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Contents
Vol.16, No.3; March 2003
www.siliconchip.com.au
FEATURES
8 GM’s Hy-Wire Fuel-Cell Car
World-first concept car from GM combines a hydrogen fuel-cell power plant
with drive “by-wire” technology. And just look at the styling!
13 A Look At Emergency Beacons
An emergency beacon could save your life. Here’s a rundown on the various
types that are available and how they work – by Peter Holtham
GM’s “Hy-Wire”
Fuel-Cell Car – Page 8.
76 Review: Canon’s Image Stabilised Binoculars
Whether you’re into bird watching or astronomy (or anything else), these
image-stabilised binoculars will get rid of the shakes – by Leo Simpson
PROJECTS TO BUILD
LED Lighting For
Cars – Page 22.
22 LED Lighting For Your Car
Replace your car’s filament lamps with LEDs for improved safety. There are
several designs to build, all using high-brightness LEDs – by Peter Smith
36 Peltier-Effect Tinnie Cooler
It’s based on a Peltier-effect module fitted with a fan-cooled heatsink. You just
install it in a 6-pack Esky and to keep your tinnies cool – by Ross Tester
56 The PortaPAL Public Address System; Pt.2
Here’s the good oil on putting it together and getting it to work. We even
describe an easy way to build the box – by John Clarke & Leo Simpson
66 12V SLA Battery Float Charger
It’s intended for the PortaPAL but it also makes a great general-purpose
12V SLA battery charger – by John Clarke & Leo Simpson
68 The Little Dynamite Subwoofer
Build this compact subwoofer for very little money. It’s ideal for use in a car
or home unit – by Julian Edgar
79 More Fun With The PICAXE: A Shop Door Minder
Peltier-Effect Tinnie Cooler –
Page 36
Part 2 of this series shows you how to build a “Shop Door Minder . . . With
Attitude” – by Stan Swan
82 SuperCharger Addendum
Did you build the SuperCharger described in Nov-Dec 2002. If so, you need
this simple 2-transistor add-on board – by Peter Smith
SPECIAL COLUMNS
32 Circuit Notebook
(1) Automatic Headlight Switch; (2) Simple Universal PIC Programmer; (3)
Bat Detector Picks Up Ultrasound; (4) Junkbox-Parts Oven Timer
12V SLA Battery Float Charger
– Page 66.
40 Serviceman’s Log
Bring your hammer-drill and muscles – by the TV Serviceman
84 Vintage Radio
Antennas & earthing systems for crystal sets – by Rodney Champness
DEPARTMENTS
2
4
53
55
Publisher’s Letter
Mailbag
Product Showcase
Silicon Chip Weblink
www.siliconchip.com.au
90
92
93
95
Ask Silicon Chip
Notes & Errata
Market Centre
Advertising Index
The Little Dynamite Subwoofer –
Page 68.
March 2003 1
PUBLISHER’S LETTER
www.siliconchip.com.au
Publisher & Editor-in-Chief
Leo Simpson, B.Bus., FAICD
Production Manager
Greg Swain, B.Sc.(Hons.)
Technical Staff
John Clarke, B.E.(Elec.)
Peter Smith
Ross Tester
Jim Rowe, B.A., B.Sc, VK2ZLO
Rick Walters
Reader Services
Ann Jenkinson
Advertising Enquiries
Leo Simpson
Phone (02) 9979 5644
Fax (02) 9979 6503
Regular Contributors
Brendan Akhurst
Rodney Champness, VK3UG
Julian Edgar, Dip.T.(Sec.), B.Ed
Mike Sheriff, B.Sc, VK2YFK
Philip Watson, MIREE, VK2ZPW
Bob Young
SILICON CHIP is published 12 times
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Postal address: PO Box 139,
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Fax (02) 9979 6503.
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2 Silicon Chip
LED lighting for cars
– it’s about time
This month we feature a major article on using high
brightness LEDs in cars. We have wanted to do this
for some time but it is only recently that really bright
LEDs have become available at reasonably cheap prices.
In this article, we have majored on the Centre High
Mount Stop Lamp (CHMSL) and stop lights, plus the
so-called festoon lamps used for vehicle interiors. We
would have liked to have taken the concept much further
but you have to stop somewhere if you are ever going to
publish. Fairly obviously, the bayonet lamp assembly
could be modified to make a bayonet stop/tail light assembly and the smaller festoon LED assembly could be fitted with high-brightness
amber LEDs to be fitted into traffic indicator repeater lights on the sides of cars.
However, the broad thrust of the article is rear end collision avoidance. The
extra stopping time given by LED stop lights could mean the difference between
a severe collision with major damage and injuries and maybe no accident at all
- just some fevered breathing afterwards. If you do nothing else, you probably
should convert your own car’s centre high mount stop lamp to LED operation – it
could save a life.
Victoria to stop DIY mains wiring?
This issue just won’t go away. A recent issue of the Melbourne Herald-Sun
notes that “Electrical goods such as cabling, power points and safety switches
will be banned from public sale under proposals to be presented to the State
Government this week.”
“Electricians, tired of having their lives endangered by “dodgy” cabling
installed illegally by home handymen, have called for a new code of practice
that would restrict the sale of cabling and switches to licensed operators”.
In fact, the proposed code of practice is already part of a new Enterprise
Agreement between the Victorian branch of the ETU and the National Electrical Contractors association. Isn’t that nice and cosy? This has nothing to
do with safety.
Electricians aren’t in danger from DIY wiring. Check the website of the
Office of Chief Inspector: www.ocei.vic.gov.au and click on “incidents”. Not
only does it show that fatalities over the last 10 years have been very low,
it also shows that members of the public have very low fatalities. We doubt
whether any electrician has ever been killed by DIY wiring. If an electrician
is in danger, he shouldn’t be practising – he is not competent.
In fact, I have seen plenty of dodgy wiring done by licensed contractors
installing kitchens, dishwashers, air-conditioners and hot-water systems. DIY
wiring is not a safety issue. In fact, if sales of cables, switches, etc are banned,
safety will be prejudiced. Whereas before, if a power point or wall switch
failed, the competent handyman would just replace it, now it is likely to be
left in an unsafe state. And if an appliance cord frays, it will be left unsafe;
if you can’t buy the cord, you can’t do the repair.
And will all lighting stores close their doors? After all, most light fittings
are fitted by home handymen, aren’t they? So if you have been quietly and
happily doing your own 240VAC wiring up till now, you can forget it. We did
mount a campaign to make it legal but apathy got in the way. Once again, if
you’re not happy about this revolting development, contact your local MP
and make a lot of noise.
Finally, in an encouraging development, a group is being formed in
Queensland to have the Electrical Safety Act changed or repealed. If you
are a technician repairing anything from air-conditioners to sewing machines, computers or anything else powered by 240VAC, contact the AETA
(All Electronic Technicians Association) by fax on 07 4093 9700 or email:
cairnscomms<at>iprimus.com.au
Leo Simpson
www.siliconchip.com.au
FireWire Interfaces
A new desktop computer that requires
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Low Profile FireWire card for
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“designer” cases
Cat 2992-7 $99
FireWire Card with Video
Studio PCI Cat 2621-7 $199
FireWire 3 Port PLUS USB
2.0 4 Port Cat 2873-7 $189
A really nice, VERY
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Cat 1149-7 $649
Smart Card
Readers
Cat 8860
A quality keyboard with an
inbuilt Smart Card reader Cat 8860-7
$129
USB Smart card reader/writer with API library and
demo source code Cat 8981-7 $189
Foreign Language Keyboards - $69ea
Cat 8989-7 Chinese/US
Cat 8991-7 UK English Cat 8992-7 Italian
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Need ISA Slots?
Industrial P4 motherboard
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Cat 2877
Multi-PC Controllers
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Cat 3486
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These reliable tools apply either a
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Cat 1008081-7 Integrated Controller and proximity
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a “lockup”; ideal for remote
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Watch Dog = software reset
Cat 1008058-7 Proximity Card
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Cat 17050-7 Watch Dog 2 ISA $399
Cat 1008059-7 Proximity Key Tag $6.50
Cat 17044-7 Watch Dog ISA $165
Cat 1008057-7 Proximity Reader
Cat 17070-7 Watch Dog PCI $332
(200mm range)
$269
Cat 17076-7 Watch Dog 2 PCI $649 Cat 17070
Cat 1008080-7 Proximity
Cat 2857
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Reader (80mm range) $209
Cat 2857-7 Use your spare
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Controller – Stand alone
front access for FireWire, USB (1.1) and Serial,
$269
plus an Audio in and Audio out (RCA) $89
Cat 1008079
More than one computer? Control them with one
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Cat 11658-7
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Cat 11658
and a VGA cable
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Cat 11659-7 USB KVM switch - 4 comps $449
BlueTooth
Cat 11902-7 BlueTooth Compact
Flash Card for Pocket PC’s with CF
slot $199
Cat 11902
Cat 11907-7 BlueTooth Head Set, no more
wires or “radiation” issues, try this
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Cat 11907
with a 10-metre
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Cat 11901-7 BlueTooth
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Access Point
Cat 11906
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Cat 11904-7 BlueTooth
USB Dual-Dongle 100 metre
range $259
Cat 11903-7 Bluetooth USB Single-Dongle 100
metre range $149
Cat 11905-7 Bluetooth USB adapter (plastic case)
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All “range” capabilities are for “free-air”
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MAILBAG
Motherboard for a silent PC
I have a brief response to the query
by Peter Humphreys, in Mailbag, October 2002 issue, for a silent personal
computer. VIA make a fanless motherboard – the web address is:
http://www.via.com.tw/en/Digital%20Library/pr_luckystar.jsp
To ensure complete quietness, a
linear power supply would be required
as well.
Geoff Perrin,
via email.
Nokia Datasuite is great
After “bagging” Nokia in these columns some time ago for being unable
to produce a decent comms suite at
a reasonable price to go with their
phones, I thought I must set the record
straight now.
I have just purchased their latest
CDMA offering, the “6385” and I must
say I am impressed with the connectivity offered now. Everything works as
expected, including infrared link-up
with current versions of Windows.
What’s more, the software is available
free to download from their website.
And to top it all, all the gadgetry,
including car kits from the 5100 and
6100 series can be used as well. Good
one, Mr Nokia.
Horst Leykam, via email.
Multi-sport scoreboard wanted
After spending a winter struggling
with rusty steel number plates hanging on bent nails (Footy scoreboard),
I started dreaming about an electronic
scoreboard. Suddenly, it was cricket
season – back to the drawing board!
So how about a multi-sport scoreboard
project ?
Many features are common to all
sports but a modular approach would
allow it to be configured to suit. Features needed would include large
character displays, optional multiple
displays, programmable control unit,
timer/clock function, IR remote control and team ID display.
There must be thousands of sporting
clubs: cricket, soccer, footy, bowls, etc
all with this need but which cannot
afford a commercial unit. You could
4 Silicon Chip
start with a single-character display
with a simple rotary switch.
Martyn Davison,
Paynesville, Vic.
Comment: how about it readers? Get
your thinking caps on.
Shamrock monitors
not popular
I read Serviceman’s Log in the
December 2002 issue with some bad
memories of the same situation I was
in with a Shamrock monitor. A lot
of the older computer monitors use
Shamrock cir
cuits. We had a few
waiting for the scrap heap. I emailed
the company that made these boards
and asked if we could acquire a circuit
diagram in Australia. They responded
with “No, we do not give out circuit
diagrams”!
I could not believe this response. I
work at a TV station and we can usually source a diagram for just about
anything, either from the manufacturer
or good ol’ High Country Service.
Needless to say these monitors did
go to the scrap heap and we have not
bought anything with their logo on
it again!
Jamie Marschke,
Coffs Harbour, NSW.
Out-of-date website
Could you tell me why your website
is so out of date? I went there recently for information on the December
2002 issue and the “current issue”
displayed on the opening page was
July 2002. Hardly current!
Can’t you guys spend a bit of time
and fix it? You refer readers to the site
for software and PC boards and so on
but that’s not much use if we have to
wait months for them.
J. S., via email.
Comment: the www.siliconchip.
com.au website is updated at least
once a month, usually just after the
issue goes to the press. Where necessary, (eg, to repair faulty links, etc),
updates are done even more regularly.
Because our website is operated “in
house” we can make changes almost
immediately.
We get this “out of date” comment
quite regularly and invariably when
we contact the writer, he or she doesn’t
realise their computer is caching
websites – not just ours but every one
they visit. Or even worse, the person
has installed web “go-fast” software
which often does the same thing (but
worse).
The answer is simply to hit your
browser’s refresh button on a regular
basis. Having said that, we do appreciate feedback if you do find an error,
broken link, etc.
Queensland licences
in the police state
We l c o m e t o p o l i c e s t a t e ,
Queensland. I waded through the
many pages of officialspeak on www.
eso.qld.gov.au as referred to in the
Publisher’s Letters on January and
February 2003. I did confirm that mere
mortals, ie, non electrical workers, are
still allowed to insert or remove 3-pin
plugs and replace faulty light globes.
Other than that, I am at a loss to understand if they have really changed.
I have a restricted licence that allows
me to work on medical and electronic
equipment.
Last week, I assisted a licenced
electrical contractor with the repair of
a portable compressor with a capacitor-start/capacitor-run single phase
motor. He had absolutely no idea what
function the capacitors filled, apart
from “they help the motor start”. He
was unable to test the capacitors for
low capacitance or leakage and had
no idea what sort of capacitor to get
to replace the one that proved faulty.
This is not only sad but downright
scary.
I have worked in radio (including high-powered transmit
ters), the
www.siliconchip.com.au
power generation industry and in
medical electronics; most of this experience was overseas. According to
the Queensland electrical authority
though, I am not competent to fit a
3-pin plug onto a portable appliance.
What does a qualified person like myself do in Queensland? Drive a taxi?
This makes me seriously consider
returning overseas where technical expertise can actually gain you
employment. All this Labor Party
sloganeering about “clever country”
and “Queensland Smart State” is
totally the reverse of the legislation
we get saddled with. It is no wonder
that countries with more intelligent
governments regularly outperform
Australia.
Keith Johnson,
Brisbane, Qld.
Schools caught in
the legislation as well
I run my own consultancy business
(The Computer Bloke) as well as being
the sole IT/Network administrator/
PC support at a northern Gold Coast
private college.
As a result of the Publisher’s Letter
in the January 2003 issue, I down
loaded the legislation, amendments
and other forms from the ESO website
and started reading. I very quickly
dismissed my first impression of the
editorial as a silly New Year joke and
now suspect this is actually a case
of farcical stupidity on behalf of the
Queensland Government.
As a computer consultant/repair
person running my own busi
ness,
I am breaking some law every time
I open a PC case (Section 18(1)) to
work on any components. Yet, as the
IT/network administrator of a private
school, using the same tools, doing the
same tasks, on the same equipment,
the work I do is quite legal. Or am I
missing some arcane point? That is,
the school needs to be licenced as an
electrical contractor.
The implications of such a proposal
are too monstrous to consider when
the entire education system, both public and private, repair their own PCs.
But then again, that can’t happen, as I
am my own supervisor, and according
to Section 41(1) (c) (amended) need to
be personally licenced.
This draconian legislation will not
www.siliconchip.com.au
further the notion of “the smart state”
as frequently proposed by the Premier.
Smart businesses will move south,
others will close their doors, all to the
detriment of the state and ordinary
Queenslanders. This legislation will
not save any extra lives. Education
and training will.
Although it would be presumptuous
to think any revenue raised as a result
of the licence fees would be used for
such a purpose, there can be no other
justification for this legislation. Personally, I can’t see that happening.
I’m now seriously considering moving
back to Australia.
Kris Zalkalns, MCSE,
via email.
Repairers going
out of business
I am writing in response to Paul
Betterige’s letter in the February 2003
issue. Paul seems to have confused the
issue of being qualified to work in the
electrical industry as a tradesman or
technician, and being allowed to by
virtue of buying, at some expense,
membership of the Contractors’ Club.
The point being, in Queensland at
least, that if you are not a member of
the club then you cannot carry out the
business of electrical work.
The membership of the Contractors
Club has recently been dressed up in
quasi-safety and consumer protection
terms however the basic issue was
that Contractors felt that there were
too many people ‘back-yarding’ and
competing ‘unfairly’ because they
did not have the overheads of larger
businesses. This was spelled out to
me by an employee of the Electrical
Safety Office early in the ‘consultation’
process. Just by the way, I don’t see
TETIA or TESA complaining about the
issue . . .
I have operated as an electronics
repairer employing at one stage three
technicians in a Queensland country
town. I had $10M public liability insurance, $30K of insurance on customers goods (2 - 3 times the average level
of items under my control), Workers
Compensation Insurance, Fire Insurance, Flood Insurance, Motor Vehicle
Insurance, Electrical Workers Licences
and all sorts of other guff to carry on
business.
On top of that, were I still in busi-
The Tiger
comes to
Australia
The BASIC, Tiny and Economy
Tigers are sold in Australia by
JED, with W98/NT software and
local single board systems.
Tigers are modules running true compiled multitasking BASIC in a 16/32 bit core, with typically
512K bytes of FLASH (program and data)
memory and 32/128/512 K bytes of RAM. The
Tiny Tiger has four, 10 bit analog ins, lots of
digital I/O, two UARTs, SPI, I2C, 1-wire, RTC and
has low cost W98/NT compile, debug and
download software.
JED makes four Australian boards with up to 64
screw-terminal I/O, more UARTs & LCD/keyboard support. See JED's www site for data.
Intelligent RS232 to RS485
Converter
The JED 995X is
an opto-isolated
standards converter for 2/4 wire
RS422/485 networks. It has a
built-in microprocessor controlling TX-ON, fixing Windows
timing problems of PCs using RTS line control.
Several models available, inc. a new DIN rail
mounting unit. JED995X: $160+gst.
Www.jedmicro.com.au/RS485.htm
$330 PC-PROM Programmer
This programmer plugs into a PC printer port and
reads, writes and edits any 28 or 32-pin PROM.
Comes with plug-pack, cable and software.
Also available is a multi-PROM UV eraser with
timer, and a 32/32 PLCC converter.
JED Microprocessors Pty Ltd
173 Boronia Rd, Boronia, Victoria, 3155
Ph. 03 9762 3588, Fax 03 9762 5499
www.jedmicro.com.au
March 2003 5
Mailbag: continued
ness, I would now have to greatly
increase my in
surance levels (the
ESO seems to feel that one size, large,
fits all).
I gave up the unequal struggle
against costs some five years ago and
sold the business. My successor ran on
until the end of last year. Faced with
increasing his insurances to levels way
out of proportion with the size of his
turnover and paying for a Contractors’
Licence he too has given up and shut
down. By the way, I don’t do repairs
for anybody any more.
David Pennycuick,
via email.
An electrician’s view
After reading the January editorial,
I felt I would be letting myself and
other electricians down if I didn’t
make an effort to state my case over
both the implications that electricians
are somehow working in collaboration
with bureaucracy to force electronic
repair businesses to shut up shop, and
that technicians are smarter cookies
than electricians.
I have been disappointed with the
way your editorials have covered this
licensing issue over the last couple of
years, and fellow sparkies have agreed
with me. You make a few unquantified
statements regarding the impact of
these requirements but it remains to be
seen how things really pan out. Believe
me, we are all in the same boat when it
comes to having more and more rules,
regulations, fees, charges and the rest
imposed on us.
I sometimes think that Governments
are trying to force small businesses out
of existence with new and additional
costs and requirements. But what the
Government is requiring of electronic
and appliance repair shops is what
has been required of us in the electrical trade for years and the burden is
increasing.
Peter Cairns, via email.
Quiescent current trimpot
should be fail-safe
I am writing concerning the new
SC480 power amplifier fea
tured in
the January & February 2003 issues.
In regards to the trimpot (VR1) which
6 Silicon Chip
sets the quiescent current of this
and many other amplifier designs,
there is no “safety valve” if this goes
open-circuit. Fitting a fixed resistor
of suitable value in parallel with the
trimpot stops the output stage from
having no control of quiescent current
whatsoever, usually taking out a pair
of output transistors, at least.
Commenting on the ETI480 in
general, I’ve used it in many general
purpose applications and never had it
oscillate. Attention to proper earthing
procedures and layout produces a very
stable unit.
The ETI480 module can be run from
±63V to give much more grunt than
originally designed (into 4Ω too!) with
some tweaking and appropriately substituted devices. How’s does the SC480
go on higher supplies? Yeah, I know,
“you don’t recommend it” but if you
start from scratch with new devices,
not reusing the old 2N3055s, why not?
Brad Sheargold,
via email.
Comment: VR1 is fail-safe. If the
wiper goes open circuit or the pot itself
goes open-circuit, Q7 is biased into
full conduction. This drops the bias
on the output transistors and reduces
the output stage quiescent current to
near zero. In fact, the same comment
applies to the ETI480 circuit.
Stability is a relative thing – we’ll
bet that many of the ETI480 amps
you thought were stable were in fact
prone to parasitic oscillation at 10MHz
or above – you just never observed it.
As you predict, there is no way we
would recommend an in
crease in
supply to the SC480. You will probably
get away with it when driving resistive
loads but as soon as you start driving complex loudspeaker loads, the
output transistors will be taken far in
excess of the SOAR ratings and you
will pop ‘em.
Don’t use WD-40 on
noisy volume controls
I refer to the “tip” on curing noisy
volume controls in the “Ask SILICON
CHIP” pages of the October 2002
issue, in which the writer is a proponent of the WD-40 school of electrical
fix-alls. Spraying a highly flammable
residual liquid in an area where there
is a high likelihood of arcing switch
contacts (ie, the back of an old pot) is
a recipe for disaster. I have seen many
efforts by WD-40 jockeys, spraying
entire amplifier chassis, TV PC boards
and my favourite, the mechanism of
a VCR.
WD-40 is for loosening rusty nuts in
the engine bay of Dad’s Holden, not for
electronic switch, wiper or pot cleaning. There are plenty of far superior
products that spring to mind, the most
useful being CRC2-26 which, by the
way, is not flammable, non-damaging
to plastic or rubber, doesn’t attract dust
and smells a lot nicer.
Please don’t publish such “tips”
as they only encourage people to
squirt the wretched stuff into the
innards of anything electronic that
isn’t working.
John, via email.
Move to stop DIY wiring
I thought I’d let you know that my
“rights” are under threat once again.
I read in the Sunday edition of the
“Herald-Sun” (dated 26/1/03 on page
30) under the title of “Union Bid To
Switch Off DIY” that the electrical
union wants to outlaw the sale of power points, cabling and safety switches
from public sale. Is this all they want
to ban?
Below is a copy of the text as printed:
“Electrical goods such as cabling,
power points and safety switches will
be banned from public sale under
proposals to be presented to the State
Government this week.
Electricians, tired of having their
lives endangered by “dodgy” cabling
installed illegally by home handymen,
have called for a new code of practice
that would restrict the sale of cabling
and switches to licensed operators.
Electrical Trades chief Dean Mighell
said the proposed code of practice was
already part of a new Enterprise Agreement between the Victorian branch of
the ETU and the National Electrical
Contractors association.
The Union has met with Victoria’s
chief electrical inspector and this week
will seek support for the code from the
State government.
Mr Mighell said electrical wholesalers and hardware stores which sold
specialist electrical parts to the public
www.siliconchip.com.au
were ignoring their duty of care.”
Is this another Labor government/
union ploy to seal the closed shop
approach on a protected industry?
Are they so desperate for a dollar that
they want to seal up the market place
so we treat them as gods? That’s what
they will be when you phone them up
and ask to have a faulty power point
replaced. We will all be put into a queue
depending on how much work we give
them or are prepared to pay.
As a repairer of electrical/electronic
equipment, I occa
sionally require
items from these businesses to complete repairs. I use an assortment
of parts which can only come from
electrical wholesalers. Are they going
to stop me from earning an honest
dollar?
I don’t advocate the illegal wiring of buildings but common sense
must prevail when we look at the
big picture.
Name supplied but withheld
at writer’s request.
Contractor licences
in Queensland
Thank you for bringing to the Industry’s attention the issue of ‘Contractor
Licensing’ for appliance repairers, in
the January 2003 Publisher’s Letter.
Our Association understands your
concerns. There are many facets to
this debate and I am sure it will divide
opinion in Queensland as well as the
rest of the Australian States!
Unfortunately, the Electronics
Industry in Australia, both Manufacturing/Supply and the Service/Repair
side has no single, united voice. The
closest we ever came to a single voice
was the Australian Council of Electronics Associations (ACEA) which,
although still an entity, is in a state
of limbo due to lack of unanimous
support in the Service sector (and we
had not even started on the manufacturing sector)!
Due to this lack of unanimity and
the diversified nature of the industry,
it is very difficult to access the opinion
and input of the many people involved
(and let us just talk about the Service
Industry here). Thousands of Australians beaver away at repairs having
absolutely no idea of what others are
doing and what commonalities they
share. The CETA Information List
www.siliconchip.com.au
(CINL
IST) has made some inroads
into bringing these people into con
tact although it does suffer from the
anonymity of a List Server.
In the issue of the introduction of
Contractor Licensing for Repairers in
Queensland, the case for this was put
through the Queensland Electrical
Safety Office as you are aware and,
as you have commented in SILICON
CHIP, was open for discussion for
many months before the legislation
was enacted. As a Trade Association,
we at CETA (Certified Electronic Technicians Association) received very little comment on this issue even though
we brought it to the attention of our
members over the same long period.
I’m afraid that we can only blame
ourselves for this appalling situation
in the Electronics Industry and until
we can learn to get on together and
take a united approach to the obsta
cles and decisions that affect us, I’m
afraid that things will only get worse,
not better.
Martin Shepherd,
Executive Officer, CETA.
BBC still broadcasts
shortwave
I was amazed to learn from the
December 2002 article on receiving
satellite TV that “the BBC no longer
transmits on shortwave” as I listen
to them almost every night. While
it’s true that they’ve cut back on
shortwave in recent years, choosing
to reach audiences via broadcast FM,
AM or streaming Internet audio, they
do broadcast comprehensively via
shortwave. There’s a listing at:
http://www.bbc.co.uk/worldservice/
schedules/frequencies/index.shtml
I’m sure that shortwave enthusiasts
are looking forward to the launch of
DRM which promises high quality
digital audio over shortwave. See
http://www.drm.org/ for more information and downloadable software
for decoding.
Peter Marks, via email.
Degradation of CDs
I note with interest the comments
of your correspondent, John Tingle,
about the degradation of CDs from
storage problems and other damage,
in the January 2003 issue. Some years
ago, it came to my attention that it was
the top or non-reading side of discs
which was more prone to damage.
In an effort to overcome deterioration from ‘dulling’, scratching and
chipping of the reflective layer, I developed a self-adhesive label which
covers the entire top side of the disc.
Much work went into the design to
come up with the right adhesive/
stock combination to ensure that it
was entirely inert and did no damage
to the disc or degraded the sound or
data quality in any way. As the labels
are virtually non-removable, they also
provide a bonus benefit of permanent
security marking of any disc they
are applied to. They have since been
patented.
We sell hundreds of thousands per
year into the video games and DVD
hire industry but (not surprisingly) we
cannot interest the record producers
in them. What we do find astonishing is that music retailers are almost
completely uninterested in stocking
them, although they stock read-side
protectors and scratch repair kits.
Our protective covers have been
fitted to discs for the last 10 years
and not one is showing any signs of
degradation. The material also stops
the disc from sticking to the leaves in
CD storage folders, a problem we have
found in that type of storage.
If any of your readers are interested
in obtaining some covers, they are
available from our web site at: www.
disc-over.com.au
A. Bryan Fricker,
Managing Director, via email.
ABC radio delay
explained
I noted the letter from a reader in
the “Ask SILICON CHIP” pages of the
January 2003 issue concerning the 1
to 2-second delay between ABC TV
sound and ABC Radio on Parliament
broad
casts. Your response attributed the delay to propagation delays
through the possibly long path that
the signal has to travel.
The delay is probably to do with
the 2-second delay that talkback radio
stations add to the transmitted signal.
This is done so that the announcers
have time to stop calls if they get
abusive, without the abusive words
being transmitted.
SC
Shuni Francis, via email.
March 2003 7
GM’s HyGeneral Motors has unveiled the Hy-wire
concept car, the world’s first drivable vehicle that
combines a hydrogen fuel cell with by-wire technology.
The heart of the Hy-wire is an innovative “skateboard” chassis, which
contains all of the sedan’s propulsion,
transmission, steering and braking
components within its 279mm high
frame and provides a single electrical
connection to the body.
In essence, fuel cells enable a
skateboard chassis and this flat plane
provides unprecedented freedom for
designing the vehicle body.
8 Silicon Chip
Complementing this, the by-wire systems allow a single docking connection
between the skateboard chassis and
the body, and this creates great opportunities for reinvesnting the interior
layout.
Hy-wire was literally designed from
the inside out, with form following
function. The flexibility of the chassis
accommodates multiple interchangeable “snap on” body styles that can be
customised to meet customers’ various
lifestyles.
Fuel Cell Propulsion System
Inside, between the aluminium
beams of the skateboard chassis, GM
engineers have integrated an impressive technology package. A 3-phase
electric motor, mounted transversely,
drives the front wheels via a single-stage planetary gear with a transwww.siliconchip.com.au
mission ratio of 8.67:. It generates a
maximum power of 60kW and delivers
a maximum torque of 215Nm. Maximum
speed is 12,000 rpm.
The fuel cell stack consists of 200
single fuel cells connected in series and
is roughly the size of a PC tower. It is
located in the rear of the skateboard chassis and is cooled
using a conventional
radiator.
The stack, which
operates under a
pressure of 1.52.7 Bar, has a
power density of 1.60kW/l
and produces
94kW continuously, with
a peak power
of 129kW. This
delivers between 125V and 200V DC,
depending on the load. This is boosted
to 250-380V and then converted to
3-phase AC to drive the electric motor.
Unlike other fuel cell vehicles, there
is no battery in Hy-wire to provide extra
power for peak loads. It uses only the
fuel cell to provide power, thus simplifying the development and integration.
The fuel cells obtain the hydrogen
fuel from tanks mounted securely in the
centre of the skateboard. The three cylindrical compressed hydrogen storage
tanks are made of carbon composite
material, have a total weight of only
75kg and store a total of 2kg of gaseous
hydrogen at 350 Bar.
Yes, you read that correctly – 350 Bar,
about 5,000 pounds per square inch!
Incidentally, the next stage of development will increase the tank pressure
from the current 350 Bar to 700 Bar.
GM and QUANTUM Fuel Systems
Technologies Worldwide received
certification from the top
German safety
-wire
www.siliconchip.com.au
institute for a 700 Bar (10,000 psi)
hydrogen storage system that could
ultimately allow fuel cell vehicles to drive
300 miles depending on the storage
volume.
Drive-By-Wire, BrakeBy-Wire, Steer-By-Wire,
Docking Connection
Developed by Swedish-based SKF,
the “by-wire” technology enables all of
Hy-wire’s major driver-control functions,
including steering, accelerator and
brakes, to be consolidated into a flexible,
hand-controlled unit called the X-drive.
