This is only a preview of the November 1992 issue of Silicon Chip. You can view 52 of the 104 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Items relevant to "A 2kW 24VDC To 240VAC Sinewave Inverter; Pt.2":
Articles in this series:
Items relevant to "An Automatic Nicad Battery Discharger":
Articles in this series:
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|
Build An lnfrared Night Viewer
SIMPLE FM
.RADIO RECEIVER
~
c..
It uses just two chips &
runs off a 9V battery
z"'
~ AUfOMATIC NICAD
0
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._:
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0
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<(
BATTERY DISCH~RGER
11
Puts new zip" into your: mobile
telephone batteries
::i
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a:
LOW-COST SPEED
; CONTROLLER FOR MODELS
!;;
:::,
<(
>
a:
w
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a
w
a:
Compact design can handle motor:
currents of up to 50 amps
* A Brief Look At Liquid Crystal Displays
* DC-DC Converter Circuit For The 2kW Inverter
~ ACCURATE
M
COMPACT
RUGGED
RELIABLE
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The reasons for choosing Tektronix stack up as well as
our bench test equipment
Tektronix TM 250/fM 2500 Series bench test equipment is
designed to cater for a wide range of applications ranging
from basic to advanced.
It is equally suitable for teaching situations, industrial
applications and for the advanced hobbyist.
The rugged, affordable Tektronix bench test range includes:
• Power supplies for lab and field work.
• Digital multimeters to measure AC and DC voltage and
current plus resistance and decibels.
• Function generators for testing amplifiers, filters and
digital circuits.
• Stackable multi-function counters, especially useful
standards for calibrating other equipment.
• The versatile, multi-purpose basic bench set: ideal for
schools, labs and production lines.
Call now for full details and specification information.
Tektronix
h
st and Measurement
Free Call (008) 023342
Vol.5, No.11. November 1992
FEATURES
6 A Brief look At liquid Crystal Displays by Daniel Katznelson
How they work & why they're popular
BASED ON a Motorola 6BHC705CB microcontroller, this project is
designed to teach the basics of
programming & microprocessor
control. Tum to page 34.
32 The Oriel: Jamo's Flagship Loudspeaker System by Leo Simpson
Three-way system has no expense spared
79 The Story Of Electrical Energy, Pt.21 by Bryan Maher
How electric lighting came to Sydney streets
PROJECTS TO BUILD
16 Build An FM Radio Receiver by Darren Yates
Uses just two chips & runs off a 9V battery
22 Modifications To The Drill Speed Controller by Leo Simpson
Amended circuit has longer gate pulses
24 A 2kW 24VDC To 240VAC Sinewave Inverter, Pt2 by John Clarke
The DC-DC converter circuitry
34 The M.A.L. 4.03 Microcontroller Board by Barry Rozema
Uses a 68HC705C8 microcontroller
40 An Automatic Nicad Battery Discharger by Bernie Gilchrist
Puts new "zip" into your nicad batteries
62 An lnfrared Night Viewer by Branco Justic
It lets you see in the dark
74 Simplifying The lnterphone Telephone Exchange by Leo Simpson
Simple modification eliminates up to 18 !Cs
.
SPECIAL COLUMNS
44 Serviceman's log by the TV Serviceman
I did it; but it wasn't my fault
58 Vintage Radio by John Hill
Converting a battery set to mains operation
PUT MORE ZIP INTO your
mobile telephone batteries with
this low-cost device. It automatically discharges a nicad battery
pack to its correct end-point
voltage so that the pack can then
be recharged to full capacity.
Details page 40.
IFYOU'RE
new to
electronics,
here's a great
project to get
you started.
It's a simple
FM radio that
uses just two
low-cost ICs & runs off a 9V
battery. See page 16.
66 Amateur Radio by Garry Cratt
A PLL demodulator for amateur receivers
84 Remote Control by Bob Young
A low-cost speed controller using discrete !Cs
88 Computer Bits by Darren Yates
The PHd pocket hard disc drive
DEPARTMENTS
Publisher's Letter
Mailbag
Circuit Notebook
Subscriptions Page
68 Product Showcase
2
4
B
57
96 Back Issues
98 Ask SIiicon Chip
101 Order Form
102 Market Centre
104 Advertising Index
EVER WANTED TO SEE in the
dark without a flashlight? This
infrared night viewer will let you
do just that. All you have to do is
build the high-voltage supply.
Tum to page 62.
NOVEMBER
1992
1
Publisher & Editor-in-Chief
Leo Simpson, B.Bus.
Editor
PUBLISHER'S LE'I*l'ER
. Greg Swain, B.Sc.(Hons.)
Technical Staff
John Clarke, B.E.(Elec.)
Robert Flynn
Darren Yates, B.Sc.
Reader Services
Ann Jenkinson
Sharon Macdonald
Sales & Marketing Mgr.
Sharon Lightner
Phone (02) 979 5644
Mobile phone (018) 28 5532
Regular Contributors
Brendan Akhurst
Garry Cratt, VK2YBX
Marque Crozman
John Hill
Jim Lawler, MTETIA
Bryan Maher, M.E. , B.Sc.
Jim Yalden , VK2YGY
Bob Young
Photography
Stuart Bryce
Editorial Advisory Panel
Philip Watson , MIREE, VK2ZPW
Norman Marks
Steve Payor, B.Sc., B.E.
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: Magazine Printers Pty Ltd,
Alexandria, NSW; Macquarie Print,
Dubbo, NSW.
Distribution: Network Distribution
Company.
Subscription rates: $42 per year
in Australia. For overseas rates, see
the subscription page in this issue.
Liability: 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.
Editorial & advertising offices:
Unit 1a/77-79 Bassett Street, Mona
Vale, NSW 2103. Postal address:
PO Box 139, Collaroy Beach, NSW
2097. Phone (02) 979 5644. Fax
(02) 979 6503.
ISSN 1030-2662
2
SILICON CHIP
Light pollution wastes energy
The subject of this month's "Publisher's Letter" was triggered by one of the
projects featured in this issue, the Infrared Night Viewer. Naturally, as part of the
work involved in presenting this unit, we used it at night. And while it is more
effective if used with an infrared torch, it does work quite well on moonlit
nights. Interestingly, it can also work quite well on cloudy nights when the
Moon is completely blocked out. How can this be so?
First of all, if you live in any Australian city or major town, it no longer gets
really dark at night. There is so much light around at night that we now have a
major new form of pollution to contend with - light pollution. And it is the
infrared portion of all this light that enables the aforesaid infrared night viewer
to work. But this is not good.
Most Australians, unless they have an interest in astronomy, could not give a
fig about light pollution. It is now so bad in Australian cities that many city
residents cannot even see, let alone identify, the symbol on our flag, the
Southern Cross. Yet the Southern Cross is one of the brightest constellations in
our skies. And nor should light pollution be thought of as a problem just in the
inner city areas. It is particularly bad in the newer suburbs which have very
bright street lighting, where the houses have so-called security lighting, plus
lighting for the pool, barbecue and garden. And there is the super bright lighting
used for sporting venues, shopping centres, car sales yards and so on.
Maybe most people don't care whether they can see stars in the sky or not.
Maybe most of them are afraid of the dark. But the level of lighting now being
employed is downright wasteful. It costs a lot of money to install all that lighting
and it takes a lot of energy to run it. Not only is it over-bright, most of the lighting
fixtures are badly designed and aim a good portion of their light straight up into
the sky instead of down at the ground. In fact, driving along roads near nighttime sporting venues can often be unpleasant because there is so much glare
from the lighting.
It is about time we came to our senses about this subject. While we may regard
countries such as the USA as being very wasteful of energy, when it comes to
light pollution we are right up there at the top of the list. In the USA and other
countries , there is an organisation called the "International Dark Sky Association" and this has had considerable success in mitigating this problem. It is
probably about time we had a branch of this organisation in Australia. If we start
now, we could save a huge amount of fossil fuel and maybe children of the
future will be able to see the stars at night, perhaps even more than we can now.
If you want to write to the International Dark Sky Association, their address
is: 3545 North Stewart, Tucson, Arizona 85716, USA.
Leo Simpson
Message Stopper
This inexpensive device, which connects direct
to your answering machine will automatically
d isconnect your answering machine w bcocvcr
ANY PHONE is answered ! If your answering
machine answers your call before you do,
simply pick. up any pbone, your answering
mach ine will immediately disconnect and you
can speak. without interference. With tbe
MESSAOE STOPPER you can now leave your
answering machine on and not have to worry !
Are your customers having trouble getting through
to your phone/fax line ? and you've Jost the sale
because your exsisting fax switch is not doing what
YOU want it to do ? WE HAVE THE SOLUTION I
The VSI EASY CONNECT Phone-Fax/Line Sharer
The most advanced Phone-Fax (or Modem) /Line Sharing Device. Now available in Australia.
Integrate ANY fax, with ANY answering machine on ANY telephone system,
WITHOUT the limitations of faxswitch devices or 3 in I fax systems.
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New projects wanted
As usual, the minute I saw SILICON
CHIP at the newsstand I purchased it.
I am usually rapt in the magazine but
I was a little dissatisfied with the August edition.
I agree that one sealed lead-acid
battery charger is a good idea, and
perhaps an update, but another? How
many people who built the first one
would build a second, if the first one
fulfilled their needs? If you are short
of ideas, how about a constructional
project for the CB enthusiasts, like
UHF antennas and/or a UHF SWR
meter? I have been searching for something on this line for a while.
I am sure there are many others
who would love to build an antenna
at a fraction of the cost of a commercial unit I would also love to see an
antenna rotator using reasonably
priced components. Any other UHF
users think the same?
I would also like to comment on the
statement made by Leo Simpson in
the April 1992 edition about Bulletin
Boards being a trouble area for computer viruses. As a former BBS operator, and a co-sysop currently, I would
like to mention that most BBSs nowadays scan for viruses before a file is
allowed to be downloaded.
Whingeing aside, I still think that
the magazine is the most comprehensive in its field and look forward to
further issues, perhaps with some
UHF radio projects.
J. Adler,
Broadbeach Waters, Qld.
Another fan of peanuts
sticks to his blanket
A fair amount of hysteria has been
generated recently by articles in the
media and electronic journals about
the real or imagined dangers of 50Hz
power lines, electric blankets, etc. I
believe that case is closed as millions
of people have used electric blankets
etc for decades without any statistically significant effects becoming evident.
However, very recently, there has
come into common use a device which
4
SILICON CHIP
I believe could be decidedly iffy. I
refer to the mobile radio telephone,
handheld, where the aerial of a UHF
transmitter is about 50mm from the
brain of the user! I'll stick with my
blanket, thank you.
While I'm at it, here's one for the
design department. I believe the 9V
switchmode supply idea in the August issue could have a much wider
application. Many thousands (millions?) of instruments and appliances
are powered by 1.5V dry cells arranged
in a stack. In many cases, it would be
an advantage if these were replaced
by nicads, plus a switchmode supply
which would produce a regulated dry
cell voltage equivalent over the range
of the nicad cell stack voltage.
Bill Jolly,
Hahndorf, SA.
Video switcher for S-VHS
I find SILICON CHIP as interesting
and full of features as ever. Keep it
up! The Video Switcher Project as
described in June 1992 is a fine example and it certainly would tidy up a
situation of mine. However, I have SVHS video equipment which means
the project would unfortunately not
be suitable.
As you would know, in S-VHS and
8mm Pro formats, the video is split
into chrominance and luminance signals which are processed separately.
This results in a vastly superior picture. (Both formats use 4-pin miniDIN connectors for the video instead
of the usual RCA or BNC connector).
The audio is processed as normal using RCA plugs.
Would you consider a version of
the Video Switcher for use with SVHS equipment? I'm sure other readers with S-VHS or 8mm Pro would be
interested.
G. Suttle,
Sydney, NSW.
Applix microcomputer board
Readers looking for a build-it-yourself microcomputer kit may be interested in attending Applix User Group
meetings in Sydney or Melbourne, or
SILICON CHIP,
PO Box 139,
Collaroy Beach 2097.
logging onto one of the four Applix
bulletin boards that use this computer.
Although the kit comes from a garage in Yerrinbool, it is a full 7.5MHz
or 15MHz Motorola MC68000 computer, built using lots of standard 74LS
and VLSI chips (6821, 6545, 8530,
5380 and three PALs - nothing exotic). It can run from a serial port or
provide its own CGA or EGA video,
and has the entire operating system in
on-board EPROM. Although you can
run it without discs, it includes support for floppy drives and SCSI hard
discs, via an optional Z80-based disc
controller card (that can even run
CP/M and MicroBee programs).
User group members are attempting to fill up the four expansion slots
by designing n ew hardware. An
EPROM programmer has just been
completed and I have seen prototypes
for a Transputer card, a 25MHz MC68030 card, and an Ethernet and memory card.
The free C and assembler source
code available fills more than 30 discs
and includes many utilities derived
from Unix. It includes assemblers and
disassemblers and a C-like interpreter.
Software for sale includes BASIC and
Forth, a C compiler from Brisbane
softw are developer HiTech, plus
windowing systems, com:munications
packages and Unix utilities.
Readers wishing to read up on this
system can obtain copies of Applix
manuals from the User Group. Manuals available include Users, Programmers , Technical Reference, Construction, Assembler, Disk. We must ask
for $10 each to cover our photocopying costs. We can also make manuals
available free in Postscript form, on
IBM format discs. Please note that
most manuals are so large that a high
density disc mu st be used. We would
be pleased to send copies of some of
the Applix User group newsletters to
any of your readers who may be interested in learning more.
Eric Lindsay, Applix User Group,
6 Hillcrest Ave,
Faulconbridge, NSW 2 776.
We've recently taken on a new line in so ldering irons - Hakko - and they are excellent value for money
offering features usually costing much more. We have the full range available, but check out the 926
adj ustable temperature iron, the memory card 927 and dual station 928. If you 're thinking about buying or
upgrading you r soldering equipment can in and discuss your requirements.
~
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• Compact unit with two 926 units
Hakl<0926
Hakko 928 Dual
in one station and easy to use.
Cost effective and practical in
Soldering Station Solder.Ing Stat"IOn •production
using up less space.
The Hakko 926 (above) is a super- • Two soldering irons of different
• Super quick heat up and faster
quick heat-up (3 sec cycle) and
fast recovery iron offering high
quality soldering at lower tip
temperatures. The built-in ceramic
heater maintains temperature to
within 0.5°C of the setting. Yes
this is an ADJUSTABLE
temperature iron covering the
range from 200°C to 480°C using
a full wave zero-crossing
switching system. Meets MILSTD-2000 and operates at safe
24V. Also available in ESD for
antistatic environments. We stock
a wide range of tips to suit. Ask
for listing.
Hakko927
Soldering Station
Incredible memory card iron.
Just look at the features • Digital adjustment/display
system using built-in
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• Accurate Temperature
Adjustment and Monitoring Simply insert the card , set the
desired temperature and push the
set ("S") button. Once the
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changed without -re-inserting the
card .
• Temperature Memory System The tip temperature value is
stored in the memory of the builtin computer allowing you to turn
the power off and on without
having to reset the temperature
each time.
The HAKKO 927 ESD Soldering
Station is available for static
safety and meets MIL- STD-2000
thermal capacities may be used
thermal recovery, permitting
simu ltaneously
quality soldering at lower
• Choose the exact irons you need temperatures.
for your so ld ering appl1cat1ons
• Separate controls for each iron
• ±0.5°C dial setting
• Meets MIL-STD-2000
ASK ABOUT OTHER PROFESSIONAL SYSTEMS
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154
As 153 but for Axial Components 5mm
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155
Cutting for Radial Components
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POA
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PdrtS Feeder for 153 and 154
POA
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Thermometer with Large Digital Display
$250.00 $278·80
191 -211 191 Sensors per Pack of 10
$17.25
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470
Desoldering Tool
1945 .00 $1079 .00
471
Desoldering Tool
848.00 $965.40
483.1 Complete Desoldering Gun
415.70 $473 .85
POA
485
Solder/Desolder Stati on with Solder Bath POA
1
493
Smoke Absorber
v.i
!:l::
iS
~
u:.
a
Solder
1.25, 0.9 and 0.71 mm
250 gm
500gm
Solder Wick
diameter
$7.95
$14 .95
$2.95
~ 8.30am to 5.00pm Mon to Fri. 8.00am to 12 noon Saturday.
:::,. Mail Orders add $5.00 min to cover postal charges.
v.l Next day delivery in Sydney add $8.00.
~ All prices include Sales tax unless stated otherwise.
u Tax exemption certificates accepted if the line value
~ exceeds $10.00.
u:. BANKCARD, MASTERCARD, VISA, CHEQUES or CASH
cheerfully accepted.
§
~
$195 .75
$233 .15
700C 50/60W Combi Solder/Desolderer
$1095 .00 $1253 .00
745
Battery Powered Iron 7.2V Operation
160.00 $182 .40
804
Glue Gun with Temperature Control
279.00 $318.80
850
SMD Hot Air Rework Station with N-7 Tip 990.00 $1129 00
741 ·oo
851
SMD Station
650.00
221 :40
883
HotAirGun-1000W, 1250m 3/min
194.40
183.95
926
Solder Station - 60W Temperature Control 159.95
359.65
926ESD926 Station with Antistatic Feature
315.90
482.50
927
Key Card Station - 60W with Digital Display 423.30
532.80
927ESD927 Station with Antistatic Feature
467 .45
605 .85
928
Dual Individual Control -60W, Antistatic
531.55
a
§
TAX
TAX
PAID
1
Safewash 2000- the complete
environment-friendly cleaning
System
The Safewash 2000 aerosol
offers a break through in PCB
Safewash 2000 is a unique blend
of biodegradable 100% ozone
friendly solvents in an aqueous
blend formulated to provide
effective cleaning of printed circuit
boards. Safewash cleans to
military standards (MIL-P-28809A)
using conventional methods at
room temperature.
Application
• Removal of flux residues and
other contaminants from
~r·Inted c·1rcu·1t boards and
urface Mount Assemblies
• Removal of unused solder paste
from sc reens
• Degreasing and cleaning prior
to conformal coati ng.
·
Features
e 100% ozone friendly
• Non-flammable
• Biodegradable
• Removes both polar and nonpolar contam inants
• Removes ionic flu x residues to
MIL P 28809A
• Ambient temperatu, e operation
• Low toxicity
rework technology. There are a
number of aeroso l products on
the market which either still
contain CFC's, or otherwise leave
a sticky residue after 'cleaning '.
Safewash 2000 uses a unique
foaming action to break down a
wide range of fluxes, in fact up to
_three times more flux types than
most alternatives. Once applied,
the foam action 'scrubs' the
b d rfr
th fl
·d
oar ' 1 mg e ux resi ue away
from the PCB. After a few minutes
the flux residues are sufficiently
broken down to be rinsed away
using Saferin se 2000. The printed
circuit board can then be dried off
using an Electrolube Air Duster or
another form of forced or warm
air drying.
Because Safewash 2000 uses a
foaming action, manual scrubbing
with a brush, wh ich can cause
damage, is not req uired, thereby
saving money on unnecessary
extras. An add itional operator
benefit is that Safewash does not
have the citrus smell often
~ - - - - - - - - - ~ associated with aqueous or non
CFC cleaners.
Safewash 2000
Electrolube
Positive Photo
Resist Aerosol
Now in 200gm can for one to one
reproduction of printed circuits
and images on metals using film
positive masters.
Gives excellent resolution with
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edge coating thickness.
Safe, easy to app ly an d process.
Can covers approx. 5sq.m. $33 .00
Also from Ele~trolube Clear lacquer (250gm)
113.10
Freezer (550gm)
23.80
Cleaning Solvent (300gm) 10.70
i~~~w;,;;rosol
0
i~r B~st::osol
550gm aerosol
$19.80
$18.10
$26 .60
We can supply
Electro lube
products in
aerosols or in
bulk. Call us for
pricing
A brief look at
liquid crystal displays
Liquid-crystal displays are everywhere
these days; they're even used as TV
screens. This articles describes how
they work & explains why they've
become so popular.
By DANIEL KATZNELSON
The liquid-crystal display or LCD
made its commercial debut in the early
1970s. It represented a quantum leap
in display technology that manufacturers of digital watches were quick
to exploit.
Today the LCD is the most widely
used display type except, of course,
for the ancient CRT, which has proven
to be remarkably durable. The introduction of colour LCDs, combined
with constantly improving resolution
and speed, has brought about the development of highly portable flatscreen TVs and laptop computers.
We are undoubtedly heading to-
wards an age of "tubeless" consumer
products, although that time is still a
long way off.
How LCDs work
LCDs are amazingly efficient at performing their jobs. The smallest LED
(light-emitting diode) display consumes a few milliwatts while an LCD
uses power measured in microwatts.
For electronics enthusiasts, the implications are obvious - a project's
display-current requirements can
practically be ignored. Frequently, circuits that use LEDs must be designed
around the display because a glowing
FRONT
POLARIZER
GLASS
PLATE
PATTERN
ELECTRODE
BACKPLANE
ELECTRODE
PASSIVATION
LAYER
LIQUID
CRYSTAL
POLYMERIC
SEAL
PASSIVATION
LAYER
ALLIGNMENT
COATING
GLASS
PLATE
REFLECTIVE
COATING
\
REAR POLARIZER
Fig.1: this sectional view shows the physical construction of a typical LCD. Note
the backplane electrode that runs behind the liquid crystal material.
6
SILICON CHIP
diode demands over 1000 times more
power than a liquid crystal segment.
The physical arrangement of an LCD
is totally different from other display
devices because it does not produce
light. Instead, it modifies the available ambient light to produce the required digits and characters.
Liquid crystals have some of the
characteristics of a liquid and some of
the characteristics of a solid. The liquid crystal particles can be visualised
as twisted ribbons that can be moved
around. The crystalline medium in
an LCD is ari organic compound that
is scientifically referred to as being
dielectrically anisotropic. That means
that the properties of the crystals
change when an electric field is
present. If unenergised (ie, with no
potential present), the crystals "rotate" any incoming light by go Conversely, when they are under the influence of a field, any passing light
remains unaffected.
For simplicity, you can imagine
light as a wave moving up and down
as it travels forwards . But in the real
world, one light wave might be vertically polarised, while another wave
is horizontally polarised. A slew of
others could have any orientation between these two.
A polarising filter allows only those
light waves travelling with a particular orientation to pass through it. If
you place one polarising filter behind
another and position them so that one
passes vertically polarised light while
the other passes horizontally polarised light, then light will not be able
to pass through both filters. But, if
you take the vertically polarised light
that passes through the first filter and
"rotate" it through go 0 so that it becomes horizontally polarised, it can
then pass through the second filter.
You can do just that be placing an
-unenergised liquid crystal of the right
thickness between the filters. Light
will travel through the first filter and
0
•
v00 ___0JL~ OFF
Vss __ _---..J
L-
CONTROL
INPUT
32 TO 60 Hz.
SQUAREWAVE
OSCILLATOR
PATTERN
ELECTRODE
.J'lJ'1...
- - - - -- - --f
____...t.J'lJ'l...
BACKPLANE
LIQUID-CRYSTAL CELL -
-•~
Fig.2: this is the most popular drive
circuit for an LCD. The gate's control
input determines whether it inverts or
buffers the oscillator signal.
LCD BACKPLANE (OSCILLATOR)
in the shape of a display segment and
consists of a grid of fine wires composed of indium tin oxide. They are
etched into the glass by a process
called photolithography.
Another electrode (to the rear of the
display) forms the backplane or common connection. As its name implies,
·it is electrically common to all segments in the display. The external
connection for that electrode is
brought to the front of the display to
be level with the connection points
for the front pattern electrodes.
Voo
Vss
Voo
LCD SEGMENT Vss
RESULTANT LCD
DRIVE WAVEFORM
SEGMENT Off
SEGMENT ON
SEGMENT OFF
Fig.3: these LCD drive waveforms show how the circuit works. The bottom
waveform is derived by subtracting the backplane signal from the segment
drive waveform.
be rotated by the crystal through 90°
so that it can then pass through the
second filter.
However, if we energise the crystals in a certain area, they will not
rotate any light that passes through
the first filter. This light will then
"slam" into the second filter, which
won't allow it to pass. Thus, if you try
to look through the three layers (the
first filter, the liquid crystal, and the
second filter), the energised region
will appear dark.
And that's basically how LCDs
work; each segment-forming digit is
an energised region. A reflective coating is placed behind the second filter
so that no light has to be generated
behind the display to make the dark
area apparent. This coating reflects
any light making it through the assembly back towards the viewer again.
How LCDs are built
Fig.1 illustrates a single cell from
the most common type of LCD called
a Twisted Nematic Liquid-Crystal Display or TNLCD.
Ambient light of the correct orientation passes through the front polariser and the front glass. It then passes
through a transparent pattern of information electrodes. Each electrode is
Note the passivation layer next to
both electrodes. It acts to prevent current from flowing through the liquidcrystal layer, which would limit its
life.
The light waves continue their journey, penetrating the liquid-crystal
layer and the second passivation layer.
Finally, they pass through the alignment coating. That coating ensures
that the crystals will line up properly
when energised.
The light continues to pass through
the component parts of the rear glass
sub-assembly, which are essentially
the same as the front half of the display. Light that has not been rotated
because it passed through energised
regions of the liquid crystal doesn't
make it though the rear polariser. The
rest of the light passes to the reflector
at the back, which is often a coating of
highly luminescent material or may
be provided with some kind of backlighting. The polymeric seal prevents
the crystalline compound from leaking out In multi-cell displays, it also
separates the liquid in each cell.
LCD drive considerations
Many readers have undoubtedly
built devices that use LED displays.
When LEDs are included as part of an
overall design, the prime consideration is DC power consumption. If the
regulator can handle the load, your
problems are over.
That is definitely not the case with
LCDs. In fact, any DC voltages over
25mV will quickly lead to a chemical
melt-down. To make matters worse,
you may not be immediately aware
that something is wrong until a critical measurement fails to materialise
on the display. To keep from taxing
the display, an LCD should be driven
by an oscillator producing a clean
square-wave with a 50% duty cycle.
Fig.2 shows a widely accepted
method that's used to drive LCDs. The
basic idea is to apply a square-wave
(with a frequency between 32Hz and
60Hz) to both the pattern electrodes
and the backplane of an LCD. When
the pulse train delivered to a pattern
electrode is the same as the signal
received by the common electrode (ie,
the control input of the XOR gate is
low), they have the same potential
Thus, the segment controlled by the
pattern electrode does not appear.
However, if you make the gate's
control input high, it inverts the oscillator's output. Thus, the pattern
electrode is at some potential relative
to the backplane, the crystals align,
and the relevant segment darkens. The
signal action for that is shown in Fig.3.
LCDs are typically operated at 3-5V
RMS.
There are many specialised ICs designed to drive LCDs. Two such CMOS
chips are the CD4543 BCD-to-7-segment latch/ decoder/ driver and its high
speed equivalent, the 74HC4543.
Finally, although TNLCDs are mass
produced in huge quantities and can
be purchased at rock-bottom prices,
they are by no means the only display
type that uses liquid-crystal material.
Stricter requirements, such as for colour-reproduction and faster response
time, have contributed to the expansion of the LCD family. Better contrast
ratios combined with wider viewing
angles have made necessary other LCD
formats ·besides the twisted nematic.
Some of those other types are ThinFilm Transistor (TFTLCD), Metal-Insulator-Metal (MIMLCD), Dynamic
Scattering, and Smectic LCDs.
Reprinted with permission from Popular Electronics Magazine, June 1992
issue. Copyright© Gernsback Publications, Inc, 1992.
sc
NOVEMBER
1992
7
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.
Reversing light chaser
for 12V lamps
This low-cost reversing light chaser
can drive either 12V or 24V automotive lamps and has six outputs.
ICl is wired as an astable oscillator
which runs at about 10Hz. This clocks
ICZ which is a divide-by-10 counter.
Its Q0 and Q5 outputs drive Darlington
transistors Q1-Q6 via 3.3kn current
limiting resistors, while the remaining outputs drive their corresponding
transistor output stages via diode OR
gates (D1-D8).
Because of the diode OR gates, the
counter first turns on transistors Q1Q6 in sequence to light the lamps (1116), then reverses the sequence so
that the lights appear to run backwards. The sequence then reverses
direction again and so the process
is repeated indefinitely while ever
power is applied.
The optional light dependent resistor (LDRl) sets the chase rate according to the ambient light level. The
higher the light level, the greater the
oscillator frequency and the higher
the chase rate. Replace the LDR with
1k
16
IC1
555
14
IC2
4017
6
07!"----HN--lf--l
9
08!"--f-N-1----.....J
09
AS
15 13 8
.,.
a link if you don't want this option.
Note that small heatsinks should
be fitted to the Darlington transistors
8
SILICON CHIP
(Q1-Q6) for lamps rated above 20W.
M. Schmidt,
Edgewater, WA. ($15)
-
A low cost
crystal checker
Ever needed to check a crystal to
.ensure that it is operating correctly.
Although this circuit won't indicate the frequency of a test crystal,
it will at least show that it is capable of oscillation.
Transistor Ql is configured as a
Pierce oscillator and provides the
test bed for the crystal. If the crystal is OK, an RF voltage appears at
the emitter of Ql. This is then rectified by voltage doubler Dl & DZ
and the resulting voltage across the
.00lµF capacitor then turns on QZ
which lights LED 1.
However, if the crystal is defective , there will be no RF signal at
Ql 's emitter and so both QZ and
1
TEST
S1
CRYSTAL
UNDER
TEST
,.
+
9V :
..L.
.01
the LED will remain off.
The prototype was built on a
small piece of matrix board and
shielded inside a box made ofblank
PC board material. Two leads with
alligator clips are used to connect
the test crystal. The unit is powered from a 9V battery.
P. Parker VK6BWI,
Bentley, WA. ($15)
2-chip electronic
blackjack game
This simple electronic game uses
just two low-cost ICs plus a 7-segment LED display, and can be used
to play electronic blackjack.
IC1 is a CMOS 7555 timer and is
connected in astable mode to provide clock pulses to counter/decoder IC2.
When S1 is pressed, pin 4 (reset)
of IC1 is pulled high. IC1 is now
enabled and its pin 3 output provides 30Hz clock pulses to counter
stage IC2. After about five seconds,
the 47µF capacitor is charged to
2/3Vcc and pin 4 goes low again,
disabling IC1 and stopping the
.----.--------...------r--..--------11-•9V
16
DEALI
S1
27k
IC2
4026
100k
6 b
13
4
2
15
.,.
count. The 7-segment display then
shows a number between O and 9.
IC2 is a 4026 CMOS decade counter/7-segment decoder IC. This is
used for counting and driving the
7-segment display. When IC1 stops,
16
a/
/c
.,.
6
.,.
10 g
2
.,.
the number displayed is the card
drawn. A zero represents a 10, Jack,
Queen or King and a 1 represents
an Ace (1 or 11).
G. Taylor,
Werribee, Vic. ($15)
16
01
BC549
Q10 14
IC1
4020
011
15
10
IC2
4020
011
RESET
11
a
C
9 t
.,.
10 CK
a
1/ g /b
d 18
d
7
Timer safeguards
rechargeable cells
The effective life of rechargeable
nicad cells can be severely shortened
by over-charging. Many users save
their cells from the dire effects of too
high a charging rate by using a welldesigned charger, only to fall into the
trap of leaving them on charge for too
long.
This problem can be solved by adding this simple timer circuit to the
charger. It provides both 6-hour and
15-hour charging periods before automatically switching the charger off.
When S1 is pressed, the commercial charger provides 8V AC for the
timer, where it is rectified and filtered
to provide a +12V supply rail. At this
stage, the outputs from IC2 are all low
and the outputs of IC3a & IC3b are
high. Thus, Q1 and RLY1 turn on so
that power is maintained when the S1
button is released.
The timer is inactive for the first
100ms until the .033µF capacitor on
pins 8 & 9 of IC3c charges and pin 10
switches low and releases the counter
resets. IC1 is now clocked by a halfwave rectified signal which is derived
from ,the 8V secondary of the transformer, a 1ookn resistor and D2. This
provides 50 pulses per second and so
the Q11 output of IC1 goes high once
every 2048/50 = 41 seconds.
Q11 ofIC1 in turn clocks IC2 and so
Q10 (pin 12) ofIC2 goes high after 41
x 512 sees= 5.8 hours. This switches
pin 3 ofIC3a low and so Q1 and RLY 1
7- - - -
11
IC1
7555
.,.
10 7x33011
12
RESET
11
6
15
D3
1N4004
S2
6
0912
8
10
IRLY1
D2
1N914
.~::---:....
240VAC
D1
1N914
100k
10k
+12V
--:- - - - -
....
I
I
I
N--------~
av
ov
I
turn off to end the charging period
(assuming that the 6HR setting is selected by S2). This setting is the one
to use for AAA cells which require
only six hours of charging.
Alternatively, if the 15HR setting is
selected, pin 4 of IC3b goes low and
turns offQ1 and RLY1 after 41 x (1024
+ 256) sees= 14.5 hours.
In my case, there was insufficient
room for the relay within the charger,
so I mounted it on one end of the
charger's plastic case. The other components were mounted on a small
perf-card which slotted into a vacant
internal space. The charger has LEDs
to indicate which cells are charging,
otherwise it would be advisable to fit
an on/ off indicator.
One last word - beware of the mains
and keep mains wiring as far as possible from the low voltage circuitry. I
put a small mound of silicone sealant
over the relay contact wiring tabs and
a piece of insulation card in another
possible danger spot. Both the start
button (S1) and the relay contacts
should be rated at 240VAC and 1A.
G. Wormald,
Florey, ACT. ($20)
NOVEMBER
1992
9
DIC
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Mains powered projects.
NICAD BATTERY DISCHARGER Q
Get the best performance from your NiCads with this stylish battery discharger. With switchable
voltage (3.6, 4.8, 7.2, 9.6, 10.8 & 12V) and automatic cut-off. This easy to build kit is ideal for
most types of NiCads as used in cam-corders, cordless phones, radio controlled cars, cordless
drills and laptop computers, etc. The unit continuously monitors voltage and automatically cutsoff the discharge current once the battery as a whole is fully discharged . As well, there's a
switchable current discharge of 50mA and 200mA and a push to start button . This full form kit
has all components, hardware, case and a pre-punched (black anodised) screened front panel.
Cat K-3126
NEW
0
ETO[[DN=
~ ~..
LOW COST AUDIO SWEEPER
];Hll':~~,
~
:~~~;-:, , ~
a
~,,,.- ~
I~
MIN
MAX
ORIL c SPEoD coarRDLLER
Q
· New Improved Design
UNIVERSAL MOTOR SPEED
CONTROLLER Q 11]
This easy to build kit is designed to regulate
t he speed on heavy-duty power tools. It's
ideal for circular saws, electric drills, lawn
edgers, jig-saws, sanders, grinders and
other equipment rated at 5 amps, with a
'b rush type' motor. What's more, this
improved design has a higher current rating
and uses a Triac rectifier instead of a SCR.
As well, it monitors t he 'back-EMF' voltage
from the motor, so though the drill speed is
contro lled, it won't bog down when the
going gets tough . Complete with delu xe prepunched black anodised screened front
panel, components, PCB and flush mounted
mains socket.
Cat K-3085
$4695
Here's a useful kit for audiophiles, sound experts,
enthusiasts and anyone interested in sound. This
affordable audio test system analyses the
performance (mid, treble & bass) of speakers,
speaker enclosures, filter circuits and room
acoustics. It consists of a sweeping audio test
signal generator and a metering amplifier which
measures the results. It comes complete with a
deluxe pre-punched front panel, plastic
instrument case, PCB, hardware (including dB
meter), components, mic insert and plug pack.
s1 09
Cat K-7352
QQ
<at>AUG'92
Coming Soon To A
Store Near You!
VHF/UHF SPECTRUM QQ [zJ
ANALYSER
Here's a simple yet inexpensive instrument with
all the circuitry and controls you need to convert
almost any standard oscilloscope or 'CRO' into a
sensitive and easy to use spectrum analyser. It
covers the three major segments of the VHF / UHF
spectrum : 50-105MHz, 138-225MHz and 470B?0MHz. What's more you can even use it as a
wideband FM monitoring receiver. A full form kit
complete with deluxe case, pre-punched
screened front panel, all components and
hardware is supplied.
~
Cat K-7620
~ SEP '92
$
7
1
rP1e~se contact your nearesttiio~~-,o~availability as some kits may still be in
production.
I
99
EASY TO BUILD FM RADIO QQ l1J .
1
If you 're new to the world of kit building, then this one's
for you! This simple FM radio receives all your favourite
FM stations, uses only two low-cost integrated circuits
(IC's) and runs off a 9V battery. In fact, you could even
experiment and design your own tuner/ amplifier. It's easy
to g\J,ild and is a great hands-on way to learn about radio
.. frequency (RF) circuits and audio frequency (AF)
amplifiers. This short form kit comes with FM radio IC &
audio IC, PCB , speaker, components and hardware bits.
Cat K-5014
s299s
B1387
N O V EMBER
1992
13
I•
DIC
TEST EQUIPMENT
3.5 DIGIT
MULTIMETER
QUALITY 3.5 DIGIT
MULTIMETER
Here's an affordable 14 range digital
multimeter for the hobbyist or student. It
has a handy battery checker for 1.5 & 9
volt cells, as well as diode test. Comes
complete in a safety yellow casing.
Ranges:
2V, 20V, 200V, 500V
DCV:
ACV:
200, 500V
DC(mA):
200mA
Resistance: 2K, 20K, 200K, 2M
Cat Q-1420
Incredibly compact and easy to use! This
accurate 19 range multimeter measures
DC/ AC voltages, DC current and
resistance. It has a diode test, 10Amp
(DC) current range and a low frequency
output range. With safety yellow casing.
Ranges:
DCV:
0.2V, 2V, 20V, 200V, 1000V
ACV:
200, 750V
DC Current: 200uA, 2000uA, 20mA, 200mA
Resistance: 200, 2K, 20K, 200K, 2M
Cat Q-1422
995
1.25GHz HANDHELD
DIGITAL FREQUENCY
COUNTER
LCD DIGITAL CALLIPERS
This incredibly easy io use 10Hz to 1.25GHz
frequency counter has an 8-digit LCD display,
data hold, relative measurement and data
record (min, max & average). There's also
selectable resolution, period meas.urement
and more. Complete with telescopic antenna
and BNC to alligator clip test leads.
Cat Q-1322
Ideal for engineers, designers, students and the serious hobbyist.
These callipers give an extremely precise measurement of the external
and internal diameter of just about anything from 0.01mm to 150mm.
With metric/inch conversion, zero setting for measuring deviations,
accuracy of 0.03mm and repeatability of 0.01 mm. As well, it has an
automatic 'off' function and more! Complete with carry case.
Cat Q-1412
Specifications
Measuring
Range
lmpedence
Accuracy
Range
Max Voltage
Channel A: 5V P-P
Channel B: 250V P-P
MAJOR DICK SMITH ELECTRONICS AUTHORISED STOCKISTS:
NSW: ARMIDALE: New England Electronics 711655 BALLINA: Ballina Electronics 867022 BATEMAN'S
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Supplies 611861 BROKEN HILL: Hobbies & Electronics 884098 COOTAMUNIJRA: Cootamundra Music &
Ute 422561 COFFS HARBOUR: Coifs Harbour Electronics 525684 DENILIOIJIN: Deni Electronics 813672
DUBBO: Chris's Hi Fi 828711 FORSTER: Forster Village Electronics 545006 GOULBOURN: Tunlive 221288
GRAFTON: Repairs &Spares 421911 GRIFFITH : Miatronics 624534 INVERELL: lnverell Electronics 221821
KEMPSEY: P&L Leonard 631134 LEETON: Leeton Audiotronic 532800 LIGHTNING RIDGE: Lightning Ridge
Solar Power 29 1013 LITHGOW: Douroy Photographies 513173 LISMORE: Deere Electronic Services
214137 MOREE: Moree Electronics 522091 MUDGEE: Headware 723895 MURWILLUMBAH: Strings &
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813685 NOWRA: Nowra Electronics 210722 PARKES: Strad MusicCtr623366PORT MACQUARIE: Hastings
Computer Service 840255 RICHMOND: Silicon Crafts 784101 TAREE: Manning Electronics 512233
ULLADULLA: Coastal Electronics553989 WAGGA WAGGA: Phillips Electronics 216558 WALGm: Wal!jt!tl
Electronic Centre 281116 WELLINGTON: Wellington Service 452325 WINDSOR: Hawkesbury Electronics
776722 VASS: Warmington Electrical 261116 YOUNG: Keith Donges Electronics 821279 VIC: ARARAT:
Jerram Electronics 522345 BAIRNSDALE: LH & LM Crawford 525677 BENALLA: North East Electronics
622710 CASTLEMAINE: Inspect Electrics 723773 CDLAC: Colac Electronics 312847 ECHUCA: Gilmour
Electronics 822956 MILDURA: Pullman Auto Pro 232882 MORWELL: Roylaine Ply Ltd 339458
SHEPPARTON: Andrew Guyatt Electronics 219497 SWAN HILL: Nyah District TV Service 329303 ST.
ARNAUD St Arnaud Appliances 951069 WARRAGUL: Roylaine 234255 WARRNAMBOOL: Komit St Elec
Services 627417 WONTHAGGI: South Gippsland Photo Service 721411 OU): AYR: Delta Electrix 831566
BLACKWATER: Cool Tronics 825827 BOWEN: Delpro Agencies 86 ~77 BLNDABERG: Bob Elkin
Electronics 521785 CALOUNDRA: Electr(rfTlart 918533 DALBY: Hobby & Electronics 625770 DYSART:
Dysart Videotronixs 582107 GLADSTONE: Electronic Enterprises 726660 INGHAM: Masons Electronics
763188 INNISFAIL: lnnisfail Hi-fi 612014 KINGAROY: MD & MM Siegle 624535 LONGREACH: Longreach
Sound & Communications 583307 MACKAY: Stevens Electronics 511723 MARYBOROUGH: Keller
Electronics 214559 MT ISA: Outback Electronics 433331 NAMBOUR: Nambour Electronics 411966
PIALBA: Keller Electronics 283749 STANTHORPE Granite Belt Communications 813333 TAS: BLRNIE:
Electronic City 314760 DEVONPORT: Al Electronics 248322 SA: MT GAMBIER: Hutchesson's
0
~=
~f54n:1,
~ioLW~~:i:~1h!o"~~ut~t~~~Jrio~~~~~~A~~2~YGJi:bfriFi
Batavia Lighting & Electrical 211278 KALGOORLIE: Today's Electronics 215212 KARRATHA: Pllbara Office
Supplies 854836 MANDURAH: Mandurah Hi Fi 5812206 PORT HEDLAND: Ivan Tomek Electronics
732531
B1387
14
SILICON CHIP
$199
10Hz to 1.25 GHz
1M OHM
+/- (1PPm +1d)
Channel A: 500MHz/1250MHz
Channel B: 10MHz (10Hz to 10MHz)
Typical Sensitivity
Channel A: 10-1000 MHz (3-50mV RMS)
= 1-1.25GHz r10 -150mV RMS)
Channel B: 10Hz-1MHz (15mV RMS)
1MHz-5MHz (20mV)
5MHz-10MHz (40mV)
Dual trace,
dual trigger
20 MHzCRO
An affordable 20MHz
oscilloscope suitable for
a wide range of applications .
It's a dual trace, dual trigger
CAO with a fully adjustable
sweep time (in 20 steps), variable hold-off, fully adjustable sensitivity,
switch selectable X-Y operation, selectable trigger modes, AC/TV H/TV V
trigger coupling, front-panel variable trace rotation and a sweep rate from
10nS/DIV to 1S/DIV.
Specifications
Vertical Sensitivity:
5 mV/ div to 5 V/div (x1 mode)
1 mV/div to 1 V/div (x5 mode)
1-2-5 sequence, 10 step attenuator.
Sweep Speed:
0.1 uS/Div to 0.2 S/Div in 1-2-5
sequence, 20 steps
Sweep Magnification:
Rise Time:
l~~roximately 17.5ns
Operating Modes:
Ch 1, Ch2, Alt, Chop, Add
Trigger Coupling:
AC, TV-H, TV-V
Trigger Sensitivity Internal:
0.5 division (1 division with TV coupling)
External:
500mV
Trigger Source:
Ch1, Ch2, Alt, Ext, line.
Cat 0-1802
$699
SHORTWAVE
This Month's Top Value
EXCELLENCE POWER SUPPLIES
frof11
SANC:i&AN
& ACCESSORIES
MULTI VOLTAGE CONVERTER
Here's a smart alternative to batteries.
This converter is ideal for battery
operated toys, mini-TV's ... even
shortwave radios. With six voltage
selections (3, 4.5, 6, 7.5, 9, 12V DC<at>
500mA), a multi-way ouput adaptor and
selectable polarity.
