This is only a preview of the March 1996 issue of Silicon Chip. You can view 28 of the 96 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Articles in this series:
Articles in this series:
Items relevant to "Programmable Electronic Ignition System For Cars":
Items relevant to "Automatic Level Control For PA Systems":
Articles in this series:
Items relevant to "A 20ms Delay For Surround Sound Decoders":
Articles in this series:
|
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which is now out of date and the advertiser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.3; March 1996
Contents
DISCOVER HOW THESE IMPORTANT
TEST INSTRUMENTS WORK – PAGE 12
FEATURES
4 Traction Control: The Latest In Car Technology
Traction control offers important new advances in vehicle safety and dynamics and
some manufacturers already have systems that work in conjunction with ABS. We
take a look at how it works – by Julian Edgar
12 Cathode Ray Oscilloscopes, Pt.1
Learn how these important items of test equipment work! This first article in the
series looks at analog oscilloscopes and describes how they operate – by Bryan
Maher
PROJECTS TO BUILD
22 Programmable Electronic Ignition System For Cars
Program your own ignition advance curve with this simple system. It can be easily
added to the “Silicon Chip” High Energy Ignition System – by Anthony Nixon
32 A Zener Diode Tester For Your DMM
Plug this simple adapter into your DMM to directly read the values of zener diodes.
It covers the range from 2.2V to 100V – by John Clarke
42 Automatic Level Control For PA Systems
Keep the volume from your PA system at a constant level with this easy-to-build
system and forget about riding the gain control – by John Clarke
60 A 20ms Delay For Surround Sound Decoders
Add this to your surround sound decoder for more realistic rear channel sound. It
uses just one IC and a handful of other parts – by John Clarke
84 Build A Simple Battery Tester For Around $5
The recipe is simple: take one green tester strip from a Mallory® battery pack, add a
battery clip, a case, and a sprinkling of nuts and bolts – by John Clarke
PROGRAMMABLE IGNITION SYSTEM
FOR CARS – PAGE 22
ZENER DIODE
TESTER
PLUGS INTO
YOUR DMM
– PAGE 32
SPECIAL COLUMNS
48 Serviceman’s Log
Sound reasons for confusion – by the TV Serviceman
54 Remote Control
Multi-channel radio control transmitter; Pt.2 – by Bob Young
74 Computer Bits
Electronic organisers & your PC – by Geoff Cohen
77 Satellite Watch
The latest in satellite TV reception – by Garry Cratt
86 Vintage Radio
A console with a difference – by John Hill
AUTOMATIC LEVEL CONTROL FOR
PA SYSTEMS – PAGE 42
DEPARTMENTS
2 Publisher’s Letter
3 Mailbag
40 Circuit Notebook
63 Order Form
64 Bookshelf
80 Product Showcase
92 Ask Silicon Chip
95 Market Centre
96 Advertising Index
March 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: $55 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
Selling Telstra is the
wrong move
So Telstra is to be sold off. Regardless of
the election outcome this month, it seems
that the sell-off of Telstra is a certainty. Both
the Labor and Liberal parties appear to be
mesmerised by the huge amount of cash that
Telstra will realise. The estimates range from
24 billion to around 40 billion. In the face
of that sort of money and the need to reduce Government deficits, there
does not appear to be much prospect of a careful analysis of the costs and
benefits of such a sale. We’ve seen Qantas sold, the Commonwealth Bank
sold and Telstra is likely to be next cab off the rank.
The really bad aspect of selling off Telstra now is that telecommunications
is one area of the economy guaranteed to have huge growth over the next 10
years or more. So if Telstra is worth a motsa today, it’s going to be worth a
great deal more in years to come. But if the Government sells it off now, it
won’t get the benefits of that growth; it won’t get the dividends and it won’t
have the asset. Sure, it will get tax revenue on the profits but somehow I
don’t think that will amount to anywhere near as much.
Moreover, if Telstra is sold, you can bet that many of the factors which
have prevented it from raising its charges or which force it to provide service
in uneconomic sectors will no longer apply. Timed local calls (for everyone)
are a certainty. After all, if Government controls still apply to an asset to be
sold, that would reduce the asking price, wouldn’t it? You can also bet that
a fully privatised Telstra would reduce its workforce even further and that
will have undeniable costs to the Government budget. And let’s not forget the
considerable benefits that flow to Australian industry because Telstra is such
a large buyer in the marketplace. Would that continue after Telstra becomes
controlled by an overseas company? Oh, I haven’t mentioned that, have I?
If you are unhappy about Telstra being sold off but think it might be
worthwhile because of good effects on the budget or maybe the environment,
as envisaged in the Liberal Party policy, then think about overseas control.
Qantas is now controlled by an overseas company; ie, British Airways. With
$40 billion as the asking price for Telstra, it’s highly likely that an overseas
corporation will be the major buyer. Do we really want to see that happen?
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
MAILBAG
Software piracy protection
As you would no doubt be aware,
software piracy is costing legitimate
publishers millions, perhaps hundreds of millions, of dollars annually
in lost earnings.
I have devised a scheme for
copy-protecting software which could
help reduce this problem.
My scheme is based on the concept
of laser marking floppy discs with an
encoding process so that software is
usable only if installed from the original
disks. Special user-installed hardware,
such as a dongle, is not required.
I have applied for a patent and
would like to offer licences with options for the Australian and foreign
patent rights to interested parties.
Specially designed laser marking
equipment is required, so I would prefer to negotiate with a company with
design expertise in that area.
To the best of my knowledge, my
scheme is novel, although I am aware
of a system which involves laser marking CD ROMs. If anyone knows of a
similar system which applies to floppy
discs, I would greatly appreciate them
informing me, either directly or via
your magazine.
H. Nacinovich,
63 Belmore St, Gulgong,
NSW 2852.
Outboard motor electronics
I enjoy reading Silicon Chip every
month and using any informa
tion
from it that interests me. I am writing
to ask if it is possible for you to run
a series of articles on outboard motor
electronics, the same way as you do
with car engines?
M. Bougourd,
Hamersley, WA.
More tips on making PC boards
In one of my recent letters to you I
mentioned the article in April 1995
Silicon Chip p.7 on “photocopies for
PC boards”. I have found that a much
better method is to iron on the reverse
photocopy but it must be removed
while hot. This puts a nice print on
the copper and if you sharpen a felt
tip pen (water resistant ink) with a
balsa knife, the tracing can be gone
over accurately and quickly. My PCB
was a lovely job. Forget the thinners.
D. Schofield,
Caloundra, Qld.
Delay a tad longer than 20ms
After seeing your Surround Sound
Mixer & Decoder in Silicon Chip January 1996 it was just what I wanted,
particularly when you mentioned that
you would be describing a 20ms delay
unit in the February issue.
So I built the unit, waiting for the
next issue of Silicon Chip: no appearance, Your Worship. I think that you
should at least stick to your guns.
I have been waiting now 3 weeks
for this issue, now another four weeks
before the next issue before I can finish
it off. I am not at all happy with this
situation, as it is not the first time this
has happened.
K. Lloyd,
Sth Tweed Heads, NSW.
Comment: as you will have noted, the
20ms Delay is in this issue .
And another anniversary
The 12th July, 1996 marks the 90th
anniversary of the first overseas wireless message sent from Australia.
The enclosed photograph (reproduced below) shows a cairn which
marks the spot from where the messages were sent, near Point Lonsdale,
at the southwest corner of Port Phillip
Bay, Victoria.
The cairn is on the footpath in Port
Lonsdale Road, near Lawrence Road,
but is not visible from the road because
of the presence of a high hedge along
the edge of the footpath.
At Wahroonga, NSW (cnr Stuart and
Cleveland Sts), there is an even more
impressive and imaginative memorial
marking the spot where early wireless
transmissions took place.
John Richardson,
West Pymble, NSW.
70 years of electric trains
Readers who recall Bryan Maher’s
series of articles entitled “The Evolution of Electric Railways” from the
first issue of “Silicon Chip”, until
1990, may be interested to know that
1st March, 1996 will be the 70th Anniversary of the first electric train in
revenue service in Sydney.
This was a very significant event of
70 years ago. What would Sydney be
like if that first electric train had not
entered service and without the technology that was developed for electric
trains? (And would have Silicon Chip
have had such a fine series of articles
to kick the magazine off?)
What is remarkable is that one of
the cars from that first train has been
preserved and is fully operation
al.
Some of the technology that was
developed in the 1920s is still in use
today – which is just as remarkable!
So why let this event pass unnoticed? The Sydney Electric Train Society intends marking the event with
the assistance of CityRail.
P. Maljevac,
Sydney Electric Train Society Inc.,
Broadway, NSW.
The inscription on the bronze
plaque reads:
"FROM THIS SPOT ON TWELFTH JULY
1906 THE FIRST OVERSEAS WIRELESS
MESSAGES FROM AUSTRALIA
WERE SENT BY LORD NORTHCOTE,
GOVERNOR GENERAL. SIR R TALBOT,
GOVERNOR. HON A DEAKIN, PRIME
MINISTER. HON A CHAPMAN,
POSTMASTER-GENERAL.
HON RA COUCHMAN, MP FOR CORIO.
EQUIPMENT SUPPLIED
AND OPERATED BY
MARCONI WIRELESS PTY LTD"
March 1996 3
The Volkswagen Golf VR6 has an
engine power of 128kW channelled
through the front wheels. It uses
a traction control system where
individual front wheels are braked.
s
ic
m
a
n
y
D
&
y
t
afe
S
e
l
c
i
h
e
V
n
I
ces
Advan
Traction Control
Traction control was first used in
heavy locomotives but is now applied
to vehicles as diverse as heavy trucks
and small front-wheel drive cars. Until
recently, it was also used in Formula 1
racing as an aid to handling.
By JULIAN EDGAR
4 Silicon Chip
Why have traction control? The
need for traction control is based on
the idea that a driven wheel that is
slipping excessively is not providing
the maximum possible power transfer
to the road surface. However, completely preventing slip is not the aim;
some slippage actually increases the
tractive force obtainable.
On dry road surfaces, the maximum
accelerative force is available at slip
rates of between 10% and 30%, while
on loose sand and gravel the coefficient of accelerative force continues
to increase with slip rate, with the
Wheel speeds are sensed through the use of a toothed tone
wheel and an inductive pick-up. The same sensors usually
provide information for the anti-lock braking and the traction
control systems.
maximum being achieved at a slip rate
of more than 60%!
Traction control systems usually
work within the slip range of 2-20%
and so will not provide adequate
traction under all conditions. For this
reason, most systems can be disabled
with a dash-mounted switch.
Wheel spin may occur on icy,
muddy or gravel surfaces, where the
coefficient of friction between the tyre
and the road surface is low. It may be
as a result of an increase in engine
Electronic control of the throttle position is already
carried out in some cars, using this geared motor.
Integrating a traction control system which uses
throttle control can therefore be carried out more
easily in certain cars.
torque being unable to be transmitted
through the tyre to the road surface,
as a result of too great a retardation
through excessive engine braking, or
as a result of large cornering and propulsive loads simultaneously being
transferred to the wheels.
Spinning drive wheels cause
problems because they: (a) inhibit
propulsion; (b) create handling instability because they can transmit little
cornering force; and (c) lead to a high
rate of wear on the tyres and drive
mechanicals, especially when they
pass onto a high friction surface and
suddenly stop spinning.
Control methods
A number of approaches can be
taken to limit wheel spin. The most
obvious is that the engine torque output can be reduced by partially closing
the throttle. This is easily done in cars
using an electronical
ly controlled
throttle butterfly (“drive-by-wire”) but
the reaction time using throttle control
Fig.1: the layout of the Vehicle
Dynamics Control system. In addition
to the sensors required for ABS/ASR
operation, sensors for vehicle yaw,
lateral acceleration and steering
angle are also used (photo:
Bosch).
March 1996 5
A combined anti-lock braking and traction control system for a commercial
vehicle: (1) wheel speed sensors; (2) ABS/ASR electronic control unit; (3)
pressure control valve; and (4) solenoid valve.
alone is slow. In diesel engines, the
amount of injected fuel can be reduced
to achieve torque reduction, while in
turbocharged engines, boost pressure
can be controlled.
In petrol engines, the ignition
system can be used to very quickly
reduce the engine’s output. The
spark advance angle can be altered
or ignition pulses can be suppressed,
causing a “miss”. However, an engine
running with either excessive ignition
retard or a deliberate misfire can produce excessive exhaust emissions and
can have high exhaust gas temperatures. The latter is the case because
the unburnt charge may ignite in the
exhaust port!
Simultaneous suppression of the
fuel injector operation can be carried
out to reduce these problems. The suppression of fuel injector signals will
also cause a misfire and a consequent
reduction in engine torque. Injector
cutoff is often used on a rotating basis,
6 Silicon Chip
with a cylinder shut off for a single cycle or “half” a cylinder shut off by the
deactivation of a cylinder every other
720° cycle. This maintains engine
smoothness and minimises crankshaft
torsional stresses.
The brakes can also be applied to
the spinning wheel to slow it until its
speed matches that of the non-driven wheels. By using this approach,
the existing ABS (anti-lock braking
system) hydraulic hardware can be
utilised, with some hardware additions to cater for the extra traction
control function.
Truck traction control
An example of a traction control
system is the Bosch unit used on trucks
and other heavy vehicles. It is integrated with the ABS system, making
use of the ABS wheel speed sensors
and hydraulic control unit. It uses a
mix of engine intervention and brake
application to control wheel spin.
The Traction Control System (ASR
in Bosch-speak) monitors the speed
of the powered and unpowered
wheels and recognises when a wheel
is tending towards spinning. At this
time, a dashboard light is illuminated,
warning the driver of the presence of
slippery conditions.
The system controls the wheel speed
of the powered wheels by two means:
(1) Brake control – at speeds up to
30km/h, if a powered wheel is tending
towards spinning it is braked and the
speeds of the driven wheels synchronised.
(2) Engine control – if both powered
wheels are losing traction, the torque
of the engine is reduced. At speeds
above 30km/h, the spinning of either
of the wheels is also prevented by a
reduction in engine output.
In addition to the braking and engine torque reduction approaches,
trucks with air suspension on the leading or trailing axles can have the load
on the powered axle briefly increased
by up to 30%.
This occurs when the traction control system relieves the non-powered
Some Mercedes models use the sophisticated Vehicle
Dynamics Control, where any of the four individual wheels
are braked to aid car stability during cornering. Sensors for
yaw, steering angle and lateral acceleration are amongst
those used.
Above & right: the hydraulic control unit of a Bosch 2E
ABS/ASR system. The electronic control unit (seen at
right) uses hybrid circuits on a ceramic substrate and is
combined with the hydraulic control unit.
March 1996 7
Traction Control In Action
WITHOUT TRACTION CONTROL
WITH TRACTION CONTROL
1
4
2
5
3
6
This amazing sequence of photos showing the affect
of the Vehicle Dynamics Control system, with the car
cornering on a skid pan at high speed. Picture 1 shows
the car understeering off line, mowing down the cones.
By picture 2, the front outside tyre is giving off smoke as
the car slides across the track in plough understeer. In
Picture 3, it can be seen that the car is more than its own
axle of its load by bleeding its air
suspension bellows.
Car traction control
Powerful front wheel drive cars
can have major wheel-spin problems, especially when accelerating
from standstill. This is especially so
because limited slip differentials are
uncommon in FWD cars, because of
the excessive torque reaction which
would be felt through the steering
wheel during differential lockup. The
Volkswagen Golf VR6 uses a traction
control system dubbed an Electronic
8 Silicon Chip
width outside the appropriate cornering line. The righthand sequence (pictures 4-6) shows the same corner, same
speed and same car – but with the VDC system operating.
The amount of front wheel slip angle remains the same,
as shown by the tyre smoke and amount of steering lock
being used. But because the lefthand rear wheel is being
braked, the car follows the chosen line.
Differential Lock (EDS in German).
The system uses only brake intervention to slow the spinning wheel.
As with the truck system discussed
above, EDS largely uses components
already in place for ABS. The ECU
continuously compares the speed of
the front wheels, using appropriately placed sensors. If the difference
in speed is greater than 110RPM,
the slipping wheel is braked until it
reaches approximately the speed of
the non-slipping wheel. The system is
activated until a road speed of 40km/h
is reached, whereupon the effect of
the system is gradually reduced. EDS
also works in reverse gear, which may
be desirable for those with very steep
driveways!
In very slippery conditions, the
possibility exists that excessive brake
temperatures may be realised – remember, this system doesn’t reduce
the engine output. The electronic
control unit continuously monitors
the duration and frequency of EDS
operation, with the probable temperature of the braking components
calculated from these factors. When
a preset level is reached, the EDS
Fig.2: the VDC system controls understeer and oversteer by braking one of the wheels (photo: Bosch).
system is disabled, although the ABS
remains fully functioning.
The system is very effective when
one wheel is on a much more slippery
surface than the other. In fact, with the
left-hand wheels on dry tarmac and
the right-hand wheels on a wet and
icy road, a non-EDS Golf is able to
transfer a drive force of 692 Newtons
to the road, while an EDS-equipped
car in identical circumstances can
transfer 3112 Newtons – nearly 4.5
times as much.
Interestingly, the VW EDS system
can be retrofitted to recent ABS Volks
wagens, with an additional valve block
used on the hydraulic control unit
and a new ECU used together with a
redesigned wiring harness.
Vehicle dynamics control
This system, currently fitted to some
Mercedes cars, is designed to prevent
skidding during cornering. Unlike
ABS and ASR, Vehicle Dynamics Control (VDC – I love all these acronyms!)
can be activated even when the car is
free-wheeling and when the driver is
neither deliberately braking or accel-
erating. Fig.1 shows a schematic of the
system layout.
While anti-lock brakes and traction
control prevent longi
tudinal wheel
slippage, VDC attempts to prevent
lateral slip, particularly when cornering. Both understeer (the front wheels
laterally slipping and the nose of the
car running wide) and oversteer (the
rear wheels sliding sideways, with the
tail of the car moving out of line) can
be countered.
If a car understeers when being cornered, the system corrects by braking
the inner rear wheel, effectively rearwheel steering the car back into line.
The controller can brake the chosen
wheel almost to the point of locking
and so the correcting effect can be very
strong. Simultaneously with the braking of the single wheel, the speed of
the car is slowed to a level appropriate
for the situation. This is achieved by
reducing the engine torque output by
partially closing the throttle and/or by
braking the other wheels.
If oversteer is starting to occur, the
system stabilises the car by braking
the outer front wheel. Fig.2 shows the
effect on vehicle stability of braking
just one wheel.
In addition to ABS and ASR components, the VDC requires sensors
for yaw rate, lateral acceleration and
steering angle. Furthermore, the controller needs information on whether
the car is accelerating, free rolling or
being braked.
Longitudinal slip is derived from
the wheel speed sensors, while a
lateral accelerometer responds to the
forces occurring in curves, with the
analog sensor very sensitive in the
range of ±1.4G. In addition, a yaw rate
sensor is used to measure the speed at
which the car rotates around its vertical axis. This device uses four pairs
of piezo elements to excite a hollow
steel cylinder. The yaw is a measure
of the shifting vibration nodes which
occur within the cylinder.
The ECU for the VDC system has a
memory capacity of 48Kb – more than
double that required for a combined
ABS/ASR system.
Next month we’ll discuss the traction control systems used on Formula
SC
1 racing cars.
March 1996 9
ALL REFURBISHED PRODUCTS CARRY MINIMUM 90-DAY WARRANTY ● COUNTRY/INTERSTATE: FREE CALL 1800 680680
● ALL REFURBISHED PRODUCTS CARRY A MINIMUM 90-DAY WARRANTY ● CONTACT MA
HEWLETT PACKARD
334A Distortion
Analyser
HEWLETT PACKARD
200CD Audio Oscillator
• measures distortion 5Hz600kHz
• harmonics up to 3MHz
• auto nulling mode
• high pass filter
• high impedance AM
• 5Hz to 600kHz
• 5 ranges
• 10V out
• balanced output
detector
HEWLETT PACKARD
8614A UHF Sig. Gen.
HEWLETT PACKARD
8640B Sig. Generator
HEWLETT PACKARD
654A Test Oscillator
• 0.5-1024MHz freq. range
• int. audio osc. 20Hz-600kHz
• 800-2400MHz freq. range
• select. functions: CW, levelled • reverse power protection
• internal phase lock/synch.
output, sq. wave mod., ext.
• +19 to -145 dBm output
AM, FM & pulse mod.
power range
• output attenuation 0 to -127
• low SSB phase noise
dBm
• sig. gen. can be phase locked • digital frequency readout
• 10Hz - 10MHz freq. range
• +11dBm to -90dBm output
level in 1dB steps
• calibrated impedance 50Ω
•
+ 75Ω unblanced; 135Ω,
150Ω + 600Ω balanced
distortion <at> 1-10MHz >
34dB below fundamental
$795
$79
$525
$3995
$695
HEWLETT PACKARD
3336B Synthesizer/
Level Generator
HEWLETT PACKARD
3586B Selective
Level Meter
HEWLETT PACKARD
1740A Oscilloscope
HEWLETT PACKARD
1710A Oscilloscope
HEWLETT PACKARD
141T/8552/8555A
Spectrum Analyser
• variable
• Frequency coverage 10Hz- • Frequency coverage 50Hz20.9MHz
32.5MHz
• Precise frequency & spectral • Excellent measurement
purity 1 Microhertz res up
accuracy ±.2dB
to 100kHz
• Autoranging & automatic
• Absolute amplitude accuracy
calibration
±.05dB at 10kHz
• SSB mode provides
• Unique levelled sweep
demodulation capability
capabilities
• HPIB programmable
$1650
Austron 2010B Oscillator 1MHz........................... $400
AWA A215-2 Transmission Measuring Set .......... $175
AWA E221 Level Meter ........................................ $650
AWA F240 Distortion & Noise Meter ................... $375
AWA G231 Audio 10Hz-30KHz ............................ $495
AWA G250 Test Oscillator 10Hz-610kHz .............. $525
AWA G251 Level Oscillator 50Hz-2MHz .............. $600
BECKMAN L10A Megohmeter ........................... $1400
EATON 2075 Noise Gain Analyser ...................... $6500
ESI DB62 Decade Box ......................................... $350
EUROCARD 6 Slot Frames ..................................... $40
FLUKE 408B 6kV 20mA Power Supply................. $800
GR 1381 Random Noise Generators .................... $160
HP 204C Oscillator............................................... $225
HP 332A Distortion & Noise Meter ...................... $495
HP 353 Audio Attenuator...................................... $170
HP 400EL AC Voltmeter ....................................... $195
HP 403B AC Voltmeter......................................... $150
HP410C Multimeter ............................................. $295
HP 427A Voltmeter ................................................ $95
HP 432A Power Meter C/W Head & Cable ........... $825
HP 435A Power Meter.......................................... $495
HP 652A Test Oscillator ....................................... $375
HP 1200B Oscilloscope DC-500kHz..................... $425
HP 3400A RMS Voltmeter (1mV - 300V)............. $475
HP 3406A Broadband Sampling Voltmeter .......... $575
HP 3455A 61/2 Digit DVM ................................... $650
HP 3490A 51/2 Digit Digital Multimeter ............... $295
HP 3555B Transmission & Noise Meas. Set......... $325
HP 4204A Oscillator 10Hz-1MHz ......................... $350
HP 4260 LCR Bridge............................................ $295
HP 5245L/5253/5255 Electronic Counter ............ $550
HP 5300/5302A Universal Counter to 50MHz ...... $195
HP 5326B Universal Timer/Counter/DVM ............ $295
HP 5328A Universal Counter to 500MHz.............. $695
HP 5335A 200MHz Universal Counter ............... $4500
HP 6002 50V/10A Power Supply........................ $1495
HP 8005A Pulse Gen. 20MHz 3-Channel ............. $350
HP 8690B/8698/8699 400KHz-4GHz
Sweep Osc ..................................................... $2450
HP 8690B/8707A/8706A 4GHz-18GHz
Sweep Osc ..................................................... $1500
MARCONI TF2006 FM Sig. Gen. 1000MHz........... $800
MARCONI TF2300A FM/AM Mod Meter
500kHz-1000MHz ............................................ $450
MARCONI TF2500 AF Power/Volt Meter .............. $180
MOTOROLA Sinad Meter ..................................... $325
NORTHEAST 4002A Transmission Meas. Set ...... $600
RACAL DANA 9500 Universal Timer/Counter ...... $350
SD 6054B Freq. Counter 20Hz-18GHz ............... $2500
SD 6054C Microwave Freq Counter 1-18GHz .... $2000
SD 6152A 512MHz Counter/Timer....................... $350
TEKTRONIX CFC 100MHz Freq. Counter.............. $270
TEKTRONIX CDC 175MHz Univ. Counter.............. $405
TEKTRONIX FG504/TM503 40MHz Fun. Gen...... $1290
TEKTRONIX 067-0502-01 Scope Calibrator......... $550
TEKTRONIX 464 Storage Scope DC-100MHz..... $1400
TEKTRONIX 465 Oscilloscope DC-100MHz ....... $1190
TEKTRONIX 475 Oscilloscope DC-200MHz ....... $1550
TEKTRONIX 485 Oscilloscope DC-350MHz........ $2400
TEKTRONIX 602 XY Display ................................ $350
TEKTRONIX 7603NIIS Scope DC-65MHz ............ $650
TEKTRONIX 7904 Oscilloscope DC-500MHz ..... $2800
W&G SPM3 Selective Level Meter C/W; W&G
PS3 Signal Generator 300Hz-612kHz (pr)........ $450
WAVETEK 143 Function Generator 20MHz .......... $475
WAVETEK 907 Signal Generator 7-11GHz.......... $1600
• DC-100MHz bandwidth
• 2-channel display mode
• trigger - main/delay sweep
• coupling AC, DC, LF & HF rej
$990
• HP 1741A var. persistence
expansion to full screen
model available
$1325
$1250
$3995
BALLANTINE
323 AC Voltmeter
BALLANTINE
6310A Test Oscillator
BALLANTINE
3440A Millivoltmeter
$1450
BALL EFRATOM M100
Rubidium Frequency
• factory cal certs
• perfect for ISO accreditation
• GPS applications
• ruggedised military design
•
•
•
•
•
•
•
•
•
•
•
•
• bandwidth DC-150MHz
• trigger source channel A,
B or composite
• delay timebase with
single sweep
• main intensify timebase
persistence
storage
mainframe
internal graticule eliminates
parallax error
IF section 10Hz minimum
bandwidth
log & linear sens. control
absolute amplitude accuracy
to ±1.6dB
direct coax input to 18GHz
high res. 100Hz bandwidth
true RMS
response
including
harmonics +
crest factors
300µV to 300V full scale
1% basic accuracy
freq. range 2Hz - 25MHz
full field portability
fast response without
thermal lag
$2950
• true RMS
•
•
•
•
• 2Hz-1MHz freq. range
• digital counter with 5 digit
LED display
• output impedance switch
selectable
• output terminals fuse
protected
$425
response to
30mV
frequency
coverage 10kHz-1.2GHz
measurement from 100µV
to 300V
accuracy ±1% full scale to
150MHz
list price elsewhere over
$5500
$350
$795
NEW EQUIPMENT
Affordable Laboratory Instruments
The name that
means quality
PS305 Single
Output Supply
•
•
•
•
•
•
•
•
SSI-2360
60MHz Scope
60MHz dual trace,
dual trigger
Vertical sens.
1mV/div.
Maximum sweep
rate 5ns/div.
Component tester
Delay sweep,
single sweep
Two high quality
probes
$1110 + Tax
•
•
•
•
PS8203 Digital
Dual Supply
0-30V & 0-5A
Load & line
regulation
<=0.01%+3mV
Ind. & tracking
modes
Low ripple output
Constant current
voltage
2 x 3.5 dual purpose
digital voltmeters
•
PS303D Dual
Output Supply
• 0-30V & 0-3A •
• Four separate
output meters
• Independent or
Tracking modes
• Low ripple output
$420 + Tax
PS305D Dual
Output Supply
0-30V and 0-5A
$470 + Tax
0-30V & 0-5A
$300 + Tax
PS303 Single
Output Supply PS8112 Single
• 0-30V & 0-3A Output Supply
• Two output
meters
• Constant I/V
•
0-60V & 0-5A
$490 + Tax
$265 + Tax
Audio Generator
AG2601A
Pattern Generator
CPG1367A
$640 + Tax
PS8201 Digital
Single Supply
digital display
• 0-30V & 0-5A
• Load & line regulation • Constant current
analog display
<=0.01%+3mV
• Constant voltage
$320 + Tax
• 10Hz-1MHz 5 bands • Colour pattern to test PAL
• High frequency
system TV circuit
stability
• Dot, cross hatch, vertical,
• Sine/Square output horizontal, raster, colour
$245 + Tax
$275 + Tax
● ALL REFURBISHED PRODUCTS CARRY A MINIMUM 90-DAY WARRANTY ● CONTACT
TEKTRONIX 100kHz to 1800MHz
Spectrum Analyser System
Consisting of:
7613
7L12
7A17
TR501
TM503
WAVETEK Signal Generator/Deviation Meter
Model 3000-200 incorporates a complete 1 to 520MHz FM,
AM and CW Signal Generator with an FM Deviation Meter in
one convenient instrument.
Storage Mainframe
1.8GHz Spectrum Analyser Plug-In
Amplifier
1.8GHz Tracking Generator
3 Slot Mainframe
$4250
Please phone or
fax today for a full
specification sheet
incorporating all the
system’s features.
SPECIAL OFFER: DM501 MULTIMETER
ONLY $100 EXTRA
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.
Spectral Purity: harmonic output > 30dB below
fundamental from 10-520MHz; 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
$1250
IMPORTANT: GARAGE SALE!
This is our first ever Garage Sale and represents an opportunity to purchase a whole range of “as traded” and imported stock that has been accumulated over years.
Some equipment is tested, others “as is” . . . You’re sure to find a bit of everything mechanical, etc.
INTERSTATE/COUNTRY BUYERS: Send or phone for lists . . . All interstate lists returned to us for this sale will be opened on 1st May 1996 and drawn from a hat.
First opened letter gets whatever – it could not be fairer for people out of town. All successful customers will be notified.
PRICES START FROM $1.00
LOCAL BUYERS: LOCAL SALE SUNDAY 5TH MAY 1996 – 9AM to 3PM. Located at warehouse 26 Fulton St, South Oakleigh. Phone for further details.
100MHz Tektronix 465M Oscilloscope
2-Channel, Delayed Timebase
VERTICAL SYSTEM
Bandwidth & Rise Time: DC to 100MHz (-3dB) and
3.5ns or less for DC coupling and -15°C to +55°C.
Bandwidth Limit Mode: Bandwidth limited to 20MHz.