It is similar to today’s advanced aircraft controls, where commands are
transmitted digitally from the cockpit
through electrical cables, or “by wire”,
to the various parts of the plane.
Hy-wire uses the same technology,
allowing the driver to easily control the
vehicle with either the right or left hand
from the X-drive unit. Drivers also have
the option of driving from the left or right
driving position because the X-drive is
located in a centre console that shuttles
from left to right.
Because it uses fully electronic
connections and controls, the by-wire
system simply plugs into the docking
connections on the Hy-wire chassis.
At the heart of the by-wire system
March 2003 9
are smart electro-mechanical actuating units, which convert the driver’s
commands from electronic signals to
motion. The by-wire system also provides dynamic feedback to the driver
via electronic signals.
The advantages of by-wire technology in automobile applications include
the elimination of steering columns and
foot pedals and allows greater design
freedom, simplified production of left
and right-hand drive models and improved passive safety for
the driver.
The elimination
of mechanical
and hydraulic
linkages saves
weight and simplifies maintenance because
there are fewer
moving parts that
can wear out.
By-wire is more environmentally friendly because hydraulic fluids required for steering
and braking are eliminated. Software
allows the driver to personalise the
handling characteristics of the vehicle
by adjusting the feel of steering, braking
and acceleration. Adjusting them is as
simple as loading a new program.
10 Silicon Chip
The Hy-wire’s X-Drive replaces the
usual round steering wheel and pedals,
giving drivers the option to brake and
accelerate with either the right or left
hand. The driver accelerates by gently
twisting either the right or left handgrip
and brakes by squeezing the handgrips.
The handgrips glide up and down for
steering, somewhat different
than today’s vehicles
where the steering
wheel revolves
around a steering
column.
The X-Drive also incorporates an electronic monitor for rear-
view and vital
car functions and
shuttles easily from
side-to-side on a horizontal
bar that stretches across the full
width of the vehicle.
The steering system highlights
the basic functions of the by-wire
controls. A conventional vehicle
uses a direct mechanical or hydraulic
connection between the driver’s control
www.siliconchip.com.au
Specifications: GM Hy-Wire
Vehicle:
Seating capacity:
Fuel storage system:
device and
the relevant component. For example,
the commonly used rack-and-pinion
steering system uses a small toothed
wheel (the pinion) to engage the rack
and to shift it left or right. Tie rods then
carry the motion to the steering arms
at the wheel.
By-wire technology, in contrast,
translates the driver’s commands into
electrical impulses. If the driver turns
the handgrips of the X-Drive, sensors
capture this motion digitally and send a
signal to an electrical motor that moves
the steering rack as instructed.
Acceleration is similar to the throttle
on a motorcycle, except that a throttle
cable does not mechanically activate
the throttle valve of the power plant. The
by-wire system transmits an electronic
signal to the electric motor that drives
the Hy-wire’s front wheels.
Braking is achieved by squeezing
either the left or right hand grip. Grip
www.siliconchip.com.au
Length/diameter:
Total capacity:
Total weight:
Fuel cell stack:
Voltage:
Length/width/height:
Pressure:
Continuous rating:
Power density:
Electrical traction system:
Operating voltage:
Maximum rating:
Maximum torque:
Maximum rpm:
Transmission ratio:
Total weight:
Skateboard chassis:
Body:
Length:
Vehicle weight:
Wheel base:
Fuel cell and by-wire technology, front-wheel drive,
luxury sedan
Five
Three cylindrical high-pressure tanks of carbon
composite material, mounted in the middle of the
skateboard chassis
1,161/241mm
2kg
75kg
200 single fuel cells; connected in a series
125-200 Volt
472/251/496 mm
1.5-2.7 Bar
94kW, peak of 129kW
1.60 kW/l, 0.94 kW/kg
3-phase asynchronous electric motor with
integrated power electronics and planetary gear
250-380 Volt
60kW
215Nm
12,000
8.67:1
92kg
Length/width/height: 4,357/1,670/ 279mm
Aluminium frame
Steel and fibreglass
5 metres
1,900kg
3,114mm
March 2003 11
sensors determine how much hand
pressure the driver is exerting and
these transmit a signal which applies
the brakes.
The system, developed together with
the Italian specialist, Brembo, works
with conventional brake calipers but
responds faster.
Maximum reliability and safety are
essential features of the data-transmission system in by-wire control. All safety
systems have built-in redundancy and a
back-up power supply similar to those
used in fly-by-wire systems.
Body and Interior
Since Hy-wire’s skateboard-like
chassis contains all of the propulsion
and control systems – a fuel cell and
by-wire technology – designers were
free to consider a number of body
styles and interiors with what amounts
to a fresh canvas to explore an endless
range of possibilities for the body style
and interior package.
GM wanted an obvious transition from
where vehicle design is now to where the
technology could take it and intentionally
designed a vehicle that will highlight the
openness in the interior and leave it to
the occupant’s imagination to consider
the possibilities.
The break with conventional automobile architecture is obvious on the
very first encounter with the car, which
is 5-metres long, 1.87-metres wide and
1.57-metres high.
Glass is used extensively, giving
12 Silicon Chip
passers-by a full view inside and the
passengers a perfect view of the world
outside.
The absence of a conventional engine
means there is no need for a grille up
front. So the question became what
to do with the open front face where
you’d typically put a grille. The designers
chose to enclose it with glass, allowing
the driver to have a view of the road
ahead that has never been possible
before.
You can see immediately that there
is no engine at the front, the pedals and
instrument panel are superfluous and
the floor is flat from front to back.
Hy-wire features large side windows
and no B-pillars (the traditional post
between the front and rear windows).
The rear doors are hinged at the back,
allowing the four doors to open very
wide, providing very easy access.
Anyone who accepts the invitation
aboard can look forward to a comfortable and exciting journey. Apart from
the unmatched panoramic view for the
driver and passengers and spacious
interior, Hy-wire offers several other
key features.
The fuel cell and by-wire systems
eliminate the need for a traditional engine bonnet and centre tunnel, resulting
in improved legroom. The lack of foot
pedals means the driver is not restricted
to a specific leg position.
Flexibility
The X-Drive can slide across for left or
right side driving, emphasizing Hy-wire’s
outstanding flexibility.
Pressing a button on the X-Drive
starts the Hy-wire vehicle. Buttons also
engage the vehicle’s forward, reverse,
and neutral drive conditions.
The X-Drive attaches to a very light
and transparent-looking centre console.
Integrated in this console is a second
15cm colour monitor which allows the
driver to view radio controls, heating,
ventilation, air conditioning and navigation systems.
The design team’s work was characterised by a feeling of freedom – freedom, for example, to position the seats
and control module where they wanted
to, without any restrictions.
They paid particular attention to the
seats when developing the Hy-wire’s
interior.
The five-passenger vehicle has front
and rear bucket seats; the centre rear
seat folds up to create a table.
Lightweight materials accentuate
the vehicle’s openness, and the overall environmental-friendly concept is
expressed by the choice of natural
colours.
The sporty yet elegant four-door vehicle has short overhangs, eight-spoke
light-alloy wheels with 20-inch tyres in
front, and 22-inch tyres in the rear.
Cameras have replaced the rearview mirrors and the headlamps and
tail-lamps feature LED technology. This
technology allows the lamps to be packSC
aged in a very small space.
www.siliconchip.com.au
Emergency
beacons
Australia is a huge continent, surrounded
by the vast Indian, Pacific and Southern
oceans. If you get lost in the outback or
have to abandon ship far out to sea,
you could be in very serious trouble.
T
wenty years ago you almost certainly would have
been in trouble. Rescuers might have searched for
days to find you – once they even knew you were
overdue.
Today the Cospas-Sarsat satellite system, set up by
Russia, Canada, France and the USA in 1982, takes much
of the search out of search and rescue.
A constellation of satellites quickly detects
signals from emergency radio beacons and alerts
search and rescue authorities around the world.
Since the system became fully operational in
1985, 29 other countries, including Australia,
have become involved and more than 11,000
people have been rescued. Carrying an emergency beacon means you can be certain help
will be on its way when you need it.
If you activate a beacon, it starts transmitting
a low-power radio signal. Satellites in geostationary and low earth orbits pick up the signal
and relay it to ground receiving stations, called
Local User Terminals (LUTs). The LUTs locate the
beacon position and pass it to Mission Control
Centres (MCCs) which coordinate the search and
rescue effort (Fig.1).
Beacons
Beacons come in many shapes and sizes. There
are Emergency Locator Transmitters (ELTs) fitted
in aircraft, Emergency Position Indicating Radio Beacons (EPIRBs) in ships, and hand-held
www.siliconchip.com.au
By
PETER HOLTHAM
Personal Locator Beacons (PLBs).
The oldest type of emergency beacon operates
on 121.5MHz (Table 1). They were originally
designed in the mid 1970s as ELTs for crashed aircraft. Nowadays there are about 600,000 low-cost
EPIRBs and PLBs also using this technology
worldwide.
Designed for detection by search aircraft
not satellites, their simple analog signal doesn’t tell the rescue authorities
who or what is in trouble, or exactly
where the emergency is. What is
worse, only about three in 100 alerts
worldwide are genuine.
Accidental or malicious activation, faults in the beacons,
non-beacon transmissions on
121.5MHz, even ‘hard’ landings by
aircraft with G-switch activated ELTs
cause the rest.
But each alarm must be tracked to its
source, wasting the time and resources
of search and rescue teams. Because the
false alarm rate is so high, Cospas-Sarsat
will stop processing signals from these
beacons after February 1st 2009, and they
will be obsolete.
Newer beacons, specifically designed for
detection and location by satellites, operate
on 406MHz (Table 2). Frequencies in the
March 2003 13
Fig 1: Basic Concept of the Cospas-Sarsat System
406-406.1MHz band are reserved solely for these beacons,
which helps minimise the number of false alarms.
The beacons transmit a 5W burst of radio frequency (RF)
every 50 seconds. The high power increases the chance
of detection, while the low duty cycle saves power and
allows more than 90 beacons to be operating at once in
view of one satellite.
Each burst of RF carries a digitally encoded message,
which identifies the owner of the beacon and its country
of origin. Search and Rescue authorities worldwide keep
a register of owners and can quickly make a phone call to
check if an emergency is genuine or not.
Most 406MHz beacons also include a 121.5MHz
transmitter and a flashing strobe light for search vessels to home in on during the last stages of a rescue.
Second-generation beacons, available since 1997, add
position data in the digital message, from an internal or
external GPS receiver.
Because the performance of the Cospas-Sarsat system
depends on the quality of the 406MHz beacons, manufacturers must get type-approval. Australian and New Zealand
Standard AS4280 describes the rigorous durability tests
a beacon must pass before it is approved for use. Only
two Australian companies have gained type-approval for
their beacons, and they manufacture them only for the
Defence Forces.
Table 2: 406MHz beacon data
Transmitted power
5W ± 2dB
Transmission life
at least 24 hours at minimum
temperature
50-100 mW peak effective radiated
power relative to a quarter wave
monopole
Frequency
406.025 ±0.005MHz
Modulation
phase modulation, bi-phase L data
encoding
Transmision life
48 hours
Transmission time
Frequency
121.5MHz ±6kHz
440ms (short message)
520ms (long message)
Modulation type
AM (amplitude modulation),
greater than 85%
Message length
112 bits (short)
144 bits (long)
Modulation
Swept audible tone, 300-1600Hz
(at least 700 Hz) at a rate of 2-4Hz
Message repetition time
50s
Operating temperature
-40 to +55°C
Table 1: 121.5MHz beacon data
Transmitted power
14 Silicon Chip
www.siliconchip.com.au
Fig 3: Approximate 121.5MHz Beacon Coverage from Australian and New Zealand LUTs.
Fig 2: Satellite in Polar Orbit Showing a Single Orbital
Plane.
Inmarsat, the organisation responsible for worldwide
ship-to-shore communication, also operates an EPIRB
tracking system using satellites as part of its commitment
to the safety of life at sea.
Inmarsat EPIRBs operate at 1.6GHz (Table 3). Like
406MHz beacons, they also transmit identification and
GPS-derived position information. Some also have a ‘will
to live’ feature – as soon as an Inmarsat land earth station
(LES) receives an emergency signal, it bounces it back to
the beacon. The beacon recognises its own code and shows
a telltale visual indication. Survivors in the water can see
that their distress signal has been received and that help
is on the way.
Satellites
The Cospas-Sarsat system uses low-earth orbiting
(LEOSAR) and geostationary (GEOSAR) satellites. The
LEOSARs are in polar orbits 800-1000km above the Earth.
They complete an orbit every 100 minutes or so, listening
for both 121.5MHz and 406MHz beacons.
The system uses a minimum of four LEOSARs to speed
Table 3: Inmarsat-E Beacon Data
Transmitted power
1W
Transmission life
48 hours minimum
Frequency
667 channels at 1.645GHz
Modulation
Frequency shift keying.
www.siliconchip.com.au
up detection of activated beacons (Table 4). With a single
satellite, it takes at most one half rotation of the Earth
(twelve hours) for any location to pass under the orbital
plane (Fig.2).
A second satellite with its orbital plane at right angles to
the first reduces the time to six hours. Using four satellites
ensures the time taken to detect a beacon is less than one
hour at mid-latitudes and slightly longer nearer the equator
where the LEOSARs are more spread out.
With 121.5MHz beacon signals, LEOSARs simply act as
repeaters, relaying the signal to a LUT for processing. For
an emergency beacon to be noticed, a LEOSAR has to be in
view of the beacon and a LUT simultaneously for at least
four minutes. If it is not, the emergency will be missed until
a more suitable pass occurs, which can take several hours.
This constraint limits the use of these beacons to within
a 3000km radius of the LUT (Fig.3).
Table 4: LEOSAR Satellites
Satellite
Spacecraft
Status
Cospas-6
Nadezda-3
Operational
Cospas-8
Nadezda-5
Operational
Cospas-9
Nadezda-6
Operational
Sarsat-4
NOAA-11
Operational
Sarsat-6
NOAA-14
Operational
Sarsat-7
NOAA-15
Operational
Sarsat-8
NOAA-16
Operational
March 2003 15
Looking for all the world like the lighthouses of yesterday, Australia's two Local User Terminals (LUTs) are located at
Albany, WA (left) and Bundaberg, Qld (right). The inset in the middle is an on-ground shot inside a LUT antenna dome.
Because LEOSARs were specifically designed to detect
406MHz beacons, they do more than just relay the signal. An on-board Search and Rescue Processor (SARP)
decodes and time-stamps the beacon’s digital signal and
measures the Doppler shift (the change in frequency
caused by the relative movement between the satellite
and the beacon), locating the beacon to within 5km. In
95% of cases, the location is determined on the first orbit
after detection.
Second generation 406MHz beacons transmitting
GPS-derived position data can be located to within 120m.
In local mode, the satellites immediately transfer the
information to the 1545MHz downlink, for transmission
to any LUT that may be in view.
In global mode, the satellites also store the data in
memory and continuously re-broadcast it on the downlink
frequency. This means all LUTs tracking the satellite are
able to locate the beacon, giving the system global coverage. There is no waiting until the satellite can see both
the beacon and a LUT simultaneously, reducing the time
taken to launch a rescue.
Data storage gives the LEOSARs global but not continuous coverage; there may still be a delay before a satellite comes into view. So the Cospas-Sarsat system also
uses three geostationary satellites (GEOSARs) orbiting
Table 5: GEOSAR Satellites
Satellite
Status
GOES-8
Operational 75° W
GOES-10
Operational 135° W
GOES-11
In orbit spare
INSAT-2B
Operational 93.5° E
16 Silicon Chip
36,000km above the equator (Table 5). These communications and weather satellites carry 406MHz beacon receivers
as secondary payloads.
GEOSARs provide a continuous watch and can send an
alert as soon as a beacon is activated but there are some
disadvantages. As GEOSARs are stationary relative to the
Earth, there is no Doppler effect on the received signal to
provide position information. Unless it is encoded in the
digital message, LEOSARs must still be used for beacon
location.
Hilly ground or other obstructions can also hide the
GEOSARs from view, especially at high latitudes; neither
can they cover the polar regions, latitudes greater than 75°
(Fig.4). But even with this limitation, GEOSARS can see
about 97% of the Earth’s surface.
Four geostationary communication satellites spaced
around the equator detect Inmarsat EPIRBs. Like GEOSARs,
Inmarsat satellites cannot see the polar regions but this is
not a major problem as very little commercial shipping
enters these regions.
Local User Terminals (LUTs)
Local User Terminals are unmanned ground stations that
receive the downlink signal from the orbiting LEOSARS
as a 2400kbps data stream. They consist of an antenna, a
1545MHz receiver, a computer to process the data, and an
MCC interface. The antenna and receiver automatically
acquire, track and receive the downlink signal from all
non-conflicting LEOSAR passes.
There are 45 LEOSAR LUTs worldwide (Fig.5). Two are
in Australia, one on the east coast at Bundaberg and one
on the west coast at Albany. New Zealand has one LUT,
near Wellington, while to our north there are LUTs in Indonesia, Singapore and Guam. All LEOLUTs are expected
to be available 24 hours a day, every day, with less than
5% downtime a year.
www.siliconchip.com.au
Fig 4: Geosar Footprints
Fig 5: Worldwide location of Leoluts and Geoluts
Once a 121.5MHz beacon signal is received, the LUT
roughly fixes its position from the Doppler shift. Initially
two mirror-image positions are calculated, one on either
side of the satellite ground track. It takes until the next
orbit, 90 minutes later, to resolve the ambiguity and fix
the position to within 20km.
The data from 406MHz beacons is simpler to deal with,
since the Doppler shift is measured and time-tagged by
the SARP onboard the LEOSAR. Within minutes of the
satellite disappearing over the horizon, all stored data
has been processed and passed to the nearest Mission
Control Centre.
Another seven GEOLUTS worldwide receive
and process alerts relayed by GEOSAR satellites (Fig.5). In the southern hemisphere,
there are GEOLUTS in New Zealand
and Chile. Separate Land Earth Stations (LES) operated by Inmarsat
(including one in Perth) monitor
the signals from the Inmarsat-E
beacons.
Inmarsat Land Earth Stations. Because a 406MHz emergency is usually processed by more than one LUT, the
MCCs are networked together so that alerts can be rapidly
sorted and passed to the nearest search and rescue team
for action.
The MCC for the Australasian region is in Canberra and
is operated by Australian Search and Rescue (AusSAR),
part of the Australian Maritime Safety Authority. About
60 search and rescue specialists and support staff work
in the Centre, which operates 24 hours a day, 365 days
of the year.
As well as managing the Australasian segment of the
Cospas-Sarsat system, AusSAR coordinates Australia’s
Search and Rescue Region. Covering 53 million
square kilometres or one tenth of the Earth’s
surface, it includes the nation as well as vast
areas of the Indian, Pacific and Southern
Oceans.
The search and rescue teams coordinated
by the Centre come from the private sector,
the police, volunteer groups and the Defence
Forces.
How long will it be before you’re rescued
once you’ve switched on your beacon? AusSAR
has one of the best search and rescue response
times in the world. During 2000-2001, it took an
average of just 57 minutes to get a rescue underway
after receiving an alert. But how long it takes to get
to you will depend on where you are and whether
there are ships or aircraft nearby.
But unlike 20 years ago, at least you can be certain
SC
that you will be found.
Mission Control Centres (MCCs)
24 Mission Control
Centres around the
world receive alert
and location data
from LUTs, other MCCs and
The GlobalFix
406 is the next
generation of
EPIRB featuring an
internal GPS engine
to add latitude/longitude
coordinates to the emergency
signal. It is available in either Category
I (automatically deployable) or Category
II (manually deployable) models. The beacon’s self-test
features include a thorough analysis of the GPS’s circuitry
(each time you self-test the EPIRB, the GPS is tested as
well). When used in an emergency, the GlobalFix 406 will
automatically change its operating “red” flash to “green”,
to confirm the exact time the GPS coordinates are received
and re-broadcast in the EPIRB’s transmission.
(EPIRB pictures supplied by Tony Smith & John Bell, ACR
Electronics Inc.)
www.siliconchip.com.au
Acknowledgement:
Thanks for the assistance of Ben Mitchell of AusSAR in
preparing this feature.
Cospas
Sarsat
ELT
EPIRB
LES
LUT
MCC
PLB
Abbreviations
COsmicheskaya Sistyema Poiska Avariynich Sudov
(Space system for the search of vessels in distress)
Search and Rescue Satellite Aided Tracking
Emergency Locator Transmitter
Emergency Position Indicating Radio Beacon
Land Earth Station (Inmarsat)
Local User Terminal
Mission Control Centre
Personal Locator Beacon
March 2003 17
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
dicksmith.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
dicksmith.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
dicksmith.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
dicksmith.com.au
Replace your car’s filament lamps with
LEDs for improved safety
By PETER SMITH
LED Lighting
For Your Car
I
NCREDIBLY BRIGHT Light Emitting Diodes (LEDs) have recently
become available in standard 5mm
packages – bright enough, we believe,
to rival incandescent bulbs in some
applications.
This month, we present five simple
and easy-to-build modules based on
these new, ultra-bright LEDs. These
modules can be used to replace or
supplement a variety of existing automotive lights to improve safety.
Safer, huh?
Do you know why the centre highmount stop lights of some vehicles
use LEDs rather than conventional
filament lamps? For the “high-tech”
look, perhaps?
Maybe, but there’s a much more
important reason; LEDs reduce the
22 Silicon Chip
incidence and severity of rear-end
collisions!
So how is this possible? The answer
is based on the fact that filament lamps
typically take between 120ms and
250ms to ‘light up’ when you hit the
brakes. If that doesn’t sound like much,
Convert These to LEDs
•
•
•
•
•
•
•
•
High-mount stop lights
Trailer lights
Breakdown lights
Clearance lights
Interior (festoon) lights
Bayonet lamps
Wedge lamps
Almost anything!
then consider the distance travelled in
200ms at 100km/h:
100km/h x 1/3600 x 200ms = 5.5m
Those 5.5 metres could make all the
difference in an emergency braking
situation – a serious accident or none
at all!
The good news is that you can get
that distance back with LED-based
stop lamps, because LEDs ‘light up’
almost instantaneously. Not only that
but the fast turn-on of LEDs makes
them more conspicuous; they have
greater attention-getting power.
LEDs have a number of other advantages over filament lamps, too. They
load vehicle electrical systems by at
least one third less, generate little heat,
require less space and have a very long
service life.
siliconchip.com.au
With all these positives, it seems ludicrous that most new vehicles aren’t
fitted with the latest high-brightness
LED technology. Sure, you’ll see them
in high-end vehicles like the Jaguar
and Maserati. Less-expensive vehicles,
such as Holden’s Monaro, use them
in the centre high-mount stop light
(CHMSL) but generally speaking, their
use in tail, stop and turn indicators is
not widespread.
We’re ignoring spoiler-mounted
CHMSLs here, by the way, because
they’re available only on a limited
number of models and are usually
optional.
As far as we can determine, the
only reason for this apparent short
sightedness is cost. And that, of course,
is poised to change in the very near
future, as LED prices come down (and
intensities go up). But why wait? You
can now convert your old-technology
CHMSL to the latest and greatest with
the aid of our LED CHMSL module and
a few simple tools.
This particular module consists of
a single, 150mm-long PC board strip
carrying 16 high-intensity red LEDs,
four resistors and two diodes. It should
fit inside most CHMSL housings without too much difficulty, replacing the
standard 21W filament lamp. But before we describe how that’s done, let’s
take a look at how it works.
How the modules work.
All modules are of the simplest design possible. They consist of one or
more strings of LEDs, current limiting
resistor(s) and in most cases a diode
or two as well.
Referring to the circuit diagram for
the CHMSL module (Fig.1), you can
see than the LEDs are arranged in four
strings. Each string consists of four
LEDs in series with a current limiting
resistor. The resistor sets the current
through the string, as follows:
I = V/R
= VBATT – VDIODE – (4 x VLED) / R
= 12.8V – 0.7V – (4 x 2.0V) / 150Ω
= 27.3mA
VLED is the forward voltage of the
LEDs at the intended current, in our
case about 27mA. This value will
vary between LED types, so you may
need to adjust your resistor values for
optimum results.
Although the high-brightness red
LEDs we’ve specified can be driven
at much higher current levels (up to
siliconchip.com.au
Fig.1: circuit diagrams for all of the red LED modules. Note that we’ve
reduced LED current on the Multidisc and Wedge lamp modules by
increasing the resistor values from 150Ω to 180Ω. This is to allow for the
higher temperatures present in tightly grouped LED arrays.
50mA), we recommend derating to a
maximum of 30mA to allow for the
high temperatures found in automo-
tive interiors. If you’re using different
LEDs, then derate even further to
25mA.
March 2003 23
Fig.2: follow this diagram when assembling your centre high-mount stop lamp board.
This view shows the fully-assembled CHMSL board,
ready for installation inside
the housing. Note that this
particular unit is fitted with
a “wedge” plug, made by
sandwiching two blank PC
boards together as described
in the text.
VDIODE is the forward voltage of the
1N4004 diode. The purpose of this
diode is to protect the LEDs from the
large negative voltage transients (up
to 400V) often present in automotive
electrical systems.
Typical LED reverse breakdown
voltage is somewhere in the region
of 5-6V, so with four LEDs in series
the best we could hope to “stand off”
without the additional diode would
be about 24V.
In cases where there are less than
three LEDs in a string, the 1N4004 also
provides reverse polarity protection.
Without protection, accidental lead
reversal could cause your megabuck
LED bank to glow brighter than the
Sun for a few milliseconds!
An example
OK, let’s look at an example. Suppose you’re using different LEDs to
those shown in the parts list and
you’ve determined that they drop
about 1.8V at 25mA (the forward voltage can be determined from the LED
data sheets or by trial and error). What
value resistors would you use on the
CHMSL module?
24 Silicon Chip
R = V/I
= 12.8V – 0.7V – (4 x 1.8V) / 25mA
= 196Ω
The closest readily available value
to 196Ω is 200Ω, so that would be your
final choice. A 0.25W power rating is
sufficient in most cases.
So far, we’ve only talked about the
CHMSL module but there is little dif-
WARNING
If you have a late-model car, it may
have a lamp failure detector in the brake
lamp circuit. If you convert just the
CHMSL to LED operation, it is unlikely
to be affected. However, if you also convert the stop lamps to LED operation,
the lamp failure detector will almost
certainly operate each time you press
the brake pedal. The fault may even be
recorded in the computer’s diagnostic
memory.
In some prestige cars, such as the
Lexus LS400 and LS430 models, the
CHMSL also has a lamp failure detector
and it will “detect” a lamp failure if the
LED conversion is present. At present,
we have no solution for this problem.
Fig.3: you
may need to
trim away
the standoffs on the
LED leads
so that they
can be positioned right
down on the
PC board
surface.
ference in operation between the five
modules. Some have less LEDs per
string, some have just one (the 10mm
LED on the wedge lamp, for example)
and one requires the diode to be fitted
externally.
Note, however, that we’ve listed
LED colours with each module. This
is because white and blue LEDs have
a significantly higher forward voltage
than red (and other colours) and therefore will not work on modules that
have four LEDs in series.
Likewise, reds (and other colours)
cannot easily be used on the modules
specified for white and blue without
considering the increased resistor
power dissipation requirements.
CHMSL module assembly
Referring to the overlay diagram
in Fig.2, begin by installing the two
diodes and four resistors. Take care
with diode orientation, noting that D1
and D2 go in different ways around.
Next, install all 16 LEDs, aligning
the side with the ‘flat’ (the cathode) as
indicated. This should also be the side
with the shorter lead. We mention this
because the 10mm LEDs we received
siliconchip.com.au
Converting A High-Mount
Stop Light To LEDs
Fitting the CHMSL module (shown at left) to
an existing housing can be achieved with a
little ingenuity. Here’s how we did the job on a
late-model Honda Accord.
(1). The Accord’s CHMSL sits on the parcel shelf and
is retained with two clips accessible from within the
boot space. The entire assembly came away in less
than 10 seconds!
(3). In our case, the replacement LED module was
just the right length for the job. We made a couple
of small right-angle brackets to hold the board
and screwed these to the top of the reflector. Many
other mounting methods are possible, depending
on shape and available space; eg, nylon stand-offs,
cable ties, M2.5 screws, neutral cure silicone sealant, etc. Make sure that the rear of the PC board
cannot contact anything metallic, though.
(2). Once we had the assembly on the bench, it was a
simple matter to separate the red lens from the
reflector to get to the insides. Be careful with the
clips that hold these parts together, as the plastic is
very brittle.
recently were incorrectly polarised;
the flat side was next to the anode
(longer lead). If you’re not sure, use
your multimeter on “diode test” to
verify polarity.
The LEDs should be seated right
down on the PC board surface. Some
LEDs have large standoffs formed into
their leads, making this impossible. If
you have this problem, then measure
between the underside of the LED and
the start of the standoffs (see Fig.3). If
you measure 2.5mm or more, then you
can cut the leads off right at the edge of
the standoffs, as there will be sufficient
length remaining for soldering. Try just
one LED first, though!
siliconchip.com.au
If the standoffs are closer than
2.5mm to the body, then shorten the
leads to about 4mm and using a fineedged pair of electronics sidecutters,
carefully snip away the shoulders of
the standoffs (see Fig.3).
To finish, install the +12V link and
two 150mm flying leads for the +12V
and 0V connections. Any light duty
multi-strand hook-up wire will do.
CHMSL module installation
We chose a late model Honda Accord for our prototype installation
– see photos. We didn’t hack off any
“unnecessary” bits along the way,
thus allowing return to the standard
(4). We didn’t want to
modify the vehicle’s
wiring, so we powered
the LED module
directly from the old
filament lamp socket.
A suitable plug can be
fashioned from two
pieces of PC board,
some glue and a length
of tinned copper wire
(see wedge lamp
details). Be sure to tin
all bare copper areas to
prevent corrosion.
filament lamp configuration if need
be. Adapt our methods to suit your
particular vehicle.
If the module is too long for your
housing but there is plenty of vertical
space, then you can cut it in half and
mount one section directly above the
other. This is possible because we’ve
designed the two sides of the board in
“mirror image”. These smaller sections
could be useful for other applications
as well.
Multidisc module assembly
As the name suggests, the Multidisc
module has multiple uses, some of
which will require the PC board to be
March 2003 25
Fig.4: the overlay diagram for the Multidisc module.
Form the leads of each resistor so that its body sits
directly between adjacent LEDs.
circular in shape. Manufacturers will
probably supply this PC board as a
square, so if you need it to be round,
now is a good time to cut and/or file
it to shape.
That done, install the LEDs, aligning
all cathodes (flat sides) towards the
centre of the board. The LEDs must be
mounted right down on the PC board
surface. If your LEDs have large standoffs that prevent this, then refer to the
assembly instructions for the CHMSL
module for the solution.
Install the three resistors next. Now
turn the board over to the copper side
and install an insulated wire link as
shown on the overlay diagram (Fig.4).
Finally, solder two lengths of light
duty hook-up wire to the +12V (+) and
0V (-) points and pass the ends through
the cable hole.
