatures, parti-
cularly considering that the IC is not

Figure 2. The prototype built on a piece of perforated prototype board.

used in a linear application. If in doubt
you can always try to get your hands
on a version with the I-suffix (that is,
TLC271IP: -40 to 125°C). But that is
only necessary if you expect it to be
real cold in the monitored room...

Quick assembly

The circuit contains very few parts and
can therefore be easily built on a small
piece of prototyping board. There is no
need to calibrate anything, once built
it is ready to go.

( 070785 - 1 )

2/2008 - elektor

75

INFOTAINMENT

PUZZLE

Puzzle with an
electronics touch

Are you bothered by spring depressions? Then hopefully a few hours of puzzle solving will cheer you up.
Elektor's Hexadoku is great medication, free but admittedly slightly addictive. Solving a Hexadoku is
harder than a Sudoku and should take much longer. Correct answers again enter a prize draw for one of
the prizes: 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 1 6 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 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 our website.

SOLVE HEXADOKU AND WIN!

Correct solutions received enter a prize draw for an

E-blocks
Starter Kit
Professional

worth £248.55

and three

Elektor SHOP
Vouchers worth
£35.00 each.

We believe these prizes should encourage
all our readers to participate!

The competition is not open to employees of Elektor International Media
b.v., its business partners and/or associated publishing houses.

PARTICIPATE!

Please send your solution (the numbers in the grey boxes) by email to:

editor@elektor.com - Subject: hexadoku 2-2008 (please copy exactly).

Alternatively, by fax or post to: Elektor Hexadoku

Regus Brentford - 1000 Great West Road - Brentford TW8 9HH

United Kingdom - Fax (+44) 208 2614447

The closing date is 1 March 2008.

PRIZE WINNERS

The solution of the December 2007 puzzle is: 97C65.
The E-blocks Starter Kit Professional goes to:

Tim Eames (UK).

An Elektor SHOP voucher worth £35.00 goes to:

Kjell A. Lover (N); Terje Daleng (N) and
Charles Metcalfe (SA).

Congratulations everybody!

D

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76

elektor - 2/2008

RETRONICS

INFOTAINMENT

Programmable disco lights array (1984)

Jan Buiting

Some time during the ear-
ly 1980s, a trend grew to add
light effects and someone called
'disc jockey' to parties originally
about drinking, socializing and
getting your ears slammed with
loud music. 'Disco' was born
and what a hype it was — not
just pounding electronic drums
and synthesizers but also glam-
orous matching attire for all &
sundry under 20 or so.

The drinks and music were hand-
ed down by the 70's scene but
the lights were relatively new. The
best disco was one with several
dark nooks and crannies, badly
lit bars, a very loud PA, a disc
jockey with a not too small ego
and, most importantly, a brutally
illuminated dance floor for eve-
ryone to show off nimbleness or,
like Mr Bean, make a complete
fool of himself.

Elektor in 1984 saw a niche for
a disco lights controller that was
unusual and novel in not being
limited to dull, fixed light pat-
terns. In other words, the keen

user of the ambitious project
printed in the February 1984 is-
sue of Elektor could really make
the crowd go bezerk with light
effects far more 'groovy' than
those of a simple light organ,
a couple of coloured floodlights
and of course the corny globes
on the ceiling.

The Elektor project offered no
fewer than 32 programs in mem-
ory to control up to 30 lights in-
dividually. The associated triac
driver unit was a separate unit
described in, you guessed it, the
March 1 984 issue.

The disco lights controller used
four 2 k x 8 static RAMs type
6116 or 5517 for its memory.
The light patterns were 'pro-
grammed' using flip switches
and LEDs on the front panel. A
couple of 7-segment LED dis-
plays were provided to act as
readouts for addresses, banks
and programmes. Funny to think
that all three terms have survived
right into the microcontroller and
FPGA era we're enjoying right
now.

A clever speed control ('clock')

was added to the circuit, helping
the DJ or MC to link the speed of
the light effects to the bpm (beats
per minute) of the music played.
Patterns could be 'stepped' too,
and there was even a repeat
timer with a range of 1 / 8th to
16 minutes. How primitive it
looks now compared with auto-
bpm-locking sound and light
equipment available today.

To make sure the many hours of
meticulous programming of light
patterns into all four banks were
not a waste a time when the
unit was switched off, a mem-
ory backup battery was provid-
ed on the CMOS RAM supply.
It consisted of three AA Nicads
or 1.5 V alkalines in a plastic
holder mounted off the board
(good! no risk of corroding the
board). If dry cells were used, a
resistor had to be cut to prevent
charging.

