This is only a preview of the April 2003 issue of Silicon Chip. You can view 29 of the 96 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Items relevant to "Video-Audio Booster For Home Theatre Systems":
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It’s April, It’s Silcon Chip...
Where’s the Jaycar Catalogue?
Well, if you bought this issue of Silicon Chip in Australia (or you are an
Australian Silicon Chip subscriber) you would not be asking this
question because it would have been included with the magazine.
NEW ZEALAND CUSTOMERS: Silicon Chip subscribers in New Zealand will
receive their special New Zealand edition of the Jaycar 2003 catalogue
in the mail separately. Over the counter sales of Silicon Chip Magazine
will have the NZ Catalogue included.
ALTERNATIVES: You may be able to obtain a copy of the Jaycar
catalogue from a Jaycar dealer at the cost of $2.95. Quantities are
limited, however.
Alternatively, you can get a copy for yourself or a friend by
completing the coupon below.
Note: The catalogue is free until the end of May 2003 but there is still
a postage cost of $2.00.
CD ROM: The 2003 CD ROM will be available in May 2003. The CD ROM
also contains 3,315 pages of data! The CD ROM only costs $2.50 plus
postage & handling so this represents a true bargain & fewer trees
chopped down.
•The free catalogue offer is not available in stores - mail ordered only.
•Free catalogue offer expires end May 2003.
Kits
A Taste of our 650+ New Products.
Power Supplies
Velleman 10MHz Handheld
Oscilloscope
Smart Card Reader /
Reprogrammer Kit
Boxes
Transformers
Chassis Hardware
Switches
Plugs & Sockets
Passive Components
Semiconductors
Wire & Cable
Mains Hardware
Inverters
Batteries
SC-480 50 Watt Amplifier Kit
Alarms
Surveillance
Telephone / Cat-5
Audio & Video Leads
Computer
Test Equipment
TV Antennas
See page
241
Soldering
See page 15
Cat. QC-1916
$349
Cat. KC-5342
Please post me my copy of the fabulous 2003 388
page catalogue with hundreds of new products
inside. I acknowledge that the catalogue is free until
the end of May 2003 but I enclose $2 (Aust or NZ) to
help defray postage costs. (Stamps OK).
$29.95
$49.50
Car Sound
Lighting
Address:
Clocks & Weather
General
Suburb:
NEW ZEALAND: Jaycar Electronics. P.O. BOX 9667,
Newmarket, Auckland. Fax: (09) 377 6422.
Postcode:
MAIL ORDERS - FREE POST TO:
Cat. KC-5345
Speakers & Audio
Name:
AUSTRALIA: Jaycar Electronics. P.O. BOX 6424
Silverwater
NSW 1811. Fax: (02) 9741 8500.
NSW - BANKSTOWN
•363 Hume Hwy •Ph: (02) 9709 2822
BONDI JUNCTION
•112 Spring St •Ph: (02) 9369 3899
BROOKVALE
•549 Pittwater Road •Ph: (02) 9905 4130
CAMPBELLTOWN
•Shop 2/49 Queen St. •Ph: (02) 4620 7155
ERINA
•Unit 1/217 The Entrance Rd •Ph: (02) 4365 3433
NEWCASTLE
•990 Hunter Street •Ph: (02) 4965 3799
PARRAMATTA
•355 Church St. •Ph: (02) 9683 3377
PENRITH
•199 High St •Ph: (02) 4721 8337
Tools
See page 11
State:
SILVERWATER
•100 Silverwater Rd •Ph:(02)9741 8557
ST. LEONARDS - GORE HILL
•188 Pacific Hwy •Ph: (02) 9439 4799
SYDNEY CITY
•129 York St •Ph: (02) 9267 1614
WOLLONGONG
•354 Keira Street •Ph: (02) 4226 7089
ACT - CANBERRA
•121 Wollongong Street. Fyshwick
•Ph: (02) 6239 1801
TAS - HOBART
•140 Campbell St. Hobart •Ph: (03) 6231 5877
SA - ADELAIDE
•191-195 Wright Street
•Ph: (08) 8231 7355
Reply Paid 6424. Jaycar Techstore Mail Orders. PO Box 6424
Silverwater NSW 1811 Enquiries: (02) 9741 8538 Fax: (02) 9741 8559
Phone:
Cases
Books
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•Shop 2,45 A’Beckett St •Ph: (03) 9663 2030
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•141A Maroondah Hwy •Ph: (03) 9870 9053
SPRINGVALE
•887-889 Springvale Rd Mulgrave. •Ph: (03) 9547 1022
WA - PERTH
•326 Newcastle St Northbridge •Ph: (08) 9328 8252
QLD - ASPLEY
•1322 Gympie Rd. •Ph: (07) 3863 0099
BRISBANE - Woolloongabba
•65 Ipswich Rd •Ph:(07) 3393 0777
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•2474 Gold Coast Hwy. •Ph: (07) 5526 6722
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•177 Ingham Rd, West End. •Ph: (07) 4772 5022
NZ - Newmarket - Auckland
•231 Khyber Pass Rd. •Ph: (09) 377 6421
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•135 Wairau Road. •Ph: (09) 444 4628
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•23 Kent Terrace. •Ph: (04) 801 9005
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•409 Columbo St. •Ph: (03) 379 1662
All prices in Australian dollars.
FREECALL FOR ORDERS
1800 022 888
w w w. j a y c a r. c o m . a u
ELECTRONICS
Contents
Vol.16, No.4; April 2003
FEATURES
8 IMAX: The Giant Movie Screen
www.siliconchip.com.au
Build A
Quiet PC –
Page 15.
Everything about IMAX is big! Here’s a rundown on this giant-screen system
that can show both 2-D and 3-D movies – by Barrie Smith
15 Silent Running: Building A Quiet PC
Do you hate the noise your computer makes. Here’s how to build one that’s
not only quiet but compact and unobtrusive as well – by Peter Humphreys
72 Soldering: A Closer Look
Poor soldering is the reason most kit projects don’t work. Here’s how to make
a perfect joint every time – by Maurie Findlay
PROJECTS TO BUILD
18 Video-Audio Booster For Home Theatre Systems
Having problems with long cable runs? This unit can boost both composite
and S-video signals, or even component video signals. And it boosts stereo
audio signals as well – by Jim Rowe
28 A Highly-Flexible Keypad Alarm
Versatile unit can be used for keypad door entry and as a stand-alone alarm.
It can also be added to a much larger alarm system – by John Clarke
Video-Audio Booster For Home
Theatre Systems – Page 18.
48 Telephone Dialler For Burglar Alarms
Easy-to-build circuit dials a pre-programmed number via a modem and sends
a warning tone if your alarm is triggered – by Leon Williams
58 Three Do-It-Yourself PIC Programmer Kits
These low-cost kits are easy to build, come with sample programs and are
just the shot for getting started – by Jim Rowe
66 Electric Shutter Release For Cameras
Commercial remote shutter releases are usually expensive. Here’s one you
can build for just a few dollars – by Julian Edgar
Keypad Alarm
– Page 28.
80 More Fun With The PICAXE, Pt.3: Heartbeat Simulator
Nine components are all you need to build this simple circuit. The effect is so
realistic, it almost seems alive! – by Stan Swan
Telephone Dialler For Burglar Alarms – Page 48.
SPECIAL COLUMNS
38 Serviceman’s Log
So what if it’s ancient technology – by the TV Serviceman
44 Circuit Notebook
(1) Super-Regenerative Receiver for AM & FM; (2) Neon Scintillator With
300V Up-Converter; (3) LED Carnival Game; (4) Low-Cost Pistol Shooting
Game; (4) Simple SLA Battery Charger
84 Vintage Radio
The AWA R154 battery console – by Rodney Champness
DEPARTMENTS
2 Publisher’s Letter
4 Mailbag
43 Book Review
69 Silicon Chip Weblink
70 Product Showcase
www.siliconchip.com.au
90 Ask Silicon Chip
92 Notes & Errata
93 Market Centre
95 Advertising Index
Do-It-Yourself PIC Programmers
– Page 58.
April 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
a year by Silicon Chip Publications
Pty Ltd. ACN 003 205 490. ABN 49
003 205 490 All material copyright
©. No part of this publication may
be reproduced without the written
consent of the publisher.
Printing: Hannanprint, Noble Park,
Victoria.
Distribution: Network Distribution
Company.
Subscription rates: $69.50 per
year in Australia. For overseas
rates, see the subscription page in
this issue.
Editorial & advertising offices:
Unit 8, 101 Darley St,
Mona Vale, NSW 2103.
Postal address: PO Box 139,
Collaroy Beach, NSW 2097.
Phone (02) 9979 5644.
Fax (02) 9979 6503.
E-mail: silchip<at>siliconchip.com.au
ISSN 1030-2662
Thunderstorms – nature’s
monster light show!
As we go to press, New South Wales is getting
a fresh bout of drought-breaking rains over the
state. In fact, it has been bucketing down over
wide areas. No-one is complaining though; after
such a severe drought, city dwellers are happy
to endure the rain, in the hope that country districts are getting their fair share. But I enjoy it for
another reason - I love thunderstorms.
We haven’t really had a lot of thunderstorms
in Sydney lately, having missed out on the usual
summer storms because of the drought. So why
do I like thunderstorms? Well, perhaps I had better qualify that. I don’t
actually like being out in them, getting wet. I am not keen on that at all.
I am also concerned about damage to electrical and electronic equipment
during storms, so that is another negative. If a big storm is coming close, I
go around the house and disconnect just about everything that is practical.
The reason I love thunderstorms is the great spectacle - nature’s monster
sound and light show. I like to sit in a darkened room with the curtains open,
watching the progress of storm cells as they move up the coast. And while
lightning strikes to ground can be very spectacular, the real fascination is in
the constant and ever-changing internal lighting of storm clouds - so-called
“sheet lighting” or cloud-to-cloud discharges. In fact, even when storm
cells are a very long distance away, so far that no thunder can be heard, the
constantly flickering light in the clouds can be marvellous.
Just why is the electrical charge within the cloud bank changing so constantly? One reason is that each lightning strike causes the local charge
distribution to be radically altered and it then has to equalise within the
rest of the cloud. Another is that the storm cell is dynamic, with massive
up-draughts and down-draughts, as more moist air is sucked in.
I like to think of the charge distribution within a large cloud as akin to that
on the ultor electrode on the back of your TV’s CRT (or the moving plate in
an electrostatic loudspeaker). This large sheet electrode is a poor conductor
and each local discharge (ie, lightning strike) causes all the charge distribu
tion to readjust (the sheet lightning). Nor does this happen instantaneously
and it can take several seconds for the dislocation caused by one lightning
strike to ripple all around the cloud mass which can be huge – perhaps 50km
or more across in a big storm system. All this happens constantly and so we
have a wonderful random light display.
And of course, each lightning strike that we see to ground is accompanied
by an unseen equivalent discharge up into the stratosphere - the so-called
“sprites” observed by astronauts. Sprites are a pinky, red colour, just what
you would expect from an electrical discharge in a near-vacuum.
With all that going on and the enormous energy involved in the dumping
of perhaps millions or even billions of tonnes of water onto the land, how
can you possibly watch some trivial show on TV during a big storm? Turn
it off and watch nature’s vast and wonderful spectacle!
Leo Simpson
* Recommended and maximum price only.
2 Silicon Chip
www.siliconchip.com.au
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MAILBAG
Smart card article
unnecessarily coy
In the January 2003 article on the
Smart Card Read
er/Programmer, I
was surprised by your coyness in
not wanting to supply the software! I
simply do not believe what you say on
page 18 about Australian federal law.
I use exactly the same software in my
Atmel programmer kits. It is trivial –
serial port, I2C, MAX232 to data I/O!
The only difference is the Smart Cards
are not in DIP packages (and they are
Microchip, not Atmel brand).
All chip programmer software
always has a Read option. So if you
follow the same logic you would not be
supplying microcon
troller programming software because, like a pencil
and paper, it could be used to defeat
encrypted systems! Security issues
with Smart Cards are well discussed
on the web.
There is an excellent introduction
to smart cards at:
http://egov.gov/smartgov/tutorial/
smartcard_foyer.cfm
Peter Crowcroft,
DIY Electronics (HK) Ltd,
Hong Kong.
Credit to Edwin Armstrong
Regarding Andrew Woodfield’s
super-regenerative receiver article
in December 2002 magazine, some
credit is due to Major Edwin Armstrong, US Army, for his invention
of regenerative, super-regenerative,
superheterodyne and FM receivers,
in the early valve age of electronics.
Super-regenerative receivers were
used extensively in WW2 due to their
high sensitivity at VHF and economy
of valve numbers.
Their most important and numerous
use was in VHF, IFF (Identify Friend
or Foe) transponders, fitted to Allied
aircraft. Super-regenerative receivers
were also used in portable battery
operated VHF transceivers and radar
beacons.
Back to Andrew Woodfield’s super-regenerative circuit, a single turn
coil link coupling to L1 is another way
of connecting an external antenna to
the detector’s inductor.
4 Silicon Chip
On another subject, Garry Cratt’s
article on satellite TV (also in the
December 2002 issue) made the statement that the BBC no longer transmits
on shortwave. The BBC can still be
heard in Australia on shortwave, although not intended for us, directly
in English.
J. Grace,
Kirrawee, NSW.
Comment on
Serviceman’s Log
In regard to the Sony television from
South Africa in the Serviceman’s Log
section of your January 2003 issue,
the set is described as having an FM
receiver built-in, yet only being mono.
The reason for this (and I have a
Philips set with this feature from South
Africa) is that you can broadcast TV
programs in more than one language.
While one language is attached to the
main TV signal, the FM tuner can pick
up another.
In Australia, the system was probably used for stereo though the two
sound channels would be used simultaneously on two separate speakers. I
hope this clears it up for you.
I would also like to mention that
your SC480 looks very good and that I
will soon upgrade my amps! It is great
that I won’t need to buy another case,
transformer, output transistors, caps,
bridge, etc since the new one literally
drops into the old one’s place without
much cost at all! Well done.
Rory Shillington,
via email.
Extending memory in VCRs
If we turn the power off at the wall
socket instead of leaving our VCRs,
etc on stand-by, we can save on our
electricity bills. That is all very well
but when we switch the power back
on we have to reset the clock, or do
we?
I have a Philips mono video which
has a super cap to hold the memory
for a short time. By adding a one Farad
super cap to this I was able to extend
this time to over 40 hours which suited
my requirements. To get the same time
on my Panasonic hifi video, I had to
fit three one Farad super caps. I hope
this is of interest.
Cyril D. Vickers,
Elizabeth Downs, SA.
Circuit Notebook policy
Would it be possible for you to
publish an article concern
ing your
magazine’s policy on what it will or
won’t publish in your Circuit Notebook section
For example, will you publish valve
circuits, improvements to existing
designs or improvements to designs
in long-dead magazines? Are you prepared to use two pages for one design
submitted and how good does it have
to be before you want to touch it?
As a matter of policy, everybody
would like to know where they stand.
Gregory Freeman,
Mt. Barker, SA.
Comment: in general, we don’t publish
valve circuits, unless they are featured
in the Vintage Radio pages. We would
not rule out publishing improvements
to circuits from deceased magazines;
eg, Electronics Australia, ETI, Popular
Electronics, AEM, etc.
Some designs featured have run
over two pages (see this month, for
example). How good does it have to
be? Hard to answer – innovative, novel,
clever, simple and complex circuits
can all get a run.
Many homes have
unsafe wiring
The Victorian union attempt to
outlaw electrical hardware sales for
home wiring installations is another
piece of stupidity. I feel that far too
many homes are sold without the
buyers being aware of the state of the
wiring and a certificate of compliance
www.siliconchip.com.au
should be issued. The same should be
done for rental properties every four
years or so.
As a dishwasher serviceman, I have
seen many instances of dangerous
points wired behind the dishwasher,
with it in turn being tiled into place
after installation. This makes removal
and disconnection from live wiring
impossible, as well as extremely hazardous in case of fire or malfunction.
You could not turn these off if you
wanted – the only way would be via
the main fuse box.
John Vance,
Melbourne, Vic.
Government/union bashing?
I have been reading your Publisher’s Letters in recent issues. What on
earth are you on about? Is this a bit of
government/union bashing I detect.
Where are your facts to support your
statement that electricians are less
skilled than TV/washing machine, etc
repair persons?
At least to become an electrician
you must attend an accredited TAFE
course and pass the appropriate
competency levels before your can
call yourself an electrician. Have all
repair people completed and passed
the appropriate qualifications before
setting up to call themselves qualified
repairers?
I looked up the Queensland ESO
site and read through the requirements
of the legislation. It is not an Electrical Contractor’s License that they
are asking for but an Electrical Con
tractor Business License. You know
of the “Gold Card” license, so that the
customer has some protection against
shoddy workmanship. No Gold Card,
no work. Someone has to regulate
these businesses and this seems to be
the generally accepted method to have
a government body to do this.
You also make light of the fact that
no service person has been electrocuted on the job but I wonder how many
of his/her customers have. How would
you know this, because without any
regulation they are not required to
report any incidents? But an electrical
contractor must under OH&S legislation report all incidents, or risk fines
and loss of license.
I think you are missing the point of
the legislation, which is to introduce
www.siliconchip.com.au
The Tiger
comes to
Australia
some accountability on the service
person part and to provide some guarantee to the paying customer that their
work is of a minimum standard.
I could go on but then you might
think I was just a disgruntled unskilled
electrician.
Jeff Ezzy,
via email.
Comment: all electrical deaths are
reported and investigated, no matter
what the cause or circumstances. Our
statement was that “there probably
never has been a fatality because of an
appliance fault caused by a repairer”
(page 4, February 2003).
It turns out that there is just one
recorded electrical fatality, due to a
wiring fault in a repaired appliance –
in a vacuum cleaner! This sole fatality
is the only one recorded in Australian
records going back some 50 years, in
a population now approaching 20
million people. Plainly, this is a very
tiny problem!
The BASIC, Tiny and Economy
Tigers are sold in Australia by
JED, with W98/NT software and
local single board systems.
Another method for
de-sulphating batteries
Intelligent RS232 to RS485
Converter
In the Circuit Notebook section of
the February 2003 issue, you showed
a circuit which claims to reverse sulphation in lead-acid batteries and you
expressed some doubt as to whether it
would be effective.
There is another method which reverses sulphation by using chemical
regeneration. This method has been
around for many years and definitely
works. I used it on the 6V batteries
used to power the underwater lights of
flounder fisherman in the small coastal
country town in which I lived in the
early fifties.
The problem was that as soon as the
flounder season ended, the batteries
would go on the shelf in the shed and
be forgotten. When the next storm
started, not only would they be flat
but also well sulphated.
Using the method described in
“Salving Accumulators – A Simple
Method” (Radio and Hobbies in Australia, December 1942) definitely did
the job and yours truly made a little
money as well.
David Allen,
Findon, SA.
Comment: we have the article on file.
The method involves replac
ing the
battery acid with sodium sulphate and
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.
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
April 2003 5
Mailbag: continued
then giving a long charge. The battery
is then washed out thoroughly with
distilled water and refilled with fresh
sulphuric acid.
AC operation
of halogen lamps
Just a note to thank you for the
review of “Motor Home Electrics &
Caravans” in the February 2003 issue.
The halogen globe life issue is a
curious one. I recollect way back that
they were only recommended for AC
on the grounds that was necessary for
the depletion cycle or something –
but they are used extensively on DC
(including by me). The (alleged) problem concerns only the 12V 10/20W
globes – mainly the 10W units. Car
headlight and other such globes are
designed to run on 14.2-14.4V. They
are far more rugged and as you say,
work fine.
The boat people are adamant about
this issue. You’ll find any number of
references to this in marine electrical
manuals. We could all be wrong of
course – the problem might be salt
water, dirty DC or something else!
Collyn Rivers
www.caravanandmotorhomebooks.com
Loves the PICAXE article
Just wanted to say thanks for the a
great article about a great little chip.
As soon as I had read Stan Swan’s
February article about the PICAXE
chip, I went onto the UK site and
ordered some. They arrived in six
days.
I set up the LED flashing experiment after dinner and it worked
straight off. I then set about experimenting with it and now have it
sending CQ in Morse. I can see a great
future for this little chip and look
forward to many more uses for them
down the road.
Eric van de Weyer, VK2KUR,
via email.
Possible cruise control problem
with LED tail lights
With regard to the LED tail lights
featured in the March issue, you refer
to the brake light out sensors giving
incorrect readings if these are used.
6 Silicon Chip
There is another piece of automotive
equipment which may be adversely
affected by the LED tail light replacements, namely cruise control (CC).
Many cruise control units use the
brake pedal and stop lamp globes
to sense when the brakes of the car
have been applied, disengaging the
CC unit. They use the cold resistance
of the globes to take a sensing input
to ground which allows the CC to be
engaged. When the brakes are applied,
this input goes to +12V as the lamps
light, disengaging the CC.
If all the globes are replaced with
LED units, the CC may not work as the
input might not “see” a low resistance
to chassis.
In regards to “lamp out” sensors and
CCs, probably the best solution is to
fit small globes in parallel with the
LEDs and hide them inside the car. The
rating of the lamp would be selected
to allow for these sensors to work but
this tends to defeat the purpose of the
exercise (except for the faster turn on
time of the LEDs).
Brad Sheargold,
via email.
Electrical contractors
often negligent
Once all Queensland electrical
appliance repairers are licenced as
contractors, will it eliminate incidences of negligence investigated by
the Electrical Safety Office? I don’t
think so! In reviewing electrical accident reports, I note that contractors
and their employees are amongst the
worst offenders on safety issues, often
resulting in electrical workers, nonelectrical workers and members of the
public suffering electrocution.
Requiring all repair persons to become contractors will only skew the
statistics, with less accidents due to
“unauthorised” work and more accidents caused by “licenced persons”.
I can even visualise more accidents
because the public will not pay high
prices for a “licenced contractor” to
replace faulty switches, power cords,
etc and will just wrap them in more
sticky tape and hope for the best.
Still, at least the Queensland government coffers will benefit from the
increased licence revenue.
If states do go ahead and regulate
that only contractors may purchase
and install electrical products, thus
cutting out the home handyman, I
wonder if the manufacturers like
Clipsal and HPM, and retailers like
K-mart, the hardware stores, etc will
suddenly wake up as they lose their
lucrative DIY market? (Name supplied
but withheld at writer’s request).
LED lighting
is irresponsible
Five point five metres! With the
Road Authorities, NRMA and others
trying to educate the public to drive
in a responsible manner, with a rule
of thumb, suggesting not travelling
closer to the car in front equal to two
seconds at the speed in question, the
distance at 100km/h is a reasonably
healthy 55 metres.
Taking the official view that some
people have a reaction time of up to
1.5 seconds, the March 2003 article on
“LED Lighting For Your Car” is not in
the public’s interest.
It is up to the driver in front to
drive his vehicle at a speed and so
placed that the risk from a shunt from
a following car is minimised – not
place his faith in bright lights that
give a mathematical saving of 200
milliseconds. Having the advantage
of a 60-year history of driving Australia’s roads and never been hit in
the rear, your article belongs in the
rubbish bin.
Jim McCloy,
via email.
Comment: how can you seriously suggest that our article advocates driving
too close to the driver in front? Read
the article again to discover what we
actually said.
Regardless of which type of stop
lights are fitted, safe following distances will always be required. However, anything which gives you extra
braking time in an emergency must be
worthwhile.
Your statement that it is up to the
driver in front to maintain a safe following distance is puzzling. Surely
that responsibility lies with the driver
behind? We also understand that the
rule of thumb is to leave a three-second gap to the car in front, not two
seconds.
SC
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February 2015 7
IMAX
The
TheGiant
GiantMovie
MovieSc
S
8 Silicon Chip
www.siliconchip.com.au
Most readers have seen or heard about
IMAX – the giant screen which can show
movies in two and three dimensions (3D).
This is the story of IMAX.
By BARRIE SMITH
P
EOPLE ARE ENTRANCED with
the big picture. In the early
1800s, Robert Fulton amazed audiences with his Cyclorama, a 16-metre high by 130-metre long painting
that ran on rollers. The Lumiere brothers, not content with their pioneering
35mm film efforts, even managed to
screen movies shot on 75mm film.
The 3-strip 65mm Cinerama process emerged in 1963, quickly followed by CinemaScope, VistaVision,
Circa-rama, Technirama, Todd-AO
and so on. Then came IMAX, a process
that side-stepped the perception that
audiences just wanted a big, wide
picture.
Instead, the Canadian developers
of the IMAX process headed for a
screen picture that was just huge .
. . very enveloping, very sharp and
almost grainless, swamping the eye’s
peripheral vision; the field of vision is
50° vertical and 130° horizontal.
X
The IMAX camera uses 65mm negative film (from which 70mm projection
prints are made). An IMAX film frame
measures 48.5mm high by 69.6mm
wide – a total area of 3375.6mm2, over
10 times the frame area of conventional
35mm film.
Each IMAX film frame has fifteen
perforations; a single frame races
past the camera’s aperture in 6 milliseconds; each second, 1.7m of film
rips past; each minute exposes an ex
pensive 102.6 metres of Mr Kodak’s
famous product.
A Cumbersome Beast
The discipline required in shooting
an IMAX production is extraordinary.
A 2D camera can be a cumbersome
beast, even though there are smaller
units for difficult location work. In
IMAX, it is advisable to avoid pans
or quick movements of the camera.
Sharpness and the utmost depth of
Every way you look at it, IMAX
is big. The diagram at left
compares the IMAX filmstrip
(also shown below) to ‘normal’
70mm and 35mm.
creen
Screen
www.siliconchip.com.au
April 2003 9
Australian producer, Michael Caulfield (seated right)
working on his film “Horses – The Story of Equus”.
field is essential. Then there is the 3D camera, with its
doubled film path and optics!
Australian producer, Michael Caulfield has made two
IMAX films: “Africa’s Elephant Kingdom” and “Horses
– The Story of Equus”. In his experience “Wherever you
turn in the IMAX format you’re going to have problems
. . . the camera is very big; this means very, very big mechanical gearing and cogs to pull the film past the lens
at a stable rate.
“There are really only about 10 decent cameras in the
world. They’re worth a lot of money and they’re also quite
peculiar, so you have to send your camera assistants and
focus pullers, if they’ve never worked with one before, to
Toronto to learn it.
“You have to book the camera a long way ahead”,
Caulfield cautions. “You have to be able to schedule and
re-schedule with a fair degree of certainty. And of course
The Sydney venue at Darling Harbour is profitable, relying
on 65% audience attendance of Sydney residents plus local
and overseas tourists as well as school groups.
In Sydney’s IMAX theatre
biobox, chief projectionist
Tim Gunn fires up the 2D/3D
projector.
10 Silicon Chip
www.siliconchip.com.au
The schematic of Ron
Jones’ “Rolling Loop”
invention which is
the core technology of
IMAX projection.
if you’re making natural history films
that can be very difficult”.
He has found the cameras are “surprisingly, very reliable. They have to
be heavy-duty, otherwise yanking that
amount of film through, they’d fail”.
“However, if they do ‘go’, explode
inside or the film snaps, they internally
haemorrhage. It takes you ages to fix
them”.
Costs are another matter. “Every roll
of film is 300 metres or three minutes
long. Film and processing cost is about
US$8000 for each roll. That’s just stock
cost and processing. If you want to do
print-downs to 35mm, which we do
for everything we shoot, then that’s
another cost altogether”.
I asked him what is the shooting
ratio (raw film shot vs final edited
length) on a typical film. Caulfield:
“A normal natural history film is
around 30:1. We shoot around 11:1.
You have to. You just can’t afford any
more”.
“And you have to make a lot of
IMAX rotor paths: the right eye is uppermost and its aperture slightly advanced
on the left. In these shots, film travels right to left.
www.siliconchip.com.au
Ron’s Loop
The late PRW (Ron) Jones created a
rolling-loop film transport for projectors
in the ‘60s, the invention revealed in a
paper given at the SMPTE in 1969. The
young IMAX group snapped up the
patent for its process, having realised
that while you can whip 100 metres
or so of 65/70mm film past a camera
gate’s intermittent movement once, it
won’t survive repeated journeys in a
projector.
In the projector, the primary film drive
is by means of a 952.5mm diameter
rotor with eight windows and driven at
180 RPM by a synchronised 3-phase
motor. Pulsed air jets at each of the
windows form a loop or wave in the
film as it passes the input sprocket and
then advances the film past the aperture; here a cam and four registration
pins momentarily hold each frame in
the plane of the aperture against a
curved quartz glass rear lens element.
Steadiness on screen is high – less
than 0.04% in any direction; print life
can run to at least 1500 showings.
Norman McLaren
Scottish-born, Canadian resident, Norman McLaren was determined to explore new techniques. The late 1940s,
early 1950s saw him experiment with
animated 3D films and hand-drawn
films, scratching and painting not only
the film image but scribbling and gouging over the soundtrack area to make
his own audio effects. Still well ahead
of his time.
Wescam
Arguably the world’s best gyro-stabilised camera platform, Wescam
was first used in 1969. Today there
are hundreds used worldwide by TV
news crews and police video units. But
the really heavy use is by a handful
of 35mm film units in major world
capitals.
Its capabilities to produce rock-steady
shooting at low frame rates (12fps for
example) and with long lenses (such
as a 250mm telephoto) has helped
the creation of memorable images in
the cinema. The Wescam mount uses
three high speed gyros that control the
roll, pitch, and yaw axes; a fourth gyro
attends the vertical axis and helps
further stabilise the camera platform
when acceleration, deceleration and
April
G forces impinge
on2003 11
the mount.
successful IMAX theatre in the world, most times running
in the top three or four. About 65% of its business comes
from Sydney metropolitan residents, 15% from school
groups and the remainder a mix of domestic and international tourists.
Sydney IMAX has found that 3D titles are proving more
and more popular. As Mark Bretherton, Sydney IMAX Marketing Manager, says: “A 3D film can actually be weaker in
terms of content but it will draw more. The most successful
films in 2001 were two 3D films, “Cyberworld” and “Haunted Castle”, plus a 2D film called “Shackleton’s Antarctic
Adventure” (still running in early 2003) and probably one
of the best crafted IMAX films I’ve seen”.
Projection Top Gear
Clever dual feed/takeup spools enable the next film to be
nearly laced up, ready for showing.
allowances as well because you don’t really ‘see’ the film
until you’ve ‘locked off’ the edit. You can’t afford to print
out everything you’ve shot onto 70mm. So what happens
is that every so often you’ll print up a roll or two of shots
you may be concerned about.
“You cut the film on a digital editing
machine from 35mm print-downs.
That’s all fine and well but you don’t
really know until the film is finished
and locked off. The lab strikes a first
answer print and then you look at it
and you go ‘Oh my God!’ There may
be a shot with a tourist van in it or
the shot has a bit more shake than
you thought, which renders it unacceptable. So you need to have an
allowance in your budget to go back
and reshoot”.
Perched way above the audience in the Sydney IMAX
theatre is the projection biobox, operated on most days
by chief projectionist, Tim Gunn. He well remembers the
days of short reel changeovers and, in one way, welcomes
IMAX’s approach where the loaded film will run 40 minutes
or more from the one roll. However, the call for “action
stations” at reel’s end sees him race into top gear.
A 2D print can weigh around 100kg so a forklift is used
to trolley the film rolls around the biobox. The Sydney
projector is a 2D/3D machine, fed by two film paths – or
four for a 3D title. The films are threaded all the way to
the projector input. At the end of a screening, the machine
is stopped and the tail unlaced. Then the lacing up of the
new print(s) commences.
Normally the 2D and 3D films alternate; in this case Tim
will take “a good 10 minutes” to make the change-over.
This entails the lace-up and the change of projector optics
and back condenser lens as well as a clean-up of the film
path itself.
The lenses are different for every theatre, depending on
the projector-screen throw.
