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2 Silicon Chip
Contents
Vol.12, No.8; August 1999
FEATURES
4 Cleaning The Smokestacks
How Hazelwood Power Station cuts pollution – by Sammy Isreb
10 Internet Access – Reduced Prices
No time limits, no download limits, no fine print – and no hassles
53 SPECIAL OFFER: Subscribe At 1998 Prices
Beat the magazine price rise – and GST – by subscribing now
78 Making Negatives From Positives
Remote Modem Controller –
Page 16.
Simple DOS & Windows utilities let you reverse Protel PCB files
82 Electric Lighting, Pt.14
Illuminating the indoors using natural light & light pipes – by Julian Edgar
PROJECTS TO BUILD
16 Remote Modem Controller
Want to control and/or measure things from a distance? – by Leon Williams
26 Daytime Running Lights For Cars
Improves safety, reduces the glare and no flat battery! – by John Clarke
Daytime Running Lights For
Cars – Page 26.
35 Build A PC Monitor Checker
Stand-alone unit tests VGA, MGA and composite video types – by C. Roher
54 Switching Temperature Controller
Cool or heat anything accurately & easily – by Branco Justic & Ross Tester
60 An XYZ Table With Stepper Motor Control; Pt.4
Building the electronic control circuits – by Rick Walters
SPECIAL COLUMNS
Build a PC Monitor Checker –
Page 35.
42 Vintage Radio
A killer; the set from hell – by Rodney Champness
74 Serviceman’s Log
Not every write-off is written off – by the TV Serviceman
DEPARTMENTS
2
9
53
70
80
Publisher’s Letter
Mailbag
Subscriptions Form
Circuit Notebook
Electronics Showcase
86
90
93
94
96
Product Showcase
Ask Silicon Chip
Notes & Errata
Market Centre
Advertising Index
Build A Switching Temperature
Controller – Page 54.
AUGUST 1999 1
PUBLISHER’S LETTER
www.siliconchip.com.au
Publisher & Editor-in-Chief
Leo Simpson, B.Bus., FAICD
Production Manager
Greg Swain, B.Sc.(Hons.)
Technical Staff
John Clarke, B.E.(Elec.)
Robert Flynn
Ross Tester
Rick Walters
Reader Services
Ann Jenkinson
Advertising Enquiries
Rick Winkler
Phone (02) 9979 5644
Fax (02) 9979 6503
Mobile: 0414 34 6669
Regular Contributors
Brendan Akhurst
Rodney Champness
Garry Cratt, VK2YBX
Julian Edgar, Dip.T.(Sec.), B.Ed
Mike Sheriff, B.Sc, VK2YFK
Philip Watson, MIREE, VK2ZPW
Bob Young
SILICON CHIP is published 12 times
a year by Silicon Chip Publications
Pty Ltd. A.C.N. 003 205 490. All
material copyright ©. No part of
this publication may be reproduced
without the written consent of the
publisher.
Printing: Macquarie Print, Dubbo,
NSW.
Distribution: Network Distribution
Company.
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in Australia. For overseas rates, see
the subscription page in this issue.
Editorial & advertising offices:
Unit 8, 101 Darley St, Mona Vale,
NSW 2103. Postal address: PO Box
139, Collaroy Beach, NSW 2097.
Phone (02) 9979 5644.
Fax (02) 9979 6503.
E-mail: silchip<at>siliconchip.com.au
ISSN 1030-2662
* Recommended and maximum price only.
2 Silicon Chip
Faith & hope are no
substitute for
measurements
As time goes on and new technology presents consumers with ever more gee-whiz
choices, it is surprising just how many people
still have an abiding interest in hifi amplifiers
and speakers.
In one aspect this is not surprising though,
because it really is only in the area of amplifiers
and speakers that hifi enthusiasts have an opportunity to have an input in producing their
“ultimate system”. Designing and building
your own hifi equipment is very satisfying, for all sorts of reasons.
That said, I am quite often button-holed by people who want me to consider their latest amplifier creation which sounds, to them, truly wonderful.
Typically, this amplifier will be a compilation of the design features of
notable designers and reviewers from around the world. It may have low
feedback or no feedback, to give really “natural” sound, or it may have
lots of feedback and have a very fast slew rate (maybe 300V/µs) to give a
really “fast” sound.
According to the person’s beliefs, the amplifier may use Mosfets because of their indestructibility or bipolars because they sound “cleaner”
and so on.
Whatever the particular person’s design philosophy, he will always be
adamant that it is the best system he has ever heard (perhaps it is) and that
it is probably the best available in the world (highly unlikely).
But when I ask about distortion measurements, the conversation always
gets bogged down. In fact, it often turns out that no measurements have been
made at all, not even for power output and frequency response.
Now while these people may genuinely believe that they have produced
a masterpiece, the odds of them doing so, without having made exhaustive
measurements to confirm their beliefs, are extremely long. In fact, it’s just
not possible.
We have found on any number of occasions, the number of variables
effecting an amplifier’s performance is very large and even the position of
a single supply or signal wire can have a major effect on the distortion and
therefore, the sound quality.
Moreover, if you randomly vary something, you usually get a worse result! So if you make any alteration to a design, you must then do exhaustive
measurements to see if the results are better.
But try and tell this to anyone who is convinced of the beauty of his own
design and you will usually not get a good reception. In fact, it is better to
just nod sagely and say something vague and complimentary.
So if you are in the same situation and someone tells you that he has
produced a wonderful new amplifier or speaker design, by all means have
a listen to it. It will probably be very enjoyable.
But if measurements haven’t been made somewhere along the line, there
could be a large proportion of delusion in the enjoyment.
Leo Simpson
*Full details at www.tol.com.au
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FreeFax 1 800 625 777
AUGUST 1999 3
HAZELWOOD POWER
Leading the way
to a cleaner
environment
By Sammy Isreb
When you burn coal, you get ash. However, these days no-one
tolerates a thick plume of ash-laden smoke emerging from a
chimney – or in the case of a power station, multiple, highvolume chimneys. But with exhaust temperatures of 200°C or
more, it’s not quite as simple as putting a filter in the flow . . .
About two hours east of Melbourne,
nestled in the heart of Victoria’s
Gippsland region lies the Latrobe
Valley. While the valley thrives on
farming there is another noticeable
industry: power generation.
It’s been a major part of the valley
since the first station was synchronised to the Melbourne grid on the
afternoon of Tuesday, 24th June, 1924.
In fact, power stations are so much
a feature of Gippsland that anybody
who has driven through the region
will surely remember the myriad of
chimney stacks rising into the sky.
So why did the former SECV (State
Electricity Commission of Victoria)
4 Silicon Chip
decide to build more than 80% of the
state’s generating capacity in the area?
Under the region’s pastures lies
billions of tonnes of brown coal, one
of the richest deposits in the world.
The brown coal is burnt to turn water
into superheated steam, which drives
the turbines.
As a byproduct of burning the coal,
ash is produced, which brings us to
the topic of this article: dust removal
by electrostatic precipitation.
Hazelwood Power Station
Hazelwood Power Station was commissioned during 1964-1971 (in four
stages). When completed the plant
had a total capacity of 1600MW, made
up of eight 200MW units.
Each unit has an independent
boiler, turbine, generator, condenser,
precip-itator and draft systems, along
with independent controls. Two of
these units make up what is known
as a “stage”, sharing a bare minimum
of equipment. Common equipment
is basically limited to forms of data
logging and the “Pondage” – Hazelwood’s 506 hectare, 30,850 megalitre
cooling pond. The Pondage eliminates
the need for cooling towers, providing
a relatively cool supply of water for
the eight condensers.
Brown coal is supplied to the plant
from an open cut mine, a massive
hole in the ground with a perimeter
of approximately 12 kilometres and a
depth of around 100 metres in places.
Dredgers weighing up to 1800 tonnes
remove coal from the mine face, sending it down conveyor belts to bunkers
from where it is sent to the plant.
The station uses roughly 15 million
tonnes per year or about 1700 tonnes
per hour.
With this sheer amount of coal, one
can see how rigorous environmental
procedures must be put into place in
order to avoid waste products polluting the area.
Privatisation
In August 1996, Hazelwood Power
Corporation was sold to a private
consortium for $2.35 billion.
Since the sale, one could only describe the renovations to the station
as staggering. When it was purchased,
the operational capacity of the plant
was 1200MW, with Unit 7 damaged
(due to an overheating incident in the
boiler) and Unit 8 mothballed.
Shortly after the purchase, Unit
8 was recommissioned. In January
1998, the newly rebuilt Unit 7 was
brought into service, ending a yearplus long project worth tens of millions of dollars.
During the following summer
months of 1998, the operational
capability of the plant was restored
to 1600MW, with a peak of 1679MW
recorded.
Why clean the emissions?
One of the biggest problems in coal
fired power generation is pollution
from the ash in emissions from the
chimneys. Fortunately, the brown
coal in the area has very low sulphur
content, eliminating the acid rain
which plagues some other countries.
The major constituent of pollution
from brown coal is ash, formed in the
combustion process. If no action is
taken, it is ejected from the chimney.
It is the role of the electrostatic dust
precipitator (EDP) to remove this dust
from the exhaust gas, allowing it to be
collected for disposal.
When the SECV commissioned
Hazelwood the best EDP technology
available at the time was installed.,
The old EDPs still met the Environmental Protection Agency (EPA)
licensing requirements, but only just.
In 1977, Hazelwood Power management decided to replace the current
precipitators.
Several factors led to the program
being conducted on a unit-by-unit
installation basis, with completion
not being scheduled until 2007.
Unit 3 was chosen to be the first
recipient of the new precipitator due
to it being the worst performer on an
emission basis.
What’s wrong with a screen?
Commonsense would suggest the
application of some sort of particle
screening or filtration solution. And
why not? All around us common
devices use a multitude of screening
techniques, from vacuum cleaners to
dust masks, to keep unwanted airborne particles under control.
So why deviate from this seemingly
Hazelwood Power Station, looking across one of the ash-settling dams with Hazelwood Pondage (supplying cooling water)
at the rear right. The eight units which make up the station are capable of generating 1200MW.
AUGUST 1999 5
Out with the old, in with the new: three of the old EDP flows at Hazelwood (you
can just see the new flows behind). The old units were only just capable of
meeting environmental specs but the new ones are significantly better.
simple solution into electrostatics, fluid flow and
vibration mechanics? The answer lies in economics
and practicality of scale.
On full load, each unit’s boiler at Hazelwood Power
Station emits roughly 10 tonnes of ash per hour at
a temperature in excess of 200°C.
The high temperature is only one problem; the
smoke also contains a high moisture content, due
to that of the brown coal.
Standard filtration through a filter medium is
impractical. Even if the medium did not immediately try to combust due to the high temperature or
become clogged due to the high moisture content
of the exhaust gas, the need to constantly replace
or clean the filters would prove to be the downfall
of the system.
Also, the twin 1768kW induced draught (ID) fans,
responsible for extracting the exhaust gases from the
boiler, would be unable to to pull the gas through
the extremely fine filters necessary to remove ash.
In fact, EDP is one of the most efficient and convenient solutions to many gas cleaning situations. It
is impervious to high temperatures and high moisture
content, allowing removal of filtrate while in operation and providing little resistance to the gas flow.
How does this technology work? As its name
suggests, electrostatic rather than mechanical forces
are the key.
In a nutshell, the ash particles are charged by a
high voltage while in the gas flow and are then attracted to an opposite-charge collection plate. The
particles cake on the plate, the cake drops and the
ash is transported away. (For a more detailed explanation, see the separate panel).
Modern EDP design
The first few generations of EDPs used thyristor-controlled transformer/rectifier HT sets, with
6 Silicon Chip
little control of the output. While
this arrangement achieved dust extraction, several flaws existed in the
design.
Firstly, there was no accurate
method to determine optimum voltage/current settings to maximise ash
collection.
Second, arcing would often occur
between the discharge and collection
electrodes.
When arcing was detected, the
thyristor would simply be turned off
for several cycles, allowing quenching
of the spark. However, this minimised
power flow through the EDP.
Manufacturers of new generation
EDPs have recognised the advantage
of automation in improving efficiency.
The biggest breakthrough has been
the use of “pulsed” controllers for the
removal of “tough” particles from gas.
Rather than simply increase the
voltage for tough dust, which would
The specially-made trolleys can be seen underneath the EDP unit
with one of the enormous prime movers carefully moving it into
position. Each 400-tonne EDP was manufactured on site, then
moved into place during the generating unit’s scheduled
maintenance shutdown.
be ineffective due to arcing and
back-corona, the new microprocessor
controlled EDPs send high “pulses”
of power into the EDP. Overall, the
average power entering the EDP will
be the same but this method results
in increased efficiency.
While it might be imagined that
between pulses of power, dust-laden
gas would be escaping the EDP, there
is no loss of collection capacity.
In fact, the dust/ash layer represents a resistive/capacitive circuit
with a time constant significantly
greater than a second or so.
Therefore the pulses of high power
can break down the resistive dust
layer and before back-corona or arcing occurs, power is reduced greatly,
with no net effect due to the slow step
response of the dust/ash system.
As well as implementing this
“pulsed” system, modern controllers
determine optimum power levels for
performance right up to the point at
which back-corona and arcing occur.
Hazelwood’s EDP system
Adapted directly for Hazelwood
Power by ABB, the new EDP consists
of three “flows”, basically separate
units connected in parallel.
The rationale behind this modular
setup is not only for ease of construction and installation but also for
maintenance. If one or more flows are
to be taken out of service for repair,
the remaining flows are able to operate
under heavier load in the meantime.
Each of the three flows consists of
main components integrated to form
the EDP:
• Main support structure.
• Six collection hoppers at the base
to collect waste ash.
• Three electrically isolated bus
sections containing emitting and
collecting electrodes (along with
the associated rapping equipment)
and T/R (Transformer/Rectifier)
sets.
• Inlet and outlet distribution evases/transitions which contain gas
distribution screens designed to
maintain optimal gas flow distribution within the EDP.
• Roof structure, comprised of HT
chambers and T/R sets.
• Insulation around the unit to minimise heat losses during operation.
• Ash disposal system, consisting of
conveyor from ash hoppers into a
mixing system which forms a slurry
Each of the 8 units at Hazelwood consumes nearly 200 tonnes of coal and emits
10 tonnes of ash each hour. That ash would be a major source of pollution if it
wasn’t removed from the exhaust.
to be discharged into sluice ways.
Controlling each of the three T/R
sets per flow is the EPIC II (the initials
standing of Electrostatic Precipitator
Integrated Controller), a microprocessor based system, mounted in the
switchboards on ground level. Therefore, there are nine EPIC II systems per
unit, as there are three T/R sets per
flow, and three flows per unit.
Each of these nine EPIC II microprocessors feed into a remote terminal unit (RTU) in the control room.
Information on each EDP such as
sparks, general alarms and trends can
be displayed.
Mode settings can be altered
for each of the EPIC II units, with
anything from the standard mode,
to “sootblowing” mode, in which
current is kept artificially high, even
during sparking.
Rapping sequences are also available to be viewed and altered from
the RTU.
As part of Hazelwood Power’s reporting obligations to the EPA, dust
monitoring equipment is installed
throughout the station.
On each chimney is an Erwin Sick
opacity dust monitor, which log the
dust levels to remote control rooms
and dataloggers throughout the station.
Wired into the engineering office
via the internal network, a dedicated
dust monitoring PC logs half-hour
averages of dust levels throughout the
units against their megawatt outputs.
Monthly databases are then stored
for record keeping and for reporting
to the EPA.
Installation
The new 26m high EDP flows, ready
for installation, are dwarfed by
Hazelwood’s eight chimney stacks.
Construction of the new Unit 3 EDP
began about six months before the unit
was taken offline, in March 1998. The
EDP was constructed in three separate
flows, with the plan being to remove
the old EDP casings and place their
newly constructed successors on the
same foundations.
AUGUST 1999 7
How An Electrostatic Dust Precipitator Works...
1: Corona generation
Inside an EDP are alternating rows of collecting electrodes (rigid steel plate curtains) and
emitting electrodes. A high voltage negative DC
supply, typically -50kV or more, is connected
to the emitting system.
In the region known as the corona (near
the emitting electrodes where the electric field
strength is greatest) the gas is ionised.
The ionisation of gas produces positive and
negative ions. The positive ions are attracted to
the negatively charged emitting electrode and
the negative ions are attracted to the grounded
collecting electrodes.
Fig 1: a cut-away view of an
2: Particle Charging
Along the way, the negative ions collide electrostatic dust precipitator.
with suspended dust particles, charging them
proportionally as a squared function of their size. Once charged, the dust particles are
attracted towards the collection plates. Hence, the particles “migrate” towards the plates
with a velocity dependent on their size (larger particles travelling faster). When they reach
the collection plate, they stick and begin to form a layer.
It is at this stage in the process that problems sometimes occur. As the dust begins to
build up on the collection plate, it will exhibit a resistance to the flow of current.
If the resistance of the particles is too low, a high current flow will occur, causing the
particles to quickly lose their charge and possibly re-enter the gas stream. Conversely, if
the accumulating layer is of high resistivity, an abnormally high electric field will be present
in the dust layer.
A “back-corona” can occur, breaking down interstitial gas and producing ions and
spontaneous electrical discharges from the dust layer.
The resulting reduction in performance is twofold: the electrical discharge from the dust
layer allows collected dust to re-enter the gas stream and the positive ions counteract the
approaching charged particles.
The resistivity of the particles will depend on the type of fuel and how well it has burnt.
Luckily for Hazelwood, the ash passing through the EDPs is of moderate resistivity and
causes no problems of this nature.
Each of the three flows of the Hazelwood EDPs are divided into three equal-sized fields
(or zones) operating in series.
Because the larger particles are much
easier to collect, the first field removes approximately 80% of the ash and dust entering
the EDP, with the second field removing
around 15% and the third field 5%.
3: Rapping
The layer of ash and dust particles on
the collector plate is removed by a process
called “rapping”.
This simply uses heavy metal hammers
to strike an anvil on a shockbar, to which
four collection plates are attached by huckbolts. The hammers produce a force of up
to 300Gs.
This effectively shears the dust from the
plate surface, dislodging “cakes” of dust
which fall into hoppers below.
From there it is carried away by screw
conveyors before being mixed with water
and removed via sluiceways to settling dams.
8 Silicon Chip
Built on temporary foundations, the
three flows each measured 26m high
x 13.5m x 19.5m and weighed around
400 tonnes.
Once the new Unit 3 EDP flows had
been successfully fabricated about 50
metres from their final resting places
and with the unit offline for its major outage, it was time to commence
the gargantuan task of moving and
installing them.
To begin with, each old flow was
disconnected from its foundations
and placed on a hydraulic trailer,
containing 144 wheels on nine separate axles. With the aid of three prime
mover trucks the flows were moved
to their storage place.
The new EDP flows, also jacked
up and pre-positioned onto a similar
trailer, were then guided into place
and anchored. The entire operation
took just 13 days.
Once the new EDP had been
positioned and with the relevant
ducting and electrical connection
work completed, it was time for the
commissioning.
The ultimate test
While computer models predicted
what modifications to the inlet and
outlet screens and deflectors were
needed to ensure uniform airflow
throughout each flow, these models
were only a guide, being no substitute
for real testing.
Flow testing began, in late October
1998. The 12 painstaking tests, conducted around the clock and requiring
modifications after each test, took
eight days.
The tests were conducted with the
unit still offline, with the test team
running the ID fans and taking air
flow readings in a multitude of places
in the EDP.
Finally, the unit was brought back
into service on the 7th January 1999,.
Dust emissions for Unit 3 on full load
dropped from around 300-400mg per
cubic metre to a new level of less than
100mg/m3.
Acknowledgement
Fig 2: a somewhat stylised representation of the inside of the precipitator
above. Exhaust gases flow in the direction of the arrow.
I would like to thank the following
engineering staff from Hazelwood
Power for their extensive help in
the compilation of this article: Tony
Innocenzi, Chris Morley and Daryl
Anderson, along with Sara Stigsson,
Wayne Bassee and Jason Price from
SC
ABB.
MAILBAG
Home wanted for
antique electronics gear
I am looking for a caring home for a
lot of antique electronics gear. I have
a lot of valves, 5R4, 807, TV & radio
types, 18-inch rack mount test equipment, oscilloscope, amplifiers, tuners
and magazines going back to 1948.
I was working in the Kriesler factory
during the 1956 Olympics and built
the family’s only TV from bits. It sat
uncovered on an old traymobile for a
year or so. I got a lot of stuff from the
old Zenith Radio factory in Rydalmere. It is still on the 18-inch racks,
taking up space.
It would be nice if there was
someone in Sydney who could pick
through for any historical Items. I
am really only looking to avoid any
further costs to clear the stuff as I will
not be able to take it to the new house
we have purchased.
Peter Fitzpatrick,
14 Jenkins Street,
Chatswood, NSW 2067.
Phone (02) 9411 3672.
email: peterf<at>intercoast.com.au
Clearing the carry flag
in the PIC programmer
I read Kerry Helman’s letter on the
PIC programmer in the note in the
May 1999 issue with interest. Like
him, I had experienced the double
LED syndrome and (very slowly) came
to the same conclusion. I used “addlw
0” as a way of clearing the carry flag.
His method of “bcf STATUS,7” will
indeed clear bit 7 of the status register
but that is the IRP bit. He needs “bcf
STATUS,0” to clear the carry bit. I
found that the double LED effect was
intermittent and it may be that he has
been lucky since changing the code.
I can simulate his “Hardware not
found” problem by leaving the PIC
in the programmer while the NOPP
program is searching for the device.
The programmer should be plugged
into the parallel port without the PIC
and without power until, after selecting the appropriate PIC, the message
“Insert PIC in socket and apply power
to programmer now” is received.
Thanks for a useful article.
John Nestor (via email).
Editorial errors
are a concern
Firstly, thanks for a great magazine.
However, I must take exception to
errors that I believe are creeping into
your editorials. I am not concerned
about your opinions, because we all
have opinions. However, you must get
the facts right. I have put off writing to
you in case this was a one-off event,
possibly as a result of tight publishing
deadlines. But twice in a year?
Firstly, I believe your description
and explanation of the extended
Auckland power outage (April 1998)
was wrong. As soon as I read it, I went
straight to various NZ Energy web
sites to learn the facts. Of the four
affected power cables, two were in
fact gas-filled and two were oil-filled.
And a lack of maintenance was not
the cause of the problem as you suggested. Was this just a hopeful guess
as a result of media hype?
We now know that the error
occurred decades prior, when an
engineering design flaw resulted in
a section of cable being under-specified, given the amount and density
of traffic flowing above. The resulting
high density surface layers caused lo-
CS cable for
hard disk drives
A CS cable can be made by cutting conductor 28 between the
master & slave connectors.
I write in regard to your article,
“Hard Disk Upgrades”, in the June
1999 issue.
Specifically, I was surprised by
your statement that “CS cables
are not easy to obtain”. In fact the
“CS cable” is merely a standard
40-pin IDE cable with conductor
28 (CSEL) cut from the end of the
chain, as shown above.
Franc Zabkar (via email).
calised heating which then damaged
the cable. All the pressurised gas
and oil insulation on all four cables
remained intact and within service
flow parameters. There was no lack
of maintenance.
Secondly, your explanation of
graphite bombs in the June 1999 issue
sounds wrong. These ‘bombs’ are not
powdered graphite as your editorial
seems to suggest. The Melbourne
‘Age’ newspaper had photographs of
the actual payload – millions of golfball sized pellets of solid graphite,
covered in conductive ‘hairs’. They
actually look like pellets of ‘steel
wool’. They therefore do not “permeate the surface of all insulators and
switchgear”.
They can in fact be washed off, the
circuit breakers recharged, pressurised and reset, and power restored
after a few hours. That’s exactly what
happened and that’s the whole idea –
to temporarily disrupt, not to plunge
the largely innocent population into
weeks without power. And to ‘take
out a few of the high voltage towers’
as you suggest would in fact cause
immense disruption to the population
at large.
Please take more care with your
editorials. They are usually the first
thing I read in the magazine.
Martyn Leicester (via email).
