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SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.altronics.com.au
Vol.9, No.2; February 1996
Contents
THREE REMOTE CONTROLS
TO BUILD – PAGE 76
FEATURES
4 Fluke 98 Automotive ScopeMeter
This versatile, comprehensive vehicle engine test centre fits in the palm of your
hand. Along with "on board" measurements, it has the option of later analysis of
measured data with a personal computer – by Julian Edgar
26 Racing On Air: Germany's New MagLev Train
Imagine a train without wheels, safely and almost noiselessly gliding along at
500km/h, thanks to magnetic levitation. It's not just a designer's dream – the
prototype TransRapid has already clocked up 200,000km on its test track.
PROJECTS TO BUILD
8 Fit A Kill Switch To Your Smoke Detector
A simple and cheap modification to your smoke detector will stop it shrieking every
time someone burns the toast! – by Rick Walters
12 Build A Basic Logic Trainer
Learn all about the basic operation of digital ICs. It makes a great teaching and
demonstration aid – by Rex Callaghan
22 Low Cost Multi-Tone Dashboard Alarm
Take one $4 toy phone, add a few components and you'll have a 9-tone
alarm module to alert you to a range of vehicle problems – by Julian Edgar
36 Woofer Stopper Mk 2 - Now It's Even Better!
FIT A 10-MINUTE KILL SWITCH TO
YOUR SMOKE ALARM - PAGE 8
Troubled by barking dogs in your neighbourhood? The Woofer Stopper barks back with
an ultrasonic blast that can help train Fido to be socially responsible! – by John Clarke
60 Surround Sound Mixer & Decoder - Part 2
We continue our description of a state-of-the-art mixer and decoder for surround sound:
this month, final construction details and test procedure – by John Clarke
76 Three Remote Controls To Build
Your choice of a single channel UHF, a dual channel UHF or an eight channel infrared
remote control. Full constructional details included – by Branco Justic
SPECIAL COLUMNS
A $4 TOY PHONE MAKES A GREAT
DASHBOARD ALERT – PAGE 22
54 Serviceman’s Log
The dingiest corner of a dingy room – by the TV Serviceman
85 Computer Bits
Use your personal computer as a reaction timer – by Rick Walters
88 Vintage Radio
The basics of reflex receivers – by John Hill & Rodney Champness
CONTROL BARKING DOGS WITH THE
WOOFER STOPPER Mk.2 – PAGE 36
DEPARTMENTS
2 Publisher’s Letter
7 Mailbag
25 Order Form
32 Circuit Notebook
72 Product Showcase
92 Ask Silicon Chip
94 Notes & Errata
95 Market Centre
96 Advertising Index
February 1996 1
Publisher & Editor-in-Chief
Leo Simpson, B.Bus., FAICD
Editor
Greg Swain, B.Sc.(Hons.)
Technical Staff
John Clarke, B.E.(Elec.)
Robert Flynn
Rick Walters
Reader Services
Ann Jenkinson
Advertising Enquiries
Leo Simpson
Phone (02) 9979 5644
Regular Contributors
Brendan Akhurst
Garry Cratt, VK2YBX
Julian Edgar, Dip.T.(Sec.), B.Ed
John Hill
Mike Sheriff, B.Sc, VK2YFK
Philip Watson, MIREE, VK2ZPW
Bob Young
Photography
Stuart Bryce
SILICON CHIP is published 12 times
a year by Silicon Chip Publications
Pty Ltd. A.C.N. 003 205 490. All
material copyright ©. No part of
this publication may be reproduced
without the written consent of the
publisher.
Printing: Macquarie Print, Dubbo,
NSW.
Distribution: Network Distribution
Company.
Subscription rates: $49 per year
in Australia. For overseas rates, see
the subscription page in this issue.
Editorial & advertising offices:
Unit 34, 1-3 Jubilee Avenue, Warrie
wood, NSW 2102. Postal address:
PO Box 139, Collaroy Beach, NSW
2097. Phone (02) 9979 5644. Fax
(02) 9979 6503.
PUBLISHER'S LETTER
Welcome to the 100th
issue of SILICON CHIP
Can it really be? Yes, this issue is our
100th. SILICON CHIP started operations back
in August 1987 and the November 1987 issue, Volume 1, Number 1, was launched in
the preceding month, October. At the time,
there were many people who thought we
were extremely foolhardy in starting this
magazine, given that there were already three
Australian contenders well established and
lots of imported electronics magazines as well.
Indeed, we felt rather audacious ourselves. There were tough times in
those first few years but I am glad to write that virtually all of the people
who were involved in the production of that first issue are still associated
with us today. And many of our readers who purchased our first issues are
still buying it and looking forward to its arrival each month. To those people in particular, we extend our thanks because without a large and loyal
readership no magazine can exist for long.
Our thanks too, to our regular advertisers, whose loyalty also contributes
to the content and viability of SILICON CHIP. I should also single out Gary
Johnston of Jaycar Electronics for special thanks. Without his promise of
advertising support and his encouragement in our tentative beginnings,
SILICON CHIP would not have started.
Today, the electronics magazine field has changed markedly from the
position when we started. Now there are only two Australian electronics
magazines and many of the foreign magazines have dropped by the wayside
as well or at least they are no longer available in newsagents.
As we look forward to producing our 200th issue, we are sure that the
electronics scene will continue to be as dynamic as it has been. Computers
will continue to inexorably make their presence felt in every line of human
endeavour and integrated circuits will continue to get smaller and yet more
powerful. Most importantly, people who know and keep informed about
electronics will continue to have an edge. They will always be more likely
to be employed and they will enjoy rather than shun new technology.
We feel that as technology and society grow ever more complex, those
who have at least some understanding of electronics will always be better
prepared to adapt and prosper. It is our continuing challenge to keep you,
the readers, always informed about and entertained by electronics. Thanks
for your continuing support.
Leo Simpson
ISSN 1030-2662
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.
2 Silicon Chip
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.
Macservice Pty Ltd
Engine Analysis On The Run . . .
Fluke 98
Automotive
ScopeMeter
Every auto shop these days has
an extensive array of electronic
engine analysis equipment.
Now there's one that fits in the
palm of your hand for "real
life" measurements and even
personal computer analysis.
By RICK WALTERS
T
HE FLUKE 98 AUTOMOTIVE
ScopeMeter provides a compact
measuring system with a large
liquid crystal display which will allow
auto mechanics to carry out a wide
range of diagnostic measurements, both
on the bench and on the road.
When it was released, the Fluke
ScopeMeter was a clever concept
which was immediately accepted by
the electronics industry. Now Fluke has
produced a new version aimed at the
car service industry, the Automotive
ScopeMeter.
The measurements available include
voltage, resistance, dwell angle, oxygen
sensor, general sensors, RPM, primary and secondary ignition, relative
compression and EFI duty cycle. In
addition, by using the optional diesel
probe set, diesel injector pressure pulse
4 Silicon Chip
and diesel advance measurements
can be made.
Engines catered for include three,
four, five, six and eight cylinders,
two and four cycles, diesel or petrol
and 6V, 12V & 24V batteries. It also
can measure conventional Kettering
ignition systems with a distributor,
vehicles such as the Holden V6 with
distributorless ignition and vehicles
with a coil for each spark plug.
Probably one of the most useful
features of the ScopeMeter, especially
for new users, is the help system. The
trouble with most modern electronic
equipment, from the humble video
to even the mobile phone, is that the
number of functions packed into the
unit is so great that the manual is
needed each time you need to carry
out more than the basic operations.
The Fluke has a big yellow MENU
button which, when pressed, brings up
the menu screen. The selected function is shown in reverse video and the
up and down arrow buttons are used
to scroll through the menus. Above the
F5 button the SELECT legend is shown
(1-7). Once the choice is made, full
instructions appear, showing which
leads to use and which ScopeMeter
input to connect (1-8). This “connection help” function can be turned off
once the user is completely familiar
with the unit.
As well as the menu help, there
is a key labelled “i” which, when
pressed, displays information about
the highlighted menu choice, while
you are in the menu program (1-12) or
information about the function keys,
when a test is running (1-14).
Fig.1: this graph shows the relative
compression of each of the eight cylinders
in a Holden V8, recorded at a cranking
speed of 133RPM. The "best" cylinder (in
this case cylinder 6) is rated at 100%, with
all others relative. The variations between
cylinders in this 85,000km-old motor are
clearly evident.
The ScopeMeter is normally powered from its internal nicad battery,
with a mains plugpack supplied to
recharge or trickle charge it. In emergencies, four standard “C” cells can be
used but these cannot be recharged.
The use of batteries allows “on-road”
testing to be readily carried out.
One very useful accessory supplied
as standard is the automotive demonstration board. This small PC board
simulates five functions, allowing you
to become familiar with the operation
and functions of the ScopeMeter at
your leisure instead of under the
bonnet of a car.
The board outputs are labelled
injection, secondary ignition, sweep,
general sensors and oxygen sensor.
Chapter two of the comprehensive
manual includes a tutorial using the
demonstration board to carry out eight
simulated tests.
It starts by taking you through the
process of measuring the voltage of
the 9V battery supplied to power the
PC board. The next tests are resistance
measurement and two plots of the voltage across the SWEEP potentiometer
on the PC board for clockwise and
anticlockwise rotation.
This is followed by a measurement
of the oxygen sensor signal, using the
RPM potentiometer to vary the viewed
waveform. Next are general sensor
Fig.2: data from the Fluke 98 (screen shot at left) has been transferred to
the personal computer database for this particular vehicle. A profile of
vehicle performance over time is a very handy aid in vehicle diagnostics.
and RPM measurements, again using
the RPM potentiometer to vary the
displays. The last tests measure a simulated secondary ignition coil voltage
and an injector waveform.
By the time you have worked
through these examples you will be
quite conversant with the selection of
the menu screens and the interpretation of the readouts.
The tutorial continues with a description of the methods used to plot
one parameter over a period, how to
plot a trend which will compute the
maximum, minimum and average
values over the period and how to use
the “flight record”.
This flight record is a very useful
function, allowing you to store up to
1280 divisions in a cyclic memory,
the length in time being equal to 1280
times the timebase setting in seconds.
This means, for example, that if the
timebase speed is 10ms per division,
you could store 12.8 seconds of information. So what use is it?
Let’s say that you have a vehicle
with an engine misfire under load and
you don’t have a dynamometer. To
diagnose the problem, you turn on the
Fluke, select ignition, secondary, OK,
record and flight record, connecting
the leads as instructed. You then take
the car for a run and when the fault
occurs, you press the clear memory
button. This starts saving the measurements into memory. Once you have
felt the misfire, you press any button
to store the information. When you get
back to the workshop you can analyse
the stored information and decide on
the steps necessary.
Among the options is SW98W,
FlukeView 98 for Windows Software.
This allows the transfer of any stored
waveforms to an IBM or compatible
PC with, at minimum, an 80386
processor and Windows 3.1. Once in
the computer, you are able to read,
document, save and print any results
from the Fluke.
The software allows you to keep a
record of the relevant parameters for
particular cars or perhaps even particular clients. By comparing current
data with previously stored information, the present state of tune can be
readily established.
These records are kept in a database
which can be set up in a way which
best suits your application. For example, you can group the information as
Manufacturer, Model, Engine Capacity, Test Category, Test 1, Test 2, or
Manufacturer, Engine Capacity, Test
Category, Test 1, etc.
A neat feature of the database is that
when you are selecting a previously
saved screen, as you change the model
or capacity, the thumbnail sketch of
February 1996 5
Fig.3: this graph shows the firing voltages for each of
the cylinders of the Holden V8 engine. Note again the
variations from cylinder to cylinder.
the graph changes immediately, to reflect your choice. This helps greatly in
locating a particular record, especially
if you know what the waveform you
are searching for looks like.
Once you have become familiar with
the operation of the ScopeMeter, the
94 pages of chapter five of the manual, headed automotive applications,
describe the procedures for testing all
vehicle sensors, along with expected
readings and waveforms.
Fig.4: an "ideal" injection pulse for a specific engine as
shown by the Fluke 98 software database. This allows
mechanics to instantly compare results achieved during
tests with manufacturer's specifications.
Sections follow on air/fuel, ignition,
electrical system and finally diesel
RPM and advance measurements.
This review has only covered some
of the wide range of measurements of
which the unit is capable. Features
such as single shot function, dual trace
operation, etc are all fully covered in
the comprehensive user manual.
The current cost of the Fluke 98
Automotive ScopeMeter is $3990.
An automotive temperature probe is
Protect your valuable issues
Silicon Chip Binders
$330. The FlukeView 98 for Windows
software is $435 which includes the
optical connecting cable. The diesel
probe set is $440. All the above prices
exclude sales tax which must be added
to the figures quoted.
The review sample came from
Philips Test & Measurement. For
further information, contact the distributors, Obiat Pty Ltd, 129 Queen St,
Beaconsfield, NSW 2014. Phone (02)
698 4111. Fax (02) 699 9170.
sub Buy a
get scriptio
a di
n&
the scount o
bind
n
er
These binders will protect your copies of SILICON CHIP. They feature
heavy-board covers, are made from a distinctive 2-tone green vinyl and
hold up to 14 issues.
★ High quality with heavy board covers
★ Each binder holds up to 14 issues
★ 80mm internal width
★ SILICON CHIP logo printed in gold-coloured lettering on spine & cover
Price: $A11.95 plus $3 p&p each (NZ $6 p&p).
Just fill in & mail the order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number.
6 Silicon Chip
MAILBAG
There's many a myth
in sound reproduction
In his criticism of your July review
of Jamo speakers, R. W. Field in the
September issue seems to be putting
Martin Colloms on something of a
pedestal.
Mr Colloms undoubtedly has a great
knowledge of loudspeakers, having
made a very successful career in this
field. I have the 3rd edition of his
“High Performance Loudspeakers”
and a skim through the 4th edition did
not reveal any significant additional
information. He does not mention
bi-wiring in the 3rd edition so has
physics changed from one edition to
the next or is it simply fashion?
Sound reproduction is wide open
for the dissemination of myths and
folk-law because the golden-eared fraternity can always hear things which
are denied to us lesser mortals. There
is no compelling reason to conduct
rigorous AB testing to clear away the
fantasies and the GEF would not believe the results anyway.
Mr Colloms is sufficiently commercially aware not to rock the boat
too much and indeed there are many
controversial aspects of speaker design. For example Mr Colloms says at
one point “... asymmetrical placement
of the drive units is beneficial as it
results in unequal path lengths from
the drivers to the edge of the enclosure”. At another he says “the need
for a uniform, symmetrical directivity
in the horizontal plane dictates that
the main drivers be mounted in a
vertical-in-line formation”. At another
point he quotes work by KEF and B&W
on complaint driver mounting which
was thought to be beneficial at one
stage. However, it was subsequently
found that there was then a loss in
upper range detail and designers
returned to rigid driver fixing with
which conclusion I totally agree.
As you say, there is simply no justification for bi-wiring. In my cynical
view, the meretricious bi-wiring fashion was dreamed up by those same
characters who decided we all needed
monster OFC cables, simply to double
their market!
The choice of drivers, cabinet design, crossover frequencies, filter de-
sign, speaker placement and listening
room acoustics will all far outweigh
any real or imagined consequence of
such esoteric matters as bi-wiring or
monster cables, whether oxygen free
or not.
A. March,
North Turramurra, NSW.
Making a case for a larger case
With regard to the Digital Effects
Unit for Musicians – a great idea and
all of the most useful effects for a melodic musician!
My comments are: a unit of this
type could easily be in a box twice the
size (and reasonably) – with a printed
circuit not so jam-packed together.
The fun of assembling a kit such
as this is largely negated by absurdly
having to use a magnifying glass to find
out if some parts of the print are shorts
or not, and in some places requiring
unreasonable demands on dexterity
in soldering .
All OK for those with microscope
eyes and “pin” soldering irons! These
kits should be laid out to a size to suit
assemblers of reasonable dexterity;
eg, such as the ETI 1424 preamplifier which has reasonably spaced PC
tracks.
I’ve had to separate two places that
were, or were almost, shorts on print
01301951, leaving one or two others
that are too close for comfort. The
main circuit’s mate, board 01301952,
is more reasonable and easy to track.
I suggest in future the main printout
should be larger to accommodate
similar spacing!
T. Ford,
Malanda, Qld.
Comment: your remarks highlight the
dilemma that we have concerning
many of our designs. Some readers
regard our boards as much too large
and state that we could shrink them
to less than half the size and indeed
we could. Then there are readers
such as you who say that the end
product is too small. We should also
comment that the cost of metal work
is a major item in kits and if we can
base a design on a standard plastic
case, then that can be a big factor in
a kit’s success but it does also set the
size of the board.
Serviceman cartoonist
is a genius
After some years of thinking about
it I am at last compelled to write and
congratulate you on your perspicacity
and business acumen in seizing upon
the very considerable talents of the
illustrator supreme who applies his
genius to the “Serviceman” in your
worthy monthly.
This genius (and I use the word in
its fullest meaning) is apparently an
electronics tradesman of considerable
experience, as shown by the many
convolutions of electronic parts in his
drawings, all of which demonstrate a
thorough practical knowledge. He also
shows a grasp of the psychology of his
human (and animal) subjects. These
convey at a glance the impression of
flawlessly catching the theme of each
situation in the very human terms portrayed. The animation of each portrait
(I can no longer use the lesser term
‘drawing’) captures the very essence
of the infinite variety of everyday life
in the day of a serviceman, from the
humorous to the scary.
Although I have never been employed in the public sector of servicing, half my own career has been spent
repairing so-called professional equipment. A common thread runs through
this work in this age of increasing costs
and decreasing incomes.
This forces me to buy SILICON CHIP
and I cheerfully admit to buying an
issue or two for the artistry of this
man alone. He is a real asset to your
magazine and is certainly streets in
front of any illustrator I have ever seen
in any technical magazine.
If, as I expect, the illustrator and the
Serviceman are one and the same, then
this man’s future is assured should
he ever put away his soldering iron
in favour of the pen. Thank you again
SILICON CHIP for the many moments
of light relief afforded me, from involuntary chuckles to deep belly laughs,
all of which have done me a power of
good over the years.
John Byers,
Midland, WA.
Comment: our cartoonist and Serviceman writer are actually two separate
people. Together, we think they produce a brilliant result.
February 1996 7
No more morning din!
Fit a kill
switch to
your smoke
detector
These days, with more and more homes being
fitted with smoke detectors, a problem has
arisen. The alarm goes off when you burn
the toast! This little circuit copes with that
problem.
By RICK WALTERS
You are in your normal early morning daze preparing breakfast, when
the smoke alarm starts screaming. The
toast has jammed in the pop-up toaster
and smoke is wisping (billowing?) up
into the alarm.
Sure, you can turn the toaster off
but how long does it then take to
clear the smoke? In the meantime
the alarm is sounding off, giving you
and the rest of the household a high
stress factor. The only solution is to
climb up on a chair and disconnect
the battery.
Peace and quiet at last!
Of course, you don’t have time to
reconnect the battery now, as you
have to get away, but you will do it
tonight or as soon as you get round to
it. Well, that is your plan anyway. How
long will it be before you actually do
it? Smoke detectors with the battery
disconnected are useless.
Problem solved!
The problem is solved with this
simple kill circuit which will cost
about $2 and take five minutes to
build. It won’t stop you from burning
the toast but it will disable the alarm
for 10 minutes to allow the smoke
to clear.
Only a few components are required, including a miniature pushbutton switch which is mounted on
8 Silicon Chip
Fig.1: FET Q1 is normally
turned on fully because the
330µF capacitor at its gate
is charged to +9V. When
kill switch S1 is pressed,
the capacitor is discharged,
Q1 turns off and the smoke
alarm is disabled for about
10 minutes while the 330µF
capacitor charges up again
via the 4.7MΩ resistor.
Fig. 2: this is how easy it is to build. Most of the components (three
out of four) are mounted on the back of the 9V battery connector,
while the 100Ω resistor is wired directly to the kill switch (S1).
If you are seeing a blank
page here, it is
more than likely that it
contained advertising
which is now out of date
and the advertiser
has requested that the
page be removed to
prevent
misunderstandings.
Please feel free to visit the
advertiser’s website:
www.avico.com.au
the lid of the smoke detector – this is
the “kill” switch.
Now, when you burn the toast and
the alarm goes off, climb on a chair
or grab a broom handle and push the
“kill” switch. The alarm will stop and
will be disabled for 10 minutes.
After that time, the smoke detector
will be powered up again. If smoke
is still present, it will immediately
sound off again but if the smoke has
cleared, the alarm will merely “chirp”
to indicate that it is back in business.
The smoke alarm we modified for
this article was a Kambrook unit but
most battery operated smoke detectors
should work equally as well with this
kill circuit.
How it works
Fig.1 shows the circuit. A low cost
Be sure to disconnect the battery
before soldering the parts to the
connector.
February 1996 9
Most smoke detectors will
easily accommodate the extra
parts on the battery snap
connector. The switch mounts
on the lid of the case.
Left: be sure to sleeve
the switch contacts
and the 100Ω resistor
with plastic sleeving, to
prevent shorts when the
case is assembled.
N-channel Mosfet (Metal Oxide Silicon Field Effect Transistor) is used
as a switch. It is connected between
the battery and the smoke detector
circuit.
As you can see from the circuit
(Fig.1), the gate is connected to the
battery positive via a 4.7MΩ resistor.
Normally, this will keep the 330µF capacitor charged to +9V and so the FET
will be turned fully on and the smoke
detector will work. If it detects smoke
10 Silicon Chip
it will sound the alarm
in the normal way and
will keep sounding until
the smoke has dispersed.
However, if you’ve burnt
the toast and pressed the kill
switch, the capacitor will be
discharged, thereby turning the
FET, and the alarm, off. The 4.7MΩ
resistor will now take about 10 minutes to charge the 330µF capacitor to
around +5V.
At this point, the FET will start to
turn on but will not be fully turned
on until the gate reaches more than
+6V. It is while the FET is turning on
that the smoke detector will give an
audible chirp or two, telling you that
it is back in business.
The audible chirp is not a part of
the kill circuit but is a feature of most
battery-operated smoke alarms: when
PARTS LIST
1 BS170 or BS170P Mosfet (Q1)
1 330µF 10VW PC electrolytic
capacitor
1 4.7MΩ 0.25W, 5% resistor
1 100Ω 0.25W, 5% resistor
1 pushbutton momentary contact
switch, DSE Cat P-7560 or
equivalent (S1)
the battery gets low, they chirp once
every thirty seconds or so.
Building it
Because there are so few components, a PC board is not necessary.
Instead, the parts are mounted on
the top of the battery connector – see
Fig.2. You will need to drill a 6mm
hole in the lid of the smoke detector
to accommodate the kill switch and
run a couple of insulated wires to it.
When you have installed the kill
switch circuit, check the smoke detector for normal operation. Do this
by pushing the test button and also
by exposing it to smoke. If it responds
by sounding the alarm, then all is
well. It should then be mounted on
the ceiling.
Now try not to burn the toast. It
SC
makes such an awful smell!
SATELLITE
WATCH
1996 looks set to be a bumper year for
satellite enthusiasts with a number of
new satellites due to be launched.
• INTELSAT 704-66 E longitude, C
band: No new reports from this satellite.
Worldnet programming, as well as CFI
from Paris continue to be visible. CFI
operate a rather low sound subcarrier
of 5.84MHz.
• APSTAR 2R—77 E longitude, C band:
Although not yet launched, the APT
satellite company have advised that this
will be the new location for APSTAR 2R
(APSTAR 2 failed at launch December
1994). As there are also 2 THAICOM
satellites co-located at 78 E, and a current
ITU reservation exists for ASIASAT III
at 77.5 E, there is bound to be plenty of
controversy over this move. China is not
a member of the ITU, and is therefore not
bound by ITU convention.
• GORIZONT 24—80 E longitude, C
band: Russian signals can be seen on IF
1475MHz on a 24 hour basis. Watchable
signals can be achieved using a 3m dish
and low threshold receiver from the east
coast of Australia, as long as the dish is
located for a very low “look” angle (7
degrees).
• GORIZONT 28—90 E longitude, C
band: Network 1 programming can be
seen at IF 1475MHz. East coast dishes
must have a look angle of 15 degrees
or so.
• GORIZONT 19—96.5 E longitude,
C band: The Russians seem to have
changed their Network 1 logo, and now
identify with “OPT” in the top right hand
corner of the screen. CCTV 4 continues
at 1325MHz, but Az Tv has disappeared
from 1425MHz.
• ASIASAT II—100.5 E longitude, C
band: November 28 1995 saw the successful launch of Asiasat 2, with test
pattern first observed December 18. Covering 53 countries, the signals from this
satellite promises to provide an enormous range of free to air programming.
*Garry Cratt is Managing Director of
Av-Comm Pty Ltd, suppliers of satellite
TV reception systems.
Compiled by GARRY CRATT*
A Russian satellite has been
park
ed at this location since
early December, broadcasting
Network 1 programming. Precisely why this location has
been chosen is unknown, and
would seem to contravene ITU
designated orbital allocations.