Deflection Factor: 5mV/div to 5V/div in 10 steps (1-2-5
sequence). DC accuracy: ±2% 0-40°C; ±3% -15-0°C,
40-55°C. Uncalibrated, continuously variable between
settings, and to at least 12.5V/div.
Common-Mode Rejection Ratio: 25:1 to 10MHz; 10:1
from 10-50MHz, 6cm sinewave. (ADD Mode with Ch
2 inverted.)
Display Modes: Ch 1, Ch 2 (normal or inverted),
alternate, chopped (250kHz rate), added, X-Y.
Input R and C: 1MΩ ±2%; approx 20pF.
Max Input Voltage: DC or AC coupled ±250VDC + peak
AC at 50kHz, derated above 50KHz.
HORIZONTAL DEFLECTION
Timebase A: 0.5s/div to 0.05µs/div in 22 steps (1-25 sequence). X10 mag extends fastest sweep rate to
5ns/div. Timebase B: 50ms/div to 0.05µs/div in 19
steps (1-2-5 sequence). X10 mag extends maximum
sweep rate to 5ns/div. Horizontal Display Modes: A, A
Intensified by B, B delayed by A, and mixed.
CALIBRATED SWEEP DELAY
Calibrated Delay Time: Continuous from 0.1µs to at
least 5s after the start of the delaying A sweep.
Differential Time Measurement Accuracy: for
measurements of two or more major dial divisions:
+15°C to +35°C 1% + 0.1% of full scale; 0°C to +55°C
additional 1% allowed.
TRIGGERING A & B
A Trigger Modes: Normal Sweep is triggered
by an internal vertical amplifier signal, external
signal, or internal power line signal. A bright
baseline is provided only in presence of trigger
signal. Automatic: a bright baseline is displayed
in the absence of input signals. Triggering is the
same as normal-mode above 40Hz. Single (main
timebase only): The sweep occurs once with the
same triggering as normal. The capability to re-arm
the sweep and illuminate the reset lamp is provided.
The sweep activates when the next trigger is applied
for rearming.
A Trigger Holdoff: Increases A sweep holdoff time
to at least 10X the TIME/DIV settings, except at
0.2s and 0.5s.
Trigger View: View external and internal trigger
signals; Ext X1, 100mV/div, Ext -: 10, 1V/div.
Level and Slope: Internal, permits triggering at
any point on the positive or negative slopes of the
displayed waveform. External, permits continuously
variable triggering on any level between +1.0V and
-1.0V on either slope of the trigger signal.
A Sources: Ch 1, Ch 2, NORM (all display modes
triggered by the combined waveforms from Ch 1 and
2), LINE, EXT, EXT :-10. B Sources: B starts after delay
time; Ch 1, Ch 2, NORM, EXT, EXT :-10.
X-Y OPERATION
Sensitivity: 5mV/div to 5V/div in 10 steps (1-2-5
sequence) through the vertical system. Continuously
variable between steps and to at least 12.5V/div.
MACSERVICE PTY LTD
$900
Optional cover for CRT
screen – $35
X Axis Bandwidth: DC to at least 4MHz; Y Axis Bandwidth: DC to 100MHz; X-Y Phase: Less than 3° from
DC to 50kHz.
DISPLAY
CRT: 5-inch, rectangular tube; 8 x 10cm display; P31
phosphor. Graticule: Internal, non-parallax; illuminated. 8 x 10cm markings with horizontal and vertical
centerlines further marked in 0.2cm increments.
10% and 90% markings for rise time measurements.
Graticule Illumination: variable. Beam Finder: Limits
the display to within the graticule area and provides a
visible display when pushed.
Australia’s Largest Remarketer of
Test & Measurement Equipment
20 Fulton Street, Oakleigh Sth, Vic, 3167. Tel: (03) 9562 9500; Fax: (03) 9562 9590
**All illustrations are representative only. Products listed are refurbished unless otherwise stated.
Countr
Interstate y &
Call
Free Ca ers
1800 680 ll
680
T MACSERVICE P/L FOR ALL YOUR FLUKE REQUIREMENTS ● FREE CALL: 1800 680680
REFURBISHED PRODUCTS: MINIMUM 90-DAY WARRANTY ● CONTACT MACSERVICE FOR ALL YOUR FLUKE REQUIREMENTS
ACSERVICE FOR ALL YOUR FLUKE REQUIREMENTS ● FREE CALL 1800 680680 ● ALL
In this short series, we
will investigate those
most useful electronic
instruments, Cathode
Ray Oscilloscopes.
In this first part we
will look at analog
oscilloscopes and
delve into their basic
operation.
By BRYAN MAHER
T
HE CATHODE RAY Oscilloscope, commonly referred to as
a CRO or scope, is an extremely
useful instrument for experimenters
and designers, and for servicing.
The purpose of any oscilloscope is
to enable us to observe a light pattern
in the shape of a graph of whatever
electrical signal is applied to the instrument, as depicted in Fig.1.
Many details of voltage waveforms
can be inspected, such as peak values,
rise and fall times, frequency, period,
glitches, interferences, oscillation or
instability. Also, we can trace signals
through circuits for the source of gross
distortion, if present, as shown in the
photo next to Fig.1. The pure sinewave
is the input voltage to an audio power
amplifier which is faulty, while the
distorted signal is the output of that
amplifier resulting from severe crossover distortion.
A CRO can be used with radio
transmitters or receivers to display
amplitude modulated (AM) signals
and show clearly the modulation percentage and any over-modulation, if
present. With suitable probes, current
waveforms can be displayed. Also, we
can display the magnetic properties of
iron or ferrite materials, draw the B/H
curve and illustrate hysteresis. In fact,
the range of device parameters which
can be measured and displayed on an
oscilloscope is virtually unlimited.
The heart of any oscilloscope is the
12 Silicon Chip
cathode ray tube, sometimes called a
CRT. A simplified cross section of an
oscilloscope tube is shown in Fig.2.
The long glass vacuum tube has a
screen at one end, the inside surface
of which is coated with a fluorescent
phosphor materi
al. Also the inside
surface of the glass side walls, near
the screen, is coated with a conductive material called Aquadag which
is connected to an external terminal.
At the opposite (socket) end is a
heater filament and a coated cathode
which emits electrons. A high voltage
DC source has its positive output connected to the aquadag coating near the
screen while the negative terminal is
connected to the cathode.
Electrons emitted from the cathode are attracted and accelerated to
the front screen by the high positive
voltage. The electrons arrive at the
The Hitachi V223A is a modern dual-channel oscilloscope. This portable
model, intended for field service as well as laboratory work, offers DC to
20MHz bandwidth, 1mV/div sensitivity and numerous "creature comforts".
Above: most oscilloscopes
can display two separate
signals simultaneously.
In this off-screen photo,
a dual input CRO is
being used to signal trace
through an amplifier
under repair, to find the
point at which the signal
becomes distorted. By
comparing the input
(sinewave) signal with the
signals found at different
points along the circuit,
the faulty section can be
identified.
Fig.1: by moving a spot of light on its front
screen, a cathode ray oscilloscope (CRO)
can draw a graph of any voltage signal
applied to its vertical deflection plates.
screen with sufficient energy to cause
the sensitised material on the inside
surface of the front screen glass to
fluoresce, or to emit light, at point L.
This material, or phosphor, consists of
extremely fine grained compounds of
specially selected light metals.
Screen persistence
Any point on the CRO screen will
give off some light for a little time after
the electron beam has moved away.
The time taken for this lingering light
to fade away to 1% of its initial value
is called the persistence time.
A typical value for screen persistence in the phosphors used in oscilloscopes is 250 microseconds.
Imagine that the frequency of the
vertical deflection signal applied to the
Y1-Y2 plates in Fig.2 is increased – so
that the spot moves up and down the
screen faster in less than 250 microseconds. The light spot will be moving
faster than screen persistence time and
so the spot will trace the whole vertical
pathway before any one point can fade
away. As a result, we will see a complete vertical line drawn on the screen.
When the emitted light ceases al-
Fig.2: simplified part
diagram of a CRO tube,
showing only the evacuated
hard glass envelope; the
heater and cathode at the
lefthand end; the vertical
deflection plates Y1,
Y2; and the fluorescent
phosphor screen at right.
The heated cathode emits
electrons. A conductive
coating called aquadag
(AQD) is deposited on the
inside surface of the tube
near the righthand end.
This is connected to the
positive end of high voltage
supply.
March 1996 13
Fig.3: cutaway drawing of a simple CRO tube showing the heater h, cathode K, control grid
G1, focus grid G2, accelerating grid G3, vertical deflection plates Y1 & Y2, and horizontal
deflection plates X1 & X2. This example shows a 5kV acceleration potential between G3/
screen and cathode K. A1-A5 form the vertical deflection amplifier system, while A6-A10
make up the timebase generator which provides the sawtooth horizontal sweep voltage.
Oscilloscopes are such useful instruments that two or more are often used simultaneously
on an electronic workbench, as in the scene above. The scope at the right is actually a
spectrum analyser and is showing the harmonics of the waveform on the scope at left.
14 Silicon Chip
tence time. Some of the common
screen phosphors and their specific uses are listed in Table 1.
Vertical deflection
In Fig.2, a pair of metal plates,
Y1 and Y2, are placed above and
below the beam of electrons. If a
voltage is applied between these
plates, with Y1 more positive
than Y2, then the resulting electric field will attract the electron
beam upwards in the direction
of Y1. Thus the electrons will
strike the screen material at
point M and cause light to be
Fig.4: simplified horizontal sweep voltage which deflects the electron beam across
emitted there.
the CRO tube screen. The rising ramp voltage from time t1 to t3 sweeps the beam
Similarly, if the potentials on
forward from left to right of screen. During the short time t3 to t5 the beam is swept
Y1 and Y2 are reversed, the elecback (retrace or flyback) from right to left of screen. In very simple systems the next
tric field will deflect the electron
forward sweep then commences.
beam downwards, striking the
screen material at point P, where
most immediately after the electron
removed (ie, a long persistence time),
light will be emitted. Y1 and Y2 are
irradiation has been removed (ie, a
we call that screen phosphorescent.
called the vertical deflection plates.
very short persistence time), we say
If a very low frequency repetitive
Phosphor numbers
that the screen is fluorescent.
voltage, which swings through both
Conversely, in cases where light conpositive and negative values, is
These days oscilloscope tube mantinues to be emitted for a considerable ufacturers can produce screens with
applied between plates Y1 and Y2,
time after the electron beam has been
the electron beam will follow this
almost any desired colour and persis-
Table 1: Commonly Used Phosphor Numbers & Screen Properties
Phosphor Number
Screen Colour
Persistence Time to 1%
Uses and comments
P1
Green
50ms
Cathode Ray Oscilloscopes and RADAR
P2
Yellow/Green
200us to 4%
CRO tubes and RADAR
P4
White
Blue 150us
Yellow 480us
TV B/W Px tube. Blue component dominates
the yellow component; giving daylight white.
P5
Blue
52us
High speed CRO, for off-screen photography
P7
B/G/Y
Blue 500us
Yellow >3 sec.
RADAR cascade screens. Blue image fades fast
leaving lasting yellow record.
P11
Blue
500us
CRO off-screen photography
P12
Orange
420ms
RADAR receivers
P14
(B+R)/Y
Purple 200us
Yellow 120ms
RADAR two-layer cascade screens
P15
UV/Violet/G
(time to 10%)
Violet 3us
UV 0.05us
Flying-Spot scanning TV camera tube. Fastest
screen made
P16
UV/Violet
0.12us (10%)
Flying-Spot scanning TV camera tube. Fastest
visible screen made
P22
Blue/Green/Red
Blue 5ms
Green/Red 50ms
Colour TV
P28
Yellow/Green
Yellow 7 sec
RADAR
P31
Green
250 microsec
Preferred phosphor for Oscilloscopes.
P33
Orange
8 seconds
RADAR
P34
B/G/Y
400 seconds
RADAR long persistence
March 1996 15
Fig.5: a sinewave
signal (a) applied
to the vertical input
terminal of an
oscilloscope deflects
the beam (and the
consequent spot of
light on the screen) in
a vertical direction
in proportion to
the voltage value of
(a) at any time. At
the same time, the
electron beam is
deflected horizontally
by the ramp voltage
(b) generated by
the sweep system
and applied to the
horizontal deflection
plates. The combined
action of both
voltages (a) and (b)
draws a graph on the
screen of voltage (a)
as a function of time.
changing Y1-Y2 field up and down.
Observing the screen, we would see
the light spot travel slowly up and
down, following a straight line.
Horizontal deflection
When you draw a voltage waveform
16 Silicon Chip
on paper, for instance a sinewave, you
use a vertical scale of volts to represent
the signal and a linear horizontal scale
to represent time. To show the same
waveform on the screen of the CRO,
the spot of light is moved horizontally
at constant speed (X input) and at the
same time moved vertically, corresponding to the vertical input signal.
Fig.3 depicts a cutaway view of a
simple oscilloscope tube, with vertical
deflection plates Y1 & Y2. In addition,
there are a pair of horizontal deflection
plates, X1 & X2, one each side of the
electron beam. Any voltage waveform
applied to these plates will deflect the
electron beam sideways.
For the electron beam to move horizontally at constant speed, the voltage
applied to the horizontal deflection
plates must increase in a straight line
with respect to time.
So a linear ramp voltage signal (or
sawtooth) is applied to the horizontal
plate. This waveform is shown in Fig.4.
This horizontal deflection voltage must
run from negative values, through zero,
to positive values, to take the spot from
far left to far right of screen.
In Fig.4, this horizontal deflection
voltage is at its most negative at time
t1. Therefore, the spot of light will be
at the left of the CRO screen.
Below: in research laboratories,
oscilloscopes are often dedicated
to specific tasks. The scopes in this
photo are permanently connected in a
measurement setup.
As the voltage rises towards zero,
the light spot moves horizontally to the
right, reaching centre screen at time
t2. Continuing on, the trace reaches
extreme right of screen at time t3.
Now let us start again but this time
with the vertical input signal applied
to the Y1-Y2 plates. The light spot on
the screen will trace out a graph of the
vertical signal, as depicted in Fig.5, as
its voltage values change with time.
Notice that in Fig.5 we have arranged for the horizontal signal to start
at time t1, just as the signal applied to
the vertical plates passes through zero.
This is called synchronisation, a topic
we will go into a little later.
This is an old 100mm CRO tube made by
Cossor. The black aquadag conductive coating,
extending from about the middle to near
the screen end, can be seen on the inside
of the glass envelope. These days, all
but the cheapest CRO tubes have
a rectangular screen.
Flyback & blanking
We have drawn the first trace on
the screen, from time t1, through t2 to
t3. Usually, to obtain a bright picture,
we repeatedly redraw this trace many
times, superimposed. To do this, the
electron beam must return from the t3
position (at far right of screen) to the
starting point at far left of screen as
quickly as possible, so that it is ready
to draw the trace over again, restarting
at time t1.
We cannot change the voltage of the
horizontal deflection signal in Fig.4
from maximum positive to maximum
negative instantaneously (ie, it cannot
be done in zero time).
Therefore, in Fig.4, t3 (RHS of
screen), t4 (mid screen) and t5 (LHS of
screen) are not simultaneous. But they
can occur in a very short interval of
time. This fast return of the horizontal
signal is called the “retrace” or “flyback” because the electron beam has to
fly back to its initial starting position.
To prevent a confusing trace being
drawn on the screen by the spot of light
flying back at high speed, the electron
beam is turned off during retrace. This
is called flyback blanking.
Vertical & horizontal stages
The vertical amplifier is also shown
in schematic form on Fig.3. There are
five amplifier stages shown although
typical scopes may have more or less
amplifier stages. A1 accepts whatever
input signal you want to view on your
oscilloscope, reduced if too large by
attenuator VR1. A3 provides a phase
change action so that A4 and A5 can
deliver a push-pull or complementary
drive to the vertical deflection plates
Y1 and Y2.
The basic essentials of a timebase
generator and X or horizontal sweep
amplifiers are also shown in Fig.3. A6
is an oscillator which produces the
linear ramp voltage signal. It is also
referred to as a sawtooth waveform
generator. CX indicates that capacitors
can be switched in the A6 circuit to
produce different rates of rise of voltage; ie, different amounts of time to get
from t1 to t3. This is called changing
the sweep rate.
A9 provides a phase change for the
drive to A10. Thus, A8 and A10 put out
a complementary signal sufficient for
the horizontal deflection plates X1 and
X2 to deflect the electron beam across
the full width of the CRO screen.
Beam current
In Fig.3, the CRO tube heater heats
the cathode which emits copious
quantities of electrons. The conductive coating (aquadag) and grid G3 are
connected to the positive end of a high
voltage supply, shown in this example
as 5kV. The relatively positive G3 grid
and screen end attract the electrons
emitted from the cathode, K.
The voltage applied to grid G1 is
even more negative than that on the
cathode. This allows G1 to control the
quantity of electrons in the electron
stream (the beam cur
rent), by the
voltage difference between G1 and
the cathode.
Yes, that stream of electrons is an
electric current. Its value may be 20
microamps for some simple CRO
tubes, or 50 milliamps or more in some
high brightness top performance tubes.
However, electron beam current
does not obey Ohm’s Law. Instead, it
is proportional to the square root of
the acceleration voltage which causes
it to flow! Hence, the G1-K potential
decides the brightness of the trace on
the CRO screen.
G2 is called the focus grid. The mass
of electrons is focused, by the potential
difference between G2 and G3, into
a stream, to arrive at the screen at a
fine point.
G3 is a hollow metal cylinder called
the accelerating grid. Being more
positive than the cathode, G3 attracts
electrons away from the cathode. The
electron stream passes straight through
G3 without touching it and continues
on to the screen. In this example of a
simple CRO tube, G3 and the screen
are at the same poten
tial. In more
complex tubes this is not so, as we
shall see in a future article.
Grounding of 5kV supply
To prevent deceleration of the electrons, everything to the right of G3
must be either at the same potential
as G3, or more positive. Because all
deflection plates are part of the vertical
(Y) or horizontal (X) amplifier circuits,
their voltage levels are at amplifier
potentials: usually no more than a few
hundred volts above or below ground.
The above two statements together
imply that G3 and the CRO tube screen
must be no more than a couple of
hundred volts above ground, about
the same potential as Y1, Y2 and X1,
continued on page 83
March 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
Programmable
Electronic Ignition
System For Cars
From time to time, many enthusiasts wish that
they could vary the ignition advance curve or
alter the dwell angle on the distributor of an old
car or motorbike. This simple but sophisticated
system will readily meet those needs.
By ANTHONY NIXON
This user programmable ignition
system can be easily integrated with
the SILICON CHIP High Energy Ignition
System (see May 1988), or readily
adapted to suit other systems. Its main
features are listed in Table 1.
As shown in the photographs, the
Ignition Programmer is built on a small
PC board which carries a keypad. All
data is entered via this keypad, so that
22 Silicon Chip
new advance curves and dwell angles
can be quickly programmed. To simplify the circuit and make construction
easy, the unit is based on the versatile
PIC16C84 microprocessor.
The following parameters can be
programmed into the system:
• The revs (RPM) at which ignition
advance begins;
• The revs (RPM) for full advance;
•
•
•
•
•
•
Maximum advance angle;
Rev limit;
Dwell angle;
Vacuum advance;
Number of cylinders; and
A 2-digit security code.
A useful feature of the system is that
it allows two sets of data to be entered,
either of which can be selected when
the ignition is turned on. For example, the module can accommodate
an engine which runs on both petrol
and gas, as it allows the timing to be
quickly changed for these different
fuels to get the best performance.
How it works
The circuit (see Fig.1) is fairly
simple, thanks to the PIC microprocessor (IC1). In operation, ignition
timing information from the points
Fig.1: the circuit is based on a PIC16C84 programmed microprocessor (IC1).
This processes timing information from the points (or some other pick-up) and
drives the High Energy Ignition System to switch the coil.
Table 1: Main Feat
ures
• User programmable
• Keypad data entry
• Security coded (2 di
gits)
• Can store two sets
of data
• Tachometer drive ou
tput
• Points or other sens
or input
• Automatic coil curre
•
•
nt switch
nning
off if motor not ru
7-segment LED di
splay
LED indicator for
initial timing
setup
conditioning circuitry on the High
Energy Igni
tion module is fed into
pin 1 (RA2) of IC1, while the ignition
coil is controlled from pin 2 (RA3).
This pin 2 output drives the coil via
the “business-end” of the High-Energy
Ignition System.
The keypad used is a standard 12key unit with * and # symbols. Its rows
connect to the RB3-RB6 outputs of the
microprocessor, while its columns
go to RB0-RB2. As it operates, the
microprocessor alternately takes its
RB3-RB6 outputs high and low. Thus,
when a key is pressed, the logic level
is sensed by one of the inputs RB0RB2 and the microprocessor takes the
appropriate action.
For example, if key “3” is pressed,
then RB3 of IC1 (pin 9) will be connected to RB2 (pin 8). Resistors R5-R7
(10kΩ) normally pull RB0-RB2 low.
RA4 (pin 3) of IC1 is the vacuum advance input, while S1 is a microswitch
which is actuated by the vac
uum
advance motor (see photo). When the
manifold vacuum is high, S1 is held
open and RA4 is pulled high via R8
(10kΩ). Conversely, when the vacuum
is low, S1 is closed and RA4 is pulled
low so that the microprocessor retards
the timing.
The 7-segment display is driven
from IC2, a 74HC164 serial-to-parallel
shift register. This receives serial information from pin 17 (RA0) of IC1 and is
clocked from pin 18 (RA1). It displays
such things as errors, programmable
system variables and which set of data
will be used.
IC3, an MC34064 undervoltage
sensing circuit, is used to ensure that
the microprocessor resets reliably
when the ignition is turned on. An
8MHz crystal, in conjunction with
C6, C7 & R4, sets the microprocessor
clock, while LED1 is driven from pin
13 (RB7) to provide points status indication (ie, it indicates whether the
points are open or closed).
The power supply uses a series
diode (D1) for reverse polarity protection, a zener diode (ZD1) to clip
any large spikes, and a 5V 3-terminal
regulator (REG1). The latter provides
a +5V supply rail for the ICs.
Fig.2 shows how the Programmer
Module interfaces with the SILICON
CHIP High Energy Ignition System. As
shown, the voltage across the points
is filtered and fed to Q2’s base via D5
and a 10kΩ resistor. The signal at the
collector has a 5V logic level and this
is the “POINTS” input signal to the
microprocessor on the programmer
module. The “COIL” output from the
programmer module is used to trigger
IC1, the MC3334 ignition chip.
IC1 in turn drives Q1 which is the
coil switching transistor. Zener diodes
D1-D4 protect Q1 from the high voltage
spikes generated by the back EMF of
the coil.
Ignition timing
In older engines, the centrifugal
force generated by weights spinning
in the distributor causes the engine
March 1996 23
Fig.2: here’s how the Ignition Programmer module interfaces with the High
Energy Ignition System. The coil output triggers the MC3334 ignition chip (IC1)
and this in turn drives the coil switching transistor (Q1).
timing to advance with increasing
revs. Additionally, a vacuum advance
mechanism increases the advance as
the manifold vacuum rises. This either
adds to or subtracts from the centrifugal advance, so that varying degrees
of advance are obtained for different
engine speeds and loads.
Electronic advance
In this system, the centrifugal advance is calculated according to engine RPM, while the vacuum advance
is either on or off, as determined by
the logic level on the vacuum advance
input (RA4, pin 3) of the microprocessor.
Because the advance is now determined electronically, the mechanical
centrifugal advance mechanism in
the distributor is clamped in the fully advanced position. To do this, the
advance weight return springs are
removed and the weights themselves
are wired so they are held in the fully
out position. In addition, the movable
vacuum advance plate must be clamp
ed so that it can’t move when the
vacuum actuator is removed.
In operation, the Ignition Programmer retards the ignition timing from
its preset maximum value, to give the
correct amount of advance to suit the
operating conditions.
As already mentioned, microswitch
S1 is operated by the vacuum advance
motor. It operates when the required
vacuum is reached in the intake manifold (note: this system is also used on
some production engines).
24 Silicon Chip
Rev limiting is achieved by excessively retarding the ignition when the
preset value is reached. All other variables are then ignored until the engine
revolutions fall below this value.
Microprocessor functions
Instead of generating look-up tables
for engine data, the program calculates
a set of variables based on the data
entered by the user and stores these
in the PIC’s internal EEPROM. When
the motor is sensed to be running, the
microprocessor uses these variables
to generate the timing of the output
waveform.
Some of the microprocessor’s ignition functions include monitoring the
engine RPM, advance timing, dwell
pulse width, maximum RPM, vacuum
advance pulse width and number of
cylinders. As all but the last of these
are dynamic and constantly changing,
the processor has to continuously
recalculate new data.
It is interesting to note that to create
the various pulse widths and functions while the engine is running, the
microprocessor only executes about 50
bytes of code and takes about 30µs to
do it. Most of the program memory is
taken up by the user interface, while
the rest is used for data generation, the
serial display and setup.
When the ignition routine is first
activated, the coil is turned on. If
the motor is not started within 10
seconds, the coil will switch off and
the system will enter MENU mode.
This eliminates the possibility of any
damage to the coil caused by leaving
the ignition on, without the motor
running.
The coil will also be switched off
if the motor stalls. In this case, the
system will stay in the ignition routine
and wait for the engine to be restarted
or the power to be switched off.
Construction
The Ignition Programmer is easy to
build, since all the parts except for
microswitch S1 are installed on a PC
board coded 05103961. Fig.3(a) shows
the parts layout on the PC board.
As always, check the PC board for
open circuit or bridged tracks before
you begin assembly. This done, fit
the resistors, diodes and sockets for
IC1 and IC2, then install the capacitors and other components. The LED
display plugs into a wire-wrap socket
(install this at full lead length), while
the keypad plugs into an 8-pin header
socket.
Make sure that the LED display is
correctly oriented when plugging it
into its socket – it must be mounted
with the decimal point(s) towards the
bottom of the board. The 8MHz crystal
can be mounted either way around but
take care with the polarity of the ICs
and LED1 – the anode lead of LED1
will be the longer of the two.
It will be necessary to solder a wire
to the +5V stake which is adjacent to
pin 18 of IC1 before you fit the keypad.
The keypad on the prototype was
secured using machine screws and
nuts (use nylon washers on the track
Fig.3(a): install the parts on the PC board as
shown here and take care if using a different
keypad to that shown – see text.
side of the board, to prevent shorts).
Adjust the assembly so that the keypad
is parallel to the PC board when it is
plugged into its pin header socket.
There’s just one wrinkle here – many
keypads have their connections at the
bottom instead of at the top. If you have
this type of keypad, then it’s simply a
matter of running a length of 8-way
ribbon cable between the keypad and
the PC board.
Note, however, that the pin connections to the keypad matrix will differ
from keypad to keypad. The numbers
Fig.3(b): this is the full-size etching pattern for
the PC board. Check the board carefully for
defects before installing any of the parts.
in brackets on the circuit diagram
(Fig.1) indicate the connections for
a Jaycar keypad (Cat. SP-0770) – (ie,
pin 2 of the keypad goes to pin 6 on
the PC board, pin 7 goes to pin 8, etc).
If you buy some other keypad (eg,
the Altronics Cat. S-5381), then use
the data supplied with the unit to
determine the connections.
Once the assembly is complete,
check all your soldered joints carefully and check the polarity of D1.
When you are satisfied that all is OK,
connect 12V from a power supply or
car battery to the terminals adjacent
to the keyboard connector.
Installation
The exact installation will depend
on your particular vehicle. If the unit
is going in a car, the programmer could
be mounted on the dashboard or centre
console. Note that the microprocessor
board should not be installed under
the bonnet, as the components used
are not rated for high temperatures.
For a motorbike installation, the unit
could be mounted in a weatherproof
box on the handlebars.
Be sure to run all wiring
in a professional manner,
using proper automotive
connectors to ensure reliability.
Fig.4 shows how the
unit is interfaced to the
SILICON CHIP High Energy Ignition System. Note
that it will be necessary
Fig.4: this diagram
shows how the Ignition
Programmer is connected
to the High Energy
Ignition (HEI) module.
Note that it is necessary to
remove some parts from
the HEI board if you are
adapting an existing unit.
March 1996 25
Make sure that all parts are
correctly oriented when building
the PC board and don’t forget the
wire link next to crystal X1.
to remove a number of parts from the
centre of the board if you are adapting
an existing ignition module.
Fig.5 shows the mounting details for
the microswitch S1. It is mounted on
a rightangle bracket which is attached
to the vacuum motor. The arm of the
microswitch sits in a slot cut into the
vacuum motor actuator and, in the
absence of vacuum, is normally held
Fig.5: the microswitch (S1) is mounted on the vacuum motor using a
right-angle bracket. At low vacuum (ie, ignition off or at high engine
loads), the microswitch arm is held down. Conversely, when the
manifold vacuum is high (ie, at light engine loads), the microswitch
arm is released.
26 Silicon Chip
down. When vacuum is present, the
actuator moves upwards and the microswitch arm releases.
Be sure to connect the leads to the
microswitch contacts exactly as shown
(ie, the lead from pin 3 of the microprocessor goes to the contact marked
“NO”). As mentioned previously, the
advance plate in the distributor must
be clamped at the maximum advance
position (see photo).
When the ignition is timed (using
a timing light), the vacuum advance
must be disabled. This is accomplished by removing and blocking the
vacuum hose, so that it can have no
effect on the vacuum switch.
To time the ignition with the engine
stopped, turn the crankshaft to the
correct position, then rotate the distributor until the LED just turns on.
This indicates that the points have just
opened. The LED will be off when the
microprocessor detects that the points
are closed.
Note that because the LED drive
signal frequency is proportional to the
engine RPM, this signal can be used to
drive a suitable tachometer.
Operation
When the module is initially powered up, it will enter one of three states.
These are as follows:
(1). If there is no valid data in the
EEPROM, the system will enter the
MENU mode and the display will show
“-”. This is what should be displayed
at the initial power up.
(2). If there is valid data but no security code has been programmed, the
system will begin its ignition routine
and wait until the motor is started.
The display will show the selected
data channel.
If the “9” key is pressed before the
motor is started, the system will exit
the ignition routine and enter the
MENU mode to enable the user to
make data changes. This option will
not work after the motor has been
started.
(3). If there is valid data and a security code has been programmed, the
display will be blank and the system
will not oper
ate until the security
code is entered. It will then show the
selected data channel.
If a mistake is made when entering
the first digit, you can press the “#”
key, then enter the digit again. This
function does not work for the second
digit, however. If it is entered incor
rectly, the microprocessor shuts down
until it is reset by turning the power
off and on again.