The prototype of the Elektor Dis-
colights unit I rescued from our
old offices in Beek, Holland,
measures 48x17x8.5 cms in a
clear attempt at making it 19-
inch rack compatible. The unit

was impeccably built by Jan Viss-
er who's still on our lab staff. At
Jan's advice I removed 3 Nicads
from the battery holder and
found that they were certainly
beyond rescue after a good 25
years.

A large sub-D connector is avail-
able at the rear side to hook up
the triac power controller. The
large blue circuit board is typi-
cally 'Elektor', single-sided (!)
and stuffed with components
like 0.25 watt carbon resistors,
high 1C sockets, blue electrolyt-
ics, wire links, solder pins and
of course those horrible 'na-
ked' grey&silver MKT capacitors.
These parts now strike me as
'bulky' but then that's no more
than a heavily SMD-affected
perception.

With 3 kilowatts or so flashing
under triac control the complete
discolights kit must have been a
regular EMC nightmare but then
nobody cared about such EU
regulations any more than be-
ing home in bed after the disco
closed!

( 070856 - 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

2/2008 - elektor

77

ELEKTOR

SHOWCASE

To book your showcase space contact Huson International Media

Tel. 0044 (0) 1 932 564999

ATC SEMITEC LTD

www. atcse m itec . co . u k

Thermal and current-sensitive components
for temperature control and circuit protection;

• NTC Thermistors • Current Diodes

• Thermostats • Re-settable Fuses

• Thermal Fuses • Temperature Sensors

Call today for free samples and pricing

Tel: 01 606 871 680 Fax: 01 606 872938

AVIT RESEARCH

www.avitresearch.co.uk

USB has never been so simple...
with our USB to Microcontroller Interface cable.
Appears just like a serial port to both PC and
Microcontroller, for really easy USB connection to
your projects, or replacement of existing RS232

interfaces.

See our webpage for more
details. From £10.00.

BETA LAYOUT

www.pcb-pool.com

Beta layout Ltd Award-
winning site in both
English and German
offers prototype
PCBs at a fraction of the cost of the usual
manufacturer’s prices.

Fj

43

B0W00D ELECTRONICS LTD

www. bowood-electronics.co.uk

Suppliers of Electronic Components

• Semiconductors

• Opto Electronics

• Passives

• Enclosures

• Switches

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• PCB Materials

• Popular Special Offer Packs
Online Store, all major cards
Same day despatch upto 3.00pm

Personal Service sales@bowood-electronics.co.uk

BYVAC ELECTRONICS

www.byvac.co.uk

32Bit ARM
Microcontroller,

USB, built in RTC
with itis own

operating system,
no complex
tools, just a

terminal emulator, start writing programs in 20
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100 Page Foundation book

DECIBIT CO.LTD.

www.decibit.com

Smallest 2.4 GHz ISM band MCU embedded
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Professional product development services.

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• Audiovisual ((HD)DVD accessories & controllers)
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We design & supply low cost USB/RS232 based
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EASYSYNC

http://www.easysync.co.uk

EasySync Ltd sells a wide
range of single and multi-
port USB to RS232/RS422
and RS485 converters at competitive prices.

ELNEC

www.elnec.com

• device programmer
manufacturer

• selling through contracted
distributors all over the world

• universal and dedicated device programmers

• excellent support and after sale support

• free SW updates

• reliable HW

• once a months new SW release

• three years warranty for most programmers

YOUR ELECTRONICS OPEN SOURCE

http://dev.emcelettronica.com

Website full of Projects and Resources for
Electronics Engineers and DIY.

• Tutorial

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Everyone can submit a story as a useful source!
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FIRST TECHNOLOGY TRANSFER LTD.

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and Assembly f^^eTwpjw

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• Distance learning / instructor led

• Assembly / C-Programming of PIC1 6, PIC1 8,
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• Foundation / Intermediate

FLEXIPANEL LTD

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TEAclippers - the smallest
PIC programmers in the world,
from £20 each:

• Per-copy firmware sales

• Firmware programming & archiving

• In-the-field firmware updates

• Protection from design theft by subcontractors

FUTURE TECHNOLOGY DEVICES

http://www.ftdichip.com

FTDI designs and sells
USB-UART and USB-FIFO
interface i.c.’s.