The Go-Anywhere
Receiver
10 BAND
PORTABLE
SHORTWAVE
RECEIVER
s259s
Cat M-9627
Ideal for trucks!
s799s
24/ 12V VOLTAGE
CONVERTER
The Sangean SG-789 is an incredibly compact receiver with the power
to pull in broadcasts from around the world! Listen to local AM and FM
stations (FM stereo with optional headphones) as well as 8 popular
international shortwave bands. With bandspread tuning and an LED
tuning indicator. finding the station you want quickly and accurately is
easy. The SG-789 combines all this with excellent sound reproduction,
a solidly built chassis, headphone and AC adaptor sockets and a soft
carry case.
Save $10 on this handy converter. It's
ideal for CB's and stereo systems, etc in
trucks and vehicles with a 24 volt
system. Provides 13.BV<at> 2 amps DC
continuously (BA surge rating) from a 24
volt supply. Complete with mounting
hardware.
Cat M-9810
Now Only
s5995
Cat D-2834
12-240V INVERTER
With
Cassette
Player!
Save a massive $100 on this quality
inverter! It produces 240 volts from a
12V supply and is ideal for caravans,
boats, mobile workshops and even as
part of a solar power system . Quality
features include a low battery
indicator, overload indicator and
protection, power indicator, electronic/
temperature shutdown , low/high
battery shutdown, 2 mains sockets and
circuit breaker.
ALL-BAND
WORLD
RECEIVER
DC Input Voltage: 10.5 -14.5 (12V nominal)
AC Output Voltage: 240V RMS
Output Frequency: 50Hz (+/-1%)
Output Power: 1500W (surge), 600W (20
minutes), 325W continuous
Take your ears overseas with the stunning Sangean ATS-818CS. This
fantastic receiver covers Longwave and continuous shortwave
frequencies from 1.62 to 30MHz and local AM/FM stations (FM stereo
with optional headphones). What's more, with a BFO (beat frequency
oscillator) it receives many HF SSB transmissions including marine,
aircraft, amateur and commercial broadcasts. An inbuilt tape deck
with timer allows you to record broadcasts, even when you're asleep.
As well, it has five-way tuning, 45 station memories, full function digital
display, dual time and alarm clock. With a dual conversion receiver
design it otters switchable filters and an adjustable RF gain control for
optimum reception. It's brilliant!
Cat D-2842
Also Available: ATS 818 (no cassette recorder)
Cat 0 -2828
s349
0
~~~i;J_~~0~
a::w
Only $
3 99
A Great Gift Idea
CORD WINDER
Cord Winder is neat, tidy and incredibly
useful! It has a 11.5m cable with two power
outlets and includes an inbuilt 10A circuit
breaker.
Cat M-7092
s249s
DS XPRESS PHONE & MAIL ORDER SERVICE HOTLINE
Outside Sydney (Free call) 008 22 6610 Sydney & Enquiries (02) 888 2105
Or write to DS XPRESS, PO BOX 321 N/RYDE 2113
FAX (02) 8051986
STORE LOCATIONS:
NSW • Albury _21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Brookvale 905 0441 • Bondi 3871444 • Campbelltown 27 2199 • Chatswood Chase 4111955 • Chullora
842 8922• Gore Hill 439 5311 • Gosford 25 0235 • Hornsby477 6633• Hurstville580 8622• Kotara56 2092• Liverpool600 9886• Maitland 33 7866• Miranda525 2722• Newcastle611896
• North Ryde 878 3855 • Orange 618 400 • Parramatta 689 2188 • Penrith 32 3400 • Railway Square 211 3777 • Sydney City 267 9111 • Tamworth 661711 • Wollongong 28 3800 ACT
• Belconnen(06) 2531785• Fyshwick 280 4944 VIC• Ballarat31 5433• Bendigo43 0388• Box Hill 8900699• Coburg383 4455• Dandenong 794 9377• East Brighton 592 2388 • Essendon
379 7444 • Footscray 889 2055 • Frankston 783 9144 • Geelong 232 711 • Melbourne City 399 Elizabeth St 326 6088 & 246 Bourke St 639 0396 • Richmond 4261614 • Ringwood 879 5338
• Springvale 547 0522 QLD • Booval 262 6200 • Brisbane City 229 9377 • Buranda 391 6233 • Cairns 311 515 • Capalaba 245 2670 • Chermside 359 6255 • Rockhampton 27 9644
• Sou1hport 32 9033 • Toowoomba 38 4300 • Townsville 72 5722 • Underwood 341 0844 •SA• Adelaide City 2321200 • Beverley 3471900 • Elizabeth 255 6099 • Enfield 260 6088 • St.
Marys 277 8977 WA• Cannington 451 8666 • Fremantle 335 9733 • Perth City 481 3261 • Midland 250 1460 • Northbridge 328 6944 TAS • Hobart 31 0800 • Launceston 344 555 NT• Stuart
Park 811977
STORES ACROSS AUSTRALIA AND NEW ZEALAND
81387 .
NOVEMBER
1992
15
Tune your favourite stations
with this low-cost
_IQ RECEIVER
FM
If you're new to the world of electronics, then
here's a great project to get you started. This
simple radio tunes in all your favourite FM
stations, uses only two low-cost ICs & runs off a
9V battery.
By DARREN YATES
Many moons ago, if you were about
to get stuck into your first electronics
project, the odds were that you'd start
with an AM radio.
There were several reasons for this.
First, AM radios in the 50s and 60s
were relatively expensive and you
could save lots of money by building
one for yourself. Often, the parts could
be scrounged from the junkbox and
from derelict receivers and this added
to the sense of achievement when the
project was completed.
Building an AM radio was also a lot
of fun and it was educational. The
constructor could learn all about radio frequency (RF) circuits and audio
amplifiers, and could carry out any
r.f. input
18
17
15
,.
13
12
11
10
1,4V
TDA7000
2,2k0
Vp
1+4,SVI
• 7286939 . 1
a.f. output
16
2,2k0
SILICON CHIP
repairs if the set later required servicing.
During the last 20 years, AM radios
have become progressively easier to
build with the development of-specialised ICs. One such chip is the
ZN414 AM radio IC. This device is a
complete tuned radio frequency (TRF)
receiver in a tiny 3-pin transistor style
case and it only requires a 1.5V cell to
power it. It gives quite useful results
and many a "matchbox radio" has
been built using this device.
By contrast, FM receivers were always somewhat more complicated to
build, although that situation has also
changed during the last decade. In
particular, the Philips TDA7000 FM
radio IC is virtually a complete FM
radio on a single chip. All that's required is the addition of an audio
amplifier stage and a few external
components to produce a working FM
receiver.
Apart from the TDA7000 FM radio
chip, the design presented here uses
just one other IC to give an economical 2-chip design. This second device
is an LM386 audio amplifier IC. So
most of the circuit functions are taken
care of by the two ICs.
But why build your own when you
can buy a personal FM stereo radio
for less than $20? The answer is to
have fun and to learn about electronics. Provided you can solder and follow a simple wiring diagram, you
Fig.1 (left): block diagram of the
Philips TDA7000 FM radio circuit.
This device is virtually a complete FM
tuner on a single chip. All that's
required to make a working receiver
are a few external parts plus an audio
amplifier stage.
PARTS LIST
1 PC board, code SC06111921,
129 x 85mm
2 SPOT toggle switches (S1, S2}
1 100k.Q log potentiometer (VR1}
1 knob to suit potentiometer
1 57mm 8.Q loudspeaker
1 F29 ferrite slug
1 5mm coil former (Altronics Cat.
L-5210; Jaycar Cat. LF1224;
DSE Cat. L 1010)
4 3 x 25mm-long tapped spacers
4 screw-on rubber feet
1 9V battery
1 battery snap connector
1 60-160pF tuning capacitor
Semiconductors
1 TDA7000 FM receiver (IC1}
1 LM386 audio amplifier (IC2}
All the parts for the FM Receiver are mounted on a small PC board & this can
be installed in a plastic project case. The antenna consists of a 75cm length of
light-duty hook-up wire.
should have little difficulty building
up the design presented here.
Admittedly, our design is mono only
but then most of the low-cost commercial units can only drive headphones. This unit can drive a small
loudspeaker to quite useful volume
levels and it can produce good quality sound from all local FM stations
from 88-108MHz. Why not tackle it as
your first project?
Block diagram
FM signals are more difficult to decode than AM signals because of the
way the information is transmitted.
In AM radio, the audio signal is encoded by modulating the amplitude
of a fixed-frequency carrier signal.
After transmission, this audio signal
can be quite easily recovered from the
tuned carrier using a simple diode
detector.
With FM, however, the carrier amplitude is kept constant and it is the
frequency of the carrier that is varie.d
to encode the audio frequency signal.
The method of detection (or demodulation) in this case is much more
complicated but, fortunately, this
function is taken care of by the TDA7000 IC.
Fig.1 shows the various circuit
blocks inside the TDA7000, as well as
the external parts required to make a
complete FM tuner. It is easy to get
going since only the local oscillator
(VCO) requires adjustment during
alignment. All the other components,
with the exception of the tuning capacitor (Cvl, are fixed .
The TDA7000 IC functions pretty
Capacitors
1 470µF 16VW electrolytic
1 220µF 16VW electrolytic
1 100µF 16VW electrolytic
2 10µF 16VW electrolytic
1 0.15µF MKT polyester
1 0.1 µF MKT polyester
2 0.1 µF ceramic
1 .01 µF MKT polyester
2 .0033µF MKT polyester
1 .0027µF MKT polyester
1 .0022µF MKT polyester
2 330pF ceramic
1 220pF ceramic
1 180pF ceramic
1 150pF ceramic
1 56pF ceramic
1 47pF ceramic
1 39pF ceramic
1 33pF ceramic
Resistors (0.25W, 1%}
1 18k.Q
1 10k.Q
1 4.7.Q
Miscellaneous
30cm of 0.63mm diameter ECW,
75cm of light-duty hook-up wire
for antenna.
much as a conventional superheterodyne tuner. This means that the incoming signal is mixed with a local·
oscillator signal to produce an intermediate frequency (IF). This IF is then
filtered to remove any mixer artefacts
and, finally, demodulated to produce
the desired audio signal.
There's just one deviation from norN ovEMBER 1992
17
ONO
ANTENNA
MUTE
S2
POWER
S1
4.70
OFF
.01
10k
220 +
.0033
0.15
220pF
4
0.1
330pF
18
17
16VW+
150pF
15
OFF
ON
<>-'---0+6-9V
12
10
13
*
39pF
*
47pF
14
10
16VW
+ -
180pF B
IC1
TOA 7000
5
8
.,.
VC1
2-&0pF
.,.
33pF
L1
.,.
56pF
100 +
16VW+
0.1
+
.,.
16
FM RADIO
Fig.2: the circuit uses just two ICs - the TDA7000 FM radio chip & an LM386
audio amplifier. Variable capacitor VC1 tunes IC1 across the FM broadcast band
(88-108MHz), while L2 & its associated capacitors form a bandpass filter at the
antenna input to eliminate interference from signals outside the tuning range.
mal practice. The majority of FM receivers use an IF of 10. 7MHz whereas
the TDA7000 uses a very low IF of
70kHz.
The advantage of such a low IF is
that it can be filtered with standard
active op amp circuits instead of coils
or ceramic filters. Normally though, a
low IF results in really bad distortion
when used with wideband deviation
FM; eg, the normal broadcast band
FM which has a maximum deviation
of ±75kHz.
However, the TDA7000 successfully
manages to demodulate wideband
deviation (±75kHz) FM while only
having a 70kHz IF. What happens is
that the recovered audio is used to
modulate the local oscillator so that
the received FM deviation is always
less than ±15kHz. In effect, the recovered audio signal is compressed to
internal mixer (on pins 13 & 14) via a
bandpass filter. This bandpass filter
consists of inductor L2 and the 39pF
& 47pF NPO capacitors. Its job is to
filter signals that lie outside the desired tuning range and thus eliminate
interference.
Tuning capacitor VCl and inductor
Ll ensure that the voltage controlled
oscillator (VCO) tunes across the FM
broadcast band. Inductor Ll carries a
ferrite slug and this is adjusted during the alignment procedure so that
VCl covers the desired frequency
range (88-108MHz).
Pin 1 of !Cl is the mute control
line. Pulling this line high via a 10kQ
resistor disables the muting functions
and allows weaker stations to be tuned
if desired. Switch S2 is used to switch
the muting function in or out of action. When S2 is set to ON, the circuit
mutes the background hiss that otherwise occurs when tuning between stations.
The recovered audio signal appears
reduce its dynamic range. Although
this isn't desirable in a hifi FM receiver, the results are still very good
and this technique considerably simplifies the circuitry required.
In fact , the distortion is typically
less than 2.3% at ±75kHz deviatio:n,
so your favourite FM station will still
come in loud and clear.
Circuit diagram
Now take a look at Fig.2. This shows
the complete circuit diagram for our
simple FM radio receiver.
At the centre of the circuit is the
TDA7000 FM radio IC (ICl) and this
drives the LM386 audio amplifier (IC2)
via volume control VRl. Let's take a
quick run through the various circuit
functions.
The RF signal is picked up by the
antenna and fed to the TDA7000 's
TABLE 1: RESISTOR COLOUR CODES
u
Q
0
0
18
,:•:}
470
18k
No.
1
1
SILICON CHTI'
Value
18kQ
10kQ
4.7Q
4-Band Code (1%)
5-Band Code (1%)
brown grey orange brown
brown grey black red brown
brown black black red brown
yellow violet black si lver brown
brown black orange brown
yellow violet gold brown
8
This close-up view clearly shows the construction of coil Lt. The F29
ferrite slug at the top of the former is adjusted during the alignment
procedure so that the receiver tunes the required frequency range.
on pin 2 and is fed to volume control
VR1 via a low-pass filter consisting of
an 18kQ resistor and a .0039µF capacitor. This filter stage, in conjunction with VRt , provides the necessary 50µs de-emphasis for the recovered audio signal. From there, the signal passes to the LM386 audio amplifier stage (IC2).
IC2 operates with ap. AC gain of 200
by virtue of the 10µF feedback capacitor connected between pins 8 and 1.
The amplified output appears on pin
5 and is coupled to a miniature 8Q ·
loudspeaker via a 4 70µF capacitor.
Power for the circuit is derived from
a 9V battery and is switched on and
off using Sl. The supply rail is de~
TABLE 2: CAPACITOR CODES
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Value
0.15µF
0.1µF
.01µF
.0033µF
.0027µF
.0022µF
330pF
220pF
180pF
150pF
56pF
47pF
39pF
33pF
IEC Code
150n
100n
10n
3n3
2n7
2n2
330p
220p
180p
150p
56p
47p
39p
33p
EIA Code
154
104
103
332
272
222
331
221
181
151
56
47
39
33
coupled using a 220µF capacitor and a 4. 7Q resistor.
Construction
*MOUNTED ON COPPER SIDE
Fig.3: install the parts on the PC board as
shown in this wiring diagram. The wiring
shown dotted is installed on the copper
side of the board.
All of the components for
the FM Radio, including the
battery and loudspeaker, are
fitted to a small PC board coded
SC06111921.
Before starting construction, check
the board carefully to ensure that it
has been correctly etched. Correct any
faults that you do find immediately
(in most cases, there will be none).
Now check that the mounting holes
for coil former Ll, potentiometer VRl,
tuning capacitor VC1 and the two
switches (Sl & S2) are large enough to
accept these parts. Enlarge the holes
if necessary using a small drill.
Fig.3 shows the parts layout on the
PC board. Install the wire link first,
then solder the resistors into place.
Table 1 shows the colour codes for the
resistors but you should double-check
them with your digital multimeter.
When you've completed that job,
solder in the ceramic and MKT polyester capacitors. Table 2 shows the
capacitor codes and their equivalent
values. Check the value of each capacitor carefully before installing it
on the board. If you get them mixed
up, the tuned circuits in the front end
of the receiver could be thrown off
frequency and the project wont work.
Note particularly that one of the
0. lµF ceramic capacitors is installed
on the copper side of the board, directly beneath ICl. Keep all capacitor
leads as short as possible.
At this stage, the two ICs can be
installed. These should be soldered
directly to the PC board. Take care
with the polarity of each device and
make sure that you don't overheat
them when soldering their pins. Pin 1
of each device is adjacent to a small
notch or dot in one end of the plastic
body.
Tuning capacitor VC1 is installed
from the component side of the board,
L2
L1
Fig.4: coil Lt consists of 2½
turns of 0.63mm enamelled
copper wire on a 5mm former,
while L2 is made by winding 6
turns of 0.63mm enamelled
copper wire on a 6mm drill bit.
NovEMBER
1992
19
The pen in this photograph points to the O.tµF ceramic capacitor that's mounted
directly beneath ICt on the copper side of the PC board. Note also the wire link
that's used to connect VR1 's metal case to ground.
coil off the drill bit and push it all the
way down onto the board before soldering its leads (don't forget to scrape
away the enamel from the leads first).
The volume control (VRl) is installed from the copper side of the PC
board. Before doing this, solder three
short tinned copper wire leads to its
pads (ie, install these leads on the
copper side of the board). The volume
control can then be mounted in position and the three wire leads soldered
to its terminals.
VRl 's metal case should now be
earthed by connecting it via a short
wire link to the adjacent groundplane
on the PC board (see photo). This is
done to prevent hum pickup from
breaking through into the audio path.
Note that it may be necessary to scrape
away some of the oxide on VRl's case
to ensure a good solder joint.
The leads shown dotted in Fig. 3 are
run on the underside of the PC board.
Use light-duty hook-up wire for the
loudspeaker and switch leads and be
sure to wire the battery snap connector so that the supply polarity is correct. The antenna lead consists of a
75cm length of light-duty hook-up
wire which is soldered directly to the
PC board.
Once the wir~ng is completed, secure the loudspeaker to the top of the
board using a suitable adhesive. The
battery can be secured using a clamp,
double-sided sticky tape, or even a
large rubber band.
Finally, fit four 25mm-long tapped
spacers to the four corner positions of
the board. These spacers are then fitted with screw-on rubber feet to prevent scratches to the resting surface.
Test & alignment
The two toggle switches (S1 & S2) are installed from the copper side of the PC
board, as is the volume control pot (VR1). The four standoffs at the corners of
the board should be fitted with rubber feet.
with its central shaft protruding
through to the copper side. Secure it
using the two small screws supplied,
then mount the two toggle switches
in position.
The next step is to wind the two
inductors. 11 is simply 2½ turns of
0.63mm-diameter enamelled copper
wire (ECW) wound on a 5mm former
with an F29 ferrite slug - see Fig.4.
Note that each end of the coil should
finish on opposite sides of the former.
Strip the enamel from the ends of
20
SILICON CHIP
the leads before soldering the coil to
the board and use a small dab of adhesive to hold the former in position.
Don't just rely on the coil to secure
the former. If the former (and thus the
ferrite slug) moves about, it will alter
the tuning. The ferrite slug should
initially be screwed about half-way
into the top of the former.
Inductor 12 is made by winding six
turns of 0.63mm diameter ECW onto
a 6mm drill bit or something similar.
Wind on the six turns, then slide the
To test the unit, wind the volume
up to about half way, set the MUTE
switch to "off", and switch on. You
should immediately hear noise from
the loudspeaker (if not, try setting the
MUTE switch to its other position).
Now flick the MUTE switch to "on";
the noise level should drop appreciably, although you should still be able
to hear some hiss if you put your ear
close to the loudspeaker.
Now try tuning in some stations. If
you're in a normal house environment and within about 40 or 50km
from some reasonably strong stations,
you should be able to pick them up.
Sweep through the entire frequency
range with the tuning capacitor and
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•
•
•
•
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HARBUCH ELECTRONICS PTY LTD
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Phone (02) 476 5854 Fax (02) 476 3231
Fig.5: check your PC board carefully against this full-size
etching pattern before installing any of the parts.
keep a record of the radio stations you hear. Make sure
you have the MUTE switch turned off.
If there are some stations that you can't pick up at one
end of the band and the tuning capacitor has run out of
travel,adjust the slug in coil 11 by winding it out of the
former a couple of turns. This should shift the stations
further tov\;ards the centre of the tuning capacitor.
If, after repeated adjustments, you still don 't have
enough range, try adjusting the two small screws on the
back of the tuning capacitor. To do this, tune in a station
and then, using an insulated screwdriver, slowly turn
one of the screws to shift the station position (note: only
one of screws will have any effect). Make only small
adjustments at any one time before re-checking the frequency range. If you move the station the wrong way,
rotate the adjustment screw in the other direction.
By the way, it's important to use an insulated screwdriver for this job. If you don't, the ?,dditional capacitance provided by your hand will detune the front end of
the receiver and it will be difficult to judge the effect of
any adjustments.
In normal use, you should find that an alkaline battery
lasts about 40 hours , depending on the setting of the
volume control (VR1). If you strike problems at any stage,
switch off immediately and check the board for wiring
errors.
SC
Protect your valuable issues
Silicon Chip
Binders
These beautifully-made binders will protect your
copies of SILICON CHIP.
*
* Each binder holds up to 14 issues
* SILICON CHIP logo printed in gold-coloured lettering
on spine & cover
Heavy board covers with 2-tone green vinyl
covering
Price: $A11.95 plus $3 p&p each (NZ $6 p&p) .
Just fill in & mail the order form on page 101; or fax
(02) 979 6503; or ring(02) 979 5644 & quote your credit
card number.
NovEMBEH
1992
21
Modifications to the
drill speed controller
The Drill Speed Controller featured in September
1992 requires a couple of modifications in order
to work reliably with all motors. These changes
are incorporated on a new PC board.
F1
10A
A-r--0-...0----4>-------------,
A2
TRIAC 1
BTA41-600
A1
GPO
240V AC
D1
1N400 4
FRONT
PANEL
r 2 0 r1
. ~,
VIEW ED FR OM
BELOW
A2
SPEED CONTROLLER
Fig.1 : the amended circuit provides a longer gate trigger
pulse to the Triac than before, to ensure reliable triggering.
Two problems have arisen with the
design of the Drill Speed Controller
featured in the September 1992 issue
of SILICON CHIP. The first is the occurrence of flash over between one of the
lugs on the 2AG fuseholder and the
earthed tab of the Triac when heavy
duty appliances are being controlled.
This has necessitated a change in the
position of the fuseholder.
The second problem is the occasional failure to operate on some universal motors when settings near maximum speed are used. In these cases, it
appears that the inductance of the
motor is such that the current through
the Triac does not rise above the holding current before the end of the gate
trigger pulse.
If the load current does not rise
above the holding current, the Triac
will not maintain conduction after
the trigger pulse ends. The solution is
to increase the duration of the gate
trigger pulse. This has meant increasing the gate trigger capacitor from
.04 7µF to O. lµF and adding a 100Q
resistor in series with the gate of the
Triac. The amended circuit is shown
in Fig, 1.
Amended PC board
~
~ ------E S8S1 - - - - - ~
II
I
~- ' G
Q
~
.
-[JL}-ill<at>-
1•
'c§=EG
I O
I
I
TRIAC1
VR2
01
A2
A1
I
I
I
~.-,~
N '\
-
Fig.2: the new circuit board
includes the additional 100Q
resistor & can accept both 2AG
& 3AG fuses. The fuse has
also been moved to prevent a
possible flashover problem.
22
S 1LICUN C IIII'
GPO
The new PC board, code SC10109922, is shown on page 100. Fig.2
shows the revised wiring diagram.
If you want to incorporate the necessary changes on an origin al PC
board, as featured in the September
1992 issue, we suggest that the 100Q
resistor be installed by first lifting the
Tl leg of the SBS. The resistor can
then be soldered between this lead
and the pad vacated by the SBS lead.
Note that this will change the position of.the lkQ gate resistor but this is
immaterial.
The fuse should be taken off the
board and an in-line fuseho lder substituted.
As noted in the original article, this
circuit is suitable for universal motors with nameplate ratings up to 5
amps. Do not use it with higher rated
motors.
SC
A unique family of full function
pocket-sized digital multimeters.
Large LCD Digits
Large digits for easy viewing. The 0.7" high
numerals allow you to easily read your
measurement values from a distance.
Safety Tester
The Safety Tester™ on
Model DMlOXL safely detects and
displays the presence of particular
AC or DC voltage (positive or
. negative) levels through a series
of LEDs. This unique feature does
not use the meter's internal battery
so you can always detect live
voltage levels if your DMM battery
is dead.
Safety Test Leads
Now you can safely make measurements
in those dense component areas without
causing shortS with long exposed test lead tips.
Insulation on the probes allows only 3 1/2 mm of metal exposure at the
tips, (insulation is removable, if desired). Plus, the test lead plugs are
shrouded with plastic to eliminate
the pos~ibility of shock.
r-- -.----- ----
Fused 1 OA Current Jack
Designed into the Models DMlOXL and DM15XL is
another innovative feature to protect you and your
meter. Fusing the lOA jack is an industry recognized
safety feature which, before now,
was only found in more
expensive DMMs. Now
a low-cost meter brings
you protection from
meter damage and
personal injury.
1
I
• ST LUCIA ELECTRONICS
·M~u: _____________
I _________ P'code: _____
I
- - - - - - - - - - - - - -- - -- - - - - - - - - - - - 1 0 Bankcard
24 Campbell St. Bowen Hills Q 4006. Tel: (07). 252 7466 Fax (07) 252 2862.
I I I I jI
ECONOMIC ELECTRONICS: 22 Campbell St. Bowen Hills Q 4006. P.O. Box 481, Fortitude Valley 4006. Tel: /07) 252 3762.
Fax /07) 252 5778. SOUTHPORT ELECTRONIC SHOP: Shop 1, 10 Welch St. Southport Q 4215. Tel: /075) 32 3632. Fax: /075) 51 0543.
ACN 010 378 588.
anywhere in Australia in an overnight
I.Post
satchel. $7.90
I Name: _______________
I
0 Visa Card
O Mastercard
I I I 11 I II 11 I II I
ISigned___ ___ _ _ Exp. Date___
I
I
A 2kW 24V/240VAC
sinewave inverter; Pt.2
This month, we present the DC to DC converter
circuitry of our 2kW sinewave inverter. This
circuit steps up from 24V DC to 365V DC & uses
Mosfets to drive a high-frequency transformer.
By JOHN CLARKE
Converting 24V DC to 365V DC at a
power level of more th an ZkW is n o
simple task. If the step-up transformer
is to be kept reasonably small an d
light in w eight, it must run at qu ite a
high frequ ency an d this presents considerable problems in making sure
that the Mosfets are switched cleanly.
Special measures are required. to ensure that interaction between the con-
trol an d switching circuitry is kept to
an absolute minimum.
Befo re we dive into the full circuit
description, let's have a look at a
basic converter circuit so that we can
get a picture of what h appens. Fig.5
shows the sch ematic of a basic converter. It uses a centre-tapped step-up
transfo rmer which is driven by two
Mosfets . The secondary winding of
the transformer is fed to a bridge rectifier and a capacitor (Cl) to develop
the DC output.
The Mosfets are driven by a pulse
width modulator which has feedback
applied from the DC output via a voltage divider consisting of Rl and RZ.
This feedback acts to reduce the width
of the pulses from the pulse width
modulator if the voltage starts to rise.
Similarly, if the voltage starts to drop ,
the width of the pulses is increased.
Push-pull drive
Note that the centre-tap of the transformer's primary winding is connected
to +24V DC, while the two legs of the
primary winding are each connected
to a Mosfet. The pulse width modula-
tor drives the gates of the Mosfets
with a complementary square w ave
signal so that when Mosfet Ql is on,
Q2 is off and when Ql is off, Q2 is on.
Now consider what happens when
Ql is on and Q2 is off. With Ql on, the
full 24V DC is applied to the top half
of the transformer primary winding;
ie, Ql 's drain is virtually at zero volts.
At the very instant that current starts
to flow in the top half of the transformer winding, transformer action
operates so that 24V appears across
the other half of the transformer primary winding. This means that when
Ql is on, the drain of QZ will have
+48V applied to it.
Similarly, when Q2 turns on and
Ql turns off, QZ 's drain will be at OV
and Ql 's drain will be at +48V. So if
you can imagine a complementary
square wave applied to the Mosfet
gates, then the primary of the transformer will have a square wave of 48V
peak-to-peak applied to it, or 24V
RMS. This is stepped up by the transformer so that the secondary voltage
will be 24V multiplied by the turns
ratio - in this case, 18:1. The secondary voltage therefore will be a square
wave of 864V peak-to-peak or 432V
RMS.
This AC waveform is rectified by
the bridge rectifier and filtered by capacitor Cl to give 432V DC. Note that,
RE CTIFIER
PULSE
WIDTH
MODULATOR
Q2
+
o--------'
24V
'------------+--0-
Fig.5: this block diagram shows the basic converter circuit. It uses a pulse width
modulator to drive complementary Mosfet stages & these in turn drive a centretapped step-up transformer. The transformer output is then fed to a bridge
rectifier & to capacitor Cl to produce 365V DC.
for the purposes of th is description ,
we have neglected any losses which
occur in the Mosfets, the transformer,
the rectifier or filter capacitor.
If you now look closely at Fig.5,
you will notice that its output is shown
as 365V. Why does this differ from the
figure of 432V just mentioned? Well,
remember the fe edback referred to
earlier? It controls the width of the
pulses applied to the Mosfet gates . So
the Mosfets don 't actually have a full
square wave app lied to them. Instead,
the pulses fed to the gates have a duty
cycle that's less th an 50% (ie, they're
on for less th an 50% of th e time). This
means that the circuit has plenty of
margin so that it can maintain the
output at 365V, regardless of variations in the load an d input voltage.
The full circuit
Fig.6 shows the full circuit details.
It uses 24 transistors, 23 ICs , 13 di-
Below: this close-up view shows the
DC to DC converter board, with part
of the high-frequency transformer
visible in the foreground. The 12
Mosfet transistors are bolted to the
chassis on either side of the PC board.
NOVEMBE R
1992
25
:;;
n:i:
z
n
0
r=:
CFJ
N
Cl
PO~R
L....o--:"'1 0 T
OF~Ao
MOTOR START
4.7k
f
uoo
151 IN2
1r-e
3
1l•IN1
116
~a
;
.001!
+IN2
E1 1g
10k
10k
f
f
150k
+15V ,..
f
T
101 .Ii:'
35VWJ
f
101 ..:-
IOUT
35VWl
01t
.,.
E21101
I
5
112
vcc
_t;_T
IC1
TL494
111
C2 -
T
+15V
~w
V#t
+24V
DC-DC CONVERTER
j
27k :
41DEAD
TIME
RT
' 141VAEF
13
~
E'...:___:JC!
VIEWED FROM'
BELOW•
r-'\
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•
♦
+
r-11
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f
.,.
10
25VW ,_
47k
;
♦
t
I
o.1 I
T
A
POWER •
LED1 •
18
UNDER VOLTAGE DETECT 21 Cl
- IN1
. .,.
10k ~
L1
100uH
1A
...L.
~SQ5-Q16 S
!:I:-
24V :
F1
100A 125V
-0--.0--
I
+24V SWITCHED
47k
.,.
385V
,- •OUTPUTI:
01I ADJUST
VR1
.,. 100k -.,.
V-, I
CHASSIS
400VD1
0.1·
IC5
IL300
i.73
4.7M
(1J~37)
~
10k
0.5W
T .......,.___.
D3-D6
4xMUR1560
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.0011
•12k
ZD6 ( j + l
15V
1W
·0.1
r n n ~~-
-----------~~----~
--- ------~
r,-----,-~) ~--
+GND
., +15V
.,
680
400VW, , _
OV
F4
15AI +365V
OUTPUT
CONTROL
VCC
13
OSCILLATOR
Q t--,:J-+-t
FLIPFLOP
CK
Q~ ~ - t
D
RT
.,.
11
10
.,.
12
VCC
.,.
UV
LOCKOUT
ERROR
AMP 1
REFERENCE
REGULATOR
o--+--J
16
FEEDBACK PWM
COMPARATOR INPUT
ERROR
AMP 2
15
14
REF
OUTPUT
Fig. 7: this block diagram shows the internal circuitry of the TL494 PWM
controller. It includes a sawtooth oscillator, two error amplifiers, a PWM
comparator, a dead-time control comparator & a 5V reference. Emitter followers
Ql & Q2 provide the complementary output signals at pins 9 & 10.
odes and 14 zener diodes. There are
also several inductors and transformers, plus numerous capacitors and resistors. Many of the components are
specially selected for this application,
while others are relatively common.
At the heart of the DC-DC converter
is a dedicated switchmode integrated
circuit, a TL494 from Texas Instruments. It contains all the necessary
circuitry to generate complementary
square wave pulses at pins 9 & 10, to
drive the gates of the switching
Mosfets. Facilities for output voltage
regulation and under voltage dropout
are provided. The TL494 is equivalen l Lu Lhe "pulse width modulator"
shown in the basic circuit ofFig.5.
Paralleled Mosfets
While the simple circuit of Fig.5
Fig.6 (left): the full circuit for the DCDC converter. ICl is the pulse width
modulation controller. It generates
complementary square wave outputs
at pins 9 & 10 and these drive the
Mosfet switching devices (Q5-Q10 on
one side & Q11-Q16 on the other) via
buffer stages IC2a-IC2f & transistors
Q1-Q4. IC4, IC5 & IC3 provide voltage
feedback to control the pulse width
modulator.
shows just two Mosfets driving the
step-up circuit, the real circuit uses
12 Mosfets (six per side). These drive
paralleled windings of one turn on
the transformer, in order to carry the
very large currents required (in excess of 100A at full load). Just how
you make a 1-turn winding which
carries these huge currents is a story
in itself and we'll give those details in
a future issue.
On the secondary side of the transformer, four bifilar windings drive a
bridge rectifier made up of soft recovery diodes D3-D6. The output from
this bridge rectifier then charges a
680µF 400VW electrolytic capacitor
via a lO0µH toroidal inductor. This
inductor is there to reduce the peak
charging currents through the diodes
in the bridge rectifier.
The voltage feedback system runs
along the bottom of Fig.6. The output
voltage (ie, across the 680µF capacitor) is sampled by a voltage divider
(4.7MQ & 12kQ) and applied to pin 5
ofIC4 which then drives optocoupler
IC5. IC5 then drives op amp IC3 which
in turn drives an internal error amplifier in IC1 to control the pulse width
modulation.
The complementary outputs from
IC1 appear at pins 9 & 10 and drive
paralleled Mosfets Q5-Q16 via CMOS
buffer stages and bipolar transistors
GND
Q1-Q4. These stages provide the necessary current amplification to drive
the gates of the Mosfet stages.
The TL494
So that's the converter circuit description in a nutshell. Now let's look
at it in more detail, starting with IC1,
the TL494.
A block diagram showing the internal features of this device is shown in
Fig. 7. It is a fixed frequency pulse
width modulation (PWM) controller
containing a sawtooth oscillator, two
error amplifiers and a PWM comparator. It also includes a dead-time control comparator, a 5V reference and
output control options for push-pull
or single ended operation.
The PWM comparator generates
variable width output pulses by comparing the sawtooth oscillator waveforms with the outputs of the two
error amplifiers. By virtue of the di ode gating system, the error amplifier
with the highest output sets the pulse
width.
Fig.9 shows the two output waveforms generated by IC1.
Dead~time comparator
The dead time comparator prevents
the push-pull outputs at pins 9 & 10
from changing over at the same time.
It does this by providing a brief delay
between one output swinging low and
the other swinging high (ie , both outputs are low for a short time at the
transition points). This delay is called
NOVEMBER
1992
27
PARTS LIST FOR THE 2kW 24V/240VAC SINEWAVE INVERTER
1 aluminium case, 400 x 400 x
170mm
4 170mm-long radial finned
heatsinks
8 4mm-dia. screws & nuts for
securing heatsink
1 self-adhesive front panel label,
230 x 170mm
2 25mm cable entry glands (Clipsal
282/25)
1 Delta 10DRCG5 mains filter
1 dual power point, 250V 10A
2 2AG 250VAC panel mount fuse
holders
1 500mA 2AG fuse (F2)
1 10A 2AG fuse (F5)
1 5mm LED & bezel (LED 1)
1 panel mount rocker switch (S1)
2 80°C thermal cutouts (TH 1, TH2)
8 large rubber feet
16 6mm metal standoffs plus
screws & nuts
12 12mm metal standoffs plus
screws & nuts
2 6. 7mm nylon cable clamps
27 100mm cable ties
4 200mm cable ties
6 150A tinned copper cable lugs
with 10mm mounting holes
47 insulated crimp lugs, 4mm stud
size, 2.5mm wire size
9 insulated crimp lugs, female
quick connect, 2.5mm wire size
2 solder lugs
1 50ml packet of heatsink
compound
Wire & cable
1 1.5m-length 130A black
automotive cable , 19610.4mm
(25mm 2)
1 1.5m-length 130A red automotive
cable, 19610.4mm (25mm 2 )
1 Sm-length 30A 240VAC cable,
4110.32mm (3.3mm 2)
1 2.5m -length red or brown 15A
240V mains cable
1 2.5m-length black or blue 15A
240V mains cable
"dead time" and constitutes about 5%
of the switching time available.
Dead time is essential in a very
high power push-pull circuit such as
this. Without it, the Mosfets driving
one half of the step-up transformer
28
SrucoN CrnP
1 50mm -length green/yellow 15A
240V mains cable
1 2.'?m-length yellow heavy duty
hook-up wire
1 2m-length green heavy duty
hook-up wire
1 3m-length blue heavy duty hookup wire
1 2.2m 0 1ength red heavy duty hookup wire
1 500mm-length black heavy duty
hook-up wire
1 1m-length 2-core shielded cable
Primary PC board
1 PC board, code SC 1130992·1 ,
204 x 157mm
9 PC stakes
12 4mm brass nuts, screws &
shakeproof washers
1 200mm-length 0.8mm tinned
copper wire
1 100µH 1A choke (Siemens
B82111-E-C25) (L1)
1 3mm screw & nut for 3-terminal
regulator
12 TOP-3 mica washers, bushes,
15mm long screws & nuts
1 100kQ horizontal mount cermet
trimmer (VR1)
Semiconductors
1 TL494 switchmode controller
(IC1)
1 4050 hex buffer (IC2)
1 LM358 dual op amp (IC3)
2 BC338 NPN transistors (01, 03)
2 BC328 PNP transistors (02, 04)
12 Siemens BUZ349 N-Channel
30A 100V Mosfets (05-016)
1 7815 3-terminal regulator (REG1)
1 33V 1W zener diode (ZD1)
2 75V 1W zener diodes (ZD2, ZD3)
2 18V 1W zener diodes (ZD4, ZD5)
2 1N4002 1A diodes (D 1, D2)
4 0.1 µF 63VW MKT polyester
1 0.01 µF 63VW MKT polyester
Resistors (0.25W, 1%)
3 1Mn
1 3 .3kQ
1 150kQ
1 2.2kQ 0.5W
3 47kQ
1 82!.15W
1 27kQ
12 10!.1
3 10kQ
2 4.7Q
2 4.7kQ
24 1Q
Transformer board
1 fibreglass sheet, 175 x 370mm
(eg, PC board material)
2 U93/76/30 N27 cores (Siemens
B67345-B1 -X27)
2 coil formers (Siemens B67345A 1000sT1)
1 sheet of aluminium, 135 x 76 x
1.6mm
2 8 x 80mm bolts plus nuts &
washers
1 100A/125A motor start cartridge
fuse, lug mounting, 94mm
centres (Hawker Siddeley
CEO100M125, GEC
TCP100M125) (F1)
2 Clipsal 2DLA 12C 165A brass link
bars
2 Clipsal BP165C12 165A brass
link bars
2 Clipsal DLA6 165A brass link
bars
14 screws for mounting link bars
2 4-way 30A PVC 240VAC mains
connector strips (Clipsal BP535
or 593/30)
2 3mm countersunk screws & nuts
for mounting connector strip
2 3mm screws & nuts for mounting
connector strip
4 pieces of 28 x 60mm 0.6mm
sheet copper
4 solder lugs
Capacitors
Capacitors
3 10µF 35VW PC electrolytic
2 0.47µF 63VW MKT polyester
would still be switching off while the
Mosfets driving the other half of the
transformer were switching on. This
would place a brief but direct short
circuit across the 24V battery supply.
As a result, the Mosfets would be
8 10µF 63VW MKT (Siemens
B32523-B106-K)
1 0.1 µF 400VW polyester capacitor
destroyed - they would literally blow
them themselves apart.
Under-voltage cutout
In Fig.6 , one of the error amplifiers
in IC1 is used to provide the under
Rectifier PC board
1 PC board, code SC11309924,
214x162mm
1 100 x 55mm sheet of fibreglass
material
2 45 x 45mm sheets of fibreglass
material
2 20 x 20 x 12mm aluminium right
angle brackets (1 .6mm thick)
2 3 x 10mm screws & nuts for
brackets
1 8 x 80mm bolt & nut
1 6mm ID rubber grommet
· 1 45mm-dia. vertical mount
capacitor clamp
2 3mm screws & nuts for clamp
2 0.75mH 10A toroid chokes (L3,
L4)
1 iron powdered ring core , Neosid
17-745-22 (L2)
1 500mm-length of 2mm enamel led
copper wire
1 50mm -length 0.8mm tinned
copper wire
2 PC stakes
4 3AG fuse clips
2 15A 3AG fuses (F3, F4)
1 4-way 30A 240VAC mains
connector strip
2 $ x 10mm screws & nuts for
connector strip
8 4mm brass nuts plus star
washers & screws ·
4 TO220 mica washers , insulating
bushes, screws & nuts
Semiconductors
1 LM358 dual op amp (IC4)
1 Siemens IL300 linear optocoupler
(IC5)
4 MUR1560 15A fast recovery
600V diodes (D3-D6)
1 15V 1W zener diode (ZD6)
Capacitors
1 680µF 400VW LL electrolytic
(Siemens B43570-E0687-O)
1 25µF 370VAC motor start
capacitor with spade lug
connectors (Plessey P331 1340)
1 0.1 µF 63VW MKT polyester
1 .001 µF 63VW MKT polyester
voltage cutout feature. This prevents
the batteries fro m being excessively
discharged . Pin 2, the inverting input, is connected to th e 24V supply
via a voltage divider consisting of a
lOkQ resistor and a 3.3kQ resistor.
Resistors (0.25W, 1%)
1 4.7MQ high voltage resistor
(Philips VR37)
1 56kQ
510kQ 1W
1 12kQ
1 820Q
Resistors (0.25W, 1%)
4 4.7kQ
410Q
2 100Q
41 Q
1 47Q
Sinewave PC board
H-drive PC board
1 PC board, code SC11309922,
204 x 157mm
1 50mm-length insulating sleeving
4 4mm brass nuts, screws & star
washers
14 PC stakes
1 300mm-length 0.8mm tinned
copper wire
8 metal oxide varistors (Siemens
S14K275)
16 TOP-3 mica washers, insulating
bushes , 12mm screws & nuts
3 EFD15/8/5 ferrite transformers
(T2, T3 , T4) (ie, each with 2 x
Philips 4312 020 41001 cores, 1
x Philips 4322 021 35201 former
& 2 x Philips 4322 121 35141
clips)
1 2.5m-length of 0.125mm
enamelled copper wire
1 200mm length of insulation tape
Semiconductors
4 Siemens SFH6136 fast
optocouplers (IC6, IC8, IC10,
IC12)
4 4049 CMOS hex inverters (IC?,
IC9, IC11 , IC13)
4 Siemens BUP304 1000V 35A
IGBTs (017-020)
3 15V 1W zener diodes (ZD7, ZD9,
ZD11)
4 18V 1W zener diodes (ZD8,
ZD10, ZD12, Z013)
3 1N4148, 1N914 switching diodes
(D7-D9)
4 Siemens BYP102 1000V 50A
diodes (010-013)
Capacitors
3 10µF 25VW PC electrolytics
4 1µF 50VW RBLL (low leakage)
PC electrolytics
1 1µF 500VW axial electrolytic
(Siemens B25839~B6105-K)
Pin 1, th e non-inverting in put , is conn ected the chip's 5V internal referen ce (Vref) at pin 14 , via a 4.7kQ
resistor.
When the voltage at pin 2 drops
below 5V (ie, when the battery volt-
1 PC board , code SC11309923,
181 x 131mm
17 PC stakes
1 700mm-length 0.8mm tinned
copper wire
1 miniature TO-220 heatsink
(Thermaloy 6038 type)
1 3.2768MHz parallel resonant
crystal , 22pF loading (X1)
1 3 x 10mm screw & nut
Semiconductors
1 7555 CMOS timer (IC1 4)
2 4049 hex inverters (IC15, IC16)
1 74HC04 hex inverter (IC17)
4 74HC193 4-bit binary counters
(IC18-IC21)
1 74HC08 quad 2-input AND
gate (IC22)
1 NMC27C64N250 CMOS OTP
PROM (IC23)
4 BC337 NPN transistors
(021-024)
1 7805 3-terminal regulator
(REG2)
1 33V 1W zener diode (ZD14)
Capacitors
3 10µF 35VW PC electrolytic
11 0.1 µF 63VW MKT polyester
1 220pF 63VW MKT polyester
2 22pF ceramic
Resistors (0.25W, 1%)
1 10MQ
1 2.2kQ
1 100kQ
4 220Q
1 47kQ
1 150Q 5W
4 2.7kQ
Note: this project has been
sponsored by Rod Irving Electronics (1992) & full kits will be
available from this company in
ea rly 1993. Copyright of th e
associated PC boards is assigned to Rod Irving Electronics.
age is below 20V), the output of this
error amp li fier goes high (pin 3) and
switch es off both outputs at p ins 9 &
10. This effectively shuts down th e
circuit.