MENU access using the “9” key is
as detailed in (2) above.
The keypad used in the prototype has its connecting pads at the top and plugs
directly into the connector on the PC board. If you use a Jaycar or Altronics
keypad with the pads at the bottom of the unit, the connections will have to be
run using ribbon cable. Note, however, that the pin connections to the keypads
will be different (see text).
Keypad modes
(1) Keypad Power-up Mode: if key
7 is pressed while powering up, the
alternative channel is selected (other
keys have no function).
(2) Keypad Security Mode (after
power is first applied and if data is
valid):
Key
Function
#
Enter/exit code entry
0-9
Code entry (2 digits)
*
No function
(3) Keypad Ignition Mode (ignition on,
engine not running and data valid):
Key
Function
9
Enter menu mode
Other
No function
When the system is initially turned
on and no data has been entered into
the internal EEPROM, the ignition
won’t work. The system switches to
MENU mode automatically and this
is indicated by the display coming on
with only the centre segment lit.
When in MENU mode, the keypad
functions are as shown in the follow
ing list:
This close-up view shows how the microswitch arm is normally held down by
the vacuum motor actuator. The common contact (COM) of the microswitch is
connected to ground, while the NO contact goes to the PC board.
March 1996 27
are shown. Data needs to be entered
in the following manner, taking care
to enter the digits properly and in the
correct sequence:
Variable
Data
Digits
Allocated
Start advance RPM
800
4
Finish advance RPM
2000
4
Advance angle
30°
2
Cylinders
2
2
Dwell angle
30°
2
Rev limit RPM
5000
2
Vacuum advance angle 10°
2
Security code
59
2
Because all timing in now controlled electronically, the advance plate inside the
distributor must be securely clamped in the fully advanced position. In effect,
the Ignition Programmer retards the timing from this preset maximum to give
the correct value according to engine speed and load.
Key
1
2
3
4
5
6
7
8
9
*
0
#
Menu Mode
Clear EEPROM
Clear RAM data
Read RAM data
Write EEPROM data
to RAM
Enter new data to
RAM
Clear display
No function
Display data set
selected at power-up
(1 or 2)
No function
Create ignition data
No function
Exit to ignition
A more detailed explanation of
these various keypad functions is as
follows:
• Key 1: Clears the user data stored
in EEPROM.
• Key 2: Clears the user data stored
in RAM.
• Key 3: Displays the data stored in
RAM. Each data value entered has a
letter assigned to it. A decimal point
lights with the letters, to help differentiate between them and the numbers
while they are being viewed.
The data functions indicated by the
letters are as follows:
28 Silicon Chip
A. – RPM at start of advance
b. – RPM at end of advance
C. – Advance angle
d. – Number of cylinders
E. – Dwell angle
F. – Rev limit
G. – Vacuum advance angle
H. – Security code
To cycle through the data, press the
“*” key. After the security code has
been shown, the display wraps around
to the RPM at start of advance again.
To exit this display mode, press the
“#” key. No other keys has any effect
while reading data.
A typical example display is as
follows: A.0800, b.2000, C.30, d.02,
E.30, F.50, G.10, H.59.
Key
Data Read
0-9
No function
*
Cycle to next data
#
Exit data read routine
• Key 4: Gets the data from EEPROM
and puts it into RAM. To view this
data, press the “3” key and use the
“*” key to cycle through the data, as
explained above. Any data previously
in RAM will be overwritten.
• Key 5: Enters new data into RAM.
Initially, an “A” will be dis
played
to indicate the first data entry. For
simplicity, and as internal memory
is limited, no further letter delimiters
This data is entered exactly as follows: 0800 2000 30 02 30 50 10 59
There are a few things to note here:
(1) No further letter delimiters after
A are shown;
(2) After entering the security code,
“-” is displayed, indicating the end of
data entry;
(3) There are leading zeros for the
Start Advance RPM and for the Cylinder;
(4) 50 is entered for the 5000 RPM
limit; and
(5) Make sure that you don’t forget
the security code!
If valid data is detected on power-up with a non-zero value in the
security code, then this code must be
entered when the system is to be used
–eg, turn ignition on, press #, press
5, press 9 (code from data above).
The ignition routine will now begin
and the display will show the data
set selected.
If an incorrect code is entered, the
ignition routine will not begin and no
further response will be available from
the keyboard. Turning the ignition off
and then on again will allow the code
to be re-entered.
If you forget the code, the only way
to gain access to the system is to start
entering the 100 combinations one
by one.
Another example, this time with no
security code, is shown below:
Variable
Data
Digits
Allocated
Start advance RPM
650
4
Finish advance RPM
1500
4
Advance angle
12°
2
Cylinders
8
2
Dwell angle
0°
2
Rev limit RPM
4500
2
Vacuum advance angle 9°
2
Security code
None
2
Example Programming Sequence
A complete programming sequence (with no data entered) is as follows:
Action
Turn power on
Press 5
Enter all data
When finished
Display
A
DATA
-
Reviewing Data
Press 3
A
?
DATA
-
Press *
Press #
Calculate & Store Data
Press *
if OK
if error
& delimiters
finish reading
display flashes
?
if OK
when finished
if error
?
A
?
DATA
-
if OK
if error
if OK
if error
& delimiters
finish reading
Review EEPROM
Press 4
Press 3
Press *
Press #
To program the second data set, first turn the power off and then turn it on again
with key 7 pressed. The data is then programmed in and reviewed exactly as set
out above.
This data is entered exactly as follows: 0650 1500 12 08 00 45 09 00.
As well as the previous items
noted, if a zero dwell angle is entered, then a 1ms dwell angle will
be set automatically. If any angle is
calculated to be less than 1ms, then
1ms will be used. In addition, as the
engine RPM increases, a point will
be reached when the dwell width is
theoretically less than 1ms. When the
microprocessor detects this, it sets the
minimum to 1ms.
Important note: the dwell angle
referred to above is the angle through
which the points are open and not the
angle through which they are closed,
as is normally the case. The dwell
angle from any input device has no
effect on the system dwell setting.
However, it is good practice to set the
points normally, as specified by the
manufacturer. The microprocessor
debounces the input, whether points
or electronic sensors are used.
•
Key 6: Clears the display, so that it
shows “-”.
• Key 7: No function.
• Key 8: Shows current data set selected (1 or 2).
• Key 9: No function.
• Key *: Calculates and stores, in EE
PROM, new data that the system will
use when the ignition routine is active.
Valid data must have been entered by
the user. Care should be taken when
choosing this data, as values which
are too far away from standard may
not work with the system. Memory
constraints prohibit all but minor error
checking of input data.
If the number of cylinders is entered
as zero then an error will occur in the
calculations, as this will result in an
internal division by zero.
Data entry can be aborted by pressing the “#” key. If this is done, no
calculations can occur and there will
be no data in RAM which can be read.
Nor can it be stored in EEPROM.
PARTS LIST
1 PC board, code 05103961, 76
x 70mm
1 12-key keypad (see text)
1 8MHz crystal (X1)
1 8-pin PC male connector
(6mm pins)
1 8-pin PC female connector
(6mm shroud)
1 14-pin wire wrap IC socket
1 18-pin IC socket (for IC1)
4 3mm x 20mm bolts
12 3mm hex nuts
4 3mm insulating washers
9 PC stakes
Semiconductors
1 PIC16C84 programmed
microprocessor (IC1)
1 74HC164 shift register (IC2)
1 MC34064 power-on reset (IC3)
1 78L05 regulator (REG1)
1 1N4002 diode (D1)
1 1N4745 16V 1W zener diode
(ZD1)
1 LTS312 common anode
7-segment LED display (DS1)
1 red LED (LED1)
Capacitors
1 100µF 25VW PC electrolytic
1 47µF 25VW PC electrolytic
3 0.1µF 100VW MKT polyester
2 18pF ceramic
Resistors (0.25W, 1%)
6 10kΩ
9 1.5kΩ
1 2.2kΩ
1 22Ω
Note: the programmed micro
processor can be purchased for
$27.00 including postage from Mr.
A. Nixon, 20 Eramosa Road East,
Somerville, Vic. 3912.
Note that the display will flash
while it is calculating the new variables, then turn off when finished.
One major limitation of the system
is that the total value of the advance,
dwell and vacuum advance angles
must not exceed the angle between
cylinders. If this did happen, the
microprocessor would still be in the
middle of controlling the timing sequence from the previous trigger when
the points opened again. This in turn
would force new parameters to be
calculated, which would overwrite the
old ones and cause erratic operation.
In practice, this is not a problem
March 1996 29
angle of 15°, the dwell angle results
in a distributor angle of 30°, and the
vacuum angle results in a distributor
angle of 15°. This gives a total distributor angle of 60°, which is well over
the 45° maximum.
A more suitable set of parameters
would be:
Variable
Start advance RPM
Finish advance RPM
Advance angle
Cylinders
Dwell angle
Rev limit RPM
Vacuum advance angle
Security code
The completed unit can be installed on the dashboard or centre console, or fitted
into a weatherproof case and mounted on a motorbike. Do not mount the unit
under the bonnet, as the parts are not rated for high temperatures.
unless some “out of the ordinary”
values are entered, especially for
an 8-cylinder engine. The following
example explains this more clearly:
Variable
Start advance RPM
Finish advance RPM
Advance angle
Data
800
2000
30°
Cylinders
Dwell angle
Rev limit RPM
Vacuum advance angle
Security code
8
30°
5000
30°
59
The cylinder angle for an 8-cylinder
engine is 45°. From the above data, the
advance angle results in a distributor
Data
800
2000
12°
8
20°
5000
10°
59
The total distributor angle now becomes 31° and this represents reasonable ignition timing for an 8-cylinder
engine.
• Key 0: No function.
• Key #: This key terminates the
data entry mode while entering data.
Alternatively, it exits to the ignition
routine if valid data is available while
in MENU mode.
If a keypress error occurs, then ?
will be displayed. Keypress errors are:
(1) Pressing key 3 with no RAM data;
(2) Pressing key 4 with no EEPROM
data;
(3) Pressing key * with no data entered;
(4) Pressing key # with no valid
SC
data.
Fitting The Programmable Ignition System To A Motorbike
I have tested this system on a 1948
Harley Davidson motorcycle which
originally only had a twist grip advance retard on the handlebars.I also
replaced the points with a Hall Effect
transducer and thereafter had a fully
programmable, maintenance-free
ignition system. The major problem
was how to run it off a 6V supply
and this was overcome with a small
switchmode supply.
Another problem that I encountered was that the microprocessor
behaved erratically while the engine
was running. The solution involved
removing the old copper-core plug
leads and replacing them with suppressed ones.
The program as it stands at the
moment can only support distributors
30 Silicon Chip
that have even spacing between
cylinder angles – which covers most
vehicles. However, engines that have
irregular spacing (eg, Harley V Twins
with two cylinders and a 45° angle)
will fool the processor into retarding
the timing for one of the cylinders.
This is because the processor will
calculate an advance value for one
cylinder but the calculated value for
the other cylinder will be different
because the two cylinders are not
equally spaced at 180° around the
crankshaft. In my case, a spe
cial
program was written to cater for this.
If you want to eliminate the points,
one option is to strip down the existing
distributor and modify it for electronic
operation. Alternatively, you can use
a secondhand electronic unit from a
wrecker if one is available.
One advantage of keeping the
points is that if the electronics decide
to fail, the points can be connected
directly to the coil and the ignition
retarded (by rotating the distributor)
to provide a limp-home mode.
The next stage of development
would be to eliminate the distributor
completely and use the crank position as the timing reference. A crank
sensor is certainly favourable when it
comes to installing an electronic system but cost is another consideration
– a “distributorless” ignition requires
one dual output coil for every two
cylinders and these would be fed by
their own driver circuits, which in turn
would be controlled by dedicated pins
on the microprocessor.
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
Build this useful test accessory
A zener diode tester
for your DMM
Plug this simple adaptor
into your DMM and you can
directly read the values of
zener diodes. It covers the
range from about 2.2V right
up to 100V.
By JOHN CLARKE
32 Silicon Chip
H
OW MANY ZENER DIODES do
you have stashed away which
cannot be used simply because
their value is unknown? In many cases, the type number will be missing
(rubbed off) or will be very difficult
to read because the print is so small.
And even if it can be read, the type
number will not directly give you the
value you anyway – instead, you have
to look it up in a data book.
This Zener Tester is the answer to
this problem. It plugs directly into
your DMM, so that you can directly
read the breakdown voltage of the zener being tested. The unit can measure
all the common types from very low
values of around 2.2V right up to 100V.
It’s best for 400mW and 1W power
devices, although it will also provide
a reasonably accurate measurement
for 3W zeners.
Testing zener diodes
Testing zener diodes has always
been difficult. This is because the current needed to test a low-voltage zener
is vastly different to that required for
a higher voltage type.
In the past, many zener testers
tried to circumvent this problem by
applying a constant 5mA and then
reading off the value of breakdown
voltage. Thus, for a 5V zener, the
power dissipated would be 25mW
and for a 30V zener, 150mW. While
these values may appear OK, let’s see
why the constant current idea does
not work in practice.
Fig.1 shows the typical zener
characteristic. In the forward direction, the zener behaves as a diode
and begins to conduct at about 0.7V.
Conversely, in the reverse direction,
there is very little current flow (as
in a normal diode), until the “knee”
is reached. At this point, the zener
breaks down and the voltage remains
essentially constant over a wide range
of currents.
Note the maximum power position
(the power rating of the zener) and the
10% maximum power location. These
two power limits set the operating
range of the zener.
If the current is taken below the
10% maximum power position, the
zener voltage will drop markedly as
it follows the knee in the curve. This
means that if we read the zener voltage
below the 10% position, the reading
will be well under the correct zener
voltage which can only be obtained
Fig.1: the typical zener characteristic. In the reverse direction, there is
very little current flow until the “knee” is reached, at which point the
zener breaks down and the voltage remains virtually constant over a wide
range of currents.
at higher currents.
Note: some zener diode types have
a very sharp knee, which enables the
diode to operate at very low currents
Features
•
Tests 400mW and 1W zener
diodes
•
•
Test range from 2.2V to 100V
•
Connects to a multimeter for
zener voltage reading
•
Battery powered
Constant power testing at
200mW
while maintaining its rated breakdown
voltage.
Fig.2 shows the curves for both 1W
and 400mW zener diodes for voltages
from 3-100V. The lower two traces
show the 40mW (10% of 400mW)
and the 100mW (10% of 1W) power
curves, while the upper two traces
show the maximum power curves for
400mW and 1W.
To properly test 400mW and 1W
diodes, we must have the zeners operate between the 100mW and 400mW
curves. In this way, we will be above
the 10% power point for both types
and below their maximum limits.
The trace (dotted) for a zener tester
using a constant 5mA current shows
Specifications
Zener diode test power �������������������� 200mW
Test power linearity �������������������������� within 10% of 200mW for zener
diodes from 4V to 100V; less than
3.5% change for battery supply
variation from 6-9V
Battery current drain ������������������������ 35mA <at> 9V; 47mA <at> 6V
Open circuit output voltage �������������� 112V nominal
Overall efficiency ������������������������������ 63%
Converter efficiency ������������������������� >90%
March 1996 33
Fig.2: voltage vs.
current curves for
both 1W and 400mW
zener diodes, for
voltages from
3-100V. The lower
two traces show
the 40mW (10% of
400mW) and the
100mW (10% of 1W)
power curves, while
the upper two traces
show the maximum
power curves for
400mW and 1W.
that while zeners from 20-80V fit
between these limits, the maximum
dissipation is exceeded for 400mW
diodes above 80V. At the other end,
the 10% limit prevents 1W diodes
from giving accurate readings below
20V (for 400mW diodes, the limit is
extended to below 8V).
One way around this is to use a
fixed resistor tester operating from
a 110V supply. This will enable all
400mW and 1W zener diodes to be
34 Silicon Chip
tested down to about 3V. Note, however, that this type of tester will go
close to the 400mW limit at about
66V.
At the same time, the tester will also
need to provide up to 1.42W of power
to dissipate 40mW in a 3V zener. This
represents an efficiency of just 3%.
While efficiency may not appear to
be a problem, it does present a strain
on a small 9V battery when it is called
upon to deliver 160mA.
The final trace shows the 200mW
power curve and this fits neatly between the limits specified. The SILICON
CHIP Zener Tester follows this curve
closely. It always provides the same
power to the zener diode, regardless
of voltage. And, as a bonus, battery
drain is much lower at 35mA.
Block diagram
The Zener Tester is based on a high
voltage supply, produced by stepping
Fig.3: block diagram of
the Zener Tester. It uses a
converter to step up the
voltage from a 9V battery
so that high-voltage
zeners can be tested. The
error amplifier and pulse
controller ensure that
the power delivered to
the zener diode remains
constant.
up from 9V using a converter – see
Fig.3. This converter produces up to
about 112V, so that high-voltage zeners
can be tested.
The current supplied to the converter is monitored by error amplifier IC1b
which in turn drives a pulse controller (IC2). This maintains a constant
current to the converter from the 9V
battery. Since the battery voltage is
also constant, the power delivered to
the converter and thus to the zener is
also constant.
In practice, this means that the
converter alters its current output depending on the zener voltage. At high
zener voltages, the current is low and
at low voltages, the current is high.
A LED reference is used to provide
a fixed voltage for the error amplifier,
so that current can be maintained.
Note that this reference is also compensated for input voltage, so that as
the battery voltage falls, the reference
voltage rises and allows more current
flow through the converter. This
maintains the constant power to the
converter, regardless of variations in
the supply voltage.
A standard digital or analog mul-
timeter is used to read the value of
zener voltage.
How it works
The full circuit for the Zener Tester
is shown in Fig.4. It consists of just a
few low-cost components and a stepup transformer.
The step-up circuit uses the two
windings of transformer T1 to produce up to 112V. Mosfet transistor
(Q1) is used as a switch to charge the
primary winding via the 9V supply.
When Q1 is switched off, the charge
is transferred to the secondary and
delivered to a 0.1µF capacitor via
diode D1.
The advantage of using a 2:1 stepup transformer is that the voltage
developed across Q1 is only half that
developed across the secondary winding. This means that a 60V Mosfet can
be used rather than a 200V type.
Q1 is driven by an oscillator formed
by 7555 timer IC2. This operates by
successively charging and discharging
a .0039µF capacitor via a 6.8kΩ timing resistor connected to the output
(pin 3).
When power is first applied, the
.0039µF capacitor is discharged and
the pin 3 output is high. The capacitor
then charges to the threshold voltage
at pin 6, at which point pin 3 goes low
and the capacitor discharges to the
lower threshold voltage at pin 2. Pin
3 then switches high again and so the
process is repeated indefinitely while
ever power is applied.
The current through Q1 is monitored by measuring the voltage across
the 1Ω source resistor. This voltage is
filtered using a 120Ω resistor and a
0.1µF capacitor and applied to error
amplifier IC1b. Its output (pin 7) directly drives the threshold pin (pin
5) of IC5.
If the current is too high, IC1b
pulls pin 5 of IC2 slightly lower, so
that the pulse width duty cycle to Q1
Fig.4 (below): the circuit diagram of
the Zener Tester. IC1b is the error
amplifier and this controls the
duty cycle of oscillator IC2. IC2 in
turn drives Q1 which switches the
primary of step-up transformer T1.
The secondary output of T1 is then
rectified via D1 and applied to the
zener diode.
March 1996 35
The PC board fits neatly into a standard plastic case,
with room for the battery at one end. Take care to
ensure that the test terminals are correctly wired.
is reduced. This in turn reduces the
current. Conversely, if the current is
too low, IC1b pulls pin 5 of IC2 higher.
This increases the duty cycle of the
drive to Q1’s gate and thus increases
the current.
IC1b compares the average current
value with a reference at its pin 5
(non-inverting) input. This reference
is derived from the power supply and
LED1 via IC1a.
In operation, pin 2 of IC1a monitors
a voltage dependant reference derived
from a voltage divider (100kΩ & 560Ω)
across the supply rails. This reference
is fed to pin 2 via a 100kΩ resistor,
while a 100kΩ feedback resistor gives
the amplifier a gain of -1 for this signal
path.
Similarly, the 1.8V that appears
across LED1 is divided using 100kΩ
and 2.4kΩ resistors to give about
42mV at pin 3 of IC1a. IC1a then amplifies this signal by a factor of 2 (1 +
100kΩ/100kΩ) to give 84mV.
To understand how this all works in
practice, let’s assume that the power
supply is at 9V. In this case, the voltage across the 560Ω resistor will be
50mV and so the output (pin 1) of IC1a
will be at 84 - 50 = 34mV. However,
if the power supply falls to 7.5V (for
example), then the voltage across the
560Ω resistor will be 42mV. The pin
Fig.5: this diagram
shows the winding
details for the stepup transformer (T1)
– see text. Note that
both windings are
wound in the same
direction.
36 Silicon Chip
1 output of IC1a will now be at 84 42mV = 42mV.
Thus, as the supply voltage goes
down, the reference voltage applied
to pin 5 of IC1b goes up. This ensures
that greater current is supplied at lower voltages, to maintain the constant
power. As the accompanying specifications panel shows, this scheme
works well, with the power varying by
only 3.5% for battery voltage ranging
from 6-9V.
Power supply
Power for the circuit is derived from
the 9V battery via switch S1. Note that
the battery condition is indicated by
the brightness of the LED. If LED1
is dim, then it is time to change the
battery. The fact that the circuit will
work down to below 6V means that
battery life is quite good.
Construction
Construction of the SILICON CHIP
Zener Tester is straightforward, with
most of the parts mounted on a PC
board coded 04302961 (56 x 104mm).
Begin construction by checking the
PC board for shorted tracks or small
breaks. In addition, the corners of the
PC board will need filing out so that
it will fit inside the case. The actual
shape is shown on the copper side of
the PC board.
This done, install PC stakes at the
Fig.6 (right): make
sure that transformer
T1 is correctly
oriented when
installing the parts
on the PC board
(ie, pin 1 to bottom
left). Fig.7 (far right)
shows the full-size
PC pattern.
external wiring points – see Fig.6.
These are located at the positive (+)
and negative (-) battery wiring points,
at the positive and negative terminal
connection positions, and at the
switch (S1) and LED1 positions. Once
these are in, install the two wire links
(next to IC1 and next to IC2).
Next, install the resistors, followed
by the diodes and ICs. Table 1 lists the
resistor colour codes but it is also a
good idea to check them using a digital
multimeter. Make sure that the diodes
and ICs are correctly oriented.
The capacitors can now be installed,
taking care to ensure that the 100µF
electrolytic is oriented correctly.
This done, install Mosfet Q1 on the
board (metal tab towards IC2). LED1
is mounted on the end of its leads, so
that it will later protrude through the
front panel. Similarly, switch S1 is
soldered on the top of its corresponding PC stakes.
end on pin 6; (2) wind on 20 turns
side-by-side in the direction shown
and terminate the free end on pin 3; (4)
wrap a layer of insulating tape around
this winding.
The secondary is wound on in
similar fashion, starting at pin 5 and
winding in the direction shown. Note
that the 40 turns are wound on in
two layers (20 turns in each), with a
layer of insulating tape between them.
Terminate the free end of the winding
on pin 4.
The transformer is now assembled
by sliding the cores into each side of
the former and then securing them
Transformer winding
Transformer T1 is wound using
0.25mm enamelled copper wire – see
Fig.5. The primary is wound first, as
follows: (1) remove the insulation
from one end of the wire using a hot
soldering iron tip and terminate this
TABLE 1: RESISTOR COLOUR CODES
❏
No.
❏ 1
❏ 1
❏ 4
❏ 1
❏ 1
❏ 2
❏ 1
❏ 1
❏ 1
❏ 1
Value
10MΩ
470kΩ
100kΩ
6.8kΩ
2.4kΩ
1kΩ
560Ω
120Ω
10Ω
1Ω
4-Band Code (1%)
brown black blue brown
yellow violet yellow brown
brown black yellow brown
blue grey red brown
red yellow red brown
brown black red brown
green blue brown brown
brown red brown brown
brown black black brown
brown black gold gold
5-Band Code (1%)
brown black black green brown
yellow violet black orange brown
brown black black orange brown
blue grey black brown brown
red yellow black brown brown
brown black black brown brown
green blue black black brown
brown red black black brown
brown black black gold brown
brown black black silver brown
March 1996 37
+
+
-
+
Ζ
+
ENER TESTER
POWER
+
Fig.8: this full-size artwork can be
used as a drilling template for the
front panel.
The test leads are fitted with banana plugs (red for positive, black for negative),
so that they can be plugged into standard multimeter terminals. The zener
breakdown voltage is the read directly off the multimeter display.
with the clips. This done, insert the
transformer into the PC board, making
sure that it is oriented correctly, and
solder the pins.
Final assembly
A plastic case measuring 64 x 114 x
42mm is used to house the assembled
PC board. This is fitted with a self-adhesive label measuring 55 x 103mm.
Begin the final assembly by affixing
the label to the front panel (lid), then
drill out mounting holes for the LED
bezel, switch S1 and the two banana
plug terminals. You will also need to
drill a hole in one end of the base to
accept a small grommet. This done,
mount the two test terminals (red for
positive, black for negative) and fit
the grommet and LED bezel in place.
Next, fit the board inside the case (it
38 Silicon Chip
sits on four integral mounting pillars)
and secure it using four small self-tapping screws. The lid can now be test
fitted to check that the switch and LED
line up correctly with the front panel.
Adjust them for height as necessary,
then solder the battery clip leads to
their respective PC stakes.
Finally, run short lengths of hookup wire from the PC board to the test
terminals. Additional leads are then
attached to the test terminals and
brought out via the grommet fitted to
one end of the case. Terminate these
leads using banana plugs (red for positive, black for negative). This lets you
plug the leads directly into a standard
DMM or analog multimeter.
Testing
You are now ready to test the unit.
Apply power and check that the LED
lights. If is doesn’t, check that the LED
is oriented correctly. Now measure the
voltages on IC1 using a multimeter.
There should be about 9V DC across
pins 4 & 8 and a similar voltage between pins 1 & 8 of IC2.
If these voltage checks are correct,
plug the output leads into your multimeter and press the Power button.
Check that the meter reads 112V. If it
doesn’t, switch off immediately and
check for wiring errors.
If everything is OK so far, connect a
1kΩ resistor across the test terminals
and check the voltage again (press the
Power button). This time, you should
get a reading of about 14V across the
resistor, which means that the resistor
is dissipating about 200mW. If this
reading is quite different, check that
the voltage across LED1 is 1.7-1.8V
and that about 42mV at present on
pin 3 of IC1.
Assuming a fresh battery, you
should also get about 50mV across the
560Ω resistor. If the latter two reading
are incor
rect, check the associated
voltage divider resistors.
If all is working correctly, you are
now ready to measure zener diodes.
PARTS LIST
1 PC board, code 04302961,
104 x 56mm
1 plastic case, 64 x 114 x 42mm
1 front panel label, 55 x 103mm
1 pushbutton momentary contact
switch (S1)
1 9V battery and battery clip
1 red banana socket
1 black banana socket
1 red banana plug
1 black banana plug
1 EFD20 transformer assembly
(Philips 2 x 4312 020 4108 1
cores, 1 x 4322 021 3522 1
former, 2 x 4322 021 3515 1
clips) (T1)
1 2-metre length of 0.25mm
enamelled copper wire
1 100mm length of red hook-up
wire
1 100mm length of black hookup wire
1 30mm length of 0.8mm tinned
copper wire
8 PC stakes
4 3mm screws
1 small grommet
1 3mm LED bezel
Semiconductors
1 LM358 dual op amp (IC1)
1 7555, TLC555, LMC555CN
CMOS timer (IC2)
1 MTP3055E or A version
N-channel Mosfet (Q1)
1 3mm red LED (LED1)
1 1N4936 fast recovery diode
(D1)
1 56V 3W zener diode (ZD1)
Capacitors
1 100µF 16VW PC electrolytic
2 0.1µF MKT polyester
1 0.1µF 400VDC polyester
1 .0039µF MKT polyester
Resistors (0.25W, 1%)
1 10MΩ
2 1kΩ
1 470kΩ
1 560Ω
4 100kΩ
1 120Ω
1 6.8kΩ
1 10Ω
1 2.4kΩ
1 1Ω
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
❏
Floppy Index (incl. file viewer): $A7
❏
Notes & Errata (incl. file viewer): $A7
❏
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
POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5
Disc size required: ❏ 3.5-inch disc
❏ 5.25-inch disc
TOTAL $A
Enclosed is my cheque/money order for $A__________ or please debit my
❏
Bankcard
❏
Visa Card
❏
MasterCard
Card No.
Signature_______________________________ Card expiry date______/______
Name ___________________________________________________________
PLEASE PRINT
Suburb/town ________________________________ Postcode______________
Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your
order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number
(Bankcard, Visa Card or MasterCard).
✂
There’s just one important thing to
watch out for here – be sure to connect
the zener diode to the test terminals
with the correct polarity; ie, cathode
(banded end) to positive, anode to
SC
negative.
Street ___________________________________________________________
March 1996 39
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.
Model railway level
crossing control
This circuit was used to control the
boom gates for a model railway level
crossing. It is based on light dependent
resistors (LDRs).
The LDRs are fitted between the rails
and a “yard” light above illuminates
them. As the train interrupts the light
to the LDR beam, it operates the relay
which then operates the gates long
enough for a second LDR circuit to
take over.
The delay also takes care of any
tendency for the booms to lift as the
various wagons pass through the beam.
Units 3 and 4 could be added for double track operation.
Only one LDR circuit is shown and
it essentially uses the 555 timer as a
one-shot timer which is triggered by
pin 2 being forced low; this occurs
when the LDR is covered, raising its
resistance.
E. Scharenguivel,
Cloverdale, WA. ($25)
Binary counting
demonstrator
This circuit is used to demonstrate
binary counting. IC1, a 555 timer, is
wired in astable mode and clocks
IC2, a 4024 7-stage binary counter.
VR1 allows the speed of clocking to
be varied.
S1 is added to allow a count to 63
while in the early learning stage and
then switched to allow a count to 127.
S2 is the reset switch. The circuit can
be run from a 9V rechargeable battery.
E. Humphreys,
Barrack Heights, NSW. ($25)
Charge controller
for a transceiver
This circuit is based on one that originally appeared in “Amateur Radio”. It
maintains the charge on a 12V battery
which powers a transceiver. When the
battery voltage drops below 12.5V, as
set by VR1, op amp IC1 turns on Q1
and the relay. This connects the 14V
trickle charger.
The battery is trickle charged until
it reaches 13.8V at which stage the
relay is switched off. It remains in
this state until the battery voltage
drops below 12.5V, at which point
40 Silicon Chip
the relay is again activated and the
cycle is repeated.