Complete with PC drivers,
these devices simplify the task of designing or
upgrading peripherals to USB

FUTURLEC

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Save up to 60% on

• Electronic Components

• Microcontrollers, PIC, Atmel

• Development Boards, Programmers
Huge range of products available on-line for
immediate delivery, at very competitive prices.

ILP ELECTRONICS LTD

www.ilpelectronics.com

Tel +441233750481
Fax +441 233750578

ILP have been manufacturing audio modules since
1 971 and apart from our standard range we also
offer a custom design service for the OEM market.

LONDON ELECTRONICS COLLEGE

http://www.lec.org.uk

Vocational training and education for national
qualifications in Electronics Engineering and
Information Technology (BTEC First National,
Higher National NVQs, GCSEs and Advanced
Qualifications). Also Technical Management and
Languages.

78

elektor - 2/2008

products and services directory

MARCHAND ELECTRONICS INC.

www.marchandelec.com

• power amplifier modules

• electronic crossovers
solid state / valve /
passive

• valve amplifiers

• phono preamps

• handheld sinewave generator

• kits or assembled

• software electronic instruments

• custom design services

MQP ELECTRONICS

www.mqp.com

• Low cost USB Bus Analysers

• High, Full or Low speed captures

• Graphical analysis and filtering

• Automatic speed detection

• Bus powered from high speed PC

• Capture buttons and feature connector

• Optional analysis classes

NEW WAVE CONCEPTS

www.new-wave-concepts.com

Software for Hobbyists:

• Livewire - circuit simulation
software, only £34.99

• PCB Wizard - PCB design
software, only £34.99

• Circuit Wizard - circuit, PCB and breadboard
design software, only £59.99

Available from all Maplin Electronics stores and

www.maplin.co.uk

RADIOMETRIX

www.radiometrix.com

The leading global developer
of ISM band, low power radio
modules for wireless data transmission:

• Transmitters • Receivers • Transceivers

• RF modems • Evaluation Kits

ROBOT ELECTRONICS

http://www.robot-electronics.co.uk

Advanced Sensors and Electronics for Robotics

• Ultrasonic Range Finders

• Compass modules

• Infra-Red Thermal sensors

• Motor Controllers

• Vision Systems

• Wireless Telemetry Links

• Embedded Controllers

ROBOTIQ

http://www.robotiq.co.uk

Build your own Robot!

Fun for the whole family!

• MeccanoTM Compatible

• Computer Control

• Radio Control

• Tank Treads

• Hydraulics
Internet Technical Bookshop,

1-3 Fairlands House, North Street, Carshalton,
Surrey SM5 2HW

email: sales@robotiq.co.uk Tel: 020 8669 0769

COMPONENTBIN.COM

www.componentbin.com

Kickstart your development with
modules and parts from
componentbin.com

• ARM7 modules

• Ethernet modules

• Superb Graphic LCD displays (all with example
software)

and much much more...

Online ordering and great prices!

ULTRALEDS ui trai *

http://www.ultraleds.co.uk

tel: 0871 7110413/01625 576778
Large range of low cost Ultra bright leds and
Led related lighting products. Major credit cards
taken online with same day depatch.

USB INSTRUMENTS

http://www.usb-instruments.com

USB Instruments specialises
in PC based instrumentation
products and software such
as Oscilloscopes, Data
Loggers, Logic Analaysers
which interface to your PC via USB.

VIRTINS TECHNOLOGY

www.virtins.com

PC and Pocket PC based
virtual instrument such
as sound card real time
oscilloscope, spectrum
analyzer, signal generator,
multimeter, sound meter,
distortion analyzer, LCR meter.
Free to download and try.

SHOWCASE YOUR 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
your products and services.

For just £220 + VAT (£20 per issue for
eleven issues) Elektor will publish your
company name, website address and a
30-word description
For £330 + VAT for the year (£30 per
issue for eleven issues) we will publish
the above plus run a 3cm deep full colour

image - e.g. a product shot, a screen shot
from your site, a company logo - your
choice

Places are limited and spaces will go on
a strictly first come, first served basis.
So-please fax back your order today!

_ n

I wish to promote my company, please book my space:

• Text insertion only for £220 + VAT • Text and photo for £330 + VAT

NAME: ORGANISATION:

JOB TITLE:

ADDRESS:

TEL:

PLEASE COMPLETE COUPON BELOW AND FAX BACK TO 00-44-(0)1932 564998

COMPANY NAME

WEB ADDRESS

30- WORD DESCRIPTION

2/2008 - elektor

79

BOOKS, CD-ROMs, KITS & MODULES

Going Strong

A world of electronics
frQiMrtigle shop!