Comment: Your letter highlights the
fact that editorials are sometimes
written when there is a dearth of hard
information and as you say, there is
media hype. However, if you go back
to the editorial on the Auckland power crisis, the remarks were prefaced
with the word “supposedly”. While
lack of maintenance may not have
been the problem we stand by the
editorial on that subject. Auckland
was and still is a timely lesson for us
in Australia.
As far as the graphite bomb was
concerned, we did go to the Internet
to search for info on graphite bombs
and could find none. It was extremely
frustrating to subsequently find the
reference to the conductive hairs after
the editorial had been written and
printed. It may well be true that they
SC
can be easily washed off.
AUGUST 1999 9
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10 Silicon Chip
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(a) Fill in this form and either post it or fax it to SILICON CHIP – (02) 9979 6503; or
(b) Call SILICON CHIP on (02) 9979 5644; 9am-4pm Mon-Fri and we'll guide you through it!
(c) WE WILL THEN FAX YOU OR POST YOU your password and EASY setup details.
Date of Application: ________________
YOUR DETAILS
Name ___________________________________________________________________________________
Company Name (if applicable) __________________________________________ACN: ____________________
Address _________________________________________________________________________________
__________________________________________________________________Postcode ________________
Postal address (if different to above) ____________________________________________________________
____________________________________________________________ Postcode_______________
Phone No. (
) ______________________________Fax No. (
)_______________________________
Current email address (if applicable): ________________________ Signature:__________________________
PAYMENT DETAILS: CREDIT CARD ONLY!
❏ Bankcard
❏ VisaCard ❏ Mastercard
Card No:
Card expiry date ____ /____ Cardholder Name (if different from above) ____________________________________
SERVICE TYPE One month minimum. If you prepay for three months you avoid paying the setup fee of $10.00
One Month ($10.00 SETUP FEE APPLIES)
Three Months (NO SETUP FEE)
❏ Low Vol: $10 + $10 setup fee (5hrs then $2.00/hr)
❏ Low Vol: $30 no setup fee (15hrs then $2.00/hr)
❏ Regular: $20 + $10 setup fee (10hrs then $1.80/hr)
❏ Regular: $60 no setup fee (30hrs then $1.80/hr)
❏ Power: $49.95 + $10 setup fee (25hrs then $1.60/hr)
❏ Power: $149.85 no setup fee (75hrs then $1.60/hr)
Note: charges are made on a calendar month basis. When do you wish to start: straight away beginning of next month
Choose your email address (user name of 2-8 letters), eg, yourname<at>silchip.com.au
First Choice:__________________Second Choice:___________________Third Choice:___________________
Choose your Dial-In Location (also known as POP - Point of Presence) from this list:
❏ Sydney (inc outer metro) ❏ Newcastle ❏ Wollongong ❏ Gosford, Windsor, Wiseman's Ferry
❏ Penrith, Mulgoa, Camden ❏ Campbelltown, Helensburgh ❏ Melbourne (inc outer metro) ❏ Geelong
❏ Cranbourne, Mornington ❏ Healesville, Emerald, Pakenham ❏ Gisborne, Romsey, Kilmore, Kinglake
❏ Lara, Balliang, Bacchus Marsh ❏ Brisbane (inc outer metro) ❏ Gold Coast ❏ Perth ❏ Adelaide
❏ Hobart ❏ Canberra
(Note: Some locations within these areas may be community or STD calls. Please check with your telephone service provider if in any doubt)
Initial charges (Credit card charged ONLY after password & setup information have been forwarded):
Monthly/3-monthly plan charge: $________ Plus setup fee: $10.00 (if applicable) $ _______ = Total: $ __________
AA
UGUST
ugust 1999 11
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.dse.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.dse.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.dse.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.dse.com.au
Remote Modem
Are you a ‘control freak’? Want to control and measure
things from a distance? If you have an old modem sitting
idle, here’s the ideal project.
It simply connects to a standard modem and the flexible
interfacing makes it suitable for a vast array of control and
measurement applications.
By Leon Williams
H
ave you ever been away from
home, say on holidays, and
wished that you could turn on
the lights, feed the dog, see what the
temperature of the tropical goldfish
tank is or measure the voltage of your
burglar alarm battery?
Or ever been at the office and forgotten to water the garden, or worse,
forgotten to turn the sprinkler off?
Well, the answer is to build the
Remote Modem Controller (RMC).
Together with a PC and modem, the
RMC you can turn things on and off,
monitor inputs, measure voltages,
measure the temperature and count
events whether you are next door or
on the other side of the world.
You don’t need any
fancy software, as it
interfaces with just
about any PC running
terminal emulation
software.
The RMC is housed
in a standard plastic
instrument case and has
room for extra interfacing or transducer circuits.
The rear of the unit has a
DC input socket, a 9-pin male
D connector for the modem
and a 25-pin female D connector
for the serial cable to the PC.
Operation is simple. Before you
leave home, you connect the RMC
FEATURES
Easy to build single sided PC board
PIC16C73A microcontroller
6-digit password login security
Idle timeout protection
Individually turn on/off four outputs
Monitor four opto-isolated digital inputs
Measure temperature between -10°C to +60°C in one-degree steps
Measure two separate voltages from 0 to 20V DC in 100mV steps
Capture or count slow-occurring events (maximum count of 255)
9V DC input at low power
No special software required
Easy interactive menu operation; single key-stroke commands
Simple 3-wire RS232 control interface (4-wire for modem)
EEPROM stores password and system data
Operated remotely via a modem or by direct connection to a PC
16 Silicon Chip
to your modem which is plugged into
the telephone line. Later on, when
you are far away, you dial into your
RMC from a remote PC and modem.
The modem answers the call and the
RMC asks for a password. If the password is accepted, you are presented
with the main menu, from where you
select the various options. When you
are finished you select logoff and the
RMC commands the modem to terminate the call, ready for the next one.
As well as doing all this remotely,
m Controller
the RMC can be directly controlled
by your PC to measure and control
things locally.
Inputs/Outputs
The RMC’s inputs and outputs can
be used for an unlimited number of
The outputs are open-collector
transistors and incorporate a clamping diode which is used if relays are
being controlled. If a logic output is
required, then a pull-up resistor can
be connected between the respective
collector and the positive DC rail.
With these features it is simple to
interface with logic I/O, switches,
relays, sensors and transducers.
Fig.1 shows some input and
output circuits.
PIC microcontroller
applications. The inputs and event counter are isolated
by optocouplers and only require a
few milliamps to operate.
The analog voltage inputs, while
not being electrically isolated, are
protected against over-voltage and
reverse polarity. A resistive divider
has an input impedance of 10kΩ and
converts the maximum measurable
input voltage to a safe voltage for the
microcontroller’s A-to-D converter.
The temperature sensor input is designed to match a LM335 temperature
sensor, which has an output voltage
of 2.73V at 0°C.
The star of the show is undoubtedly
the PIC16C73A microcontroller. It
comes in an unusual 28-pin skinny
(0.3") DIP package but it has a lot
packed inside it. Some of the internal
features are:
* 4K OTP (One Time Programmable)
program memory
* 192 bytes of user RAM
* 22 I/O pins
* 3 timer/counters
* a full duplex UART
* a 5-input A-to-D converter
Circuit description
Fig.2 shows the complete circuit
diagram. IC1 is the PIC16C73A micro-
controller. Pins 9 and 10 provide the
crystal oscillator using X1, C10 and
C11. The frequency of 3.6864MHz
was chosen to allow the internal Baud
Rate Generator to provide accurate
baud rates.
Pin 20 is the positive supply input
while pins 8 & 19 are connected to 0V.
Pin 1 is the reset input, connected to
+5.12V via a 10kΩ resistor.
The PIC has an intelligent internal
power up reset circuit and as long
as Vcc rises quickly, no extra power
reset circuit is required. Pins 21 to 28
are assigned to general purpose port
B with pins 21 to 24 configured as
outputs and pins 25 to 28 as inputs.
Pins 11 to 18 are assigned to port C.
Pin 18 is the UART Receive data input,
pin 17 is the Transmit data output and
pin 15 is the DTR output. Pin 16 is
used to control the LED.
Pins 11 to 14 are used to interface to
the EEPROM (IC3). It is used to hold
the password, speed setting and other
system data in case of a power failure.
It can store 64 by 16 bit words. Data is
written to and read from the EEPROM
in serial form synchronously with the
rising edge of the clock input.
The Chip Select (CS) input, pin 1,
must be high for any read or write
commands to be accepted. A 10kΩ
resistor (R4) is used to pull the CS
line low when powering up or down
to avoid possible data corruption.
Data to the EEPROM is at pin 12,
data from the EEPROM is pin 11, the
clock signal is pin 13 and the Chip
Select signal is pin 14.
The last port, port A, is associated
with the Analog to Digital (A-to-D)
converter. Pins 2 and 3 are configured
as A-to-D inputs 0 and 1. Pin 4 is a
digital input that is sampled at power
up to determine if the Default pins are
shorted. More on this later.
Pin 5 is the temperature sensor
input and the voltage on this pin is directly proportional to the temperature.
Pin 6 is not connected to the A-to-D
converter but instead is connected to
the clock input of an internal counter
(Timer 0). Pin 7 is not used. The referAUGUST 1999 17
Fig. 1: some of the input and output circuits which could be used with the
Remote Modem Controller. There are many more which could be devised.
ence voltage for the A-to-D converter
is internally connected to the +5.12V
rail (Vcc).
IC2, an MAX232, is a standard
RS232 transceiver used to interface
the 5V logic signals in and out of the
PIC to the modem and serial ports.
It only requires a +5V power supply
and produces the required plus and
minus RS232 voltages by an internal
inverter which employs capacitors
C1 to C4.
IC2 has two receivers and two
transmitters but one receiver (pin 8)
is not used here. Pin 13 is the receive
data input, pin 7 is the transmit data
output and pin 14 is the Data Terminal
Ready (DTR) output.
P1 is a 9-pin male D connector and
J1 is a 25-pin female D connector. In
case some communications packages
running on the PC require active CTS,
DSR and DCD signals, they have been
looped to PC outputs so that they will
be on whenever the PC is connected.
LED1 has the following states: Off
when power is disconnected or off for
five seconds when clearing a call. It
flashes at a slow rate when powered
up and the unit is attempting to match
the interface speed with the modem
or PC.
When the unit has matched the
modem or PC and is waiting for a
connection, it flashes at a faster rate
of around 1Hz. When a call is in pro18 Silicon Chip
gress, LED1 is permanently on.
Connector J2 is the connection
point for the analog inputs. Each input
has an attenuator made up of three
resistors, 1.8kΩ, 6.2kΩ and 2kΩ.
This unusual combination is used
to allow easy software manipulation
of the A-to-D value. The A-to-D converter has a resolution of 8 bits or
a maximum value of 255. With this
attenuator, an input voltage of 20V
gives 4V at the A-to-D input pin and
a conversion value of 200 – making
the software task a lot simpler.
Zener diodes ZD1 & ZD2 protect
the PIC inputs from over-voltage and
reverse voltage, although reverse
voltage inputs should be avoided.
The maximum voltage that can be
measured is 20V, however the inputs
can withstand overvoltages up to say
50V for a short duration.
A .01µF capacitor is connected
across each PIC input to filter out
noise and minimise A-to-D conversion errors.
Op amp IC5b, one half of an LM358,
is the temperature sensor interface
and intended to be used with an
LM335 temperature sensor.
This gives an output voltage relative
to zero degrees Kelvin and which
increases by 10mV/°C.
At 0°C the calibrated voltage is
2.7315V. IC5b has a gain of -4 which
results in the output voltage at pin
6 changing at a rate of 40mV/°C, decreasing with increasing temperature
and vice versa. Trimpot VR1 acts as
the calibration control.
A 4N28 optocoupler, IC6, is used
to interface the Events input (J4) to
pin 6 of IC1. Resistor R18 limits the
current passing through the internal
LED in the optocoupler, while diode
D2 protects it against reverse voltages.
The value of R18 (560Ω) is chosen to
provide about 5mA of input current
when interfaced to a 5V logic output.
Higher voltage input signals will require an external resistor – see Fig.2.
R17 pulls up the open collector output
of IC6 and provides a high when the
input is off (no input current) and a
low when the input is on (current
flows into the optocoupler).
Capacitor C13 acts as an integrator,
filtering out any high frequency edges
which may occur if switches without
debouncing are used as inputs. The
Event input connects to an edge-sensitive counter within IC1 and any
transitions other then the one wanted
will result in false Event readings.
However if the inputs are very noisy,
an external debouncing circuit will
be needed.
IC7, IC8, IC9 and IC10 and associated resistors and diodes are the
optocoupled inputs. They operate
in the same way as the Events input.
IC4 is a ULN2003A which interfaces
four outputs of IC1 to connector J6. It
has open-collector transistors which
can each sink 350mA and have a maximum collector voltage of 50V. IC4 is
suitable for driving relays as well as
providing a logic output by connecting a resistor between the collector
of the transistor and the +5V supply.
Connector J5 has a +5V point which
can be used for this purpose.
Note that when using the digital
output option, the output is low (0V)
when it is on and high (+5V) when the
output is set to off. The +5V point on J5
is only intended for this purpose and
the internal power supply is not designed to power multiple relay coils.
The power supply consists of an
LM317T 3-terminal adjustable voltage
regulator (REG1). The DC input is
filtered by C14 and protected against
reverse voltages by diode D1.
The output voltage is adjusted to
5.12V by trimpot VR2. It is set to 5.12V
rather than 5V to provide the correct
reference voltage for the A-to-D converter within IC1.
Fig. 2: the circuit diagram for the complete controller. Calibration of the
temp-erature input (based around IC5b and using VR1) is not covered in the text
but is menu-driven and will be self-explanatory when this menu is displayed.
Voltage setting (using VR2) is important and is fully covered in the text.
AUGUST 1999 19
Parts List
1 PC board, code 07408991
1 Plastic instrument case 200mm x 160mm x 70mm
4 3 way PC board mount screw terminals
5 2 way PC board mount screw terminals
1 9 pin male right angle PC board mount D connector (P1)
1 25 pin female right angle PC board mount D connector (J1)
1 DC chassis socket (to match plug pack)
2 200 ohm horizontal trimpots (VR1, VR2)
1 3.6864MHz crystal (X1)
1 28 pin 0.3" IC socket (can be 2 14 pin sockets)
6 PC stakes
4 No 4 x 6mm self tapping screws
1 LED mounting clip
Hookup wire
Semiconductors
1 PIC16C73A-04/P pre-programmed microcontroller (IC1)
1 93LC46B 64 x 16 bit EEPROM (IC3)
1 MAX232 RS232 transceiver (IC2)
1 ULN2003A solenoid driver (IC4)
1 LM317T 3-terminal regulator (REG1)
1 LM358 dual op amp (IC5)
5 4N28/4N25 optocoupler (IC6 - IC10)
1 5mm green LED (LED1)
1 1N4004 1A diode (D1)
5 1N4148 signal diode (D2 - D6)
2 18V 1W zener diode (ZD1,ZD2)
Capacitors
1 470µF 25VW PC electrolytic
6 10µF 16VW PC electrolytic
1 1µF 16VW PC electrolytic
4 0.1µF monolithic (code 100n or 104)
2 .01µF ceramic (code 10n or 103)
2 22pF ceramic
(code 22p or 22)
Resistors (0.25W, 1%)
1 120kΩ 1 30kΩ
9 10kΩ
1 1.5kΩ
1 1.3kΩ
5 560Ω
2 6.2kΩ
1 620Ω
3 2kΩ
1 330Ω
2 1.8kΩ
1 240Ω
A pre-programmed PIC16C73A microcontroller and a 93LC46B EEPROM
are available for $30.00 including postage (cheque or money order) within
Australia from L. Williams, 14 Powell Street, Bungendore NSW 2621. email
lmwill<at>alphalink.com.au, http://www.alphalink.com.au/~lmwill
blocks, noting that there are 2-way
and 3-way types. Follow these with
the PC stakes and finally the two D
connectors.
With the PC board complete, place
it on the pillars in the bottom righthand half of the case. You will find
that some of the pillars are directly
under soldered connections and the
PC board does not sit flat. The solution is to remove the offending pillars
with a large pair of side cutters or drill
them out.
Now comes the tricky part: you
need to mark and cut out the rear
panel so that the two D connectors
protrude through it with enough room
around them to clear the mating cables. Slide the rear panel into its slot,
place the PC board up against the rear
panel and mark where the rectangular
cutout should be.
Take your time with the cutout.
Although the plastic is soft, forcing
the cuts can easily break the panel.
Before installation, drill a suitable
hole and mount the DC power supply
socket on the rear panel.
You will also need to drill a 10mm
hole in the rear panel and fit it with
a grommet so that you can easily run
wiring into the case at a later stage.
The lefthand side of the case has
ample room for interfacing circuits.
Once this is done, place the rear
panel into the slot in the bottom half
of the case and screw the PC board
down with four self-tapping screws.
Drill a hole in the front panel for the
LED, install it with a mounting clip
and then slide the panel into the
bottom case half. Wire the LED and
the DC input socket to the PC board
stakes with hookup wire, noting that
they are polarised.
DC supply adjustment
The power supply input voltage
is nominally 9V DC but a 12V DC
plugpack will be acceptable. The
circuit draws about 40mA at 9V and
REG1 should not normally require a
heatsink with this voltage.
Construction
Before you start assembly, check
the PC board for any faults, especially
where the tracks run between IC pads.
Check also that all the PC board holes
are correctly drilled.
Refer to the component overlay
diagram of Fig.3 and solder the resistors in first. If in doubt use your
20 Silicon Chip
multi-meter to check each value.
Install the IC sockets and the
trimpots, followed by the capacitors,
double checking that the electrolytics
are in the correct way.
The diodes can be installed next,
again checking their polarity. Install
the voltage regulator, the crystal and
all the ICs except for the PIC which is
plugged into its socket later on.
The ICs don’t all face the same way,
so study the component overlay closely. Any mistakes here could result
in PSD (premature semiconductor
death).
Install the PC-mount terminal
Leave the PIC chip out of the socket
at this stage. Adjust trimpot VR2 to
its mid position and plug the power
supply into the DC socket. Using a
digital multimeter, measure the power
rail (Vcc); it should be around 5V.
If not, switch off immediately and
check your work. Look for shorts or
components in the wrong way or
simply that the DC connector is wired
incorrectly.
Once everything is OK, adjust
VR2 until Vcc is exactly 5.12V. The
accuracy of the voltage measurements
depends on the setting of Vcc. The expected calibrated accuracy is ±100mV.
The resistors in the input atten-uators can also introduce some errors
but with 1% values the accuracy of
measurements should be acceptable
under most circumstances.
Turn off the power and insert the
PIC micro. Now comes the big moment – turn on the power again. The
LED should come on for a few seconds
and then flash slowly with a period
of about five seconds. The flashing
is good news; the microcontroller is
alive and well! Turn the power off
again.
Initial set-up
Now that you have your Remote
Modem Controller built, it can only
be accessed by entering a correct
password. The password is stored in
the EEPROM along with the speed
and other system data. When the unit
is powered up for the first time, the
EE-PROM contents and hence the
password, are unknown. We need
a way of bypassing the unknown
password and this is done with the
default operation.
When the unit is powered up it
senses the state of the default pins
and if they are shorted, the EEPROM
is programmed to set the speed to 9600
and the password to 123456. Note that
this default operation requires physical intervention at the actual unit and
cannot be done remotely.
Follow the steps below to set the
password and speed for the first time:
1. Power up the PC and run the terminal emulation software. This can
be Windows 3.1x or Windows 95
Hyperterminal, for example. Set
the communications parameters
to 9600bps, 8 data bits, no parity
and 1 stop bit.
2. Connect the PC to the RMC with a
9 to 25-pin cable. The 25-pin end
plugs into the RMC.
3. Short the default pins and apply
power. Note that a default mode
message is displayed on the PC
screen. You will also be asked to
remove the link and press any key
to continue.
4. Remove the link on the default
pins. If you do not remove the link,
the message will be displayed
again after a key is pressed. This
will continue until the link is removed and is protection against
the possibility of leaving the link
in place.
5. Press any key as prompted. The
Setup menu will be displayed.
If a key is not pressed within 30
seconds, the default operation is
aborted.
6. Enter P to access the Password
sub-menu and then C to change
the password.
7. Enter your new password. It must
be six characters long, can be any
combination of printable ASCII
characters and is case-sensitive.
Press S to store the password and
return to the Setup menu.
8. Press S to access the Speed submenu. Select the desired speed,
by pressing 1, 2 or 3 and then M
to return to the Setup menu.
9. Press M to go to the Main menu,
then L to logoff and finally press
Y when prompted.
10. Turn the unit off for 10 seconds
and then on again.
11. If you have changed the speed
from the default of 9600, change
the PC speed to suit. You will
now see the letters AT appear on
the screen. This will be the unit
training the connected device
to the correct speed. Press the
letters OK within two seconds of
AT appearing. If you are too slow,
AT will be displayed again in five
seconds.
12. Type in the word LOGIN (upper
or lower case) to log into the unit.
You will be asked to enter the
password.
13. Type in the new password exactly
as entered above.
14. If the password and speed are
correct, the RMC opening banner
will be displayed. Press any key
as prompted.
15. The Main menu will be displayed.
Note the message indicating that a
power reset has occurred. This is
only displayed if there has been a
power off/on cycle since the last
login time.
16. Enter L to logoff but enter N to
cancel when prompted. The Main
menu is displayed again and note
that the power reset message has
disappeared. The password and
speed settings can be changed
anytime in the future, once you
are logged on.
Modem and cables
The RMC should work with just
about any modem as long as it is
AT command set compatible. This
means that you ‘talk’ to the modem
by sending it commands preceded
by the AT attention sequence and the
modem responds to these commands.
Although modems that are AT-compatible are basically all the same,
there are differences between them
Table 1: Resistor Colour Codes
No.
1
1
9
2
1
2
1
1
1
5
1
1
Value
120kΩ
30kΩ
10kΩ
6.2kΩ
2kΩ
1.8kΩ
1.5kΩ
1.3kΩ
620Ω
560Ω
330Ω
240Ω
4-Band Code (1%)
brown red yellow brown
yellow black orange brown
brown black orange brown
blue red red brown
red black red brown
brown grey red brown
brown green red brown
brown orange red brown
blue red brown brown
green blue brown brown
orange orange brown brown
red yellow brown brown
5-Band Code (1%)
brown red black orange brown
orange black black red brown
brown black black red brown
blue red black brown brown
red black black brown brown
brown grey black brown brown
brown green black brown brown
brown orange black brown brown
blue red black black brown
green blue black black brown
orange orange black black brown
red yellow black black brown
AUGUST 1999 21
Fig. 3: all components, with the exception of the “data” LED and the DC power
socket, mount on the PC board. Terminations are made directly to the screw
terminals while the modem and PC connections are via rear-panel sockets.
and so you will need to check your
modem user manual and ensure that
it is configured correctly.
The RMC needs to detect the string
RING to indicate an incoming call
from the modem and the string CONNECT to indicate that the modem has
made a connection to the remote PC.
As a result, the modem must be configured to enable the call progress results
in verbal form (typically ATV1). The
RMC forces the modem off-line at the
end of a call by turning the DTR line
off. The modem must be con-figured
to return to command mode when
the DTR line is taken low (typically
AT&D2).
The speed at which a modem talks
to the connected PC can be configured
in a number of ways. The RMC has the
ability to remotely change its speed
in the Setup sub-menu. If the modem
was set to a permanent speed and the
RMC speed was changed, the two
22 Silicon Chip
could never communicate. To avoid
this situation, the RMC sends the
command AT to the modem to train
the modem to the new speed.
This is done after power up every
five seconds until answered with OK
and in call-waiting mode every 30
seconds but does not require the OK
response. The modem therefore must
be programmed so that it monitors the
PC data and sets its interface speed to
that of the PC (typically AT&I1).
Note that this does not refer to the
actual data rate between the modems
but the speed at which the modem
talks to the RMC. This is often referred
to as ‘auto-bauding’.
The other important modem settings are asynchronous operation
(typically AT&M0) and no-flow control (typically AT&K0). The RMC does
not provide a modem RTS signal and
if the modem is set for RTS/CTS flow
control, the modem will not send and
receive properly.