• GORIZONT 25-103 E longitude, C band: Signals from
this satellite have increased in
strength. This satellite regularly
carries the Australian soapie
“Neighbours”, and various
music videos, in PAL from 0800
AEST. No further active tran- Fig.1: the test pattern from the new Asiasat II
sponders have been observed. satellite, launched last November
• ASIASAT 1-105.5 E longitude, C band: Regular proAustralia, ATVI has begun a double hop
gramming continues without change.
link via Subic Bay (Phillipines) linking
For those able to receive this satellite,
their Palapa B2P signal to Rimsat G1 (IF
a fax polling service, operated by Hong
1325MHz). The signal is being carried
Kong Telecoms, is available. Dial 852 172
by at least one cable operator in India.
77700/01/02/16 or 20 for STAR TV ser• GORIZONT 25-140 E longitude, C
vices on this satellite (normal IDD rates)
band: Two transponders have been
• PALAPA B2P-113 E longitude, C
noted operating on this satellite. Russian
band: This satellite was finally placed
network 1 programming is broadcast
into an inclined orbit on December 8,
using RHCP on 3760MHz IF, whilst Mosto conserve station keeping fuel. The
lem Television (MTA) is broadcast on
replacement satellite Palapa C1 promises
IF 1430MHz every evening from 10pm,
good signal levels across Australia. It is
using LHCP.
anticipated a 2.3m dish will be required
• RIMSAT G2-142.5 E longitude, C
along the east coast of Australia for good
band. ATN continue to operate two
reception.
adjacent half transponders, at great
ly
• JCSAT 3-128 E longitude, C band: No
reduced power. A 3.7m dish will be renew reports from this satellite. We do
quired for reasonable reception of these
know that the spacecraft testing is comtwo channels. New Zealand viewers
plete, and that a full 50 channel digital
report a 5m dish is required for half
TV service is planned for Japan mid 1996.
transponder reception. EM TV from New
• RIMSAT G1-130 E longitude, C band:
Guinea remains at the same power level.
Testing of two adjacent half transponders
• OPTUS B3-156 E longitude, K band:
(IF 1460 and 1480MHz) carrying RAJ
The OTEN educational TAFE channel,
TV programming has been seen since
shared by NSW and Victorian Education
late November. Noise free signals have
Departments and carried on transponder
been observed using a 1.8m dish along
5, has now been encrypted using “Crypto
the east coast of Australia. New Zealand
vision” addressable decoders. E-PAL
viewers report noise free signals using
vision has been seen on transponders 4L
3M dishes across that country. Although
and 5L some weekends.
SC
this signal is barely visible from northern
February 1996 11
Build This
Basic Logic Trainer
And learn all
about digital ICs
This Basic Logic Trainer from Dick Smith
Electronics is just the shot for teaching digital
electronics and demonstrating digital logic
concepts. It’s easy to build, easy to operate
and runs from a 9V DC plugpack supply.
Design by REX CALLAGHAN
As shown in the photograph, the
Basic Logic Trainer is built around a
central prototyping board. The trainer
provides the necessary power supply
rails (5V DC), clock signals and logic
inputs to this board, while a number
of LEDs are used to indicate logic
outputs.
The connections to and from the
prototyping board are made using
single strand telephone cable, as are
the connections between IC pins on
the board itself. You can make the test
12 Silicon Chip
circuit as simple or as complicated
as you like – anything from just one
digital logic IC to 10 or more ICs.
Two large banana plug sockets are
used for the power supply terminals
and these are located directly above
the prototyping board. This regulated 5V supply is current limited and
is there
fore protected against short
circuits. Because it has no heatsink or
securing bolt, the regulator will thermally shut down somewhere near its
rated current if there is an overload.
The choice of a single 5V DC supply makes this unit suitable for use
with 74 series TTL integrated circuits
(74xx, 74LSxx, 74HCxx, 74Cxx, etc)
and with 4000 series CMOS logic ICs.
The latter will operate over a supply
range from 3-15V DC and therefore
will work from a 5V supply without
problems.
All logic inputs to the test circuit
are buffered and these are set by four
switches immediately to the left of the
prototyping board. When a switch is
in the up position, the corresponding
logic input is high. Conversely, when
a switch is in the down position, the
corresponding logic input is low.
These buffered inputs are labelled
B0-B3 and are brought out via a 5-way
vpin header socket.
The fifth terminal on the header
socket provides the clock pulses
from an additional circuit hidden
behind the front panel. The pulse
Fig.1: IC1 (a TLC555 timer) is used to provide the clock pulses, while IC3a and
IC3b form a window comparator to provide the logic probe function. IC2b-f
and IC4a-d buffer the logic signals to and from the test circuit.
is high or low, or is alternating between
these two logic states.
How it works
output provides either a single pulse
if its associated switch (at top, left) is
pushed down momentarily, or a stream
of clock pulses if the switch is in the
clock position.
At the other end, the logic output(s)
from the test circuit are fed to a 4-way
pin header socket. Each output is then
fed to a buffering circuit and these in
turn drive four LEDs (labelled Q0-Q3)
to show the logic states at up to four
different points on the test circuit.
By the way, the fact that the outputs
from the test circuit are “buffered”
means that they do not need to be
driven with the full LED current.
That’s taken care of by the buffering
circuitry. Each buffer stage has a high
input impedance, to avoid loading the
outputs of the test circuit.
Logic probe
Another very worthwhile feature is
the provision of a simple logic probe.
This uses a standard multimeter test
lead which plugs into a 3.5mm socket on the front panel. The probe can
be used to establish the logic states
at various points on the test circuit.
Connecting the probe to a logic 0 level
will cause a green LED to light. Conversely, connecting to a logic 1 level
will illuminate a red LED.
The two indicator LEDs are immediately to the right of the probe socket.
They simply indicate whether a point
Refer now to Fig.1 for the circuit
details of the Basic Logic Trainer. As
stated above, power for the circuit
comes from a 9V DC plugpack supply.
Diode D1 provides protection against
reverse supply polarity. Its output
feeds 3-terminal regulator REG1 which
produces a regulated +5V DC rail at its
OUT terminal. LED 1 provides power
on/off indication, while R101 limits
the current through the LED.
The output from the regulator is also
connected directly to the +5V output
terminal and it supplies the ICs. The
negative output terminal connects to
the negative supply line.
IC1, a TLC555 timer, is used to
provide clock pulses. It is wired as
February 1996 13
Take care with the orientation of polarised components (ICs, diodes, LEDs
and electrolytic capacitors) when assembling the PC board. The LEDs and pin
header sockets are soldered after the board is secured to the front panel.
an astable oscillator, the frequency
of which is determined by the total
resistance present between pin 3 and
the 0.47µF capacitor (C2) on pin 2.
Normally, when SW1 is in the
centre-off position, pin 3 of buffer
stage IC2a is held low by R1 and so
pin 4 (reset) of the timer is also held
low. This effectively holds IC1 in the
reset state, with its output at pin 3
remaining low.
When SW1 is in the CLOCK position,
pin 4 of IC1 is pulled high via SW1a
and IC2a and the reset is released. At
the same time, SW1b shorts out R3
and so the timing for the circuit is set
by R2, R4 and C2. This causes IC1 to
oscillate at a 2Hz rate.
Conversely, when SW1a is in the
PULSE (spring loaded, momentary
contact) position, R3 is switched in
series with the timing circuit. As a
result, IC1 runs much more slowly
than before, to produce one pulse
about every 1.6 seconds. Thus, by
momentarily flicking SW1 to the
PULSE position, IC1 outputs a single
clock pulse.
Diode D2 ensures that C2 rapidly
discharges when SW1 returns to its
centre-off position.
The output from IC1 is fed to pin
14 of non-inverting buffer stage IC2b.
This in turn drives the PULSE terminal,
to provide either a continuous clock
signal or a one-shot pulse signal.
Switch logic
The PC board is mounted on the rear of the lid using 12mm tapped spacers
and secured using short machine screws. Note how the 1000µF electrolytic
capacitor is mounted.
The remaining gates in IC2 (IC2cIC2f) are used to buffer the logic
setting switches (SW2-SW5). When a
switch selects the +5V rail, the output
of its corresponding buffer is high.
Conversely, when ground is selected,
the output of the buffer is low. The
RESISTOR COLOUR CODES
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
No.
1
1
2
1
1
8
1
1
1
1
4
6
14 Silicon Chip
Value
1MΩ
470kΩ
390kΩ
150kΩ
130kΩ
100kΩ
62kΩ
47kΩ
36kΩ
10kΩ
2.7kΩ
220Ω
4-Band Code (1%)
brown black green brown
yellow violet yellow brown
orange white yellow brown
brown green yellow brown
brown orange yellow brown
brown black yellow brown
blue red orange brown
yellow violet orange brown
orange blue orange brown
brown black orange brown
red violet red brown
red red brown brown
5-Band Code (1%)
brown black black yellow brown
yellow violet black orange brown
orange white black orange brown
brown green black orange brown
brown orange black orange brown
brown black black orange brown
blue red black red brown
yellow violet black red brown
orange blue black red brown
brown black black red brown
red violet black brown brown
red red black black brown
buffered logic outputs appear at pins
10, 6, 12 & 4 of IC2 and are fed to the
B0-B3 terminals respectively.
LEDs 2-5 are used to indicate the
logic states. These LEDs are driven
using inverting buffer stages IC4a-IC4d
via 220Ω current limiting resistors.
Normally, R13-R16 hold the inputs
to these buffer stages low. This means
that their outputs are all normally high
and so the LEDs are all off. However,
if any of the Q0-Q3 inputs is pulled
high, the corresponding buffer input
is also pulled high and so its output
switches low and lights the relevant
LED. Resistors R9-R12 protect the
inputs of the 4049.
Logic probe
IC3a and IC3b form the logic probe
circuit. These two op amps are wired
in a standard window comparator
configuration and drive two logic indicator LEDs (LED6 & LED7).
Resistors R22-R26 set the bias
voltages on the op amp inputs. As indicated on the circuit, pin 5 is biased
to +2V, pins 6 & 3 to +1.4V and pin 2
to +0.9V. As a result, the non-inverting input of each op amp is normally
above the inverting inputs and so the
op amp outputs are normally high and
the LEDs are off.
If, however, the probe input is connected to a logic high (ie, 2- 5V), pin 6
of IC3a will also be pulled high. As a
result, pin 7 of IC3a switches low and
this lights LED7 (red) to indicate that
the high logic state has been detected.
IC3b will not change state and so LED6
will remain off.
Conversely, if the probe input is
connected to a logic low (ie, less than
0.9V), pin 3 is also pulled low and the
output of IC3b switches low instead.
This lights LED6 to indicate that a logic
low has been detected. Diode D3 is
there to clip any large negative-going
pulses that might be picked up via the
probe input, to prevent damage to the
op amps.
Construction
Construction of the Basic Logic
Trainer is easy, since virtually all the
parts mount onto a single large PC
board. The exceptions are the banana
sockets which mount directly onto
the front panel and the 3.5mm panel
socket for the plugpack supply.
Refer to Fig.2 when installing the
parts on the PC board. Begin by installing the resistors, followed by the
Fig.2: install the parts on the PC board as shown here. Note particularly that the
1000µF electrolytic capacitor is mounted on the copper side of the board.
February 1996 15
PARTS LIST
1 console case
1 front panel
1 prototyping board
1 PC board (© DSE)
1 test lead (for logic probe)
1 9V 200mA plugpack supply
4 SPDT miniature toggle switches
1 DPDT centre off, momentary on
toggle switch
1 red banana socket (large)
1 black banana socket (large)
1 yellow banana socket
4 12mm tapped spacers
1 3.5mm DC panel socket
1 14-pin wire-wrap socket
4 self-tapping screws (to secure
front panel)
Semiconductors
1 TLC555 timer IC (IC1)
1 4050 hex non-inverting buffer (IC2)
1 LM393 dual op amp (IC3)
1 4049 hex inverting buffer (IC4)
1 78M05 3-terminal regulator
(REG1)
1 1N4004 silicon diode (D1)
2 1N4148 silicon diodes (D2,D3)
6 5mm red LEDs (LED1-5, LED7)
1 5mm green LED (LED6)
Capacitors
1 1000µF 16VW electrolytic
1 0.47µF monolithic
5 0.1µF ceramic
1 .01µF ceramic
Resistors (0.25W, 1%)
1 1MΩ
1 62kΩ
1 470kΩ
1 47kΩ
2 390kΩ
1 36kΩ
1 150kΩ
1 10kΩ
1 130kΩ
4 2.7kΩ
8 100kΩ
6 220Ω
Wire & cable
1 200mm-length 0.71mm tinned
copper wire (for links)
1 500mm-length single strand
telephone cable
2 400mm-lengths of hook-up wire,
red & black
WHERE TO BUY A KIT
A kit of parts for the Basic Logic
Trainer is available from Dick Smith
Electronics stores & by mail order
from PO Box 321, North Ryde,
NSW 2113. Phone (02) 888 2105.
The cost is $129 + $8 p&p. Please
quote catalog number K3010 when
ordering.
Note: PC artwork copyright © Dick
Smith Electronics.
16 Silicon Chip
ceramic capacitors, the diodes and the
ICs. Note that D1 is a 1N4004 type,
while D2 and D3 are 1N4148s.
The five wire links can be installed
now, using the off-cuts from resistor
leads. This done, install the 7805
3-terminal regulator, noting that its
leads are bent through 90° so that its
metal tab sits flat against the PC board.
The 1000µF electrolytic capacitor is
installed on the underside of the PC
board. Its leads are also bent through
90°, so that it can be laid flat against
the board surface. Be sure to install
this part the right way around.
The five toggle switches are mount
ed directly on the PC board. Push
them right down onto the board before
soldering their leads and note that S1
must be oriented with its momentary
(ie, spring-loaded) position towards
the bottom. The switch nuts can be
either omitted or screwed all the way
down.
By this stage, the board will be
complete except for the LEDs and the
pin headers. The LEDs can be installed
now (the green one is LED 6) but do
not solder their leads yet, as they must
first be adjusted for height when the
front panel is in
stalled. Take care
with the orientation of the LEDs – the
cathode (K) lead will be the shorter of
the two. In addition, the cathode lead
is adjacent to a flat edge at the bottom
of the LED body.
The 4-way and 5-way pin headers
are obtained by cutting down a single
14-pin wire-wrap socket. To do this,
first cut the wire-wrap socket in half
using a pair of sharp sidecutters, to
obtain two 7-pin sockets. The unwanted pins can then be removed and the
socket bodies carefully trimmed and
filed to size to that they fit the slits in
the front panel.
Do not mount the pin headers yet;
that step comes later when the front
panel is fitted.
Hardware assembly
Begin the hardware assembly by
attaching the prototyping board to the
front panel using double-sided tape.
This done, fit the three banana sockets
to the front panel. Use the red socket
for the positive terminal, black for the
negative terminal and yellow for the
logic probe terminal. Do these sockets
up tight and connect appropriately
coloured leads (eg, red for positive,
black for negative) to their solder
lugs. These leads should all be about
60mm in length, so that they can be
run to their respective points on the
PC board.
The 3.5mm DC socket is mounted on
the bottom lefthand hand side of the
rear panel (as viewed from the rear).
This socket is wired via two 150mm
long leads (red for positive, black for
negative) to the plus (+) and minus (-)
inputs on the PC board. Twist these
leads together to keep things neat
and tidy.
Note that the positive lead must go
to the tip terminal of the DC socket,
while the black lead must go to the
collar (or sleeve) terminal.
Now for the final assembly. First, fit
the four 12mm-long spacers to the PC
board and secure them with the short
screws supplied. This done, fit the
4-way and 5-way pin headers to the
PC board, then fit the front panel and
secure it in position.
The various LEDs and the pin headers can now be pushed through their
respective holes on the front panel and
carefully aligned. When everything
looks OK, solder the leads to secure
them in position. Finally, fit the lid to
the case and secure it using the four
self-tapping screws supplied.
Testing
When power is applied, the red
LED next to the +5V socket should
illuminate. If it doesn’t, then the LED
is either in backwards, there is a fault
in the regulator circuit, the supply
polarity is incorrect, or the regulator
output is short-circuited to ground. In
particular, check that D1 and REG1 are
correctly oriented.
The 5V DC output terminals are
a convenient place to check the 5V
supply at any time. The power on/
off LED will provide a handy quick
visual indication of the state of the
5V supply; eg, you may see this LED
dim if a heavy load is placed across
the supply, or extinguish if the power
supply is inadvertently short-circuited
on the protoboard.
Assuming that the power supply is
OK, the next step is to check out the
logic probe circuitry. To do this, simply plug the probe in and touch the
positive and negative supply terminals
in turn. Check that the red LED (High)
lights when the positive terminal is
touched and that the green LED (Low)
lights when the negative terminal is
touched.
If the logic probe doesn’t work, first
check that the voltages on pins 2, 3, 6 &
5 of IC3 match those marked on the cir
cuit. If they don’t, then it’s likely that
one of the bias resistors (R22-R26) is
incorrect or D3 is back to front. Check
also that D3, IC3 and the two LEDs are
correctly oriented.
Once the logic probe is working correctly, it can be used to check the rest of
the circuit. For example, by touching
the probe on the PULSE terminal, you
can check the clock circuitry (IC1).
The green LED should light when S1
is in the centre-off position, while
the red LED should flash at a 2Hz rate
when S1 is in the CLOCK position; ie,
the logic probe should show the indi
vidual positive going clock pulses as
they occur.
You should get a much slower rate
if S1 is held in the PULSE position (ie,
one pulse about every 1.6 seconds).
If you don’t get any clock pulses,
check the circuitry around IC1. Similarly, use the logic probe to confirm
that SW2-SW5 can be used to set their
corresponding outputs (B0-B3) high
or low.
The output indicator circuitry can
be tested by setting B0 high and connecting a lead from this terminal to
Q0, Q1, Q2 & Q3 in turn. In each case,
the corresponding output LED should
light. If it doesn’t, check the resistor
values at the inputs to IC4a-IC4d.
Using the trainer
By this stage, you have checked
that the individual components of the
Basic Logic Trainer are functioning
correctly. Having done this, you will
have a basic knowledge of how to use
these components; ie:
(1) the logic switches (SW2-SW5) are
used to set the logic states on B0-B3
(high or low);
(2) the Q0-Q3 terminals are continually monitored and their status indicated
by individual LEDs;
(3) the clock/pulse generator switch
can provide either a train of clock
pulses or individual pulses as required; and
(4) the logic probe can be used at any
time to check the logic state at different
positions on the test circuit.
We recommend using the insulated
single-strand wire to make the various
wiring connections. One length of
500mm can be cut into many smaller
lengths, each of which should have
about 5mm of insulation stripped back
SC
at either end.
Basic Logic Trainer Demonstration
As an example, we’ll wire up a
common CMOS flipflop and exercise
it. The device is the 14-pin CMOS
4013 which is a dual D-type flipflop.
Its pin connections are shown in
Table 1.
Table 1: 4013 Pin Connections
Function
Pin No.
Function
Pin No.
Q1
1
Vdd (+)
14
Q1
2
Q2
13
Clock 1
3
Q2
12
Reset 1
4
Clock 2
11
Data 1
5
Reset 2
10
Set 1
6
Data 2
9
Vss (-)
7
Set 2
8
The step-by-step procedure is as
follows:
(1) Insert the IC into the proto
board, such that pin 1 is at the top
left and pin 14 at the top right. The
IC should be inserted so that the two
vertical columns of pins are either
side of a channel in the prototyping
board, so that they are not shorted
together.
(2) Using suitable leads, connect
the +ve and -ve supply terminals to
the +ve and -ve supply buses on the
prototyping board. A short lead can
then be connected from the +ve bus
to pin 14, while a second lead can
be connect from the -ve bus to pin 7.
You can check that these two
connections are correct by using
the logic probe. This should show a
low state at pin 7 and a high state
at pin 14.
(3) Configure flipflop 1 by connecting:
(i) a wire from pin 6 to B0;
(ii) a wire from pin 4 to B1;
(iii) a wire from pin 5 to B2;
(iv) a wire from pin 1 to Q3;
(v) a wire from pin 2 to Q2; and
(vi) a wire from pin 3 to PULSE/
CLOCK
The above procedure connects
the four inputs and the two outputs of
flipflop 1 on the 4013. Table 2 shows
these various test connections.
Now let’s explore the basic operation of the flipflop:
(1) set B0-B2 to logic 0;
(2) push the Pulse switch once.
LED Q3 should be off (logic low or
0) and LED Q2 should be on (logic
high or 1);
(4) set switch B2 to a logic 1; and
(5) Push the Pulse switch once.
This should clock the new data (ie,
a logic 1 from B2) through to the
outputs and so the logic states on
Q3 and Q2 should reverse (ie, Q3
now on, Q2 now off). Further pulses
should not alter this, until the DATA 1
input (B2) is altered again.
This shows the basic operation of
a D-type flipflop; ie, the logic level on
the Data input is transferred through
to the Q output (pin 1) on receipt of
a clock pulse.
What this means is that you can
get the flipflop to automatically toggle
on the receipt of each clock pulse
by connecting its Q-bar output to its
Data input. To do this:
(1) remove the wire between B2
and pin 5 of the 4013; and
(2) connect a wire between pin 2
and pin 5 of the 4013.
Now when you work the pulse
switch or switch to the CLOCK position, the two output LEDs should
flash on and off alternately.
Further experiments
(1) Connect an additional wire
between pin 3 of the 4013 and LED
output Q1. This will allow you to observe the relationship between the
clock input to the 4013 (on LED Q1)
and the 4013 Q and Q-bar output
levels (on LED Q2 and LED Q3).
Because the Q-bar (inverted) output of flipflop 1 is fed into the Data
input, each clock pulse will change
the existing state of the Q output.
This is the classic divide-by-two
configuration of the basic flipflop and
is used in many circuit applications.
Table 2: Test Connections
Protoboard
Connections
IC Pin
Function
Pin No.
Clock/pulse Switch
Clock 1
3
Switch B1
Reset 1
4
Switch B2
Data 1
5
Switch B0
Set 1
6
LED Q3
Q1
1
LED Q2
Q1
2
February 1996 17
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
dicksmith.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
dicksmith.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
dicksmith.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
dicksmith.com.au
The starting point for the
multi-tone warning module
is this toy cellular phone. It
cost just $4.
A low-cost multi-tone
dashboard alarm
An audible alarm in a car is a useful indicator.
It could accompany an oil pressure warning
light, it could remind you to turn off the fullhouse car alarm or provide an engine overtemperature alarm. Here, we show you how to
organise a 9-tone alarm module for about $4!
By JULIAN EDGAR
The basis of the alarm is a toy cellular telephone – yes, you read that
right! Toy phones have an integrated
circuit, sound transducer (often a
small speaker) and a battery holder
all combined into an incredibly cheap
package. Pressing the phone’s button
makes noises and these can be useful
for more than just entertaining 2-year
olds. However, before throwing down
this magazine and charging off to the
local discount store, read on.
During the extensive research for
this feature, I investigated three different toy phones – and beware, only
one was suitable.
Suitability of the phone for this
22 Silicon Chip
application requires the following:
(1) continuous sound when a button
is held down. Some phones emit the
tone only for a short time, irrespective
of how long the button’s pressed. (2)
a number of different tones. Some
phones have very few different tones,
even though there’s lotsa buttons! (3)
tones which are appropriate in a car
warning situa
tion. But then again,
maybe you’d like your dash to yell in
monkey-talk “Sorry the line is busy
now”. (4) as loud a sound output as
possible.
These toy phones vary in price from
$2 to $4, too – so shop around. The
phone which I used was unbranded
but don’t let that worry you. Any toy
phone which satisfies the above criteria will be adequate.
Pull it apart
OK. You’ve got the phone home and
extracted it from the grasp of your little
brother/kid who lives across the road/
intelligent dog/your own baby. You’ve
put up with the sweet smile of your
partner who has decided that your
movement back towards childhood
has become extreme and you’re waiting breathlessly for the next piece of
invaluable advice. It’s pretty simple:
pull the phone apart.
Mine took a couple of turns of a
Phillips head screwdriver; others inspected pulled apart with brute force.
Once opened, you should be able to see
the sound transducer, the keypad and
the integrated circuit (no, it’s not a neat
little package with legs but instead a
blob on the board).
Talking about the keypad, if it seems
to have fallen apart don’t worry. On
the printed circuit board there should
be a pattern of tracks, with the tracks
coming close together in a meshed
The toy phone pulls apart to reveal a speaker, sound generator integrated
circuit (the blob on the board) and a keypad.
pattern under each key. When the keys
are pressed, a conductive material on
their ends squashes down onto the
printed mesh, bridging the circuit and
making the thing work. It’s just a cheap
switch – and a wetted finger will often
work in the same way.
Now this bit’s for Serious Modifiers only. You can change both the
loudness of the tones and their pitch
by making some electronic modifications. The simplest way of increasing
the sound volume is to connect the
module to a 200 watt amplifier ... er,
just kidding. The cheapest way of increasing the sound output level is to
use a more efficient speaker than the
one provided. I happened to have an
old 8-ohm cone tweeter lying around
and that worked fine.
If you don’t, then investing $2.50
in a 57mm speaker will almost certainly lift the sound output level. If it
doesn’t, then give the newly-bought
speaker to the little brother/kid who
lives across the street/intelligent dog/
your baby to eat.
Changing the tone and speed of the
recital on my phone was as easy as
changing the value of about the only
component which was accessible – a
resistor. It started off as 268kΩ but
experi
mentation showed that add-
ing a 1MΩ resistor in parallel both
increased the speed with which the
sounds were played (the guy inside
the blob went into overtime) and
also increased the pitch at which it
happened.