L. Toussaint,
Shelley, WA. ($25)
Precision timer uses
cheap crystal
This precision timer can be set for
periods ranging from 15 minutes to
16 hours. ICI, an MM5369 oscillator/
divider, is accurately controlled by a
commonly available 3.579545MHz
TV colour burst crystal. The variable
trimmer at pin 5 can be replaced with
a fixed 6.8pF capacitor. The output
at pin is 60Hz and this is fed to IC2,
a 4040 binary counter configured to
provide a count of 3374 via IC4. In
effect, IC4 (a 4073 triple 3-input gate)
sums the selected binary outputs of
IC2 to 3374.
At the 3374th count, pin 10 of
IC4 goes high, resets IC2 via pin 11
and recommences the next counting
cycle. This output also provides a
clock input pulse to pin 10 of IC3,
another 4040. The net effect is that an
accurate clock input pulse of 56.233
seconds duration is provided to pin
10 of IC3. The decoded binary outputs
of IC3, Q4-Q10, are then switched as
required. Com
mencing with pin 3/
Q4, a 15 minute delay (actually 449.83
seconds) is obtained as pin 3 transits
from low to high.
The .047µF capacitor and 100kΩ
resistor at pin 11 of both 4040s provide
an auto-reset function at switch-on.
Pin 3 of IC2 pulses LED1 at approximately 0.5Hz intervals to indicate that
the circuit is operational.
Technically, the correct reset count
through IC4 should be 3375 for an
exact 15 minute delay at pin 3/Q4
of IC3. To achieve this, pin 9 of IC2
(providing the extra count of 1) would
also have to be ANDed but this would
require another AND gate IC. As it is,
the circuit is accurate to better than
10 seconds in 16 hours. Note that a
battery backup is desirable in areas of
mains interruptions – each momentary
glitch will otherwise cause the circuit
to auto-reset.
C. O’Donnell,
Hoppers Crossing, Vic. ($40)
Brake pedal
alarm circuit
This circuit was designed to
sound a buzzer after about 30 seconds to let the driver of a car know
that he has had his foot on the brake
pedal for too long. The car was fitted
with a manual transmission and the
owner complained that his brake
pads were wearing out too quickly.
The reason was that he had his foot
on the brakes for too long and thus
the need for this timer.
The +12V supply comes from
the car’s brake switch. When the
pedal is depressed, C1 charges via
R1. After about 30 seconds, the
voltage at the junction of C1 and R1
reaches approximately +10V. This
causes ZD1 to con
duct and bias
Q1 on. This pulls down the base of
Q2 and turns it on to apply 12V to
the relay or a buzzer (in place of a
relay). Thus, if the brake pedal is
depressed continually for more than
30 seconds, a buzzer will sound or
the relay will energise. R2 and D1
are used to discharge C1 quickly
after each brake application.
P. Howarth,
Gunnedah, NSW. ($30)
March 1996 41
Build a high-quality
ALC for PA systems
Designed specifically for PA systems, this
high quality Automatic Level Control will
maintain a constant output level over a wide
range of input levels. It is ideal for setting the
volume level in applications which are not
monitored by a sound system operator.
By JOHN CLARKE
Maintaining a consistent volume
level from a public address (PA) system is a constant problem requiring
continuous adjustments. This is because as people speak, they continually move towards and away from
the microphone or even sway from
side to side. While this movement can
42 Silicon Chip
be almost imperceptible, it can have
a drastic effect on the volume level.
Whenever there is a different person
speaking or when music is played,
there is again a volume change. These
variations can be adjusted by the
sound system operator who rides the
volume control to maintain an audible
level at all times. This can be satisfactory in most instances where there is
an operator but for unattended sound
systems, an automatic control is a great
advantage.
Again where there are remote
loudspeakers driven by a sepa
rate
amplifier, adding an automatic volume
control can ensure that the sound
levels are consistent regardless of the
source level.
Ideally, an automatic level control
should have as little effect on the
sound quality as possible. To this end
we have used low distortion and low
noise components and have provided
adjustments for all the main paramet
ers. In this way, the control operation
can be tailored to your requirements.
For example, you may wish to use
the unit as a compressor, where the
dynamic range of the sound is restricted. This type of response is useful in
areas which have high ambient noise.
In this case the attack and decay times
would be adjusted close to their fast
response settings.
The gain limit control is adjusted
to set the threshold below which the
output signal will drop off in level.
If set to its lowest setting, the ALC
will maintain a constant output for
signals down to 2.5mV. This is a very
low signal level and will probably be
too sensitive for most applications.
Adjustment of this control is usually
made during listening tests so that
the normal range of input signals are
effectively amplified.
The Automatic Level Control is
housed in a small plastic case. A potentiometer is provided for the output
level adjustment, while the gain limit,
attack and decay controls are trimpots
which can be accessed by a screwdriver through holes in the front panel. A
power switch and indicator LED are
also provided.
On the rear panel are two RCA sockets for the input and output signals and
a DC socket for the plugpack.
Block diagram
The general arrangement of the ALC
circuit is shown in Fig.1. The input
signal is amplified by 5.5 before being
fed to IC2, a voltage controlled amplifier (VCA). IC2 is an Analog Devices
SSM2018 VCA which features a 117dB
dynamic range, .006% THD at 1kHz
and unity gain, and a 140dB gain control range. In addition, it has the option
to set the output amplifier in class A
or AB modes. We opted for the class
A mode since this provides excellent
distortion characteristics. The AB
mode improves noise performance by
3dB but distortion is 10 times higher.
The change from one mode to the other
is easily implemented by altering a
resistor value.
IC2 feeds the output level control
VR5 and thence the output amplifier
IC1b. It also feeds a precision fullwave rectifier. This rectifier monitors
both the positive and negative signal
excursions which are converted to a
DC level by the following filter. The
resulting output is applied to the VCA
control input which adjusts the gain
of this device so that the signal level
is constant. The response of the filter
will determine how quickly or slowly
the gain of the VCA is controlled.
Fig.1: the signal output from the VCO drives a precision full-wave rectifier
to derive a control signal. This signal is then used to control the gain of the
VCO, so that its output remains constant.
A gain limit adjustment by way of
VR4 and buffer amplifier IC3d prevents the control input from going
below a certain preset voltage. This
limits the overall gain of the VCA so
that automatic level control is initiated
from a preset minimum signal.
Circuit description
Fig.2 shows the complete ALC circuit. Input signals to amplifier IC1a
are AC-coupled to pin 5. The 100kΩ
feedback resistor and the 22kΩ resistor to ground set the gain to 5.5. Thus,
a 1V input signal produces a 5.5V signal at pin 7. IC2 is the VCA, with the
gain controlled by the voltage level
at pin 11. The 18kΩ input resistors to
pins 4 & 6 and between pins 3 & 14 set
Features
•
•
•
•
•
•
•
Low noise and distortion
Constant level over a 52dB
input range
Adjustable control level (gain
limit control)
Adjustable attack and decay
times
Output level control
12VAC plugpack powered
Compact size
the VCA gain to 1 when pin 11 is at
ground. The 47pF capacitors at pins
5 & 8 and 3 & 14 are for compensation
Performance
Frequency response ��������������������-3dB at 40Hz and 20kHz (measured
below compression limit)
Signal-to-noise ratio ����������������������87dB with 22Hz to 22kHz filter and
89dB A-weighted at 100mV signal
limiting; 74dB with 22Hz to 22kHz filter
and 76dB A-weighted at 15mV limiting;
with respect to 1V RMS output.
Harmonic distortion at slowest
attack and decay settings...............<.015% at 1kHz, 10kHz and 20kHz for
.......................................................18mV to 1V input levels
ALC input range ����������������������������2.5mV to 1V
Attack time ������������������������������������1ms to 150ms
Decay time ������������������������������������20dB/second to 6dB/second
Maximum input before clipping �����1.35V RMS
Output level �����������������������������������0-1V RMS
March 1996 43
Fig.2: the circuit is based on an Analog Devices SSM2018 VCA (IC2). Op amps
IC3a & IC3b, together with diodes D1 and D2, form the precision full-wave
rectifier. Its output appears at pin 1 of IC3b and is applied to pin 11 of IC2 via
D3 and VR1.
and rolloff at high frequencies.
Op amps IC3a & IC3b, together
with diodes D1, D2 and asso
ciated
resistors, form a precision full wave
rectifier. When the input signal goes
positive, the output of IC3a goes low
and the gain set by the 20kΩ input and
feedback resistors is -1. This signal is
seen at the anode of D2 and is coupled
to the inverting input of IC3b via the
10kΩ resistor. The gain for IC3b is set
by the 10kΩ and 180kΩ resistors at
-18. The overall gain for the input
signal is therefore -1 x -18 = +18.
Note, however, that there is an extra
path for the input signal via the 20kΩ
resistor at pin 2 of IC3b. This signal
gives a negative signal at the output
of IC3b with a gain of -9. Adding the
two gains gives us +9.
For negative signals, the output of
44 Silicon Chip
IC3a is clamped due to the conduction
of diode D1. The signal then passes via
the 20kΩ resistor connecting to pin 2
of IC3b. IC3b inverts the signal and
provides a gain of -9. Since the input
signal is negative, the signal at pin 1
of IC3b is positive.
The full-wave rectified signal is fed
via D3 and VR1 to two back-to-back
100µF capacitors. Diode D3 allows
the 100µF capacitors to be charged up
via VR1 but they are only discharged
using VR2 and a 470kΩ resistor. This
allows separate control over attack and
decay times of the voltage applied to
pin 11 of IC2.
Trimpot VR3 sets the ALC threshold
and it is buffered by IC3c which then
offsets the inverting inputs of IC3a
and IC3b. VR3 is set so that the signal
output at pin 14 of IC2 is at 1V under
high signal conditions.
Op amp IC3d and VR4 set the gain
limit. Basically, VR4 is set so that the
voltage at pin 11 of IC2 cannot go below the level clamped by D4 and the
output of IC3d. Naturally, pin 11 of IC2
can go above this clamp voltage since
D4 is then reverse biased.
After it has varied the gain of the input signal, the output of IC2 is AC-coupled to the output level control, VR5.
This is buffered by unity gain buffer
IC1b. Its output is AC-coupled to the
external amplifier via a 10µF bipolar
electro
lytic capacitor and a 100Ω
resistor.
Power for the circuit is derived from
a 12V AC plugpack. This is fed via S1
to D5, D6 and two 470µF capacitors to
provide positive and negative supply
rails. These are then fed to two 3-terminal regulators (REG1 & REG2) to
provide balanced ±12V supply rails.
Construction
The automatic level control is built
PARTS LIST
1 PC board, code 01303961, 98
x 98mm
1 plastic case, 111 x 45 x
140mm, Arista UB14
1 12VAC 300mA plugpack
1 self-adhesive front panel label,
95 x 33mm
1 self-adhesive rear panel label,
95 x 33mm
1 SPDT toggle switch (S1)
1 1MΩ miniature vertical trimpot
(VR2)
1 50kΩ miniature vertical trimpot
(VR1)
1 22kΩ miniature vertical trimpot
(VR4)
1 5kΩ multiturn top adjust
trimpot, Bourns 3296 (VR3)
1 20kΩ log pot. (VR5)
1 15mm knob
2 panel mount RCA sockets
1 insulated panel mount DC
socket
1 400mm length of hook-up wire
1 100mm length of shielded
cable
1 60mm length of tinned copper
wire
9 PC stakes
Semiconductors
1 LM833 dual op amp (IC1)
1 SSM2018TN VCA (IC2)
(available from HarTec Ltd)
1 LF347 quad op amp (IC3)
1 7812 +12V regulator (REG1)
1 7912 -12V regulator (REG2)
4 1N4148, 1N914 signal diodes
(D1-D4)
2 1N4004 1A diodes (D5,D6)
1 3mm red LED (LED1)
Fig.3: install the parts on the PC board as shown here. Make sure that all
polarised parts are correctly oriented and take care to ensure that REG1
and REG2 are not transposed, as they are different devices.
on a PC board coded 01303961 and
measuring 98 x 98mm. It is housed
in an Arista UB14 plastic case measuring 111 x 45 x 140mm. Two selfadhesive labels, each measuring 95 x
33mm, are fitted to the front and rear
panels. The PC board layout and wiring diagram is shown in Fig.3.
Start your assembly by checking the
PC board against the published pattern. Repair any broken tracks or shorts
that may be evident. This done, insert
the ICs, diodes, resistors and links in
the locations shown. Take care with
the orientation of the ICs, noting that
IC2 is oriented differently to the other
two. The accompanying resistor colour
code chart should be used in selecting
each resistor value. Alternatively, use
a digital multimeter to measure them.
The diodes must be oriented with the
polarity shown – the banded end is
the cathode (K).
Nine PC stakes are required for
external connections to the PC board.
When these are in, install the capaci-
Capacitors
2 470µF 16VW PC electrolytic
2 100µF 16VW PC electrolytic
3 10µF 25VW PC electrolytic
1 10µF bipolar electrolytic
1 3.3µF bipolar electrolytic
5 0.47µF MKT polyester
1 270pF ceramic
1 68pF ceramic
2 47pF ceramic
1 10pF ceramic
Resistors (0.25W 1%)
1 470kΩ
3 20kΩ
1 180kΩ
2 18kΩ
3 100kΩ
1 10kΩ
1 24kΩ
1 4.7kΩ
4 22kΩ
1 100Ω
March 1996 45
Fig.4: full-size etching pattern for the PC board.
46 Silicon Chip
tors taking care to orient the electrolytics with
the polarity shown. The regulators are next and
they are oriented with their metal tabs away
from the 470µF capacitors. Insert the 7812 into
the location nearest D5.
Take care to insert each of the trimpots into
its correct position. The LED is mounted at
full lead length and bent over at right angles
so that it goes into its matching front panel
hole. It would be a good idea to sleeve one or
both of the LED leads to prevent them from
shorting together.
When complete, the PC board can be secured
inside the case by mounting it on the integral
standoffs, using the self-tapping screws provided.
Affix the adhesive labels to the front and rear
panels and drill out the holes for the output
level pot, the power switch and the rear panel
components. Drill 3-4mm holes for the limit,
attack and decay trimpots. A 3mm hole is required for the LED.
Secure these components to the front and rear
panels, attach the knob and slide the panels
into the case. Affix the rubber feet to the base
of the case.
You can now do the remaining wiring inside
the case. Use short lengths of shielded cable for
TRIMPOT CODES
Value
1MΩ
50kΩ
22kΩ
5kΩ
The rear panel
carries RCA sockets
for the input and
output connections,
plus a DC power
socket.
Code
105
504
223
502
the input and output connections as
shown in Fig.3.
Adjustment & voltage checks
Check your work before applying
power. Using a multimeter, check that
pin 8 of IC1, pin 2 of IC2 and pin 4
of IC3 have +12V present. Similarly,
check that pin 4 of IC1, pins 16 & 10
of IC2, and pin 11 of IC3 are at -12V. If
the LED does not light, it is probably
connected the wrong way around.
Trimpot VR3 can only be set by
applying a signal to the input. You
can use a signal generator set to about
500mV and 1kHz or use a signal such
as that from a CD player, tape deck or
the audio output from a video player.
Connect your multimeter to the output terminals and adjust it to read AC
volts. Turn VR4 (the gain limit trimpot)
fully anticlockwise and adjust VR3 for
a 1VAC reading.
Now the ALC is ready for testing
on a signal. You can hook the unit up
to the line output of the PA system
or signal source as mentioned above
and the output to the input of a power
amplifier. Set the output level and
adjust the gain limit so that with no
signal there is no evidence of noise.
Now you can experiment with the
attack and decay controls for the type
of compression or automatic level
SC
control required.
AUTOMATIC LEVEL
CONTROL
OUTPUT
+
MIN
GAIN LIMIT
MAX
+
12VAC IN
DECAY
ATTACK
POWER
+
+
+
+
LOW HIGH
SLOW FAST
SLOW FAST
+
OUT
+
+
IN
Fig.5: these full-size artworks can be used as drilling templates
for the front and rear panels.
RESISTOR COLOUR CODES
❏
No.
❏ 1
❏ 1
❏ 3
❏ 1
❏ 4
❏ 3
❏ 2
❏ 1
❏ 1
❏ 1
Value
470kΩ
180kΩ
100kΩ
24kΩ
22kΩ
20kΩ
18kΩ
10kΩ
4.7kΩ
100Ω
4-Band Code (1%)
yellow violet yellow brown
brown grey yellow brown
brown black yellow brown
red yellow orange brown
red red orange brown
red black orange brown
brown grey orange brown
brown black orange brown
yellow violet red brown
brown black brown brown
5-Band Code (1%)
yellow violet black orange brown
brown grey black orange brown
brown black black orange brown
red yellow black red brown
red red black red brown
red black black red brown
brown grey black red brown
brown black black red brown
yellow violet black brown brown
brown black black black brown
March 1996 47
SERVICEMAN'S LOG
Sound reasons for confusion
Yes, audio problems are the order this month.
And before you sniff disdainfully, let me assure
you that audio problems in TV sets “ain’t what
they used to be”. Like everything else, they’ve
gone high-tech.
The first story is about an NEC
colour TV set, a model N-4830 using
a C500 chassis and made by Daewoo.
The fault was straightforward enough;
it was completely dead. More than
that, the reason was obvious, at least
to anyone who had seen it before.
This set has an inherent weakness.
The power supply uses a 10-pin IC
switching regulator (I801), a type
STK-73410II. This IC overheats and
fails, taking a lot of components with
it. And that is what had happened in
this case. But there is more to the fault
than that.
It appears that the failure is not
the fault of the IC itself. Rather it is
in the associated circuitry and the
makers have issued a modification
instruction to cover this. Attention to
this is most important because if I801
is simply replaced, the set will back
again in a few months with exactly
the same fault.
The modifications are quite extensive and I don’t propose to set them
out here. Quite apart from the space
needed, I under
stand that since I
did this job, further modifications
have been issued which I have yet
to receive.
My original modification sheet
came from NEC Spares, 23-25
Coombes Drive, Penrith, NSW 2750
– phone (047) 21 7655. It would be
wise to contact them for the latest
information.
Suffice it to say, for the purpose of
this story, that I carried out all the
modifications prescribed at that time,
replaced the IC, then switched on with
my fingers crossed. And, initially, all
seemed well. There was no smoke,
48 Silicon Chip
fire or confusion and the picture tube
warmed up normally and presented
a first class picture. There was only
one thing wrong; there was no sound.
In the good old days, audio faults
were relatively rare and, when they
did occur, they were usually quite
easily found and fixed. It’s not quite
the same these days, at least on some
of the more elaborate sets such as
this one.
Signal tracing
I commenced searching with an
audio probe attached to a test amplifier, starting where the audio comes
out of the IF module, at pin 9 (AUDIO
OUT). Well, there was audio there all
right, which was encouraging. All I
had to do now was trace it through
to the output stage and speaker. And
that, as they say in the classics, was
the hard part.
The audio path is a real aroundthe-world-for-sixpence arrangement.
From pin 9 it goes to pin 7 of I701 (on
a separate page), comes out of I701 on
pin 5, goes back to the IF module on
pin 8 (ATT IN), comes out again on pin
10 (ATT OUT), and is finally fed to the
audio output stage, I602.
Tracing all this out on the circuit –
with much turning of pages – was an
exercise in itself. Then I had to relate
this to the set itself, which involved a
similar order of complexity. But laborious though it was, it paid off.
Audio was being applied to pin 7
of I701 but there nothing coming out
on pin 5. At this stage, I hadn’t paid
a great deal of attention to the role of
I701 but now I needed to know.
It wasn’t hard to work out. This set
Fig.1: the terminal connections
for the IF module in the NEC
N4830. Audio comes out on pin
9, goes back in on pin 8, and
comes out on pin 10 to be fed to
I602 (the power output IC).
features audio and video input sockets
(J202, J703) on the rear of the chassis,
which allow external video and audio
signals (eg, from video recorders and
cameras) to be fed directly to the appropriate parts of the set. This avoids
the losses involved in modulating a
carrier, feeding it through the front
end, then demodulating it to recover
the original signals.
And I701 is a switching module
which feeds the audio and video sections of the set from either the front
end or from the external audio/video
inputs.
Why no audio?
So why wasn’t audio coming out
of I701? In an effort to clarify the
situation, I fed an audio signal into
the audio input socket, J702, and, lo
and behold, the signal went straight
through to the speaker. What’s more,
this situation remained, regardless
of the switching signal instruction
to pin 11. In short, the audio signal
path through I701 was jammed in the
external position.
The most likely possibility was that
the IC itself was faulty. The only other
one was that power supply or switching voltages to it were at fault but I
tended to rule this out on the grounds
that the video switching function was
normal.
Nevertheless, I went through the
motions. The IC is powered from the
12V rail at pin 6 and this was quickly
cleared. The switching voltage is applied at pin 11 and this was turning on
or off according to instructions from
the control unit.
That didn’t really surprise me. After
all, the device was switching the video
signal, so it should have been switching the audio signal as well. More to
the point, it pointed the finger fairly
and squarely at the IC.
So I pulled it out, fitted a new one,
and that was it. And as is often the
case, it all seemed so simple and obvious once I’d found it.
Why did the IC fail the way it did?
Who knows? It could have been a
simple random failure which just
happened to occur at this time, or it
could have been a byproduct of the
power supply failure. But it’s worth
keeping in mind.
The set involved was a Philips type
02CR035, model 20CT6750/75Z, using
a CTO-S chassis. It is a 48cm set, about
10 years old, with remote control and
options built in for Teletext. More
about the type number and options
later.
I didn’t deal directly with the customer – a hazard in itself, as it turned
out – but with a colleague who was
short of time and needed some help.
The complaint was intermittent
loss of picture, with a bright raster.
He had tried to find it but the intermittent nature had made it difficult.
He suspected a dry joint and nomi
nated “the board on the left” as his
prime suspect.
The board on the left was the VST
decoder board and I had my reservations about this diagnosis. It seemed
unlikely that a fault here would produce the symptoms described and
my experience with this board is that
Another sound failure
My next story is also about a sound
failure but that is the only similarity.
By comparison, the previous fault was
not unduly difficult to find, whereas
this fault was one of the most frus
trating I have encountered for a long
time. And the irony was that it didn’t
even start out as a sound problem.
Fig.2: the audio from the IF module in the NEC N4830 is fed to pin 7 of
I701 and comes out on pin 5. Note the external audio/video jacks, J702
and J703.
March 1996 49
Fig.3: the relevant sound circuitry in the Philips 02CR034/35. Audio comes
out of IC7664 (left) at pin 8 and goes to board 1070 via plug 3M12. It is
subsequently applied to pin 7 of IC7681 via plug 2M12.
it is remarkably free from dry joint
problems.
As it turned out, all this speculation
was wasted. When I switched the set
on, the fault appeared immediately – a
brilliant white raster with no picture
and no sound. And, as it turned out,
this condition was permanent.
I immediately suspected a voltage
error around the picture tube; most
likely a loss of cathode voltage, which
is effectively the bias between the
cathode and G1. And since the raster
was white, rather than coloured, it
suggested a fault common to all three
guns. The cathodes are coupled to
the RGB drive transistor collectors,
so this voltage supply was the prime
suspect.
And so it proved to be. The collectors are fed from a 180V rail but there
was no 180V. It didn’t take much
tracking to find out why. A 4.7Ω resistor, R3583, in the power supply
was open circuit. Apparently it had
been intermittent but had finally failed
completely.
I fitted a new resistor and we had our
180V and a first class picture. So far
so good but there was still no sound. I
wasn’t particularly worried about this,
as I imagined a spot of audio signal
tracing, as described earlier, would
quickly solve the problem.
Before doing this, however, I went
over the motherboard, checking it for
50 Silicon Chip
dry joints. In particular, I checked the
horizontal output transformer connections and remade several which looked
suspicious.
Having done this, I came back to
the sound problem. And, in order to
follow what happened next, it is necessary to describe the relevant part of
the circuit – see Fig.3.
The section shown is from the
motherboard. The audio comes out
on pin 8 of the demodulator module
(IC7664 – left) and goes via plug 3M12
to an auxiliary board designated 1070
(Tone Control/Headphone Panel). It
is then supposed to come back to pin
7 of IC7681, the power output IC, via
plug 2M12. I say “supposed” because
it didn’t. Using the audio signal tracer,
I detected audio at 3M12 but there was
nothing at 2M12.
Fun & games
So the fault was on board 1070
which, as its name implies, provides
remote control of the volume, treble,
and bass levels. And this was where
the fun and games started. I didn’t
have a manual for the 02CR035; the
closest I had was one for an 02CR034
which I believed used essentially
the same circuit. And it did, at least
for the main circuit, and I had used
it to track down the original power
supply fault.
But board 1070 was another matter.
There was a general similarity in that
the same IC, a TDA1524 (IC7001), was
used for the level control functions.
However, there were significant differences between my circuit and the
board in this set, which used additional circuitry and components.
This didn’t worry me unduly at first.
I confirmed that audio was coming into
the board (connection 4C6) and to pin
15 of the IC but there was nothing at the
IC’s output (pin 11). Next, I checked
the supply voltage to the IC (pin 9)
and all the associated components. I
could find nothing wrong and that put
suspicion squarely on the IC itself. I
ordered one and fitted it but no joy;
everything was just as before.
I was getting worried now. The IC
and everything around it tested OK,
yet I couldn’t get any audio through
it. I needed to delve into things at
greater depth and, clearly, I needed an
updated circuit. Fortunately, I found
a colleague with a CR035 manual but
my complacency was short lived.
Although this circuit accounted for
some of the additional circuitry, it
still wasn’t complete. Apparently
the set on the bench was a different
version again!
Service department
My next stop was the Philips service
department. I set out the circuit problem in some detail and was assured
that a manual was available –price $84.
I did a mental double take on that; it
was high, even by current standards.
Still, I needed it, and could need it
again. I placed an order.
The manual duly arrived and I
turned eagerly to the 1070 circuit.
Imagine my frustration when I realised
that it was no different from the one
my colleague had loaned me. I went
back to the Philips service department
– they were just as puzzled as I was
and could find no record of a circuit
which fitted the details I described.
Granted, after 10 years, the trail would
be cold. However, they agreed to take
the manual back and credit me and,
at the time of writing, the search is
still on.
In the meantime, the silly situation
remained; I could find nothing wrong
with the IC or its associated circuit
but it would not process the signal. I
sought the assistance of various col
leagues but without any real success.
Some had experienced a similar failure
but it had been traced to a faulty IC.
And they, too, had sought an updated
circuit without success.
In desperation I finally decided to
trace out the extra circuitry on the
1070 board in the hope that it might
provide a clue. And it did. The extra
components were connected to pins
1 and 17 of the IC. There was a 10µF
electrolytic capacitor (C2010) to chassis; a 6.8kΩ resistor (R3010) to plug
1C3; and a 100Ω resistor (R3000) to a
single additional plug, C7.
Hot trails & smelly rats
This plug connection went to a
yellow lead which ran to the VST
board, 1220, via pin 1 of a 3-pin plug
and a mating connector on that board,
marked V17. And this was where I
began to smell a rat. Pin 1 on the VST
board went straight to chassis which,
even with the limited knowledge I had
gleaned of the circuit, didn’t seem to
make sense.
Hot on the trail, I disconnected
the yellow lead, most conveniently
at the 1070 board end, whereupon I
had sound – lots of it and quite uncontrollable. That was both gratifying
and confusing but it clearly indicated
that there was something amiss with
that part of the circuit.
And there was something else I
noted at that time. In both the manuals, the board pattern showed V17 as
a 7-pin arrangement, whereas the set
actually used a 3-pin combination, as
already mentioned. But, with all the
other differences, I didn’t attach much
importance to it.
I also noted that the yellow lead
was anchored at the corner of the VST
board and that it was pulled quite tight
Fig.4: the circuitry for board 1070 in the Philips 02CR035, as shown in the manual. The
actual board used in the faulty set contained extra circuitry and components. Audio goes
into the IC on pin 15 and comes out on pin 11.
March 1996 51
Serviceman’s Log – continued
The result was music to my ears
and this time it was completely controllable. But it was not without some
mixed feelings.
Predominant, of course, was the
relief at having solved the problem.
On the other hand, I muttered some
rude words about those responsible
for the debacle in the first place.
Mental abuse
against the anchor tie to reach V17.
Again, I thought little of it.
But another observation proved
more productive. Apparently, this
board was designed to permit retrofitting of Teletext circuitry and there
were several unused connectors on the
board. And one of these, V19, was a
52 Silicon Chip
3-pin type, sited close to and at right
angles to V17.
Way ahead of me? I’ll bet you are! I
pulled the plug off V17 and fitted it to
V19, noting in the process that the yellow lead was no longer strained against
its anchor point. Then I switched on,
for the umpteenth time.
My colleague copped some of this
mental abuse as well but that wasn’t
really fair. Most of it was directed at
whoever the bright spark was who put
two identical plugs almost side by side
on the same board. It was a disaster
waiting to happen.
With the benefit of hindsight, it was
easy to work out how it had happened.
My colleague had told me that he
had suspected dry joints on the VST
board, which meant that he must have
removed the board for an inspection
and work over. And in putting it back
in place . . .
Talk about Murphy’s law. And
I don’t mean the fictitious leprechaun-like character who lurks in
the corner of the workshop, wrecking
everything we try to do. I mean the real
Murphy. More correctly Lieutenant
Murphy of the US armed forces (I’m
not sure which branch).
As I understand it, Lieutenant
Murphy was in charge of a series
of tests involving acceleration
and impact effects on military
equipment, using a rocket
propelled sled. In one
such test, in which the
equipment was tested
to destruction, the
measurements which
were supposed to be
recorded during the run
and impact were lost.
The reason turned to be – wait for
it – that two interconnecting leads,
fitted with identical plug and socket
connections, had been transposed. I’ve
no doubt Lieutenant Murphy muttered
some rude words of his own but,
for the record, he offered the classic
statement “if anything can go wrong,
it will go wrong.”
I couldn’t agree more. But, again
with the benefit of hindsight, I suppose I should have woken up sooner,
knowing that the board had been
removed and replaced. I wonder if
anyone else out there has been caught
SC
like that?
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.jaycar.com.au
REMOTE CONTROL
BY BOB YOUNG
Multi-channel radio control
transmitter; Pt 2
This month, after a long hiatus, we continue the
description of the Mk.22 transmitter by presenting details of the encoder module. This is a great
deal more flexible than was envisaged in the
June 1995 issue and is still based on discrete ICs
rather than a microprocessor.
Here it is at last! What can I offer
in my defence for the long delay?