Note that the voltage divider fee dNovEMBER
1992
29
Fig.8: the inverter delivers a clean
sinewave, as these scope photos show.
It provides 250VAC at no load (top), ·
243VAC at lkW (centre) & 230VAC at
2kW (bottom). Note that the waveform
improves with increasing load.
ing pin 2 is connected via two thermal cutout switches. These are mounted on two of the four heatsinks in the
inverter chassis and are preset to open
when the temperature exceeds 80°C.
Thus, when one or both of the heatsinks becomes too hot, the thermal
cutout opens and the circuit is shut
down. When the heatsinks cool down,
normal operation resumes.
Voltage feedback
The second error amplifier in !Cl is
used to control the output voltage of
the converter. The feedback voltage
from the optocoupler and IC3 is fed to
pin 16 and compared to the internal
30
SILICON CHIP
5V reference, applied to the pin 15
input via a 4. 7k0 resistor.
Normally, the feedback voltage from
IC3 should be close to 5V. If the output rises above this, the output of the
error amplifier also rises and this reduces. the output pulse width. Conversely, if the output voltage falls, the
error amplifier output also falls and
the pulse width increases.
The gain of this error amplifier at
low frequencies is set by the lMO
feedback resistor between pins 3 & 15
(giving a gain of 213). At higher frequencies, the gain is set is set to 22 by
virtue of the 47k0 resistor and O. lµF
capacitor in series across the lMO
resistor. This reduction in gain at high
frequencies prevents the error amplifier from responding to hash on the
supply lines.
The 27k0 resistor and .OOlµF capacitor at pins 6 and 5 of !Cl set the
internal oscillator to about 40kHz. This
is divided by the internal flipflop to
give complementary output signals
from pins 9 & 10 and so the resultant
switching speed of the Mosfets is
ZOkHz.
Pin 4 of !Cl is the dead-time control. When this input is at the same
level as Vref, the outputs at pins 9 &
10 are off. As pin 4 drops to OV, the
dead-time decreases to a minimum.
At initial switch on, the lOµF capacitor between Vref (pin 14) and pin 4 is
discharged. This prevents the output
transistors in !Cl from switching on.
The lOµF capacitor then charges via
the associated 47k0 resistor and so
the duty cycle of the output transistors slowly increases until full control is gained by the error amplifier.
This provides a soft start for the converter.
Complementary outputs
The outputs at pins 9 & 10 of !Cl
come from internal emitter follower
transistors and these each drive 10k0
load resistors. These outputs also each
drive three paralleled CMOS non-inverting buffers (IC2a-IC2f). These buffers stages then drive transistors Ql &
QZ on one side of the circuit, and Q3
& Q4 on the other.
Thus, when pin 10 ofICl goes high,
Ql turns on and drives the paralleled
gates of Mosfets Q5-Q10 via a 4. 70
resistor. Note that each Mosfet gate is
connected via a .100 "stopper" resistor to minimise any parasitic oscillations which may occur while the
Fig.9: these are the complementary
pulse signals from the TL494 PWM
controller. Note that both waveforms
do not switch over at the same points,
in order to give dead time.
Mosfets are switching on and off.
When pin 10 goes low again, QZ
switches on to discharge the gate capacitance of each Mosfet, thus switching them off. The complementary
process occurs with pin 9.
Circulating currents
While it is not obvious from the
circuit of Fig.6 , there must be two
connections to the drain and source
of each Mosfet. For example, the
drains ofMosfets Q5-Q10 are connected in parallel to one side of the transformer primary. In addition, each
drain must be connected back to the
PC board so that the zener diode protection can work.
Similarly, the source connections
of the Mosfets are all connected to the
OV line and thence to the battery negative pole. In addition, the sources all
need to go back to th~ PC board because otherwise the gate drive circuitry would not work properly.
The problem with this need for double connections is that unless we take
precautions to stop it, very heavy currents will flow on the relatively flimsy
copper tracks of the PC board. This
must be avoided because the PC board
cannot carry such currents.
To stop heavy currents flowing on
the board, 10 resistors are used in all
the drain and source connections.
Thus , the gate circuitry and zener diode protection circuitry works properly but the main currents flow in the
direct cable connections.
But even with this precaution, the
source currents from the Mosfets still
tend to flow in the PC board tracks. To
stop this, two grounds are provided.
The first is for the load current and
connects directly to the negative ter-
Despite the complex circuit, the 2kW Sinewave Inverter is relatively easy to
build since most of the parts are mounted on PC boards. The DC-DC converter
board is at the bottom of the photograph, with the high-frequency switching
transformer immediately above it.
minal of the battery. The second provides the circu it earth and is connected to the n egative battery terminal via a 100µH ch oke (11). This choke
prevents the load current from flowing through the parallel H2 source
resistors. It does this because the inductance between the PC board and
the negative battery terminal is far
greater than the in ductance of the
source leads.
In addition , eight 10µF 63VW bypass capacitors are connected across
the battery input leads , following the
100A fuse. These capacitors effectively cancel out the indu ctance of
the battery cables and th ereby provide full power to the transformer
and Mosfets at the switching fre quency of 20kHz.
The secon dary windings of the
transformer con sist of four 9-turn
windings wh ich are then connected
to form two centre-tapped 18-turn
windings in parallel. This arrange-
ment minimises the leakage inductance of the transformer.
Zener diodes ZD2-ZD5 provide protection for the Mosfets. ZD4 and ZD5
are 18V zeners which protect the gates
of the Mosfets against over-drive. ZD2
and ZD3 are 75V zeners which protect the drains of the Mosfets from
spikes as they switch off. These zeners
clamp the drains to about 80V peak
and thus prevent damage.
The response time of this overvoltage clamp action is about lµs
which is not really fast enough. To
provide protection during this initial
lµs period, we have specified Mosfets
which have avalanche protection. This
means that at the breakdown voltage
of the Mosfet (100V), an internal zener
provides protection for a short time
until the external protection circuitry
takes over.
Voltage feedback
As noted above, IC4 and optocou-
pler IC5 are used to provide voltage
feedback to the switchmode controller (ICl). IC4 and the optocoupler must
be fully isolated from the 24V input
supply, which means that they must
be powered from the high voltage DC
output. Thus, the 365V supply is fed
to a network consisting of five series
10kQ dropping resistors plus a 15V
zener diode, ZD6. This provides the
15V supply for IC4 and IC5.
The voltage feedback network consists of a high-voltage 4. 7MQ resistor
(Philips VR37) and a 12kQ resistor
connected to 0V (ie, the 0V of the high
voltage supply, not the 24V battery).
IC4 monitors the voltage across the
12kQ resistor and drives the linear
optocoupler, IC5.
IC5 provides the necessary electrical isolation between input and output. This device has high linearity
and this is due to the use of two internal photodiodes, one on the isolated
side to supply the output (pins 5 & 6)
and a second (pins 3 & 4) to provide
feedback to the LED driver circuit.
The isolated photodiode output at
pins 5 & 6 of IC5 is connected between the+ 15V supply rail and pin 3
of IC3. The current from the photodiode develops a voltage across trimpot VRl which is amplified with a
gain of about four by IC3. IC3 then
feeds pin 16 of ICl and thus completes the feedback loop.
Power supply
The 24V input from the battery bank
is connected via heavy duty cables
(ie, starter motor cables) and a 100A/
125A cartridge fuse to the centre tap
of the transformer. Because of the high
currents involved, there is no on/off
switch for this main supply; the 24V
. input is permanently applied to this
part of the circuit.
Switch Sl feeds 24V to the lowpower part of the circuitry and LED 1
indicates when the power is switched
on. The 24V supply from switch Sl is
fed via an 82Q 5W resistor and clamped against transient voltages using
ZDl. T·he 24V supply then feeds the
input ofa 15V regulator (REGl) which
supplies the ICs. The 10µF capacitors
at the input and output of the regulator are for supply decoupling.
That's all for this month. In Pt. 3, we
will describe the circuitry for sinewave generation and the H-pack
switching output which converts the
365V DC to 240VAC.
SC
NovEMBEH
1992
31
The Oriel: Jamo's flagship
loudspeaker system
Jamo is one of Europe's largest manufacturers of
high fidelity loudspeaker systems and for some
time they have been working on this state of the
art design in which no expense has been spared.
The result is a monumental loudspeaker with
outstanding sound quality.
By LEO SIMPSON
When there are so many loudspeaker systems available in the marketplace, how do you set out to produce a unit which is truly outstanding? That was the target set by the
Danish manufacturer, Jamo, a couple
of years ago. The result is a little surprising, both in appearance and the
number of drivers it uses. The Oriel
system is certainly large and heavy
but it is also elegant, eye-catching and
nothing like conventional loudspeakers in appearance.
The Oriel system stands 1.8 metres
tall and weighs 72 kilograms so that
once they are installed there will be
very little incentive to move them. In
fact, it requires a minimum of two
strong men to move them safely.
A major part of this weight comes
from the enclosure itself and the heavy
concrete base. The enclosure is essentially oval in cross-section, which ensures great rigidity, minimises diffraction effects from the drivers at medium and high frequencies and visibly reduces the apparent bulk of the
system.
Medium density fibreboard (MDF,
also known as Customwood) is used
A great deal of care has gone into the design and layout of the crossover
network. Notice how the air-cored and powdered iron-cored inductors have
been oriented so that the mutual coupling between them is minimised. The
capacitors are of conventional foil construction (ie, not bipolar electrolytics)
and have very low power factor combined with high current capability. The
total number of components in the network is 22.
32
SILICON CHIP
for the cabinet. The curved sections
are built up from segmented sections
of MDF while the flat sections are
laminated from seven layers of2:Smm
MDF. The curved sections are finished
in matt grey while the flat sections are
covered and stiffened with toughened
glass - another reason why the enclosures are so heavy. The glass is trimmed with cherry wood to give a subtle
emphasis to the shape.
To lower the cabinet's centre of gravity and increase its stability, the widened base is cast in concrete.
Three-way system
At first sight, with the speaker grilles
removed, the Oriels look to be a two
way system, since a dome tweeter
and a modestly sized cone driver are
all that are visible. However, the Oriel
is a 3-way system, with two bass·drivers in addition to the midrange and
tweeter.
The dome tweeter is perhaps the
most expensive unit of its kind ever
made. With a 28mm dome, a voice
coil wound with hexagonal wire and
ferrofluid cooled, and a magnet-weighing more than 1kg, the tweeter is
claimed to be able to handle prngram
transients of up to 1000 watts. It covers the frequency range from 31<.Hz to
above the limit of audibility.
The 18cm midrange driver is
housed in its own sealed enclosure
within the Oriel cabinet. Its cone is a
honeycomb construction which
renders it very rigid and free of any
break-up over its frequency range from
100Hz to 3kHz. Again, it has a powerful magnet and its pole piece is ventilated to avoid damping the motion of
the cone due to pressure build-up
behind the dust cap.
The two 21cm woofers each have
their own sealed enclosure within the
Oriel cabinet. As one of the photos
accompanying this article shows, one
woofer is at the top of the cabinet
while the other is at the bottom. The
woofer enclosures are bandpass tuned,
a concept presently used in a number
in the concrete base of the cabinet and it
has separate terminals for the bass, midrange and tweeter. This means that the
system can be bi-wired or tri-wired (ie, two
or three sets of cables from the power amplifier), or bi-amped or tri-amped (ie, two
or three amplifiers driving the separate sections of the network but not using an electronic crossover) .
Overall sensitivity of the Oriel is quoted
as 8 7dB for 1 watt at 1 metre and the
recommended amplifier rating is from 70
to 300 watts.
And the price for this acoustic masterpiece? Around $17,000 for a pair. For further information, contact the Australian
distributors, Scan Audio Pty Ltd, PO Box
242, Hawthorn, Vic 3122. Phone (03) 429
2199 or fax (03) 429 9309.
SC
A pair of Oriel loudspeaker systems will require a large room to
accommodate them but their rounded column shape means that their bulk
is not over-powering. They stand on concrete plinths and can be set on
spikes or rubber feet.
of subwoofer designs , including the
Bose Acoustimass.
The principal advantage of bandpass tuning is that it tends to suppress any harmonics produced by the
woofer and thus gives a cleaner bass
response. The woofer enclosures in
the Oriel are tuned to 40Hz and 75Hz,
giving an effective bandpass of about
30-l00Hz. The woofers' sound output exits via angled ports above and
below the midrange enclosure.
Crossover network
As you might expect, the Oriel's
crossover network is fairly complex
and uses no less than 22 components.
It has five air-cored inductors , two
powdered iron-cored inductors, 12 AC
rated foil capacitors and three wirewound resistors. As well as providing
the 6dB/octave slopes for the woofer,
midrange and tweeter crossover frequencies, the network provides group
delay for the tweeter. This obviates
the need for "time delay compensation " which would otherwise require
the tweeter to be stepped back on the
baffle to match the acoustic centre
line of the midrange driver.
The inductors are mounted on the
crossover network PC board in such
as way as to minimise any mutual
coupling. Mutual coupling can reduce
the filter slopes and cause distortion
by feeding bass energy to the tweeter
and so on.
The crossover network is mounted
The internal construction of the Oriel
system is shown in this photograph.
The midrange has its own sealed
enclosure while the two bass drivers
each have their own bandpass tuned
enclosures. Their sound output
emerges via ports above and below
the midrange enclosure.
NOVEMBER
1992
33
MAL-4: Microcontroller
Aid for Learning
Here is a microcontroller design which can be used
to learn programming and computer c~ntrol. It
features the Motorola 68HC705CB microcontroller
and has serial and parallel ports. You can program
it via its own hexadecimal keyboard or via a
standard IBM computer keyboard.
34
SILICON
CHIP
By Barry Rozema
A
single chip microcomputer, as
the name implies, is a microcomputer in a single chip package. This means that all the building
blocks of the microcomputer are in
the one integrated circuit. The building blocks for most computers are the
central processing unit (CPU), memory
(RAM & ROM), parallel and serial input/output (I/0) ports, address decoding, clock, interrupt timer and watchdog timer.
Single chip microcomputers or
microcontrollers have found a very
important niche in the computer industry. Due to their size and low cost,
they are very effective when used for
control applications such as in washing machines, microwave ovens, VCRs
and burglar alarms.
The microcontroller used in this
project is the Motorola MC68HC705C8. It is an 8 bit microcontroller
with a user programmable EPROM inst~ad of mask programmable ROM.
This makes prototyping and development a reasonably easy task.
Why use the MC68HC705C8? The
main reasons were cost and availability plus the fact that I like Motorola's
"easy to understand" data sheets and
manuals.
And why design and build a single
chip microcontroller learning aid? I
realised when I first started programming the 68 705 that it would be handy
to run some small test programs to
familiarise myself with the devicA.
After some enquiries, I discovered that
there are some development tools for
the 68705 but the prices were out of
my league. So the idea of designing a
cheap single chip learning aid was
born.
Main Features
• Processor - Motorola MC68HC705C8S.
• Clock speed - 2MHz/2 (1 MHz internal clock).
• Display - 2-l ine by 16-character alphanumeric LCD.
• Keyboard - Hex keypad with option for different types.
• Power supply - either 9V AC or 12V DC.
• Monitor - resides in EPROM (5Kb) and includes disassembler.
• Two modes - MAL-4 or single chip monitor mode.
• Emulates the Motorola M68HC05PGMR programming board.
• Battery backup of RAM.
• Ports:
A - 8-bit input port with 8-way DIP switch.
B - 8-bit outpuVinput port with 8 LEDS.
C - 8-bit control port with 8 LEDS.
D - 7-bit input only port with 8-way DIP switch or asynchronous
(RS232) and synchronous (IBM keyboard) .
• Ease of construction
• Stand alon e operation
• Possible u se as a controller
The MC68HC 70 5C8S microc ontroller is a recent addition to th e
Motorola 6805 family and is similar
to the 68 705P3 processor featured in
the Sprinkler Controller published in
the July 1992 issue and the Burglar
Alarm publish ed in th e September &
October 1992 issues of SILICON CHIP.
The " HC " des ign ation of the
68HC705C8 signifies that it is a high
speed CMOS version (ie, high speed,
low power). It is one of m any versions
of this chip so that once you have
learnt h ow to program it , you w ill
have no trouble with the other versions and indeed you will have a good
grounding in programming any microprocessor.
Block diagram
The block diagram of Fig.1 shows
MAL-4
Entitled "Microcontroller Aid for
Learning, Version 4.03" or MAL-4, for
short, this project is the fourth in a
series which have been designed primarily as a learning tool for TAFE
colleges. I paid close attention to the
following points:
• Low cost
• Current processor technology
• Simple design
The MAL-4 uses a 2-line alphanumeric readout which plugs into a socket on the
PC board. It is an intelligent unit which accepts ASCII code.
NOVEMBER
1992
35
TABLE 1: MAL-4 MEMORY MAP
Input/Output
32 Bytes·
$00
Port A Data Register
$01
Port B Data Register
$0020 - $002F
Unused 16 Bytes
$02
Port C Data Register
M.A.L. Zero Page Ram
144 Bytes
$03
Port D Input Register
$0030 - $00BF
$04
Port A Data Direction Register
$00C0 - $00DF
M.A.L. Scratch Pad
32 Bytes
$05
Port B Data Direction Register
$06
Port C Data Direction Register
$00E0 - $GOFF
System Stack
32 Bytes
$07
Unused
$08
Unused
$0100 - $01 5F
M.A.L. Page 1 RAM
96 Bytes
$0000 - $001 F
Unused
Serial Peripheral Control Register
$0B
Serial Peripheral Status Register
$0160 - $12FF
M.A.L. Monitor EPROM
4512 Bytes
$1300 - $1 EFF
Spare User EPROM
3072 Bytes
$DC
Serial Peripheral Data 1/0 Register
$OD
Serial Communications Baud Rate Register
$1 FOO - $1 FOE
Bootstrap ROM
223 Bytes
$OE
Serial Communications Control Register 1
$OF
Serial Communications Control Register 2
$1FDF
Option Register
$10
Serial Communications Status Register
$1FE0 - $ 1FEF
Bootstrap ROM Vectors
16 Bytes
$11
Serial Communications Data Register
$12
Timer Control Register
$1 FF0 - $1FF3
Unused 4 Bytes
$13
Timer Status Register
$1 FF4 - $1 FFF
M.A.L. EPROM Vectors
12 Bytes
$14
Input Capture High Register
most of the significant features of the
MAL-4. It leaves out essentials like
the power supply, speaker driver and
even an external EPROM which the
unit can be used to program.
The 68HC705C8 has 24 bidirectional input/output (1/0) lines and 7
input-only lines. These are arranged
as three 8-bit 1/0 ports (A, B & C)
while the 7 input-only lines are port
D. Interestingly, while these 7 lines
are specified by Motorola as input
only, the first line (PD0) is also used
as an output line, to provide the Tx
line for RS-232 serial communications
(via a MAX232 chip on the board).
Port A is used to drive the 2-line
liquid crystal display, along with a
couple of the lines from port C. The
liquid crystal display is an intelligent
device and it accepts ASCII characters on its parallel data lines.
Ports B and C drive a bunch of
LEDs which show the state of the
lines. One data line of port C also
36
$09
$0A
SILICON CHIP
$15
Input Capture Low Register
$16
Output Compare High Register
$17
Output Compare Low Register
$18
Counter High Register
$19
Counter Low Register
$1A
Alternate Counter High Register
$18
Alternate Counter Low Register
$1C
Program Register
$10
COP Reset Register
$1E
COP Control Register
$1F
Unused
drives the speaker to provide the occasional beep or two, to acknowledge
that the micro is receiving or feeding
out data. The 16-button hexadecimal
keyboard is connected to ports A and
C via row and column driver ICs. Port
A also provides the external parallel
port.
An IBM keyboard can be connected
to the unit and it drives four of the
lines of port D.
DIP switches are also provided for
data input to port A and port D.
Two pushbuttons are provided for
"Interrupt Request" (IRQ) and "reset" .
All of _the above features can be
gleaned by examining the block diagram of Fig.1 but let's face it, that will
not really tell you much about how
the micro works. That understanding
will come gradually as you learn more
about programming the device and
DIPSW1 PORT-A
,I, 1,1\'
l ll
:\'
1/0 CONNECTOR PL2
I, I
l l
PORT-A
PORT•B
LCD
J
I
...<
a..
.,J
PORT-A
INPUT
BUFFER
'
PC3
,,
A BUS
-.
E RS R/W
8-BIT DATA
ca.. "'a..<
.,J
<
a..
.,J
<
a..
"'<
ca..
<O
<
a..
a..
,,
•
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a..
a..
0
<O
0
a..
.,J
(
.,J
[
0
,,
,,
,
"
PA7
PA6
PAS
,,
< PA4
PORT-B
LED MONITORS
.:.
~
PAS
a.. PA2
l.
PA1
PAO
XTAL1
2MHz
[
PB7
OSC1
Ir
r
PBS
OSC2
m P84
,J
~ P83
,J
PB2
.,J
.:.
a..
RESET
T
P81
.,J
PBO
~
PORT•C
LED MONITORS
PC7
.,J
PC6
,J
.:.
IRQ
PC2
.,J
PC1
,J
PCO
.,J
'I
0
0
,1, I, I, I,~\'
I l I
r
.,J
"
.:.
~ PD3
a.. PD2
.,J
PD1
.,J
PDO
,,
TXIPD1
MAX232 ]PDO
RX
1
TX .I
DATA
IIDATA
RX
RS232
PLUG
8
U6
74LS139
COLUMN DRIVER
II
.A
D BUS
a PD4
'
'
"'00..
:::,
"'
"'
<
PD5
PD4
IBM
PD3 KEYBOARD
SOCKET
PD2
8x4 X-Y
KEYPAD
UP TO 32 KEYS
U7
74LS541
KEYPAD ROW
BUFFER
I
Fig.1: this block diagram shows the main features of the MAL-4 microcontroller
board. It has three 8-bit input/output ports (A, B, & C), while Port D has seven
input lines. Two of these lines do double duty as the RS232 serial port. Data
entry can be via the on-board hex keypad or via a standard IBM keyboard.
how it handles data to and from its
ports.
Physically, the MAL-4 is constructed on a double-sided PC board
measuring 223 x 153mm. It has a zero
insertion force (ZIF) socket to allow
an external EPROM to be used or programmed. It has a hex keyboard as
u
0..
A
~\
PD7
PD5
....
IL
.,J
T
~
DIPSW2 PORT-D
~ PC3
a..
l
C BUS
r
u PC4
Ir
SPEAKER
,,
PCS
KEY6
ESCAPE
~
PB6
U2
MCUHC705C8
MCU
KEYS
RESET
B BUS
_,,
already mentioned. The board is used
free-standing and it only requires the
connection of a 12V AC or DC plugpack to have it up and running.
As a point of interest, the MAL-4
board also emulates all functions of
the Motorola M68HC05PGMR "Programmer Board".
The MAL-4 microcontroller board
is available from the author as a complete kit and sells for $249. The address is E.S.D. Electronic System Designs, PO Box 73, Glenbrook, NSW
2773. Phone (047) 39 4039. The kit
comes with a detailed assembly & operation manual which includes listings.
Next month, we will continue the
description of the MAL-4 board, giving the complete circuit, construction
details and the parts list.
SC
NOVEMBER
1992
37
0-25V 1•10A PROFESSIONAL POWER
SUPPLY
S0003 $84.00
Profess ional Power Supp ly, S0003, is
designed for use in low voltage and
high current system. Its special features
include short-circuit o verload protection ,
LED and phonic- indicators, and
continuously adjustable current from 1A
to 10A. It is particularly suitable for use
in C.B. Transmitter, battery charger, etc .. .
ADJUSTING AND TESTING:
•
60W + 60W OCL DC PRE-MAIN
STEREO AMPLIFIER S0309 $99.00
Th is amplifier uses no capac itors
in the si gnal pa t h and has unsu rpassed low
freq uen cy resp o nse.
The S0309 has a pre- ampl ifier
se ct ion , three band tone co ntrols, speaker
protecti on circu it with anti- th ump delay
and larg e heat sink for co ol op eration .
SPECIFICATIONS
Po wer Output
60 watts ea ch channel
into 8 ohms
Freque ncy res ponse: 10 Hz to 20 KH z
Tot al harmo ni c
distortion:
Less than 0.05 %
Sensiti vity :
Phono:
3mV at 47K
Aux an d tap e:
130mV at 47K
Dimen sions:
9.07" x 8" x 2.25"
Reco mmended pow er transformer is T0217
Suggested cabinet is Mark V LG192 4.
After assembly, chec k the c ircu it
twice before testing. Connect the
voltm eter and ampere -met er as
shown in fig. 2, after which power
suppl y is co nnec ted. Test the voltage
control by turning the VR. and noting
the change from 0-25V
• To test the c urrent limiting functi on ,
the cur re nt limiter is turned to its
minimum during w hich time the LED
and bu zzer wou ld be act ivated. Adjust
VR1 just to make the LED and buzzer
inactive again .
• The outp ut vo ltage is then adjusted
to about 5V while the maximum
current is adjusted to 1A (v ia the
VR1 ). The output term inals are then
short-circuit ed, th e beeping of buzzer
and flashing of LED indicate that t he
cu rrent limiter is funct ional.
• The output c urrent is adjusted
between 1A to 10A by turning the
current limiter.
CHECK FOR FAULTS:
Fault at output voltage : Check 723 I.C,
Q1-Q5.
Fault at output current: Check I.C .2,
1458.
Non-functioning LED or buzzer:
Check LED, Q6 , Q7, tran sistors.
SPECIFICATION:
120 Wr. m.s. per
ch annel into 4 ohm s
load.
Frequency response : 10 to 20 KHz
Total harmon ic
Less th an .01 %
di storti on:
Bass ±1 2 dB ,
Tone control:
Mid : ±8 dB ,
Treble: ±8 dB.
Ph ono input , 3 mv into
Sensiti vity:
47K.
Line , 0.3 V into 47 K.
Signal to noise rat io: 86 dB
Power requirement: 40V De at 6 amp
. Suggested tra nsformer for power supply is
T0217. Suggested rack mount cab inet:
MARK V LG1924 or LG1 92 5.
Output Voltage: 0-25V
Output Current: 1-10A
Method of protection : current limited
Ind ication of overload. " BB" sound
effect and LED fli c ker.
Ripple and noise : <1 mV.
Stability of output voltage : ,0.08 % .
Power Output:
LCD THERMOMETER
10301 $21.00
CLOCK
FEATURES:
•
•
•
•
•
•
0.34" DIGITAL thermometer with
Hi & Low temperature alarm function
and 12 hours clock combination.
Measuring range: 0°F to 160°F or -20°C
to 70°C.
Resolution reading : ±1.8°F.
Dimensions: 3.2" x 0.86" x 2.08".
T-1 with In/ Out Door sensor.
T-3 with In/Outdoor all-weather proof
sensor.
~,,,,,,,,,,~~
HIGH PRECISION SOUND CONTROL
SWITCH
S0201 $19.00
This sound activated on-off switch can
be activated by a whistle or hand clap.
Sensitivity is adjustable. The output can
switch a 200 watt load. May also be
converted to a touch switch. Uses two ICs
and relay output for complete load isolation
and high reliability.
Dimensions: 2-7/8" x 1-7/8" x 1" .
0-SA REGULATED DC POWER
SUPPLY
S0002 $37.00
S0004 $37.00
When used with an external power
transformer, this module makes a very
stable, well filtered, well regulated power
supply. It employs bui lt-in overload
protection with LED indicator. Perfect for
lab or shop use. There are two versions
available, A and B.
A. 0 to 15 VDC at 5 amps. Use with
transform er T02 33 .
B. Oto 30 VDC at 3 amps. Use with
transformer T0234.
The supplies are also current limited
making them virtually failure free and foolproof.
Dimensions: 5-1/2" x 2-5/8" x 1-7/8'' .
0-S0V 3A POWER SUPPLY WITH
SHORT CIRCUIT AND OVERLOAD
PROTECTION
S0001 $42.00
This module requires an external
transformer to make a high quality lab type
power supply. It is short circuit proof and
has overload protection also. Output
voltage is var iable over a range of 0 to 50
volts and can supply up to maximum of
3 amps. Current limit trip is adjustable.
Use with transformers supplying 22 to
36 VAC. A perfect match is the T0210.
Dimensions: 6" x 2-5/8" x 1-7/8".
ss
s
If you own a mobile
telephone, this simple
gadget will dramatically
increase the life of your
nicad batteries. It does
this by correctly
discharging the battery
pack to its endpoint
voltage, so that it can then
be recharged to full
capacity.
By BERNIE GILCHRIST*
An autoillatic nicad
battery discharger
I
N RECENT YEARS, lots of people have thrown perfectly good
nicad batteries on the scrap heap
in the mistaken belief that they had
reached the end of their useful service life. Often, however, such batteries are perfectly OK apart from having
their apparent capacity drastically
reduced by what is known as the
"memory" effect.
This memory effect is acquired
when nicad batteries go through repetitive discharge cycles in which
only part of their rated capacity is
Research & Development Department,
Dick Smith Electronics, North Ryde,
Sydney.
*
40
SIL/CON CH I P
used before recharging. As a result,
the battery acquires a "memory" so
that it only discharges to the point
from which is was recharged and then
behaves as though it had gone flat.
When you think about it, it is quite
easy for this situation to occur. Acommon problem is when people recharge
partially flat camcorder batteries or
batteries from mobile telephones. After a number of cycles, the batteries
acquire a memory effect and this drastically reduces the operational time
of the equipment.
So how do we prevent this memory
effect? The solution is to discharge
the battery all the way to its endpoint
voltage (1.1 V per cell) before recharging it to full capacity. A few such
deep cycles are usually required to
rejuvenate a battery that is already
suffering from a memory effect, after
which it should deliver its full rated
capacity.
Automatic discharger
The easiest way of correctly discharging your nicad battery packs is
to use·a special discharger such as the
unit presented here. It can discharge
nicad battery packs ranging from 3.6V
to 12V and, unlike other units on the
market, switches itself off when the
endpoint voltage has been reached so
that no further discharge takes place.
This automatic switch-off feature
means that you don't have to constantly check the discharger and dis-
-
START
S2
12V
1.2k
16k
VR1
Sk
1.2k
47k
1.2k
1.2k
1M
+
D2
1N4002
7.3k
T
NICAD
BATTERY I
1.2k
1.2k
..a...
BATTERY
VOLTAGE
S1
B
B
1.2k
2.2k
A
3.6k
3.3k
LE01
RED
K
PLASTIC SIDE
B
EOC
NICAD BATTERY DISCHARGER
Fig.1: the circuit is powered by the battery under discharge. When S2 is pressed,
pin 6 ofIC1b goes high & turns on Q4, Q5, Q6 & Q1. As the battery discharges,
IC1b compares the voltage on its pin 3 input with a reference voltage derived
via S1 from IC1a. When the voltage on pin 3 falls below the selected reference
voltage, pin 6 ofIC1b switches low again & Q4, Q5, Q6 & Q1 switch off.
connect the leads at the appropriate
time. This is important, because if
discharge continues after the endpoint
voltage is reached, the weakest cell in
the pack can eventually be forced to
reverse its polarity and this causes
permanent damage and drastically
reduced capacity.
To avoid this risk, the Nicad Battery Discharger discharges the pack to
1.1 V per cell and then switches off
before any damage can occur. Thus,
for a 7.2V battery pack, the endpoint
voltage is 6.6V. (Note: nicad cells
maintain a virtually constant output
voltage until they are fully discharged).
During operation, the unit is powered by the battery under discharge.
The battery pack is simply connected
via two clip-on leads and the battery
voltage selected by means of an 8position rotary switch. The DISCHARGING LED now comes on to indicate that the unit is operating correctly and you can set a toggle switch
(CURRENT) so that the battery dis-
charges at either 50mA or 200mA.
When the endpoint voltage is reached, the DISCHARGING LED goes out.
The battery can now be disconnected
and recharged to full capacity in the
usual manner.
How it works
At the heart of the circuit is ICl , an
LMlOCL op amp and voltage reference - see Fig.1. This IC contains a
stable Z00mV reference which is permanently connected to the non-inverting input of the reference op amp
(ICla). ICla amplifies this reference
voltage by an amount depending on
the setting of VRl, so that 0. 73V is
applied to the following resistive divider chain.
This divider chain sets the cut-off
voltages for the various battery packs.
It is tapped off using switch S1 and
the sampled reference voltage is then
fed to pin 2 of IClb where it is compared with a sample of the battery
voltage on pin 3. Let's look at this in
greater detail
VIEWED FROM
BELOW
~
ECB
When the battery pack is first connected, virtually no current flows in
the circuit (except for negligible leakage current). The circuit operation is
now initiated by pressing the START
button (S2). When this happens,
power from the battery is applied to
pin 7 of IC1 via a lOmA constant
current source consisting of transistors QZ and Q3. The current drawn by
the LMl0 is only about 500µA at most
and so most of the lOmA from the
constant current source flows through
LED 1.
LED 1 serves two purposes. First, it
acts to provide a regulated supply of
about 1. 9V to ICl. Second, it lights to
indicate that the battery is being discharged.
Assume initially that the battery
voltage is greater than the endpoint
voltage. In this case, the sampled battery voltage applied to pin 3 of IClb
will be greater than the reference voltage on pin 2. Thus, pin 6 of rc1b
swings high; ie, to within about 50mV
of the 1.9V supply. This then turns on
transistors Q4 and Q5 to discharge
the battery.
Because Q4's emitter will be at 1.3V,
Q6 also turns on and the discharge
current will be either 50mA or 200mA,
depending on the setting of switch
NOVEMBER
1992
41
PARTS LIST
1 plastic case, 41 x 68 x 130mm
1 single pole 8-position rotary
switch (S1)
1 momentary contact pushbutton
switch (S2)
1 SPOT miniature toggle switch
(S3)
1 T0-126 mica washer
1 10 x 3mm machine screw &
nut (for transistor mounting)
4 nuts to suit toggle and
pushbutton switches
1 star washer to suit switch S1
1 red crocodile clip
1 black crocodile clip
1 400mm-length of red mediumduty hook-up wire
1 400mm-length of black
medium-duty hook-up wire
1 60mm length of 3-way rainbow
cable
1 knob to suit rotary switch
1 5kQ miniature vertical trimpot
(VR1)
Semiconductors
1 LM1 0CL op amp & voltage
refererice (IC1)
1 BC328 PNP transistor (01)
2 BC557 PNP transistors
(Q2,Q3)
2 BC549 NPN transistors
(Q4,Q6)
1 8D140 PNP transistor (05)
4 1N4002 silicon diodes (D1-D4)
1 5mm red LED (LED1)
Capacitors
1 10µF 16VW PC electrolytic
1 1µF 50VW PC electrolytic
Resistors (0.25W, 1%)
1 1MQ
1 2.2kQ
1 47kQ
7 1.2kQ
1 16kQ
1 100Q
1 7.3kQ
2 56Q
1 3.6kQ
1 43Q
1 3.3kQ
1 8.2Q
Where to buy the parts
A kit of parts for this project is
available from any Dick Smith
Electronics store or by mail order
from PO Box 321, North Ryde,
NSW 2113. Phone (02) 888 2105
or, if outside Sydney, (008)226610.
The kit comes complete and includes a pre-punched & silkscreened front panel. The price is
$29.95 plus $5 p&p. Quote Cat. K3126 when ordering.
Note: copyright of the PC artwork
associated with this project is
retained by Dick Smith Electronics.
42
SILICON CHIP
S3. Note that some of this discharge
current flows via the constant current
source (QZ & Q3} and via Q6 and its
associated 56Q resistor.
When Q6 turns on, its collector current is sufficient to saturate Ql and so
this transistor remains on when the
START button (SZ} is released. The
circuit thus remains on and the battery continues to discharge at either
the 50mA or 200mA rate until it
reaches its endpoint voltage.
When the endpoint is reached, the
voltage on pin 3 of IClb falls below
the reference voltage on pin 2 and pin
6 switches low. This removes the bias
from transistors Q4, Q5, Q6 & Ql and
so the circuit switches off, the LED
goes out and the battery ceases discharging. The lMQ feedback resistor
between pins 6 & 3 of IClb provides
the op amp with a small amount of
hysteresis so that it switches cleanly
at the transition point.
If the battery is already below its
endpoint voltage when the START
button is pressed, the output of IClb
will remain low and so Q4, Q5, Q6 &
Ql will remain off. However, the LED
will light while ever the button is
held down. As soon as the button is
released, the LED will go out again
and the supply voltage on pin 7 ofICl
will quickly fall as the l0µF capacitor
discharges.
Diodes D1-D4 protect the circuit
against reverse battery connection. If
the battery is connected the wrong
way around, a small reverse current
flows via the lO0Q resistor and the
base-collector junction of Ql but this
cannot damage the transistor and the
IC is protected by DZ. The l00Q resistor between the base and emitter of
Ql ensures that it fully turns off at the
end of the discharge period.
Construction
Fig.2 shows the wiring details for
the Nicad Battery Discharger. Most of
the parts, including the switches, are
mounted on a PC board (code ZA1373) and this is housed in a small
plastic utility case measuring 41 x 68
x 130mm.
Start the construction by installing
all the resistors and diodes, then install the transistors and the two capacitors. The resistor values should
be checked using a digital multimeter,
since the colour bands can sometimes
be difficult to read.
Make sure that all polarised corn-
Fig.2: make sure that all polarised
parts are correctly oriented when
installing them on the PC board &
don't mix up the transistor types. Q5
is mounted on the front panel & is
connected to the board via flying
leads - see Fig.a.
ponents (transistors, diodes & capacitors} are correctly oriented and that
the correct transistor type is used at
each location. If you use the wrong
transistor or install a part the wrong
way around, that part could self-destruct at switch-on and possibly take
other parts out with it.
The IC, switches and trimpot can
now be installed as shown in Fig.2.
An IC socket was used for the prototype but there's no reason why the IC
cannot be soldered directly to the
board. Be sure to install the IC with
the correct polarity.
As supplied, the rotary switch will
have 12 positions but it can easily be
changed to an 8-position type by moving the selector ring at the end of the
threaded bush. Check that the switch
is seated properly against the board
before soldering its pins. Switch S2
should be mounted so that it sits about
4mm above the board surface, while
S3 should be pushed all the way down
onto the board.
At this stage, the only part not fitted to the board will be the indicator
LED. We'll come to that later. In the
meantime, cut two 400mm lengths of
medium-duty hook-up wire for the
battery connections (one red and one
black} and solder them to the PC board.
Similarly, solder three 60mm-long
leads to the PC board for the connec-
tions to the power transistor (Q5).
Because it handles most of the current, Q5 requires a modest amount of
heatsinking and this is achieved by
mounting it on the metal lid of the
case. Fig.3 shows the mounting details. Note that Q5 must be electrically isolated from the lid using a
mica washer.
Before mounting the power transistor, check that the contact area is perfectly smooth and free of metal swarf.
If you detect any roughness, use a
small file and a piece of wet and dry
paper to smooth the contact area so
that there is no risk of the metal punching through the mica washer when
the assembly is bolted together.
When you are satisfied that the contact area is OK, smear both sides of
the mica washer with heatsink compound, then bolt the assembly together
as shown in Fig.3. The three connecting leads from the PC board can then
be soldered to the transistor pins.
Finally, use your multimeter to confirm that Q5 's collector is indeed electrically isolated from the lid.
Final assembly
The PC board is secured to the lid
of the case by the pushing the switch
bushes through matching holes and
doing up the locking nuts. Before doing this, however, fit the LED to the
lid of the case by pushing it into its
mounting bezel. This done, rotate the
LED so that its anode and cathode
leads will mate with the appropriate
holes on the PC board (the anode lead
is the longer of the two) and fit the
locking ring.
Two sets of mounting nuts are supplied for switches SZ and S3 and one
nut should be fitted to each switch to
provide support for the back of the
lid. The nut for SZ should be done all
the way up, while the nut for S3
TABLE 1
Battery Voltage
Endpoint
3.6V
3.3V
4.8V
4.4V
6V
5.5V
7.2V
6.6V
8.4V
7.7V
9.6V
8.8V
10.8V
9.9V
12V
11V
The assembled PC board is secured to the lid of the case as shown in this
photograph. Note that although LED 1 is shown here mounted on the board, it is
normally fitted to its bezel first & its leads slid through matching holes in board
when the latter is mounted in position.
should be positioned just over half
way up the bush. In addition, star
washers should be fitted to all the
switches (see photo).
The PC board can now be mounted
on the lid by guiding the switch bushes
through their mounting holes and
making sure that the leads from the
LED pass through their mounting
holes in the PC board. This done,
install the switch locking nuts, then
solder and trim the LED leads.
The battery leads exit through a
hole in the top of the case. Tie a knot
in these leads just before the exit point,
so that the leads cannot be pulled out,
and terminate their free ends with
alligator clips (or some other suitable
connector). Use a red alligator clip for
the positive lead and a black alligator
clip for the negative lead.
MICA
WASHER
~
NUT
\
PLASTIC~r
SIDE
SCREW
~
-CASE LID
/
T0128
DEVICE
Fig.3: transistor Q5 must be
electrically isolated from the
lid of the case using a mica
washer as shown in this
mounting diagram. Check that
the mounting surface is smooth
& smear both sides of the mica
washer with heatsink
compound before bolting the
assembly together.
Test & adjustment
The unit is tested by substituting a
variable power supply for the nicad
battery pack. First, set the discharger
to the 12V range, then connect it to
the power supply and set the supply
to give an output of 15V. Trimpot VR1
should initially be set to its mid-range
position.
Now press the START button. The
DISCHARGING LED should immediately come on and should stay Qn
when the button is released. If it does ,
the circuit is working correctly and
you can check that it automatically
switches itself off at some point by
slowly winding the supply back until
the LED suddenly goes out.
Finally, the circuit can be calibrated
by setting the supply to 11 V (exactly)
and adjusting VR1 until the LED just
goes out. Make sure that the discharger
is set to the 12V range during this
procedure. The remaining seven
ranges can then be checked. The
endpoint voltages should be very close
to those listed in Tabie 1.
If there are any significant variations from the listed values, check the
resistors in the divider chain.
SC
NOVEMBER
1992
43
SERVICEMAN'S LOG
I did it; but it wasn't my fault
That heading probably sounds like a half-baked
admission by a mayhem suspect who maintains
that he was influenced by an evil spirit. In fact, it
is an admission by the author but I still maintain
it wasn't my fault.
This all started when I was conned
into a job which, in the normal way, I
wouldn't have touched with 12.192metre (40ft) barge pole. Which brings
me to the real background for this
month's notes - the problem facing
servicemen when presented with
faulty appliances which are completely out of their field. They are jobs
which usually result from a plea by a
relative or personal friend.
It matters not that the particular
appliance is one that you know nothing about; that you've never seen inside one and have absolutely no technical data or circuits for reference. If
it "works by electricity", you're it
mate!
In this case, it was a telephone answering machine, owned by an inlaw and presented to me during a
FRACARRO
SAVES•••
... more than $10. from every UHF
television antenna you buy.
Fracarro's
4PUN
for better
performance
from weak
UHF
signals.
Peter C. Lacey Services Pty. Ltd.
P.O. Box 678 (74Fulton Rd.) Mount Eliza 3930
Tel:03 787 20TT Fax:(03) 787°3460 ACN006893438
44
SILICON CHIP
social visit. And the bloke concerned
introduced it with a typical con µ1an's
approach; the supposedly flattering,
"You know all about these things". I
made a feeble attempt to disclaim such
expertise but in vain.
So what was the problem? Having
moved beyond the "it doesn't go"
stage, I learned that it had failed to
deliver its "no-one-at-home" spiel (or
the outgoing message as it is described
in the user's manual), leaving the caller
with the impression of a lifted handset but no reply.
Further study of the manual put me
more in the picture, at least at a general level. It was a combined telephone
and answering machine and used a
single tape. This latter point was
important, because it meant that the
outgoing message was recorded digitally in a chip. In fact, the length of the
message is limited to 16 seconds;
enough, but only just.
Volatile recording
Naturally, this is a volatile recording; it needs to be continually powered. This prompted the obvious
query; had the outgoing message been
lost due to power failure? The unit is
powered from the mains via a 9V AC
plugpack, but also takes some power
from the telephone line and is fitted
with a backup battery. Had the unit
been left disconnected from the phone
line or mains? And how old was the
battery?
As far as we could determine, no
such failures had occurred. The batteries were fairly new and, I assumed,
would be limited by their shelf life.
In any case, I realised that it was
possible to check the message quite
readily; pressing one button (START)
replays it through the speaker for
checking. And it did, very faintly; so
faint that I had to put my ear down to
the speaker to follow it.