Sydney has a Leitz Canada 38mm 2D lens and two
52mm lenses for 3D; the projected 3D screen image is
Sydney IMAX Cinema
The purpose-built Darling Harbour
building is owned by MTM Entertainment Trust. The projection equipment
is owned by IMAX Canada and leased
to the Sydney company while the films
are rented.
There are IMAX cinemas in Sydney,
Melbourne, Dreamworld at Coomera
in Queensland and one in Townsville.
The Sydney venue is the eighth most
12 Silicon Chip
Yes, you need a forklift to move the 100kg
film loads.
www.siliconchip.com.au
IMAX in space: Expedition 1 Commander Bill Shepherd (left, pale shirt) and
Flight Engineer Sergei Krikalev (right) frame and focus a shot on the Video
Display of the IMAX 3D cabin camera just before filming in the U.S. “Destiny”
lab module of the Space Station. (Photo: NASA).
smaller, because it “eats a lot more
light”, thanks to cross-polarisers on
the projector and those in the audience viewing headsets. Light loss is
estimated to be at least 30%.
Early on, the Sydney cinema used
the original electronic 3D system
which employed pulsed LCS (Liquid
Crystal Shutters) as well as the cross
polarisers. This method has given way
to polarisation due to audience theft
of the headset battery packs!
Lamp power is from two 15kW xe-
nons; the illumination is directed to
the film aperture/lens point by means
of a folded light path, using two aircooled mirrors.
The projector itself is massive
and aside from the dual light source
and lens assemblies, has a double
deck rotor to transport the films (see
“Ron’s Loop”). The right eye film is
uppermost.
An interesting feature of the setup
is that the left-eye film is projected
a few degrees of rotation before the
IMAX
First shown at Expo ‘70 in Japan, the
wide-screen process has been with
us for decades and one of its earliest
achievements was the 1984 Challenger and Discovery missions which were
chronicled by an IMAX camera carried
on three missions. The 14-astronaut
crew were trained as movie cameramen for five months. The camera was
the largest ever to travel in a space
shuttle and needed special accommodation in the zero-G conditions.
The whole scheme, comprising IMAX
cameras, projectors, theatre design
and sound system, was conceived in
Toronto, Canada with virtually no input
from Hollywood. A specialist Norwegian engineer built the first camera;
the camera and projector lenses came
from Germany and Japan; the first
projector was built in Toronto – and
the mechanical heart of it invented
by Ron Jones, a Brisbane engineer.
Generously, Hollywood recognised
this innovative ‘heart’ – the rolling
loop film transport – by awarding it
an Oscar for technical achievement.
OMNIMAX
This is IMAX with ‘the roof rolled
back’ and first seen in 1973 in a US
planetarium. A Leitz f2.8/29mm fish
eye lens is used to throw a razor sharp
picture onto the inside of a spherical
section, similar to a planetarium. The
picture overfills your peripheral vision.
The Townsville OMNIMAX screen
forms a 160 to 165° segment of a
hemisphere. The screen and audience are tilted at an angle of 25°, with
the projection lens located a short
distance beyond the hemisphere’s
centre.
The Edge
The Edge, at Katoomba, NSW, is a
purpose-built cinema, designed to
run a 70mm format as well as 35mm
movies. It was developed by ex-Disney veteran Ub Iwerks.
The format uses eight perforation
70mm film running vertically. Frame
area is 1775 sq mm – 5.5 times that
of 35mm at 319 sq mm.
And here’s a frame from the result, the first IMAX film in space and in 3D:
Space Station 3D.
www.siliconchip.com.au
More IMAX?
The IMAX process was described in
much more detail in an article in “Electronics Australia”, February 1972.
SILICON CHIP can supply reprints of
this articel for $8.80 including GST
and postage.
April 2003 13
Twin rotors and twin film paths are the secret to the
elec-tronic 3D on-screen image. The offset is about 12° or
0.01 seconds approximately.
The original electronic 3D system employed pulsed liquid
crystal shutters as well as cross polarisers. This method
has given way to polarisation, not for technical reasons
but due to audience theft of the headset battery packs!
other film. This rotor offset (about 12° or 0.01 seconds
approximately) allows the rotary shutter to expose the
left lens and fire the left lens of the E3D viewer, while the
right lens remains covered and the right E3D viewer LC
lens is closed – then vice versa. The rotor offset ensures
that the projected image is not partly obstructed by the
rotor shutter.
As you might expect, most functions are computer
controlled. Below is the projector LCD control touch panel.
Multi-track sound
IMAX has had multi-track sound while suburban
cinemas were still living in caves – so to speak! IMAX
originally began with a 6-track 35mm magnetic dubber.
The sound source is synchronised by projector drive
shaft-encoded pulses.
The IMAX sound system is quite distinct from Dolby.
It was developed by Sonics in Alabama, now owned by
IMAX.
It is basically a 6-channel system with left, centre and
right signals coming from the front; left and right signals
from the rear, plus there is a channel issuing from the
top of the screen for effects. Another channel, using a
subwoofer with a stack of eight 15-inch drivers, derives
its signal from all six channels.
These days, the magnetic dubber is still used as back
14 Silicon Chip
up but most times a setup of three digitally-synched CD
players (Digital Disc Player or DDP) is employed, each
carrying two channels per disc. Total running time is 80
minutes.
There is also a 6GB hard drive system, becoming important as a sound source for longer, feature-length films.
Some films use all three sources.
SC
www.siliconchip.com.au
Are you sick of the constant whirring noise your
PC makes? Get rid of the racket by building a
silent PC – by Peter Humphreys.
B
ACK IN October 2002, I wrote a
letter to Mailbag about building a
silent PC. What? A silent PC? Are you
crazy? Look in any computer magazine
and you will see “more power”, “more
GHz”, “more fans”, more noise!
Our computer lives in the living
room where we can all share it without being unsociable. That’s great
but try watching a movie while a
conventional PC is on and you’ll
soon tire of the constant whir from
the cooling fans. Want proof as to just
how much noise your PC makes? Just
sit quietly with your PC for five minutes and then turn it off – the silence
is deafening!
Yeah, maybe we should turn the PC
off before watching a movie. But what
if someone wants to use the Internet
while the movie is on or use the computer for homework or to play games?
Alternatively, perhaps you have
built an MP3 box. Doesn’t the noise
from the PC spoil the sound from your
latest album? Or perhaps you want to
add the PC to your home entertainment
system so that you can watch DVD
movies and listen to music.
Clearly, it’s preferable to quieten
down the PC so we can live with it
instead of banishing it to the study.
Getting rid of noisy fans
The “Silent PC” is not only very quiet but is compact and unobtrusive as well.
The silver LCD monitor matches the keyboard and the brushed aluminium case.
www.siliconchip.com.au
Getting rid of noisy fans is a major
step towards quietening any PC. However, that’s not really practical in existing machines as disconnecting the
power supply fan and/or the proces
sor fan will quickly lead to frazzled
components and catastrophic failure.
The best approach is to start from
scratch and build a quiet PC from
special components. This article describes a PC that is almost silent and,
as a bonus, is extra small. The accom
panying panel shows the parts used.
The total cost was around $2000,
including the LCD monitor. The real
magic is in the $220 motherboard. This
price includes an Eden 533MHz CPU
April 2003 15
It’s a tight fit inside the case but everything goes in neatly. The 90° PCI riser card is supplied with the case.
and unlike other CPUs, this one runs
quite happily without a fan. Instead,
a large heatsink provides all the cooling that’s necessary (and it does this
without making a sound).
As an aside, I’m already thinking
of swapping the bedroom TV for a
computer monitor, plugging a TV tuner
card into the motherboard and hiding
the assembly in a drawer. With a cordless keyboard and mouse, it doesn’t
matter where the PC is!
Special case
The special aluminium case used
measures just 260 x 190 x 166mm and
is very well designed. Air enters the
holes in the lower front, passes over
the power supply and motherboard,
and then flows over the hard drive and
out the rear exhaust.
The fact that the case is all aluminium helps with the cooling. The
fan in the power supply was a noisy,
small, high-speed type. Since the
power supply is situated at the front
The Parts Used In The Silent PC
• ClipperPro I-box Mini-ITX aluminium case with 180W power supply.
• VIA EPIA-5000 Motherboard with Eden 533MHz “ fan-less” CPU
• 256MB PC-133 SDRAM
• Seagate ST360021A 60GB ATA100 hard disk drive
• Pioneer DVD-106S slot-load DVD-ROM drive
• Samsung 151BM 15-inch LCD monitor with built-in speakers
• Logitech cordless Navigator Duo (white/silver) keyboard and mouse.
of the case and the airflow passes
right over it, I removed the power
supply fan and cover which made a
big difference.
(Editor’s note: we strongly recommend that the original power supply
cover be replaced with a new cover
with improved ventilation; eg, with
expanded mesh aluminium panels.
Much of the circuitry inside PC power
supplies operates at dangerously high
voltages – ie, at 240V AC. They should
always be fitted with a suitable cover,
to guard against accidental contact.
Similarly, a suitable cover should be
fitted over the fan slots in the supply
case, if the fan is removed).
The case fan is at the top rear of the
case and is lost in the ambient noise in
the house. This lone fan does a good
job and nothing gets too hot. The BIOS
reports that the fan is running at just
over 2000 RPM and the PC has been
running 14 hours a day, seven days a
week for four months now without a
hiccup. It’s possible that if a power
The lone fan at the back of the case operates quietly and does a good job keeping everything cool. Note the antenna – this
is attached to the wireless LAN card which occupies the sole PCI slot on the motherboard (via a 90° PCI riser card).
16 Silicon Chip
www.siliconchip.com.au
comparable Celeron CPUs.
Disk drives
The Seagate Barracuda ATA IV drive
is one of the quietest around, due to
the use of fluid bearings. It can only
be heard if I place my ear near the case
and watch for the HDD LED!
The DVD drive makes the most
noise, especially at high speed. That’s
par for the course – all DVD and CD
drives make a lot of noise.
If the PC is to be used standalone,
a CD-RW or combination drive (CD,
DVD and CD-RW) is recommended.
My motherboard doesn’t have a floppy
drive interface but the latest mother–
boards now feature this instead of a
second IDE interface.
Wireless LAN
The VIA EPIA-5000 motherboard comes complete with an embedded Eden
533MHz “fan-less” CPU (shown here without the heatsink). It also features
integrated graphics, 10/100 ethernet and Sound Blaster Pro compatible sound.
supply from a notebook computer was
used, the PC could run completely
“fan-less”.
Via motherboard
The EPIA-500 motherboard from
VIA comes in the ultra-compact Mini-ITX form factor and is claimed to
be the world’s smallest. It measures
just 170 x 170mm.
Just about everything is integrated
onto this board: VGA video, VIA
10/100 Ethernet LAN, Sound Blaster
Pro compatible sound with S/PDIF
output, two IDE Ultra DMA 33/66/100
connectors and all the other standard
motherboard connectors.
Basically, the Mini-ITX motherboard is intended for “entry level”
PCs, thin-clients, wireless network
devices, digital media systems, set-top
boxes and more. It is also becoming
increasingly popular with enthusiasts
due to its small size, quiet operation
and low profile (the I/O ports are the
tallest components on the board).
Want to know more? Have a look
at http://www.mini-itx.com for information on how people have built PCs
out of things like model cars, cigar
humidors, motorcycle helmets, picture
www.siliconchip.com.au
frames and more!
In my case, the key advantage of this
VIA Mini-ITX motherboard was the
“fan-less” VIA Eden processor. This
CPU is embedded on the motherboard
to reduce costs and streamline production but it does have one drawback
– the CPU is not upgradable.
VIA processors have built a reputation for reliable, low-temperature
operation. This is due to careful design
and low power consumption – the
Eden 533MHz CPU consumes just
2.8W. By comparison, recent Athlon
CPU’s consume about 70W of power!
By the way, a 667MHz Eden “fanless” processor in now also available,
along with a range of more powerful
C3 processors which run up to 1GHz.
The latter are fan-cooled, however.
Despite this, the C3 range still run a
lot cooler and have quieter fans than
A wireless LAN card fills the single
PCI slot via a 90° PCI riser card (supplied with the case). One good thing
about the VIA motherboard is the use
of standard components. Many other
“small PC” solutions use laptop components and these can be expensive.
LCD monitor
A Samsung 15-inch LCD monitor
(silver) was chosen to complement
the brushed aluminium case used for
the PC. This has built-in speakers, in
keeping with the tidy appearance.
Fast enough
With CPUs now running at 2GHz
or more, a 533MHz PC might sound
rather slow by modern standards.
However, for everyday home (and
probably business) use, it’s fine – at
least my applications. I use it everyday
for email and web browsing – and for
playing Solitaire of course!
No more beige boxes for me!
Footnote: although we haven't tested
it, Microgram Computers sell a 300W
low-noise power supply with a thermostatically-controlled fan (Cat. 8957). It’s
well worth checking out if you want
to build a silent PC. Enquiries to (02)
4389 8444 (see ad on page 3).
SC
Useful Links
http://www.viavpsd.com/product/epia_mini_itx_spec.jsp?motherboardId=21
http://www.seagate.com/cda/products/discsales/marketing/detail/0,1081,383,00
http://www.pioneeraus.com.au/multimedia/products/dvd-rom/dvda06s/dvd-106s_116.htm
http://www.samsung.com.au/samsung.asp?cat=52&obj=650
http://www.mini-itx.com
April 2003 17
Clean up your video signals with this:
Video-audio booster
for home theatre
If your home theatre setup involves sending
video signals over fairly long cables, you’ll
really appreciate this project. It’s a wideband
amplifier that can boost both composite and
S-video signals, or even component video
signals with the right cables. And it handles
stereo audio signals as well.
By JIM ROWE
W
HEN SETTING UP a home theatre, there’s often a need to run
fairly long video cables between your
signal sources (DVD player, VCR and/
or laserdisc player) and your big screen
display. The reason for this is simple it isn’t always convenient to have the
signal sources and the display at the
18 Silicon Chip
same end of the room.
Of course, there’s no great problem
feeding audio signals over long cables,
provided that the cables are of reasonable quality. However, that’s not the
case with video signals due to their
much greater bandwidth. Video signal
frequencies can range up to 5MHz or
more (as against just 20kHz for audio)
and can suffer quite noticeable degradation when fed through cables longer
than about five metres.
This signal degradation is due mainly to cable capacitance. This causes
high-frequency losses and occurs even
when you use high-quality coaxial cable that has been correctly terminated
at each end. The resulting pictures
lack contrast and colour saturation,
and also become noticeably “softer”
(ie, lacking in fine detail) due to the
lower bandwidth.
Video booster
The best way to tackle this kind of
problem is to use a video “booster”
every five metres or so. Basically, you
take a 5-metre cable run and plug it
into the booster – essentially a wideband video amplifier. The booster
siliconchip.com.au
Fig.1: this diagram shows how the video booster is connected for composite video signals (top), S-video signals centre
and component video signals (bottom). It’s basically a matter of buying (or making up) the necessary cables.
restores the incoming signal so that it
is close to original before feeding it to
the next 5-metre cable run and so on.
A booster for conventional “composite” video signals needs just a single wideband video amplifier channel.
However, if you want to take advantage
of the higher quality available from
the “S-video” output of your DVD
player, the booster needs two chan
nels. That’s because, in S-video, the
luminance (“Y”) or black-and-white
picture information is not combined
with the chrominance (“C”) or colour
information. Instead, the two signals
are fed along separate cables to prevent
them interacting – see Fig.1(b).
The video booster described here
can handle either composite or S-video
signals as required, because it uses
an IC which actually contains four
wideband amplifier channels. This
siliconchip.com.au
allows us to devote one channel to
the composite video input and output,
while two more are dedicated to the
S-video input and output sockets.
This means that there’s no switching
and the composite video and S-video
channels can even be used at the same
time; eg, to pipe composite signals to
another room while you’re watching
S-video signals to your home theatre
display.
The fourth channel is spare and can
only be accessed internally.
What about handling the even higher quality “component video” signal
outputs? With this type of signal, as
well as the luminance (Y) being kept
separate, the two “colour difference”
signals (R-Y or “Cr” and B-Y or “Cb”)
are also kept separate – ie, instead of
being combined as the chrominance
(C) signal.
If your DVD player provides these
outputs and your display can also handle them, the video booster can help
here too. All you need to do is buy or
make up some adaptor cables, so that
the three component video signals can
be fed through the three main booster
channels – see Fig.1(c).
Audio amplifier
As well as the video amplifier channels, the booster also includes a pair
of low-noise audio line amplifiers.
This means that it can also be used to
handle any stereo audio signals which
accompany the video, so these too will
reach the far end of the cables in good
condition.
Probably the main use for the audio
channels will be where you’re feeding
the video and audio to a different
room. They’ll also come in handy if
December 2005 19
Parts List
1 PC board, code 02104031,
117 x 102mm
1 plastic instrument case, 140 x
110 x 35mm
2 PC-mount 4-pin mini-DIN
sockets
6 PC-mount RCA sockets
1 PC-mount 2.5mm concentric
male “DC” connector
1 9V AC plugpack (500mA) with
2.5mm female connector
Semiconductors
1 MAX497 quad video amplifier
(IC1)
1 LM833 dual op amp (IC2)
1 LM7809 +9V regulator (REG1)
1 LM7909 -9V regulator (REG2)
1 LM7805 +5V regulator (REG3)
1 LM7905 -5V regulator (REG4)
1 3mm green or red LED (LED1)
2 1N4004 1A diodes (D1,D2)
Capacitors
2 2200µF 16V RB electrolytic
2 100µF 16V RB electrolytic
2 10µF 10V RB electrolytic or
tantalum
2 2.2µF 35V TAG tantalum
2 1.0µF MKT
2 220nF MKT
4 100nF monolithic ceramic
Resistors (0.25W, 1%)
4 100kΩ
8 75Ω
2 47kΩ
2 10Ω
3 1kΩ
Where to buy a kit
The design copyright for this project is owned by Jaycar Electronics.
Complete kits will be available from
Jaycar Electronics by the time this
article appears in print.
you need to send one or more of the
signals in a 5.1, 6.1 or 7.1-channel
surround sound system to remote
power amplifiers; eg, you might want
to send the SB (surround back) signals
from your 6.1/7.1-channel decoder to
the rear of your home theatre room,
to drive a power amplifier for the rear
centre speaker.
Alternatively, you might want to
drive an active subwoofer with the
LFE (low frequency effects) channel
signals.
Presentation
As you can see from the photos, the
20 Silicon Chip
The A/V output sockets are all accessible from the rear of the unit. They include
a 4-pin mini-DIN socket for the S-video signals, plus three RCA sockets for the
composite video and left & right channel audio output sockets. The socket at far
right is the DC power connector.
booster is very compact. Everything
fits in a small ABS instrument case
measuring just 140 x 110 x 35mm.
Power comes from a 9V AC plugpack.
Incidentally, Jaycar Electronics
will be making a complete kit for the
booster available, so you should be
able to build it up very easily and at
an attractive price.
How it works
The booster’s video amplifier channels are all provided by IC1, a Maxim
MAX497. This high-performance device is designed expressly for handling
video signals. It includes four closedloop buffer amplifiers, each operating
with a fixed voltage gain of 2.0.
Other features of the MAX497 include a full-power -3dB bandwidth
of over 200MHz, exceptional gain
flatness (±0.1dB up to 120MHz),
low distortion, very low differential
phase/gain error between the four
channels and the ability to drive four
back-terminated 75Ω (or 50Ω) output
cables simultaneously.
As shown in Fig.1, we’re using one
amplifier for the com
posite video
channel and another two amplifiers for
the Y and C channels for S-video. Each
amplifier has a 75Ω resistor across its
input and these ensure correct termination of the cables from the video
source. In addition, 75Ω resistors are
used in series with each output to
give correct “back termination” of the
output cables.
As mentioned, the amplifiers in the
MAX497 have a feedback-controlled
gain of exactly two. This compensates
for the attenuation produced by the
interaction between the back termination resistors and the termination
resistors at the far end of the output
cables.
In effect, the Video Booster “restores” the incoming signal before
feeding it to the next cable segment.
The input and output connections
to the composite video amp channel
are made via RCA sockets, as these are
now standard for domestic equipment.
Similarly, the connections for the
S-video channels are made via 4-pin
“mini DIN” sockets, as these too are the
accepted standard for S-video.
Note that the fourth “spare” amplifier in the MAX497 is also provided
with input and output termination
resistors. This is done to ensure that
it doesn’t interact with the three active
channels. The resistors will also make
it easy to use the spare channel if you
ever need it.
The two audio line amplifier channels are provided by the two halves
of an LM833 dual low-noise op amp
(IC2). As shown, these two stages are
identically connected as non-inverting buffers, with the 100kΩ resistors
providing negative feedback for a gain
of two.
The performance of these audio
buffers is quite respectable. They have
a frequency response from 30Hz to
120kHz at the -1dB points, a THD (total
harmonic distortion) below .006% for
2V RMS output, a signal-to-noise ratio
of better than 91dB relative to 2V RMS
output, and an output clipping level
of just on 14V peak-to-peak (5V RMS).
siliconchip.com.au
The audio buffers operate with a
gain of two to ensure sufficient signal
to drive your remote power amplifiers,
etc. However there may be cases where
even this small amount of gain could
cause problems - producing distortion
due to input stage overloading, for
example.
If that turns out to be the case with
your particular application, there’s
a simple modification which can be
done to solve the problem. All you
need do is remove the 100kΩ resistors connecting pins 2 and 6 of IC2
to ground. This turns the buffers into
unity-gain voltage followers, increasing the overload margin by 6dB.
Power supply
The power supply section is quite
straightforward, even though the video and audio amplifiers require four
separate DC supply rails. The MAX497
requires ±5V supply rails, while the
LM833 require ±9V rails.
Because the overall current drain
is quite low (about 100mA total), two
simple half-wave rectifier circuits
(D1 & D2) are used to derive nominal
±12.8V DC rails from 9V AC plugpack.
These rails are filtered using two
2200µF capacitors and then fed to
3-terminal regulators REG1 and REG2.
REG1 and REG2 produce the +9V
and -9V rails respectively. They also
drive 3-terminal regulators REG3 and
REG4 which produce the ±5V rails.
LED1 is driven from the +9V rail via
a 1kΩ current-limiting resistor and
provides power on/off indication.
The associated 100µF and 10µF capacitors are used to filter the regulator
outputs. The ±9V supply rails are then
further decoupled using 10Ω resistors
and 2.2µF capacitors before being fed
to IC2. Four 100nF capacitors provide
additional filtering for the ±5V rails
to IC1.
Construction
All the parts are mounted directly
on a small PC board, so the unit is easy
to build. This includes all the connec
tors, so there’s no off-board wiring at
all inside the booster box.
The PC board measures 117 x
102mm and is coded 02104031. It’s
double sided, with copper tracks
on both top and bottom, but the top
pattern is mainly an earthed ground
plane. Only a handful of component
leads are soldered to this top pattern,
so we don’t need a board with expensiliconchip.com.au
Fig.2: the booster circuit is based on a Maxim MAX497 quad video buffer
IC (IC1). One amplifier in IC1 is used for the composite video channel,
while another two are used for the Y and C channels for S-video. Op amps
IC2a & IC2b (LM833) boost the left and right channel audio signals.
December 2005 21
This photo shows how the
power indicator LED is
mounted on the PC board
and pushed through a
matching hole in the front
panel.
Left: inside the completed
booster unit. Keep all
component leads as short as
possible and be sure to
solder the leads to both sides
of the board where
necessary, as indicated by
the red dots on Fig.3.
sive plated-through holes.
Fig.3 shows the assembly details.
Begin by fitting all the input and
output connectors, as they often need
a small amount of juggling and pin
straightening before they’ll mount
without stress. Make sure that they’re
pushed down hard against the board,
while you make the solder connections
underneath.
Next, fit the two PC board terminal
pins (for the input and output of the
spare video channel), followed by the
resistors and the diodes D1 and D2. Be
sure to fit each diode the correct way
around as shown on Fig.3.
Note that some of the resistors have
their “earthy” ends soldered to the top
copper pattern as well as to the pad
underneath. The leads concerned are
shown with a red dot on the board
overlay diagram.
The four voltage regulators can go
in next. These are all TO-220 packages
and are mounted horizontally on the
top of the board. Be sure to fit each one
in the correct position, as all four are
different and mixing them up could
result in component damage when
you apply power.
All regulator leads are bent downwards 6mm from the package body.
This allows you to mount them by
pushing the leads down through the
mating holes and then fastening their
tabs down against the copper using
6mm x M3 machine screws and nuts.
The leads are then soldered to the pads
underneath and, in some cases, to the
top pads as well - see Fig.3.
The two 2200µF capacitors and the
two 100µF capacitors adjacent to REG1
and REG2 can go in next. Make sure
you fit all of these polarised parts the
correct way around, as shown in Fig.3.
LED1 is fitted with its “flat” cathode
side to the left (ie, furthest away from
CON4). To install it, first bend both
its leads bent down 90°, 6mm away
from the LED body. That done, it can
be soldered into place with its axis
exactly 8mm above the PC board.
Power supply checks
At this stage, it’s a good idea to
check all of the power supply wiring
by plugging the lead from your 9V AC
plugpack into CON9 and turning on
the power. LED1 should immediately
light and you can now check the regulator outputs. You should get +9V
from REG1, -9V from REG2, +5V from
REG3 and -5V from REG4.
These voltages are all measured relative to earth and at the righthand pin
of each regulator, as indicated on Fig.3.
Table 1: Resistor Colour Codes
o
o
o
o
o
o
No.
4
2
3
8
2
22 Silicon Chip
Value
100kΩ
47kΩ
1kΩ
75Ω
10Ω
4-Band Code (1%)
brown black yellow brown
yellow violet orange brown
brown black red brown
violet green black brown
brown black black brown
5-Band Code (1%)
brown black black orange brown
yellow violet black red brown
brown black black brown brown
violet green black gold brown
brown black black gold brown
siliconchip.com.au
Table 2: Capacitor Codes
o
o
o
o
Value
IEC Code EIA Code
1.0µF 1u0 105
220nF 220n 224
100nF 100n 104
If everything is correct, you can
switch off and continue fitting the
remaining parts to the PC board.
Conversely, if one or more of the
regulator outputs is incorrect, switch
off immediately and check for wiring
errors. Most likely, you’ll have made
a mistake fitting D1 or D2, one of the
electrolytic capacitors or one of the
regulators. With a bit of luck, you’ll be
able to fix the problem and not have
to replace any parts.
Completing the PC board
The remaining parts can now be
fitted to the board, starting with the
MKT audio coupling capacitors, the
2.2µF tantalum bypass capacitors and
the 10µF electrolytic capacitors. The
two ICs can then be installed, taking
care that you fit each one the correct
way around.
Note that the pins for IC2 (the
LM833) are only soldered to the copper
pads underneath, while some of the
pins for IC1 (the MAX497) are soldered
to the top copper pattern as well. This
applies to pins 1, 3, 5, 7, 9, 11 & 13.
The next components to fit are the
two 100nF bypass capacitors, which
are at each end of IC1. These mount
with their “earthy” leads soldered to
the top copper pattern as well as the
pads underneath. That done, fit the
two remaining 100nF bypass capacitors for IC1 and the remaining 10µF
electrolytic capacitor for the -5V rail.
As before their leads are soldered to
pads on the top of the board, with their
“earthy” leads soldered to the bottom
pads as well.
Final assembly
All that remains now is to fit the
booster board to the case.
First, you have to fit the front and
rear panels over their respective RCA
connectors, before lowering the three
items together into the bottom of the
case. That done, LED1 can be pushed
into its 3mm mating hole on the front
panel and the board secured to integral
pillars in the bottom of the case using
eight 6mm self-tapping screws.
siliconchip.com.au
Fig.3: install the parts on the double-sided PC board as shown here. The red
dots indicate where component leads must be soldered to the copper tracks on
the top of the board (and usually underneath as well).
Be sure to use all eight screws to
secure the PC board. These are necessary to give the board added support
in the vicinity of the various input and
output connectors.
The final step of all is to fit the top
of the case, using the two long countersink-head self tappers provided. Don’t
lose these screws by the way, because
they’re a special size and surprisingly
hard to get.
Your Video & Audio Booster is now
be finished and ready for use.
Component video cables
Before we end up, let’s take a look
at the adaptor cables required if you
want to use the booster for component
video signals.
There’s nothing terribly complicated about this. All you need to do is
buy or make up four cables - two for
the luminance (Y) signals and two for
the chrominance (Cb and Cr) signals.
The cables for the Y signals each
consist of single lengths of coax with
an RCA plug at each end. These connect to the booster’s composite video
channel, as shown in Fig.1(c).
The other two cables are each of
double coax, with a mini-DIN plug
connected at one end and a pair of
RCA plugs at the other. They are used
to carry the Cb and Cr chrominance
signals and are connected to the booster’s S-video channels.
Note that both RCA-RCA and 2 x
RCA-miniDIN video cables are available from many suppliers. However,
you may want to make up your own
using high quality coaxial cable, to
ensure lower signal degradation - especially if you have fairly long cable
runs. Some prewired cables leave a bit
to be desired in this respect.
By using the correct adaptor cables,
the booster will operate just as effectively with component video as it does
with composite video or S-video.
Happy home theatre viewing! SC
December 2005 23
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
The control circuitry
can either be mounted
remotely from the
keypad (and connected
to it via a cable) or
plugged directly into
the back of the keypad
unit.
Tiny circuit uses a PIC & has
lots of features
A highly flexible
keypad alarm
This versatile little alarm can be used as a
stand-alone alarm system for your home,
commercial premises or car and also for
keypad door entry. Or it can be incorporated
into a larger main alarm system if required.
By JOHN CLARKE
K
EYPADS ARE OFTEN used in
security systems since they avoid
having to use a key or remote control,
both of which can be lost or copied.
Keypads are widely used in commercial
buildings to allow access through doors.
Here we are presenting a standalone keypad alarm system which,
with the addition of a siren, a passive
infrared detector and door switches,
will provide a basic security system
for the home, office, church or hall.
Installed in a car, the keypad alarm
can incorporate an engine immobilis28 Silicon Chip
er, as well as standard burglar alarm
features.
To use the system, a number is
entered in using the keypad. If the
entered number is correct, the unit
will respond accordingly and either
arm or disarm itself and operate a door
lock release, if connected. Exactly how
the keypad alarm responds depends
on the application and how the timer
and options are set.
For example, when used for keyless
door entry, the unit needs to be always
armed and must operate the door lock
release each time the correct code is
entered.
Features
The list of features of this alarm
is so extensive that it will take more
space to briefly describe them all than
to describe the circuit itself. That’s
because all the features are a result
of the programming of the PIC microcontroller. Nevertheless, describe the
features we must, so we will keep it
as brief as possible.
For use as an alarm, the system
needs to be armed on exit and disarmed on entry. Each application requires different operating characteris
tics and the alarm has a host of features
which can be tailored to suit. External
inputs and outputs include delayed
and instant alarm inputs, and armed
and alarm outputs.
The alarm output can only be activated by the inputs after the exit delay.
Instant and delayed inputs can be a
siliconchip.com.au
passive infrared detector and door or
window switches. Alternatively, the
alarm can sound when the keypad is
tampered with or if a duress code has
been entered.
The tamper alarm is activated if
more than five incorrect attempts are
made within a 90-second period. The
3-digit duress code sounds the alarm
when required. In each case, the alarm
is deactivated by entering the correct
code.
Three separate codes are available:
Master, User and Service codes. All
three codes can be different but must
be of the same length. Either the Master
or User code can be used to arm and
disarm the alarm. The two different
codes are included for use when several keypads are installed to operate door
lock releases on separate doors. The
Master code will gain access through
all keypad operated doors, while the
User code only allows entry to selected
doors. These codes can be anywhere
from 1-12 digits long. The last three
digits of the user code become the
Duress code.