Nothing much except that the size
and complexity of this project has
grown alarmingly and has necessitated
calling in additional help in order to
get it finished. I am indebted to Dean
Herbert (Microherb Electronics) for the
design of the basic encoder module
presented here.
Once again, I set out to design one
construction of the basic 8-channel
transmitter.
This transmitter is intended as a
companion to the Silvertone Mk.22
AM receiver published in the December 1994 & February, March & April
1995 issues of SILICON CHIP. However,
it will also act as a replacement for
almost any AM PPM transmitter currently on the market.
While most transmitters on the
As can be imagined, this transmitter
did not fall out of a tree but came as
a result of months of gruelling proto
typing and missed deadlines.
thing and instead ended up with something completely different; the best
transmitter that Silvertone has ever
produced. The complete transmitter
consists of four PC boards: RF module
(AM), basic 8-channel encoder, an
expansion PC board with an additional 16 channels, and a configuration
module. In the next few articles, we
will be dealing with the design and
54 Silicon Chip
market have a moulded plastic case,
the new Silvertone Mk.22 has a more
rugged powder-coated aluminium
case measuring 170 x 140 x 47mm
which is quite compact. Apart from
being more robust, the metal case is
a desirable feature as it reduces the
possibility of interference (third-order
intermodulation) from other transmitters close by.
Packed into the case is a glittering
array of features. Most are routine,
common to all modern R/C systems
but some are completely unique. As
noted previously, it is expandable
from 8 to 24 channels and has capabilities for channel allocation, servo
reversing, gain control, dual rate, servo travel length adjustment, pseudo
endpoint adjustment and mixing on
every channel.
Also included are four programmable on-board mixers (two inverting and
two non-inverting), two programmable
on-board toggle switch control modules, fully programmable front panel
switches and controls, and an expansion port for a configuration module
of which there are four at the moment:
F3B, Helicopter, Aerobatics and the
very exciting and completely unique
formation flying module. These
modules plug into the configuration
port (mix expand) and configure the
transmitter into a task-oriented unit.
Finally, as a topping for this culinary
delight, we add a dash of exclusive Silvertone relish: frequency interlock and
mixed mode dual control (buddy box).
As can be imagined, this transmitter
did not fall out of a tree but came as
a result of months of gruelling proto
typing and missed deadlines. By far
the most difficult task was keeping
the system user friendly. A great deal
of work has been done on the development of the input networks to each
channel and much care devoted to
maintaining a completely identical
board layout so that mastering one
channel results in the mastery of all
channels.
For example, there is only one type
of front panel switch – a SPDT toggle
fitted with a 3-pin socket. Thus, any
switch may become a retract switch,
dual rate switch, mix in-out switch
etc, depending on which set of header
pins it is connected to. The mix select
switch only calls for a 2-pin socket, so
any pair on a 3-pin socket will suffice.
The sockets on the switches provide
an added advantage in that the action
of the switch (UP-ON) may be quickly
and easily reversed (DOWN-ON).
In other words, the front panel
switches are fully program
mable.
Alternatively, the switches may be
replaced by shorting links on the
header pins for permanently installed
features. Thus, for example, coupled
Aileron/Rudder (CAR) may be installed permanently with a shorting
link or set up to operate in the switch
in/out mode from the front panel. On
the other hand, Flap/Eleva
tor auto
compensation is more usually installed as a permanent feature and thus
a simple shorting link on the header
pins will suffice.
Likewise, any channel may be programmed either to be pro
portional
or switched and there are two toggle
switch modules onboard for this
purpose.
The major compromise in the system came about as a result of reducing
the number of potentiometers to be
adjusted and the number of shorting
link combinations available. This was
achieved by making the gain control
pot programmable and is probably
the most clever feature in the user
interface. Thus, we ended up with
only a single potentiometer to adjust
for each channel, which in turn may
be the servo travel volume adjust
(ATV), endpoint adjustment, dual rate
set pot, mix ratio set pot or whatever,
depending upon how the channel is
programmed.
As a result of this simplification, certain combinations tend to compromise
the action of this pot. A good example
is the simplification that took place in
the dual rate programming. Originally
the NORMAL/DUAL RATE programming pins TB1, TB3 etc consisted of
six pins arranged in two rows of three;
a very cumbersome programming arrangement with many combinations.
Now the way we achieve 120% servo travel is to remove the 33kΩ input
resistor from circuit, in the GAIN VARY
setting. Thus, the NORMAL range
is 1-2ms and with the 33kΩ resistor
removed, 0.9-1.1ms. By placing the
33kΩ input resistor on the control pot
side of TB1, it was possible to reduce
the programming to a simple 3-pin
plug which allowed the use of an
SPST switch for remote operation. The
trade-off is that the dual rate pot will
actually increase instead of decreasing the servo travel as it approaches
full clockwise rotation. This comes
about because VR1 effectively shorts
out R2 as it approaches the clockwise
terminal.
Thus, when setting the dual rate
throw, starting from full clockwise rotation will give 120% servo travel. As
the pot is rotated anticlockwise, this
will drop back to 100% then on down
to 20%. All of this will be explained
in detail in future issue.
Whilst this action is a little unusual,
it is still dual rate even if it does go
higher than normal throw. It is only tra-
encoder circuit.
Circuit operation
The basic encoder follows the design philosophy pioneered in the early
1970s which culminated in the Signet
ics NE5044. It uses a multiplexed ramp
generator IC3b to generate standard
pulse position modulation (PPM) –
see Fig.1. Neutral for all 24 channels
is set by a single pot, VR2, associated
with IC1b. This feature represents a
significant cost saving in transmitters
with more than four channels.
IC4 is the 8-channel multiplexer, a
4051. In a full system, there are three
of these which will allow 24 channels,
via the expansion PC board. IC4 samples each control input sequentially
until all inputs are examined and then
there is a pause (sync pause) before the
process begins again. The rate at which
Packed into the case is a glittering
array of features. Most are routine,
common to all modern R/C systems
but some are completely unique.
dition that states that dual rate must go
down from the normal control throw.
Another good example of this sort
of compromise is the situation that
arises when programming for dual
rate combined with coupled channel
mixing; CAR, for example. In this
case, the Aileron gain set pot becomes
primarily the dual rate set pot and
the mix ratio adjustment is set on the
auxiliary mix pot which is part of the
four on-board mixers. This feature
was a particularly difficult one to
achieve, for in the beginning I could
not switch the mix ratio with the dual
rate switch. By utilising the spare pins
on the MIX EXPAND port, I found the
programming combination I required.
This called for the pins on the MIX
EXPAND port to be double-sided and
we will cover this point in detail in the
following articles. Now we have full
mixing with dual rate on the mix ratio.
Actually, I’ve got a little ahead of
myself in talking about these circuit
details but they are really operational
features so it was hard to avoid. Let’s
now get down to the nitty gritty of the
this sampling takes place is called the
FRAME RATE and is typically 16-24ms
in the 8-channel system.
The eight identical input stages each
contain a 3-pin plug (TB2, TB4, etc), to
which the control stick pots are connected. These provide the channel allocation and servo reversing features.
The second set of 3-pin plugs (TB1,
TB3, etc) are used to select NORMAL
or GAIN VARY modes, depending on
how the associated shorting link is
plugged in to short between the centre
and one outside pin.
Setting the shorting link on the
NORMAL pair gives a fixed 1-2ms
pulse width variation. Setting the
Fig.1 (next page): the circuit uses an
8-input multiplexer (IC4) which is
switched by counter IC5. IC4 samples
all eight inputs in sequence and this
creates a staircase waveform at the
output of IC3a. the two comparators
(IC1a & IC1b) then transform this into
the pulse position modulation (PPM).
March 1996 55
56 Silicon Chip
March 1996 57
each individual channel or input in
the encoder.
Thus, the output of IC3a will be
DC but stepped up and down (ie, a
staircase), according to the settings on
each of the eight inputs. This output
is fed to pin 2 of comparator IC1a
where it is compared with the ramp
generator (IC3b) at pin 3. The output
of the comparator is a series of narrow
pulses whose timing, relative to each
other, is a function of the DC input
and the ramp; so the higher the DC
input, the longer the time between
successive pulses.
Thus, the output of the comparator
is a block of eight pulses which have
times between them proportional to
the gain settings on the inputs. This
is known as pulse position modula
tion (PPM).
Synchronising
This scope photo shows how the encoder produces PPM (pulse position
modulation) from the eight multiplexed input channels. The upper trace is the
staircase waveform at pin 1 of IC3a (following the multiplexer) while the locked
pulse waveform is from pin 7 of IC1b. The long positive pulse the sync pause.
shorting link on the GAIN VARY pair
provides 20-120% servo travel controllable from VR1, VR3 etc. The shorting
links on TB1, TB3, etc may be each
replaced with an SPDT switch which
allows remote programming from the
front panel.
VR1, VR3, etc are gain controls
and can perform multiple functions
depending on how the terminal blocks
TB1, TB3, etc are set up (programmed).
Thus, they can provide the dual rate
adjust, servo gain (ATV) and mix ratio.
Mixing expansion port
TB10 is the mixing expansion port
and this is normally fitted with a
shorting plug for the main 8-channel
input leads. This is removed when
the configuration module is plugged
into this port. The pins for this port
are double-sided and they also act as
pick-up points for the mixers involved
with IC6. We’ll come to those later.
TB11 is the 24-channel expansion
port. TB12, TB13 and TB14 are the
channel number select connectors and
select 8, 16 and 24 channels respectively. For example, if TB13 is shorted,
then 16-channel operation is selected.
The main board comes with a shorting
bar on TB12 (on the PC tracks) which
must be cut if you intend to install
more than eight channels. Likewise,
58 Silicon Chip
R25 must be removed for more than
eight channels.
These connectors may be hard wired
or fitted with header pins if you intend
to swap backwards and forwards from
8 to 16 or 24 channels. These pins
could even be wired to a 3-position
switch on the front panel which would
allow front panel selection of 8, 16 or
24 channels. As pointed out previously, the flexibility of this system is
virtually unlimited.
TB7 is the power input connector
and it also carries the modulation to
the RF module.
Let’s start our analysis with IC5, a
4024 counter which continually feeds
a series of binary numbers to the A, B
& C pins of IC4. Thus, IC4 sequentially switches each of its eight inputs
through to R20, the input resistor for
IC3a which is a DC amplifier.
Because IC4 is an addressable
analog switch, any resistance in series
with its inputs (ie, R3, R6, R9, R12,
R26, etc) must be considered to be in
series with R20. This total resistance
will therefore determine the gain of
each individual input.
From this simple fact derives the
magic of the Mk.22 encoder. The ratio
of this total resistance (including R20)
and IC3a’s feedback resistor R18 will
determine the servo travel (GAIN) for
The 8-pulse block is synchronised
by the sync pause generator, IC3c, an
op amp functioning as a one-shot. Each
time Q4 of IC5 goes high, it charges C9
via diode D2 and R16 and the resultant
high pulse from IC3a resets IC5 via
R21. So IC5 starts again and switches
the first of the eight inputs through to
IC3a and the sequence continues.
The length of the sync pause is
controlled by the RC time constant of
R15 & C9, which set it at 8ms.
This is a very important point,
particularly in 16 and 24-channel
transmitters, as it gives the minimum
frame (repetition) rate and thus helps
to minimise servo slow down. This can
arise in some servos if the servo pulse
stretcher cannot cope with the long
repetition rates used in the high level
transmitters. The alternative system
found in some transmitters is to use
a fixed frame rate which must be long
enough to encompass the maximum
width control pulse (2ms) plus the sync
pause (8ms). Thus, a 24-channel transmitter of this type would use a fixed
frame rate of [(24 x 2) + 8]ms = 56ms.
By contrast, the Mk.22 uses a
swinging frame rate which varies
between [(24 x 1) + 8]ms = 32ms to
56ms, depending upon where each
of the control pots is set. In high level
transmitters, it is a good idea to leave
all unused channels set at 1ms to speed
up the repetition rate.
In the 8-channel transmitter, we use
a frame rate which will vary from 1624ms. The form of frame rate generation used in the Mk.22 also has another
advantage when changing from 8, 16
or 24 channels. As the sync pause is
tacked onto the last pulse, the frame
rate increase is adjusted automatically
to suit the number of channels in use.
For people who are concerned about
achieving the minimum frame rate
(maximum data refresh rate), the sync
pause may be set lower but be aware
that there is no standard for the sync
pause in commercial receivers. Some
will operate comfortably on 4-5ms
but others will fly out of sync even
at 6 or 7ms. From past experience, I
have found 8ms to be a fairly safe time
constant. As the Mk.22 Tx is intended
as a replacement for all commercial
transmitters, we have been a little
conservative here.
Unfortunately, the picture of the
circuit operation presented so far is
a lot more complex in reality. IC2a,
a D-type flipflop, is actually the controller of everything. And to further
confuse things, it is not even used like
a conventional D-type. Instead, it is
used as an RS flipflop which is “set”
by the pulse output from IC1a and
“reset” by IC1b, another comparator.
Neutral comparator
IC1b is the neutral comparator and
is set by VR2. The voltage from VR2 is
compared with the same ramp generator signal from IC3b and this produces
a similar series of narrow pulses with a
1.5ms spacing between them. So each
time IC2a is set by IC1a, it is reset by
IC1b a little later.
IC2a not only clocks counter IC5 but
it also drives the ramp generator, IC3b,
which is actually an RC integrator; it
“integrates” the output of IC2a and so
we have a sawtooth waveform which
is locked to IC2a, to the counter and
to everything else.
So how do the pulses from IC3a
actually get to the modulation output
on plug TB7? The answer is that they
don’t. The pulses generated by IC1b,
since they are locked to everything
else, actually become the modulation.
Comparator IC1b drives transistor
Q1 and thence D-type flipflop IC2b
which functions as a monostable
multivibrator. Its Q output will go high
when ever it is clocked by comparator
2 (IC1b) and stay high for a period set
by the RC network of R11 & C5 which
drives the reset pin. R52 and D3 speed
up the recovery time and eliminate
variations in the modulation pulse
length due to variations in the width
of the control channels. The nominal
length of the modulation pulse is set
at 350µs.
IC3d is the pulse shaper, an op amp
integrator used to adjust the rise and
fall time of the modulation pulse to
the RF modulator, an important point
when we come to the RF module. A
correctly set modulation pulse will result in a bandwidth of around ±10kHz.
IC3 is a TLC 2274, specified to provide
near rail-to-rail switching for the RF
modulator. R55 and C4 also help to
reduce the modulation rise and fall
times to reduce RF harmonics. Whilst
in theory C6 should provide symmetry
on both leading and trailing edges,
in practice we found C6 controls the
leading edge slope and R55 and C4
control the trailing edge slope.
YOU CAN
AFFORD
AN INTERNATIONAL
SATELLITE TV
SYSTEM
SATELLITE ENTHUSIASTS
STARTER KIT
Mixers
Op amp IC6 provides four mixers
with gain set by VR8, VR10, VR12
& VR15, respectively. The two small
modules at bottom right – TB17, 20
and TB21, 24 – are toggle switch control modules. TB27 and TB28 (middle
left) are mixer select programming
pins. These mixers are connected to
the main circuit by small patch cords
to the appropriate pins on the mix
expand port, TB10.
Another very important feature of
the circuit is the voltage reference
rails provided by R22, R23, R58 & R61
which are 1% resistors. These accurate
voltage references are derived from
REG1, an LP2950 low drop-out 5V
regulator This regulator allows reliable
operation down to 5V or less on the
transmitter battery.
These accurate reference rails allow
servo reversing on all channels by simply reversing the control pot polarity.
In the Mk.22 encoder, this is done by
reversing the 3-pin socket associated
with each control pot. This function
could be achieved with switches but
it would mean the loss of channel
allocation.
Channel allocation in the Mk.22 is
achieved by simply connecting any pot
to any channel. Channel allocation is
a vitally important feature when we
come to the F3B module for example,
where two channels are required for
ailerons and another two for flaps;
using only one stick axis for each pair
of channels.
So there we have it, a basic no frills
8-channel encoder with expansion to
SC
24 channels if required.
YOUR OWN INTERNATIONAL
SYSTEM FROM ONLY:
FREE RECEPTION FROM
Asiasat II, Gorizont, Palapa,
Panamsat, Intelsat
HERE'S WHAT YOU GET:
●
●
●
●
●
●
400 channel dual input receiver
preprogrammed for all viewable satellites
1.8m solid ground mount dish
20°K LNBF
25m coaxial cable
easy set up instructions
regular customer newsletters
BEWARE OF IMITATORS
Direct Importer: AV-COMM PTY. LTD.
PO BOX 225, Balgowlah NSW 2093
Tel: (02) 9949 7417 / 9948 2667
Fax: (02) 9949 7095
VISIT OUR INTERNET SITE http://www.avcomm.com.au
YES GARRY, please send me more
information on international band
satellite systems.
Name: __________________________________
Address: ________________________________
____________________P'code:
__________
Phone: (_______) ________________________
ACN 002 174 478
March 1996 59
Build this 20ms delay
board to add to your
surround sound unit
or use it to enhance
musical instruments.
It uses the latest
digital conversion
and memory storage
techniques to provide
quality sound. Only
one integrated circuit
is required, plus a
handful of passive
components.
By JOHN CLARKE
A 20ms Delay For
Surround Sound Decoders
I
F YOU HAVE BUILT a low cost
surround sound decoder, you
won’t be getting the best sound
effect unless it has a delay for the rear
channel. Now you can fix this drawback by adding our 20ms delay board.
A typical lounge room with a
surround sound setup will have the
front, left, right and centre channel
loudspeakers located well in front of
the lounge and adjacent to the TV set.
The rear loudspeakers will be directly
behind the listener.
Because of this, the sound from the
rear will arrive at the listeners ears before that from the front loudspeakers.
When this occurs, the sound from the
surround loudspeakers will tend to
dominate the perceived direction of
the sound field.
However, if a delay is added to the
rear channel, its sound will arrive later
than from the front and so the sound
field will be correctly perceived by the
60 Silicon Chip
ear. The normal delay time required
is 20ms and this will cater for most
lounge rooms.
For public address use, it is also
sometimes an advantage to add a delay
to the sound fed to the loudspeakers at
the rear of a hall compared to those at
the front. For listeners at the rear of the
hall, the sound from the loudspeakers
near to them will normally arrive before the sound from the loudspeakers
at the front.
The result will be an echo that
can cause considerable difficulty in
understanding the person speaking.
By adding a delay to the rear speakers,
Performance
Delay
20ms (fixed)
Gain
Unity
Frequency Response
-1dB at 10Hz, -3dB at 7kHz
Maximum Input
1.2V RMS
Input Impedance
20kΩ
Output Impedance
1kΩ
Harmonic Distortion
0.3% at 1kHz and 300mV RMS (see graph)
Signal To Noise Ratio
With respect to 1V RMS: 97dB unweighted
(20Hz-20kHz); 101dB A-weighted
Fig.1: the M65830 IC
converts in the incoming
signal to digital form, stores
it in memory, reads it out
again and converts it back
to an analog signal. The
delay is a function of the
size of the internal RAM
and the clock speed, as set
by the oscillator.
this echo effect can be considerably
reduced.
A 20ms delay represents the time
that it takes sound to travel 6.7 metres.
Several delay units could be connected
in series to increase the delay if necessary or, better still, you can alter the
circuit components to obtain a 40ms
delay.
The circuit is based on the Mitsu
bishi M65830P digital delay IC. This
works by first converting the incoming
analog signal to a digital format which
is then clocked into memory. This
digital signal is then clocked out at the
end of the delay period and converted
back to analog form.
In addition, the M65830P contains
AUDIO PRECISION THD-FRQ THD+N(%) vs FREQ(Hz)
5
21 DEC 95 13:16:35
1
0.1
0.010
10
100
1k
5k
Fig.2: this graph plots the harmonic distortion for the 20ms Delay Circuit. The
ripple evident in the curve is an artefact of the A-D (analog-to-digital) and D-A
processes but is not audible.
several op amps so that input and output filters can be added to the circuit
without using additional ICs.
Circuit details
The circuit is shown in Fig.1. The
input signal is coupled to an inverting
op amp input at pin 23 via a low pass
filter comprising C1, C2, R1, R2 and
R3. This rolls off signals above about
8.5kHz to prevent high frequencies
affecting the following digital conversion which can cause spurious effects
in the output.
Capacitor C6 and resistor R7 control
the rate of delta modulation which is
the type of analog to digital conversion
used in IC1. Similarly, C5 controls the
digital to analog conversion output
signal appearing at pin 15. This output
is applied to a 7kHz filter comprising
resistors R4, R5 and R6 and capacitors
C4 and C5. The output of the filter op
amp at pin 13 is AC-coupled via a
10µF capacitor.
The circuit can be powered from a
DC rail from 9-25V, although we have
shown +12V as the supply input on
Fig.1. Three-terminal regulator REG1
provides +5V to the IC’s Vcc and Vdd
pins (1 & 24).
Options
Some readers may have an application which requires a longer delay time
than 20ms or may desire a frequency
March 1996 61
18kΩ; C1 & C3 should be 560pF
and C2 & C4, 150pF.
Note that using 15kHz filters
will lead to a slight increase in
residual noise and distortion.
The harmonic distortion char
acteristic for the 20ms circuit,
with 7kHz filters, is shown in
Fig.2.
Construction
Fig.3: follow this parts layout when
building the PC board. An IC socket is
optional.
Fig.4: this is the full-size artwork for
the PC board. Check the etched board
carefully before installing the parts.
response above 7kHz.
If you want a 40ms delay, the crystal
must be 1MHz (instead of 2MHz), C5
& C6 should be .022µF and R7 should
be 82Ω.
To obtain a frequency response to
15kHz, the following components
should be changed: R1, R2, R4 & R5
should be 39kΩ; R3 & R6 should be
All of the delay circuit components are assembled onto
a PC board coded 01401961
which measures 63 x 60mm. It
is designed to fit horizontally
into a plastic case measuring
130 x 67 x 32mm.
This case is optional – we
envisage many constructors
will install the board into existing equipment (presumably
the same case as the surround
sound decoder).
The component overlay is
shown in Fig.3. Begin construction by checking the PC board
for shorted or broken tracks.
Repair any faults before assembling the components.
Start with the PC stakes for all
the input and output terminals.
Next, the links can be installed,
followed by the resistors. Use
the accompanying table to assist you in selecting the correct
colour code.
Once the resistors are in, the
IC and the capacitors can be
installed. Make sure that the IC
and the electrolytic capacitors
are correctly oriented. Finally,
install the 3-terminal regulator. It is
oriented so that its tab faces the adjacent 10µF capacitor.
Testing
To test the unit, apply power to
the DC input and check with your
multimeter that the regulator output
is close to +5V.
PARTS LIST
1 PC board coded 01401961,
63 x 60mm
1 plastic case 130 x 67 x 32mm
(optional)
1 2MHz crystal (X1)
6 PC stakes
1 50mm length of 0.8mm tinned
copper wire
Semiconductors
1 M65830P delay (IC1)
1 7805T 5V 3-terminal regulator
(REG1)
Capacitors
1 100mF 16VW PC electrolytic
1 47µF 16VW PC electrolytic
4 10µF 16VW PC electrolytic
3 0.1µF MKT polyester
2 .068µF MKT polyester
1 .0027µF MKT polyester
1 .0022µF MKT polyester
1 680pF ceramic
1 560pF ceramic
2 100pF ceramic
Resistors (0.25W, 1%)
1 1MΩ
2 10kΩ
1 100kΩ
1 30Ω
4 22kΩ
If you have access to an audio signal
generator, you can use it to check the
circuit operation. Note that the gain
of the circuit from input to output is
unity.
A dual trace oscilloscope can be
used to verify the delay between input
and output. At 25Hz, the two signals
should be 180° apart, while at 50Hz
they will appear in-phase again.
Final testing can be made after
installation in your equipment. Note
that the delay unit will only handle
signals up to 1.2V RMS. For higher
level signals, an input attenuator will
SC
be required.
RESISTOR COLOUR CODES
❏
❏
❏
❏
❏
❏
62 Silicon Chip
No.
1
1
4
2
1
Value
1MΩ
100kΩ
22kΩ
10kΩ
30Ω
4-Band Code (1%)
brown black green brown
brown black yellow brown
red red orange brown
brown black orange brown
orange black black brown
5-Band Code (1%)
brown black black yellow brown
brown black black orange brown
red red black red brown
brown black black red brown
orange black black gold brown
ORDER FORM
BACK ISSUES
MONTH
YEAR
MONTH
YEAR
PR ICE EACH (includes p&p)
TOTAL
Australi a $A7.00; NZ $A8.00 (airmail ); Elsewhere $A10
(airmail ). Buy 10 or more and get a 10% discount.
Note: Nov 87-Aug 88; Oct 88-Mar 89; June 89; Aug 89;
Dec 89; May 90; Aug 91; Feb 92; July 92; Sept 92; NovDec 92; & March 98 are sol d out. All other issues are
currently i n stock.
$A
B INDERS
Pl ease send me _______ SILICON CHIP bi nder(s) at
$A12.95 + $5.00 p&p each (Australi a only). N ot avail abl e
elsewhere. Buy five and get them postage free.
$A
SUBSCRIPTIONS
New subscription – month to start____________________________
Renewal – Sub. No.________________ Gift subscription
RATES (please tick one)
2 years (24 issues) 1 year (12 issues)
Australia (incl. GST)
$A135
$A69.50
Australia with binder(s) (incl. GST)** $A159
$A83
New Zealand (airmail)
$A145
$A77
Overseas surface mail
$A160
$A85
$A250
Overseas airmail
$A125
**1 binder with 1-year subscription; 2 binders with 2-year subscription
YOUR DETAILS
Your Name_________________________________________________
GIFT SUBSCRIPTION DETAILS
Month to start__________________
Message_____________________
_____________________________
_____________________________
Gift for:
Name_________________________
(PLEASE PRINT)
Address______________________
_____________________________
(PLEASE PRINT)
Address___________________________________________________
State__________Postcode_______
______________________________________Postcode_____________
Daytime Phone No.____________________Total Price $A __________
Signature
Cheque/Money Order Bankcard Visa Card Master Card
______________________________
Card No.
Card expiry date________/________
Phone (02) 9979 5644
9am-5pm Mon-Fri.
Please have your credit card
details ready
OR
Fax (02) 9979 6503
Fax the coupon with your
credit card details
24 hours 7 days a week
Mail order form to:
OR
Reply Paid 25
Silicon Chip Publications
PO Box 139, Collaroy 2097
No postage stamp required in Australia
March 1996 63
BOOKSHELF
Satellite TV installation & repair
Ku-Band Satellite TV; Theory
Installation & Repair, by Frank
Baylin. 4th edition published
1991 by Baylin Publications. Soft
covers, 420 pages, 275 x 215mm,
ISBN 0-917893-14-X. Price $59.00.
This book is devoted to all
aspects of the transmission and
reception of signals in the 10.95
to 14.50GHz region of the electromagnetic spectrum. It is a very
difficult book to review as there is
so much information packed into
its 400 odd pages. The volume is
divided into nine chapters which
range from the basics of satellite
communication to scrambling
technologies and erecting your
own antenna.
In the first chapter we are
introduced to uplink and down
link paths, worldwide frequency
allocations and understanding
satellite footprint maps. One of the
paragraphs gives details of “station
keeping”. This refers to the need
for a satellite in geostationary orbit
(35,786km above Earth) to have
its thrusters fired every 3-4 weeks
to maintain its E/W location and
every 60-90 days to keep it on the
equatorial plane.
Chapter two covers all you need
to know about antennas, including mounts, actuators, feedhorns,
low noise block downconverters
(LNBs), satellite receivers, modulators, TV receivers, monitors and
audio reception. Much of this is
useful background information,
although the average reader wishing to acquire a satellite receiver
system will probably purchase a
package with a guarantee of performance for the location in which it
will be used.
A US study on judging picture
quality concluded that a S/N ratio
of 33dB gave passable results;
40dB was good and 45dB rated as
excellent. These figures have been
confirmed in subsequent studies
and give potential owners an idea
of the quality of the reception they
can anticipate at their particular
location.
Chapter three covers the design
and testing of Ku-band systems.
Things that we do not normally
consider, such as rain, atmospheric
attenuation, ambient temperature
and antenna size all play an important role when the signal from
PC-based instrumentation & control
PC-based Instrumentation and Control by M. Tooley. Published 1995 by
Butterworth-Heinemann Australia.
Soft covers, 388 pages 235 x 155mm,
ISBN 0-7506-2093-5. Price $55.00
In the introduction to this book, the
author states that it is aimed primarily at “the professional control and
instrumentation specialists. It does
not assume any previous knowledge
of microprocessors or microcomputer
systems.” He also claims that his aim
is to provide sufficient information to
solve problems in the shortest time
and without recourse to any other
64 Silicon Chip
texts. For this reason there is a large
amount of information in this book
which will be readily available, and
probably quite familiar, to the majority of PC owners.
The first chapter charts the history
of the IBM PC and compatibles, beginning with the 8088 processor and
working through to the 80486. Maths
co-processors, DMA (direct memory
access) controllers, interval timers and
interrupt controllers are only some of
the programmable devices which are
then detailed. The chapter continues
with a discussion on RAM and ROM
(random access and read only mem
ory), BIOS (basic input output services) and concludes with details of
power supplies, video standards and
floppy and hard discs for PCs.
Chapter two covers PC expansion
systems in some depth. It begins by
listing the PC bus connections, then
detailing the requirements for bus
expansion cards. A number of cards
which are suitable for use with the
PC, along with their specifications,
are then detailed. The chapter concludes with information on Eurocard
(160 x 100mm) modules which suit
the satellite is usually less than
10-17 watts/m2.
Chapters four and five detail the
selection of equipment for, and the
installation of, Ku band receivers.
For ideal locations with relatively
strong signals, a small antenna is
all that is required but for difficult
sites a 3m dish is necessary and this
must be well anchored to support
it against high wind gusts.
The sixth chapter covers the
retrofitting of C band systems to
receive Ku band signals. In Australia, all channels are transmitted
in the Ku band but a number of C
band signals from overseas can be
received (see SILICON CHIP, July
1995, page 40).
Chapter seven explains the
methods used in multiple receiv
er and distribution systems. These
could be required in hotels, etc
where perhaps one or two satellite
TV channels, as well as the local
TV stations and perhaps several
VCR channels would be made
available to guests. This means
that the satellite signals have to
be down-converted to VHF so that
they can be distributed over the
existing installation and received
by commercial TV receivers.
Chapter eight is titled “Worldwide Ku band satellite television”
in which just over one page is
devoted to Australia, New Zealand
and New Guinea. It gives details of
the three Aussat satellites and their
the STE bus. These cards plug into
a backplane and normally contain
a processor, memory and assorted
peripheral chips. One of those described is also fitted with a hard disc
controller and a multimode graphics
controller.