But it was quite clear. And when I
pressed the button a second time, it
came forth at full bore. The next time
I tried, it was at mid level. And so it
went on; each time I pressed the button, the level varied and sometimes it
was so faint that there was little chance
it would be heard at the end of a
typical phone line.
A bench job
Well, that was enough on-the-spot
diagnosis. To have any chance of real
progress, I would have to tackle it on
my own bench. Not that I was very
confident. The best I could hope for
was an obvious faulty connection - a
dry joint, a faulty plug and socket
assembly, or something similar.
On the bench I established that I
could take it apart by releasing four
screws. But one of the screws was
under the backup battery - four AA
cells - so I had to plug it into the
mains, remove the cells, undo the
screw, then replace cells to restore the
backup. That done I could remove the
top of the case. This carried the tape
deck, the dial pad and the control
buttons, plus the handset receptacle
and switch hook. It was connected to
the main board in the lower half of
the case via a short 18-conductor flat
cable, which proved quite a nuisance
at times.
I was even less confident when I
looked at the board. Oh, it was well
enough put together but the vast array
of components and the complex wiring pattern, for which I had no circuit, were very off-putting; it made
me realise that I was flying completely
blind.
Anyway, I plugged it into the mains,
hoping that the backup battery had
held the fort while all this was going
on, and pressed the START button
again. As it turned out, the message
was still there but it was very erratic.
In one sense, that was the good news.
If it was all that sensitive, some careful prodding and tapping might find
the cause.
And so I started. I didn't get far at
first; the whole board was touchy. I
found a couple of more sensitive areas and went over them with the jeweller's loupe, looking for dry joints. I
picked a couple of suspects, which I
resoldered, but it didn't do any good.
Nor was the job made any easier by
the need to activate the message continually, with only a 16-second burst
each time.
Still, I persevered. Eventually I
found myself in one corner of the
board, near a 16-pin IC mounted in a
socket. I had no idea what this IC did
but it was very sensitive to even the
slightest touch. Naturally, my first
suspect was the IC socket - after all,
I've seen enough faulty sockets in TV
sets.
So, as a first step, I pulled the IC
out, squirted the socket with contact
cleaner, and put the IC back in. Result
- the unit went completely dead, at
least initially. It did show some life
after some more prodding but it still
wouldn't deliver the message. Had
the IC or the socket finally failed for
good?
And if the IC had failed, could I get
a replacement? It was identified simply as a type 250K. I rang around my
most likely suppliers but no-one could
p1ace it. And the situation wasn't
helped by the fact that I didn't have a
clue as to its function.
It was time to ask for help. I don't
know where the machine is made but
it is handled by a local company,
which I tracked down via the phone
book. I rang them and asked for the
service department: No joy; the service technician was out for the day. But
the young lady took my name, phone
½. Price
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Address
0
~9:z •...
l: WA.S FL-"<ING COW\~L-E.'T"E-\...Y ~L-\Nt>
Postcode
L-------------.J
NOVEMBER
1992
45
SERVICEMAN'S LOG - CTD
number, and brief details of the unit,
and promised he would call nie the
next day.
Surprise, surprise! He did. And he
was most helpful. When I related my
story, he immediately identified the
IC. It was the outgoing message
memory chip-which explained a lot.
Was a replacement chip available? Yes,
it was worth only a few dollars.
Crook socket
But his bet was the socket. He suggested that I replace it first to see if
that cured the problem and then,
if that failed, replace the chip.
But he ruled out a suggestion that
I solder the chip directly into the
board. These chips are quite temperature sensitive and don't like
being soldered. He also promised
to send me a circuit, which turned
up in the mail the following day.
Full marks all round!
And so, from my local supplier, I purchased a machine pin
type IC socket; beautifully made,
with solid, gold-plated, contacts.
This was duly fitted and bingo ,
that was it. I recorded a new message and it played perfectly. It
was almost an anti-climax.
Normally I would have returned the unit at that stage but it
wasn't convenient for either of
us to make the journey. So I took
it home for the weekend, plugged
it into a convenient extension
outlet, and set it up to say its piece.
Of course, no-one rang, not even a
cladding salesman. At least not until
late Sunday. Unfortunately, when that
call did come through, the machine
ignored it but not as it had done before. This time, the machine didn't
respond at all; it simply didn't know
that the call was there.
Well, that was a real setback. As I
have remarked before, there is nothing more frustrating than to cure one
fault and then discover that you have
apparently created another. So what
had· I done? And how should I tackle
it?
Most importantly, I needed a ringing signal to work with. I considered
a number of possibilities but settled,
initially, for Telecom's own ring-back
facility, as used by their technicians
46
SILICON CHIP
to check ring functions (don't ask me
how I know this).
Back on the workbench on Monday
motning, I first used the ring-back to
confirm that the failure was not just a
one off - which it wasn't. This also
revealed something else; something
which had been masked in my home
set-up by the nearby regular phone.
There was no ring tone being given
out by the machine.
At this point I fished out the circuit
and began analysing it in detail. I
started with the incoming phone line
a standard arrangement in handset
circuits; it takes power from the phone
line to drive the handset. And it is
necessary because although the supply is DC, its polarity reverses with
certain functions, such as answering
an incoming call.
So I mentally wrote that one off for
the moment. The other bridge would
·also have its counterpart in a handset.
It can respond only to the AC ringing
pulse and drives the ringing tone generator. It obviously performed this
function in this circuit but did other
things as well, such as instructing the
answering circuit to (electrically) lift
the handset and then initiate the outgoing message.
So, since I was getting neither
a ring tone nor the answering
function, it was the obvious circuit to check. I checked the bridge
diodes first but they were OK. I
then went back to the incoming
line and worked towards the
bridge. It went through one of
the hook switch contacts, then
the lµF capacitor and a 4.7kn
resistor. The bridge output circuit involved several more components, including a zener diode
and an electrolytic capacitor.
Crook joint
so
FO'R
--root< ,.,.. 1-\0M~
11-\e:. WG:~i<: ~NP.....
~
which is marked "R" and "T" for some
reason which escapes me.
Slowly it began to make sense. The
first thing I realised was that the telephone circuitry, which is normally
contained within the handset, formed
part of the main board. This is natural
enough,Isuppose,butitaddedtothe
complexity of both the board and the
circuit.
However, I soon had the circuit
mentally divided into three sections;
the aforesaid telephone section, the
tape recorder section, and the answering section proper with its control
switches and housekeeping circuitry.
So back to the incoming line. This
goes to two bridge rectifiers - directly
to one in the DC sense and indirectly
to the other via a lµF polyester capacitor. The direct-coupled bridge is
The soldered connections to
the switch lugs checked out OK
visually and the ohmmeter confirmed the switch function. Next
was the lµF capacitor and this
was where things began to happen. One soldered joint was
clearly OK but the other one
looked suspicious. About half of the
joint was covered with flux (not unusual on this board), while the visible
solder that remained just didn't look
right.
Although the solder extended over
the track, it was tucked under, rather
than flowing over the surface. Naturally, I wanted to see the rest of the
joint to be sure it had flowed onto the
pad proper. So I started picking away
at the flux, which turned out to be a
substantial lump. In fact, it was all
flux; I finished up right down on the
board and still no solder.
More importantly, there was no copper either; I was looking at bare board.
I reached for the solder wick and
soaked up the remaining solder. And
what a sight! The copper pad was
completely missing; it had broken off
at the end of the track. And the only
indication of a soldered connection
was a barely visible run of solder along
the broken edge of the copper track,
so faint as to need the jeweller's loupe
to confirm it. There was no solder on
the surface of the track.
How this had happened I can only
guess. It seems likely that the original
joint had been faulty and someone
had tried to repair it, but they had
been too heavy handed with the iron
and the copper pad had lifted and
broken off. They had then tried to run
the solder onto the track but it had
taken only to the bare copper along
the edge of the break.
This had made a genuine soldered
joint but a very fragile one. It may
have lasted indefinitely had I not gone
through my prodding and tapping routine, looking for the first fault. And
I'm quite sure that the 1µF capacitor
was one of the components that I had
wiggled and pushed in the process.
So, yes, I did it but it wasn't my
fault.
The repair was simple. A short
length of fine tinned copper was
wrapped around the capacitor pigtail
TETIA TV TIP
Akai VS-4E Video Recorder
Symptom: can 't remember channels after power failure. The set
works quite normally and remembers all settings, so long as power
is kept up. And it wasn't the backup
battery!
Cure: With the power off, check
for 3.5V on pin 41 of the "syscon"
microprocessor. If the voltage is
present, replace this chip. If not,
replace switching transistors TR5
and TR6.
TETiA TV Tip is supplied by the
Tasmanian branch of the Electronic Technician's Institute ofAustralia. Contact Jim Lawler, 16
Adina St, Geilston Bay 7015.
and soldered to it. This was then run
directly to the switch contact at the
other end of the track, only about
20mm away, and soldered to that. And
from somewhere a voice muttered,
"muck about with that if you can."
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Computer illiterate
As a serviceman, I long ago swore I
would have nothing to do with them
- computers that is. In my opinion,
they were only ever invented for one
reason: to provide incompetent clerical staff with an irrefutable excuse
when they foul up one's account, or
order, or payment. And the computer
can't defend itself.
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0.02Hz-2MHz, with SWEEP
■
That fixed it, of course. I ran it on a
workshop extension for a couple days,
allowing it to answer calls, then overriding it manually. It never faltered.
So it was duly returned to the inlaws. They were very grateful but obviously had no idea of the problems
the monster had created. But I've no
doubt I'll get the choice cut of the
turkey at the next Christmas get-together. Oh well.
(Just one final thought. Once it was
established that the type 250K IC was
a memory chip, someone made the
smart suggestion that 250K meant just
that: the storage capacity of the device. Why didn't I think of that?)
So what was the next unfamiliar
territory in which I found myself.
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Perth
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Adelaide ........................ (08) 362 7548
Hobart
.......... .... (002) 34 2233
NOVEMBER
1992
47
SERVICEMAN'S LOG - CTD
,-..,\,-\\CS F~e.:R AA"'D C?I\IE.N 1-\W\
"PgRlll\\'Ss,ol'\\ -ro us~ "™e: C.Otv\?o'f"6.R.
......_, 'c.V"\ W\-\E-N \\ E. SW rt""C\-\E-"D \T
<,N ON i\i\S oC(AS\ON, ,.,WE:.N1"" ''A\.-\- FUNN'<:~-.
More to the point, in the practical
sense, I know nothing about them. I
don't know a bit from a byte, or a ROM
from a RAM, although I remember the
hydraulic ram from my boyhood days
in the country. (My dictionary tells
me that I am "incomputerate; without
a working knowledge of computers or
their technology". Couldn't have put
it better myself).
So this is a story about my being
forced into a computer service, job,
and breaking my solemn oath. But, in
defence, I must claim that it was only
a little job, so perhaps my oath was
only a little bit broken.
And again, the job resulted from a
plea based on personal friendship,
coming from the 14-year old boy who
lives next door. His father had given
him permission to use the computer
to write his school assignments but,
when he switched it on on this occasion, it went "all funny".
I started to present my stock reply;
that I knew nothing about computers
and could easily do more harm than
good. But curiosity overcame my caution and I made the fatal mistake of
asking in what manner it had failed.
48
SILICON CHIP
And apparently it had presented a
message saying "insert disc" - which
I am given to understand is quite normal - but this message was rolling
and also jittering sideways.
I was caught. The assignment was
fairly urgent and getting a repair
through normal channels would take
time. I simply didn't have the heart
not to try. I said I'd take a look and see
if there was anything I could do.
More to the point, I had gained the
impression that it was simply a monitor fault and, I told myself, a monitor
is only another type of TV set. Granted,
there was probably a lot of signal decoding circuitry in it which would be
double Dutch to me but I was hoping
for a simple power supply fault.
The hula girl
My first look at the screen pattern
seemed to support this. When it wasn't
rolling, I gained the impression of a
typical hula girl fault; hum in the
horizontal scan. But the rolling was
less easily explained. I decided to take
everything along to the workshop,
where I could use the CRO an<l have
time to think.
The monitor carried the "Magic"
brand, was made in Taiwan, and was
fairly old. I opened it, found the video
input, connected the CRO to it, and
powered up the whole system. This
seemed to clear the computer, because
the video signal, with horizontal and
vertical pulses, appeared normal.
But further investigation was hampered by the physical layout. The
power transformer was mounted on a
separate rear panel and connected to
the main board via a pair of very short
leads and a 2-pin plug. This made it
very difficult to access the main board,
so I unplugged the transformer and
put it and the panel to one side.
Examination of the board revealed
a very conventional supply; the transformer fed a bridge rectifier, which in
turn fed a conventional 12V regulator
IC, plus the usual filter capacitors.
The next step was to restore power
and check the supply. I had two options: (1) extend the transformer leads;
(2) or feed in power from another
source. The latter was the easiest and
it so happened that a low voltage DC
supply was the most convenient
source. OK, so that should go straight
through the rectifier and into the voltage regulator.
As soon as I connected the supply,
the monitor came good, with no rolling and no hula dancing. So what was
the problem? I found out by accident.
In order to gain better access to the
circuit, I disconnected the DC supply
leads, moved things around and then
reconnected them. And at that point,
everything went dead.
I then realised that I had probably
transposed the power supply leads
but, of course, that shouldn't matter
when feeding a bridge rectifier. If it
was a bridge rectifier, that is. Well, it
was supposed to be but it wasn't; one
of the diodes had gone open circuit.
Yes, it was as simple as that. A few
cents worth of power diode and it
was going like a bought one.
I took it back home at lunch time
and delivered it to a very grateful
neigh):mur. And my fee? I didn't have
the heart to charge him. He is obviously a diligent student, prepared to
work hard; and youngsters like this
need a break now and again. (Must be
getting soft in my old age).
So I wrote it off to experience. At
least I can now claim - albeit tongue
in cheek - that I have had some experience in servicing computers.
SC
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FINALLY AVAILABLE AGAIN . ..
MINI VACUUM ATTACHMENT KIT
Cat XV-5060 $19. 9 5
12" 200WRMS GUITAR
SPEAKER SALE
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etc.
AM7910 World Modem Chip
ASl461/BF010 Dual NCH JFET
XR2240 Prag Time/count
4164120ns DRAM
611 6 Stat RAM
6264 RAM
LM348 Quad 741 OP Amp
Red rectangular LED
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TRANSFORMER BARGAIN
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There are so many different mini vacuum cleaners on the market, most of them are expensive and don't
really work all that elfectively. This unique
product simply plugs into the end of your
existing household vacuum cleaner hose
and away you go .
OVAi BRUSH
Supplied wilh: • an adaptor to suit all
vacuum cleaner hoses • 1 x 80cm clear
ROUND BRUSH
flexible tubing • 1 x straight and curved
extension pipe • 1 x oval brush • 1 x
round brush • 1 x crevice tool. Great for
ANY WACUU ■ HOSE
cleaning computers, typewriters, office
machines, stereo and video equipment,
~lOlP~ER
$29.95
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Save $10 this month. Power handling 60 watis rms.
Frequency response 55-4kHz. See catalogue for full
specifications.
Cat cwNormally $42. 95
2114
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Another surplus job lot Th is time an Arlec brand supply. Input
.ECTRO
240V AC output 6V AC 3 amp.
.ECTRO
.EC TRO
TURN YOUR SURPLUS STOCK INTO CASH!
It's housed in its own box with the 240V power lead from one side
.ECTRO
Jaycar wil l purchase your surplus stocks of components and equipment. We are continually on the
and 1he 6V cable lead from th e 0ther terminating to a 2-1mm DC
.ECTRO
plug. Cat. MP-3023
.EC TRO
lookout for sources of prime quality merchandise.
O
.ECTRm
.E CTRO
Call Mark Harris or Bruce FJoutley now (02) 743 5222
.ECTRO
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" ICS JAYCAR ELECTRONICS JAYC AR ELECTRONICS JAYCAR Fl FCTRONfCS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAY CAR ELECTRONIC S JAYCAR
" ICS JAY CAR ELECTRONICS JAYC AR ELECTRONICS JAYC AR FLFCTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONfCS JAYC AR ELFCTRONICS JAY CAR
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Huge 50oz magnet. Frequency response 45 - 5kHz. See
catalogue for fu ll specifications.
Cat CG-2381
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Many of these transistors can be substituted for each other despite differences in
their part numbers. The reader can easily identify these transistors from 8 major
manufacturers with different type numbers but identical performances.
Cat. BM-4570
$17.95
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ELECTRo,::cs
ELECTf,ON ICS
ELFCTRON ICS
ELECTRONICS
ELfCTRONICS
EL~CTRONICS
JI\YCAR
J AYCAR
JAYCAR
JAYCAR
JAYCAR
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ELECTRONICS
ELECTRONICS
ELECTRON ICS
EcLECTRONICS
FLECTRONICS
FLECTRONICS
JAYCI\R
JAYCAR
JAYCAR
JAYCI\R
JAYCAR
JAYCAR
ELECTRON ICS
ELECTRONICS
ELECTRONICS
FLECTRONICS
ELECTRON ICS
ELECTRONICS
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
ELEC TRONICS
ELECTRONICS
ELECTRON ICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
JAYCI\R
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
ELEC TRON ICS
ELFCTRONICS
ELECTRONICS
ELECTRONICS
ELECTRON ICS
ELECTRON ICS
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
ELECTRONICS
ELECTRONICS
ELECTRON ICS
ELECTRONICS
ELECTRONICS
ELECTRON ICS
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
ELECTRON ICS
FLFCTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELFCTRONICS
ELECTRONICS
ELECTRONICS
JAYCAR
,JAYCAR
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JAYCAR
JAYCAR
JAYCI\R
ELECTRON!
ELFCTRONI
ELECTRON!
ELECTRON!
ELECTRON!
ELECTRON!
~ICS
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~ICS
~ICS
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JAYC AR
JAYCAR
JAYCAR
JAYCAR
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ELECTRON ICS
ELFCTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONI CS
ELECTRONICS
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
ELEC TRON ICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
ELECTR ONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONIC S
ELECTRONICS
J AYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELFCTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
ELECTRONICS
ELFCTRONICS
ELECTRONICS
ELECTRONICS
FLECTRONICS
ELECTRONICS
JP
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LCTRO
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LC THO
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KITS
KA-11 09
KA-1115
KA-11 16
KA-1117
KA-11 19
KA-1 390
KA-1550
KA-1556
KA-1 574
KA-1630
KA-1660
KA-1675
KA-1682
KA-1683
KA-1690
KA-1 692
KA-1693
KA-1696
KA-1699
KA-1702
KA-1 706
KA-1 717
KA-1 718
KA-1719
KA-1720
KA-1724
KA-1725
KA-1726
KA-1728
KA-1729
KA-1730
KA-1731
KA-1 732
KA-1733
KA-1 734
KA-1735
KA-1736
KA-1737
KA-1738
KA-1739
-
Electric Fence
300W amp module
300W power supply
300W speaker protector
Transistor tester
Freq counter 50MHz
Deluxecar alarm
Ultrasonic move delector
30V 1A power supply
12V lamp flasher
Electric fence
Screecher car alarm
Dual track power supply
Baltery monitor
DI box
Voice operated relay
Metronome
Econ. Temp probe DMM
Bench amp-signal trace
50MHz Dig Freq meter
Cheap capacitance meter
Subwoofer Adaptor
Auto NiCad charger
NiCad discharger
RGB to PAL encoder
Volt up 1.5Vto 9V
Pro series 1 power amp
Pro module less mosfets
VHF powermatch
RF probe - suit above
Pro series 2 pre-amp
Transistor/Fet tester
Flexi timer
CRO adaptor
Quad 01box
CROAdaptor for Monitors
18V 1A Bench Supply
Speech Proc for Transceiver
Karoake Box
Low Voltage Cutout
KITS
$24.95
$89.95
$115.00
$19.95
$21.50
$169.50
$59.50
$34.95
$99.50
$12,95
$64.95
$39.95
$149.95
$14.95
$39.95
$24.95
$19.95
$19.95
$44.95
$79.00
$21.95
$29.95
$39.95
$29.95
$49.95
$19.95
$599.00
$47.95
$52.50
$7.50
$329.00
$32.00
$17.95
$24.95
$69.95
$159.50
$79.95
$29.95
$27. 95
$22.95
KA-1740
KA-1741
KA-1742
KA-1743
KA-1744
KA-1 745
KC-501 2
KC-5013
KC-5019
KC-5021
KC-5028
KC-5030
KC-5031
KC-5032
KC-5038
KC-5039
KC-5041
KC-5042
KC-5051
KC-5052
KC-5058
KC-5059
KC-5072
KC-5075
KC-5076
KC-5077
KC-5079
KC-5080
KC-5083
KC-5084
KC-5085
KC-5089
KC-5090
KC-5091
KC-5092
KC-5094
KC-5095
KC-5096
KC-5097
KC-5098
AND
240V Power Relay
Dolby Surround Sound
Sine/Square Wave Generator
1MHz Pulse Generator
Audio Sweeper - Low Cost
Flexible Speaker Protector
Car radio power supply
16GHz Digilal Freq meter
100W amp module
Protector car alarm
Train controller
High Energy Ignition
Optical lacho
Disco Light
Universal power supply
Vader Voice
Mini Mitter
Knightrider LEDs
CD Compressor
Touch Lamp Dimmer
Multimeter Kit
Radfax decoder
Digital voice recorder
CAP meter 1pF - 9999uF
Reluctor high energy
Stereo PRE AM P
Sine/Square Wave Gen
Horace the cricket
3 Digit counter
VCR Remote control ext
Discol ight dimmer
Two Tone Siren
Sinewave Oscillator
20WFluoro Inverter
12V Lighl chaser
Stereo Audio Expander
DTMF Decoder
4 Ch Lighting Desk
Masthead Amp
Digital Tacho
$49.50
$39.95
$55.00
$89.50
$99.00
$29.95
$28.95
$249.00
$45.95
$49.50
$89.00
$55.00
$49.95
$169.50
$12.95
$19.95
$34.95
$17.95
$49.50
$34.95
$38.95
$44.95
$79.50
$89 .00
$46.95
$32.95
$149.50
$18.95
$23.95
$32.95
$39.95
$9.95
$16.95
$32.95
$21.95
$39.95
$79.95
$329.00
$49.95
$34.95
WHAT A FLOP!
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We've made a bulk purchase of pink high quality 13/. 12
tinned hook-up wire. Not terribly exciting, but at this price
grab a rol l or two, you cou ld even use pink instead of red.
Note: extra postage may apply if several rolls are ordered
on th eir own.
Cat. WH-3018
We don't know why, but nobody wants them I
They are IEC297 32 slot card frame (3U). See
our 1992 catalogue page 38. BELOW COSTSAVE A FORTU NE
Cat. HB-5360 WAS $129
$39
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NORMALLY $11 per 100mt roll
This pack co ntains even more capacitors than the
one it replaces. It contains about 175 assorted
capacitors. Many are normal stock lines. Includes
greencaps, ceramics, high voltage ceramics,
polystyrene, electrolytics in RT and RB. Every
pack includes one 1000µF 63V can electrolytic
(Cat. RU-6743) worth $4.50 alone! At normal
prices these capacitors wou ld cost over $80 1
cat. RE-6260
ON•v $10
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*
SAVE $i
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XC-4722
3.5" DSHD
XC-4726
XC-4727
5.25 ' DSOD
5.25" OSHD
_ _ __
catalogue for fu ll details.
Cat. KC-5071
"
WAS $69 NOW
SAVE $30
$39
_ _ _ _ _ _ __
JAYCAR WILL NOT BE
UNDERSOLD ON GOODS OF
THE SAME QUALITY
ELECTRONICS
ELECTRONICS
ELECTRONI CS
ELECTRONICS
JAYCAR
JAYCAR
JAY CAR
JAYCAR
,
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
JAYCAR
JA YCAR
JAYCAR
JAYCAR
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRONICS
JAYCAR
JAYCAR
JAYCAR
JAYCAR
ELECTRONICS
ELECTRONICS
ELECTROt, ICS
ELECTRONICS
JAYCAR
JAYCAR
JAY CAR
JAYCAR
ELECTRONICS
ELECTRONICS
ELECTRON ICS
ELECTRON ICS
JAYCAR
JAYCAR
JAYCAR
JAYCAR
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ELECTRONICS
ELECTRONICS
ELECTRONICS
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department for
quantity prices
9.50 $39.50
$18.95 $14.95
$26.50 $19.50
E
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NU A TURERS
Contact our
wholesale
ave a ortune over normal prices. Not all types
~vailable at all stores. Limited quantities ,
at
Type
WAS
NOW
XC-4721
3.5" DSDO $26.50 $19.50
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PRESENTS
$39.95 NOVEMBER
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ONE FOR
CHRISTMAS
$4
Ref: Silicon Chip March 1990
It's been replaced with a new model, but
still works O.K. Short form kit. See 92
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NUMBER
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$32.95
$42.95
$19.95
$34.95
$1 10.00
$24.95
$34.50
$49.95
$99,00
$399.00
$329.00
$29.95
$84.95
$59.95
$89.50
$37.95
$129.95
$49.95
$17.95
$24.95
$27.95
$69.50
$13.95
$39.95
$22.95
$22.50
$14. 95
$27.50
$34.50
$29.50
$34.95
$11.95
$26.95
$45.00
$13.95
$37.95
$27.95
$12.95
The phone holder is like a hand and holds the phone. This "hand " can then be mounted very easily in
different places in the car. It has a suction disc which allows the phone to be mounted on the drivers
side window, from the cigarette lighter plug, or on the door. The phone holder fits any brand
telephone and car, and there is virtually no instal lation. It is a quality, we ll made product that will
BRAND NEW RUN OF
MIXED CAPACITOR PACKS
"
PCVoice Recorder
Talking Vollmeter
Steam Sound Mk2
Solar Batt Charger
TV Pattern Gen
Baby Monitor
Light Beam Relay
Guitar Mixer - 4 Channel
12-240V 40W Inverter
Power Supply 0-45V BA
SOW+ SOW Stereo Amp
Telephone CalI Timer
Substation Intercom PSU
Substation Intercom
VHF TV Transmilter
Thermostatic Switch
Video Switcher
12-240V 15W Inverter
Off Hook Telephone Timer
12VGel Baltery Charger
NiCad Battery Discharger
240V 6/12V Gel Battery Charger
1.5V - 9V DC Converter
5A Drill Speed Control
Mini Stereo Amp
Si gnal Speaker protector
NiCad battery charger
ETl480 SOWamp module
ETl480 1OOW amp mod
ETl480 power supply
4 sector house alarm
Mini FM transmitter
Parametric equaliser
Guitar preamp
Solar Generator
Workhorse amp
RS true 232 interface
FM minder bug
...J
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KC-5099
KC-5100
KC-5101
KC-5102
KC-5103
KC-5105
KC-5106
KC-5107
KC-5108
KC-5109
KC-5110
KC-511 1
KC-51 12
KC-511 3
KC-5114
KC-5115
KC-5116
KC-5117
KC-5118
KC-5119
KC-51 20
KC-5121
KC-5122
KC-5123
KC-5124
KE-4023
KE-4029
KE-4050
KE-4052
KE-4048
KE-4698
KE-4711
KE-4724
KE-4729
KE-4730
KM-3050
KM-3065
KM-3068
NOW
SA"E
A
MASSIVE
$90
'"'Y
~::::::::::::::::::::::::::::..-
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JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
;s JAYCAR
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,S JAYCAR
'S JAYCAR
;s JAYCAR
JAYCAR
;s JAYCAR
'S JAYCAH
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;s JAYCAR
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r
SAVE 25% ON CELLULAR PHONE HOLDER
NOW $3.50/l00mt
_ECTRC
_ECTRC
LEC TRC
LEC TRC
ELECTRONICS
ELECTRONIC S
ELECTRONICS
ELECTRONICS
ELECTRONICS
ELECTRON ICS
,S
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MORE KITS
PINK HOOK-UP WIRE!
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JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
JAYCAR
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N O VEMBER
1992
57
VINTAGE RADIO
By JOHN HILL
Converting a battery set to
mains operation
I recently completed a particular vintage radio
project that had been at the back of my mind for
quite some time. A fairly ambitious scheme, it
involved the conversion of a battery receiver to
240V AC operation.
The reason for such an insane idea
is simple. I live in country Victoria
and the area abounds with old battery
receivers of various types. In some
localities, SEC power was not available until the late 1960s, hence the
abundance ofbattery sets. If these battery radios could be successfully c·onverted to mains operation, then such
a conversion could be well worthwhile in some instances. Well, that
was the theory anyway.
There are two ways of going about
such a conversion. One would be to
build a power supply that would duplicate the receiver's battery requirements. Although the receiver would
operate on mains power, it would still
be a battery set in both design and
performance.
The alternative approach is a fullyfledged AC conversion whereby the
set has additions such as a power
transformer, rectifier valve, and a suitable complement of AC-type signal
valves. An appropriate loudspeaker
and output transformer would also be
needed. I was to find out, however,
that this approach was not without its
problems and that it wasn't as easy as
I originally thought.
In theory, battery to AC conversion
should not be that difficult and should
be a straightforward project. After all,
it only involves totally rebuilding
about two thirds of the receiver and
adding a power supply!
The radio I converted was a 1935 4valve table model Radiola. I have two
of these receivers and the idea was
that if one ended up wrecked due to
an unsuccessful experiment, then the
other could still be retained as a battery set. That theory didn't work out
as planned either.
The project was nearly abandoned
at an early stage because I could not
remove the chosen chassis from its
cabinet. Due to mouse infestation, the
much piddled-on mounting bolts were
well rusted into round brass nuts
which were riveted to a turned-under
flange at the bottom of the chassis.
Three of the four bolts "squawked"
their way free but the last one only
turned the nut.
The big hole
A large hole had to be cut in the cabinet of the old Radiola to gain access to a
rusted nut & bolt so that the chassis could be removed. Eventually, the bolt had
to be cut with a hacksaw blade to free the chassis.
58
SILICON CHIP
It was at this stage that I realised
why there was a big hole in the bottom of the other cabinet. It hadn't
been' chewed by rats as I had first
assumed. Instead, it had been hacked
in by some distraught serviceman so
that he could obtain access to a problem brass nut that turned with the
bolt.
I did likewise but, despite the size
of the hole and the use of a pair of
locking pliers, I could not prevent the
round nut from turning. Eventually,
All this garbage didn't blow in during the last storm. Mouse infestation can
cause serious problems when it comes to restoring old radio receivers.
This photo shows one of the two 1935
Radiolas mentioned in the text. The
chassis and knobs from this set were
combined with the cabinet of the
other. Both were originally batteryoperated receivers.
adding an additional socket for the
rectifier.
Power transformer
The coils & IF transformers were mounted underneath the original chassis,
leaving the top of the chassis fairly bare. The dial drive mechanism was a
friction type but this was converted to cord drive for more reliable operation.
after cutting through the bolt with a
hacksaw blade, the chassis was freed
from its cabinet.
The original Radiola circuit is typical of the early to mid-1930s. Although
the tuning capacitor is a 3-gang type,
the set does not have any radio frequency (RF) amplification. The extra
tuning gang is for a preselector bandpass stage, which was a fairly common arrangement for a superhet of
that vintage with a 175kHz intermediate frequency. The extra tuned stage
was essential to avoid double spotting, a natural characteristic of the
low IF.
The valve complement of the bat-
tery-powered Radiola was as follows:
1A6, 34, 32 and 33. The 33 output
valve was one I had not encountered
before and while it looks like a 1D4, it
is a little different. According to the
valve specification manual, the 33 has
twice the output; ie, 0.7W as compared to 0.35W. Wow - what power!
Replacement valves
Suitable valves for the AC conversion were next on the list. The following were used: a 6A7 converter; a 6D6
IF amplifier; a 75 detector, AGC and
first audio stage; a 42 output; and an
80 rectifier. Unfortunately, this meant
changing every existing socket and
A power transformer was the next
item to be obtained and I was sure
that I had an AWA type that just might
fit the holes already punched in the
chassis. Unfortunately, it was different and the mounting lugs did not
match the hole positions.
The next transformer to bt3 considered was an old "Red Line" . It had 5V
and 6.3V filament windings and a
290V high-tension winding. It seemed
a bit of an odd one but it would have
to do. A rectangular hole was cut in
the chassis to mount it and it was
relatively easy to install. The 5V winding and the high-tension winding were
connected to the appropriate type 80
valve socket pins.
High tension filtering consisted of
a 550Q resistor with appropriate electrolytics on either side. This produced
a relatively hum-free DC supply of
around 250V, under a 50mA load.
Once into the conversion, it quickly
became apparent that there would be
only one complete receiver at the end
of the project. An open oscillator coil
and IF transformer set a pattern for
stripping the other set for spare parts.
What's more, one of the cabinets had
been previously refurbished and the
NOVEMBER
1992
59
stitution box, components of differing values can be switched in and out
of circuit at the turn of a knob:
IF stages
The AC conversion resulted in the chassis being almost completely stripped.
Note the mounting hole for the power transformer at front left. One of the end
panels is from the other chassis.
The IF transformers and the IF amplifier valve were the next to be wired
and this was a straightforward job.
What was to follow the IF stage was
quite another matter, however.
The AC version of this receiver uses
a reflex circuit whereby a particular
valve amplifies both radio frequency
and audio frequency signals simultaneously. But no way was I going to
invite trouble by converting to a reflex circuit!
I had on hand a 5-valve Airzone
circuit which uses a 6Q7 as a detector, AGC and first audio stage, ahead
of a 6F6 output. This circuit was followed fairly closely and was the basis
for the audio stages of the conversion.
The general wiring layout underneath the chassis ended up a bit of a
mess. There were connections on top
of other connections, joins in the wiring and some of the components used
were far from the 1935 originals. It
would make any purist throw up his
hands in horror, hence there is no
under-chassis photograph accompanying this story.
Next time, I will use a few more tag
strips to make component mounting
neater and more secure. One really
needs to do a few of these AC conversions in order to know where best to
arrange all the components.
Dial mechanism
This old "Red Line" power transformer worked in well with the receiver's
requirements. The 80 rectifier valve is immediately behind the transformer.
veneer had been rubbed down to paper thin.
The plan was to retain the front end
of the receiver as it was. The tuner, its
associated coils and the IF transformers would remain as original. The
leads to the 1A6 and the 34 valve
sockets were disconnected and tagged
with labels -Gl , GZ, A, etc. That way,
they would be easy to reconnect to
the new valves with their different
socket connections.
In the original wiring, the 1A6
pentagrid converter had no dropping
resistors to supply the valve elements.
The plate and screen grid voltages
came straight from the B battery.
60
SILICON CHIP
When using a 6A7 converter, grid 2
(anode grid) and grids 3 and 5 (screen)
require dropping resistors from the
HT rail so that they operate at the
correct voltages. The old wiring cannot simply be reconnected to the new
valve without these circuit modifications.
A conversion of this nature requires
such additions so that the substitute
valves will function properly. One
must be prepared to experiment a little, though. Without a suitable circuit
diagram, one plays the trial and error
game and a couple of substitution
boxes (resi~tance and capacitance) are
handy in this regard. By using a sub-
Like many other receivers from the
mid 1930s, the old Radiola had a friction drive dial mechanism that was
chronically lacking in friction. But
although I have repaired many friction drives in the past, this particular
design is not an easy one to fix.
For this reason, I tried a different
app'r oach and converted the dial
mechanism to cord drive. This involved making a new control shaft
and fitting a dial drum to the tuning
capacitor spindle. There were a few
problems (mainly not enough room
for the drum) but eventually it all
went together and worked OK.
When the time arrived for the big
try out, it was a very exciting moment. But optimism soon turned to
despair! The best the set could manage was a few squeals on some of the
stronger stations. What could I expect
RESURRECTION
RADIO
Vintage Wireless Specialists
This rear view of the tuning capacitor shows the dial drum that was fitted in
place of the original friction drive mechanism. Lack of space between the drum
& the front plate of the tuning gang made the conversion difficult.
Repairs .,.. Restoration - Sales
Our skilled technicians offer QUALITY repairs and restoration.
We also have a large stock of bakelite and
timber radios fully restored and for SALE.
Parts are available for the enthusiast, including over 900 valve types, high voltage
capacitors, transformers , dial glasses,
knobs, grille cloth etc.
Circuit diagrams for most Australian makes
and models.
Send SAE for our catalog.
WANTED: Valves, Radios, etc.
Purchased for CASH
Call in to our showroom at:
51 Chapel Street (PO Box 1116),
Windsor, Vic 3181.
Phone: (03) 529 5639; Fax (03) 510 4486
counter a few minor problems, and
these must be tracked down and corrected. An additional resistor here and
a capacitor there can make the difference between the receiver just working and working really well.
Well that's the interesting part of
the project finished. The cabinet work
is all that remains to be done. It should
be a good cabinet to work on, due to
The finished battery-AC conversion - it's marvellous what a clean-up and a coat
its flat ;;urfaces and small size, as comof paint can do. The speaker is an 8-inch AWA "permag" from the late 1930s.
pared to a console cabinet.
Note the depth of the chassis.
Finally, a few words of advice. Battery to AC conversion is not as straightfrom such an outfit - part modified to blame for this and the substitution forward as one might think. If conoriginal and part Airzone? Time to boxes worked overtime.
templating such a task, give it plenty
The components causing most of of thought and try to pick a receiver
give it a rest for a while. Tomorrow
the problems were the resistors con- that's more suitable for conversion
would be another day!
After tracing through the web-like trolling the converter valve grids, couthan the one I chose. If it has octal
mess of wiring, it transpired that I pling capacitors in the audio stages
valves, it will be an advantage in that
had overlooked something very im- (0.02µF seems a good all-round figall the valve sockets will be compatportant - there was no bypass capaci- ure) and the plate bypass capacitor on ible with whatever AC valves are used.
the first audio valve. The Airzone cir- Using a proven circuit is also better
tor on the IF amplifier's screen grid.
cuit I was following used a 500pF than making up your own as you go.
Adding this vital component made
all the difference and the receiver burst mica bypass capacitor on the plate.
Converting a battery receiver to AC
This needed to be increased and a operation can be just as involved as
into life.
But although the conversion was value of 3300pF really smoothed out building a receiver from scratch. Unactually working, there were problems the harshness.
less you are prepared for that, then
When converting a battery set to . leave your battery set as you found it
with harshness and distortion. Incorrect component values were mostly AC operation, one must expect to en- and enjoy it for what it is.
SC
NOVEMBER
1992
61
See in the dark with this low cost
INF
RED NI
This infrared night viewer is simple to build. The
viewer itself requires no assembly. All you have
to do is assemble a battery powered high voltage
supply and connect it to the viewer. You can then
see in the night time to your heart's content.
By BRANCO JUSTIC
Ever wanted to see in the dark, when
it's pitch black and you're sure that
something sinister is lurking out there?
Of course you have. Everyone would
like to be able to see in the dark but
humans just don't have this capability. Or at least they didn't until infrared night viewers became available.
Infrared night viewers were first
used by the military at the end of the
second world war and were used extensively by the allied forces during
the Vietnam war. These days, they are
used by police forces around the world
for crime detection and also for identifying marijuana crops hidden in
otherwise apparently undisturbed
bushland.
Now you can have your own night
viewer for quite a small outlay and
with very little electronics assembly
required. With the night viewer to be
described here you will be able to see
in the dark as clearly as in the day - it
literally turns "night into day". There
are two ways of using it. First, you
can use it to observe night time scenes
under moonlight. For example, you
could use it to observe possums in
trees. Possums can be very hard to see
at night -you can often only see their
shadow but with the night viewer you
can see them as easily.
Alternatively, you can use the night
viewer in pitch darkness, together
with a torch fitted with an infrared
filter. This is the most dramatic demonstration. You can walk into a room
in pitch darkness, turn on a torch
fitted with an infrared filter and not
be able to see a thing. Then if you look
through the night viewer you will be
able to see just as clearly as if the
room was brightly lit.
IR viewers such as this do have
serious uses as well, such as examining the output of infrared lasers and
IR LEDs in appliance remote controls,
fibre optics, medical equipment and
so on. By the way, you should never
directly examine the output of an infrared laser or fibre optic cable. Shine
it on to a flat surface and then you can
safely observe the reflected IR light
with the viewer.
IR night viewers have been described in other magazines in the past
but they have generally required some
fairly specialised work in adapting
lenses to an irifrared imager module.
The unit described here requires none
of this work. It looks just like a set of
binoculars cut in half - which is effectively what it is. It has a length of
shielded cable which must be connected to a suitable high voltage supply.
So all you have to do is build the
battery powered high voltage supply,
connect it to the cable from the viewer
and the project is complete.
How infrared imagers work
The image converter tube is powered by a high-voltage power supply (left)
which develops about 13kV. This 13kV supply is derived using a single 9V
battery & a special voltage multiplier circuit.
62
SILICON CHIP
The special tube used in an infrared night viewer is sometimes referred
to as an "image converter tube". It is a
type of cathode ray tube but it does
EHT TO
VIEWER
680pF
3kV
680pF
3kV
not have a filament. It has a cathode,
an anode and a focus electrode. A
lens system in front of .the tube focuses the infrared image onto the cathode face. The cathode is coated (on
the inside of the glass) with a photoemissive material which responds
mainly to infrared light in the region
from 800 to 1200 nanometres but they
also have some response in the visible light region. When the target materials are hit by infrared light, they
emit electrons which are accelerated
by the high voltage which is applied
between the anode and cathode.
The anode of the image converter tube is
just like the screen of
an oscilloscope. It is
coated with a green
phosphor which gives
off light when it is hit
by high velocity electrons. So what happens is that the invisible irifrared image
which is focused onto
+
the cathode is convertT
9V I
ed to a visible green
......I
image on the anode
screen. This image is
then observed through
the eyepiece lens of the
viewer.
The focus electrode
on the image converter
performs the same
function as the focus
electrode on any cathode ray tube such as
an oscilloscope or television picture tube - it brings the
image into focus. However, later model
infrared image ·converter tubes such
as the one used in this monocular
viewer are of the prefocused type and
therefore do not require an external
focus electrode.
Since the monocular viewer de-
680pF
3kV
Fig.1: the circuit of the high voltage
power supply uses a transistor
blocking oscillator which produces
about 1.3kV peak to peak at the
transformer secondary. This is
rectified by the Cockroft-Walton
multiplier to produce about 13kV
DC. The link in series with the
2.7kn resistor allows a small
resistor to be added into circuit to
adjust the high voltage output but
this is not required for the tube
used in this project.
680pF
3kV
680pF
3kV
680pF
3kV
680pF
3kV
LINK
(SEE
TEXT)
680pF
3kV
01
1N914
2.7k
680pF
3kV
+
10
FOCUS
B
680pF
3kV
EOC
VIEWED FROM
BELOW
NIGHT-VIEWER POWER SUPPLY
scribed here comes complete with
lenses and is prefocused, all you have
to do is build the power supply shown
in Fig.1. This is essentially a one transistor blocking oscillator driving a
Cockroft-Walton :voltage multiplier.
Let's have a look at how the oscillator works first. It consists of a transis- ·
tor with its emitter connected to the
centre-tap (point 4) of the transformer
primary while its base is connected to
one side of the primary (point 3) via a
lOµF capacitor. The other side of the
primary (point 1) is connected to the
negative side of the 9V battery.
When power is first applied, tranNovEMBER
1992
63
The voltage multiplier "stack" occupies most of the space on the
power supply board. Keep all component leads short & don't handle
the board after power has been applied - it can deliver a nasty shock.
tor so that the base of the
transistor is driven harder.
The transformer core then
saturates and transformer
action ceases so that point 3
A special torch can be used to illuminate the
collapses to 0V which turns
target with infrared light when natural light
off Q2. This also causes the
levels are extremely low. Often though,
lOµF capacitor to be dismoonlight or reflected skylight (in cities) will
charged and so all action
be sufficient to let you view objects with
ceases.
reasonable clarity.
The lOµF capacitor must
then charge up to the point
sistor Ql obtains its base current via where the base of Ql again starts to
diode Dl and the 120n resistor. The conduct and the cycle recommences.
transistor conducts and applies 9V The result is a square wave signal
between the centre-tap and the 0V with a frequency of about 1 lkHz apside of the transformer winding (ie, plied to the transformer primary and
battery negative). Transformer action this is stepped up in the secondary to
then causes +18V to appear at point 3 about 1300 volts peak to peak. This is
and this "jacks up" the lOµF capaci- then rectified and stepped up in the
The completed PC board is mounted "edge-on" inside a plastic utility case. Note
the plastic barrier strip that's used to isolate the board from the battery & the
power switch.
64
SILICON CHIP
Cockroft-Walton multiplier stage to
around 13,000 volts DC.
Cockroft-Walton multiplier
The Cockroft-Walton multiplier
consists of 20 high voltage silicon diodes and associated high voltage capacitors. For those who wonder where
this rectifier circuit came from, it has
been around for a long time. It was
first used to generate voltages as high
as 200,000 volts to drive an atomic
particle accelerator developed by
Cockroft and Walton at Cambridge
University in the 1930s. These days it
can be used in a pressurised vessel
containing silicon hexafluoride to develop voltages as high as two million
volts.
For everyday use, the CockroftWalton rectifier configuration is suitable for any application which .requires very high voltages at low currents.