Next up is the decision about which
tones you want to use. The keypad
pushbuttons will still work while
pulled apart if they’re pressed against
the PC board or alternatively, you
can simply bridge the conductors by
using a screwdriver to replay all of the
sounds. Pick the keypads which give
the right sounds and then carefully
solder two wires to the PC pads, with
each wire soldered to the different
conductors on the intermeshed grid.
Check that when these wires are joined
the wanted tone sounds continuously.
The power supply can be either de-
The keypad uses these conducting buttons which, when pressed, squash down
on a PC grid pattern, joining the two conductors.
February 1996 23
The resistor
seen here can
be changed in
value to modify
the sound
output. Adding
a 1MΩ resistor
in parallel made
the man inside
the blob go into
overtime!
Pairs of wires are soldered to the selected switch pads, to trigger the different
sounds. The pads are picked on the basis of the sound generated – you pick
which warning tones you want to use.
The finished warning module. The wire pairs on the left are used
to trigger the different sounds, while an old cone tweeter has
been substituted for the original speaker to increase the output
volume.
24 Silicon Chip
rived from the original button cell or
from AA batteries (both last a very long
time in this application), or a trimpot
can be used to provide the supply
voltage from the car battery. You don’t
need to supply an exact (regulated) 3V
to power the thing; anything around
that value will work fine.
Making the connections
So how do you connect the Sound
Module (you don’t call it a toy phone
any more) to the engine? If you’re
monitoring temperature sensors which
trigger warning lights by switching to
ground, then wiring the switch output
directly to a module input (with the
other module input wire earthed) will
trigger the sound at the same time as
the light comes on.
If the trigger is an output voltage,
for example, when monitoring an
ECU “Check Engine” light, then a
low-current relay (less than $3) can
be wired into the warning circuit to
work the module.
The module can be mounted in a
Jiffy box or simply wrapped in electrical tape and mounted under the dash.
The speaker doesn’t need to be close
to the module, meaning that it can be
located where the sound will be heard
the loudest.
When you consider the horrible
possibilities of a missed warning light,
$4 and a few hours’ work doesn’t seem
SC
too bad, does it?
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February 1996 25
26 Silicon Chip
February 1996 27
M
AGLEV TRAINS USE roughly
30% less energy than conventional trains travelling
at the same speed and they compare
even more favourably with cars and
airplanes.
In terms of energy demand per
passenger, cars consume 3.5 times as
much energy, while airplanes consume four times as much as a maglev
travelling at 400km/h.
Dispensing with wheels also means
that Transrapid generates no audible
rolling noise, even during acceleration
and braking.
Its aerodynamically related noise
becomes perceptible only at speeds
over 200km/h, making it ideal for
densely populated areas. And because
it wraps around its guideway, rather
than perching on a track, it cannot
derail.
Furthermore, since the guideways
are usually elevated, nothing can cross
a maglev’s path.
All of this should add up to an
unprecedented level of safety. In fact,
28 Silicon Chip
studies indicate that maglev trains
should be 250 times safer than conventional rail transportation, 20 times
safer than air travel and 700 times safer
than road transportation.
Nor does maglev technology pose
problems for passengers with pacemakers, as the magnetic field inside the
cabin is the same order of magnitude
as the Earth’s natural field.
Made of non-flammable materials
developed for aviation, Trans
rapid
also offers the very best in fire prevention.
Magnetic levitation represents the
most environmentally responsible
form of mass transportation available.
In addition to minimal energy demand
and low noise, maglev technology
allows for grades as steep as 10% and
a track radius of 2.2km for a speed of
300km/h.
This means that the maglev guide
way can be flexibly adapted to the
landscape. Whether elevated or at
ground level, it requires less area and
has less environmental impact than
other ground transportation systems.
Magnetic attraction
Transrapid uses the forces of
magnetic attraction and repulsion
for suspension and guidance, while
propulsion and braking are managed
by a synchronous long-stator motor.
The levitation system is based on the
attractive and repulsive forces of the
electromagnets that are in the vehicle
and on the ferromagnetic reaction rails
in the guideway. Suspension magnets
draw the vehicle along the guideway
and guidance magnets keep it laterally
on “track”.
The maglev propulsion system is
based on a synchronous long-stator
linear “motor”. The motor consists
of stator cores with a three-phase
winding installed under the guideway together with vehicle-mounted
electromagnets. An electric travelling-wave field generated by current
in the windings of the stator cores
pulls the vehicle along by attracting
its suspension magnets which also
act as the exciter section of the linear motor. In other words, unlike the
drive principle behind traditional
propulsion systems, the maglev’s
primary propulsion system is not on
the vehicle itself but in the guideway.
Compared to conventional locomotives which must have enough
on-board propulsion capacity to
overcome the steepest grades, maglev
trains rely on individual track sections
to supply them with the appropriate
amount of power.
Thus, in sections requiring greater
thrust, the output of the guideway
motor is boosted as the vehicle passes. Furthermore, by activating only
those sections of track being used at
Right, a section of the highly
automated Transrapid modular
control system, developed by
Siemens.
February 1996 29
Energy
supply
Switch (closed)
Guidance rail
Guidance magnet
Switch
(open)
Switch
(closed)
Motor winding
Stator pack
Energy
supply
Support magnet
Fig. 1: Transrapid’s levitation system is based on the
attraction of electromagnets in the vehicle and the
ferromagnetic (steel) guidance rails.
any given moment, energy losses are
minimised.
Financing the project
Officially authorised by Germany’s
lower house of parliament, the Bunde
stag, on March 2nd, 1994, the DM 8.9
billion ($A8.4b) Transrapid project
will be financed by a combination of
public and private interests.
A government holding company
will be responsible for managing
DM 5.6 billion in right-of-way and
site preparation investments, while
a consortium that includes banks,
insurance companies, German Rail
(DB) and Lufthansa will provide
the remaining financing. Based on
technology developed in cooperation
with the German Federal Ministry for
Research and Technology, the trains
are being built by Thyssen, AEG and
Siemens.
Siemens has developed a highly
automated operations control system
for the management of maglev trains.
Fig. 2: the linear motor, essentially a stretched out stator
in the guideway, is divided into sections. A given section
is energised only when the train is crossing it.
When a maglev train leaves a station,
a control centre takes responsibility
for all the associated operational tasks
and peripheral systems.
A fundamental subsystem is the
“wayside-installed decentralised
vehicle control”. Responsible for set
point optimisation, as well as route
and vehicle protection, this system is
in constant contact with the propulsion unit, vehicle and guideway, as
well as systems within the operations
centre.
As the train travels along the guide
way, decentralised control and operation units exchange information with
the main control centre in what is
essentially a local area network.
Siemens’ decentralised operations
control equipment has been extensively tested and meets the demanding requirements of multiple train
operation. In addition, under the
leadership of Maglev Systems Testing
and Planning Ltd, Transrapid has been
tested since the mid-80s under near
Transrapid
105
TGV-A
100
IC
95
Suburban
train
90
85
TRANSRAPID 07
80
Freight
train
75
70
A competitor for air travel
Transrapid is far more than a stylish
new train. Because of its remarkable
speed, it offers an unbeatable alternative to the automobile and the airplane.
Operating at ten minute intervals, as
plans for the Berlin-Hamburg route
call for, Transrapid can be expected
to significantly reduce traffic density
and associated air pollution between
major cities. In fact, planners expect
the train to attract some 14.5 million
passengers each year.
Because of its minimal space requirements it can, in many cases, be
added to existing railway right-ofways while freeing up conventional
SC
track for freight traffic.
Track-mounted drive
Maximum Noise Level at 25 m Distance
Ref.: Noise Measurements T†V Rheinland and Others (1989)
110
routine service conditions at a facility
in Emsland in northern Germany.
In November, 1991, German Rail
pronounced the maglev system ready
for revenue service and by June 1995
Transrapid had clocked more than
200,000km on its test track.
0
50
100
150
200
250
300
350
400
450
500
km/h
Fig. 3: travelling below 200km/h, magnetic levitation trains
generate no audible rolling noise, even during acceleration
and braking.
30 Silicon Chip
Power
supply
Railroad
Gradient
(10%)
Vehicle-mounted drive
Gradient
(max. 4%)
Fig. 4: the guideway motor system provides increased
power in those sections with steeper gradients. Because
the guideway linear motor rather than on-board engines
does the work, maglev trains can be lighter and negotiate
much steeper grades than conventional trains.
Acknowledgement: this article has been reproduced by
arrangement from Siemens Review, Volume 62, May 1995.
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.
Australian Defence Force – Navy
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.
Reluctor circuit for
high energy ignition
This modified reluctor circuit has
been produced to provide more sensitivity from the circuit which was
originally published in the May 1990
issue of SILICON CHIP.
The modifications are only minor
and provide a small bias voltage to the
reluctor and a negative-going pulse
via diode D1 to the dwell reference
buffer at pin 4 of IC1. This ensures
reliable operation at starting. In other respects, the circuit operation is
unchanged.
C. Daly,
South Hobart, Tas. ($35)
Intercom uses
surplus telephones
This circuit provides a 2-way intercom
based on standard telephone handsets.
It operates as follows. At first, both phones
are “on hook” and both relays are at rest.
Assuming that phone 1 is picked up, relay
RLY1 operates, its NC contacts open and the
NO contacts close. The NO contacts feed
+Vcc to pin 8 of IC1, a 555 timer operating
as a pulse generator. IC1 then sends pulses
via R3 to Q1. Negative supply is then fed via
the NC contacts of relay RLY2 to buzzer BZ/B.
When phone 2 is picked up, relay RLY2
operates and its NC contacts open. Buzzer
BZ/B stops buzzing. Both parties can then
talk across the “Stone Transmission Bridge”
consisting of RLY1/TXA/C1/C2/RLY2/TXB.
Older 800 series dial phones and the new
T-2000 phones will work equally well with
this circuit. The DC supply (Vcc) can range
from 15 to 18VDC at 500mA. The two relays
can be any 6 or 12V DPDT type.
A. Hellier,
Alice Springs, NT. ($40)
32 Silicon Chip
The circuit for the intercom is based on two surplus telephones.
4-channel mixer
modifications
These modifications to the 4-Channel Guitar Mixer board featured in
the January 1992 issue will convert
two of the line inputs to microphone
inputs and provide an inverted output
to drive bridged amplifiers.
In the modified circuit, the feedback
resistors have been altered for inputs
three and four to give a gain of 565 instead of 19, which should be adequate
for all types of microphones.
If the gain is too high for your
application, just reduce the value of
the 220kΩ feedback resistor. Using a
100kΩ resistor will reduce the gain to
257 (gain = 100k/390 + 1).
Provision is shown to terminate a
600Ω microphone should you require
it. You would need to mount a switch
on the front panel for each channel.
Keep the mic gain controls at
minimum when no microphone is
connected. The reason for this is that
these stages have much higher gain
than the line input stages and so hum
and noise could otherwise become a
problem.
The inverted output only requires
four additional components and employs an unused op amp, IC6b.
These components could all be
mounted on the copper side of the
PC board although, if you were really
keen, you could drill 0.9mm holes
and mount them on the component
side, bending the leads to reach the
required IC pin. Pin 5 of IC4b is
already connected to ground on the
PC board.
SILICON CHIP.
WANTED: YOUR CIRCUIT & DESIGN IDEAS
Do you have a good circuit idea? Is so, why not sketch it out, write a brief
description and send it to us. Provided your idea is original, we’ll pay up to
$60 for a really good circuit. Send your idea to: Silicon Chip Publications,
PO Box 139, Collaroy Beach, 2097; or fax (02) 9979 6503
February 1996 33
NICS
O
R
T
2223
LEC
7910
y, NSW
EY E
OATLBox 89, Oa8t5leFax (02) 5s7a0 C a rd
MANY OF THE PRICES LISTED APPLY DURING
APRIL AND MAY ONLY
Vi
PO
49
fax
) 579 e r C a rd ,
2
0
(
ne & rs:
choice for a special price. Choose motors from
e
o
t
n
s
h
o
a
p
h
P
M17 / M18 / M35. $44.
, M
ith
rde
d
o
w
r
a
d
d
c
e
You can also purchase this kit with the
B a n k x accepte most mix 0. Orders
stepper motor pack described above: $65.
e
r
1
o
m
$
f
A
)
l
i
P
Kit without motors is also available: $32.
&
&
ma
r
i
P
a
(
.
s
order 4-$10; NZ world.net
FLUORESCENT TAPE
$
<at>
High quality Mitsubishi brand all weather
Aust. IL: oatley
50mm wide red reflective tape with self
A
by EM
adhesive backing: 3 metres for $5.
MISCELLANEOUS ITEMS
LED BRAKE LIGHT INDICATOR: make a 600mm long high
intensity line display, includes 60 high intensity LEDs
plus two PCBs plus 10 resistors: $20 (K14). AC MOTOR:
1RPM geared 24V-5W synchronous motor plus a 0.1 to
1RPM driver kit to vary speed; works from 12V DC: $12
(K38 + M30). TOMINON SYMMETRICAL LENS: 230mm
focal length - f1:4.5, approximately 100mm diameter an
100mm long: $25 (O14). SPRING REVERB: 30cm long
with three springs: $30 (A10). MICROSONIC MICRO
RECORD PLAYER: includes amplifier: $4 (A11). MOTOR
DRIVEN POTENTIOMETER: dual 20k with PCB: $9. ANGLED
TELEPHONE STANDS: Angled, smoky perspex: 4 for $10
(G47). LARGE METER MOVEMENTS: moving iron, 150 x
150mm square face, with mounting hardware: $10. New
ARLEC brand 24VDC-500mA approved plugpacks: $9. One
FARAD 5.5V capacitors: $3.
SPECIALS – POLLING FAX LINE
Poll our 579 3955 fax number for new items and some very
limited quantity specials.
ALCOHOL TESTER KIT
Based on a high quality Japanese thick film alcohol sensor.
The kit includes a PCB, all on board components and a
meter movement: $30. The circuitry includes a latching
alarm output that can be used to drive a buzzer, siren etc.
We should also have other gas sensors available for this kit.
WIND POWER GENERATOR KIT
In late April we will have available a low cost kit that employs
a low cost electric motor, as used in car radiator cooling
systems, to serve as a wind powered electricity generator.
Construction drawings for an 800mm 2 blade propeller are
supplied. The combination puts out up to 30W of power in
high winds. Electronic kit price should be approximately
$30. Price of a used suitable motor (available from car
wreckers) should be under $40. We will have a limited
quantity available for $35.
LED FLASHER KIT
3V operated 3 pin IC that can flash 1 or two 2 high intensity
LEDs. Very bright and efficient. IC plus 2 high intensity LEDs
plus small PCB: $1.30.
SIMPLE MUSIC KIT
3V operated 3-pin ICs that play a single tune. Two ICs that
play different tunes plus a speaker plus a small PCB: $2.50.
CD MECHANISMS AND CD HEADS
Used CD mechanisms that have a small motor with geared
worm drive assy. Popular with model railway enthusiasts:
$5. Also new CD heads that include a laser diode, lenses
etc: $3.
STEPPER MOTOR PACK
Buy a pack of 7 of our stepper motors and save 50%!!
Includes 2XM17, 2XM18, 2XM35 and 1 used motor. Six new
motors and one used motor for a total of: $36.
COMPUTER CONTROLLED STEPPER MOTOR DRIVER
KIT
This kit will drive two 4, 5, 6 or 8-wire stepper motors
from an IBM computer parallel port. The motors require a
separate power supply (not included). A detailed manual on
the computer control of motors plus circuit diagrams and
descriptions are provided. Software is also supplied, on a
3.5" disk. NEW SOFTWARE WILL DRIVE UP TO 4 MOTORS
(2 kits required), with LINEAR INTERPOLATION ACROSS
FOUR AXES. PCB: 153 x 45mm. Great low cost educational
kit. We provide the PCB and all on-board components kit,
manual, disk with software, plus two stepper motors of your
34 Silicon Chip
UHF REMOTE VOLUME CONTROL SPECIAL
As published in EA Dec 95-Jan 96. We supply two UHF
transmitters, plus a complete receiver kit, including the
case and the motorised volume control potentiometer: $60.
PC CONTROLLED PROGRAMMABLE POWER SWITCH
MODULE
This module is a four channel programmable on/off timer
switch for high power relays. The timer software application
is included with the module. Using this software the operator
can program the on/off status of four independent devices
in a period of a week within a resolution of 10 minutes. The
module can be controlled through the Centronics or RS232
port. The computer is opto isolated from the unit. Although
the high power relays included are designed for 240V
operation, they have not been approved by the electrical
authorities for attachment to the mains. Main module: 146
x 53 x 40mm. Display panel: 146 x 15mm. We supply: two
fully assembled and tested PCBs (main plus control panel),
four relays (each with 3 x 10A / 240V AC relay contacts),
and software on 3.5" disk. We do not supply a casing or
front panels: $92. (Cat G20)
STOP THAT DOG BARK
Troubles with barking dogs?? Muffle the mongrels and
restore your sanity with the WOOFER STOPPER MK2,
as published in the Feb 96 edition of Silicon Chip. A high
power ultrasonic sweep generator which can be triggered
by a barking dog. We supply a kit which includes a PCB and
all the on-board components: all the resistors, capacitors,
semiconductors, trimpotentiometers, heatsinks, and the
transformer. We will also include the electret microphone.
Note that our kit is supplied with a solder masked and silk
screened PCB, and a pre-wound transformer!: $39.
Single Motorola piezo horn speakers to suit (one is good,
but up to four can be used): $14. Approved 12VDC-1A
plugpack to suit: $14.
UHF REMOTE CONTROL FOR THE DE-BARKER OF
ANNOYING DOGS
Operate your Woofer Stopper remotely from anywhere in
your house, even your bedside. Allows you to remotely
trigger your Woofer Stopper at any time. Nothing beats
a randomly timed “human touch”. We supply one single
channel UHF transmitter, one suitable UHF receiver and
very simple interfacing instructions: $28.
Based on the single channel transmitter and a slightly
modified version of the 2 channel receiver, as published
in the Feb 96 edition of Silicon Chip. Note that the article
features 3 low cost remote controls: 1 ch UHF with central
locking, 1-2 ch UHF, and an 8 ch IR remote.
MOTOR DRIVEN VOLUME CONTROL/POT
New high quality motor driven potentiometer, intended for
use in commercial stereo sound systems. Includes clutch,
so can also be manually adjusted. Standard 1/4" shaft,
stereo (dual 20k pots) with 5V/20mA motor: $12 (Cat A13).
MINI HIGH VOLTAGE POWER SUPPLY
Miniature potted EHT power supply (17 x 27 x 56mm)
that was originally designed to power small He-Ne Laser
tubes. Produces a potent 10mm spark when powered from
8-12V / 500mA DC source. Great for experimentation, small
portable Jacobs Ladder displays, and cattle prods. Use on
humans is dangerous and illegal. A unit constructed for
this purpose would be would be considered an offensive
weapon. Inverter only: $25.
CCD CAMERA SPECIAL
Very small PCB CCD camera including auto iris lens: 0.1
Lux, 320K pixels, IR responsive; overall dimensions:
38 x 38 x 25mm. We will include a free VHF modulator
kit with every camera purchase. Enables the viewing of
the picture on any standard TV on a VHF Channel. Each
camera is supplied with instructions and a 6 IR LED
illuminator kit. $170.
CCD CAMERA - TIME LAPSE VCR RECORDING SYSTEM
This kit plus ready made PIR detector module and “learning
remote control” combination can trigger any domestic IR
remote controlled VCR to RECORD human activity within
a 6M range and with an 180 deg angle of view! Starts
VCR recording at first movement and ceases recording
a few minutes after the last movement has stopped: just
like commercial CCD/TIME LAPSE RECORDING systems
costing thousands of dollars!! CCD camera not supplied.
No connection is required to your existing domestic VCR as
the system employs an “IR learning remote control”: $90
for an PIR detector module, plus control kit, plus a suitable
“lR learning remote” control and instructions: $65 when
purchased in conjunction with our CCD camera. Previous
CCD camera purchasers may claim the reduced price with
proof of purchase.
SOUND FOR CCD CAMERAS/UNIVERSAL AMPLIFIER
(To be published, EA). Uses an LM386 audio amplifier IC
and a BC548 pre-amp. Signals picked up from an electret
microphone are amplified and drives a speaker. Intended for
use for listening to sound in the location of a CCD camera
installation, but this kit could be used as a simple utility
amplifier. Very high audio gain (adjustable) makes this unit
suitable for use with directional parabolic reflectors etc.
PCB: 63 x 37mm: $10. (K64)
LOW COST IR ILLUMINATOR
Illuminates night viewers or CCD cameras using 42 of our
880nm/30mW/12 degrees IR LEDs. Power output (and
power consumption) is variable, using a trimpotentiometer.
Operates from 10 to 15V and consumes from 5mA up to
0.6A (at maximum power). The LEDs are arranged into
6 strings of 7 series LEDs with each string controlled by
an adjustable constant current source. PCB: 83 x 52mm:
$40 (K36).
MASTHEAD AMPLIFIER SPECIAL
High performance low noise masthead amplifier covers
VHF - FM UHF and is based on a MAR-6 IC. Includes two
PCBs, all on-board components. For a limited time we will
also include a suitable plugpack to power the amplifier from
mains for a total price of: $25.
VISIBLE LASER DIODE KIT
A 5mW/660nM visible laser diode plus a collimating
lens, plus a housing, plus an APC driver kit (Sept 94 EA).
UNBELIEVABLE PRICE: $40. Suitable case and battery
holder to make pointer as in EA Nov 95 $5 extra.
SOLID STATE “PELTIER EFFECT” DEVICES
We have reduced the price of our peltiers! These can be
used to make a solid state thermoelectric cooler/heater.
Basic information supplied. 12V-4.4A PELTIER: $25. We
can also provide two thermal cut-out switches and a 12V
DC fan to suit the above, for an additional price of $10.
PLASMA EFFECTS SPECIAL
Ref: EA Jan. 1994. This kit will produce a fascinating
colourful changing high voltage discharge in a standard
domestic light bulb. Light up any old fluorescent tube or
any other gas filled bulb. Fascinating! The EHT circuit is
powered from a 12V to 15V supply and draws a low 0.7A.
Output is about 10kV AC peak. PCB: 130 x 32mm. PCB
and all the on-board components (flyback transformer
included) and the instructions: $28 (K16). Note: we do not
supply any bulbs or casing. Hint: connect the AC output to
one of the pins on a fluorescent tube or a non-functional but
gassed laser tube for fascinating results! The SPECIAL???:
We will supply a non-functional laser tube for an additional
$5 but only when purchased with the above plasma kit:
TOTAL PRICE: $33.
400 x 128 LCD DISPLAY MODULE - HITACHI
These are silver grey Hitachi LM215 dot matrix displays. They
are installed in an attractive housing. Housing dimensions:
340 x 125 x 30mm. Weight: 1.3kg. Effective display size is
65 x 235mm. Basic data for the display is provided. Driver
ICs are fitted but require an external controller. New, unused
units. $25 ea. (Cat D02) 3 for $60.
VISIBLE LASER DIODE MODULE SPECIAL
Industrial quality 5mW/670nM laser diode modules.
Consists of a visible laser diode, diode housing, driver circuit,
and collimation lens all factory assembled in one small
module. APC control circuit assures. Features an automatic
power control circuit (APC) driver, so brightness varies little
with changes in supply voltage or temperature. Requires 3
to 5V to operate. Overall dimensions: 12mm diameter by
43mm long. Assembled into an anodised aluminium casing.
This module has a superior collimating optic. Divergence
angle is less than 1 milliradian. Spot size is typically 20mm
in diameter at 30 metres: $65 (Cat L10).
This unit may also be available with a 635nm laser diode
fitted.
dimensions: 25 x 43mm. Construction is easy and no coil
winding is necessary as the coil is pre-assembled in a
shielded metal can. The solder masked and screened PCB
also makes for easy construction. The kit includes a PCB
and all the on-board components, an electret microphone,
and a 9V battery clip: $12 ea. or 3 for $33 (K11).
CYCLE/VEHICLE COMPUTERS
BRAND NEW SOLAR POWERED MODEL! Intended for
bicycles, but with some ingenuity these could be adapted
to any moving vehicle that has a rotating wheel. Could
also be used with an old bicycle wheel to make a distance
measuring wheel. Top of the range model. Weather and
shock resistant. Functions: speedometer, average speed,
maximum speed, tripmeter, odometer, auto trip timer,
scan, freeze frame memory, clock. Programmable to allow
operation with almost any wheel diameter. Uses a small
spoke-mounted magnet, with a Hall effect switch fixed to
the forks which detects each time the magnet passes. The
Hall effect switch is linked to the small main unit mounted
on the handlebars via a cable. Readout at main unit is
via an LCD display. Main unit can be unclipped from the
handlebar mounting to prevent it being stolen, and weighs
only 30g. Maximum speed reading: 160km/h. Maximum
odometer reading: 9999km. Maximum tripmeter reading:
999.9km. Dimensions of main unit: 64 x 50 x 19mm:
$32 (Cat G16).
FM TX MK 3
This kit has the most range of our kits (to around 200m).
Uses a pre-wound RF coil. The design limits the deviation,
so the volume control on the receiver will have to be set
higher than normal. 6V operation only, at approx 20mA.
PCB: 46 x 33mm: $18 (K33).