The Service code is provided to
change the codes, the various timers
and options. The Service code itself
can be changed and if a new Service
code is entered, it also sets the length
of the User and Master codes. If, for
example, the Service code is six digits,
then the User and Master codes must
MAIN FEATURES
• 1 to 12-digit codes
• Separate Master and User codes
• Service code to alter codes and
parameters
• Duress code to start alarm
• Instant and delay inputs
• Inputs triggered on change
• Optional easy exit input
• Exit delay
• Keypad tamper alarm
• Door lock output and indicator
• Armed output and indicator
• Alarm warning period
also be six digits. Generally, a 4-digit
code is sufficient to provide adequate
security. With four digits, the possible
combinations are more than 14,000
(using digits 0-9 digits plus the * key.
If the entry or Service codes for the
keypad are lost or a mistake is made
on changing a code and the keypad
becomes inoperable, there is a way
to restore operation. This involves
having several inputs tied to ground
when power is applied to return to the
default codes and settings.
Timers
The service mode also allows the
• Audible key entry acknowledge
• Key entry reset using #
• Keypad entry timeout
• All codes can be changed via
keypad
• Adjustable timing parameters
• Alarm mode and keyless door
entry options
• Default return facility for all
codes, parameters and options
• Powers up in armed mode
• 12V operation <at> 15mA
(ancillaries extra)
various timing delays involved with
keypad and alarm operation to be
changed. All time periods can be set
from 1-99s in 1-second increments.
The delayed and instant input timers
determine the time before the alarm
is sounded after being activated. This
delay gives time to enter the building
and switch off the alarm before it
sounds and is necessary if the keypad
is mounted inside. The default settings
are one second for the instant input
and 10 seconds for the delayed input.
Similarly, the default for the exit delay (allowing you to leave the building
after arming the alarm) is 15 seconds.
This view shows how it all goes together. The 7-way SIL socket at the bottom of
the PC board connects directly to a matching pin header on the back of the keypad.
siliconchip.com.au
December 2005 29
Fig.1: a PIC16F84 microcontroller (IC1) forms the heart of the circuit and is used to monitor the keypad and the
delayed and instant inputs. It also controls the various outputs.
In addition, the instant input can be
configured as an exit input – a switch
on this input will arm the keypad
alarm instead of the user having to
enter the code on the keypad.
A door timer sets the duration that
power is applied to an electric door
striker, to give sufficient time to open
the door. The default value here is
five seconds.
Yet another time sets the alarm duration (the default is 60 seconds). By
the way, when we speak of a “default
setting”, it is the setting you get if you
don’t program in a setting.
There is also an “alarm warning
timer”. This sets the time period
before a small piezo transducer in
the keypad sounds and serves as a
warning before the main alarm. The
default is five seconds. Note that the
alarm time starts at the beginning of
30 Silicon Chip
the alarm warning period. Thus, the
alarm warning period reduces the
main alarm duration. There is no alarm
warning if the keypad is tampered with
or the duress code has been entered.
Finally, there is the keypad entry
timer which sets the period during
which the code must be entered. The
default is five seconds but may need to
be extended if the code is 12 digits long
If you make a mistake when entering the code, you can either press
the hash (#) key to reset the timer or
wait for it to time out before trying
again. If an incorrect code is entered
but with the correct number of digits,
the correct code can be immediately
entered in again.
Arming options
Various options are also available
to configure the following operations:
arming, the door lock, the instant input and the armed output. For alarm
installations, the unit must be armed
and disarmed alternately, with each
code entry. By contrast, keyless door
applica
tions will require that the
unit be rearmed each time the code
is entered.
Operation of the door lock will also
depend on the application. For alarm
use, for example, you may need to be
able to arm the unit with the door lock
activated – eg, so that you can exit
the door when the keypad is mounted
inside.
By contrast, an outside mounted
keypad will need to operate the door
lock on disarming, so that you can
gain access. And in some cases, the
door lock will need to operate on both
arming and disarming. All of these
options are available.
siliconchip.com.au
Operation of the armed output
can be altered as well. The default
setting is with the output transistor
conducting to ground when the unit
is armed. When disarmed, the output
can be pulled high with a resistor to
the +12V supply.
Alternatively, you can have the
output transistor conducting (to
ground) when the unit is disarmed
and open-circuit (pulled to +12V using
a resistor) when armed. The armed
output can control a main alarm unit
or switch on an immobiliser in a car. It
generally would not be used in keypad
entry applications.
Status LEDs
The armed and door lock functions
are both indicated with LEDs. First,
the status LED (red) flashes once a
second when the unit is armed and is
off when the unit is unarmed. In alarm
mode, this LED also flashes at a 2Hz
rate to indicate the exit delay period,
reverting to the 1Hz rate afterwards.
In “service mode”, however, the status
LED is constantly lit.
The door lock LED (green) lights
only while the electric door striker
plate is powered. There is no alarm
indication, except for the tone that occurs during the alarm warning period.
Circuit details
The circuit for the keypad alarm is
shown in Fig.1. IC1, the PIC16F84 microcontroller, is the heart of the circuit
and it is used to monitor the keypad
and the delayed and instant inputs. It
also controls the various outputs.
The keypad is a matrix of four rows
by three columns. Two of the switch
column connections go to outputs
RB2 and RB3 respectively, while the
third column connection goes to 0V
(ground). The row connections are
monitored by the RB4-RB7 inputs
which are normally held at +5V via
internal pullup resistors within IC1.
The delayed and instant inputs at
Fig.2: install the parts on the PC board as shown here. The PIC microcontroller (IC1) is installed in a socket and is left out of circuit until after
the initial power supply checks have been made.
RB0 and RB1 are normally held at +5V
via internal pullup resistors. However,
the micro can detect changes of state
of either polarity, so if these inputs are
held low by normally closed switches
and they are opened, this can trigger
the alarm condition.
False triggering is prevented in the
following way. After the micro first
detects a change in level at RB0 or
RB1, it then checks again, after a short
delay. If the voltage remains at the new
level, the micro decides that this was
a genuine change in level. Conversely,
if the level is different after the delay,
the program then decides the original
change in level was a glitch or only
a very momentary change and so is
ignored.
The piezo transducer is driven via a
square-wave signal at the RA2 output
of IC1 to produce a tone. It is used to
acknowledge each key entry and provide the alarm warning tone. Diodes
D2 and D3 are included to prevent
sound in the piezo transducer when
the RA2 output is nominally low (ie,
at 0V). What actually happens is that
switching operations at other inputs or
outputs can be reflected as very small
voltage excursions above 0V and these
would be heard in the transducer if the
diodes were not included.
Outputs at RA3, RA1 and RA0 drive
the alarm out, armed out and door
strike transistors respectively. When
RA3 is high, the base of Q1 is driven
via the 220Ω resistor to switch on the
transistor. The alarm out signal at the
collector can sink a nominal 600mA
maximum to drive a siren and flasher.
Diode D4 protects Q1 against backEMF spikes if the siren is an inductive
load.
Transistor Q2 is driven via the 220Ω
base resistor at the RA1 output. This
transistor can also sink up to 600mA.
It can be configured to switch on
when armed and off when disarmed,
or switched off when armed and on
Table 2: Capacitor Codes
Value Old Code EIA Code IEC Code
100nF 0.1µF 100n 104
39pF 39pF 39p 39
Table 1: Resistor Colour Codes
o
No.
o 1
o 2
o 3
o 2
o 1
siliconchip.com.au
Value
4.7kΩ
2.2kΩ
1kΩ
220Ω
10Ω
4-Band Code (1%)
yellow violet red brown
red red red brown
brown black red brown
red red brown brown
brown black black brown
5-Band Code (1%)
yellow violet black brown brown
red red black brown brown
brown black black brown brown
red red black black brown
brown black black gold brown
December 2005 31
Fig.3: this diagram shows the cutout dimensions for mounting the keypad
into a Clipsal blank plate. Make the cutout by drilling a series of holes
around the inside perimeter first and then knocking out the centre piece.
when disarmed. If required, a pullup
resistor can be connected between Q2’s
collector and the 12V supply.
Output RA0 drives Darlington trans
istor Q3 which is suitable for powering
an electric door strike. This comprises
a solenoid which releases the striker
plate to allow a door to be opened. Diode D5 quenches the back-EMF caused
by the inductive load of the solenoid
when switched off. The transistor is set
to sink a nominal 1.3A with the 2.2kΩ
base resistor. Up to 4A can be handled
if a 680Ω base resistor is fitted.
The door open operation is indicated with the Lock LED (LED2), driven
from the same RA0 output.
IC1 uses an RC oscillator as its reference to set the various timing functions
within its program. The oscillator
components are the 39pF capacitor
and 4.7kΩ resistor at pin 16. It runs
at about 2.7MHz.
32 Silicon Chip
Power for the circuit is provided
from a 12V SLA (sealed lead acid) battery or car battery (when used in a car).
The SLA battery is kept charged using
a plugpack style SLA charger. Power is
fed to the input of the regulator via a
10Ω resistor and diode D1. The diode
provides polarity protection while the
10Ω resistor limits current when the
16V zener conducts due to voltage
spikes in an automotive installation.
REG1 provides the 5V supply for IC1
while the 100µF and 10µF capacitors at
the input and output filter the voltage
and ensure stability of the regulator.
Construction
The keypad alarm is constructed
on a PC board coded 03104031 and
measuring 78 x 48mm. It is mounted
behind a Clipsal blank plate and in a
small plastic utility box. The keypad
sits in a cutout in the blank plate. An
aluminium dress plate is clipped over
this to produce a professional finish.
As an alternative to one-piece
construction, it could be built as two
separate units with the keypad remote
from the circuit box and connected
with 7-way cable. The component
wiring diagram is shown in Fig.2. We
recommend the separate construction
method if the keypad is to be installed
outside a building, to prevent any
tampering with the electronics.
Begin construction by checking the
PC board for any shorts between tracks
or any breaks in the copper pattern.
Check also that the holes are drilled
to suit the components. The corners of
the PC board also need to be shaped
to clear the integral pillars inside the
plastic case.
Install the resistors and wire link
first. Table 1 shows the resistor colour
codes. Use your multimeter to check
the resistor values as well. That done,
install the diodes, taking care to install
the zener in the correct place. Install
and solder in the two PC stakes.
Q1 and Q2 are both mounted with
the top of the transistor body 8mm
above the PC board. Transistor Q3
mounts with its leads bent over at
90 and sitting on top Q1 and Q2. Q3
should have its metal face upwards.
Next, install the 5V regulator, the
capacitors and IC socket. Take care to
orient the socket and the electrolytic
capacitors with the correct polarity.
The keypad connection uses a 7-way
socket cut from a 14-pin DIL IC socket. Cut the socket with a sharp utility
knife to obtain the two socket strips.
The second strip is soldered to the
underside of the keypad.
The LEDs are soldered with their
tops 21mm above the PC board. Finally, install the 8-way terminal strip.
Mounting the keypad
Mounting the keypad into the
Clipsal blank plate is done by placing
the keypad with the terminal end as
close to the internal mounting hole
bushing as possible. The cutout dimensions are shown in Fig.3. Mark out
the required cutout for the keypad and
cut this shape out by drilling a series
of holes around the perimeter first
and then knocking out the piece. File
to shape afterwards. If you make this
cutout very neatly, it can be used as
the template to cut out the front panel
aluminium dress plate.
Four holes (marked C on Fig.3) are
siliconchip.com.au
Parts List
The piezo buzzer is mounted on top of a 10mm untapped spacer and secured
using a 15mm machine screw and a 10mm tapped spacer which screws on from
the underside of the board.
1 PC board, code 03104031, 78
x 48mm
1 plastic utility box 83 x 54 x
30mm
1 blank plate and blank
aluminium plate (Clipsal
CLIC201VXBA or similar)
1 12-key numeric keypad (Jaycar
SP-0770, Altronics S-5381 or
similar)
1 8-way PC-mount screw
terminal strip with 0.2" spacing
1 piezo transducer (DSE L-7022,
Jaycar AB-3440 or similar)
1 14-pin DIL IC socket (cut for 2 x
7-way sockets)
1 18-pin DIP socket
1 7-way pin header 0.1" spacing
1 6mm spacer
1 10mm untapped spacer
1 10mm M3 tapped spacer
4 4G x 20mm self tapping countersink screws or M3 x 20mm
csk screws
4 4G x 6mm self-tapping cheesehead screws or M3 x 6mm
cheese-head screws
1 M3 x 25mm cheese-head
screw
2 M3 x 15mm cheese-head
screws
1 M3 nut
2 PC stakes
1 50mm length of 0.8mm tinned
copper wire
A brick wall may require the unit to be mounted onto a standoff box, such as the
Clipsal No.449A shown in this photograph.
Semiconductors
1 PIC16F84 programmed with
Keypad.hex (IC1)
1 78L05 3-terminal regulator
(REG1)
2 BC337 NPN transistors
(Q1,Q2)
1 16V 1W zener diode (ZD1)
3 1N4004 diodes (D1,D4&D5)
2 1N914, 1N4148 diodes (D2,D3)
1 BD681 NPN Darlington
transistor (Q3)
1 3mm red LED (LED1)
1 3mm green LED (LED2)
required for mounting the keypad. Use
a 2.5mm (3/32-inch) drill. The holes to
mount the plastic box directly beneath
the plate are shown as B (countersunk).
If you intend to mount the keypad
and electronics separately, these four
countersunk holes will not be required
– see Fig.4 for the mounting details.
As shown in Fig.4, the PC board
is secured in the plas
tic box using
screws when installed directly behind
the blank plate or clipped into the
integral side clips of the box when
mounted separately. The integral side
clips will need to be snipped out with
siliconchip.com.au
side cutters to a depth of about 10mm
when the PC board is mounted directly
behind the plate.
The keypad is connected to the PC
board using the IC socket strips on
both the keypad and PC board, with a
7-way pin header plugged in-between
these. For the separate unit version,
connection is via 7-way cable plus two
extra wires for the piezo transducer.
The piezo transducer can be either
mounted on top of a 10mm standoff
for the single-unit installation or on
the back of the keypad for separate
units. The piezo transducer should be
Capacitors
1 100µF 16V PC electrolytic
1 10µF 16V PC electrolytic
1 100nF MKT polyester
1 39pF ceramic
Resistors (0.25W 1%)
1 4.7kΩ
2 220Ω
2 2.2kΩ
1 10Ω
3 1kΩ
December 2005 33
Fig.4: these diagrams show how to install the control box directly on the
back of the keypad to make a single unit (top), or remotely to improve
security when the keypad must be mounted outside. Note the location of
the piezo transducer in each case.
loud enough with the sound coming
through the keypad itself. Extra holes
can be drilled through the plate and
aluminium cover if more sound level
is required.
Testing
Connect power to the +12V and
ground terminals and measure the
voltage between pins 5 & 14 of the IC
34 Silicon Chip
socket. This should be close to +5V. If
correct, disconnect power and insert
IC1.
Now reapply power with the keypad connected – the status (red) LED
should be flashing at a one-second
rate. Enter 1000 and the armed LED
should extinguish. There should be
a beep from the piezo transducer on
each key press.
Enter 1000 again and the status LED
should begin flashing twice per second
and the green (door strike) LED should
light for five seconds. After 15 seconds
(the default exit delay), the status LED
should return to the 1-second rate.
Enter in 2000 and the same results
should be available as for the 1000
code. These are the default Master
and User codes. Any mistake when
entering a code can be cleared with
the # key. Enter 000 for the duress
code and the piezo transducer should
sound for around one second and the
alarm output should go low. This can
be checked with your multimeter
switched to a low Ohms range. To
cancel the alarm output, re-enter the
Master or User code.
Try entering more than six incorrect
codes until the alarm output goes low
again. Entering a correct code will stop
the alarm.
Now enter the Service code – 3000.
The status LED should now light continuously. Press # to cancel.
The Service mode allows changes
to be made to the codes, delays and
options. These are summarised in the
Table 3. Changing the Master and User
codes is done by entering the Service
code, then a 1 for the Master code or
a 2 for the User code.
Enter a new number code (maximum 12 digits). The * key can be used
siliconchip.com.au
The keypad is secured to the wallplate using four M3 x 20mm CSK
screws. The modified aluminium
dress cover then clips over the top to
give a neat finish.
as part of the code. The # key exits and
returns the unit to normal operation.
The new code will be stored and can
then be used. Changing the code again
will require the same steps.
Note that the code entry length is
set by the Service code and initially,
with this being set at 3000, the Master
and User codes can only be four digits
long too. Also note that the 10th, 11th
and 12th digits of the User code will
set the duress alarm code if entered
first. So be sure that any User, Master
or Service codes do not start with these
numbers, otherwise the duress alarm
will sound.
Changing the service code
This can be done by entering the
current Service code, pressing key
3 and then entering the new code.
Pressing 12 keys will set all codes to
12 digits. Pressing only a few keys and
then the # key will set the code at the
entered length.
Note that the Master and User codes
have defaults of 100000000000 and
200000000000 respectively (12 digits)
and these are normally truncated to
1000 and 2000 when the code is four
digits long. So if the Service code is
increased in digits, then more zeroes
will need to be entered for the default
Master and User codes.
If you forget the Service code, it
siliconchip.com.au
Fig.5: the input, output and power options for the keypad unit. Both the
delayed and instant inputs can be connected to either normally open (NO)
or normally closed (NC) switches but do not mix these two switch types on
the same input.
December 2005 35
TABLE 3: PROGRAMMING THE ALARM KEYPAD
For all service operations, enter the Service code, press the designated function key and
then enter the code or value. Press the # key to end each single digit entry.
Key
Codes
Range
Default
1
Master Code
0-9 and * (1-12 digits)
1000
2
User Code
0-9 and * (1-12 digits)
Duress Code is last three digits of 12-digit
code
2000 (User Code)
000 (Duress Code)
3
Service Code
0-9 and * (1-12 digits) - sets code length
3000
Note: for codes less than 12 digits or timer numbers less than 10 digits, press # to enter value. Do
not make the first three digits the same as the Duress Code.
Key
Timers
Range (seconds)
Default
(seconds)
4
Delayed Input
1-99
10
5
Instant Input
1-99
1
6
Door Lock
1-99
5
7
Exit Delay
1-99
15
8
Alarm
1-99
60
9
Alarm
Warning
1-99
5
0
Keypad Entry
1-99
5
Option
Mode
Default
Alarm mode, lock powered on arming, instant
0# (16)
0
alarm input
Alarm mode, lock powered on arming, exit
2# (18)
0
input
Alarm mode, lock powered on disarming,
4# (20)
0
instant alarm input
Enter
Alarm mode, lock powered on arming, exit
Service
6# (22)
0
input
Code &
Alarm mode, lock powered on both arming
Press *
8# (24)
0
and disarming, instant alarm input
Alarm mode, lock powered on both arming
10 (26)
0
and disarming, exit input
Keyless entry mode, lock powered on
1#
0
rearming, instant alarm input
Keyless entry mode, lock powered on
3#
0
rearming, exit input
Note: entering the first option number means that the armed output is pulled to ground when the
alarm is armed. Conversely, entering a bracketed number means that the armed output is pulled to
ground when the alarm is disarmed.
Resetting To Default Values
Tie instant & delay inputs
low, hold down the 3 6 9 and Resets all codes, timing parameters & options to default values.
# keys, and power up.
is possible to redeem the situation.
First, switch off the power and tie the
instant and delayed inputs to ground.
Now hold down the 3, 6, 9 and # keys
simultaneously and re-apply power.
The status LED will light and stay lit
until power is again disconnected. All
codes and settings will then be set to
36 Silicon Chip
their default values.
The delay values can be altered using keys 0 and 4-9, after entering the
Service code. The delays can be set
to any time from 1-99 seconds. Entry
of a single digit time period needs to
be ended with #, to store the value
and exit the Service mode. Entry of a
Suitable Accessories
Sirens: 12VDC at 500mA max Altronics S-6127, S-6120, S-6125;
Jaycar LA-5254, LA-8908, LA5258, LA-5256; Dick Smith Elec
tronics L-7031, L-7025, L-7029.
Siren strobe: Jaycar LA-5308.
Battery charger: 12V SLA 1.2
to 7Ah - Altronics M-8520; Jaycar
MB-3517.
Security door latch: 12V DC DSE L-5809; Altronics S-5385;
Jaycar LA-5078.
2-digit value will automatically store
and exit the service mode.
Options
The options are entered in a slightly
different way in that the * key is entered after the service code and then
a number which matches the required
operation mode is entered. The main
change that can be made to the unit is
from alarm operation to keypad entry
mode operation. Alarm mode means
that the unit is armed on entry of the
Master or User code and disarmed on
the second entry of the code. You can
also select whether the door striker is
operated on arming, disarming or both.
Input wiring
Fig.5 shows the connections that
can be made to the keypad alarm.
The delayed and instant alarms can
be connected to normally open (NO)
or normally closed (NC) switches. NO
switches can be connected in parallel
while NC switches are connected in
series. It is not possible to mix NO
and NC switches on the same input.
The switches can be set up in a
doorway to detect opening or can be
a part of an ancillary component such
as a passive infrared detector. You can
also use doormat switches, window
switches and glass breakage tape, or
similar.
Power options for the keypad unit
are also shown in Fig.5. For automotive applications, it is simply connected between chassis for the ground
supply and to +12V via the fusebox
for the positive supply. The supply
must be continuous 12V and not the
switched supply used for ignition or
accessories.
For other applications, the unit
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75
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needs a 12V SLA battery rated from 1.2 to 7Ah capacity.
1.2Ah should be adequate for most applications but heavy
usage of the door
strike may require a larger battery.
100
This really depends on your application. For most
installations, the
75 keypad will be installed on a wall near
the exit door. A brick wall may require the unit to be
mounted onto a standoff box such as the Clipsal No.449A
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December 2005 37
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Fig.5: this is the full-size etching pattern for the
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SERVICEMAN'S LOG
So what if it’s ancient technology?
I am still happily surprised at the amount of
ancient technology that is brought to my door
to repair. Most of it is probably not worth fixing
but I am happy to oblige, where I can, if the
client insists and is prepared to pay the cost.
R
ecently, I had a 1977 Sony KV9000UB 22cm (9-inch) portable
TV in for repair. I really couldn’t
believe anyone would want to fix
such an old set but it had sentimental value for its owners. They were
complaining of a seized UHF tuner
and so were unable to get anything
on the UHF bands.
Fortunately, access to the rotary
tuner was easy and after removing its
cover spring, I was able to get right
inside it. The bearings of the variable
capacitor had seized and the resulting
strain (from trying to turn it) had broken the solder joints to the mounting
plates. A hot iron soon fixed this and
the bearings were freed with CRC.
38 Silicon Chip
Now the tuner could pick up channels easily. I then had to modify the
UK specification sound system to the
Australian system. This meant replacing ceramic filter CF201 to convert the
6.0MHz IF to 5.5MHz. I then had to
tune T213 and T211 until the sound
was loud and clear and the colour was
free from herringbone patterning.
When I’d finished, I was amazed at
how a vintage TV a quarter of a century old could give such a good sound
and picture with such a basic circuit.
One wonders how long all the new
technology will last?
Philips VCRs
I’ve had a number of Philips and
JVC VCRs in for repair. These include
the Philips VR 250, 350, 450 & 550
series and the JVC HR-J240 series, etc.
Philips uses the same JVC mecha-deck
(PMC 0011A) in their models and
they no longer service them. Instead,
they offer exchange units and long
warranties.
One common problem that develops in the 1994-1997 range of models
is that the VCR is unable to eject the
tape. Discovering the cause and fixing
this the first time around was long and
arduous but now I am quite adept at
this repair.
What happens is that the tension
spring to the change arm assembly
www.siliconchip.com.au
Items Covered This Month
• Sony KV9000UB TV set.
• Sony SLV-EZ7AS VCR.
• Samsung SV-641 VCR.
• Philips VR 250, 350, 450, 550
series and JVC HR-J240 series
TV sets.
• 1993 Mitsubishi Diva CT29ATS(A)TX TV set.
• NEC FS-59T90 TV set.
• Philips 29PT2255/79R TV set
(L01.1A chassis).
• Philips 29PT4873/79R TV set
(L9.1A chassis).
• Akai CT2007A TV set.
• Yamaha VR-5000 100W guitar
amplifier.
comes off because the support bracket clip breaks on the latter. The part
numbers are 4822 403 71304 (Philips)
and PQ46353A-2 (JVC). You have to remove the whole deck and the cassette
ejector cage assembly first before you
can get access to it. You then have to
remove the slide plate assembly.
That done, you can remove the
change arm and swap the change gear
onto the new one. Care needs to be
taken refitting the spring as the new
change arm doesn’t look any different
from the old one and will probably
break again in exactly the same spot
in a few years time (you would have
thought they would have improved
this assembly by now). Refitting the
slide plate can be a bit fiddly but
with gentle perseverance, it will soon
all slip in with spring-loaded brakes
(place in OFF position). Reassembling
the rest is a breeze.
What can cause a lot of confusion
is the tension spring from the take-up
lever. The reason for this is that it
isn’t fitted on all models and yet the
spring support clips are still there.
This has been known to cause panic
as you carefully comb the entrails of
the VCR looking for the missing spring.
My policy is that I haven’t ever known
this to break off, so if it’s not there, it’s
not supposed to be there.
On the later JVC decks, (eg, HRJ457MS), I have also found that the
drive gear axle (LP30243-001B) can
sometimes break (this connects onto
the cassette holder assembly).
I also had a Sony SLV-EZ7AS video (S-MECHA) with a right old mess
www.siliconchip.com.au
inside, which I think can only be put
down to forcing the mechanism. Anyway, the main cam and stopper, the
slider and reverse brake arm were all
smashed. The whole thing had to be
stripped right down and reassembled
and it was a good job I had the complete set of service manuals to do this.
Going crackers
A Samsung SV-641 hifi stereo VCR
came in with the complaint that it
was chewing tapes. This wasn’t too
surprising considering that I eventually retrieved a cheese cracker from
within the mechanism – one to add to
my collection of diamond engagement
rings, false fingernails, cake, money, an
ants’ nest and, of course, the proverbial
cockroach infestation.
When it came to testing the VCR,
however, I discovered I couldn’t tune
it in on a TV set. In fact, it wasn’t until
I removed the antenna that I found the
answer – it was slap bang on an SBS
channel. The owner was unaware of
this, as that SBS station was not available in his area but he did have a lot
of patterning and interference on his
VCR. Relocating it to Ch68 and using
AV leads fixed this problem.
Faulty NEC
Mrs Jocelyn Gale, a charming old
lady of 84, asked me to look at her
2-year old NEC FS-59T90 TV set (actually a Daewoo CP-785A) which had
intermittent sound.
In deference to her age and her polite
manner, I agreed to call round but I
said there was a good chance it might
have to go to the workshop, as it was
intermittent. I told her to try giving
the set a good belt when it played up
and tell me about it before I called.
In retrospect, this was bad advice, as
osteoporosis may have done her more
damage than the set.
Anyway, she told me this procedure
hadn’t broken her arm and did have
an effect. I was delighted with this
news because it was highly probable
there was a crack or dry joint and I
probably had a good chance of fixing
it in her unit.
When I arrived, I noticed she was
using headphones on the set, so as not
to disturb her neighbours. Experience
told me straight away that it was highly
likely that the headphone jack socket
had been damaged due to tension on
the cord.
I removed the back and withdrew
the chassis. It was soon apparent
that my suspicions were spot on. I
re
soldered the PC-mounted socket
(HP01) and also checked the audio
output IC (IC602) and anything else
that looked suspicious.
That fixed that problem but Jocelyn
then wanted to try an infrared cordless headphone set to take the place
of her wired headphones. I set them
up for her and then spent some time
patiently explaining that the receiver
unit’s batteries needed recharging
when they weren’t being used.
An old Panasonic
I had another 1991 Panasonic
TC68A61 (M16M chassis) to attend to
the other day. The owner complained
of poor colour, which could mean
anything.
When I got there, it was immediately
obvious from the pink picture that
there was no green. This fault can be
caused by anything from the jungle
IC to the picture tube. I started with
the output transistors and measured
the voltages around them and on the
picture tube cathodes (M68KPH167X).
I was mostly comparing the voltages
between the three colours and looking
for differences, particularly on the
green gun. Unfortunately, there was
very little to pick, which really meant
there was a problem with the tube
itself. Just in case, I swapped the red
and green transistors over and also
tried using links to swap entire colour
amplifiers over but to no avail.
The CRT analyser quickly showed
April 2003 39
Serviceman’s Log – continued
the problem. Unusually, it reported
that the green gun had G2 open circuit
and G1 to cathode short circuit.
Apart from changing the tube
(which isn’t cost effective), the only
other option is to try to “boost” the
tube by “blasting” the cathode with
an AC voltage.
I did this and was extremely happy
when the green came up immediately.
I put the set on soak test but then, 10
minutes later, the picture (all colours)
went very dull.
Over the next couple of days, I tried
again and again to boost the tube and
on each occasion I was successful for
up to 10 minutes before it went dull
again. Obviously, when the tube got
sufficiently hot, the electrodes were
touching again under the influence of
gravity. In the end, there was nothing
for it but to return the set to the owner
and advise that it be scrapped.
Dead & ticking
A 1993 Mitsubishi Diva CT29ATS(A)TX (ATMV691 chassis) was
delivered to the workshop with the
40 Silicon Chip
complaint that it was “dead and ticking”. Its owner, Mr Plumley, thought
it was the on/off power switch. Well,
of course he would. I mean, there are
only four components in a TV set,
aren’t there? – the fuse, the switch, the
picture tube and its valve!
After all, what else would you expect for the money?
After spending half the morning
undoing the 50,000 screws that held
the back on, I finally managed to
remove it. Next, just to satisfy my curiosity and Mr Plumley’s conviction,
I measured the on/off switch and the
fuse. After all, they do occasionally
fail. But not in this case – they were
perfect.
The power supply is a complex twin
IC (master and slave) switchmode
unit, designed to give good regulation
of several rails in both manual and
standby conditions. It also features full
over-current, short-circuit and over
and under-voltage protection.
So, where do you start? I measured
full voltage going in and nothing coming out. There were no short circuits
on the secondaries, only the usual load
conditions.
I resoldered any likely dry joints but
to no avail. Everything looked pretty
good, so I diverted my attention to
the electrolytic capacitors – and there
were an awful lot of them.
There were two options here – I
could either get all scientific and make
lots of measurements to try to track
down the faulty capacitor, or I could
simply adopt a blanket approach and
change them in batches. I opted for
the latter.
Judging by the smell of fish as I unsoldered the first batch, I was immediately on the right track. After replacing
just seven of them (C9B7, C9C1, C9C2,
C9E1, C9E5, C9E9 & C9F1), the set was
working perfectly. I soak tested it for a
week before returning it to Mr Plumley
who didn’t know what a capacitor was.
However, he did understand a 90-day
warranty – I do hope the switch lasts
that long!
Philips L01.1A chassis
I am beginning to see a few late-model 29PT2255/79R and 29PT2252/79R
Philips TVs. I am talking about the
L01.1A chassis, which came onto the
market about 2001 onwards. The usual
problem is that the set is dead due to
the fact that the switchmode power
supply is cactus.
The cause is not yet fully understood but this fault normally occurs
during power surges. To fix it, I order
and install what I call “Fred’s Mod
Kit”, named after a friend of mine who
repairs these sets under warranty. He
found that eight parts usually need
replacing – the chopper tran
sistor
(7521), its driver (7522), IC7520,
R3523, R3530, D6523, D6524 and
possibly D6525, which is not always
fitted.
Of course, strictly speaking, this
isn’t a modification kit but only a
replacement parts list. Perhaps a modification will come out in due course?
Another problem that is occurring is
hum in some Philips models. One in
particular comes to mind, the model
29PT4873/79R (L9.1A chassis), which
can get particularly bad if placed on a
resonating wooden table.