Detect stuffy air before you doze off

C0 2 Measurement

(January 2008)

Carbon dioxide (C02) is not just a threat to the environment, it is also an important and often
ignored factor in determining air quality in the office and at home. Too high a concentra-
tion of C02 leads to feelings of tiredness, disturbs concentration, and causes headaches.
The Elektor C02 meter makes it easy to determine the concentration of carbon dioxide in the
air. A microcontroller monitors the measured value and can trigger an alarm or start up a
ventilation system when a preset threshold is exceeded.

Kit of parts, PCB, Sensor PCB, ATtiny26 and display

Art.# 070802-71 • £107.50 • US$215.00

Reflow Solder Controller

(December 2007)

The Elektor lab needs to solder SMDs
more often these days, something that
undoubtedly also applies to many of our
readers. In the January 2006 issue we
described in some detail how you could
build your own reflow oven using an in-
expensive electric oven. That article result-
ed in many comments from our readers,
which confirmed to us that there was a
lot of interest in such a project. We now
present a completely new version of the
control electronics for a DIY SMD oven.

Populated PCB with enclosure
Art. #060234-91 • £171.80 • USS 343.60

USB Flash Board

(November 2007)

Flash microcontrollers are easy to pro-
gram. In the past, program code was
usually downloaded via a serial inter-
face, but nowadays many PCs (espe-
cially laptops) only have USB ports. This
versatile Flash Board provides a solu-
tion to this problem. It is built around
an AT89C5131A, which is an extend-
ed 8051 -family microcontroller with an
80C52 core and a Full Speed USB port.
As a sort of bonus, the 1C has a complete
update interface for downloading new
firmware. Atmel also provides suitable
software in the form of its FLIP program,
which is available free of charge.

Construction kit including the PCB and
all parts

Art. #070125-71 • £36.20 • US$ 72.40

v y v y

Prices and item descriptions subject to change. E. & O.E

80

elektor - 02/2008

All articles published in 2007

Elektor 2007

Year volume CD-ROMs are among the
most popular items in Elektor's product
range. This CD-ROM contains all edi-
torial articles published in Elektor Vol-
ume 2007. Using the supplied Acrobat
Reader program, articles are presented
in the same layout as originally found in
the magazine. An extensive search ma-
chine is available to locate keywords in
any article.

978-90-5381-218-1 • £16.90 • US$33.80

PIC Microcontrollers

W jVs.r.Tli A: - llr^jrcnm l

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 ex-
planations, schematics, and pictures of
each project on a breadboard make this
a fun activity. You can also use it as a study
guide. The technical background infor-
mation in each project explains why the
project is set up the way it is, including the
use of datasheets. This way you'll learn a
lot about the project and the microcon-
troller being used. Even after you've built
all the projects it will still be a valuable ref-
erence guide to keep next to your PC.

446 pages • ISBN 978-0-905705-70-5
£27.00 • US$ 54.00

More than 68,000 components

Elektor's Components
Database 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 col-
our band decoder is included for de-
termining resistor and inductor values.
ECD 4 gives instant access to data on
more than 68,000 components. All
databank applications are fully in-
teractive, allowing the user to add,
edit and complete component data.
This CD-ROM is a must-have for all elec-
tronics enthusiasts.

ISBN 978-90-5381-159-7 • £15.90 • US$31.80

v '

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

r^llektor

LT3shop

309 CIRCUITS

r \

Fully elaborated electronics projects

309 Circuits

The present tenth edition of the popular
'30x Circuits' series of books once again
contains a comprehensive variety of cir-
cuits, sub-circuits, tips and tricks and de-
sign ideas for electronics. Among many
other inspiring topics, the following cate-
gories are well presented in this book:
test & measurement; RF (radio); com-
puters and peripherals; audio & video;
hobby and modelling; microcontrollers;
home & garden; power supplies & bat-
tery chargers; etcetera.

432 pages • ISBN 978-0-905705-69-9
£19.95 -US$39.95

for

Electronics
Engineering
Applicant] b$

5.0, 6.0, VBA, .NET, 2005

Visual Basic for
Electronics Engineering
Applications

This book is targeted towards those peo-
ple that want to control existing or self-
built hardware from their computer. After
familiarizing yourself with Visual Basic, its
development environment and the tool-
set it offers are discussed in detail. Each
topic is accompanied by clear, ready to
run code, and where necessary, sche-
matics are provided that will get your
projects up to speed in no time.