Unlike the other modules, this one
doesn’t have a diode in series with
the supply. We recommend installing
a 1N4004 diode in series with either
the positive or negative lead and insulating it with heatshrink tubing.
tube with a fine scouring pad or ink
rubber and clean with alcohol. Insert
the tube 2-3mm into the base rim and
solder in place.
(4). Centre the Platform PC board
over the end of the tube and solder in
place. Apply your iron to the copper
tube rather than the PC board so as not
to overheat the latter.
(5). Trial fit an assembled Multidisc
module on the Platform board to de
termine the required lead length. Trim
the +12V wire to length and strip and
tin the end. Pass it through the centre
hole in the Platform board and solder
it to the base tip, building up the solder as needed to get a nicely curved
“bump”.
(6). Pass the 0V (GND) wire through
the outer board hole and trim to 1015mm in length. Stip and tin the end.
(7). Trim both leads of a 1N4004 diode to about 6mm in length and solder
the anode end to the 0V (GND) wire.
Slip a length of heatshrink tubing over
Bayonet lamp assembly
Below are the instructions for the
bayonet lamp assembly, presented in
a step-by-step format to help make the
job easier – see Figs.5 & 6.
(1). Remove the glass bulb and filament from a standard 21W automotive
bayonet lamp. Clean the glue from
around rim of base and several millimetres into the interior. Polish the area
with a fine scouring pad or ink rubber
and clean with alcohol.
(2). Remove solder from the tip.
(3). Cut a standard 14.5mm O.D.
copper water pipe joiner in half and
chamfer one end with a file. Polish the
26 Silicon Chip
Fig.5: the Platform PC board is
unetched (blank copper). To make
one, cut the 26.5mm disc from
blank circuit board material and
drill six 2.5mm holes as show
here. The Multidisc PC board can
be used as a template.
the diode to insulate the connection.
Solder the other (cathode) end of the
diode to the underside of the Platform
PC board.
(8). Attach the Multidisc assembly
to the Platform board using small cable
ties, or for a more permanent job, use
several ‘blobs’ of neutral cure silicone
sealant.
Wedge lamp “skeleton”
assembly (Fig.7)
(1). Prepare the blank (non-copper)
sides of two wedge PC boards so that
all edges are free of burrs and the
surfaces are completely smooth and
clean.
(2). Bond the blank sides together
(copper sides facing out) using a very
thin smear of cyanoacrylate-based
adhesive. Pay particular attention to
alignment; the boards must be exactly
aligned, such that they appear to be
one single unit after bonding.
(3). Touch up the sides with a fine
jewellers file to bring the edges into
perfect alignment. Also, file the shoulders if necessary to ensure that they
are horizontal and in line.
(4). Trial fit the assembly to a wedge
lamp socket. A small chamfer on the
leading edges of the wedge assembly
may make insertion easier.
(5). As supplied, the Disc PC board
may have a series of three holes rather
than a slot in the middle. You’ll need
to file a slot that is just large enough to
accept the head of the wedge assembly.
Make the fit as firm as possible. You
may also need to cut and/or file the
board outline into a circular shape, as
some manufacturers will undoubtedly
supply it as a square.
(6). Assemble the boards, making
siliconchip.com.au
Bayonet Lamp Assembly Details
Fig.6: follow this diagram and the step-by-step instructions in the text to make the Bayonet lamp assembly. The
Multidisc assembly can be fixed in place with neutral cure silicone sealant.
sure that the shoulders of the wedge
assembly firmly contact the underside
of the Disc board. Solder the three pads
on the wedge assembly to the pads on
the underside of the Disc board. Repeat
for the second side.
If the Disc board is double-sided
(has copper on both sides), then repeat
on the top side.
(7). Mount all components as per
the overlay diagrams in Fig.8 and the
text that follows.
The LED bayonet lamp is made by
scrounging the base from a conventional
bayonet lamp and fitting it with a
Multidisc module. Note that the latter
sits on top of a Platform PC board (the
two are secured using silicone sealant).
Wedge lamp assembly
With the wedge lamp “skeleton”
complete, it’s time to mount all the
components. Begin with the eight
5mm LEDs on the Disc board, aligning
the cathode (flat) sides towards the
centre of the board.
Fit the 10mm (centre) LED last. The
flat (cathode) side must be aligned
towards the “dot” side of the board.
The “dot” side is marked with a small
copper dot (pad without a hole) on the
underside. Form the leads as shown
in Fig.7 and push the LED down until
it makes contact with the head of the
Response Times: LEDs Versus Conventional Filament Lamps
After upgrading the Honda’s CHMSL to LEDs, we decided to “get technical” and actually measure the difference
in response between the old and the new. We made up a
couple of phototransistor-based sensors and positioned
one behind the CHMSL and the other behind one of the
stop lights. Our Tektronix scope captured the waveforms
at right when we tapped the brake pedal.
As you’d expect, the blue trace represents the LED
CHMSL light output whereas the yellow represents the
conventional stop light. A rough estimate shows the
filament lamp to be about 150ms behind the LEDs, with
full brilliance at least 200ms later. The rounding on the
leading edge of the LED waveform is caused by voltage
drop in the wiring loom, a result of the stop lamps’ cold
filament current, which momentarily exceeds about 40A.
siliconchip.com.au
March 2003 27
Wedge Lamp Skeleton
Fig.7: here’s how to put together the Wedge lamp “skeleton”. After soldering the Wedge and Disc boards together,
inspect your work for potential solder bridges between pads. This is only important on the “dot” side, as all pads
on the opposite side will be connected with a wire link anyway (see Fig.8).
wedge board assembly.
The three resistors and 1N4004
diode can go in next (see Fig.8). Note
that it is vital that these components
go on the right sides of the wedge
assembly. As shown in Fig.7, the resistors mount on the “dot” side and
the diode on the other.
Component mounting is unconventional in that the leads should not pass
through both PC boards and protrude
from the opposite side. The PC board
holes have been deliberately offset to
prevent this from happening. You’ll
need to bend the leads of each component and trial fit it in place, trimming
back lead lengths just enough so that
they enter their respective holes before
soldering in place.
Finally, solder lengths of tinned copper along the tracks exactly as shown
in Fig.8. The vertical lengths at the
bottom take the place of the filament
Fig.8: the Wedge lamp assembly
details. Be sure to assemble the
“skeleton” before mounting any of
these components. Orientation of
the Disc board can be determined
by a dot on the copper side. This,
strangely enough, is the “dot” side!
The wedge lamp is made up using the Disc board and two
identical Wedge boards. It all goes together as shown in
Figs.7 & 8.
28 Silicon Chip
The LED-powered wedge lamp can be used to replace a
conventional filament lamp in some situations and will
generate much less heat.
siliconchip.com.au
31mm & 41mm
Festoon Lamp Assemblies
Fig.9: the circuit details for the
41mm & 31mm festoon lamps.
Fig.10: the assembly details for the 31mm (left) & 41mm (right) festoon
lamp modules. The end caps are soldered to the PC boards after the parts
have been installed.
The completed festoon lamp assemblies can be plugged
straight into a conventional festoon lamp holder but must
be oriented with the LEDs facing outwards.
lead-outs on the base of a wedge lamp
and need to be positioned so that they
mate with the contacts in the wedge
socket. The horizontal lengths replace
the “bump” on the wedge bulb base
that is captured by a spring clip in the
socket in order to retain the bulb.
The three current-limiting resistors
are mounted vertically on the wedge
assembly and can be insulated with
heatshrink tubing if desired.
The diode goes on the other side of the
wedge assembly. The three long pads
on both wedge boards are soldered to
matching pads on the disc board.
siliconchip.com.au
Festoon lamp assembly
This LED equivalent of the festoon
(interior) lamp can be built in either
a 31mm (2 LED) or 41mm (3 LED)
version. As mentioned previously, you
have the choice of using either white
or blue LEDs.
Referring to Fig.10, begin by installing the LEDs, aligning the flat (cathode)
sides as shown. Be sure that you have
the PC board oriented as shown on the
overlay; the positive side must be on
the left. The “+” and “-” symbols on
the copper side allow you to determine
correct polarity.
Now flip the board over and install
the resistor and diode on the copper
side. Both of these components should
be insulated with heatshrink tubing to
prevent short circuits. However, only
the leads of the resistor should be insulated (not the body), otherwise heat
dissipation will be impaired.
Next, solder 10mm lengths of
0.71mm tinned copper wire to each
end of the board, forming axial “pigtails”. These wires will make the
March 2003 29
Parts List
High-Mount Stop Lamp (HMSL) Module
1 PC board, code 05103033, 11.45mm x 149.2mm
16 5mm 20,000mcd red LEDs (LEDs1-16) (Vishay TLCR5800)
2 1N4004 diodes (D1, D2)
4 150Ω 0.25W 1% resistors
200mm length of red light-duty hookup wire
150mm length of black light-duty hookup wire
Multidisc Module
1 PC board, code 05103036, 26.5mm diameter
12 5mm 20,000mcd red LEDs (LED1 - LED12) (Vishay TLCR5800)
1 1N4004 diode (D1)
3 180Ω 0.25W 1% resistors
10mm length of 0.71mm tinned copper wire
20mm length of 5mm-diameter heatshrink tubing
150mm length of red light-duty hookup wire
150mm length of black light-duty hookup wire
Wedge Lamp
1 PC board, code 05103031, 22mm diameter (Disc)
2 PC boards, code 05103032, 31.5mm x 16mm (Wedge)
8 5mm 20,000mcd red LEDs (LEDs1-8) (Vishay TLCR5800)
1 10mm 6,000mcd (min.) red LED (LED9)
1 1N4004 diode (D1)
1 470Ω 0.5W 1% resistor
2 180Ω 0.25W 1% resistors
60mm length of 0.71mm tinned copper wire
Cyanoacrylate-based adhesive (super glue)
Bayonet Lamp
1 assembled Multidisc module
1 PC board, code 05103037, 26.5mm diameter (Platform)
1 14.5mm O.D. copper water pipe joiner
1 12V 21W single filament automotive bayonet lamp
31mm Festoon Lamp
1 PC board, code 05103034, 8mm x 24mm
2 5mm 15,000mcd white LEDs (LED1, LED2)
1 1N4004 diode (D1)
1 220Ω 0.5W 1% resistor
1 31mm automotive festoon lamp
20mm length of 0.71mm tinned copper wire
35mm length of 5mm diameter heatshrink tubing
5-minute epoxy
41mm Festoon Lamp
1 PC board, code 05103035, 8mm x 33mm
3 5mm 15,000mcd white LEDs (LED1 - LED3)
1 1N4004 diode (D1)
1 82Ω 0.25W 1% resistor
1 41mm automotive festoon lamp
20mm length of 0.71mm tinned copper wire
35mm length of 5mm-diameter heatshrink tubing
5-minute epoxy
30 Silicon Chip
connections to the end caps.
With the board assembly complete,
the next step is to fit the end caps.
Begin by removing the glass cylinder
and filament from a standard festoon
lamp. Take care to remove all glass
fragments from inside the caps.
Desolder the holes in the cap peaks
and then slip them over the pigtails.
Push the PC board as far as it will go
into each cap. The assembled size
should be close to the 31mm (or 41mm)
mark. Snip the wires off so that they
only just protrude through the cap
peaks. Now solder in place and smooth
off with fine glass paper or similar.
Check that your completed lamp
works in-situ and, assuming all is well,
fill the end caps with 5-minute epoxy
to make the job permanent.
Automotive lamps vs. LEDs
The extremely narrow emission
angle of these ultra-bright LEDs (4°)
makes them well suited for use in
high-mount stop lights. However, in
the case of conventional tail, stop
and turn indicators, there are some
potential visibility issues.
When viewed on-axis, a tight grouping of these LEDs certainly appears to
equal (or even surpass) the intensity of
a 21W filament bulb. The bulb, however, emits light over a much larger
area, resulting in good visibility over
more than 180°.
Naturally, the reflector and diffuser
in light housings is designed to take
this into account, so if we were to
simply switch the standard bulb for
a bunch of LEDs, the resultant light
pattern would be entirely different.
Simply put, direct replacement of
filament lamps with LED lamps in
existing automotive tail, stop and
turn assemblies will not always be
possible. This applies particularly
to “wraparound” styles, which must
provide light to both the rear and side
of the vehicle. This problem is easily
solved by designing the assemblies
Where To Get The LEDs
Jaycar Electronics stock suitable
5mm red LEDs (20,000mcd), Cat.
ZD-1790. Oatley Electronics have
the 5mm white LEDs (15,000mcd)
and a good selection of other colours as well. Our 10mm red LEDs
came from Dick Smith Electronics,
Cat. Z-4067.
siliconchip.com.au
Fig.11: here are the full-size etching patters for all the PC boards. Check your boards carefully for
defects before installing any parts.
specifically for LEDs, a task best left
to the experts.
Having said that, we believe that
our modules have a multitude of
highly practical uses. Here are just a
few examples:
Where to use LED lamps
Why not add a centre-mount stop
light to your trailer or van? The small
size and shape of the Multidisc module will allow it to fit neatly within
commonly available trailer stop light
assemblies. Do you own a motorcycle?
What about a truck? Install LED lamps
and get noticed!
A couple of these hooked up to a
simple flasher circuit and mounted under the boot lid or on a moveable panel
would make the ultimate emergency
beacon for late-night breakdowns.
They will flash for days without running your battery flat!
In addition, the Multidisc module
could be fitted with IR LEDs for use
with CCD cameras and night viewers.
The LED festoon lamps don’t put
out as much light as the originals but
they don’t get hot and they won’t run
your battery flat in a hurry. Fit a couple under the hood, in the boot, along
siliconchip.com.au
Although not readily apparent from the photo, the modified high-mount stop
lamp with the LEDs is brighter than the conventional lefthand & righthand stop
lamps. Its response time is quite a bit shorter as well (ie, it turns on much faster
when the brakes are applied).
the floor line or in the door panels. For
that high-tech look, try blue (or even
true green) LEDs instead of white.
If you don’t want to modify existing
light housings, then the LED wedge
or bayonet lamps are a good option.
They’re plug-in replacements for two
popular auto lamp styles. If your vehicle uses different lamp styles, then
you may be able to modify our designs
to come up with something suitable.
SC
Have fun!
March 2003 31
CIRCUIT NOTEBOOK
Interesting circuit ideas which we have checked but not built and tested. Contributions from
readers are welcome and will be paid for at standard rates.
Automatic
headlight switch
This circuit will switch on your car’s
headlights at a presettable ambient
light level. It has a delayed switch-on
time of about 15 seconds so that the
headlights don’t switch on unne
cessarily when driving under trees,
overpasses, etc.
The circuit is based on a 555 mono
stable timer circuit which is triggered
by a decrease in light level. Power is
applied permanently to the circuit
from the 12V battery but the circuit is
disabled by the relay contacts which
pull pin 2 high. When the 12V relay
is energised (when the ignition is
turned on), the relay contacts open and
the voltage at pin 2 is now set by the
voltage divider comprising the light
dependent resistor (LDR1), resistor R1
and trimpot VR2.
Sudden changes in this voltage are
impossible due to the 470µF capacitor
C1, connected across LDR1. It eliminates sensitivity to sudden changes
in light level. However, once the light
level drops, the resistance of LDR1
increases and so the voltage at pin 2
drops and triggers the timing circuit.
At the same time, the base of Q1 is
pulled low and this discharges the
timing capacitor, C3.
The pin 3 output of IC1 now goes
high to turn on Q2 which drives the
headlamp and parking lights relays.
Q2 remains on while capacitor C3
charges towards +12V via resistor R2
and the delay trimpot VR1. VR1 sets
the on-time for a period of up to two
minutes. However, if the light level
stays low, Q1 holds C3 in the discharged state and the lights stay on.
The 2-minute delay time avoids any
erratic switching of the headlights
due to street lights and also allows
the headlights to stay for a short time
after you turn off the engine.
Rick Goodwin,
Moonah, Tas. ($35)
Simple universal
PIC programmer
This simple programmer will accept any device that’s supported by
software (eg, IC-Prog 1.05 by Bonny
Gijzen at www.ic-prog.com).
The circuit is based in part on the
ISP header described in the SILICON
CHIP “PIC Testbed” project but also
features an external programming
voltage supply for laptops and for
other situations where the voltage
present on the RS232 port is insufficient. This is done using 3-terminal
regulators REG1 & REG2.
The PIC to be programmed can
be mounted on a protoboard. This
makes complex socket wiring to
support multiple devices unnecessary. 16F84A, 12C509, 16C765 and
32 Silicon Chip
other devices have all been used
successfully with this device.
Luke Weston,
Wycheproof, Vic. ($30)
Note: this simple circuit will not
work with older laptop computers
that use low voltage (5V) RS-232
signals.
www.siliconchip.com.au
Bat detector
picks up ultrasound
It is well known that bats use
ultrasound for navigation and the
location of prey. Typically, bats
emit rapid bursts of ultrasound in
the region of 15-200kHz (ie, beyond
the range of human hearing), with
wide variations in frequency, depending on the species.
This bat detector is a highly
sensitive circuit that “hears” bats
in the range of about 20-80kHz.
Although this does
n’t cover the
full range of sounds that many bats
emit, it is more than sufficient to
detect the average bat at a range of
tens of metres.
In operation, the circuit uses an
array of LEDs to give a visual indication of a bat’s presence, instead
of reproducing the audio at a lower
frequency. This has two advantages: (1) the absence of headphones
en
ables you to hear sounds that
would otherwise be obscured –
eg, the flutter of a bat’s wings or
the lowest frequencies which a
bat emits (sometimes audible as
high-frequency, “scratchy” sounds);
and (2) it effectively eliminates low
frequency sounds (such as hands
holding the detector), which can
be the bane of budget bat detectors.
The ultrasound is picked up with
www.siliconchip.com.au
a standard 40kHz ultrasonic transducer. This transducer is effective
up to about 80kHz, although its
sensitivity drops off either side of
40kHz. A quality piezo transducer
could also be used here but note
that this will only be effective up
to about 50kHz (if that).
Op amps IC1b-IC1d are wired
as a very high gain preamplifier,
amplifying the signal millions of
times. This produces suffi
cient
signal amplitude at pin 14 of IC1d
to directly clock decade counter
IC2 (4017).
IC2 is reset at regular intervals by
op amp IC1a which is wired as an
oscillator. This resets IC2 at about
one tenth the rate of the highest
detected frequency. Therefore if,
for an example, a 30kHz signal is
received, IC2 might only sequence
two or three LEDs before being reset. By contrast, if an 80kHz signal
is received, IC2 will sequence all
the LEDs.
This technique thus provides a
visual indication of the received
frequency. Note that ultrabright
LEDs are recommended for LEDs
1-6, since the LEDs have only a 10%
duty cycle.
In use, trimpots VR1 (frequency
adjust) and VR2 (gain) are initially
both set to mid-position. These may
then be further adjusted later on, as
required.
Once the circuit has
been built, switch on
and rub your hands
together near the ulThomas Scarbo
rtrasonic transducer.
ough
is
th
is
m
onth’s winThis should light at
ner of the Wav
etek
least one (and perMeterman 85XT
haps all) of the LEDs.
true RMS digita
l
If the circuit is funcmultimeter.
tioning correct
ly, it
should respond to
your hands being
rubbed together at
a 1-metre distance.
If VR1 is set so that IC1a operates
at 10kHz, LEDs 1-6 will represent
20-80kHz in 10kHz increments. At
least, that’s the theory – in practice,
IC1a is adjusted using VR1 so that
the LEDs match the range of the
transducer that’s been used.
Besides being used as a Bat
Detector, the circuit could also be
used as a simple tool to indicate
frequency, to find tyre punctures
(which emit ultrasound), and to
detect other creatures which emit
ultrasound (such as certain insects). And at its lowest frequency
setting, it could even be used as
a simple frequency-to-light convertor, with the LEDs dancing to
nearby music.
Thomas Scarborough,
Cape Town, South Africa.
March 2003 33
Circuit Notebook – continued
34 Silicon Chip
www.siliconchip.com.au
Junkbox-parts
oven timer
The motivation for this project
came when the timer on our oven
failed for the second time. It uses parts
that were mostly scrounged from my
junkbox.
The resulting timer is very user
friendly. You simply dial in the required timing interval in minutes
using rotary switches S2 (units) and
S3 (tens) and then hit the start switch
(S1). Any time up to 99 minutes can
be selected.
When S1 is turned on, the display
LEDs light, initially indicating “00”
and then advancing “01”, “02”, . . . ,
“09”, “10”, “11”, etc until the selected timing interval has been reached.
The timer then stops counting and
sounds a buzzer until the start switch
is turned off.
The indicator LEDs can be arranged
in semicircular fashion around the
switches (ie, one LED at each switch
position), thus giving a very effective
display. This was much simpler than
using a digital readout.
The circuit itself is based on four
low-cost CMOS ICs. IC1, is a 4060
14-stage binary counter/divider/
oscillator. It’s set up to produce a
positive-going pulse at its pin 3 output (O13) every minute, as set by the
timing components on pins 9, 10 &
11. This means that O13 must have
a period of two minutes – ie, it will
be low for the first minute and then
go high for the next minute. This
high-going pulse is then applied back
to IC1’s reset pin (pin 12) via AND gate
IC4b and diode D3. The counter thus
restarts and begins counting the next
minute interval and so on.
The period of oscillation is approximately 2.2RC where R is the resistance
connected to pin 10 of IC1 (27kΩ, VR1
& VR2) and C is the capacitance on
pin 9. VR1 and VR2 provide coarse
and fine adjustment of the oscillator
frequency, respectively.
IC2 & IC3 are two 4017 decade
counters, each having 10 outputs (O0,
O1, O2 and so on up to O9). Only
one output of each counter will be
high at any one time. The counters
are reset by taking their pin 15 (MR)
inputs momentarily high and this
takes the O0 outputs of each counter
high. These outputs in turn drive
www.siliconchip.com.au
LEDs 1 & 11 and this indicates zero or
“00” (the initial state of the counting
process).
Each positive-going pulse on pin
14 (CP0) of IC1 advances the count
by one, with LEDs 2-10 turning on in
sequence to indicate the number of
elapsed minutes. When nine pulses
have been counted, LED10 will be
on. The tenth pulse then resets IC2
(ie O0 goes high and turns on LED1).
In addition, IC1’s carry out pin (pin
12) goes from low to high and this
clocks IC3. As a result, IC3 counts
in tens on minutes while IC2 counts
the units.
By using the 1-minute pulses from
IC1 to clock IC2, the two counters
are capable of recording the elapsed
time up to 99 minutes, after which
both counters are reset to zero and
the count restarted.
Both counters can be halted at any
time by taking their enable pins (pin
13) high. If this is done, the counter
outputs will remain locked at the prevailing count at the time of receiving
the disable signal.
As well as driving LEDs 1-9, IC2’s
outputs are also connected to S2, a
single-pole 10-position rotary switch.
Similarly, IC3’s outputs are connected
to rotary switch S3. The wipers of S2
and S3 connect to AND gate IC4a and
when both inputs to this gate are high,
its pin 3 output goes high and disables
the counters.
At the same time, the output of
IC4d (pin 11) goes high and turns on
transistor Q1 to sound the buzzer. The
counters then remain locked in this
count position and the alarm continues to sound until the start switch,
S1, is turned off.
Because the 4017 ICs can only
source a small amount of current, special low-current LEDs must be used.
The types used in the prototype were
from RS Components, stock number
590-547. These operate with just 2mA
of current, with a maximum forward
current of 7mA.
Power for the circuit comes from a
9V DC plugpack. Note that the start
switch is placed after the 1000mF
reservoir capacitor. This prevents the
buzzer from making an awful “dying
noise” as the capacitor discharges
when the timer is switched off.
Jack Holliday,
Nathan, Qld. ($50)
Five identical Video and Stereo outputs
plus h/phone & monitor out. S-Video &
Composite versions available.
Professional quality.
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Visitors by appointment only
March 2003 35
Last century, we described a Peltier-powered tinnie cooler
which could be built into a reasonably large Esky and so keep
your food and drinks cool. Here’s another one – quite a bit
smaller and just right to build into a 6-pack Esky to really cool
down the tinnies. As a bonus, it will also keep food warm!
By Ross Tester
E
very true-blue Aussie knows
there is nothing worse than a
warm beer (or soft drink, for
that matter). But how do you get your
drinks cold – and keep them cold?
There’s the old ice-in-the-Esky routine.
But ice melts – especially if you keep
putting warm cans in.
Wouldn’t it be nice to have the
cooler itself cool your cans? This one
does! Just plug it into your car cigarette
lighter (or any other 12V DC supply)
and it will silently cool cans down to
the “aaaaaaahhhhhh” level.
Like the cooler we presented back
in September 1999 (see, it was last
century!) this one is based on a Peltier
Effect device. We explained this semiconductor device and its operation in
some detail in that issue (and in the
August 1999 issue) so we won’t go into
too much detail again.
Suffice to say that it consists of a
number of P-N junctions sandwiched
between two metal plates. Pass current
through the junctions one way and
they absorb heat – one of the plates
gets very much colder than the other.
Pass current through the other way and
the reverse happens, the plate which
was cold heats up.
If you thermally bond the Peltier
(that’s shorthand for Peltier Effect
device!) to another object, that object
will either cool down or heat up, depending on the polarity of supply to
the Peltier. That’s why a Peltier can
be used for both cooling and heating.
If you’d like more info on the op-
eration of Peltier Effect devices, we
suggest you refer to the issues mentioned above.
Peltier “module”
There are two major differences between this project and the earlier one.
First, it’s much smaller – this one
is designed to fit into a 6-pack cooler
(the earlier one fitted a larger cooler).
It really is intended as a drink cooler,
not a mobile fridge!
Second, and most importantly, this
Just in case you haven’t seen one
before, this is what the Peltier device
looks like. This is a lower rated
device than the one in this module.
36 Silicon Chip
www.siliconchip.com.au
in mind the comments above before
switching over!
Thermal bonding
(Above): the Peltier module attached to the top of the cooler lid while below is
the view from inside the cooler.
The reason we placed the module
in the lid of the cooler was that it was
convenient to do so. It’s also true that
cold air falls, so theoretically the air
inside the cooler would eventually
cool down via convection currents.
However, as every good cook will
tell you, the secret in heating or cooling food or drinks is the thermal bond
between the cold/heat source and the
item being cooled/heated.
Now we have to say that the thermal
bond between the aluminium plate
and the cans in the cooler is not that
great. The reason for this is that air is
not particularly efficient at transferring
cold/heat.
It’s a bit like trying to boil a kettle
by holding it above a hotplate rather
project is based on an almost-complete
Peltier module.
The earlier project required you to
source the bits individually; this one
has a pre-assembled Peltier module
which includes a fan, heatsink, thermal switch, aluminium block and
gasket.
All you have to supply is an aluminium plate (size to suit your cooler)
and a small piece of, say, 15mm-wide
polystyrene foam (such as used for
packaging).
The aluminium sheet needs to be as
large as possible to ensure good heat
transfer. We used a sheet 3mm thick
because it was available – even thicker
would be better still.
Incidentally, the module comes
from Oatley Electronics and costs the
princely sum of just $33.00 (plus p&p).
Not real shabby, that: we’ve seen similarly rated Peltier Effect devices alone
advertised for the best part of $150.00
Oh, nearly forgot: you also have to
supply the cooler!
Thermal shock
Before we go too much further, a
warning: one thing you cannot do with
a Peltier is switch it between heating
and cooling (or vice versa) without
waiting for it to cool (or heat) back to
room temperature. This would place
enormous stresses on the device and
would quite likely damage or even
destroy it.
We have shown a “reversing” switch
in our circuit of the device but bear
www.siliconchip.com.au
March 2003 37
than placing it on it. Sure, the kettle
will eventually get hot – but nowhere
near as fast or efficiently as it would
placed directly on the hotplate.
Similarly, it would be much better
if the cans could be placed in intimate
contact with the aluminium plate attached to the Peltier.
One way to achieve this would be to
place the Peltier module not on the lid
but on the side of the cooler, with an
“L” shaped aluminium plate running
down the side of the cooler and across
the bottom, so that the cans actually
sat on the cooling plate.
Even better would be to sit the cans
in a small amount of water because this
would achieve a much better thermal
bond with the cans than the air in the
cooler.
Indeed, using a cooler is not the
only possibility. We’ve had thoughts
about using a small length of suitably-sized aluminium tube, maybe a
yacht mast extrusion, which often has
a flat on one side suitable for mounting
the block (or maybe even the Peltier
This very simple circuit could be made even simpler if you don’t want
the “heat” option: leave out the switch and thermal switch.
direct). We haven’t tried this yet – but
will do so when we find a suitable
extrusion.
We’ll leave you with those thoughts
in case you want to experiment. Placing the module in the lid of a cooler,
as we have done, is certainly not the
only possible approach.
Assembly
Because the Peltier module is
pre-assembled, building this project is
pretty simple: you cut an appropriate
hole in the cooler (slightly larger than
the aluminium block), pass the cooler
module through it, fit the styrene foam
seal and screw on your aluminium
plate. Connect power and it’s done.
The power lead would ideally be
a suitable length (but shorter rather
than longer) of polarised (red/black?)
10A figure-8 cable, fitted with a car
Here's how the whole thing fits together. As
mentioned in the text, the majority of this project
is pre-assembled as a single module – everything
between the finger guard and the aluminium
block, in fact. All you have to do is fit it to the
cooler and attach the aluminium heat transfer
plate.
38 Silicon Chip
www.siliconchip.com.au
cigar lighter plug at one end. Note that
there are some “cheap” cigar lighter
plugs around that are real junk – their
springs aren’t and deform badly after
a few uses. It’s better to pay a little bit
more and get a good’n.
For safety’s sake we have incorporated a 10A fuse in the + line between the
changeover switch and the cigar lighter plug. 10A is more than is needed by
the Peltier and fan but should protect
in case of catastrophic short circuit.
Speaking of catastrophic, we have
shown an “exploded” drawing of the
assembly but that’s just in case you
need to know how it all goes together.
However, you should not need to disassemble the Peltier module.
One thing you will note on the drawing is the use of heatsink compound,
especially between the aluminium
block and the aluminium plate. This
will ensure maximum heat transfer.
The thickness of the styrene block
depends on the thickness of the lid (or
wall) of your cooler. The idea is that
it compresses slightly when the aluminium plate is screwed to the block,
making a nice airtight seal against the
cooler lid/wall but still allowing the
block to make intimate contact with
the aluminium plate.
The high density foam gasket (supplied with the module) forms the airtight seal on the outside of the cooler.
The two seals probably won’t be
watertight but with a bit of work with
silicone sealant could possibly be
made so. Just make sure you don’t get
any sealant between the heatsink and
Peltier, the Peltier and block or the
block and plate – it is a good way to
stop heat transfer!
The thermal switch
The project has a 65° thermal switch
mounted on the side of the aluminium
block.
This only comes into play when
used as a heating device and is designed to prevent the thing getting
so hot it starts melting (or at least
Upside-down view of the module as supplied by Oatley. Note the liberal use of
heatsink compound on the aluminium block – you cannot see it in this photo
but there is also a good dollop of the stuff on both sides of the Peltier device.
deforming) the plastic lid or body of
the cooler.