PASSIVE TUBE - SUPPLY SPECIAL
Russian passive tube plus supply combination at an
unbelievable SPECIAL REDUCED PRICE: $70 for the pair!
Ring or fax for more information.
27MHZ RECEIVERS
Brand new military grade 27MHz single channel telemetry
receivers. Enclosed in waterproof die cast metal boxes,
telescopic antenna supplied. 270 x 145 x 65mm 2.8KG.
Two separate PCBs: receiver PCB has audio output; signal
filter/squelch PCB is used to detect various tones. Circuit
provided: $20.
BATTERY CHARGER WITH MECHANICAL TIMER
A simple kit which is based on a commercial twelve-hour
mechanical timer switch which sets the battery charging
period from 0 to 12 hours. Employs a power transistor and
five additional components. It can easily be “hard wired”.
Information that shows how to select the charging current
is included. We supply the information, a circuit and the
wiring diagram, a hobby box with an aluminium cover
that doubles up as a heatsink, a timer switch with knob,
a power transistor and a few other small components to
give you a wide selection of charge current. You will also
need a DC supply with an output voltage which is greater
by about 2V than the highest battery voltage you intend
to charge. As an example, a cheap standard car battery
charger could be used as the power source to charge any
chargeable battery with a voltage range of 0 to 15V. Or you
could use it in your car. No current is drawn at the end of
the charging period: $15.
SIREN USING SPEAKER
Uses the same siren driver circuit as in the “Protect
anything alarm kit”. 4" cone / 8 ohm speaker is included.
Generates a very loud and irritating sound that is useful
to far greater distances than expensive piezo screamers.
Has penetrating high and low frequency components
and the sound is similar to a Police siren. Output has
frequency components between 500Hz and 4KHz. Current
consumption is about 0.5A at 12V. PCB: 46 x 40mm. As a
bonus, we include all the extra PCBs as used in the “Protect
anything alarm kit”: $12.
FM TRANSMITTER KIT - MKII
Ref: SC Oct 93. This low cost FM transmitter features preemphasis, high audio sensitivity (easily picks up normal
conversation in a large room), a range of around 100
metres, and excellent frequency stability. Specifications:
tuning range: 88-108MHz; supply voltage 6-12V; current
consumption <at> 9V: 3.5mA; pre-emphasis: 75uS; frequency
response: 40Hz to greater than 15KHz; S/N ratio: greater
than 60dB; sensitivity for full deviation: 20mV; frequency
stability with extreme antenna movements: 0.03%; PCB
MOTOR SPEED CONTROLLER PCB
Simple circuit controls small DC powered motors which take
up to around 2 amps. Uses variable duty cycle oscillator
controlled by trimpot. Duty cycle is adjustable from almost
0 - 100%. Oscillator switches P222 MOSFET. PCB: 46 x
28mm. $11 (K67). For larger power motors use a BUZ11A
MOSFET: $3.
ELECTROCARDIOGRAM PCB + DISK
The software disk and a silk screened and solder masked
PCB (PCB size: 105 x 53mm) for the ECG kit published in
EA July 95. No further components supplied: $10 (K47).
DC MOTORS
We have good stocks of the following high quality DC motors.
These should suit many industrial, hobby, robotics and
other applications. Types: Type M9: 12V. I no load = 0.52A
<at> 15800 RPM at 12V. Weight: 150g. Main body is 36mm
diameter. 67mm long: $7 (Cat M9). Type M14: made for slot
cars. 4 to 8V. I no load = 0.84A at 6V. At max. efficiency I
= 5.7A <at> 7500 RPM. Weight: 220g. Main body diameter is
30mm. 57mm long: $7 (Cat M14).
MAGNETS: HIGH POWER RARE EARTH MAGNETS
Very strong. You will not be able to separate two of these by
pulling them apart directly away from each other. Zinc coated.
CYLINDRICAL 7 x 3 mm: $2 (Cat G37)
CYLINDRICAL 10 x 3 mm: $4 (Cat G38)
TOROIDAL 50mm outer, 35mm inner, 5mm thick: $9.50
(Cat G39)
CRYSTAL OSCILLATOR MODULES
Small hermetically sealed, crystal oscillator modules. Used
in computers. Operate from 5V and draw about 30mA. TTL
logic level clock output. Available in 4MHz, 4.032MHz,
5.0688MHz, 20MHz, 20.2752MHz, 24.74MHz, 40MHz, and
50MHz.: $7 ea. (Cat G45) 5 for $25.
XENON FLASH BOARDS
Flash units with small (2cm long) xenon tube, as used
in disposable cameras. Power from one AA 1.5V battery.
Approx 7 joules energy: $3 (Cat G48).
INDUCTIVE PICKUP KIT
Ref: EA Oct 95. Kit includes coil pre-wound. Use receiver in
conjunction with a transmit loop of wire which is plugged
in in place of where a speaker is normally used. This wire
loop is run around the perimeter of the room / house you
wish to use the induction loop in. We do not supply the
transmit loop wire. Also excellent for tracing AC magnetic
fields. PCB: 61 x 32mm. Kit contains PCB and all on board
components: $10 (K55).
SLAVE FLASH TRIGGER
Very simple, but very effective design using only a few
components. Based on an ETI design. This kit activates a
second flash unit when the master, or camera mounted,
flash unit is activated. This is useful to fill in shadows and
improve the evenness of the lighting. It works by picking
up the bright flash with a phototransistor and triggering an
SCR. The SCR is used as a switch across the flash contacts.
This circuit does not false trigger even in strongly lit rooms,
but is sensitive enough to operate almost anywhere within
even a quite large room. Of course, by making more of
these and fitting them to more slave flash units even better
lighting and more shadow reduction is obtained. PCB: 21
x 21mm: $7 (K60).
SOUND ACTIVATED FLASH TRIGGER
Based on ETI project 514. Triggers a flash gun using an
SCR, when sound level received by an electret microphone
exceeds a certain level. This sound level is adjustable. The
delay between the sound being received and operation of
the flash is adjustable between 5 and 200 milliseconds. A
red LED lights up every time the sound is loud enough to
trigger the flash. This is handy when setting the unit up to
suit the scene, without waiting for the flash unit to recharge
or flatten its batteries in the process. This kit allows you take
interesting pictures such as a light bulb breaking. PCB: 62
x 40mm: $14 (K61).
OPTO
PHOTO INTERRUPTER (SLOTTED): an IR LED and an
phototransistor in a slotted PCB mounting assembly.
The phototransistor responds to visible and IR light. The
discrete components are easy to separate from the clip
together assembly. Great for IR experiments: $2 ea. or
10 for $15.
IR PHOTODIODE: similar to BPW50. Used in IR remote
control receivers. Peak response is at 940nm. Use with
940nm LEDs:
$1.50 ea. or 10 for $10.
VISIBLE PHOTODIODE: this is the same diode element as
used in our IR photodiode but with clear encapsulation, so
it responds better to visible and IR spectrum: $1.50 ea.
or 10 for $10.
LDRs: large, 12mm diameter, <20ohm very bright
conditions, >20Mohm very dark conditions: $1.
LEDs
BRIGHTNESS RATING: Normal, Bright, Superbright,
Ultrabright.
BLUE: 5mm, 20mA max, 3.0V typical forward voltage
drop. $2.50
RED SUPERBRIGHT: 5mm, 0.6 to 1.0 Cd, 30mA max,
forward voltage 1.7V, 12 degrees view angle, clear
encapsulation:
10 for $4 or 100 for $30.
BRIGHT: 5mm. Colours available: red, green, orange, yellow.
Encapsulation colour is the same as the emitted colour.
30mA max.: 10 for $2 or 100 for $14.
BRIGHT NARROW ANGLE: 5mm, clear encapsulation, 30mA.
Colours available: yellow, green: 10 for $2.50 or 100 for $20.
TWO COLOUR: 5mm, milky encapsulation, 3 pins, red plus
green, yellow by switching both on: $0.60.
ULTRABRIGHT YELLOW: Make a LED torch!: $2.50.
PACK OF 2mm LEDs: 10 each of the following colours:
red, green, amber. We include 30 1.0K ohm resistors for
use as current limiting. Great for model train layouts using
HO gauge rails: $10.
IR LEDs: 800nm. Motorola type SFOE1025. Output 1mW
<at> 48mA. Forward voltage 1.7V. Suitable for use with a
focussing lens. At verge of IR and visible, so has some
visible output. Illuminates Russian and second generation
viewers: $2.
HIGH POWER IR LEDs: 880nm/30mW output <at> 100mA.
Forward voltage: 1.5V. The best 880nm LEDs available.
Excellent for IR illumination of most night viewers and
CCD cameras. We use these LEDs in our IR illuminator
kit K36. Emits only a negligible visible output. Both wide
angle (60 degrees) and narrow angle (12 degrees) versions
of these LEDs are available. Specify type required: 10 for
$9 or 100 for $80.
IR LEDs: 940nm. Commonly used in IR remote control
transmitters. Good for IR viewers with a deeper IR response.
No visible output. 16mW output. 100mA max. Forward
voltage is 1.5V: 10 for $5.
18V AC <at> 0.83A PLUGPACKS
Also include a diecast box (100 x 50 x 25mm): Ferguson
brand. Australian made and approved plugpacks. Output
lead goes to diecast box with a few components inside.
Holes drilled in box where LED and 2 RF connectors are
secured: $8 (Cat P05).
CASED TRANSFORMERS
230Vac to 11.7Vac <at> 300mA. New Italian transformers in
small plastic case with separate input and output leads, each
is over 2m long. European mains plug fitted; just cut it off
and fit the local plug. This would be called a plugpack if it
sat on the powerpoint: $6 (Cat P06).
FREE CATALOGUE WITH YOUR ORDER
Ask us to send you a copy of our FREE
catalogue with your next order. Different
items and kits with illustrations and
ordering information. And don’t forget our
website at:
http://www.hk.super.net/~diykit
February 1996 35
Control barking dogs
with the
Woofer Stopper Mk.2
This completely new version of the
Woofer Stopper has much higher
power, with pulsed and variable output
frequency between 20kHz and 25kHz.
It automatically senses the barking of a
dog using an inbuilt electret microphone.
By JOHN CLARKE
36 Silicon Chip
Now it’s your turn to get back at
your neighbour’s barking dog without
anyone knowing about it. The Woofer
Stopper will give a blast of high intensity sound every time the dog barks.
When subjected to this treatment, most
dogs quickly learn that barking means
punishment and they stop.
Don’t get us wrong. The Woofer
Stopper Mk.2 will not stop all dogs
from barking. Some dogs are deaf or
are completely stupid and would continue to bark under any circumstances.
Provided they are not too far away
from the Woofer Stopper though, say
30 metres or less, most dogs will be
deterred from barking.
Our first Woofer Stopper, published in the May 1993 issue,
created a huge amount of interest. Obviously, barking dogs are
a source of much annoyance to
many people. While the Woofer
Stopper was successful in many
cases, we have had readers calling
for more power and for automatic
sensing of the dog barking.
The result is the Woofer Stopper Mk.2. This version has a far
greater voltage output and can
drive a maximum of four piezo
Fig.1: this is the block diagram of the Woofer Stopper Mk.2. An electret microphone
electric tweeters. These can be in
is used to pick up the sound of a dog barking, to provide an automatic trigger for
the form of four single devices or
the circuit. The output stage can drive up to four piezo tweeters.
two duals.
To obtain the maximum possible sound output, we have resorted to two types of tweeter. The first is the 1177A TD Twin Tweeter. It produces
Motorola KSN 1005A Super Horn.
99dB SPL at 1-metre and 2.82V RMS
a number of measures. First, instead
It can produce a 94dB SPL (sound drive and is rated at 28V maximum.
of driving the tweeter with a constant
Note that the second type is a dual
high frequency of around 20kHz, pressure level) at 1-metre with 2.82V
we frequency modulate the signal RMS drive. They are rated at 15V RMS tweeter and this accounts for the 5dB
continuous and 24V RMS maximum. increase in SPL. Other types can be
between 20kHz and 25kHz. This has
The second type is the Motorola KSN
used, although we do not know how
been done to overcome the inevitable
peaks and dips in the response of piezo
tweeters. By modulating the output
frequency over a 5kHz range, we obtain
a high effective output.
Second, instead of driving the
tweeters at a constant vol
tage, we
pulse them at a voltage much higher
than their continuous rating – again
to produce a higher output level. And
third, instead of driving them with a
square wave signal, we drive them
with a sinewave.
While developing the Woofer Stopper Mk.2, we found that driving piezo
tweeters with high-voltage square
These are the two piezo tweeters
waves caused them to fail. This is
recommended for use with
because they are essentially a capacthe Woofer Stopper Mk.2. The
Motorola KSN 1177A TD Twin
itor, with a capacitance ranging from
Tweeter is at left while the KSN
.01µF to 0.3µF, depending on the mod1005A Super Horn is shown
el. Driving such a capacitance with
above.
high-voltage square waves at around
20kHz or more causes very high peak
currents and this caused the internal
SPECIFICATIONS
connecting wires to fuse. Since we
wanted a lot more power than proSupply Voltage: 12VDC
duced by the previous design, we
Output Voltage (two transducers driven; deduct 20% for four devices):
could not use square waves; sinewave
(a) 21.4VRMS peak and 14.2VRMS continuous with 13.8V supply
drive was the way to go.
(b) 18.5VRMS peak and 12.4VRMS continuous with 12V supply
Recommended tweeters
Peak burst duration: 100ms every 1 second
Since the Mk.2 version produces
a lot more output than the original
version, it makes sense to team it with
highly efficient piezo tweeters which
can handle the high power levels
involved. Using cheap tweeters will
be a waste of money. We recommend
Total output duration: 5,10,20,40 & 160 seconds
Standby current: 30mA
Current while driving transducers: 1A average
Output frequency: shifted continuously between 20kHz and 25kHz
every 220ms
February 1996 37
Fig.2: the full circuit diagram of the Woofer Stopper Mk.2. Note the audio
amplifier involving IC6 and transistors Q1 & Q2. These provide increased power
and can drive up to four piezo tweeters via step up transformer T1.
they will respond to the high voltage
drive.
Bark sensing & timer
The Woofer Stopper Mk.2 has an
inbuilt electret microphone to sense
38 Silicon Chip
the sound of a dog barking and start
the unit operating. While this is adjustable in sensitivity, it is quite likely
that it will be triggered by other loud
sounds and this could ultimately be
counterproductive. We see the pur-
pose of the Woofer Stopper Mk.2 as a
teaching aid – to stop a dog from barking. If it is triggered by other noises,
it may not be as effective. However,
we have included this feature because
it has been requested frequently by
readers.
The unit can also be triggered into
operation by pushing a button and in
either case, the tweeter will sound
for a preset period which can be programmed, from five seconds to 160
seconds. The idea of having the timer
is to avoid the possibility of the unit
being turned on for long periods which
would waste power and possibly reduce its effectiveness in teaching the
dog not to bark.
The Woofer Stopper can be run from
a 12V battery or a DC power supply
capable of delivering one amp or more.
Block diagram
Fig.1 shows the block diagram of
the Woofer Stopper Mk.2. It shows an
electret microphone fed to IC1a & ICb,
comparator IC2 and flipflop IC3 which
controls the counter IC4.
IC5 and IC2c comprise the 20kHz
oscillator which is frequency modulated by IC2b. Finally, there is the power
amplifier comprising IC6, Q1 and Q2,
which drives a step-up transformer
T1. The gain of the power amplifier
is periodically increased by the burst
oscillator IC2d and Q3.
Counter IC4 resets the flipflop after
a preset time and the 20kHz oscillator
is reset. Thus, sound from the transducer is stopped until retriggered by
the microphone. Note that because
the microphone will also respond to
the transducer sound, the reset time
for the flipflop is made long enough
to prevent retriggering at the end of
the time period.
Circuit details
The complete circuit for the Woofer
Stopper Mk.2 is shown in Fig.2. The
electret microphone is biased by a
4.7kΩ resistor and its signal is coupled
to op amp IC1 via a .022µF capacitor.
IC1a is a non-inverting amplifier with
its low frequency response curtailed
below 1600Hz, by virtue of the 10kΩ
resistor and .01µF capacitor at pin 6.
Its gain is set by trimpot VR1.
IC1a’s output is coupled to a virtually identical stage, apart from the
sensitivity control, comprising op amp
IC1b. Its gain is 19 and is also rolled
off above 5kHz by the 150pF capacitor
shunting the 180kΩ feedback resistor.
IC2a squares up the output signal of
IC1b. IC2a is connected as a Schmitt
trigger with positive feedback between
the non-inverting input at pin 3 and
its output at pin 1. When flipflop IC3
is triggered by a high-going pulse from
IC2a, its Q output goes high which
allows IC5, a 7555 timer, to begin os-
PARTS LIST
1 plastic case, 198 x 113 x 63mm
1 PC board, code 03102961, 153
x 103mm
1 self-adhesive label, 107 x
193mm
1, 2, 3 or 4 KSN 1005 Motorola
superhorn loudspeakers (DSE
Cat C-2205) or 1 or 2 KSN
1177 Motorola twin tweeters
(DSE Cat C-2204)
1 red binding post
1 black binding post
1 2.5mm DC panel socket
1 2.5mm DC panel plug
1 SPDT toggle switch (S1)
1 momentary pushbutton switch
(S2)
1 electret microphone insert
1 ETD29 3C85 or 3F3 transformer cores, bobbin and clips
(Philips 2 x 4312 020 37502 ,
1 x 4322 021 34381 , 2 x 4322
021 34371) (T1)
2 mini heatsinks, 25 x 30 x 13mm
1 4.5m length of 0.5mm diameter
enamelled copper wire
1 140mm length of black hook-up
wire
1 200mm length of red hook-up
wire
1 200mm length of 0.8mm tinned
copper wire
8 PC stakes
2 3mm screws and nuts
2 5mm LED bezels
1 200kΩ horizontal trimpot (VR1)
1 20kΩ horizontal trimpot (VR2)
Semiconductors
1 LF353, TL072 dual op amp
(IC1)
1 LM324 quad op amp (IC2)
cillating. At the same time, the Q-bar
output of IC3 goes low to release the
reset on counter IC4 which begins to
count the clock pulses from oscillator
IC2b.
IC4 counts for a period selected by
installing the appropriate link (LK1LK5). When the selected Q output
goes high, the 33µF capacitor at pin
4 of IC3 is charged via D2 to reset
the flipflop. The Q output of IC3 now
goes low to stop IC5 from oscillating
and the Q-bar output goes high to
reset counter IC4. Now the selected Q
1 4013 dual D flipflop (IC3)
1 4020 binary counter (IC4)
1 7555, LMC555CN, GLC555
CMOS timer (IC5)
1 NE5534N op amp (IC6)
1 MJE3055 TO220 NPN transistor (Q1)
1 MJE2955 TO220 PNP transistor (Q2)
1 BC338 NPN transistor (Q3)
1 1N4004 1A rectifier diode (D1)
2 1N914, 1N4148 switching
diodes (D2,D3)
1 5mm red LED (LED1)
1 5mm green LED (LED2)
Capacitors
2 470µF 16VW PC electrolytic
1 47µF 16VW PC electrolytic
1 33µF 16VW PC electrolytic
2 10µF 16VW PC electrolytic
1 2.2µF 16VW PC electrolytic
1 0.1µF MKT polyester
2 .022µF MKT polyester
3 .01µF MKT polyester
1 .0022µF MKT polyester
1 150pF ceramic
1 120pF ceramic
1 82pF ceramic
1 39pF ceramic
Resistors (0.25W, 1%)
1 1MΩ
15 10kΩ
1 560kΩ
2 6.8kΩ
1 180kΩ
2 4.7kΩ
5 100kΩ
2 2.2kΩ
1 68kΩ
1 560Ω
1 47kΩ
1 100Ω
1 15kΩ
Miscellaneous
Solder, insulating tape.
output on IC4 goes low and the 33µF
capacitor at pin 4 of IC3 discharges
(or actually charges) via the 100kΩ
resistor to ground. This means that
IC3 is again ready to respond to the
signal from IC2a and recommence
the sequence.
20kHz oscillator
The main oscillator is based on IC5,
a CMOS 7555 timer which is connect
ed in an unconventional way. It successively charges and discharges the
.0022µF capacitor at pin 2 & 6 via the
February 1996 39
Fig.3: install the parts on the PC board and complete the
wiring as shown here. In particular, take care to ensure that
all polarised parts are correctly oriented and note that the
metal tabs of audio output transistors Q1 and Q2 are bolted
to small U-shaped heatsinks and to the PC board.
15kΩ resistor from pin 3. Instead of
using the square wave output signal at
pin 3, we take the triangle waveform
at pin 6. This triangle waveform is
buffered by unity gain op amp IC2c
and then fed to a low-pass filter comprising a 100kΩ resistor and 120pF
capacitor. This network effectively
40 Silicon Chip
removes the higher harmonics and the
result is a clean sinewave at around
20kHz.
However, the timer/oscillator IC5
is also frequency modulated by the
triangle signal applied to pin 5 from
pin 6 of IC2b, a low frequency oscillator. Op amp IC2b is connected as a
Schmitt trigger oscillator. It charges
and discharges the 2.2µF capacitor at
pin 6 via the 100kΩ resistor from pin
7. The result is a square wave at about
2.5Hz at pin 7 and a triangle waveform
of the same frequency at pin 6 (ie,
across the 2.2µF capacitor). As noted
above, the square wave pulses from
CAPACITOR CODES
❏
❏
❏
❏
❏
❏
❏
❏
❏
Value
0.1µF
.022µF
.01µF
.0022µF
180pF
120pF
82pF
39pF
IEC
100n
22n
10n
2n2
180p
120p
82p
39p
EIA
104
223
103
222
181
121
82
39
IC2b are used to clock counter IC4
while the triangle pulses frequency
modulate IC5.
IC6 amplifies the frequency-modulated sinewave from IC2c. Its current
drive capability is boosted by common
emitter output transistors Q1 & Q2.
The 560Ω resistor between the base
and emitter connections provides a
current path for the output of the amplifier whenever Q1 or Q2 is biassed
off and helps prevent instability. The
39pF compensation capacitor between
pins 5 & 8 and the 82pF feedback capacitor roll off the amplifier gain above
about 40kHz.
Gain boosting
The gain of IC6 is pulsed up and
down by the waveform from oscillator IC2d which switches transistor
Q3 on and off. With Q3 off, the gain
is about 1.5, set mainly by the 68kΩ
resistor across Q3. When Q3 is on, the
gain can be set between 11 and 2.9
The electret microphone insert is a flush fit in one end of the case, as shown
here. Connect the microphone so that its positive terminal goes to the 4.7kΩ
resistor. The terminal that’s connected to the case goes to ground.
by adjusting trimpot VR2. Thus, the
gain varies between about 1.5 and a
figure set by VR2 at a rate controlled
by IC2d.
IC2d operates in a similar manner
to oscillator IC2b. The 10µF capacitor at pin 13 is charged via the 10kΩ
resistor and diode D3 when pin 14 is
high and discharges via the 100kΩ
resistor when pin 14 is low. Thus, the
output is high for only a short time.
The duty cycle of the pulse waveform
is about 1:10.
Transformer T1 steps up the voltage
from the output amplifier by a factor of
10. Thus, the output across the piezo
tweeters can be as much as 75V peakpeak. In practice, the actual setting will
depend on the tweeters used. Above a
certain voltage level, the tweeter will
overload and will protest audibly. It
would not be wise to run tweeters
under this overload condition for long
as you risk burning them out.
Power supply
Power for the circuit is derived
from a 12V battery or DC power supply capable of supplying at least 1A.
Diode D1 provides polarity reversal
RESISTOR COLOUR CODES
❏
No.
❏ 1
❏ 1
❏ 1
❏ 5
❏ 1
❏ 1
❏ 1
❏
15
❏ 2
❏ 2
❏ 2
❏ 1
❏ 1
Value
1MΩ
560kΩ
180kΩ
100kΩ
68kΩ
47kΩ
15kΩ
10kΩ
6.8kΩ
4.7kΩ
2.2kΩ
560Ω
100Ω
4-Band Code (1%)
brown black green brown
green blue yellow brown
brown grey yellow brown
brown black yellow brown
blue grey orange brown
yellow violet orange brown
brown green orange brown
brown black orange brown
blue grey red brown
yellow violet red brown
red red red brown
green blue brown brown
brown black brown brown
5-Band Code (1%)
brown black black yellow brown
green blue black orange brown
brown grey black orange brown
brown black black orange brown
blue grey black red brown
yellow violet black red brown
brown green black red brown
brown black black red brown
blue grey black brown brown
yellow violet black brown brown
red red black brown brown
green blue black black brown
brown black black black brown
February 1996 41
These two oscilloscope photos show the output waveform of the Woofer Stopper. The photo at
left shows the frequency modulation while the shot at right shows the pulsed waveform.
protection while the associated 470µF
capacitor decouples the supply for
the high current pulses drawn by the
amplifier.
Construction
Fig.4: the full-size etching pattern for the PC board. Check the board
carefully for defects before installing any of the parts.
42 Silicon Chip
The Woofer Stopper is housed in
a plastic case measuring 198 x 113 x
63mm and the components are mount
ed on a PC board coded 03102961
and measuring 153 x 103mm. The
component layout for the PC board is
shown in Fig.3.
Start construction by checking
the PC board against the published
pattern. Repair any shorts or breaks
in the tracks before assembly of the
components. There should be 3mm
holes drilled for mounting Q1 and Q2
on their heatsinks.