The cause is a deflection yoke with
vibrating windings and the solution
is to remove it and dunk it in Estapol
varnish. Beforehand, it is a good idea
to mask any areas that might be critical
such as where it contacts the picture
www.siliconchip.com.au
QLD ELECTRONIC REPAIRERS
GOING ..... GOING ..... GONE!!
The new Electrical Safety Act will affect YOUR income!
If you previously thought this new law did not apply to you please be very careful because it most likely does! You may hold a restricted
electrical licence but this is no longer enough in Queensland. There are several repairers that have closed already because of this law.
Before this law was enacted it is claimed that there was widespread consultation. Electronics repairers were not consulted and indeed at the
meetings that were held far and wide only electricians turned up. This is not surprising because electronics technicians were never invited! Even
more interesting is that electronic products such as TVs, photocopiers, pinball machines, sewing machines, marine electronics, computers
and every other item repaired by electronics technicians were never even mentioned at these meetings!
The fine print of this new law means that a very large percentage of electronic repairers (who are not electricians) cannot obtain this
licence even if they want to spend more than $1000 per year to comply. Electrical safety will not improve because of this law.
When the ESO inspectors call, and they will call, if you are found to be operating without a current Electrical Contractors Licence you can be
fined up to 500 penalty units; that translates to $35,500 (for an individual) or $187,500 for a corporation or SIX MONTHS JAIL!
AETA is a newly formed “not for profit” association legally incorporated in Queensland with the aim of fighting for a better outcome from
this bad legislation. We are technicians from all areas of electronics who are demanding fair treatment. AETA (All Electronic Technicians
Association) will fight to have this ridiculous law amended and we urge you to join forces with us to sensibly oppose this new impost on
your livelihood.
You cannot ignore this, it will not go away. It is now law, you must do something.
The time for apathy has long passed. If you do not act today and join AETA you WILL be stuck with this situation. Give AETA the power to
fight for a better deal. JOIN RIGHT NOW or face becoming extinct. Your $100 investment may well protect your current & future income.
We can email an application form to you or better, you can post your cheque or money order for $100 (include your details, GST is not
applicable and a receipt and GST statement will be emailed to you, membership is tax deductable) to:
AETA, PO Box 6926, Cairns, Qld 4870
email: cairnscomms<at>iprimus.com.au
We must have your email address as AETA is unable to answer postal or phone enquiries. This drains our time & money resources. AETA
is a volunteer association & every cent we have will be spent fighting this problem. Authorised by M Kalinowski President & R Brinkman
Secretary.
tube and the three rubber spacers.
The procedure should be repeated
three times, allowing it to dry after
each dunking before reassembling it
onto the tube neck. That should stop
the windings from vibrating and fix
the problem once and for all.
Kong Wah TV sets
I see a lot of the Kong Wah or
similar Chinese-manufactured TV
sets made for Teac, Akai and others.
Most problems stem from electrolytic
capacitors, particularly those located
near heatsinks and other heat sources.
The other day, I had a slight variation on this theme that caused me to
lose even more hair. It was an Akai
CT2007A and it was dead. To begin
with, I replaced the main culprits –
ie, C911 and C909 (47µF). That done,
I got stuck into the collateral damage,
namely R917 and R421 (0.68Ω), plus
12V zener diode ZD401.
I now had sound and picture but
unfortunately the picture was really
crook! I connected a colour bar generator to the TV to try and make sense of it
www.siliconchip.com.au
all. This resulted in large vertical black
bars, a floating picture (intermittent
horizontal sync) and colour reversal
on every alternate bar.
All in all, it looked like a titanic failure of the jungle IC (IC301,
AN5601K) – ie, a general flooding in
all major com
partments! However,
before ordering, paying for and replacing this 42-pin high-density IC, I
thought I would first check out some
of the voltages and waveforms being
fed into it.
This turned out to be a good move,
because I measured just 3.2V on pin
10 (the 5.2V Vcc pin). This voltage
didn’t improve even after I had
desoldered the IC pin. Following it
back, I discovered ZD301 (a 5.1V
zener) and R357 (270Ω 1W) coming
from the +12V line. The latter was
getting hot and it was fairly obvious
that the zener was more than half
dead.
Replacing it fixed all the symptoms
and restored a healthy picture.
And now, here is a contribution
from one of our readers. It comes from
A. P. of Kuranda, Qld. Here’s how he
tells it . . .
Yamaha guitar amplifier
I recently started to do repairs for the
local music store. So far I have had a
steady stream of faulty cables, crack
ling volume control pots, faulty phone
sockets and the like. Occasionally a
more juicy morsel turns up.
The Yamaha VR-5000 100W guitar
amplifier came with a brief note saying
that the “power board” had “blown
up”. This amplifier has two fuses accessible from the rear panel. There is
a 1.6A fuse which is in-circuit when
the unit is set to run on 240VAC, plus
a second fuse, rated at 3.15A, which is
always in circuit and protects the unit
when it is run on 110VAC.
In this case both fuses were intact
but the 1.6A fuseholder held a 3.15A
fuse. When I removed the amplifier
from its case, it was clear that this
overrated fuse had permitted exten
sive damage to occur. There were two
charred areas on the PC board where
1/8W resistors had formerly resided
April 2003 41
Serviceman’s Log – continued
and it was clear that a couple of 0.22Ω
2W resistors had also overheated.
I tested all the components in the
power amplifier section and made an
inventory. The damaged parts were
the two 2SC3181 NPN output transistors (Q711 & Q713); their 0.22Ω
2W emitter resistors (R717 & R719);
a 2SC1980 transistor (Q652) in the
speaker protection circuitry; two
150Ω 1/8W resistors (R655 & R656),
connected between the base of Q652
and the emitters of Q711 and Q713
respectively; and two 100Ω 1/8W
resistors (R741 & R742), spanning the
emitters of the driver transistors.
So what had caused the failure?
Everything pointed to PNP driver
transistor Q709 (2SC3421) but this
tested OK. In the end, I shrugged my
shoulders, replaced the damaged parts
and repaired any PC-board tracks that
had been damaged by the heat. But I
hedged my bets a little and installed
only one set of output transistors.
When I picked up the mains plug to
insert it into the wall socket, I noticed
that it wasn’t the original OEM plug
and that the neutral and active wires
had been transposed. I made a mental
note to correct this before returning
the amplifier to the customer but left
it as it was for the time being. Why?
The active line visits both fuses and
the connections are not in any way
protected against accidental contact.
It would actually be safer for me while
I worked on the amplifier if all these
connections were at neutral potential.
The switch-on was an anticlimax
42 Silicon Chip
– there was absolutely nothing. The
supply rails were showing 0V and I
traced the problem back to the transformer. The 150°C thermal fuse in the
transformer primary was open circuit.
I couldn’t easily get at it but there was
electrical access to both sides, so in
the interests of getting things going, I
simply bridged it for the time being.
This time, when I switched on,
there was again no apparent activity.
However, when I checked the 1.6A
fuse afterwards it had blown and so
had the replacements for Q711 and
its emitter resistor. So there was still
a fault somewhere but at least I had
demonstrated that the correct fuse
protects most of the circuitry.
I decided to try the amplifier
without the output transistors, to see
whether the feedback was effective at
keeping the DC levels on the driver
transistors in check. To maintain the
feedback, which is critical to the DC
balance, I disconnected R721 from the
output line and connected it instead to
the junction of R741 and R742.
At the next switch on, I was immediately greeted by a stream of smoke
coming from R741 and R742. I quickly
switched off. Q709, the NPN driver
transistor, was very hot but both it and
the resistors seemed to have survived.
Just to be sure that there wasn’t a fault
in Q709, I lifted one end of R713 (its
base resistor) and switched on again.
This time, Q709 remained cool.
Clearly, Q709 was being turned hard
on. With R713 still out of circuit I
measured the voltage at the junction of
the two 100Ω emitter resistors. It was
-44.9V. Perplexed, I checked the base
voltage of Q710. It was -41.1V. –Q710
should be off.
And then the penny dropped:
Q710 must have emitter-collec
tor
punch-through. I hadn’t spotted it in
my initial testing because I had only
tested for diode action between base
and emitter and between base and
collector. Now wiser, I checked the
collector-emitter resistance – it was a
dead short in both directions.
So Q710 was dragging the output
very negative. Q709 was getting hot
because it was driven hard on into a
low resistance load. And Q709 was
driven hard on by the fully functional first stages of the amplifier, which
were desperately trying to correct that
-44.9V output to match the 0V input.
Replacing Q710 brought everything
back into line. I replaced Q709 too, just
to be safe, since it had been seriously
overheated.
I now considered what I should do
about the power transformer, which
no longer had its thermal fuse. I could
easily fit a new thermal fuse but it
would have to sit on the outside of
the transformer where it might not
respond quickly enough to prevent
the wooden cabinet from catching fire.
This put me into an ethical dilemma. I didn’t expect that the owner
would be happy forking out $150 for
a new transformer when the old one
was working perfectly. But I also didn’t
want to return the amplifier in a state
where it might cause a fire – even if that
situation was precipitated by someone
again replacing the 1.6A fuse by one
with a higher rating.
Fortunately, when I contacted the
owner he gave the go-ahead to replace
the transformer. The replacement arrived in a few days. I fitted it, swapped
the active and neutral connections in
the mains plug and we were back in
SC
business.
www.siliconchip.com.au
book review
–
THE DICK SMITH WAY, By Ike Bain.
Published 2002, Mc-Graw Hill, Sydney.
Soft covers, 135 x 207mm, 234 pages.
ISBN 0074 71160 1 $22.95
When Dick Smith mentioned to me over
a year ago that Ike Bain was writing a book
about the old days at Dick Smith Electronics
and Australian Geographic, I thought to myself, “This will be interesting!” I realised that
Ike would have to be careful that he did not
write a book which was simply a sentimental
roam down memory lane.
At 234 pages, the book is not a long read.
It is divided into two parts: Part 1 is entitled
“Working With Dick Smith” (chapters 1-6)
while Part 2 is “The Dick Smith Way” (chapters 7-16). These distinctions are in fact, quite
arbitrary. Part 1 slides right through the book
almost to the end.
Clearly, Ike loves Dick. Indeed, much of
the book is a gushing hagiography. Dick is
truly a remarkable Australian and it takes
a book like this to make one realise that a
quality biography on Dick is long overdue.
However, Ike unfortunately does not
mention the most powerful factor in Dick’s
success, his wife Pip, until page 83. As I
feared, Ike indulges in more than a little reminiscing. You could be forgiven for thinking
that the book is also part autobiography. We
learn about Ike’s childhood in Canada and his
decision to come to Australia.
We are regaled with stories about early
days at DSE. If you took these stories at
face value, you could reasonably conclude
that Ike and Dick alone were responsible for
the success of DSE. They were big factors
but not the only ones. Ike was very good
at managing retail operations but he is
mean-spirited in his praise of others. Very
few names are mentioned in passing and
none are given much credit. Worse, many
hard-working and talented people have been
omitted entirely. The people who established
the hugely successful business operations
in New Zealand were not mentioned at all.
On too many occasions Ike simply gets
the facts wrong. For example, Ike claims
on page 67 that Dick Smith picked the then
future trend of CB radio. In fact, being a
radio amateur, Dick was against CB radio at
first, even though he may have been aware
of the well-known popularity of CB radio
in the USA. In those days, much of the
27MHz band was allocated in Australia to
amateurs as the 11-metre band. But while
the amateurs considered it a ‘trashy’ part of
the spectrum, they weren’t about to give it
up to a bunch of non-technical yahoos who
did not hold a licence. So Dick was justifiwww.siliconchip.com.au
by Gary Johnston*
ably concerned that lending his name to a
proposal to establish an American-style CB
radio system would diminish his standing in
the amateur radio fraternity.
I was not an amateur and had no such
qualms. At first, I was the guy doing the TV
interviews and the press interviews. We were
quickly so successful in selling CB radios
that Dick relented and decided to become
the voice of CB for the company. That was
how Dick got the handle “Tricky Dicky,” not
as Ike claims in the book on page 66.
On page 119, Ike claims that DSE had “no
money for marketing”. This is simply not
true. In fact, at that stage the company was
spending hundreds of thousands of dollars
on catalogs, brochures, advertising, etc. On
pages 50-51, Ike suggests in June 1987
that it was he who was first to suggest that
Australian Geographic should sell goods by
mail order. On page 72 however, Ike reprints
a letter from Dick to him a year earlier suggesting to Ike the very same thing. There are
many other factual errors, some minor but
still annoying.
Perhaps to some this criticism may sound
rather pedantic. There is a point to it, however. On pages 79-80 he quite rightly tells us
about the “paranoia” of avoiding errors by
exhaustive means when he worked at AG.
It’s a pity that that lesson was lost on him
in this book.
To be fair, most of Ike’s recollections are
sound. I distinctly recall the refreshing openness at DSE (page 147). I also appreciated
Ike’s retelling of those legendary stories
about the April Fool’s day fake iceberg, the
Antarctic trips, etc.
However, if you did not know better, after
reading this book you would think that Ike
was there every step of the way, deeply
involved in setting up importing operations,
reviewing new products (pre-video), establishing the dealer network, closely working
on the catalogs, coming up with marketing
ideas (the big flag was his), keeping an eye
on slow-moving stock, product costing,
working with the electronics magazines on
new project kits, etc.
In fact, I don’t recall Ike doing much of this
at all, certainly not during the 1970s, anyway.
I mainly remember Ike flat out running the
existing shops and opening new ones (and
doing a good job at it, as well).
The things mentioned above were part
of the ‘engine room’ of the DSE business.
It took a second reading of the book to
realise that Ike clearly missed a lot of
the experience derived from this period.
I say this because Ike neglects to men-
tion possibly the biggest factor in the
incredible profitability of DSE – that
goods were directly imported from overseas and retailed without a local wholesale
middleman. This was quite rare at the time.
This inexperience shows at the very end
of the book as well. Ike’s rather quaint and
folksy business ‘wisdom’ grates. On pages
153-154 he tells us to “give away as little
of your position as possible” when negotiating, and to be “tough” when negotiating
with landlords. Unbelievable. He also tells
us to hire “miserly” accountants on page
166. The fact is, accountants are there for
other reasons. It is usually up to middle/
upper management to keep an eye on costs.
By the time the bill comes to accounts, the
transaction is complete.
On page 159, Ike instructs us to trust noone. This is not only ridiculous, it’s sad. You
simply cannot do everything yourself. You
have to learn to trust people and 99% of the
time if you are prudent with your choices of
employee, you will be fine.
There are also a couple of mysterious
omissions in the book: what happened to
Dick Smith USA, or the reasons Woolworths
would put DSE up for sale in 1986 if it was
such a profitable company, irrespective of
Woollie’s problems elsewhere?
In the end, the book is a disappointment.
The clumsy structure, confusion of purpose,
factual errors, the omissions and the rather
dated folksy wisdom add up to a fairly
self-indulgent effort. However, it may be of
some use to those who are interested in the
corporate history of Dick Smith Electronics
and Australian Geographic in the early days or
as fodder for the corporate motivation junkie.
*Editorial note: Gary Johnston worked
very closely with Dick Smith and Ike Bain
for many years. In 1981, he left Dick Smith
Electronics to buy John Carr & Co, which
went on to become Jaycar Electronics.
April 2003 43
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.
Super-regenerative receiver for AM & FM
This little super-regenerative receiver is essentially an AM receiver,
with “slope detection” used for FM.
By tuning to one side of the carrier,
the receiver’s tuned circuit converts
FM to AM. The bandwidth is about
200kHz so wideband FM stations
can be demodulated by tuning the
receiver to the most linear point of
the response curve, rather than the top
of the curve as one would for AM. In
practice, this simply means tuning for
clearest sound.
The heart of the receiver is Q2 which
is a Hartley oscillator, with its tuned
circuit in the base circuit. It determines
the frequency of oscillation and hence
the receiving frequency.
RF amplifier Q1 is a self-biased
untuned common emitter amplifier
44 Silicon Chip
stage, included to prevent aerial
loading from affecting the detector’s
oscillation frequency and amplitude.
It also reduces any RF radiated from
the aerial. RF is coupled into the oscillator coil by C2. The aerial can be
a piece of wire cut to 75cm. A 75cm
telescopic rod aerial is better but a
proper outdoor FM aerial is preferred
for non-portable use.
Most simple super-regenerative
detectors are self-quenched, however
this makes it difficult to obtain the
optimum quench waveform. Particularly for wideband FM, the quench
waveform has a considerable effect on
sound quality.
In this receiver, the quenching
of the detector is achieved by Q6,
a unijunction tran
sistor (UJT) relaxation oscillator. The base of the
UJT provides an approximate sawtooth waveform, which as it also
John Hunter
is this month’s
winner of the Wav
etek
Meterman 85XT
true RMS digita
l
multimeter.
provides the bias
supply for Q2, takes
the detector in and
out of oscillation
at about 50kHz.
It is necessary to
be able to set the optimum quenching
voltage and this is done by adjusting
Q6’s supply by trimpot VR2. This effectively functions as the regeneration
control.
Present at the collector of Q2 is
the demodulated AM or FM signal
as well the supersonic quench. This
is of sufficient amplitude to overload
the following audio stages, so C6, R7,
C7 and C9 provide simple low-pass
filtering.
Transistors Q4 and Q5 form a
class-A amplifier which can provide
about 80mW output. Bias stabilisation
is automatic using current feedback. If
the current rises in Q5 then Q4 turns
www.siliconchip.com.au
on harder, reducing the bias for Q5.
Negative feedback is obtained from the
secondary of the speaker transformer
and fed into Q4 via R18. The windings
of the transformer must be phased
correctly, otherwise the amplifier will
oscillate. The transformer is a standard
DSE/Jaycar 500Ω to 8Ω output type.
The prototype receiver uses the local oscillator section of a plastic AM
radio tuning capacitor, in the same way
as SILICON CHIP did with the TDA7000
FM receiver (November 1992 issue).
(The aerial section tunes a ZN414 AM
receiver in the same enclosure, sharing
the same audio amp).
The air-cored coil (L1) consists of
four turns of 18-gauge B&S tinned
copper wire on a former with a 3/8inch ID and tapped at one turn. With
this coil, frequency coverage is about
60-150MHz depending on tuning
capacitance.
As with all VHF circuitry, some care
needs to be taken with construction.
My portable version was built on a
small piece of Veroboard. When using
this, or any other super-regenerative
receiver, it may often be found that
an audible tone is heard in the background when listening to a station
transmitting stereo or SCA programs.
This is a result of subcarriers beating
with the quench frequency. Adjustment of the quench frequency will
usually minimise the problem.
In this receiver, if adjusting VR2
doesn’t get rid of it, then it’s worth
experimenting with C11. It’s important
to note that raising the quench frequency too high will reduce receiver
sensitivity. Decreasing the quench
frequency will improve sen
sitivity
but the subcarrier beat will be more
evident.
Further decreasing it will make
the quench audible at all times. For
non-FM stereo/SCA applications, C11
can be increased until just before the
quench becomes audible.
Optimum sensitivity occurs with
VR2 adjusted to the point where the receiver has just gone into oscillation. At
this point, a “rushing” noise becomes
evident and stations can be tuned in.
With very weak signals, it will become
obvious that the settings of VR2 and C4
interact slightly. I tested this receiver
with an HP 8654 signal generator and
could receive a 3µV signal, albeit with
some noise.
John Hunter,
St Leonards, NSW.
www.siliconchip.com.au
Neon scintillator with
300V up-converter
Years ago, small neon lamps were
fairly common in electronics. You
could make a simple relaxation
oscillator flasher as shown in Fig.1
or an astable multivibrator as in
Fig.2, or a multi-lamp flasher, the
Scintillator, as in Fig.3.
If you connect the last lamp,
through a capacitor, back to A,
you get a ring counter in which
the lamps turn on in sequence. If
this connection is not made, you
get a random flasher. With enough
lamps and a not-too-fast sequence
you get an eye-catching scintillating
display.
Neons have the advantage for
scintillation in that they flicker rather than glow with the unwinking
stare of a LED. The trouble with
neon circuits is that they need at
least 100V to operate, though they
take very little current.
Now you can get a 1.5V to about
300V up-converter for nothing! Just
ask your 1-hour film processor to
give you one of the used disposable
cameras with a flash in it and you
have all you need. Warning: this
is not a beginner’s project because
these cameras charge a capacitor
to nearly 300V which could give
you a lethal shock. For others, the
camera will already be partly open.
You should remove the outer
case; it’s just ‘clicked’ to
gether.
Take great care to keep away from
the circuit board. On the board is
a high grade electrolytic capacitor
which can hold a charge for days
and days. Even if there’s no battery
in the camera, do not assume that
the capacitor is dead. As soon as
you have clear access to the board,
short circuit the capacitor until it
is discharged. Remove the board
completely from the camera. Mark
on the board the polarity of the capacitor leads and then remove the
capacitor. You now have a 1.5-to300V up-converter of ade
q uate
rating to run your Scintillator.
Next, find the press switch on the
front of the board and short its contacts so that the board is energised
as soon as a battery is connected.
The battery contacts are not marked
for polarity but a test with an AA
cell will soon sort it out. One way
works – the other doesn’t!
Connect your Scintillator to the
pads from which you removed the
capacitor. The battery could be connected to its pads through a switch.
The components can be mounted
on a strip board in a jiffy box with
the neons set out in wheel spoke
fashion and viewed through some
red perspex.
Neons are available from Dick
Smith Electronics and Jaycar but if
you want to save the cost, beg several dead cameras from the shop. Each
has a neon lamp on its board, – the
‘ready’ light. These used cameras
were thrown away in their early
days but now they are recycled, so
you may have to visit a few labs.
The current drain on the AA cell
is fairly high so if you want a continuous display, feed it from a 9V DC
plugpack and an LM317 regulator
set to give 1.5V DC.
A. J. Lowe,
Bardon, Qld. ($35)
April 2003 45
Circuit Notebook – continued
LED carnival
game
This little game circuit has an interactive feature which combines a
degree of control, chance and pretty
lights. It was originally constructed as a gift for a procrastinating
neighbour to elicit a decision by
nominating different LED colours
for “Yes” and “No”.
The LEDs are arranged in a circle
and the effect is similar to a roulette
wheel except that in this case you
get to determine how long and how
fast you “spin” it.
Low cost pistol
shooting game
This circuit uses just two 555
timer chips, one in the pistol and
46 Silicon Chip
At power up, only one LED is on.
Pressing S1 causes the LEDs to light
on and off in sequence, with the
display running around the circle.
The longer the switch is held down,
the faster it runs.
When the switch is released, the
LED chaser slows down and comes
to a stop in a random fashion.
The circuit consists of a 4017
decade counter (IC1) which is
clocked by IC2, a 555 configured as
an astable oscillator. JFET Q1 and
resistor R1 provide the charging
path to the astable oscillator. The
drain-source resistance of Q1 is de-
one in the target. The pistol circuit
uses the 555 in monostable mode
to pulse a laser module available
from Jaycar Electronics (Cat ST3115). The module has a small
termined by its gate voltage which,
in turn, is determined by the charge
on capacitor C3.
Capacitor C3 is charged slowly
via resistor R3 when pushbutton
switch S1 is pressed. Fully charged,
C3 will produce the lowest drainsource resistance in Q1 and hence,
the fastest clock speed from IC2 to
the “one-of-10” counter IC1.
When C3 is virtually discharged,
Q1 is turned off and IC1 will not
receive a clock signal, so it will stop
with one LED lit.
Filippo Quartararo,
Tranmere, Tas. ($35)
on/off switch which must be unsoldered and replaced with a wire
jumper.
Switch S1 is the power switch
(could be regarded as the safety)
www.siliconchip.com.au
Simple SLA
battery charger
This circuit can be used to charge
6V and 12V sealed lead acid (SLA)
batteries. The 3-terminal regulator
REG1 is used to regulate the voltage and set the maximum charge
current of 1A. It must be mounted
on a heatsink.
When S1 is off, the charger is set
to 12V mode which charges at a
constant 13.8V. When S1 is closed,
the charger is set to 6V mode and
charges at a constant 6.9V.
When in 12V mode, the voltage
across ZD1 is added to the voltage
of the regulator. As the current
through pin 2 of REG1 is so low, the
zener diode voltage is lower than
specified (ie, 9.1V nominal), so the
total output voltage is around 13.8V.
When S1 is closed, the voltage
across the LED (2.2V for a green
LED) bypasses ZD1 and so the output voltage drops to around 6.9V.
Resistor R1 is included to protect REG1 from the sudden current
spikes which would otherwise
occur when the charg
er is first
connected to the battery. This could
destroy REG1 before its inbuilt current-limiting cuts in.
Car or motorbike batteries can be
charged with this circuit although
REG1 would have to be on a large
heatsink (or fan-cooled), as it will
be operating at 100% capacity for
quite a few hours.
Philip Chugg,
Launceston, Tas. ($35)
while the trigger is S2, a momentary
contact pushbutton. When pressed,
it pulls pin 2 low via the uncharged
1µF capacitor and the output at pin
3 goes high for about 100 milliseconds for a short burst of light from
the laser module. This short pulse
stops any cheating. The trigger must
be released before the pistol can be
fired again.
The target uses a second 555,
again in monostable mode. If the laser hits the light dependent resistor
(LDR), pin 2 is pulled low and pin
3 goes high for about one second to
sound the piezo buzzer.
Jack Holliday,
Nathan, Qld. ($40)
www.siliconchip.com.au
April 2003 47
BEEF UP YOUR HOME’S SECURITY
A Telephone Dialler
For Burglar Alarms
By LEON WILLIAMS
This project will dial a preprogrammed telephone number and
send a warning tone via a modem when its input is triggered.
Although primarily intended to connect to the output of an alarm
system, it could be used for any purpose where you need to be
notified immediately when an event has occurred.
I
T’S A SAD FACT of life today that
a great many homes are fitted with
burglar alarms. Many of these
alarms, especially low-cost self installed ones, don’t have the facility to
telephone the owner when an alarm
occurs. If you were unfortunate
enough to be away from home and
have an unwanted visitor, you are
dependent on someone making the
effort to contact you, probably well
past the time the incident occurred.
With this Alarm Dialler project
connected to your alarm system, you
will be notified within seconds of an
alarm occur
ring, through a call to
your telephone. And if you own a mo48 Silicon Chip
bile telephone there’s the added bonus
that you can be virtually anywhere in
the country and still receive the call.
Once you are notified, you can then
contact the authorities or a neighbour
or friend for assistance.
As well as this obvious application,
the project could also be used for other
less critical uses; any time you want
to be immediately informed that a
particular event has happened.
The Alarm Dialler is an easy-tobuild project using a PIC microcontroller and a handful of other inexpensive components, all housed in a
small plastic box. The unit connects to
a modem via a standard serial inter-
face. It uses the modem to make and
answer calls via your telephone line.
There are four alarm connection
points on the rear panel, two for the
alarm input and two that can be used
to reset an external device. When in
idle mode, it flashes a front panel LED
and continually scans the alarm input
connections.
If an alarm condition occurs, it
sends commands to the modem to
dial a preprogrammed telephone
number. When you answer the call,
you will hear a calling tone, and if the
telephone has a calling identification
display, you can also confirm that it
is your alarm system calling.
siliconchip.com.au
The Alarm Dialler has many options, allowing it to be used in a broad
range of applications. The various
alarm input configurations are selected
with a multi-way DIP switch, while
other settings such as stored telephone
numbers are programmed using a PC
and a simple menu system.
Why use a modem?
You may ask yourself, why do we
need to use a modem? While it may
seem an unnecessary complication,
it does provide an easy solution to a
number of design problems. First, it
avoids us having to connect our device
directly to the telephone line, as the
modem provides the necessary safety
isolation. Second, a modem provides
all the functions we need to make and
answer calls, which greatly simplifies
the Alarm Dialler hardware circuit.
These functions include looping the
line to establish and answer calls, dialling DTMF digits, ring detection, tone
generation and connection timers.
The Alarm Dialler communicates
with the modem via an RS232 interface. The speed is permanently
set in the PIC at 2400bps and while
this is slow by today’s standards, it’s
fast enough for our needs and more
importantly, eases the burden on the
PIC software UART.
The modem requirements are very
modest and so it only needs to be a basic type. More than likely you have an
old modem lying around somewhere
that can be put to service. If you don’t,
you can buy one secondhand or even
a new one at a very reasonable price.
Basically, all modems are ‘AT’
compatible. This means that they
communicate with a PC using the
AT command set. The PC sends commands to the modem preceded with
the letters AT meaning ATtention. The
modem also sends messages to the PC
on this interface.
The modem can be configured to
talk to the PC using strings of letters
(verbose) or single digits (terse). Single digit messages are generally used
when a human is not viewing the
responses and this is how the modem
must be configured to work with the
Alarm Dialler.
Alarm input options
The Alarm Dialler has a 2-wire connection point and can accept either
a contact or switched voltage alarm
system output (see Fig.1).
The contact output could be from
a standard relay, a switch or perhaps
a reed relay, using either normally
open (N/O) or normally closed (N/C)
contacts. When a contact input is
Main Features
• PIC microcontroller based.
• Alarm input can monitor N/O
or N/C contacts or an external
voltage .
• Alarm reset output.
• No direct connection to the
telephone line. Uses a standard modem to make and
answer calls.
• Dial in and test if system
operational.
• Programmed easily via a PC.
• Programmable retry attempts.
• Primary and Secondary
telephone number store.
• Alarm input inhibit switch.
• Automatic alarm reset option.
• EEPROM stores settings in
case of power outage.
• Uses low-power 12V AC or
DC power supply.
• Cheap and easy to build.
used, the main board is electrically
connected to the outside world. For
this reason, it is important that the
The rear panel carries spring-loaded terminals for the
Alarm Input and Alarm Reset signals, a DB9M connector
for the modem and a DC socket for the power supply.
siliconchip.com.au
December 2005 49
Table 1: Alarm Input Options
Normal
Condition
Alarm Condition
S1/1
S1/2
S1/3
S1/4
S1/5
S1/6
Open contacts
Closed contacts
On
Off
On
Off
On
Off
Closed contacts
Open contacts
On
Off
On
Off
On
On
Voltage Off
Voltage On
Off
On
Off
On
Off
Off
Voltage On
Voltage Off
Off
On
Off
On
Off
On
external alarm contacts do not have
any voltage applied to them and that
the cable to the Alarm Dialler is not too
long. A very long cable could possibly
get noise induced into it, which could
lead to false alarms.
Alternatively, if using the external
voltage option, the normal state can be
either voltage “on” (up to 50V DC) or
voltage “off”. The normal state means
that this is the condition when the
alarm is not active.
With this type of input configuration, the Alarm Dialler circuit is
electrically isolated from the alarm
input by an optocoupler (OPTO1).
Only a few mA of current is needed
to operate the optocoupler and this is
achieved with around 4V on the alarm
input terminals.
If you want to use a much higher
voltage than this, an external resistor
should be placed in series with the
input to limit the current through
the optocoupler LED. Note that DIP
switches typically have a maximum
rating of 50V DC at 100mA.
The alarm input options are set with
DIP switches 1-6 and Table 1 shows
the settings for each option.
Alarm reset output
The Alarm Dialler provides a set of
output relay contacts that operate for
one second and can be used to reset the
alarm or some other external device.
The PC board has provision to connect
either the N/O or N/C contacts for this
purpose. The relay will only operate
after three incoming calls have been
received within 90s after an alarm has
been detected or, if Automatic mode is
selected, after all outgoing calls have
been made.
Program menu items
The program menu is produced by
the Alarm Dialler and displayed on
the connected PC screen. Each menu
item is described below.
Automatic mode: The Alarm Dialler
has the option to be in either Auto50 Silicon Chip
matic mode or non-Automatic mode.