The next chapter covers the PC operating system’s internal and external
commands, copying discs, files and
their structure and the use of Debug.
It concludes with a couple of pages devoted to Windows 3.10 and Windows
NT. All this information will be readily
available to the PC owner in the DOS
and Windows manuals.
Chapter four is titled “programming” and gives process control
channel allocations.
The last chapter is devoted to
troubleshooting and repair. These
20 pages give an indication of the
problems that can arise, from the
movement of a dish, the damage
to a buried feed cable by a keen
gardener, to the routine electronic
failures that have become familiar
to the industry.
Subtle faults are discussed, like
“solar outages”, when the sun
lines up directly along the antenna
boresight (the direction along the
principal axis) during the equinoxes and causes loss of, or very weak,
signal reception. These can only be
learned about by reading or word
of mouth. The chances of finding
a fault of this nature intuitively
must be zero.
The book concludes with a series
of appendices covering things like
antenna gain and beamwidth, noise
temperature, anten
na geometry,
satellite footprints throughout the
world, a glossary of terms and a
listing of satellite channels.
This book has a wealth of information on satellite TV and while
the information is specialised and
some not applicable to this country, it will prove an invaluable
reference for anybody desiring to
learn more about this fascinating
subject. Our copy came from AvComm Pty Ltd, PO Box 225, Bal
gow
lah, 2093. Phone (02) 9949
7417. (R.J.W.)
engineers an insight into the features
they should ensure are available in
programming languages which they
may propose to use. For example IF
..ELSE ..END IF, DO WHILE ..LOOP,
and WHILE ...WEND are often likely
to be used in process control applications. Tooley then explains the steps
involved in software development,
which should normally be a top-down
process, moving from the general to
the specific.
Flow chart symbols are introduced
and several flow chart examples
are shown. Explanations of control
structures, pseudo-code (a mixture
of English and the programming language being used) and program loops
are examined in some detail. The
chapter concludes with several pages
stressing the importance of adequately
documenting all software and gives
several examples.
Chapters five, six and seven cover
programming in Assembler, Basic and
C respectively. None is a step by step
introduction but more a background
for each and by reading all three
chapters a beginner would have some
appreciation of the great differences
between these languages.
The IEEE-488 bus – also known as
the HPIB (Hewlett Packard Instrumentation Bus) or the GPIB (General
Purpose Instrumentation Bus) – is
explained in chapter eight. This bus
provides the means of interconnecting
a microcomputer with a vast range
of test and measuring instruments.
In the past, only the more expensive
instruments were fitted with this bus
but thanks to the development of low
cost IEEE-488 chips it is becoming
commonplace, even on cheaper equipment. This setup allows automated
measurements to be made under the
control of a computer.
Interface cards are available for the
PC, the one discussed being the MetraByte MBC-488. This plugs directly
into the IBM bus and has an IEEE 24pin connector as its output. It can be
controlled from the PC using any high
level language.
Interfacing the computer to the
outside world is the subject covered
in the next chapter. Input devices are
discussed first. Some simple digital
devices can be readily connected
through the parallel or serial ports,
but any analog device will need an
interface card with an A-D (analog
to digital) converter. A-D cards for
the PC are readily available, usually
with multiple inputs, which enable a
number of different transducers to be
monitored simultaneously.
Some of the different types of sensors are explained, including position,
liquid level, optical, temperature and
pressure sensors. The author then
details methods of adapting these
and other devices to interface to the
computer. He also covers areas where
optical isolation may be required (eg,
for monitoring mains voltages) and
describes how this is achieved.
Once the data is processed by the
computer, the results need to be displayed somehow. It may be inconvenient or impossible to use the screen of
March 1996 65
Bookshelf: PC-Based Instrumentation & Control – continued
the computer and usually the requirement will be for an alarm or relay to
be actuated. Methods of interfacing
to LEDs, relays, lamps, audible alarms
and motors are shown.
Software Packages are the subject
of chapter 10. The author details the
criteria in selecting a software package,
such as ease of use, flexibility, performance and functionality. He then
describes three commercial packages:
Asyst, Asystant and DadispII.
He goes on to detail two of the most
popular tool kits, Norton Utilities and
PC Tools. These both contain essential
routines which are missing from DOS.
Chapter 11 discusses the differing approaches which can be taken
to solve a problem, depending on
the complexity of the task. Simpler
measurements might only require
the addition of one extra card (perhaps a 16 channel A-D converter) to
a standard PC. On the other hand, a
system requiring a greater variety of
measurements might require several
expansion cards in an external card
frame, while a very large system might
consist of several external pieces of
instrumentation linked to the PC via
the IEEE-488 bus.
The chapter continues by describing
the steps involved in analysing an
application. These include the performance of the system, I/O devices,
displays and operator inputs, storage
devices, communications and future
expansion.
It concludes with the solutions to
four applications: measurement of the
stability of a VCO (voltage controlled
oscillator); testing crystal filters; development and testing of a speech
synthesiser; and, finally, strain measurement and processing on an aircraft
undercarriage.
“Reliability and Faultfinding” is the
title of chapter 12. Reliability comes
from good quality control procedures
during the manufacture and installation of any system. The process control
specialist should ensure that the quality is built in right from the beginning.
Methods for monitoring performance,
such as hardware watchdog timers and
software diagnostics are expounded,
along with a brief discussion on the
POST (power on self-test) routines
of the PC.
A list is given of the necessary test
equipment, which comprises a multimeter, logic probe, logic pulser and,
perhaps, an oscilloscope. The last
few pages of this chapter explain the
methods of using these tools in fault
finding procedures.
Chapter 13 is titled “System Configuration” and covers device drivers,
RAM drives, memory managers, printer.sys and autoexec.bat. The chapter
concludes with autoexec.bat and
config.sys listings for seven different
computer systems.
Appendices A-F cover a glossary
of terms, SI units, multiples, decimal-binary-hex-ASCII tables, a bibliography and finally a list of suppliers
of PC boards and PC based expansion
boards.
To sum up, the book certainly fulfils
the author’s claim that there is no
need to refer to other texts. However,
since the first edition of the book in
1991, many more people now have
a computer and there are probably
very few instrumentation engineers
who would not be familiar with a
personal computer. Nevertheless the
convenience of having all the information together and the reasonable
price makes this book a worthwhile
investment. (R.J.W.)
20 Electronic Projects For Cars
$8.9s5
plu
$3 p&p
Yes! Please send me ___ copies of 20 Electronic Projects For Cars
Enclosed is my cheque/money order for $________ or please debit my
❏ Bankcard ❏ Visa Card ❏ Master Card
Card No.
Signature________________________ Card expiry date_____/______
Order by phoning (02) 979 5644 & quoting your
credit card number; or fax the details to (02) 9979
6503; or mail the coupon to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097.
66 Silicon Chip
Name _______________________Phone No (_____)____________
Street
PLEASE PRINT
_________________________________________________
Suburb/town _____________________________ Postcode_________
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
Silicon Chip
October 1990: Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator;
DC Offset For DMMs; Using The NE602 In Home-Brew
Converter Circuits.
BACK ISSUES
November 1990: How To Connect Two TV Sets To One VCR;
A Really Snazzy Egg Timer; Low-Cost Model Train Controller;
Battery Powered Laser Pointer; 1.5V To 9V DC Converter;
Introduction To Digital Electronics; Simple 6-Metre Amateur
Transmitter.
September 1988: Hands-Free Speakerphone; Electronic Fish
Bite Detector; High Performance AC Millivoltmeter, Pt.2;
Build The Vader Voice.
Tips For Your VCR; Speeding Up Your PC; Phone Patch For
Radio Amateurs; Active Antenna Kit; Speed Controller For
Ceiling Fans; Designing UHF Transmitter Stages.
April 1989: Auxiliary Brake Light Flasher; What You Need
to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2;
LED Message Board, Pt.2.
February 1990: 16-Channel Mixing Desk; High Quality
Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random
Wire Antenna Tuner For 6 Metres; Phone Patch For Radio
Amateurs, Pt.2.
May 1989: Build A Synthesised Tom-Tom; Biofeedback
Monitor For Your PC; Simple Stub Filter For Suppressing
TV Interference; LED Message Board, Pt.3.
July 1989: Exhaust Gas Monitor (Uses TGS812 Gas Sensor);
Extension For The Touch-Lamp Dimmer; Experimental Mains
Hum Sniffers; Compact Ultrasonic Car Alarm.
September 1989: 2-Chip Portable AM Stereo Radio (Uses
MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero
Module for Audio Amplifiers (Uses LMC669).
October 1989: FM Radio Intercom For Motorbikes Pt.1;
GaAsFet Preamplifier For Amateur TV; 1Mb Printer Buffer;
2-Chip Portable AM Stereo Radio, Pt.2; Installing A Hard
Disc In The PC.
November 1989: Radfax Decoder For Your PC (Displays Fax,
RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2;
2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive
Formats & Options; The Pilbara Iron Ore Railways.
December 1989: Digital Voice Board; UHF Remote Switch;
Balanced Input & Output Stages; Data For The LM831 Low
Voltage Amplifier IC; Index to Volume 2.
January 1990: High Quality Sine/Square Oscillator; Service
March 1990: 6/12V Charger For Sealed Lead-Acid Batteries;
Delay Unit For Automatic Antennas; Workout Timer For
Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The
UC3906 SLA Battery Charger IC.
April 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch (VOX) With Delayed Audio; 16-Channel Mixing
Desk, Pt.3; Active CW Filter For Weak Signal Reception; How
To Find Vintage Receivers From The 1920s.
June 1990: Multi-Sector Home Burglar Alarm; Low-Noise
Universal Stereo Preamplifier; Load Protection Switch For
Power Supplies; A Speed Alarm For Your Car; Fitting A Fax
Card To A Computer.
July 1990: Digital Sine/Square Generator, Pt.1 (Covers
0-500kHz); Burglar Alarm Keypad & Combination Lock;
Simple Electronic Die; Low-Cost Dual Power Supply; Inside
A Coal Burning Power Station.
August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace
The Electronic Cricket; Digital Sine/Square Generator, Pt.2.
September 1990: Remote Control Extender For VCRs;
Power Supply For Burglar Alarms; Low-Cost 3-Digit Counter
Module; Simple Shortwave Converter For The 2-Metre Band.
December 1990: DC-DC Converter For Car Amplifiers; The Big
Escape – A Game Of Skill; Wiper Pulser For Rear Windows;
A 4-Digit Combination Lock; 5W Power Amplifier For The
6-Metre Amateur Transmitter; Index To Volume 3.
January 1991: Fast Charger For Nicad Batteries, Pt.1; Have
Fun With The Fruit Machine; Two-Tone Alarm Module; LCD
Readout For The Capacitance Meter; How Quartz Crystals
Work; The Dangers When Servicing Microwave Ovens.
February 1991: Synthesised Stereo AM Tuner, Pt.1; Three
Inverters For Fluorescent Lights; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design
Amplifier Output Stages
March 1991: Remote Controller For Garage Doors, Pt.1;
Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner,
Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal
Wideband RF Preamplifier For Amateur Radio & TV.
April 1991: Steam Sound Simulator For Model Railroads;
Remote Controller For Garage Doors, Pt.2; Simple 12/24V
Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical
Approach To Amplifier Design, Pt.2.
May 1991: 13.5V 25A Power Supply For Transceivers; Stereo
Audio Expander; Fluorescent Light Simulator For Model
Railways; How To Install Multiple TV Outlets, Pt.1.
June 1991: A Corner Reflector Antenna For UHF TV;
4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply
For Transceivers; Active Filter For CW Reception; Tuning In
To Satellite TV, Pt.1.
July 1991: Loudspeaker Protector For Stereo Amplifiers;
4-Channel Lighting Desk, Pt.2; How To Install Multiple TV
Outlets, Pt.2; Tuning In To Satellite TV, Pt.2.
August 1991: Build A Digital Tachometer; Masthead Amplifier
ORDER FORM
Please send me a back issue for:
❏ July 1989
❏ September 1989
❏ January 1990
❏ February 1990
❏ July 1990
❏ August 1990
❏ December 1990
❏ January 1991
❏ May 1991
❏ June 1991
❏ October 1991
❏ November 1991
❏ April 1992
❏ May 1992
❏ September 1992
❏ October 1992
❏ April 1993
❏ May 1993
❏ September 1993
❏ October 1993
❏ February 1994
❏ March 1994
❏ July 1994
❏ August 1994
❏ December 1994
❏ January 1995
❏ May 1995
❏ June 1995
❏ October 1995
❏ November 1995
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
September 1988
October 1989
March 1990
September 1990
February 1991
July 1991
December 1991
June 1992
January 1993
June 1993
November 1993
April 1994
September 1994
February 1995
July 1995
December 1995
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
April 1989
November 1989
April 1990
October 1990
March 1991
August 1991
January 1992
July 1992
February 1993
July 1993
December 1993
May 1994
October 1994
March 1995
August 1995
January 1996
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
May 1989
December 1989
June 1990
November 1990
April 1991
September 1991
March 1992
August 1992
March 1993
August 1993
January 1994
June 1994
November 1994
April 1995
September 1995
February 1996
Enclosed is my cheque/money order for $______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card
Signature ____________________________ Card expiry date_____ /______
Name _______________________________ Phone No (___) ____________
PLEASE PRINT
Street ________________________________________________________
Suburb/town ________________________________ Postcode ___________
72 Silicon Chip
Note: all prices include post & packing
Australia (by return mail) ............................. $A7
NZ & PNG (airmail) ...................................... $A7
Overseas (airmail) ...................................... $A10
Detach and mail to:
Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097.
Or call (02) 9979 5644 & quote your credit card
details or fax the details to (02) 9979 6503.
✂
Card No.
For TV & FM; PC Voice Recorder; Tuning In To Satellite TV,
Pt.3; Step-By-Step Vintage Radio Repairs.
September 1991: Studio 3-55L 3-Way Loudspeaker System;
Digital Altimeter For Gliders & Ultralights, Pt.1; The Basics
Of A/D & D/A Conversion; Windows 3 Swapfiles, Program
Groups & Icons.
October 1991: Build A Talking Voltmeter For Your PC, Pt.1;
SteamSound Simulator For Model Railways Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders &
Ultralights, Pt.2; Getting To Know The Windows PIF Editor.
November 1991: Colour TV Pattern Generator, Pt.1; Battery
Charger For Solar Panels; Flashing Alarm Light For Cars;
Digital Altimeter For Gliders & Ultralights, Pt.3; Build A
Talking Voltmeter For Your PC, Pt.2.
December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Solid-State Laser Pointer;
Colour TV Pattern Generator, Pt.2; Index To Volume 4.
January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A
Power Supply, Pt.1; Baby Room Monitor/FM Transmitter;
Experiments For Your Games Card.
March 1992: TV Transmitter For VHF VCRs; Studio Twin Fifty
Stereo Amplifier, Pt.1; Thermostatic Switch For Car Radiator
Fans; Telephone Call Timer; Coping With Damaged Computer
Directories; Valve Substitution In Vintage Radios.
April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Studio Twin Fifty Stereo
Amplifier, Pt.2; Understanding Computer Memory; Aligning
Vintage Radio Receivers, Pt.1.
May 1992: Build A Telephone Intercom; Low-Cost Electronic
Doorbell; Battery Eliminator For Personal Players; Infrared
Remote Control For Model Railroads, Pt.2; Aligning Vintage
Radio Receivers, Pt.2.
June 1992: Multi-Station Headset Intercom, Pt.1; Video
Switcher For Camcorders & VCRs; Infrared Remote Control
For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look
At Hard Disc Drives.
July 1992: Build A Nicad Battery Discharger; 8-Station Automatic Sprinkler Timer; Portable 12V SLA Battery Charger;
Multi-Station Headset Intercom, Pt.2.
August 1992: Build An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; Dummy Load Box For Large
Audio Amplifiers; Troubleshooting Vintage Radio Receivers.
September 1992: Multi-Sector Home Burglar Alarm;
Heavy-Duty 5A Drill speed Controller (see errata Nov. 1992);
General-Purpose 3½-Digit LCD Panel Meter; Track Tester
For Model Railroads; Build A Relative Field Strength Meter.
October 1992: 2kW 24VDC To 240VAC Sinewave Inverter;
Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For
Personal Stereos; Build A Regulated Lead-Acid Battery
Charger.
January 1993: Peerless PSK60/2 2-Way Hifi Loudspeakers;
Flea-Power AM Radio Transmitter; High Intensity LED Flasher
For Bicycles; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.4;
Speed Controller For Electric Models, Pt.3.
February 1993: Three Projects For Model Railroads; Low Fuel
Indicator For Cars; Audio Level/VU Meter (LED Readout); An
Electronic Cockroach; MAL-4 Microcontroller Board, Pt.3;
2kW 24VDC To 240VAC Sinewave Inverter, Pt.5.
March 1993: Build A Solar Charger For 12V Batteries;
Alarm-Triggered Security Camera; Low-Cost Audio Mixer
for Camcorders;A 24-Hour Sidereal Clock For Astronomers.
April 1993: Solar-Powered Electric Fence; Build An Audio
Power Meter; Three-Function Home Weather Station; 12VDC
To 70VDC Step-Up Voltage Converter; Digital Clock With
Battery Back-Up.
May 1993: Nicad Cell Discharger; Build The Woofer Stopper;
Remote Volume Control For Hifi Systems, Pt.1; Alphanumeric LCD Demonstration Board; The Microsoft Windows
Sound System.
June 1993: Build An AM Radio Trainer, Pt.1; Remote Control
For The Woofer Stopper; Digital Voltmeter For Cars; Remote
Volume Control For Hifi Systems, Pt.2.
July 1993: Single Chip Message Recorder; Light Beam Relay
Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator;
Programming The Motorola 68HC705C8 – Lesson 1; Antenna
Tuners – Why They Are Useful.
Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low
Distortion Sinewave Oscillator; Clifford – A Pesky Electronic
Cricket; Cruise Control – How It Works; Remote Control
System for Models, Pt.1; Index to Vol.7.
August 1993: Low-Cost Colour Video Fader; 60-LED Brake
Light Array; A Microprocessor-Based Sidereal Clock; The
Southern Cross Z80-Based Computer; A Look At Satellites
& Their Orbits.
January 1995: Sun Tracker For Solar Panels; Battery Saver
For Torches; Dolby Pro-Logic Surround Sound Decoder,
Pt.2; Dual Channel UHF Remote Control; Stereo Microphone
Preamplifier; The Latest Trends In Car Sound; Pt.1.
September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1;
In-Circuit Transistor Tester; A +5V to ±15V DC Converter;
Remote-Controlled Cockroach.
February 1995: 50-Watt/Channel Stereo Amplifier Module;
Digital Effects Unit For Musicians; 6-Channel Thermometer
With LCD Readout; Wide Range Electrostatic Loudspeakers,
Pt.1; Oil Change Timer For Cars; The Latest Trends In Car
Sound; Pt.2; Remote Control System For Models, Pt.2.
October 1993: Courtesy Light Switch-Off Timer For Cars;
Wireless Microphone For Musicians; Stereo Preamplifier With
IR Remote Control, Pt.2; Electronic Engine Management,
Pt.1; Programming The Motorola 68HC705C8 – Lesson 2.
November 1993: Jumbo Digital Clock; High Efficiency
Inverter For Fluorescent Tubes; Stereo Preamplifier With
IR Remote Control, Pt.3; Siren Sound Generator; Electronic
Engine Management, Pt.2; Experiments For Games Cards.
December 1993: Remote Controller For Garage Doors;
Low-Voltage LED Stroboscope; Low-Cost 25W Amplifier
Module; Build A 1-Chip Melody Generator; Electronic Engine
Management, Pt.3; Index To Volume 6.
January 1994: 3A 40V Adjustable Power Supply; Switching
Regulator For Solar Panels; Printer Status Indicator; Mini
Drill Speed Controller; Stepper Motor Controller; Active Filter
Design; Electronic Engine Management, Pt.4.
February 1994: 90-Second Message Recorder; Compact &
Efficient 12-240VAC 200W Inverter; Single Chip 0.5W Audio
Amplifier; 3A 40V Adjustable Power Supply; Electronic Engine
Management, Pt.5; Airbags – How They Work.
March 1994: Intelligent IR Remote Controller; Build A 50W
Audio Amplifier Module; Level Crossing Detector For Model
Railways; Voice Activated Switch For FM Microphones;
Simple LED Chaser; Electronic Engine Management, Pt.6.
April 1994: Remote Control Extender For VCRs; Sound &
Lights For Model Railway Level Crossings; Discrete Dual
Supply Voltage Regulator; Low-Noise Universal Stereo
Preamplifier; Build A Digital Water Tank Gauge; Electronic
Engine Management, Pt.7.
May 1994: Fast Charger For Nicad Batteries; Induction
Balance Metal Locator; Multi-Channel Infrared Remote
Control; Dual Electronic Dice; Two Simple Servo Driver
Circuits; Electronic Engine Management, Pt.8; Passive
Rebroadcasting For TV Signals.
June 1994: 200W/350W Mosfet Amplifier Module; A Coolant
Level Alarm For Your Car; An 80-Metre AM/CW Transmitter
For Amateurs; Converting Phono Inputs To Line Inputs;
A PC-Based Nicad Battery Monitor; Electronic Engine
Management, Pt.9
July 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp
2-Transistor Preamplifier; Steam Train Whistle & Diesel
Horn Simulator; Portable 6V SLA Battery Charger; Electronic
Engine Management, Pt.10.
August 1994: High-Power Dimmer For Incandescent Lights;
Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner
For FM Microphones, Pt.1; Build a Nicad Zapper; Simple
Crystal Checker; Electronic Engine Management, Pt.11.
September 1994: Automatic Discharger For Nicad Battery
Packs; MiniVox Voice Operated Relay; Image Intensified
Night Viewer; AM Radio For Aircraft Weather Beacons; Dual
Diversity Tuner For FM Microphones, Pt.2; Electronic Engine
Management, Pt.12.
October 1994: Dolby Surround Sound – How It Works;
Dual Rail Variable Power Supply (±1.25V to ±15V); Talking
Headlight Reminder; Electronic Ballast For Fluorescent
Lights; Temperature Controlled Soldering Station; Electronic
Engine Management, Pt.13.
November 1994: Dry Cell Battery Rejuvenator; A Novel
Alphanumeric Clock; 80-Metre DSB Amateur Transmitter;
Twin-Cell Nicad Discharger (See May 1993); Anti-Lock
Braking Systems; How To Plot Patterns Direct To PC Boards.
December 1994: Dolby Pro-Logic Surround Sound Decoder,
March 1995: 50W/Channel Stereo Amplifier, Pt.1; Subcarrier
Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers, Pt.2; IR Illuminator For CCD Cameras; Remote
Control System For Models, Pt.3; Simple CW Filter.
April 1995: Build An FM Radio Trainer, Pt.1; Photographic
Timer For Darkrooms; Balanced Microphone Preamplifier &
Line Filter; 50W/Channel Stereo Amplifier, Pt.2; Wide Range
Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For
Radio Remote Control.
May 1995: Introduction To Satellite TV; What To Do When
the Battery On Your Motherboard Goes Flat; Mains Music
Transmitter & Receiver; Guitar Headphone Amplifier; FM
Radio Trainer, Pt.2; Low Cost Transistor & Mosfet Tester
For DMMs; 16-Channel Decoder For Radio Remote Control.
June 1995: Build A Satellite TV Receiver; Train Detector For
Model Railways; A 1W Audio Amplifier Trainer; Low-Cost
Video Security System; A Multi-Channel Radio Control
Transmitter For Models, Pt.1; Build A $30 Digital Multimeter.
July 1995: Low-Power Electric Fence Controller; How To Run
Two Trains On A Single Track (Plus Level Crossing Lights
& Sound Effects); Setting Up A Satellite TV Ground Station;
Build A Door Minder; Adding RAM To A Computer.
August 1995: Vifa JV-60 2-Way Bass Reflex Loudspeaker
System; A Fuel Injector Monitor For Cars; Gain Controlled
Microphone Preamp; The Audio Lab PC Controlled Test
Instrument, Pt.1; The Mighty-Mite Powered Loudspeaker;
An Easy Way To Identify IDE Hard Disc Drive Parameters.
September 1995: A Keypad Combination Lock; The Incredible Vader Voice; Railpower Mk.2 Walk-Around Throttle For
Model Railways, Pt.1; Build A Jacob’s Ladder Display; The
Audio Lab PC Controlled Test Instrument, Pt.2; Automotive
Ignition Timing, Pt.1.
October 1995: Build A Compact Geiger Counter; 3-Way Bass
Reflex Loudspeaker System; Railpower Mk.2 Walk-Around
Throttle For Model Railways, Pt.2; Fast Charger For Nicad
Batteries; Digital Speedometer & Fuel Gauge For Cars, Pt.1;
Automotive Ignition Timing, Pt.2.
November 1995: LANsmart – A LAN For Home Or A Small
Office; Mixture Display For Fuel Injected Cars; CB Transverter
For The 80M Amateur Band, Pt.1; Low Cost PIR Movement
Detector; Dolby Pro Logic Surround Sound Decoder Mk.2,
Pt.1; Digital Speedometer & Fuel Gauge For Cars, Pt.2.
December 1995: Engine Immobiliser For Cars; Five Band
Equaliser For Musicians; CB Transverter For The 80M Amateur
Band, Pt.2; Build A Subwoofer Controller; Dolby Pro Logic
Surround Sound Decoder Mk.2, Pt.2; Knock Sensing In Cars;
RAM Doubler Reviewed; Index To Volume 8.
January 1996: Surround Sound Mixer & Decoder, Pt.1; Build
a Magnetic Card Reader & Display; Rain Brain Automatic
Sprinkler Controller; IR Remote Control For The Railpower
Mk.2; Recharging Nicad Batteries For Long Life.
February 1996: Three Remote Controls To Build; Woofer
Stopper Mk.2; 10-Minute Kill Switch For Smoke Detectors;
Build A Basic Logic Trainer; Surround Sound Mixer & Decoder, Pt.2; The Fluke 98 Automotive ScopeMeter.
PLEASE NOTE: November 1987 to August 1988, October 1988
to March 1989, June 1989, August 1989, May 1990, February
1992, November 1992 and December 1992 are now sold out.
All other issues are presently in stock. For readers wanting
articles from sold-out issues, we can supply photostat copies
(or tearsheets) at $7.00 per article (includes. p&p). When
supplying photostat articles or back copies, we automatically
supply any relevant notes & errata at no extra charge.
March 1996 73
COMPUTER BITS
BYhttp://www.pcug.org.au/~gcohen
GEOFF COHEN
Electronic organisers
& your PC
Like many other computer people, I have an
electronic organiser (a Sharp ZQ-5200) which
I use constantly. As well as storing phone
numbers and memos, I also use it to store details
of the work I do for clients.
A major reason I like organisers is
that, being inherently lazy, I hated
having to manually write stuff down
three times – once in a pocket diary I
carried around, then into a desk diary,
and then by typing it out in a word
processing program, to finally get it
into the PC.
As soon as I found out about organisers, I rushed out and got one. I then
spent the next week learning how to
actually use it.
Anyhow, enough of the history
lesson. Suffice it to say that if you
write lots of text when you are away
from the home/office, and don’t want
to lug something around that won’t
fit in your pocket, an organiser is the
way to go.
I am about to upgrade mine to a
74 Silicon Chip
Fig.1: Text Exported Directly From The Organiser
19951215,”21:30",”hh:mm”,”21:30",”ARRIVE AT CARAVAN.”,”N”
19951226,”hh:mm”,”hh:mm”,”hh:mm”,”TODAY SMOKE DETS POLAROID CLIPON, “N”
19951226,”18:30",”hh:mm”,”18:30",”YES MINISTER”,”N”
19960102,”hh:mm”,”hh:mm”,”hh:mm”,”MAKE ERROR RECOVERY MENU OPTION.”,”N”
19960103,”13:00",”16:35",”hh:mm”,”SILICON CHIP:START ARTICLE ON ORGANISERS”,”N”
19960104,”10:00",”12:20",”hh:mm”,”SILICON CHIP:LAST PART OF ARTICLE.”,”N”
19960108,”hh:mm”,”hh:mm”,”hh:mm”,”TAX DUE”,”N”
19960108,”20:00",”hh:mm”,”20:00",”FRONTLINE”,”Y”
newer model with 256Kb of RAM and
a much bigger screen (40 characters/
line instead of 16). Alas, I have not
been organised enough to get one yet.
Transferring data to a PC
An essential extra for my organiser
is its PC Link cable/adaptor, which
allows data to be transferred to the
PC (or vice versa). You can also export
data from the organiser’s PC software
to other programs, although this is not
very elegant without extra software.
With that proviso, I like the Sharp
software – it is simple to install and
use.
For anyone who is considering the
purchase of an organiser, and intends
using it for “serious stuff”, I recommend the PC Link as an essential item.
I have had two organisers. The first
stopped working when it got dropped
in the drink – fishing and organising
don’t go together too well. If I hadn’t
backed up the data before I went fishing, I would have been forced to spend
hours retyping 60K of text, all retrieved
from my own (fallible) memory.
With the backup copy on my PC
and the Link cable, it took only a few
domain, so feel free to give it to anyone
who wants a copy.
I hope you find this combination
of organiser and utility program as
useful as I have. If any Clipper programmers want a copy of the source
code, this is available from me either
by email (no charge) or from my snail
mail address ($10) at the end of the
column.
More on ZIP drives
The Missing Link V.2 is a Windows-based organiser-to-PC linking program.
minutes to restore the data to the new
organiser.
Data modes
There are two modes of transferring
data from the organiser to your PC: (1)
the BACKUP menu option which does
a complete backup to a named file (I
use this option once a month); and (2)
the GET applications menu option (I
use this one daily).
The latter copies the data to an emulator program on your PC and allows
you to both view and, by using the
advanced menu option, export this
data to other programs.
Unfortunately, the standard output
format is not really suited to a word
processing program, as you can see
from the sample “comma delimited “
text shown Fig.1.
What we really want to do is to extract the SILICON CHIP text, strip out
the unwanted stuff, and convert it to
The DOS version of ZIP works well.
It only takes around 26Kb of RAM
for its device driver and is compatible enough that Norton Disk Doctor
(Version 8) runs quite happily on the
ZIP drive, although it is a little slower
than on a “real” hard disc. The more
I use mine, the more uses I think of
for it.
I have tried it on DOS, Windows
3.11 and Windows 95 and apart from
some glitches caused by not plugging
in the connectors properly, I haven’t
found any problems so far. On the basis of my own experience, it’s a good
word processing compatible text. For
those of you who don’t want to write a
“C” or “BASIC” program, I have a little
Clipper database program (ZQ.exe) to
extract any desired text, for a
specified date range.