First, install the eight PC stakes and
the bare wire links. Insert LK2 at this
stage. This gives a 10-second period
of operation and you can change this
later to the desired setting. Next, the
resistors can be inserted and soldered,
using the accompanying resistor code
table as a guide when selecting each
value. If in doubt, use your multimeter
to check the resistance values.
Next, insert the ICs, making sure that
each one is in its correct place and oriented correctly, then do the capacitors.
Note that the electrolytic capacitors
must be oriented as shown in Fig.3 for
correct polarity. Mount trimpots VR1
& VR2 and transistor Q3. Transistors
Q1 and Q2 are mounted horizontally
on small heatsinks. Bend their leads
so that they will fit neatly into the PC
board and secure the transistor tab to
the heatsink with a 3mm screw and
0N
+
+
START
+
+
TRIGGERED
WOOFER STOPPER
MKII
SPEAKER TERMINALS
nut before soldering the leads to the
PC board.
Winding the transformer is straightforward. The winding details are
shown in Fig.6. Terminate one end of
the 0.5mm enamelled copper wire to
pin 9 of the bobbin. To do this, you
will need to strip the end of the wire of
insulation and then tin it with solder.
Wind on eight turns and terminate the
end of the winding to pin 11 of the
bobbin. Apply a layer of insulating
tape over this winding. The secondary
winding is done in a similar manner
by starting at pin 2 and winding on 80
turns in several layers. Insulate each
layer with tape and finally terminate
onto pin 5.
The transformer is then assembled
by sliding the cores into each end of
the bobbin and securing them with the
clips. Mount the transformer onto the
board and solder the pins in place.
Work can now begin on the case.
Attach the adhesive label to the case
lid and drill the switch, LED bezel and
corner mounting holes. Drill holes in
one end of the box for the DC socket
and electret microphone and at the
opposite end for the tweeter terminals.
Make sure that the electret microphone
is a tight fit in its mounting hole. If
necessary, secure it with a drop of
5-minute epoxy adhesive.
Clip the PC board into the base of
the case. The tweeter terminal eyelet
connections can be soldered directly
to the PC stakes or you can use short
lengths of tinned copper wire.
Testing
When wiring is complete, you
should check your work carefully for
errors. Once you are satisfied that all
is correct, you are ready to connect
up power.
The Woofer Stopper will operate
from a 12V gel cell battery rated at
1.2Ah or higher. It can also be run from
a DC power supply capable of at least
1A at 12V. Apply power and check
voltages on the circuit. There should
be +12V at pin 8 of IC1, pin 4 of IC2,
pin 14 of IC3, pin 16 of IC4, pins 8 of
IC5 and pin 7 of IC6. Check that the
power LED lights.
Connect your multimeter across
the output terminals and set it to
read 20VAC. Wind trimpot VR1 fully
clockwise for maximum microphone
sensitivity and check that there is
an output signal on the meter when
triggered by tapping the microphone.
POWER IN (12VDC + )
Fig.5: this full size artwork can be photocopied and used as a drilling
template for the front panel.
You will find that the microphone
sensitivity is very high at this setting.
Reduce VR1 to a setting which will
only retrigger the circuit with a reasonable amount of noise. Trying barking
yourself if the mood takes you. Test
the manual trigger switch as well. Note
that LED2 should light whenever the
circuit is triggered.
Note that the reading on the meter
will not necessarily be the true output
level. This is because some multi
meters do not respond well at 20kHz.
Connect up your piezo tweeters
and again apply power. The level of
VR2 should be adjusted so that you
do not hear the sound output during
the bursts. Unless you can actually
February 1996 43
Fig.5: follow this winding diagram when
making the step-up transformer (T1). The
primary is wound on first and is covered with
a layer of insulating tape. The secondary is then
wound over the top of the primary.
hear 20kHz, any audible sounds from
the tweeters is distortion and is quite
small relative to the fundamental output at 20kHz.
If you want to check that the circuit
is working you can lower the frequen-
Transistors Q1 and Q2 are mounted horizontally on small heat
sinks. Bend their leads so that they fit neatly into the PC board
and secure their tabs to the heatsinks and the PC board using
machine screws and nuts.
cy of oscillation by adding a second
.0022µF capacitor between pins 2 and
1 of IC5. This will halve the output
frequency to 10kHz. Be warned that
the output is extremely loud and will
damage your ears if you do not use ear
plugs. You can also use a 1kΩ resistor
or high value resistor in series with
the tweeter to reduce the output level.
Return the circuit to 20kHz operation by removing the capacitor and
you are ready to test it on an unsuspecting dog.
As mentioned, you can use up to
four piezo tweeters in parallel (two
KSN 1177A or four KSN 1005A
tweeters). These can be mounted on
a board and oriented either horizontally or vertically, depending on the
sound pattern you require. Do not
use conventional tweeters (ie, those
with voice coils). The circuit cannot
handle them.
Note that you can omit the electret
microphone if you wish and just use
manual triggering. Alternatively, you
could add in a switch to turn off the
microphone when you want to use
manual triggering only.
You could also incorporate UHF
remote triggering, as was used for the
original version of the Woofer Stopper.
The details were published in the June
SC
1993 issue of SILICON CHIP.
Warning!
This internal view of the Woofer Stopper shows how the board fits neatly in the
case. The step up transformer and operation with sinewave drive are the main
factors in the increased output.
44 Silicon Chip
The output from this Woofer
Stopper is at a very high level.
Even though you cannot hear
the noise, take care to keep away
from the front of the tweeters
when they are being driven. They
may cause ear damage.
SILICON
CHIP
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more than likely that it contained advertising
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SILICON
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SILICON CHIP
BOOK SHOP
Newnes Guide
to Satellite TV
336 pages, in paperback at $49.95.
Installation, Reception & Repair.
By Derek J. Stephenson. First
published 1991, reprinted 1994
(3rd edition).
This is a practical guide on the
installation and servicing of
satellite television equipment. The
coverage of the subject is extensive, without excessive theory or
mathematics. 371 pages, in hard
cover at $55.95.
Servicing Personal
Computers
By Michael Tooley. First pub
lished 1985. 4th edition 1994.
Computers are prone to failure
from a number of common causes
& some that are not so common.
This book sets out the principles
& practice of computer servicing
(including disc drives, printers &
monitors), describes some of the
latest software diagnostic routines
& includes program listings. 387
pages in hard cover at $59.95.
The Art of Linear
Electronics
By John Linsley Hood. Published
1993.
This is a practical handbook from
one of the world’s most prolific
audio designers, with many of his
designs having been published in
English technical magazines over
the years. A great many practical
circuits are featured – a must for
anyone interested in audio design.
Optoelectronics:
An Introduction
By J. C. A. Chaimowicz. First
published 1989, reprinted 1992.
This particular field is about to
explode and it is most important
for engineers and technicians to
bring themselves up to date. The
subject is comprehensively covered, starting with optics and then
moving into all aspects of fibre
optic communications. 361 pages,
in paperback at $55.95.
Digital Audio & Compact
Disc Technology
Produced by the Sony Service
Centre (Europe). 3rd edition,
published 1995.
Prepared by Sony’s technical
staff, this is the best book on
compact disc technology that we
have ever come across. It covers
digital audio in depth, including
PCM adapters, the Video8 PCM
format and R-DAT. If you want to
understand digital audio, you need
this reference book. 305 pages, in
paperback at $55.95.
Power Electronics
Handbook
Components, Circuits & Applica
tions, by F. F. Mazda. Published
1990.
Previously a neglected field, power
electronics has come into its own,
particularly in the areas of traction
and electric vehicles. F. F. Mazda
is an acknowledged authority on
the subject and he writes mainly
on the many uses of thyristors &
Triacs in single and three phase
circuits. 417 pages, in soft cover
at $59.95.
Surface Mount Technology
By Rudolph Strauss. First pub
lish-ed 1994.
This book will provide informative
reading for anyone considering
the assembly of PC boards with
surface mounted devices. Includes
chapters on wave soldering, reflow
soldering, component placement,
cleaning & quality control. 361
pages, in hard cover at $99.00.
Electronics Engineer’s
Reference Book
Edited by F. F. Mazda. First pub
lished 1989. 6th edition 1994.
This just has to be the best reference book available for electronics
engineers. Provides expert coverage of all aspects of electronics
in five parts: techniques, physical
phenomena, material & components, electronic design, and
applications. The sixth edition has
been expanded to include chapters
on surface mount technology,
hardware & software design,
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semicustom electronics & data
communications. 63 chapters, in
paperback at $140.00.
Radio Frequency
Transistors
Principles & Practical Appli
cations. By Norm Dye & Helge
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This timely book strips away the
mysteries of RF circuit design.
Written by two Motorola engineers, it looks at RF transistor
fundamentals before moving on
to specific design examples; eg,
amplifiers, oscillators and pulsed
power systems. Also included are
chapters on filtering techniques,
impedance matching & CAD. 235
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Newnes Guide to TV &
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By Eugene Trundle. First pub
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1992.
Eugene Trundle has written for
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Title
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Newnes Guide to Satellite TV
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The Art Of Linear Electronics
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Power Electronics Handbook
Surface Mount Technology
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Radio Frequency Transistors
Newnes Guide to TV & Video Technology
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TOTAL $A
February 1996 53
SERVICEMAN'S LOG
The dingiest corner of a dingy room
I have a story about another long-in-thetooth set this month – one with a nasty sting
in its tail. And the situation wasn’t helped by
having to work in an anything-but comfortable
environment.
The set in question was a Pye model
48SL1, a 48cm set, fitted with what
Pye called a T38 chassis. It was, in
fact, a Philips KT3A-1 chassis, one of
several Philips KT3A chassis, some
of which were live. The KT3A-1 had
an earthed chassis, however, and this
particular model would be about 13
years old.
It was owned by a lady and the complaint, as nearly as I could determine
from her description, was a virtually
54 Silicon Chip
complete failure which possibly involved a hiccuping condition. Well,
that was fair enough and I didn’t anticipate that it would be a particularly
difficult job.
But there was one snag – the lady
insisted that the job be done in her
home; she didn’t want the set to leave
the house. Don’t ask me why but she is
not the first person I have struck who
had a thing about not letting a set out
of their sight. And, as I was to discover,
the lady was rather eccentric in other
ways as well.
I try to avoid house calls if possible.
It is impossible to take everything
one is likely to need for the job and
it invariably transpires that the one
thing you do need is back at the shop.
But the lady was insistent and, since
she was willing to pay any additional
costs, I agreed.
The lady’s house turned out to be
what was once undoubtedly a Victorian-style luxury home but which had
seen better days. But what really struck
me, even before I pulled the bell knob,
was the modern security fittings. The
door was fitted with heavy security
bars, was obviously fitted with more
than one lock, and every window was
fitted with heavy security shutters.
All of which should not have worried me except that, when I moved
inside, I realised that the security
Fig.1: the vertical output
stage of the Pye 48SL1.
The blanking pulse is
derived from the junction
of resistors R531 and
R532 and is fed to line
A51. Note the waveform
at this point.
to tackle a fault like that anywhere
away from the shop, let alone in this
Victorian chamber of horrors.
Naturally, the lady protested at this
suggestion but I explained, as politely
as I could, that there was no alternative; I needed equipment and facilities
which I simply could not provide
in her lounge room. So, finally, she
agreed, albeit reluctantly.
Back at the ranch
shutters not only kept out the burglars
but kept out the light as well. It would
not have been so bad if the rooms were
reasonably well lit. However, I doubt
that any of the light fittings boasted a
globe larger than 40 watts.
Again, I cannot explain why. I can
only assume that it was an attempt
to recreate what she imagined would
have been the dingy atmosphere of
the house in its heyday. It was a weird
setup; the only thing that seemed to
be missing was a black cat named
Salem!
But speculation aside, the result was
that I found myself down behind the
set, in the dingiest corner of a dingy
room, hoping that I could manage to
see what I was doing.
In fact, when my eyes became dark
adjusted, and with the aid of a hand
lamp, I was able to find my way around
without too much difficulty. These
chassis are well laid out and this,
cou
pled with the fact that I am
reasonably familiar with them,
also helped.
The hiccups
And so to the problem itself. My
original assumption was correct;
the set was hiccuping madly, which
invariably means an overload on the
power supply due to a breakdown
of some kind. But the question was,
where?
My first checkpoint was the main
electrolytic capacitor, C298, off the
bridge rectifier. This can produce
symptoms like this if it dries out
and, with a set of this age, it
was a prime suspect. But no; it
checked OK and there was about
350V across it, which was normal.
I also made a routine check for dry
joints but, as far as I could see, there
was nothing obvious.
The next step was to isolate the
horizontal output stage and the quickest way to do that was to pull the
deflection yoke plug, which carries a
protective link. That cured the hiccups
and allowed the main HT rail to come
up to a steady 131V.
So, the fault was somewhere in the
output stage. I narrowed this a little,
after replacing the yoke plug, by short
ing the base and emitter of the output
stage transistor, Q562. This also cured
the hiccups.
I spent some time checking various
possibilities. I disconnected the tripler
and, in turn, the various auxiliary
voltage rails off the output transformer secondary. And I went over the
transistor stage itself, checking all the
components around it. I even checked
the output transformer for shorted
turns but to no avail. And, remember,
all this was done in the confined space
and poor lighting I have previously
described.
I sat for a few moments and had a
bit of a think. Somehow, my thoughts
came back to the transistor itself
(Q562). Perhaps it had a weird fault in
it. I decided to pull it out and check it
or, if necessary, replace it.
I didn’t get that far. As I removed the
transistor there was the fault staring
me in the face; a black spot on the
insulating washer, where the voltage
had punched through. Fancy being
caught with that old chestnut.
I fitted a new washer, the hiccups
vanished, and I had a picture on the
screen. But it was a hollow victory;
the top half of the picture was riddled
with horizontal retrace lines.
I baulked at that. No way was I going
When I got back to the ranch, I
hoisted the monster onto my workbench and set to work. Since it
was obviously a vertical blanking
problem, I went over the circuit to
familiarise myself with the blanking
circuitry. It is fairly straightforward
really. A deflection pulse is taken off
the vertical deflection output stage
(Q530 & Q532) and goes to a pulse
processing stage (Q535).
This stage is biased so that it conducts only during the vertical flyback
period and delivers a series of square
pulses of about 1V amplitude to the
blanking section (pin 9) of the chomi
nance/luminance IC (IC192).
At least, that is the theory of the
circuit. And as far as I could determine, this was what appeared to be
happening. There was an appropriate
waveform at the vertical output stage
and a replica of it, somewhat attenuated, at the base of the processing stage
(Q535). And there were pulses out of
Q535 being applied to pin 9.
So why wasn’t the system blanking?
The only clue I had – if it could be
called that – was the discovery that
the problem varied with the height
control setting; reducing the height
would eliminate the lines, as would
increasing it beyond a normal setting.
And that, if it suggested anything,
pointed to the vertical stage.
As a result, I made a whole swag of
checks around this stage, including
changing transistors, likely electro
lytics and any resistors which were
marginally high. It was all to no avail.
Next, I went back to the shaping
stage and, in spite of what the CRO had
told me, I changed transistor Q535. It
wouldn’t have been the first time that
such a trick had paid off, contrary to
all the tests. But not this time. Nor did
a detailed check of all the associated
components.
In a fit of desperation, I hooked
up the CRO again and made another
check of the waveforms around this
February 1996 55
not contain much detail. It simply indicated
a square pulse with
an amplitude of 0.9V
and this amplitude
appeared to be correct.
But the manual gave
no indication of the
pulse width and this
was what I was now
querying. It wasn’t an
easy point to check.
Apart from the lack
of detail in the manual, the CRO wasn’t too
happy trying to resolve
the pattern. Pin 9 takes
in both vertical and
horizontal pulses and,
while in theory one
can resolve either one,
Fig.2: the vertical blanking pulse from the
according to the selectvertical output stage in the Pye 48SL1 comes
ed timebase, this is not
in on line A51 (bottom, centre) and is fed to
always so in practice
the base of Q535 via R540. The base bias on
this transistor is set by R529 and R534. The
and there was some
processed blanking pulse at the collector is
difficulty locking the
fed via D467 to pin 9 of the chrominance +
image.
luminance IC (IC192).
Nevertheless, now
that my suspicion was
aroused, the CRO patstage. There didn’t seem to be any
tern seemed to confirm it. And from
doubt about the waveform into Q535 this observation came the thought that
but closer examination of the pulses
Q535 was not being turned fully on
coming out made me suspicious. I during this portion of the waveform.
couldn’t be sure they were exactly as
That, in turn, directed my attention to
they should be. The waveform given
resistors R529 and R534, both 6.8kΩ.
in the manual – waveform 32 – did These set the bias for this stage; 15V at
the base – from the 30V rail – against
13V at the emitter.
Suppose I reduced that 15V bias
on the base? Suiting the action to the
thought, I unsoldered one end of R534
and substituted the nearest appropriate value to hand, which happened
to be 10kΩ.
And, presto! – the lines vanished.
Problem solved? Well, fault cured,
which is not exactly the same thing.
Naturally, there was a temptation to
leave the circuit like that, since it obviously worked. But I’m never happy
with such situations. Was I simply
curing the fault by brute force without
actually finding it?
While trying to decide how to resolve this question, the answer was
almost literally served up to me on
a plate – well, on the shop counter
to be correct. It was another Philips
set, this time with a KT3A-2 chassis,
which is virtually identical. Its fault
was simple enough and I soon had
it up and running, which provided
an excellent opportunity to make
comparative voltage and waveform
measurements.
In fact, I didn’t need to go that far.
As soon as I moved to this part of the
set the answer was plain to see; R534
in this set was 8.2kΩ. And it was obviously the original component, which
I subsequently confirmed by reference
to the KT3A-2 circuit. I fitted an 8.2kΩ
in place of my 10kΩ and it worked just
20 Electronic Projects
For Cars
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56 Silicon Chip
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Fig.3: the power
supply circuitry
for the NEC
N-3540. Note
the “HOT”
and “COLD”
designations
and the COLD
secondary of
T601. IC651
is at top left
and portion of
IC1001 at right.
as well. Problem solved.
Obviously, the fault I’d been chasing was not the first in this type of
set. There must have been previous
cases which had prompted this modification. Nor does it answer all the
questions. Why did this set suddenly
develop the fault when it had obviously performed satisfactorily for all
those years?
I can only assume that the original
design was a bit marginal, so that minor changes in components as the set
aged were enough to tip the balance.
Anyway, that was the end of the
story. All that remained was to return
the set to the dingy recesses of the
customer’s abode. I hope I don’t have
to go back, although it was a valuable
lesson learned.
Hot & cold NEC
My next story is from the much
more convenient and familiar atmosphere of my own workshop. It
concerns an NEC colour set, model
N-3450, the 34 indicating 34cm. It was
fitted with a typical infrared remote
control system.
According to the owner, the set
was completely dead but he didn’t
think there was much wrong with it,
because the stand-by LED was on. He
also indicated that he didn’t want to
spend a great deal on a repair.
Apart from the fault itself, the
interest in the set concerns a rather
unusual circuit arrangement. It is a
live chassis arrangement but with
considerably more of it being live
than in most cases. And the circuit is
clearly marked “HOT” and “COLD”, as
appropriate – see Fig.3. Well, at least
one is warned.
As is usual, the mains connects
straight to a bridge recti
f ier and
thence to a switchmode power supply, involving a trans
former T601
plus a switching transistor and error
amplifier in one package (IC601). The
primary winding of T601 and one of
two secondary windings is on the
HOT side, but the other secondary is
COLD. This provides a 20V rail via
diode D650.
Back on the HOT side, the output
from IC601 is the main HT rail at 115V.
This supplies the horizontal output
section, consisting of horizontal driver
transistor Q501, horizontal output
stage Q502, and the primary of the
output transformer, all still on the HOT
side. The input to Q501 is from the
main IC (IC701) via transformer T503,
which has a COLD primary and a HOT
secondary. All the output transformer
secondaries are COLD.
Having digested all that, I turned
my attention to the problem itself.
The fact that the stand-by LED was
on suggested that at least some part
of the power supply was working.
And, in fact, checks confirmed that the
previously mentioned 20V and 115V
rails were functioning.
On the other hand, there was no
horizontal waveform on any part of
the horizontal system. This made
me suspect that the fault could be in
the remote control system; either the
remote control receiver (PWC 3607C)
or the microprocessor (IC1001) which
it controls. In other words, the set was
simply not being switched on.
With the aid of the CRO, I established that the remote control receiver
was working and delivering a signal to
pin 14 of IC1001 (not the easiest path
to trace on the circuit). However, there
was no signal coming out on pin 33 of
February 1996 57
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58 Silicon Chip
IC1001 to switch the set on.
The signal from pin 33 is applied to
transistor Q1072, then to Q1071 to turn
it on – see Fig.3. Q1071 functions as a
voltage regulator, generating a 12V rail
from the 20V rail. This 12V rail powers
IC701 which contains the horizontal
oscillator and this feeds horizontal
driver transistor Q501.
And that is how the set is turned on
and off – by switching this 12V rail.
With no 12V rail, there is no signal to
drive the output stage or, in fact, any
other function depending on IC701.
Voltage checks
OK, so why no signal on pin 33? It
could be a fault in IC1001 of course
but I wanted to check everything else
before I pulled that out. And the first
and obvious check was the voltage
supplying this IC. It is a 5V supply,
derived from a 3-terminal voltage
regulator (IC651) operating from the
20V rail.
Well, it was delivering voltage all
right – too much voltage; it was closer
to 8V than 5V. At the same time, I was
prompted to look more closely at the
20V rail. In fact, that 20V figure is a
nominal one. According to the circuit,
it can vary from 22.4V on stand-by to
18.7V when the set is running. This
is why I was deceived when I first
confirmed that this part of the set was
working.
With the set switched off, that rail
should have been at 22.4V, whereas
it was slightly less than 20V, a value which had appeared to be close
enough at first glance.
But it was the 8V at the regulator
output which was the real clue. I
pulled IC651 out and replaced it. And
that was it – there were now normal
input and output voltages and the
set was up and running. IC651 had
broken down and was acting more
like a resistor than a regulator, thereby
placing a heavier load on the 20V rail
and applying excessive voltage to the
microprocessor.
And it would appear that it was
that excessive voltage which upset
the microprocessor. The 5V rail feeds
several pins on this IC and it is not
surprising that the excessive voltage upset some of the internal logic
functions.
After all, it was not without good
reason that the rail was regulated in
SC
the first place.
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.
Macservice Pty Ltd
KITS-R-US
PO Box 314 Blackwood SA 5051 Ph 018 806794
TRANSMITTER KITS
$49: a simple to build 2.5 watt free running CD level input, FM band runs from 12-24VDC.
•• FMTX1
FMTX2B $49: the best transmitter on the market, FM-Band XTAL locked on 100MHz. CD level input 3
stage design, very stable up to 30mW RF output.
$49: a universal digital stereo encoder for use on either of our transmitters. XTAL locked.
•• FMTX2A
FMTX5 $99: both FMTX2A & FMTX2B on one PCB.
FMTX10 $599: a complete FMTX5 built and tested, enclosed in a quality case with plugpack, DIN input
•connector
for audio and a 1/2mtr internal antenna, also available in 1U rack mount with balanced cannon
input sockets, dual VU meter and BNC RF $1299. Ideal for cable FM or broadcast transmission over
distances of up to 300 mtrs, i.e. drive-in theatres, sports arenas, football grounds up to 50mW RF out.
FMTX10B $2599: same as rack mount version but also includes dual SCA coder with 67 & 92KHz
subcarriers.
Protect your valuable issues
Silicon Chip
Binders
•
AUDIO
Audio Power Amp: this has been the most popular kit of all time with some 24,000 PCBs being
•soldDIGI-125
since 1987. Easy to build, small in size, high power, clever design, uses KISS principle. Manufacturing
rights available with full technical support and PCB CAD artwork available to companies for a small royalty.
200 Watt Kit $29, PCB only $4.95.
AEM 35 Watt Single Chip Audio Power Amp $19.95: this is an ideal amp for the beginner to construct;
uses an LM1875 chip and a few parts on a 1 inch square PCB.
Low Distortion Balanced Line Audio Oscillator Kit $69: designed to pump out line up tone around studio
complexes at 400Hz or any other audio frequency you wish to us. Maximum output +21dBm.
MONO Audio DA Amp Kit, 15 splits: $69.
Universal BALUN Balanced Line Converter Kit $69: converts what you have to what you want, unbalanced
to balanced or vice versa. Adjustable gain. Stereo.
•
•
••
COMPUTERS
I/O Card for PCs Kit $169: originally published in Silicon Chip, this is a real low cost way to interface
•to Max
the outside world from your PC, 7 relays, 8 TTL inputs, ADC & DAC, stepper motor drive/open collector
1 amp outputs. Sample software in basic supplied on disk.
PC 8255 24 Line I/O Card Kit $69, PCB $39: described in ETI, this board is easy to construct with
•onlyIBM3 chips
and a double sided plated through hole PCB. Any of the 24 lines can be used as an input or
output. Good value.
19" Rack Mount PC Case: $999.
•• Professional
All-In-One 486SLC-33 CPU Board $799: includes dual serial, games, printer floppy & IDE hard disk drive
interface, up to 4mb RAM 1/2 size card.