Also you need to ensure that there
are at least two rings, before answering so that the string RING can be
detected. This is normally set in S register 0. All these settings will probably
be invoked by forcing the modem into
its default configuration (typically
AT&F), but as indicated, not all modems are the same. Remember to store
the modem settings in non-volatile
memory with the AT&W command
after you have made your changes.
The RMC has two ports. The first
is the 9-pin male D connector for the
modem. Only four signals are used:
Receive Data from the modem (pin
2), Transmit Data to the modem (pin
3), Data Terminal Ready (pin 4) and
Signal Ground (pin 5). The second
port is a 25-pin female D connector
which is used to connect directly
to a PC. Only three signals are used:
Transmit Data from the PC (pin 2),
Receive Data to the PC (pin 3) and
Signal Ground (pin 7).
RTS and CTS are looped and DSR,
DTR and CD are also connected together internally. You can easily make
up your own cable but the interfaces
have been designed to support a
standard 9-pin to-25 pin PC to modem cable.
The input Data (Pin 2) of each D
connector is connected in parallel, so
ensure that only one cable is plugged
in at a time to avoid loading the RS232
drivers in the modem and PC.
Operation and menus
Using the RMC is very easy. From
the menu system all functions are
accessed with a single keystroke,
without the need to use the Enter key.
As discussed before, when the unit is
powered up it sends out the letters AT,
waiting for an OK response.
This OK will come automatically
from a modem if it is powered on
and connected, but if you have the PC
connected you will need to enter this
manually. After a call is finished, the
unit polls the connected device every
30 seconds, again with the letters AT.
This is done to avoid a problem
that could arise if the unit is powered
up but the modem is powered off
and then on. In this case it could be
poss-ible for the unit and the modem
to be ‘talking’ at different speeds. The
30-second spaced AT makes sure that
the modem is at the correct speed
when a call comes in. Incidentally,
Looking from the rear to the front panels across the PC board. As you can see, there's plenty of room inside the case if you
wish to add in other sensor/controller devices. Power is from an external 9V DC plugpack, closely regulated on board.
the temperature is read at this point,
updating the minimum and maximum
temperature settings.
If you are directly connected, you
need to type the letters LOGIN in upper or lower case to access the unit. If
it is connected to a modem and a call
is detected, it sends ATA and raises
the DTR signal. One or both of these
steps may not be necessary, especially
if the modem is set to auto-answer,
however it is good insurance. In any
case, the DTR signal should be used
to drop the modem off line at the end
of a call.
When the unit has answered the
call, it waits 30 seconds for the CONNECT message from the modem. If
this fails to be recognised within the
30-second period, the call is aborted.
When either the login command has
been entered from a PC or the connect message has been received from
the modem, the password prompt is
displayed.
Here you are given two chances
to enter the password correctly. The
password must be entered within 30
seconds and is case-sensitive. If the
password is twice entered incorrectly,
the call is aborted. Once the password
is entered correctly the opening
banner is displayed. You are asked
to press any key to proceed. Once a
key is pressed, the Main Menu is displayed. If a key is not pressed within
30 seconds the call is aborted.
If there has been a power failure
since the last call or log in, a message
will be displayed indicating that there
has been a failure, that the outputs
are turned off and the Event counter
has been reset.
This is done to avoid possible dangers that could be caused by turning
the outputs on again when the power
is restored, if it has been off for a long
period. Also the Event counter could
provide a meaningless result if lots
of events were missed during this
period. This message is not displayed
again during this call.
Each of the sub-menus are accessed
from the Main menu by pressing the
first letter (in brackets) of the submenu required. There is a programmable idle timeout on the menus
–selected in the Setup menu.
If you are in a sub-menu and a
character is not entered within the
timeout period, you will be asked to
press any key to continue.
If a key is pressed you will be returned to the Main menu, however if
a key is not pressed within 30 seconds
the call will be aborted. If you are in
the Main menu and no characters are
entered within the timeout period you
will be advised that the idle timer has
expired and you are asked if you want
to continue.
Again pressing any key will restart
the timer and if there is no response
to this question within 30 seconds the
call is aborted.
AUGUST 1999 23
The rear panel is positively spartan with a DB25 socket (computer connection),
DB9 socket (modem connection) and a 2.1mm DC power socket. The grommeted
hole (right side) is for cabling which connects to the internal terminal strips.
Fig. 4: this full-size front panel artwork
can be copied and glued to the front
panel and/or used as a drilling template.
In the Volts measurement screen, the
voltages on the two analog inputs are
measured and the results displayed.
Pressing the letter U forces a new measurement and updates the screen while
pressing M returns you to the Main
menu. If the input voltage is measured
24 Silicon Chip
as being over 20V then an OVER V
warning message is displayed.
The Input screen shows you the
state of the four inputs as being ON
or OFF. Again pressing the letter U
updates the screen and ‘M’ returns
you to the Main menu.
The outputs sub-menu allows you
to individually turn each output on
or off by pressing 1, 2, 3 or 4. Each
time the number is entered the corresponding output changes state and
the screen is updated. As long as the
power to the unit is not removed between calls, the outputs will remain
unaltered. Pressing M once again
returns you to the Main menu.
The Event counter is displayed in
the Events sub-menu. If the counter
has passed 255, the word OVERFLOW! will be displayed. The result
can be reset to zero by entering the
letter R.
Pressing U will update the display
and pressing M returns you to the
Main menu.
Entering T moves you to the temperature sub-menu. Here the current
temperature is displayed as well as
the maximum and minimum temperature since they were last reset.
Pressing R resets the maximum
and minimum temperatures to be
the same as the current temperature.
Pressing U updates the display and
M returns you to the Main menu.
Entering the letter L tells the unit
that you wish to end the call, however it asks if you are sure. If you wish
to continue, press the Y key or the N
key to end the call.
To access the Setup menu, enter
the letter S. The same technique is
used here as in the Main menu; ie, the
first letter of the required function is
entered to access that function.
Pressing P takes you to the password screen where you are shown
the current password. Pressing M
returns you to the Setup menu, while
pressing C opens the change password screen. The password must be
six characters long and can be any
printable characters. For example
&%Re1Z would be acceptable...if you
could only remember it!
If you make an error press R to clear
your entry and try again. When you
are finished press S to store it and
return to the Setup menu. Only if S is
entered at this point, will the currently stored password be overwritten.
The speed screen allows you to
select 300bps, 2400bps or 9600bps by
entering 1, 2 or 3. While this is primarily included to match to the speed
of the interface, ideally it should also
match the modem line speed.
For example, if your modem is
an older type with say a maximum
speed of 2400bps then select 2400 as
your speed. Press M to return to the
main menu.
Note that the new speed selected
does not take effect until the present
call is finished.
The Event trigger screen allows the
selection of the edge that the internal
PIC counter is incremented. An on to
off signal into the Events optocoupler
results in a rising edge input, while
an off to on signal results in a falling
edge input to the counter.
Enter a C to change the trigger and
update the screen or M to return to
the Setup menu. This feature is handy
if you are trying to capture a state
change (high to low or low to high)
rather then counting a series of pulses.
To do this you would select the edge
required and then go to the Events
menu and enter R to reset the count
to zero. A count of 1 would indicate
that the edge has occurred.
Pressing I takes you to the Idle
timer screen. You can choose 1, 15 or
60 minutes by pressing 1, 2 or 3. The
Idle timer will disconnect the call if
a key has not been pressed within the
timeout period.
Without the Idle timer, it could
be possible for the RMC to hold the
tele-phone line in a busy state or not
allow you to log in again if you did
not log off properly. The default value
is one minute.
Input/Output testing
Access the Input menu and verify
that all inputs are off. Connect a power
supply of 5V to Input 1. Update the
screen and check that Input 1 is on.
Remove the power supply, update the
screen and check that input 1 is off.
Repeat this procedure for the other
inputs.
Go to the Outputs menu and turn
all the outputs off if not already done.
Connect a LED in series with a 220Ω
resistor between +5V and output 1,
with the anode of the LED connected to the +5V terminal. Check that
the LED is off. Turn output 1 on and
check that the LED comes on. Repeat
this procedure for the other outputs.
In the Setup menu, select the Event
trigger sub-menu. Change the trigger
to OFF to ON if not already done.
Return to the Events menu and reset
the counter. Connect 5V to the Events
connector. Update the display and
check that the counter has increm-ented to 1.
Remove the power supply, update
the display and check that the counter
has not changed. This verifies that the
counter has incremented on the OFF
to ON edge.
If any of these tests fail, you will
need to check the circuit around the
faulty input or output.
Installation
The RMC is intended to sit alongside the modem or PC and connect us-
Fig. 5: even if you purchase a commercial PC board, this same-size pattern can
be used to check the tracks before assembly. Many readers still make their own
boards from these patterns, too.
ing a standard PC to modem interface
cable. If you connect to a modem and
have it powered on and connected in
parallel with the telephone line, it
will answer incoming calls and override your telephone.
To avoid this problem, leave the
modem disconnected while you are
at home.
If you are away and you have the
RMC and modem enabled and someone else unknowingly calls your telephone, the call will be automatically
answered.
The caller will hear the modem
tones but the RMC will time-out
after 30 seconds and release the call,
because the password won’t have
been entered.
Security & safety
The RMC is equipped with a 6-digit
password. No commands will be
accepted until the correct password
is decoded.
If the password is entered incorrectly, the caller is offered a second
attempt. If this second attempt fails,
the call is aborted automatically. The
caller has to connect again and retry
the password.
While this provides a high degree
of security, it is not impossible for
a ‘hacker’ to eventually crack the
password and gain access to the RMC.
It is therefore recommended that
the RMC not be used in situations
where damage to property or personal
injury could occur because of unapproved access to the system.
The RMC input and output circuits and PC board are not intended
to control mains voltages (240VAC)
directly. While optocouplers are used
for some inputs, they are included for
DC isolation and limited overvoltage
protection of the PIC inputs only.
If control of 240VAC devices is
required, then suitably rated external
relay circuits will be needed.
SC
AUGUST 1999 25
Daytime Running
Lights For Cars
This circuit automatically switches on your
car’s headlights during the day, so that your
vehicle is more visible to other road users. It
drives the low-beam circuit at 80% duty-cycle
to prevent unnecessary glare but switches to full
brightness in low light conditions.
By JOHN CLARKE
One of the first things the visitor to
Canada notices is that all cars have
their headlights on during the day.
The Canadians call them “daytime
running lights” and claim that they
have significantly reduced the accident rate.
The headlights turn on automatically when the engine is started but
are not quite as bright as a conventional low-beam circuit. Instead, they
26 Silicon Chip
run at only about 80% brightness so
that the glare doesn’t annoy other
drivers.
It’s certainly a very effective system
and you really do notice other vehicles on the road much sooner than
would other
wise be the case. And
that can only be a good thing when it
comes to improving road safety.
In Canada, daytime running lights
make a lot of sense. Canada has long
winters with very short hours of
daylight and light levels are generally
lower than in Australia.
But daytime running lights make
sense in other countries as well. Several state government authorities in
Australia now encourage motorists to
drive with their headlights on during
the day, particularly on long trips. It
certainly works – cars coming towards
you with their headlights on are much
more noticeable than other vehicles.
It stands to reason that the sooner
you are noticed, the better. It gives
other drivers more time to make decisions and that greatly reduces the
chances of an accident. And in some
situations, having the lights on can
make the difference between being
seen or not being seen at all.
On a related theme, just think how
many drivers neglect (or forget) to
turn on their lights at dusk or when it’s
raining heavily. An automatic “lightson” circuit solves this problem.
Main features
In Canadian cars, the daytime running lights are provided by a separate
filament in the main headlight housing. When the engine is started, both
the daytime running lights and the tail
lights come on. In addition, there is a
sensor that automatically switches the
headlights to full low-beam in lowlight conditions but they can also be
turned on at any time by the driver.
The circuit described here provides
all these features and is completely
automatic in operation. However, because Australian cars don’t have separate headlight filaments for daytime
running lights, our circuit drives the
low-beam filaments. It doesn’t drive
the low-beam lights at full brightness
though. Instead, it pulses the lights
with an 80% square-wave duty cycle
and this reduces their brightness to
a comfortable level for other drivers.
The accompanying panel shows the
main features of the Daytime Lights
circuit. Note that it also activates the
tail-lights, although these are driven at
normal brilliance. Why do we activate
the tail-lights as well? The reason is
that we don’t want to be driving around
at night with the headlights on while
remaining blissfully unaware that the
tail-lights are off.
Our circuit also incorporates a light
sensor and this automatically switches
the low-beam lights to full brightness
when it gets dark. This is an important safety feature – it means that you
cannot drive around at night with the
headlights only operating at 80% of
normal brightness.
Another important feature of the
unit is that the daytime lights only
come on if the battery voltage is above
12.7V. This ensures that the lights
remain off while you are starting the
engine, since the battery voltage will
be below this figure. It also prevents
the lights from coming on if the car is
being serviced and the ignition switch
is simply turned “on” (but the engine
not started).
Once the engine has started, the
voltage from the alternator will exceed
the 12.7V threshold and so the daytime
lights will come on.
The headlights switch operates
normally. It effectively overrides the
Daytime Lights circuit, so that the
headlights can be manually switched
Main Features
•
•
•
Headlights automatically switch on at 80% brightness when car starts.
•
•
•
•
•
Powers headlights rated up to 200W total.
Automatic switch off with ignition.
Dark sensor switches lights to full brightness at night-time and in lowlight conditions.
Headlight switch works normally and overrides circuit operation.
Daytime lights activated only after engine starts.
Efficient circuit has minimal losses.
EMI suppressed.
on by the driver. The Daytime Lights
circuit immediately takes over again if
the light switch is turned off.
Finally, the circuit is designed so
that when the engine is stopped, the
daytime lights automatically switch
off. This means that you cannot accidentally leave the lights on and flatten
the battery, unless you leave your
conventional lights switch on (and
even here, many modern cars have
you covered).
Basic operation
Fig.1 shows the basic operating
principle of the Daytime Lights circuit.
It’s based on Mosfet Q1 which is connected across the existing headlights
switch. When the Mosfet is turned on
(ie, conducting), the headlights are
lit via the +12V supply. Conversely,
when the Mosfet is switched off, the
lights are off.
By pulsing the Mosfet on and off at
a fast rate, the average voltage applied
to the lamps is reduced. This voltage
will depend on the duty cycle of the
waveform applied to Q1’s gate.
The gate driver circuit connects
between Q1’s gate (G) and source (S)
terminals. When the gate voltage is
about 12-15V above the source, the
Mosfet switches on and current flows
from the positive supply rail to drive
the low-beam headlights. Conversely,
when the voltage between gate and
drain is 0V, the Mosfet is open circuit
and the lights are off.
Note that the gate driver must be
capable of floating above ground and
must follow the source voltage. When
Q1 is on, the source is at +12V and
when Q1 is off, the source is at 0V as
it is pulled low by the lamp filaments.
We used a Mosfet rather than a
transistor here because a Mosfet
switches on with a considerably lower
resistance than a transistor. This both
reduces power dissipation in the device and ensures that almost the full
rail voltage is applied to the lamps. A
Mosfet also requires much less drive
current.
Block diagram
Fig.1: the Daytime Lights circuit
uses a Mosfet (Q1) to pulse the lowbeam headlights on and off, with a
duty-cycle of 80%.
Now take a look at Fig.2. This shows
the block diagram for the Daytime
Lights for Cars. Its basic operation is
quite simple but as they say, the devil
is in the detail.
IC1 is a 555 oscillator which produces a pulse waveform with a duty-cycle
of 80%. Its output drives optocoupler
IC2 via a gating block (D1, D2 & Q2),
which then feeds the oscillator signal
to Mosfet driver stage IC3. The signal
from this stage then drives Mosfet Q1
to activate the low-beam circuit at
about 80% of normal brightness.
In addition, the Mosfet output stage
AUGUST 1999 27
Fig.2: this diagram shows the main circuit blocks in the
Daytime Lights circuit. It uses an oscillator (IC1) to drive
an optocoupler via a gating circuit. The optocoupler then
pulses the Mosfet (Q1) via a driver stage.
turns on relay RLY1. This activates the
parking lights circuit, so that the taillights switch on.
The gating circuit determines
whether or not the oscillator output
is fed through to the optocoupler.
This is controlled by the 12.7V voltage
detector block (IC4a, ZD2), which prevent the lights from coming on when
the engine is being started. The dark
detector block automatically switches
the lights to full brilliance in low-light
conditions.
Circuit details
Refer now to Fig.3 for the full circuit details. IC1, a 555 timer, is the
oscillator and is wired in conventional
fashion. Its frequency of operation is
set to 1.14kHz by the RC timing components on pins 2, 6 & 7 and this is
high enough to prevent any flicker in
the headlight filaments.
In operation, pin 3 of IC1 is high
while the capacitor charges via the
8.2kΩ and 2.2kΩ resistors and low
while it discharges into pin 7 via the
2.2kΩ resistor. This gives a duty cycle
of just over 80% (82.5%, to be exact).
The 1.14kHz square wave signal
drives pin 2 of optocoupler IC2 via
diode D1 and a 470Ω resistor. The LED
inside the optocoupler is switched on
28 Silicon Chip
when pin 3 is low, assuming that the
+12V switched rail is present on pin 1.
Each time the LED switches on, the
internal phototransistor also switches
on and pulls pin 3 of inverter stage
IC3a low. Conversely, when the LED
turns off (ie, the oscillator output is
high), the transistor turns off and pin
3 of IC3a is pulled high (to the +12V
supply) via a 10kΩ resistor.
Note that the base terminal of the
internal transistor is tied to the emitter
via a 100kΩ resistor. This improves the
response time of the phototransistor at
the expense of sensitivity.
IC3a buffers and inverts the signal
from the optocoupler. Its output appears at pin 2 and is fed to parallel
inverter stages IC3b-IC3f. These inverters drive the gate of Q1 via the 47Ω
resistor. Each time the buffer outputs
switch high, Q1 turns on and current
flows through the low-beam lamps via
inductor L1.
L1 is included to suppress any electromagnetic interference which would
otherwise be heard in the car radio.
Diode D8 is included to suppress any
switching spikes from the inductor,
which could damage Q1.
The scope shot of Fig.4 shows the
signal applied between the gate and
source of Q1. Its duty cycle is shown
as 84% and with a 13V peak-to-peak
amplitude. Note that the gate drive
voltage follows the voltage on pin 5
of IC2. This means that a non-inverting buffer (a 4050) could be used in
place of the 4049 inverter without any
changes to circuit operation.
Fig.5 shows the drive to the lamp
filaments on the Ch1 (top) trace and
the gate drive to the Mosfet on the
Ch2 trace. Note that the gate drive
is shown here as 27.6V, since we are
now referring the signal to ground
rather than to the source voltage of
Q1. This means that the gate voltage
is 13.4V (27.6-14.2) above the source
when Q1 is on.
Battery voltage detector
IC4a is the battery voltage detector.
This stage functions as a voltage comparator, with positive feedback via a
1MΩ resistor to give the circuit a small
amount of hysteresis.
As shown, IC4a’s non-inverting input (pin 3) monitors a 4.7V reference
(ZD2) via a 68kΩ resistor, while the
inverting input (pin 2) monitors a
voltage divider connected across the
+12V supply line from the ignition
switch (ie, from the battery). When the
battery voltage is less than 12.7V, pin
3 is higher than pin 2 and so the com-
Fig.3: the final circuit includes an LDR which, in company with IC4b, switches
the headlights to full brilliance when it gets dark. ZD2 and IC4a prevent the
lights from coming on when the engine is being started.
parator output at pin 1 will be high.
As a result, the voltage on pin 3 will
be about 5.1V (ie, slightly higher than
the 4.7V reference) due to the positive
feedback.
When the ignition is first switched
on and the vehicle is being started,
you can expect the battery to be below
12.7V. Thus, pin 1 of IC4a will be high
and this turns on transistor Q2 which
now shunts the signal from IC1 to
ground via D2. At the same time, pin
5 of comparator stage IC4b is pulled
low via D3 and so its pin 7 output will
also be low.
This low output from IC4b turns
on PNP transistor Q3 and so the +12V
from the battery is applied to pin 1 of
the optocoupler (IC2). The internal
LED will thus be permanently on,
since there is a path to ground via the
470Ω resistor, D2 and Q2. As a result,
pin 5 of the optocoupler will be low
and Q1 is held off.
When the engine is started, the
battery voltage quickly rises. When
it exceeds 12.7V, the output of IC4a
switches low and Q2 turns off. The
output of IC1 now pulses the opto
coupler LED on and off via D1 and so
Q1 drives the lamps with an 80% duty
cycle, as described previously.
When pin 1 of IC4a switches low,
its pin 3 input is pulled down to
about 4.36V due to the 1MΩ feedback
resistor. This means that the battery
AUGUST 1999 29
Fig.4: this scope shot shows the waveform applied between
the gate and the source of Q1. It has an amplitude of 13V
peak-to-peak and a duty cycle of 84%.
voltage rail must drop below 10.9V
before IC4a’s output switches high
again and the lights go off. Normally,
this could only happen if the vehicle
is just idling and there is a heavy load
on a battery which is “on the way out”.
Dark detector
IC4b and light dependent resistor
LDR1 form the dark detector circuit.
The op amp is wired as a comparator
with positive feedback, just like IC4a,
and its inverting input (pin 6) is biased
to 4.7V by ZD2. The non-inverting input (pin 5) monitors a voltage divider
consisting of a 47kΩ resistor, trimpot
VR1 and the LDR.
During daylight hours, LDR1 will
have a low resistance and so the voltage on pin 5 of IC4b will be lower than
that on pin 6. As a result, pin 7 will be
low, Q3 will be on and the +12V supply
Fig.5: the top trace of this scope shot shows the drive to
the lamp filaments, while the bottom trace shows the gate
drive to Q1 with respect to ground.
will be switched through to IC2, so that
the circuit can operate.
When it gets dark, the resistance
of the LDR rapidly increases (up to
several megohms in total darkness).
As the resistance of the LDR rises, so
does the voltage on pin 5. When this
voltage rises above 4.7V, pin 7 of IC4b
goes high and Q3 switches off the +12V
supply to IC2.
VR1 sets the light level at which the
circuit operates, while the 1MΩ feedback resistor provides a small amount
of hysteresis so that the circuit doesn’t
oscillate if light levels fluctuate rapidly
close to the trigger threshold.
is provided by IC1, T1, diodes D4-D7
and ZD3.
In operation, pin 3 of IC1 drives
transformer T1 via a 1µF capacitor.
T1 is a standard isolation transformer
with 3kΩ windings and its primary
winding is centre-tapped. By driving
only half the winding, we can use
the transformer to step up the output
voltage.
D4-D7 rectify the AC voltage on
the secondary winding to produce a
DC rail and this is filtered by a 1µF
capacitor. ZD3 regulates the output
voltage to 15V and this rail supplies
the optocoupler transistor and IC3.
Power for the entire circuit is derived from the +12V ignition rail. This
rail is decoupled using a 4.7Ω resistor
and a 100µF capacitor, while ZD1 protects the circuit from voltage transients
above 16V. A 10µF capacitor provides
Power supply
Because Q1’s source must be floating, we need a separate isolated power
supply to provide the gate-source
turn-on voltage. This isolated supply
Table 1: Resistor Colour Codes
No.
2
1
4
1
1
3
1
1
2
1
1
1
1
1
30 Silicon Chip
Value
1MΩ
150kΩ
100kΩ
68kΩ
47kΩ
10kΩ
8.2kΩ
4.7kΩ
2.2kΩ
1kΩ
470Ω
330Ω
47Ω
4.7Ω
4-Band Code (1%)
brown black green brown
brown green yellow brown
brown black yellow brown
blue grey orange brown
yellow violet orange brown
brown black orange brown
grey red red brown
yellow violet red brown
red red red brown
brown black red brown
yellow violet brown brown
orange orange brown brown
yellow violet black brown
yellow violet gold brown
5-Band Code (1%)
brown black black yellow brown
brown green black orange brown
brown black black orange brown
blue grey black red brown
yellow violet black red brown
brown black black red brown
grey red black brown brown
yellow violet black brown brown
red red black brown brown
brown black black brown brown
yellow violet black black brown
orange orange black black brown
yellow violet black gold brown
yellow violet black silver brown
LOOK AT THIS
JUNE SALE!!! Did you miss it? Well you were not the only one!!!