If you are not intending to use the
device as a food heater, it (and of
course the reversing switch) can be
left out.
Power supply
The 50W Peltier device draws
around 3.5A at 12V (DC). Therefore
it is going to place a fairly significant
load on your car battery if the engine
is not running – certainly enough to
prevent you starting the car after a
day out.
Still, if you are caught out in the
sticks with a battery that’s too flat
to start your car, your drinks will be
beautifully cold. . .
Of course, you could also run it
from a suitable 12V (or 13.8V) DC
power supply – a typical “CB” power
supply is rated at about 4-5A so would
be perfect.
Parts List – Tinnie Cooler
1 Peltier Effect module (Oatley Electronics)
1 6-pack plastic cooler
1 3mm thick aluminium plate, size to suit cooler
Suitable fig-8 connecting cable with car cigar lighter plug
In-line fuseholder and 10A fuse (can be integrated with cigar lighter plug)
Heatsink compound
1 DPDT switch, 5A DC contacts (optional, see text)
www.siliconchip.com.au
Where from,
how much?
The Peltier Device Module,
complete with heatsink, fan,
aluminium block, thermal switch
and gasket, is available from
Oatley Electronics for $33.00. The
various components may be purchased separately elsewhere but
be prepared to pay at least $100!
You need to supply the cooler
(and the drinks to go in it!), aluminium plate, polystyrene foam,
power lead, inline fuseholder and
fuse, cigar lighter plug, heatsink
compound and (if required) the
DPDT changeover switch.
As a special bonus, Oatley
Electronics will also include a
quality car cigar lighter plug,
with integral fuseholder already
connected to a 1.8m length of
heavy duty figure-8 cable, if you
tell them you are building the
SILICON CHIP Cooler project.
Contact Oatley Electronics
via phone (02) 9584 3563; fax
(02) 9584 3561; email – sales<at>
oatleyelectronics.com or via
www.oatleyelectronics.com
March 2003 39
SERVICEMAN'S LOG
Bring your hammer-drill & muscles
A serviceman does not just fix faults, advise
customers on new equipment, or fit a new
antenna. Many new, large sets often require
a lot of muscle and constructional skills
outside electronics. And I had another job
this month which should have been avoided.
I can’t help myself. Yes, I did it
again; lumbered myself with a repair
that I should have stayed well clear
of. But I did have some mitigating
circumstances.
It’s my wheels. Because I’m so badly
paid, I have to use secondhand vehicles
and my old Ford Laser was just about
to dump its gearbox. Ouch!
Anyway, I was sulking over this
latest problem one morning when in
40 Silicon Chip
waltzes an old colleague. And in the
ensuing conversa
tion, he mentions
that he is trying to fix a Philips FL1.1
with an east-west pincushion fault. I
told him to wash his mouth out for
mentioning such words in my presence. But grateful that it was someone
else who was suffering from such
misfortune, I of
fered as much free
advice as I could – as long as he was
doing the work.
That is, until it turned out that his
client was a Ford transmission expert
and repairs them all day long. Suddenly I realised that a dangerous contra
deal was in the air but I quickly lost
all sense of reasoning. I mean, how
bad can a TV fault be? And after all, I
could end up saving many hundreds
of dollars.
In due course, my car went east and
his TV set came west; straight into my
workshop. And being a 33-inch (80cm)
set, I almost had to rebuild the workshop around it to get it to fit.
The set turned out to be a model
33FL1880/75R, the same as one I wrote
about in last month’s issue. This set
had the same problems as the one in
that article and my friend patiently
worked through it until, finally, he
too discovered that capacitor C2523
(8.2nF, 2kV) capacitor was the cause.
He then replaced all the blown
up bits and that fixed everything
except the east/west fault which
had him stumped. I had hoped for
a minute that it was just transistor
Q7610 (2SA1359) that was faulty, as
in the earlier set, but he had already
changed that.
Anyway, I own two working FL1
TV sets and another which also has
an east-west pincushion fault, though
none of them are 33-inch models. I
checked all my friend’s work first and
apart from replacing the horizontal
output transistor ON4673 with a
BU508A (a BU508AF is an even better choice), nothing apart from a few
faulty joints was obvious. However,
the voltage on the emitter of Q7610
was only 1.8V instead of 14V and neither the width adjustment (VR-3601)
nor the pincushion control (VR3602)
had any effect.
I had heard that shorted turns in
coil L5526 could cause this fault, so I
swapped this coil with the one in the
good set. Unfortunately, it made no
difference to either model and both
coils had an inductance of 11mH.
I then decided to try similarly swapwww.siliconchip.com.au
ping transformers 5521. This turned
out to be a monstrous mistake, as it
instantly took out both horizontal output transistors. After replacing these,
I still couldn’t get the set to start and
there was no 141V rail. Eventually,
after a lot of messing about, I discovered that Q7610 was short circuit but
the set was still dead when this was
replaced.
Next, I unsoldered pin 8 (141V
input) to the horizontal output transformer and horizontal output stages
and fitted a 100W globe across the rail
instead. This time when I switched it
on, there was an enormous bang, like
a shotgun going off. Believe me, it was
loud enough to have awoken the New
Zealanders.
Well, at least I had produced a measurable reaction – a small earthquake!
The only trouble was I didn’t have a
Richter meter to measure it!
In fact, it was C2512 in the horizontal centring circuit which had exploded. It took quite a while to realise that
Q7512, Q7513, R3514, R3537, R3515
and D6515 had also been destroyed.
When I finally put it all back to where
I started, I made an emphatic mental
note: not all FL1.1S chassis are the
same and not everything is interchangeable.
However, the east-west circuits are
similar and therefore the voltages and
waveforms between the sets should
also be similar. As a result, I spent
an hour or so measuring the good 29inch set’s east-west correction circuit
voltages and drawing the oscillograms.
As I have mentioned on previous
occasions, access to this chassis is
rather difficult. The so-called service
position is with the main chassis
(small and large signal panel) pulled
right back and up. You then have to
balance it on its edge, taking care
not to short out the CRT socket with
the heatsinks. The control panel and
mains filter panel remain behind.
The chassis is bulky and heavy, with
modules and heatsinks everywhere –
mostly soldered in. The voltages in
some parts are very high, with sensitive surface mounted components
nearby. Replacing a part requires access to both sides of the board, which
means moving them up and down.
Finally, just to make life interesting, the 315V main HT line remains
charged even after the set is switched
off – not to mention the 200V rail
for the RGB output amplifiers. And
www.siliconchip.com.au
because the whole chassis is
precariously balanced in the
“service” position, it’s impossible to safely attach a probe onto
a subminiature component and
take a reading.
It’s also impossible to
make any service adjustments while in this service
position, as the controls
are all on the inacces
sible side of the board. In
fact, even in the so-called
“accessible” position, they
aren’t easy to get at! For
example, to meas
ure and
adjust the 141V rail, it’s
necessary to attach the
probe onto test point TP57
(cathodes of D6237 and
D6238). What they don’t
tell you is that these sit
right between a heatsink
and the SOPS module
and there is very little
clearance between these
two parts.
In practice, it is necessary to go to standby,
connect an insulated
crocodile clip onto the
diode, then switch on
using the remote control and adjust R3371.
And you really have
to watch yourself: one
third of the large signal
panel is at full mains
potential and the other two
thirds is at chassis – and the dividing
line is not easy to see. No wonder noone likes fixing these beasts.
Basically, the east-west circuitry
converts vertical pulses derived from
the vertical deflection output into
upside-down parabolas. These are
then fed to the east-west output transistors which in turn drive one end
of the deflection yoke via a variety of
tuning components. The other end of
Items Covered This Month
• Philips Matchline
•
•
•
•
33FL1880/75R TV set.
Panasonic “Progressive Wide
Plasma Displays” (Model TH42PWS) – installation.
Akai TX-140 stereo unit.
JVC AV-21 TEAU TV set (MZ2
chassis).
Faulty remote controls
the deflection yoke is fed with 1000V
horizontal pulses. EHT information is
also applied to prevent picture blooming on bright screens.
The preamplifier stages consist
of four surface-mounted transistors
which are controlled by the width
and pin controls. Unfortunately, the
circuit diagram is full of errors, with
few voltages and waveforms.
I replaced all the surface-mount
transistors and all the electrolytics
but the fault persisted. Despite that,
the two sets compared quite well,
although factors such as the control
positions, the size of the sets and the
beam current due to picture content
made it difficult to work out what was
important and what wasn’t.
The main factor was the voltage on
the emitter of the east-
west output
transistor (Q7610) which was constantly far too low. The breakthrough
came when I noticed that one of the
March 2003 41
Serviceman’s Log – continued
east-west modulator diodes, D6526
across the horizontal output transistor,
went to C2504 and not to the emitter.
I also noticed a thick black jumper
lead across the two emitters of Q7504
and Q7506. However, this lead was
unnecessary because they already had
a link on the other side.
Granted, it’s not uncommon in TV
sets to have what may be considered redundant links. Sometimes it’s because
there is high current and sometimes
it is to limit inductance. However,
the link was not fitted in the 29-inch
model, so what was it’s purpose?
There seemed to be no reason – unless the link was in the wrong place.
Could it be that, in the course of changing the horizontal output transistors,
my friend removed the link and put it
back in the wrong position?
Well, of course, it was in the wrong
position. Both C2504 and D6526 weren’t connected properly
into the circuit – and
rerouting this link
quickly fixed that.
But I wasn’t quite
42 Silicon Chip
out of the woods yet. The east-west
controls now had an effect but not
enough. The voltage on the emitter of
transistor Q7610, which was previously too low, was now too high – at
times nearly 60V!
More careful examination revealed
that R3611 (2.7kΩ) and R3614 (1.5kΩ)
were both high. Replacing them
brought both controls within a tolerable range.
Finally, I replaced the back and left
the set on soak test. I hope that its
owner has done as good a job on my
transmission!
Plasma sets
My next story is not, strictly speaking, about a conventional service job;
rather, it was an installation job. More
exactly it involved installing two
Panasonic “Progressive Wide Plasma
Displays” (Model TH-42PWS). These
are very large units, measuring 1020 x
610 x 89mm (plus the speakers), and
are designed for wall mounting using
special brackets.
It needs at least two people to safely
manhandle these monsters, since the
total weight (display and speakers)
is 32.7kg. The special wall-hanging
brackets (TY-WK42PV1) that are used
to support the display are made of
heavy-gauge steel and weigh a further
6kg each!
Panasonic recommends that the
brackets be mounted using at least six
bolts but I fitted 12 just to make sure.
After all, plasma displays don’t take
too kindly to a fall, this being the most
common reason for failures.
The first thing to do was work
out the optimum height for the
display (in most cases, eye
height) and then drill one
hole at top centre to hang
the bracket. The bracket
is then initially attached
using a single M6 bolt, then
adjusted with the aid of a
spirit level and used as a
template to drill the holes
for the remaining bolts.
It was also necessary to
mark a cable access hole on
the bottom lefthand side.
This hole (30 x 100mm)
needs to be drilled right
through to the brick cavi-
ty in order to accommodate the cables.
Another hole then has to be drilled
where the cables are to emerge and
connect to the associated AV equipment – VCR, DVD player, digital set-to
box, amplifier, etc.
I was annoyed that most of the accessories were not immediately available
from Panasonic and I hope they will
fix this soon. For example, I wasn’t
able to get the TV-PT600E (and TY42TM5H, TY-SCP15C03, TY-42TM5T)
tuner/receiver. Instead, I had to use an
existing NV-FJ630A hifi VCR as the
main tuner.
One of the display units had to be
fitted across a corner, which I thought
was a waste. However, that’s what the
customer wanted and he was paying.
To do this, we made up a solid metal panel which was bent over at 45°
at each end and mounted vertically
in the corner. We used 2mm-thick
aluminium for this and I was initially worried about its rigidity but
when the set was mounted, it was
very solid.
I also fitted brackets to hold and
conceal the VCR, which I modified so
that the infrared remote control receiver was external and just peeping over
the top of the display. Interestingly, I
found it to be more sensitive facing the
wall than looking back out towards
the viewer.
When it was all finally connected,
the digital reception was exceptionally good. Overall, the effect was fantastic. I just wish I could afford one!
Akai TX-140 stereo unit
A young woman brought in her
Akai TX-140 stereo unit with the
complaint that it wouldn’t play CDs.
As sometimes happens with these
types of systems, I was expecting that
either the laser and/or the disc motor
had failed. In the former case, the disc
starts to spin and the laser comes on
and tries to focus. If it fails to read,
the CD stops.
I removed the top cover to watch
what happened and found that the
three CDs on the carousel would not
stop rotating around the platter. What’s
more, they would not line up with the
CD reader.
I prised off the platter and saw
how the deck worked. Each disc had
a series of plastic tongues on the
underside of the platter, one for disc
one, two for disc two, etc. These gave
a digital pulse as they passed between
www.siliconchip.com.au
an optocoupler. What was fairly obvious was that the optocoupler wasn’t
working.
The optocoupler is mounted on a
small board with a 5-strand flexi-lead
between it and the platter motor. The
flexi-cable seemed to be the obvious
culprit and I checked the continuity
with an ohmmeter. As I suspected,
two of the conductors were open
circuit.
I tried repairing it by running a parallel wire with flexi-cable but it wasn’t
possible to solder it on, so I ordered a
longer generic flexi-cable.
When this arrived, I cut it to size
and stripped back the insulation about
2mm to solder onto the sub-board.
Because of its size and the heat of
the iron, it was quite difficult not to
make a complete mess of it but with a
bit of perseverance, I finally managed
to solder it on. The reassembly was a
breeze and the job was done.
JVC TV set
When a rather ordinary-looking
51cm JVC AV-21 TEAU (MZ2 chassis)
was brought in, I wasn’t really expecting anything other than a mundane
repair. The set was dead and it didn’t
take a mental giant to figure out that
the horizontal output transistor (Q522,
2SD1878-YD) was short circuit.
The only replacement I had was a
2SD1878, which wasn’t fully isolated
like the original but this was easily
fixed with a mica washer. However,
when I switched the set on there was a
split second during which the normal
static field around the picture tube was
very much higher than normal. As I
say, it was only very brief, then it was
back to square one.
But while it lasted, the effect was so
great that I received a shock and there
was also a flash-over inside the picture
tube. Initially, this made me think that
perhaps the picture tube was down to
air. It took another transistor failure to
prove it wasn’t the tube, as I had totally
disconnected it by then.
The most common problems that
can cause horizontal output transistors
to cark it are: (1) a faulty horizontal
output transformer; (2) a faulty deflection yoke; (3) excessive HT; and
(4) crook tuning capacitors – although
not necessarily in that order.
I unsoldered and measured tuning
capacitor C524 as well as C525, but
both were spot on. I then removed
the deflection yoke and examined it
www.siliconchip.com.au
carefully but it too appeared to be
OK. I also reworked the solder on the
motherboard but no joy.
Unfortunately, my copy of the service manual didn’t have the circuit
diagram or service adjustments for this
set, which was extremely frustrating. I
did have the circuits for an AV-G21AU,
which is a CA2, and an AV-G25AU,
which also uses an MZ2 chassis, but
neither was quite close enough.
I assumed that the HT (B1) rail, at
test point TP-91, should be at 114V.
To confirm this, I had to replace the
horizon
tal output transistor, short
out its base and emitter and connect
a 100W globe. It was spot on at 114V.
So all that seemed to be left was
the horizontal output transformer. My
shorted turns tester could not detect
any shorts across pins 9 and 10 but
that doesn’t mean very much; high
voltage failure in the secondary can’t
be detected at low voltage.
Finally, I ordered a new horizontal
output transformer, confident that
that was it. However, after fitting it,
the set behaved exactly as before and
then died.
I can’t lie that I was the great brain
that discovered the cause of this one
– instead, it was Technical Support at
Hagemeyer.
Though I thought I had been
completely thorough in resol
dering
everything on the motherboard, I had
in fact neglected to check and resolder the connection to the horizontal
oscillator ceramic resonator/crystal
(CF-561) on pins 14 and 17 of the
jungle IC (IC201). And that was what
wrong with the set in the first place,
causing it go wildly off frequency and
the EHT to rise spectacularly.
After realigning the yoke and CRT
p/c magnetic rings, everything was
fine except for one slightly bizarre
problem. I didn’t have the remote control but I noticed that by pushing the
channel (CH) up and down buttons on
the set itself, I could select “AV” input.
The problem was that the video from
March 2003 43
Serviceman’s Log – continued
my signal generator wasn’t going in
via the AV sockets at the rear.
Conversely, I could tune it in
when I plugged the generator into
the antenna socket while still in the
AV mode.
Initially, I thought that the AV
switching ICs had failed, along with a
transistor controlled by the microprocessor. Later, when I read the instruction book on this model, I learnt that
it is necessary to select either “TV”
or “Video” with the remote control to
change the source. The “AV” mode in
this set really just denotes the change
in sync time constant that is required
to prevent “flag waving”.
Now, on a lighter note, here is a
contribution from K. A. of Kingston,
Tasmania. This is how he tells it.
Unreliable remotes?
A friend had been grizzling on
and off over several months that all
44 Silicon Chip
the remote controls for her new and
expensive TV, DVD, and VCR were
unreliable. The problem wasn’t so
much presented as “It’s busted, will
you fix it?” but during dinners as part
of idle chit-chat about growing old and
coping increasingly less well with new
fangled gadgets.
It took ages for the various bits of
information to completely emerge. Apparently, the batteries in the remotes
had been replaced umpteen times,
the gadgets had been taken back to
the shop umpteen times (they were
still under warranty) and experts had
visited umpteen times. Furthermore,
red herrings like too much sunlight,
too much light in general, interference
from modern high efficiency lights, etc
had all been eliminated.
There was some hazy information
that the various remotes weren’t all
equally unreliable. However, the
details were confused and this infor-
mation was no help at all.
One day, a really weird piece of
information emerged; the remotes all
worked well for my friend but not
for her teenage son. Now if this had
been the other way round, it wouldn’t
have been significant; teenagers often
successfully use gadgets that have
adults baffled.
Lacking any solid clues, I continued
to offer sympathy rather than useful
advice and left the problem as one
of life’s little puzzles. And then one
day, I was visiting their home while
the teenage son was watching TV and
wrestling with one of those (expletive
deleted) remote controls.
Aha! Problem solved!
Have you seen the way teenagers sit
in chairs to watch TV?
His feet were on a footstool, his
backside was dangling over the edge
of the cushion, his back was where
his backside should have been and
his head was propped up against the
back rest. Bone surgeons will make
a fortune 30 years from now recon
structing his neck!
But that’s not all. The remote control was on his tummy and his great
big size-15 feet were between it and
the IR sensors on the TV, VCR and
DVD!
IR light doesn’t shine through feet!
– no wonder it wouldn’t work.
The equipment itself was installed
in a typical cabinet with the VCR on
the bottom, then the DVD and the TV
on top. The TV could occasionally get
a glimpse of the remote control over
the teenage son’s toes and so it worked
sometimes. By contrast, the VCR was
in a deep, dark, gloomy shadow and
SC
almost never worked!
www.siliconchip.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.jaycar.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.jaycar.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.jaycar.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.jaycar.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.jaycar.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.jaycar.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.jaycar.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.jaycar.com.au
PRODUCT SHOWCASE
The ultimate hard disk music
storage system?
Looking for somewhere to store (and
retrieve) all your music? Linn Products
have a solution – if you’re prepared to
pay for it!
The Kivor Index music library is a
storage/retrieval and playback harddisk-based system that can be used
as a stand-alone unit or together with
other Knekt Kivor products.
It provides up to 500 hours of full
bandwidth, pitch accurate hard disk
music storage and allows up to eight
users to have concurrent access to high
quality, full bandwidth music in a
multi-room system or a hard disk component source in any audio system.
Whether you have a huge library of
LPs or CD discs, or like to download
MP3 music, the Kivor Index hard disk
records and creates playlists of your
favourite tracks by genre, artist, mood
or date. Available in two configurations, the Kivor Index provides either
250 or 500 hours of storage that can be
increased up to tenfold when using
compressed audio.
Music is
simply loaded into the
Kivor Index
via its integrated CDROM and a built-in modem downloads
Internet material for ‘manipulation’ on
Linntek, Linn’s PC set up and control
utility software.
Available in either black or silver,
the Linn Kivor Index music library is
rack mountable for installation with
any multi-room amplification system.
Covered by a two-year parts and
labour warranty, the Kivor Index (250
hours storage) has an RRP of $14,999
and the Kivor Index (500 hours storage) has an RRP of $19,999.
Contact:
Linn Products
Ph: 1800 642 922
email: info<at>audioproducts.com.au
330-1500µF, ultra-low ESR tantalums
A new series of solid tantalum chip
capacitors from Vishay Intertech-nology, Inc. features ultra-low equivalent
series resistance (ESR) and high capacitance values in new “E” and “R”
case sizes.
The Vishay Sprague conformal-coated 597D multi-anode capacitors
provide increased reliability and
improved reception in DC-DC conversion, line cards, mother boards
and power supply applications in end
products including test equipment,
PCs and base stations.
The devices’ ultra-low maximum
ESR values range from 13mΩ to 35mΩ
at +25°C and 100kHz. Capacitance
values range from 330µF to 1500µF
with standard tolerances of ±10% and
±20%, and working voltage ranges
from 4-10VDC. Maximum current
leakage ranges from 27µA to 68µA,
and the maximum dissipation factor
is 6% at +25°C and 120Hz.
www.siliconchip.com.au
Foxie lowpower SBC
The LP3500
Fox low-power
single-board
computer is intended for applications
where power is limited, such as in
portable, hand-held, battery-powered,
and remote monitoring systems.
It features built-in analog and digital
I/O and consumes less than 20mA
when fully operational and less than
100µA in power-save mode
It has 25 industrialised I/Os plus
a relay and has eight analog/digital
converter inputs with programmable
gain. Six serial ports are provided (1x
RS-485, 3x RS-232 and 2x TTL) and
there are optional peripherals including keypad/display, serial flash, etc.
Contact:
Dominion Electronics
Ph: (02) 9906 6988
Website: dominion.net.au
TOROIDAL POWER
TRANSFORMERS
Manufactured in Australia
Comprehensive data available
Contact:
Vishay Intertechnology Inc
PO Box 231, Sanford, ME 04073 USA
Seaford Vic 3198
Ph: (0011 1) 207 490 7240
Website: vishay.com
Harbuch Electronics Pty Ltd
9/40 Leighton Pl. HORNSBY 2077
Ph (02) 9476-5854 Fx (02) 9476-3231
March 2003 53
Cellular call diverter:
50-80% telephone bill
savings claim
A Gold Coast-based telecommunications company, Powertec,
has announced the development
of a new Cellular Diverter that they
claim will save users between 50%
and 80% off their regular landline
and mobile telephone accounts.
The Managing Director of Powertec, Mr Ray Smith, says the new
diverter revolutionises the manner in which small and/or home
business operators are charged for
landline calls diverted to mobiles.
“At present whenever a home or
office telephone call is diverted
to a mobile phone the owner pays
charges for the diversion, in conjunction with the caller paying
costs as well,” said Mr Smith. “The
new Powertec CellularDiverter
turns that landline component into
a mobile call, so users can then benefit from special mobile-to-mobile
rates,” he said.
“This means that a 10 minute
diverted call which would normally
cost up to $2.50 will now only cost
20 cents,” he added. “Any business
making calls to mobiles or receiving calls from their own mobiles
can take advantage of the new cost
saving system even when they do
not use the diverter,” he said.
Mr Smith says the new Powertec Cellular Diverter is the result
of more than two years of research
and development, at a cost of
thousands of dollars. He says the
device is Australian compliant and
has patents pending. They are used
in conjunction with the Ericsson
Fixed Cellular Terminal which was
released on the Australian market,
late last year.
Powertec is offering to loan the
system to approved customers at no
cost to prove that the technology
is beneficial in saving on phone
bills for small business and home
users.
Contact:
Powertec Telecommunications
19 Short St, Southport Qld 4215
Ph: 1800 MOBILE
Website: powertec.com.au
54 Silicon Chip
Increased airflow inside racks and enclosures
American Power Conversion (APC)
has available a new compact air distribution unit that increases airflow
inside racks and enclosures.
APC’s NetworkAIR Rack Mounted
(RM) Air Distribution unit works in
tandem with an existing precision air conditioning system in
enclosed environments to pull
air from beneath the raised
floor directly into the rack enclosure, before it can mix with room air.
It eliminates dangerous hot spots
in data centres by boosting the conditioned air volume within the rack itself
and improving air delivery in poor
static pressure areas. In environments
without raised floors, the NetworkAIR
RM Air Distribution unit uses air
from under and around the bottom
of the rack or enclosure where the air
is coldest. This boosts the amount of
air supplied to ensure the necessary
amounts of airflow to equipment.
Contact:
American Power Conversion (APC)
Ph: 9955 9366
Website: apcc.com
Need more “oomph” from your wireless LAN?
When your wireless LAN needs more
output, these cards
will do the job. They
represent the next
generation of wireless equipment offering both robust
construction and a
choice of a both high
power (200mW) and
standard (100mW)
models.
They are ideal for
wireless ISPs.
The detachable external antenna
further enhances their overall perfor-
mance. If you use them with a high
gain antenna, make sure you don’t
exceed the 4W EIRP legal limit.
They support both peer-to-peer and
infrastructure communications and
are usable with WiFi (WECA) certified
products. Operating systems supported
include Win 95, 98, 2000, NT, ME and
XP. Memory size is 128K x 16 SRAM
and 128K x 8 flash ROM.
Contact:
Microgram Computers
Unit 1/14 Bon Mace Cl, Berkeley Vale
NSW 2261
Ph: (02) 4389 8444 Fax: (02)4389 8388
Website: microgram.com.au
TDK’s one-chip smart card terminal controller
TDK Semiconductor
Corp. now offers the
73S1121F smart card
terminal controller –
said to be the first true
system on a chip for
smart card terminals.
The new low-cost
device integrates all the
functionality for implementing a complete range of smart card
terminals for network access security,
e-purse terminals, payphones, vending
machines and inexpensive POS terminal applications. It includes an 8052
processor, a USB interface, two built-in
smartcard interfaces with a dedicated
hardware ISO7816 UART, multiple
card terminals.
development software
layers, extensive I/Os,
64KB of Flash, 4KB
of user-RAM and a
PIN pad interface all
on a single chip. This
solution will significantly reduce cost and
component count for
implementing smart
Contact:
Adilam Electronics Pty Ltd
Ph: (03) 9737 4900
Fax: (03) 9737 4999
Website: adilam.com.au
www.siliconchip.com.au
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Your company or business can be a part of SILICON CHIP’s WebLINK . For one low rate you receive a printed entry
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details plus up to 50 words of description– and this is repeated on the WebLINK page on the SILICON CHIP website
with the link of your choice active. Get those extra hits on your site from the right people in the electronics industry – the people who make decisions to buy your products. Call SILICON CHIP today on (02) 9979 5644
SPECIALISTS in AUDIO, VIDEO, CD, DATA
Media and Multimedia manufacturing
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Production & editing. We can produce Short
Run or Bulk CD Audio, CD Rom & DVD projects. Distributor of Emtec (by Basf) TDK,
HHB and Quantegy Professional Products.
PRO-COPY
JED designs and manufactures a range of
single board computers (based on Wilke Tiger
and Atmel AVR), as well as LCD displays and
analog and digital I/O for PCs and controllers.
JED also makes a PC PROM programmer and
RS232/RS485 converters.
Jed Microprocessors Pty Ltd
Tel: (08) 9375 3902 Fax: (08) 9375 3903
Tel: (03) 9762 3588 Fax: (03) 9762 5499
WebLINK: procopy.com.au
WebLINK: jedmicro.com.au
We specialise in providing a range of Low
Power Radio solutions for OEM’s to incorporate in their wireless technology based
products. The innovative range includes
products from Radiometrix, the World’s
leading manufacturer.
TeleLink Communications
Tel:(07) 4934 0413 Fax: (07) 4934 0311
WebLINK: telelink.com.au
A 100% Australian owned company supplying frequency control products to the highest
international standards: filters, DIL’s, voltage,
temperature compensated and oven controlled oscillators, monolithic and discrete
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Hy-Q International Pty Ltd
PIC chip specialists –
microEngineering Labs and others.
Easy to learn, easy to use, sophisticated
CPU based controllers & peripherals.
See our website for new range of ATOM
products!
MicroZed Computers
Tel:(03) 9562-8222 Fax: (03) 9562 9009
Tel: (02) 6772 2777 Fax: (02) 6772 8987
We’re one of Australia’s most innovative
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days.Custom & production boards too!
· Hifi upgrades & modification products - jitter
Tel: (02) 9482 1944 Fax: (02) 9482 1309
WebLINK: clarke.com.au
Tel: (02) 9738 0330 Fax: (02) 9738 0334
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WebLINK: www.hy-q.com.au
RCS Radio
WebLINK: cia.com.au/rcsradio
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reduction and output stage improvement.
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Syd: (02) 9660-1228 Melb: (03) 9859-0388
WebLINK: soundlabsgroup.com.au
Controller upgrade brings new life to old machine
JAR Engineering faced the prospect of
scrapping their Kasuga Machining Centre
while the core of the CNC machine was still
fully functional. The problem: the Kasuga
controller was: “Old and slow – a case of a
still young body under the direction of an old,
slow brain!” said Roy Milan of JAR.
But scrapping the machine and buying
a new system would have involved a large
capital investment. Instead, JAR Engineering contacted H & H Machine Tools and
investigated the possibility of a controller
www.siliconchip.com.au
transplant. The result: the Kasuga is now
working at double the previous feed rate.
Mr Milan says: “The system used to operate in a jerky, stop, start motion. The new
Fidia controller provides a continuous smooth
movement and reads at a very high rate of
knots. We are frequently recording savings
of $500 a day or higher —savings that will
rapidly pay out the upgrade cost.”
He adds that his company has found the
Fidia controlled machine “very user friendly,
with the need for operator training minimised.”
Contact:
H&H Machine Tools
Ph: (03)9719 7729,
Fax: (03) 9719 7298
email: gmann<at>h-h.com.au
March 2003 55
Building The
Our state-of-the-art portable public address amplifier
Last month, we introduced this compact and powerful portable PA
amplifier based on the Philips TDA1562Q 70W class-H power IC. This
month, we conclude with the description of the power supply, cabinet
and PC board construction and the parts list.
A
S NOTED last month, the power
supply is effectively a battery
charger with the 7 amp-hour SLA battery permanently connected.
Since the charger has other uses
and could be used in any situation
where a float charger is required, we
are describing its circuit operation
and construction separately, on pages
64 and 65.
We’re also detailing the box construction separately – you’ll find this
on pages 66 and 67. While we give detailed dimensions, this is not the only
approach possible. We’re sure some
readers will come up with completely
different ideas for the enclosures.
Construction
The PortaPAL PA Amplifier is housed in a timber cabinet measuring 480
x 280 x 240mm which is covered in
speaker carpet. Corner protectors, a
speaker grille, a speaker stand socket
and a handle are included.