When Automatic mode is set to Yes, a
non-interactive mode is selected. This
is simply where the preprogrammed
number or numbers are dialled with
a 45-second delay in between calls.
After all the calls have been made,
the relay operates for one second.
The Alarm Dialler will not return to
scan mode until the non-alarm state is
found. This prevents it from continually calling if the alarm is not reset.
When Automatic mode is set to
No, the Alarm Dialler is in interactive mode and it is possible to reset
the alarm without having to wait for
all the calls to be dialled. During the
45-second wait period between outgoing calls, the Alarm Dialler monitors
the modem for a ring message.
If an incoming call is detected during this 45-second inter-call period
it then waits a further 90 seconds for
two more. It is necessary to receive a
total of three calls within the 90-second period to reset the alarm. If only
a single incoming call was allowed to
do this, a random call from someone
else could accidentally reset the alarm
before you were contacted.
If three calls are detected, it considers that you called in response to
the alarm. It then resets the alarm,
cancels all further calls and returns
to scan mode.
If an incoming call is not detected or
less than three are counted during the
90-second period, the next outgoing
call is attempted, unless all the retries
have been completed.
Primary number: This is a 19-digit
store to hold the telephone number of
the first number dialled after an alarm
is detected.
Secondary number: This is a 19-digit store to hold the telephone number
of the second number dialled after all
the Primary number retries have been
completed.
Use secondary: If this option is set
to Yes, the Secondary number will
be dialled after the Primary number
is finished. If set to No, the Primary
number is the only one dialled and the
Secondary number is ignored. While
this option is valid in Automatic mode,
in general it will only be set to Yes in
Non-Automatic mode. In this case, if a
response to the Primary number calls
is not received, the Secondary number
will then be dialled.
Retries: This is the number of retry
attempts allowed for each telephone
number. The range is 1-9.
Full details of how to program the
Alarm Dialler are covered later in this
article.
Remote status checks
The Alarm Dialler incorporates extra features that allow you to remotely
check its status.
If everything is normal and there
are no alarms, the front panel LED
will flash and incoming calls will be
ignored. However, if there are three
separate incoming calls within 90 seconds, the first two calls will be ignored
but the third call will be answered.
When the modem answers the call
by going on-line, it sends an answer
tone and then drops off-line after 20
seconds. By using this feature, you
can tell if the unit is powered up and
operating normally from anywhere
that you can use a telephone.
The only indication the Alarm Dialler has of an incoming call is a ring
message from the modem. The modem
sends the digit “2” each time a burst
of ring is received. The Alarm Dialler
counts the time in seconds between
ring bursts to distinguish between
those within the same call and those
from separate calls.
When an incoming call is being received from the telephone exchange,
ring bursts are two seconds apart.
However the time between the last ring
burst from one call and the first ring
burst from the next call will be much
greater than this. The Alarm Dialler
will register a new call if the gap is
larger than six seconds.
It would be unusual to receive three
calls within 90 seconds in normal use
and so the unit should rarely answer
a random call. Even if someone does
call three times in quick succession,
all that will happen is that the unit
will answer on the third call send the
answer tone and then drop off line
again. Obviously, if you are unable
to get the Alarm Dialler to answer at
all, either the unit or the modem has
siliconchip.com.au
Fig.1: a PIC16F84 microcontroller (IC1) forms the heart of the circuit. It accepts
the Alarm Input signal and drives an RS232 transceiver (IC2, MAX232) which
interfaces to the modem. The modem, in turn, connects to the telephone line and
carries out the dialling.
failed, the power is off or the telephone
line is faulty.
Failed call state
If an alarm has occurred and the
Alarm Dialler has exhaust
ed all its
call retries and did not get an incoming three-call response, it goes into a
failed-call state. In this mode, it will
not return to normal scan mode until
it has received three calls within 90
seconds.
This is done for two reasons. First,
it avoids continually sensing an alarm
condition and re-dialling if the alarm
has not been reset. Second, it allows
you to check if an alarm has occurred,
if you have not been previously contacted.
siliconchip.com.au
While in failed-call mode, the Alarm
Dialler will answer every incoming
call. So if you call the unit to check
its status and it answers immediately,
this indicates that an alarm has almost
certainly occurred.
To double check that this is the case,
call again two more times, within the
90-second period. If the unit answers
every call then an alarm has occurred.
This three-call sequence will also reset
the alarm and return the Alarm Dialler
to scan mode. Note that this alarm
checking and reset feature is only
available in non-Automatic mode.
Receiving an alarm call
If the Alarm Dialler is programmed
for Automatic mode, it will simply call
the Primary and Secondary numbers,
depending on the values set for ‘Use
secondary’ and ‘Retries’. It is not possible to call the Alarm Dialler during
this process and cancel the calls. For
this reason, it’s probably a good idea
to keep the ‘Retries’ number low and
only use the Secondary number option
if really necessary. Each time you answer the call, the modem calling tone
will be heard for 20 seconds and then
the call will be terminated.
In non-Automatic mode, it is possible to reset the alarm without having
to wait for all the calls to be dialled.
During the 45-second wait period
between outgoing calls, the Alarm
Dialler monitors the modem for a ring
message. Note, however, that because
the modem is online for 20 seconds
after the call is made, there is only
effectively 25 seconds for you to call
the Alarm Dialler before the next call
is made.
December 2005 51
Parts List
1 PC board, code 03204031,
115 x 99mm
1 plastic case, 140mm x 110mm
x 35mm (Jaycar Cat. HB5970)
10 PC board stakes
1 8-way DIP switch (S1)
1 4MHz crystal (X1)
1 DC panel-mount socket
1 9-pin male ‘D’ connector with
locking nuts
1 4-way speaker connector
(Jaycar Cat. PT-3002 or equivalent)
1 12V SPDT relay (RLY1)
1 18-pin IC socket
2 10mm x 3mm screws and nuts
4 small self-tapping screws
Light duty hook-up wire, tinned
copper wire
Semiconductors
1 PIC16F84-04P (IC1; programmed with ALARM.HEX)
1 MAX232 RS232 transceiver
(IC2)
1 4N25 optocoupler (IC3)
1 BC337 NPN transistor (Q1)
6 1N4004 power diodes (D1-D6)
1 7805 positive 5V regulator
(REG1)
1 5mm green LED (LED1)
Capacitors
1 470µF 25V PC electrolytic
5 10µF 16V PC electrolytic
2 100nF (0.1µF) MKT polyester
2 22pF ceramic
Resistors (0.5W, 1%)
4 10kΩ
1 330Ω
2 4.7kΩ
1 100Ω
2 470Ω
When you receive an alarm call you
will hear the modem calling tone and
you must wait for the modem to time
out and go off -line before calling back.
Circuit description
The full circuit for the Alarm Dialler is shown in Fig.1. As you can
see, there’s not a lot to the hardware
because, as mentioned before, the line
interfacing functions are handled by
the modem.
The microcontroller used is a
PIC16F84 (IC1) which does all the
hard work. It has 1K of ROM (which
is just about all used in this project),
52 Silicon Chip
68 bytes of user RAM and 64 bytes of
non-volatile EEPROM. The EEPROM
holds the configuration settings in case
of power failure.
Pin 14 is the power supply pin,
while ground (0V) is connected to pin
5. The reset input (pin 4) is held permanently high via a 100Ω resistor and
this simple reset system has proved
to be effective. The internal oscillator
appears at pins 15 and 16 and a 4MHz
crystal is used to supply accurate timing for the internal counters.
Pin 10 is connected to the Program
switch (S1/8) with an external 10kΩ
pull-up resistor, so that with the switch
open, the pin is read as high or a one.
When the switch is closed, the pin is
read as low or a zero. Pin 11 is connected to the Inhibit switch (S1/7) and
works in the same manner.
Pin 7 is the transmit data pin and
is normally high, pulsing low when a
zero data bit is sent. Pin 6 is the receive
data pin and is used to both interrupt
the PIC when a character is received
and to receive the actual data bits.
Normally, pin 6 is high with no data
present and goes low when a character
start bit is received. This negative edge
interrupts the PIC and forces it to enter the interrupt routine. This routine
samples the eight character bits and
stores them in an internal PIC register.
After the stop bit has been received,
it exits the interrupt routine and the
main code processes the character.
Software UART
More complex microcontrollers
have a dedicated hardware UART to do
this receiving but in this less-qualified
PIC we must do this in software. The
UART operates in half-duplex mode,
meaning that it cannot send and receive data at the same time.
Pin 18 controls the LED and when it
is low the LED is on and when it is high
the LED is off. A 330Ω resistor limits
the LED current to around 10mA.
Pin 8 is the relay output pin, which
is normally low and goes high for one
second to turn on transistor Q1. When
the transistor is biased on, relay RLY1
operates, providing the reset signal to
the alarm system.
Pin 13 is the alarm input pin. The
normal state can be high or low, depending on the input switch settings.
Switch S1/6 tells the PIC whether the
voltage on the alarm pin is the normal
or the alarm state. If S1/6 is off, pin
12 is held high and the alarm state is
when pin 13 is low. If S1/6 is on, pin
12 is held low and the alarm state is
when pin 13 is high.
IC2 is a MAX232 RS232 transceiver
used to interface the 5V logic signals
in and out of the PIC to the 9-pin
interface. It only requires a 5V power
supply and produces the required plus
and minus RS232 voltages by an internal inverter using four external 10µF
capacitors. IC2 has two receivers and
two transmitters but only one receiver
and transmitter are used in this circuit.
On the RS232 side, pin 13 is the
receive data input and connects to pin
2 of the ‘D’ connector, while pin 7 is
the transmit data output connecting
to pin 3 of the ‘D’ connector. On the
logic side, pin 12 is the receive data
pin and pin 10 the transmit data pin.
A 4N25 optocoupler (IC3) is used to
isolate the PIC from external voltages
on the alarm input. When about 3mA
of current flows in the internal LED,
the transistor within IC3 is turned on.
This takes pin 5 of IC3 low and consequently pin 13 of IC1 low.
When DIP switches S1/1, 3 and 5 are
off and S1/2 and 4 are on, the input
is configured to accept an external
voltage input. The current through
the optocoupler LED is limited by
a 470Ω resistor and protected from
reverse polarity by diode D5. In this
configuration, the input circuit is
completely isolated from the main
PC board components. The external
positive voltage must be connected to
the “+” alarm point, otherwise diode
D5 will be reversed-biased and the
alarm will not be recognised.
When DIP switches S1/2 & 4 are off
and S1/1, 3 & 5 are on, the input is
configured to accept a contact input. In
this mode there is no external voltage
to operate the optocoupler LED, so the
internal +5V rail is supplied through
the same 470Ω limiting resistor and
diode D5.
Power supply
The power supply is a 3-terminal
voltage regulator circuit providing
5V from a range of input voltages. A
diode bridge comprising diodes D1-D4
allows both AC and DC supplies to be
employed. If a DC supply is used, the
positive lead will be directed to the
regulator input, irrespective of the polarity of the power connector wiring.
The main reason for using this circuit is to allow a wide range of power
supply possibilities. The Alarm Dialler
siliconchip.com.au
Fig.2: install the parts on the PC board as shown here, taking care to ensure that all polarised parts go
in the right way around. The Alarm Reset output has only two connections, so select either the N/O or
N/C contact, depending on your application (ie, use one or the other but not both).
draws minimal current – only about
50mA maximum when using a 12V
DC supply.
Construction
Fig.2 shows the assembly details.
Start construction by installing the
parts on the PC board. There are three
wire links to be installed, so do these
first. Ensure they are straight and lay
flat on the PC board. Follow these with
the smaller components, such as the
resistors, diodes and IC socket.
Next, install the capacitors, ensuring
that the electrolytics are installed with
correct polarity. The relay, DIP switch
and PC stakes can be installed next.
Follow this with the transistor (Q1),
crystal and ICs, leaving the PIC chip
until later.
The LED is installed with 15mm
of lead length and then bent at right
angles so that it can push out through
the hole in the front panel when the
PC board is secured in place. The 5V
regulator (REG1) runs quite cool and
won’t need a heatsink under normal
circumstances.
Once the PC board is loaded, you
can prepare the case – see the pho-
Resistor Colour Codes
o
o
o
o
o
o
siliconchip.com.au
No.
4
2
2
1
1
Value
10kΩ
4.7kΩ
470Ω
330Ω
100Ω
4-Band Code (1%)
brown black orange brown
yellow violet red brown
yellow violet brown brown
orange orange brown brown
brown black brown brown
5-Band Code (1%)
brown black black red brown
yellow violet black brown brown
yellow violet black black brown
orange orange black black brown
brown black black black brown
December 2005 53
Fig.3: a serial crossover
cable is required to
connect the Alarm
Dialler to a PC for
programming. If you
don’t have a crossover
cable, just wire a
couple of female DB9
connectors together as
shown here.
tographs as a guide. Start by drilling
holes in the rear panel to mount the
power socket, the alarm connector and
‘D’ connector – see Fig.6. The alarm
connec
tor used in the prototype is
a 4-way speaker terminal strip and
requires four holes for the connector
tabs and two for the mounting holes.
Finally, drill a hole in the centre of
the front panel just large enough to
allow the LED to slide through.
Once the case has been prepared,
install the power socket, the alarm
connector with 3mm screws and nuts,
and the ‘D’ connec
tor with locking
nuts. Mount the PC board in the case
with four small self-tapping screws.
Slide the rear panel into place and
then wire the rear panel connectors
to the PC board stakes with light duty
hook-up wire. The alarm input is
polarised, so make sure that the red
terminal is wired to the “+” alarm PC
stake. The alarm reset output has only
two connections, so select either the
N/O or N/C contacts, depending on
your application.
Note that because we are using a
diode bridge at the supply input, you
don’t have to worry about the polarity
of the supply wiring.
When all the wiring is completed
push the LED backand slide the front
panel into place. Now slide the LED
into the hole in the front panel so that
it pokes through by a few millimetres.
Initial testing
Once construction is complete,
connect the power supply and, using
your multimeter, measure the voltage
at the power supply stakes on the PC
board. The power supply can be anywhere between 12-20V DC or 9-16V
AC without requiring a heatsink on
the 5V regulator.
If you are going to operate the unit in
areas of high temperature, then either a
heatsink should be added to the regula
tor, or preferably, reduce the voltage of
the power supply. Although the relay
coil is rated for 12V operation, using
a higher supply voltage shouldn’t be a
concern, because the relay is energised
for only one second at a time.
Next, measure the voltage at the
output of REG1. You should get a reading close to +5V and the same voltage
should be at pin 14 of the PIC socket.
Pins 2 & 6 of IC2 will be a volt either way of +9V and -9V, respectively,
if this IC is working correctly. If not,
remove the power source quickly and
look for errors, especially with the
power wiring and the installation of
the polarised components.
If everything looks OK, remove the
power, wait a few seconds and insert
the programmed PIC chip into the
18-pin socket. Apply power again and
after a short period you should see the
LED flash briefly and then repeat after
a few seconds delay. Each time the LED
flashes, it is sending AT to the modem
and looking for an OK (0) response.
This is done each time the Alarm
Dialler powers up and is used to ensure that the modem is connected and
the interface is operating at the correct
speed before normal alarm monitoring
commences.
Alarm Dialler programming
Turn off the power to the Alarm
Dialler and connect a PC running a
terminal emulation program such as
HyperTerminal using a serial cross
over cable. The PC needs to be set to
2400bps, 8 data bits, no parity and 1
stop bit with flow control off (Fig4a).
Note that the Alarm Dialler’s RS232
interface is similar to the one on your
PC and to get them to talk to each other,
you need to cross the data lines over.
This means that the transmit data pin
of the Alarm Dialler goes to the receive
data pin of the PC and vice versa.
Fig.3 shows how to make a simple
Fig.4a (left) shows how to set up the PC’s COM port to communicate
with the Alarm Dialler when you start HyperTerminal, while Fig.4b
(above) shows the menu that appears in the HyperTerminal window
when the Alarm Dialler is in programming mode.
54 Silicon Chip
siliconchip.com.au
The PC board is secured to integral pillars in the base
of the case using self-tapping screws. Note that the N/O
relay output has been used here but you could use the
N/C contact instead.
crossover data cable, with a couple of
9-pin female ‘D’ connectors and three
pieces of hook-up wire. Or you can buy
one if you prefer.
Once connected, place S1/8 into the
on position and apply power to the
Alarm Dialler. Now move S1/8 to the
off position, the LED should turn on
and the menu appear on the PC screen.
The menu is easy to understand and
navigate and the items will be self-explanatory. Simply select the desired
option by pressing the character in
brackets for that option and remember to use upper-case characters – see
Fig.4b.
Programming options are stored in
the EEPROM as they are entered and
there is no need to do a separate save
action. If an out-of-range or illegal
entry is made, an error message is dis
played and the menu refreshed.
siliconchip.com.au
To exit the programming mode,
place S1/8 into the on position again
and then back to the off position. Once
this is done successfully, a goodbye
message will appear on the screen.
Alarm inhibit
To inhibit alarm detection at any
time, move S1/7 to the on position.
This could be used to avoid the Alarm
Dialler immediately sensing an alarm
condition if you are experimenting
and changing the input connection or
DIP switch settings. When the alarm
input wiring and switch settings are
in place, S1/7 can then be placed in
the normal off position.
Switch S1/7 can also be used to
manually reset an alarm after it has
been triggered. When an alarm occurs,
a software flag is set within the PIC and
stored in EEPROM. The reason for this
is to remember that an alarm occurred
if there is a power outage during an
alarm calling sequence. When power is
reapplied and an alarm call sequence
has not been completed, it starts the
sequence again.
To manually reset the alarm flag,
switch off power, place S1/7 into the
on position, turn on the power again
and move S1/7 back to the off position. The alarm flag is also reset each
time you enter program mode to make
changes to the configuration.
Configuring the modem
To ensure the modem you are using
works properly with the Alarm Dialler,
you must first configure it with the
required settings. To do this, connect
a PC running a terminal emulation
program such as HyperTerminal to
the modem, using a standard serial
December 2005 55
your modem and see if it is an available
option, or get another modem!
The time to wait online after making
or answering a call is determined by
the value in the modem S7 register.
You may find that some modems
actually wait longer then the programmed 20 seconds and you may
not be able to make three calls within
90 seconds. If you find the wait is too
long, then you will need to experiment
with the value programmed into the
S7 register.
Now for the test procedure. Start
by programming the Alarm Dialler
with Automatic mode set to Yes. That
done, program the Primary and Secondary numbers to relevant telephone
numbers, the ‘Use secondary’ option
to Yes and the ‘Retries’ to 2. Once
programming is finished, leave the PC
connected using the serial crossover
cable.
You will notice that after you exit
programming mode the letters AT appear on the screen. This is the Alarm
Dialler look
ing for a modem. Type
the number 0 followed by the Enter
key. When the Alarm Dialler receives
this it thinks it has found the modem,
starts flashing the LED and goes into
scan mode.
At times during the remainder of
the testing we will be simulating the
sequence that the modem sends to the
Alarm Dialler when it detects an incoming burst of ring. We do this by typing
the number 2 on the PC keyboard,
followed by the Enter key. An incoming call from the telephone line has a
burst of ring every two seconds and so
a 10-second call would be comprised
of five bursts, each two seconds apart.
Final testing
Checking that it’s alive
To fully check the Alarm Dialler
functions, programmable settings and
modem operation, you need to make
real telephone calls. However, while
call charges are relatively inexpensive,
you probably don’t want to make a lot
of calls until you know everything is
working OK.
We get around this problem by
checking most of the Alarm Dialler
functions without making any real
calls. The way we do this is to simulate
the actions of the modem using the PC.
First, to make life as easy as possible for testing purposes, set the alarm
input up for N/O contacts as shown in
Table 1. That way, you can later simulate an alarm condition just by shorting
the two alarm input terminals.
The first test is to simulate calling
the Alarm Dialler from a remote location three times within 90 seconds to
check if it is alive.
Ensure the Alarm Dialler is in idle
mode and that the LED is flashing normally. Simulate an incoming call for 10
seconds (ie, by repeatedly typing 2 and
pressing Enter on the PC’s keyboard)
and check that the LED stops flashing
after the first ring burst.
Now wait at least another six seconds and simulate another call. The
LED should remain on and nothing
else should happen. Finally, wait another six seconds and simulate a third
incoming call. If the Alarm Dialler
is working correctly, the letters ATA
will appear on the screen and, after a
Table 2: Modem Configuration
Typical Command
Required Options
&K0
Disable RS232 data flow control lines.
S0=0
No auto answer - Alarm Dialler determines when the modem
will answer a call by sending it ATA.
&D0
Ignore DTR lead on RS232 interface.
E0
Wait 20 seconds after making or answering a call before
releasing the line when a carrier is not detected.
Use digits rather than character strings for modem
responses.
Do not echo characters received by the modem back to the
Alarm Dialler.
&W
Write the settings to non-volatile memory.
S7=20
V0
cable (ie, not a crossover type). Now
type the letters AT followed by the
Enter key.
If the modem receives and decodes
this properly, it will respond with the
letters OK. Now type AT&F and then
Enter to reset the modem to its factory
default settings.
Once this is done type the sequence
AT&K0S0=0&D0S7=20V0E0&W,
exactly as shown and terminate by
pressing Enter. Notice that the 0 is a
digit zero and not an upper-case letter.
If the modem accepts the settings,
it will respond with a zero, indicating
that all is OK. If not, and this is very
unlikely, your modem does not recognise these standard commands. In
this case, consult your modem’s user
manual and read the explanations in
Table 2 to find and enter the commands
that match your modem.
Calling-tone option
A modem option not shown in
Table 2 but referred to throughout
this article is the calling-tone option.
Some modems will send a calling tone
automatically every call, while some
do not have this facility. Some others
have the capability but require it to
be enabled.
If you need this feature and it doesn’t
seem to operate, you will need to check
Fig.5: the full-size front panel artwork. There’s just one hole to be drilled & that’s for the indicator LED.
56 Silicon Chip
siliconchip.com.au
Fig.6: this full-size artwork can be used as a drilling template for the rear panel. The cutout for the DB9 connector
can be made by drilling a series of small holes around the inside perimeter and knocking out the centre piece.
couple of seconds, the LED will start
to flash again. The sequence ATA
instructs the modem to go online and
answer the call.
Checking automatic mode
The next test will check that Automatic mode operates correctly. First,
simulate an alarm condition on the
input. The screen should now show
the letters ATDT, followed by the digits
for the Primary number that you have
entered during programming. The
sequence ATDT is the command sent
to the modem to tone dial the following number. Wait 45 seconds and the
same sequence should appear on the
screen again.
At this point the primary number
has been dialled twice which is the
number set in Retries. As we have set
Use Secondary to Yes, the same delayed dialling sequence should occur
again, however this time the Secondary number is used. Once all the calls
have been made, the Alarm Dialler
waits 45 seconds, operates the relay
and the LED starts to flash normally.
Checking non-automatic mode
Once you are satisfied that Automatic mode is working correctly, you can
test Non-Automatic mode. Program
the Alarm Dia
ller with Automatic
mode set to No, leaving everything
else the same.
Simulate an alarm as before and
check that the letters ATDT followed
by the digits for the Primary number
are seen on the screen.
Wait around 20 seconds and simulate an incoming call comprised of
two bursts of ring. When the Alarm
Dialler is in alarm mode it will only
answer an incoming call after it has
received two ring bursts. After the
second burst, the Alarm Dialler should
respond by displaying ATA on the
screen, instructing the modem to go
online and answer the call.
siliconchip.com.au
Fig.7: this is the full-size etching pattern for the PC board.
Wait 20 seconds and simulate a second incoming call in the same way. If
the second call is detected the letters
ATA should appear again indicating
that the Alarm Dialler is answering
the second call.
Finally, wait another 20 seconds
and simulate a third incoming call.
The Alarm Dialler should send ATA
as before, however this time the relay
will operate and the LED will start
flashing. This is because three calls
within 90 seconds have been regis
tered in response to an alarm call.
If all these off-line checks perform
correctly, you can be assured that the
Alarm Dialler is working properly. If
you want, you can test other features
such as the failed call state, changing
the number of retries and using the
Primary number only and so on.
When you are satisfied that every
thing is OK, you can con
nect your
modem to the Alarm Dialler and tele
phone line and test the system for real.
Don’t forget to reset DIP switch S1 to
the alarm input option you require
SC
(see Table 1).
Where To Get The PIC Software
To obtain the Alarm Dialler software, download the file “ALARM.ZIP”
from the SILICON CHIP website and unzip it. You can use “ALARM.HEX”
to program your own PIC chip, while you can get a better understanding
of how it all works by reading the “ALARM.ASM” file.
December 2005 57
The K149 kit is
supplied with the
FT232BM USBinterface chip presoldered in place
on the underside
of the PC board.
The new K149 PICmicro programming
kit features both serial RS-232C and
high speed USB interfacing. It currently
supports some 61 different PICmicro
chips, including the 16F84/A, the
16F627/8, the 12C508/9, the 16C63A and
many others.
As well as releasing new Windows software and
updated documentation for its existing low cost
K81 parallel-port PIC16F84 programmer kit,
DIY Electronics has also produced a completely
new PICMicro programming kit (K149) which
offers both serial RS-232C and high speed USB
interfacing. Here’s a hands-on look at both kits.
By JIM ROWE
M
ICROCONTROLLER CHIP
maker Microchip Technology Inc has been phenomenally successful with its low-cost
PICmicro family in the last few years.
PICs are now probably used in more
applications than any other family, as
well as being embedded in a high proportion of smart cards. Small wonder
that many people are keen to learn how
58 Silicon Chip
to program them and get themselves a
programmer.
The most popular kind of programmer is one that’s driven from a PC,
probably because Microchip Technology has made available (for free
downloading) an excellent suite of
program development software called
MPLAB which runs under Windows.
So with a PC-driven programmer, you
can develop your PIC firmware on the
PC using MPLAB and then program it
into a chip with a minimum of hassle.
A PC-driven programmer is the
way to go then and the easiest and
cheapest way to get one is to assemble one of the many kits that are now
available.
In this article, we’re taking a look at
two such kits from Hong-Kong based
DIY Electronics, which are available
in Australia from Ozitronics. One is
an updated version of DIY’s existing
low-cost introductory kit designed
specifically for the very popular
PIC16F84 chip. The other is a completely new kit which can not only
be used to program many different
PIC chips but also offers a choice of
either RS-232C or high-speed USB
interfacing to the PC.
The simpler kit
DIY’s PIC16F84 Programmer & Exwww.siliconchip.com.au
Fig.1: the circuit details of the K81 PIC16F84A Programmer & Experimenter. IC1, a 74LS07 hex inverter, provides
the interfacing between the PIC’s programming socket and the PC’s printer port. The test section is shown at bottom
right – it flashes five LEDs, depending on the program loaded into the PIC’s EEPROM.
perimenter kit (K81) was first released
a few years ago and has been very
popular. As well as providing a lowcost programmer which interfaced to
the PC via a standard parallel printer
www.siliconchip.com.au
port, it came with some DOS-based
programming software, a sample
PIC16F84 chip and some simple programs. These programs demonstrated
just how easily the PIC16F84 could be
used as a simple LED chaser/flasher.
You could easily check out the operation of these programs too, because
the programmer board included a “test
circuit” area on the side, with a PIC
April 2003 59
Fig.2: here’s how
the parts are
installed on the
K81 programmer’s
PC board. It’s
fairly simple and
should only take
about 30 minutes
to build.
socket connected to a row of LEDs.
With these features, K81 made an
excellent kit for anyone just getting
into PIC programming and wanting a
low-cost PC-based 16F84 programmer.
That’s still true, although in the last
couple of years there’s been a growing
number of people who only have experience with Windows-based software
and who also have little experience
assembling electronic kits.
Understandably, these people found
the DOS-based software a little unfriendly and required more guidance
with the kit assembly. As a result, DIY
has produced a revamped version of
K81, with new and easy-to-use programming software running under
Win9x/NT/2000 and an expanded
49-page manual. This not only gives
detailed assembly instructions for the
programmer but also works through
the source code details of the four test
programs, to help you understand how
they operate.
The kit’s hardware remains unchanged – it uses a well-proven
circuit which is just as suitable for
programming PIC16F84/A devices
today as it was when first released.
It uses Microchip’s serial method of
programming the chip’s EEPROM,
wherein the programming voltage
(Vpp) is applied to the MCLR pin (4),
serial programming data is applied to
(and read back from) the RB7 pin (13)
and programming clock pulses are
applied to the RB6 pin (12).
How it works (K81)
Fig.1 shows the circuit details of
the K81 PIC16F84A Pro
grammer &
60 Silicon Chip
Experimenter. It’s really quite straightforward.
First of all, power for the programmer is derived from an external plugpack, which can be either a 17-30V
DC type or a 13-20V AC type. A bridge
rectifier is used both to protect against
reverse polarity damage and also to
rectify incoming AC. Regulator REG1
is then used to provide the +5V Vdd
supply rail, while REG2 is “piggybacked” on this 5V rail to provide a
+13V Vpp rail.
Interfacing between the chip’s programming socket and the PC’s printer
port is provided via IC1, a 74LS07 hex
inverter. This allows the PC software
to control the Vdd voltage switching
via pin 5 of CON1, inverter IC1a and
transistor Q2. Similarly, the Vpp voltage switching is controlled via pin 4
of CON1, IC1f and Q1.
In addition, programming clock
pulses are sent to the chip socket via
pin 3 of CON1 and IC1b, while the
programming data is sent to the socket
Fig.3: this is the user interface
you get when you fire up the
DIYK81.EXE program. The top
four buttons are used to access
the main programming functions:
Program, Read, Verify and Erase.
via pin 2 of CON1 and IC1e. Finally, it
can also read back data from the chip’s
EEPROM via inverter IC1d and pin 10
of CON1.
Note that because the inverters are
of the open collector type, pullup
resistors R7 and SIL1a/b are used to
ensure correct operation.
At the bottom right of Fig.1 is the test
circuit section of the K81 board. There
are five LEDs connected between the
SIL2 current limiting resistors and
pins RB2-RB6 of the PIC socket, while
the 3.9kΩ resistor and 22pF capacitor
form a simple RC timing circuit for the
PIC’s internal clock.
Depending on the program you’ve
loaded into the PIC’s EEPROM, the
LEDs either count up or down in binary fashion, glow in sequence from
left to right and back again, or the LED
connected to RB2 simply flashes on
and off alone.
Trying it out
DIY sent us a fully assembled K81
kit, so we were able to try it out with
a minimum of fuss. However we did
look through the assembly instructions, which form the first few pages
of the kit’s new 49-page manual. These
are quite clear, so if you’ve built electronic kits in the past you shouldn’t
have any problems with this one.
The PC board overlay details are
shown in Fig.2. It should only take
you 30 minutes or so to assemble it.
Software (K81)
The software for the kit must be
downloaded from the DIY website
(www.kitsrus.com) and comes zipped
in a single 1.32MB file (DIYK81.ZIP).
When you unzip this to a temporary
folder, it provides the necessary files,
including a setup file, to install the
main DIYK81.EXE program in any
folder you nominate.
By the way, it’s only when you
have installed the main program that
you discover the file K81.PDF, the
electronic version of the kit’s 49-page
manual. This is one of the files that
are unpacked during installation. So
the next step is to open up the PDF file
with Adobe’s trusty Acrobat Reader
and print it out to guide you the rest
of the way.
In the same folder, there’s also a file
called DRIVER.TXT. This is a guide to
installing the software drivers which
allow the main DIYK81.EXE program
to communicate with and control
www.siliconchip.com.au
the K81 hardware via a printer port.
For systems running Win9x, all you
have to do is right-click on another
file called SETUP_9X.INF and then
select “Install”. This causes the appro
priate driver files to be copied to the
windows\system folder and away you
go.
When you fire up DIYK81.EXE,
it presents you with the small user
interface shown in Fig.3. There are
basically just eight control buttons,
with the top four used to access the
main functions: Program, Read, Verify
and Erase.