SUGAR CUBE
SIZED CAMERA
The ads we placed were so small that most people missed the ads
BIGGER
So we are going to run it again as the Much
September Sale.
To see just what’s on sale just check out the September Sale link on our new web page
or if you have a polling fax you can see our text list of sale items on
02 95843562 or 02 95707910. But don’t forget our web page
BARGAIN CORNER where we sell all of our regular specials
like runout end of stock & special one or few of items like used
security cameras with an incredible zoom lens Canon "C"
mount, motor driven zoom lens. zoom, aperture and focus.
F2.8 and the zoom range is 15-150mm!! or a large Pan /
Tilt unit. 280 x 280 x170mm: 8Kg
DRAW ACTUAL
SIZE 16 X16 X14mm
The smallest monochrome camera we
have offered yet. They don’t have the
greatest resolution but are very small and
only draws 10mA <at> 5V (a 9V bat. +
regulator would run one of these for days)
Camera in its own plastic housing plus free
VHF modulator and suitable power
adaptor for special intro price $80
NEW SUPER LOW PRICE + LASER
AUTOMATIC LASER LIGHT SHOW KIT:
MKIII. Automatically changes every 5 - 60
secs. Countless great displays from single
to multiple flowers, collapsing circles,
rotating single and multiple ellipses, stars,
etc. Easy mirror alignment with “Allen
Key”. Kit inc. PCB, all on board components, three small DC motors, mirrors,
precision adjustable
mirror mounts:
(K115) + very
bright 650nM
laser (LM2) module.
Kit with laser module $55
Kit + laser module + plug-pack + instument
style case all at a special price of $70
***NEW*** *HIGH QUALITY 4 FREQU.
CRYSTAL LOCKED 2.4GHz AUDIO /
VIDEO LINK KIT
COMING SOON.
Will suit VCRs or Video
cameras. Range of
up to 50 M 2.4 GHz.
12V operation VCRs..
***NEW KITS ***
PCB plus all on-board components, connectors,
switch, metal case, telescopic antenna, twin RCA A/V
lead, all that is needed to complete the full kit. 12Vdc
<at>10mA operation. Ideal for transmitting audio and
video around you home.. Complete Kit for just $25
NEW ULTRA-SONIC RADAR KIT
Just like the top European cars you can fit a reversing radar that will sound a buzzer or flash a light on
your dash to let you know when your car is near
another car or object. Features include adjustable
range upto1M output to drive relay or buzzer. kit
includes PCB plus all on-board components including Ultra-sonic transducers and buzzer for $16
$55
NEW MOSFET STEPPER DRIVER
This kit is designed to work below 5V &
greater than 35V (higher voltage
MOSFETS avail.)Very efficient (very little
heat) & work with software like DANCAD
etc.(for step/dir-ection signals) & is ideal
for CNC projects. It works well with the
stepper motors in our
famous German
printer $45 or$35
with new or previous printer purchase
$199
PAIR
***NEW***
35-140 LED IR
ILLUMINATOR KIT
Switches on when it
gets dark or can be
controlled by alarm
system. Kit includes
mount ing tray & universal swivel mount.
35 LEDs $25.
Extra 35 LED pack
(3extra packs max)
$14 per pack. 140 LED
kit:$67 Ideal for use with our monochrome cameras to see in the dark.
NEW...PC MOTHERBOARD
UMC-486 CACHE ISA SX 40Mhz.
Original package, 486-40Mhz CPU,
booklet & QA report. inc..., 5 X 16 bit & 1 X
8 bit slots, space for 4 X 30 pin & 1 X 72
pin Mem. 220 X 170mm $18
GREAT TEST GEAR BARGAINS
$25
KEY-CHAIN LASER POINTER
in a presentation box. Quality
metal housing + 3X LR44
/AG13 bats. FREE.
Extra bats. 50c Ea.
$10
Line lens+$0.80...X-hair lens
+$0.80...Module (no case) only $8
suitable
plugcack
$5
UHF AUDIO / VIDEO TRANSMITTER KIT
Kit includes all components needed......
X 465 100Mhz used
TEKTRONIC
CROs $440......HP 54501A 100
Mhz used digitizing CROs
$970... HP3300A used Function
Generators with 3302A plug-in
$280 SEE WEB PAGE FOR MORE
BUILD YOUR OWN COMPUTER
CONTROLLED 2/3 AXIS MACHINE
using our now famous $46 surplus
GERMAN PRINTER & CNC shareware
(DANCAD) Using the parts of our printer
that is chock full of steppers, toothed belts,
pulleys, bearings etc (see EA June 99). we
have plans/notes for $9 (on floppy) & links
to find lots of info on the net .
LASER LEVEL
Kit includes laser module with columnating
lens plus battery holder plus suitable case
plus construction notes $14
NICAD BATTERY PACK
Removed from equipment for routine
maintenance. We can’t fault them. Some 4
some 6 cell. $0.20 / cell. Guaranteed!
CHARGER PCB (to suit above 6 cell
packs) 7.2V trickle charger add $5
16 X
2 LINE LCD CHARACTER
DISPLAY
LAS ER LE VE L
+ 1M IDC
ext. cable,
TWO MOTOR LASER LIGHTSHOW KIT
LED, buzzer
Kit includes motors, mirrors, reversing
& switch on
$12 or 3 for $30 switch
and all electronic components. Can
a PCB.
be controlled with a variable DC input.Lots
TOLL FREE PHONE NUMBER of patterns, flowers, stars etc. $16
Sorry but we don’t have one but if Laser module to suit $8
you call 02-95843564 24hrs & (NEW) 12V / 2.3Ah AUDIOVOX LEAD
leave a message & your number ACID BATTERY (Model BTR-1900).
Priced at a fraction of their real value (as
we will call you back ASAP at our used in video cameras & older mobile
cost. (orders only please)
phones - same as Panasonic batteries we
sold before). 180 (L) x 60 (H) x 22 (W) mm,
0.67Kg, made in Japan. The contacts
PO Box 89 Oatley NSW 2223
(which are easily solderable) are at one
Ph ( 02 ) 9584 3563 Fax 9584 3561 end of the battery. 2 batteries + suitable
orders by e-mail: oatley<at>world.net 500mA float
www.oatleyelectronics.com charger.
major cards with ph. & fax orders,
Post & Pack typically $6
Prices subject to change without notice
CAUTION LASER!!!
OATLEY ELECTRONICS
OATLEY ELECTRONICS
$20
$25
+
$16
4093
+
+
+
INFRA-RED SHOP DOOR MINDER
IR transmitter & receiver
kits (2 separate PCB’s),
basic range is 20M can
be increased by adding
a lens. Output to drive
piezo buzzers or relays
etc. 2 PCB’s + all onboard parts: $17. 2 X
suitable boxes + 2 swivel
mounts: $6, Buzzer: $3, 12A
relay: $3 (fits on PCB) Lens: $0.80
12V Automotive Relays
with 30A SPDT Contacts (73 ohm relay
coil). RRP $7. our price $3 ea. $10 for 4
***NEW***WHITE LED 5mm 3500mcd.
Very bright Ideal for mini torch etc.... $4
POWERFUL IR ILLUMINATORS
With strong universal swivel
mount & 50X50X50mm
housing:10 LED $10...
30 LED $20...80 LED $36
AMAZING MOSFET BARGAINS
IRFZ-44...$2.50
60V/50A/0.028 ohm
IRF-540...$2.50
100V/28A/0.077 ohm
IRFP460...$2.50
500V/20A/0.27ohm
IRF-820...$5
500V/2.5A/3.0 ohm
NEW***NEW***NEW***NEW
PELTIER CONTROLLER: This kit is a swmode design & correctly controls temp. of
peltiers to 10A (very efficient design) PCB
+ onboard parts + new surplus case. $15
NEW AUSTRALIAN
PLUG PACKS AT BELOW
WHOLESALE PRICES
GENERAL ELECTRIC 20VA
14VDC <at> 700mA.....
AUDIOVOX 9V
<at> 500mA
AUDIOVOX 12V
<at> 400mA....
$5 Ea. or 5 for $20
***KIT SPECIAL***
FM
FM
FM TRANSMITTER
TRANSMITTER
TRANSMITTER
MKII
MKII
KIT / RADIO MIC.
This kit has good
range and stability &
can be configured as
a hand held mic or
lapel mic or musical
instrument transmitter. Kit includes
PCB, all onboard
88-108MHz
88-108MHz
com-ponent,suitable
small case, lapel
OATLEY
OATLEY
microphone
with clip.
ELECTRONICS
ELECTRONICS
(02)-95843563
(02)-95843563
$17
OATLEY ELECTRONICS
OATLEY ELECTRONICS
4 CHANNEL VIDEO SWITCHER KIT
This kit can switch manually or
sequentially up to 4 audio/video sources.
Features inc. VCR relay output for STOP /
REC, can be switched with PIR or alarm
inputs Add a security channel to your TV
with a VHF modulator, watch TV & flick
channels & see who’s at the door can be
auto switched using PIR units Kit + PCB +
all on-bourd parts $50. Optional VHF
modulator / mixer $18
PELTIER EFFECT DEVICES
Make a solid state food cooler / warmer for
the car etc. with 2 heatsinks, a fan and one
of the following. Could be used for cooling
overclocked PC CPUs. All 40 X 40mm.
4A
T 65deg. Qmax 42W $25
6A
T 65deg. Qmax 60W $27.50
8A
T 65deg. Qmax 75W $30
Device comes with instructions to build
cooler / heater plus data. Some used
surplus heatsinks avail.
***NEW*****NEW*****NEW*****NEW***
QUALITY AUSTRALIAN MADE
FEATURE PACKED MINI ALARM
SYSTEM. Features inc. boot release,
central locking
output, imobiliser
output, indicator
flash relay. Has
with 2 key-fob
transmitter keys. Drawn in proportion
***NEW******NEW*****NEW******NEW***
SAW RESONATOR LOCKED. NO
TUNING 433 MHz UHF DATA TX & RX
MODULES +ENCODER PCBs TO SUIT.
Many security
codes, 4 zones,
multi channel.
100
See our WEB
SITE for more
TX module $11
TX + encoder $18
RX module $18
RX + encoder $25
AT LAST! A COLOUR CMOS CAMERA
WITH GOOD RESOLUTION + BUILT
IN AUDIO + FREE PLUG PACK
+ F R E E V H F M O D U L AT O R .
Available with swivel mount or dome mount
housing.
$160
$160
BNC connector (video), DC connector
(power), RCA connector (audio). 330000
pixel. 330 TV line res.
7-12Vdc 55mA max. INTRO PRICE $160
NEW 12VDC-240VAC/300VAINVERTER
This new design is very efficient, is rated
at 300VA constant not peak (when our
transformer is used). It has auto switch on
and uses High power MOS-FETS that
require very minimal heat-sinking. The kit
inc. PCBs, all onboard components, 4 high
power MOSFETs and
all for $35
To save
money you
can use your
own transformer
or we can supply
the Kit + a high quality compact toroidal
transformer plus wiring kit plus a used
large electrolytic capacitor for $89
** CCD CAMERA SPECIAL **
WITH A FREE UHF MODULATOR
The best "value for money" CCD camera
on the market! 0.1 lux, High IR response &
hi-res. Better than most
cheaper models. 32 X 32mm
$99... With 1of these
lenses pinhole
(60deg.), 92 deg.;
120 deg.A
orUGUST
for
1999 31
(150 deg) add $10
SC-AUG-99
Fig.6: here are the
mounting details
for the Mosfet (Q1).
Its metal tab must
be insulated from
the case using an
insulating pad and
bush.
further supply decoupling for IC1.
Power for the headlights is obtained
from the +12V rail via the lights fuse.
The ground for the circuit is connected
to the vehicle chassis.
simplified. In practice, the high and
low beam circuits usually operate via
relays but the circuit shows the basic
scheme.
Parking lights relay
Fortunately, the circuit is a lot easier
to build than to understand. All the
parts, except for the LDR and the relay
(RLY1), are installed on a PC board
coded 05408991 and measuring 87 x
57mm. This is housed in a metal diecast case which provides the necessary
heatsinking for Mosfet Q1.
Fig.7 shows the assembly details for
the PC board. Before installing any of
the parts, check the board carefully for
defects by comparing it with the published pattern. You should also check
that the board fits into the case – you
may need to round the corners off using
a small file, so that it fits correctly. You
may also have to file three slots into
each long side of the board, to clear
the vertical ribs along the case walls.
Begin the assembly by installing PC
stakes at the six external wiring points
on the PC board. Once these are in,
install the three wire links (one runs
under IC4), then install the resistors.
Table 1 shows the resistor colour codes
but you can also use a digital multimeter to check the values.
Next, install the diodes and zener
diodes, taking care to ensure that they
are all correctly oriented. The 16V
zener (ZD1) will probably be marked
1N4745, the 15V zener (ZD3) 1N4744,
and the 4.7V zener (ZD2) 1N4732.
The ICs and transistors can all be installed now. Again, take care with their
orientation and be sure to install the
correct type in each location. Mosfet Q1
is mounted with its metal tab towards
the edge of the PC board. The hole in
the metal tab should be about 16mm
above the board surface, although this
is not critical.
The capacitors can go in next but
Relay RLY1 turns on the parking
lights, although it’s the tail-lights that
we really want. Its normally open (NO)
contacts are wired in parallel with the
parking lights switch. When Q1 is
being pulsed, RLY1 turns on, the NO
contacts close and the parking lights
come on.
Note that RLY1 does not pulse on
and off as Q1 does. Its response time
is too slow and the pulse frequency too
high for it to do that. Instead, when Q1
is pulsed, RLY1 turns on and stays on.
Finally, note that the circuitry
inside the dotted line, showing the
connections to the headlights and
parking lights, has been considerably
This close-up view shows the
mounting details for the Mosfet (Q1)
and for inductor L1. Secure the toroid
to the board using silicon sealant and
keep the winding away from the metal
case so that it cannot short out.
32 Silicon Chip
Construction
make sure that the positive leads of
the electrolytic types go towards the
positive (+) terminals marked on the
overlay.
The transformer T1 is a standard
part and can only go in one way. On
the other hand, you will have to wind
L1 for yourself. It’s made by winding
12 turns of 1.25mm enamelled copper
wire onto the specified toroid (see parts
list). This winding should be installed
so that it only covers about one half of
the core.
Be sure to install the toroid so that
the windings are clear of the side of
the case. If the wires touch the case,
the enamel insulation will eventually
wear through and the inductor will
short the supply to the headlights to
ground (taking out the fuse).
Terminate the leads from L1 to the
positions shown and scrape away the
enamel insulation before soldering.
The toroid can be secured using a cable tie. This loops through the centre
of the toroid and passes through two
holes in the PC board, on either side
of the toroid.
Now that all the parts are in position,
temporarily place the assembly inside
the case and mark out the position for
the Mosfet mounting hole. This done,
remove the board and drill the hole,
plus an extra hole for the earth lug
screw. You will also have to drill and
shape a hole at one end of the case for
the cordgrip grommet.
Carefully deburr the Mosfet mounting hole using an oversize drill. The
area around the mounting hole must
be perfectly smooth to prevent punchthrough of the insulating washer.
Before installing the board in the
case, attach the flying leads to the external wiring points. The leads to the LDR
The LDR connections are covered
with heatshrink tubing, to make a
neat assembly. Mount the LDR inside
the vehicle and facing the floor, so
that it doesn't pick up street lights.
can be run using light-duty figure-8 cable, while all other leads should be run
using heavy-duty automotive hookup
wire. With the exception of the chassis
lead, these external leads should all be
about one metre long or more.
You can now fasten the PC board to
the four mounting posts on the bottom
of the case using the supplied screws.
This done, attach the earth solder lug to
the side of the case and fit the cordgrip
grommet.
Fig.6 shows the mounting details
for the Mosfet. Note that its metal tab
must be electrically isolated from the
case using an insulating pad and bush.
If you are using a mica washer for the
insulating pad, smear all mating surfaces with heatsink compound before
assembly. This isn’t necessary if you
have a silicone impregnated glass fibre
washer.
After mounting the unit, use your
multimeter (switched to a high ohms
range) to confirm that the metal tab of
the Mosfet is isolated from the case. The
meter should indicate an open circuit
between the two.
Fig.7: install the parts on the PC board as shown in this wiring
diagram. Inductor L1 is made by winding 12 turns of 1.25mm
enamelled copper wire onto the specified toroid.
Testing
The circuit can be tested using a 12V
adjustable power supply and a small
12V lamp. Tie the two +12V inputs together and connect these to the positive
terminal of the power supply. The 0V
rail of the power supply connects to the
case of the unit. Connect the 12V lamp
between the headlight/relay output
and the case.
Set the supply voltage to 12V and
apply power. Now use a multimeter
to check for +12V on pins 4 & 8 of IC1,
pin 8 of IC4 and pin 1 of IC2. Pin 1 of
IC4a should be high at about 10V (or
more), while pin 7 of IC4b 7 should be
low, at about 0.6V.
You can also check that ZD2 has 4.7V
across it and that ZD3 has 12-15V across
it. This same voltage should appear between pins 1 & 8 of IC3. Note that you
cannot measure these latter voltages
with one multimeter probe connected
to the case, as this is a fully floating
supply. Instead, you must measure
between the points indicated.
Now slowly wind the 12V supply
up to above 13V and check that pin
1 of IC4a goes low (0.6V) and that Q1
lights the lamp. The voltage across the
lamp should measure about 10.4V. This
represents the average voltage applied
to the lamp (due to the 80% duty cycle).
Finally, cover up the LDR so that it
Fig.8: the full-size etching pattern for the PC board. Check your
board carefully before installing any of the parts.
is in darkness. Check that pin 7 of IC4b
goes high and that the lamp brilliance
increases. The voltage across the lamp
should now be close to 13V.
If you don’t have a variable power
supply, you can test the unit by connecting it to the car’s battery instead.
Starting the engine should be sufficient
to raise the battery voltage above 12.7V,
so that the test lamp comes on (but be
sure to do this in a well-ventilated area).
Installation
The completed unit can be installed
either under the dashboard or in the
engine compartment, which ever is
the easiest for your car. Either way,
the case should be secured to the
vehicle chassis using self-tapping
screws. The ground connection to
chassis can be run via an automotive
eyelet connector, secured with a
self-tapping screw.
Do not rely solely on the case
connection to chassis to make a good
earth.
The external relay for the parking
lights can be mounted in any convenient location, while the LDR can be
mounted facing the floor in one corner
AUGUST 1999 33
Parts List
1 PC board, code 05408991, 87
x 57mm
1 diecast metal box, 115 x 65 x
55mm
1 iron-powdered toroidal core,
28mm OD x 14mm ID x 11mm
(Jaycar LO-1244) or Neosid
17-742-22 (L1)
1 coupling transformer, 3kΩ-3kΩ,
centre-tapped (T1)
1 cordgrip grommet
8 PC stakes
1 cable tie
2 crimp eyelets
2 M3 x 10mm screws, star
washers and nuts
1 TO-220 mounting kit (insulating
pad and bush)
2 extra self-tapping screws to
mount PC board
1 1m length of 1.25mm diameter
enamelled copper wire
1 100mm length of 0.8mm tinned
copper wire
4 1m lengths of automotive
hookup wire, various colours
1 1m length light-duty figure-8
cable
1 light dependent resistor
(LDR1)
1 200kΩ vertical trimpot (VR1)
1 12V 20A automotive relay
(RLY1) – Jaycar Cat. SY-4068;
DSE Cat. P8035; Altronics Cat.
S4335
Semiconductors
1 555 timer (IC1)
1 4N28 optocoupler (IC2)
1 4049 hex inverter (IC3)
1 LM358 dual op amp (IC4)
1 BUK456-60A N-channel
Mosfet (Q1)
1 BC337 NPN transistor (Q2)
1 BC327 PNP transistor (Q3)
1 16V 1W zener diode (ZD1)
1 4.7V 1W zener diode (ZD2)
1 15V 1W zener diode (ZD3)
The completed unit can be installed close to the fusebox, either under the
dashboard or under the hood (keep it away from the engine). If you do mount
it under the hood, waterproof the case by running silicone sealant around the
edge of the lid and over the cord entry grommet.
of the dashboard (so that it doesn't pick
up street lights).
You will need to locate the following
four wiring points:
(1) the +12V ignition supply after
the fuse;
(2) the headlight supply after the
fuse;
34 Silicon Chip
(3) the lead between the lights
switch and the dipswitch; and
(4) the parking lights supply lead
after the fuse.
Use automotive cable for all wiring
connections and terminate all leads
in automotive-style crimp connectors.
When the installation is complete,
7 1N914, 1N4148 switching
diodes (D1-D7)
1 1N4936, FR104 1A fast
recovery diode (D8)
Capacitors
2 100µF 16VW PC electrolytic
2 10µF 16VW PC electrolytic
2 1µF 50VW RBLL electrolytics
1 0.1µF 250VAC X2 class
polyester
1 0.1µF 63VW MKT polyester
Resistors (1%, 0.25W)
2 1MΩ
1 4.7kΩ
1 150kΩ
2 2.2kΩ
4 100kΩ
1 1kΩ
1 68kΩ
1 470Ω
1 47kΩ
1 330Ω
3 10kΩ
1 47Ω
1 8.2kΩ
1 4.7Ω
Miscellaneous
Automotive connectors, etc.
check that the low-beam headlights
and tail-lights come on automatically
when the engine is started. If they do,
check that the lights switch overrides
the circuit. The headlights should
increase in brightness as soon as the
lights switch is turned on and dim
slightly when it is turned off again.
Now check that the low-beam
headlights come up to full brilliance
when you cover up the LDR. Finally,
check that all the lights go out when
the engine is stopped (assuming, of
course, that you’ve turned off the
lights switch).
When you are sure the circuit is
operating correctly, it is a good idea to
secure inductor L1 and its windings in
place using some non-corrosive neutral cure silicone sealant (eg, Selleys
“Roof and Gutter Sealant”). This will
prevent the solder joints cracking due
to vibration.
Finally, you will have to adjust
VR1 so that the headlights come up
to full brightness at the desired light
level. This is a trial and error adjustment and will have to be carried out
at dusk.
Please note: a modification to allow
thus circuit to be used with cars having
headlight switching in the negative
line was published in Circuit NoteSC
book, November 1999.
This handy test
instrument is just
the shot for testing
PC monitors,
including VGA,
MGA and
composite video
types. It’s
especially valuable
for servicing and
for checking
whether it’s the
monitor or the
video card that’s at
fault.
Design by C. C. ROHER*
Y
OU STARE AT the blank screen
and it stares right back, as you
wonder: “Is the monitor faulty
or is it the video card?” If it’s simply
the video card, there might be a couple
of hours of work involved in getting the
system up and running again. Simply
buy another circuit card, install it, and
away you go. On the other hand, if the
monitor is sick, you might be looking
at a lot more than just a few hours of
down time – not to mention, lightening
your wallet by at least $200.
If you are like me, then you do your
own repairs regardless of how much
hair pulling it might entail. But to do
this, you need effective diagnostic
tools. A decent video source for testing
the display is a good first step in the
right direction.
The PC Monitor Checker presented in this article doesn’t generate
numerous PAL/NTSC colour signal
patterns, nor does it possess the
special functions found on commercial-grade video testers. However, it
also doesn’t cost upwards of $1000
as do most of the off-the-shelf units.
Instead, this is a fairly basic unit that
generates vertical bars, which can
AUGUST 1999 35
Fig.1: the PC Monitor Checker uses oscillator IC3a and appropriate decoding circuitry to generate the horizontal and
vertical sync signals. IC8 produces the RGB signals for the EGA & VGA sockets, plus a video signal for the MGA socket.
be fed to VGA, and Hercules MGA
(monochrome) displays, as well as to
composite-video monitors.