To understand how the CockroftWalton multiplier works, let us consider just the first few stages. Look
first at the circuit consisting of diodes
D2 and D3 and the two associated
capacitors. The rest of the diodes and
capacitors in the ladder above D3 can
be ignored for the moment.
In the first negative half cycle from
the transformer, diode DZ conducts
and charges the 680pF 3kV capacitor
in series with the transformer secondary. In the next positive half cycle, the
charged capacitor's voltage is added
to the peak of the transformer voltage
to cause diode D3 to conduct and
charge up its associated capacitor to
1.3kV. So far then, what we have de-
PARTS LIST
Fig.2: the component wiring diagram for the PC board. Make sure that
you get all the diode polarities correct otherwise the high voltage output
will be reduced.
scribed is the classic "halfwave voltage doubler" or "diode pump".
Subsequent negative and positive
half cyles from the transformer cause
this step-up pumping action to continue so that each capacitor in the
ladder is eventually charged to 1.3kV.
After twenty or so cycles from the
transformer, the voltage at the cathode of diode D21, at the top of the
stack, reaches about 13kV DC.
Also shown on the circuit of Fig.1
is a point marked "focus" at the junction of diodes D3 and D4. This is
intended to supply the focus electrode on IR imager tubes that require
it but, as previously mentioned, it is
not relevant to this project.
Construction
The circuit of Fig.1 is built onto a
PC board measuring 125 x 41mm. This
is designed to fit into a standard plastic utility case measuring 130 x 70 x
45mm.
The assembly of the PC board is a ·
repetitive job but it needs concentration otherwise you will find that some
diodes are in the wrong way around.
The high voltage diodes are BY509s
which are normally potted into triplers
for colour TV sets.
The ferrite potcore transformer is
supplied ready wound and the pins
are marked. All you have to do insert
it into the board and solder it. A battery snap needs to be soldered to the
board and the job is all but finished .
To finish the job, the board must be
installed in the plastic case and the
cable from the IR viewer connected to
it. You will need to cut a square hole
for the rocker switch (Sl) and drill a
hole for a grommet to fit around the
coax cable from the IR viewer.
With these holes cut and drilled,
fit the rocker switch to the case (it
just snaps into place), then pass the
cable from the IR viewer through the
grommeted hole and solder it to the
appropriate points on the PC board.
This done, slide the PC board into
place inside the case, as shown in one
of the accompanying photographs .
A sheet of 2mm thick plastic cut to
size is then placed in slots above the
PC board. This provides a separate
compartment inside the case for the
battery. This is necessary because the
metal case of the battery must not
come into physical contact with the
high voltage capacitors. A piece of
self-adhesive foam stuck to the bottom of the battery compartment will
stop the battery from rattling around
inside the case.
The 9V battery should be an alkaline type for long life. A clip fitted to
the lid of the case will allow you to fit
the supply to your belt for convenient
carrying.
Testing
With the battery fitted and the lid
of the case screwed on, you are ready
to try out the viewer. This can be done
in a dimly lit room. Turn on the power
-you should hear a high pitched w histle (provided you can hear 1 lkHz)
from the inverte'r - and then look
through the viewer. You should see a
greenish image. Try focussing the image for increased clarity.
And now for the pitch dark test.
While objects such as human bodies
do emit infrared radiation, the wavelengths are too long to be observed
WARNING!
This project generates an output
voltage of 13kV & is capable of
delivering a nasty shock. Always
make sure that the capacitors
have discharged before handling
the board after switching off the
power & never handle the board
while power is applied.
1 monocular IR viewer assembly
1 plastic case, 130 x 70 x 45mm
1 PC board, 125 x 41 mm
1 sheet of 2mm thick plastic, 125
x 41 mm (insulating panel)
1 prewound potcore transformer
1 belt clip (with adhesive back}
1 9V alkaline battery
1 battery snap connector
1 rocker switch (S 1)
Semiconductors
1 2N2219A NPN transistor (01)
1 1N914, 1N4148 diode (D1)
20 BUY509 high voltage diodes
(02-D21)
Capacitors
2 10µF 16VW PC electrolytic
20 680pF 3kV ceramic disc
Resistors (0.25W, 5%)
1 2:?kQ
1 1kQ
1 120Q
Where to buy the kit
The complete kit for this project,
including monocular IR viewer,
parts for the high voltage power
supply and 75mm infrared filter, is
available from Oatley Electronics,
PO Box 89, Oatley, NSW 2223.
Phone (02) 579 4985. The price is
$279 plus $6 for packing &
postage. Oatley Electronics can
also supply the power supply
separately and other types of IR
image converter tubes.
Note: copyright of the PC board
associated with this project is
retained by Oatley Electronics.
with the night viewer. So in a pitch
dark room it is unlikely that you will
see anything at all. In order to see
with the IR viewer, you will need an
infrared torch. "Where do I get that?"
you might ask.
The answer is that you will fit a
supplieq infrared filter to a standard
torch and that will do the job admirably. From then on, you really will be
able to see in the dark.
Just one thing though; after you have
finished playing around in the dark,
don't forget to turn off your newly
acquired torch. Since you can't see
the infrared beam it emits, it is all too
easy to forget to turn it off.
SC
NOVEMBER
1992
65
AMATEUR RADIO
BY GARRY CRATT, VK2YBX
A PLL demodul-ator for FM
•
amateur receivers
The use of a phase locked loop to demodulate
FM signals is largely overlooked in conventional
receiver designs, which normally use quadrature
detectors.·By comparison, a PLL FM detector can
be simpler, cheaper and easier to align.
To understand why a PLL is such a
good FM detector, it is necessary to
first know how such a circuit operates. The basic PLL concept has been
known and widely used since 1922.
Since that time, PLLs have been used
in instrumentation, -space telemetry,
and many other applications requiring a high degree of noise immunity
and narrow bandwidth.
PLL block diagram
A block diagram of a PLL is shown
in Fig.1. Phase locked loops operate
by matching their internal oscillator
frequency to that of an input signal,
Fin• In the "locked" condition, any
variation in the input frequency appears as a phase change between Fin
and the internal oscillator frequency.
This phase shift acts as an error signal
which causes a change in the internal
oscillator frequency to "track" the input frequency. The action of locking
onto the phase difference between Fin
PHASE
COMPARATOR
and the local oscillator frequency is
the basis of the name, "phase locked
loop".
Conventional circuitry for the reception of FM signals involves the
use of a quadrature detector, such as
the ever popular MC3357 and its derivatives. But although such circuits
provide good performance, they invariably require the use of an external
oscillator or, at the very least, a crystal
to mix to a (lower) frequency before
detection takes place.
In addition, the bandwidth of such
a circuit must be set by an external
filter, incurring additional costs and
complexity. In short, such circuits may
be suited to mass production but they
cannot easily be duplicated on the
kitchen table.
PLL advantages
A PLL circuit has significant advantages over the quadrature detector
as far as complexity is concerned. The
LOW-PASS
FILTER
VOLTAGE
CONTROLLED
OSCILLATOR
Fig.1: this is the block diagram for a phase lock loop (PLL). The
phase comparator produces the error signal to control the oscillator.
This configuration is widely used in both digital and analog circuits.
66
SILICON CHIP
frequency range over which the PLL
operates is controlled by a single DC
voltage which sets the centre frequency. No external filter is required
to produce an operational circuit.
The NE564 PLL featured in this
article can be configured to "detect"
at input frequencies of up to 50MHz
without external mixers. Hence, it is
ideally suited for operation at the
intermediate frequencies (IF) used in
typical VHF or UHF transceivers; ie,
10.7MHz, 21.4MHz and 45MHz.
Practical PLL detector
In fact, a complete IF strip can be
built using less than 20 passive components, with frequency adjustment
controlled by a single trimmer capacitor. Fig.2 shows our circuit for a
10. 7MHz PLL detector.
The input signal is fed to pin 6 of
the NE564 and the audio output is
produced at pin 14. Loop filtering is
provided by the network attached to
pins 4 and 5, while the oscillator frequency is set by the capacitance between pins 12 and 13.
Apart from DC connections to pins
1, 3, 9 & 10, the only other control
required is the "bandwidth" control,
and this is provided by the lOkQ trimpot (VRl) feeding pin 2 of the PLL. As
with all FM communications systems,
use is.made of pre-emphasis and the
RC network at pin 14 performs the
appropriate de-emphasis.
The entire circuit is designed to
operate from 5V, although it can be
run from 12V by changing the value
of the lkQ resistor feeding pins 3 and
9 to 4700 and adding a 220n resistor
in the DC feed to pin 10.
The layout of the circuit is not critical at 10. 7MHz, although more care
...---------~+SV
VR1
10k
1k
~---
3
9
1
10
RF
INPUT .0022
14
IC1
NE584
1k
AUDIO
OUTPUT
39k
.0022+
.022!
8
4
22011
22011
.0022+
.0022+
":'
Fig.2: this circuit
is intended to act
as a demodulator
following a
10.7MHz IF stage
in an FM receiver.
It requires
virtually no
alignment and is
easy to build .
Silicon Chip Binders
13
12
39pf
VC1
0-20pf
should be taken if you wish to operate
the circuit at 50MHz, particularly regarding the length of component leads.
At this frequency, it's important that
component leads be kept short.
Alignment
Alignment is easy and requires only
a frequency counter. The local oscillator frequency (and hence the detection frequency) can be measured at
either pin 12 or 13, both of which are
connected to the internal VCO circuit. Hence, to set up the PLL for
operation at 10.7MHz, you simply
adjust trimmer capacitor VC1 while
measuring the frequency.
To calculate the frequency of the
VCO for a given capacitance, the following formula should be used:
f0 = 1/[22Rc(C1 + Cs)l
where Re is an internal 100n resistor,
C1 is the external frequency setting
capacitor, and Cs is stray capacitance.
Comprehensive applications notes
and data on the NE564 are provided
in the Signetics Linear Manual, Volume 1: Communications, 1987. SC
These beautifully-made binders
will protect your copies of SILICON
CHIP. They are made from a distinctive 2-tone green vinyl & will
look great on your bookshelf.
Price: $A 11 .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) 979 6503; or ring (02)
979 5644 & quote your credit card
number.
1
IAN J. TRUSCOTT S ELECTRONIC WORLD
30 Lacey Street, Croydon 3136 . Phone: (03) 723 3344. Fax: (03) 725 9443.
Now also at: 200 Smith Street, Collingwood. Phone: (03) 419 2808.
Mail and Credit Card Orders Welcome
We now have a range of 5,6,8,9 & 1O pin
Ask about our range of E.A.O. precision
resistor networks and a comprehensive
push button switches, motor start
range of micra's and eproms at ridiculous capacitors and Beckman Industrial
prices. Quote this ad and receive another multimeters.
5% discount.
$16.80ea.
27C010-15 1 meg eprom 150ns ....... $8.l0ea.
SAB8031 P Romless Micro ........ $2.50ea.
MAB8049H Romless Micro ....... $2.50ea.
62256-LP S-Ram .. ................... $9.75ea.
41256 D-Ram ................................. $2.60ea.
27C020-15 2 meg eprom 150ns....
.~t1ii!ter
$119
$10.00 ea.
3mw Laser Tube & inverter $99.00 ea.
6 volt 1 watt Solar Panels
Infra Red Night Viewing Monocular (kit)
$269.00.
COMPONENT PHONE ORDER HOTLINE (03) 723 3344
NOVEMBER
1992
67
I
PRODUCT SHOWCASE
I
measurement ranges. Alternatively, it
can be configured for custom setups,
using 10 save/recall states.
A variety of test leads is available
in the optional HP 16338A test lead
kit which permits easy testing of batteries, cables, PC boards, connectors,
switches and contacts. The HP 4338A
has built-in HP-IB and handler interfaces for fast control of testing. It also
has a comparator function for making
decisions automatically for rapid results. ·
The HP 4338A milliohm meter is
priced at $5000 while the HP 16338A
test lead kit is listed at $1150. For
further information, contact Hewlett
Packard Australia Ltd. Phone (008)
033 821.
High performance
milliohm meter
Hewlett-Packard has released the
HP 4338A milliohm meter which offers a test measurement range from 10
microhms to lO0kQ; a 5-digit resolution for five measurement parameters;
a four-terminal pair and short-correc'
New·car CD player
from Panasonic
Those in the market for a new
car sound system will be interested in the CQ-DP37 radio/compact disc player which has just
been released by Panasonic.
Power output from the CQ-DP37
is listed as 4 x 20W while the new
"sound" feature allows the listener
68
SILICON CHIP
tion function that minimises errors
introduced into the test by fixtures ,
cables and switch parasites; and a
basic accuracy of 0.4%.
Instead of using a high-current
source, the HP 4338A uses a lkHz test
signal clamped at 20 millivolts to perform dry-contact testing. Operators
can select current-source and voltage
Shorted turns tester
for TV servicemen
,
··----~
.
., ,-:' 1 \,i
i
to program his/her preference for
bass and treble.
The new CD player has 32 times
oversampling for excellent sound
quality. A quick release bracket
allows the unit to be removed and
taken with you when you leave
the car. The recommended retail
price is $699. For further information, contact Panasonic Australia
on (02) 986 7400.
This handy little tester can save a
lot of time, money and frustration by
allowing suspect transformers to be
tested. This means that unnecessary
changing of transformers in TV repair
work can be avoided.
The unit will test for shorted turns
as well as indicating open circuit and
short circuit windings. As well as conventional transformers, it can be used
to test EHT transformers (including
those with triplers), as well as the
vertical and horizontal windings of
deflection yokes.
Using the tester is quite simple -
just turn it on by rotating the switch
knob and then turn it clockwise until
the meter indicates about 40 milliamperes. You then connect the winding of the transformer. According to
the instructions, a good transformer
will cause the meter reading to increase while a faulty unit will cause it
to reduce or drop back to zero.
The procedure is a little different
when testing yokes and checking for
shorts on line output transformers but
again, it can be a boon in removing
these components from the suspect
list. The unit is available at a cost of
$78 including sales tax.
For more information, contact the
manufacturer, J.V. Tuners, 216 Canterbury Road, Revesby NSW 2212.
Phone (02) 774 1154.
CCD colour camera for
low light conditions
A new colour CCD camera from
Philips is able to produce good colour
images regardless of lighting conditions. The LDH 0801/20 has high resolution and sensitivity and is suitable
for safety and security applications
where previously only monochrome
cameras could be used.
With a sensitivity enabling good
colour pictures below the 1 lux level,
the LDH 0801/20 overcomes the problem of picture-degrading noise at low
light levels without sacrificing the
colour of the image. This represents a
breakthrough in its field and allows
differentiation between objects and
their background, even when the contrast is extremely low.
The shutter sensitivity control (SSC)
automatically selects a shutter speed
to match ambient light conditions,
which means that manual iris lenses
can be fitted for virtually all indoor
applications. Standard auto iris lenses
are generally utilised in more demanding outdoor situations. Enhancement
circuitry accentuates the picture detail both horizontally and vertically.
New turbo card
& data saver
Astec's newly released Turbostart Card is an internal full-length
card that provides full protection
against loss of data due to breaks
in mains power, including brownouts.
The Turbostart Card and software package can be interfaced
with IBM and compatible p ersonal
computer systems, both of which
are user installable. The card itself
utilises just one slot when mounted
adjacent to a half-length card.
When mains power is lost or
fluctuations occur, the Turbostart
Card saves all memory to the system's hard disc, then parks the
drive in an orderly manner and
shuts down the computer. When
power is restored, the automatic
resumption feature will restore the
system, permitting the session to
be continued from precisely the
same point at which the power
loss occurred.
For more information, contact
Eltec Australia Pty Ltd, Level 7, 91
Phillip St, Parramatta, NSW 2150.
Phone (02) 893 1800.
For further information, contact
Philips Scientific & Industrial, 25-27
Paul St, North Ryde, NSW 2113. Phone
(02) 888 8222 .
Genius HiPoint
trackball for laptop PCs
Genius Australia has released a mini
trackball mouse for a variety oflaptop,
notebook and portable PCs. The onebutton pointing device has 200dpi resolution and reliable opto-mechanical
technology.
The HiPoint can be attached to any
convenient position. Its output orientation can then be changed using a
graphics menu that's included in the
package. You just roll the trackball in
the direction that naturally serves as
"up" and the system automatically
sets itself to the user's choice.
HiPoint's anti-slip bottom ensures
a firm position, even when used on a
desktop as a conventional trackball
mouse. The device also features a
breakaway clamp mechanism that prevents damage to delicate keyboards.
The mouse mechanism is fully compatible with Microsoft and other popular brands.
The HiPoint mouse sells for $131
and comes complete with 9-25 pin
and 9-6· pin PS/2 adaptors, 1500mm
extension cable, different size clips
and clamp, Genius Mouse Driver and
carrying case. It operates on DOS, Windows and PS/2 compatible computers.
For further information , contact
Genius Australia, 4 Briar St, Fulham
Gardens, SA 5024. Phone (08) 356
7337.
NOV E MBER
1992
69
110V isolation
transformer
New Scope
soldering stations
A new range of soldering stations incorporating the latest Japanese element technology has been
released by Scope Laboratories.
Designated the PX-1 and PC-lE,
they feature a 75W tungsten/zirconium element. This is claimed to
provide faster heat recovery after
use, super low current leakage and
extended element life.
For further information, contact
Scope Laboratories. Phone (03) 338
1566.
Digital vernier
micrometer
The micrometer and vernier calliper are the two instruments commonly
used for making precise measurements of physical dimensions. The
micrometer is perhaps the easiest to
use but the vernier calliper is more
flexible since it can measure both inside and outside dimensions, as well
as depth. The only problem is that
many people have trouble reading the
scale of vernier callipers.
This problem is neatly solved by
using a digital vernier calliper which
has a liquid crystal display, such as
the Digilog model from Dick Smith
Electronics. It measures dimensions
up to slightly more than 150mm (6
inches) and has a 5-digit LCD.
Perhaps this instrument should now
be called simply a digital calliper since
the vernier scale is not used. Instead,
the instrument uses a "non-contact
linear cap measuring system", according to the instruction leaflet. We interpret this to mean that the unit reads
its position along the scale by means
of a digital bargraph with capacitive
pickup.
Whatever the method, it works very
well. Claimed accuracy is ±0.03mm,
while resolution of the 5-digit readout
70
SILICON CHIP
is .0lmm. There are two buttons on
the sliding portion, one to change the
measuring mode from millimetres to
inches (or back again) and one to zero
the instrument at any portion along
the scale. This is very handy when
measuring deviation in dimensions
from a specified figure - something
you can't easily do with a conventional vernier calliper.
There is no on-off switch. Instead,
you close the callipers and the readout
extinguishes after four minutes. Opening the jaws turns the display back on
and the instrument can be used immediately. The display is powered from
a single silver oxide 1.5V cell with a
claimed life of 12 months in continuous use. End of battery life is indicated by a flashing display.
The Digilog digital callipers are
available from all Dick Smith Electronics stores at $169 (Cat No Q-1412).
Many people come back from an
overseas trip with audio, video or computer equipment which will only run
at 110V. They get caught. But all is not
lost and some of this equipment will
run quite happily via a 110V isolation
transformer.
Pictured is one of a range of 110V
isolation transformers manufactured
by Harbuch Electronics. All are based
on the company's toroidal transformers and thus they are compact and
have a low residual hum field.
Units are available with ratings of
60VA, 120VA, 300VA, 500VA and
625VA. The units up to 300VA are all
housed in the same size case, measuring 125 x 75 x 185mm.
The 300VA model will probably
meet most needs and it sells for
$127.50 plus sales tax. For further
information, contact Harbuch Electronics, Pty Ltd, 90 George St, Hornsby
NSW 2077. Phone (02) 476 5854. Fax
(02) 476 3231.
Optical drive with
hard drive performance
Pinnacle Micro Systems of Irvine,
California, has introduced the PMO650, a rewriteable optical drive of 650
megabytes capacity. Its performance
is claimed to be the fastest currently
available and to rival that of many
hard drives.
The PMO-650 can replace existing
hard drives for general data storage or
can be used for vertical applications
such as digital audio , digital video or
multimedia. The unit is a plug-andplay optical drive that is recognised
by Unix operating systems as a standard removable hard drive. Unix commands such as mount, unmount and
format can be used to access the drive.
For further information contact
Elmeasco Instruments, 18 Hilly St,
Mortlake, NSW 2137. Phone (02) 736
2888.
PCB and
SCHEMATIC CAD
:----- -~
i
I,,_
l
· ···---· ---·::t__~
/ TV IF AMPLIFIER
,._
.
•
~~~~- U,.,
~
provides recording speeds of 20Mb/
minute. It has received endorsement
from numerous computer companies
including Meridian Data, Digital,
Young Minds and Optical Media International. Platforms supported include MS-DOS, Unix, Apple and
Novell networks.
According to Philips, the unit will
make desktop CD-ROM publishing a
reality for many corporate, government and educational bodies. It has a
list price of $9750. For further information, contact Philips Components,
34 Waterloo Rd, North Ryde , NSW
2113. Phone (02) 805 4455.
CD ROM ·recorder for
professional use
Philips Components has released
an optical disc recorder that can make
one-off copies of all CD formats - CDROM(XA), photo CD, CD-I and audio
CD.
The unit is the first CD recordable
double speed drive on the market and
f ---- -------- --
-l
t.:l!
:J!
-·· "
=.:
:
I
IIT'nllll
lltllll l lltllllllltlllltll l llllllll<I
J.fS, l,l"Nlltllllll•.,R • t.J
EASY-PC
;,,_u,onix
i~~:i~t
~./
• Runs on PC/XT/AT/286/386 with
Hercules, CGA, EGA or VGA.
DM25lO
Mtx:NL~}(h
.,
-
Wfl/TEMP
r-?A
. ---&:;JEJ.
AflM • •
• Design Single sided, Double sided
and Multilayer boards
CJ.1? L/
.,
.
.,
. e
N
"~-'i,lli
~
1
'
-~ "", . . ·'<:r;:•/·;~~~:;:;c"'f'
• Provides Surface Mount support
• Standard. output includes Dot
Matrix/Laser/Inkjet printers,
Pen Plotters, Photo-plotters and
NC Drill
• Award winning EASY-PC is in
use in over 12,000 installations in
70 Countries World-Wide
• Superbly Easy to use
• Not Copy Protected
Options: • ~000 piece Schematic
symbol library
Benchtop DMMs
from Tektronix
Tektronix Australia has released
the DM2510 and DM2510G
Autoranging Digital Multimeters
(DMMs). Designed for benchtop
use, the DM2510 and DM2510G
feature full programmability with
41/z-digitaccuracy, an integral power
supply and autoranging or manual
operation.
The TM2500 series provide features and accuracy usually found
only in higher priced instruments.
Both products offer voltage, current or resistance measurements;
true RMS AC volts measurements
(200mV to 500V range); dB calculation; temperature measurements;
DC volts from 200mV to 1000V
with 0.03 % accuracy; and DC amps
from lO0µA to 10A with 0.06%
accuracy.
For further information, contact
Tektronix, 80 Waterloo Rd, North
Ryde, NSW 2113. Phone (02) 888
7066.
• Surface Mount symbol
library
• Gerber Import facility
For full .info 'phone, fax or write:
BTC
PO BOX432
GARBUTT 4814 QLD.
PH (077) 21 5299
FAX (077) 21 5930
N OV EMBER
1992
71
SILICON
CHIP
PRODUCT REVIEW
More circuit software from
Breakthrough Computers
Last month, we looked at the ANALYSER III circuit
design software and now we take a look at the
digital half, the PULSAR digital circuit simulator.
These packages run in the same manner - once
you've learnt to drive one, the other is just as easy.
PULSAR has a simulation speed of
over 1000 gate changes per second
and can pick out glitches in a circuit
down to 1 picosecond. To program a
circuit, you simply enter a netlist similar to that used in the many SPICE
programs that are around. PULSAR
then produces a screen display of all
output lines over any time period from
microseconds to hours.
As before, the package is very easy
to follow and the well-written manual
has screen shots showing you exactly
what happ ens. PULSAR expands as
you go, allowing you to add new logic
ICs and their pinouts and then combine them to produce modules, which
can be linked together.
This makes it easier when use you
the same circuit block often. You can
also use netlists generated by EASYPC's schematic program (another package from this company, reviewed below), to save more time.
If you have problems generating the
netlist (ie , parts list), the manual gives
examples on how to do this, as well as
a comprehensive listing of TTL and
CMOS ICs and their printouts.
Once you have the circuit's outputs
displayed on the screen, you can print
it either to file, to a 9 or 24-pin printer,
Cont i9,,1rat ion
0.-r;ator
~1-..r
File :CtJUNTDCO .NET OJ'B.IMex :8 FFEF
Libniri•
EASY-PC
PRL"IIl!D CIRC:IJIT ROAJID LAYOIJT ,
AND
ClRC'.UIT DIAGRAM DRAUGHTING PROGRAM
IIY
NumlterOne
or to a HPGL LaserJet II compatible
printer.
PULSAR will run on anything compatible with an XT to a 486 and requires a minimum of 512Kb RAM,
MS-DOS 3.2 or later. It will also drive
EGA or VGA displays.
EASY-PC CAD package
AJ1d now we will have a look at
I DOI
IIESETO
110'\ll
I=~~;~§:~=~E~~~~~~~~~E;~E:~=~~:
ENABLELca, _
72
1--- -- - . . . - - - - -
____
SILIC ON CHIP
Ltd..1
Fig.1: reproduced from
the manual, this
diagram shows how the
program displays
waveforms from a
typical digital circuit,
including glitches down
to one picosecond.
EASY-PC, a well-known CAD package
which has been around for-some time
but not readily available in Australia
until now. It comes very well packaged with a British Design Award
label proudly displayed on the front
cover.
The package contains one 3.5-inch
and two 5.25-inch discs and, once
again, an easy-to-follow and well-written manual. The beauty ofEASY-PC is
that you can do your PC board layouts
and draw your circuit diagrams in the
one package.
Not only that but it also comes with
a comprehensive symbols library the TTL library alone contains symbols for over 400 ICs. Also available is
a 500 symbol surface mount library,
so this is no lightweight CAD package. It Cclil produce boards up to about
43cm s·quare with up to 1500 ICs, as
well as 5000 tracks on up to eight
layers.
You can also choose from any of
128 different track widths and pad
sizes from 0.002-inch up to 0.5-inch.
So what's it like to use? Well, it's
quite easy, with pull-down menus in
case you get lost as well as keyboard
function control if you don't wish to
use the mouse all the time.
The schematic feature of the program was also quite good and uses the
same procedure as that used for producing PC board layouts, so you don't
need to learn two methods.
EASY-PC will also run on anything
from an XT to 486 with a minimum of
512Kb RAM and can drive Hercules,
CGA, EGA and VGA displays. It also
contains a number of printer and plotter drivers for 9 and 24-dot matrix
printers, HPGL pen-plotters, Gerber
photo-plotters and HPGL LaserJet II
compatible printers.
EASY-PC is priced at only $275,
which is a great deal less than many
other CAD packages that are currently
available. The PULSAR digital circuit
simulator is priced at $540. For further information on these packages,
contact the Australian distributors,
Breakthrough Computers, PO Box 432,
Garbutt, Qld 4814. Phone (077) 21
5299 or Fax (077) 21 5930.
SC
..iO LAR PANEL
GIVEAWAY
Brand new 6 volt 1 watt
amorphous solar panels,
150m x 150mm, wi ll
deliver one Watt whilst
charging 6-BV batteries.
Two of these in series
make a great 12V battery
maintainer/charger. Have
weather protection , and
terminating clips are
provided. Incredible
pricing:
s10
ea or 10 for $85
CRYSTAL
OSC ILLATOR
MODULES
LARGE LCD
DISPLAY MODULE
LASER TUBE
BARGAIN
If you always wanted a
laser tub but couldn't
afford it how about a
BRAND NEW small
0.2-0.5 mW tube for an
. incredible
Brand new large Hitachi
LM21 5XB display, as used
in some laptop
computers. Yellow-green
LCD reflective type, 480 X
128 dot display, effective
display area of 242 X 69
mm, has 14 LSI !Cs
mounted on the rear of
the PCB. Includes four
pages of data sheets.
Limited stock at a small
fraction of their $
real value.
39 ea.
Controller IC (LSI-surface
mount) available $5 ea.
Data sheets (28 pages): $3.
$J!t
I.A . BINOCULAR
VIEWER
GEL BATTERIES
Similar to the ones used
in computers. 5V DC in at
approx. 30mA. TTL logic
level clock output.
Available in four
frequencies: 4, 20, 40 and
50 MHz.
Famous "high-spec"
Gates brand dual cell
batteries, enclosed in a
plastic moulding. 4V-5AHr
per pack. Connect 3
packs in series to obtain a
12V/5AHr battery. Brand
new, fresh stock, fully
charged. Limited stocks at
a giveaway price of:
s7
$
are hermetically sealed.
ea or 5 for $25
LtGtH MOTION
DETECTOR
Small PCB assembly
based on a ULN2232 IC.
This device has a built in
light detector, filters, timer,
narrow angle lens, and
even a siren driver circuit
that can drive an external
speaker. Will detect
humans crossing a
narrow corridor at
distances up to 3 metres.
Much higher ranges are
possible if the detector is
illuminated by a remote
visible or IR light source.
Can be used at very low
light levels, and even in
total darkness with IR
LED. Full information
provided. The IC only is
worth $16' Our price for
the assembly is:
$6
ea. or 5 for $25
18
or 3 packs for $45
VISIBLE LASER
DIODE
POINTER-PEN
Improve and enhance all
deg. steps, coil resistance
ONLY
High quality military binocular IR viewer. Self
powered, and originally
intended to be mounted
adjustable from 1 metre to
infinity. Requires some IR
illumination. Powered by
one single 1.5V battery.
Original fibreglass carry
case provided.
Limited stock.
ON SPECIAL
ssoo
$12
620
INFRA RED
NIGHT VIEWER
ea.
We have accumulated a
good supply of some new
and used tubes and
heads with powers in the
range of 0.5-2 mW. These
may have some small
beam geometry problems.
The tubes and the heads
are guaranteed for one
year! You can purchase
one of these tubes/heads
with our Universal 12V
laser inverter kits for the
price of the inverter only!
s79
Brand
.matrix
Isp ays. er
size is 120 X 265mm. Buil
drivers. 4 bit TTL interface
required for signal and po
( +5V, -12V) . Capable of
displaying characters, gra
patterns, etc. 28 page
information included.
LIMITED SUPPLY AT A
SMALL FRACTION OF
THEIR REAL PRICE!
Note that an LSI surface
display is available. This I
generator and many other
with 8080 and 6800 MPU'
elsewhere for about $35,
information upon request.
TO CLEAR
Stereo Headphones.
Similar to ones used for
stereo "Walkmans" at $2
a pair.
TV Antenna. Dual
telescopic TV antenna
similar to ones used on
many portable TVs. At $3
each.
J}
These matching
components were
removed from brand new
IR tank viewers. They
include a large low light
objective lens, a large
prefocussed IR image
converter tube, a power
supply or power supply kit
to suit the tube and an
adjustable eyepiece
assembly.
Make a professional infra
red night viewer
at_a ridiculous
price of:
For the set.
$199
total of 14 connections are
EHT GENERA TOR
PROJECTION LENS
Brand new large precision
projection lenses, which
were originally intended
for big scree n TV
projection systems. Will
project images at close
proximity, onto walls and
screens and lt has
adjustable focussing.
Main body has a diameter
of 117mm and is 107mm
long . The whole assembly
can be easily unscrewed
to obtain three very large
lenses: two plastic and
one glass. The basis of
the cheapest large
magnifier or projection
system? Experimenters
delight at
ONLY
$28
LASER GUNSIGHT
PIEZO SIREN
incredible price!
ON SPECIAL AT
s1so
VISIBLE LASER
DIODE BARGAIN
LG>G>K
Brand new 5mW-670nM
laser diode, plus a
collimating lens, plus a
driver kit, plus
instructions.
Special introductory price
for a short time
only. BE QUICK
SSS
KIT SPECIALS !
s259
ll
We have a limited supply of
some 18mm fibre optically
coupled 2nd generation image
intensifier tubes. These are
ex.military and may have some minor blemishes, but all
produce'full gain. With low light lenses these will
produce useful images with as little as starlight
illumination. Car, also be IR assisted with IR LED's or
low power torches, in rare situations where this may be
required. The tubes require a 3V battery and a switch to
make them operational. The viewer illustrated uses one
of these tubes. It was constructed using some low cost
plastic tubing and matching fittings for the case, a
camera lens, and a low cost eyepiece.
$
Plastic jewellers eyepieces can be used.
FOR THE TUBE AND THE SPECIFICATION SHEET
your presentations. Not a
kit, but a complete
commercial pen sized
laser pointer at an
THE CHEAPEST 5mW
VISIBLE LASER DIODE
EVER OFFERED
A very small but comp lete
IR telescope which only
needs an EHT power
supply, which is provided
in kit form. PCB and all
on board camp's only.
Limited stock at a
reduced special price.
These are brand new
units, main body has a
diameter of 58mm and a
height of 25mm. Will
operate from 5V, has 7.5
: SECOND GENERATION TUBES
6.6 ohm and it is a two
phase type. Six wires.
on a helmet. Focus is
These small TTL Quartz
Crystal Oscillator modules
STEPPER
MOTORS
Electron ic Key. Use it to
activate door st rikers for
entering buildings, car
alarms, central locking ,
etc. The most secure key
ever (see E.A. July '92).
On special at
$49.90
for two keys and one
decoder kit.
Stock up on this limited
stock surplus item. Brand
new, 6-12V (6V/50mA.
12V/150mA). Giveaway at:
$6
ea or 5 for $25
NICAD BATTERY
PACK
A complete nicad battery
power pack that was
intended to be used in an
emergency lighting
application . Contains 17
" D" size 1.2V/4 AHr
batteries which can be
easily separated into
individual cells. New
packs in their original
packing.
$75
per pack
UV PENS
The writing of these pens
is only visible under UV
"Black Light".
s2
ea or 5 for $18
Very small tube and
inverter to suit; suit long
range gunsights, laser
pointers. Incredible value
s1so
at
Includes tube, supply and
ballast resistor
Based on a brand new,
very compact modern
EHT flyback transformer
which includes an EHT
diode rectifier. We supply
the transformer, a very
simp le circuit, and the
components to suit. All
you need to make a very
s imple EHT or DC or
pulsed AC supply.
Powered from 12V DC
supply. Great for EHT
experiments, EHT testing ,
plasma displays (large
light bulbs can be used)
etc. Total price for the
transformer and the $
components ,s only:
17
Small black anodised
metal body. Removable
pressure switch. Vertical
and horizontal adjust·
ments. Battery life more
than 10 hours continuous.
SmW 670nM class IIIA
laser. Range is about
150m, some would claim
three times more. Shock
tested to 2000g. One year
warranty.
ON SPECIAL AT
$249
Price includes one rifle or
pistol mount.
Simplifying the Interphone
telephone exchange
The Interphone 10-station telephone exchange
has created a lot of interest since it was
published in the August & September 1992
issues. Since then though, one of our readers has
pointed out that the circuit can be simplified
with a saving of two ICs on each remote station
board.
When the Interphone was first designed by the author, Geoff Monegal,
it was intended that each remote station board would be mounted in a
small case near its associated extension phone. Subsequently, when it
was presented ln SILICON CHIP, all the
circuitry was housed in the one case.
This means that there is now an opportunity to simply the circuit without prejudicing any of its functions.
To explain the modification, we reproduce the remote station circuit on
this page. A remote station board is
required for each extension phone.
The key components are IC9 (an
MC14536 DTMF decoder chip) and
IC10 (a 4028 1-of-10 decoder). IC9
and IC10 are there to decode the
specific DTMF (dual-tone multi-frequency) code for each extension. As
originally presented, the design specified that IC9 and IC10 were required
on each extension board.
However, one of our readers, Anthony Fouracre, of Tahmoor, NSW has
Fig.1 (below): the remote station
circuitry. IC9 & IC10 need only be
installed on one board, since the same
ICs can perform the DTMF decoding
for all _extensions.
+5VO-----------------------<I---------------6
4
16
3
10
1M
IC9
MC1 45436
+50Vo-----~
0.1
10 A
13 B
14
10k
12 C
11 D
IC10
4028
2.2k
10k
1W
220pfJ
.,.
D20
+
-:-
PHONE
..,.
..,.
STATION
SET
022
1N914
-:-
Off
HOOKO-----------------------'
120k
+
10 .,._
r-------•50V
-:!:.
22k
+5V
RING
.,.
01+
INTERPHONE REMOTE STATION
74
SILICON CHIP
-:
010
-[ill]-
I
---1u(;)~
Fig.2: this diagram
shows the revised parts
layout for a 3-station
board. Note that IC9 &
IC10 are only installed
in one section. Flying
links are then run from
the decoded outputs of
IC10 to the other
stations. Two of these
links are shown here,
designated as A & B.
o--CD-.....Jil.023
22k
• • 06
•B
•C 07
E•
Il
pointed out that only one MC14536
and one 4028 can do the DTMF decoding for all 10 extensions. All that
needs to be done is to install IC9 and
IC10 on one remote station board and
then take the 10 decoded outputs from
IC10 and wire each one to its corresponding D22 cathode on each remote station board. This is blindingly
obvious once it is pointed out and
comes under heading of "Why didn't
we think of that?". Well, we didn't
and we thank Anthony Fouracre for
his suggestion.
Wiring layout
We have also reproduced the wiring layout of the remote station boards,
i q I tf"'
in Fig.2. This shows three remote stations on the one board. We have modified it to show just one MC14536 and
one 4028 (ie, in the centre of the
board). IC9, IC10 and all the associated components - ie, the 3.58MHz
crystal, diodes D20 and D21, and various capacitors and resistors - have
been omitted from the other two remote stations on the board.
Flying links are then run from the
10 decoded outputs of IC10 to the
other remote station circuits. Two of
these are shown in Fig.2.
If you are building the Interphone
with 10 extensions, this simple modification means that you can save nine
MC14536s, nine 4028s, nine 3.58MHz
crystals, 18 diodes, 18 capacitors & 18
resistors.
Some readers may be tempted to
take this modification further and this
possibility does exist. Consider that
the base station board also features a
4028 and an MC14536 to decode the#
and* buttons. This raises the possibility of running the four decoded
data lines from that DTMF decoder
chip to another 4028 IC to decode the
10 extensions. That could be done but
there is the possibility that noise on
the necessary ribbon cable might
prejudice circuit operation.
Our recommendation is to simply
follow the modification to the remote
station boards described above. SC
YOU
For many years you have probably looked at satellite TV
systems and thought "one day"
You can riow purchase the following
K-band system for only:
Here's what you gel:
• A 1.6 metre prime focus dish antenna,
complete with all the mounting hardware.
• One super low-noise LNB (1.4d8 or better).
• One Ku-band feedhorn and a magnetic
signal polariser.
• 30 metres of low-loss coaxial cable with a
single pair control line.
• lnfrared remote control pre programmed
satellite receiver with selectable IF & audio
bandwidth, polarity & digital readout.
Your receiver is pre-programmed lo the popular
OPTUS transponders via the internal memory.
AV-COMM Pty Ltd, PO Box 225, Balgowlah NSW
2093. Ph: (02) 949 7417. Fax: (02) 949 7095.
All items are available separately. Ask about our C-band
LNBs, NTSC-to-PAL converters, video time date generators,
FM2 &EPAL & Pay"TV hardware.
r,-------------->{;
I
YES GARRY, please send me more information on K-band
.
Name: _ _ _ _ _ _ _ _ _ _ _ _ __
I satellile systems.
I
I Address
_ _ _ _ _ _ _ _ _ __ __
: _ _ _ _ _ _ _ _ _ P'code: _ _ __
I Phone: - - -- - ~ - - -- - - - -
! ACN 002 1744 78
NOVEMBER
1992
75
Phone Your Order To Us Toll Free
We guarantee our Jetservice Courier will deliver
to your doo( faster than any other Australian
supplier (including that local supplier just up the
road). If we fail, I'll give you your money back
plus $5.00 for your inconvenience.
Mini Home PABX Telephone Exchange
Kit (SC Aug/Sept '92)
NEW
KIT
This great unit allows you to place
calls on hold, intercom other
I
extensions. answer calls from any
extension and transfer calls. It is
expandable up to 10 extensions, and
is compatible with all DTMF (touch
tone) telephones. Operation is as
!I; .
simple as pressing '*' to place a call
on hold , press the ex~ension_nu~ber
(0-9) and the respective station rings.
Once answered, you have a two way 1,· · · ·
.
.
.
intercom, with which you can announce a call. To pi.ck _up the incom_ing c~II from .
hold press'#'. A neat feature is that all extensions will ring when an ~nc~~ing call 1s
placed on hold for 30 seconds sothat it won't be forgotten . The Basic kit Is complete
with power supply, case and fac1l1t1es for 3 extensi ons. Extra extension boar~s al lo w
expansion in multiples of 3. Simple operation, fantastic for ho me or small office. No
more shouting from room to room. Not Auster Approved.
l'111Jili!WI
'':=:=:;::;:::;::::;:;i::;:.EJL.__.._"':':"-:---'
K 1430 Basic Kit
$189.oo
K 1435 Expansion Board
$79.95
3½ Digit LCD Panel
Meter Kit (S.C. Sept '92)
Ideal addition to power supplies, voltage
meters, current meters etc. It can be
calibrated to accuratel y read 2mV, 2V.
200V. Requires 9 volt power supply.
Programmable decimal point. NEW
2528 $34 .95
Sub-Woofer Adaptor
Kit (EA May '89)
K
Get an amazing bass improvement from
your stereo system. This fantastic
adaptor simply " samples" your stereo
amp output and provides a single
c hannel output to feed a separate subwoofer amp. Requires 12V AC or M 9020
plug pack.
K
5560 $29 .95
2 Way Active Crossover
5250 Station Mod ule $7 4.95, K 5255 Power Supply $64.95
Ni-Cad Battery Drill Speed Controller Kit
Discharger Kit ~~~~b~!pstp·::~
K
Designed to rid your nicad
batteries of the 'memory effect'
and regain full recharge
potential. It discharges your
nicads correctly to enable a full
recharge. Suits most battery
packs. Great for mobile phones,
battery drills, toys etc.
1640 $24 .95
Four Digit Combination
Lock Kit
.
(SC Dec '90) K 1925 $44.50
KIT!
K
controller for 240V
po wer too ls
N
including drills,
IL
power saws,
"
engravers etc .
suitable for brushtype tools up to SA.
Not suitable for
globes or radiator
heaters.
0 -r-------
;;...__.....;._ _ _ _T"""......,1.,;,;.::.::..:::.:.;:;;...__ _
This 4 Digit Combination
Lock is bound to prove useful
in many applications. Such as
accessing alarm systems,
electronic doors, ignition
.
killers or just about anything that comes to mind.
Momentary or latched rela y output.
This great new kit enables you to
customize your sound system in
your car or at home. The circuit
simply connects between the audio
source and the amplifiers. There
are tw9 outputs, one for bass
and another provides signal for the. upper range.
us each amp is dedicated to a
frequency range (i.e. one for bass, one for midrange and treble) . Because no
passfve crossover is required in the speaker one per chan nel is require~ . Operates
on+ and -15V rails. The result is a muc h better sound wit h less distortion.
K
(SC June/ Jul y '92)
This multi-station headset intercom is
designed to provide clear communication in
high noise environments such as at race
tracks and rock concerts. It is designed to
operate with a headphone and mic
co mbination. Each headset requires a station
module. Stations are simply connected in a
daisy-chain fashion. Up to 12 units (stations)
can operate from the power supply. Features
low noise circuitry and compares favourably
to many commercial equivalents. Mics can be
switched on continuously at one ti me for
hands free operation of all stations. Also
includes visual and audio call function.
Ideally suited to our C 9055 headset/mic and
the C 9070 noise attenuating Av iation
Headset.
Door Strike
Apo/ogles
Ideal for security access
areas, thi s high quality
lock will fit most door
jams. Operates from 12V
AC or DC. Ideally suited
to K 1925 Combo Lock
Kit .
.
In September &
October ads we
incorectly advertised a
K 3301 Power Supply
Option for $4.50 . This
should read $29.50.
ALTRONICS
apo logises for the
inconvenience.
s4390$39.95
High Power Amplifier Modules Kit
(SC Dec '87)
All components, including o utput transisto rs mount on a single
PCB. Suitabl e for high quality guitar amp, public address or in a
high fidelity stereo amplifier. Kit includes ang led heatsink
brack et, main heatsink and a in-built polyswitch for loudspeaker
protection. Full specs available on request.
$
5140 100W Ve rsion $6j:l,efs NOW ON LY 55.oo
K 5150 150W Version $9e,efs NOW ONLY $85.oo
K
LED Digital
Tacho Kit
5570 $19.95
(SC Aug '91)
This dig ital
tac hometer will tell
you how many revs
your car's eng ine is
doing. It works w ith all
ignition systems and
4, 6 and 8 cyli nder
cars. Indicates that 09900 RPM wit h a
resolution of 100 RPM .