The remaining four buttons are for
selecting the printer port address, testing for correct communication with
the K81 hardware, opening the on-line
help file and stopping the program
ming prematurely. A small “progress
bar” below the buttons shows that
operations are proceeding.
It’s all very straightforward and
easy to use.
Initially, though, I couldn’t get the
program to “find” the K81 hardware,
even though it was connected to the
right port and powered up. I then
realised that I had sent various documents to the printer via the same port,
earlier in the same session. This can
cause problems with other devices that
interface via the printer port, as I discovered recently when developing my
EPROM Programmer. I rebooted the
PC and suddenly the DIYK81 software
could now “see” the hardware. After
that, it was all plain sailing.
The sample PIC16F84 programs
that come with the software are
supplied in both hex and assembler
source code form, so it’s very easy to
program the sample PIC using any
of the hex files. You do this simply
by clicking on DIYK81’s “Program”
button and selecting the hex file you
want from the dialog that appears.
This then erases the PIC’s EEPROM
and programs it with the new hex file
instead – an operation that only takes
a few seconds.
Writing your own PIC16F84 software for programming via the DIYK81
software is quite straightforward too,
if you follow DIY’s advice and download a copy of the MPLAB software
suite from the Microchip website
(www.microchip.com). MPLAB is
quite a big file (the current version
6.10 is about 25MB) and it has to
be downloaded in floppy-disk sized
chunks. But it’s well worth getting,
www.siliconchip.com.au
The K81 PIC16F84A Programmer
& Experimenter will take you next
to no time to assemble. The test
section of the board is at bottom
right.
because it’s a complete IDE (integrated development environment) which
includes a source code editor, an assembler and linker, a simulator and a
debugger.
It also includes programming software for Microchip’s own PIC programmers, but the DIYK81 software
performs this function with the K81
programmer.
Overall then, the K81 kit and its
matching Windows-based software
are very easy to use, and provide
a low cost entry path for would-be
PIC16F84 programmers. The new
49-page manual also provides a lot
of good tutorial information, not just
about building the kit but also on
the basics of PIC assembly language
programming, using the K81 sample
programs as examples.
Considering that the K81 still costs
less than $A40 from Ozitronics, this
surely makes it excellent value for
money.
USB PIC programmer (K149)
Good though it is, though, the K81
kit does have its limitations. For example, it only handles the popular
Where To Buy The Kits
Kits for the K81, K149 & K160 PICmicro programmers are available in Australia from Ozitronics (www.ozitronics.com) for the following prices:
K81 Parallel Programmer ............$37.40 each (includes postage & GST).
K149 USB/Serial Programmer ...$73.70 each (includes postage & GST).
K160 Serial Programmer ............$28.60 each (includes postage & GST).
Contact Ozitronics as follows: phone (03) 9434 3806; mail 24 Ballandry
Crescent, Greensborough 3088; email sales<at>ozitronics.com; website
www.ozitronics.com
More information on these and other kits from DIY Electronics is available
on their website: www.kitsrus.com You can also contact the company by
email at peter<at>kitsrus.com, if you have any suggestions to make regarding
these or other kits.
Note that copyright of the PC boards and software source code for both the
K81 and K149 kits is retained by the designers.
April 2003 61
62 Silicon Chip
www.siliconchip.com.au
Fig.5: the K149 USB/RS232C PIC Programmer is built on a double-sided PC board. This board is supplied
with FT232BM USB interface chip (IC4) already soldered in place on the underside.
PIC16F84/A chips, so it’s not much
use if you want to program one of the
many other PIC micros.
The printer port interface may also
be a problem with some late-model
PCs, which often don’t have a “legacy”
parallel printer port at all. Apparently,
it’s assumed that you’ll be either using
a USB printer or printing via a network
printer.
It’s these limitations which have
prompted DIY to develop the new
K149 programmer kit, using hardware and software designed by Tony
Nixon – www.bubblesoftonline.
com This kit will provide you with
a much more “serious” programmer,
which can currently support about 61
different PIC micro models. These include the 16F84/A, the 16F627/8, the
Fig.4 (left): the K149 USB/RS232C
PIC Programmer features both RS232
(MAX232) and USB (FT232BM
interfaces. These forward and receive
data to and from a pre-programmed
PIC-16F628 (IC3), depending on the
position of switch S1. IC3, in company
with IC2, also provides the pulses to
the programming socket.
www.siliconchip.com.au
12C508/9, the 16C63A and of course
many others.
The K149 doesn’t just support a lot
more PICs, though. It’s also DIY’s first
kit programmer with a USB interface,
so it should be fully compatible with
virtually any of today’s (or tomorrow’s)
PCs. It also offers an alternative RS232C serial interface, which you can
select by flicking an on-board switch.
So as well as coping with a wide
range of PIC chips, the K149 should
be useable with virtually any PC, old
or new.
As you can see from the photo, the
K149 programmer has a bit more in
it than the K81. For starters, it’s on
a double-sided PC board about 50%
larger than its little brother, with space
for a wide-slot 40-pin ZIF socket for
the devices to be programmed.
The kit actually comes with three
20-pin IC sockets to be installed on
the board, but 40-pin ZIF sockets are
available separately for those who expect to be doing a lot of programming.
These ZIF (or “zero insertion force”)
sockets allow chips to be inserted and
removed very easily, with much lower
risk of pin or device damage.
USB interface
To provide it with the new USB
interface, the K149 takes advantage
of a fairly new “USB UART” chip
from Scottish firm Future Technology Devices International (FTDI).
The FT
232BM chip provides all of
the circuitry required to transfer data
between a USB port and a high speed
asynchronous serial data line, in both
directions and at speeds up to 3Mb/s
(megabits per second).
The full details of this chip can be
downloaded from FTDI’s website at
www.ftdichip.com
The FT232BM is in a very compact
32-pin LQFP (low profile quad flat
pack) surface-mount package, with
leads spaced only 0.8mm apart. However, to save inexperienced constructors from getting into strife soldering
this tiny chip’s leads, DIY Electronics
supplies the K149 board with the FT232BM chip already pre-soldered in
place on the underside copper. All you
have to do is mount the larger parts on
the top of the board.
To allow the K149 programmer to
cope with the various PIC chip models, its control circuitry is based on
a pre-programmed PIC16F628 chip.
This takes the data and control instructions coming to the programmer
via either the USB or RS-232C interfaces and controls the programming/
April 2003 63
Fig.6: this is the main user interface for the K149 programmer. As well as the
control buttons (arranged along the bottom), there’s also a large text box where
you can examine hex program listings – either before programming or read back
from a programmed PIC. There’s also a picture box (far right) which shows you
how to plug the selected PIC into the K149’s programming socket.
verifying/reading operations accord
ingly.
Circuit details
Fig.4 shows the circuit of the K149
USB/RS232C PIC Programmer.
The RS-232C serial interface is provided by IC1, which is an ICL232 level
translating transceiver device very
similar to the well-known MAX232.
The USB interface is provided by the
FT232BM (IC4), which uses a 6.0MHz
crystal to lock its USB clock oscillator
(multiplied to 48MHz via an internal
PLL).
IC3 is the pre-programmed PIC16F628, which receives the incoming
serial data at its RB1 pin (7) and provides return data via it RB2 pin (8).
As you can see, these pins are both
switched using S1 to communicate via
either IC1 or IC4 – ie, S1 provides the
USB/RS232C mode selection.
Inverters IC2a-IC2c (74LS06) are
used to control transis
tors Q1, Q3
& Q2 respectively. These switch the
Vcc supply and the Vpp supply (x2)
to various pins on the programming
socket. This all takes place under the
direction of IC3, via pins RB5-6-7.
LEDs2-4 are used to indicate when
these voltages are being applied to
the socket.
Inverter IC2e is used with diodes
D1 & D3 to form an OR gate. This
allows the PC software to reset the
64 Silicon Chip
programmer’s 16F628 (IC3) when desired via the interface (USB or RS232)
that’s is being used. As shown, IC2e’s
output is connected to the MCLR-bar
input of IC3 (pin 4). The remaining
two inverters inside IC2 (IC2d & IC2f)
are not used and have their inputs
tied high.
The power supply section is very
similar to that used in the K81, with
piggybacked 7805 (REG1) and 7808
(REG2) regulators to provide the +5V
and +13V rails. The only difference
is that they’re fed via a single series
protection diode (D2), instead of a fullwave bridge rectifier. This means that
the K149 should only be powered from
a nominal 18V DC plugpack.
Trying out the K149
DIY again supplied us with a pre
assembled K149 kit, so we could
try it out with minimum hassle. As
before, we looked at the assembly
instructions and although fairly brief,
they should be quite adequate for anyone who has previously assembled
electronics kits.
Fig.5 shows the parts layout on the
double-sided PC board.
Trying it out
We decided to test the K149 using
the USB interface, because this is probably the most interesting feature of this
kit. There weren’t any real problems,
although there was initially a minor
hassle in connecting the programmer
up to a USB port of the PC we were
using for evaluation.
That’s because we had to get a special USB cable to link them up, as the
programmer is fitted with a USB Type
A socket – ie, the “flat” type normally
used only for the host PC ports in a
USB network or the output ports of
a hub. This means that you can’t use
a standard USB cable with a Type A
plug at one end and a Type B “square”
plug at the other – instead, you have to
use a special cable with Type A plugs
at both ends.
However, these cables are readily
available from a number of local suppliers. We obtained one and were then
able to connect the K149 to one of the
PC’s USB ports.
The main software to operate the
K149 again needs to be downloaded
via the web, in this case from www.
crowcroft.net/kitsrus/ It’s a single
1.7MB file called K149DISK.ZIP.
When you unzip this file, it produces two smaller zip files which then
have to be unzipped in a temporary
folder. This gives a set of files (including SETUP.EXE), after which you
can install the main software files on
a folder of your own choosing. The
main program is called MicroPro.EXE,
which currently runs under Win9x/
NT/2000.
If you’re going to be using the USB
interface, you also need to download
and install the USB drivers which
allow Windows to communicate with
the programmer’s FT232BM chip.
These must be downloaded from the
FTDI website at www.ftdichip.com/
FTDriver.htm The drivers to get are
called “VCP Drivers for Win98/2000/
ME/XP (without PnP support)” and
they come zipped up in a single file.
While you’re at the FTDI site, it’s
also a good idea to get the installation
notes which are in PDF format. These
are at www.ftdichip.com/FTApp.
htm – be sure to get the one for your
particular operating system.
Once you have downloaded the
USB drivers, you unzip the files into
a “USB” subfolder, just below the one
where you installed the MicroPro software. When you subsequently power
up the K149 board and connect it to
one of the PC’s USB ports, Windows
senses its presence and prompts you to
install the appropriate USB driver – it’s
just a matter of going to the \K149\
www.siliconchip.com.au
USB folder, where you just unzipped
the drivers.
This basically installs the programmer on a high-speed USB-supported
“virtual serial port”, which in my case
turned out to be COM4. When you fire
up the MicroPro software, it can then
communicate with the programmer
once you select that port.
K160: PIC16F62x Experimenter & Programmer
The K149 software
Not surprisingly, the MicroPro
software that comes with the K149
is more complex than that supplied
for the K81. That’s because it has to
cope with a wide range of PIC chips.
However, it’s still quite friendly and
easy to use.
Fig.6 shows the main user interface. It has a similar set of programmer control buttons along the bottom
but now there’s also a large text box
where you can examine hex program
listings – either before programming
or read back from a programmed PIC.
To the right of this box, there’s also
a picture box where you first see an
image of the K149’s programming
socket.
At first, I was a bit confused about
the correct placement of a PIC to be
programmed in the K149’s socket,
because this wasn’t indicated either
on the K149 board itself or in the
documentation. Nor could I find where
you selected the type of PIC to be
programmed on the MicroPro user interface (it wasn’t evident on any of the
top pull-down menus, for example).
It was then that I discovered the
purpose of the small uncaptioned
drop-down list box near the bottom
right-hand corner, just above the Cancel button. Clicking on its drop-down
arrow brings up a list of all supported
PICs – and when I selected one, the
picture in the box above changed to
show the correct way to plug that device into K149’s programming socket.
It’s a very neat feature – except for
the lack of a caption on the drop-down
list box.
After that, I had no problems at
all using the K149 and MicroPro to
program PICs. And thanks to the USB
interface, it programs them very quickly and efficiently.
It turns out that MicroPro even
provides a “Fly Window” option, to
allow you to program PICs directly
from MPLAB once you’ve written a
program and assembled it. When you
select the Fly Window option, Microwww.siliconchip.com.au
Also recently introduced by DIY Electronics is the K160 PIC16F62x Experimenter & Programmer kit, designed for programming the PIC16F62x series
of PIC chips (ie, 16F627, 16F627A, 16F628 & 16F628A). The 16F628-04/P
chip is used in the kit.
As well as programming PIC16F62x chips, the kit is also designed to teach
you the basics of programming. It comes complete with the following:
• a Windows 9x/NT/2000/XP user interface;
• Five detailed code examples to flash LED’s; and
• A 40-page PDF (Adobe Acrobat) file which introduces the MPLAB program
from Microchip for program development and assembly.
The K160 Programmer connects to the serial port of the PC. You simply
program the 16F628 using the user software provided. The software then
runs immediately and flashes the LEDs on the board.
Fully-commented source code is provided for the example programs: binaryup.asm, binarydn.asm, binarylr.asm and flash.asm. These programs flash
the LEDs in a variety of patterns. The compiled object code is also provided
(ie, the hex files).
Kits for the K160 IC16F62x Experimenter & Programmer are available from
Ozitronics – see price panel. For further information on the kit itself, visit the
DIY Electronics website at www.kitsrus.com
Pro produces a little “remote control”
dialog and minimises itself. Then,
when you’re in MPLAB, the small
dialog allows you to access MicroPro’s
Program and Verify functions – which
is also very neat.
Summary
My impressions of DIY’s new K149
programmer are very favourable indeed, apart from those little niggles
about the need to get a special USB
cable and the software’s unmarked list
box to select the PIC device you want
to program. Those points aside, it gives
every evidence of being well-designed
and it is very easy to use.
So if you’re after a fast and convenient PC-driven programmer for most
of the commonly used PICs, the K149
can be recommended. It’s also a very
cost-effective way to get yourself such
a programmer, because the K149 sells
in Australia for only $73.70 (including
postage & GST). The pricing panel has
SC
all the details.
April 2003 65
Remotely triggered photography
Electric Camera
Shutter Release
By Julian Edgar
Triggering a camera remotely allows you to take photos
that might otherwise not be possible: dangerous locations
or situations, wildlife photography and so on. You could
also generally improve your photographic creativity. But
how do you press the shutter release from a distance?
O
NCE, ALL CAMERAS had a female cable release
thread in the shutter release button, allowing the
use of a long (often pneumatic, sometimes electric)
cable release to let you to trigger the camera from afar.
But these days, plenty of cameras (most?) don’t have this
facility. In some cases, you can buy a dedicated electric
cord that plugs into the camera – but you’ll certainly have
to pay big dollars for it.
Remotely triggering a camera – any camera – is a problem
no longer! What we have here is a simple and cheap DIY
project that will allow any camera to be fired from a good
distance. With a little ingenuity it could even be adapted
for radio control.
The camera doesn’t have to be fitted with a threaded
shutter release button and it doesn’t need a socket for an
electrical cable release. In fact, all that it really needs to
have is a tripod mount (we haven’t found a “real” camera
yet that doesn’t!) and a button that gets pressed to take
the picture (ditto!).
It uses a small solenoid – a device which consists of
66 Silicon Chip
www.siliconchip.com.au
a coil usually wound around some form of armature or
plunger. When the coil is energised by current, the armature moves due to the magnetic attraction (or repulsion)
of the coil. It is this movement which is used to push the
camera release button.
The design
The solenoid is mounted so that its extended plunger
pushes the camera shutter release button. A mount for
the solenoid – folded from aluminium sheet – is attached
securely to the camera via a screw into the tripod socket.
The solenoid is fired by the use of a pushbutton switch
mounted on a remote handpiece which also contains one
or two batteries.
The solenoid used here was salvaged from an electric
typewriter. Pretty well any small solenoid can be used – so
long as it has an adequate amount of ‘push’ and can be operated at low voltage. The
handpiece was made
from an old personal
deodorant container,
while the pushbutton,
battery clips and cable
were bought specifically
for the project. But you
might even have these
in your junk box!
So depending on how
you source the parts, this device shouldn’t cost much at all.
out and then cut to shape
using an electric jigsaw.
The sheet is 2.5mm in
thickness – strong enough
to have the required stiffness but still light and easy
to cut and bend. Note that
offcuts of sheet aluminium
are available from non-ferrous scrap metal dealers very
cheaply.
They’ll cost a lot more
if you go to a specialist aluminium supplier!
The piece of aluminium
was then bent to the right
shape in a vice and the
holes for the solenoid and
tripod mount drilled.
The mount was painted
black, and a short ¼ -inch
screw used to attach it firm-
Building it
1. The Bracket
The typewriter solenoid selected for this project normally pushes the daisywheel letter against the ribbon and
paper. To facilitate this, the plunger of the solenoid has a
groove machined in its end. This results in a sharp edge
– not really what you want striking your camera’s shutter
release button!
To get rid of these sharp
edges the solenoid was
disassembled and the
plunger end smoothed
with a file.
Once that was done, a
piece of cardboard was
cut out and formed into
a template for the bracket.
This bracket needs to place
the solenoid at the right angle
and position so that as the
plunger extends, the shutter
release button is depressed.
to join the solenoid to the
handpiece, as shown below.
ly to the camera tripod
mount.
This shows how the
solenoid is positioned
so that its plunger is at
the right angle to push
on the shutter release
button.
A long cable is used
2. The Handpiece
How you make the handpiece depends a little on
the amount of “juice” you
need to actuate the solenoid.
This can be best found out
by actually triggering the
In the case of this Nikon
F60 SLR, this required an
‘L’-shaped bracket which
was then folded into the
right shape – see photos.
With the shape organised, a piece of scrap aluminium sheet was marked
www.siliconchip.com.au
April 2003 67
solenoid when it’s in place on the bracket. When operated
on the bench, a solenoid may work perfectly well on 9V
(or lower), but with the voltage drop of a long cable and
the effort of having to push the camera’s shutter release
button, more voltage might be needed.
I found this out the hard way: the typewriter solenoid
bench-tested fine on 9V, so I built this small hand controller using a commercially available box and a single 9V
battery. But this system simply didn’t have enough power
to trip the camera!
Time for a rethink. Because the power is applied in
such a short burst (you
should never leave you
finger resting on the
button), much higher
voltages than the normal working voltage
of the solenoid can
be used without problems. In my case, I simply used two 9V batteries in series,
giving 18V output. That triggered the solenoid decisively
and hard!
The new handpiece
was made from a deodorant container –
emptied of course!
The two 9V batteries – complete with
their battery clips – fitted into it very nicely,
while the pushbutton
switch was placed through a hole drilled in the cap. Making a battery change is as easy as lifting off the cap and
sliding the old batteries
out but they should last
for ages, depending how
much you use the remote
trigger.
Using it
It makes things a lot
easier if the camera that
you are using has an inbuilt motorised wind-on.
But other than that, just about any camera can be used. The
camera should be pre-focused – and the auto focus disabled
if possible – and in some cameras the viewfinder should
be blocked (eg, using a rubber
cap) to prevent extraneous light
from causing metering problems.
Then it’s simply a case of setting up the camera (you should
still be able to use a tripod if required, with the tripod threaded
fitting long enough to go through
the alloy plate), standing back
and pressing the handpiece button at the right moment.
The circuit
could hardly be
simpler – that’s
the beauty of
this project.
Whether you
need one 9V
battery or two
depends on both
the solenoid and
the cable length.
digital cameras require a significantly longer “firing” time
than conventional cameras – the best are about 100-200ms,
while many of the “happy snap” (ie, cheaper) variety
require half a second or so. Therefore, you will need to
experiment with the release to determine just how long
you need to hold the button down to get your picture.
The earlier comments about turning off auto focus, etc,
still apply – that is, if you can manually focus the camera.
Some simply don’t let you!
Also note that apart from some cheap digital cameras,
most are capable of being remotely controlled via their bus.
However, the chances of finding a remote control cable in
your new camera box are pretty slim and the earlier comments about the cost of special cables certainly applies to
digital cameras – if not dramatically more so!
This project is definitely a cheaper alternative, especially
SC
if you can scrounge the parts!
Radio Control
We mentioned earlier that this project could be adapted to radio control with a bit of ingenuity. In fact, it’s not
rocket science: just about any of the remote controls we
have recently published could be used.
All that is required is to wire the output device of the
remote control receiver, whether that be a relay or a
switching transistor, in place of the pushbutton switch (as
shown below).You may well find that the battery required
to power the radio receiver can also power the solenoid.
The radio control must be set for momentary (as distinct from alternate) action. It needs to actuate when you
press the button and let go when you let go the button.
(Alternate action requires two pushes of the button to
actuate and then let go).
One point to note: the solenoid, being a coil, generates
a significant back-EMF when the power is removed. This
won’t worry either a pushbutton or a relay contact but
could be disastrous for a switching transistor. If unsure,
place a reverse-biased small power diode (1N4001 etc)
across the solenoid coil, with its cathode (the banded
end) towards the positive supply.
Digital cameras
This project is just as suitable
for use on a digital camera, with
one important proviso: most
68 Silicon Chip
www.siliconchip.com.au
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pril 2003 69
April
PRODUCT SHOWCASE
Gigabit Ethernet Switch and Interface Card
I
t’s all very well having a 100Mbs
office network but if lots of users
are trying to access a single server
at the same time, things can get very
slow indeed.
The answer to this problem is to
have a 1-gigabit link to the server to
eliminate this bottleneck but until
recently, such links have been quite
expensive. Not any more – prices have
fallen over the last six months and the
hardware is now quite affordable.
Slotting into this category is the Edimax ES-5108D Fast Ethernet switch
from MicroGram Computers. This
switch features a single 1-gigabit port
plus eight 10/100Mb ports, all capable of operating at both full and half
duplex. All ports are auto-negotiating
and an array of LEDs on the front panel
indicates port status.
The unit comes in a solid metal case,
has its own internal power supply and
comes complete with a power cord and
a users manual.
Of course, having a 1-gigabit port
is not much use without a matching
interface card at the other end – ie, in
the server. The Edimax EN-9210TX
1-Gigabit Ethernet Adapter is suitable here. This 32-bit card plugs into
a standard PCI slot, can operate both
full and half-duplex, is fully auto-ne-
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Ph (02) 9476-5854 Fx (02) 9476-3231
70 Silicon Chip
gotiating and supports Windows 98/
Me/NT/2000 Netware Server 4/5 and
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Supplied with the card are all the
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The Edimax ES-5108D Fast Ethernet Switch (Cat. 11353) costs $639.00
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www.mgram.com.au
Automated video
signal analyser
Tektronix has recently released
the world’s first fully-automated
component analog video signal
analyser that measures high-definition, progressive scan and PC
format signals for consumer video
equipment manufacturers, video
network operators and others that
require fast and repeatable testing.
The VM5000HD provides fast,
accurate and repeatable video measurements in 1080i, 720p, 480p, and
SXGA formats utilising multiple industry-standard video parameters,
without the need for complicated
instrument set-ups, algorithm selection, time-consuming manual
measurements or tedious results
correlation.
It can make 100 different para-
metric measurements in eight specific test categories within 10 seconds so that product performance
can be objectively assessed. It also
offers a unique high-definition matrix test signal set for the creation of
standardised test signals including
colour bars, multi-burst, sweep and
five other signal types, for testing in
Y/Pb/Pr and RGB color space.
Contact NewTek Sales Pty Ltd on
(02) 9888 0100 for more information.
www.siliconchip.com.au
The mother of all
remote controls
Is your coffee table littered
with remote controls? Get
rid of them and just use
this single remote control
instead. It can control up
to 16 audio-video devices
– including a TV set, DVD
player, CD player, satellite
receiver and VCR – and
features a touch-sensitive
backlit LCD panel, making
it perfect for home theatre
set-ups.
Press a button to select
a device and the large LCD
panel instantly changes its
control icons to suit. The
device comes programmed
with a huge range of popular remote control codes and for most devices, it’s
simply a matter of entering a 4-digit code from the
supplied list.
Alternatively, the unit can be used to select the
code automatically during setup or it can learn from
your existing remote controls.
Other features include a macro function (up to
60 commands), automatic switch-off, the ability to
re-label individual devices and the ability to classify
channels into groups (eg, news, movies, etc). It even
has an inbuilt clock and calendar.
This mother of all remote controls is available
from Altronics for $269.00 (Cat. A 0990) for $269.00.
Phone 1300 797 007 or visit www.altronics.com.au
2-Channel Digital Oscilloscope
Yokogawa has recently introduced the DL1620 2-channel digital oscilloscope, featuring 200MHz bandwidth and
a maximum sampling rate of 200Msample/s.
The DL1620 is small, portable and weighs less than
4kg. Users can control the instrument from any network
connection using the inbuilt web server and 100 Base-T
Ethernet connector, or they can control it using a PC via
a USB, RS-232 or GP-IB interface.
The DL1600 offers three types of removable media:
floppy disk, ZIP disk or Type II PCMCIA card and comes
with an inbuilt printer as standard. The maths function
computes values in real-time when the instrument operates in roll mode. That means that when measuring
slow signals, the calculated values are determined and
displayed immediately, rather than having to wait for the
measurement to finish.
Inbuilt probe power for use with Yokogawa’s current
and differential probes is optionally available. And an
optional Waveform Viewer program lets users view waveform signals on a PC just as they appear on the DL screen.
Contact Yokogawa Australia Pty Ltd, Private Mail Bag
24, PO North Ryde, 1670. Phone (02) 9805 0699.
www.siliconchip.com.au
April 2003 71
It’s one of the fundamental skills in electronics,
required at every level from beginner to
rocket scientist. Everyone knows how to solder
. . . or at least think they do! Yet kit suppliers will tell
you that 99.9% of failures in home-built kits are due to
poor soldering. Let’s try to help lower that statistic!
Soldering
by MAURIE FINDLAY
72 Silicon Chip
www.siliconchip.com.au
A
LMOST ALL OF the constructional articles apppearing inSILICON CHIP involve soldering to
make electrical connections.
With modern tools and solder, most
readers are able to do a good job.
However, an understanding of the
soldering process, plus some practical
experience, can make for reliability
and professional appearance.
Typically, a project will involve a PC
(printed circuit) board plus some ICs,
discrete transistors, diodes, resistors,
capacitors and so on: all new and shiny
with leads finished with materials
specially designed for easy soldering.
You have a length of solder wire and
a small soldering “iron”. The solder
is placed to touch, say, a resistor lead
and PC board track to be joined. The
soldering iron tip is applied to the solder (more often than not, in the form
of a thin wire). The solder wire melts
and molten solder flows over the two
component leads. The soldering iron
tip is then moved away and the solder
solidifies in a few seconds and leaves
a reliable connection.
In most cases, it is that easy. But it’s
not always so. For example, the solder
may not flow over the component
leads – it may look like it has but the
lead is not actually coated. Or it may
have moved before the joint solidifies.
Or the heat of the solder might have
damaged the component . . .
Soldering is not quite as simple as
it sounds. For this reason, it’s well
worth knowing a bit more about the
fundamentals of soldering so that you
can handle situations which are not so
straightforward.
In the electronics industry, solder
is used to make the majority of electrical connections. Even an ordinary
domestic television receiver may
contain thousands of connections
between components, PC boards and
cables and in most cases the failure of
one connection can make the receiver
inoperative.
Satellites, military equipment and
so on make use of solder joints in
much greater numbers – and require
even greater reliability. It’s not easy
whipping out the hot stick when the
PC board is a few hundred kilometres
out in space!
But so much have soldering techFacing page: the budget-priced “Auto
Temp” soldering station. About $185
from Dick Smith Electronics.
www.siliconchip.com.au
Fig.1: solder, a
mixture of lead and
tin, has a lower
melting point than
either lead or tin.
Lower heat means
less likelihood of
damage to sensitive
components.
niques improved over the years that
most electronic equipment is now
extremely reliable.
What is solder?
First of all, a fundamental question:
what is solder ?
Solder is an alloy, or mixture of
metals, used for joining other metals. While general-purpose solder is
almost always a mixture of tin and
lead, other metals can be included for
special purposes.
For example, a small amount of
copper is sometimes added to help
preserve soldering iron bit life. And
there are specialised solders which
don’t contain any lead at all. But they
are not the types you will normally
come across in electronic work.
The tin and lead are closely mixed
together but not chemically bonded.
The tin-lead alloy has a very useful
characteristic – it melts at a lower temperature than that of tin or lead alone.
What’s more, the melting point can be
controlled by altering the proportions
of the two metals.
For fine electronic work, an alloy of
62% tin and 38% lead (by mass) is a
good choice. It melts at 183°C, much
lower than for either metal alone (lead
melts at 327°C and tin at 232°C). This
lower melting point means that there
is less chance of damage being done
to components, the PC board and
other parts.
At the other end of the scale, a
different tin/lead mix solder is used
for joining sheet metal. Examples are
galvanised iron roofing components
and tin-plated food containers.
Plumbers use solder in relatively
large quantities and there usually isn’t
A beginner’s generalpurpose soldering kit,
with a 25W mainspowered iron, a
soldering iron stand
complete with tipcleaning sponge, a roll
of de-soldering wick and
some solder. All up?
– about $35.00. (Courtesy
Jaycar Electronics).
April 2003 73
the solder wire, in tiny
hollow tubes, there is
flux.
Flux helps the solder
to flow and to “wet”
the metal being soldered, especially the
more difficult-to-solder metals. Because
the flux melts along
with the solder, exactly the right amount is
applied to the joint as
you solder it.
Most general-purpose flux is made
from rosin – often (but
wrongly) called resin.
This Micron 60W temperature-controlled
The flux itself is a ressoldering station from Altronics has a LED
in, made from rosin.
readout to tell you the exact tip temperature.
Thoroughly confused
You can dial up the temperature you want and it will
now?
hold it there within 2°. It includes the tip cleaning
sponge shown but the solder holder on top is an
You need to rememoption.
ber that as the flux
melts, it releases fumes
a problem about overheating the comand these fumes may adversely affect
ponents being soldered. The solder
some people. There is also some evisticks they use may be about 300mm
dence that melting solder releases lead
long and up to 80mm2 in cross section. fumes which could also be dangerous.
Lead is cheaper than tin and an alloy
The moral of the story – don’t breathe
of 50% tin and 50% lead, melting at
in fumes when soldering.
210°C, is used.
Incidentally, you can buy nifty little
fan units which suck fumes away from
Flux
your soldering area. If you’re worried
Sheet-metal solder should not be about your health, they are worth
used for electronic work – not so looking at.
much because of the different alloy
Before finishing with flux, there is
mix but because of the type of flux
another common type of solder (the
used (if at all).
type you find in hardware stores)
By far the majority of solder you will which contains an acid flux and is
use in day-to-day electronics work has
intended for sheet metal work.
more in it than tin, lead and perhaps
Never use this for electronic work –
some other metals. Down the centre of
the acid will quite quickly eat away the
copper on the PC board and probably
the component leads as well.
Tools
OK, so what do you need besides
the solder? For starters, you need a
soldering iron) and perhaps something
to remove solder if you inadvertently
put a component in the wrong place.
Some fine tweezers to hold components in place and a heatsink to clip
onto the leads of heat-sensitive components would be worthwhile extras.
A heatsink, by the way, is merely
a device to draw away heat from a
device’s lead(s) so that the heat from
the soldering iron doesn’t reach the
sensitive parts of the device. Heatsinks
are often made like alligator clips (but
with flat blades, rather than serrated
teeth), which clip onto a device’s leads
under spring pressure.