PC104 486SLC CPU Board with 2Mb RAM included: 2 serial, printer, floppy & IDE hard disk $999; VGA
•PC104
card $399.
KIT WARRANTY – CHECK THIS OUT!!!
If your kit does not work, provided good workmanship has been applied in assembly and all original parts
have been correctly assembled, we will repair your kit FREE if returned within 14 days of purchase. Your
only cost is postage both ways. Now, that’s a WARRANTY!
KITS-R-US sell the entire range of designs by Graham Dicker. The designer has not extended his agreement
with the previous distributor, PC Computers, in Adelaide. All products can be purchased with Visa/Bankcard
by phone and shipped overnight via Australia EXPRESS POST for $6.80 per order. You can speak to the
designer Mon-Fri direct from 6-7pm or place orders 24 hours a day on: PH 018 80 6794; FAX 08 270 3175.
These beautifully-made binders will protect your copies
of SILICON CHIP.
★ Heavy board covers with 2-tone green vinyl covering
★ Each binder holds up to 14 issues
★ SILICON CHIP logo printed in gold-coloured lettering
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Price: $A11.95 plus $3 p&p each (NZ $6 p&p).
Just fill in & mail the order form on page 101; or fax (02)
9979 6503; or ring (02) 9979 5644 & quote your credit
card number.
February 1996 59
Surround Sound
MIXER & DECODER
PART 2 – By JOHN CLARKE
Last month, we described the circuit details
for the Surround Sound Mixer & Decoder and
gave the parts layout for the main PC board.
This month, we complete the construction
and give the test procedure.
We’ll begin this month with the
display driver PC board assembly –
see Fig.5(a). Among other things, this
board carries the four display driver
ICs (IC12-IC15) plus four 11-way pin
header sockets which make the connections to the display board.
Begin by installing PC stakes at the
external wiring points. This done,
60 Silicon Chip
install the wire links, resistors, capacitors and diodes D1-D4, taking care
with the diode orientation.
The four ICs (IC12-IC15) can now
be installed, followed by transistors
Q1-Q4. Trimpot VR1 (shown dotted)
must be mounted on the underside
of the board – see also Fig.6. Do not
insert the pin headers yet; that step
comes later when the display board
is mounted.
Fig.5(a) also shows the LED display board. Begin by soldering in the
four 150Ω resistors. This done, the
40 LEDs can all be mounted, taking
care to ensure that they are correctly
oriented (the anode lead is the longer
of the two – see Fig.3). Do not solder
the LED leads yet, since the LEDs must
all be later adjusted for height when
the board is fitted to the front panel.
Preparing the case
The Surround Sound Mixer and
Decoder is built into a cabinet with
a sloping front panel. This cabinet
measures 170 x 213 x 31 x 82mm and
is fitted with two self-adhesive labels.
Begin by affixing the appropriate
label to the rear panel, then drill pilot
holes for the DC power socket, the RCA
sockets and the 6.35mm stereo jack
sockets. These holes can then all be
Fig.5(a): install the parts on the display driver
board and the LED display board as shown here.
Do not solder the LED leads until after the board
has been fitted to the front panel.
carefully reamed to size. This done,
mount the DC socket and the three top
6.35mm sockets in position.
Once the rear panel is completed,
the front panel can be prepared in
similar fashion. Note that the holes
for the LEDs and the display board
Fig.5(b): these are the full size etching patterns
for the display driver and LED display PC boards.
Check the boards carefully for etching defects
before installing any of the parts, as this can
eliminate a lot of hassles later on.
mounting holes should all be drilled
to 3mm. The four mounting holes for
the lid can be cut out using a knife and
lightly finished using a reamer.
Final assembly
The major hardware items can now
be fitted to the recommended case.
Attach the small plastic feet to the
underside of the case first, then install the main PC board. This board is
simply slid into the bottom of the case
so that the input and output sockets
protrude through their matching holes
February 1996 61
62 Silicon Chip
Fig.6: shielded audio cable is used for most of
the wiring from the main PC board to the front
panel controls and the input sockets. Check the
wiring carefully as it is installed, as it is easy
to make a mistake which would be difficult to
trace afterwards.
in the rear panel. Attach the nuts to
the 6.35mm sockets, then secure the
board to the integral standoffs in the
base using the self-tapping screws that
come with the case.
Cut each pot shaft to length before
mounting all the pots on the front panel. The pots should all be oriented so
that the markers on the knobs line up
correctly with the front-panel markings. The toggle switches all mount
towards the rear of the front panel.
Once all the hardware items are in
position, the LED display board can
be completed. First, mount the board
to the underside of the front panel
using four untapped 6mm spacers
and 12mm-long screws, with the four
9mm tapped spacers used as nuts to
hold the board in position. This done,
push each LED into its front panel
hole, check that the top surfaces are
all aligned and solder the leads.
Next, solder the 11-way pin headers
to the underside of the display board,
adjacent to each row of LEDs. Now
plug the display driver board into
these pin headers and secure this
board to the tapped spacers using
6mm-long screws. Complete the assembly by soldering the pin headers
to the driver board – see photo.
Fig.6 shows the internal wiring
details for the unit. Use medium-duty hook-up wire for the wiring to the
display driver board and for the power
supply connections. It’s a good idea to
use red wire for the +12V wiring, green
for the GND wiring, blue for the 0V
wiring, and yellow for the DC socket
and power switch (S7) wiring.
The remaining wiring must all be
run using shielded audio cable. This
includes the wiring between the main
board and all the pots, the top row of
6.35mm sockets and the remaining
toggle switches. Keep these leads as
short as possible while still allowing sufficient length for the lid to be
opened comfortably and use cable ties
to bundle them into neat looms – see
photo in Pt.1.
Test & adjustment
Before applying power, check
thoroughly for possible wiring errors.
This done, apply power and check the
voltages on the main PC board.
If all is well, there should be 12V
between the +12V and GND terminals,
while the GND terminal should be at
about 5.45V with respect to the 0V rail.
If these are incorrect, switch off power
February 1996 63
immediately and locate the fault before
proceeding.
Assuming that all is OK, check that
pin 8 of each LM833 IC (IC1-IC10) is
at +12V with respect to 0V. You can
also check the supply to the ICs on
the display driver board (IC12-IC15).
In each case, pin 3 should be at +12V.
All other voltages are measured
with respect to GND. Check the pin 1
and pin 7 outputs of IC1-IC11. These
should all be within 100mV of the GND
voltage. If all these voltage checks are
OK, set VR1 to midway, then rotate it
clockwise so that all the LEDs in each
display are just extinguished.
The mixer can now be tested with
a signal. However, before doing this,
it may be necessary to make up some
adaptor leads; eg, leads with an RCA
to mono 6.35mm plug and/or leads
with an XLR socket to stereo plug.
This latter adaptor is depicted in Fig.9.
The rear panel carries the six phono input sockets, four RCA output sockets (L,
R, C & S) and a power socket.
This view shows the completed display board assembly,
prior to installation on the front panel. Make sure that the
LEDs are all correctly oriented.
The LED display board in mounted on the driver board
using 12mm spacers and the connections made via four
pin header sockets.
Fig.7: this full-size artwork
can be used as a template
when drilling the rear panel.
+
12VAC
IN
A INPUT
L INPUT
C INPUT
+
+
+
L
OUT
+
+
C
OUT
B INPUT
R INPUT
S INPUT
R
OUT
+
+
S
OUT
+
+
+
64 Silicon Chip
Fig.8: this is the
full-size etching
pattern for the main
PC board. Check the
board carefully for
etching defects by
comparing it against
this pattern before
installing any of the
parts.
To test the unit, first secure the lid
and rotate all level controls fully anticlockwise. This done, connect a signal
to the Left input and adjust the output
and left level pots so that a reading
appears on the left bargraph display.
Check that there is a 20dB change in
level when switching between the
LINE and MIC inputs.
If the Left channel checks out OK,
Fig.9: this diagram shows how to wire an adaptor cable with
an XLR socket on one end and a stereo phono plug on the
other. Be sure to use 2-core shielded audio cable.
February 1996 65
4-CHANNEL
+
L
+
C
MIC
LINE
+
A-CHANNEL
MIC
+
LINE
SURROUND
SOUND MIXER
& DECODER
B-CHANNEL
MIC
+
LINE
+
R
POWER
S
+
OUTPUT
INPUTS
+
C
C
+
+
3
0
L
LEFT
PAN
R
L
PAN
R
-3
-6
-9
+
-12
+
+
-15
-18
CENTRE
C
PAN
S
C
PAN
-21
S
-24
SIGNAL LEVEL (dB)
L
+
C
R
S
RIGHT
+
+
+
+
SURR
LEVEL
LEVEL
OUTPUT
LEVEL
Fig.10: this full-size artwork can be used as a drilling template for the front panel.
you can test the Centre, Right and
Surround channels in exactly the
same manner.
Now feed the signal source into the
A channel input and check the opera66 Silicon Chip
tion of the Pan and Level pots. Note the
interaction between each channel as
the knobs are rotated. This done, test
the B channel in the same way.
Assuming that everything checks
out, you are now ready for some
surround sound recording. You will
probably need some practice to get
everything just right but the results
SC
will be well worth the effort.
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.
Rod Irving Electronics Pty Ltd
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:
Rod Irving Electronics Pty Ltd
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.
Rod Irving Electronics Pty Ltd
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:
Rod Irving Electronics Pty Ltd
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.
Rod Irving Electronics Pty Ltd
PRODUCT SHOWCASE
New CD changers from Yamaha
Yamaha Music Australia has introduced three CD changers which incorporate a new drive mechanism which
allows the disc drawer to open fully,
allowing removal and replacement of
all five discs simultaneously.
The three models, designated
CDC-755, CDC-655 and CDC-555,
also feature the company’s patented
PlayXchange system, which permits
up to four discs to be removed and
replaced while the fifth is still playing.
The top of the range model CDC-755
incor
porates S-Bit Plus technology
and PRO-Bit processing, previously
only available on Yamaha’s flagship
CDC-845.
According to Yamaha engineers, the
new models are also quieter than in
the past thanks to the new drive system. Newly designed and improved
gear drives and roller mechanisms
provide nearly silent disc drawer
operation.
PRO-Bit produces a more accurate
and musical representation in the
digital domain prior to the S-Bit Plus
D/A conversion. The major advantage claimed for the 20-bit format is
lower quantisation noise during the
analog-to-digital conversion, which
results in better sound quality for low
amplitude signals.
The output of the translator goes to
a 22-bit 8-times oversampling filter,
which in turn delivers the signal to a
22-bit to 18-bit noise shaper, and from
there to Yamaha’s S-Bit Plus DAC and
then to high quality analog output
circuitry.
Another new feature, incorporated
in all three new models, is an “intelligent” digital servo system. The new
circuitry uses a Yamaha-developed
microprocessor to monitor the signal
and adjust the laser pickup’s tracking
and focus and the motor speed to
EPROM writer can also operate
from a PC printer port
The “Leaper 3”, a new EPROM
writer introduced by L&M Satel
lite
Supplies, can not only operate in the
normal stand-alone A to B EPROM
“copy” mode but also write an EPROM
using data stored in a personal computer.
A software driver and connecting
cable are included to enable the Leaper 3 to operate from any PC parallel
(printer) port.
The device, measuring 160 x 110
x 45mm, can operate from a mains
supply via a 9V/500mA supply (included) or from an internal battery
(9V) for on-site EPROM burning. Along
72 Silicon Chip
with 2732-27080 EPROMs, it will also
handle a range of EEPROMs, Flash
EPROMs and SRAM devices.
Various function keys can be used
to set the programming flow chart,
voltages, pulse width and other par
ameters.
A 2-line, 16-character liquid crystal
display ensures the operator is kept
fully informed.
For further information on this, or
other EPROM writers in the Leaper
range, contact L&M Satellite Supplies,
33-35 Wickham Road, Moorabbin, Vic
3189. Phone (03) 9553 1763; fax (03)
9532 2957.
better compensate for disc warpage
and dust.
The new CDC-755 has been restyled
and features Yamaha’s new, more
rounded, front panel. It has a recommended retail price of $599. The new
CDC-655 incorporates many of the
features found on the more expensive
755 at $499 and features 10-key front
panel operation. The model 555,
priced at $399, incorporates the intel
ligent digital servo system and S-Bit
D/A conversion.
For further information, please contact Yamaha Music Australia. Phone
(03) 9699 2388, 1800 805 413, or fax
(03) 9699 2332.
Hand-held satellite
GPS unit from DSE
Global Positioning Systems have now reached the
point where it is completely
practical for bushwalkers, for
example, to keep a unit in the
back-pack.
The Magellan GPS2000
Satellite Navigator from Dick
Smith Electronics is small
enough to hold in the hand
(it’s about the same size as
a mobile phone and weighs
in at 283 grams), yet accurate enough to give you your
position – anywhere in the
world –to within a hundred
metres or so.
GPS units such as the Mag
ellan rely on the US Department of Defence’s 24-satellite
network which continuously
update position information,
ensuring very high degrees of
accuracy. Unlike terrestrial or
stellar navigation or positioning methods, the GPS2000 is
unaffected by cloud, fog or
other similar barriers.
The device can also be used
to direct you from your current
location to a position with known map
co-ordinates, or you can store up to
100 “way points” and the GPS2000
will display the distance travelled,
the remaining distance to travel, the
speed and course direction.
As such, The Magellan GPS2000 is
certain to find a ready market amongst
the boating and fishing fraternity (that
favourite “hot spot” can be always
found again and again).
The unit is priced at $595 and is
available from Dick Smith Electron
ics stores.
Second generation
2.5-inch hard drives
A new “second generation” family
of disc drives has been introduced by
Hitachi Australia, offering high performance and sizes up to 1.3Gb.
With a density of 450 bits per inch,
they are 50% denser than Hitachi’s
previous 2.5-inch models.
The new drives have an operating
shock resistance of 150G and a non-operating shock resistance of 250G’s,
suiting notebook computers.
They offer a 300,000 hour MTBF
(mean time between failure) rating
(approximately five years) and have
a power consumption (for seek and
read/write operations) of 2.0 watts.
The DK212A series (height 19mm)
is available up to 1.08Gb, while the
DK222A series (height 12.5mm) is
available up to 1.3Gb. Both types have
an average seek time of 12ms and an
ATA-2 interface.
The drives are marketed through
Hitachi distributors DCS Australia Pty
Ltd, phone (03) 9878 0344.
February 1996 73
Programmable
video generator
The Black Star PVG100
Programmable Video Generator is a high performance
instrument which enables
virtually all CRT monitors
to be evaluated, qualified,
tested and aligned.
The instrument has a
2048 x 2048 pixel capability, with 1600 x 1280 pixels
displayed at 16 colours
from a palette of 16 million
colours.
The test patterns include text,
grating, dots, horizontal and vertical lines, circles, colour bars,
greysc ale, checke rb oard and a
border pattern, plus multiburst,
purity, high voltage regulation and
windows.
The clock speed is 100MHz
(135MHz optional) with a resolution of 100kHz. The non-volatile
system memory incorporates 100
standard systems and allows for
up to another 100 user-defined sys-
tems to be programmed. Automatic
sequencing of selected programs is
available.
TTL outputs for programmable
sync and video are provided,
along with analog outputs for both
SMPTE and NTSC levels and an
RS232 interface for connection to
a PC or terminal to allow remote
programming.
The front panel of the PVG1000
is laid out in a clear, easy-to-use
format, making the instrument
suitable for both production and
servicing environments. All timing, parameters, patterns etc, are
programmed from the front panel,
while all system information is
displayed on a 2-line LCD and
status LEDs. The pushbutton keyboard ensures error-free setting and
programming.
For more information contact
Obiat Pty Ltd, 129 Queen Street,
Beacons
field, NSW 2014. Phone
(02) 698 4111, fax (02) 699 9170.
Free quarterly EMC
newsletter
Schaffner’s EMC
WORLD 12-page
newsletter is distributed every
three months and
covers many EMC
issues that are relevant to the new
mandatory standards being introduced by many
countries around the globe.
A worthwhile feature is the
guide to Electromagnetic Immunity
Standards, “Standards-UPDATE”,
which lists the types of EMC test, the
relevant IEC test number and a brief
description of the test parameters.
Other issues commonly covered
are EMC instrument calibration/
certification, new products, application notes and new publications
and handbooks.
For further information on EMC
WORLD, contact John Thompson,
Westinghouse Industrial Products,
Locked Bag 66, South Melbourne,
Vic. 3205. Phone (03) 9676 8888.
74 Silicon Chip
Loudspeaker design
course at Sydney Uni
Neville Thiele and Glenn Leem
bruggen will be running a 26 hour
loudspeaker design course during
Semester 1 this year as part of the
Sydney University Audio Program or
as a standalone course. Some enrol
ments may still be available – contact
the Audio Program Coordinator on (02)
351 2686; fax (02) 351 3031.
A new series of
Megger testers
Nilsen Technologies has released a
new range of the famous brand "Megger" insulation and continuity testers
– the BM120 series.
The BM121, with a test voltage
of 500V, will measure insulation resistance to 0.5MΩ, while the BM122
measures insulation resistance to 1MΩ
(test voltage 1kV). The full measuring
range is from 0.01MΩ to 999MΩ on
insulation resistance and automatic
discharge of the circuit under test is
provided.
They are protected against accidental connection to phase to earth
voltages of 300V and 440V AC phaseto-phase. In addition, a warning signal
will flash if the unit is connected to a
circuit with more than 25V present.
Continuity tests, which can be done
hands free, have a maximum current
of 200mA and an open circuit voltage
of 5V. Continuity range is from .01Ω
to 99.9Ω.
The instruments are provided with
automatic shutdown of power after
five minutes of non-use.
For further information, contact
Nilsen Technologies, 150 Oxford St,
Collingwood, Vic 3066. Phone (03)
9419 9999; fax (03) 9416 1312.
STEPDOWN
TRANSFORMERS
60VA to 3KVA encased toroids
Proposed CD-erasable
specifications
Philips Electronics has announced
proposed specifications for an erasable compact disc format, indicating
significant progress in enabling companies to bring CD-erasable products
to market in 1996. With a data capacity
of up to 680Mb per disc, CD-erasable
provides additional benefits to applications currently served by CD-recordable products.
CD-recordable discs provide more
Harbuch Electronics Pty Ltd
9/40 Leighton Pl. HORNSBY 2077
Ph (02) 476-5854 Fx (02) 476-3231
permanent data storage, while CD-erasable allows data to be updated and disc
space to be reused. CD-E drives will
be capable of reading all existing CD
formats.
For more information, please contact Philips Electronics Australia Ltd.
Phone (02) 925 3281 or fax (02) 929
SC
4784.
TWO MORE UNBEATABLE OFFERS FROM MACSERVICE
TEKTRONIX 100kHz to 1800MHz
Spectrum Analyser System
WAVETEK Signal Generator/
Deviation Meter
Consisting of:
7613
Storage Mainframe
Model 3000-200 incorporates a complete 1 to
520MHz FM, AM and CW Signal Generator with an
FM Deviation Meter in one convenient instrument.
7L12
1.8GHz Spectrum Analyser Plug-In
7A17
Amplifier
TR501
1.8GHz Tracking Generator
TM503
3 Slot Mainframe
$4250
Please phone or
fax today for a full
specification sheet
incorporating all the
system’s features.
Frequency Range: 1-520MHz selectable
in 1kHz steps; 1kHz resolution; frequency
programmable via rear-panel connector.
RF Output Level: +13dBm to -137dBm (1V
to .03µV RMS); output level continuously
adjustable in 10dB steps and with an 11dB
vernier; impedance = 50 ohms.
RF Output Protection: resettable RF circuit
breaker; RF trip voltage = 5V RMS nominal;
maximum reverse power = 50W.
Specrtal Purity: harmonic output > 30dB below fundamental from 10520MHz; residual AM > 55dB below carrier in a 50Hz to 15kHz post-detection bandwidth; residual FM <200Hz in a 50Hz to 15kHz post-detection
bandwidth (100Hz typical).
Amplitude Modulation: internal 400Hz and 1kHz ±10%; external DC to
20kHz; range 0-90%; distortion 3% to 70% AM at 1kHz.
Frequency Modulation: internal 400Hz and 1kHz (±10%); 50Hz to 25kHz;
accuracy ±500Hz on x1 range, ±5kHz on x10 range; distortion 4% at 1kHz.
FM Deviation Meter: frequency range 30-500MHz; input level range 10mV to
5V RMS; impedance 50 ohms; deviation range 0 to ±5kHz, 0 to ±50kHz
MACSERVICE PTY LTD
Australia’s Largest Remarketer of
Test & Measurement Equipment
20 Fulton Street, Oakleigh Sth, Vic, 3167. Tel: (03) 9562 9500; Fax: (03) 9562 9590
$1250
**Illustrations are representative only. Products listed are refurbished unless otherwise stated.
February 1996 75
Do you have an application for a
remote control? If you do, then take
your pick from these three units.
Two operate at UHF, while the
third is an infrared unit which can
handle up to eight channels. All are
inexpensive and easy to build.
3
Remote
Controls
The first of these units, operating in the UHF band at 304MHz,
has been designed specifically for retrofitting central locking to a
car but any project that requires a simple on-off control could use
it. The second, also operating at UHF (304MHz), is a
2-channel unit. The compact keyring transmitter (50 x 35 x
15mm) has two buttons, each of which controls a latching relay
in the receiver. The third unit is the 8-channel infrared remote
control and it operates in the same way as the remotes for your
TV, VCR or audio gear. Now to the nitty-gritty.
Designs by BRANCO JUSTIC
76 Silicon Chip
Remote Control 1 – Single Channel UHF
T
HE KEYRING TRANSMITTER
case for the single channel
transmitter is 57 x 30 x 12mm
and has an 18mm dimple for your
thumb. Very cunningly, there is no
external pushbutton; you actually
squeeze the two halves of the case
together and this actuates the internal
switch. A 3mm LED comes on when
the unit is transmitting. The circuit,
shown in Fig.1, consists of one IC, one
transistor and a few small components.
ly into the main PC board. Its output,
pin 5, connects to the input (pin 14)
of decoder IC1.
For the receiver to acknowledge the
transmitter, both units must be set to
the same code; ie, the corresponding
pins on the encoder and decoder ICs
must be connected in the same way
(high, low or open circuit). Provided
they are identical the decoder output,
pin 17, will go high (+5V) and clock
IC2 whenever a valid code is detected.
When power is first applied, IC2 is
reset by C9 and R4, which causes pin
1 to go low. Conversely, pin 2 will go
high, locking the doors.
When IC2 is clocked, pin 1 will go
high, operating RL1 and RL3 for about
one second and turning RL4 on. RL1
will unlock the doors and RL3 will
flash the indicators if the relay is fitted
and wired to these lights. RL4, if fitted,
could be used to turn a car alarm on
and off. It would be wired to turn the
alarm off now.
The next time a valid code is re-
The keyring transmitter
(above) is shown only
slightly smaller than full
size. This mates with the
receiver (right). While
intended for motor
vehicle use, this remote
control has many other
applications.
When SW1 is closed, power is
applied via LED1 to encoder IC1 and
also to L1, the feed to the oscillator.
The code at IC1 pin 17 depends on
whether the coding inputs are tied
to pin 18 (high), pin 14 (low) or left
floating. This code gates oscillator Q1
on and off, which results in bursts of
304MHz.
If you look at the PC board pattern
you will see that L1 is a conventional
inductor but L2 is actually a loop of
copper on the board. As well as being
the oscillator tank coil, this loop is
used as the antenna. L1 isolates the
tank circuit from the battery supply.
The receiver (Fig.2) consists of a tiny
pre-built, pre-aligned UHF receiver
module with 12 pins that solder direct-
Fig.1: the transmitter is based on encoding chip IC1 (AX5326) and a single
transistor transmitter. It outputs a coded pulse stream which is interpreted by
the receiver. The circuit fits neatly into the keyring case above.
February 1996 77
Fig.2 (left): the receiver circuit may
look complex but is mostly controlled
by just three ICs. The various relays,
along with their appropriate driver
components, may be included or
omitted to suit the application.
ceived, IC2 will be clocked again. Pin
2 now goes high, pulsing RL2 for one
second and locking the doors. R12 is a
2.2MΩ resistor and this will give a one
second flash from the indicator lamps.
PARTS LIST
Single Channel UHF
Transmitter
1 plastic case
1 PC board
1 12V alkaline battery
1 PC board mounting switch
1 AX5326 encoder (IC1)
1 BF199 NPN RF transistor
(Q1)
1 3mm red LED
1 10µH choke
Capacitors
2 .001µF ceramic
2 4pF NPO ceramic
1 2-10pF variable
Resistors (0.25W 1%)
1 1MΩ
1 100Ω
1 22kΩ
Single Channel UHF
Receiver
1 PC board
1 UHF receiver module
2 or 4 SPDT 12V PC-mount
relays
Semiconductors
1 AX5328 decoder (IC1)
1 4013 dual D flipflop (IC2)
1 4093 quad Schmitt trigger
(IC3)
5 C8050 NPN transistors (Q1Q5)
8 G1G diodes (D1-D8)
1 5.6V 500mW zener diode
(ZD1)
Capacitors
2 100µF 16VW PC electrolytic
6 0.47µF monolithic ceramic
1 .015µF ceramic
Resistors (0.25W 1%)
5 2.2MΩ
5 4.7kΩ
2 1MΩ
1 3.3kΩ
4 10kΩ
1 22Ω
78 Silicon Chip
If you want a longer indication,
change R12 to 10MΩ, which will
cause RL3 to operate for around five
seconds when the doors are locked.