The electronics is accommodated
on four PC boards: the microphone
PC board coded 01103032 (64 x
73mm), the auxiliary PC board coded 01103033 (109 x 35mm) and the
main PC board coded 01103031 (199
x 90mm). These are mounted on an
L-shaped metal bracket, the reverse of
which becomes the front panel.
The charger PC board coded
01103034 (132 x 66mm) mounts on the
side of the box with its indicating LEDs
protruding through the front panel.
You can begin construction by
checking the PC boards for shorted
tracks or any breaks in the copper
patterns. Also check that the holes are
drilled to the correct sizes to suit the
components. In particular, check the
56 Silicon Chip
siliconchip.com.au
PortaPAL
FEAT
P RO J U R E
ECT
PART 2:
BY JOHN CLARKE
& LEO SIMPSON
corner mounting hole sizes and the
holes for the pots, RCA, 6.35mm jack
and XLR sockets.
Microphone board
Assembling the microphone PC
board is simple, as shown in Fig.1.
Begin by installing the LM833 op amp
(IC1), together with all the resistors
and capacitors.
Use the resistor colour code and
capacitor code tables to guide you in
selecting the correct values, and/or
check the resistor values with a digital
multimeter. Also, the electrolytic capacitors need to be oriented with the
polarity shown.
Note that the 10kΩ resistors and
10µF capacitor marked with an asterisk (*) are optional for powering
electret microphones. These components are not needed for dynamic
microphones but will not do any harm
to a dynamic mic if you regularly swap
microphones.
There are a couple of PC stakes
required to be installed for test points
TP1 and TP2.
Next, insert the 90° 6-way pin header into the PC board as shown.
Before mounting the two XLR sockets, screw the M3 x 10mm screws into
the mounting pillars from the back
of the socket and then secure the M3
tapped 6mm long spacers from the
front side of the sockets. Then mount
the XLR sockets directly into the PC
board holes provided.
Main PC board
The main PC board accommodates
all the potentiometers and the TDA1562Q power amplifier module. Its
component layout is shown in Fig.2.
siliconchip.com.au
Apart from the charger/supply
board, everything mounts on an
L-shaped bracket, the opposite
side of which also acts as the
front panel. Here everything is
assembled, ready for placing
inside the enclosure. Aaah . . .
the enclosure. Did we forget to
mention you have to build that too?
You can start its assembly by installing
all the links, the resistors and then the
ICs but not the TDA1562Q.
The 2.2Ω 1W resistors need to have
an over-wind of 16 turns of 0.5mm diameter enamelled copper wire. These
windings are shown on the circuit
published last month, as L1 & L2.
Start with a short length of 0.5mm
copper wire, strip and tin one end and
solder it to one end of the 2.2Ω resistor.
Then wind on 16 turns. Strip and tin
the other end and solder it to the other
end of the resistor. Repeat the process
for the second 2.2Ω resistor. Then
solder each resistor into the PC board.
Insert all the PC stakes used for the
test points and also the PC-mount
spade connectors. Mount the capacitors as shown with the electrolytics
marked as polarised with the correct
orientation.
Electrolytics marked BP (ie, non-polarised) can be inserted either way.
March 2003 57
The main PC board shown here without the heatsink attached. Note the inductors wound over the resistors (near IC9).
Note also that the 10µF capacitor near
IC2 must be bent over the top of IC2.
This is to allow clearance when the
microphone PC board is plugged into
the header socket.
Insert the 6-way and 8-way headers,
as shown. Transistor Q1, diodes D1
and D2 and the power amplifier (IC9)
can be inserted. IC9 is positioned with
the centre-line of its mounting holes
exactly 12mm above the top face of
the PC board. Be sure to solder all the
pins of the amplifier and
take care not to have any
of the pins shorted.
Diode D3 is mounted
onto a 6mm spacer and
secured with a nylon
screw and another 6mm
tapped spacer on the underside of the PC board.
The nylon screw is
required to prevent the
tab of the diode shorting
to the metal panel when
it is finally assembled.
The two LEDs are
mounted using LED
mounts. The LEDs are
inserted into the mounts
from the front and the
leads bent over at 90°
within the mount before
being inserted into the PC
board. Be sure that the
58 Silicon Chip
orientation is correct before bending
the leads.
Finally, the potentiometers can be
installed – take care to place each one
in its correct position. The potentiometer bodies are all tied together with a
length of 0.8mm tinned copper wire
soldered to the top of each body. It is
difficult to solder to the passivated
metal, so you will need to scrape away
the passivation coating (with a knife or
screwdriver) before soldering the wire.
The wire is then connected to the PC
stake adjacent to the 330nF earthing
capacitor.
Place a dab of red paint or nail polish
next to the positive spade lug near the
22Ω resistor and the TP GND PC stake.
Fig.1: PC board overlay and same-size photo of the
microphone input board.
siliconchip.com.au
shown. Finally, install the PC stake for
the test point, TP3.
Support bracket
The bracket which supports the
amplifier also doubles as the front
panel. It is made from 195 x 240 x
1.5mm aluminium, bent at 90° to form
an L-shape.
The dimensions of the panel, hole
positioning and sizes are shown in
Fig.4. The panel can be drilled and
the larger holes cut before the panel
is bent and the label attached.
We expect that if you purchase a kit,
the panel will already be drilled and
bent and will come screen printed.
Those building from scratch will need
to prepare the panel as shown.
The dress panel artwork (like the
PC board artwork) can be downloaded
from the SILICON CHIP website, siliconchip.com.au and printed, then glued
to the aluminium panel.
Place nuts on all the pot bushes
for the main board and then mount
the board on M3 tapped 6mm standoffs, with M3 x 6mm screws and star
washers. The standoff beneath D1 is
secured in place with an M3 nut and
star washer. Secure the pots with nuts
on the outside of the panel.
Drilling the heatsink
Fig.2: install the parts on the PC board as shown on this wiring diagram. Note
how the potentiometer bodies are linked together and earthed at a single point.
This is for easy identification when
connecting the supply wires.
Auxiliary board
The auxiliary PC board carries the
four RCA sockets and the jack sockets. Its component layout is shown
in Fig.3.
siliconchip.com.au
First, install all the resistors and the
TL071 (IC3) op amp. Then insert the
capacitors, again taking care with the
polarity of the electrolytic capacitors.
The 6.35mm jack sockets and the stereo RCA sockets are directly mounted
onto the PC board. An 8-way pin
header is mounted with the orientation
The holes in the main heatsink can
be drilled as shown in Fig.6. Apply a
smear of heatsink compound on the
face of the power amplifier and attach
the heatsink to the baseplate with M6
screws into the heatsink mounting
screw points. Then attach the amplifier
to the heatsink with two M3 x 15mm
screws, two flat washers and two nuts.
Attach the auxiliary board to the
front panel by first fitting fibre washers
onto the 6.35mm jack socket bushes
and then mating them up the relevant
panel holes; secure with the nuts. The
RCA stereo sockets are secured with
M3 x 6mm screws tapped into the
plastic mounting pillars.
Plug the microphone board pin
header into the control PC board socket
and push the sockets into the front
panel holes. Secure with M3 x 6mm
screws into the 6mm standoffs already
attached to the XLR sockets.
Make up a lead that connects the
8-way pin header sockets using 8-way
rainbow cable. This connects the auxiliary board to the main board. Make
sure the orientation is correct, with no
twist in the wiring.
March 2003 59
Power switch S1, the fuseholder
and the 3-pin DIN socket can now be
attached. The DIN socket is secured
with M3 x 6mm screws, star washers
and nuts.
Connecting the boards
Fig.3: the auxiliary PC board has the line in/out and guitar input sockets – it
connects to the main board via the 8-way header.
Fig.5 shows the wiring to the boards,
battery and speaker. The battery and
speaker connections are run in 7.5A
figure-8 wire and crimp plugs. Use the
lengths detailed on the diagrams for
the charger and Fig.5.
Be sure to use blue crimp connectors
for the negative lead connections and
red connectors for the positive leads.
That way, there is less chance of wrong
polarity connections.
Also note that the amplifier power
leads should be connected to piggyback connectors for the battery terminals, so that the charger leads can also
be connected to the battery.
Making the cabinet
The box is made using 16mm Medium Density Fibre board (MDF) or
craftwood and 16 x 16mm Meranti
for the cleats. Because many home
constructors may not have precision
Fig. 4: this
drilling template
should help you
with the front
panel/amplifier
bracket.
60 Silicon Chip
siliconchip.com.au
Parts List – PortaPAL PA (Main Section)
1 mic input PC board, code 01103032, 64 x 73mm
1 auxiliary input PC board, code 01103033, 109 x 35mm
1 control PC board, code 01103031, 199 x 90mm
2 450 x 900 x 16mm sheets of MDF board or craftwood
1 4m length of 12 x 12mm Meranti
1 195 x 240mm sheet of 1.5mm aluminium for panel
1 aluminium vent strip, 240mm long 15 x 12mm channel
with holes or slots (eg, slotted shelf support strip)
1 200mm (8-inch) 4Ω coaxial loudspeaker (Altronics C
2006)
8 speaker box corners, 55 x 35 x 35mm
1 speaker box “top hat” stand socket (Altronics C 3602)
1 200mm speaker grille (Altronics C 3708)
1 strap handle (Altronics C 3660)
1 1m x 1.8m length of speaker box carpet
(Altronics C 3530)
1 heavy duty heatsink 110 x 33 x 72mm
(Altronics H 0560)
1 M205 fuse holder (Altronics S 5992)
1 7.5A M205 fuse (F1)
4 blue knobs
2 grey knobs
3 16mm PC-mount 10kΩ log pots (VR1-VR3)
1 16mm PC-mount 5kΩ log pot (VR4)
2 16mm PC-mount 100kΩ linear pots (VR5,VR6)
1 SPST 6A rocker switch (S1)
2 6.35mm PC-mount jack sockets (Altronics P 0073)
2 stereo PC-mount RCA sockets (Altronics P-0210)
2 PC-mount XLR/6.35mm jack socket without locking tab
(Altronics P-0960)
1 6-way header connector with 90° bend pins (2.54mm
spacing)
2 8-way header connectors with straight pins (2.54mm
spacing)
2 8-way header sockets (2.54mm spacing)
1 6-way PC-mount header socket (2.54mm spacing)
2 piggy-back 6.3mm crimp connectors
7 red female 6.3mm spade lug crimp connectors
5 blue female 6.3mm spade lug crimp connectors
4 6.3mm spade PC board connectors with 5mm pitch PC
lugs (Altronics H 2094)
10 6mm tapped standoffs
10 M3 shakeproof washers
2 M3 flat washers
3 M3 nuts
10 M3 x 6mm screws
2 M3 x 15mm screws (for amplifier to heatsink connection)
4 M3 x 10mm screws (for 6mm standoffs on XLR sockets)
1 M3 x 20mm nylon screw (for diode D3 mounting and PC
board mounting point)
2 M6 x 15mm screws (to secure heatsink to baseplate)
6 4G x 16mm countersunk wood screws for securing
control panel and charger PC board
4 6G x 10mm cheese-head wood screws for mounting
loudspeaker
4 6G x 20mm to mount speaker stand socket
3 6G x 30mm countersunk wood screws to secure MDF
battery cover
2 8G x 25mm cheese-head wood screws to mount handle
siliconchip.com.au
32 4G x 16mm countersunk wood screws to mount
corner protectors
2 5G x 20mm countersunk wood screws to mount
aluminium vent strip
1 500mm length of 0.5mm enamel copper wire
1 2m length of 7.5A rated figure-8 wire
1 600mm length of 0.8mm tinned copper wire
1 120mm length of 8-way rainbow cable
Semiconductors
3 LM833 op amps (IC1,IC2&IC4)
1 TL072 op amp (IC5)
2 TL071 op amps (IC3,IC8)
1 LM358 op amp (IC6)
1 7555 CMOS timer (IC7)
1 TDA1562Q power amplifier (IC9)
1 BC337 transistor (Q1)
2 1N914, 1N4148 diodes (D1,D2)
1 15A diode (MUR1550 or similar TO-220 package) (D3)
2 5mm high brightness red LEDs (LED1,LED2)
2 PC board LED mounts (Altronics H 1543)
Capacitors
2 4700µF 16V PC electrolytic
1 2200µF 25V PC electrolytic
2 100µF 16V PC electrolytic
8 47µF 16V PC electrolytic
14 10µF 16V PC electrolytic
2 2.2µF BP* electrolytic
1 2.2µF 16V PC electrolytic
4 1µF 16V PC electrolytic
5 1µF BP* electrolytic
1 330nF MKT polyester
4 220nF MKT polyester
1 100nF MKT polyester
2 15nF MKT polyester
2 1.5nF MKT polyester
1 680pF ceramic
1 560pF ceramic
2 390pF ceramic
3 330pF ceramic
2 220pF ceramic
4 150pF ceramic
1 39pF ceramic
1 22pF ceramic
1 10pF ceramic
Resistors (0.25W, 1%)
1 10MΩ
1 1MΩ
1 47kΩ
1 39kΩ
4 15kΩ
21 10kΩ
8 1kΩ
5 150Ω
* BP (bipolar)
capacitors are
also known as
NP (non-polarised)
3 470kΩ
2 22kΩ
4 4.7kΩ
2 2.2Ω 1W
5 100kΩ
2 18kΩ
5 2.2kΩ
Miscellaneous
PVA (timber) adhesive, contact adhesive, black paint,
Bag of TEK particle board screws (for box assembly)
Optional: 3-pin mains socket, panel mounting – not
connected but mounts inside bottom of box to act as a
storage holder for plugpack when not in use.
March 2003 61
Fig.5: when you have all the boards
assembled, connecting them together
is as simple as following this diagram.
Parts List – PortaPAL SLA Float Charger
1 SLA battery charger PC board coded 01103034,
132 x 66mm
1 16VAC 1.5A plugpack 3-wire earthed type
(Altronics M 9332)
1 PC board fin heatsink 84 x 24 x 28mm
(Altronics H 0668)
1 12V relay with 6A contacts (RELAY1)
(Altronics S 4160A)
1 3-pin 180° DIN plug
1 3-pin 180° DIN chassis socket
2 5mm high brightness red LEDs (LED3, 4)
2 PC board LED mounts (Altronics H 1543)
4 6.3mm spade PC board connectors with 5mm pitch
PC lugs (Altronics H 2094)
2 M3 x 6mm screws (for DIN socket)
2 M3 x 10mm screws (for heatsink)
4 M3 nuts
4 3mm star washers
1 50mm length of 0.8mm tinned copper wire
62 Silicon Chip
4 4G x 16mm countersunk wood screws for securing
charger PC board
Semiconductors
1 LM317T regulator (REG1)
2 BC337 transistors (Q2,Q3)
9 1N4004 1A diodes (D4-D12)
Capacitors
1 4700µF 25V PC electrolytic
1 4700µF 16V PC electrolytic
1 470µF 25V PC electrolytic
2 10µF 16V PC electrolytic
Resistors (0.25W, 1%)
2 2.2kΩ
3 1kΩ
3 470Ω
1 220Ω 0.5W, 5%
1 1Ω 5W wirewound
1 500Ω horizontal trimpot (VR7)
1 120Ω
siliconchip.com.au
Resistor Colour Codes
No.
p
1
p
1
p
3
p
5
p
1
p
1
p
2
p
2
p
4
p 21
p
4
p
7
p 11
p
3
p
1
p
5
p
1
p
2
Value 4-Band Code (1%) 5-Band Code (1%)
10MΩ brown black blue brown
brown black black green brown
1MΩ
brown black green brown
brown black black yellow brown
470kΩ yellow violet yellow brown
yellow violet black orange brown
100kΩ brown black yellow brown
brown black black orange brown
47kΩ
yellow violet orange brown
yellow violet black red brown
39kΩ
orange white orange brown
orange white black red brown
22kΩ
red red orange brown
red red black red brown
18kΩ
brown grey orange brown
brown grey black red brown
15kΩ
brown green orange brown
brown green black red brown
10kΩ
brown black orange brown
brown black black red brown
4.7kΩ yellow violet red brown
yellow violet black brown brown
2.2kΩ red red red brown
red red black brown brown
1kΩ
brown black red brown
brown black black brown brown
470Ω yellow violet brown brown
yellow violet black black brown
220Ω red red brown brown
red red black black brown
150Ω brown green brown brown
brown green black black brown
120Ω brown red brown brown
brown red black black brown
2.2Ω
red red gold brown
red red black silver brown
woodworking equipment (nor skills!)
we have described the box construction in detail overleaf.
Once the box is completed you
can install the speaker in its rebated
hole in the front panel. We used some
self-adhesive foam tape underneath
the speaker to make it an airtight seal.
Fit the speaker grille over the front
of the speaker and screw in the four
mounting screws. The grille may seem
like overkill because the speaker cone
is so far back from the front panel – but
if you don’t fit one it won’t be long
before you wished you did!
Testing
Before installing the assembly into
the box, you can test the circuit by
applying power using the battery.
At switch-on, the power LED should
flash at a one-second rate. Check that
there is power to the op amps by testing for 12V between pins 4 and 8 of
the LM833, TL072 and LM358 op amps
(IC1, IC2, IC4, IC5, IC6) and at pins
4 and 7 for the TL071 op amps (IC3,
IC8). IC7 should have 12V between
pins 1 and 8.
The output of IC4b (pin 7) should
be at half supply, at around +6V. Similarly, the outputs of IC1a (pin 1), IC1b
(pin 7), IC2a (pin 1), IC2b (pin 7), IC3
(pin 6), IC4a (pin 1), IC5a (pin 1), IC5b
(pin 7) and IC8 (pin 6) should be also
at about +6V.
Check that the circuit works by consiliconchip.com.au
Capacitor Codes
Value
330nF
220nF
100nF
15nF
1.5nF
680pF
560pF
390pF
330pF
220pF
150pF
39pF
22pF
10pF
IEC Code
330n
220n
100n
15n
1n5
680p
560p
390p
330p
220p
150p
39p
22p
10p
EIA Code
334
224
104
153
152
681
561
391
331
221
151
39
22
10
the cleat frame with 4G x 16mm long
screws. The battery leads for the amplifier and charger pass through from
the rear of the battery compartment .
The battery cover is secured with
three 6G x 30mm countersunk screws.
With the dimensions shown, the
battery should be a snug fit but if necessary, pack some pieces of foam into
the compartment to stop it moving
around in transit.
Finally, a chassis-mounting 3-pin
mains socket, screwed to the inside
bottom of the case but not connected
to anything, makes an ideal plugpack
holder when the plugpack is not being used to charge or power the
SC
PortaPAL.
necting the loudspeaker and applying
an audio signal to one of the inputs.
Turn up the volume and the speaker
should begin to produce sound. The
power LED should light continuously
when not muted.
Check operation of the charger by
connecting the output leads to the
piggyback battery terminals (make
sure the polarity is correct) and connecting the DIN socket to the AC input
on the charger.
Switch on power to the plugpack
and the charger LED
should light and possibly the charging LED
will light depending on
battery charge.
Mount the charger
board on the inside of the
cabinet, making sure that
the two LEDs align and
protrude through their
respective holes in the
control panel.
Use 4G x 16mm screws
to attach it in place. We
used a small rubber
grommet cut in half to lift
the two front mountings
of the PC board off the
cleats by about 1mm.
The L-shaped amplifier bracket/panel is
installed into the box by
sliding it into the 2mm
Fig.6: this template can be used to ensure your drill
gap and securing it to
holes on the heatsink are in exactly the right place!
March 2003 63
MAKING THE BOX
One of the areas where home constructors come unstuck
is in the cutting-out of speaker box panels. It is essential
that the edges are not only straight and square but opposite
panels also need to be exactly the same size – otherwise
the box may be crooked or there may be air gaps.
For a typical part-time woodworker using typical home
workshop tools (as distinct from a pro who does it all the
time!), achieving perfectly straight, smooth and square cuts
with a hand saw or any type of hand-held power saw is
difficult. Yes, it can be done – but it is difficult.
However, there is a delightfully easy way to ensure that
at least three sides of each panel have perfectly straight
and parallel sides/right angles – and that is to use sheets
of pre-cut board. (If the manufacturers can’t get it straight
and square then we are all in trouble!)
For this reason, we have elected to use two sheets
of 16mm, 450 x 900mm craftwood (MDF would also be
suitable). We have made the three vertical panels (ie front
and both sides) 450mm high. Originally we had planned to
use a single sheet of 900 x 900mm board but fortunately
couldn’t find any in our local hardware store. So we purchased two 450mm wide sheets and suddenly realised
what an advantage that was!
Cut the two sides (240mm wide) from the top of each
sheet and the front (247mm wide) from the bottom of one
of the sheets (as shown on the cutting diagram) and you’ll
have three edges on each panel perfectly square. The fourth
edge depends on how accurately you cut.
The identical top and bottom pieces (240 x 280mm) and
the various bits and pieces which form the battery holder,
etc, can be cut from what is left over.
The vertical panels sit between (ie, inside) the top
and bottom pieces, making the overall height of the
box 482mm (450+16+16). One reason for placing
the vertical panels inside the top and bottom, rather
than vice-versa, is for strength. As made, the box
will easily handle someone using it as a seat (as will
inevitably happen).
The front panel and the various rear pieces are
recessed – the front back far enough to accommodate the speaker grille, while the rear is even further
recessed. Recessing both front and back will allow
the box to fall over and not break or damage the
speaker itself, pot knobs or other controls.
It might appear that 247mm is wrong for the front
panel: if the base is 280mm wide and the two sides
are 16mm wide, surely it should be 248mm (28016-16)? That extra 1mm off allows the front panel
to be a snug, but not too tight fit.
We cut suitable lengths of 16 x16mm meranti
(which we happened to have on hand – just about
any softwood will be OK) for the cleats – all around
the front inside of the box for the box front (speaker
baffle) to attach to and in strategic locations on the
rear inside as shown by our drawings.
Before assembling the box proper, we
64 Silicon Chip
glued’n’screwed the cleats in position.
The “L”-shaped aluminium plate holding most of the amplifier electronics screws to these cleats.
After the cleats were done, the top, bottom and two side
box panels were glued and clamped together, and allowed
to dry overnight. The (unglued) front panel was placed in
position as formwork to keep the whole thing square,
When dry, we pushed out the front panel and on it marked
and cut (with a jigsaw) a 185mm circle right in the centre.
Naturally enough, this is where the speaker mounts – but
first, the hole needs a 7mm deep, 10mm rebate all around
from the front (using a router) to allow the speaker to sit flush.
A 200mm metal speaker grille goes over the speaker later
on to protect it.
The final bit of woodwork is the mounting of the various
bits of craftwood (or MDF) which hold the battery and other
components in place. These mount as shown in our detailed
drawing opposite.
The finished box, measuring 280(w) x 240(d) x 482mm(h),
can be painted, veneered, or as we have done, covered in
speaker “carpet”. A lot of pro audio gear is covered in this
stuff because it helps it absorb knocks and scrapes on the
job or in transit. It also hides any “sins” you might have created along the way.
The carpet is glued on with contact adhesive, making sure
it is stretched nice and tight over and around the box. Edges
are trimmed with a sharp knife and also glued.
We also completely covered the inside of the box (and
even the back of the speaker magnet) with the carpet to
act as a sound deadening and resonance-reducing agent.
siliconchip.com.au
It looks schmick, too! All these pieces need to be cut to the
appropriate size before gluing in place.
Eight plastic speaker box corners were fitted on all corners
(top and bottom) to protect them from damage. For ease
of transportation we added a flexible carry handle. As we
mentioned before, a metal speaker grille is fitted over the
front of the speaker cone to protect it.
In perhaps a bit of overkill, we added a “top hat” stand
mount to the bottom of the box. This allows the box to be
mounted “up high” on a standard 35mm speaker stand (or
even a length of 35mm OD water pipe driven into the
ground). Raising the box above the heads of an audience
dramatically improves the sound “throw”, allowing greater
coverage without the use of a second box or extension.
Finally, the “aluminium air vent” shown above is simply
an offcut from a length of U-shaped slotted aluminium
channel used for shelf support verticals (the kind that
brackets clip into to hold shelves). This should be available at any hardware store. It even comes with the slots
pre-cut for you!
These three shots, along with the diagram above, give a pretty good idea of how we constructed our box. Of course,
other approaches may be just as valid – and because it is for PA (not hifi) use, dimensions are not particularly critical
with the exception of the speaker cutout, battery compartment and, of course, the amplifier mounting arrangement.
siliconchip.com.au
March 2003 65
12V SLA BATTERY
FLOAT CHARGER
Some readers will be aware that we produced a 12V DC float charger in October
1998. Why not simply employ that circuit
in the PortaPAL PA amplifier?
The answer is that we did try it in our
first prototype but it was found to be
unsuitable for this application, for the
following reasons:
First, the October 1998 charger feeds
pulses of rectified AC to the battery and
while this is perfectly valid for battery
charging, the resulting ripple across the
battery and hum radiation from the battery
leads was enough to be picked up by the
sensitive microphone circuitry to become
quite audible.
Plainly, this was a major drawback,
especially as most users would want to
use mains power where it was convenient
and available.
Second, once power is removed from
the input to the charger, it pulls a significant
current from the battery. This would totally
discharge the battery if the PA system was
66 Silicon Chip
not used for a few weeks. Such an occurrence
would destroy the battery. Not good.
Hence, our new float battery charger
feeds pure DC to the battery and is disconnected from the battery when the AC input
is removed. With no input power and the
PA amplifier also switched off, there is no
current drain from the battery and it should
have a shelf life of many months, if not years.
The charger circuit is shown below. As
mentioned before, this also makes a perfect
general-purpose 12V SLA battery float charger.
Power for the charger circuit comes from
a 16V 1.5A AC plugpack which feeds diodes
D4-D9 to produce two DC supplies. The main
supply comes from diodes D4-D6 and the
siliconchip.com.au
You’ll find the complete parts list for the 12V SLA Battery
Float Charger on page 62.
4700µF capacitor. The capacitor is necessary
to ensure that the battery is charged with DC
that is free from ripple. Any ripple would be
heard in the amplifier’s output.
3-terminal regulator REG1 sets the maximum battery charge voltage to 13.8V. It
operates as follows. The voltage between
its output and adjust (ADJ) pin is fixed at
1.25V and this voltage is applied across the
120Ω resistor (neglecting the small current
drawn by the ADJ pin). The resulting 10mA
through the 120Ω resistor flows through the
1kΩ resistor and series 500Ω trimpot VR7
to provide a voltage across them, effectively
jacking up the regulator voltage. Trimpot VR7
is adjusted for an output of 13.8V.
The 10µF capacitor connected to ADJ
terminal of REG1 should be omitted, if used
with the PortaPal.
When power to the charger is switched
off, the battery could be drained back via the
resistors across REG1. To stop that, we added
the relay circuit, to disconnect the battery from
the charger if no mains power is present.
Diodes D8 & D9, in conjunction with
diodes D4 & D6, produce a separate supply
from the 16VAC plugpack. This is filtered
with a 470µF capacitor and then fed through
a 220Ω resistor so that the relay is driven
with 12V. The 4700µF capacitor across the
relay coil delays the relay switch-on until the
4700µF capacitor for REG1 is fully charged.
Without this delay, the initial switch-on of
the charger would cause a loud hum in the
loudspeaker until the 4700µF capacitor for
REG1 was fully charged.
LED4 provides power ON indication.
Current limiting
The 12V SLA float charger is assembled on
a PC board measuring 133 x 66mm, coded
01103034. It has a single-sided heatsink for
the regulator (REG1) measuring 84 x 24 x
28mm (Altronics H-0668 or equivalent). The
component overlay is shown above.
Once you have checked the board for
obvious defects such as open-circuit tracks,
shorts and undrilled holes, install the small
components such as diodes and resistors
first. Watch the polarity of the diodes. That
done, install the two transistors, 500Ω trimpot, the electrolytic capacitors and the relay.
Again, watch the polarity of the electrolytics.
When mounting the 1Ω 5W wirewound
resistor, make sure there is about 1mm clearance between the resistor body and the PC
board. This improves cooling for the resistor.
The two high brightness LEDs are mounted in right-angle PC mounts (Altronics
A 1Ω 5W wirewound resistor is used
to monitor the charging current. The voltage developed across it is monitored by
transistor Q2. When the voltage across the
1Ω resistor reaches 1V, corresponding to
a charging current of 1A, the base voltage
of Q2 reaches about 0.5V and it begins to
conduct, pulling the ADJ pin of REG1 lower
to reduce the output voltage of REG1. This
limits the charging current to 1A.
Transistor Q3 also monitors the voltage
across the 1Ω resistor. Q3 turns on whenever the resistor voltage is above about 0.5V
to drive LED3, the charging indicator. So
provided the charging current is more than
about 500mA, LED3 will be alight.
Once the battery voltage reaches 13.8V,
the charging current drops to zero and the
battery is effectively “on float”.
siliconchip.com.au
Charger board assembly
H-1543 or equivalent). These enable the
LEDs to mate precisely with the control
panel of the amplifier.
The 3-terminal REG1 is mounted on
the heatsink with its leads bent, inserted
and soldered into the PC board holes.
The heatsink and regulator tab are then
secured to the PC board with two M3 x
10mm screws. Nuts and star washers are
used on the underside of the PC board.
Four spade lugs are inserted and soldered into the PC board for the input and
output connections. The positive spade
lug output near the relay should be marked
with red paint or nail polish, to ensure
correct connection to the battery.
Testing
Before you can test the charger board,
you will need to wire up the 16VAC
plugpack which comes with bare 3-wire
cable, one lead of which is intended to
be earthed.
The cable is wired to a 3-pin DIN plug.
The earth wire must go to the centre pin
of the DIN plug while the other two wires
go to the remaining pins. You will then
need to temporarily wire up a DIN socket
with the two AC wires going to pins 1 & 2
(not the centre pin) of the socket. These
wires then should be fitted with spade
connectors to fit the spade lug inputs on
the charger board.
Switch on the plugpack and the charger LED should light and possibly the
charging LED will also light depending
on battery charge. That done, disconnect
the battery and then set the trimpot for an
output of 13.8V, using a digital multimeter.
SC
The charger is now ready to go.
March 2003 67
By JULIAN EDGAR
Little Dynamite
Subwoofer
Build your own compact subwoofer – ideal
for use in a car or home unit
S
UBWOOFERS ARE NOW almost universal in any car system that attempts to produce
quality music. They’re also prevalent
in home theatre systems and also make
a great upgrade for a compact sound
system that needs a bit more punch.
The subwoofer described here is
dead-easy to make and gives excellent
performance, considering its compact
size and low cost.
And if you think that it’s really a
68 Silicon Chip
bit too limited in power handling
and low-down frequency response,
stay tuned – we’ve got another more
complex, higher-power design coming
soon. But honestly, unless you want
to make a social statement to sidewalk
pedestrians or your neighbours, this
subwoofer will be more than adequate
for most music!
The design
We’d been considering doing a sub-
woofer project for some time – and in
fact went as far as designing a bandpass model using a 10-inch driver.