Which iron?
There are lots of soldering irons to
choose from. At the bottom end of the
scale, a simple tool will set you back
about $20 or less and will do a good
job if your only need is to assemble a
few PC boards with small components.
Typically, it will plug directly
into the 240V mains, will be rated
at 25-40W, and will be set up for a
tip temperature of about 370°C. This
temperature is about right for most
situations, considering the losses in
transferring heat to the components.
The disadvantages of some “el
cheapo” irons may not be obvious –
after all, they solder, don’t they?
A very basic selection of hand tools but probably all that the novice constructor needs. On the left is a pair of sidecutters
(sometimes called nippers or nipping pliers); next is a pair of needle-nose pliers. The red gizmo is a heatsink (these come
in various shapes and sizes) while rounding out that group is a pair of pointy-nose tweezers. At right is a set of flat-nose
and Philips screwdrivers. They are bigger than “jewellers” screwdrivers but not much bigger – a hobbyist would normally
have some larger flat and Philips (or Pozidriv) screwdrivers. All of these tools are from Jaycar Electronics.
74 Silicon Chip
www.siliconchip.com.au
Well, yes . . . but cheap irons
sometimes are too hot for very small
components, yet not able to maintain
a high enough temperature to ensure
good, sound joints with larger ones.
of work where it is difficult to set up
an electrical supply – eg, service work
in the field.
Butane gas, supplied from an internal reservoir, burns to heat the tip.
They will usually operate for about an
hour on a single refill and at a moderate
temperature. However, they are a bit
fiddly and you normally wouldn’t consider them against the electric version
for general bench work.
Electrostatic damage
Some cheap mains-powered irons
(and even some more expensive ones!)
can cause damage to some sensitive
components due to electrostatic discharge. This can occur if the iron tip
is not properly earthed (and even irons
which are properly earthed when new
can develop this problem with age).
What happens is that a relatively
high electrostatic voltage builds up
on the iron tip which can exceed
the rating of the component being
soldered. The result: one “cooked”
component – and not by the heat of
the iron!
To avoid this problem you can run
a strap (such as a length of wire fitted
with two alligator clips) between the
barrel of the iron and the earth plane
of the job.
Next up the list is a similar type of
iron but with some sort of temperature
control. A power rating of 60W would
be typical and the maximum temperature set would be around 350°C. This
will handle bigger jobs than the $20
iron while being kinder to very small
components.
You could expect to pay more than
$100 for a simple temperature-controlled iron, powered directly from the
mains. The comments above regarding
an earth strap still apply.
The next step up in temperature-controlled irons gets us into real
money – but you get what you pay
for. If are doing quality work over a
period of time, you should consider a
variable temperature-controlled iron
(actually they’re normally called “soldering stations”) in the price range
$200-$500.
There are quite a few brands to
choose from. Most operate through
a mains transformer, with the heating element rated at 24V and about
50-60W.
The tip temperature is controlled by
a circuit which switches the power on
and off. In some cases, the switching
action happens as the AC voltage
passes through zero, ensuring that no
transients appear at the tip.
You can set the actual temperature
via a control knob – some have a
scale behind the knob while others
www.siliconchip.com.au
Suckers!
It might say “for soldering and tinning
most metals” but this soldering fluid –
and most fluxes – are a definite no-no
when it comes to electronics. The roll
of solder at right might look the same
as you see at your electronics shop
but this higher-melting-point type is
meant for copper pipes, etc. It has a
50/50 tin/lead mix (instead of the
normal 62/38 mix) and is also quite a
lot thicker than most electronic solder.
provide a digital display for the set
temperature.
The beauty of a temperature-controlled iron is that its tip temperature
stays much closer to that set, whether
the iron is at rest or supplying its
maximum heat.
Weller produces a relatively inexpensive but very reliable soldering station that uses a series of tips to select
the temperature. The system makes
use of the “Curie” effect, where a metal
can be designed to lose its magnetic
properties at a particular temperature.
Unfortunately, this system does not
allow for zero voltage switching.
There are other versions of electric
soldering irons which don’t run from
the mains (well, not directly anyway).
These use batteries (usually, but not
always, rechargeable via a mains plugpack or adaptor) and are handy for use
away from a power outlet.
Other versions of low-voltage irons
run from 12V and are designed to
operate from a car battery – either
connecting directly with large alligator
clips or plugging in via the cigarette
lighter. These are obviously intended
for automotive uses.
Gas irons
Just to complete the story, we must
consider gas-powered soldering irons.
They are not too expensive and are
very handy for doing a small amount
Whether it’s to remove solder on
joints soldered incorrectly (hey, we all
make mistakes!) or to remove faulty
parts, a “solder sucker” is all the go.
It is a cylinder with a piston, the
latter set in sharp motion by a spring.
Air is sucked into the cylinder via a
tip that concentrates a partial vacuum
above the molten solder, drawing it
into the cylinder. These usually sell
for between $10 and $20.
There are also professional solder
suckers which have an electric vac
uum pump but these generally cost
the earth. While not out of place on
a service bench, they’re overkill for
most hobbyists.
Smaller amounts of solder can efficiently be removed from PC boards,
in particular, by means of de-soldering
wick. This is a woven copper braid
impregnated with flux, which solders
very easily.
As you start to build more projects,
devices such as this mechanical “third
hand” become almost essential. The
PC board can be held at any angle
and, importantly, easily flipped over
for soldering.
April 2003 75
GAS IRONS
Jaycar TS1620 kit
Typical of gas irons, this “Vulkan” from Jaycar is very handy if you’re away from
a power source. They run from butane gas which can refill the iron in seconds.
You place the braid over the soldered joint and then apply the iron –
the braid sucks up the solder from the
joint (just like a wick, hence its name).
Other tools
Pliers and tweezers for holding
and bending components can be very
handy aids to soldering – but don’t go
overboard and purchase every one in
the catalog until you are sure of what
you actually need.
In general, the hobbyist can get away
with one pair of fine (needle-nose)
pliers, one pair of heavier pliers, one
small pair of sidecutters and (perhaps!)
one larger pair of sidecutters. Usually
(though not always), you get a better
tool by spending a bit more money.
We mentioned heatsinks before.
They are essential if you are dealing
with components which may be damaged by high temperatures. Heat that
would otherwise flow the length of the
lead is shunted to the heatsink and the
component kept cooler.
Most small parts, including semiconductors, can be soldered safely
without a heatsink, provided the usual
60/40 solder is used and the joint made
quickly.
Lets start soldering!
Now let’s look at the actual technique of making a good solder joint.
First and foremost, the parts to be
soldered must be clean – oxidation of
component leads and PC board tracks
is one of the main causes of poor solder
connections.
Sometimes we have to use compo76 Silicon Chip
nents that have been stored for a long
time or for some other reason do not
“tin” easily. And believe it or not, many
a solder joint has failed simply because
the clear insulation on the wire (eg, on
coil wire) was not scraped off.
The idea is to get the surfaces mechanically and chemically clean by
removing oxides, sulphates and other
substances that may come from handling or from the atmosphere.
Bright copper (and bright tinned
copper) solders very easily. Oxidised
copper and tin does not.
Wiping with a clean rag will often
do the job. Stubborn cases may need
a touch of fine emery paper or even
scraping with a blade – but beware of
too much abrasion if you are dealing
with plated components.
The wires should be bright and shiny
before soldering. If in doubt, do a “trial
run”, pre-soldering the wires to see if
the solder takes properly. If it doesn’t,
you don’t have much of a chance of
making a good soldered joint.
The main point to keep in mind
is that both of the parts to be joined
must always be raised to a temperature
above the melting point of the solder.
Ideally, the tip of the soldering iron
would be applied to both parts, left
for the necessary short time and then
the solder wire (with its resin core)
applied.
The resin melts, spreads across
the surface with a cleaning action,
followed by the molten solder. The
soldering tip is then removed and
the solder solidifies to give a sound
mechanical and electrical joint.
If, as is the case with most modern
small components, they wet very easily with the molten solder, it is OK to
place the solder wire across the parts
to be joined, and apply the iron to the
solder wire which then melts and, by
conduction, raises the temperature of
both parts to the necessary temperature. This is exactly what we do when
assembling PC boards: touch the joint
with the solder wire, apply the iron,
remove the iron, wait a sec and bingo!
Just to get things into perspective,
easy to solder metals include: gold,
tin-lead, tin, silver, palladium and
copper.
Slightly harder to solder are brass,
bronze, Monel and nickel silver, while
metals that are difficult to solder include Kovar, nickel-iron, nickel, steel
and zinc.
Metals that are almost impossible
to solder without special techniques
and/or equipment include aluminium,
alloyed steel, chromium, magnesium,
molybdenum, tungsten and beryllium.
Some components may have tinplated steel leads. The steel wire provides the mechanical strength needed
to support the component while the tin
plating makes it easy to solder.
Sometimes, and particularly in the
case of high-density ICs, the coating
of easy-to-solder material is only a
few microns thick and gentle cleaning
methods are required. If you remove
the coating, it may be impossible to
make a good joint at a temperature that
is safe for the component.
Other methods of soldering
With the increasing complexity
of electronic equipment, assembly
methods and soldering techniques
have undergone a revolution.
These two solder
suckers from Jaycar
are typical of springpowered, low-cost
models. On the left
is an economy
type with plastic
body, while the
one on the right
is of metal
construction.
Both have hightemperature,
replaceable
Teflon tips.
Powered solder
suckers are
also available.
www.siliconchip.com.au
Component and equipment manufacturers go to enormous trouble to
ensure that their products are easy
to solder and reliable. Most of the
advances in soldering techniques
have occurred over the last 40 years
or so, in parallel with the increasing
sophistication and reliability of semiconductor devices.
Before then, most components had
wire leads and were strung between
tag strips, switches, valve sockets
and so on. Interconnections between
various parts of the circuit were made
with wires and, when there were a
number of wires going in the same
direction, they were made up into
looms.
The idea of having many of the
interconnections made by conductive
tracks on an insulating board (“printed
circuit”, or PC board) made it possible
to eliminate many of the wires and tag
boards. Some of the earliest PC boards
were made to accommodate valves!
Initially, the sort of components
used for tag board construction were
the only ones available and they were
used in PC boards by bending the
leads and pushing them through holes
where they were soldered, by hand, to
copper tracks on the board. These are
still used and are known as “through
hole components” – see Fig.2.
With this technique, the most expensive part of production was often
the hand-soldering operation. Indeed,
high-quality equipment produced in
small quantities with through-hole
components is still hand-soldered.
Wave soldering
Wave soldering was introduced
to allow consumer electronics items
(eg, VCRs, radios and TV receivers)
to be manufactured cheaply and in
quantity.
Before assembly, the areas of the
board which are not to be soldered are
coated with a “solder mask” which, as
its name suggests, prevents the copper
underneath being soldered.
The boards, loaded with components (often by “pick and place”
robots) are then placed on a conveyer
system. The components are on the
upper side of the board with the leads
pushed through the holes and pointing
down. The excess lead lengths may
either be clipped off before soldering
or left until afterwards.
The conveyor draws the board over a
bath which applies flux and then over
www.siliconchip.com.au
Fig.2: through-hole assembly and surface-mount assembly techniques.
Note that surface-mount assembly usually requires special equipment.
a heater which brings the underside of
the board and the component leads up
to a temperature just below the melting
point of solder. From there, the board
moves over a bath of molten solder
which is pumped to form a wave of
the liquid.
The crest of this wave comes in
contact with the underside of the PC
board, which stays in the wave just
long enough for the tracks and the
leads to reach a temperature above
the solder melting point. Solder then
flows over the tracks and leads and
completes the joints.
Finally, the conveyor takes the soldered board away from the solder bath.
Sometimes the board is simply allowed to air-cool but there are some
processes which actually drop the
whole PC board into a bath of cold,
fresh water. This has the added feature of “shocking” the soldered joints,
revealing any weaknesses or poorly
soldered joints.
If the component leads have not
been pre-cut, the cooled board is then
taken through a saw which trims all
the leads to the required length.
For wave soldering to succeed, flux,
preheating and solder flow adjustments are all critical. The board itself
must also be carefully designed so that
solder bridges do not cause shorts. It
takes experience to get good results.
Reflow soldering
Another technique called reflow soldering is used where complex circuitry
and high volume are involved. (Did
anyone mention computers?)
This makes use of special “surface
mount” components and requires a
substantial investment in plant and
operator training. As such, it is not a
technique that’s suitable for home conFig.3: solder works
by combining metallurgically with the
surface of another
metal to form very
thin, brittle intermetallic layers. It is
these layers which
actually form the
electric and mechanical connections in
the soldered joint.
April 2003 77
If you’re worried about
fumes from soldering, this
powered fume filter from
Altronics could be the
answer. It is designed to
suck the air in from around your
work and filter it, so you dont
breathe in the fumes.
struction but it should be mentioned
that there are special hot-air-flow hand
tools available for attaching and/or
replacing surface-mount parts.
Increasingly, there are components
that are available only in surfacemount versions and the serious home
constructor may well wish to use them.
Mostly, they are smaller than similar
through-hole components and keen
eyes (or a good magnifying glass!) and
steady hands are needed to place even
a small number on a PC board.
For professional assemblers, a wide
range of resistors, capacitors, transistors and ICs is available. Indeed,
most components are now available
in surface-mount packaging and some
exclusively so.
In principle, the idea of reflow soldering is very simple. A paste made up
of fine particles of solder and flux is
placed on the tracks where the solder
joints are to be made (probably tin-plated copper). The component leads are
then placed in the paste, heat is applied from above and the solder paste
melts (its flow being assisted by the
flux) so that it forms a bond between
the component lead and the track.
In practice, it is somewhat more
complicated than this. Three expensive machines are required: a screen
printer, a pick-and-place machine and
a reflow solder machine.
The paste is applied to the PC board
by a screening process similar to that
used to screen-print signs or T-shirts.
The screen may be made of metal
rather than silk in order to maintain
precise dimensions and handle the
solder particles mixed with the flux.
The paste is thick enough to keep
the components in place while the
board is transferred from the pick-and-
place machine to the reflow solder
machine.
A PC board may have hundreds (if
not thousands) of components, each
of which has to be placed in an exact
position. Often, polarity is important
as well. The components are supplied
on a continuous tape that is wound
on a reel – maybe several thousand
components on each reel. The machine
can usually handle a number of reels
at the same time, pick the components from the tapes and place them
in precisely predetermined positions
on the board.
In the solder machine, the carrier
moves the board slowly through the
several stages of the process. The time
Fig.4: the basic principles of wave soldering – see text. Compare this with
the wave soldering system shown in the photo on the facing page.
Fig.5: reflow soldering doesn’t use a soldering iron at all – temperature-controlled hot air is used to melt the solder “paste” applied to the
component and copper tracks to be soldered. The board passes through
the hot air, the solder paste melts and presto – a soldered joint.
Before soldering
Looking through the PC board, with
the components on the bottom, here's
the lead ready for soldering.
78 Silicon Chip
Notice how the tip is applied to both
of the bits to be soldered at once and
not to the solder?
Here’s what you’re aiming for: a
bright, shiny fillet-shaped solder joint
which has taken to both surfaces.
www.siliconchip.com.au
taken for it to emerge complete and
soldered is in the order of 10 minutes.
During the first few minutes, the
board is raised to a temperature of
about 100°C and held at that temperature to ensure uniformity. At this
temperature, the flux surrounding the
solder is activated.
Further into the machine, the board
is brought up to a temperature of about
170°C and held again, to make sure
that the heat distribution is even.
The board then moves on via the
conveyer to the soldering phase where
the temperature increases to around
215°C (30°C above the melting point
of solder) and held at this for a period
that can be from a few seconds up to
one minute, depending on the components. As it mover further along, the
assembly is allowed to cool naturally
and comes out of the machine only a
little above room temperature.
There are a several different methods currently used in the industry to
provide the heating but the general
trend is to use a forced hot-air flow.
Not only does the time and temperature of the reflow soldering process
have to be carefully controlled but
the design of the PC boards requires
considerable care and experience.
For example, the solder pads used
for surface-mount components have
to exactly match the components.
Provided this is done, the surface tension of the molten solder will pull the
components into their exact positions
during soldering.
Here’s wave soldering in action. The PC board is carried along over the solder
bath by a conveyor. At one point, the solder is forced up in a “wave” so that the
bottom of the board passes through it. The components and copper tracks are
soldered and the board then emerges from the bath. Photo: Ohio State University.
UHF) but when this is not a consideration, it’s usually easier to stick to
components with leads.
At this point, it is appropriate to
consider the idea of soldering surface- mount components when they
are used in home projects. For ICs
and transistors, where there is a short
lead with some flexibility, a very fine
solder tip and a steady hand can result
in good work.
The problem arises with surfacemount resistors and capacitors, most
of which have a ceramic base. You can
usually solder one end of the component to the PC board with no problems
but when it comes to soldering the
other end, the cooling process places
the component in a state of mechanical
stress. This raises and the possibility of
breaking the ceramic body and hence
ruining the part.
This stress does not occur when
both ends of the component cool down
together. Be aware of this problem if
using an ordinary soldering iron to
attach surface-mount components:
always check each component after
it is in place.
SMD resistors and capacitors have
the advantage of low series inductance
(important when working at VHF and
“Dry” joint no. 1 . . .
“Dry” joint no. 2 . . .
A brittle joint . . .
Oh no! The solder hasn’t taken to the
PC board track at all – it’s just made a
blob on the lead. This is a “dry” joint.
Here’s another type of dry joint. Some
solder has taken to the PC board but
only flux has stuck to the lead.
Not a “dry” joint but one destined to
fail. It is brittle because something
has moved as the solder hardens.
SMDs for the hobbyist
www.siliconchip.com.au
Health considerations
Finally, a reminder: solder contains lead and lead compounds are
poisonous. There does not appear
to be any hard evidence that people
doing occasional hobby or service
work are exposed to any real health
risks although on production lines,
an exhaust fan is often used.
Commonsense would suggest that
you avoid breathing the vapours
given off when soldering. Likewise,
fumes from molten flux should also
be avoided.
Finally, always wash your hands
after soldering, especially before eating. Provided you follow these simple
precautions, you should have nothing
SC
to worry about.
April 2003 79
MORE FUN WITH THE PICAXE – PART 3
This circuit
has HEART!
The PICAXE circuit this month approximates
animal breathing and heart beats to such an
extent that it seems almost alive!
T
HIS PROJECT AROSE while
discussing heart and breathing
rates with a sports medicine
workmate. It quite convincingly
generates both “heartbeats” and
breathing sounds that alter with
temperature.
Left in a darkened room, it could
easily convince the gullible that it’s a
robot taking a snooze!
For the medics (and non-medics)
amongst you, the three variables wide
ly known as TPR (Temperature, Pulse,
Respiration) are perhaps the most fundamental “what’s up with the patient”
nursing vital signs measure. As an
example, check your own pulse and
breathing rates, both while exercising
and relaxing.
The “heartbeat” LED effect is quite
entrancing, since it slowly increases in
brightness to a maximum, then fades
away again to darkness.
A normal flashing LED of course
just turns on and off , with no dimming action. The beating action here
looks most eye-catching in comparison.
It could even be used as a status
light in a more professional application, perhaps to add a “human touch”
to some otherwise bland piece of
equipment. You may even feel more
affectionate towards your photocopier
by Stan Swan
if it was fitted with one of these heatbeat circuits!
Incidentally, while this is a quite
simple, indeed simplistic, type of
project, it does point towards some of
the “grown up” uses for this type of
circuit in the real world. Many devices
use visual and aural indicators to help
us humans quickly work out what they
are doing – you can easily envisage
this type of circuit being adapted for
such a purpose.
The sensor
The sensor used – a negative temperature coefficient (NTC) thermistor
– has a resistance that decreases as
Even the one-eyed cat was
convinced . . . it was fascinated
by the breathing sound but
couldn’t quite find the person
to whom it was attached.
80 Silicon Chip
www.siliconchip.com.au
the temperature increases – and vice
versa.
This action is, of course, similar
to an LDR as we used last month –
(low resistance in bright light, high
in darkness). However, thermistors
have nothing like the rapid response
or resistance range of an LDR, so the
effects are somewhat slower and less
dramatic.
Typically, an NTC thermistor such
as the 100kΩ <at> 25oC type used here
(Dick Smith Cat. R-1895), shows a
resistance of about 300kΩ near 0oC,
reducing to about 30kΩ when warmed
to 50oC.
A suitable voltage divider network
again exploits this so that a varying
voltage from the thermistor is fed to
the pin 1 I/O channel input – see Fig.1.
Suitable juggling of the “top half”
resistor to 15kΩ yielded some six discrete steps over a 0-50oC temperature
range. If you use thermistors other than
the 100kΩ <at> 25oC type specified here,
you may have to alter this resistor – a
resistance wheel greatly eases the fine
tuning.
Pulse width modulation
The PICAXE-08 can output a Pulse
Width Modulation (PWM) signal that
effectively generates analog voltages
(0- 5V) from digital inputs – in effect
a simple Digital-to-Analog Converter
(DAC).
Rather than a neat train of fixed
width pulses, a “noisy” jumble of 0s
& 1s is produced instead. However,
the overall ratio of highs to lows is as
specified by the duty cycle.
Quite elegant uses of this analog
output can result, such as capacitor
Fig.1: without wanting to sound repetitious, you can instantly see the
similarities between this month’s circuit and the previous two: a thermistor
replaces the LDR in the input “voltage divider”.
charging (and refreshing) to a desired
level but the “heartbeat” use here just
illustrates the PWM action and syntax. (PWM will also be used in a later
PICAXE circuit involving a small DC
motor driven via a transistor).
warm lamp or cup (try to keep water
drops off the electronics of course) or
by placing the unit in the fridge.
Be sure to alert your family first
though, to avoid “there’s something
breathing in the fridge” concerns.
The program
Footnote
Perhaps the most obvious program
need is to prevent the LED action
briefly halting while the piezo sounds.
It’s rather like your heartbeats ceasing
when you breathe! “08s” execute program instructions sequentially, so this
may be hard to overcome, however.
Ample memory space is left for your
own tweaking, with any number of
refinements possible! Wider temperature ranges can be organised by a
Some users report PICAXE programming may be unreliable using
fresh battery packs, since the upper
6V operating voltage may then be
significantly exceeded.
Removing a cell or two, so that only
4.5V or even 3V is supplied, seems to
overcome this problem.
See over for program listing.
Once again, we’ve made a few changes (for clarity) from the PICnic box photo above
to the Protoboard layout at right. Follow the layout and you shouldn’t go wrong!
www.siliconchip.com.au
April 2003 81
PICAXE-08 COMMANDS USED THIS MONTH: PWM
PWM syntax takes the basic form – PWM pin, duty, cycles
(duty & cycle can be program variables or constants).
Pin refers to the PICAXE I/O output pin (0 ,1, 2, 4).
Duty (0-255) specifies the analog level desired (0-5 volts).
Cycles (0-255) specifies the number of cycles (~5ms) delivered.
Example: PWM 1, 100, 8 refers to the pin 1 I/O channel, 100/255
duty, 8 cycles (ie, 100/255 = 39% duty cycle; hence 39% of 5V =
1.96V output).
BASIC PROGRAM LISTING
(This can also be downloaded from http://picaxe.orconhosting.net.nz/heartled.bas)
‘ Demo PWM “Heartbeat/breathing “ PICAXE-08 April.03 SiChip Ver 1.0 14th Feb.03
‘ Best assembled & tested with solderless “PICNIK” box as detailed SiChip Feb.03
‘ Refer http://picaxe.orcon.net.nz for background info & potential of PICAXE-08
‘ Extra parts = 100k NTC thermistor (DSE R-1895),Red LED, 1 x 15k ,1 x 330 Ohm
‘ NTC can be moved off board, but water proof(epoxy/hot melt glue?) if outdoors
‘ New commands here = PWM , SOUND 255 (=hiss),
‘ Ref.PICAXE prog.editor.pdf help files,& BASIC Stamp 1 manuals for insights
‘ via Stan. SWAN (MU<at>W, New Zealand) => s.t.swan<at>massey.ac.nz <=
‘————————————————————————————————
‘ Byte b0= NTC measure-increases as temp rises b1= loop counter 0-255
‘ Variables b2= divided NTC measure (approx.= R) b3= “heartbeat” delay
‘
b4= loop counter 1-6 to give suitable pulse/respiration ratio
‘————————————————————————————————
‘ Lines beginning ‘ are program documentation & could be ignored if need be.
‘ Program available for web download => http://picaxe.orconhosting.net.nz/heartled.bas
‘————————————————————————————————
heartbeat:
‘ LED/PWM thermistor resistance monitoring routine
‘ approximates human TPR heartbeat & breathing!
for b4=1 to 6
readadc 1,b0
b2=b0/4
debug b0
‘ cycle heartbeat loop so approx 10 breathes/min
‘ low res.read NTC value via 15k voltage divider
‘ sub zero temps may give b0=0 & beating ceases!
‘ divide for a conveniently smaller step value
‘ show variable NTC value(s) to attached PC VDU
for b1= 0 to 255 step b2
pwm 2,b1,1
next b1
‘ counter loop so LED has multiple PWM cycles
‘ PWM pin 2 LED one cycle increasing pulse width
‘ effect is a pleasing surging brightness increase
for b1= 255 to 0 step -b2
pwm 2,b1,1
next b1
‘ When warm b2 decreases so step less/beat faster
‘ PWM pin 2 LED one cycle decreasing pulse width
‘ gives a fading brightness instead of sudden off
b3= 100/b2 *10
pause b3
next b4
‘ “invert” NTC b2 value & limit to a useful range
‘ delay decreases as temp rises
‘ continue heartbeat loop until time for breath!
sound 4,(255,80)
pause 400
sound 4,(255,40)
‘ inhale = breathe in “hiss” approx. 1sec
‘ hold 400 millisecs (seems ~normal ?)
‘ exhale = breathe out “hiss” approx. 1/2 sec
goto heartbeat
82 Silicon Chip
‘ repeat routine
Some more references
and parts suppliers
1. http://picaxe.orconhosting.net.nz – author’s enthusiastic PICAXE-08 web page.
Some
more references and
2. http://picaxe.orconhosting.net.nz/heartled.
parts
suppliers.
. . & paste.
bas – program
listing to copy
3. http://www.healthmedialab.com/html/
president/mckin3.html
– a fascinating 1901 TPR chart of then US
President McKinley,
recorded while he was hospitalised with
gunshot wound complications.
4. SILICON CHIP, February & March 2003 –
introducing PICAXE
circuits.
5. www.cpemma.co.uk/pwm.html
– typical of web sites explaining PWM.
6. Dick Smith Electronics stock 100kW/25oC
NTC thermistors – Cat. R-1890 or R-1895.
7. Dick Smith Electronics have large (heart
sized?) 10mm red LEDs –
Cat. Z-4060.
8. Oatley Electronics
(www.oatleyelectronics.com)
and Microzed (www.microzed.com.au)
now stock PICAXE-08 ICs and many
accessories.
PIC, PICAXE, mEL,
ATOM, & Various
Components
ALL IN STOCK
MicroZed Computers
Tel: (02) 6772 2777
Fax: (02) 6772 8987
WebLINK:
www.microzed.com.au
www.siliconchip.com.au
110mm
$29
$199
2W 315 X 162 X 19 ... $29 (SP2)
4W 315 X 315 X19... $59 (SP4)
14W 315 X 925 X19... 199 (SP14)
IN
A
G
R
BA $33
77mm
All of our panels are
amorphous, aluminium
framed, backed
and water-proof.
28mm
NEAR HALF PRICE SOLAR PANELS
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
in your ESKI or insulated cooler box & fit an aluminum
Kit hole
plate or heat-sink (not supplied) to this assembly to turn
your ESKI into a fridge for the car or boat. requires 12VDC
Special intro price of only $33 (pelt1).
SWITCHING SOLAR REGULATOR KIT: This easy to assemble kit is designed to
efficiently charge batteries from solar cells. It has charge / discharge indicator LEDs.
contains PCB plus all on-board components. KIT PRICE: (K008B) $15
10 LED LAMP KIT:This kit uses 10 Ultra-bright LEDs (equivalent to around 6W
incandescent) with far less current drain than normal incandescent light bulbs but with a NEW PRODUCT
BARGAIN
brighter, whiter light. It uses a constant current circuit & draws 120mA. (This means is your
12VAC
POND PUMP
get many more hours of light with a smaller & cheaper battery & solar cell. Kit contains a
small PCB, 10 White Ultra-bright LEDS & all on-board components. Easy to assemble. 10 Why spend a small fortune on
a new water feature when you
LED Kit $20 (K199_10)
could build your own. Requires
12V / 7AH SEALED LEAD ACID BATTERY: Fresh stock batteries, now is the time to pick 12VAC (We have a suitable
plug-pack available for
up a real bargain, 2.6kg, 150 x 65 x 92mm.(PB6) $25 each
just$6). Pumps a head of up
ST
JU 4.50
$1
to 500mm at 300L p/h via a
8mm outlet. (PP1)
(NEW)ICOM BRAND VOX HEADPHONE /
MICROPHONE AMP
This new item has the original headset removed. It can be returned to its
original use by adding a headphone
set and microphone(see below).
Features include small size (50X30
X20mm), VOX gain control and TOT /
PTT / VOX switch (ICM01)$3
<---BATTERY--->
< SOLAR CELL >
+
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+
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12V 7AH
SEALED LEAD ACID
BATTERY
UPGRADE TO A BIGGER
PANEL!!! For just $25 more.
You can upgrade from a 2W to a
4W panel in your Solar Lighting
System . (SL4W) total
price.$124
HOW ABOUT A COMPLETE
SOLAR LIGHTING SYSTEM
FOR YOUR CAMP, CARAVAN
OR WEEKENDER: There are 4
main components to this
system, 2W Solar Panel,
Switching Solar Regulator kit,
Battery and 2 X 10 LED Lamp
Kits. This combination of solar
panel, charger and battery will
power 1 of the LED lamp kits for
over 7hrs with only 5hrs of
sunlight. Central Australia
receives around 10 hrs per day.
(SL2W): $99
LOTS OF AMAZING OPTICAL BARGAINS
***LOOK***LOOK***LOOK***
H I G H P O W E R E D L E D S , L A S E R S WARNING!!! These magnets are so strong they are
dangerous!!! new neodymium rare earth magnets.
POINTERS & LASER DIODES
Dew to popular request we have introduced some
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.
smaller magnets to our range similar to those used in
magnetic therapy etc. 20 X 10mm$6.00... 10 X
5mm$1.20... 10 X 3 mm$0.70... 7 X 3mm $0.55... 7 X
2.5mm $0.45... 3 X 2mm $0.25... 3 X 1.5mm$0.20.
NEW...NO FRILLS PICAXE PROGRAMING KIT
Kit contains suitable plug-pack PCB &
some components to experiment with
20 or more red LEDs for $0.60ea
& all other onboard components inc.
20 or more white LEDs for $1.70ea
10cD White...$2.00 ea Red...80c Yellow ...70c the PICAXE chip. What you see in
the picture is what you get. Features
Green...$2.10 Blue...$2.20 UV LED's ..$1.60
include socket for
Less 10% for 10 or more of any mix
the Picaxe & large
Money Detector Pens
These use a very bright UV LED. Check Australian tinned copper pads
currency for counterfeits by looking at the hidden UV with component
holes.(PAE01)$16.50
printing on them. ...$4.50
BULK LED SPECIAL
Extra AG13 batteries ...15c as used in the key-chains,
3 req. Extra AG3 batteries...6c as used in pens, 4 req.
Don't forget our bargain OPTO PACK...K147
Pack inc. total of 103 opto semiconductors. 91 various
colours & types of visible LED's, 1 x IR LED, 6 x Phototransistors, 2 x high speed PIN photodiodes, 1 x HC312 IR
Receiver Module. KIT PRICE: (K147) $10 each pack
PICAXE-08 CHIPS
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.