476 pages • ISBN 978-0-905705-68-2
£29.00 • US$ 58.00

v j

02/2008 - elektor

81

PRODUCT SHORTLIST, BESTSELLERS

~\

February 2008 (No. 374)

LEDBUS System

070459-1 PCB, power module

070459-2 PCB, central

070459-41 ....Programmed microcontroller, power module

070459-42 .... Programmed microcontroller, central

RGB LED Mood Lighting

070892-1 Printed circuit board

070892-2 Printed circuit board

070892-3 Printed circuit board

070892-41 ....Programmed microcontroller

Surround Light for PC Monitor

070491 -1 Printed circuit board

070491 -2 Printed circuit board

070491 -91 .... PCB, partly populated with SMDs

LED Ringflash

07061 2-1 Printed circuit board

07061 2-41 .... Programmed controller

070612-81 ....Software on CD-ROM

TV Surround Light

070487-1 Printed circuit board

070487-41 ....Programmed microcontroller

070487-42 .... Programmed microcontroller

070487-81 ....Software on CD-ROM

CAN Explorer

060201 -1 Printed circuit board, MCP251 5 and MCP2551 SN

060201 -W Testing & Error Sources Manual

Thermometer / Thermostat

070852-11 ....Software

£ US$

see www.elektor.com
see www.elektor.com
see www.elektor.com
see www.elektor.com

see www.elektor.com
see www.elektor.com
see www.elektor.com
see www.elektor.com

21.50 43.00

5.00 10.00

see www.elektor.com

www.thePCBshop.com

10.50 21.00

5.20 10.40

21.50 43.00

12.70 25.40

10.50 21.00

5.20 10.40

see www.elektor.com
see www.elektor.com

see www.elektor.com

January 2008 (No. 373)

C0 2 Measurement

070802-1 PCB, bare

070802-41 .... Programmed controller ATtiny26

070802-71 .... Kit of parts, PCB, Sensor PCB, ATtiny26

and display

070802-81 Software on CD-ROM

Anti-Standby Switch

070797-1 PCB, bare

070797-41 .... ATtiny25, programmed

Control for Energy-saving Lamps

070638-71 .... PCB, FAN771 ON and 2.5mH coil

Versatile DC Power Meter

070559-1 PCB, bare

070559-41 .... Programmed controller ATmega8-l 6P

December 2007 (No. 372)

Reflow Solder Controller

060234-91 .... Populated PCB with enclosure

AVR Web Server

060257-1 Printed circuit board

060257-41 .... ATmega644, programmed

Craft Drill Controller

060291 -1 Printed circuit board

Christmas Flasher

010032-91 ....Kit of parts

LED's Dive!

07001 1 -1 Printed circuit board

November 2007 (No. 371)

USB Data Acquisition Card

070148-1 PCB, bare

070148-41 .... PIC1 8F4550 DIP40, programmed

070148-81 ....Software on CD-ROM

Line Switcher

060288-1 PCB, bare

Headphone Amp with 3D Sound

070393-1 PCB, bare

..14.40 28.80

....7.20 14.40

107.50 215.00

....5.20 10.40

..14.40 28.80

....5.20 10.40

..14.40 28.80

....9.30 18.60

....9.00 18.00

171,80 343,60

9,60 19,20

13,80 27,60

www.thePCBshop.com

3,60 7,20

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9.50 19.00

15.50 31.00

5.20 10.40

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Prices and item descriptions subject to change. E. & O.E

Bestsellers

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PIC Microcontrollers

ISBN 978-0-905705-70-5 £27.00. USS 54.00

309 Circuits

ISBN 978-0-905705-69-9E1 9.95

USS 39.95

Visual Basic for Electronics Engineering Applications

ISBN 978-0-905705-68-2 £29.00 .....USS 58.00

Microcontroller Basics

ISBN 978-0-905705-67-5 E19.50.....USS 39.00

PC Interfaces under Windows

ISBN 978-0-905705-65-1 £27.25 .....USS 54.50

ECD4

ISBN 978-90-5381-159-7.