On top of that, the PC Monitor
36 Silicon Chip
Checker is inexpensive to build, is
battery operated to make it portable
and can be assembled in a few hours.
All the parts, except for a rotary
switch and two composite video connectors, fit on a single PC board, so the
construction is really easy.
Note that, in its present form, the
unit is not suitable for testing flat-panel LCD monitors.
Circuit description
A complete schematic diagram of
the PC Monitor Checker is shown in
Fig.1. It consists of three sections: an
oscillator (IC3a) with decoders for
horizontal and vertical sync frequency generation, a sync section and an
output section.
Power is derived from a 9V battery
which is connected to a 5V regulator (REG1) through switch Sla. The
maximum current drain from the
fully loaded unit is 15-20mA, so the
battery should last about five hours.
Alternatively, you could use a 9V DC
plugpack supply.
The unit has provision for VGA,
EGA and Hercules MGA monitors,
as well as composite video displays.
Special Notice*
Oscillator/sync frequencies.
The circuit uses a crystal oscillator
(IC3a & X1) to generate a 2MHz squarewave signal. This signal is fed to pin
3 of IC1a, part of a 4013 dual D-type
flipflop, and then to pin 11 of IC1b.
The 4013 divides the oscillator frequency to produce 1MHz and 500kHz
square-wave signals, which are used to
generate three horizontal sync frequencies and a 60Hz vertical sync pulse. In
addition, the 1MHz signal is further
divided and decoded by IC8 and used
to produce the various video pulses.
The sync section is divided into
two sub-sections. One produces the
horizontal sweep frequencies, while
the other produces the vertical sync.
Most common monitors use horizontal
sweep frequencies in the 15kHz to
32kHz range, while 60Hz (or more) is
used for the vertical sync.
The 1MHz square-wave output
from IC1a is also fed to IC2, a 4024
7-stage ripple-carry binary counter.
The output of IC2 is then applied to
MGA Socket (J1 )
1
This project and article has been
adapted with permission from an article
which appeared in the May 1999 issue
of the American magazine “Popular
Electronics”. The original design did not
include a PC board and so this has been
produced by SILICON CHIP staff.
Our prototype PC Monitor Checker
worked well with a variety of VGA and
MGA monitors and those with composite
video inputs. The design also features a
9-pin socket for EGA monitors but when
we tested it, it did not give colour bars
with the two EGA monitors we were able
to obtain.
If you do not anticipate using it with
EGA monitors, the relevant 9-pin D socket
could be omitted.
IC3b, IC4a, IC4b IC3c & IC5c, where
the signal is decoded to provide three
selectable (via S1b) signals: 15kHz,
20kHz and 32kHz.
The selected output provides a fast
VGA Socket (J2 )
EG A Socket (J5)
Ground
1
Red Video
1
Ground
Green Video
2
Ground
2
2
R. Intensity
6
Intensity
3
Blue Video
3
Pri. Red
7
Video
5
Ground
4
Pri. Green
8
H. Sync
6
Ground
5
Pri. Blue
9
V. Sync
7
Ground
6
G. Intensity
These three tables show the
pin connections for the MGA,
VGA & EGA sockets. These
are designated on the circuit
as J1, J2 & J5 respectively.
8
Ground
7
B. Intensity
10
Ground
8
H. Sync
13
H. Sync
9
V. Sync
14
V. Sync
negative-going pulse that is applied
to 555 timer IC7. This IC is wired as
a monostable and is used to generate
the horizontal sync signal. Note that
the selected output is also fed back
through IC10c (1/6th of a 4069 hex
inverter) to provide the reset signal
for IC2, which then starts counting
over again.
The output from IC7 appears at pin
3 and is buffered by parallel inverter
stages IC10a, IC10b, IC10e & IC10f. The
resulting horizontal sync signal is then
fed to pin 13 of the VGA socket (J2)
and to pin 8 of the EGA socket. The
horizontal sync signal for the MGA
socket (J1, pin 8) is derived directly
from pin 3 of IC7.
Because the counter and decoders
do integer division only, the 15kHz
sweep frequency is really 15.15kHz (ie,
divide by 132). That’s not a problem.
Adjusting the horizontal sweep on
older monitors produces a good lock
while in VGA monitors, the sweep
is automatically/internally adjusted,
within certain limits.
The horizontal sync signal is another story. Every monitor that was
tested or researched appeared to have
different sync time periods that range
from 5-20µs, with most hovering at
the greater time period. The retrace
time determines how much picture is
displayed horizontally. Potentiometer
VR1 can be adjusted to produce sync
widths of about 10-25µs.
Now let’s see how the vertical sync
signal is derived. In this case, the
500kHz output from IC1b at pin 13 is
fed to IC6 (a 4020 14-stage ripple-carry
binary counter) at pin 10. The binary
counter then produces several output
signals that are applied to IC9a (half
AUGUST 1999 37
pulse widths seem to be unique for
every monitor and ranged from 75µs
to 1ms. In some of the monitors tested
(MGA and composite types), a dark
horizontal space appeared at the top
and bottom portions of the screen.
With the newer VGA types, however, the vertical size of the picture is
adjustable and the spaces could be
eliminated.
The vertical sync signals from IC11
are directly applied to pins 14 & 9 of
the VGA and EGA sockets, respectively. The signal from IC11 is also
inverted by IC5f to produce the vertical
sync signal for the MGA socket (pin 9).
Monitor outputs
Fig.2: take care when installing the transistors on the PC board. They are
available in two different packages and the pin connections are different.
of a 4012 dual 4-input NAND gate).
This NAND gate decodes the signals,
producing a positive pulse through
IC5d that is fed back to the reset input
of IC6 at pin 11.
The fast negative-going pulse from
IC5e is fed to pin 2 of 555 timer IC11,
causing it to generate a 220µs wide,
fixed vertical-sync pulse. Like the horizontal-sync pulse, the vertical-sync
Many older model monitors, along
with a few newer models, use the
composite format. This format uses a
serial signal that’s composed of video,
vertical sync and horizontal sync.
The video signal “rides” on top of
the peak sync signal level in between
the sync pulses. The entire signal is
approximately 1V peak-to-peak, with
the sync level being about 0.2V and
the video ranging between 0.5V and
1V. The video amplitude determines
the intensity of the displayed picture.
In this circuit, composite video/
sync is generated by first ANDing the
horizontal sync signal from IC10d
and the vertical sync signal from IC5f
using IC3d. The combined sync signal
is then inverted using IC5a and mixed
with the video signal from pin 10 of
IC8 at the base of transistor Q1. Q1 is
configured as an emitter follower and
provides composite video/sync to both
J3 (an RCA jack) and J4 (a BNC jack).
Although there are no longer many
MGA (monochrome graphics adapter) monitors out there, the checker
provides an MGA output at J1. All of
the MGA-format outputs are TTL compatible except intensity. The intensity
output mimics the video output but at
Resistor Colour Codes
No.
1
1
1
1
5
5
1
2
1
4
38 Silicon Chip
Value
100kΩ
47kΩ
22kΩ
15kΩ
10kΩ
4.7kΩ
1kΩ
330Ω
100Ω
82Ω
4-Band Code (1%)
brown black yellow brown
yellow violet orange brown
red red orange brown
brown green orange brown
brown black orange brown
yellow violet red brown
brown black red brown
orange orange brown brown
brown black brown brown
grey red black brown
5-Band Code (1%)
brown black black orange brown
yellow violet black red brown
red red black red brown
brown green black red brown
brown black black red brown
yellow violet black brown brown
brown black black brown brown
orange orange black black brown
brown black black black brown
grey red black gold brown
Fig.3: the leads to switch S1 and to the
battery can be run using light-duty hookup
wire (eg, rainbow cable), as shown here.
Note, however, that the connection between
the board and the BNC socket must be run
using 75Ω coaxial cable.
a maximum level of 0.7V. As with the
composite video level, the greater the
amplitude of the intensity signal, the
brighter the picture.
Here, the MGA video output signal
appears on pin 10 of IC8 and is fed
directly to pin 7 of the MGA socket (J1).
In addition, the signal from pin 10 is
fed to a voltage divider and buffered
by emitter-follower Q5 to provide the
intensity signal. This is fed to pin 6
of the MGA socket and also to pins 2,
6 & 7 (R. intensity, G. intensity & B.
intensity) of the EGA socket (J5).
The VGA signal is made available
through J2 (a 15-pin D-type connector).
The 4017 decade counter (IC8) divides
the 1MHz square-wave from IC1a into
three separate video signals: PRIMARY
RED, PRIMARY GREEN and PRIMARY
BLUE. These signals appear on pins 2,
4 & 7 of IC8 respectively.
In the VGA format, video-colour
intensity is determined by an analog
representation of the signal level,
with 0.7V representing the brightest
illumination. For this reason, the RGB
outputs from IC8 are fed to resistive
voltage dividers to produce the correct
levels, after which the signals are buffered by Q2, Q3 and Q4, respectively.
Buffering is required because the VGA
video source impedance should be
approximately 75Ω.
The sync signals are at TTL/CMOS
logic levels and are applied to pins 13
& 14, as described previously.
EGA monitors are now fairly rare.
However, we have included an EGA
output in case you ever do have to
service one of these monitors.
As before, the primary RGB colour
outputs (which are TTL/CMOS compatible) are provided by IC8 (pins 2, 4 &
7). These signals are fed directly to pins
3, 4 & 5 of the EGA socket. The colour
intensity is controlled by the output of
Q5 at its emitter. This transistor drives
the RGB intensity control pins (2, 6 &
7) which are connected in parallel. The
voltage on these pins, approximately
0.7V, gives the maximum intensity.
Construction
OK; now that you know how it
works, let’s put it together. Virtually all
the components mount on a PC board
coded 04108991. Only the horizontal
frequency selector switch and the two
composite video output sockets (RCA
and BNC) are mounted off the board,
on the front panel.
Check the board for etching faults
before installing any of the parts,
by comparing it with the published
pattern (Fig.4). If the board corners
are square, they should be filed away
using a round file, until the edge of
the arc is reached. This is necessary
AUGUST 1999 39
Fig.4: this is the
full-size etching
pattern for the PC
board. It’s a good
idea to check your
board for etching
defects by
comparing it with
this pattern, before
mounting any of
the parts.
for the board to clear the corner posts
of the case.
Fig.2 shows the assembly details.
Begin by installing the 27 wire links.
Some of these are quite long, so you
will not be able to use resistor pigtail
offcuts. Instead, you should use tinned
copper wire for the links but first, you
have to straighten it.
The procedure is to clamp one end
of the wire in a vice, then stretch it
slightly by pulling on the other end
with a pair of pliers.
The resistors can go in next, followed by the MKT and monolithic
capacitors. This done, install PC stakes
at the external wiring points, then fit
the transistors, electrolytic capacitors,
crystal X1, voltage regulator REG1,
trimpot VR1 and the three “D” connectors. Make sure you solder both
mounting lugs on each connector, as
the 15-way unit uses them to link two
ground tracks.
The PC board has been laid out to
suit 2N2222 transistors in the TO-18
(metal can) package. It’s also possible
to get these transistors in a TO-92
plastic package but the two packages
don’t have the same pinouts – see the
base diagrams on Fig.1. If you have
TO-92 transistors, the trick is to bend
the base lead of each transistor towards
the flat on its body. The transistor will
then slot straight into the board.
Take care to ensure that the transistor pin connections are correct;
the circuit won’t work if you get them
mixed up.
The ICs can now be installed. Our
prototype used IC sockets but we
recommend that you solder the ICs
directly to the board. Make sure that
they are all correctly oriented and be
sure to fit the correct device to each
location.
Final assembly
As shown in the photos, the board
mounts on the lid of the case, with
the three “D” connectors protruding
through one side.
Use the board as a template to mark
and drill the mounting holes, then
15kHz
OFF
COMPOSITE
VIDEO
MGA MONITOR
SILICON
CHIP
40 Silicon Chip
20kHz
32kHz
secure it to the lid on 5mm standoffs.
This done, sit the lid on top of the
plastic case and mark the cutouts for
the three “D” connectors. The cutouts
can then be made by drilling a series
of holes and filing to get the correct
shapes.
The front panel label can now be
fitted, after which you can drill a hole
for the switch plus holes for the RCA &
BNC video output sockets. The wiring
between the PC board and the front
panel hardware can then be completed, as shown in Fig.3.
Note that the composite video
outputs sockets are wired using 75Ω
coaxial cable. The cable braid at the
board end is attached to an earth solder
lug, which is secured by one of the
EGA-socket mounting nuts.
Finally, solder short lengths of red
and black hookup wire to the battery
holder (red to +, black to -). The other
end of the red lead connects to the
4-position switch; the black to the
appropriate PC pin on the board. Make
sure that you don’t get the battery
COMPUTER
MONITOR
CHECKER
EGA MONITOR
VGA MONITOR
Fig.5: this full
size artwork
can be used as a
drilling template
for the front
panel.
Parts List
1 PC board, code 04108991,
148 x 85mm
1 plastic case, 158 x 95 x 53mm,
Jaycar HB-6011 or equivalent
1 2MHz crystal, 10 x 3.5 x 13mm,
Jaycar RQ-5268 or equivalent
2 9-pin right-angle PC-mount
female “D” connectors
(Altronics P3030 or equiv.)
1 15-pin high-density right-angle
PC-mount female “D”
connector (Farnell 210-535 or
equivalent)
1 3-pole 4-position rotary switch
1 panel-mount BNC connector
1 panel-mount RCA connector
1 9V battery
1 9V battery holder
2 doubled-sided adhesive tabs
1 1kΩ horizontal PC mount
trimpot (VR1)
1 220mm-length 75Ω coaxial
cable
4 5mm spacers
8 3 x 10mm countersunk head
machine screws & nuts
4 flat washers
1 solder lug
This is the view inside the prototype. Note the insulation placed over the earth
lead of the coaxial cable, where it attaches to the solder lug.
leads mixed up, as there is no reverse
polarity protection.
The battery holder is attached to the
inside of the case using double-sided
adhesive foam tabs (available from
most stationery suppliers).
Testing
Some precautions are in order when
using the unit. First, it helps to know
what kind of monitor you are testing
so that you can select the appropriate
horizontal sweep frequency. Second,
always use the appropriate cable type
with the required plugs for a particular
monitor. And third, be sure to plug the
monitor connector into the appropriate
socket.
Note that you won’t do any damage
if you choose the incorrect socket.
If you plug an EGA monitor into
the MGA socket or vice versa (they
both use 9-pin sockets), the monitor
simply won’t work. There shouldn’t
be any confusion when it comes to
VGA monitors, since they have 15-pin
connectors.
As mentioned earlier, the checker does not produce elaborate test
patterns. When it’s connected to a
working composite-video monitor operating with a 15kHz horizontal sweep
frequency, six vertical evenly-spaced
bars of video should be seen. When
testing MGA monitors, which have
horizontal sweep frequencies of about
18kHz, set S1 to the 20kHz position
– in this case, the monitor should
display four to five vertical bars.
Finally, EGA and VGA monitors
have sweep frequencies that are automatically adjustable from 31kHz to
37kHz and are internally set. Set S1 to
the 32kHz position for these monitors.
Two to three groups of red, green,
and blue vertical bars should be seen
on the display and there should be
evenly spaced dark regions between
these groups.
Note that the red bar in the first
group may be slightly narrower than
those in the remaining groups. This
simply reflects the influence of the
horizontal retrace time.
Please note: circuit modifications
to give more ideal scan frequencies
are published in Circuit Notebook,
SC
November 1999.
Semiconductors
1 4013 dual D-type flipflop (IC1)
1 4024 7-stage ripple-carry
binary counter (IC2)
1 4011 quad 2-input AND gate
(IC3)
2 4012 dual 4-input NAND gates
(IC4, IC9)
2 4069 hex inverters (IC5, IC10)
1 4020 14-stage ripple-carry
binary counter (IC6)
2 7555 CMOS timers (IC7, IC11)
1 74C4017 decade counter (IC8)
5 2N2222 transistors (Q1-Q5)
1 7805 5V regulator (REG1)
1 1N914 small signal diode (D1)
Capacitors
1 10µF 16VW PC electrolytic
3 0.1µF monolithic
1 .022µF MKT polyester
1 .01µF MKT polyester
2 .0022µF MKT polyester
1 270pF 5% ceramic disc
1 100pF 5% ceramic disc
1 33pF 5% ceramic disc
Resistors (0.25W, 1%)
1 100kΩ
5 10kΩ
2 330Ω
1 47kΩ
5 4.7kΩ
1 100Ω
1 22kΩ
1 1kΩ
4 82Ω
1 15kΩ
AUGUST 1999 41
VINTAGE RADIO
By RODNEY CHAMPNESS, VK3UG
A killer – the set from hell
Vintage radio sets can be dangerous devices, as
this story illustrates only too well. It certainly
pays to keep your wits about you when
servicing such equipment and to expect the
unexpected.
Some months ago, a chap arrived
at my house with a 4-valve Operatic
TRF set, circa 1932. He wanted me to
get it operating for him but not worry
about cleaning up the chassis. He was
in a hurry and left quickly without
either of us really defining just what
he meant by “getting it going”.
And that’s a big mistake. One
should always make very sure that
there is no misunderstanding as to
what each expects of the other. In
any case, I fully expected that the job
would be reasonably routine for a set
of that vintage.
Sets of this age commonly suffer
from a number of problems including
wiring errors from previous service
attempts, faulty components, perished wiring and one or more weak
and/or inoperative valves. Once the
faults have been corrected they also
usually require a general tune up (not
all that much to do in a TRF set) and
they must be run for a few days to
prove their reliability.
Replacement valves and transformers for sets of this vintage are quite
expensive, so one always hopes that
they are all in operational order. One
of the first things to do is to look at
the power transformer and hope that
it too is in good condition. Fortunately, most are but if it is faulty, I leave
the decision to restore the set up to
the owner.
On closer examination, more and
more things were noticed that needed attention. The power transformer
leads were perished, although it
checked out OK on a high voltage
tester. However, safety must be a
prime concern, so the transformer
was removed from the chassis and
dismantled. It had a form of terminal
block inside it and it was possible
to install a fresh set of leads. It was
then reassembled and reinstalled on
The Operatic is a
4-valve TRF
receiver from the
early 1930s. Vintage
radio receivers are
potentially lethal
devices and this one
was no exception.
42 Silicon Chip
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Fig.1(a) at left shows the original lethal tone control circuit,
while Fig.1(b) (right) shows the modified “safe” circuit.
the chassis.
In addition, the perished twinlead power cord was replaced with a
modern 3-core brown fabric covered
mains lead. I always try to keep sets
looking as authentic as possible. The
transformer was then run on no load
to be quite sure that it had no hidden
faults. It stayed cool and the voltages
from the various windings were as
expected, so it was pronounced in
good order.
Next, the first high tension (HT)
filter capacitor was replaced and the
power supply tested with the rectifier in but with the speaker plug out.
There was no output and the 280
recti
fier valve proved to be faulty.
The owner supplied an 80, which is a
plug-in replacement, and the voltage
was as it should be.
A wrong call
I still believed that there weren’t
likely to be too many more problems. Unfortunately, this assumption
proved to be quite wrong.
To begin with, the schematic had to
be traced out as no circuit was available. Initially, the set didn’t look like it
had been butchered but the evidence
soon showed that it had been. When I
checked around the 247 output stage,
I found that it had no bias, as the
heater was earthed at the centre tap
of the 2.5V heater winding. I checked
the data on the 247 (47) and soon
worked out appropriate capacitor
and resistor values to place between
heater and earth. The grid coupling
capacitor was also replaced to make
sure that all was well.
Next, I turned my attention to a
large multi-tapped adjustable resistor.
This ran from HT to earth and various
voltages were tapped off from it. It was
broken but it was possible to measure
the resistance of each section and
replace it with several fixed resistors.
A check of the speaker transformer
revealed an open-circuit primary, so
a more modern one was fitted. The
loudspeaker itself was also checked
over. The field and voice coils were
intact but there was some poling so
the speaker ended up in pieces (fortu
nately, it could be disassembled).
It was full of dirt and all that was
required was a thorough clean-out
with a brush and a vacuum cleaner.
Putting it back together again was
a challenge as the three main subassemblies must line up so that the
voice coil doesn’t rub on the centre
pole of the electromagnet. It took quite
some time but the end result was quite
satisfactory.
A close call
Having cobbled together the circuit
as best I could for a test, the set was
turned on with the speaker in place
and only the 80 and 247 valves in their
sockets. And then, for some reason
or other, I looked at the tone control
circuitry, as it seemed a bit odd as
far as the values were concerned.
The moving arm of a 10kΩ pot was
connected to the HT and a 0.1µF capacitor was connected to the plate of
the 247. The values seemed to be all
wrong so I switched the set off for a
closer look.
An examination of the tone control
revealed that it had insulating washers underneath the star washer and
nut. It was largely covered and not
obvious. I wondered why this should
be so and so a check was made to determine why it was insulated. I soon
found out – the shaft of the tone control was connected to the moving arm
of the potentiometer (which, in turn,
was connected to the HT)! Some early
potentiometers were made this way.
I broke out into a cold sweat. I could
have easily touched the chassis and
the control shaft at the same time. Had
I done so, I would have received 400V
across my body and almost certainly
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AUGUST 1999 43
probably not agree with this modification. However, it is hidden inside the
aerial coil can and can be removed if
desired. The set isn’t all that sensitive
and requires 3mV of signal across 50Ω
for good volume.
Back to the owner
The old Operatic is easy to work on, since all the parts are readily accessible as
this under-chassis view shows. This particular set had more than its fair share
of faults.
would not be writing this if I had. This
set was a potential killer.
Having realised how close to death
I had come, the circuitry was immediately changed so that the moving arm
was at earth potential. This involved
changing the location of the lead going to the moving arm. Fig.1(a) shows
the original tone control circuit, while
Fig.1(b) shows the modified “safe”
circuit.
It’s only a simple modification but
it’s a much safer way of doing the
same job.
I also found that the values in the
tone control caused too much “top
cut”, so the capacitor and potentiometer were changed to correct this.
The replacement pot also had its
moving arm isolated from the control
shaft. How anyone could have made
such a death trap is beyond me. The
strange thing is that so much of the
set appeared to have original wiring
and this part certainly did, so was it
the manufacturer?
Having overcome the tone control
problem, various other resistors and
capacitors were tested and replaced as
needed. The other valves, a 235 and a
224, were then plugged in and the set
was tried out. It performed reasonably
but on checking around the 235 and
224, I found that the screen voltage on
both was 170V, well above the valve
data recommendations.
To overcome this, the potential
divider was modified to give the
correct voltages to all stages and as
44 Silicon Chip
could be expected, the performance
of the set deteriorated. The valves will
last a lot longer though! The volume
control was found to be like the tone
control, with its shaft above earth
potential – however, only by about
50V maximum as originally wired.
This control was replaced as it was
faulty and the new one didn’t have
the shaft attached to the moving arm.
Some perished wiring was also
replaced and it was noted that the wiring to the coils was also in a bad way.
As a result, the coils were dismantled
and the wiring to the terminals was
replaced.
Performance
When tuning across the broadcast
band, it was found that the trimmer
capacitor had to be altered to give
reasonable sensitivity at both ends.
The two tuned circuits were obviously not tracking and this meant
that one coil had too many turns on
it. After removing two turns from
the tuned winding of the detector/
RF transformer, the set tracked quite
well. For the first time in its life, the
set was working properly. It fact, one
could argue that it now works better
than new.
By placing a low-value RF peaking choke in series with one of the
aerial terminals, the set now has
even better performance right across
the band – provided that the owner
is prepared to change the aerial tap
for best reception. The purists will
The owner had great trouble understanding that it was imperative that
the set had to be safe. He expected all
the work on the set at a bargain basement price too. However, I’m sure he
would not have been impressed if the
set had destroyed an expensive old
valve because I had not taken care to
make it reliable and had simply “just
got it going”.
To prove this point, he claimed
the set didn’t work when he took it
home. He left it bumping around in
his car for some time before bringing it
back. When it arrived, I found that the
speaker transformer had come adrift
(I probably hadn’t got the mounting
screws really tight). More seriously,
the speaker cone had been damaged
due to various odds and ends that had
been left on the seat and had pressed
against it. When these things were
put right and one of the valves was
pushed back into its socket (it was
sitting at an angle), the set worked.