PCB only.
Digital Altimeter for Gliders
This compact digital altimete r can
display altitude up to 19,990 feet with 10 feet resolution .
Accurate to better than 3.5 percent. A rnust for
hang-gliders, ultralights etc. Operated on 9V battery .
K
2580 $299.oo
1GHz Digital Frequency Meter Kit
K 4320
(S.C. Nov '87 to Jan '88)
Feature■: Professional mach ined and screen printed red perspex front panel, easy to
a~semble and c~nstru_ct, no sp~cial t_oo ls required , bright Hewlett Pa cka rd 8 digit
display, electronic switch latching, high performan ce IC's, high quality components
Specifications: Operational Modes:
--··
Period, freq to 10MHz, freq to 1GHz.
Freq. Range: 10Hz-1GHz (1 .7GHz
typical) in frequency mode; 10Hz2.5MHz (5MHz type) in period mode.
Gating Times: o.o,, 0.1, 1 and 10
seconds (10MHz and 100MHz); 0.128, ,
1.28, 12.8 and 128 sec (1GHz range).
K
2515·$299 .00
~
compares·
·, . pQlll!R
Favourably to_
•
commercial units
COO""'"~
Low Cost Dual Tracking Supply
Kit (SC Jan '88)
Ideal for experimenting and prototyping with
Memory, Logic and Op Amps
Adjustable+ or - 18.SV at 1.7A, volt
meter, floating ground , dropout indicator,
load switch, compact sturdy "ABS"
instrument case
K 3325
.00
Fe ■ turea:
$S
9
$31 .00
now In ,er,lce througho
Inc ude Unl•erlltl••• Re,eerch E•
Famous Labtech 20
Oscilloscope
Get 240V AC from your car, truck or boat battery. The A_ltronics ran_ge
includes an inverter for nearly every appllcat,on. Fantastic for camping,
boating, farms and anywhere else 240V AC isn't available. Each size inverter
is available in kit form or fully built and tested. The 300 and 600 Watt
Inverters now feature new improved circuitry using multiple mosfet outputs
making them even more reliable with a genuine 300 or 600 watt continuous
This model is a dual trace 20MHz
oscilloscope using a high brightness CRT. The vertical amplifiers
have high sensitivity of 5mV/ div and ,' .·l
a frequency characteristic response
!j
with smooth roll off exceeding 20MHz~ '
The TV sync signal operator circuit
is provided to ensure stable observation of video signals. Triggering is
obtained by sampling the AC power
waveform, external waveform or
power rating . Our latest model, the 1200 Watt Powerhouse offers excellent
value for money and performance. It features crystal locked circuitry and a
massive 2400 watt power surge making it ideal_for small fridges, vacuum
cleaners, power tools etc.
Any model an absolute necessity where 240V isn't avai lable. Call Altronlcs
today for more information on freecall 008 999 007.
300 Watt
K 6750 Kit Version $279
' internally generated trigger. ;;
K 6755 Built-up $379
Ideally suited to Q 0156 (
equired) . Superb quality
C to 80 MHz Max 600
Olis DC Lead length
prox 1.5m.
600 Wall
1
-•:• .,..
~· ..
\:··.1.:::p.::• a
Mi
j~.::.; .
M~~
4
9
~
NIMROD Gas Soldering Iron
Now you can solder anywhere with this new gas soldering iron. Feature,:
See through gas chamber (no more guessing how much gas is left) • Built
in ignition cap • Uses standard butane gas • Comes with _safety bench
stand • Supplied with 2mm soldering tip and blow torch tip • Ad1ustable
temperature from 400'C to 12000c • Can be easily refilled with standard
butane lighter gas • Replacement tips are less than half price of some
other brands.
T 2455 Exhaust Port $6.50
REPLACEMENT TIPS - ALL $6.00 ea
T 2451 Replacement 1mm Conical Tip
T 2456 Hot Knife Tip $6.00
T 2452 Replacement 2mm Conical Tip
T 2457 Hot Blower Tip $12.50
T 2453 Replacement 3mm Conical Tip
T 2458 Blow Torch Tip $12.50
T 2454 Replacement 3mm Chisel Tip
T 2448 Butane Gas Refill $6.95
I
Car Voltage Adaptor
This handy unit simply plugs into your car's cigarette
lighter socket and presto! Gives you switchable 3, 4.5, 6,
7.5, 9 and 12V DC at up to SOOmA. Includes a range o(
output plugs. Reversable polarity . .Great for pocket TVs,
radios, portable CDs etc .
As used in security systems, battery backup
for computers, solar power systems etc ...
Premium Grade Long Life
S 50~9
S 5070
Logic Probe $37.so
Probe Pulser $54.95
Our Top Selling
j-.
Digital Multimeter ~ •. .,1~ .
With quality and features you would
expect only on expensive meters the
Q 1056 represents excellent value for
money. 17 Ranges include DC and
AC volts, resistance, diode check,
DC current with 1.5V and 9V battery
a 1056 t49_95
a 1057
Q 1067 Thermocouple to Suit $29.95
.
a 1272 20MHz
a 1280 50MHz Logic
check.
Q 1065 Carry Case to Suit $12.50
Turn 12V DC to 240V AC. This fantastic
inverter will power lights, TV's tools,
electric shavers and a whole host of
other appliances. Great for camping, out
in the bush and any place where 240V is
not available. Featurea: Complete with
over current circuit breaker • Fused 240V
output • Built in panel meter to monitor output voltag_e • panel meter to
monitor output voltage • Strong steel case and chassis
$2
$29.95
$44.95
This fully featured meter offers
performance and facilities
which are normally only found
on far more expensive meters.
Features include DC and AC
v, DC and AC current (up to
10A), transistor check,
capacitance check (up to
20uF), resistance and
continuity, frequency count,
temperature via optional
thermocouple ('C or °F) and
high impact case just to
mention a few.
a 1064 t149.5o
300 Watt Economy ·
· inverter
12V/1.2AH
Two models available. Both feature audio and
visual 'hi' and 'low' indication, and TTL/CMOS
-D
- ·1 _
g_l_t_
a_l_E_n_g_1·_n_e
_e_r_l_n_g
___.., compatibility:
Deluxe version includes a logic
pulser function making it even more versatile for
•1meter
fault finding, and a 50Hz logic probe. Economy
Mult
version includes 20MHz logic probe only.
K 6770 Kit Version $499
K 6774 Built-up 12V Input $625
K 6775 Bui lt-up 24V Input
S 5065
£ig,_.;;:;:::;:-"111111iiijjii,i;,i;;:;:=---.-;:;-;;;r.;:-iji;.;;j;;:~
,,
~
-;; •·•· .. ,
~ f<at>
~ -- 'j"
-..-.-
Carry Case To Suit $12.50
Flush/Surface Mount Alarm Paner -·With stylish compact good looks this alarm blends s_mooth ly into
any residential or office decor by either flush mounting into the
wall, or surface mount. 3 sectors include 24 hour panic/ fire,
perimeter and internal which can ~e i.solate~ ena~Hng the ~larm to
be armed at night with occupants inside whilst still protecting
entries. Simple 4 digit access code for operation. See Altronics '92
catalogue for full details.
S
$119.oo
5490
Super Small PIA
Alarm Power Su_pply
Incorporates Pulse Count
Triggering which virtually
eliminates false alarms.
Operates on 8-16V DC .
Features: walk test LED,
wide 12x12m detection, N.C.
tamper switch, interfaces
with most alarm panels. See
AL TRON/GS '92 catalogue
for full details.
s 5302 Normally $}!f.oo
This UPS (Uninterruptable
Power Supply) will supply 12V
at 1.2 Amps via its internal
inbuilt sealed lead acid
battery even when the mains
has failed. Ideal for use
with alarm system power
supplies monitoring systems,
warning systems etc .
M 9090 $69,95
This Month $69.oo
Siren
Cover
Weatherproof
Horn Speaker
Protects external
siren from
tampering, weather
etc. Also ideal for .
mounting strobe.
Suits C 2015 horn speaker.
Tamper switch available.
S 5460 $28.95
10 watt, 8 ohm. Ideally
suited to S 5460 siren
cover and our alarm
panels. Th is horn can
s 5160 Tamper Switch $1.85
C 2015' Normally $ ~
This Month
High Energy Siren .
Absolutely ear
.
splitting SPL
120dB. Handy bracket
for wall mounting
etc. 12V 300mA.
Ideal for industrial
applications or alarm systems.
Dlmenlfons: 100mm Diam. 125mm L.
s 5177 Normally $ ~ 5
deliver in excess of 120dB
when driven by an appropriate
driver circuit.
, •
'
'
. ·
Alarm Strobes
Uses Xenon Strobe tube
for high energy flash. Output
rate approx 1 per second . 12V
DC, 320mA. Dimensions : 97mm
diam, 50mm High.
$
12 .95
Amazing Nlcad Battery Bargain
from $2.oo
..
~ u11
it1«<•,u,11'!
WR
At full specification premium quality. Good tor up to 1000 recharges.
- ,
~~,: .
S 5020
S 5022
S 5023
10-24
$2.50
$7.oo
$13.oo
1-9
$2.95
$8.oo
$14.oo
AA 500 MAH
'C' 1.8 AH
'D' 4AH
Passive Infra-Red
Flood Light Control
~~~~~~r
S
5350
$
. .95
49
This universal infra-red
remote contro l makes all
other remote units
superfluous. Will control
CD players, videos, TV's
and stereos etc.
Controls up to 6
different appliances .
Easy to use and
programme from an
existing functional
remote
High performance Series II. Features•
Noise attenuating earphones • Noise
cancelling mic • Sturdy construction •
Cushioned head pad • Includes standard
aircraft jacks • Over 4000 sold Australia
wide • Don't pay $400 or more!
$189.oo
$19 .50
Case To Suit
A
Redford PECC
Woofers
This new bullet
tweeter looks and
sounds great.
Genuine Motorola
KSN 1165A. Features
400 watt maximum
power capability
frequency response 1.BkHz to 30kHz and
SPL at 93dB (2.83v/ 1m) . 91 x 91mm
mounting hole centres. Specifications
available on request. Simply wires in
parallel to your woofer. No crossover or
capacitor required. As it presents almost
no load to your amp it doesn 't effect the
overall speaker system's impedance.
Fantastic for hi-fi or disco speakers.
C 6160
$39.95
A
A
0492 $119.9s
0493 Optional Remote $24.95
Universal Remote
Control
Altronics Aviation
Headset
9075 Carry
1------.
M9000 3, 4.5, 6. 7.5, 9, 12v<at> 300mA $'95 $17.95
M 9005 6, 9, 12V <at> 500mA $pl"5o $19 .95
Telecom approved
Features: Variable length outgoing
message (maximum 30 seconds •
Secl.}rity code access for remote • Call
screening• 12 month replacement
guarantee • Optional Full function DTMF
Remote Control tor Playback, Reset,
Save, Outgoing Message change.
vT~(oafs~~:r~h~~?in~:ig~:i
or even to find the keys in the dark! Features
daylight sensing circuit which means unit will
not activate during daylight hours (save on your
power bill). Includes manual override facility to
turn lights on continuously or automatically. Features
movement sensitivity adjustment, and turn on period. Great for the driveway or backyard .
Complete with two screw In type sockets for standard 150W floodlight globes (not
included).
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The Story Of
Electrical Energy, Pt.21
Electric lighting came to Sydney's streets on 8th
July, 1904. Suddenly, at 5.16pm, the city streets
were a blaze of light from Circular Quay to
Redfern & from Hyde Park to Darling Harbour.
By BRYAN MAHER
Back in the new Pyrmont power
station, the Lady Mayoress, Mrs. S. E.
Lees, had turned a gold presentation
key. That simple act had closed the
exciter field circuit of a 5.2kV alternator. This supplied 3-phase AC to new
substations at Town Hall and Lang
Park. At each site, a high-voltage induction motor began to spin, driving
two direct-coupled 240V DC genera-
tars. With the generators in series,
240/480V DC 3-wire circuits buried
under the city's footpaths supplied
231 arc lamps to illuminate the streets.
These 2000 candlepower electric
lamps so overpowered the old gas
lamps that the future of electricity
was assured. Each set of 10 carbon arc
lamps was connected into a series
group which was supplied by the 480V
DC mains. The grounded centre neutral wire was used to provide odd sets
of five series arc lamps with a 240V
DC supply. The carbon rods had a
burning life of only 16 hours and then
had to be replaced.
But we have begun our story in the
middle. Though practical electric
lighting became possible from 1831
followfng the discoveries made by
Michael Faraday in England, Sydney
was then only a struggling convict
Top of page: this photo shows the
interior of Pyrmont power station as it
was originally built, with Ferranti
high speed twin-cylinder steam
engines.
NOVEMBER
1992
79
dangerous, that the electricity leaked
away in the ground, and that it could
cause fires and/or electrocution. These
companies made no mention of their
own dubious installations, where
cables were sometimes just flung over
the roofs of buildings.
As well, there were numerous new
entrants to the field, like the Empire
Electric Company Ltd, whose advertised rate per kilowatt hour (kWh)
forced the council to reduce its tariffs.
And this was before the said company had even commenced operations.
Commercial/domestic supply
Manufactured by Belliss and Morcom, this 300 horsepower twin-cylinder steam
engine measures about four metres long. The engine with its 4-tonne flywheel is
direct-coupled to a Bruce Peebles alternator which once supplied 210kVA at
420V 3-phase to drive the machinery in a biscuit factory. The small generator at
the righthand end is the exciter, which can produce up to 90V DC at 61A to
supply the rotor field coils of the alternator. This 14-pole machine ran at 428.57
RPM & generated a 50Hz AC supply. However, the frequency would not have
been all that stable, regulated as it was by a simple but fairly effective steam
valve governor. The unit is today a working exhibit at the Power House Museum
in Sydney.
village. And even though Sir Humphrey Davy's arc light invention had illuminated the Paris Opera House in
1846, practical electric illumination
had a long gestation period.
The illumination of Sydney's streets
was by oil lamps in 1843, then by gas
three years later. But the city fathers
were slow to adopt electric light.
Other towns were more progressive.
On 8th November, 1888, Tamworth
had the honour of being the first town
in the Southern Hemisphere to have
electrically lit streets. The town of
Young was soon to follow and then
the towns ofLambton, Moss Vale, Broken Hill and Redfern got into the act.
The electricity bill
Moving slowly, the NSW government took 10 years.to pass a bill au~
thorising the Sydney Municipal Council (SMC) to acquire generating plant.
Finally, the council appointed one
Major Cardew as its consultant. He
advised the building of a power station in Kent street to supply an 8km
radius with illumination.
The Kent Street site was resumed
80
SILICON CI-IJP
by the Government due to an outbreak of bubonic plague, so Pyrmont
became the second choice. With incredible foresight, the Council anticipated the coming demand from homes
and private factories. However in entering the electricity supply business,
the City Council faced competition
from five well established private DC
generating enterprises.
At the forefront of this competition
were th_e Oxford Street Electric Light
Company, the Imperial Arcade Electric Light Company, and the Strand
Electric Company whose 100-volt DC
system spread like a spider's web
around the Strand Arcade and adjacent shops.
In the long run, the City Council's
greatest competitor was the implacable Australian Gaslight Company.
Well entrenched for over 60 years before the advent of electricity, the gas
company was a formidable adversary.
A lot of quite unethical propaganda
emanated from the Council's competitors . The private electric companies
spread false tales to the effect that the
council's underground supply was
The Council power also supplied
city buildings and homes where the
new incandescent filament lamps,
invented by Swan in England and
Edison in the USA, were a great boon.
These globes were more suitable for
indoor lighting than arc lamps which
generated lots of heat and copious
quantities of carbon dioxide and other
noxious gases.
City building owners immediately
saw the advantages of lifts powered
by DC motors. These were much
cheaper than the steam powered hydraulic elevators previously used by
the largest companies. Some big city
stores retained their hydraulic lifts
for 50 years or more, simply replacing
the steam engine with a DC motor.
However most new buildings went
straight to electric elevators, many
later changing to the Ward Leonard
control system for more accurate positioning. Little did those people realise that their DC lifts would dominate
electrical supply policy for the next
80 years.
Home owners and tenants in city
apartments quickly saw the advantages of electric appliances. After lighting, there was a big demand for electric irons and European hair curlers,
as in this field gas had no equivalent.
Slowly, electric heating and cooking
replaced gas appliances.
Sydney Municipal Council charged
lighting either at a flat rate of five
pence per kWh or a two-part rate
which cost more for primary units
and two pence for each subsequent
kWh. Power for all motors, lifts, cooking and heating was charged at the
lower rate.
One year's operation saw 86 private and government consumers connected to the DC mains supply, in
Sydney Council linesmen used to do all the work without any heavy machinery.
This photo shows how the heavy cable reels were grappled off the horse-drawn
drays prior to the cable being laid in the trenches.
addition to the street lighting, with a
total loading of just over 1MW. Generating and distribution costs were 1. 99
pence per kWh.
Pyrmont power station
The original Pyrmont station was
equipped with three Ferranti twincylinder high speed steam engines.
Each was direct coupled to a Ferranti
5200-volt 50Hz alternator. Two of
these units were rated at 1000 horsepower (746kW) each, while the third
was rated at 500hp (373kW).
Five Babcock and Wilcocks boilers
supplied steam at 160 psi (1.1 MPa) to
drive the engines. Coal was brought
in by rail (or ship in emergencies),
while cooling water came straight from
Darling Harbour. This installation was
state of the art in its day, with economisers and feed water heaters to increase thermal efficiency.
So fast was electricity accepted in
Sydney town that within 12 months
of Pyrmont opening, additional machinery was ordered to almost double
the original capacity.
The 45km of underground cabling
around the city was extended and the
existing DC substations enlarged. Today, we can only marvel at the speed
at which such work progressed without the aid of heavy machinery. All
trenching was done by pick and shovel
and all carting by horse and dray.
While the City Council was busy
wiring up the city and close surrounds,
a few industries further out set up
their own plants. Some of these were
state-of-the-art AC systems. One notable engineering effort was installed
in a biscuit factory.
AC/DC system
True to the preferences of Thomas
Edison, and with lift motors in mind,
Sydney Council supplied all the in-
ner city with a 240/480V 3-wire DC
system. But the AC/DC rotary substations were expensive to install and
operate. Therefore, the outer city areas were supplied by 240/415V AC
mains from transformer substations
at Darlinghurst, Athlone Place and
the power station itself.
This was the first normal AC supply for Sydney horn:es. In outer city
regions, streets were lit by the same
arc lamps as in the city, except that
groups of nine lamps were arranged
in series across the 415V AC mains.
Thus electricity was ushered into
Sydney as two incompatible systems :
DC and AC. This dichotomy was to
persist for more than 80 years, until
1986, often to the despair of city
shopkeepers.
As late as the 1950-1960 period,
some business establishments in York
and Clarence Streets still operated on
the 240V DC supply. The custom was
for electrical businesses to provide
their own motor generator set to provide 240VAC 50Hz, so that radios and
NOVEMBER
1992
81
DC in the inner city caused Sydney
Municipal Council to upgrade its biggest and longest lasting DC substation
in Clarence Street. Originally installed
in 1904, this substation used high volt. age induction motors driving series
connected pairs of DC generators.
Later, rotary converters generating 240
volts DC were connected in pairs to
give the 240/480 volt 3-wire supply.
The first mercury arc rectifiers were
installed in 1933.
Mercury arc rectifiers
This photo shows three of the 36 600kW mercury arc rectifiers installed in the
Clarence Street substation in 1959. These mercury rectifiers used six anodes, for
3-phase full wave rectification. The cubicles underneath them house auxiliary
equipment and the cooling fans.
appliances could be demonstrated.
Problems came with television, because the in-house AC supply was
usually of uncertain frequency. Any
deviation from the nominal 50Hz
caused drifting hum bars on the
screens of early TV receivers, to the
consternation of shop owners and prospective customers.
So fast was the electrical growth in
1904 that within three years an extension was added to Pyrmont to house
new more efficient machinery, thus
reducing the cost per kWh. The City
Council then shocked its competitors
by dropping the council's rate from 2
pence to 1.5 pence per kWh. Subsequently, each private electric company
asked the council to buy it out as they
could no longer compete.
The goodwill of four companies was
eventually purchased by the Council
for a total of 110,375 pounds, each in
proportion to its yearly unit sales.
The largest was the Strand Electric
Lighting Company which had been
selling 1.24 million kWh units annually. The Council then refurbished those
customers' installations to bring them
up to 240V standards.
Legal tussle
A legal tussle, previously unheard
of in Australia, ensued in 1905. The
new Royal Hospital for Women, in
Oxford and Young Streets, Padding82
SILICON CHIP
ton, was designed and built assuming
an electricity supply. It was four storeys high and electric lifts and lights
were essential for safety reasons.
But Paddington Council wanted to
charge Sydney Municipal Council
rates for the narrow land corridor occupied by the high voltage power line
to the hospital. Further argument
raged over a substation site. Sanity
eventually prevailed; the substation
was built within the hosp.ital and
agreement between the councils was
reached.
Sydney Council mounted an intensive campaign to electrify the city.
Arc lamps were hired out to commercial users who could not afford the
purchase price. Similarly, businesses
could rent DC motors in any size from
375 watts to 22.5 kilowatts. The small
units were 240V types, while the larger
units ran off the 480V supply.
The conservative rates charged encouraged businesses to hire a total of
361 motors in the first two years of
the scheme. More than 50 different
types of factories and stores took
advantage of this facility.
Three years after its commencement, the Council undertaking had
1600 customers using 6 million kWh
units annually. And the system was
growing daily, taxing the power stations' 6.7MW installed capacity.
The increased use of 240/480 volt
On 1st June 1959, the substation
was changed over to mercury arc rectifiers exclusively. Six sets of six
600kW glass bulb mercury arc rectifiers with main and interphase transformers and accessories were provided. When placed on load, the mercury arcs bathed the interior of the
cabinets in a beautiful (but dangerous)
violet glow. Together, the 36 mercury
rectifiers could deliver 7300 amperes
DC.
The large glass bulbs came by sea
from Hersham in England, the final
shipment arriving in early 1959. During shipment, the bulbs were suspended in a large timber crate using
ropes and steel springs. The bulbs
were shipped upside down with the
large quantity of mercury sloshing
about in the head of the condensing
chamber.
In Sydney, each glass vessel was
mounted within a steel cabinet, its
mercury cathode at the bottom and
the condensation void at the top. Each
glass vessel had anode arms with external copper plated molybdenumiron alloy contacts. These connected
via the glass/metal weld to join the
dense graphite anodes inside. The
glass arms each provided a separate
pathway for the mercury arc from the
cathodic pool at the bottom to each
graphite anode. This isolation prevented any chance of a flashover between the AC anodes of any two adjacent phases.
The auxiliaries consisted of a cooling fan and starter electrodes for each
glass bulb. The fan was automatically
speed controlled by passing its AC
supply through a saturable reactor.
These were commonly used to control AC currents before the days of gas
thyratrons or Triacs and SCRs.
A saturable reactor is an iron-cored
inductor with two AC windings and a
DC winding. The AC windings car-
ried the current to the fan while the
DC winding carried the output current from the mercury arc rectifier.
When the rectifier was supplying little output current, the inductance of
the AC windings was so high that the
fan would not run.
As the rectifi er was called upon to
supply more current, that current
passed through the DC winding of the
saturable reactor. This increased the
magnetising force in the iron core and
so reduced the reactance of the AC
windings. This in turn increased the
AC voltage to let the fan run.
At full DC load current in the rectifier circuit, the reactor core would be
completely saturated, cancelling all
the inductance of the AC windings
and allowing the fan to run at full
speed. Thus, the fan speed was automati cally varied to give the right
amount of cooling at all times.
Exciter circuit
When first switched on, the rectifier bulb contained cold mercury. To
initiate an arc and thus ionise the
liquid metal, a magnet pulled down a
spring arm within the bulb to make
contact with the mercury. That passed
a current into the mercury.
A second magnet would then attract the spring arm upwards , drawing an arc sufficient to initiate ionisation. To maintain ionisation, even with
no load current, two subsidiary electrodes continually maintained a sma 11
arc to the mercury surface.
Because the cathode mercury pool
must be the positive output terminal,
there is no such thing as a negative
output 6-phase glass rectifier. Therefore, in a 3-wire positive/zero/negative DC system, the negative 240V DC
bus must originate at the transformer
secondary star point.
To obtain balance in the 480V /240V
system, the council linesmen would
connect some lighting circuits between positive 240V DC and zero.
Other circuits would be connected
between zero and negative 240V DC .
With roughly equal loads on both
sides , only a small difference current
would flow in the zero line returning
to the substation. Motors and other
heavy loads were made for a 480V DC
supply and were thus connected between the +240V and -240V lines.
Because th e major lo ad current
flowed out on the +240V line and
returne_d via the -240V line, four recti-
This photo shows smaller mercury arc rectifiers than were used in the Clarence
Street substation. These units have only three anodes and a somewhat lower
current rating.
fiers out of the six were used in parallel to supply this current. The fifth
and sixth rectifiers of a set provided a
zero centre line potential.
Each set of six rectifiers could supply 1215 amps continuously, or 1520
amps for a 2-hour peak period. In
addition, heavy loads of up to 2430
amperes mulrl be supplied for up to
15 seconds , allowing the starting of
large motors anywhere in the city.
Out-of-balance current in the zero line
could be as high as ·1 20 amperes indefinitely.
As late as 1986, Sydney City still
drew just over 4000 amperes from the
last remaining three sets of glass rectifiers.
Apart from their high efficiency,
these mercury arc rectifiers were designed for zero maintenance. They
had no moving parts, the critical components were sealed under vacuum ,
and neither the mercury nor the graphite anodes deteriorated during full
load operation. These rectifiers thus
had a very long working life.
You might ask why so much DC
load still existed in Sydney as late as
1986? In truth , much of that load exists to this day but it is now hidden.
The advent of the AC supply in later
years saw the replacement of most DC
machinery with 3-phase squirrel cage
induction motors. But from the very
first days, DC motors were found to be
superior for controlling city lifts and
indeed this is still the case.
Many buildings in York, Clarence,
George and Pitt Streets, as well as
around the waterfront area, date from
early days before modern building
standards were in force. Any attempt
to rebuild the lifts in these buildings
to modern design using AC motors
would be very costly. Therefore, the
DC driven lifts remain to this day, and
will probably continue for years to
come.
By the mid 1980s, the advent of
high current solid state rectifiers allowed building owners to install their
own rectifier systems to run from 415V
AC mains. But until 1986, the supply
authority, Sydney County Council,
was obliged to maintain the 480/240V
DC reticulation throughout the city.
Thus Clarence Street substation remained a_s a supplier of DC for 82
years.
Acknowledgement
Special thanks to Phil Parsonage
and Des Barrett, and grateful acknowledgement to the staffs of Sydney El ectricity, Pacific Power and the Museum
of Applied Arts and Sciences, and to
Gordon Anderson.
SC
NovEMB EH
1992
83
REMOTE CONTROL
BY BOB YOUNG
A low-cost speed controller
using discrete ICs
This speed controller for electric models is very
small and uses surface mount devices in the
decoder circuitry. It can have up to eight FETs
and will easily handle motor currents of up to 50
amps or more - all this is on a PC board
measuring only 55 x 38mm.
Back in the March 1992 issue, I
indicated that the speed controller I
would ultimately present would have
all the bells and whistles, including a
dynamic brake. However, the way
things have worked out, the circuit
presented here is quite different from
that originally intended.
While the circuit does not include
a dynamic brake, it has provision for
more FETs than originally proposed
and it can therefore handle very high
currents without a heatsink.
may be expensive but they really are
sophisticated devices.
To complicate matters further, I did
promise that I would use only readily
available components and this precluded the use of specialised servo
ICs and microprocessors, which require software drivers.
And that brings me to the heart of
the delay: the problems offitting all of
the promised features including a dynamic brake into a small, low-cost
unit using standard components. The
"The design allows up to eight FETs to
be fitted and these can be driven at
switching rates varying from 500Hz to
2500Hz"
This project has surprised me from
the very beginning in just how subtly
complex the problems involved with
designing a speed controller really
are.
I take my hat off to those early pioneers who developed the commercial
speed controllers of today. Let me tell
you, modern FET speed controllers
brake introduces more complexity into
the circuit and requires a foolproof
interlock and virtual duplication of
the entire drive circuits. As a result,
the component count soars out of
sight, as does the size and cost.
In hindsight, I can see that I was
gradually drawn into the project while
not fully understanding its complex-
ity. As I researched the problems and
discussed desirable features with
other modellers, the design began to
grow like topsy.
The circuit featured this month is
the design I had in mind when I accepted the project, with some added
features. I called the original Speed 1.
Speed 2 and Speed 3 followed in quick
succession and then one day I looked
at the proposed design and realised
that the cost of putting it into production was far too high.
Speed 3 had all of the features promised. It was a very clever, fully-digital
design by Dean Herbert, using eight
4000 series logic chips. However, it
would have required a 4-layer PC
board to reduce its size to that required by modellers. It was also too
difficult for the average modeller to
construct. In other words, we had lost
the plot.
So it was back to the drawing board
for Speed 4, a very promising design,
again by Dean, with all of the features
of Speed 3 and not as much complexity. We are currently working on that.
By this time, however, the clamour
for publication was deafening, so without further ado, here is Speed 18.
Design features
This design is a variable switching
rate (500 - 2500Hz) single ended speed
controller without a brake or reverse
facility. It is intended for the experimenter who wants to know more about
achieving the maximum performance
from a particular speed controller and
electric motor combination. As all
motors vary in their inductance, capacitance and commutator speeds,
they tend to respond best to a particu-
R12
47k
+5V
R11
47k
R1
100k
INVERTER
PULSE DETECTOR
7
R6
47k
7
+5V
C2
.001
VR1
1M
R19
100k
J2
R2
47k
R4
47k
J1
C3
.01J
R3
47k
R18
1k
PWM
COMPARATOR
7
7
MONOSTABLE
R9
47k
ERROR
INTEGRATOR
7
-------R27
R22
R28
7
R21
MOTOR
DB
100V
5A
M1
-----
C14
0.1
V1
+
T
MOTOR I
SUPPLY I
..I..
Q3-Q10
8xlRFZ44
C9
0.1
M2
SPEED CONTROLLER
Fig.I: this speed controller decodes the pulses from a remote control receiver
and converts them into a variable duty cycle pulse train to drive the motor. The
circuit can use up to eight FETs for handling motor currents of up to 50 amps.
lar switching speed.
To this end, the design allows up to
eight FETs to be fitted and these can
be driven at switching rates varying
from 500Hz to 2500Hz. By monitoring motor RPM and load current, the
running current can be set to the minimum by varying the switching speed,
thus obtaining the best efficiency from
that controller/motor combination (see
previous issues for a discussion on
the interaction between switching
rates, motor types, commutation rates
and so on).
Only off-the-shelf components have
been used, as can be verified by a
glance at the circuit - see Fig.1. The
PC board will be a surface mount unit
with all the surface mount devices
already soldered into place; ie, the
VIEWED FROM
ABOVE
GDS
board will be "populated" apart from
the FETs. Modellers may mount up to
eight FETs on the board, depending
on the current rating they want. The
PC board will be available from
Silvertohe Electronics, PO Box 580,
Riverwood, NSW 2210.
Circuit description
Let's now have a look at the circuit
shown in Fig.1.
The main components of the circuit are a voltage controlled monostable, an error integrator, a triangle
NovEMBEH
1992
85
' Speed Controller for Electric Models - ctd
wave oscillator, a voltage tripler, a
PWM comparator and a missing pulse
detector. Most of these functions are
based on an LM358 dual op amp and
an LM339 quad comparator. Both of
these ICs are designed for single supply operation.
Op amp ICla, transistor Ql and
associated components form a voltage controlled monostable. Positive
pulses (RX IN) from the receiver momentarily turn on Ql via CZ and RZ,
thus discharging C3. C3 then charges
via resistor R4 and trimpot VRl. The
op amp thus delivers a positive output until the voltage on its inverting
input (pin 2) exceeds the voltage at
pin 3.
The pulse signal from the receiver
is also inverted by comparator IC2c.
The pulse output from the voltage
controlled monostable (ICla) is then
subtracted from the inverted input
pulse by comparator IClb which also
performs integration. The output of
the integrator, pin 7, then feeds back
to the non-inverting input of the monostable, ICla.
If the input pulse is longer than the
monostable pulse, IClb's output increases until the pulse lengths are
equal. Similarly, if the input pulse is
pin 13. The frequency is adjustable
from about 500Hz to 2500Hz although,
in practice, the range is less than that
if a lO0kQ trimpot used for VRZ. With
this value oftrimpot, the range is about
640 to 1640Hz. If higher or lower
switching rates are desired, then the
values for R13 or R14 will have to be
changed.
The triangle wave generated by IC2d
is compared with the proportional
control voltage from IClb by ICZa, the
PWM comparator. The output at pin 2
is a constant frequency, variable duty
cycle pulse train. The duty cycle determines the power output of the motor; ie, a 50% duty cycle gives half
throttle regardless of the switching
rate. At 100% duty cycle, the input to
the FETs is straight DC, equal to the
output of the voltage tripler.
A set of jumpers at the inputs to the
PWM comparator (IC2a) enable its
sense to be inverted. This facility is
necessary if the transmitter does not
have a servo reversing switch.
Voltage tripler
Mosfets require a gate drive signal
of at least 12V to ensure a low "on"
resistance. Unfortunately, the drive
batteries on 020 and 035 motors are
"To make the Mosfets switch rapidly,
they must be driven by a gate signal
which has very fast transitions"
shorter than the monostable pulse,
IClb's output decreases until the pulse
lengths match. The end result is that
the duration of the incoming pulse
has been changed into a proportional
control voltage.
This proportional control voltage
will ultimately determine the length
of the DC pulses fed to the motor and
thus will control its speed.
Triangle wave generator
Comparator IC2d and its associated
components operate as a Schmitt trigger oscillator with the result that a
triangle waveform is produced at pin
10 (across C6) and a square-wave at
86
SILICON CH/I'
only four or five cells, so they cannot
be used for this. A voltage tripler,
running off the +5V supply solves the
problem. It consists of diodes D5, D6,
D9 and DlO, plus the associated lµF
capacitors.
The square-wave output of oscillator IC2d drives the voltage tripler circuit and this then charges lµF capacitor C13 to close to +14.4V (assuming a
fully-charged 4.8V battery).
Transistor Q2 acts as a high current
driver for the paralleled gates of the
Mosfets. It is driven by the PWM comparator and since its output is open
collector, it acts as a level converter
between the nominal +5V signals and
the higher voltage of the tripler. R19
sets the stick travel on the transmitter.
Zener diode ZDl clamps the signal
from the emitter of Q2 to prevent overdrive to the gates of the Mosfets. Resistors R20-R29 (lOQ) act as "stoppers" to prevent the possibility of parasitic oscillation.
Gate capacitance
One peculiar feature about Mosfets
is that although they are voltage controlled devices and thus require essentially no power to turn them on,
that is really only theory. In practice,
when the devices are actually switching, they soak up power like a sponge.
The problem is gate capacitance.
In order to make the Mosfets switch
rapidly, they must be driven with a
gate signal which has very fast transitions, from low to high and from high
to low. This means that the gate driver
circuit must charge and discharge the
gate capacitance of the Mosfets each
time they are switched on or off. That
charging and discharging process
takes quite a lot of power. And the
more gates you put in parallel, the
more power required to drive them.
The driver circuit provides enough
current to drive the eight FETs. One
stipulation here is that as the switching frequency increases, the effect of
the gate capacitance increases. Depending upon how many and which
type of FET is used, there comes a
point at which the input drive will
begin to fall significantly and therefore the Mosfets will not be driven
hard enough.
The result of this is that their drainsource resistance will not be at the
absolute minimum and so the Mosfets
will dissipa_te a lot more power than
they should (perhaps more than they
can handle). And the corollary of this
is that the motor will not get as much
power as it should.
The data books rate the typical FET
as having an input capacitance of
about 1500pF, although some such as
the IRFZ44 are as high as 3000pF. In
my ex'perience though, they are much
higher than this, or at least they certainly behave as if they are, in most of
the speed control circuits I have tested.
(Editor's note: perhaps a more relevant specification in this instance is
Qg, or total gate charge. The specification for gate capacitance does not givt
the whole picture by any means, since
the capacitance actually changes dur-
ing the switching process, as the drainsource voltage changes. Miller Effect
is very significant. Gate charge is the
total charge which must be fed to or
removed from the gate in order to turn
the device on or off.
For the IRFZ44, the total gate charge
is quoted as a maximum of 100 nanocoulombs, for a Vgs of 10V and an ID
of 52 amps. Using the formula Q = CV,
the effective gate capacitance is 10
nanofarads; ie, 0.01µF or four times
the typical quoted IRFZ44 gate capacitance of 2500pF. This explains why
Mosfets behave as though they have a
much higher gate capacitance than
the specified figures) .
With eight FETs fitted, the limit on
switching frequency will be about
1400Hz for this circuit.
Another very important factor to
keep in mind when choosing the size
of the FET array is the behaviour of
FET junctions with temperature
changes. The rise in the "on" resistance of the drain-source region is
linear with temperature and so there
is little point in putting a few very
expensive FETs in the array and then
running them at an elevated temperature. It is much better to use a greater
number of cheaper FETs.
Remember also that the switching
rate is the heart of any speed controller design. Switching times must be
fast enough to prevent excessive heating of the Mosfet channels during their
on-time, but slow enough to avoid
serious rounding of the PWM waveform due to the gate capacitance. The
ideal switching speed should be decided upon after considering the type
of FET, how many, the type of motor,
its current drain and commutation
rate. In other words, there is plenty of
scope for experimentation.
•
speaker that performs with equal
A excellence on both classical and
rdck music is a rare speaker indeed.
While this is probably the ideal loudspeaker, the sad fact is that most
speakers are leaning towards either
one or the other type of music.
So when a speaker comes along which
truly performs equally well with such
different types of music, it's no wonder
the critics sit up . This is what Stereo
Buyers Guide had to say about the new
DALi 400:
"The soundstage was large, very large,
but unlike most speakers which give a
large stage, the 400s didn 't fluff the
imaging inside it. The detail was surprising in its clarity and placement- surprising because ourreference speakers didn't
deliver as much on the same tracks. This
doesn't happen very often!
The bass was simply stunning- as clean
as we've heard in a long time, yet so
controlled and strong, especially in the
lowest octave. No wool here; the 400s
shook the foundations. The highest frequencies glistened. ... the stage showed
lots of air; there was plenty of room in
the image for all the musicians.
The 400s won us over completely without any trouble at all. These speakers
are great value in build quality, aesthetic appeal, and especially in musical
temperament. We 're recommending
them without reservation".
Audition the new DALi 400 at your
nearest DALi dealer today.
DALi 400 SPECIFICATIONS:
Cabinet type .. ........ ....... ... ......... Bass reflex
Woofers ........ .. ... 2 x 1 70mm Polypropylene
Tweeter .... .......... .. .......... . 25mm soft dome
Freq 'cy response(+/- 3dB) ..... 35-18,000Hz
Sensitivity .... ... .. .............. 93dB (2.83V/1m)
X-over frq 'cy ............ 250GHz (Lin.Directivity)
Long Term Power Handling ........... 140 Watt
Timber finishes .... .. .... .... Black or mahogany
R.R.P . .................. ......... ... $2500 per pair
For a free information kit on the full range of DALi speakers, please contact Australian Distributor:
SCAN AUDIO, 52 Crown Str, Richmond VIC 3121. Ph: (03)429 2199. Fax (03)429 9309
Missing pulse detector
Comparator IC2b operates as a missing pulse detector. While ever pulses
are present at the output of IC2c ,
diode D4 charges capacitor C5 and
therefore holds pin 6 of IC2b low.
· Thus, the open collector output at pin
1 will be off. If the pulse signal is lost
(due to radio interference or radio or
connector failure), C5 discharges via
R7 and therefore pin 6 rises above pin
7. This causes pin 1 to turn on and
thereby remove the base drive current
to transistor QZ. This kills all drive to
the Mosfets and so turns the motor
off.
If the pulse signal is restored, ICZb
will again be disabled by diode D4
and normal circuit operation will
resume.
Interference suppression
Electric motors with commutators
are appalling sources of radio interference, so a few precautions must be
taken. Capacitor C14 helps filter out
commutator hash while diode DB prevents inductive spikes from destroying the Mosfets. V1 is a varistor which
is rated 50% higher than the motor
supply voltage and which helps hold
down spikes in both directions. These
components - ie, V1, DB and C14 must be mounted directly across the
motor terminals.
The total current drain for the speed
controller is 5mA.
Performance
The circuit has been tested with
motors drawing up to 50 amps with
little or no warming of the FETs. Further test results must wait for next
month's issue.
SC
NOVEMBER
1992
87
COMPUTER BITS
■
BY DARREN YATES
Mass data storage in the palm
ofyourhand
This month, we take a look at the Pocket Hard
Disc or PHd from KT Technology. It runs as a
logical hard drive from your PC's parallel
port, can be removed in seconds & can store
up to 120Mb of data.
If you need to transfer a large
number of files from·one place of work
to another, your options are fairly limited. You could back up your files to
floppy disc, but as soon as your files
become larger than about 1.2Mb, it
starts to get messy keeping track of
which disc is first, second, third and
so on. Backing up large amounts of
data is also very time-consuming.
Alternatively, you could use your
trusty modem. However, with a maximum data transfer rate of 9600 baud,
it could be quite some time before you
get your telephone line and your computer back again. Even with the various data compression systems, . the
best serial transfer rate you can get is
Pocket hard disc
backing up) large files in the form of
the Pocket Hard Disc (PHd). This
amazing piece of technology is just
148 x 75 x 28mm in size and fits in the
palm of your hand but it can store up
to 120 megabytes (120Mb) of data.
The beauty of the PHd is that it's
fully external - it requires no internal
driver card and simply plugs into the
parallel printer port on your PC. The
sneaky thing about it is the way it
obtains its power supply - it pinches
it from the keyboard socket via an
adaptor which is supplied with the
unit.
In operation, the disc is set up as
the next logical drive in your system.
So if you already have a hard disc
designated as your C: drive, then the
PHd becomes the D: drive.
It then behaves just like a normal
hard disc drive, yet is removable in
seconds and can then be transported
to any AT/386/486 system anywhere.
Pretty neat, huh?
Now KT Technology has come up
with the answer to transferring (or
Setting it up
around 57,000 bits per second or 7Kb
per second, which is still slow if you
have to transfer megabytes of data.
Another option is to use one of the
new "floptical" disc drives. These use
a disc very much like a normal 3.5inch disc and can store up to 20Mb.
While this may sound great, the problem is that you have to assume that
the user at the other end also has a
floptical drive to read the disc. It is
also surprising just how quickly a
20Mb disc can be filled with just a
few large files.
The PHd pocket
hard disc is not
much bigger than
a 3.5-inch floppy
but, depending on
the version, can
hold up to 120Mb
of data.
88
SILICON CHIP
The Pocket Hard Disc comes complete with its own installation software. This software ensures that the
drive is recognised and checked when
the computer boots up. In normal operation, there is no change to any of
your existing software and the unit is
used just like an ordinary hard disc
drive, You can copy files to and from
the PHd disc drive in the normal manner, or use it as the logged drive when
working in a word processor or some
other application.
Before you install the PHd, you need
to make sure that the system is turned
oft otherwise it may be damaged or
the data lost.
The adaptor power cable is con-
This delay period is cut to about five
seconds on a 386DX machine.
The data-transfer rate is greater than
700Kb/ second and the maximum seek
time is 19ms, which is comparable to
the faster internal hard disc drives
available. This can be increased by
using a _h ard disc caching program
such as Windows SmartDrive.
Applications
The PHd pocket hard disc plugs into the computer's printer port & obtains its
power from the keyboard socket via an adapter cable. The device has no effect
on normal printer operation & can be unplugged in seconds.
nected. to the keyboard socket and
one printer port and you wish to use
then the keyboard plug fitted to the
your printer and the PHd? No probback of the adaptor socket. The power · lem. The PHd has another 25-pin D
cable is then connected to the PHd.
socket at the other end and so you just
This makes it independent of exterplug your printer into that. From then
nal power supplies which means that
on, you just print files in the normal
it can be used all over the world.
way as though the PHd was not there.
There is also a printer port cable
But back to the installation of the
which is suppliedwith 25-pin D sockPHd.
ets at each end tci connect the PHd to
Formatting
the parallel port.
Before you can start using the PHd,
Once the appropriate file has been
there are a number of changes needed
copied across, you need to format the
on your C: drive, The first of these is
PHd and check the data transfer to
and from your printer port. Formatmade to your CONFIG.SYS file so that
each time the computer boots up, it ting is done in the usual way (ie,
format D:), while the supplied disc
looks for the PHd. This is done by
adding the following lines:
contains a file called PHDINITB.COM
(for the 80Mb version) which checks
INSTALL=C: \DOS\SHARE.EXE
the data transfer and initialises the
DEVICE=PHDLPTB0.SYS
PHd.