£15.90. US$31.80

Ethernet Toolbox

ISBN 978-90-5381-214-3 £1 8.90..... USS 37.90

Home Automation

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USB Toolbox

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Robotics

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USB Flash Board

Art. # 070125-71 £36.20 .....USS 72.40

Reflow Solder Controller

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C0 2 Measurement

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INFO & MARKET

SNEAK PREVIEW

Data logger with flash memory

Sure, data loggers have been published before in Elektor, but this one's special with an LCD and a serial connection.
The logger has four analogue inputs and a measurement range of 0 to 5 V. Data is stored in flash memory using an
SD memory card fitted on the board. Five different logging modes are available: manual triggering, external trigger-

ECIO PLC board

Here's the first real-life application of ECIO modules introduced in the October 2007 issue of Elektor. An ECIO
module acts as the brains of a PLC board that has relays, opto-isolators, CAN connectivity and an LCD. All this I/O
capacity together with Flowcode allow the board to act as versatile, powerful PLC for quite complex control and
automation projects. The LCD module is used to display ASCII characters to the user as a means of troubleshooting
during the software development stage or for monitoring the system.

I 2 C analyser

The l 2 C or 'Inter-IC' bus has seen applications for many years already as 'glue' between complex ICs in electronic equipment. The simplicity of the l 2 C bus really calls for DIY ap-
plications. Unfortunately, tracing error conditions on the l 2 C bus is not trivial and in fact requires special test equipment. Our l 2 C analyser is simple and easy to use. The compact
circuit is hooked up to an l 2 C bus and displays received data on the PC via a USB connection. The PC does all the data dissecting using clever software.

RESERVE YOUR COPY NOW! The March 2008 issue goes on sale on Thursday 28 February 2008 (UK distribution only).

UK mainland subscribers will receive the magazine between 22 and 25 February 2008. Article titles and magazine contents subject to change, please check www.elektor.com.

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Total 1

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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
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January 2008

Formula

Flowcode Buggy

USB-programmable robot vehicle

A

1

• A complete solution:

robot + software + curriculum

• Line following and maze solving

• High-tech specifications

• Also programmable with C or ASM

• E-blocks compatible

• Motivating for education and hobby

Ready to use only £85.00 • US$ 169.00

Order now using the Order Form in
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Index of Advertisers

Allendale Electronics Ltd www.pcb-soldering.co.uk 11

Antex Electronics Ltd www.antex.co.uk 41

ATC Semitec Ltd, Showcase www.atcsemitec.co.uk 78

Avit Research, Showcase www.avitresearch.co.uk 78

Beijing Draco www.ezpcb.com 49

Beta Layout, Showcase www.pcb-pool.com 59, 78

Bitscope Designs www.bitscope.com 3

Bowood Electronics Ltd, Showcase www.bowood-electronics.co.uk 78

Byvac Electronics, Showcase www.byvac.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.elnec.com 78

Euro circuits www.eurocircuits.com 57

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

Futurlec, Showcase www.futurlec.com 78

ILP Electronics Ltd, Showcase www.ilpelectronics.com 78

Jaycar Electronics www.jaycarelectronics.co.uk 2

Labcenter www.iabcenter.com 88

London Electronics College, Showcase . . . www.iec.org.uk 78

Marchand Electronics Inc, Showcase www.marchandelec.com 79

Mikro Elektronika www.mikroe.com

13

MQP Electronics, Showcase www.mqp.com 79

New Wave Concepts, Showcase www.new-wave-concepts.com 79

Newbury Electronics www.newburyelectronics.co.uk 59

Number One Systems www.numberone.com 49

Nurve Networks www.xgamestation.com 59

SK Pang Electronics www.skpang.co.uk 49

Peak Electronic Design www.peakelec.co.uk 59

Pico www.picotech.com 15

Quasar Electronics www.quasarelectronics.com 65

Radiometrix, Showcase www.radiometrix.com 79

Robot Electronics, Showcase www.robot-electronics.co.uk 79

Robotiq, Showcase www.robotiq.co.uk 79

Showcase 78, 79

Tsien (UK) Ltd, Showcase www.componentbin.com 79

Ultraleds, Showcase www.uitraieds.co.uk 79

USB Instruments, Showcase www.usb-instruments.com 79

Virtins Technology, Showcase www.virtins.com 79

Your Electronics Open Source, Showcase. . http:/ /dev.emcelettronica 78

Advertising space for the issue of 25 March 2008
may be reserved not later than 26 February 2008

with Fluson International Media - Cambridge House - Gogmore Lane -
Chertsey, Surrey KT 1 6 9AP - England - Telephone 01 932 564 999 -
Fax 01 932 564998 - e-mail: aerrvb@husonmedia.com to whom all
correspondence, copy instructions and artwork should be addressed.

2/2008 - elektor

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