Some restorers give a “kerbside
warranty” which means that the set
goes OK as demonstrated but because
of the radio’s age its long-term reliability cannot be assured. I have found
that old sets are remarkably reliable
after they have been thoroughly
serviced and I’m quite prepared to
give them a warranty that’s the same
as when they were new. Very few
develop troubles during this period.
Technically, many lessons were
learnt through working on the “Set
from Hell and hopefully readers will
not fall into the various traps that I
did. The only things not requiring
attention were the tuning capacitors
and three of the valves that were in
good order.
You could ask how could so many
things be wrong with a set? It was a
job that looked to be reasonable to
start with and then it became a real
monster, with one nasty problem after
another. And having started work and
gone so far, it wasn’t really possible to
stop without either the owner or me
losing out. In retrospect, the question
is, should the set have been restored
SC
at all?
SILICON
CHIP
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prevent misunderstandings.
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CHIP
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which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
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CHIP
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$
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AUGUST 1999 53
Looking for something to control temperature accurately
and easily? This switching temperature controller can either
heat or cool and can hold a temperature constant. Best of all,
it’s cheap and easy to build.
There are many processes which require temperatures to be closely maintained, from film and
photo developing through to home brewing and
even egg incubation. When temperatures change,
things go haywire: colours change, the brew goes
off, chooks cook . . .
It’s fairly easy to control temperature when things
get too cold – simply heat them up until they get to
the right temperature and turn off the heater.
It’s not quite so easy if things get too hot and require cooling. But this controller can do either – heat
or cool – depending on your application.
SWITCHING
TEMPERATURE
CONTROLLER
Heats OR
Cools
Design by Branco Justic*
Article by Ross Tester
54 Silicon Chip
T
he heater can be any standard
resistive heating device such
as a jug or electric heater element, an incandescent globe or even
a resistor. The specifications depend
on the application: more on this anon.
Cooling, on the other hand, is
done via a Peltier-effect device. For
those who haven’t come across these
before, see the separate panel for an
explanation on what they are and
what they do.
Suffice to say at this stage they are
a solid-state device which absorbs or
gives off heat when a current passes
through their junction.
Normally, designers of semiconductors go to great lengths to minimise
the effect. However, in a Peltier-effect
device the action is exploited. The heat
can only be absorbed from, or released
to, the area surrounding the device. So
the device either cools, or heats, the
surrounding area.
Provided certain precautions are
taken, they can be quite effective
coolers or heaters. They do require
significant current (several amps) but
typically can raise or lower the temperature by 50°C or more.
There are three Peltier-effect devices
specified for this project; you choose
which one you want. They are rated at
42, 60 and 75W and draw 4A, 6A and
8A respectively for a ∆T(or difference
in temperature between the two sides
of the device) of 65°C.
Unlike most temperature controllers
which simply switch a heater on or
off to maintain temperature, this controller switches the heater or cooler by
varying the duty cycle.
This form of control is not only very
accurate; in this application it’s also
a requirement of the Peltier device
which must be switched on and off
at a minimum of 2kHz. Repeatedly
switching on and off DC would result
in mechanical stress to the device and
its possible damage or destruction.
That’s not to say you cannot use a
Peltier device on DC. If the device is
turned on and left on for relatively
long periods, DC is fine.
It’s only when used in a temperature
control application where the device is
switched on and off many times over
relatively short periods to maintain a
constant temperature that mechanical
stress really becomes a problem.
And while on the subject of Peltier
devices, there is nothing to stop you
using one as a heater, if you wish. But
A typical Peltier-effect device. Actual size is 40mm square and about 4mm
thick. When connected to power, one side of the device becomes about 65°C
warmer than the other. This can be used for heating or cooling.
given their cost and the low cost of
a resistive element, we know which
we’d prefer!
The circuit
Operation is most easily understood
if you break the circuit down to its basic functions. Fig. 1 shows the circuit
diagram for the controller.
Transistors Q1, Q2 and Q3, along
with ZD1 and associated components,
form a series voltage regulator supplying a reference voltage of about 7.5V to
op amp IC1. Q1 and Q2 are in parallel
and are both driven by Q3, effectively
forming a Darlington transistor. The
stable voltage at the emitters of Q1
and Q2 is important because it gives
the controller its accuracy.
Temperature setting and sensing is
performed by a preset pot and thermistor connected to the input of IC1a,
one of the four op amps in an LM324
quad package.
The voltage at the inverting input
(pin 13) is set by the preset pot and
held stable by the 10µF capacitor. The
voltage at the non-inverting input,
though, varies with temperature due
to TH1, a negative-temperature-coefficient (NTC) thermistor. While
nominally 68Ω in resistance, the NTC
thermistor decreases its resistance
with an increase in temperature (and
conversely, of course, increases its
resistance with a decrease in temperature).
Therefore, if the temperature rises,
the thermistor’s resistance falls and the
voltage at pin 12 of the op amp will
drop slightly. If the temperature falls,
the voltage will rise.
The op amp has a gain of roughly
221, set (mostly) by the 220kΩ and
1kΩ resistors and the slight change in
voltage at the input results in a much
larger change in voltage at the output.
For example, if the voltage rises just
10mV at the input, the output voltage
will rise by more than 2V.
This voltage is applied to the pin
9 inverting input of IC1c and to the
non-inverting input of IC1d, pin 5.
You will note, though, that there is
another op amp in the circuit, IC1b.
It is connected as a sawtooth oscillator, with an output voltage varying
between about 1/3 and 2/3 of the rail
voltage at about 2.2kHz.
When power is applied, the + input
of IC1b is held at nearly 4V via the
voltage divider (R8 & R9) across the
regulated supply. C6 is discharged but
immediately starts to charge via R11.
When C6 reaches the input threshold
voltage of the of IC1b, it discharges
via R11 and the whole process begins
again. This sawtooth waveform is
applied to IC1c and IC1d.
IC1c and IC1d are comparators – that
is, they compare the voltage between
their + and - inputs and turn their high
or low accordingly. If the voltage is
higher on the + input than the - input,
the output goes low. If it is higher on
the - input than the + input, the output
goes high.
Perhaps this is most easily explained by referring to Fig. 2.
The output of each comparator then
is a pulse waveform at 2.2kHz with a
duty cycle (or on to off ratio) which
is in inverse proportion to the output
voltage of IC1a.
Depending on whether heating or
cooling is required, this waveform is
used to switch Mosfet Q5 or Q6.
A short duty cycle means very little
power is applied to the Mosfet gate
while a long duty cycle means it is
being powered most of the time. Hence
it cools (or heats) for most of the time.
In the cooling circuit (IC1c), a green
LED (LED2) connected to ground gives
a visual indication of the degree of
cooling. Even though the circuit is beAUGUST 1999 55
NOTE: INSTALL
EITHER HEATER
OR COOLER BUT
NOT BOTH.
ing driven at 2.2kHz (essential for the Peltier-effect
device) you cannot see the LED turning on and off
this quickly.
The heating circuit is slightly more complex, due
in part to ensuring that the gate of the P-channel
Mosfet (Q5) is not over-driven; however, it operates
in much the same way – the main difference being
it is opposite in effect. The 9.1V zener and series
diode ensure that the gate cannot be taken more
than about 10V below the source, when transistor
Q4 is turned on.
A red LED (LED3) in series with the base of Q4
shows the degree of heating.
One area not yet mentioned is the power supply. This depends to a large extent on the amount
of heating or cooling required – naturally, this is
limited when you use a 12V supply.
PULSE-WIDTH MODULATION EXPLAINED
Op amp 1 is connected as an oscillator, producing
a sawtooth waveform across the capacitor. This is
connected to one of the inputs of op amp 2. The
other input has its voltage fixed at a certain level by
the voltage divider across the supply.
As the sawtooth waveform voltage rises, it reaches
this threshold voltage and the op amp output goes
high until the sawtooth waveform voltage again falls
below the threshold.
If the threshold voltage is high, op amp 2’s output is high for a very short period compared to its
low-time each cycle. If the threshold voltage is low,
the op amp output is high for a significantly greater
length of the cycle.
The difference between high and low time is called
the “duty cycle”.
OP AMP 1
OP AMP 2
Fig. 1: the temperature controller is capable of either heating or
cooling, depending on which device is installed.
Fig. 2 (right): how pulse-width modulation works. At top is a
simplified circuit which you can see corresponds to IC1b and IC1d
in the circuit above. Below are the waveforms showing the inputs
and the output for a high voltage and a low voltage. The duty
cycle, or on time to off time, is in inverse proportion to the input.
56 Silicon Chip
Parts List
1 PC board, 114 x 77mm
1 plastic case#, with label,
85 x 120 x 28mm
1 14-pin IC socket
1 U-shaped heatsink,
32 x 28 x 13mm
2 3mm x 10mm screws & nuts
4 lengths figure 8 cable (see text)
Virtually the same size as the finished project, this photo shows how and where
all components are placed. Note the electrolytic capacitor at the bottom of the
PC board – it is a PC mounting type but is mounted lying down. We have shown
both Mosfets & heatsinks installed for clarity: normally there would be only one.
The circuit as shown is suitable for
supplies up to 50V or so with only
one resistor change (R15). The voltage ratings of C3 and C6 should also
reflect the higher supply voltage – they
should be at least 30% and preferably
about 50% higher than the supply. As
with most circuits, you can use higher
voltage rated capacitors if you wish
but these tend to be more expensive.
Regardless of the supply voltage,
it needs to be fairly well filtered. Remember, too that a heating element or
Peltier device will each draw significant current – quite a few amps, in fact.
The switching Mosfets (Q5 & Q6)
are both rated at 12A with a maximum dissipation of 88W. The heater,
or P-channel Mosfet could therefore
be used to control loads up to 1kW
with adequate heatsinking (certainly
much larger than the heatsinks specified). For even higher loads, higher
rated Mosfets could be used or even
paralleled.
A heating element of about 4Ω and
a 12V supply would be acceptable
with the heatsinks supplied. Larger
heatsinks would allow a 2Ω element
(72W). With a higher supply voltage,
much higher load powers can be produced while maintaining the same dissipation in the Mosfet. A 50V supply
and a 16.6Ω heater element would be
about 150W; an 8.8Ω load would be
about 300W.
In practice, a 36W heating load
(12V<at>3A) would produce acceptable
heat dissipation from Q5, mounted on
the PC board and using the heatsinks
specified.
What type of heating element?
That’s up to you: series or parallel
combinations of low voltage light
globes are one idea.
Or perhaps you could use an electric jug element stretched out to full
length and cut to a suitable length. A
1kW jug element is about 60Ω in water
– cut in half (30Ω each) and twisted
Resistor Colour Codes
Value
220kΩ
100kΩ
47kΩ
10kΩ
2.2kΩ
1kΩ
680Ω
10Ω
4-Band Code (1%)
red red yellow brown
brown black yellow brown
yellow violet orange brown
brown black orange brown
red red red brown
brown black red brown
blue grey brown brown
brown black black brown
5-Band Code (1%)
red red black orange brown
brown black black orange brown
yellow violet black red brown
brown black black red brown
red red black red brown
brown black black brown brown
blue grey black black brown
brown black black gold brown
Semiconductors
1 LM324 quad op amp (IC1)
4 2N5551 NPN transistors
(Q1, Q2, Q3, Q4)
1 Power Mosfet – either
IRF9530 P-channel (Q5) or
BUK453 N-channel (Q6)
1 GIG power diode (D1)
1 1N4148 signal diode (D2)
2 9.1V zener diodes (ZD1, ZD2)
1 4mm yellow LED (LED1)
1 4mm green LED (LED2)
1 4mm red LED (LED3)
1 Peltier-effect device (see panel)
Capacitors
1 1000µF 25VW# electrolytic (C3)
1 220µF 16VW electrolytic (C4)
1 100µF 25VW# electrolytic (C6)
2 10µF 16VW electrolytic (C1,C2)
1 0.1µF 16VW ceramic or
polyester (C5)
1 .0022µF 16VW ceramic or
polyester (C6)
Resistors (0.25W, 1%)
2 10Ω (R2, R3)
2 680Ω (R1, R16)
1 1kΩ (R6)
6 2.2kΩ (R4, R5, R12, R13,
R15, R17)
1 10kΩ (R10)
3 47kΩ (R8, R9, R11)
1 100kΩ (R14)
1 220kΩ (R7)
1 100Ω horizontal trimpot (VR1)
1 68Ω NTC thermistor (TH1)
A kit, not including Peltier device, is
available from Oatley Electronics for
$15 plus p&p. #Some components in
the Oatley kit may be recycled from
existing equipment.
Capacitor Codes
Value
IEC Code EIA Code
0.1µF
100n
104
.0022µF 2n2
222
AUGUST 1999 57
together would give 15Ω;
cut in quarters (15Ω) and
all twisted together would
give about 4Ω, and so on.
The cooler, or N-channel, Mosfet should be more
than adequate to handle
any of the specified Peltier
devices. If you want to use
more Peltier devices (in
parallel) you will probably
need better heatsink-ing
and perhaps a higher rated
Mosfet as well.
Fig. 3: the PC board component overlay. Compare this to the
photograph when assembling the board and you shouldn’t
have any problems. Again, both Mosfets are shown installed –
you choose the one you want for heating or cooling.
Construction
All components with the
exception of the thermistor
(TH1) are mounted on a
PC board measuring 114
x 77mm. This is designed
to fit into a small plastic
case measuring 120 x 85
x 32mm.
The cases supplied in
the kit are recovered from
surplus stock so are not
new but still perfect for the job. A label
fixes to the front of the case with the
power, cool and heat LEDs showing
through. This label is printed on paper
and will need some covering to protect
it. (We use adhesive plastic).
Begin construction by checking
the PC board pattern for any obvious
defects. If so, either correct or replace
the board. There are six holes on the
PC board which may need to be enlarged – the four mounting holes (in
the corners) all need to be drilled out
to 5.5mm (7/32in) while the two holes
for the Mosfets (in the middle of the
large copper areas) should be 3mm
(1/8in).
Start by inserting all resistors in
their appropriate positions, soldering
as you go. The three links on the board
can be made from cut-off resistor
pigtails.
There are seven capacitors to be
inserted, of which all but two are polarised electrolytics. One of these, the
100µF electrolytic (C6), is a PC board
type (ie, both leads emerge from the
same end) but is actually mounted lying down on the board. A dab of super
glue or silicone sealant underneath it
would help keep it in place.
If you need to fit a higher voltage
rated capacitor here (which will
normally be larger), there is plenty of
room to do so.
Next mount all the small semicon58 Silicon Chip
ductors, taking special care with the
diodes ZD1, ZD2 and D2. Sometimes
they look almost identical to the naked
eye – you may need a magnifying glass
to properly identify them.
Fortunately the power diode, D1,
normally looks quite different!
Solder in the pot (VR1) and the IC
socket but don’t insert the IC just yet.
Then solder in the three LEDs so that
their tops are 25mm above the surface
of the PC board. The yellow LED is
LED1 (power), the green LED2 (cool)
and the red LED3 (heat).
The last component to mount is the
appropriate Mosfet, Q5 or Q6. Again,
these look virtually identical so be
careful. It mounts flat onto its heatsinks with the legs bent down. Before
mounting, hold its three legs with a
pair of needle-nose pliers and bend
the ends of the legs down 90°, 5mm
away from the Mosfet body.
Check a second time that you have
the right Mosfet in the right spot: the
BUK453 is for cooling, the IRF9530
is for heating. Before soldering, slip
the heatsink underneath and secure
both the heatsink and Mosfet with
3mm screws and nuts. No insulation
is necessary between the Mosfet and
heatsink but a small dob of heat transfer compound wouldn’t go astray.
You could, of course, install both
Mosfets and install either the heater
or cooler (but not both). Conversely,
if you will only ever require cooling
(or heating), all components after IC1d
(or IC1c) could be left out.
Solder in a suitable length of figure-8
cable (or two individual wires) for the
thermistor, the heating element and
the Peltier cooler, along with suitable
red and black wires for power connection. Ensure that the cables have
a high enough current rating to cope
with the current drawn.
To complete the PC board, insert the
LM324 IC into its socket, making sure
it is the right way around.
Put the project aside for a while.
Enjoy a cup of coffee before you check
over all your component placement
and soldering.
Checking it out
Don’t connect your Peltier cooler or
the heating element just yet. However,
you will need to connect the thermistor to its leads.
Apply power and confirm that
the yellow LED comes on. Measure
the voltage across C4 – it should be
around 8V – and if you have either an
oscilloscope or frequency meter, check
that there is a 2.2kHz output from pin
1 of IC1b. You can also check that the
heating and cooling LEDs come on as
you vary VR1 over its travel.
If everything checks out OK, turn
off and connect the heating element
or Peltier device to their appropriate
leads. Note that the heating element
should not be polarised but the Peltier
device is: the black lead connects to
the Mosfet drain for correct use.
Now you can check that the appropriate devices really do heat or cool
as they should. You will probably find
that it takes a lot longer for a Peltier
device to cool than a heating element
to heat – that’s the nature of the beast.
Finishing off
As mentioned before, the case
supplied with the kit was intended
for another device. It has a number
of holes and cutouts down one side
which are handy to take the external
leads through.
You will need to drill three 4mm
holes through the lid of the case (and
the label) for the three LEDs to poke
through. It’s easiest to do this with
the label fixed to the case – we used
spray adhesive. The label itself might
need some protection – we use plastic
contact on our projects (see the article
in the April 1999 issue).
With the LEDs soldered in place as
noted above, they should just poke
through the holes in the front panel
when the PC board is mounted in
the case lid. The board sits on small
rebates in the case mounting posts and
does not require any further securing.
Take all of the external wiring
through any suitable holes in the
side of the case and pop on the bottom, securing it with the four screws
provided.
The thermistor needs to be mounted
in very close contact with the item
being temperature controlled but away
from the Peltier device.
If it’s a liquid, ideally the thermistor
needs to be actually immersed in it but
this is often impractical or dangerous
WHICH PELTIER DEVICE?
As well as the kit of parts, Oatley
Electronics currently have three Peltiereffect devices available to suit this project.
All measure 40mm x 40mm and have a
∆T of 65°.
4 Amp – Qmax 42W $25.00
6 Amp – Qmax 60W $27.50
8 Amp – Qmax 75W $30.00
Contact Oatley Electronics on (02) 9584
3563, Fax (02) 9584 3561 or email oatley<at>world.net (or visit their website,
www.oatleyelectronics.com)
* Branco Justic is the Manager of Oatley
Electronics.
(the metal leads could contaminate or
be damaged by the liquid). The thermistor could be “potted” for protection
but this could inhibit its ability to
detect temperature changes. This part
SC
is left to you!
WHAT IS A PELTIER-EFFECT DEVICE?
The “Peltier effect” occurs when current flows across
the junction of two dissimilar metals or semiconductors.
In one direction, heat is absorbed into the junction; in the
other direction, heat is given off. This effect can be used
to make a solid-state heater or cooler. They are usually
called Peltier-effect devices or Peltier devices but you may
see them referred to as thermoelectric modules.
A typical Peltier device is composed a number of P-type
and N-type Bismuth Telluride dice “sandwiched” between
two ceramic plates. While both P-type and N-type materials
are alloys of Bismuth and Tellurium, both have different free
electron densities at the same temperature. P-type dice
are composed of material having a deficiency of electrons
while N-type has an excess of electrons.
As current flows through the module it attempts to establish a new
equilibrium within the materials. The
current treats the P-type material as
a hot junction needing to be cooled
and the N-type as a cold junction
needing to be heated.
Since the material is actually at the
same temperature, the result is that
the hot side becomes hotter while the
cold side becomes colder.
Typical Peltier devices draw between 4A and 10A <at> 12V but there are “industrial” types
drawing 100A or more.
In a resistive load, the heat created is proportional to
the square of the current applied (I2R). In a Peltier device,
the heat created is actually proportional to the current
because the flow of current is working in two directions.
Therefore, the total heat ejected by the module is the sum
of the current times the voltage plus the heat being pumped
through the cold side.
Typically, the difference between hot and cold sides can
be 65°C or more. The ability to add or remove heat is mainly
a function of the current-handling capability of the dice.
With no moving parts, Peltier devices are rugged, reliable
and quiet. They are typically 40 x 40mm square or smaller
and approximately 4 mm thick. The industry standard mean
time between failures is around 200,000 hours or over 20
years for modules left in the cooling mode.
While not polarised in the true sense, most devices have
a red and black lead attached, signifying the positive and
negative connection. The convention is that with the device
lying flat and the leads pointing towards you with the red on
the right side, the lower plate is the “hot” side.
Reversing the power connections has no effect except
for swapping which of the two plates
becomes the “hot” side.
The Peltier device works as a heat
pump. In a cooling application it takes
heat from the surrounding area (or
more correctly anything in intimate
contact with the cold side) and passes
it through to the hot side. Normally the
hot side is itself thermally bonded to
a heatsink, often fan-cooled, to disperse the heat into the atmosphere.
Because the two ceramic plates of
the device are bonded together and one side expands as
it gets hot while the other contracts as it gets cold, thermal
stresses occur. If cycled on and off too often, damage or
failure may occur.
For this reason, where Peltier devices are to be turned on
and off repeatedly, they are fed with a pulse-width modulated
waveform instead of DC.
To finish, some trivia: heat one side of a Peltier device and
you’ll generate a tiny electric current – the “Seebeck” effect.
AUGUST 1999 59
YZ TABLE
WITH STEPPER
MOTOR CONTROL
Part.4: Motor
Control Boards
This month, we describe the modified
motor controller boards for the XYZ Table.
The new controller boards include the
motor voltage interlock circuit described in
the May 1999 issue, to prevent possible
damage to the driver transistors.
By RICK WALTERS
The operation of the stepper motor
controller cards was first covered in
the August and September 1997 issues. There are two boards involved:
(1) a single controller which controls
the Z-axis stepper motor; and (2) a
dual controller which drives the X
and Y stepper motors. All motors are
driven under software control from
the PC.
For the sake of completeness, we
shall briefly cover these items again,
especially for those who may not have
the relevant issues to hand. Fig.21
shows the circuit for the single con
troller, while Fig.22 shows the dual
controller.
As can be seen, the front ends of the
two circuits are identical. It’s only the
output stages following IC2 that differ.
The data input to all cards is from
the parallel port of a PC via the Port
A data lines D0-D7. These are the signals that would normally determine
the character that would be printed
by a printer. In this application, they
determine which motor will step and
in which direction.
The Port C lines, C0-C3, are used
to select which card accepts the Port
A information. As there can be up to
eight different cards in a system, each
card’s address is selected by a jumper
C1-C8. We set the jumper to select
card 2 for the dual stepper driver and
card 3 for the single stepper.
Let’s look at this in a little more
detail. IC1, a 74HC137 one-of-eight
active low decoder, is used as the
address latch. This IC looks at the BCD
address data on its A, B & C inputs
and pulls the corresponding decimal
output (Y0-Y7) low. However, this can
only happen when the strobe goes
Fig.21 (facing page): this is the circuit
for the single motor controller. IC1
is the card select circuitry, while IC2
latches the data on the parallel port of
the PC and drives the stepper motor
via two H-bridge transistor circuits
(Q1-Q12).
60 Silicon Chip
AUGUST 1999 61
62 Silicon Chip
Fig.22: the dual motor controller is
similar to the single controller. In
this case, however, the 8-bit latch
(IC2) drives four H-bridge transistor
circuits to control two motors.
high and thus the output from inverter
stage IC4b goes low. This momentarily
pulls the latch enable (LE) input of IC1
low via the series .001µF capacitor.
As a result, the card will be addressed if the decoded output is
selected by the address link. In that
case, the decoded low will be fed
to pin 2 of IC4a and to the cathode
of D1. When the strobe signal goes
low, pin 3 of IC4a goes low and pin 1
momentarily pulls the LE input (pin
11) of IC2 high.
IC2 is a 74HC573 8-bit data latch.
When its LE input is taken high, it
latches the data fed to its D0-D7 inputs from Port A of the parallel port.