However, by the time we’d priced the
particle board and added in carpet,
glue, terminals and a grille, the cost
was around $130 for the enclosure
alone. What’s more, it would have
taken quite some effort to build.
It was about this time that Jaycar Electronics released a range of
sub-woofer enclosures, all pre-built
www.siliconchip.com.au
Main Features
•
•
•
•
•
Small enclosure
125 watts power handling
Excellent in-car response
Competent in-room response
Easy to build & low cost
and finished with carpet and loudspeaker terminals. Their boxes start
at just $59.50, so we made a radical
change to our plans. The bandpass
design was scrapped and we set about
designing a traditional ported design
instead.
A ported enclosure is one of the
oldest box types around (see “Ports
Enclosure Size & Other Design Considerations”). However, the design
of this type of enclosure has been
revolutionised in recent times with
the development of loudspeaker design computer software. Rather than
building a box and then laboriously
testing it in many different configurations, computer software now allows
the virtual construction of dozens of
different enclosures.
In addition, good subwoofer design
software (like the Bass
Box package
that we used) makes various suggestions during the design process. However, if you want to aim for an optimal
trade-off in terms of size, response,
sensitivity and power handling, such
a design process can still take many
hours to complete.
The first step in the design can be
either the selection of the driver or
the enclosure. In our case, we did a
The driver used in the Little Dynamite subwoofer is 10 inches (25.4cm) in
diameter, is rated at 125W RMS and uses a voice coil 50mm in diameter. It
costs $99 and is available from Jaycar.
bit of both. First, the enclosure – the
new pre-built subwoofer boxes come
in 25, 35 and 45-litre nominal interior
volumes (we’ve written “nominal” for
good reasons which we’ll come back
to later) and the hole for the driver is
already cut. This means that if you
want to use a 10-inch driver, then the
25-litre box is the only one to go for
(the 35-litre box is precut for a 12-inch
driver, while the 45-litre box is cut for
a 15-inch driver).
Note that the boxes are available in
both sealed and ported designs.
We leaned towards a 10-inch driver
as in general terms they’re cheaper
than larger sizes and can usually be
fitted into a smaller box, which again
has a cost advantage.
Choosing the subwoofer
So with the 25-litre box the chosen
BassBox: Loudspeaker Design Software
The BassBox software package is
available in two forms – BassBox Lite
and the BassBox Pro professional version. The Lite version is quite sufficient
for any speaker design work that most
people will want to carry out and is
the package that was used to design
this subwoofer.
In addition to being able to model the performance of bass-reflex
(ported) speaker enclosure designs,
this software can also model sealed
and passive radiator boxes and a
range of bandpass designs. The Lite
version comprises just a single CD
www.siliconchip.com.au
and the Help and background explanations are all available on-screen.
In fact, this information is very good
indeed – with some study, there’s
enough information for even a beginner to start designing sophisticated
speaker enclosures.
And if you have a background in
audio, the flexibility and detail of the
program will be even more useful.
BassBox Lite is available in Australia for $165 from ME Technologies
at www.me-au.com and also from
Harris Technologies at http://www.
ht-audio.com
March 2003 69
The “step” in the inner surface of the
port that would otherwise be formed
between the flared ports and the
plastic pipe is smoothed away using a
half-round file and sandpaper.
The port is formed from two flared speaker vents (available from Jaycar) joined
by a length of 65mm-diameter plastic pipe.
we’d like is sensitivity – with a sound
pressure level (SPL) of 88.2dB at 1
Watt 1 metre, it needs to have both
an enclosure design which is efficient
and a power amplifier with at least 100
watts RMS behind it.
Port size
The completed port – the two flared ends reduce turbulence so that there are
no problems with port noise. Make sure that you don’t glue the ends on at this
stage, though – otherwise you’ll never get the assembly into the box!
enclosure, which speaker would be
suitable for it? Keeping it in the Jaycar
family, we opted for the CS-2274, a
10-inch “titanium” finish driver with
125W RMS power handling, an X-max
(maximum cone movement) of 9mm,
a voice coil diameter of 50mm and a
70 Silicon Chip
resonant frequency of 33Hz.
What these specs add up to is a
competent driver that should be able
to produce good bass in the right
enclosure without breaking the bank
(the driver retails for just $99). The
only spec that isn’t quite as good as
While free speaker design software
is available on the web, we’ve not
seen any program that comes close to
BassBox – so it makes sense to pay the
necessary dollars if you want this kind
of package. One area that we were very
conscious of when software modelling
the design was the behaviour of the
air within the port. Typically, ports
are made too small in diameter – it’s
easy that way because then they can be
made shorter for the same box tuned
frequency.
However, small ports give rise to
high air velocities, which in turn causes port noise or “chuffing”. Bass-Box
can predict maximum port velocities
and recommend minimum port diameters to eliminate this problem.
However, after looking at the modelled
behaviour of a system using the prebuilt ported enclosures (the 25-litre
box comes with one 50mm ID port),
we decided to buy a sealed box and
then cut a hole for a port of our own
making.
So what does the final design look
like? First, the Jaycar “25-litre” box is
actually 23 litres – an important difference when it comes to the design.
Second, the volume taken up by both
the driver and the port need to be
subtracted from the available internal
volume (BassBox does both of these
things automatically if the right data
is entered). In addition, the effect of
www.siliconchip.com.au
Ports, Enclosure Size & Other Design Considerations
A speaker’s role in life is to create
sound waves and it does this by moving its cone back and forth in response
to electrical signals. When it pushes
forward, higher air pressure is created
in front of the cone; conversely, when
it moves back, lower air pressure is
the result.
If a bare woofer is sat on the bench
and driven by a bass signal, the pressure waves find their way around the
edge of the frame and partially cancel
each other out. A fundamental task of
a loudspeaker enclosure is to prevent
this wave cancellation and its adverse
effect on bass response. A sealed
enclosure, for example, dissipates the
energy from the back of the cone into
the box (and/or the box filling). However, because these pressure waves
are being wasted, the efficiency of a
sealed enclosure is not as high as for
a ported enclosure.
In a ported enclosure, radiation
from the back of the cone is used to
reinforce the pressure waves being
generated by the front of the cone.
This is achieved by using a tunedlength port or vent, which has the
effect of altering the phase of the
waves emanating from the rear of
the speaker. Put your hand near the
port used in this type of design and
you’ll notice that as the woofer cone
moves forward, so does the air in the
port – the pressure waves from the
back of the cone are now reinforcing
those coming from the front.
However, if the port isn’t just the
right length and dia
meter, the response of the speaker can be all
“wrong”. For example, in this design,
we used a port 63mm in diameter and
360mm long. But what if the port had
been only 150mm long?
the acrylic speaker fill also needs to
be taken into account (confus
ingly,
the fill expands the volume that the
driver sees).
In the end, we had 19.5 litres available and chose to use a port 63mm in
diameter and 360mm long. This gives
a box tuned frequency of 33Hz. Note
that the tuned frequency in a ported
design is often close to the speaker’s
resonant frequency (in this case, it is
identical).
www.siliconchip.com.au
Fig.1: the red curve show the in-car response of the subwoofer using a
360mm-long port, while the yellow curve plots the predicted response if the
port is reduced to just 150mm long.
Fig.2: the green curve here shows the effect of dropping the enclosure volume
to 12 litres and using a 75mm-diameter port that’s just 100mm long.
Fig.1 shows the changed response
– the red line is the in-car performance
of the subwoofer as described in this
article, while the yellow line shows the
predicted response with the shorter
port. As shown, with the shorter port,
the bass falls away more quickly and
is also “peakier”. (Actually, the selected driver is quite tolerant of design
changes – with some speakers, the
results of such a port mismatch would
be much worse!)
The speaker enclosure volume is
Modelled in a car environment, the
response is effectively strong down to
15Hz, while in a room the -3dB point is
at 38Hz. The modelled maximum port
velocity is only 23 metres/second at
125W input power and 22Hz which –
not coincidentally – are also the exact
conditions where the cone reaches its
maximum excursion.
To avoid any possibility of port noise
in this long vent, both ends of the vent
are flared. This is achieved by using
also a vital part of the design. In the
case of the response curve indicated by the green line in Fig.2, we’ve
dropped the enclosure volume to
12 litres and used a short, fat port –
75mm in diameter and 100mm long.
The resulting in-car response is very
peaky at 100Hz.
As a result, this type of enclosure
design that would give “one-note”
bass, a problem often found in ported
loudspeakers enclosures that are not
well designed.
two Jaycar CX-2688 flared speaker
vents, joined with 65mm-dia
meter
plastic pipe. The two vents slip tightly
into the pipe, allowing the easy construction of a double-ended flared port.
Building It
If you have available an electric
jigsaw, some hand tools and a tube
of general purpose building adhesive
(eg, water clean-up Liquid Nails),
building the complete subwoofer will
March 2003 71
Parts List
1 10-inch Response Subwoofer;
Jaycar Cat. CS-2274
1 25-litre sealed subwoofer enclosure; Jaycar Cat. CS-2520
1 acrylic speaker damping material; Jaycar Cat. AX-3690
1 10-inch protective grille; Jaycar
Cat.AX-3522
2 flared speaker ports; Jaycar
Cat. CX-2688
1 500mm (approx.) length
65mm-dia. plastic pipe
1 short length heavy-duty speaker wire
1 tube building adhesive (eg,
Liquid Nails)
8 speaker attachment screws
The hole for the port is marked on one side of the enclosure, towards the back
of the woofer. This 85mm-diameter food tin was an ideal size for marking out
the hole which was the cut out using a jigsaw.
take you nearly no time at all – in fact
an hour, tops!
The first step is to remove the sharp
inside edge of the flared speaker vents;
ie, at the end opposite the flare. This
is done to eliminate any sharp steps
between the flared vents and the plastic pipe when they are joined together.
You can use a round or half-round file
for this job, finishing off with some
fine sandpaper.
If you don’t have any sandpaper
handy, a stainless steel kitchen scourer
works quite well on the soft plastic.
With these edges smoothed, cut the
plastic pipe to the right length so that
when both flared ends are pushed
firmly into it, the total port length is
360mm. Don’t be tempted to glue both
flared ports to the plastic pipe at this
stage – you still need to fit the port
into the enclosure!
Once the port has been assembled,
spray some black paint inside it to cov-
Drill a hole just inside the marked area for the port cutout to allow the insertion
of the electric jigsaw blade.
72 Silicon Chip
er any scratches that you have made
and to hide the white plastic.
The next step is to cut the hole for
it in the side of the speaker box. An
85mm hole is ideal – we drew the
cutting line with the help of a can of
food that conveniently had the right
diameter. The port must be placed at
the magnet end of the speaker to give
sufficient clearance, with the hole cut
in an end wall. Before marking the
hole, consider the placement of the
terminal strip and how you intend
positioning the box in its final home,
as these might have a bearing on where
you want the port to be.
The hole should be cut so that the
edge of the flare ends up about 20mm
in from the edges of the box. This
causes the other end of the port to sit
with its flared outer edge against the
inner walls of the box, allowing it to
be further held in place with some
dobs of adhesive. For environments
where the subwoofer will be subjected
to lots of shaking, use an additional
internal fastening to hold the port
tube in place – for example a bracket
made from aluminium strip wrapped
around the port and then attached to
the inner panel of the box with short
woodscrews.
The flared port can now be assembled within the box. If you push the
ends on after you’ve applied a smear
of adhesive to the pipe, they will be
held in place firmly. The flared end
that sits flush on the surface of the
box needs to be thoroughly sealed
from behind using Liquid Nails or a
www.siliconchip.com.au
silicone sealant. Make sure that you
give the sealant time to set!
Next, the acrylic speaker damping
material can be cut to size and stuck to
the inner walls of the box. We suggest
350 grams/square metre material (Jaycar AX-3690) but any similar material
is fine – eg, acrylic quilt wadding. Be
careful that you don’t block the port
– in fact it is wise to be quite sparing
in your use of the material around the
port entrance.
Next solder some heavy duty speaker cable to the box terminals and attach
the other ends to the screw terminals
on the loudspeaker. Make sure that
the positive terminal on the box is
con
nected to the positive terminal
of the loudspeaker and similarly for
the negative terminals! The woofer
can then be slipped into its precut
hole and the positions marked for its
mounting screws.
That done, remove the speaker and
drill small diameter pilot holes for the
screws. Clean away any shavings, then
reinstall the driver and fasten it into
place using eight coarse-thread MDF
screws. Here’s an important note: the
carpet will compress as you tighten the
screws, so go right around the speaker
at least three times, tightening them
each time.
You’ll note that we’ve left off the
protective grille at this stage. Instead,
it’s time to do some testing.
A jigsaw will make quick work of the port hole. The rim of the flared port
covers the edge of the hole so don’t worry if you don’t cut a perfect circle.
Testing
two reasons for this buzz. First, at high
output levels, the interior of the car
was getting excited – ie, bits of trim
inside the car were resonating. And
second, we were driving the 150 watts/
channel amplifier so hard that it was
going into distortion.
The latter is pretty important to
avoid – while this is a rugged speaker
with cone movement well controlled
down to about 22Hz, start pumping
up the SPL and you might find that
The first step is easy – apply a 1.5V
battery across the terminals and make
sure that when the positive and negative battery terminals are applied to
the positive and negative subwoofer
terminals respectively, the woofer
cone moves forward. If it moves
backwards, open up the enclosure
and swap the wiring connections at
the speaker!
The next step is to connect the
subwoofer to an amplifier. Begin by
driving the unit quite gently. Moisten
a finger and move it around the edge
of the driver, to check for any air
leaks past the frame. Now do the same
around the edge of the port – there will
be air movement within the port itself
but there shouldn’t be any around the
edge of the flare.
Next, listen carefully for buzzes,
rattles and whistles. During the
prototype’s development, we had a
buzz that we chased and chased and
chased. It turned out that there were
The flared speaker port inserted through the hole. The striped background is
the rug on which the box is sitting while the work is being done – unlike an
untrimmed box, this one needs to have its finish protected during the build
process.
www.siliconchip.com.au
you’re working the amplifier harder
than you thought. And remember:
more speakers get destroyed by pushing the amplifier into distortion than
ever get damaged by exceeding the
speaker’s limits!
If everything seems fine at low
volume, wind up the wick a bit more.
Naturally, during this test procedure,
you should disconnect all the other
speakers, so that you’re just listening
to the subwoofer. It won’t sound won-
March 2003 73
This is the inside view – the plastic pipe is slid over the external flared port after which the second flared port
is added at the other end.
derful (no subwoofer does on its own)
but it will allow you to easily identify
any problems.
As stated earlier, because of its relatively low sensitivity, this subwoofer
isn’t going to deliver ear-splitting SPLs
from modest amplifiers. However,
if you have 100-125W available, it
should be capable of delivering lots
of low-end bass.
If all is well, you can now reconnect
the other speakers and then balance
the system for the bass response that
you want.
Finishing
Acrylic filling is glued to the walls of the enclosure, making sure that the port
entrance remains clear. The port is held in place by sealant/glue applied at each
end. If the subwoofer is going to be subjected to lots of movement, add an extra
bracket to secure the port tube in place.
74 Silicon Chip
The final step is to attach the protective speaker grille. To do this, you’ll
have to take the driver out again so that
you can place the “T” nuts on the back
of the baffle. While the speaker is out,
check that the port is still rigidly held
in place by its glue and/or brackets
and that none of the acrylic speaker
filling has moved around. You should
especially check that the port entrance
has remained clear.
It’s then just a matter of completing
the assembly and enjoying the fruits
SC
of your labours!
www.siliconchip.com.au
110mm
NEAR HALF PRICE SOLAR PANELS
$199
2W 315 X 162 X 19 ... $29 (SP2)
4W 315 X 315 X19... $59 (SP4)
14W 315 X 925 X19... 199 (SP14)
N
28mm
I
A
G
R
BA $33
77mm
$29
All of our panels are
amorphous, aluminium
framed, backed
and water-proof.
COOL NEW ITEM HEATER / COOLER
This new cooler / heater assembly includes a 90mm fan,
heat-sink, 65deg. thermal cut-out switch (used when
heating), spacer block and a 50W Peltier device. Just cut a
hole in your ESKI or insulated cooler box & fit an aluminum
plate or heat-sink (not supplied) to this assembly to turn
your ESKI into a fridge for the car or boat. requires 12VDC
SWITCHING SOLAR REGULATOR KIT:
This easy to assemble kit is designed to efficiently charge batteries from solar cells. It has Special intro price of only $33 (pelt1).
charge / discharge indicator LEDs. Kit contains PCB plus all on-board components. KIT NEW PRODUCT
PRICE: (K008B) $15
BARGAIN
12VAC POND PUMP
10 LED LAMP KIT:
Why spend a small fortune on
This kit uses 10 Ultra-bright LEDs (equivalent to around 6W
a new water feature when you
incandescent) with far less current drain than normal incandescent
ST 0
could build your own. Requires
U
J
light bulbs but with a brighter, whiter light. It uses a constant current
12VAC (We have a suitable
4.5
plug-pack available for
$1
circuit & draws 120mA. (This means is your get many more hours of
just$6). Pumps a head of up
light with a smaller & cheaper battery & solar cell. Kit contains a
to 500mm at 300L p/h via a
small PCB, 10 White Ultra-bright LEDS & all on-board components.
8mm outlet. (PP1)
Easy to assemble. 10 LED Kit $20 (K199_10)
(NEW) 433.92MHz MINI
12V / 7AH SEALED LEAD ACID BATTERY:
TRANSMITTER
Fresh stock batteries, now is the time to pick up a real bargain, 2.6kg,
AND RECEIVER MODULE:
150 x 65 x 92mm.(PB6) $25 each
NEAR
ACTUAL
HOW ABOUT A COMPLETE SOLAR LIGHTING SYSTEM FOR YOUR CAMP,
SIZE
CARAVAN OR WEEKENDER: There are 4 main components to this system, 2W Solar Pre-built superhetrodyne surface mount transmitter
module which is saw resonator locked at 433.92MHz.
Panel, Switching Solar Regulator kit, Battery and 2 X 10 LED Lamp Kits. This combination Operates from 3 ~ 12V DC and has 7 connections. When
of solar panel, charger and battery will power 1 of the LED lamp kits for over 7hrs with only use in conjunction with RX434, the pair can give a range
of up to 2km when the transmitter is powered by 12V DC.
5hrs of sunlight. Central Australia receives around 10 hrs per day. (SL2W): $99
Dimensions: 20mm (L) x 8mm (W). (Same diameter as a
UPGRADE TO A BIGGER PANEL!!! For just $25 more.
5c coin). Click here for data: (TX434) $11
You can upgrade from a 2W to a 4W panel in your Solar Lighting System . (SL4W) total (NEW) 433.92MHz MINI RECEIVER MODULE:
price.$124
(RX434) $21(
"LOOK NEW KIT"
LOTS OF AMAZING OPTICAL BARGAINS
***LOOK***LOOK***LOOK***
STEREO FM TRANSMITTER KIT
HIGH POWERED LEDS, LASERS
WARNING!!!
This professionally designed stereo transmitter
These magnets are so strong they are
POINTERS & LASER DIODES
uses a special IC that produces the MPX
AMAZINGLY BRIGHT MINI KEY-CHAIN LED
TORCHES, ALL ARE AROUND 8 TO 10 Cd.
WHITE ...$7 RED ...$4 BLUE ...$6
GREEN ...$6
All of the following are up to 10cD, 20mA max and
narrow angle.
dangerous!!!
signal only plus a stable transmitter
new neodymium rare earth magnets from 20 that uses discrete components:
$22.50 for a complete kit inc. case. (k094b)
cents each
Dew to popular request we have introduced some
smaller magnets to our range similar to those used in
magnetic therapy etc. 20 X 10mm$6.00... 10 X
Bulk Red LED SPECIAL
5mm$1.20... 10 X 3 mm$0.70... 7 X 3mm $0.55... 7 X
20 or more red LEDs for $0.60ea
2.5mm $0.45... 3 X 2mm $0.25...
10cD White...$2.00 ea Red...80c Yellow ...70c 3 X 1.5mm$0.20.
Green...$2.10 Blue...$2.20 UV LED's ..$1.60
Less 10% for 10 or more of any mix
Money Detector Pens
These use a very bright UV LED. Check Australian
currency for counterfeits by looking at the hidden UV (USED) BWD 603B FUNCTION GENERATOR MINIprinting on them. ...$4.50
LAB: This single unit includes a 0.1Hz to 1MHz Function
Extra AG13 batteries ...15c as used in the key-chains, Generator, a power differential amplifier with an ad3 req. Extra AG3 batteries...6c as used in pens, 4 req. justable gain of 1 to 100 <at> 1A out, a bi-polar power
supply / power amp with a voltage range of -15 to +15V <at>
Don't forget our bargain OPTO PACK...K147
1A, a +voltage power supply with a voltage range of 1 to
Pack inc. total of 103 opto semiconductors. 91 various 15V <at> 1A, a negative voltage power supply with an
colours & types of visible LED's, 1 x IR LED, 6 x Photo- voltage range of 1 to 15V <at> 1A, a 0 to 200V + power
transistors, 2 x high speed PIN photodiodes, 1 x HC312 IR supply & a 12.6V center tapped 50Hz AC voltage source
Receiver Module. KIT PRICE: (K147) $10 each pack
(6.3V 0 6.3V). In excellent condition: (ZC0211) $250
PICAXE-08 CHIPS... See Silicon Chip FEB 03
The PICAXE processors use a R.I.S.C (Reduced
Instruction Set Controller ) system, and
are easy to program. It is said to be like a
Basic Stamp clone in single chip. $5.50ea.
Lots of info available on the Internet. We
may have other PICAXE chips in
the future.
MINI FM TRANSMITTER KIT K189
This kit is easy to build with
just a few simple steps to
complete and test it.
It measures only 32mm X
13mm X 24mm and draws
only 5.8mA from it's 1.5V
LR44 button cell (supplied).
Kit comes complete with a
metal case, battery, prebuilt PCB and double sided tape
for quick and easy installation.
(K189) $39
NEW 6mm MINI ELECTRET MICROPHONE
Recover this mini electret microphone and other
parts from this NOKIA 5110 / 6110 personal hands
free kit (or use them as is). snaps apart in just
seconds. Don't pay $3 or more for just one, Our
price... 6 for $2
FERRITE CORES
Ideal for switch mode power supplies
and experimenters. 15mm X 29mm
X 9mm. Sorry we don't have any
bobbins to suit. 4 pairs for $2 (FC1)
Our famous wiring looms are still available
for just $1 ea
Suppliers of kits and surplus electronics to hobbyists, experimenters, industry & professionals.
Orders: Ph ( 02 ) 9584 3563, Fax 9584 3561, sales<at>oatleyelectronics.com, PO Box 89 Oatley NSW 2223
major credit cards accepted, Post & Pack typically $7 Prices subject to change without notice ACN 068 740 081 ABN18068 740 081
www.oatleyelectronics.com
SC_MAR_03
product review
Canon’s
image stabilised
binoculars
W
hether you like to watch whales, birds or sport,
a pair of binoculars is a great accessory. How
ever, they do have disadvantages. Most
binoculars are not light and the longer you use them, the
more tired you become.
And the more tired you become, the harder it is to hold
them steady and this problem is worse if you are using
magnification of x10 or more.
The only practical solution to both of these related
problems is to use a tripod. This relieves the
strain on your arms and holds the
binoculars absolutely steady
but most people would
find a tripod just another piece of gear that
they don’t want to
carry.
Canon’s solution to the problem is to produce binoculars
with inbuilt image stabilisation.
They compensate
for the inevitable
“shakes” you get
when using binoculars
and they are much more
pleasant to use.
We reviewed two of the Canon
range: the 15x50IS model which has
50mm objective lenses and x15 magnification and the 10x30IS which has
30mm lenses and x10 magnification.
Cutting straight to the chase, the
x15 model is the one of most interest,
since that degree of magnification
is almost impossible to use without
having a tripod. In fact, unless you are
experienced in using binoculars, it is
difficult to imagine how difficult such a seemingly modest
degree of magnification is.
76 Silicon Chip
This cutaway diagram shows the disposition of the major
components in the Canon image stabilised binoculars. Note
the compact Porro prisms which erect the inverted image
for normal viewing.
www.siliconchip.com.au
by Leo Simpson
The Canon 10x30IS binoculars (above) are much more
compact and half the weight of the higher power 15x50IS
model (left) but use the same image stabilisation system.
In effect, even
if you are pretty steady
on your feet, and
you brace yourself against a wall, table or whatever, you
will find the object you are looking at shakes around so
much that you quickly get frustrated with the attempt – it
is that hard.
But switch on the Image Stabilisation and all of a sudden the images snap into a rock steady condition and you
can view in much more comfort. You can pan around
and even view from a boat or moving car. In short, Image
Stabilisation makes viewing at x15 magnification entirely
practical and satisfying.
It is even more effective on the smaller x10 binoculars
and their much lighter mass means that you can view for
much longer before arm fatigue gets you.
flat glass connected by flexible bellows which can expand
and contract as required. The bellows are filled with a
silicone-based oil which has a high refractive index (presumably the same as that of the glass plates). One glass is
driven to compensate for pitch movement while the other
is driven to compensate for yaw movement.
The drive system is a yoke (coil) and magnet system for
both X and Y axes with Hall Effect sensors for feedback
while the movement sensing is done by accelerometers.
While there is a separate vari-angle prism for the left and
right eye optical paths, both prisms are linked together and
driven by the X and Y axes yoke/magnet systems.
We include a cut-away diagram showing the major internal features of the Canon binoculars. Notice that they
do include Porro prisms to erect the image but the overall
So how do they work?
shape of the Canons might suggest that they are using the
more compact roof prism construction. Another diagram
Broadly speaking, there are two methods of image
shows more detail of the image stabilising mechanism,
stabilisation. The first is widely used in camcorders and
including the yoke and magnet drive systems.
involves using only part of the image produced by the CCD
By way of explanation, all binoculars (except opera glasssensor. In effect, the internal computer looks for the steady
es) require prisms to erect the inverted virtual image for
part of the image from the sensor and continually “edits
normal viewing. Most
out” the shaking borders,
conventional binoculeaving a much steadier cenSpecifications
lars use Porro prisms
tral image to be displayed as
15 x 50
10 x 30
which give a Z-path
the video output.
Magnification
15
10
to the light beams –
The second method, used
this accounts for the
in these Canon binoculars
Objective lens diameter
50mm
30mm
big offset between
and in some high-priced
Real field of view
4.5°
6°
the objective lenses
telephoto lenses, is to staField of view at 1000m
79m
105m
and the eye-pieces. In
bilise the image itself by
binoculars with roof
Focus
range
6m
to
infinity
4m-infinity
passing it through a prism
prisms, the light travwhich can be continually
Exit pupil diameter
3.3mm
3mm
els in a straight line
moved to compensate for
Eye relief
15mm
14.5mm
and therefore they
the shaking of the binoculars
Dimensions
152
x
193
x
81mm
127
x
150
x
70mm
are generally more
themselves.
compact.
Canon uses what they call
Weight (excl batteries)
1200g
630g
The Canon Image
a “vari-angle prism” which
Battery life (alkaline)
2.5 hours
4 hours
Stabilisation are obconsists of two pieces of
www.siliconchip.com.au
March 2003 77
The drive system for the vari-angle
prisms uses yoke coils and magnets
to compensate for pitch and yaw of
the binocular body. Motion sensing is
performed by solid-state accelerometers.
viously using a different arrangement of Porro prisms
because the two objective lenses are solidly fixed within
the binocular body while the two eye-pieces can be rotated
to change the inter-ocular distance. The result is that the
Canons are quite a bit more compact than conventional
roof prism binoculars.
Another interesting feature is the inclusion of a doublet
field flattener in the eye-piece lenses. This reduces the
curvature of the field and avoids the usual distortion at
the periphery of the image. It also gives long “eye relief”
which means that people with glasses can comfortably use
the binoculars.
The Canon 15x50IS binoculars are powered by two
AA cells which last for up to 2.5 hours continuous use
for alkalines or Nicad cells (at 25°C). If you use lithium
batteries, this can be extended out to 8 hours continuous
use. Alkaline battery life for the smaller 10x30IS model
is 4 hours.
Using them
Referring to the Canon 15x50IS model first, they are
comfortable to hold and easy to focus. However, people
with small hands will find them difficult to grasp, even
though they do have a non-slip rubber skin. And at over
1kg, most users will find that they are tiring to use for more
than a few minutes at a time. They do have a tripod socket,
so a monopod would be very worthwhile if you need to
use them for extended periods.
78 Silicon Chip
Since I am interested in astronomy, I was keen to check
how they would perform when viewing planets and stars.
Unless you have a tripod/chair setup, the common way to
use binoculars when viewing the sky is to lie down on the
ground or on a reclining chair. But even this method can
be very tiring and the star images tend to dance about all
over the place after a few minutes.
With the Canon 15x50IS, it is a much more satisfying
experience. Stars and planets can be held steady and you
can easily achieve optimum focus. There is some flare and
signs of chromatic aberration on star images but generally
this is at a low level; after all, they are not really intended
for astronomical use.
By contrast with the Canon 15x50IS, the 10x30IS are
much more comfortable to grasp and hold, due to their
much smaller size and weight (630g). However, with a
magnification of x10 and good optics, they are very usable
and compare very well with conventional 10x50 binoculars.
We like them a lot.
Pricing
This is great technology but there is no getting away from
the fact that these Canon Image Stabilisation binoculars are
expensive. The recommended retail price for the 15x50IS
model is $2499 including GST while the 10x30IS sells for
$1249 including GST.
For further information, contact Canon at 1800 816 001
SC
or www.canon.com.au
www.siliconchip.com.au
MORE FUN WITH THE PICAXE – PART 2
A
Shop
Shop
A Shop
Door
Minder
.
.
.
Door
Minder
.
.
.
Door Minder . . .
with
attitude!
with
with attitude!
attitude!
by Stan Swan
L
ast month (Feb 2003) we introduced the innovative PICAXE08 IC and a simple application, a
flashing LED, all built into a solderless
“PICNIK box”.
If you didn’t see last month’s issue,
it will pay you to get a copy and read
it because some of the concepts might
be a little different to what you’re used
to, such as BASIC Stamps, etc.
By now, readers should have familiarised themselves with basic operations and the commands high, low,
pause and goto.
PICAXE instructions are much the
same as used in classic BASIC programming. There are a lot of BASIC
texts around (no pun intended!), such
as Greg Perry’s “QBASIC by Example”
(QUE 1993) or from the Parallax BASIC
Stamp Programming Manuals. There’s
also a huge amount of information
available on the ’net.
Given that you don’t need to be a
programming guru to use PICAXE
instructions, initial applications
here will be educational rather than
exotic.
PICAXEs have only enough RAM
for about 40 program lines, so there’s
some incentive to code efficiently! Our
simple application here uses about
half the memory available, so room
remains for your own tweaking.
buzzer sound long enough to be noticed; sometimes the buzzer “locks
on” when it is actuated to behave more
like an alarm.
This month’s circuit acts as a “shop
door minder with attitude”, since it not
only sounds a buzzer when the light
beam is broken but also provides a
simple “traffic” indication by flashing
a LED at an increasingly faster rate
with each event.