The device driver you install deNote that this data transfer check
pends on which model you have. For
only needs to be done once.
example, if you have the 40Mb PHd
Once you've done that, switch off
model, the relevant device driver is
and reboot your machine.
PHDLPT40.SYS and so on.
You can make these changes using
Boot-testing
either EDLIN or nearly any wordprocessor. Alternatively, you could use
While your machine reboots, it tests
the Windows Notepad or the Winthe validity of the printer port to endows SysEdit feature.
sure that it will transfer data reliably.
Next, you have to take the floppy
During this time, a test message is
displayed on the screen.
disc provided and copy the
The only drawback, and it's a miPHDLPTxx.SYS file from it to the root
nor one, is that if you don't have the
directory of the C: drive. This is the
PHd plugged in when you boot up, it
only file the computer requires to contakes a 286 computer about 30 sectrol the PHd.
onds to figure out that it isn't there.
What do you do if you only have
One area where the PHd will really
excel is in backing up existing hard
disc drives. In fact, when we recently
upgraded one of our 286 machines to
a 386DX with a new 85Mb hard drive,
we used the PHd to back up the old
40Mb hard disc and then simply transferred everything over to the new system. It was that easy.
Previously, you'd either have to
back everything up onto floppies or
load in each piece of software again,
taking hours to do so. The PHd backed
up the complete disc in only a fraction of the time that would have been
taken for floppies, without the hassle
of changing anything.
The ·drop test
Because the PHd is designed to be
fully portable, the makers have designed it to withstand a 150G shock.
That means that it will well and truly
handle normal everyday bumps and
knocks and then some. But no, we did
not try the drop test. That would be
pushing things a bit too far.
The PHd also only weighs 350gm,
which is really a little heavy for your
shirt pocket, but the fact that it is so
compact brings up another important
_point - security. Because it can be
unplugged so easily, you can take a
back-up of your hard disc with you
wherever you go.
Price & availability
One of the best things about the
PHd is the price. The 80Mb unit has a
retail price of $799. When you consider that floptical drives retail for
about $850 and that floptical disks
are $30 fo $40 each, the PHd is good
value. The 40Mb version sells for $549;
the 60Mb for $599; and the 120Mb
version for $999.
For more information about the
PHd, contact the distributors, · KT
Technology, Building 7 Central Boulevard, Portside Business Park, Port
Melbourne 3207, Phone (03) 646 5755;
fax (03) 646 7997.
SC
NOVEMBER
1992
89
5 1/4" POWER "Y"
CONNECTOR
1:/:/#=i-ELECTRONIC
Digital
Kitchen Scales
Allows you to connect two 5 1/4"
drives from one power source.
P19049 ....................... $9.95
KRYPTON GLOBES
Whether your a professional chef or
dream about being a professional chef,
7
these are the kitchen scales that you
need. Don't rely on luck by throwing in a dash of this and a pinch of
that. With the Arlec electronic kitchen scales , it's a simple matter of
pressing a button to separate the weight of different ingredients. No
need to separately weigh different ingredients in different bowls.
The add and weigh facility enables the weight of the bowl and/or
contents to be zeroed. This allows other ingredients to be added by
weight more accurately.
The digital display displays weight in kilograms and grams or
pounds and ounces· and can be converted from one to the other at
·the touch of a key.
The Arlec Kitchen Scales also come with a beeper timer
and a plastic bowl in the form of a jug which can also double as a
mixing bowl.
""::.======~
A 15076 ......................................................................$69.95.
1:1:1!'.iit,f ~ .
RECHARGEABLE
DRIVE AND DRILL
1000
Two Speed Cordless Drill and screwdriver.
Probably one of the most handy tools you'll ever have!
This screwdriver will drill or drive screws into timber, sheetmetal, and
hardened plastic.
• Has a powerful 4.8 volt motor.
• Convenient cordless operation.
• Two speed: Drill - 325 RPM Screwdriver - 150 RPM
• Drilling capability - 250 holes
• Screwing capability - 150 screws
• Torque: 33 kg/cm
• Forward or reversible operation
• Quality Jacobs Chuck (1/4" or 6.5mm)
• Chuck key holder on the unit
• Rechargeable through an adapter which simply plugs into a regular
household powerpoint (240 Volt) and reduces the voltage to a safe low level
• Supplied with 4 screwdriver bits:- 2 slotted-heads & two Phillps-heads
• Pilot lamps adds light to dark or confined work place
• Charge indicator
• 12 month guarantee
T12298 .........................................................................$79.95
Indoor / Outdoor
Digital thermometer
You'll never have to press your nose up
against a thermometer again to read
what temperature it is.With this great
digital thermometer the temperature
can be read quickly and easily. But best of all ii will read
the temperature Indoors or outdoors at the flick of a switch.
By placing the thermometers sensor outside, the thermometer will read
outdoor temperatures of •20'C to +70'C. Then by simply pushing the
switch to the "IN" position the thermometer will read indoor
temperatures of 0'C to +50'C.
A91200 •.......•$22.95 Celsius only
(Note :Celsius & Fahrenheit
thermometer has a smaller
digital display)
A91201 .. $24.95 Celsius & Fahrenheit
2.4V KRYPTON GLOBE
S13430 Pack of 2 ..•...•............$3.95
2.8V KRYPTON GLOBE
S13432 Pack of 2 ...................$3.95
3.6V KRYPTON GLOBE
S13434 Pack of 2•....••....•.......$3.95
4.8V KRYPTON GLOBE
.
S13436 Pack of 2 ...................$3.95
A RLEC RECHARGABLE
A.EADY-LIGHT
Tl\e torch every home needs!
It's always ready for use and uses
an extra brightness Krypton globe
which is 70% brighter than a
n ormal vacuum type globe. Its
rech argeable batter ies can be
chraged over 1000 times from a
regular household powerpoint
(240 Volt). The Ready-light has a
strong magnetic base allowing It
to be clamped lo any steal or iron
surface. Comes complete with
wall bracket t o conveiniilntiy and
recharge torch
A15054 ...... .
MANNESMANN
TALLY
MT82
,,"
~~
Mannesmann Tally have for
~
many years enjoyed International
,
.
acclaim for the quality and functionality of their compU1er printers . The matrix
printer lives up this reputation. It can offer professional printing of the highest
quality. Due to the printe~s high resolution capabilities, graphics too can be printed
with outstanding clarity. The computer printer can be connected to mOS1 of the
more common compU1er systems by means of Its modular interlace. Even If you
have had little experience with computer printers. you woni have any problem
using this model because it was designed to be user-friendly. The integrated
aU1omatic she.et feeder Is a main feature of this printer. It supports different
character sizes, character densities line spacings and man y other functions, so
that you can produce printed text to your individual requirements.
SPECIFICATIONS :
Printing method
Serial printing with 24-needle matrix print head
Print Speed
Draft
160 cps at 1O cpi/192 cps at 12cpi
Letter Quality
53 cps at 1O cpi/64 cps at12 cpi
Character densities
10 cpl, 12 cpl, 15 cpl, 17 cpl, 20 cpl proportional
Resolution horizontal: 60, 80, 90, 120, 180, 240, 360, dpi.
vertical: 60, 72, 180 dots per Inch
Ribbon life
approx. 2 million characters
Dimensions
439mm x 162mm x 310mm
Automatic cut sheet feeder
Capacity of paper bin
60 sheet cU1 sheet A4 size
C93040 ........................ .... ....................... $549.00
MANNESMANN
TALLY
MT81
A Matrix printer that Is built to last.
The MT81 Is designed to meet most
of your personal computer printing requirements and will per1orm to Its highest
level without the operator requiring any previous technical exper1Ise. With various
character densities, line spacings and many more funci ions, this printer Is a
valuable addition for your personal computlng applications (e.g. Word Processing,
Graphics).
SPECIFICATIONS :
Printing method
Serial printing with 9-needle print head
Print Speed
Draft
130 char./sec.
NLQ
24Char/sec.
Characters per line
80 char. at 1Ocpl
Form length
upto 22"
Paper dimensions
width: 3• to 1o·
thickness: 0.002" to 0.004•
Ribbon
black 1.2 mill. draft char.
Power source
120 V AC, 60 Hz; 220/240 V AC, 50 Hz
Acoustic noise level
below 60dB (A)
Weight
4.5kg
Dimensions
CM xH xD) 370mm x 100mm x 250mm
C93000 ................................................... $299.00
PRICES DROP LIKE
A ROYAL BIKINI.
1
•
1
PRINTER CARD ..................... $29
GM RAM CARD ....................... $249
2 PORT SERIAL CARD .......... $39
GAMES CARD ........................ $19
CLOCK CARD ...... .................. $39
5121576K RAM CARD ............ $99
2 WAY FOO CONT................. $39
VGA 16 BIT 256K .................. $69
VGA 16 BIT 512K ....................$89
VGA 16 BIT 1 MEG, .............. $149
16M HO CACHE CARO .......... $529
HDD IDE /FDD ........................ $25
HOD IDE/FDD/SPG ................ $35
8 BIT ETHERNET CARD ........ $239
16 BIT ETHERNET CARD ...... $285
PRICES-A
HO T
PADDLE CARDS l BRACKETS
40M SEAGATE DR1Vc....----S319
85M HO 17ms ACCESS. VOICE COIL
2 YEAR WARRANTY.....................$419
105M HO 19ms ACCESS
$439
120 KALOCK DRIVE. .................... $475
126M HO 16ms ACCESS. VOICE COIL
2 YEAR WARRANTY....... _ _ _ $519
170M 2 YEAR WARRANTY............ $679
212M HO 12ms ACCESS. VOICE COIL
2 YEAR WARRANTY..................... Sn9
The first book of 1•2·3 Release 2.4
The first book of Windows 3.1 2nd Ed
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WordPerlec1 5.1 for Windows
The first book of Excel 4
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Handy Quick Rsfsrsncs Books
Word for Windows 2
DR DOS 6
Excel 4 lor Windows
PC Tools 7
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} )NUHAWADING SERVICE CENTRE ) ) Norton Utllttes 6 .Only
BEST WARRANTY
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5Mb SYSTE
1
86-16Mhz (LM21) ....... $1199
86SX•25Mhz (LM31) .. $1299
86SX·33 (LM41) ......... $1349
86-33 LM5764KCactM.$1459
86-33128K Cache ..... $1479
86-40 (LM65)64KCecha$1459
86S X·20 (LM85) ......... $1499
86DX·33 (LM157)
56K Cache ................. $2289
86DX•50 (lm172)256K... $2889
86-33 EISA ................. $4189
NEW
1T'
286-16Mhz (LM21 )........... $1349
386SX•25Mhz (LM31) ....... $1 449
386SX-33 (LM41) .............. $1499
386·33 (LM57) 64KCache $1579
386·33128K Cache .......... $1599
386•40 (LM65) 64K Cache$1599
486SX·20 (LM85) .............. $1649
486DX·33 (LM157)
256K Cache ...................... $2339
486DX·50 (lm172)256K .... $3039
486·33 EJSA ...................... $4889
WOW.
NEW
1
200Mb SYSTE
286·16Mhz (LM21) ............ $1369
16Mhz (LM21 ) ..............$1449 286-16Mhz (LM21 )......... ..
366SX•25Mhz (LM31) ........ $1469
X•25Mhz (LM31) .........$1549 386SX-25Mhz (LM31) ...... .
386SX·33 (LM41) ............... $1519 386SX·33 (LM41) ................ $1599 386SX·33 (LM41) ............... $1
386-33 (LM57) 64K Cache$1599 . 386·33 (LM57) 64K Cache.$1679 386·33 (LM57) 64K Cache.$204
386-33128KCache ............ $1609 386·33128KCache ............. $1699 386·33128K Cache ........... $212
386-40 (LM65) 64K Cache $1599 386•40 (LM65) 64K Cache $1679 386·40 (LM65) 64K Cache $214
486SX·20 (LMSS) ............... $1669 486SX·20 (LM85) ................ $1749 486SX·20 (LM85) ............... $2199
486DX•33 (LM157)
486DX·33 (LM157)
486DX-33 (LM157)
256K Cache ....................... $2359 256K Cache ........................ $2439 256K Cache ........................ $2889
486DX·SO (lni172)256K ..... $3089 486DX·50 (lm172)256K ...... $3189 486DX·SO (lm172)256K ...... $3689
486-33 EISA ....................... $4289 486•33 EISA ........ ,............... $4339 486·33 EISA ........................ 4789
11!1
4"
f'fl> 1024 x 768
~;;;;;;;;;;;:::::'J JI::::- NO~;INTERLACED
6 DOT PITCH.$1895
LET US OU~E ON~~~ o~~J/~1~~oJ~~~ REQUIRE
SUPA VGA COLOUR
MONITOR 1024 X 768
0.28" DOT PITCH
•·
•
3 VEAR WARRANTV••• $43
iiiiiiiiiiiiiiiiiiiirrr.i'im
l r:::.'niiiiiiiiiiii:R':'::ITRON POWER 200 ~ y
MEMORY
1·9
10:-99--100~1
41256-08 ........ $2.95 $2.75
$2.50 1
44256-08 ........ $7.95 $7.75
$7.50 I
44256-07........ $8.95 $8.50
$7.95 :
SIMMS
1-9 10•24 25+ 100+
1
1M x 9-70 $47 $46 $45 $44
:
1Mx9-60 $69 $67 $65 $63
1
1
256K•70
$23 s21 s19 s11
1
256K-80
$21 $19
$17 $15
4M x 9-80 $219 $209 $199 $179
:
SIPPS 1M x 9-80
·t
$79 $6
I
9
1
•
~-.
A pocket sized Inverter
_
with punch. Powers
:) - ·appliances Including rv·a
video·a, drilla, lights, laptopa etc. ·
Continuous power rating Is 140 watta.
But will run opptlancea with a name
plaleratlngol200watta... $159.00
Genius Scanner
i(6
·
Black, White & Grey•Emulation
·· ·
Scanner with powerful Photo/
'. Image Editor & Multilingual Omnilont
OCR. Windowa Compatible ...... $299.00
.
20" MONITORS
Res.1280 x 1024
•
-
PERSONAL LAMINATOR • ... .
(SAVE $10 THIS WEEK!) .
Laminate those precious
.
9-
0 .31 dot pitch
photos, and Important
•
.
$2 995 Display model
business cards. Every club or
F '
de
.
organization nG11ds one of these!
ora a-arranged monatration
.
$SS OO
ea
7155
This week only
•
.
I
FREE FREIGHT ANYWHERE IN AUSTRALIA FOR ORDERS OVER $25.00. OFFER EXPIRES 30/11/92.
"-
CHECK OUT OUR NEW RANGE OF MIXERS
VE CHANNEL
ECIAL
FECTS MIXER
SPEAKERS
INDOOR SPIRAL
ANTENNA
• 300 ohm ribbon cable
At laatl A console or lreestanding mixer with eight
inbuilt special efllects. Allows sounds and ellecta to be
mixed into existing soundtracks without the aid of
additional external sound generators.
Aa the MM6 Is designed for both DJ and studio uae the
following Inputs are provided: • 2 i turntables• 4 x iine
inputs• 2 x low impendance microphonea
Eight special elfecta are programmed into the unit:
•siren • telephone • machine gun • bombing • shooting
• ambulance • thunder • laser.
Studio outputs are availa ble for connection to a power
amplifier and a recording tape or cassette deck.
Other features include bass and treble controls
headphone (cue) monitoring, CHt to CH2 crosa'tader
microphone talkover switch, master volume level co~trol
and left and right LED
A12013 ............. $299.00
FOUR CHANNEL
MICROPHONE
MIXER
Ila size and simplicity makes this mixer portable and easy
to operate. This will accept up to lour low Impedance
microphones and mix them through to one microphone
output Each microphone volume can be Individually
controlled and a master volume control attenuate• the
overall audio output level.
A12001 ................................. $69.95
antenna
• Suits AM/FM tuners and
portable TVs.
• 1 Meter lead wtth 300
ohm spade terminals
L15040......... $9.95
Ill
FOUR CHANNEL
STEREO AUDIO
MIXER
• Compact portable desk
mount or panel mounting
atereo mixer with 5 band
equalizer and twin LED
display UV meters.
• 3 x stereo magnetic
tunable inputs switchable
• Headphone monitoring
on all channels
• 18 dB talk over switch
• Output sockets for both
the amplifier and tape
deck.
A12012.... $399.95
AUDIONIDEO
ONE INRFA RED
REMOTE
CONTROL FOR
YOUR VCR, TV,
CD, HIFI & Aux!
This unit will replace all
your existing remotes & la
programmable to replace
Mure ones. Has Uquid
crystal display, clock,
alorm, and countdown
Be the first In your office
to have a mouse that
every one will want use.
This cute little mouse
cover puta a bit of fun and
colour onto your desk
while keeping your mouse
free of duotl
Cr069. ]$795
timer ..... - ...........$67.95
COMPUTER
ACCESSORIES
31/2" HARD
DRIVE
MOUNTING KIT
MOUSE
CLEANING KIT
Keep dust and dirt from
damaging your mouse
with this handy mouse
cleaning kit. This special
rounded tool will find ita
way into all the hard to get
at places. The kit also
comes with cleaning fluid
and 5 soft cloths to keep
your mouse apoueaal
C21071 .................$9.95
MOUSE KIT
•
The MM-4 la a 4•channet stereo mixer with balanced
in/output. The trim control corre ■ ponds with all Input
signals. and it can control without any distortion by PEAK
- . - . - . • LED. Also the EFFECT control ls provided as a kind of line.
Each output level can be controlled UR independent
volumes. It can be used as a DI-BOX that so the output la
balanced. And it does not choose a apace because of the
compact s ize. The MM-4 is a mixer designed by musician••
request.
FEATURES: • CHANNEL INPUTS •TRIM control
• EFFECT level control • PAN control • PEAK LEAD
indicator • POWER SWITCH • CHANNEL VOLUME control
• MASTER INPUT • EFFECT SEND• EFFECT RETURN •
OUTPUT PEAK LED switch • EFFECT RETURN control.
ECT RETURN control• EFFECT SEND control • MASTER
VOLUME l & R control
A 12017........... $299.00
New "wet, dry, wer·
aystem cleans and dries
all parts which come Into
contact with the mag netlc
tape. Fluid la applied
direcUy on to cloth
cleaning tape prior to use.
It uses clean tape for each
cleaning operation. low
drag for use Is sensitive
mechanism•
- -.....
A12004 .............. , .................. $169.00
c21on ...............$1&.9s
Keep your computer and
accessories free of dust
and grime while not in
use.
xr• Cover Set
Stanci alone
3 pin plug
Plugo Into oocklt 1dJ1c1nt to
the equipment thot you wont
1o·prot1ct. All ouUall on 1
power boord con be
protected by ,n-Ung the
Trl1ngta'Surg1/Splk1 Plug
Into any of Iha flff ouuata.
GrHn 11f1ty neon glowo
when power 11 on.
Approvot No. V88021
Total energy roUng: 225
Jouleo (10/IOOOua)
Protection level: 275V
Nomlnol, 475V Peok.
Reoponaa Time : Better thin
10 nanoaacondo. Automatic
rea•L
MOUSE GIFT SET
~
X10060 .................$25.00
C21074 ...............$19.95
amount of dust, dirt, or
magnetic oxide particles
on your drive heada to
cause problems, errors
downtime or expenelve
service call. Regular use
of a head cleaner will keep
yo..- drive free of trouble
causing dirt and help keep
yo..- system up and
running. These disk
cleaners are limple to UN
and include cleaning
solution and Instructions.
• 3 1/2"
C12560............$6.95
• 51/4"
C12555............$4.95
•
-
10" HIGH POWER
WOOFER
• With ribbed block
paper con(!. • 40 wotta
• Black duet cap
• Cloth edge
• Rubber mounting seal
C10228 ...... ....$49. 95
1 0" DOPED
PAPER CONE
• Dark grey cone
• Black dust cap
• Black round frame
C10238 .......... $59. 95
e)
8" FULLRANGE
• Twin cone 1pe1kar
with white paper cone
ideal for public 1ddrea1
C10224 ....... ...$24.95
Here It Is! The Ultimate
mouse kit. You get the
cute little mouse cover to
protect It from dust, the
mouse cleanhg kit with
the rounded tool & 5
cloths, the mouse house
and mouse pad all In a
handy black case.
It takes only a minute
C10233 .......... $44. 95
:1i: I
C21068 ......... $16.95
HEAD CLEANER
DISKS
• Black round frame
column speakers.
• 30 watts RMS
• Foam edge
• Whizzer Cone
C21066 .............. $14.95
AT' Cover Set
. -.... u
SURGE/SPIKE
SAFETY PLUG
they can be added to existing video tape sound tracks.
Ideal for weddings. family , sporting and other recordings.
■ • Input for a video camera, VCR, CO, tape, tuner, auxiliary
and turntable.
• Magnetic/ceramic turntable inputs
• Microphone left and right panpot
• Optionally available AC power pack
• Dual output monitoring VU meters
• Linler sliding level fader controls
• Mono/stereo microphone input
• Video camera or VCA output
• Headphone monitoring
• Battery opertated 9 volt
• Battery testing facility
• Mono/atereo switch
cpver.
A11456 ....... $16.95
~
A proleulonal audio mixer designed for the aerloua home
.,...••■ video movle maker though to the home video camera uaer.
Background music and effects can be faded In and out ao
Everything you need to
keep your mouse happyl
You get a mouse pad, a
mouse holder, a cleaning
kit (previously described)
and a cute little mouse
VHS VIDEO
HEAD
CLEANERS
• Dark grey cone
• Black dust esp
rubber ■ urround.
• 60 watta RMS
X1997~....... $9.95
rr
• High compliance
rubber surround.
• 45 watta RMS
• High compliance
2 Universal brackets with
acrews to mount 3 1/2"
hard drives Into computer
cases.
MM-4 4-CHANNEL
BALANCED
MIXER
-
8 " DOPED
PAPER CONE
~~
;::' :'.$'"'~----~
,. , - ~ l'C"'> ----·&_,, ~·:_;. ~
COMPUTER
CLEANING KIT
To gain optimum
performance and prevent
damage to valuable disks,
this cleaning kit haa all
you need to keep yo..computer In top notch
performance. Anti-static
cleaning pada, cleaning
swabe, cleaning solu tion,
5 1/4" & 3 1/'l· cleaning
diskettes.
c21 on...............$19.95
12" HIGH POWER
WOOFER
• With ribbed black
paper cone • 50 wotta
• Black duet cap
• Cloth edge
• Rubber mounting seal
C102291ti4.95
6" HORN & LINE
x•FORMER
• Weatherproof plutlc
horn with 100 volt line
transformer
• 15 WIiia RMS
• Adjustable metal
bracket
C10218 ...........$74 .95
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STORE
NOW OPEN
241-243
WRIGHTST
number 1 bastselling wordprocessing book-only from QUEI
• Combined tutorial and reference
for all levels of users.
• In-depth coverage and numerous
illustrations for basic and
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• Extras include tear-out command
map, icons, margin notes and
cautions. 1,232 pages
A complete,
comprehensive
Introduction to
this popular DOS
utlllty!
• Covers all aspects of PC Tool's disk
backup, security-and disk
optimization.
• Practical examples and screen
shots.
• Features tips, tricks and cautions.
700 pages
B20204 ..........................$51.95
B20215 ...•..•.•...•.••... $57.95
USING
WINDOWS3.1
SPECIAL
EDITION
Complete and
-.•
practical resource - ·- -· ·
for great Windows Performance!
• Takes readers from installation
through customization.
• Provides tips on boosting
windows performance and
networking
• Includes application techniques
and integrations.
1,030 pages
B21282 .................... -$51.95
USING
EXCEL4
FOR
WINDOWS
SPECIAL
EDITION
The expert guide to
getting the most from Excel for
Windows!
• Includes a Quick Start tutorial and
numerous tips.
• Features a tear-out ce>mmand chart
• Provides complete coverage of all
features.
1034 pages
B20345 ..........................$61.95
3AG PACK OF 40 ($10 Value)
Contains: 4 x S00mA, 8 x 1A,
6 X 1.SA, 2 X 2A, 6 X 3A, 4 X SA, 2 x
7.5A, 4x 10A
The best selling
book on Be>rland
C++ updated for
the most recent ralaasa!
•Provides an overview of both C
and C++
• Introduces Iha Windows
application development process
and explains the major
components of a Windows
application
• Includes coverage oi Turbo C++
for Windows and a separate
chapter on Borland's Turbo
Debugger and Turbo Profiler
1,000 pages
A comprehensive
tutorial to this
popular
disk management
and repair package!
Includes step by
step instruction for optimum
performance.
• Provides many notes and tables for
at a glance reference.
Teaches users how to manage flies
and solve problems.
Make yo;.or PC a better faster and
safer place to work with Using Norton
Utilities 6 from Qua.
550 pages
USING
1-2-3
RELEASE 2.4
SPECIAL
EDITION
The performance•
boosting tutorial
reference for the
latest version of
1·2-3 for DOS!
• Provides tips and advice on how to
Improve worksheet, database, and
graphics performance
• Includes spacial icor.s to highlight
the new features of this latest version
• Includes detailed instructions for
using the latest features of 1·2·3.
1120 pagao
B20203 ..........................$55.95
B21269 ...........................$59.95 ~~-
USING
QBASIC
USING TURBO
PASCALS
2nd EDITION
Perfect tutorial and
reference for all
beginning QBaslc
programmers!
• Hands-on instruction and practical
programming samples
• Step by step tutorials Introduce
essential QBaslc concepts
Includes a comprehensive instant
reference and a complete Keyword
reference. 810 pages.
·
B21287...................... $51.95
100 per pack
1N4002 (1A 200V RECTIFIER)
The most
comprehensive look
at Turbo Pascal 61
• Prov!des a ihorough
tutorial of the Turbo Pascal language
and environment.
• Covers essential aspects of Object•
Oriented programming with Pascal
1,800 pages
B21290 .......................$61.95
LED MIXED PACK.
(MIXED COLOURS)
1N4004 (1A 400V RECTIFIER)
Approx 100 pieces, 5mm size
Contains 50 Red, 25 Yellow,
25 green.
Cat: S15992 ................$8.95
Cat: 210106...............$5.95
Cat: 210136 .............. $14.95
M205 PACK OF 40 ($10 Value)
1N4007 (1A 1000V RECTIFIER)
Contains: 5 x S00mA, 10 x 1A,
10 x 2A, 5 x 3A, 5 x SA, 5 x 10A
Cat: 210112................$6.95
MIXED SCREW PACK
Cat: S15994 ................$8.95
1N914 i 1N4148
Cat: 210135................ $3.95
Approx 100 pieces. This pack is a
must for the electronics handy person
and computer serviceman.
Contains screws for computer cases, _:_,.... •,u
Disk Drivas ate.
Cat: 210103...............$4.95
1N5404 (3amp 400V)
MIXED IC SOCKETS
100 Units ($37.00 Value)
Contains: 15 x 8 pin, 20 x 14 pin,
10 x 16 ,pin, 10 x 18 pin, 5 x 20 pin,
10 x 22 pin, 5 x 24 pin, 5 x 28 pin,
10 X 40 pin,
Cat: P10546 .............$24.95
B21290 .....................$61.95
(STUDENT ID REQUIRED)
WordPerfect {Win) Edu ...... $175.00
Coral Draw V.3 Edu ............ $340.00
MS Excel V.4 Edu ............... $240.00
PageMaker V.4 Edu ............ $300.00
d Base IV Edu ...................... $250.00
Please note: the educational software Is not kept on the
shelf. It Is ordered In when you present your student ID.
Cat: 210114..............$12.95
LED MIXED PACK
(Red only 5mm)
Approx 100 places
Cat: 210138.............. $11.95
Cat: H10960 ................$3.95
MIXED POLYESTER PACK
(In IEC Package)
Approx 50 places
Cat: R15120 ..................... $9.95
~
~
DIE CAST BOXES
Diecast boxes are excellent
mm hole, available
colours
14030 Red ......... $1.20
14032 Green ..... $1.45
14034 Yellow .... $1.45
GREYFl f
RIBBON CABLE
14way
16way
20way
24way
25way
26way
34way
36way
40way
50way
60way
$/Mir
$1.90
$2.20
$ 2 .50
$2.90
$3.20
$3.60
$3.90
$3.90
$4.90
$ 5.90
$ 6.90
10TURNWIRE
WOUND
POTENTIOMETER
quivalent (Bourns
540S Beckman 7256)
lals to suit 16-1-11,
8·1·11, 21·1·11 .
14050 SOR R14100 SK
14055 100R R1 411 0 10K
14060 200R R14120 20K
14070 SOOR R14080 1K
14090 2K
1-9
10+
$12.95
$ 10.90
14130 SOK. .............$1 6.95
14140 1001<. ........... $1 5.95
000
000
0 0 0
E]<at>J<at>)
nencoded keypad, 10
igit keys plus two utility
eys. Light grey in colour.
UTPUT ARRANGEMENT:
utput Pin No. Symbol
.......................N.A_ _ _ _ Shield plate
....................... Column 2
~- - - - .... Row 1
....................... Column 3
1>---- .... Row ·1
...................... Column t
~-----Row2
....................... Row3
O..................... N.A.
at. C19030
-9
10+
2.95
$2.50
for RF aheildingand
strength.
Screws are provided with
each box.
H11451
100 x so x 25mm ........ $8.95
H11452
110 X 60 X 30mm........ $9.50
H11453
120 X 65 X 40mrn. ...... $10.50
H11461
120 x 94 x 53mm...... $13.95
H11462
188 x 120 x 78mm .... $15.95
H11464
188 x 188 x 64mm .... $29.50
~
~-~~:~~
PURPOSE
TRANSISTORS
PN100: a NPN general
purpose medium power
amp and awitch with
continuous collector
current up to SOOmA.
PN200: a PNP general
purpose amp at collector
currents to 1 AMP.
Both are T0-&2 plastic
package.
PN100 REPLACES:
PN2221, PN2222, PN2222A,
PN3585, PN3568, PN3569,
PN3643, PN5133, 2N2219A,
2N2222A, 2N3414, 2N341S.
2N3416, 2N3417, 2N3700,
2N3704, 2N3904, 2N4123,
2N4124, 2N4401, 2N5088,
2N5210.
PN200 REPLACES:
PN2907, PN2907A, PN3638,
PN3638A, PN3640, PN3644,
PN4121, PN4143, PN4248,
PN4249, PN4250, PN4355,
PN4916, PN4917, PN5910,
2N2905A, 2N3467, 2N3702,
2N3906, 2N4125, 2N4126,
2N4291, 2N4402, 2N4403,
2N5086, 2N5087, 2N5447.
PN100 ......T90001
PN200 ......T90002
1-9
10+
100+
$0.20
$0.18 $0.15
----------
SUPER BRIGHT
LEDS
• RED ................. 210146
• GREEN ........... 210147
• YELLOW........ 210148
1-9
10+
$1 .00
$0.90
Cat No.
210135
210105
210107
210110
210115
210119
10+
$0 .05
$0.06
$0.08
$0.10
$0.18
$0.20
IN4148
IN4002
IN4004
IN4007
IN5404
IN5408
100+
$0.04
$0.05
$0.06
$0.07
$0.14
$0.16
1000+
$0.03
$0.04
$0.05
$0.06
$0.13
$0.15
10K
$0.02
$0.03
$0.04
$0.05
$0.11
$0.14
IES
XT P.S 11f)W........... $139.00
FULL TOWER
220W P.S ............... $149.00
MINI TOWER
200W P.S ............... $89.00
BABY AT
P.S 200W................. $89.00
SLIMLINE BABY AT
P.S. 200W................ $89.00
I.
.I
Sava a small fortune on
these "Dlroct Import.. low
prollle IC sockets! PCB
mounting solder tall. All tin
plated phosphor bronze or
borrylllum and dual wipe tor
rellablllty.
1·9 10+ 100+
P1osso spin t5e 12e 1oe
P1056014pin 20e 18e 1~
P10565 t6pin 20e 18e t&e
P10567 t8pin 30e 25e 22e
P10568 20pin 35e 30e 2~
P10569 22pin 35e 30e 2se
P10570 24pin 35e 30e 2se
P10572 28pin 45e 35e 30e
BREAD BOARDS
This inexpensive range of
modular interlocking unita
enables a quick easy way
of experimenting with new
circiuts and ideas. There
are two main units
consisting of a terminal
strip or distribution and a
central plug in unit.
• 100 ho!eL
P11000 ................ $2. 75
•840 + 100 holes
·
P11007............... $14.95
• 1280 +100 holes
• P11010 ............ $26.95
•2560 + 700 holes
• P11018 ............. $69.95
WIRE WRAP
IC SOCKETS
Those quality 3 level wire
wrap sockets are tin plated
phosphor bronze.
P10579 8pin $1.50 $1.40
P10580 14pin $1.85 $1.70
Pt0585 t6pin $1.95 $1.80
P10587 18pin $1.95 $1.80
Pt0590 20pin $2.95 $2.75
P10592 22pin $2.95 $2. 70
P10594 24pin $3.95 $3.50
P10596 28pin $3.95 $3.50
P10588 40pin $4.95 $4.50
WOW!
WHAT PRICES!
IDC PLUGS &
SOCKETS
WOW I FROM $1 .00
COMPUTER
CABLES
• Six conductor lhlelded
computer Interface cable.
Wt2670 • CIC6 6 con.
1•9M
10M+
100M+
$1.30M $1. tOM $1.00M
Wt2672 • CIC9 .9 con.
1-9 M
1CJM+
100M+
$t.60M $I.SOM $1.20M
Wt2674 • CIC12 12 con.
1•9M
10M+ 100M+
$2.SOM $2.20M $1.90M
W12676 • CIC16 16 con.
1-9M
10M+ 100M+
$3.SOM $3.20M $2.SOM
Wt 2678 • CIC25 25 con.
1·9M
1OM+
D TYPE IDC PLUGS
1-8 10+
• DE9P llpln plug
P12166 $1.50 $1.20
• DA15P 15pln plug
P12168 $1.50 $1.20
• DB25P 25 pin plug
P12170 $4.50 $3.95
100+
$1.00
$1.00
$3.50
DTYPE
IDCSOCKETS
1-9
10+ 100+
■ ocbt
• DA15S 15 pin eocket
NICADS
$3.95
$4.25
$4.50
$4.95
$5.95
$6.95
D
Save a fortune on
expensive throw away
batteries with these
quality Nicad• and
Rechargeral
Size AA450mAH
1-9
10+
100+
$2.95 $2. 75 $2.50
Size C 12 AH
$9.95 $9.50 $8.95
P12169 $1.50 $1.20 $1.1111
• 0825$ 15 pin ■ ocket
P12171 $4.50 $3.95 $3.50
$2.95
QUALITY 5mm LEDS
Z10150(R). S0.15 $0.12 $0.10 $0.08
Z10151(G), S0.25 $0.20 $0.18 $0.12
Z10152(Y) .. $0.25 S0.20 $0.18 $0.12
------
s==:
12V DC FANS
BO X 80 X 25.4mm
12V OC. 1.7 Watt 0.14 Amp
T12469 ................$18.95
10+ tana, only $17.95
FANS
Quallty fans for use In
power 1mp11 computer
hotspot cooling etc.
Anywhere you need plenty
of air.
240V 4 518" T12461..$16.95
115V 4 518" T12A63 ..$16.95
240V 3 112" 112465.. $16.95
""l'J""
TOGGLE
SWITCHES
RECTANGULAR
LEDS
1-8 10+ 100+
RED
~ 15e 12,
GREEN
~ 15f t2e
YELLOW ~ t5e 12,
1K
toe
toe
toe
t!<at>.mo a: _)c?i.
DB25 CONNECTOR
SPECIALS
1-9
10+
100+
P10880 DE9P $1.00 $0.80 $0.60
P10885 DESS $1.00 $0.70 $0.60
P10881 DA15S$1.00 $0.70 $0.60
P10882 DA15C$1.00 $0.90 $0.60
P10885 DA15S $1.00 $0.80 $0.60
P10902 D825C$1.00 $0.80 $0.60
P10904 D825P $1.00 $0.80 $0.60
P10905 D825S $1.00 $0.80 $0.60
~
1-9
10+
S11010 S.P.D.T$1.20 $1.10
S11020 D.P.D.T $1.30 $1 .20
MOSFET SPECIALS
ICBVOLTAGE
REGULATORS
BARGAINS '
Deecrtption 1-9
10+
1.00+
7805UC $0.50
78t2UC $0.50
7815UC $0.50
7905UC $0.60
7912UC $0.60
7915UC $0.60
78L05 $0.40
78L12 $0.40
LM324 $1.00
555
$0.40
741
$0.50
$0.45
$0.45
$0.45
$0.55
$0.55
$0.55
$0.30
$0.30
$0.90
$0.38
$0.45
$0.40
$0.40
$0.40
$0.50
$0.50
$0.50
$0.28
$0.28
$0.80
$0.33
$0.39
I
,,
t•~
9 PIN D
\
I
SWITCH BOXES
2 WAY............... $59.95
4 WAY............... $69.95
MONITOR & KEYBOARD
SWITCH BOXES $69.50
• Lever operated suction
base grip for instant
mounting & portability.
• Mounts on smooth
non-porous surfaces
• Ideal for holding &
other small objects •
Sii
...
Tp ~ S8........
IDC CENTRONICS 36
WAY PLUG & SOCKET
100+
SO.OIi
Z10141(G).. $0.20 $0.18 $0.15 $0.12
Z10143(Y).. $0.20 $0.18 $0.15 $0.12
Z10145(0).. $0.20 $0.18 $0.15 $0.12 1
FLASHING LEDS
RED 5mm 1-9
10+
210159
$1.10 $1.00 $0.80
1 OOM+
$3.90M $3.40M $3.00M
P12167 $1.50 $1.20 $1.00
. l"SPACING
P12060 10pin
P12062 20pin
Pt2064 26pin
P12066 34pin
Pt2068 40pin
Pt 2070 SOpln
1-9
10+
2155 240V 6-15V 1A
M12155 ........$8.95 $7.95
2156 240V 6-15V A2
M1215fl .......$13.95 $12.95
2851 240V 12°6V CT 250rnA
M12851 ..... ...$4.95 .. $4.50
6672 240V 15 30vc 1A tapped
M16672 .......$12.95 $11.95
LOW PROFILE
IC SOCKETS
• OE9S 9 pln
CARD EDGE
CONNECTORS
QUALITY 3mm LEDS
ECONOMY
1000+
TRANSFORMERS Z10140(R) S0.15 $0.12 $0.10
BOARD ·
HOLDER
$6.95
I.I
. ''\l,,
Better than an
V..extra pair of hands,.,...
A must for all PCB work.
T12444 .............. $9.95
1-9
$9.50
$10.00
$8.50
$9.50
$9.50
$9.50
2SJ49
2SJ56
2SKt34
2SK176
2SJSO
2SK13_5
MJ,
~
,.a
10+
$8.00
$9.50
$8.00
$8.90
$8.50
$8.50
100+
$7.00
$8.50
$7.00
$ 6.90
$7.00
$7.00
ELECTRET
MIC INSERTS
With pl"9 for uey board
ln ■ertton.
C10170
10.es
100+
1000+
$1.20 $1.00 $0.90 $0.70
!t
TRANSISTORS
BUY IN BULK
&SAVEi
1-9
10+
100+
BC 547 $0.15 $0. to $0.07
BC 548 $0.15 $0.10 $0.07
BC 549 $0.15 $0.10 $0.07
BC 557 $0.15 $0.10 $0.07
BC 558 $0.15 $0.10 $0.07
BC 559 $0.15 $0. to $0.07
BC 327 $0.20 $0.15 $0.12
BC 337 $0.20 $0.15 $0.12
BD 139 $0.75 $0.60 $0.50
BD 140 $0.75 $0.60 $0.50
II
PCB MOUNTING
SCREW TERMINALS
(INTERLOCKING ENDS)
Theae lerminala feature
interlocking enda to fonn
any number of coMeCtiona, .
Standard 5mm apacing
pina.
P10520
1·9
100+
so.rs
P10521
$1.00
VHF Channels 0-11
UHF Channels 28-36
Suitable for prime-good
signal reception area. This
antenna is used for
installation on houses, flats
and, because of installation
simplicity, on caravans and
boats.
5 ELEMENTS
L15020........ $44.95
AS RIG NO.2
Included with this antenna
is a gutter grip mast and 8
metres of twin feeder cable.
Suitable for good signal
reception areas. Ideal for
houses, flats and caravans.
Horizontal or vertical
A small compact unit that
allows transmission of
video & audio signals (RF)
to any TV set or VCR within
range of 30 metres. Ideal for
watching videos in the
bedroom or kitchen without
having to move
the entire VCR or having
long extention leads
running through the house.
Can also be used as a
transmitter for a video
camera . With power on/off
switch audio and video
leads and supplied with an
AC adaptor.
A16150 Normally.. $95.95
NOW ONLY..... $84.95
mounting is provided.
L10978 ......... $49.95
WIRELESS STEREO
TRANSMITTER
VHF channels 0-11
UHF Channels 28-36 (AS 25)
UHF Channels 36-69 (AS 25/5
Suitable for medium-fringe
signal reception areas with
good front to back ratio.
18 ELEMENTS
L10972 ........ $109.95
This wireless stereo audio
transmitter allows portable
compact disc and casstte
players to be used with any
FM tuner/radio. Ideal for the
car, boat or home Hi Fi
system . Simply play the
disc or cassette and tune in
the signal on the FM tuner.
Can also be used with radio
headphones.
• Mono or Stereo signals
can be received.
ANALOGUE
WORKHORSE
• Fuse and Diode protection
•hFE measurements O - 1000
( By x 10 range)
• Mirror scale for more
accurate reading.
RANGES
• DC Voltage: 0 • .1, 0.5, 2.5,
10, 50, 250, 1ooov.
(20k ohm/v)
• AC Voltage: 0 - 10, 50. 250,
500V, 1000V (8kohm/V)
DC Current: 0-0.05, (50uA)
2.5, 25, 250mA
• Resistance:
0-2K, 20K, 2M 20M ohm
• Load Currant:
0-150uA, 15mA, 150mA
• Load Voltage:0-3V
• Volume Level:
-10- + 22dB. + - 62dB
• DC Current Amplification
Factor: (hFE) 0-1000
ACCURACY
.
• DC Voltage & Current:
Within +/-3¾ f.s
• ·Resistance: Within :/-3¾
Of are.
• Battery: 1.5V (um-3) 2pcs.
9V (oo6p) 1 pc
• Fuse: o.5A, 50 x 20min
• Diode: 4148 x 2
• C.C: 0.04uff x 50V
• Size: 147 x 99 x 57mm
• Weight: 400g
approximately
VHF Channels 0-11
UHF Channels 28-36 (AS 20)
UHF Channels 36-69 (AS
20/5)
Suitable for medium signal
reception areas with
• - - ••improved
VHF gain.
13 ELEMENTS
L10970 .......... $99.45
• Triggering Level: Positive and Negetlve 1 continuouely variable level;
Pull for Auto.
• Sync: AC, HF Rej, TV (each+ or- ) at TV Sync. TV-H (line) and (frame)
aync are switched automatically by SWEEP TIME/Div switch.
HORIZONTAL DEFLECTION
• Deflection factor: 5mV to 20V/ Div on 12 ranges In 1-2-5 otep with fine
control
• Frequency reoponoe: DC to MHz (-3dB)
• Max Input Voltage: 300V DC+ AC Peak of 600V p-p
• X-Y operation: X-Y mode lo oelected by SWEEP TIME/.Div owitch.
• lntenoity Modulation Z Axis : TTL Level (3Vp-j>-50V) + b<igh~. dark
OTHER SPECS: • Weight: 7Kg Approx • Dimenaiona: 162 (H) x 294(W)
x 352(D)mm.
Q12105........................NOW ONLY $675.00
LOGIC PROBES
LOGIC PROBES
• Useful for TTL or CMOS
hashlgh and low Indicator
leds and also with pulse
memory.
• This Is a very handy tool
for the hobbies! or
serloustechnlclan for
tracing those hard to find
faults on logic boards.
LOGIC PULSER
• Can be used directly to Inject
a signal Into logic circuits
without removing IC
• Compatible with TTL, OTL,
RTL, HTL, MO. and CMOS.
Q11272 ..............$19.95 Q1127 4 ................. $42.95
ANALOGUE / DIGITAL
MULTIMETER
22 ELEMENTS
L 10974 ........ $119.95
• Magnifier: XS at all time•.
TRIGGERING
• Senoitivity hit: 1 Div or more Ext: 1VJ>i> or more.
• Source: INT, CH-8, LINE or EXT
a11020 ..............$59.95
A16100 ............. $69.95
VHF Channels 0-11
UHF Channels 28-39
Suitable for fringe signal
reception with improved
front to back ratio and high
gain on VHF.
CTR DISPLAY:• 150 mm rectangular
VERTIACAL DEFLECTION:
• Deflection F,ctor: SmV to 20V / Oiv on 12 rangeo in 1-2-5 otep with
fine control
• Bandwidth DC : DC to 20 MHz (-3dB) AC: 10Hz to 20 MHz (-3dB)
• Operating modeo CH-A, CH-B, DUAL and ADD (ALT /CHOP l202 only)
• Chop Frequency: 200 KHz Approx.