This data is transferred through to
IC2’s Q outputs and is used to drive
the stepper motor coils via transistor
driver circuits. The LE signal then
goes low 47ms later (as set by the
47kΩ pull-down resistor), so that the
data remains latched until the next
strobe signal arrives.
In the case of the single controller,
two transistor H-bridge circuits are
used to drive the coils in the Z-axis
stepper motor (MA & MB). Similarly,
the dual controller uses four H-bridge
circuits to drive the X-axis and Y-axis
stepper motors.
D1, IC3c and LED1 form a card
selected indicator. Normally, pins
8 & 9 of IC4c are pulled high via a
10MΩ resistor and so pin 10 is low
and LED1 is off.
When a valid address is received,
pins 8 & 9 of IC4c are pulled low via
D1. As a result, pin 10 switches high
and LED1 lights to show that the card
has been selected. The associated
0.1µF capacitor ensures that the LED
remains on for at least one second.
Motor interlock circuit
IC3 and its associated circuitry
forms the motor interlock circuit. Its
job is to switch the V+ supply to the
output transistors only after the software has set all IC2’s outputs low. This
is to prevent the driver transistors
from turning on in random fashion
at power up, which could cause one
of more transistors to self-destruct.
The circuit works like this: at
Parts List
Single Stepper Motor Card
1 PC board, code 07208992, 120
x 112mm
1 DB25 PC mounting right angle
male connector
1 8-way x 2 pin strip
1 jumper for above
1 3-way terminal block (5.08mm
pitch)
1 SPDT relay Jaycar SY4066 (or
equivalent)
Semiconductors
1 74HC137 decoder (IC1)
1 74HC573 8-bit latch (IC2)
1 74HC112 dual JK flipflop (IC3)
1 74HC02 quad NOR gate (IC4)
4 BD680/682 PNP Darlington
transistors (Q1, Q2, Q7, Q8)
4 BD679/681 NPN Darlington
transistors (Q3, Q4, Q9, Q10)
4 BC548 NPN transistors (Q5,
Q6, Q11, Q12)
1 BC338 NPN transistor (Q13)
4 1N914 small signal silicon
diodes (D1-D4)
1 5mm red LED (LED1)
Capacitors
2 100µF 25VW PC electrolytic
2 0.1µF MKT polycarbonate
2 0.1µF monolithic ceramic
2 .001µF MKT polycarbonate
Resistors (0.25W, 1%)
1 10MΩ
4 2.2kΩ
1 1MΩ
1 1kΩ
1 47kΩ
1 470Ω
9 10kΩ
1 74HC112 dual JK flip flop (IC3)
1 74HC02 quad NOR gate (IC4)
8 BD680/682 PNP Darlington
transistors (Q1, Q2, Q11-14,
Q23, Q24)
8 BD679/681 NPN Darlington
transistors (Q3, Q4, Q9, Q10,
Q15, Q16, Q21, Q22)
8 BC548 NPN transistors (Q5, Q6,
Q7, Q8, Q17-20)
1 BC338 NPN transistor (Q25)
4 1N914 small signal silicon diodes
(D1-D4)
1 5mm red LED (LED1)
Capacitors
2 100µF 25VW PC electrolytic
2 0.1µF MKT polycarbonate
2 0.1µF monolithic ceramic
2 .001µF MKT polycarbonate
Resistors (0.25W, 1%)
1 10MΩ
8 2.2kΩ
1 1MΩ
1 1kΩ
1 47kΩ
1 470Ω
9 10kΩ
Heatsink parts (optional)
1 aluminium bar 110 x 6 x 3mm
16 TO-220 insulating washers
8 3mm x 15mm bolts
8 3mm nuts
16 3mm flat washers
Case Assembly
1 PC board, code 07208991, 120
x 112mm
1 DB25 PC mounting right angle
male connector
1 8-way x 2 pin strip
1 jumper for above
1 3-way terminal block (5.08mm
pitch)
1 SPDT relay, Jaycar SY4066 (or
equivalent)
1 plastic case, 155 x 65 x 160mm,
DSE H2508 (or equivalent)
2 25-pin “D” IDC female connectors
Jaycar PS0846 (or equivalent)
1 25-pin “D” IDC male connector
Jaycar PP0842 (or equivalent)
1M 26-way IDC cable, Jaycar
WM4504 or equivalent (one
strand to be peeled off)
1 12-way terminal strip
1 4-way terminal strip
mounting nuts & bolts for terminal
strips
2 3mm x 10mm countersunk bolts
2 3mm x 6mm bolts
2 3mm x 25mm threaded spacers
Semiconductors
1 74HC137 decoder (IC1)
1 74HC573 8-bit latch (IC2)
Miscellaneous
Hookup wire, tinned copper wire (for
links).
Dual Stepper Motor Card
switch on, both flipflops in IC4 are
reset by the 1MΩ resistor and the
0.1µF capacitor connected to pins 14
& 15. This means that both Q outputs
(pins 5 & 9) are low and so the base
of Q13 (Q25) is held low via D2 & D3.
AUGUST 1999 63
The transistor will therefore be off
and so RLY1 is also off and no power
is switched through to the driver
transistors.
When the software is run, it first
sets all the Port A outputs low. It then
selects the dual motor card and so
all IC2’s outputs on this card also go
low. Next, it selects the single motor
card, again taking its IC2 outputs low.
This ensures that the motor windings
will be de-energised when the relay
is energised.
The software then takes pin 9 of
IC1 low then high, which clocks IC3b
on both cards. It then does the same
for pin 7 which clocks IC3a. As each
flipflop is clocked, its Q output goes
high. When both outputs are high, the
base of Q13 (Q25) is pulled high via
a 1kΩ resistor. Q13 (Q25) now turns
on and energises RLY1 which feeds
the V+ supply to the output drivers
on both cards. The main program is
then executed.
Card selection
Fig.23: follow this parts layout diagram to build the single motor controller. The
completed board is shown below, mounted in the case.
64 Silicon Chip
The card selection is done by applying the correct code for the card
to PORT C: C1-bar, C2, C3-bar and
C4-bar. The addresses are shown in
Table 1. The convoluted numbering is due to three of these inputs
having inverted logic (a high in the
program outputs a low on the Port C
pin). Thus, to select card 2, the value
9+STH (OUT PORTC, CARD# + STH)
is placed on PORT C (see the program
listing).
STH (STrobe High) is defined as -1,
so the actual value placed on PORT C
is 8 (9-1). Because strobe line C0-bar
is also inverted, this effectively takes
C0-bar and C1-bar high and the other
two lines low.
If IC4b’s inputs go high, its output
(pin 4) goes low. This momentarily
pulls pin 4 of IC1 low via a .001µF
capacitor. IC1 then decodes the input
levels (eg, A high = Y1 low, B high =
Y2 low & C high = Y4 low) and switches the decoded output (Y1 in this case)
low. As soon as the .001µF capacitor
charges, pin 4 goes high again and the
input data can be altered without the
output changing.
The next line in the listing is OUT
PORTC, CARD# + STL and if you
follow the logic, C0-bar will go low,
pin 4 of IC4b will go high and pin
3 of IC4a will go low. If the card selector link is in the C2 position, pin
2 of IC4a will also go low. Pin 1 of
Tabl e 1: Card Addresses
Card 1
11
Card 2
9
Card 3
15
Card 4
13
Card 5
3
Card 6
1
Card 7
7
Card 8
5
IC4a will thus momentarily pull the
latch enable (LE) input of IC2 high
via a .001µF capacitor and the data
on PORT A will be transferred and
stored on the Q outputs, as described
previously. Obviously, if the link selects a different card, the data on the
inputs of IC2 will not be transferred
to the Q outputs.
By putting high and low logic
levels on the various inputs, we can
therefore energise or de-energise the
MA and MB motor windings and determine the direction of the current
through the windings.
Construction
Fig.23 shows the assembly details
for the single motor control card,
while Fig.24 shows the details for the
dual controller. Install the parts on the
two boards as shown, taking care to
ensure that all semiconductors and
electrolytic capacitors are correctly
oriented.
Don’t mount the LEDs directly on
the boards though. In
stead, these
Fig.24: the parts layout for the dual motor controller. Power transistors
Q1-Q24 are all bolted to an aluminium heatsink – see text.
should be connected via 120mm-long
flying leads, so that the LEDs can
later be mounted on the front panel
of the case.
Be careful when fitting the transistors, as two different TO-126 types
are used. Note particularly that the
transistors don’t all face in the same
direction so be sure to orient the metal
tabs of the transistors as shown on the
layout diagrams.
The 16 TO-126 power transistors
Fig.25: this diagram
shows the drilling details
for the aluminium
heatsink that’s used for
the power transistors on
the dual controller card.
The heatsink is cut from
12 x 6mm aluminium bar
and is 111mm long.
AUGUST 1999 65
The dual controller card is attached to the base
of the case, while the single controller is mounted
above it on 25mm threaded spacers.
on the dual controller card are bolted to a common heatsink. This can be cut from 6 x 12mm
square-section aluminium rod and should be
111mm long. Fig.25 shows the drilling details
for the heatsink.
Note that the transistors must all be isolated
from the heatsink using insulating washers.
Smear all mating surfaces with heatsink compound if you are using mica washers. No heatsink
compound is necessary if you are using silicon
impregnated insulators.
The best procedure is to loosely attach all the
transistors to the heatsink before fitting the entire
assembly to the PC board. The BD682 PNP transistors are all mounted on one side of the heatsink
and the BD679 NPN types on the other. After
The rear panel carries a 12-way terminal block
for the motor connections, plus a 4-way terminal
block for the power supply connections.
66 Silicon Chip
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Fig.26: the external wiring details for the two controller cards. The card select
jumpers are set to C2 for the dual controller and C3 for the single controller.
mounting them, use a multimeter
(set to a high ohms range) to confirm
their collectors are all isolated from
the heatsink.
The two controller cards were
stacked (single board on top) and
fitted into a small plastic instrument
case. As shown in the photos, we
drilled two 3mm holes in the front
corners of both boards. The dual con-
If you need:
P.C.B. High Speed Drill
P.C.B. Guillotine
P.C.B. Material – Negative or
Positive acting
Light Box – Single or Double
Sided – Large or Small
Etch Tank – Bubble or Circulating
– Large or Small
U.V. Sensitive film for Negatives
Electronic Components and
Equipment for
TAFEs, Colleges and Schools
FREE ADVICE ON ANY OF
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40 Wallis Ave E. Ivanhoe 3079
Ph (03) 9497 3422
FAX (03) 9499 2381
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CARDS ACCEPTED
AUGUST 1999 67
Fig.28: this is the full-size etching pattern for the single controller card.
Fig.27: here's how to make the cable
that connects the controller cards to
the parallel port of the PC. The two
25D female connectors are wired in
parallel and must be at least 50mm
apart. The red stripe of the 25-way
cable goes to pin 1 of each connector.
troller board was then secured to the
base using countersunk head screws
into 25mm spacers.
The top board is secured to these
two spacers at the front. The back
of this board then simply rests on a
piece of foam glued to the top of the
heatsink on the dual controller board.
Make sure that this strip of foam is
correctly attached, so that the heatsink doesn’t short to any of the parts
on the board above it.
Fig.26 shows the case wiring details. Two insulated terminal strips (1
x 12-way and 1 x 4-way) are mounted
on the rear panel and these terminate
the wiring connections from the stepper motors and the power supply. The
leads between these terminal strips
and the boards should be run using
medium-duty hookup wire.
When the wiring is complete, attach
the front panel label and drill the
mounting holes for the LED bezels.
The two “card selected” indicator
LEDs can then be pushed into bezels
from the back.
Fig.27 shows the details of the cable
Resistor Colour Codes
No.
1
1
1
9
8
1
1
68 Silicon Chip
Value
10MΩ
1MΩ
47kΩ
10kΩ
2.2kΩ
1kΩ
470Ω
4-Band Code (1%)
brown black blue brown
brown black green brown
yellow violet orange brown
brown black orange brown
red red red brown
brown black red brown
yellow violet brown brown
5-Band Code (1%)
brown black black green brown
brown black black yellow brown
yellow violet black red brown
brown black black red brown
red red black brown brown
brown black black brown brown
yellow violet black black brown
Software Listing
10 REM Driver software for drilling PC boards using Protel file
1140 STL = 0: STH = -1 ‘Strobe low & high
1150 PORTA = PPORT: PORTC = PORTA + 2 ‘Select parallel port
1160 OUT PORTA,0 ‘set all data lines low
1170 OUT PORTC, CARD1 + STH: OUT PORTC, CARD1 + STL ‘card1 - IC2 O/P’s low
1180 FOR PAUSE = 1 TO MDELAY: NEXT
1190 OUT PORTC, CARD2 + STH: OUT PORTC, CARD2 + STL ‘card2 - IC2 O/P’s low
1200 FOR PAUSE = 1 TO MDELAY: NEXT
1210 OUT PORTC,7 + STH: OUT PORTC,7 + STL ‘Clock IC3b
1220 FOR PAUSE = 1 TO MDELAY: NEXT
1230 OUT PORTC,5 + STH: OUT PORTC,5 + STL ‘Clock IC3a, 12V to motors
1240 FOR PAUSE = 1 TO MDELAY: NEXT
1250 OUT PORTA, 153: OUT PORTC, CARD1 + STH: OUT PORTC, CARD1 + STL ‘Home motor
1260 FOR PAUSE = 1 TO MDELAY: NEXT
1270 OUT PORTA, 105: OUT PORTC, CARD2 + STH: OUT PORTC, CARD2 + STL ‘Home motor
1280 FOR PAUSE = 1 TO MDELAY: NEXT
1290 OUT PORTA, 0: OUT PORTC, CARD1 + STH: OUT PORTC, CARD1 + STL ‘Motors off
1300 FOR PAUSE = 1 TO MDELAY: NEXT
1310 OUT PORTC, CARD2 + STH: OUT PORTC, CARD2 + STL ‘Motor off
1320 FOR PAUSE = 1 TO MDELAY: NEXT
Table 2: Motor Lead Connections
Lead Colour X-Motor Y-Motor Z-Motor
Red
1
5
9
Bl ack
2
6
10
Green
3
7
11
White
4
8
12
that runs from the boards to the parallel port of the PC. As shown, the two
25D female connectors are wired in
parallel and should be at least 50mm
apart. Be sure to wire the red stripe
of the 25-way cable to pin 1 of each
connector. Note that you will have to
buy 26-way cable and peel away one
of the outside leads (not the read one).
The cable exits the case through a
step filed in the top of the back panel,
above the 4-way connector.
Connecting the motors
The stepper motors used are 1.8
degree types from Oatley Electronics
and these have four coloured leads:
red, black, green and white. Table 2
shows how the stepper motors are
wired up. As shown, the X-motor has
its red lead connected to terminal 1,
black to terminal 2, green to terminal
3 and white to terminal 4.
Similarly, the Y-motor has its red
lead connected to terminal 5, black
to terminal 6, green to terminal 7 and
white to terminal 8. The Z-motor has
red to terminal 9, black to terminal
Fig.29: the full-size etching pattern for the dual controller card.
10, green to terminal 11 and white to
terminal 12.
Next month, we will describe the
power supply for the XYZ Table. We
will also discuss the software
drives the Z-axis motor, so that
can automatically drill a board
has been laid out using Protel.
that
you
that
SC
AUGUST 1999 69
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.
Simple 3-digit
frequency counter
This simple 3-digit counter was
produced to monitor the driving frequency to a 12V synchronous motor
used to drive a telescope. Once the
correct drive speed is obtained, the
drive frequency is noted so that it can
Burglar alarm for
continuous security
This circuit was produced to ensure
that an alarm in a warehouse area
is armed after a preset delay. After
that period, anyone entering the area
will hear a buzzer and they have 30
seconds to reset the delay circuit
otherwise an external alarm siren
will sound.
The circuit allows employees to
enter the warehouse from time to
time whereby their presence will be
detected by a PIR sensor. If the buzzer
70 Silicon Chip
be set to the identical rate next time.
The circuit is based on the 3-digit
event counter published in the September 1990 issue of SILICON CHIP.
With the addition of a timing circuit
to provide “latch enable” (LE) and
“reset” (MR) signals to the 4553, the
circuit becomes a standard frequency
counter. This is achieved with IC1, a
555 connected in a standard astable
multivibrator circuit.
While the 3-digit counter was
featured with a PC board in the September 1990 issue, the added timing
circuit would need to be built up on
Veroboard or similar material.
Chris Dunn,
Nowra, NSW. ($25)
sounds they know how to reset the
system. However, any unauthorised
person entering the area will set off the
buzzer and 30 seconds later, the external alarm will sound for one minute.
The circuit is based on IC1 and IC2
which provide the preset delay. IC1
is wired as an astable timer with the
longest practical time-constant, as set
by the two 6.8MΩ resistors and 47µF
capacitor. While the timing period is
nominally 11 minutes, in practice, it
will be limited by the leakage current
of the 47µF capacitor.
IC1 then clocks IC2, the 74LS192
decade counter which counts up until its carry output, pin 12, goes low.
This multiplies the time by a factor of
10 and so pin 12 goes low after 110
minutes to turn on transistor Q1. This
energises relay RLY1 which has its
contacts arranged to latch on supply
power to the timing circuits consisting
of IC3 and IC5, two 555 timers. These
two timers provide the 30 second
warning buzzer time and the 1-minute
delay for the external siren.
Both IC3 & IC4 are disabled by
the 1MΩ resistor pulling their pins
2 high. The circuit is then quiescent
until the PIR sensor detects a person
moving and its relay contacts open.
This allows the pin 2 connections
of both timers to be pulled low via a
One chip audio
preamplifier
This circuit was designed to use a
minimum of components, yet have
common 0.1µF capacitor and 10kΩ
resistor. Both timers then run their
course unless the whole circuit is reset
by pressing switch S1 to disconnect
fairly good performance in terms of
low noise, etc. Trimpot VR1 sets the
gain of the input stage to allow for
various program sources.
The circuit draws around 5mA
and has an input impedance of
power from the 3-terminal regulator,
REG1.
John Malnar,
Gordon, ACT. ($35)
47kΩ shunted by 47pF. The TLC272
(Radio Spares part no. 638-920) is a
CMOS op amp. A TL072 could be
substituted if you desire.
S. Williamson,
Hamilton, NZ. ($30)
AUGUST 1999 71
TECHNICAL
LOOK: TEN NEW
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EXPLAINED
By Philip Miller. Published 1997.
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the Internet protocols, combining study
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given. 518 pages, in paperback, at $90.00.
LOCAL AREA NETWORKS:
An Introduction to the Technology
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A complete reference for anyone setting up a
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The book covers the main web server
software applications, how they differ, and
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With this book you can learn the principles and
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ESSENTIAL LINUX
By Steve Heath. Published 1997.
By Tim Williams. First
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Widely regarded as the standard text on EMC,
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NEW!
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Second edition 1999.
By Eugene Trundle. First published 1988.
Second edition 1996.
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This practical handbook from one of the
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DESIGNING INTERNET HOME PAGES
MADE SIMPLE
By John Linsley Hood. First published
1995. Second edition 1999.
This book is for anyone involved in designing,
adapting and using analog and digital audio
equipment. It covers tape recording, tuners and
radio receivers, preamplifiers, voltage amplifiers,
audio power amplifiers, compact disc
technology and digital audio, test and
measurement, loudspeaker crossover systems,
power supplies and noise reduction systems.
375 pages in soft cover at $79.00.
THE ART OF LINEAR ELECTRONICS
NEW!
95
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Provides all the information and software that
is necessary for a PC user to install and use the
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setp-by-step, how to obtain and configure the
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illustrated with screen shots and examples
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and compilers with their associated documentation. 257 pages, in paperback, at $85.00.
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POST TO: SILICON CHIP Publications, PO Box 139, Collaroy NSW, Australia 2097.
OR CALL (02) 9979 5644 & quote your credit card details; or FAX TO (02) 9979 6503
December
AUGUST 1999 73
SERVICEMAN'S LOG
Not every write-off is written off
It is one thing to accept that a set is a writeoff; genuinely too expensive or impractical to
repair. But if one is prepared to take a punt
privately and spend some time, the reward
can sometimes be worthwhile.
My first story is not about a writeoff but is about an NEC FS6330 TV
set belonging to one of my regular
customers, Terry Ford. He brought it
in complaining of no colour which
looked like a straightforward problem,
except that it didn’t turn out that way.
And he was right – at switch-on,
there was no colour. Pressing “Picture” on the RC1073E remote control
and pushing “control ^” (up) put the
colour back on but the control had to
be set almost fully up. And if the set
was switched to standby and then
switched back on again, the adjustment had to be redone.
To overcome this, I brought up the
standard picture-on-screen display
settings. This showed that the colour
had been turned right down. However,
after resetting it and switching off the
Standard PST switch, I found it didn’t
hold its setting.
After mucking about with the
controls for some time, I came to the
conclusion that the set wasn’t memorising anything and this included
the tuning. Whatever the set had been
programmed with when it came in,
nothing I could do would permanently alter the settings.
When I looked at the circuit for the
PWC-3518A CPU module, there is
an IC1002 marked “MEMORY” and I
felt sure that this was the problem. I
started by removing the module and
checking and soldering any suspect
joints I could find. There were none
worth writing home about, so I did
the same with the motherboard (PWC
3517).
Unfortunately, this made no difference to the memory problem, so
74 Silicon Chip
I checked the voltages on the IC and
the microprocessor to find them all
OK. I also replaced (C1021) 100µF to
the oscillator but still wasn’t getting
anywhere.
Next, I ordered a new memory IC
(CXK1006L) and fitted it as soon as it
arrived. This time I had a new range
of problems because the IC wasn’t
programmed for anything. However,
I was still unable to store any instructions permanently. I checked all the
small components around IC1002 and
they were all OK, so was it the main
microprocessor?
At this stage, I confess I took the
easy course and phoned technical
support at NEC. The technical officer
asked me what was the first display I
saw when switching on. This caught
me a little by surprise as I hadn’t
really noticed but the next time I did
switch it on from cold, it went straight
to the external AV mode with “V2”
displayed on the screen.
The technical officer told me that
this almost certainly meant the microprocessor was faulty and should
be replaced. He also advised me to
fit three 5.6V zener protection diodes
on the three data rails (PA1, PA2 and
PA3) which go to pins 7, 6, and 5
respectively of IC1001.
This I did, after installing the expensive CXP80420-130S with its 64
high-density pins. Fortunately I found
a position already drilled, punched
and marked FD1005 to fit these zener
diodes - somewhat similar to the 6.8V
zener diodes in FD1003.
And that fixed the problem. The set now tuned
and stored all its settings
correctly each time. I was
intrigued as to whether
it was just the CPU or
the memory IC as well,
so I unsoldered the latter,
fitted a socket and plugged
in the old memory chip.
The original problem was
still here, so obviously
both the ICs had been
destroyed.
I left the set on test,
fully confident that it
was all fixed - but it
wasn’t. After a while,
it began giving a “bluey/
yellowy” sort of colour
which I recognised as
indicating U(B-Y) only;
ie, loss of V(R-Y). I
thought initially that
this may have been due
to an incorrect system
setting (eg, NTSC) but
it wasn’t. I went back in and finally
found the V(R-Y) loss was due to
faulty joints on IC701, the chroma/
jungle IC, which is another high-density 32-pin device.
The owner, in the meantime, had
been popping in and asking about his
set on a regular basis. He had become
somewhat dismayed at the length of
time and different courses the saga
was taking, especially as I had so confidently assured him that it was just
the memory IC that was the trouble.
However, he stuck it out and hopefully won’t have any more problems.
A large-screen Telefunken
My next story concerns a large
screen stereo TV set. This was a 68cm
Telefunken SDX290H employing a
Thomson ICC7 (or more precisely
ICC7000+) chassis. This set had been
struck by lightning and had no sound
or picture.
I ordered a circuit for it and received
a photocopy of the basic ICC7 circuit,
which covered Nordmende, Saba,
Telefunken and Thomson models.
From this, it didn’t take long to work
out that the problem lay in a complex AV module MAV7000 on the
rear of the set. This was blocking all
the signals from the tuner/IF system,
or any other external signals, from
reaching the jungle IC IV01 and the
rest of the set.