Now that could be handy – if you
don’t happen to own a shop and wish
to count customers, this project could,
at a glance, tell you the number of
times your cat door is opened! Don’t
own a cat? You’ll think of something
to count!
The flash rate increases are not linear but counts per minute can be noted
and related to visitor numbers via a
simple lookup table. A further LED
could even be added (pin 0?) to indicate a count of 10 had been reached,
at which point the main counter could
drop back to a slow rate again. By this
means, up to perhaps 30 events can be
quite reliably “read off ”.
If a PC remains attached, the exact
count (to 255 events) can be just read
off using debug. Mmm – 255 cats visited last night ? What IS in your pantry!
The circuit
Aside from the core parts mentioned
last month, just a few extra resistors are
Shop Door Minder
A shop door minder usually consists
of a light source which creates a beam,
a light sensor which detects that beam
and a buzzer circuit which sounds
when the beam is broken. Sometimes
there is a delay circuit to make the
www.siliconchip.com.au
If you don’t happen to own a shop, you can always find something else to count
– just remember to take into account four legs and a tail . . .
March 2003 79
A “debug” screen shot. This
reveals just how useful such PC
feedback is – you can note all the
variables ticking away nicely!
used, one of which is a light dependent
resistor, or LDR.
Your setup values may vary depending on your application but 100Ω in
the voltage divider, plus similar as a
LED dropping resistor, should do.
For initial trials a small bright light
(perhaps a white LED) is also needed. More practical setups could see
the light path extended with lenses,
shrouds or even a mirror. Only small
currents pass along the wires so leads
to the LDR and light can be conveniently placed. Things really depend
on the stray background light seen by
the LDR, although this can be allowed
for to some extent by altering readadc
threshold values.
For a longer light path the lens
from a pocket torch may help to
concentrate the beam, while the LDR
could even be recessed into the torch
If this looks somewhat similar to last month’s project, it just might be! The
basic differences are the LED and LDR which provide an “analog” input to
the PICAXE. The PICAXE programming does the rest.
base to give shading from stray light.
The program’s readadc threshold value, initially 160, may need lowering
to suit of course.
To prevent false triggering from
shadows, reflections or visitor legs (or
tails!), a small delay, perhaps “pause
500”, may be needed in the readadc
loop. Obviously this delay may cause
the unit to become unresponsive if
events occur too rapidly.
Having a light on to hold the alarm
off may be wasteful of battery power
of course. Perhaps you could modify
the program so that darkness holds
the sensor off and room light alone
is enough to trigger things – much as
would occur when a medicine cupboard door was opened.
The point of these PICAXE circuits
is to stimulate your interest, to see
what can be done very cheaply and
to help you come up with your own
variations. Of course, we will help you
along the way with more applications
to keep those creative juices flowing!
Incidentally, if you come up with
a scathingly brilliant PICAXE application that you would like to share
with the world (and perhaps feature on
these pages), please feel free to email
me – s.t.swan<at>massey.ac.nz
Where to get the PICAXE-08
Currently there is no Australian
distributor. Order direct from the UK
agents (Revolution Education) on line
shop www.techsupplies.co.uk – they
are very prompt.
There are a few differences between the photo above and the Protoboard
layout at right. Follow the layout and you shouldn’t go wrong!
80 Silicon Chip
www.siliconchip.com.au
PICAXE-08 COMMANDS USED THIS MONTH
readadc
PICAXEs have a valuable Analog to Digital Conversion
(ADC) feature, which in theory converts “real world” analog
voltages into 256 steps of digital equivalents. There’s an
unavoidable deadspot on the upper range however and
the resulting 160 divisions are treated in blocks of 10, so
only 16 discrete values are available! Although obviously
unsuitable for MP3 encoding or the like, this is quite enough
for many simple applications.
In fact our circuit here uses ADC at just a yes/no level
in response to an LDR’s (light dependent resistor) resistance changes with illumination, so not even all these 16
divisions matter. Pin 1 ADC input needs a voltage rather
than a resistance, so the old voltage divider trick is rustled
up, involving two series resistors connected between +ve
and ground with their midpoint delivering a variable voltage
as the LDR value changes. The readadc command finally
assigns this ADC value to a program variable at pin 1. Alter
the readadc threshold value or resistor (here 160Ω and
100Ω) to fine tune with your LDR and light path.
Incidentally, LDRs typically have a resistance of 1 MΩ
+ in the dark and around 1 kΩ in bright light, with a quite
rapid response as illumination alters.
sound
With the suggested piezo speaker, sounds can be
directly produced from output pins using the sound
command. Most piezos are optimised for high frequencies (typically 4kHz) so fidelity may be poor for other
tones. It’s worth experimenting with your setup, since a
more distinctive “fruity” alert may be produced with two
sounds together.
debug
If the serial programming cable remains connected
during PICAXE runs, program data values can be usefully
monitored on the PC screen. Up to 16 “byte” variables
(b0 - b15) can have tabs kept on them.
pulseout
This provides timed duration output pulses (to microseconds) at specified pins, and effectively packages up
HIGH, PAUSE and LOW in one efficient command .
for - next (step)
Creates a repeating loop that executes program lines
between the FOR and NEXT statements as it increments.
The optional STEP value defaults to 1 unless specified.
maths operations
Variables to a maximum value of 255 (at which point they
roll over) can be added, subtracted, multiplied or divided,
with left to right solving but with only integer solutions. Hex
and binary are also handled but brackets are disallowed
and fractional portions of results are discarded (although
clever techniques can off set this).
BASIC PROGRAM LISTING (This can also be downloaded from http://picaxe.orconhosting.net.nz/adcprog.bas)
‘ Demo program for March 2003 SilChip PICAXE-08 article Ver1.0 20th Jan 2003
‘ Best assembled & tested with solderless “PICNIK” box as detailed SilChip Feb03
‘ Refer http://picaxe.orcon.net.nz for background info & potential of PICAXE-08
‘ Extra parts = LDR, White LED, Red LED, 2 x 100 Ohm, 1 x 330 Ohm, piezo speaker
‘ LDR & illuminating light can be moved apart- maybe use lenses & light guides?
‘ New commands here = sound, readadc, debug, pulsout, for-next & simple maths.
‘ Ref.PICAXE prog.editor .pdf help files,& BASIC Stamp manuals etc for insights
‘
via Stan SWAN (MU<at>W, New Zealand) => s.t.swan<at>massey.ac.nz <=
‘——————————————————————————————————
‘ Byte variables
b0 = LDR “resistance value” b1 = event counter
‘
b2 = pulse delay in msec
b3 = sound loop
‘ Strictly only the LHS code below is needed. Remarks (‘) can be ignored
‘——————————————————————————————————
sound 4,(100,10,80,10)
‘initial dual sounds to inform that powered up
ldrdemo:
readadc 1,b0
debug b0
if b0 <160 then beeper
b2 = 250/b1
if b2 =0 then ldrdemo
pulsout 2,1000
pause b2:pause b2:pause b2
goto ldrdemo
‘ LDR resistance monitoring routine
‘ read LDR low resolution value via voltage divider
‘ show variable LDR value(s) to attached PC screen
‘ warbling alert tones when LDR shaded
‘ produce delay value.NB max variable value is 255
‘ prevents LED flash when not yet triggered
‘ pulse LED pin 2 for 1000x10 microsec = 10millisec
‘ more events give decreasing delay between pulses
‘ continually loop unless LDR shaded
beeper:
for b3= 1 to 3
sound 4,(100,20,80,20)
next b3
b1=b1+1
goto ldrdemo
‘ piezo speaker 2 tone sound routine
‘ loop to sound tones 3 times
‘ repeating dual tones each 20 msec
‘ sound loop increment
‘ event counter increment
‘ return to monitoring routine
www.siliconchip.com.au
Some more references . . .
1. “QBASIC by Example”
Greg M Perry (Que Books 1993)
2. Parallax Inc, the BASIC Stamp originators, have free resource downloads (.PDF files) via their web site
(www.parallax.com)
BASIC Stamp Users Programming
Manual Version 2.
(351 pages, 3.2MB download)
BASIC Stamp 1 Application Notes
Ver 1.9 (126 pages, 1MB download).
3. “The Art of Electronics”
Horowitz and Hill (Cambridge University Press 1989).
Chapter 9 offers good ADC insights.
NEXT MONTH:
The Picaxe by now you should know,
Gives sounds & makes LEDs glow,
But it also does more,
Next ’tis a PWM chore,
And all for very small dough!
SC
March 2003 81
SuperCharger
Addendum
Did you build the SuperCharger described
in the November & December 2002 issues
of SILICON CHIP? If so, you need this add-on
to ensure correct operation under all
conditions.
By PETER SMITH
During finalisation of the firmware
for this project, we were surprised to
discover that under certain conditions,
the 111kHz PWM section of the circuit
became unstable. In fact, with high cell
counts, high charge currents and low
input voltages, such as could be the
case in an automotive environment,
the switching frequency halved to
about 50kHz.
When low cell counts (1-2 cells)
and low charge currents are combined, a lower operating frequency is
of no consequence. However, at high
power levels, it will cause inductor
L1 to overheat and damage the PC
board and surrounding components.
It may also eventually cause MOSFET
Q2 to fail.
Quite frankly, this problem initially
had us stumped. The data sheets for
the LTC1325 suggest that our design
operates within specifications. In addition, the LTC1325 has no provision for
external compensation, which is often
employed in switchmode circuits to
maintain loop stability.
After much head scratching, we
devised a simple little circuit that
modifies the feedback signal applied
to pin 11 of the LTC1325. The purpose
of the circuit is to both provide ramp
compensation as well as to alter the
shape of the waveform applied to
this pin, so ensuring that the internal
integrator is “reset” every cycle.
As this project includes a number
of surface-mounted components, it
would be very difficult for readers
that have already built the project to
transfer these to another, modified PC
board. Therefore, rather than modifying the main PC board layout, we have
designed a small “add-on” board that
carries the necessary components.
Construction & checking
The add-on PC board simply attaches to one of the existing corner mounting points (see Fig.4) and connects to
the main PC board via four wires. The
overlay diagram for the add-on board
is shown in Fig.2 and the wiring diagram in Fig.3.
Fig.1: the add-on circuit uses just two transistors plus a few resistors
and capacitors. Its job is to modify the sense signal to the LTC1325 IC.
82 Silicon Chip
SuperCharger Add-on
Parts List
1 PC board coded 14111024,
31.2mm x 16.1mm
2 2N3904 transistors (Q1, Q2)
Capacitors
1 1µF 50V monolithic ceramic
(C1)
1 100nF (0.1µF) 63V MKT polyester (C3)
1 1nF (.001µF) 63V MKT polyester (C2)
Resistors (0.25W 1%)
1 15kΩ (R3)
1 10kΩ (R2)
1 470Ω (R4)
1 100Ω (R5)
1 10Ω (R1)
Miscellaneous
1 M3 x 10mm tapped spacer
1 M3 x 16mm pan head screw
70mm 4-way ribbon cable
Fig.2: the extra parts all fit
on this small PC board.
www.siliconchip.com.au
Fig.3: four leads stripped from a length of ribbon cable are used to connect the
add-on board to the main PC board of the SuperCharger. The four connection
points should be present on all manufactured boards.
If you have access to an oscilloscope, you can check that the addon board is doing its job. Ideally,
you should run your tests with six
1800mAh NiMH (or 1200mAh or
higher NiCd) cells on the rapid charge
setting. If you’re providing power via
the DC input, be sure that the supply
voltage doesn’t dip below 13.8V, otherwise the charge will terminate with
error code 11.
Start the charge and measure the
switching frequency on the drain
of MOSFET Q2; it should be about
100kHz. Continue to monitor the
frequency as the cell voltage rises
and the charge nears completion; the
frequency should always be around
the 100kHz mark.
Note that switching is not continuous for the first five minutes of
operation, as the charger is in “Soft
Start” mode. You’ll also note than
switching occurs in one-second bursts
with short (about 50ms) rest periods;
this is completely normal.
We should also point out that inductor L1 normally runs quite hot to the
touch, even at 100kHz. It is rated for a
40°C temperature rise above ambient
and at higher power levels will get
close to this value.
Ventilation
Although we didn’t make mention
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Fig.4: the add-on board is mounted
at one end of the main PC board as
shown in this diagram.
of it in the original construction
details, one of the reasons we chose
the specified case is because it has
generous ventilation slots.
If you decide to use a case other
than the one shown in the parts list,
then you’ll almost certainly need to
add some ventilation holes. In particular, drill several holes directly
below the inductor (L1) and the diode
bridge (DB1). Match these with more
holes on or near the top of the case
to make the most of the “chimney”
effect.
Rubber feet
Regardless of which case you use, be
sure to fit rubber feet on the underside
to allow air to flow up through the
SC
assembly.
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THAT’S RIGHT! Buy a 1- or 2-year
subscription to SILICON CHIP magazine
and we’ll mail you a free copy of “Electronics TestBench”, just to say thanks.
Contact: Silicon Chip Publications,
PO Box 139, Collaroy, NSW 2097
Phone Orders: (02) 9979 5644
Fax Orders: (02) 9979 6503
Email Orders: office<at>silchip.com.au
March 2003 83
VINTAGE RADIO
By RODNEY CHAMPNESS, VK3UG
Antennas & earthing systems
for crystal sets
Crystal sets and other low-sensitivity receivers
require good aerial and earth systems to give
their best performance. Here’s what you can do
to improve broadcast band AM radio reception
on these simple receivers.
Due to the improved sensitivity of
receivers after the mid-1930s and the
increasing power of AM broadcast
transmitters, large antennas quickly
become redundant as far as the general public was concerned. In fact,
most people now don’t like having
to extend the whip antenna on a
portable FM receiver to get the best
reception.
Unfortunately, the use of metallic/
bituminous insulation paper in the
walls of many modern homes now
acts as an RF shield, reducing the level
of the radio signal penetration. For
this reason, good reception on older,
less-sensitive receivers may require an
outside antenna and this is particularly so for crystal sets.
In the November 1998, December
1998 and January 1999 is
sues, we
looked at various methods for improving AM radio reception and reducing
interference. This article is not intended to supersede those articles but to
give enthusiasts a few ideas on suitable
antenna systems that will achieve good
results in most situations.
The early days
Experimental broadcasting commenced not long after the end of World
War I. Amateurs produced programs
on a nightly or weekly basis and the
general populace was keen to listen to
these new transmissions.
The output power of these early
experimental stations varied considerably but most were well under 100
watts. The radiating systems connected to the transmitters were also quite
varied, some consisting simply of an
inverted “L” receiving type antenna
fed against an earth that consisted of
a metre or so of pipe driven into damp
soil. Others were more ostentatious,
being something like the smaller
broadcasting masts that can be seen
around the countryside today.
Official broadcasting commenced in
Australia in late 1923 (2SB/2BL) and
the power of the stations varied from
around 50W to 5kW (5000 watts). In
most cases, the power ratings were
for input power, not output power, so
a 5kW transmitter may have had an
output power of just 1.5kW.
Fig.1: the earth stake or pipe should be driven a metre or so
into the ground, with a small depression around the top. This
depression is filled with water at regular intervals, to keep
the soil around the earth stake moist. Fig.2 (right) shows how
to install an effective earth through concrete.
84 Silicon Chip
www.siliconchip.com.au
“Egg” insulators will be required at
the support points if you use bare
wire for the antenna. Alternatively,
you can use polyproylene pipe.
and earth system for low sensitivity
receivers such as crystal sets.
Getting a good earth
Fig.3: a “clothesline” type aerial frame can be used in back yards where
space is a problem. It’s not as effective as a long, straight run of wire but is
still quite good.
Gradually the standards for broadcast transmitting stations became
more uniform. The commercial class
B stations that came into being were
rated at an output of 2kW in the country and 5kW watts in the city, whilst
Class A (ABC) stations used upwards
of 10kW (today, the ABC stations run
upwards of 50kW in many instances.)
At the same time, strategically placed
low-power stations (50-500W) were
used to provide signals in areas where
the high power stations were relatively
ineffective (such stations are still used
today).
Because of the low power of early
transmitting stations and the general
insensitivity of receivers up until the
mid-1930s, large outside antennas
were mandatory for reasonable reception during that period. Many different
antenna types were used in an attempt
to get the best performance possible.
Some were a lot of work to install but
may not have worked any better than
much simpler structures. But they did
look commanding!
A receiver using a large earth (mat)
system (much like transmitting installations use) will work a little better
than a receiver using the common,
relatively inefficient receiver earths.
In practice, transmitting stations go
www.siliconchip.com.au
for the most effi
cient antenna and
earth system that is economically
feasible. That’s because they need to
provide the strongest signal possible
for receivers that are using inefficient
antenna systems, eg, a few metres of
wire.
The reasoning here is that it is
better to have efficient transmitting
installations so that receivers can get
by with convenient low-cost antenna
systems.
Having said that, it is still necessary
to use a relatively efficient antenna
The earth lead can be attached to the
pipe using a metal hose clamp. Wrap
the wire around the clamp several
times to ensure it makes good contact.
In an ideal situation, a 1-metre
length of pipe or metal stake driven
into the ground in a damp location
will provide an adequate earth for
most receivers. This earth should be
as close as practical to the receiver
so that the minimum length of con
necting wire is used back to the earth
terminal of the receiver. This also
helps to reduce the effect of mainsborne interference, particularly in
more sensitive receivers.
In my case, I have often used 19mm
galvanised water pipes as the earth
stake. However, because I am an amateur radio operator, I need a better
earth than a 1-metre length of pipe can
provide. For this reason, I commonly
use up to three 2-metre lengths of pipe
driven into the ground, leaving about
300mm above ground level. The tops
of the pipes/stakes are quite close and
are bonded together but their bottom
ends are quite some distance apart, as
the pipes are driven into the ground
at angles to each other.
In order for the earth to be effective,
the whole length of the pipe/stake and
the earth around it needs to be kept
moist (not just the top few centimetres
of the soil). This is achieved by making
a small depression around the top of
the pipe(s) and a bucket of water then
poured into this depression at regular
intervals.
A single pipe driven at least a metre
into the ground is usually quite adequate as an earth for radio receivers
(providing it is in moist ground). Fig.1
shows the details.
The wire (preferably multi-strand)
March 2003 85
This simple antenna tuner uses a multi-tapped coil wound on a cylindrical
former. It’s tuned by sliding the ferrite rod inside the former and by changing
the coil tapping.
Fig.4: this diagram shows how to add a dial drive system to the antenna tuner
shown in the photo at the top of this page. You can scrounge the parts from a
junk radio or buy them from an electronics retailer.
going from the earth to the receiver
earth terminal should be 1-2.5mm2
in cross-sectional area (equivalent to
the average earth wire on the mains).
It doesn’t have to be insulated but insulated wire is easier to handle if it is
likely to be close to any other metal,
including the Sisalation type material
used in the walls of modern homes.
Don’t let a bare wire brush up against
any metallic object as noise and “crackles” (interference) may be induced into
the wire and thus into the receiver.
Unfortunately, it’s not practical to
solder the end of the wire directly to
the earth stake or pipe. That’s because
the metal mass is too great to allow it to
get to the melting point of solder when
using a soldering iron that’s suitable
for electronic work.
Instead, an electrician’s earth clamp
or a screw type hose clamp can be
used to hold the earth wire firmly
against the pipe. The wire should be
wrapped through the clamp a few
86 Silicon Chip
times to make sure it will not move
once clamped. Before doing this
though, clean the pipe using sandpaper to get rid of any oxidation at the
contact point. Once the earth wire
has been clamped to the pipe, the assembly should be painted to stop any
corrosion.
Alternative methods
Not everyone has an ideal location
to install earth stakes and so other
methods of obtaining an earth must
be used. For example, many premises
today have large areas of concrete
which this can make things quite
difficult.
Drilling a hole through the concrete
to accept an earth pipe is one possibility but make sure that you check
the locations of water, drainage, gas,
telephone and electrical lines before
doing this. You will need a large
masonry bit and a hammer drill for
the job.
Begin by drilling a series of holes
around the circumference of a circle
large enough to accept a 100mm-diameter plastic stormpipe. A cold
chisel and heavy hammer will be
required to break up the pieces but
even so, it usually isn’t easy getting
the pieces out.
In fact, it’s probably a good idea to
send the family out for the day so that
they don’t learn any new words!
The storm piping should protrude
about 200mm above the ground and
can be fixed into position using cement
or silicone sealant. This stormpipe is
then filled with water to keep the earth
pipe moist - see Fig.2.
If metal water pipes are used, it’s
possible to clamp the earth wire onto
these and obtain quite good earthing.
However, earthing to a water pipe
does raise the possibility of circulating
currents through the pipe system and
anything connected to the mains earth.
To overcome any chance of electrolysis (which can cause corrosion of
the pipes), it’s a good idea to install a
capacitor in series with the earth wire
near the radio. This can range in value
from .001µF up to 0.1µF - preferably
one of each in parallel. Note that this is
necessary only if the receiver is mains
operated and has its chassis earthed
through the mains.
Gas pipes are not to be used under
any circumstances.
For people in units, an earth via the
mains may be the only viable alternative. Any piece of electrical equipment
that has a 3-core power lead and has
its metal frame earthed can be used
as the “earth”. All you have to do is
attach a wire from the metal frame
of the earthed appliance to the earth
terminal of the set.
This provides a reasonable earth
but make sure the appliance has a
relatively short lead to the power
point.
Do not attempt to obtain a mains
earth in any other way - the possibility of making a fatal mistake is much
too great.
A good antenna
The old saying of “the higher and
longer the better” when referring to
antennas for crystal sets and other
low-performance sets is still true
today.
If you live out on a farm, erecting
an effective antenna is relatively easy.
A good standby is the old standard
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Provided it’s fitted with a good aerial and earth, this simple “two circuit” crystal
set is quite a good performer.
inverted “L” antenna some 30 metres
long across the top and 13 metres
high. “Higher and longer” will capture
even more signal and possibly also
lightning, so lightning arresters are
desirable on antennas of this size.
Most of us do not have the wide
open spaces to install this type of
broadcast receiving antenna so we
have do the best we can with the
available space. It’s also necessary to
comply with local council bylaws.
In most cases, any antenna that’s
erected will be a compromise between
performance and available space. The
installation must also be safe and must
not be an eyesore to neighbours or
others living on the premises.
It is possible to run an antenna (flat
top section) around the yard, with
one end attached to the chimney (if
the house has one) or to a TV antenna
mast – see Fig.3. Specialist TV antenna
supply shops, such as Lacey’s Australwww.siliconchip.com.au
ia in Frankston, Victoria, have a wide
variety of TV antenna mounting masts,
brackets and other items which can be
used for this job.
A number of the advertisers in
SILICON CHIP, such as Jay
car, Dick
Smith Electronics and Altronics, also
have a range of TV-antenna bits and
pieces. Check out their catalogs and
you should have little difficulty in
choosing the necessary parts to make
your antenna effective, safe and aesthetically pleasing.
Commonly, in the past where there
was little space for an antenna, it was
made to look something like a clothes
line, as shown in Fig.3. This is an effective way of getting a considerable
length of wire up into the air in a confined space. It may not be as effective
as a long, straight run of wire but it is
still quite good.
Regrettably, some people are not
allowed to have any outside antenna
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March 2003 87
Above: this miniature 2-circuit crystal set uses all ferritecored coils and is quite a good performer. Its circuit is
shown in Fig.5, for those who want to make their own.
At left is an old ferrite-cored tuned circuit crystal set,
complete with wooden case and a set of high-impedance
headphones.
system at all (perhaps for “aesthetic”
reasons). However, all is not lost as
outside antenna systems can be erected at night by suitable mechanisms
and pulled down after use. Some
people have even disguised an antenna
mast as a flag pole. A little ingenuity
is sometimes needed here.
If that doesn’t suit, an antenna in
the ceiling space can be much better
than nothing at all. There are a few
provisos, however – the house must
have a gable roof and the roofing must
not be metallic. Nor should there
be any metallic foil underneath the
tiles (metal acts as a shield for radio
signals).
To build a ceiling space antenna, install several folded lengths of insulated
wire near the peak of the roof and bring
one end down to where the receiver is
located. Thirty metres of wire should
give reasonable performance. It cer-
tainly won’t be up to the standard of
a high outside antenna but it’s much
better than nothing.
Antenna wire
An outside antenna lead can be
made from single or multi-strand
copper or galvanised iron wire. It can
be insulated or bare but it must not
too thin, otherwise it will break in
the wind or if a bird flies into it. I use
common gardening tie wire (available
at hardware stores) of around 16 gauge
– it’s cheap and solders quite well.
If you use bare wire, it is necessary
to also use egg insulators (available
from stores selling electric fence components and major electronic stores)
at the points where it is supported,.
Alternatively, the polyproylene pipe
used for garden
ing systems can be
used in some situations.
The down lead to the receiver from
Fig.5: this simple “2-circuit” crystal set uses coils wound on ferrite rods.
The constructional details are in the text.
88 Silicon Chip
the antenna should be run using insulated multi-strand cable, such as one
half of twin-flex cable used on small
electrical appliances.
Any joins in the antenna wire must
be soldered. If they are not soldered,
scratchy noises will be heard in the
radio or variations in level will occur
after only a few weeks. That’s because
the wires oxidise and intermittent
good and bad contact between the
joined wires will occur.
Finally, to alleviate any stress on the
lead in, it should be attached to the
antenna proper in a manner similar
to that shown in one of the photos.
Optimising performance
A normal AM broadcast antenna is
an aperiodic device, meaning that it is
not tuned to any particular frequency.
By contrast, if it were tuned to a specific frequency, the amount of signal
picked up by the antenna would rise
noticeably.
In other words, tuning the antenna
system can greatly improve its performance and this can be done quite
easily.
Fig.4 shows the details. First, obtain 150mm of 20mm-diameter PVC
electrical conduit and wind about 180
turns of 0.5mm (24B&S) enamelled
copper wire onto it, with tappings
made at every 20 turns. The tappings
can be made by inserting a match under a turn, winding some more turns
on and then sliding the match further
along as you progress, keeping each
tapping point proud of the coil.
www.siliconchip.com.au
One end of the finished coil is then
wired in series with the antenna lead,
while a “fly lead” fitted with a small
alligator clip is soldered to the other
end. This fly lead allows sections of
the coil to be shorted out if necessary.
Alternatively, either the antenna
or the receiver aerial lead can be
terminated on one of the terminals
along the coils, as shown in one of the
photographs.
Once the coil is in place, it is then
time to trial the tuner by sliding a
180mm-long (not critical) x 9mm-diameter ferrite rod into the coil and
observing the results. Try differ
ent
coil tappings until you get the nest
performance.
Once the correct tapping is found
for the coil, altering the position of
the ferrite rod in the coil will peak
the perfor
mance on any particular
station. Note that this coil will also
work with the average domestic receiver, although its performance at
the low-frequency end of the dial can
be unpredictable due to the way some
aerial coils were designed. More turns
may be required on the peaking coil
in some cases.
Initially, the rough and ready method described above will give good
results. However, it can all be made
much tidier. Excess turns on the coil
can be removed if desired and a more
sophisticated method of adjusting the
position of the ferrite rod inside the
coil can be constructed – see Fig.4.
Jaycar Electronics can supply suitable ferrite rods (Cat. LF-1012) for an
antenna tuner but loopstick antenna
rods scrounged from defunct sets
are also quite suitable - just remove
the windings from the rod. If the rod
has been broken and you have all the
pieces, it is often possible to effectively
rejoin them provided the breaks are
clean and the two sides of a break
mate without gaps. You can use Aral
dite or some other similar adhesive
for this job.
Crystals sets & antenna tuners
On my own crystal sets, I can
receive just one station without the
antenna tuner. By contrast, if the
antenna tuner is used, I can receive
four stations, including a Melbourne
station some 150km away! The tuning
is also much sharper than normal
and the aerial tapping is quite low
on the coil.
Initially, however, I found that the
www.siliconchip.com.au
Photo Gallery: Tecnico
Aristocrat Model 651 Radio
Built in 1946, the Tecnico Aristocrat featured a distinctive “mottled”
bakelite cabinet. This cabinet was completely different to those used
by other manufacturers, some of which were still using cabinets from
their pre-war models.
The set pictured here is a 5-valve dual-wave radio with a 20cm (8-inch)
permanent magnet speaker (loudspeakers of this size were rarely seen
in mantel or table radio). A colourful badge and dial glass complete the
attractive presentation.
The set was advertised as being available in various colours and
Tecnico achieved this by painting over the bakelite. This particular
unit has been fully restored by its owner, Maxwell Johnson, Kingston,
Tasmania. (Photo: Ross Johnson).
crystal sets were not performing at all
well, barely receiving the local station
just 20km away. I tested the germanium diodes using the diode tester
function on my digital multimeter
and found that the forward voltage
drop had increased from 0.2V to 0.8V,
while the reverse voltage conduction
point was down to 3V. The diodes were
consigned to the rubbish bin and new
ones installed.
The crystal sets in the photos belong
to members of the local vintage radio
club. Two are very nice looking sets
and perform quite well. The small one
in the jiffy box (130 x 65 x 40mm) is
extremely interesting as it uses ferrite
cores on all coils and a tapped antenna
loading coil (possibly to resonate the
antenna).
I have not heard this latter set in
operation but have heard others claim
that it is a particularly good performer.
As a result, its circuit is enclosed for
readers who may care to experiment
- see Fig.5.
All the coils are wound using 0.5mm
(approx.) enamelled copper wire. L1
and L2 are wound on the same piece
of ferrite rod but at opposite ends of
the rod which is around 50mm long.
Coils L3 and L4 are wound on two
ferrite rods, each around 30mm long.
The amount of coupling between
L2 and L3/L4 is open to experimentation – around 50mm apart should
give good results.
Summary
A high and long antenna coupled
with a good earth system is important if worthwhile results are to be
obtained from crystal sets and other
low-performance sets. In some cases, it may also be necessary to tune
the antenna to the frequency of the
desired radio station (ie, by using an
antenna tuner).
As for crystal sets, the best performing types are those using two tuned
circuits – as in Fig.5. Also, it’s necessary to use a germanium diode for the
detector and a pair of high-impedance
SC
(2-4kΩ) headphones.
March 2003 89
ASK SILICON CHIP
Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line
and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097; or
send an email to silchip<at>siliconchip.com.au
Upgrading the
SC480 amplifier
doubt whether there would be any
improvement.
With respect to your new SC480
amplifier modules, how can these be
connected together or modified to produce 100W. Also, would there be any
sound quality advantage in changing
the 1µF bipolar input series capacitor
to a metallised polypropylene type,
as used in crossovers? (P. R., St Lucia,
Qld).
• We actually went through the same
process way back in February 1988
when we upgraded our original December 1987 design.
The process basically involves
increasing the main supply rails to
±50V, changing the output transistors
to MJ15003/MJ15004 (TO-3 types), Q1Q3 to BC556, Q4 & Q5 to BF469 and
Q6 to BF470 and increasing the power
supply capacitor values and voltage
ratings to 63V. Naturally a much bigger
transformer is also required.