• Channel oeporotion: Better than 60dB at 1KHz
TIME BASE
• Type : Automatic & normal triggered In automatic mode, oweep ia
obtained without input oignal
• Sweep Time: 0.2m Sec to 0.5 Sec/ Div on rangee In 1-2-5 atep with fine
control and X-Y.
DIGITAL MULTMETER
HC-3500T
DISPLAY: 3/12 DIGIT
BASIC ACCURACY: 0.5¾DC
DC VOLTAGE: 0-1000V
DC CURRENT: 0-20A
AC VOLTAGE: 0-750V
AC CURRENT: 0-20 A
RESISTANCE: 0-20M OHMS
TEMPERATURE:-20°C •
1200°c
CONTINUITY TEST,
DIODE TEST
TEMPERATURE
CAPACITANCE
FREQUENCY, hie TEST,
DATA HOLD.
Q13000 ...was $169.00
now only $149.00
• HC - 50508 3 1/2 DIGIT
• Basic accuracy: 0.5o/oDC
• DC Voltage: 0 -1000V
• DC Current: 0-10A
• AC Voltage: 0 -750V
• AC Current: 0 - 10A
• Resistance: 0 • 20M ohms
• DC AC DMS:-45dB. +50dB
• Temperature: -20°c •
1200°c
• AC Freq Spread: 50 Hz 2KHz Continuity Test, Diode
Test.
Q13020..•......... $169.00
ADELAIDE $TORE
NOWOPEN
241-243 WRIGHT ST
PH: (08) 211 7200
Silicon Chip
BACK ISSUES
July 1988: Stereo Control Preamplifier, Pt.2; Fitting A Fuel Cut-Off Solenoid To Your Car; Booster
For TV & FM Signals; The Discolight Light Show,
Pt.1; Tone Burst Source For Amplifier Headroom
Testing; What Is Negative Feedback, Pt.3; Amplifier Headroom - Is It A Con?
August 1988: Building A Plasma Display; Universal Power Supply Board; Remote Chime/Doorbell; High Performance AC Millivoltmeter, Pt.1;
Discolight Light Show, Pt.2; Getting The Most Out
Of Nicad Batteries; Data On Insulated Tab Triacs.
September 1988: Hands-Free Speakerphone; .
Electronic Fish Bite Detector; High Performance
AC Millivoltmeter, Pt.2; Build The Vader Voice;
Motorola MC34018 Speakerphone IC Data; What
Is Negative Feedback, Pt.4.
October 1988: Stereo FM Transmitter (Uses
Rohm BA1404); High Performance FM Antenna;
Matchbox Crystal Set; Electronic House Number;
Converting A CB Radio To The 28MHz Band;
Queensland's Powerful Electric Locomotives.
November 1988: 120W PA Amplifier Module
(Uses Mosfets); Poor Man's Plasma Display;
Automotive Night Safety Light; Adding A Headset
To The Speakerphone; How To Quieten The Fan
In Your Computer; Screws & Screwdrivers, What
You Need To Know; Diesel Electric Locomotives.
December 1988: 120W PA Amplifier (With Balanced Inputs) , Pt.1 ; Diesel Sound Generator; Car
Antenna/Demister Adaptor; SSB Adaptor For
Shortwave Receivers; Why Diesel Electrics Killed
Off Steam; Index to Volume 1.
January 1989: Line Filter For Computers; Ultrasonic Proximity Detector For Cars; 120W PA Amplifier (With Balanced Inputs) Pt.1 ; How To Service Car Cassette Players; Massive Diesel Electrics In The USA; Marantz LD50 Loudspeakers.
February 1989: Transistor Beta Tester; Minstrel
2-30 Loudspeaker System; LED Flasher For Model
Railways ; Build A Simple VHF FM Monitor (uses
MC3362), Pt.1; Lightning & Electronic Appliances;
Using Comparators to Detect & Measure.
March 1989: LED Message Board, Pt.1; 32-Band
Graphic Equaliser, Pt:1; Stereo Compressor For
CD Players; Amateur VHF FM Monitor, Pt.2; Signetics NE572 Compandor IC Data; Map reader
For Trip Calculations; Electronics For Everyone Resistors.
April 1989: Auxiliary Brake Light Flasher; Electronics For Everyone: What You Need to Know
About Capacitors; Telephone Bell Monitor/Transmitter; 32-Band Graphic Equaliser, Pt.2; LED Message Board, Pt.2.
May 1989: Electronic Pools/Lotto Selector; Synthesised Tom-Tom ; Biofeedback Monitor For Your
PC; Simple Stub Filter For Suppressing TV Interference ; LED Message Board, Pt.3; Electronics
For Everyone - All About Electrolytic Capacitors.
June 1989: Touch-Lamp Dimmer (uses Siemens
SLB0586); Passive Loop Antenna For AM Radios; Build A Universal Temperature Controller;
Understanding CAO Probes; 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; NSW 86 Class Electric
Locomotives.
September 1989: 2-Chip Portable AM Stereo
Radio (Uses MC 13024 and TX7376P) Pt.1 ; AlarmTriggered Telephone Dialler; High Or Low Fluid .
Level Detector; Simple DTMF Encoder; Studio
Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero
Module for Audio Amplifiers (Uses LMC669).
October 1989: Introducing Remote Control; FM
Radio Intercom For Motorbikes (Uses BA 1404 &
TDA7000) 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); Sensitive FM Wireless Microphone; FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Rad io,
Pt.3 ; Floppy Disc Drive Formats & Options; The
Pilbara Iron Ore Railways .
l
------------------------------ --- ---,
.-
Use this handy form to order your back issues
I
I
Please send me a back issue for:
D October 1988
D March 1989
D September 1989
O February 1990
o July 1990
O December 1990
D May 1991
o October 1991
O March 1992
o August 1992
D November 1988
D April 1989
0 October 1989
0 March 1990
O August 1990
O January 1991
O June 1991
O November 1991
O April 1992
O September 1992
0
O
0
0
0
O
O
0
July 1988
December 1988
May 1989
November 1989
April 1990
September 1990
February 1991
July 1991
o December 1991
0 May 1992
o October 1992
Enclosed is my cheque/money order for $___or please debit my:
o
August 1988
January 1989
June 1989
December 1989
May 1990
o October 1990
O March 1991
o August 1991
O January 1992
o June 1992
O
O
O
0
O Bankcard
Card No.
Signature _ _ _ _ _ _ _ _ _ _ _ _ _ Card expiry date_ _ /_ _
O Visa Card
O
O
0
O
O
O
O
O
September 1988
February 1989
July 1989
January 1990
June 1990
November 1990
April 1991
September 1991
o February 1992
0 July 1992
O Master Card
$5.00 each (includes p&p) . Overseas
order,s add $1 each for postage. NZ
orders are sent air mail.
Detach and mail to:
Street _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
SILICON CHIP PUBLICATIONS
PO BOX 139
COLLAROY BEACH NSW 2097
Suburb/town _ _ _ _ _ _ _ _ _ _ _ _ _ _ Postcode _ _ _ _ __
Or call (02) 979 5644 & quote your
credit card details. Fax (02) 979 6503.
Name ____________________________
L---------------------------------- ----96
SILICON CHIP
December 1989: Digital Voice Board (Records
Up To Four Separate Messages); UHF Remote
Switch ; Balanced Input & Output Stages; Data
For The LM831 Low Voltage Amplifier IC; Install
A Clock Card In Your PC; Index to Volume 2.
January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Speeding Up
Your PC; Phone Patch For Rad io Amateurs; Active Antenna Kit; Speed Controller For Ceiling
Fans; Designing UHF Transmitter Stages.
February 1990: 16-Channei Mixing Desk; High
Quality Aud io Oscillator, Pt.2; The Incredible Hot
Canaries; Random Wire Anten na Tuner For 6
Metres ; Phone Patch For Radio Amateurs, Pt.2;
PC Program Calculates Great Circle Bearings.
March 1990: 6/12V Charger For Sealed LeadAcid Batteries; Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16Channel Mixing Desk, Pt.2; Using The UC3906
SLA Battery Charger IC.
April 1990: Dual Tracking ±50V Power Supply;
VOX With Delayed Audio; Relative Field Strength
Meter; 16-Channel Mixing Desk, Pt.3; Active CW
Filter For Weak Signal Reception; How To Find
Vintage Rad io Receivers From The 1920s.
May 1990: Build A 4-Digit Capacitance Meter;
High Energy Ignition For Cars With Reluctor Distributors; The Mazzie CW Transceiver; Waveform
Generation Using A PC, Pt.3; ·16-Channel Mixing
Desk, Pt.4; What To Do When You r Computer
Goes Bung, Pt.1 .
June 1990: Multi-Sector Home Burg lar Alarm;
Low-Noise Universal Stereo Preamplifier; Load
Protection Switch For Power Supplies; A Speed
Alarm For Your Car; Design Factors For Model
Aircraft ; Fitting A Fax Card To A Computer; What
To Do When Your Computer Goes Bung, Pt.2.
July 1990: Digital Sine/Square Generator, Pt.1
(Covers 0-500kHz); Burglar Alarm Keypad & Combi nation Lock; Simple Electronic Die; Low-Cost
Dual Power Supply; Inside A Coal Burning Power
Station; What To Do When You r Com puter Goes
Bung, Pt.3; Weather Fax Frequencies.
August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes) ; Horace The Electronic Cricket;
Digital Sine/Square Wave Generator, Pt.2; What
To Do When Your Computer Goes Bung, Pt.4.
September 1990: Music On Hold For Your Telephone ; Remote Control Extender For VCRs ;
Power Supply For Burglar Alarms; Low-Cost 3Digit Counter Modu le ; Simple Shortwave Converter For The 2-Metre Band.
October 1990: Low-Cost Siren For Burglar
Alarms; Dimming Controls For The Discolight;
. Surfsound Simulator; DC Offset For DMMs; The
Dangers of Po lych lorinated Biphenyls ; Using The
NE602 In Home-Brew Converter' Circuits.
November 1990: How To Connect Two TV Sets·
To One VCR ; A Really Snazzy Egg Timer; LowCost Model Train Controller; Battery Powered Laser Pointer; 1.5V To 9V DC Converter ; Introduction To Digital Electronics ; Simple 6-Metre Amateur Transmitter.
December 1990: DC -DC Converter For Car Amplifiers; The Big Escape - .A Game Of Skill; Wiper
Pulser For Rear Windows; Versatile 4-Digit Com-
bination Lock; 5W Power Amplifier For The 6Metre Amateur Transmitter; Index To Volume 3.
January 1991: Fast Charger For Nicad Batteries,
Pt.1; The Fruit Machine; Two-Tone Alarm Module; Laser Power Supply; 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; LowCost Sinewave Oscillator; Fast Charger For Nicad
Batteries, Pt.2 ; How To Design Amplifier Output
Stages; Tasmania's Hydroelectric Power System.
March 1991 : Remote Controller For Garage
Doors, Pt.1 ; Transistor Beta Tester Mk.2; Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose 1/0
Board For PC-Compatibles; Universal Wideband
RF Preamplifier For Amateurs & TV; A Look At
The Config .Sys & Ansi.Sys Files.
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; Playing With The Ansi.Sys
File; FSK Indicator For HF Transmissions .
May 1991 : Build A DTMF Decoder; 13.5V 25A
Power Supply For Transceivers; Stereo Audio
Expander; Fluorescent Light Simulator For Model
Railways ; How To Install Multiple TV Outlets, Pt.1 ;
Setting Screen Colours On Your PC.
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 Rec·eption; Electric Vehicle Transmission
Options ; Tuning In To Satellite TV, Pt.1.
July 1991: Battery Discharge Pacer For Electric
Vehicles ; CD Error Analyser, Pt.1; 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; PEP Monitor
For Transceivers
August 1991 : Build A Digital Tachometer; Masthead Amplifier For TV & FM; PC Voice Recorder;
Error Analyser For CD Players, Pt.2; Tuning In To
Satellite TV, Pt.3 ; Installing Windows On Your
PC; Step-By-Step Vintage Radio Repairs .
September 1991 : Studio 3-55L 3-Way Loudspeaker System ; Digital Altimeter For Gliders &
Ultralights, Pt.1; Build A Fax/Modem For Your
Computer; The Basics Of AID & DIA Conversion ;
Windows 3 Swapfiles, Program Groups & Icons;
How Glass-Mount Antennas Work .
October 1991: Build A Talking Voltmeter For
Your PC, Pt.1; SteamSound Simulator Mk.11 ; 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 ; Error Analyser For CD Players
Pt.3; Modifying The Windows INI Files.
December 1991 : TV Transmitter For VCRs With
UHF Modulators; lnfrared Light Beam Relay ; Compact Solid-State Laser Pointer; Colour TV Pattern
Generator, Pt.2; Windows 3 & The Dreaded Unrecoverable Application Error; Index To Vol. 4.
January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V BA Power Supply, Pt.1 ; Baby Room
Monitor/FM Transmitter; Automatic Controller For
Car Headlights; Experiments For Your Games
Card; The GPS Satellite Navigation System; Restoring An AWA Radiolette Receiver.
February 1992: Compact Digital Voice Recorder;
50-Watt/Channel Stereo Power Amplifier; 12VDC/
240VAC 40-Watt Inverter; Adjustable 0-45V BA
Power Supply, Pt.2; The Mobile Telephone Revolution; Designing A Speed Controller For Electric
Models.
March 1992: TV Transmitter For VHF VCRs ; Studio Twin Fifty Stereo Amplifier, Pt.1 ; Thermostatic
Switch For Car Radiator Fans; Telephone Call
Timer; Updating The Resistor/Capacitor Scene;
Coping With Damaged Computer Directories;
Valve Substitution In Vintage Radios.
April 1992: lnfrared Remote Control For Model
Railroads; Differential Input Buffer For CROs; Studio Twin Fifty Stereo Amplifier, Pt.2; Understanding Computer Memory; Switching Frequencies in
Model Speed Controllers; Aligning Vintage Radio
Receivers, Pt.1.
May 1992: Build A Telephone Intercom; LowCost Electronic Doorbell; Battery Eliminator For
Personal Players; lnfrared Remote Control For
Model Railroads, Pt.2; A Look At Large Screen
High Resolution Monitors; OS2 Is Really Here;
Aligning Vintage Radio Receivers, Pt.2.
June 1992: Multi-Station Headset Intercom, Pt.1 ;
Video Switcher For Camcorders & VCRs; lnfrared
Remote Control For Model Railroads, Pt.3; 15Watt 12-240V Inverter; What's New In Oscilloscopes? ; A Look At Hard Disc Drives; Video Edit'.
ing On The Small Screen.
July 1992: Build A Nicad Battery Discharger; 8Station Automatic Sprinkler Timer; Portable 12V
SLA Battery Charger; Off-Hook Timer For Telephones; Multi-Station Headset Intercom , Pt.2 ;
Understanding The World Of CB Radio; Electron ics Workbench For Home Or Lab.
August 1992: Build An Automatic SLA Battery
Charger; Miniature 1.5V To 9V DC Converter;
The lnterphone Digital Telephone Exchange, Pt.1;
Dummy Load Box For Large Audio Amplifiers;
Internal Combustion Engines For Model Aircraft;
Troubleshooting Vintage Radio Receivers .
September 1992: Multi-Sector Home Burglar
Alarm; The lnterphone Digital Telephone Exchange, Pt.2; General-Purpose 3½-Digit LCD
Panel Meter; Track Tester For Model Railroads ;
Build A Relative Field Strength Meter; Internal
Combustion Engines For Model Aircraft, Pt.2.
October 1992: 2kW 24VDC To 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm,
Pt.2; Mini Amplifier For Personal Stereos; Electronically Regulated Battery Charger (charges 6V,
12V & 24V lead-acid batteries) ; Internal Combustion Engines For Model Aircraft, Pt.2.
PLEASE NOTE: All issues from November 1987
to June 1988 plus the August 1989 issue 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
$5.00 per article, including postage. When supplying photostat articles or back copies, we automatically supply any relevant Notes & Errata at no
extra charge .
N O VEMBER
1992
97
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.
Stereo AM radio needs
better alignment
Could you please help me with the
following questions about your stereo
AM radio project as described starting with the February 1991 issue of
SILICON CHIP. On my radio, only three
signal strength LEDs ever light up even when tuned to the ABC stations,
which in Melbourne are the strongest.
I am concerned about what I had to
do to fit the antenna coil to the ferrite
rod. Because the supplied coil was
too large for the rod I had to wrap
several layers of paper around the rod
to ensure a snug fit for the coil. Although the alignme.nt seemed to work
OK, is it likely that this electromagnetically sloppy fit is coupling insufficient RF signal into the front end of
the tuner?
In the section on IF alignment, you
say, "connect the multimeter between
TP2 and Ground". Shouldn't that be
to TPl, which is the AGC level , and
not TP2 which is the tuning voltage?
1.5V power for the
SteamSound Simulator
In the August 1992 issue of
SILICON CHIP, S. H. of Woonona,
NSW, asked if it was possible to
operate the SteamSound Simulator (October 1991) from lower
voltages. Your answer was that it is
not possible because the noise generator part of the circuit requires at
least 9-lOV to produce any noise.
Unfortunately, I'm not in possession of your October 1991 issue so
I do not know the specifications of
the unit. However, it should be possible to run it from a 1.5V cell using
your 1.5V to 9V DC Converter (SILICON CHIP, August 1992).
This circuit should also be perfect for passenger train lighting. The
lights won't blink when you speed
98
SILICON CHIP
Nevertheless, the meter response at
TPl when tuning 13 and L4 is very
flat - barely perceptible, in fact. Is
that typical?
Regarding the 3.6MHz oscillator,
your instructions imply that during
adjustment there is a working range
within which the 3.6MHz oscillator
will lock onto the 450kHz IF. I have
no range - only a point. The slightest
touch of the oscillator coil causes the
stereo to drop out and even when it is
left alone, stereo lock is intermittent
on some stations and totally absent
on others (which are transmitting in
stereo).
In describing the adjustment of the
whistle filters, you specify a resistance of 32. 76kQ However, the sum of
the resistances when all the trimmers
are set to maximum can be no more
than 33kQ (18kQ + 5kQ + 10kQ). That
leaves very little room for error. Is the
32.76kQ correct? And is the accuracy
implied in that specification necessary? That is, is a digital multimeter
required?
Do you have typical voltages for
the train up, or dim when you slow
down, or go out when the train
stops. (T. Van der Burg, Christchurch, NZ).
• This seems like an excellent idea
and, although we haven't tried it, it
should work.
S. H. wanted to run the sound
generator circuitry from batteries
so that the SteamSound Simulator
still made "hissing" noises when
the train was stationary. As suggested by Mr Van der Burg, it should
be possible to run this section from
a 1.5V cell via the 1.5V To 9V DC
Converter.
Note, however, that the sawtooth
oscillator based on Q2 & IClb
should continue to monitor . the
track voltage via the bridge rectifier (D1-D4) to control the "chuff'
frequency.
various points on the circuit other
than the AGC and tuning voltage? This
would help with troubleshooting. (B.
F., Kew, Vic) .
• Notes and Errata were published on
this project in the September 1991
issue and these cover most of your
questions. In particular, they answers
your question on the whistle filter
resistance range and the error regarding TPl in the IF alignment.
A digital multimeter must be used
to obtain the 32.76kQ resistance in
the whistle filters since the accuracy
here sets the depth of the notch filter.
The problem with your tuner is
likely to be in the alignment of trimmer Cl. This can be adjusted to a false
peak, as detailed in the Notes & Errata.
The 3.6MHz oscillator does have a
quite narrow range of adjustment.
However, we suspect that the stereo
lock is touchy because of the low signal level. Try realigning the circuit
again, taking note of the points on
adjusting Cl, and this should cure
your problem.
The ferrite rod and coil coupling is
satisfactory even though the coil diameter is larger than the ferrite rod. In
fact, we used a similar technique to
the one you have used to secure the
coil.
Incidentally, if you want to find out
when or if Notes & Errata have been
published on any of our projects, there
is a list in the index published each
year in the December issue.
Track cleaner
for model railroads
As a model railroad buff, I read
with' interest all your articles on railroad projects for sound, lighting and
model control.
The "Track Tester for Model Railroad Layouts" in the September 1992
issue is great. This device is handy for
locating and identifying trouble spots
on a layout, such as open circuits and
intermittent or dirty tracks. My own
problems in particular are due to car-
rosion and oxidisation of the track,
resulting in bad electrical contact between the track and the loco.
From articles I have read in railroad magazines, mainly American,
there is a commercial device available that rids us of this problem. It is
marketed under the name of"RELCO".
The device is a high frequency generator which converts 16VAC into
300V at 300kHz and very low current.
This high-frequency 300V signal ionises the gaps caused by dirt and oxidisation on the track.
My request is, do you have a circuit
for such a device or could you publish something in a future edition of
SILICON CHIP? (M. H., Cairns, Qld).
• We have not seen the RELCO device
but it seems possible that it would
contravene Department of Transport
and Communications regulations because it will radiate quite a high power
signal at 300kHz. We would be wary
of such a device anyway because it
could damage any semiconductor circuitry connected to the track and may
also lead to a potential shock problem.
In practice, we have found that a
pulse width modulation controller,
as featured in the April, May and June
1992 issues, is quite effective in overcoming most of the problems with
dirty track. The original PWM controller, on which this circuit was
based, was published in the April 1988
and May 1988 issues.
Comments on the
solar battery charger
I recently purchased a kit for my
Solar Battery Charger from Jaycar Electronics and assembled it using the
supplied parts.
When initially tested, the unit drew
high current but only had low output.
The problem stemmed from the transistors supplied for Ql and Q2. The
ones supplied were BD649/650 but
when I replaced these with TIP121/
126 transistors, as originally specified, the problem disappeared.
I then went a little further and replaced these transistors with the supplied BD649/650 devices and altered
the timing capacitor from 470pF to
4700pF - problem solved again.
While the BD649/BD650 transistors
may initially seem to be good "equivalents" they are not the same as the
devices specified in my original de-
Dirty heads on a
Beta VCR
I recently found that my old Beta
video recorder has some major
problems. It's fairly old and heavy
and has been sitting in my cupboard for nearly five years until
now. This particular model (Sanyo
VTC 9300) is a top load/eject type
and it has trouble loading and ejecting the tape. It also usually refuses
to fast forward, rewind or even
play a tape.
When it does play, the picture
flickers between colour -and black
and white and has interference
lines across the screen and looks
like the picture is about to break
up, all because it may have mechanical problems.
I think that the heads on the
VCR have a serious problem because I took the cover off and
looked at the playing drum. It had
a lot of grime built up on the
smooth surface of the drum assembly. I spent some time with a
specialised head cleaner fluid and
went around with cotton buds removing grit and dirt, of which there
sign. In fact, there are no equivalents
to the TIP121 or TIP126 - their specifications cannot be directly matched
with anything. However, the BD649/
650 devices can be used, provided the
timing capacitor value is changed.
The function of this project has also
been misunderstood by a few people.
If a solar panel is directly connected
to a 12V battery and its output is less
than the battery voltage, · that solar
panel will not charge the battery. The
efficiency here is 0%. The Solar Battery Charger, on the other hand, allows the battery to be charged even if
the output from the solar panel falls
below 5V.
Note, however, that the charger's
efficiency is only about 50% when
operating in step-up mode, increasing to a maximum of about 84% in
step-down mode. Of course, if a directly connected solar panel is charging a battery, the efficiency is 100%
(not counting cable losses or the efficiency of the solar cells).
One also has to remember that bat-
was quite a large amount. But even
after this, the pictur~ still didn't
change. The sound was perfect
(spot on, in fact).
I think that it's not an electronic
fault but a mechanical fault, where
the motor speed is going too fast.
The motor is a 115V type in series
with a winding on the transformer.
I removed all of the rubber belts
and found that they were all OK there wasn't any wear on them at
all. Can you help me or put me on
to someone who can assist me in
repairing different models and
types of VCRs? (J. E., Blackburn
South, Vic).
• From your description it is still
likely that the fault is caused by
dirty heads. While you may have
been fairly thorough in cleaning
grime off the drum, it is grime in
the head gaps which will cause
the problem. The reason that head
dirt causes a problem with speed
is that the speed control circuitry
relies on the sync pulses recorded
on the tape and if the heads can't
reliably pick up this signal, the
speed control circuitry will not
work.
tery voltage will change depending
on the state of charge. This circuit
will charge a battery from a discharged
state of 10.5V to a fully charged state
over a period of time and the current
will vary depending on the state of
charge. It also depends on the amount
of power available from the solar
panel.
The recommended solar panel size
is 6W and above. A 1W panel could
only ever supply 83mA of charging
current, which is not enough for charging large batteries. It would, however,
charge a 830mAh battery over 10-14
hours, or just keep a 1.2Ah battery
topped up if the equipment connected
to it drew very little current. (Steve
Calder, Parramatta,NSW).
Problems with the
masthead amplifier
A letter from R. W. of Brunswick
Heads (SILICON CHIP, June 1992) has
prompted me to write to you concerning the Masthead Amplifier article
NOVEMBER
1992
99
Modifying the FM
subcarrier adapter
I have collected all the components for the FM Subcarrier Adaptor project described in the January 1988 edition of SILICON CHIP.
Hm.vever, l have now discovered
that the particular transmission
that I want to hear is not on the
subcarrier frequency of 67kHz but
on another frequency about 30kHz
away.
It seems that it would be easy
enough to alter the VCO frequency
(refer last paragraph, page 85) but
what about the bandpass filter? I
am not into filter design - can it be
adjusted to accommodate the other
frequency?
The transmission referred to
above is on 2SER-FM. It is a relay
of the BBC from the UK. I understand it is on a subcarrier frequency
of about 96kHz. The BBC is charg-
which appeared in the August 1991
issue. I built four of these amplifiers
but only one behaves properly.
The trouble I encountered was severe oscillation throughout Band 1 to
Band 5 of the VHF and UHF spectrum. This was detected by the screen
of the tel evision showing herringbone
patterns and blacking out of the screen,
not to mention the most unusual
sounds from the audio department.
The OM350s became quite warm
and the input voltage to pin 5 of the
chip dropped to 8V DC. The use ofmy
TV field strength meter was an asset. I
detected up to lmV of RF on a multi-
ing A$150 per year for this service
and a modified FM receiver is provided to subscribers.
Regarding the answer given on
page 92 of SILICON CHIP, July 1992,
about' resistors with six colour
ban ds being "pretty rare", if you
go to Geoff Wood Electronics you'll
find plenty with six colour bands
- at least that's the way it was the
last time I was there. (W. W.,
Greenfield Park, NSW).
• It should be possible to modify
this circuit to receive the higher
subcarrier merely by changing the
capacitors in the twin-T filter circuit. All that should be required is
to change the capacitors from
0.0022µF to 0.0015µF. No other
changes to the circuit should be
necessary.
Thanks for your comments on
6-band resistors. It seems that they
may be a little more commonplace
than we thought.
tude of frequencies . After a lot of fault
finding, I put it down to a poorly
designed PC board, with poor placement of components allowing feedback to the input of the OM350.
I installed ferrite beads on some
component leads, especially that long
wire link on the PCB. This did help to
tame the amplifiers to a certain ey' ,at
but not enough. I also used mon:, '..,ypass capacitors and this also helped
to eliminate unwanted resonances, but
again this was not enough.
I cut the long PCB track that runs
from the AC input of the board to L2.
I then relocated L2 under the PCB
Drill Speed Controller - Amended PC Board
il
N
N
0
0
CJ\
CJ\
....
....u
0
0
c.?
!!.1
100
SILIC O N CHIP .
This is the revised
PC pattern for the
Drill Speed
Controller featured
in September 1992.
The circuit
modifications are
detailed on page 22
of this issue.
across the cut track right at the coaxial output to the power supply, th en
bypassed L2 on the diode side with a
1000pF disc ceramic. Where L2 was
originally located, I ran a wire link
through a ferrite bead and of course
bypassed it.
Beauty! - the amplifiers behaved
very well and I could not detect any
oscillation. So after reinstalling one
of the amplifiers in its proper place,
everything worked fine. I was watching a video and it was raining and
after switching back to watch Channel 8, I was horrified to find that the
amplifier was taking off again.
It makes me wonder why this design was used. I would think that
dispensing with the noisy OM350s
and using BFR91s or BFR94s and a
properly designed double sided PCB,
one side being used as a groundplan e,
would give better results. Like R. W.
of Brunswick Heads, all I have for my
couple of hundred dollars are four
power supplies, one amplifier and a
heap of junk.
I wonder if others have built this kit
and have encountered the same problems. I now use a commercial masthead amplifier built by Kingray with
34dB of gain to boot - a very stable
unit. (G. C., Ouyen, Vic).
• From your letter, it seems more
likely that you have experienced a
number of faulty OM350s. We cannot
agree that the board design is faulty
and indeed the layout for the 0M350
section is quite close to that suggested
in the Philips data· for this device.
Nor can we agree with the addition
of ferrite beads to various component
leads or any of your other modifications. For example, the addition of a
ferrite bead to the long link on the
board will actually increase the output impedance of the regulated supply and may even lead to spurious
oscillation in the LM317.
It is true that many commercial
masthead amplifiers do not use the
OM350 and similar hybrid amplifiers
but use discrete transistors. However,
we believe this has more to do with
reasons of economy rather than performance.
Yours is the first specific complaint
we have had regarding this design
(apart fro m R. W. in Jun e) and so we
are not aware of other readers experiencing the problems described in your
letter - this despite the many hundred of kits sold.
SC
~
J-J --J
--
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,~-;; : , ~ , - , I
JL J
.J
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ORDER FORM
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NOVEMBER
1992
101
__TCENTRE
Cash in your surplus gear. Advertise it here in Silicon Chip.
ANTIQUE RADIO
ANTIQUE RADIO restorations. Your
one-stop radio repair shop. Specialising
in restoring vintage radios, including
chassis rewiring, re-condensing, quality
new parts, valves, valve sockets,
speakers, power & audio transformers.
Secondhand radio dials & parts for most
brands & models. About 400 radios in
stock for sale, restoration & parts. Every
restored wireless is covered by a 2year warranty on parts & labour. We
restore damaged woodwork & cabinets
& French polish (approx. 40 coats).
Vintage car radios available for sale or
restoration. Repairs done on tape decks.
Open Sat. 10am-5pm; Sun. 12 .30-5pm.
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Phone (02) 645 3173 BH or (02) 726
1613 AH.
FOR SALE
WEATHER FAX programs for IBM XT/
ATs *** "RADFAX2" $35 is a high reso-
lution, shortwave fax, Morse & RTTY
receiving program. Suitable for CGA,
EGA, VGA and Hercules cards (state
which). Needs SSB HF radio & Radfax
decoder. *** "SATFAX" $45 is a NOAA,
Meteor & GMS weather satellite picture
receiving program. Needs EGA or VGA
plus "WEATHER FAX" PC card. ***
"MAXISAT" $75 is similar to SATFAX
but needs 2Mb expanded memory
(EMS 3.6 or 4.0) and 1024 x 768 SVGA
card. All programs are on 5.25-inch or
3.5-inch disks (state which) & include
documentation. Add $3 postage. Only
from M. Delahunty, 42 Villiers St, New
Farm, Old 4005. Phone (07) 358 2785.
SPRINKLER CONTROLLER KIT: get
ready for summer with this very popular
kit. Very reliable and versatile design
can control eight stations and has 32
programmable START and RUN times
(refer SILICON CHIP, July 1992). All
settings stored in EEPROM. Can be
expanded to 64 with the addition of
extra memory chip and switch. Requires
24V AC to run. Complete kit including
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SILICON CHIP
NEW 280 SINGLE BOARD COMPUTER: designed for the 1990s.Also modern kits. Local SAE for details. DIY Electronics, GPO Box 904, Hong Kong.
THE HOMEBUILT DYNAMO: (plans)
brush less, 1000 watt at 740 revs. $A85
postpaid airmail from Al Forbes, PO
Box 3919 - SC, Auckland, New Zealand. Phone Auckland (09) 818 8967
anytime.
VALVE RADIO RESTORATION BUSINESS: established 7 years. Specialising in vintage & classic car radios; sole
agents in Australia for FM conversion
units and solid state vibrators. Ideal
opportunity for technician (ex-Telecom?)
to purchase a well-established business situated in a popular, progressive
Melbourne shopping centre. Long lease
available. For further information contact: Nostalgic Wireless, PO Box 144,
Surrey Hills, Vic 3127.
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LCD & case $135 (inc. p&p). Relays
extra at $3.75 each (controller requires
9 for full kit). FROST SWITCH KIT also
available. Remote temperature probe
starts the above controller in a fully
programmable sequence, when temperature falls to a user selectable value
(controller requires modified S/W). $60
incl. reprogramming and p&p.Available
from Graham Blowes, 38 Garnet St,
Niddrie, 3042. Phone (03) 337 1917 AH
or (03) 575 3349 BH. Fax (03) 575
3369.
8051 MICROCOMPUTER PROTOTYPING PCB $30 - similar to my
ROMLoader EA Jan 92. Provision for
8255 PPI, 9346 EEPROM, 2K-32K
SRAM, 2K-32K EPROM, MAX232, DIP
switches & expansion header. Send A4
SAE for article. Tantau, PO Box 206,
Gordon 2072.
SECURITY ALARM COMPONENTS:
commercial quality alarm panels, detectors, cable, everything for complete
alarm system. DIY kits. Discounted
prices. 4-core alarm cable $35 per
100m. 2°core alarm cable (figure-8) $15
per 100m. PIR detectors pulse count
$59 ea. Horn speakers $12.50 ea. Mail
order service. Send SAE for free price
list to Security Distributors, 141 Todds
Rd, Lawnton, Old 4501. Phone (07)
882 0002.
NICAD BATTERIES: D-size 4Ah. At
less than half price it's the best deal in
town. $4.90 each plus p&p. Phone (052)
78 8298.
KIT REPAIRS: fixed price servicing for
all kits, no job too small, only quality
components used. Ph (02) 649 2134
after 5pm.
SURPLUS COMPONENTS: 747CJ OIL
ceramic $1 ea or 25 for $20; 150Q 1OW
resistors $1 ea or 10 for $8; Bourns
3386 trimpots 5kQ or 10kQ, 50c ea or
10 for $4; Eska 3AG 10A ceramic fuse,
packet of 10 $1.50; ex-computer
EPROMs, erased and blank tested,
2732, 2764, 27128, $2 ea or 10 for $15; ·
Valves, ex-government, new 12AT7 $8
ea, 5Y3GT $6 ea, KT66 $25 ea, 6AN8A ·
$9 ea, 6BL8 $8 ea. Many other valves
and components available. Send SAE
for list. Open Thursday, Friday 4pm8pm, Sat 9am-4pm. 143 Grays Rd,
Enoggera Old . Ph (07) 355 1314 or
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Secontronics, POBox 2215, Brookside
Old 4053.
HARD DRIVE: Maxtor voice coil IDEAT. Factory warranty. Great bargain.
New 120Mb $560, 200Mb $860. Mail
MEMORY EXPANSION
PRICES AT SEPT 9TH, 1992
SIMM
1Mb x 5 ?Ons
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MAC
16MbOUADRA
2MbSl&LC
4Mb P'Book
$780
$83
$260
BOARDS
8MbATW2MB
$232
8Mb PS2W2MB
$234
4Mb HP LaserW2MB $155
8Mb PANAS W2MB $170
1Mb TI W1MB
$80
Sales lax 20%. Overnight delivery. Credi! cards welcome.
Ring for Latest Prices
•
Plans Kits and PCBs
1O0W Valve Amp PCB
......................... $30
Valve Amp PSU PCB ............... ............................ .. $25
Universal PSU (±5/±12V) Dual Supply .................... $10
Digi 125 100W amp/pair
....... $1 0
ETI 1623 PIA for PCs ........................................ .. .... $40
Max 1/0 Board ............................................... .. ........ $40
Max Kit ............................... .................................. $169
LM380 3.5 amp PCB
..................................... $7
AEM 35W amp kit .................................................... $20
ETI Audio Toolkit PCB
................ $1 0
AGC Amp PCB .................... ......................... .. ......... $7
Z-80 Miniprocessor PCB .......................................... $50
6502 Miniprocessor PCB ......................................... $50
6809 Miniprocessor PCB
.............. :..... $50
8048/8049 Developers board complete B& T ........... $199
IBM PC Prototype PCB .............................................. $50
EPROM Programmer .............................................. $299
. ESL-t Electrostatic speaker kit/pair inc manual ...... $899
ESL-t Assembly Manual
........ $50
P.C. Computers (08) 332 6513
36 Regent St, Kensington SA.
PELHAM
Tel: (D2) 980 6988 Fax: (02) 980 6991
1st Floor, 100 Yarrara Rd, PO Box 382, Pennant Hills, NSW 2120.
FIX-A-KIT
KIT REPAIR & CONSTRUCTION
TRANSFORMER REWINDS
3 MONTHS WARRANTY ON REPAIRS
12 MONTHS WARRANTY ON CONSTRUCTION
TECHNICAL ASSISTANCE
ALL TYPES OF TRANSFORMER REWINDS
HVCAL ELECTRONICS
TRANSFORMER REWINDS
Design. Manufacture & Repair of Electronic
Equipment
Reply Paid No.2, PO Box 438, Singleton, NSW
2330. Ph: (065) 761291. Fax : (065) 76 1003. .
order welcome. Altec Pacific. BH (03)
800 2007. Fax (03) 800 3363. AH (03)
801 4391 Wantirna.
GAS LASER: a very small brand new
0.2-0.5mW visible red helium-neon laser tube, plus a kit of parts for a small
inverter that will run from a 7.2V nicad
battery pack. Suits laser pointers, etc.
Incredible value at $50 for the tube and
(02) 633 5477
supply.* VISIBLE LASER DIODE BARGAIN: brand new 5mW 670nm laser
diode, plus a collimating lens, plus a
driver kit plus a housing and instruc- ·
tions. Introductory price $85. * ELECTRONIC KEY: use it to activate door
strikers for entering buildings, car
alarms, central locking. The most secure key ever (see EA, July 1992). On
special<at> $49.90 for two keys and one
LOCAL TRADES & SERVICES
JV Tuners - Repairs
Transformer Rewinds
'I: A. Mowles
For all types of
transformer rewinds.
Printed circuit boards for the
hobbyist.
For ser\'ice & enquiries contact:
(02) 7741154 Fax (02) 7741154
(065) 761291 Fax (065) 761003
(08)3265590
Ian J Truscott 's
Electronic World
EEM Electronics
Silicon Chip
*
Tuner
•
•
•
•
repairs for TVs & VCRs
Shorted Turns Tester
lligh Voltage Probe
Degaussing Wand
Remote Control Tester
*
For sen ire~~ repair ,rnrk
\Jail or credit card facilities
(03) 7233344 Fax (03) 4192808
Printed cirrnit hoard assemhl~.
itch mode 1>ower supplies repaired.
Design ,1ork from start to finish.
Ring anytime 9am-9pm Mo.n-Sun.
S\\
(03) 4011393
To achertise your products or
st·n ices. please call Sharon on
(02)9795644(018)285532
N OVE MBER
1992
103
r-------------------------,
:
SILICON CHIP BINDERS
l
These beautifully-made binders will
protect your copies of SILICON CHIP.
They feature heavy-board covers
and are made from a distinctive 2tone green vinyl that will look great
on your bookshelf.
Advertising Index
All Electronic Components .. ... ... 45
Altronics .... ... ...... .... ............... 76-78
Antique Radio Restorations ..... 102
A-One Electronics ................ 38-39
Av-Comm ................................... 75
* High quality.
* Hold up to 14 issues
Breakthrough Computers .......... 71
David Reid Electronics .. ....... ..... .. 3
* 80mm internal width.
Dick Smith Electronics .......... 10-15
EEM Electronics ........ .............. 103
* SILICON CHIP logo printed in goldcoloured lettering on spine & cover.
Electronic World ..... .. .......... 67,103
Emona Instruments ................... 47
Yes! Please send me _ _ _ SILICON CHIP binder(s) at $A11.95 plus
$A3 p&p each (NZ $A6 p&p).
Geoff Wood Electronics ............ ... 5
Enclosed is my cheque/money order for $_ _ _ _ or please debit my
Hycal Instruments .................... 103
D Bankcard
O Visa Card
O Master Card
Harbuch Electronics .................. 21
lcom Australia .................. ........ IBC
Jaycar Electronics ................ 49-56
Card No.
JV Tuners ............... .. ............... 103
Oatley Electronics .. .... .... .... 73, 103
Signature_ _ _ __ _ _ _ _ __
Card expiry date_ _ _/_ __
PC Computers .. ....... ,............... 103
Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Pelham .... .. ... ........................... 103
Peter C. Lacey Services ............ 44
Street _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Suburb/town _ _ _ __ _ _ _ _ _ _ Postcode_ _ _ _ __
Philips Test & Measurement .. OBC
RCS Radio ... ................ ........... 104
Resurrection Radio .................... 61
SILICON CHIP PUBLICATIONS
PO Box 139, Collaroy Beach, NSW 2097, Australia.
Phone (02) 979 5644 Fax: (02) 979 6503.
L-------------------------J
Rod Irving Electronics .......... 90-95
Scan Audio .. ........ ...................... 87
Silicon Chip Back Issues ..:... 96,97
Silicon Chip Binders ... ........ 21,104
decoder kit.* ULTRASONIC CAR BURGLAR ALARM BARGAIN: PCB and
on-board components kit for the project
featured in SILICON CHIP May 1988 edition. No screw terminals but we supply
a pair of 40kHz transducers: $24.90. *
LIGHT MOTION DETECTOR: small
PCB assembly based on a ULN2232
IC. This device has a built-in light detector, filters, timer, narrow angle lens,
and even a siren driver circuit that can
drive an external speaker. Will detect
human beings at distances up to 3 metres. Can be used at very low light
levels and even in total darkness. With
IR LED. Full information provided. The
IC only is worth $16! Our price for the
assembly is $6 ea. or 5 for $25. *STEPPER MOTORS: 5V, 7.5-deg., 6.6-ohm,
2-phase. Brand new $12. Major cards
accepted with phone and fax orders.
104
SILICON CHIP
Certified p&p Australia $5, NZ (airmail)
$10. Oatley Electronics, PO Box 89,
Oatley, NSW 2223. Phone (02) 579
4985. Fax (02) 570 7910.
St Lucia .. .... ..... .......................... 23
T. A. Mowles ............................ 103
Tektronix ...... ........ .......... ..... ..... IFC
Transformer Rewinds .............. 103
RC§ RADIO PTY LTD
~;i~1,~
::=J
~I Ill
I
[lo16Jf
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
PC Boards
Printed circuit boards for SILICON
CHIP projects are made by:
• Jemal Products, 5 Forge St,
Welshpool, WA 6106. Phone (09)
350 5555.
• Marday Services, PO Box 19-189,
Avondale, Auckland, NZ. Phone 88
5730.
• RCS Radio Pty Ltd, 651 Forest
Rd, Bexley, NSW 2207. Phone (02)
587 3491.
0
ICOM
Count on us!
a
corn's impressive range of receivers lets
you listen to more frequencies, across the
band and around the world.
Starting with one of the·smallest receivers ever
produced, the IC-Rl covers l00kHz - 1300MHz
(2 ~ 905MHz guaranteed), with AM, FM and
Wide FM modes, Dual Frequency Selection and
100 memories.
The IC-R72 receives 30kHz - 30MHz
( 100 kHZ ~ 30 MHz guaranteed) in SSB, AM
and CW modes and comes with numerous
impressive features, including lcom's DDS System
to improve Carrier to Noise Ratio characteristics
and optional FM mode.
IC-R9000
With an lcom receiver,
the world is as wide
as your band
The mobile IC-RlO0 is packed with powerful
features, and covers the lO0kl-Iz - 1800 MHz
(500 kHz~ 1800 MHz guaranteed) range in
AM, FM, wide FM modes with multi-function
scanning and 100 memories with 20 scan edge
channels.
While the IC-R7100 covers from 25 ~ 2000
MHz in SSB, AM, FM, wide FM modes, optional
TV and FM stereo adaptor, with 900 memory
IC-R7"100
channels, sophisticated timer functions and
multiple scan functions.
The top of the range IC-R9000 expands your
listening horizons, covering 100 kHz~ 1999.8
MHz in all modes and featuring !corn's unique
CRT display, intelligent scan functions and an
amazing 1000 memory channels, in a unit that
IC-R"IOO
delivers superb high frequency stability, even in
the GHz range.
So tune in to the ones that professional
listeners use, from the wide range of lcom wide
band receivers.
For further information call free on (008) 338 915
or write to Reply Paid 1009 lcom Australia Pty Ltd
P. 0. Box 1162 Windsor Victoria 3181
IC-R"I
Telephone (03) 529 7582
A.C.N. 006 092 575
/COM Australia's warranty is only af,plicable to tyroducts purchased from their authori.sed Australian Dealers.
IC-R72
LL BROWN ADVERTISING 3907
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