As you can see from the
Fig.2: Output From ZQ.Exe
resultant output (Fig.2), the
Conversion Program
program has extracted the de03/01/96 13:00 - 16:35 - Time 03:35 (Hrs:Min)
sired text for the dates wanted
SILICON CHIP: START ARTICLE ON ORGANISERS
and has added the times up as
well (I did say I was lazy).
04/01/96 10:00 - 12:20 - Time 02:20 (Hrs:Min)
This program will be availSILICON CHIP: LAST PART OF ARTICLE.
able either from me via email
(no charge) or snail mail ($10
Total Time = 05:55
(includes disc) and is public
Above and left: information transfer is
a 2-way street. Data can be extracted
from the pocket organiser for use in
PC programs, or PC data can be sent
to the organiser. This eliminates timeconsuming re-keying of information
and avoids possible errors.
March 1996 75
JAG 1Gb DRIVE
Average seek time: 12ms
Sustained transfer rate: 6.73Mb/s
maximum; 5.51Mb/s avereage;
3.53Mb/s minimim
Burst transfer rate: 10Mb/s
Buffer size: 256Kb read/write
Capacity: 1070Mb and 540Mb (PC
formatted capacity)
MTBF: 250,000 hours
Service life: 5 years
Disc drop height: 3ft
Disc estimated shelf life in case:
10 years
Operating system compatibility:
DOS, Windows, Mac OS, OS/2
and Windows ‘95
Interface: fast SCSI-II
idea to use the connector’s attachment
screws rather than just relying on
push-fitting the connectors. Currently, I have the ZIP drive connected to
an old Windows 3.1 system, and it is
available as a network drive from my
main Windows 95 system.
Jaz 1Gb removable drive
This new drive from Iomega is similar in principle to the ZIP drive. But
instead of a measly 100Mb(!), it is a
full 1Gb removable hard disc and is
said to be as fast as a “real” hard disc. I
understand that it is due to be released
in early 1996 and should cost around
$800, with each 1Gb removable disc
costing around $150.
For the more technically minded,
the specifications I downloaded from
their Internet site are shown in the
panel at left.
I can’t wait to get one to play with.
If they work as well as the Zip drive,
they should sell like hot cakes.
Windows 95
The Windows 95 32-bit protected
mode drivers are now avail
able. I
downloaded mine from the Iomega
web site at www.iomega.com. In
November 1995, the file was called
Win95.exe (76Kb) and the full address
was: www.iomega.com/users/filearea/
win95.exe.
This file is a self extracting Zip file,
so put it in a temporary directory and
run it, then follow the installation
instructions in the file WIN95INS.RTF.
The version I was using had an error
in the documentation for the parallel
port installa
tion procedure. When
selecting the appropriate hardware
from the control panel, select “other
devices” and then “have disk”; not
“SCSI” and then “have disk”, as the
documentation instructs.
The installation and operation
NEXT MONTH
In next month's column, I
intend giving details on making
your own home page on the
Internet, with a primer on HTML
(Hyper Text Markup Language).
If you want a sneak preview, have
a look at my new home page at:
http://www. pcug.org.au/~gcohen
I will also include all software
from my SILICON CHIP columns
at this address.You can currently
obtain the Diskinfo software from
it, as well as the Organiser-related files from this issue.
worked fine, apart from this minor
glitch, and the Win 95 plug and
play loads the ZIP driver only if it is
connected, without any nasty error
messages if it isn’t.
If you have any trouble getting the
Windows 95 driver file (I have noticed
the web site gets a tad busy at times),
email me and I will send you a copy.
Alternatively, I can send you a copy via
snail mail for the normal $10 (includes
disk, postage & handling).
For snail mail copies of the software mentioned in this article, send
$10 (cheque or money order) to Geoff
Cohen, PO Box 136, Kippax, ACT
SC
2615.
POSTSCRIPT: AT LAST I'M ORGANISED!
I finally managed to (dare I say it!) get organised
enough to buy my new organiser, a Sharp 6600.
With 256k of RAM and a 40 character screen instead
of 16 characters, this is a big improvement over the
old 5200.
The only problem I had was converting the data
from the 5200 to the 6600. The main catch was that the
PC Link program uses the older term for the "memo"
function, calling it "note".
They could also do a little work on the on-line help
files to make them easier for a novice user. After all,
when you become experienced with the software you
don't need the help files!
(I always try out my software on a complete beginner.
It's really amazing that something which is completely
obvious to me means absolutely nothing to someone
who hasn't been eating and sleeping the software for
the last few weeks/months).
The new 6600 organiser needs different link soft76 Silicon Chip
ware, although the same cable can be used. I am
using the Australian organiser link package "Missing
Link", version 2, and have found it a good program.
As it is Windows-based it is much better than the old
Organiser Link II software which I was forced to use
with the 5200.
One nice feature of the new package is its script
files, which allow me to completely automate routine
functions, such as backing up and exporting files to
other programs.
With the aid of a conversion routine and some help
from Gary at Creative Binary Engineering's organiser
technical support program, I even managed to convert
my old 5200 data to the new 6600 format.
Gary emailed me a copy of their template files, which
make conversion quite easy. I have included these on
my Internet home page and, of course, they are also
available from Gary at Creative Binary Engineering
(03 9523 8057).
SATELLITE
WATCH
The planned launch of Indonesia’s Palapa
C1 satellite on February 15 will mark
another milestone in the development of
satellite communications in the Pacific Rim.
The PALAPA C1 satellite will replace
the ageing Palapa B2P satellite at 113°
east longitude. The new bird will
bring a host of signals from Indonesia, Malaysia, and the Philippines to
satellite enthusiasts in Australia and
New Zealand.
• APSTAR 1R – 88° E LONGITUDE:
Due to be launched in March, this
satellite has a footprint that will provide massive signals across Australia.
Although boresighted off the eastern
coast of Africa, the signals will cover
most of Asia, Russia and even some
parts of Europe. Unfortunately for
viewers in New Zealand, the satellite
is below the visible horizon.
• STATSIONAR 3 – 85° E longitude:
Signals from “TVI” network can be
seen from 1400 AEST on IF 1270MHz.
This is an Indian network, often
broadcasting in English. The signal
polarisation is right-hand circular.
• ASIASAT 2 – 100.5° E longitude:
Commissioning is now complete on
this spacecraft, and two signals can
be seen. RTPi Portugal operate their
PAL television service on IF 1165MHz,
vertical polarisation. They will add a
Portuguese radio service in coming
months. Star TV commenced operations of the “V” music channel in
analog, before changing to vidicrypt
late in January. There are many more
broadcasters soon to be loaded onto
this satellite. Unfortunately, due to
interference from a nearby Gorizont
satellite, Asiasat has had to de-commission up to six transponders, causing additional delay to some operators.
• PALAPA C1 – 113° E longitude: By the
time this article goes to press, spacecraft
commissioning should be well underway. The satellite was successfully
launched from Cape Canaveral in the
United States on Feb 15. Australia’s
Compiled by GARRY CRATT*
This screen shot does
not do justice to the
quality of signals
received from the new
Asiasat 2 satellite.
Shown is a soccer
match courtesy of RTPi
Portugal. The apparent
"venetian blind" effect
is not interference as
might be expected; it
is in fact an out-offocus fence behind the
player!
ATVI (international arm of the ABC)
will have a much larger potential audience, both in Asia and in outback Australia. It is expected the transition from
the old B2P satellite to this new bird
will be transparent to satellite viewers
across the region, as the new satellite
will take up the same orbital location.
• INTELSAT 511 – 180° E longitude
C band: The two main transponders of
interest are RFO Tahiti and Worldnet.
The Worldnet transponder (1175MHz
IF) is shared by Deutsche Welle and
the American C-SPAN network. As the
satellite is in an inclined orbit, tracking
equipment is required.
• GORIZONT 41 – 130° E longitude:
Formerly known as Rimsat G1 until
“repossession” by the Russian Space
Agency, this satellite still carries RAJ
TV, a Tamil language channel from
India.
• GORIZONT 42 – 142.5° E longitude:
Another “repossession” spacecraft,
formerly known as Rimsat G2, this satellite carries ATN from India and EM
TV from New Guinea. It is rumoured
that the EM TV signal will move to
Intelsat 701 (180° E) mid year.
• OPTUS B3 – 156 E° longitude: Narrowcast operator “TV Oceania” has
announced an end to their Japanese
language service. Due to cease operations at the end of March, TVO will
concentrate on their other business
activities. They quote a downturn in
subscriptions, primarily due to NHK
free-to-air broadcasting on Panamsat’s
PAS-2 satellite at 169° E.
• OPTUS B1 – 160° E longitude, C
band: This satellite is almost fully
loaded with 5 interchange channels,
5 B-MAC channels, 3 E-PAL channels,
and other omnicast and narrowcast
services. No new reports from this bird.
• PANAMSAT PAS-2 – 169 E longitude, C band: Two B-MAC operators,
ESPN and Discovery Channel, have
advised they will change format to
GI Digicypher II early in 1996, to take
advantage of reduced uplink costs.
CNN, CNBC Asia, NHK Japan and
several interchange channels are still
SC
operating in analog.
*Garry Cratt is Managing Director of
Av-Comm Pty Ltd, suppliers of satellite TV
reception systems.
March 1996 77
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
78 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
March 1996 79
PRODUCT SHOWCASE
New TDK video
cassette tape
Kenwood's latest dual
cassette deck
Kenwood's latest double cassette
deck, the KX-W8070S features Dolby
S, along with B and C noise reduction
systems, double Auto Reverse, three
motors and auto bias with fine adjust.
Double cassette decks offer a number of advantages over single-well
decks, such as tape-to-tape dubbing
and extended play, offering a potential
of three hours of music. The Dolby S
noise reduction system offers up to
23dB of noise reduction and increased
high-frequency headroom with less
noise modulation.
The KX-W8070S also features the
HX-PRO Headroom Extension system
that effectively allows more high frequency energy to be stored on the tape
without saturation. This is achieved
by varying the level of bias with the
signal to be recorded, maintaining the
signal within a certain threshold. The
end result is significantly improved
mid and high range headroom with
lower distortion.
Kenwood also employ their CCRS
(Computer Controlled CD Recording
System) that automatically scans the
contents of CDs and adjusts the recording level to assure optimum results
both in normal and high speed. The
KX-W8070S also features Kenwood's
DPSS search and Index Scan that enables quick access to specific tracks.
The KX-W8070S is covered by a two
year parts and labour warranty, has
a recommended retail price of $799
and is available at selected Kenwood
dealers. For further information on
Kenwood products phone (02) 746
1888.
Versatile infrared
headphones
The Infratronic IR-1800RC and
IR-2000SRC infrared cordless stereo
headphones allow the freedom of
untethered high quality listening.
They may be used with virtually any
audio source: TV, VCRs, hifi, audio/
video systems and computer games.
Automatic level control allows these
units to be driven directly from the
line level outputs of most CD players, cassette decks, receivers, video
disc players, computers and video
cassette recorders.
Both headsets have a 20Hz to
80 Silicon Chip
In support of recent digital VCR and
camcorder hardware advancements,
TDK have released a new digital video
tape, the DVC60 which allows up to
60 minutes of recording/playback (in
standard mode).
Unlike VHS VCRs where the video
head rotates 25 revolutions per second, in digital VCRs the head rotates
about five times that speed, placing
much greater demands on the tape,
particularly in still frame modes. For
this reason, TDK's DVC60 utilises a
specially developed coating.
Other features include an advanced
back-coating for smooth tape travel
and a highly stable cassette mechanism with a reel lock mechanism to
prevent tape slippage.
For further information on TDK's
DVC, phone (02) 437 5100.
20kHz frequency response, 50 milliwatts audio output, up to 7 metre operating range and are each powered
by two AAA rechargeable batteries.
The headsets weigh just 180 grams,
have a personal volume control and
feature automatic battery recharging
when placed on the transmitter
stand. Additional headsets may be
used and are available separately.
Both sets are supplied with an
AC/DC adaptor, 3.5mm to 6.3mm
plug, stereo to mono jack and stereo
jack. For more information, contact
Allthings Sales & Services, PO Box
25, Northlands, WA 6021. Phone (09)
349 9413; fax (09) 344 5905.
AUDIO MODULES
broadcast quality
Low-cost single-phase
chassis-mounting filters
Schaffner has launched a new series of single-phase chassis-mounting
filers for a wide range of applications.
Known as the FN 2000 series, the
filters have a very compact form factor, achieved through the use of high
performance magnetic and capacitive
components, which makes them ideal
for applications where space is at a
premium.
Excellent stop-band attenuation and
current-carrying capabilities mean
that the filters are particularly suitable for electrically noisy equipment,
such as motor drives and switchmode
power supplies.
Tektronix extends its
InstaVu family of DSOs
Tektronix has announced a new
family of lower-priced InstaVu acquisition oscilloscopes. The new TDS700A
series and TDS500B series of digital
storage oscilloscopes (DSOs) have
Tektronix' proprietary InstaVu signal
acquisition technology which lets
users capture up to 400,000 wfm/s
(waveforms per second), making these
new digital scopes as fast as the world's
fastest analog scopes.
The new TDS700A series includes
the TDS784A, TDS744A and TDS724A. It features colour displays,
bandwidths up to 1GHz, sample rates
up to 1GS/s and acquisition rates up
to 400,000 wfm/s. The new TDS500B
series includes the four-channel
TDS540B and two-channel TDS520B.
Both scopes feature 500MHz bandwidth, up to 2GS/s sampling rate,
Manufactured in Australia
Harbuch Electronics Pty Ltd
9/40 Leighton Pl. HORNSBY 2077
Ph (02) 476-5854 Fx (02) 476-3231
The FN 2000 filter series comprises
72 standard versions, covering current
ranges from 1 to 30A, each of which is
available in medical (B type) or safety
(A type) configurations.
Furthermore, the internal design
is modular which enables Schaffner
to produce custom versions of the
filters. Each filter is contained within
a chassis-mounting metal housing
with a choice of fast-on, wire or screw
feed-through connectors. The filters
are all designed for operation at up
to 250VAC and can handle supply
frequencies from DC to 400Hz.
All multistage filters in the FN 2000
series can be supplied with the capacitors connected to the load side, in order to present the best impedance mis-
match between equipment and filter.
The top of the range FN 2080 has high
inductance and capacitance values,
and employs independent differential mode, rather than common mode
chokes to ensure excellent differential
and common mode attenuation across
a broad band of frequencies.
A free 16-page design guide and
short form catalogs on the new FN
2000 series filters are available from
Westinghouse Industrial Products,
Locked Bag 66, South Melbourne, Vic
3205. Phone (03) 9676 8888; fax (03)
9676 8702.
monochrome displays and
up to 100,000 wfm/s acquisition rate.
Tektronix' InstaVu acquisition technology is designed to quickly pinpoint
and capture unpredictable,
rapidly changing signals,
infrequent glitches, metastable behaviors and time jitter,
that may never be detected
by conventional analog or
digital scopes or specialised
triggering.
InstaVu technology combines high-speed acquisition memory with highspeed display rasterisation
to increase acquisition performance
and ensure instantaneous live display
of all signal changes. For design and
debug applications, InstaVu technology cuts debug time from hours to
seconds.
Note: the Tektronix 784A was first
reviewed in the March 1995 issue of
SILICON CHIP.
For further information, contact
Tektronix at 80 Waterloo Rd, North
Ryde, NSW 2113.
March 1996 81
Wide screen TV
from Mitsubishi
Mitsubishi Electric's first wide
screen colour television, the DIVA
Wide model, is now available.
As well as giving TV viewers a
cinema-like picture, the DIVA Wide
incorporates AI Fuzzy Logic circuitry
for superb picture quality, and Auto
Turn to allow the viewer to adjust the
viewing angle of their TV.It also has
Pro Logic Sound and four extension
speakers.
Six other digital surround sound
modes are provided: Pro Logic Phantom, Theatre, Concert Hall, Stadium,
Disco and Pseudo Stereo.
The matching stand has a centre
channel speaker and a built-in woofer
as well as space to accommodate a VCR
or laser disc player.
The Mitsubishi wide screen TV also
features eight picture modes so viewers can manipulate the 4:3 broadcast to
fit the screen, as best suits the program.
A feature called "picture-out-picture"
(POP) makes the DIVA Wide different
to its competitors. Using POP, the 16:9
screen can be broken down into a 4:3
82 Silicon Chip
screen with three boxes in the remaining screen area.
Viewers can then watch the main
screen plus three other broadcast
sources (from other TV channels, audio visual or laser disc).
They can then alternate between
sources, choosing which one appears
on the main screen. The extra pictures
appear next to the main one, not within
it as is the case with picture-in-picture.
With two TV tuners, the Mitsubishi
set has both picture-in-picture and
picture-out-picture.
The full list of picture modes is:
cinema (scroll up/down); cinema
caption (scroll up/down); panorama
1 (stretches the left/right edge to fill
screen); panorama 2 (compresses top/
bottom to fill screen); 16:9 full; 14:9
(leaves narrow black bands at each
edge of screen); 4:3 normal; auto view
(automatically selects appropriate
screen size).
Recommended retail price of the
new Mitsubishi set is $6,999. For
more information, contact Mitsubishi
Electric Australia, 348 Victoria Road,
Rydalmere, NSW 2116. Phone (02)
684 7777.
DIGI ISDN Personal
Computer card
Sealcorp has announced the Australian release of the Digi PC IMAC
ISDN card.
The new PC card for ISDN connections is claimed to quadruple the
speed of Internet access and provide
much improved bandwidth on LAN/
WAN connections. The integrated terminal adaptor/network interface card
installs in any ISA PC and connects
directly to an ISDN line.
ISDN connections are available in
just one quarter of a second through
the new Digi card, compared to 30-90
seconds for a modem over the public
switched telephone network. A word
processing file, for example, can be
completely downloaded in the same
time it takes a modem to make a connection.
The new ISDN cards are manufactured by Digi International in North
America and are fully Austel approved
for Australian use. Recommended
retail prices start at $1,952 excluding
sales tax. They are supplied with a five
year guarantee.
For more information, contact Sealcorp, PO Box 670, Lane Cove, NSW
2066. Phone (02) 418 9099; fax (02)
418 9313.
Function generators
from Yokogawa
Traditionally, high-performance
function generators have been difficult
to operate, involving the manipulation
of many front panel keys.
A new generation of 2-channel,
compact function generators from
Yokogawa, which feature a large
LCD display and touch screen, has
addressed this difficulty.
The FG200/FG300 series function
generators offer 2 channels in a compact, lightweight package and feature
sweep and modulation capabilities.
The new generators provide sine
and square outputs up to +/-10V over
a frequency range of 1uHz to 15MHz,
and triangle, pulse and arbitrary (on
the FG300) outputs from 1uHz to
200kHz. Frequency resolution is 1uHz
or a maximum nine digits.
Operation of the FG200/FG300 series has been simplified by virtue of
the large LCD touch screen. The setup
and display or arbitrary sweep patterns
and simple arbitrary waveforms can
be defined by entering points within
the scaled ranges on the X and Y axes,
and can be generated using linear,
step or spline interpolations between
the points.
Alternatively, the data may be loaded in ASCII format via the internal
floppy disc drive. This interface may
also be used to load waveforms created
with Yokogawa AG series waveform
generators or captured with the company's digital oscilloscopes.
Sweeps may be made in frequency,
KITS-R-US
Cathode Ray Oscilloscopes – from page 17
X2. But for good luminescent efficiency, thousands of volts
acceleration voltage is necessary to produce bright sharp
traces on the CRO screen. In this example, we have shown
5kV, which is relatively standard for a CRO.
Therefore, in oscilloscopes using the simple CRO tubes
shown, the high voltage supply is grounded (or nearly so)
at the CRO screen end.
Consequently, the heater, cathode, control grid G1 and
focus grid G2 are all at high negative voltages with respect
to ground. As a consequence, lethal voltages exist on the
heater, cathode, grid and other wiring and terminals inside
an oscilloscope.
Next month we will dig further into how analog oscilloscopes are designed to reproduce high frequencies, up to
1000MHz (1GHz) and how the trace on the screen can be so
bright, sharp, clear, calibrated and accurate.
Acknowledgements
Thanks to Philips Scientific & Industrial and to Tektronix
Australia for data and illustrations; also to Ian Hartshorn, Jack
Sandell, Professor David Curtis, Ian Marx and Dennis Cobley.
References
"ABCs of Oscilloscopes" – Philips/Fluke USA
"Solid State Physical Electronics" – Van der Ziel A; Prentice Hall NJ, USA.
"Basic Television" – McGraw-Hill NY, USA.
Tektronix Aust. Application Notes.
SC
phase, amplitude, offset voltage or
duty cycle, in linear, log linear step,
log step or arbitrary sweep patterns.
The sweep parameters may be
controlled by an external analog or
digital signal. Output amplitude and
duty cycle are continuously variable
and by linking multiple generators together, three or more channels of phase
synchronised signals may be obtained,
with even the sweep synchronised if
required.
For further information, contact
Yokogawa Australia, 25-27 Paul St
North, North Ryde, NSW 2113. Phone
SC
(02) 888 1844.
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.
•
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.
March 1996 83
To do a worthwhile
check on a dry cell
battery, you need
to load it while
you take a voltage
measurement.
The load can be
a suitable resistor
but there is a better
way – use the green
test strip which
comes with Mallory
Duracell “Copper
TopTM” batteries.
Build a simple battery
tester for around $5
By JOHN CLARKE
Most people have seen those green
tester strips which are supplied with
9V and 1.5V battery packs. While you
might think they are a marketing gimmick, they provide a far better means
of determining the battery or cell
condition than a simple multimeter
voltage measurement since they give a
load test. In fact, they provide a more
or less constant current load which
presents a ideal battery test.
But if you use these testers often,
you will probably agree that they are
fiddly to use. Of course, the battery
manufacturer cannot be expected
to produce a perfect tester for what
amounts to a free addition to the
battery pack. However, what they
have supplied is a very good basis for
making your own battery tester.
All you need is a standard battery
holder or clip lead suitable for the tester, short lengths of wire, a few screws,
84 Silicon Chip
nuts, solder lugs and star washers, a
bracket and a small plastic case. For 9V
batteries, you have the choice of using
a battery clip or the more expensive
holder.
The accompanying photos and diagrams show how we made a 9V tester.
The same principle can be applied to
single cell testers. The main thing to
watch is that the tester strip is held
away from any electrical or heat conductive surface. This means that it
must be suspended in air to prevent
the tester giving false results.
Building it
Fig.1 shows the assembly details.
Begin the assembly by drilling and
filing out the lid to accommodate the
tester display and the battery clips.
This done, drill small holes in the +
and – contacts of the tester strip and
line the strip up with the cutout in the
PARTS LIST
1 battery tester strip
1 plastic case, 83 x 53 x 30mm
1 battery clip or holder and wire
1 bracket to support clip
1 3mm countersunk screw and
nut
3 3mm x 10mm screws
4 3mm nuts
2 3mm flat washers
2 3mm star washers
2 solder lugs
PVA glue
lid. Mark out where these connector
holes are and drill these holes in the
lid.
The tester strip can now be fastened
to the lid – see Fig.1. Use star washers
on the conductive side and flat washers on the display side of the tester
strip to ensure reliable contacts and
Finally, the free end of the tester
strip is held in place on the lid with a
small dab of epoxy adhesive.
Results
Fig.1: here are the assembly details for the simple battery tester.
Be sure to solder the wires to the lugs before bolting the assembly
together and use star washers on the conductive side of the tester
strip, to ensure reliable contacts.
We connected the 9V tester to a DC
power supply in order to find out how
the visible indications coincided with
voltage and load conditions. For a
start, the load current is about 100mA.
Under this condition, a battery delivering more than about 8V shows as
“good” and lights up all three segments
of the display.
Batteries delivering between 7V
and 8V light up two segments and are
obviously marginal, according to the
tester. Batteries delivering less than
7V will only light up one segment or
none at all and, according to the tester,
should be replaced.
Whether you do replace a 9V battery
delivering less than 7V is up to you.
In some applications, 7V will be adequate; some applications will draw a
lot less current than 100mA and so the
battery will deliver correspondingly
more voltage.
For a single cell tester, the “good”
indication comes on for battery volt
ages greater than 1.25V, while the
load current varies between 200mA at
SC
1.25V to about 240mA at 1.5V.
Silicon Chip Binders
These beautifully-made binders
will protect your copies of SILICON
CHIP. They are made from a dis
tinctive 2-tone green vinyl & will
look great on your bookshelf.
The “free” end of tester is secured to the lid using a dab of epoxy adhesive. Note
the mounting technique for the battery clip.
solder wires to the lugs before fitting
the screws.
We used a piece of clear plastic to
cover and protect the tester strip from
damage. You could also use the origi-
nal plastic cover found with the battery
pack and glue this to the underside of
the lid. The battery clip is held in place
under the lid using a suitable bracket,
countersunk screw and nut.
Price: $A11.95 plus $3 p&p each
(NZ $6 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.
March 1996 85
VINTAGE RADIO
By JOHN HILL
A console with a difference
This month, we will take a close look at an
unusual console style radio receiver – a 1948
model 4-valve Peter Pan. Although it is a very
modest little radio, its style and construction is
far from normal.
This radio is the only console I have
ever encountered that does not have a
timber cabinet. As such, there is little
doubt that it was aimed at the budget
end of the market. Any “normal”
console would have had at least five
valves, a timber cabinet and maybe
shortwave reception as well.
The cabinet is a mixture of materials.
The main portion is sheet aluminium
which is attached to a thick plywood
base. The aluminium is reinforced
inside with a few brackets, to which
other items are bolted. Even so, the
light gauge aluminium is far from rigid
and flexes quite readily.
The front of the cabinet is covered
with vinyl and it has a textured surface
which looks quite pleasing. There is a
large speaker opening in the centre of
the vinyl area and it is edged with a
brown plastic trim. Instead of the usual
grille cloth, there is a basket-weave
wicker type material made from some
natural fibre. These wicker grilles
were common on early postwar Peter
A full front-on view of the Peter Pan 4-valve console receiver. This particular
cabinet is unusual in that it is not made of timber. The only wood used in its
construction is the thick plywood base.
86 Silicon Chip
Pan radios and some Astors and other
makes also used them.
The top section of the cabinet
consists of a large bakelite moulding
which contains the dial and control
knobs, while the bottom consists of a
wide strip of thick sheet plastic to act
as a kick board. All things considered,
it is a fairly cheap outfit from top to
bottom.
However, one should not be too
critical. Here is a radio receiver which
is nearly half a century old, yet it still
looked neat and tidy on the outside
–apart from a liberal coating of dust
and grime. This is something that
cannot be said for most timber cabinet
receivers of similar vintage. Timber
cabinets can look rather shabby after
50 years, with the lacquer becoming
chipped and crazed.
Cleaning it up
As found, the little Peter Pan was
decidedly grubby. Apart from the expected dust and grime, it had also taken several drink spills down its front.
Fortunately, vinyl is a very durable
material and it allowed all this muck
to be scrubbed off. In fact, the exterior
of the cabinet cleaned up really well,
to near new condition.
The final comment about the Peter
Pan’s unusual cabinet relates to its
peculiar shape. In plan view, it is triangular (obtuse isosceles), with the long
side being the back of the receiver. The
cabinet is very narrow and although
the chassis is mounted low, the set
has very poor stability and could be
easily knocked over. When cleaning
the empty cabinet, care had to be taken
to ensure that the wind did not blow
it over and damage the bakelite top.
On the credit side, however, the
little Peter Pan doesn’t take up much
space for a console radio and it would
fit into a room just about anywhere.
somewhat better than one would normally expect from a 6-inch speaker.
The speaker also produces quite good
bass for its size.
Chassis details
This close-up view shows the wicker speaker grille. The basket weave
speaker grille was popular during the late 1940s and was used by a number of
manufacturers. The speaker opening is much larger than the speaker used.
The bottom edge of cabinet consists of a wide plastic strip which serves as a
kick board and carpet sweeper deflector. Note the textured surface of the vinyl
covering.
When flat against a wall, the front of
the receiver protrudes into the room no
more than about 18cm. Although the
mini-console really is a weird shape,
it is nevertheless a practical one as far
as space saving goes.
Rola loudspeaker
1948 was a time of change in radio
manufacturing and a new receiver
at that time could have had either
an electrodynamic loudspeaker or a
permag loudspeaker. Electrodynamic
speakers were used by some manufacturers up until 1950. The Peter Pan was
fitted with a smallish 6-inch (150mm)
Rola permag loudspeaker, although it
is not the usual Rola loudspeaker of
that era.
This particular Rola has a larger
housing at the back than most (maybe
a bigger magnet?) and it has a larger
than usual output transformer fitted
to it. The five wires connecting the
speaker to the receiver are for the
output transformer primary, negative
feedback from the secondary, and
what seems to be a fairly unnecessary
earth lead.
When combined with the excellent
baffling of the cabinet, the overall
volume and tonal performance is
The unusual construction of this
mini-console receiver continues
throughout the set and that includes
the chassis, which can only be described as an upside down installation. The chassis is positioned at
the bottom of the cabinet so as to
lower the set’s centre of gravity and
is mounted valves down and circuit
wiring up.
It is not as though the chassis
has been simply inverted, however
– the folded sides of the chassis go
towards the valves. Why this is so is
a bit of a mystery. The chassis set up
could have easily been arranged in a
conventional manner, whereby the
circuit wiring and the valve sockets
would not be subjected to dust accumulation.
Because the chassis wiring is all
exposed on top, there are no servicing
conveniences like a speaker plug and
socket, dial light wiring plugs and
sockets, or even an aerial terminal.
These wires are all soldered straight
into the circuit and must be disconnected if the chassis is to be removed.
Of course, all these wires (eight in
all) should be carefully marked before disconnecting them. It is unwise
to rely on memory when so many
connections are involved. Swapping
some of the speaker connections could
produce positive feedback and a loud
howl in the speaker, for example.
Other disconnections include the
remote mechanical linkages from the
control knobs on top of the cabinet
to the tuning capacitor and volume
control potentiometer on the chassis
below. All things considered, it is not
the most convenient of sets to service,
although most repairs can be done
without having to remove the chassis
once the dust has been removed from
the wiring.
Flexible drive
As a matter of interest, the volume
control knob is coupled to the potentiometer by a long brass rod. So too
is the tuning control, except that in
this case, the control knob is not posi
tioned directly above its counterpart
below. To overcome this problem, a
flexible drive is used to iron out the
March 1996 87
The moulded bakelite top houses the dial and control knobs. Note that the dial
is marked mainly for Victorian and Tasmanian stations, although 2AY, 2WG,
2CO and 5RM also get a mention.
misalignment – a simple yet effective
method of overcoming an awkward
arrangement.