We think a better and more cost-effective approach would be to build the
Plastic Power amplifier from the April
1996 issue. We can supply the issue
for $8.80 including postage.
You could change the input capacitor to an MKT type but we very much
Reproducing old wireless sound
Tacho fix for
positive chassis car
I’ve recently built the Digital
Tacho from the April 2000 issue
and have successfully connected
it to my 1988 Ford Laser in which
it appears to work exactly as described. My problem is that I actually want to connect it to my 1956
Austin A30 which has a positive
chassis.
When I connect the coil to the
tachometer, the numbers displayed
are wrong. At idle it shows ‘000’
when it is clearly doing about 1000
RPM. The numbers do increase with
engine revs but don’t appear to be
90 Silicon Chip
I am a member of an amateur theatre
company and we are planning to stage
a comedy “Lend me a Tenor”, set in
Chicago in 1934. There are three or
four occasions where the performer is
supposed to be listening to the radio,
to works by Giuseppe Verdi.
For effect, I’d like to try to approximate the type of reception people may
have experienced at that time. I don’t
want the audience to ‘hear’ excerpts
from Verdi’s operas via a CD and a late
1990’s full-range, 500W public address
system in the theatre – that would be
too much of an anachronism.
Clearly the radio systems were AM
(ie, limited bandwidth and noisy).
In addition to this, receivers were
low-powered but with (relatively)
efficient loudspeakers. The efficiency
came at a cost, though – that of frequency response.
What would the frequency response
of the recovered audio have been like?
What sort of signal-to-noise ratio might
have been expected? I have some ideas
stable (that is, they go up and down
by several hundred while the engine
is at a constant speed).
Do I need to do something clever to make this tachometer work
correctly with this car? The documentation makes no mention of
cars with a positive earth but I can’t
imagine that I’m the first person to
try this kit with that type of car. (R.
S., via email).
• We do not think that the positive chassis is causing the erratic
display reading. Try changing the
0.056µF capacitor at the ignition
coil input to something smaller;
0.022µF (22nF) may be small
enough for correct operation.
about the answers to these questions
but am seeking your expert opinion.
I plan to record the relevant tracks,
modify the ‘system’ frequency response to something similar to that
you nominate and add appropriate
amounts of both white and impulse
noise. Hopefully the end product will
have a big degree of realism. (R. W.,
via email).
• Your question is quite complex.
In reality, the AM broadcast system
was, and still is, capable of very good
results. Today, with the very best receivers, you can get a result which is
practically indistinguishable (for most
listeners) from FM stereo.
In years past, the main limitations
were the radio receivers but even the
best of those could sound quite good.
In reality, the frequency response from
a good console radio (wireless!) could
be up to 5kHz while the signal-tonoise ratio would be around 40-50dB
or thereabouts. A good portion of the
background noise would be hum. If
you can get to a radio museum, have
a listen for yourself.
However, there were other limitations on the sound quality. If it was a
live broadcast you need to imitate the
effects of the microphones and their
placement (they did not have multiple microphones and multi-channel
mixers). Some of the old style microphones are still available and sort
after by groups who want to produce
that “sound”.
If the performance was recorded it
would generally have been on 16-inch
78RPM transcription discs and these
also had a sound all their own because
the magnetic pickups of the day had
quite a lumpy frequency response
and recording equalisations were not
standardised. The old turntables also
suffered from wow and flutter and
there was considerable surface noise,
clicks and pops, etc.
To do what you ask and keep things
simple, we would be inclined just to
limit the frequency response to no
more than 5kHz and just see what it
www.siliconchip.com.au
sounds like. The illusion would be
helped by having the listener actually
switch on a radio. You could also take
it further and have the sound broadcast
via an AM transmitter and then mike
the sound from the radio (oops, we
mean wireless!)
We described a low power AM
transmitter in the January 1993 issue
of SILICON CHIP.
Compatibility between
DVD players and TVs
We have a Philips 26CE1991 tele
vision which when connected directly
to the DVD player pulsates its picture
light and dark. The DVD player has
been checked by two service centres
and seems to be OK.
Philips tell me that this TV is too
old and we should simply buy a new
one. Are there any mods that are
known to overcome this problem or
are we stuck with the Macrovision
protection breaking through? (E. G.,
via email).
• Our information is that this set was
made in 1991 by Sampo for Philips and
was designed before Macrovision. It
is therefore unable to cope with large
chunks of signal being removed.
The only real cure is to build the
Doctor Video kit from the April 2001
issue of SILICON CHIP. This copes well
with Macrovision 1 & 2 but not Macrovision 3. Otherwise, the only solution
is to buy a new set.
Upgrading the
24V/20A speed control
I recently assembled the 10A Motor
Speed Control from the June 1997
issue of SILICON CHIP. I did it to teach
myself more about DC motor control,
as I have started working in the electric
forklift servicing field. I increased the
controller’s capacity to 20A by installing the second Mosfet, as suggested in
the kit instructions.
I would like to know how to modify
the kit to handle the much higher currents found in DC electric machines,
from a hundred and possibly up to
1000A and also to handle higher
voltages such as 24V and 48V. Would
it simply be a matter of continuing to
add Mosfets in parallel or would the
circuit driving the Mosfets need to be
upgraded as well.
Also the instructions said the controller could be used to run 12V motors
www.siliconchip.com.au
How to control radiator cooling fans
I’m intending to use one of your
temperature switch kits to control a
pair of cooling fans which I want to
fit to an old car of mine. My ig-norance of thermocouples prompts me
to seek advice from you before I embark on this project. Jaycar’s advert
and photograph shows an already
constructed kit which is supplied
with an NTC thermocouple which,
by observation of the picture, is the
small component on one corner of
the board looking like a tag tantalum
capacitor.
Would it be possible to use a
wire type “K” thermocouple as I
reckon it would need to be able to
sense the temperature of the engine
cooling water direct. I think I could
in 24V systems. Could it be used to run
24V components in 48V machines? (P.
R., Jerrambombera, NSW).
• While in theory, the specified Mosfets could run with supply voltages up
to 48V, it would not be good practice.
We would prefer to see much more rugged Mosfets used, with much higher
voltage ratings.
Running at much higher currents is
also possible in theory but in practice,
the very small PC board would mean
that the extra Mosfets would have to
be off-board and that can lead to problems; you need individual gate drive
to each Mosfet and heavy conductors
for the commoned Drain and Source
connections.
In addition to the above, the 12V
regulator feeding the TL494 has an
absolute maximum input voltage
of 35V, so you would need to add a
pre-regulator circuit to ensure that
this rating was not exceeded, if you
wanted to run the whole circuit at
48V. In summary, the practical limit
of the circuit is 24V and not a lot more
than 20A.
24V needed for Mustang A/C
I am working on the air-conditioning
for an old Ford Mustang and I need a
12V-24V step-up inverter to operate
the clutch solenoid. Can you tell me
if there is one available or if you have
encase the business end of one of
these in a metal device to protect
it from getting wet and then the
casing complete with protected
thermocouple could be installed for
immersion in the cooling water. Is
all that practical and if so, would
I need to make any alterations? (P.
W., via email).
• The kit you refer to has not been
published in SILICON CHIP. The
fact that it uses a thermistor means
that it will not have the necessary
high gain circuitry to work with a
thermocouple. In fact, we would
not recommend this kit for control
of fans in a car.
We would suggest you consider
the thermostatic switch for car
radiator fans published in March
1992. We can supply this issue for
$8.80 including postage.
described a suitable circuit? (K. W.,
Nevertire, NSW).
• The only 12V-24V inverter that we
know of is a small one from Jaycar (Cat
AA-0264). This is said to double the
input voltage (from 6V to 12V or 12V
to 24V) and has a maximum output
current of 2A; we assume this is at
12V out.
This may not be enough to pull in
the solenoid but should be enough
to maintain it in the closed position
once it has operated. You may need to
connect a large electrolytic capacitor
across the output to provide the pullin current. We suggest you try a value
of at least 10,000µF at 25V or higher.
Delay for
Battery Guardian
I have a quick comment/observation about the Battery Guard
ian
published in the May 2002 issue of
SILICON CHIP. I like the solid state
and low current draw but I am having problems with it dropping out
on start-up, particularly if the load is
more than 10A or so.
Would it be possible to delay the
voltage sensing for about five seconds
so that it does not detect the initial load
droop? (J. H., via email).
• The solution is to increase the
10µF capacitor associated with ZD2 to
100µF. This will filter out the voltage
droop when a 10A load is applied.
March 2003 91
Hang problem with
mixture meter
I recently purchased and built
the Digital Fuel Mixture Meter, as
published in the September & October 2000 issues. It has a problem
in which at power-up, it will sit
for a few minutes, reading (L) for
low and no matter what input level
you put into it (0-1V), it will hang.
This problem often goes after two
minutes but may remain in a hang
state for longer.
It is not yet in a vehicle and is
being fed constant 13.5V and a constant input at 0.5V. (F. N., via email).
• This is indeed an unusual problem. It is possibly caused by pin 4 of
Zero voltage switch
for wall oven
Some 15 years ago I redesigned our
kitchen wall oven to something akin to
‘burst firing’ electronic control of the
heating elements. I used a combination
of an Analog Devices AD595 Ther
mocouple Amplifier with a ramp-driven 14-pin CA3059 zero voltage switch
IC to control a suitably-sized Triac. It
has proved to be accurate to ±1° and
quite reliable.
Recently though, the CA3059 failed
and I have not been able to locate a
replacement. Harris and then OnSemi
manufactured them but discontinued
about a year ago. I was wondering if
you could help with the name of a
supplier. (J. N., Tauranga, NZ).
• We do not know of a substitute for a
CA3059 but if you want a zero voltage
switching power control circuit, have
a look at the Heat Controller published
in the July 1998 issue. This used the
IC1 being open circuit, either within
the IC socket or where soldered to
the PC board.
Alternatively, the crystal may be
a slow starter, causing the software
to latch up as it will not be reset
properly. Try using smaller value capacitors from the crystal to
ground at pins 15 and 16. Values
ranging from 10pF to 15pF should
be suitable.
The other problem could be with
the power supply you are using.
If this supply rises slowly to 12V
at switch-on, the circuit could exhibit the problem you experience.
Try connecting the circuit to the
power supply terminals after it is
powered up.
1988 and October/November 1998.
We can supply the 1998 back issues
for $8.80 each, including postage and
the 1988 articles as photostats, again
for $8.80 each, including postage.
Braking system for
a wheelchair
readily available MOC3041 zero voltage switching Triac optocoupler.
We can supply the July 1998 issue
for $10 including airmail postage.
I am a Year 12 student starting my
Major Design Project. My project is a
wheeled walker for the disabled.
My current need is for a braking system and an easier way of going about
it. I want to create a one-off braking
system using electronics and two
motors with a simple on/off sequence
and a button on each handle to easily
apply the brakes.
What do you suggest? (D. G., via
email).
• We suggest you build a speed
control with inbuilt braking. Have a
look at the 50A speed control published in the May 2000 issue. We can
supply this issue for $8.80, including
postage.
Audio frequency power
meter wanted
Notes & Errata
I am in need of an audio frequency
power meter. I’m thinking of something that reads in dB and mV and
takes an electrical input (rather than
including a microphone). It needs to
be accurate across the audio spectrum.
While the option of a microphone
input would be nice, this is a considerably harder proposition, since
the characteristics of the microphone
would have to be compensated for and
accurate calibration would probably
require specialist equipment. (A. M.,
via email).
• We have published two AC milli
voltmeters which would suit your
application, in August/September
RIAA Preamplifier, March 2002: the
10µF across the ±15V rails should be
35V not 16V.
Smart Card PIC Programmer Interface, February 2003: the clock connection from the card socket should
go to pin 12 of the 18-pin socket, not
pin 16.
PortaPAL Portable PA Amplifier,
February and March 2003: there is a
circuit error concerning both the microphone MIC1 and MIC2 inputs. The
circuit shows two 10kΩ resistors in
parallel connecting from pin 2 to
ground whereas one of these resistors
should connect to pin 3 instead. The
SC
PC board is correct.
WARNING!
SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such
projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be
carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do
not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects
employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd
disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of
SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any
liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims
any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws.
Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade
Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable.
92 Silicon Chip
www.siliconchip.com.au
MARKET CENTRE
Cash in your surplus gear. Advertise it here in Silicon Chip.
CLASSIFIED ADVERTISING RATES
Advertising rates for this page: Classified ads: $20.00 (incl. GST) for up to 20
words plus 66 cents for each additional word. Display ads: $33.00 (incl. GST) per
column centimetre (max. 10cm). Closing date: five weeks prior to month of sale.
To run your classified ad, print it clearly in the space below or on a separate
sheet of paper, fill out the form & send it with your cheque or credit card details
to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details
to (02) 9979 6503.
Taxation Invoice ABN 49 003 205 490
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Enclosed is my cheque/money order for $__________ or please debit my
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www.siliconchip.com.au
FOR SALE
WEATHER STATIONS: Windspeed &
direction, inside temperature, outside
temperature & windchill. Records highs
& lows with time and date as they occur.
Optional rainfall and PC interface. Used
by Government Departments, farmers,
pilots, and weather enthusiasts. Other
models with barometric pressure, humidity, dew point, solar radiation, UV, leaf
wetness, etc. Just phone, fax or write for
our FREE catalogue and price list. Eco
Watch phone: (03) 9761 7040; fax: (03)
9761 7050; Unit 5, 17 Southfork Drive,
Kilsyth, Vic. 3137. ABN 63 006 399 480.
UNIVERSAL DEVICE PROGRAMMER: Low cost, high performance,
48-pin, works in DOS or Windows incl.
NT/2000. $1364. Universal EPROM
programmer $467.50. Also adaptors,
(E)EPROM, PIC, 8051 programmers,
EPROM simulator and eraser.
Dunfield C Compilers: Everything you
need to develop C and ASM software
for 68HC08, 6809, 68HC11, 68HC12,
68HC16, 8051/52, 8080/85, 8086, 8096
or AVR: $198 each. Demo disk available.
ImageCraft C Compilers: 32-bit Windows IDE and compiler. For AVR, 68HC
08, 68HC11, 68HC12, 68HC16. $385.00
Atmel Flash CPU Programmer: Handles the 89Cx051, 89C5x, 89Sxx in
both DIP and PLCC44 and some AVR’s,
most 8-pin EEPROMS. Includes socket
for serial ISP cable. $220, $11 p&p.
SOIC adaptors: 20 pin $132.00, 14 pin
$126.50, 8 pin $121.00.
Full details on web site. Credit cards
accepted.
GRANTRONICS PTY LTD, PO Box 275,
Wentworthville 2145. (02) 9896 7150 or
http://www.grantronics.com.au
SPEAKER AND HOME THEATRE
SUPPLIES. New and Secondhand
Speaker Drivers. Speaker Repairs and
Kits. Projectors and Screens. Delivery
anywhere in Australia. Melb. (03) 5986
1128; www.penhometheatre.com.au
KITS KITS AND MORE KITS! Check
’em out at www.ozitronics.com
March 2003 93
Silicon Chip
Binders
New New New
Mark22-SM
Slimline Mini FM R/C Receiver
REAL
VALUE
AT
$12.95
PLUS
P&P
These binders will protect your copies of SILICON CHIP. They feature
heavy-board covers & are made
from a dis
tinctive 2-tone green
vinyl. They hold up to 14 issues &
will look great on your bookshelf.
80mm internal width
•
•
•
•
•
6 Channels
10kHz frequency separation
Size: 55 x 23 x 20mm
Weight: 25gm
Modular Construction
Price: $A129.50 with crystal
Electronics
PO Box 580, Riverwood, NSW 2210.
Ph/Fax (02) 9533 3517
Or fax (02) 9979 6503; or ring (02)
9979 5644 & quote your credit
card number.
Use this handy form
Enclosed is my cheque/money order for
$________ or please debit my
❏
Bankcard
❏
Visa ❏ Mastercard
Card No:
_________________________________
Card Expiry Date ____/____
Signature ________________________
Name ____________________________
Address__________________________
__________________ P/code_______
94 Silicon Chip
Need prototype PC boards?
We have the solutions – we print electronics!
Four-day turnaround, less if urgent; Artwork from your own
positive or file; Through hole plating; Prompt postal service; 29
years technical experience; Inexpensive; Superb quality.
Printed Electronics, 12A Aristoc Rd,
Glen Waverley, Vic 3150.
Phone: (03) 9545 3722;
Fax: (03) 9545 3561
Call Mike Lynch and check us out!
We are the best for low cost, small runs.
For price list, write Acetronics
5/32 Seton Rd, Moorebank 2170 or email
acetronics<at>acetronics.com.au
Phone (02) 9600 6832
www.acetronics.com.au
Buy five and get them postage
free!
Silicon Chip Publications
PO Box 139
Collaroy Beach 2097
AV-COMM P/L, 24/9 Powells Rd,
Brookvale, NSW 2100.
Tel: 02 9939 4377 or 9939 4378.
Fax: 9939 4376; www.avcomm.com.au
email: youngbob<at>silvertone.com.au
Website: www.silvertone.com.au
SILICON CHIP logo printed in
gold-coloured lettering on spine
& cover
Price: $A12.95 plus $A5.50 p&p.
Available only in Australia.
Satellite TV Reception
International satellite
TV reception in your
home is now affordable.
Send for your free info
pack containing equipment catalog, satellite
lists, etc or call for appointment to view.
We can display all satellites from 76.5°
to 180°.
Microzed.com.au
PIC CHIP SPECIALIST
PO Box 634 ARMIDALE 2350 (296 North Cooke’s Rd)
Ph: (02) 6772 2777 – may time out to Mobile 0438 277 634.
Fax: (02) 6772 8987
RCS HAS MOVED to 41 Arlewis St,
Chester Hill 2162 and is now open,
with full production. Tel (02) 9738 0330;
Fax 9738 0334. rcsradio<at>cia.com.au;
www.cia.com.au/rcsradio
USB KITS: Stepper Motor Controller,
DTMF Transceiver, Thermometer, DDS
HF Generator, Compass, 4-Channel
Voltmeter, I/O Relay Card. Also available: Digital Oscilloscope, Temperature
Loggers, VHF Receivers and USB Active X (and USBDOS.exe file) to control
our kits from your application.
www.ar.com.au/~softmark
LABJACK USB DATA ACQUISITION
MODULE features 8 12-bit analog
inputs, 20 digital I/O, 2 analog outputs
and high speed counter. Free software
and ActiveX component. DAS005 Parallel Port Data Acquisition Module
features 8 12bit Analog inputs, 4 digital
I/Ps & 4 digital O/Ps. Free windows
software. FAB Programmable Logic
Controllers. Low cost, high performance. Programming software and
SCADA software free. Heaps of features.
Full details and credit card ordering
available at:
www.oceancontrols.com.au
Audio, Video, S-Video and VGA cables
distribution amps, switchers, adaptors,
price lists at:
www.questronix.com.au
FOR SALE: Moama TV and Video
Service. Suit sole trader. Servicing
TVs, videos, computer monitors, audio,
microwaves, etc. Large client base.
Established ten years. Owner can train.
Located busy tourist town - Echuca/
Moama. High growth area, low outgoings. $24,000 WIWO. Phone owner 03
5482 6047.
PCBs MADE, ONE OR MANY. Any
format, hobbyists welcome. Sesame
Electronics (02) 9586 4771.
sesame777<at>optusnet.com.au; http://
members.tripod.com/~sesame_elec
www.siliconchip.com.au
Subscribe &
Get This FREE!*
*Australia only. Offer valid only while stocks last.
Positions At Jaycar
We are often looking for enthusiastic
staff for positions in our retail stores
and head office at Silverwater in Sydney. A genuine interest in electronics
is a necessity. Phone 02 9741 8555
for current vacancies.
Relay version (SC, 7/2002) to its full
potential controlling 10 relays. Uses
PIC16F628.
See it at: www.ozitronics.com
ADD SPEECH, SONAR OR DIRECTION SENSING to your next project.
Fully contained modules. Full specs on
website www.robotparts.com.au Ph
0412 350671
KIT ASSEMBLY
THAT’S RIGHT! Buy a 1- or 2-year
subscription to SILICON CHIP magazine
and we’ll mail you a free copy of “Electronics TestBench”, just to say thanks.
Contact: Silicon Chip Publications,
PO Box 139, Collaroy, NSW 2097
Phone Orders: (02) 9979 5644
Fax Orders: (02) 9979 6503
Email Orders: office<at>silchip.com.au
Classifieds: continued from p.94
C.R.O. D/T as new $390, P/S.W.R.
meter $90, Freq. Counter $80 plus lots
more. (02) 6658 3181.
HALF RETAIL PRICE! Used Solar
Panels, Inverters, Batteries, Surplus
Components and more. See our specials pages at www.kcsolar.com.au
10-RELAY ROLLING CODE UHF
REMOTE CONTROL Expands the 4
NEVILLE WALKER KIT ASSEMBLY
& REPAIR:
• Australia wide service
• Small production runs
• Specialist “one-off” applications
Phone Neville Walker (07) 3857 2752
Email: flashdog<at>optusnet.com.au
Advertising Index
Acetronics....................................94
Altronics........................ loose insert
Av-Comm Pty Ltd.........................94
Clarke & Severn...........................55
Dick Smith Electronics........... 18-21
Eco Watch....................................93
Elan Audio....................................83
Evatco..........................................87
Grantronics..................................93
Harbuch Electronics.....................54
Instant PCBs................................94
Hy-Q International........................55
Jaycar .............................. 45-52,95
JED Microprocessors................5,55
Kalex............................................87
WANTED
Microgram Computers...................3
AVO VALVE CHARACTERISTIC
METER VCM163 and Marconi Bridge
TF2700. Must be in working order,
preferably with operating instructions.
dongmack<at>chariot.net.au
MicroZed Computers..............55,94
EARLY HI FI’S AMPLIFIERS, Speakers, Turntables, Valves, Books ; Quad,
Leak, Pye, Lowther, Ortofon, SME,
Western Electric, Altec, Marantz, McIntosh, Goodmans, Wharfedale, Tannoy,
radio and wireless. Collector/Hobbyist
will pay cash. 02 9440 1267.
johnmurt<at>highprofile.com.au
Oatley Electronics........................75
Printed Electronics...................... 94
Procopy........................................55
Quest Electronics.........................35
RCS Radio..............................55,94
RF Probes...............................55,87
Silicon Chip Binders............94,OBC
Silicon Chip Bookshop..........96,IBC
NOW
AVAILABLE
FROM
Silicon Chip TestBench.........95,IFC
Silvertone Electronics..................94
www.siliconchip.com.au
Project Reprints
Limited Back Issues
Limited One-Shots
If you’re looking for a project from ELECTRONICS AUSTRALIA, you’ll find it at SILICON CHIP! We
can now offer reprints of all projects which have appeared in Electronics Australia, EAT, Electronics
Today, ETI or Radio, TV & Hobbies. First search the EA website indexes for the project you want
and then call, fax or email us with the details and your credit card details. Reprint cost is $8.80 per
article (ie, 2-part projects cost $17.60). SILICON CHIP subscribers receive a 10% discount.
We also have limited numbers of EA back issues and special publications. Call for details!
visit www.siliconchip.com.au or www.electronicsaustralia.com.au
www.siliconchip.com.au
Soundlabs Group.........................55
Telelink Communications.............55
_________________________________
PC Boards
Printed circuit boards for SILICON
CHIP projects are made by:
RCS Radio Pty Ltd. Phone (02) 9738
0330. Fax (02) 9738 0334.
March 2003 95
REFERENCE
GREAT BOOKS FOR
ALL PRICES INCLUDE GST AND ARE
AUDIO POWER AMPLIFIER DESIGN HANDBOOK
PIC Your Personal Introductory Course
A handbook for professionals and students
from one of the world’s most respected
audio authorities. New edition is more
comprehensive than ever with a new
chapter on Class G amplifiers and
further new material on output coils,
thermal distortion, relay distortion,
ground loops, triple EF output stages and
convection cooling. 427 pages in paperback.
Concise and practical guide to getting up and
running with the PIC Microcontroller. Assumes no
prior knowledge of microcontrollers, introduces
the PIC’s capabilities through simple projects.
Ideal introduction for students, teachers, technicians and electronics enthusiasts – perfect for
use in schools and colleges. 270 pages in soft
cover.
by Douglas Self 3rd Edition 2002
89
$
by John Morton – 2nd edition 2001
NEW
NEW
NEW
NEW
46
$$
VIDEO SCRAMBLING AND DESCRAMBLING
AUDIO ELECTRONICS
If you've ever wondered how they scramble
video on cable and satellite TV, this book tells
you! Encoding/decoding systems (analog
and digital systems), encryption, even
schematics and details of several encoder
and decoder circuits for experimentation.
Intended for both the hobbyist and the
professional. 290 pages in paperback.
For anyone involved in designing, adapting and
using analog and digital audio equipment. It
covers tape recording, tuners and radio receivers,
preamplifiers, voltage amplifiers, audio power
amplifiers, compact disc technology and digital
audio, test and measurement, loudspeaker
crossover systems, power supplies and noise
reduction systems. 375 pages in soft cover.
By John Linsley Hood. First published 1995.
Second edition 1999.
FOR SATELLITE AND CABLE TV
by Graf & Sheets
2nd Edition 1998
4th
EDITION
$
70
87
$
EMC FOR PRODUCT DESIGNERS
3rd
EDITION
UNDERSTANDING TELEPHONE ELECTRONICS
By Stephen J. Bigelow. 4th edition 2001
Based mainly on the American telephone system, this book covers conventional telephone
fundamentals, including analog and digital
communication techniques. Provides basic information on the functions of each telephone
component, how dial tones are generated and
how digital transmission techniques work.
402 pages, soft cover.
103
$$
By Eugene Trundle. 3rd Edition 2001
3rd
EDITION
Eugene Trundle has written for many years in
Television magazine and his latest book is right
up to date on TV and video technology. includes
both theory and practical servicing information
and is ideal for both students and technicians.
382 pages, in paperback.
Widely regarded as the standard text on
EMC, provides all the key information needed
to meet the requirements of the EMC Directive.
Most importantly, it shows how to incorporate
EMC principles into the product design process, avoiding cost and performance penalties,
meeting the needs of specific standards and
resulting in a better overall product. 360 pages
in paperback.
63
$
By Ian Hickman. 2nd edition1999.
Essential reading for electronics designers and
students alike. It will answer nagging questions
about core analog theory and design principles
as well as offering practical design ideas. With
concise design implementations, with many of
the circuits taken from Ian Hickman’s magazine
articles. 294 pages in soft cover.
by Dogan Ibrahim. Published 2000.
by Steve Roberts. 2nd edition 2001.
Based mainly on British practice and first published in 1997, this book has much that is relevant to Australian systems as a guide to home
and small business installations. A practical
guide to installation of telephone wiring, ranging
from single extension sockets to PABX, with the
necessary tools, test equipment and materials
needed by installers. 178 pages in soft cover.
89
$$
Microcontroller Projects in C for the 8051
TELEPHONE INSTALLATION HANDBOOK
69
By Tim Williams. First published
1992. 3rd edition 2001.
ANALOG ELECTRONICS
GUIDE TO TV & VIDEO TECHNOLOGY
$
92
$
$
73
Through graded projects the author introduces the
fundamentals of microelectronics, the 8051 family,
programming in C and the use of a C
compiler. The AT89C2051 is an economical chip with re-writable memory.
Provides an interesting, enjoyable and
easily mastered alternative to more theoretical
textbooks. 178 pages
in paperback.
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Power Supply Cookbook
Analog Cct Techniques With Digital Interfacing
by T H Wilmshurst. Published 2001.
by Marty Brown. 2nd edition 2001.
An easy-to-follow, step-by-step design framework for a wide variety of power supplies. Anyone with a basic knowledge of electronics can
create a very complicated power supply design .
Magnetics, feedback loop, EMI/RFI control and
compensation design are all described in simple
language. 265 pages in paperback.
99
VIDEO & CAMCORDER
SERVICING AND TECHNOLOGY
by Steve Beeching (Published 2001)
$
69
$
$
Provides fully up-to-date coverage of the whole
range of current home video equipment, analog
and digital. Information for repair and troubleshooting, with explanations of the technology of
video equipment. 318 pages in soft cover.
69
Antenna Toolkit
by Joe Carr. 2nd edition 2001.
Together with the CD software included, the reader
will have a complete solution for constructing or using an antenna - bar the actual hardware. The software is based on the author’s Antler program, which
provides a simple Windows-based aid to carrying
out the design calculations at the heart of successful
antenna design. 253 pages in paperback.
NEW
NEW
NEW
NEW
PIC IN PRACTICE
O
R
D
E
R
H
E
R
E
by Howard Hutchings. Revised by Mike James.
2nd edition 2001.
63 $$63
$
Anyone interested in ports, transducer interfacing,
analog to digital conversion, convolution, filters or
digital/analog conversion will benefit from reading
this book. The principals precede the applications
to provide genuine understanding and encourage
further development. 302 pages in paperback.
PRACTICAL RF HANDBOOK
by Ian Hickman 3rd Edition 2002
by D W Smith Published 2002
Based on popular short courses on the PIC,
for professionals, students and teachers.
Can be used at a variety of levels. An ideal
introduction to the world of microcon-trollers for hobbyists, students and professionals.
255 pages in paperback.
87
$
Interfacing With C
Electric Motors And Drives
by Austin Hughes. 2nd edition 1993.
Reprinted 2001.
For non-specialist users – explores most of the
widely-used modern types of motor and drive, including conventional and brushless DC, induction,
stepping, synchronous and reluctance motors. 339
pages, in paperback.
Covers all the analog electronics needed in a wide
range of higher education programs: first degrees
in electronic engineering, experimental science
course, MSc electronics and electronics units for
HNDs. Text is supported by numerous worked
examples and experimental exercises. 312 pages
in paperback.
52 69
$$
$$
A guide to RF design for engineers, technicians,
students and enthusiasts. Covers all of the key
topics in RF: analog design principles, transmission lines, transformers, couplers, amplifiers,
oscillators, modulation, transmitters and receivers,
propagation and antennas. 279 pages in paperback.
NEW
NEW
NEW
NEW
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ANALOG CIRCUIT TECHNIQUES W/DIGITAL INT............$69.00
Your Name_________________________________________________
ANALOG ELECTRONICS..................................................$89.00
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ANTENNA TOOLKIT.........................................................$87.00
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AUDIO ELECTRONICS.....................................................$92.00
___________________________________ Postcode_______________
AUDIO POWER AMPLIFIER DESIGN...............................$89.00
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ELECTRIC MOTORS AND DRIVES..................................$63.00
STD
EMC FOR PRODUCT DESIGNERS.................................$103.00
Email___________________<at>_________________________________
GUIDE TO TV & VIDEO TECHNOLOGY............................$63.00
INTERFACING WITH C.....................................................$63.00
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M'CONTROLLER PROJECTS IN C FOR 8051..................$73.00
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PIC - YOUR PERSONAL INTRODUCTORY COURSE........$46.00
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POWER SUPPLY COOKBOOK..........................................$99.00
PRACTICAL RF HANDBOOK............................................$69.00
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