With no voltage on the base of Q5 (as
pin 1 of IC1 is now low), RL4 will be
de-energised. This relay would now
turn the car alarm on.
The circuit shows the wiring for
conventional locking systems with
bidirectional motors. Fig.3 shows the
method used to connect the relays for
two wire motors.
Assembly is reasonably straightforward, with some care being required
when soldering the components on
the rather small transmitter board. The
transmitter overlay is shown in Fig.4
while the receiver layout is shown
in Fig.5.
Fig.3: if you intend to use the single channel remote in a vehicle with
central locking, this circuit shows how the various connections should
be made. Relay 4 in the receiver is not shown: this can be used to arm/
disarm the vehicle’s alarm system.
This photograph clearly shows the mounting position for the pre-built UHF
receiver module. While IC sockets were used in the prototype, they are not
essential and, indeed, better reliability can often be achieved without them.
Fig.4: compare this
transmitter PC board
layout with the photograph above when
placing components.
Fig.5: the printed circuit overlay for the single channel receiver, reproduced actual size.
The antenna can be a short (say 250-500mm) length of insulated hook-up wire. Keep all
component leads as short as possible, both on this board and on the transmitter.
February 1996 79
Remote Control 2 – Dual Channel UHF
T
HE SECOND TRANSMITTER is
shown in Fig.6. As mentioned
previously, it has two momentary contact pushbuttons, either of
which apply power to the encoder IC
and the rest of the circuit.
Note that the encoder chip used here
is the same as for the single channel
transmitter.
Switch SW1 takes pin 13 (D3) of
IC1 high, while SW2 takes pin 12 (D2)
high. When a button is pressed, the IC
outputs one of two different codes,
depending on the linking of pins 1-8.
The oscillator is similar to the one
described in the previous transmitter.
One button on this transmitter could
be coded to operate the central locking unit previously described, while
the other could operate an automatic
garage door, using one channel of the
receiver described below.
Receiver circuit
The circuit of the dual channel
receiver is shown in Fig.7. This has
a discrete component UHF receiver
instead of the pre-built surface-mount
receiver used in the single channel
circuit of Fig.2.
L1 and L2 are copper tracks on the
PC board, with L1 being damped by
resistor R1 to broaden its response. L2
is tuned to the transmitter frequency
by variable capacitor VC1 and the
signal applied via C3 to the base of
Q1, a self-detecting regenerative UHF
amplifier.
The detected output appears at
the emitter of Q1 and is coupled via
the 4.7µF capacitor to the inverting
input of IC1a. The 2.2kΩ resistor and
the 470pF capacitor prevent any RF
signals being fed into op amp IC1a.
This has a gain of 214 and rolls off the
Fig.6: the circuit for the
dual channel transmitter
is very similar to the
single channel version but
uses separate pushbutton
switches to transmit two
different codes.
80 Silicon Chip
Fig.7: the dual channel receiver is more complex than the single channel version. It has two
decoding circuits and a discrete component receiver is used instead of the pre-built UHF module.
February 1996 81
PARTS LIST
Dual Channel UHF
Transmitter
1 plastic case
1 PC board
1 12V alkaline battery
2 battery contacts
2 PC board mounting switches
1 10µH choke
Semiconductors
1 AX5326 encode (IC1)
1 BF199 NPN RF transistor (Q1)
2 1N914, 1N4148 diodes (D1,D2)
1 3mm red LED
Fig.8: two switches, and therefore a
slightly larger case, are required for
the dual channel transmitter. Compare
the PC board overlay above, to the
photograph at right.
Capacitors
1 0.1µF monolithic ceramic
1 .001µF ceramic
1 3.9pF NPO ceramic
1 2.2pF NPO ceramic
1 2-10pF variable
Resistors (0.25W 1%)
1 1MΩ
1 100Ω
1 22kΩ
Dual Channel UHF
Receiver
1 PC board
2 SPDT 12V PC relay
Semiconductors
1 CA3401 quad op amp (IC1)
2 AX5328 decoder (IC2, IC3)
1 4013 dual D flipflop (IC4)
1 BF199 NPN transistor (Q1)
4 BC548 NPN transistor (Q2-Q5)
3 1N914, 1N4148 diodes (D1-D3)
3 1N4004 diodes (D4-D6)
1 15V 1W zener diode (ZD1)
Capacitors
1 100µF 16VW PC electrolytic
1 10µF 16VW PC electrolytic
2 4.7µF 16VW PC electrolytic
4 0.47µF monolithic ceramic
2 .001µF ceramic
1 470pF ceramic
1 330pF ceramic
1 220pF ceramic
1 33pF NPO ceramic
1 15pF ceramic
1 1.5pF NPO ceramic
1 0.5-5pF trimmer
Resistors (0.25W 1%)
1 4.7MΩ
1 33kΩ
3 2.2MΩ
1 22kΩ
4 1MΩ
7 10kΩ
1 470kΩ
1 6.8kΩ
4 220kΩ
1 2.2kΩ
1 100kΩ
1 100Ω
2 47kΩ
1 15Ω 1.0W 5%
1 39kΩ
82 Silicon Chip
Fig.9: when constructing the receiver board, ensure that the component leads
are kept as short as possible. Some resistors mount end-on to the board.
response above 2.2kHz due to the 15pF
capacitor across the 4.7MΩ feedback
resistor.
The following op amp, IC2b, has a
gain of 23 and rolls off the response
above 3.3kHz. The signal is then fed
to Schmitt trigger IC1c, which cleans
up any noise and interference on it.
The final operational amplifier, IC1d,
inverts the signal, making it the correct
polarity for the decoders.
Thus, the signal at pin 5 of IC1 is
similar to that generated by the transmitter. This is fed to two identical
decoders – IC2 and IC3. One of these
ICs has pin 13 connected to the +12V
rail, while the other has pin 12 connected to this rail. Thus, SW1 on the
transmitter will be decoded by IC3 and
SW2 by IC2. Each output (pin 17) is
fed to the clock input of one half of a
dual type “D” flipflop, IC4.
Each time the clock input goes high,
the output (pin 1 or pin 13) will toggle
(low to high or high to low), causing
relays RLA or RLB to alternately
latch or release. The outputs of IC2
and IC3 are “ORed” by D2 and D3
so that when either receives a valid
code, the collector of Q3 will go low
for about half a second. This could
be used to actuate a buzzer or if the
values of C12 and R24 are increased,
a 12V globe could be switched on for
a reasonable time.
Building it
The component overlay of the
transmitter board is shown in Fig.8.
Once again, the transmitter board is
fairly compact and extra care should
be taken with its assembly.
By contrast, the receiver board depicted in Fig.9 should not present any
difficulties. Some of the resistors stand
vertically and they should be pushed
right down against the PC board.
The alignment procedure for each
board is covered in the instructions
supplied with the kit.
Remote Control 3 – 8 Channel Infrared
T
HE THIRD OF THESE remote
controls goes from the exotics
of UHF at 304MHz to a more
mundane infrared (IR) transmitting
LED and an IR receiver module. But
while the UHF remotes had only one
or two outputs, the IR system has six
momentary and two latching outputs
available for controlling devices.
The transmitter handpiece, branded
Magnavox, measures 155 x 35 x 16mm.
The eight buttons on it are labelled
Tuner, CD, Track, Stand-by, Stop, Play
and Volume up/down. When any one
of the first six transmitter buttons is
pressed, the corresponding receiver
output (A-F) goes high momentarily.
The Volume buttons toggle the G and
H outputs; ie, latching them high on
one press, low on the next.
The transmitter circuit is shown in
Fig.10 and as with the UHF circuits,
there is not much to it; just an encoder
IC and a couple of transistors to drive
the IR light emitting diode, IRLED1.
IC1, an SM5021B, uses a 455kHz ceramic resonator as the oscillator. This
is divided internally by 12, giving near
enough to a 38kHz carrier frequency
which is gated on and off by the data.
The pulse train appears at pin 15 and
drives LED1 through Darlington transistor driver Q1, Q2.
If several of these transmitters were
to be used in the same vicinity, the
coding links LK1 and/or LK2 could
be fitted but otherwise they are not
necessary.
Receiver
The receiver circuit is shown in
Fig.11 and is almost as simple as the
transmitter thanks to the use of IC2,
a PIC12043. This device contains an
IR receiver diode, an amplifier tuned
to 38kHz, a bandpass filter, an AGC
section and a detector circuit. Its output is a digital pulse train identical
to that generated by the transmitter
but inverted.
Q1 changes the polarity to make
it suitable for IC1, the decoder. Q2
and ZD1 regulate the input voltage to
+5.7V, to prevent damage to IC2. The
coding links LK1 and LK2, if fitted,
must match those in the transmitter.
The outputs of IC1 can only supply
around one milliamp, so a buffer or
Fig.10: the infrared transmitter circuit. Links LK1 and LK2 are
coding links and are only required if another infrared remote is
used in the same area.
February 1996 83
Fig.11: only one relay driver is shown here for simplicity but each of the receiver outputs
(A-H) requires a driver. Outputs A-F are momentary action, while G and H toggle.
PARTS LIST
Fig.12: very little
assembly is required on
the transmitter board.
Watch the polarity of
the infrared LED: its
anode leg is longer than
its cathode. Compare
the overlay with the
photograph at left.
8-Channel IR Transmitter
1 Magnavox handpiece (includes
455kHz resonator & IR LED)
1 PC board
2 AAA 1.5V batteries
Semiconductors
1 SM5021B encoder (IC1)
1 BC548 NPN transistor (Q1)
1 C8050 NPN transistor (Q2)
Capacitors
1 10µF 16VW PC electrolytic
capacitor
2 100pF ceramic capacitor
Resistors (0.25W, 1%)
2 1kΩ
1 4.7Ω
8-Channel IR Receiver
1 PC board
10 PC stakes
Semiconductors
1 SM5032B decoder (IC1)
1 PIC12043 IR receiver (IC2)
2 BC548 NPN transistor
(Q1,Q2)
1 6.2V 500mW zener diode (ZD1)
Capacitors
1 100µF 25VW PC electrolytic
1 10µF 16VW PC electrolytic
1 0.47µF monolithic ceramic
1 .001µF ceramic
Resistors (0.25W, 1%)
1 39kΩ
1 4.7kΩ
1 10kΩ
1 1kΩ
84 Silicon Chip
Fig.13: the receiver board for the
8-channel infrared remote is very
simple but take care to ensure that
none of the outputs are shorted, as
their holes are close together.
relay driver (as shown on the receiver
circuit) is necessary to interface each
output to the real world. So if you want
six momentary outputs, for example,
you will need six relay drivers.
The transmitter PC board is shown
in Fig.12 while the receiver board is
shown in Fig.13. These two PC boards
are easy to build as there are very few
parts. Additionally, there are no setting-up adjustments (apart from the
SC
coding links).
Kit Availability
These remote control kits are all available from Oatley Electronics, 51
Lansdowne Parade, Oatley West. Phone (02) 579 4985.
The prices are as follows:
Single channel UHF transmitter ..............$10.00
Single channel UHF receiver (2 relays) ...$36.00 (extra relays $3.00)
Two channel UHF transmitter ..................$18.00
Two channel UHF receiver ......................$26.00 (only 1 channel: $20.00)
Eight channel IR transmitter ....................$18.00
Eight channel IR receiver ........................$18.00
COMPUTER BITS
BY RICK WALTERS
Test your reaction time using a PC
Are you are one of those people who doesn’t
believe your reaction time is affected by “a drink
or three”. This simple reaction timer will correct
that perception once and for all.
This reaction timer uses a PC-compatible computer and a simple Basic
program to generate an audio cue and/
or a visual prompt via the screen. It
then measures the time delay before
a key on the computer’s keyboard is
pressed.
Alternatively, if you connect a
switch to the games port and fabricate the equivalent of a brake pedal,
you can compare your hand and foot
response times.
When the software is run, the screen
shows all the options that are available – see Fig.2. First, you can elect to
have the trigger stimulus as an audible
beep, a visual red rectangle or both.
Second, either the keyboard (for hand
reaction time) or the external switch
(for foot reaction time) can be selected.
And finally, you can choose between
a single reaction time display or have
the display show the last five reaction
times and their average.
The test is started simply be pressing
the spacebar. The program now generates the cue (or stimulus) at some
random time up to 10 seconds later,
after which you press the spacebar
again (or the foot switch) as quickly
as possible. Your reaction time in
milliseconds (a time of 160ms is pretty
good) is then displayed along the bottom of the screen.
If you press the spacebar before the
stimulus appears, the screen displays
the message “No cheating – wait for
stimulus”.
The program
We have elected to write the software in GW-BASIC, as virtually all
computers will have a copy supplied
with DOS. If you have Qbasic, you
may need to allocate the odd line
number for subroutines. A fully
compiled version of the program is
also available.
The full listing is almost two pages
long and the chances of errors creeping
in, if you have to type all the code, are
quite high. To overcome this problem,
we have listed the minimum code
which will allow you to measure your
reaction time.
This “simple” version provides
for keyboard reaction time only and
doesn’t display any screen options.
The full listing with all the options
and the fancy screen is available
from SILICON CHIP on a floppy disc,
This optional footswitch can be
made up from scrap material and
plugs into the games port of the
computer.
February 1996 85
The optional external foot switch is
connected to the games port via a
15-pin male D-connector. Note that
the Port A and Port B inputs are wired
in parallel.
This close-up view shows the switch mounting details, Virtually any heavy-duty
pushbutton switch with normally closed contacts can be used.
Fig.1: connect the leads to the
15-pin D-connector, as shown
here. The other end of the
cable goes to the switch.
along with the compiled version of
the program.
Minimum version
If you want the simple version only,
it’s just a matter of typing in the listing
published here. If this is the first time
you have attempted to enter a Basic
program, go back to the DOS prompt
(C:>), change to the DOS directory
(CD DOS), type GWBASIC and press
ENTER. The screen should read something like this:
Fig.2: the opening screen when the program is loaded. The test is started by
pressing the spacebar and waiting for the stimulus.
GW-BASIC 3.23
(C) Copyright Microsoft 1983 1984 (etc)
60300 bytes free
OK
The message on your machine may
vary slightly from that shown above,
depending on the particular version,
but if GW-BASIC is present you are
ready to begin.
Start by typing the first line at the
cursor; ie, 10 REM REACT1.BAS #1.0
R.W. 20/09/95. At the end of each line
86 Silicon Chip
Fig.3: the reaction time is listed immediately below the visual stimulus (if
selected). Pressing the Esc key allows you to change the operating setup.
press ENTER. Don’t worry if one or two
long lines get to the righthand edge of
the screen – just keep typing. The line
will wrap automatically.
When you have finished, or are tired
of typing, finish the current line, press
ENTER, then type “SAVE C:REACT1”,A
then press ENTER, or if using a different drive, substitute that drive letter
for C. Note that the “A” suffix saves the
file as ASCII text, so that you can read
it on a word processor. If this suffix
is omitted, the file would be saved in
GW-BASIC format which appears on
the screen as “garbage”.
To run the program while in Basic,
type RUN and press enter. If you have
made any typing errors, the program
will stop and give you a message telling you the line number where the
problem occurred.
The usual troubles are commas for
colons, one pair of quote marks omitted, or a missing bracket. You don’t
have to retype the line, just move the
cursor along with the right arrow, until
you reach the problem, overtype with
the correction and press ENTER. You
don’t even have to go to the end of
the line. To exit from Basic, just type
SYSTEM.
To run the program at a later time,
type GWBASIC REACT1. To quit the
program, you just press the END key.
Full version
As mentioned above, the full version of the software allows you to
select the games port, instead of the
keyboard, as the stimulus input. To
run the compiled (executable) version
of the program, type REACTION at the
DOS prompt. Alternatively, you can
run the program in Basic by typing
GWBASIC REACTION.
We made a foot pedal using a
heavy- duty pushbutton switch with
normally-closed (NC) contacts, a
right angle bracket, some bolts and
nuts, and a couple of pieces of timber
which were hinged at one end – see
photos. The connection to the games
port is made via a 15-pin male “D”
connector, with the leads from the
NC contacts of the switch wired as
shown in Fig.1.
Reaction Timer Listing (Simple Version)
10 REM REACT1.BAS #1.0 R.W. 20/09/95
20 GOSUB 1000 ‘Initialise
30 GOSUB 2000 ‘Generate random delay, store time1
40 GOSUB 3000 ‘Wait for keypress, store time2 calc. reaction time
100 GOTO 30 ‘Do it again
999 END
1000 ‘***********
1010 ‘INITIALISE.
1020 ‘***********
1030 DEFINT A-Z: DEF FNCENTRE$(M$) = SPACE$((80-LEN(M$))/2) + M$
‘Centre text
1040 KEY OFF: CLS: SCREEN 9: COLOR 8,3
1050 DEF FNR = CSRLIN: DEF FNC = POS(X): DEF FNCEOL$ = STRING$(79FNC,” “)
1060 DEFSTR E,K: ESC = CHR$(27): ENTER = CHR$(13)
1070 KEYSP = CHR$(32): KEYEND = CHR$(207)
1080 LOCATE 2,25: PRINT “SILICON CHIP REACTION TIMER”;
1099 RETURN
2000 ‘**********************
2010 ‘GENERATE RANDOM DELAY.
2020 ‘**********************
2030 M$ = “Press SPACE-BAR to test, END to finish”
2040 GOSUB 5030
2050 IF K = KEYEND THEN CLS: SYSTEM
2060 IF K < > KEYSP THEN 2040
2070 LOCATE 23,22: PRINT FNCEOL$;
2080 LOCATE 25,1: PRINT FNCEOL$;
2090 RANDOMIZE TIMER: RANDNO = INT((RND*10)/2) + 1
2100 DEF FNSEC = VAL(RIGHT$(TIME$,2))
2110 NEWSEC = (FNSEC + RANDNO) MOD 60
2120 WHILE FNSEC < NEWSEC: WEND
2130 TIME1# = TIMER: BEEP: RETURN
2199 RETURN
3000 ‘**********************
3010 ‘COMPUTE REACTION TIME.
3020 ‘**********************
3040 K = INPUT$(1)
3050 TIME2# = TIMER
3060 DELAY = CINT((TIME2# - TIME1#) * 1000) ‘milliseconds
3070 LOCATE 23,2: PRINT FNCEOL$;
3080 IF DELAY = 0 THEN LOCATE 23,25: PRINT “No cheating - wait for
stimulus!”;: GOTO 3099
3090 LOCATE 23,22: PRINT “Your reaction time was”;DELAY;”milliseconds”;
3099 RETURN
5000 ‘*******************
5010 ‘CLS & WRITE CENTRE.
5020 ‘*******************
5030 LOCATE 25,1: PRINT FNCEOL$;: LOCATE 25,1
5040 PRINT FNCENTRE$(M$);
5050 K = INKEY$: WHILE K = “”: K = INKEY$: WEND
5060 IF LEN(K) = 2 THEN K = CHR$(ASC(RIGHT$(K,1)) OR &H80)
5099 RETURN
Software availability
The compiled and Basic listings
of the full version of the program
(Reaction.exe and Reaction.bas) are
available on a floppy disc from Silicon
Chip Publications Pty Ltd, PO Box 139,
Collaroy 2097. The price is $A7 plus
$A3 p&p (Aust., NZ & PNG; $5 p&p
elsewhere).
Payment may be made by cheque
or money order. Alternatively, phone
(02) 9979 5644 with your credit card
details, or fax the details to (02) 9979
6503. Please indicate the disc size
required (either 3.5-inch or a 5.25inch).
SC
February 1996 87
VINTAGE RADIO
By JOHN HILL & RODNEY CHAMPNESS
The basics of reflex receivers
The reflex circuit gave many early valve radio
receivers a substantial performance lift without
the expense of an extra valve. Here, we take a
look at the reflex circuit & explain how it works.
Anyone who reads this column
regularly will know that I am only a
hobbyist with a keen interest in vintage
radio. I have had no formal training
in electronics and there are no letters
after my name. But such a situation
has been to my advantage.
Because I lack a lifetime of servicing experience and a deep theoretical
knowledge of radio, most of my stories
are, at best, only semi-technical in
content. However, this seems to be
about the right mix to hold the interest
of novice vintage radio repairers, of
which there are many.
When a collector friend, Rodney
Champness, suggested that I write
something on reflexing, my eyes glazed
over a little and I mumbled incoherently in reply. Although I know the
basic function of reflexing (using the
one valve to amplify both radio and
audio frequency signals simultaneously), writing a detailed account on the
subject is quite another matter.
This month, I would like to introduce Rodney to Vintage Radio readers
and allow him to explain the function
This timber cabinet Radiola Model 27 was the first of the
Radiolette series to use a reflex circuit. Reflex receivers
were common throughout the 1920s, 1930s and 1940s and
were particularly popular in Australia.
88 Silicon Chip
of reflexing. If he is well received
(excuse the pun), we may call on him
again for an in-depth study of another
subject.
Reflexing of domestic valve radio
receiver circuitry was more common
in Australia than in other countries
and was usually done to keep manufacturing costs down – particularly
the economy sets. One of the most
expensive components in early receivers was the valve and if the price
of a valve could be saved while still
retaining good performance, then it
was well worth the effort.
The reflex concept
A reflex circuit has both audio and
RF signals amplified in the one valve
at the same time. Reflexing will only
work where the two bands of frequen-
Another reflexed Radiolette receiver. Reflexing gave
a receiver a substantial performance lift without the
expense of adding another valve but the circuit had to be
carefully designed.
Left: this little Peter Pan 4-valve radio
is reflexed and its performance is
quite outstanding. It also has excellent
tonal quality for such a small receiver.
Below: the diminutive 4-valve Philips
Philette is a typical reflex receiver. It
may have been small but it gave big
performance for its size.
cies are significantly different from
each other.
In some early sets, it was possible
to find an RF valve acting also as the
first audio amplifier. In later superhet
reflex receivers, the IF valve would
amplify both the IF signal and do the
job of the first audio amplifier. In addition to this, the same valve could also
be supplying the AGC and detection
functions using its two inbuilt diodes
– quite a busy little valve!
Reflexing not only saved the cost
of a valve but in battery receivers it
saved LT (low tension) and HT (high
tension) current as well. However,
a reflex circuit can be quite a fickle
beast if the operating conditions are
not carefully selected.
Quite often, reflexed stages did not
use AGC as it would have upset the
audio gain, caused distortion or accentuated the minimum volume effect. In
reflex sets, the volume usually could
not be reduced to zero (minimum
volume effect) due to the compromise
operating conditions.
Reflexed stage valves also usually
had to be replaced more often than
valves in other stages, due to the
Fig.1: block diagram of a reflexed radio receiver. The reflexed
valve has a signal combiner at its input which combines the IF
and audio signals, the combined signal then being fed to the
valve for amplification.
operating conditions not being optimum in some designs. However,
these things aside, the reflex circuit
is fascinating, effective and not deserving of the bad PR that it seems to
suffer. A well-designed reflexed set
works well and is no more critical
of a valve’s condition than a set not
using reflex circuitry.
I have a couple of reflex sets, have
worked on many others and find them
no more tricky than conventional sets.
Don’t be afraid of them – they are just
another variation in design that sets
have had over the years.
To make things easier for those who
have had little experience with reflex
sets and find them hard to comprehend, the following may help to make
February 1996 89
combiner which in turn applies it to
the IF/audio valve. Here, the audio
signal is amplified and then fed to the
selective filter, after which it is fed to
the audio output valve. Basically, that
is all that occurs.
A practical circuit
The Astor “Football” was a 3-valve reflexed TRF receiver. The 6B8-G valve in
the little Astor provided RF and AF amplification plus detection, so it was quite
a busy little valve.
reflexing a little more under
stand
able.
Refer now to Fig.1 which is a block
diagram of a reflexed radio receiver.
The reflexed valve has a signal com
biner at its input. This combines the
IF and audio signals, the combined
signal then being fed to the valve for
amplification. From there, the amplified signal is fed to a circuit which
selects and directs the audio to the
audio output valve. Similarly, the IF
signal is selected and fed to a detector.
Following the detector, the RF is
filtered out and virtually pure audio
is applied to the signal combiner and
thus to the valve. The circuit that selects and directs signals of differing
frequencies in different directions
can be called a diplexer or a selective
filter. However, it may be easier to understand if it is explained as follows.
The IF signal is applied via the signal combiner to the IF valve, where it
is amplified and applied via a selective
filter to the detector. The IF (RF) signal is then removed and the virtually
pure audio is applied to the signal
Refer to the schematic diagram of
Fig.2. The valve used in the reflex
circuit was often a 6AR7-GT in the
octal days, while the 6N8 and 6AD8
were used more in the miniature valve
days. These particular examples are
duo diode variable mu pentodes.
In most cases, AGC is applied to the
valve, although generally at a lower
level than if it were to be used as a
straight IF amplifier. There are two
reasons for this. First, the valve may
be taken into an operating area where
its distortion is increased. And second,
with AGC applied to what is the first
audio valve, the volume may decrease
with an increase of signal level due to
the AGC action.
The IF signal is applied to the grid
in the normal way, although it will be
noticed that C1 is much smaller than
normal. It acts as a bypass for the IF
signal but has little effect on the audio
signal.