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
(NEW) STEREO HEADPHONES:
Stereo headphones in
sealed plastic bags
as supplied by the
manufacturer to
Ansett airlines.
These have an unusual
connector that is std on
Boeing aircraft: $2 for 4
VOSFRYER CONTROLLER: These could be used as is
or with a PC to control the 4 high current outputs on the
PCB (Schematic for the output section supplied). These
items are full of useful bits like Sprecher & Shun
Contactor CA-9-10. 15VA 240V Transformer 0/ 6.3/ 7.5/
8.5/ 9.5/ 12.5/ 15 Secondary, PCB 170mm x 140mm with:
5 x H100S12-1-C Millionspot Rly, 5 x Diode bridge 1A, 2 x
Diode bridge 5A, 4 x High current Triacs TPDV1240, 5 x
Opto isolator 4N25, 4 x 440 Volt AC 0.047 caps, 1 x Mains
Rocker switch , 1 x
16 way IDC plug, Zilog
Z86E2304PSC
(Socketed), 4 MHz
XTL, High power
Piezo, Caps, IC's
Regulator etc. Also
includes Display
PCB, 4 x 2 Digit
DA56-11EWA 7
seg displays, 2 x
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display driver IC's
(NOT socketed).
All of this for just $44:
of kits and surplus electronics to hobbyists, experimenters, industry & professionals.
www.oatleyelectronics.com Suppliers
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
SC_MAR_03
VINTAGE RADIO
By RODNEY CHAMPNESS, VK3UG
The AWA R154 Battery Console
Intended for use in country areas without mains
power, the AWA R154 battery console was first
sold in 1935. It operated from three different
battery types and there were no less than 11
battery leads to hook up to the chassis.
Back in April 2001, I wrote about
Keith Lang, an enthusias
tic vintage
radio collector in Western Australia.
Recently, I had a chance to renew our
association during a trip to the west
in late 2002.
Keith has many fine examples from
the bygone era of Austra
lian-made
radios. I asked him which set was his
favourite, to which he replied: “I have
no particular favourite but my favourites are the Australian made sets”.
The AWA R154
One of Keith’s favourites is an the
AWA R154 console that takes pride
of place in the lounge room. This set
(and the re-badged Bandmaster 365B
version) appeared on the market in
1935. It had an RF stage and as such,
was intended to operate in remote
country areas.
The R154 and sets like it used a 2V
lead acid accumulator (A supply),
three 45V batteries (B supply), a 9V
tapped bias battery and a 4.5V bias
battery (C supply). It was a bit of a
nightmare connecting all the batteries
into circuit, as in this case there were
11 leads. Thankfully, they were all
The AWA R154 receiver featured a large round dial mechanism. It not only
indicated the tuned station but also the tuned frequency (in kilocycles) and the
wavelength (in metres).
84 Silicon Chip
labelled (see photo).
For the unwary owner, there was the
ever likely chance of connecting the
leads incorrectly, with the possibility
of burning the valve filaments out.
The 2V cell (battery) was charged as
necessary by the mechanic at the local
garage, while the B and C batteries
were simply replaced when they
went flat. In practice, the 2V cell had
to be recharged several times before
it became necessary to replace the B
and C batteries.
In fact, the C batteries often lasted
their shelf life, as negligible current
was drawn from them in most receivers.
No mains power
Not many farming communities
had access to the 240V AC mains
supply back in 1935. This meant that,
once outside the perimeter of the
townships, you were very much on
your own when it came to providing
electrical power. The “well to do”
often had their own power supplies
which usually took the form of a 32V
lighting plant. However, most farmers
couldn’t afford that luxury, hence the
use of battery receivers.
For example, my parents lived about
4km from the nearest town with 240V
AC power. This meant that, in 1948,
when they replaced their “Wimmera”
console (similar in power requirements to the AWA R154), they chose
a 6V HMV vibrator receiver.
In fact, my parents relied on kerosene lights until they installed a 32V
lighting plant in 1949. But even at that
stage, not many 32V sets were available and most people either relied on
battery sets such as the R154 or the
later vibrator powered sets.
R154 circuit details
Fig.1 shows the circuit of the R154
www.siliconchip.com.au
Above: the top of the set carried the controls and dial
scale. The set is a good performer and is well worth
restoring.
Right: this photo shows Keith’s fully restored AWA R154
console. This particular unit has been converted to mains
operation, to avoid battery hassles (see text).
– it is quite conventional with one or
two unusual quirks.
For example, the tuning gang is
mounted on rubber insulation which
isolates it from the chassis. This is necessary because the gang is nominally
at -4.5V with respect to the chassis
(this is the bias applied to the two 34
valves). AWA did this with a few of
their sets but the reason for this and its
advantage, if any, is unknown.
The various stages within the
receiver have the appropriate voltages applied to them via taps on the
battery supplies. There is very little
in the way of decoupling between
stages but the receiver is stable in its
operation just the same. That so little
decoupling was used is an indication
of the relatively low gain of individual
stages. In addition, the battery supply itself was used as a decoupling
medium.
RF stage
The input stage is a conventional
tuned radio frequency (RF) stage using a 34 valve, followed by a 1A6 as a
www.siliconchip.com.au
converter. It covers the tuning range
from 550-1500kHz, as can be seen on
the dial scale.
The intermediate frequency (IF)
stage operates on 175kHz and uses
another 34 as the amplifier. The IF
output is then fed to a 30 triode which
is used as a diode detector. Its output
is applied to volume control R4 and
from there to a 32 which functions as
the first audio amplifier stage. This is
then followed by a 33 audio output
stage, which gives about 0.5W of output – quite adequate with an 8-inch
loudspeaker mounted on a substantial
baffle board. A tone control (R9) is
included between the 32 and the 33.
The purpose of R2 across the volume control is not clear at first glance.
Usually, the C battery positive goes
directly to chassis as happens with
the bias battery (a). However, this set
has two bias batteries and the second
one (b) applies -4.5V to the front end
of the receiver as a standing bias via
R2 and R4.
In operation, the detector develops a
negative voltage across R3 and R4 that
increases with the signal strength. This
voltage is effectively in series with
the bias voltage and so the RF and IF
valves have their amplification controlled via the automatic gain control
(AGC) circuit.
Apparently, designers hadn’t solved
the problem of minimising the number of batteries and tappings on the
batteries at that stage. As mentioned
earlier, there are 11 battery leads in
this set – a recipe for disaster in the
hands of non-technical users.
Restoring the R154
There’s no risk of the chassis falling out of the cabinet in this set – it’s
secured in place using 6mm-diameter
bolts! Before removing the chassis, it’s
first necessary to remove the knobs,
the various battery cables and then
the chassis mounting bolts.
Because the chassis is mounted almost vertically, removing the last bolt
(or refitting the first bolt) can be rather
difficult. The way around this is to lay
the set on its front on a blanket. That
way, the chassis will remain in place
April 2003 85
Fig.1: the circuit diagram for the Bandmaster 365B is the same as for the AWA R154. The set used six valves: a 34
RF stage, 1A6 converter, 34 IF amplifier, 30 detector, 32 first audio stage and a 33 audio output stage.
This rear view of the chassis shows some of the non-original valve shields that
had to be pressed into service to complete the restoration.
86 Silicon Chip
when the last bolt is removed and it
can then be lifted out.
Keith found that the antenna coil
had been destroyed by lightning and so
it had to be replaced. The original one
was unavailable, so a midget Q-Plus
car radio type was fitted inside the
original coil can. The set works very
well with a short antenna.
The 1A6 converter was also faulty
but its replacement wouldn’t work
either. As a result, Keith decided to
replace it with a 1C6, which worked
reliably. According to Keith, the 1A6
was always an unreliable valve and the
1C6 was designed to replace it.
Some of the valve shields were also
missing and the correct ones were
unavailable, so it was necessary to
use whatever would fit. These will be
replaced further down the track if the
correct shields can be obtained.
Another job involved the loudspeaker which had quite a few holes in its
cone – presumably due to silverfish.
These were repaired by sticking
medical paper tape over each hole or
tear, then gluing from the back with
www.siliconchip.com.au
Photo Gallery: Goblin Model
CR Mantel Radio
Introduced in 1947 as the “Time Spot”, this unusual 5-valve 3-band
radio featured an 8-inch Plessey speaker and a clock-timer unit
(lefthand dial). The set is actually a Goblin Model CR and was made
by the British Vacuum Cleaner Company (England). It was obviously
intended for export to Australia, as the dial scale is embossed with
Australian stations.
The clock setting was activated by a shaft at the rear and by a large-diameter thumb-wheel on the front (between the two round dials). A similar
wheel was used for the volume control, a peephole in the dial scale
showing the setting.
This particular unit was been fully restored by its owner, Maxwell Johnson, Kingston, Tasmania. (Photo: Ross Johnson).
water-based craft glue.
Unfortunately, the silverfish had
also attacked the outer rim of the cone.
This damage was fixed using pieces of
tissue paper which was covered with
glue and rolled into shape around the
outer rim of the cone.
The speaker baffle was also replaced
but had not been finished at the time
of writing. The baffle should be matt
black in colour and a variety of finishes
can be used here – either matt black
paint in a pressure pack, or black boot
polish or even good old-fashioned
stove polish (eg, Busy Bee and other
brands).
Cabinet restoration
The cabinet needed some attention
too. Keith has not had good results
with paint stripper and prefers to
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remove the old finish mechanically
using a sharp paint scraper and a
sander. You have to be careful when
doing this though, otherwise the thin
veneer will be sanded through.
Once the sanding had been completed, black Wattyl Crafts
m an
traditional interior wood stain was
used to highlight the edges (as had
originally been done). The cabinet
was then sprayed with clear lacquer
to get the fine finish apparent in the
photographs.
Unfortunately, the set came without
knobs so Keith fitted some general-purpose AWA knobs which should be
similar to the originals.
Alignment
The alignment of the receiver was
accomplished without any problems.
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April 2003 87
The chassis was mounted vertically in the cabinet, above
the baffle (not the original) and the loudspeaker. Note the
bunched battery leads and the added AC power supply (in
the black box on the righthand side).
The plate tuning trimmer in each IF
transformer is at 135V with respect
to the chassis, so care was needed
to make sure that no short circuits
occurred during the alignment procedure.
By the way, this set is generally easy
to restore, particularly underneath the
chassis. Everything is well spread out
and there isn’t a lot underneath the
chassis anyway. If only this was true
of other vintage radio receivers – some
of them can be quite difficult when
it comes to gaining access to various
parts.
Like many sets of the era, a large
terminal board was used in this receiver. The components are mounted
in bulk on this board which is then
mounted and wired into the receiver.
Unfor
tunately, some of the components are mounted under the board,
which is fine until service work is
required.
The leads running under these
boards usually have to be carefully
traced, as they don’t always go where
expected. Unfor
tunately, the wiring
in older sets was often run using just
one colour, which made lead tracing
more difficult.
That said, only a few components
88 Silicon Chip
This under-chassis view of the R154 show the paucity of
components and the ready access to the circuit. The only
drawback is that some components are mounted on the
underside of the terminal board.
had been replaced over the life of the
set and none in recent times. It says
a lot for the reliability of most of the
components.
240V AC operation
Although originally designed as
a battery set, this particular set has
been converted to operate on 240V
AC. Keith says that even battery sets
should be able to be used – even if the
batteries to operate them are no longer
available.
As can be seen in the photograph
of the back of the set, a black box has
been attached to the side of the cabinet.
This box contains a power supply that
provides all the DC voltages necessary
to operate the receiver from the AC
mains.
This particular supply was made
from a kit but Keith has also made a
number of supplies to his own design
and all work well. The 11 power leads
are wired to two plugs, so that they
can be easily plugged into the power
supply with no confusion as to where
each lead should be connected.
Summary
The R154 (and the Bandmaster 365B
clone) are sensitive receivers and the
audio quality from them is quite good.
They would certainly have looked the
part in a 1930s or 1940s lounge room
and there is much to like about them.
There are also a few features I
dislike. First on the list is the great
tangle of power supply leads from
the batteries.
The second feature I dislike is the
“floating” gang. It appears to serve no
useful purpose and makes for more
complexity in manufacture. And third,
I’m not too keen on the way some of
the components have been mounted
on the underside of the terminal board.
Some of the valves may now be
unobtainable for a set of this age, so
substitutes may have to be used. For
example, the 33 could be quite easily
replaced with a 1D4 with minor alterations to the voltages applied to it.
A 1L5G could also be used if the
valve socket was changed to an octal
socket.
Substitutes for other valves could
be found as well. It is just a matter of
checking which valves have similar
characteristics to those requiring replacement.
Overall, these are good receivers
which are well worth restoring and
SC
having in a collection.
www.siliconchip.com.au
www.siliconchip.com.au
April 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
DIY 300W car amplifier
not practical
A friend showed me a back issue of
SILICON CHIP and I was interested
in the specs for the 300W amplifier.
Is it stable at 2Ω? If not, is it a matter
of doubling the output stage to obtain
greater stability. I’m interested in
using it together with a switchmode
power supply in a car. (A. B., via email).
• We have not described a 300W
amplifier although we did describe
a 350W Mosfet amplifier in 1994 –
it was not suitable for 2Ω speakers
though. EA described a 300W amplifier back in April/May 1995 but again,
not suitable for 2Ω. Finally, a 300W
module was published in EA in May,
June & July 1980 but it also was not
suitable for 2Ω.
In any event, if you are going to install it in a car you need a high-power
inverter to produce the DC supply rails
of about ±80V. By the time you do that
it is definitely cheaper to buy rather
than build. Have look at the car amps
available from Jaycar.
How to increase
Multi-Spark voltage
I am interested in building the
Multi-Spark CDI project from the September 1997 issue of SILICON CHIP.
DC supplies for headphone amplifier
First, I have a small complaint.
A lot of your kits do not specify (in
advertisements, etc) what power
supplies are required. A frustrating case in point is the headphone
amplifier from the May 2002 issue.
It suggests that this kit is suitable
as a general purpose headphone
amplifier. My intent in purchasing
was to adapt it to the output of my
PC as a booster for my headphones
but the requirement for ±15V was
90 Silicon Chip
I was wondering about modifying it
slightly. I’m wanting to increase the
primary voltage from 300V to around
425V or so. Is this possible? The reason
for this is to increase the output energy
from 45mJ. Most commercial units put
out 420V to 525V for the primary. (S.
M., Invercargill, NZ).
• The voltage can be increased by
another 75V using an extra 75V zener
in series with ZD1-ZD4. We do not
recommend going above this voltage
as the capacitor is not rated for more
volts. You will need to add about 50
more turns on the secondary of T1
as well.
Degaussing circuit explained
Could you tell me the function of the
dual posistor in a TV set as mentioned
in the Serviceman NEC TV set story
featured in the September 2002 issue?
(C. D., via email)
• The posistor is a positive temperature coefficient (PTC) thermistor
connected in series with the degaussing coils around the periphery of the
CRT. When cold, the posistor has a
low resistance and this lets current
flow in the degaussing coils. After a
few seconds the posistor heats up, its
resistance goes high and cuts off the
degaussing current.
not immediately evident from the
kit packaging. Nor is it covered
very well in the magazine article.
I find this oversight more than a
little vexing.
Can you advise on a suitable kit
etc, that could now achieve this
requirement? (R. C., via email).
• It did not occur to us that people
would want to use this project with
a computer. However, if you can
get access inside your PC you will
probably find that you have ±12V
DC available and this could be used
without any mods to the circuit.
Speed controller for
Meccano motor
I would like to use your 10A 12VDC
motor speed controller to run a 6V
Meccano motor using the original 6V
battery pack. Is it possible to modify
this circuit to run off 6V DC? Failing
that, do you have another project that
can be modified for the task? (C. C.,
via email).
• The 10A 12V motor speed controller cannot be used at 6V as the TL494
requires more than that to provide its
internal 5V reference. Our suggestion
is to use is the Mini PC Board Drill
Speed Controller described in the
January 1994 issue of SILICON CHIP,
with some slight modifications.
The 9.1V zener diode should be replaced with a 5.1V type and the 220Ω
resistor changed to 27Ω 1W.
Sound card
interface is noisy
I’ve recently assembled a sound
card preamp kit from the August
1998 issue of Electronics Australia,
with the intention to use it as an oscilloscope. After assembly, I’ve done
all the functionality testing as per
the instructions, with the equipment
working fine.
The problem is that the preamp is
putting out some form of background
noise (ie, with no CRO probe connected), which seems to be generated in
the preamp circuit. Unfortunately, this
makes the unit unreliable.
Would you be able to tell me if this
was maybe experienced in the circuit
built by Electronics Australia in August 1998 and if so, what did they do
to rectify it? There is a paragraph in the
article referring to the LM324 chip as
noisy. Is this what I am seeing? Also,
there is an instruction referring to fitting a higher performance TL074 quad
op amp. Will this fix the problem? (R.
C., via email).
• Our sound card interface presented
in August 2002 is far superior to that
www.siliconchip.com.au
presented in the August 1998 issue
of EA. At the time of publication,
we assumed that the kitset suppliers
would automatically kill off the old
project and present the new but it
didn’t happen.
Unfortunately, we do not know
what problems were specific to the
EA circuit. If you want low-noise
performance, build the one published
in SILICON CHIP. Note also that our
article states that the “smallest voltage
you’ll be able to measure accurately
will be in the mV range”. Our prototype had less than 1mV RMS noise but
that will depend on your sound card
and your computer.
Speed alarm
signal pickup
You have probably been asked this
a hundred times before but can you
tell me if it is possible to connect the
kit directly to the computer for speed
sensing. I have a VP Commodore
with analog display speedometer. The
speedo is driven by pulses from the
computer. What I would like to do is
use this signal instead of the magnet/
coil method. (M. G., via email).
• Yes you can use the speed signal
from the engine management system.
The speed signal connects to the signal input on the coil input terminal
on the speed alarm. The second coil
input (shield connection) is left open.
Possible damage
to 12V amplifier
I have recently constructed the 12V
Mini Stereo Amplifier kit (SILICON
CHIP May 2001). It has a few problems
when it is operating. With the bass
control anywhere in the boost region,
the speakers start to behave strangely.
Occasionally and randomly the cones
violently pull downwards, and at the
same time all sound is lost for about
half a second.
If I pull out one of the RCA connectors (left or right channel) and
have the sound coming out of just one
speaker, when the other speaker pulls
down, the one which has no sound
coming through mimics it. There is
also a lot of hiss produced, even with
no input and the volume turned fully
down.
The treble control does not seem
to make this phenomena occur and
neither does the volume. Even with
www.siliconchip.com.au
Do DVD players control 6-channel output?
The 6-Channel Volume Control in
the March 2002 issue was of interest
as I am at looking putting together
a system with separate amps combined with a DVD player which
has built-in decoding and separate
5.1 channel analog outputs, as you
discuss. However I thought that at
least some DVD players controlled
the volume out of all six channel
outputs themselves (ie, using the
DVD remote vol up/down buttons),
thereby negating the requirement
for the additional Volume Control
project.
Am I missing something or do the
DVD players only control the left
& right channel output volume for
2-speaker use, and the 5.1 channel
outputs are all at a standard, fixed
the volume very low and the bass
high, the intensity of the “pull down”
remains the same.
In an effort to fix this problem, I have
replaced IC1, the two 100µF 16V electrolytics, the two 2200µF 25V electrolytics and the 470µF 16V electrolytic.
This has partially solved the problem
but not fully. I have a feeling that all
of this occurred when I connected
the amp to a car battery and the wire
sparked and the fuse blew. I am now
running the unit off a 12V 3.4Ah SLA
battery. (D. F., via email).
• It seems you might have damaged
either the power amplifier or the op
amps used for the tone controls. Perhaps changing the op amps will solve
the hiss problem.
Also the amplifier requires heavy
gauge wiring for the power connections between the amplifier PC
board and the battery. Otherwise, the
amplifier will exhibit a tendency to
mute or “motor-boat” on loud signals,
due the supply voltage dropping. The
minimum to use is 7.5A rated wire.
Replace the supply leads before you
do anything else, as this may fix the
problem.
Electronic wind vane
decoding problem
Back in March 2000 you described
an electronic wind vane with a 16-LED
display. I have had the PC boards on
level, that would normally be handled by an integrated 5.1 channel
amp/receiver?
As you may have guessed, I haven’t acquired my DVD yet, only
read a bit on the web and looked at
some in the stores. (D. B., via email).
• As we understand it, at least
some DVD players with 5.1 output
can be made to control all channel
outputs by going through the menus
but as soon as you switch off, you
lose the settings and you have to
go back through the hoops again. It
really is a big hassle.
However, technology moves on
and you would be wise to thoroughly check the latest DVD players. Maybe some do now have this
facility in a convenient format.
hand for some time and have finally
got around to putting the project
together. But one problem has me a
little confused.
At switch-on I am greeted with
one LED, that being the North LED.
Rotation of the Gray Code disk did
not result in any other LED becoming
illuminated. A quick check of the A, B,
C & D inputs found them to be all low
which would explain the illumination
of the North LED.
The voltages on the input lines were,
on average, + 0.02V (not illuminated)
and +0.9V (illuminated). The inputs
appear to be going high but not high
enough. The application of +12V to the
inputs results in all the correct LEDs
on the display board lighting, proving
that the decoding is working correctly.
There is around 3mA flowing
through the infrared LEDs which
appears OK. Any ideas as to why
this is happening would be greatly
appreciated. The IR LEDs I am using
are DSE Z-3235 and Z-1956. (B. C.
Ballina, NSW).
• The current to the infrared LEDs
can be increased to provide greater
drive to the infrared diodes. Use a
470Ω resistor in place of the 1.8kΩ
resistor. Also, change the 10kΩ resistors for the infrared diodes to 47kΩ, to
allow a higher voltage when exposed
to light.
Make sure the LEDs and diodes line
up for maximum light transfer. Also,
April 2003 91
10A Speed
Controller
I constructed the 240VAC 10A
Speed Controller from the November 1997 issue and it works well. I
initially tested it by dimming a light
and later with an angle grinder.
Everything is fine apart from the
fact that there is around 39- 40V
AC between the speed controller’s
diecast case and the alloy blade
cover of the angle grinder. I got the
same result with a router. Is this
normal?
The angle grinder is double-insulated and does not have an earth
connection. The case for the speed
controller is fully earthed correctly,
as described in the instructions.
I haven’t been game enough to
touch it – I am not sure whether or
make sure the gap between the LEDs
and infrared diodes is at a minimum.
Kill switch for
rev limiter
I have built a rev limiter from the
April 1999 issue but I also need to
have a switch which will kill the
engine completely. The car is used
for motor sport where a kill switch is
required by the regulations. It seems
that this can be incorporated in the
ignition switcher circuit in the following two ways.
(1) Installing a second capacitor at
C1 which can be switched in to kill a
very high number of sparks, causing
the engine to stall; or
(2) Install a switch between terminals 8 and 3 of IC1. When the switch is
closed, transistor Q3 will be turned on
to kill all sparks. Solution 2 would be
not the multimeter is misreading
something?
Secondly, are the motors in vertical press (Ryobi) drills brush type?
(A. P., via email).
• The reading you are measuring
will be due to the fact that the power
tools are not earthed and that there
is some capacitance between the
metal parts and the internal wiring.
The meter will read a voltage due to
its high input impedance.
Try connecting a 10kΩ resistor
between the multimeter terminals
and do the measurement again.
You should get a very low reading.
Your speed controller is probably
working completely normally.
Drill presses usually have in
duction motors, which are not
suit
able for use with this speed
controller.
easier to install. What do you recom
mend? (D. M., via email).
• Solution 2 would be best as it completely shuts down the ignition.
Low-cost
oscilloscope probe
I am interested in building a sound
card adapter kit from Electronics
Australia, on sale at one of the kitset
suppliers for $30. However, I reckon I
need oscilloscope probes so that I can
use the adapter, right?
When I checked prices of probes at
Jaycar or Dick Smith Electronics, they
were around $44 each, much more
than the price of the kit. That is too
much for a student budget. Can we
make one probe on our own? (D. B.,
via email).
• We featured a low-cost, low-capacitance scope probe in the August 1989
edition of SILICON CHIP. It utilises a
short length of coax cable, a resistor,
trimmer capacitor and a few other bits
& pieces you’d probably find in your
junk box.
Door alarm uses electret microphone
I have searched all the indexes,
including those on your website (excellent site, by the way) and I cannot
find what I seek. It is an alarm using
a microphone as a sensor. It does not
operate on sound but on changing
air pressure as a door or window is
opened. I am certain it was in SILICON
CHIP and I have every copy from issue
number one but I just can’t find it. Can
you help? (R. C., via email).
• The article appeared in the July
1995 issue. It used an electret microphone as a pressure sensor. We can
supply the issue for $8.80 including
postage.
Notes & Errata
AVR ISP Serial Programmer, October
2002: there is an error on the circuit
on page 75. Pins 1 & 4 have been
swapped on CON3. The PC board is
correct.
12V SLA Battery Float Charger, March
2003: when this charger is used with
the PortaPAL (February and March
2003), the 10µF capacitor connecting
to the adjust terminal of REG1 should
be omitted.
Simple VHF FM/AM Receiver, December 2002: a short track is missing
from the PC board, as shown on pages
88 & 90. The track should connect the
junction of the two 3.3kΩ resistors
and L1 with the adjacent end of the
22kΩ resistor. The corrected PC board
pattern can be downloaded from our
SC
website.
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
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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
CIRCUIT WANTED: Beale Panchromatic TRF Radio 65-882 stamped in
chassis. Valves 35, 35, 24, 47, 80. Original condition. Built Annandale, Sydney,
1932. Could it be S.T.C. chassis? Reply
(08) 8087 4574.
and high speed counter. Free software,
Labview driver and ActiveX component.
DAS005 Parallel Port Data Acquisition Module features 8 12-bit Analog
inputs, 4 Digital I/Ps & 4 Digital O/Ps.
Free windows software and source
code.
Dual Relay Modules suitable for TTL
and Open Collector Outputs.
Programmers for Atmel and PIC microcontrollers.
Switch Mode and Linear Power Supplies
and DC-DC converters.
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
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
LABJACK USB DATA ACQUISITION
MODULE features 8 12-bit analog
inputs, 20 digital I/O, 2 analog outputs
10-RELAY ROLLING CODE UHF
REMOTE CONTROL Expands the 4
Relay version (SC, 7/2002) to its full
www.siliconchip.com.au
NOW
AVAILABLE
FROM
Advertising Index
Acetronics....................................94
www.siliconchip.com.au
All Electronic Tech. Assoc............41
Altronics........................ loose insert
Av-Comm Pty Ltd.........................94
Clarke & Severn...........................69
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
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.
Subscribe &
Get This FREE!*
*Australia only. Offer valid only while stocks last.
Dick Smith Electronics........... 24-27
Eco Watch....................................93
Elan Audio....................................87
Emona Instruments......................71
Grantronics..................................93
Harbuch Electronics.....................70
Instant PCBs................................94
Hy-Q International........................69
Jaycar ......................... catalog, IFC
JED Microprocessors................5,69
Kalex............................................87
Microgram Computers..............3,95
Catalog 17078. Industrial Motherboard. 533MHz
Front Side Bus, plus on-board Watch Dog Timer and
Ethernet. This is a “well sorted” quality industrial
board. For more detail: phone Microgram Computers
(02) 4389 8444 or www.mgram.com.au
MicroZed Computers.........69,82,94
Oatley Electronics........................83
Printed Electronics...................... 94
potential controlling 10 relays. Uses
PIC16F628.
See it at: www.ozitronics.com
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
Procon Technology.......................69
Quest Electronics.........................69
RCS Radio..............................69,94
RF Probes...............................69,87
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.
KIT ASSEMBLY
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
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
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
WANTED
EARLY HIFI’S, AMPLIFIERS, Speakers, Turntables, Valves, Books ; Quad,
www.siliconchip.com.au
SILICON CHIP pays up to $60 for contributions to Circuit Notebook. Send your
idea to: Silicon Chip Publications, PO
Box 139, Collaroy, 2097.
Silicon Chip Binders................89,94
Silicon Chip Bookshop..........96,IBC
Silicon Chip TestBench.............7,95
Silvertone Electronics..................94
Soundlabs Group.........................69
Splat Controls..............................37
Telelink Communications....69,OBC
TradePart.Com.............................47
_________________________________
PC Boards
Printed circuit boards for SILICON
CHIP projects are made by:
RCS Radio Pty Ltd. Phone (02) 9738
0330. Fax (02) 9738 0334.
April 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
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46
$$
VIDEO SCRAMBLING AND DESCRAMBLING
AUDIO ELECTRONICS
If you've ever wondered how they scramble
video on cable and satellite TV, this book tells
you! Encoding/decoding systems (analog
and digital systems), encryption, even
schematics and details of several encoder
and decoder circuits for experimentation.
Intended for both the hobbyist and the
professional. 290 pages in paperback.
For anyone involved in designing, adapting and
using analog and digital audio equipment. It
covers tape recording, tuners and radio receivers,
preamplifiers, voltage amplifiers, audio power
amplifiers, compact disc technology and digital
audio, test and measurement, loudspeaker
crossover systems, power supplies and noise
reduction systems. 375 pages in soft cover.
By John Linsley Hood. First published 1995.
Second edition 1999.
FOR SATELLITE AND CABLE TV
by Graf & Sheets
2nd Edition 1998
4th
EDITION
$
70
87
$
3rd
ITION
ED
UNDERSTANDING TELEPHONE ELECTRONICS
By Stephen J. Bigelow. 4th edition 2001
Based mainly on the American telephone system, this book covers conventional telephone
fundamentals, including analog and digital
communication techniques. Provides basic information on the functions of each telephone
component, how dial tones are generated and
how digital transmission techniques work.
402 pages, soft cover.
103
$$
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.
By Tim Williams. First published
1992. 3rd edition 2001.
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
EMC FOR PRODUCT DESIGNERS
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.
BOOKSHOP
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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.
by Howard Hutchings. Revised by Mike James.
2nd edition 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.
H
E
R
E
63 $$63
$
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.
52 69
$$
$$
❏ ANALOG CIRCUIT TECHNIQUES W/DIGITAL INT............$69.00
❏ ANALOG ELECTRONICS..................................................$89.00
❏ ANTENNA TOOLKIT.........................................................$87.00
❏ AUDIO ELECTRONICS.....................................................$92.00
❏ AUDIO POWER AMPLIFIER DESIGN...............................$89.00
❏ ELECTRIC MOTORS AND DRIVES..................................$63.00
❏ EMC FOR PRODUCT DESIGNERS.................................$103.00
❏ GUIDE TO TV & VIDEO TECHNOLOGY............................$63.00
❏ INTERFACING WITH C.....................................................$63.00
❏ M'CONTROLLER PROJECTS IN C FOR 8051..................$73.00
❏ PIC IN PRACTICE............................................................$52.00
❏ PIC - YOUR PERSONAL INTRODUCTORY COURSE........$46.00
❏ POWER SUPPLY COOKBOOK..........................................$99.00
❏ PRACTICAL RF HANDBOOK............................................$69.00
❏ TELEPHONE INSTALLATION HANDBOOK.......................$69.00
❏ UNDERSTANDING TELEPHONE ELECTRONICS.................$70.00
❏ VIDEO & CAMCORDER SERVICING/TECHNOLOGY........$69.00
❏ VIDEO SCRAMBLING/DESCRAMBLING..........................$87.00
Orders over $100 P&P free in Australia.
AUST: Add $A5.50 per book
NZ: Add $A10 per book, $A15 elsewhere
P&P
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
PIC IN PRACTICE
O
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D
E
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87
$
Interfacing With C
Electric Motors And Drives
by Austin Hughes. 2nd edition 1993.
Reprinted 2001.
NEW
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NEW
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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.
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
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