There was a problem with the
two mounting brackets that hold
the chassis in place. These brackets
had been fitted too close together on
the baseboard and their bolt holes
would not line up with those in the
chassis. This misfit had been solved
at the factory by forcing the brackets
to line up, thereby severely loosening the wood screws which held the
brackets to the baseboard. Completely
88 Silicon Chip
repositioning the brackets fixed that
particular problem.
Chassis repairs
The receiver itself was an easy repair, as it was in working order to start
with. It appeared to be fairly original,
with the exception of two 8µF electrolytic capacitors. These had replaced
one of the original chassis-mounted
16µF units at some time in the not
so distant past. As these capacitors
were quite serviceable, they were left
in place.
The same could not be said for the
other electrolytics, however. These
were all originals and, as they all had
leakage problems, were replaced with
modern equivalents.
One interesting aspect of the electro
lytics was the fact that all four of them
were high-voltage chassis-mounted
types. The 16µF 525V pair were used
in the high-tension filter but the 24µF
350V pair were used for quite low
voltage applications; eg; as a cathode
bypass capacitor on the output valve,
as shown in one of the photos.
Perhaps these high voltage units
were the only ones available at the
time? In 1948, the demand for radio
parts could have exceeded the supply
and set manufacturers may have been
forced to improvise at times and use
whatever components they could find
that would do the job. Well, that’s one
explanation!
The Peter Pan’s chassis used 10
paper capacitors and all of these were
originals. They were all replaced
without even a second thought. It was
interesting to note that when checked
later with an ohmmeter, more than
Below: the chassis is mounted upside
down inside the cabinet. As a result,
the components were all covered in
a thick blanket of dust and fluff, with
only the larger components showing
through. There was a resident
redback too!
ELECTRONIC VALVE
& TUBE COMPANY
VALVE SPECIALS!
NEW SHIPMENT
Sovtek
6V6GT
5AR4/GZ34
5Y3GT
6CA7 (Fat)
6L6GC
12AX7WA/7025
12AX7WB
Others
655OB (Svetlana)
KT88 (China)
$10.00
$22.00
$12.00
$24.00
$10.00
$9.00
$12.00
EL84/6BQ5
EL34G (Slim)
5881
5881WXT (Based)
6550WA
6922
12AX7WXT
$10.00
$20.00
$18.00
$23.00
$40.00
$18.00
$14.00
$48.00
$48.00
E34L (Tesla)
EL34 (Telsa)
$28.00
$23.00
Matching at $1 per valve
Prices valid until 31.3.96
This view shows the Rola permag speaker used in the set, together with its
attached output transformer. Both the magnet housing and the transformer are
larger than normal for a 4-valve radio and no doubt contribute to the receiver’s
remarkably good bass response.
Send SSAE for our catalogue listing
valves for audio, radio
and industrial use.
Also specialist valve books of all types.
PO Box 381, Chadstone Centre,
Vic. 3148
Tel/Fax (03) 9571 1160
or Mobile 018 557 380
Registered office: 10 Berrima Ave, East Malvern.
Silicon Chip
Binders
Buy
subsc a
& get a ription
discou
nt
on the
binder
Everything back and ready to go – it’s not a tidy arrangement by any means.
Note the vertical rods at each end of the chassis. These connect to the tuning
and volume controls on top.
half of them showed some degree of
leakage. If a paper capacitor leaks
under a 3V test, what is it going to
do with a couple of hundred volts
across it?
Although replacing all paper capacitors is probably unnecessary, it is
worth the effort for peace of mind, if
nothing else. Let’s face it – old capacitors can be very troublesome!
The interesting aspect of the capacitor changeover was the noticeably
better performance. Prior to working
on the chassis, it was a “1-station radio”, receiving only the strong local
station with no aerial connected. After
the capacitor job, it became a 5-station
set and that was without any alignment
– just the new capacitors.
Alignment
As far as alignment was concerned,
there was very little to do. The IF (intermediate frequency) transformers
were virtually spot on and the aerial
trimmer needed only a slight tweak to
These beautifully-made binders
will protect your copies of SILICON
CHIP. They are made from a dis
tinctive 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.
March 1996 89
The major components (valves, IF transformers, power transformer, tuning
gang, etc) are mounted on the bottom of the chassis. The valve line up is: 6J8,
6B8, 6V6 and 5Y3. The four chassis-mounted electrolytics are all high voltage
types.
bring it in line. Even then, one could
barely notice any difference. The little
Peter Pan was a good set to work on
as it had not previously been tinkered
with.
It was at this alignment stage that
some gremlins in the 6V6 output valve
decided to do some arc welding and a
series of sparks and flashes occurred
from within. A replacement 6V6 re
moved both the gremlins and their arc
welder. A valve tester had previously
passed the faulty valve as being OK.
Maybe it didn’t like working upside
down?
The restoration was nearing completion and there were only a few jobs
left to do – tighten the speaker mounts
and polish the cabinet.
The speaker mounting involves four
short pillars and all of them were loose.
Unfortunately, they could only be
tightened by turning the screw heads
on the other side of the speaker baffle
– not a big job but a bit tedious considering the number of nuts that had
to be undone in order to remove the
baffle. It was a classic case of spending
10 minutes in order to do what should
have been a 30-second job.
Cabinet refurbishment
A flexible drive shaft wass used to
compensate for the misalignment
between the tuning capacitor shaft
and its matching control knob at the
top of the set.
90 Silicon Chip
The cabinet refurbishment consist
ed of a cut and polish for the bakelite
top and the “Armorall®” treatment for
the vinyl. At this stage, the set was
ready to go back together.
There were no problems with the
assembly and everything went back according to plan, with the chassis fitting
the repositioned mounting brackets as
it should have done in the first place.
A test run for a couple of hours indicated that all was OK inside and the
little Peter Pan performed very well. It
sounded remarkably good for a small
4-valver driving a moderately-sized
speaker.
There is no doubt about it: Radio
Most of the electrolytic capacitors in
the set required replacement. The 63V
unit shown here (top of photo) was
used to replace the original 24µF 350V
original below.
Corporation knew how to make
top-performing 4-valve receivers.
While many of their products were
aimed at the bottom end of the price
scale, they were always value for
money and performed as good or
better than other comparably priced
SC
products.
electronic design, and applications.
The sixth edition has been expanded
to include chapters on surface mount
technology, hardware & software
design, semicustom electronics &
data communications. 63 chapters,
in hard cover at $120.00.
Silicon Chip Bookshop
Radio Frequency
Transistors
Newnes Guide
to Satellite TV
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.
Guide to TV & Video
Technology
By Eugene Trundle. First publish-
ed 1988. Second edition 1996.
Eugene Trundle has written for
many years in Television magazine
and his latest book is right up date
on TV and video technology. 382
pages, in paperback, at $39.95.
Servicing Personal
Computers
By Michael Tooley. First published 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.
format and R-DAT. If you want to
understand digital audio, you need
this reference book. 305 pages, in
paperback at $55.95.
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.
336 pages, in paperback at $49.95.
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.
Digital Audio & Compact
Disc Technology
Electronics Engineer’s
Reference Book
Hard cove
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
Power Electronics
Handbook
Your Name__________________________________________________
PLEASE PRINT
Address____________________________________________________
_____________________________________Postcode_____________
Daytime Phone No.______________________Total Price $A _________
❏ Cheque/Money Order
r
Edited by F. F. Mazda. version now
available
First published 1989.
6th edition.
This just has to be the best refer
ence book available for electronics
engineers. Provides expert coverage
of all aspects of electronics in five
parts: techniques, physical phenomena, material & components,
❏ Bankcard ❏ Visa Card ❏ MasterCard
Card No.
Signature_________________________ Card expiry date_____/______
Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097.
Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503.
Principles & Practical Applications. By Norm Dye & Helge
Granberg. Published 1993.
This 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, impedance matching
& CAD. 235 pages, in hard cover
at $85.00.
Surface Mount Technology
By Rudolph Strauss. First pub
lished 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.
Audio Electronics
By John Linsley Hood. Published
1995.
This book is for anyone involved
in designing, adapting and using
analog and digital audio equipment. Covers tape recording,
tuners & radio receivers, preamplifiers, voltage amplifiers, power
amplifiers, the compact disc &
digital audio, test & measurement,
loudspeaker crossover systems
and power supplies. 351 pages, in
soft cover at $52.95.
Title
Newnes Guide to Satellite TV
Guide to TV & Video Technology
Servicing Personal Computers
The Art Of Linear Electronics
Digital Audio & Compact Disc Technology
Power Electronics Handbook
Electronic Engineer's Reference Book
Radio Frequency Transistors
Surface Mount Technology
Audio Electronics
Postage: add $5.00 per book. Orders over $100
are post free within Australia. NZ & PNG add
$10.00 per book, elsewhere add $15 per book.
TOTAL $A
Price
$55.95
$39.95
$59.95
$49.95
$55.95
$59.95
$120.00
$85.00
$99.00
$52.95
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.
Motor control with
current limiter
I am currently in the process of
designing a current limiter and stall
motor protection device for 12V DC
motors. I have read through numerous
electronics magazines and circuit designs references but have been unable
to find a suitable design. I am hoping
you can help me in some way. These
are some of the specifications a design
would have to meet: limit stall current to 3-4A; operating voltage range
between 11-14.5V DC; supply voltage
11-15V DC; reverse polarity protection
and use discrete components.
The device will hopefully prevent
a motor gearbox which is running at
a speed of 20-30 RPM from stalling at
high currents. The motor is currently
stalling at about 6-8 amps with a load.
This, however, reduces the life of the
motor considerably over time and it
becomes hot when stalled for long periods. The motor stalls in both directions
as it drives a gear, which in turn drives
a shuttle nut on a 100mm long thread.
This process is repeated numerous
Power transformer
runs too hot
I have just built the SLA Battery
Charger described in the August
1992 issue of SILICON CHIP. After
evaluation, may I make the following observations?
The M2165 transformer specified
seems to be overrated because when
run at the 3A charge rate for more
than one hour it becomes very hot
and I feel it could eventually burn
out. This transformer may be intermittently rated for 3-4 amps (60VA)
but should more realistically be
rated for 30-40VA continuously.
The DSE M2000 transformer
rated at 18 volt 6 amps used in
the original version (March 1990)
I think is still overrated at 6 amps
but ideally will run coolly at 8
92 Silicon Chip
times. (E. M., W. Norlane, Vic).
While we have not produced a designed for this purpose, we can suggest
a circuit which will do the job. It is a
switchmode circuit with foldback current protection, important if you want
to limit dissipation in the regulating
devices when the overload occurs.
The circuit appears on page 15 of the
August 1992 issue of SILICON CHIP and
is a simplification of our Railpower
train controller which appeared in the
April 1988 issue.
•
Automatic
watering control
I wish to use a Hardie Irrigation
water valve for automatic watering of
a small flower bed, which is in easy
reach of a 240VAC power point. I’d like
your opinion of my proposed plan. I
would use a 240VAC timer and possibly a plugpack or transformer to suit
the valve which has the markings 50Hz
8VA 24V. Hoping you can enlighten
me on this project. (R. S., Loxton, SA)
• Your irrigation water valve can be
controlled by a 240VAC timer and powamps. Radiated heat from within charger cases will ultimately
affect the voltage operating parameters of the UC3906 IC. (M. F.,
Christchurch, NZ).
• One of the dilemmas we face in
publishing projects of this nature
is that the quality of components
such as transformers can vary,
from supplier to supplier and also
as the years pass by. Our original
prototype transformer handled the
job quite comfortably but it may
well be that the one supplied to
you does get quite red in the face.
We opted for the M2165 transformer in the second version because the M2000 supplied a little
more voltage than was necessary
and consequently caused higher
power dissipation in the series pass
transistor (Q1).
ered from a 24V 1A plugpack. Such a
plugpack is available from Altronics in
Perth (Cat. No. M9129) for $19.25 plus
p&p. Altronics’ telephone number is
1800 999 007.
Low cost high voltage
transistor wanted
Could a lower cost alternative to
the Darlington transistor MJ10012 be
made by using a 2N3055 driven by
a BC639? With the MJ10012 listed
at $14.50 in the Jaycar catalog, it is
tempting to seek an alternative. Maybe
you could feature the design considerations in making a Darlington in the
Circuit Notebook chapter of your magazine. (B. P., Port Macquarie, NSW).
• The MJ10012 is a high voltage Darl
ington transistor especially designed
to take the high voltages generated in
the primary winding of car ignition
systems. These usually generate in
excess of 250V each time the transistor switches off. Although there is a
plastic equivalent to the MJ10012, it
is not currently available in Australia,
as far as we know. The 2N3055 would
be blown up immediately power was
applied if used in conjunction with
an ignition coil.
Bridging power
amplifiers
I have a few questions regarding
the 50W Amplifier project from your
February 1995 issue. Can you join two
50W amplifiers together to produce a
100W amplifier? Is there any relatively
simple way of getting more power out
of the 50W amplifier? How do you
work out PMPO values for speakers?
(J. B., Lower Hutt, NZ).
• It is possible to combine two 50W
amplifiers together to provide a 100W
amplifier. Normally, you need an additional bridge circuit so that the phase
of the signal to one amplifier can be
reversed. We published details of such
a circuit on page 95 of our February
1988 issue. However, it is possible to
do this more simply with 50W stereo
Keep plumbers tape
for plumbing
I am writing regards the construction of the 20W fluoro inverter
designed by Otto Priboj in the February 1991 issue of SILICON CHIP.
My first kit took quite a bit of
nutting out when it came to the
transformer windings. I completed
and still use this light, even after
six months. I have had no problems
with its operation. Since then I
have purchased another kit and I
am having all sorts of problems.
I also bought enough components to make eight other lights.
The same problem keeps surfacing.
The light works for a few minutes
then a buzzing noise appears, low
tone at first, rapidly increasing to a
high pitched buzzing then the light
shuts off never to go again. I then
module you refer to and we shall
publish the details in a future issue.
There is no relatively simple way
of getting more power out of the 50W
amplifier module as it stands. Our
design runs the device to almost its
maximum ratings.
PMPO values for loudspeakers and
amplifiers are largely imaginary as far
as we can see. Typically, the PMPO
(Peak Music Power Output) values are
at least ten times the realistic RMS rating and some small music systems as
sold in department stores have PMPO
ratings which are as much as 20 times
higher than their continuous (RMS)
ratings. In this way, a system with
a small stereo power chip rated at 6
watts RMS per channel can easily end
up with a PMPO rating of 120 watts!
In simple terms, such ratings are lies.
Multiple remote
control extender
I recently completed construction of
the April 1994 Remote Control Extender project and it works as expected,
although the range isn’t what I had
hoped for. In the construction article it
says to expect a range of about a metre
which is around what I am getting.
Such a range wouldn’t be a problem
if I was only interested in controlling
a VCR as the IR LED could be attached
to the sensor on the front of the video.
change the transistors; they go for a
short time and then the same thing
happens again. I think that my problem lies in the transformer winding
though I cannot see that I am doing
anything different to the first kit,
except I am using plumbers’ tape
for insulating the windings.
On my second kit the light was
in use for a good hour or so with
no problems then the next time it
was turned on it blew within thirty
seconds. Please help. We only have
a solar power source and I need to
solve this problem for much needed light. (M. O., Bairnsdale, Vic).
• Plumbers tape? You must be kidding. As outlined in the article, the
winding of the transformer for this
project is quite critical, particularly
setting the air gap. If you don’t do
it as described, you can’t expect
reliable operation
My problem is that I wish to control
four different components comprising
a VCR, television, CD player and stereo
receiver. However, because of their
physical separation and the directional nature of the IR beam produced by
the LED arrangement, only one component at a time can be controlled by
the extender unit – even if the LED is
mounted intrusively in front of the
stack of components
What I want to know is if it is
possible to upgrade the output of the
system to significantly increase the
range to about three metres, with the
LED be mounted unobtrusively and
able to cover enough area to operate
all four components. I have already
tried exchanging the 100mA LED for
a 220mA one but the range does not
seem to have increased by any measurable amount. Another option I have
considered is to connect several other
LEDs in parallel, either to increase the
range, or as a last resort, tape one LED
to each of the four components.
Another possible solution would
be to buy a “universal” remote control
unit and, after disassembling it, connect
the output LED and lens system of the
remote control to the extender output
circuit in place of the ordinary IR LED.
That may be a little more expensive but
a typical remote control has a much
greater range than one metre and a
much wider angle of operation.
If it is at all possible, how can I do
it? A reasonable extra cost in doing so,
doesn’t unduly concern me because I
was quoted $380 for the equivalent
commercial product by a hifi store.
(D. B., Homebush, NSW).
• You should be able to connect two
IR LEDs in series plus a couple of others in parallel with an extra resistor.
Each LED can activate one of your four
individual components.
Train controller has
too much inertia
I have recently built the train controller described on page 76 of your
“14 Model Railway Projects” book. Two
features do not perform as described:
(1). Throttle control: when reducing
speed of running train, deceleration is
very slow. Braking and inertia to start
are OK but when turning down VR1,
the voltage at Q1 stays at about + 10V
almost indefinitely. I disconnected
the 4700uF capacitor and it slows. I
reduced this capacitor to 470uF and it
works but then inertia start and brake
are instant.
(2). The overload LED does not light
up on short circuit – it appears that
overload protection works as Q2 does
not get hot and voltage drops. I would
appreciate your comments or suggestions or perhaps appropriate test
procedure. (C. C., Swan Reach, Vic).
• The response time for throttle reduction can be made about the same as
for start-up by omitting diode D5. For
LED1 to glow more prominently when
the circuit is in current limiting mode,
it needs to be a high brightness type.
FM stereo transmitter
alignment problem
After much deliberating, I finally
decided to build the “FM Stereo
Transmitter” kit. I built the kit with no
dramas (it’s very simple!). However, I
cannot get it to work. I have checked
around the BA1404 chip with a DVM
and a CRO with the following results:
+1.58V on the supply pins; 38kHz on
pins 5 & 6; “hash” on pin 14 (with no
audio input); there is 19kHz on pin 13
and 1.5V DC on pin 12; pin 7 (RF out)
is sitting at 1.58V and DC only; pin 10
is at +1.58V and also DC only; and pin
9 is at about +0.8V, DC only.
Obviously the modulation oscillator
isn’t running but I can’t see why. I have
checked for track faults and obviously
March 1996 93
Oils ain’t oils when it
comes to transistors
I have built the 40W inverter
from your February 1992 issue. Like
a number of your designs I have
made, it worked first go and gave
magnificent service for a long time.
Now it has devel
oped a fault
where it runs for months then
suddenly blows either one or both
MTP3055Es apart. This is always
on start up, usually without load.
I fitted a pilot light and this
stopped the problem for a while
but it has gradu
ally got worse.
Inverters are the most unreliable
piece of equipment I have had to
contend with. I had thought at last I
had found one that I could rely on.
I hope that you can help me, as
shorted capacitors. I have double
checked component locations and
orientation. I have replace the BA1404
chip. Any ideas? (J. A., Giralang, ACT).
• We think it unlikely that the modulation oscillator is not running. In
our experience, the problem is more
likely to be incorrect alignment. In
general, unless you have a scope with
a response to at least 100MHz and 10:1
probes, you are unlikely to see any
evidence of RF output in the circuit.
If you don’t use 10:1 probes the circuit
loading is likely to stop the circuit
working at all.
We suggest you carefully go through
the alignment procedure again. This
project has proved very reliable and
many thousands have been built since
its publication eight years ago.
No mods necessary for
low ohms adaptor
One of my Christmas presents was a
digital multimeter and this prompted
me to look over the various DMM plugin accessories which I have acquired
over the years. One accessory still
needed was a low ohms adaptor so I
spent some time investigating the unit
I built from the design published in the
February 1988 issue of SILICON CHIP.
I have never had much confidence
in this device because the readings
were not consistent across the ranges
or were not in accordance with expectations from other evidence.
94 Silicon Chip
at the moment I am running a 3kVA
generator to have a shave. I consider this a bit of an overkill. Have I
got a botchy lot of MTP3055E Mos
fets? Are these problems just a part
of using this inverter or can you
suggest a way to overcome these
problems? (R. B., Heyfield, Vic).
• We hate to say it, but not all MTP
3055Es are born equal. Our experience suggests that those branded
with the Motorola batwing symbol
are the best and some of the others
are definitely dodgy. We have also
found other transistors, originated
by Motorola but second-sourced by
others, are not as good. For example, if you are building high power
audio amplifiers with MJE340s and
350s, the Motorola ones are the best.
The others work, but not as well.
I noticed an unstable reading on the
high ranges. On examination with an
oscilloscope, I found that there was
about 7mV of noise at the output of the
op amp but replacing it did not cure
the problem. The noise was being generated in the BC559 and replacement
with a BC558 (because I didn’t have
another BC559) brought the noise level
down to about 1mV.
It seemed to me that, with the very
low resistances to be measured, the
resistance of the internal connections
would have a significant effect.
I separated the wires sourcing the
current to Rx from the wires sampling
the resultant voltage developed across
it by running four wires to the terminals, a pair for each function. Thus,
any voltage drop in the supply lines is
not reflected in the measured voltage.
It was necessary to cut the appropriate
tracks on the PC board. Setting the test
currents to 1mA and 10mA was very
critical and it did not seem to retain
the settings reliably, so I put resistors
in series and in parallel with the 1kΩ
and 100Ω multiturn pots. This gives a
much smoother adjustment and seems
to hold the set value better.
Because the residual noise seemed
to be worse on the x100 range than the
x1000 range I used 10mA on the three
higher ranges and reduce the gain of
the op amp to 10 for x100. The spare
switch pole enabled me to add a 1kΩ
resistor in parallel with the feedback
resistor. Incidentally, I found that the
10kΩ resistor was actually 9.9kΩ, giving the required gain of 100 directly
without the need to subtract the input
signal. A resistor closer to 10kΩ could
be parallelled with 1MΩ to achieve
this value. I changed this part of the
circuit also to avoid the polarity reversal on the upper ranges.
There was a degree of non-linearity
on the upper ranges due to the lack of
a negative supply line for the op amp.
This was overcome by adding a couple
of diodes in series with the negative
battery lead and applying the resultant
-1.4V to pin 4.
Once the 1mA and 10mA levels are
set, final calibration is best achieved by
using a resistor of between 0.1Ω and
0.2Ω and adjusting the offset until the
reading on the x1000 range is as near
as possible to 10 times the reading on
the x100 range.
The shortest possible piece of
1.5mm copper wire clamped firmly
through the holes in the terminals
should then give a reading of between
0.2 and 0.4mV on the x100 range and
between 2 and 4mV on the x1000
range. This is about 3mΩ and is almost
entirely contact resistance. A 24cm
length of 0.66mm wire measured about
14mΩ which is consistent with a value
of 12mΩ calculated from wire tables.
The unit is now accurate to within
a couple of milliohms and testing over
the last few days has shown completely consistent results. As you suggested
in your original article, measurement
of low resistances is a rather neglected
area. I have recently been dabbling in
speaker design and I am sure that this
unit will be very useful. (A. M., North
Turramurra, NSW).
• We are glad that you have finally
made your Low Ohms Adaptor work
but apart from replacing a noisy
transistor, we don’t think any of your
modifications are really necessary.
In particular, the CA3140 op amp
was specified precisely because it can
operate from a single supply and the
addition of diodes will reduce the life
of the battery because of their voltage
drop. As the battery voltage drops
we would also expect the diodes to
introduce their own non-linearity into
the circuit.
Operating some of the ranges at
10mA instead of 1mA will also reduce
battery life. We agree that the current
adjustment is critical but we did specify multiturn pots to make the task
straightforward.
SC
MARKET CENTRE
Cash in your surplus gear. Advertise it here in Silicon Chip.
FOR SALE
KITS KITS KITS: Electronic kits for
enthusiasts of all ages and abilities. Top
quality. Large range. Free catalog and
price list available. Call Ozitronics, 24
Ballandry Crescent, Greensborough
3088. Tel/Fax: (03) 9434 3806 email:
ozitronics<at>c031. aone.net.au
START WITH A MICROZED KIT then
when your "test the market", small run
project hits the big league MicroZed
can help you with alternative schemes
and quantities ex stock at the right
pricing.
CHEAP MICROCONTROLLER SYSTEM: 8MHz 280. Program via printer
port. No EPROM or EPROM programmer needed. 32K RAM battery backed.
128 digital I/O. 32 analog inputs. Can
run stand alone. Professional software
with pulldown menus, text editor, simulator, compiler, dumper, reader and
extensive help. Min XT/AT & EGA/VGA.
Price includes circuit and all software
(components extra, cost approx $65).
Send $49.95 to N. Moxham, 23 Arizona
Tce, Glenalta SA 5052.
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.
MEMORY * DRIVES * MODEMS
SPECIAL! (Incl Tax)
1Mbx9 – 70ns Simm $60
1Mbx9 – 80ns Simm $45
SIMMS
(Parity/No Parity)
4MB 30 PIN-70
$175 $179
4MB 72 PIN-70
$177 $145
8MB 72 PIN-70
$347 $288
16MB 72 PIN-70 $695 $572
32MB 72 PIN-70 $1389 $1210
EDO SIMMS
8MB (2Mbx32)-60ns $369
16MB (2Mbx32)-60ns $683
MAC
8MB P’BOOK $470
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
$554 / $1105
DRIVES SEAGATE
850MB EIDE 11ms 3yr
$318
1080MB EIDE 10.5ms 3yr $360
1080MB SCSI 9ms 5yr
$484
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
A REAL BARGAIN: Riston type copper
clad laminate. Develop cold, no toxic
fumes, easy to use. Excellent results.
Single sided 610x304 $34; 305 x 304
$17.50; 152 x 305 $9.95; 152 x 152
$6.50. Double-sided also available. 2
litre developer mix, worth $2.50, free
this month. Add sales tax if applicable.
Delivery $6.00. Money back guarantee.
Ph (02) 743 9235. Fax (02) 644 2862.
DonTronics HAS MICROCHIP PIC
GEAR: Programmers from $20 to
$225, PICBASIC: 64 $50, 57 $40, 84
$40, EEPROM: 93LC56 $5, 24LC16B
$8, 24LC65 $16, CPU: 84/04/P $12,
57/04/P $12, 64/04/P $17. Serial and
parallel I/F kits and lots of other stuff.
VISA-MC-BC. Ask for free Promo Disk.
ftp://labyr inth.net.au/home/donmck/
public-html/index.htm. 29 Ellesmere
Crescent, Tullamarine 3043. (03) 9338
6286. Fax (03) 9338 2935.
MicroZed HAVE GOOD stock of
12-bit A/D serial I/O chips for Stamp
applications. These have two inputs
or single differential input configurable
by software.
C COMPILERS: Dunfield compilers are
now even better value. Everything you
need to develop C and ASM software
for 68HC08, 6809, 68HC11, 68HC16,
8051/2, 8080/85, 8086 or 8096: $140.00
each. Macro Cross Assemblers for these
CPUs + 68000/01/03/05 amd 6502:
$140 for the set. Debug monitors: $70
for 6 CPUs. All compilers, XASMs and
monitors: $400. 8051/52 or 80C320
simulator (fast): $70. Demo disk: FREE.
PELHAM
Suite 6, 2 Hillcrest Rd,
Pennant Hills, 2120.
Ph: (02) 9980 6988 Fax: (02) 9980 6991
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
RCS RADIO PTY LTD
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
Scott Edwards Electronics
BASIC Stamp I and II
NEW Micro
68HC11 F1 boards and now 80535 (up spec 8051)
both boards with BASIC, FORTH, ASM, Small C
80535 board has 8052AH INTEL BASIC installed
24 I/O expansion board now in stock for both boards
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.
All prices +$5 p&p. GRANTRONICS
PTY LTD, PO Box 275, Wentworthville
2145. Ph/Fax (02) 631 1236 or Internet:
lgrant<at>mpx.com.au
Versa Tech
TICkit – a 21 I/O PIC based controller
Accessories for Stamp and second source for Stamp 1
Recently developed accessories now available
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
Get your project on the way in hours, not months.
Send two 45c stamps for information package
March 1996 95
Advertising Index
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.
Altronics ....................................IFC
Av-Comm.....................................59
Car Projects Book....................OBC
Defence Force Recruiting............31
Dick Smith Electronics........... 18-21
Electronic Valve & Tube Co..........89
_____________ _____________ _____________ _____________ _____________
Harbuch Electronics....................81
Instant PCBs................................95
_____________ _____________ _____________ _____________ _____________
Jaycar .........................................53
Kits-R-US.....................................83
_____________ _____________ _____________ _____________ _____________
_____________ _____________ _____________ _____________ _____________
_____________ _____________ _____________ _____________ _____________
Macservice............................ 10-11
MicroZed Computers...................95
Oatley Electronics.................. 78-79
Pelham........................................95
Railway Projects Book...............IBC
_____________ _____________ _____________ _____________ _____________
RCS Radio ..................................95
Rod Irving Electronics .......... 67-71
Silicon Chip Back Issues....... 72-73
❏ Bankcard ❏ Visa Card ❏ Master Card
Silicon Chip Bookshop.................91
Card No.
✂
Enclosed is my cheque/money order for $__________ or please debit my
Silicon Chip Software..................39
_________________________________
PC Boards
Signature__________________________ Card expiry date______/______
Printed circuit boards for SILICON
CHIP projects are made by:
Name ______________________________________________________
• RCS Radio Pty Ltd, 651 Forest
Rd, Bexley, NSW 2207. Phone (02)
587 3491.
Street ______________________________________________________
Suburb/town ___________________________ Postcode______________
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.
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 Electronics, 22
96 Silicon Chip
McGregor St, Numurkah 3636. Ph/Fax
(058) 62 1915. E-Mail: laurie.c<at>cnl.com
.au BBS (058) 62 3303
COMPLETE WORKSHOP PROGRAM:
suit IBM compatible 386 or better computer. Handles: Stock Control, Sales,
Service Records, Debits, Credits,
Faults, Service Manuals and Phone
Directory. Full price $399.00. For demo
disk, phone or fax your details to (045)
71 1640. Jack Albers Electronics &
Software Development.
NEW SPRINKLER CONTROLLER
KITS: RAIN BRAIN version uses ‘C8
and switch mode supply. Features galore!! Contact Mantis Micro Products,
• Marday Services, PO Box 19-189,
Avondale, Auckland, NZ. Phone (09)
828 5730.
38 Garnet St, Niddrie 3042. Phone/fax
(03) 337 1917.
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.
SERVICE & REPAIRS
PATRA ELECTRONICS: assembly and
repairs of all kits. Repairs of electronic
equipment. Call Peter on (02) 718 1202
or 015 215957.
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____________
|