After amplification by the valve, the
IF signal is fed to the IF transformer primary as usual and by mutual
inductance into the secondary and
thence to a conventional diode detect
or. On the primary side, C8 is again
smaller than usual but still bypasses
the IF signal at the end of the transformer to earth.
Following the detector, the audio
Fig.2: a practical reflex circuit. The valve used was often a 6AR7-GT in the octal days, while the 6N8
and 6AD8 were used more in the miniature days
90 Silicon Chip
Fig.3: in some reflex sets,
the audio is taken from the
screen of the audio valve
instead of from the plate.
This circuit shows the
basic scheme.
K
ALEX
The UV People
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LIGHT BOXES
● Portuvee 4 ● Portuvee 6
● Dual Level
TRIMMER
signal with some IF signal imposed on
it is fed to the volume control via an
IF rejection filter. This stage consists
of a resistor-capacitor network and is
also used in non-reflexed sets.
Now the interesting things occur!
The audio level is picked off by the
moving arm of the volume control and
applied via C6 and R10 to the grid of
the IF valve as an audio signal. C1 has
little effect on the audio signal and the
secondary of the IF transformer has
even less effect.
The audio signal is now amplified
through the IF-cum-audio valve and
the amplified signal impressed across
plate load resistor R7. This gives an
alternating voltage which is applied
to C9 and thence through the network
to the grid of the audio output valve.
The audio signal is unaffected by the
primary of the IF transformer in the
plate circuit and capacitor C8 also has
little effect on this signal.
Note that many sets just apply the
signal from C9 direct to the grid of the
audio output valve. This is not a good
move although some manufacturers
did this and got away with it. In this
circuit, R8 and C10 act as an IF filter
to remove about 90% of the IF signal
left after the filtering by C8. It is important that the IF signal be reduced to
a low level as the audio output valve
will amplify IF signals as well and
these could easily feed back into an
earlier stage.
In addition, the output valve is driven harder than most other valves. If it
is amplifying unwanted IF as well as
audio signals, distortion/overload may
occur well before expected.
You will notice that R7 is much
smaller than normal for an audio amplifier such as this (the values used
are commonly 15kΩ, 22kΩ, 47kΩ
and 68kΩ). This is because the valve
must be run with a reasonably high
voltage on the plate for efficient IF
amplification. The audio amplification
is lower than normal at around 12-15
times but is sufficient for the output
valve to be driven quite hard, even
on weak stations. The screen resistor
value is within the normal range for a
valve used as an IF amplifier.
Not all reflex sets take the audio
from the plate circuit of the IF valve.
Some take it from the screen of this
valve instead. In this case, the RF
bypass capacitor is reduced to about
.001µF and the normal bypass capacitor is swung across to feed the grid
circuit of the audio output valve.
Fig.3 shows a skeleton circuit of
this. The plate circuit is as used in a
non-reflexed IF stage. The audio gain
remains much the same as for a reflex
ed amplifier using the plate circuit to
supply audio.
In Fig.2, there are two circuit points
marked “A” and “B”. If the “A” end of
capacitor C6 is lifted and attached to
“B” and C9 removed from that point,
the set will revert to non-reflexed operation. Of course, the audio gain will
be down as there will now be one less
audio stage in the receiver.
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Parts count
If you look carefully at the parts
used in a reflexed set and a set with
two normal audio stages, you will find
that there is very little difference in
the number of passive components.
The valve is really the only extra part.
As pointed out earlier in the article,
valves were much more expensive
than capacitors and resistors, so reflex sets had a small following right
throughout the valve era. However,
with the advent of the transistor, the
need to use reflex circuitry became unnecessary. Semiconductors are cheap
and using an extra transistor or so is
SC
no hardship.
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February 1996 91
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.
Power problems
in the boondocks
Living as I do right at the end of
SEQEB’s power grid, the continuity
of mains supply can best be described
as fortunate; ie, fortunate if it stays on
without ‘blips’ every 10 minutes or so.
I know exactly what’s going on at any
given blip; who’s just started which
irrigation pump, roughly how far away
and how intense the pending storm is
going to be and so on.
Trouble is, my PSU & motherboard
know all these things too ... which isn’t
exactly conducive to smooth computer
operations. Now whilst I’ve taken all
the normal steps to iron out most of
the spikes and blips on my mains feed
to the PSU & monitor, the inclusion of
a mains filter/surge buster is no match
for a ‘good’ blip, which might see the
mains voltage drop below 220VAC for
up to five seconds.
Obviously, what I really need is an
uninterruptible power supply (UPS
but the cost of such units relegates
them to the wish of dreams. Did you
ever do a UPS project by chance? If not,
would you consider doing so?
Whilst most folk who live in or
around a city might deem such things
as luxurious accessories, out here in
the country at the ends of the electrical
tendrils, they’re almost a necessity if
you run a computer. I imagine it’s a
Reversing switch for
Railpower Mk.1
I am using two Railpower Mk.1’s
(as published in the April & May
1988 issues of SILICON CHIP) on my
HO layout. I now require to add additional controllers, hence I would
like to upgrade to the Railpower
Mk.2. But . . .
I have a reversing loop and when
the loco is in the loop, I currently
flick from forward to reverse without slowing down, so that the loco
comes out of the loop reversed and
92 Silicon Chip
similar story in most other country
locations too.
The other thing I wanted to say was
about the model train projects, specifically, the sound simulator projects. I
used to have a model train layout in
my youth and wish I had all these new
sound effects and other doo
hickies
back then.
However, it occurred to me that
whilst you’ve presented projects for
whistles, horns, bells, diesel and steam
engine sounds, there’s no such project
to recreate the wonderful electric
whining of modern day real-life electric locos, especially the sound of the
traction engines as they back-EMF to
a halt. It’s not important as such, but
I figure if one never airs one’s ideas,
they might never get heard. I think
the sound of these big ’leccy motors
is really something else. I always sit
above a drive bogie when I travel by
train. (D. M., Rathdowney, Qld).
• We have not designed a UPS project.
We don’t really think it practical as the
kit would almost certainly be more
expensive than equivalent commercial
units, particularly when the cost of
batteries is included. In fact, we are
inclined to the view that if you have
unreliable power then you would be
better off with a laptop computer. That
might seem like an expensive luxury
but it really does solve the problem of
unreliable mains voltage.
at the same speed. It would seem
that this is not possible with the
Mk.2 without slowing down. Your
comments, please. (M.A. Ferntree
Gully, Vic).
• Your assumption is correct. The
Mk.2 must come to a stop before
changing direction. There is no
way this can be changed.
One possibility is to wire an additional changeover switch to alter
the track polarity while in the loop.
However, if this is not possible with
your layout, you will have to stay
with the Mk.1.
Sound effects really do add to model
railway operation but trying to simulate the sound of electric motors under
dynamic braking would be rather
tricky. It could be done but it would
probably require a microprocessor to
do it.
Using fax/modems
in computers
I use an external fax/modem (Net
comm AutoModem E7F) with my
586-75 PC. I am frustrated by the fact
that the PC must be left on in order to
receive faxes that I only expect once or
twice a month. Is it possible to make
a device to automatically switch the
PC on when an incoming fax signal is
detected? If not practical (due to boot
up time?), is there a way to drastically
cut power consumption of the PC in a
standby mode?
I also own a television without remote control but I am able to operate it
remotely via the VCR remote control,
except for muting. Is there a simple
single function IR transmitter and
receiver kit that could be put in the
audio line from VCR to TV to cut the
audio signal during commercials? (S.
G., Gooseberry Hill, WA).
• Apart from using one of the latest
PCs which has power management, we
cannot think of any easy way to overcome the delay in boot up each time a
fax call comes in. However, we suggest
that you at least turn the monitor off,
if you are not already doing so.
Check this month’s feature article on
remote controls. The single channel
version will do the job of switching
the audio line to your TV.
Modified Dolby decoder
has distortion
Help! I constructed the original
Dolby decoder published in December
1994 and it works fine. I now wish to
upgrade it by adding the power amplifiers described in the November & December 1995 issues. I have constructed
the power supply and three amplifiers
Woofer Stopper with
standard speakers
Will the Woofer Stopper described in the May 1993 issue of
SILICON CHIP work with normal
tweeters, normal woofers or stereo/hifi speakers? I thought that if
I could use one the hifi speakers,
I wouldn’t need to have an extra
speaker around my house. (J. M.,
Glen Huntly, Vic).
• You can use a conventional
speaker or tweeter with the original Woofer Stopper circuit but
we would not recommend it. For
a start, the current drain from the
according to the circuit diagrams but
when connected to the surround outlet
terrible distortion results! I have tried
several modifications to the input of
the LM1875, including the addition
of a 1MΩ resistor according to the
manufacturers’ recommendations, as
per page 212 of the Dick Smith catalog
circuit. I have fiddled around for some
hours now and am completely at a
loss to know what to do next. (A. W.,
Sunbury, Vic).
• The 1MΩ resistor is superfluous
in this situation. We suspect that the
earth connections are faulty. Note that
the original Prologic circuit had only a
single supply rail to op amp IC4. The
pin 11 supply connection was made to
ground. The Prologic Mk.2, however,
has a split supply for these op amps
(now IC4 and IC5).
Note that the surround power amplifiers IC8 and IC9 do not have their
signal earths connecting to the centre
input earth on the PC board. They were
earthed via the shielded cable. Ensure
that all earths are connected.
Jacob’s Ladder
has only one spark
I am having trouble with the Jacob’s
Ladder project as published in the
September 1995 issue. According to
the article, the spark should climb the
wires with one spark following the
other but no matter what I try I can
only get a single spark which climbs
to the top, and then starts at the bottom
again. I wonder if your technical staff
could suggest what I might have done
battery will be considerably higher
and you will probably need to fit
heatsinks to the Mosfets. Tweeters
would be better than just ordinary
speakers because of their improved
high frequency response. Don’t use
a low frequency driver (woofer)
because its response at 20kHz is
non-existent. In general though,
we strongly recommend that you
use only piezoelectric tweeters
because of their efficiency and low
current drain.
Note that the Woofer Stopper
Mk.2 described this month must
not be used with conventional
speakers or tweeters.
wrong to cause this problem. (A. P.,
Wingham, NSW.
• As outlined in the text, there is only
one spark discharge at any one time
although the sparks are produced at
about 130 per second. As you have
found, the spark discharge starts at the
bottom and then climbs up and then
restarts at the bottom again.
Earth loop in VCR/
stereo connection
I have a video and TV setup next to
my hifi unit. I would like to connect
a cable from the audio output of the
video player to an input on the amplifier. It seemed straightforward enough
until I tried it. I was rewarded by a
good audio signal and a lot of hum. I
haven’t measured it but I am sure it’s
mains hum. The only way to stop this
hum is to disconnect the TV antennas.
What do I do?
On another question, I have analog
and digital multimeters but neither
of them has a battery testing setting
on them. I believe batteries should be
tested under load. What is a good load
and what voltages should be expected
for a good cell? G. E., Armidale, NSW).
• It seems likely that both your VCR
and TV set are double-insulated but
the antennas (or masthead amplifier)
are earthed; hence the earth loop involving your earthed stereo system.
The way around this is to break the
earth connection in the antenna cable
to your VCR and this can be effectively
done with a 1:1 balun. You can wind
this yourself using a balun and a few
If you are seeing a blank
page here, it is
more than likely that it
contained advertising
which is now out of date
and the advertiser
has requested that the
page be removed to
prevent
misunderstandings.
Please feel free to visit the
advertiser’s website:
www.ozitronics.com
Silicon Chip Binders
These beautifully-made binders will
protect your copies of SILICON CHIP.
They are made from a distinctive
2-tone green vinyl & will look great
on your bookshelf.
Price: $A11.95 plus $3 p&p each
(NZ $8 p&p). Send your order to:
Silicon Chip Publications
PO Box 139
Collaroy Beach 2097
Or fax (02) 9979 6503; or ring (02)
9979 5644 & quote your credit card
number.
February 1996 93
turns of light gauge enamelled copper
wire for each winding.
As far as battery testing is concerned, the ideal load for a particular
battery really depends on your application. A battery intended for use in a
torch will have a far greater operating
load (and high current demand) than
one intended for use in a remote control handpiece. In practice, a useful
load for typical single cells and 9V
batteries is one which draws about
a watt or so.
Hence, for a single AA cell, you
would need a resistor of about 2.22.7Ω, with perhaps lower values for
C and D size cells. In fact, a good D
cell should comfortably deliver 1A or
more for a short period.
Under the above load condition, a
1.5V cell should deliver at least 1.2V;
the more, the better.
For a 9V transistor battery, the load
should draw about 100mA and this
means a resistor of around 82Ω. Under
these conditions, we would expect a
good battery to deliver at least 7.5V;
again, the more, the better.
By the way, these load tests should
only be applied for a few seconds or
so; anything more will needlessly
SC
discharge the battery.
SILICON CHIP SOFTWARE
Now available: the complete index to
all SILICON CHIP articles since the first issue in November 1987. The Floppy Index
comes with a handy file viewer that lets
you look at the index line by line or page
by page for quick browsing, or you can
use the search function. All commands
are listed on the screen, so you’ll always
know what to do next.
Notes & Errata also now available:
this file lets you quickly check out the
Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index
but a complete copy of all Notes & Errata text (diagrams not included). The file
viewer is included in the price, so that you can quickly locate the item of interest.
The Floppy Index and Notes & Errata files are supplied in ASCII format on a
3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File
Viewer requires MSDOS 3.3 or above.
ORDER FORM
PRICE
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Notes & Errata (incl. file viewer): $A7
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Alphanumeric LCD Demo Board Software (May 1993): $A7
❏
Stepper Motor Controller Software (January 1994): $A7
❏
Gamesbvm.bas /obj /exe (Nicad Battery Monitor, June 1994): $A7
❏
Diskinfo.exe (Identifies IDE Hard Disc Parameters, August 1995): $A7
❏
Computer Controlled Power Supply Software (Jan/Feb. 1997): $A7
❏
Spacewri.exe & Spacewri.bas (for Spacewriter, May 1997): $A7
❏
I/O Card (July 1997) + Stepper Motor Software (1997 series): $A7
Notes & Errata
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94 Silicon Chip
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Street ___________________________________________________________
Prologic Surround Sound Decoder
Mk.2; November & December 1995:
The +5V and GND connections for
the microprocessor board (01409954)
are shown transposed on the overlay
diagram on page 72 of the December
issue. The wiring diagram on page 74
of the same issue needs to be altered
so that wire “26” goes to the left pin
while the wire from the power supply board goes to the right pin. Wires
shown connecting to switch S4 are
correct. Also, the reference to IC4 in
the 7th line, third column on page 78
should be to IC6.
Subwoofer Controller, December
1995: the circuit diagram on page 40
should show R34 directly connected
to +12V to agree with the PC board
overlay diagram on page 41; R34 does
not connect to R7, C5 and pin 8 of
IC2a as shown on the circuit. While
the board will work, it ideally should
be altered to agree with the circuit. D1
& D2 on the same board diagram are
shown transposed although this has
no effect on circuit operation.
SC
MARKET CENTRE
Cash in your surplus gear. Advertise it here in Silicon Chip.
ETI PIC Basic Interpreter: BASIC57/
XT/P $45, BASIC84/04/P $45. 2K EEPROM $8, 8K EEPROM $16. PC serial
port driven. 18 and 28-pin PCB to suit
$20, MAX-232 $10, 4MHz Xtl $5. Windows Software free. P&P $3. Visa-MCBC. Fax (03) 9338 2935. Don McKenzie,
29 Ellesmere Cr., Tulla
marine 3043.
Phone (03) 9338 6286
SATELLITE DISHES: international
reception of Intelsat, Panamsat, Gori
zont,Rimsat. Warehouse Sale – 4.6m
dish & pole $1499; LNB $50; Feed $75.
All accessories available. Videosat, 2/28
Salisbury Rd, Hornsby. Phone (02) 482
3100 8.30-5.00 M-F.
START WITH A MicroZed KIT then
when your "test the market" small run
project hits the big league, MicroZed
can help with alternative schemes and
quantities ex stock at the right pricing.
68HC705 DEVELOPMENT SYSTEM:
Oztechnics, PO Box 38, Illawong, NSW
2234. Phone (02) 541 0310, fax (02) 541
0734. Email: info<at>oztechnics.com.au
WWW: http://www.hutch.com.au./~ozt
ech/index.htm.
EDUCATIONAL ELECTRONIC KITS:
Easy to build. Guaranteed to work.
Good quality. Latest technology. Cheap.
Good selection. LESSON PLANS
FOR TEACHERS. Send $2 stamp for
catalogue and price list. Log onto our
bulletin board for full details. DIY Elect
ron
ics, 22 McGregor St, Numurkah
3636. Ph/Fax (058) 62 1915. E-Mail: laurie.c<at>cnl.com.au BBS (058) 62 3303.
NEW SPRINKLER CONTROLLER
KITS: RAIN BRAIN version uses ‘C8
and switch mode supply. Features galore!! Contact Mantis Micro Products,
38 Garnet St, Niddrie 3042. Phone/fax
(03) 337 1917.
CLASSIFIED ADVERTISING RATES
Advertising rates for this page: Classified ads: $10.00 for up to 12 words plus 50
cents for each additional word. Display ads (casual rate): $25 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale.
To run your classified ad, print it clearly in the space below or on a separate
sheet of paper, fill out the form & send it with your cheque or credit card details
to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details
to (02) 979 6503.
_____________ _____________ _____________ _____________ _____________
_____________ _____________ _____________ _____________ _____________
_____________ _____________ _____________ _____________ _____________
_____________ _____________ _____________ _____________ _____________
_____________ _____________ _____________ _____________ _____________
_____________ _____________ _____________ _____________ _____________
✂
FOR SALE
_____________ _____________ _____________ _____________ _____________
_____________ _____________ _____________ _____________ _____________
Enclosed is my cheque/money order for $__________ or please debit my
RCS RADIO PTY LTD
❏ Bankcard ❏ Visa Card ❏ Master Card
Card No.
Signature__________________________ Card expiry date______/______
RCS Radio Pty Ltd is the only company that manufactures and sells every
PC board and front panel published
in SILICON CHIP, ETI and EA.
RCS Radio Pty Ltd,
651 Forest Rd, Bexley 2207.
Phone (02) 587 3491
Name ______________________________________________________
Street ______________________________________________________
Suburb/town ___________________________ Postcode______________
February 1996 95
MICROCRAFT PRESENTS: Dunfield
(DDS) products are now available exstock at a new low price; please ask for
our catalogue. Micro C, the affordable
“C” compiler for embedded applications.
Versions for 8051/52, 8086, 8096,
68HC08, 6809, 68HC11 or 68HC16
$139.95 each + $3 p&h • Now on special is the SDK, a package of ALL the
DDS “C” compilers for $399 + $6 p&h •
EMILY52 is a PC based 8051/52 high
speed simulator $69.95 + $3 p&h • DDS
demo disks $7 + $3 p&h • VHS VIDEO
from the USA (PAL) “CNC X-Y-Z using
car alternators” (uses car alternators as
cheap power stepper motors!) $49.95
+ $6 p&h (includes diagrams) • Device
programming EPROMs/PALs etc from
$1.50 • Fixed price electronic design and
PCB layout • Credit cards accepted • All
goods sent certified mail • Call Bob for
more details. MICROCRAFT, PO Box
514, Concord NSW 2137. Phone (02)
744 5440 or fax (02) 744 9280.
COMPLETE WORKSHOP PROGRAM:
suit IBM compatible 386 or better computer. Handles: Stock Control, Sales,
Service Records, Debits, Credits, Faults,
Service Manuals and Phone Directory.
PCB ASSEMBLY SPECIALISTS
·ALL FACETS OF THRU-HOLE & SMT ASSEMBLY
· ALL BATCH SIZES CATERED FOR · HIGH QUALITY
BRM ELECTRONICS
Highest a
quality at able
PO Box 727, Narrabeen NSW 2101.
on
ry
ve reas
price
Ph/Fax: 9948 8807 Mobile: 015 101 682
MicroZed Computers
To order or enquire:
PO Box 634, ARMIDALE 2350. (296 Cook’s Rd)
Ph (067) 722 777
Fax (067) 728 987
Mobile (014) 036 775
Credit Cards OK
MEMORY * DRIVES * MODEMS
SPECIAL! (Incl Tax)
1Mbx9 – 70ns Simm $60
1Mbx9 – 80ns Simm $45
SIMMS
(Parity/No Parity)
4MB 30 PIN-70 $179 $185
4MB 72 PIN-70 $177 $148
8MB 72 PIN-70 $353 $303
16MB 72 PIN-70 $695 $605
32MB 72 PIN-70 $1389 $1210
EDO SIMMS
4MB (1Mbx32)-70ns $198
8MB (2Mbx32)-70ns $370
MAC
8MB P’BOOK $437
VIDEO MEMORY
256KX16 70ns (SOJ) $24
256KX16 70ns (ZIP) $58
LASER PRINTER MEMORY
HP 2MB UPGRADE
$156
CO-PROCESSORS
80387SX/DX to 40MHz $90
COMPAQ
8MB CONTURA AERO $445
TOSHIBA PORTEGE/SATELLITE
8MB / 16MB
$650 / $1218
DRIVES SEAGATE
850MB EIDE 11ms 3yr $325
1080MB EIDE 10.5ms 3yr $360
2150MB SCSI 9ms 5yr $1033
MODEMS (Includes Sales Tax)
14,400 BANKSIA 5yr W $283
14,400 SPIRIT 2yr W $203
28,800 BANKSIA V.FC $321
28,800 SPIRIT V.34/V.FC $410
Phone for other products not listed
EX TAX PRICING AS AT JANUARY ‘96
Sales Tax 22%, O/Night Delivery $8. Ring For Latest Prices.
Credit Cards Welcome. We Also Buy And Trade-In Memory.
PELHAM
Ph: (02) 9980 6988
Fax: (02) 9980 6991
Suite 6, 2 Hillcrest Rd, Pennant Hills, 2120.
Full price $399.00. For demo disk, phone
or fax your details to (045) 71 1640.
Jack Albers Electronics & Software
Development.
MicroZed HAVE LARGE STOCKS of
easy to use and easy to learn controller
boards with on board interpreters. Ideal
for one offs and small run production.
Altronics ....................................IFC
Av-Comm.....................................58
Avico Electronics...........................9
BRM Electronics..........................95
Car Projects Book....................OBC
Defence Force Recruiting............31
Dick Smith Electronics........... 18-21
Emona.........................................73
Harbuch Electronics....................75
Jaycar ................................... 45-52
Kalex............................................91
Kits-R-US.....................................59
Macservice........................3, 59, 75
MicroZed Computers...................96
Oatley Electronics.................. 34-35
Ozitronics.....................................93
Pelham........................................96
Railway Projects Book...............IBC
RCS Radio ..................................95
SERVICE & REPAIRS
PATRA ELECTRONICS: assembly and
repairs of all kits. Repairs of electronic
equipment. Call Peter on 02 718 1202
or 015 215957.
NEW Micro
Rod Irving Electronics .......... 67-71
Scan Audio..................................74
Silicon Chip Bookshop.................53
Software Sales House.................94
Tortech.........................................91
_________________________________
PC Boards
68HC11 F1 boards and now 80535 (up spec 8051)
both boards with BASIC, FORTH, ASM, Small C
80535 board has 8052AH INTEL BASIC installed
Printed circuit boards for SILICON
CHIP projects are made by:
24 I/O expansion board now in stock for both boards
• RCS Radio Pty Ltd, 651 Forest
Rd, Bexley, NSW 2207. Phone (02)
587 3491.
Versa Tech
BASIC Stamp I and II
TICkit – a 21 I/O PIC based controller
Scott Edwards Electronics
Get your project on the way in hours, not months.
Accessories for Stamp and second source for Stamp 1
Recently developed accessories now available
Advertising Index
Send two 45c stamps for information package
• Marday Services, PO Box 19-189,
Avondale, Auckland, NZ. Phone (09)
828 5730.
Microprocessors For Silicon Chip Circuits
We have stocks of the 68HC705-C8P pre-programmed microprocessor ICs for the Digital Effects Unit (February 1995) and
the Remote Controlled Stereo Preamplifier (Sept.-Oct. 1993). Also available is the pre-programmed Z86E08 microprocessor
for the Railpower Mk.2 Model Railway Controller.
Price: 68HC705-C8P – $45 ea; Z86E08 $18 ea.
Price includes postage.
Payment by cheque, money order or credit card to:
Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097.
Phone (02) 9979 5644; Fax (02) 9979 6503.
96 Silicon Chip
Especially For
Model Railway
Enthusiasts
Order Direct
From
SILICON CHIP
Order today by phoning (02) 9979 5644 & quoting your credit card number;
or fill in the form below & fax it to (02) 9979 6503; or mail the form to
Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097.
This book has 14 model railway
projects for you to build, including
pulse power throttle controllers,
a level crossing detector with
matching lights & sound effects,
& diesel sound & steam sound
simulators. If you are a model
railway enthusiast, then this
collection of projects from SILICON
CHIP is a must.
Price: $7.95
plus $3 p&p
Yes! Please send me _______ copies of 14 Model Railway Projects
Enclosed is my cheque/money order for $_________ or please debit my
Bankcard Visa Card Master Card
Card No.
Signature_________________________ Card expiry date_____/_____
Name _________________________Phone No (____)_____________
PLEASE PRINT
Street ___________________________________________________
Suburb/town __________________________ Postcode____________
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