Unfortunately, the circuit contained
no reference to this AV module. This
set can select no less than four different AV connections: two rear RCA/
Phono, one front RCA/Phono, three
SVHS DIN and 1 Scart (both input and
output). There are also external DIN
and wired loudspeaker connections.
We ordered the missing circuit
and were lucky to receive one but,
much to my frustration, this was also
incomplete! More precisely, it did not
include a daughter board MOM7000
which is connected to the AV module
via nine leads. This daughter board
contains an IC (ICIM01 HCF4053BE)
and various peripheral components.
After exhausting every avenue right
back to Thomson in Europe, the missing circuit proved to be unobtainable
- and all this had taken three months
or more to determine. The module
was also unobtainable as a spare part
and even if it had been, it would have
been horrendously expensive. In any
case, I was unsure as to whether there
were any other problems with the set.
By now, the owner of the set had
lost patience and so the insurance
company decided to write it off. However, it was an attractive unit, built
in 1993 and boasting Teletext and a
subwoofer. By turning up the picture
tube screen control, I could see there
was a raster but that was all. And so,
rather than let it be broken up for spare
parts, I bought it and took it home to
fix in my spare time (huh!) - much
to my wife’s disgust (I already have
enough junk).
When I finally tackled it, the first
thing I did was to remove the module
and try to make sense of it. I started
by drawing out a simplified layout
diagram of the ICs and especially
concentrated on the daughter module,
MOM7000.
The surface mounted components
on the double sided printed circuit
board didn’t help much but I finally
constructed a layout diagram that I
could marry in with the circuits I had.
In retrospect, the final result didn’t
look much but it helped enormously
in tracing the signal routes through
the board.
Even so, the route the signal takes
is rather tortuous. The tuner/IF signal comes in as CVBS1 on connector
BEO1 pin 13 and comes out as CVBS
on BEO1 pin 10 via IV03 TEA2014A,
AUGUST 1999 75
IV02 HA118058 and IV01 TA8639P.
However, without block diagrams of
some of these ICs, it is impossible
to understand the processing and
switching that goes on internally.
However, I was extremely lucky
when I made a voltage check across
the module, because there was no
+13Vcc available any
w here. This
turned out to be due to a 3.9Ω resistor
(RE22), which was open circuit.
Replacing this restored the sound
and picture from the tuner/IF system
but not the AV inputs and outputs.
After a lot of time spent measuring
and replacing many components,
I finally traced the problem to the
daughter board. A BC548 transistor
(TM10) was open circuit and the IC
IM01 (HCF4053BE) had failed.
Replacing these still didn’t fix the
problem until I found that a part of
the printed circuit, the audio com-
76 Silicon Chip
mon return to connector BE01 pin 3,
had been vaporised. Repairing this
fixed the monitor output but most of
the inputs and outputs were still not
functioning fully.
As luck would have it, replacing
two TEA2014A ICs fixed all the remaining problems. It appeared that
these two ICs had jammed in one
mode. The “write-off now has pride
of place in my lounge room. And my
wife has (fortunately) reconsidered
her opinion that the set was “junk”.
Making a 22.5V battery
In the December 1998 notes, I
described how I discovered a faulty
silicon diode with reverse leakage.
And although replacing the faulty
diode solved the problem in the set
concerned, I had been puzzled as to
why the leakage did not show on test.
A variety of multimeters and compo-
nent analysers had been tried and all
but one failed to detect it. The only
one that did pick it was an old DSE
Peak (Hokia) AS100D 100kΩ/V unit.
Significantly, this uses a 22.5V battery for the resistance ranges and this
was most certainly the reason that it
revealed the fault – the diode leakage
was voltage sensitive.
And this highlighted another
problem – where to get replacement
batteries for there old meters. Unfortunately, 22.5V batteries – relics of
the valve era – are no longer made. So
what can be used to replace them and
keep a valuable piece of test equip
ment operational?
It was while I was cogitating thus
that an amateur friend turned up with
a similar problem and in the process,
suggested a solution. In his case, an
even older multimeter was involved
- the English-made AVO8. This was
regarded as the “cream” of multi
meters in its day and is still highly
valued by its owner.
This particular meter uses a 15V
battery, once readily available in
several forms but now quite rare. The
last time it needed replacing, he used
a Varta V74PX photographic type but
that was very hard to find and very
expensive.
This time my friend took a different
approach. The most readily available
battery now is the 9V portable radio
type, such as a 216, S3282, or similar.
Two of these would provide 18V and
the problem was to reduce this to 15V.
Series resistance was obviously not
a solution. Instead, but my friend’s
idea was to add a 3V zener diode in
series with the batteries. In theory, this
should develop a constant 3V across
it, regardless of current drain. However, he did have some reservations
about zener behaviour at the very low
current drain involved (µA rather than
mA). As it turned out, these reserva
tions were justified – the zener value
was no longer accurate.
Nevertheless, he tried it and eventually finished up with a 3.3V zener
and a 1N4148 silicon diode in series.
And this worked very well. When he
tested the unit using several close
tolerance resistors, covering a wide
range of values, the results were as
close as could be expected from a
service type ohmmeter.
His reservations regarding the zener
behaviour involved the characteristic
curve at the knee; a gentle curve com-
pared with the much sharper curve
of an ordinary silicon diode. In fact,
a string of five diodes might be theoretically more accurate.
What about that 22.5V battery situation? One possibility is to use three
9V batteries in series with a 4.5V
zener/silicon diode combination. I
haven’t tried it but I can’t see why it
wouldn’t work.
The missing tube
To finish off this month, here is a
story, in lighter vein, from a colleague
who is prepared to swear on a stack of
service manuals that it is true. I’ll let
him tell the story in his own words:
A few weeks ago a customer, an
elderly gent, appeared at the door of
the shop. He was juggling a portable
colour TV set at a dangerous angle
on his knee, against the door jam,
while he struggled with the door
knob. I hurried to the door, opened it
gently, took the set and placed it on
the counter. The set turned out to be
a 34cm AWA model.
“So, what’s the problem?”, I asked.
“Well, there’s only a thin white vertical line down the middle of the
screen”, he replied. “The sound is
OK”.
On the basis of this description, the
problem appeared to be fairly straightforward. The presence of an image on
the screen meant that the EHT system
was obviously working, so the lack
of horizontal deflection could only
mean failure of the horizontal yoke,
or a connection to it.
“OK, leave it with me and I’ll have
look at it”, I replied.
He hesitated. “Er-ah; I was wondering if you could have look at it now?
It’s the one in the kitchen and my wife
likes to watch it while she’s working.”
I looked at the pile of work on the
bench and considered how far I was
behind – as one usually is. Still, I
could perhaps stretch a point. Hopefully it should not take too long; possibly just few minutes. (Yes, I know
- these are the ones that can turn sour).
“Oh well, I guess so. Take a seat and
I’ll have a look at it.”
I took the set into the workshop and
took the cover off. And for once I was
right; there it was – a bad connection
to the yoke socket. A few moments
with the soldering iron was all that
was needed. I turned the set on and it
sprang into life. I put the cover back
on and took the set out to the counter.
He paid me and I took the set out
and put it on the back set of his car,
placing it face down, as I normally
do, to keep the centre of gravity low
so that it would travel safely. I waved
him off and went back to the bench.
Half an hour later, he was on the
phone. “Sorry to bother you but
have you got the screen there in the
shop?” I was confused momentarily,
then realised that he probably meant
one of those anti-glare screens which
some people fit to their sets. I didn’t
remember there being one on this set
but I could have been wrong. “Er! –
No; Hang on . . . I’ll check . . .”
I looked around on the workbench
and counter but there was no sign of
it. He’d probably left it at home.
“Sorry, But I don’t see it here. Perhaps you left it in the car.” He said he
would have a look.
About 20 minutes later, he appeared
at the door. I suggested he look over
my bench and counter. But there was
no sign of it anywhere in the shop or
on the street outside. I was sure he had
left it at home somewhere. Anyway;
back to work.
Some time later he was on the
phone again. “I can’t find it anywhere.
All I can find is the ribbing”.
I’m afraid the last part of that remark went over my head, “Oh well,
sorry about that. Anyway, how is the
picture?”
“I don’t know; there isn’t any
screen”, he replied.
Suddenly, something dropped. It
wasn’t “the penny”, because it was
still a mystery, but I was jolted into
realising that there was something
wrong.
“You had better bring the set back
to the shop. When you arrive, come
to the door and I’ll get the set out of
the car for you, so you don’t have to
struggle across the road with it”.
He arrived a few minutes later and I
went out and collected the set, carrying it face down as I had put it in the
car originally. I took it into the shop
and placed it on the counter. As I did
so he said, “I have looked everywhere.
In the car, the path, the house; I can’t
see any glass anywhere”.
As I tilted the set up from its facedown position, I said, “The only place
where I can see glass is there!” – this
while I pointed to the picture tube.
His face was a picture. “Oh dear,
I’m so embarrassed. What’ll I tell my
wife?”
There was a funny side to it of
course but it was not a time for laughter; I felt so uncomfortable for him.
And an ironic twist was that he used
to work on radar surveillance in the
Catalinas during the war. But that
was a long time ago. I tried my best
to make light of it. “Don’t tell her”, I
said, “Just tell her I found it and it’s
all fixed up.”
SC
And that’s how we left it.
AUGUST 1999 77
Changing Your Image. . . Software by Herman Nacinovich
Do you make or design your own PC boards? Here are two utilities
which will let you reverse Protel files or PCL files.
Many hobbyists make their own PC
boards, which is why SILICON CHIP not
only publishes PCB patterns in the
magazine but makes them available
free of charge on the website (www.
siliconchip.com.au).
Some go one step further – they
design their own boards as well. Once
upon a time, this was a messy process
involving drafting pens and clear film.
Then tapes and pads came along making the process much simpler.
Today, it’s even easier with a variety
of computer programs to make PC
board layout a breeze.
You design your board, check it
then print it onto a piece of film,
then produce your board using conventional photo-resist and etchant
techniques.
It would appear that the vast majority of people designing PC boards
use one of a variety of programs
from Protel. And despite a big effort
being made to “upgrade” users to
Windows-based software, many are
quite happy using the earlier DOSbased versions.
Autotrax from Protel is perhaps the
most popular, although the freeware
version, Easytrax, is widely used by
hobbyists. Despite these programs
not having all the bells and whistles
of their more recent counterparts, it
seems a very large number of users are
comfortable with the old versions and
are happy to stay with them.
(We speak from experience here:
guess which software and version we
use at SILICON CHIP?)
One of the bells and whistles which
the older versions of Protel lack is the
ability to print negative images. When
you have laid out your board, what
you have is what you print (should
that be WYHIWYP?)
If you work in positive photo resist,
that’s no problem. But a significant
number of resists (either liquid form
or pre-coated boards) are negative
acting.
Problem: DOS-based Protel cannot
print negative. The printed image has
to be converted photographically (and
how many hobbyists have access to
that sort of equipment?)
It’s not only time consuming, it’s
incovenient and it can be costly – possibly much more than the PC board
is worth!
Before we go any further, perhaps
we should explain the difference between negative and positive images
because they are often misunderstood.
When talking about PC board patterns
in particular, a positive image has
black tracks and pads with clear or
white holes and board background.
Negative images are, as you would
expect, reversed: white or clear tracks
and pads with black background and
holes.
Now, back to the problem at hand:
one of SILICON CHIP’s regular contributors, Herman Nacinovich, has
written a program in QuickBasic
(Left) A positive PCB board pattern, as
produced by Protel's Autotrax.
(Right) The same PC board pattern,
reversed using convert.exe
78 Silicon Chip
which will convert a Protel PCB
image file from positive to negative
format (or, indeed, vice versa) suitable for printing on an HP compatible
laser printer.
DOS Software
The software (which is available
on www.siliconchip.com.au) works
with HP PCL format image files. Fortunately, most HP or HP compatible
printers use this format.
And while it has only been used
with Protel-generated PCB files, it
may work with images produced by
other software as well.
It will probably not work with
compressed graphic files.
The program is simple – in fact, the
author points out it was written simply to do this particular job and while
it works fine for him, there may be
bugs which he hasn’t discovered yet.
On the other hand, the price is right
– it costs you the grand total of one
phone call to your ISP!
The DOS-based program is called
convert.exe. Like most software on the
’net, it will be zipped up and require
unzipping with PKUNZIP. Look for
the software called CONVDOS.ZIP
on the software downloads section
of the website.
Once downloaded and unzipped,
the procedure is as follows:
* Create the original image
* Save the output to file rather
than printer
Once set up, the Windows version of the software is very easy
to use. Simply load the file you wish to convert, choose your
options . . . and wait!
* Convert the file using the
convert.exe utility
* Print the converted file (using
DOS print)
Windows Software
And what of the readers who work
in Windows? Don't worry, you haven't
been forgotten.
The same author has written a similar utility to convert any HP PCL file
under Windows 3.x
This program, also available from
the SILICON CHIP website, actually
does a little more: it gives you the
NEW!
option of printing to an HP laserjet
(or compatible HP PCL printer) via
either LPT1 or LPT2.
It also gives you the option of printing to file and/or converting the file to
either TIFF or RLE formats.
All this is undertaken from the
Windows screen in the familiar
point'n'click manner, as demonstrated
by the screen images below.
A word of warning – it does take
quite a long time (minutes on a slower
machine) to convert the file.
The progress bar shown in the righthand image takes a long, long time to
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get through. At least, though, you can
see where you are up to.
On the website, the Windows
version is a suite of programs called
CONVWIN.ZIP, again requiring unzipping with PKUNZIP (we actually
use PKZIP for Windows).
Download the file, saving it to disk,
unzip it (again saving the unzipped
files to disk) then run the setup.exe
file from the taskbar and everything
is done for you. You have the option
of accepting or changing the default
directory into which the program is
SC
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AUGUST 1999 79
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CTRONICSHOWCASELECTR
BUSINESS FOR SALE:
SPEAKER SALE
For the very first time we are having
a sale of selected loudspeaker drivers
from the prestige MOREL line.
On sale are two drivers:
MW 265
222mm Shielded Woofer,
Fs 30Hz ,Vas 88.6L Qts 0.44
Power 150W
Hexatech voice coil
Normally $190
DMS 30S
NOW $130
27mm Shielded Dome Tweeter,
94mm dia. Fs 650Hz Power 200W
Hexatech voice coil
Double chambered Sens 90dB
Normally $129
UNIVERSAL
WIRELESS
DEVELOPMENT SYSTEM
Linx RF modules from Clarke & Severn
Electronics offer a simple, efficient and
cost-effective method of making a product
wireless. Want to know more? Contact
CLARKE & SEVERN ELECTRONICS
PO Box 1, Hornsby NSW 1630
Ph (02) 9482 1944 Fx 9482 1309
email: sales<at>clarke.com.au www.clarke.com.au
•
•
•
•
•
Escape to the sun in beautiful Coffs Harbour!
•
•
•
•
Stable electronic retail business
Easily run by husband and wife team.
Agent for GSM carrier
Access to large electronics suppliers (niche market).
Very strong customer base inc Government depts
and schools etc.
Five year rental option on current highway premises.
Full figures available.
Current owners (12 years) are moving to a new
business.
Price only $55,000 + SAV.
Enquiries: Hunter & Associates (02) 6651 6818
NOW $75
All other MOREL products
available – many ex-stock
We are sole Australian Distributors for:
•
CLIO Electro-Acoustic Measurements
• SOFIA Vacuum Tube Curve Tracer
• JASPER Power Router Circle Jigs
Australian Audio Consultants
PO Box 11, Stockport SA 5410
Phone / Fax 08-85-282-201
E-mail aac<at>rbe.net.au
IN YOUR NEXT ISSUE OF
Items planned for the September issue*, due on sale at your newsagents August 25. Subscribers receive their copies a little earlier.
POWERED COOLER
Held over from this issue (so we could bring you the
temperature controller) this Peltier-effect device keeps the
drinks or picnic lunch reall cool! Operates from your car's
cigarette lighter.
AUTONOMOUSE – THE ROBOT
This clever little critter is the ideal introduction to the
fascinating world of robotics. It's easy to build, easy
to get going . . . and loads of fun!
* These features currently in production but are subject to alteration
Even more great projects to build:
• Digital electrolytic capacitance
• Completing the XYZ plotter
Plus all the popular features:
• Serviceman's Log • Circuit Notebook
• Computer hints & tips • Vintage Radio
• Product Showcase • Ask SILICON CHIP
SUBSCRIBE TO SILICON CHIP AND $AVE REAL $$$$
As a subscriber, you will not only receive your copy earlier – you will actually save money,
especially while our special savings offer is on (A 2000 subscription at 1999 prices)!
Check it out: 12 issues from the news-stand = $71.40;
1 year subscription: $59 AND we pay the postage! We even pay the GST when it starts.
See the handy order form on page 37 of this issue.
AUGUST 1999 81
JUNE 1999 81
Pt.14: Mixing Daylight And Electric Lighting
By JULIAN EDGAR
Electric
Lighting
Using natural light to illuminate building interiors during
daylight hours could significantly reduce energy consumption
and cut power bills. The concept is simple: collect the sunlight
falling on the roof and use light pipes to distribute it throughout
the building to provide natural lighting.
82 Silicon Chip
T
RY THIS QUICK QUIZ: when,
during the 24 hours of a day,
would you expect the greatest
power consumption due to the use of
electric lighting? If you said “at night”
you would be wrong. The greatest
demand for artificial lighting is at the
very time of day when the Sun is at
its highest and natural light is most
abundant!
The cost, in both energy and dollar
terms, of switching on a light instead
of making use of daylight is considerable. In the US, the power bill for
electric lighting is about $US100
million every day and electric lighting uses about one-quarter of all the
electricity generated.
In addition to the direct energy
cost, electric lighting also has an
indirect energy cost. Electric lighting generates heat and about 10% of
total cooling and ventilation costs go
towards removing this heat.
One obvious way to reduce the cost
of lighting is to supplement artificial
light with natural light. In the past,
this meant using large windows and
skylights. However, these traditional
forms of natural lighting do not distribute light to remote locations.
One way around this is to “pipe”
natural light to dim locations and
add artificial lighting as necessary.
This approach, which relies on the
use of “light pipes”, is called “hybrid
lighting”.
A hybrid lighting system consists
of four main parts: (1) natural light
collectors; (2) artificial light sources;
(3) transport and distribution systems
for both light types; and (4) a control
system.
Natural light collection
On a cloudless day and with the
Sun high in the sky, the amount of
sunlight falling on a square metre
of the Earth’s surface is more than
1kW. All this power is in the form of
visible radiation – a quite different
situation to a 1kW incandescent lamp
that might emit only 180W of visible
radiation. One square metre of bright
sunlight is therefore equivalent to
about 55 100W light bulbs.
FACING PAGE: Oak Ridge National
Laboratory’s Mike Cates (left) and Jeff
Muhs with a light pipe of the type that
could be used in commercial hybrid
lighting systems. (Photo: ORNL).
This means that a square metre’s
worth of bright sunlight could theoretically light about 20 rooms. Or to
put it another way, enough sunlight
falls on the roof area of a multi-storey
building to light every room in the
building – even if it’s more than 100
storeys high! However, this assumes
that the light can be both efficiently
collected and then transported without loss to where it is needed.
The most efficient method of collecting sunlight is to use a collection
mechanism that tracks the movement
of the Sun across the sky. Solar furnaces and solar energy plants take
this type of approach, using large
mirrored reflectors. However, such
tracking systems are mechanical
in nature, with moving parts. They
require energy to operate and often
use sophisticated and relatively expensive electronics to maintain their
tracking position.
For these reasons, moving collectors are not frequently used in hybrid
lighting systems. Instead, efficiency is
traded off for reliability and cost-effectiveness.
Solar collectors for lighting systems
are not required to have optical quality reflective surfaces. Instead, coated
plastic collectors (concentrators) can
be cast, moulded or extruded into the
appropriate shapes. In addition, a system can use three such collectors in a
passive arrangement – one facing east,
one west and the other north (in the
southern hemisphere), so that morning, afternoon and midday sunshine
can be caught. Although much less
efficient than an active tracking system, the system can be easily scaled
up in size to more than compensate
for the reduced efficiency.
However, some systems do use
tracking reflectors. One such system
is claimed to provide enough interior
light on sunny days to make electric
lighting unnecessary from one hour
after sunrise to one hour before sunset.
Artificial light sources
If artificial light is to be used with
daylight, its colour temperature
should be about the same. However, achieving this is very difficult,
especially if light sources with high
efficacies are to be used. As one commentator put it, if we are to exactly duplicate daylight, the “artificial lights
would have to look like a 5750K black
Hybrid lighting systems use rooftop
collectors and light transmission
pipes to gather and distribute natural
light within a building. Either fixed
or tracking collectors can be used,
although the lower cost and greater
reliability of fixed collectors makes
them the preferred option for most
applications. (Photo: ORNL).
body shining through several miles
of atmosphere made up mostly of
nitrogen, oxygen, and water vapour!”
That said, the human eye quickly
adapts to light sources of varying
colours (and, of course, the colour
temperature of daylight varies during
the course of the day, anyway). As a
result, “daylight white” fluorescent
lamps are usually used in hybrid
systems.
Transport and distribution
Hybrid lighting systems use light
pipes to “transport” the natural light
from the roof to various rooms. Often
called “hollow light guides”, they
must be highly efficient in order
for hybrid lighting systems to work
effectively.
VN Chakolev in Russia and Professor William Wheeler in the US
invented hollow light guides in the
1880s. They were motivated by the
introduction of the electric carbon
arc lamp, a light source too powerful for normal indoor illumination.
However, if the light from the arc
lamp could be piped to each room,
it could become a practical means of
domestic illumination.
Unfortunately, the mirrors used
in these early light guides were both
expensive and inefficient. The metalon-glass mirrors had an absorption of
more than 10%, a figure which becomes significant when it is realised
that a great many reflections can occur
within a light guide.
Subsequently, in 1946, Henry Pear
son of the Rohm and Haas Company
AUGUST 1999 83
Either light-pipes or direct radiation can be used to distribute any artificial light
that’s being used to complement natural lighting. New developments in artificial
lighting (for example, microwave sulphur lamps) also lend themselves to lightpipe technology. (Photo: ORNL).
used acrylic rods and sheets to transmit light from one place to another.
Unlike metallic mirrors, this material
guides light with high efficiency because it employs a technique called
“total internal reflection” (TIR). This
means that very little light is lost
through the walls as the light travels
along the guide.
Another important development
was the advent of low-cost optical
surfaces in the mid-1960s, made
possible by the mass-production of
optically-treated polymeric films.
Vacuum metallisation of polyester
film can produce a flexible mirror
84 Silicon Chip
that is as specular as an ordinary glass
mirror but costs far less. These films
were commonly used in light guides
installed in the former USSR and
similar films are now employed in
many current commercial light pipes.
In 1978, Lorne Whitehead at the
University of British Columbia developed the prism light guide. This
also employs the total internal reflection technique, with the guide’s
transparent walls containing precise
longitudinal rightangle prisms. Light
rays incident on the inside surface of
the wall undergo total internal reflection at the prismatic exterior surface,
re-entering the central airspace or
gel filling to continue propagating
along the pipe. While commercially
successful, these light guides were expensive due to the precision required
for the prisms along the walls.
Most recently, researchers at the
3M company have developed a technology known as “micro-replication”.
This allows the large-scale manufacture of micro-prismatic structures
with surface irregularities substantially smaller than the wavelength
of light. The 0.5mm thick prismatic
polymethylmethacrylate film developed by 3M is now widely used in
light guides.
Incidentally, the use of glass or
silica optical fibre is generally not
considered viable for this application.
That’s because of the high expense
of the fibres, which would have to
be quite large to carry the luminous
flux required for conventional illumination.
Light guides are capable of transporting large amounts of light. The
bright sunlight from one square metre
can be focused into and transported
by a guide with a cross-sectional are
of just 1cm2. This guide, in turn, can
feed a number of smaller guides, each
about the size and weight of electrical
wiring.
However, even the best currently-available hollow light guides still
require improvement if multi-storey
buildings are to be effectively illuminated using light collected at roof
level. Today’s light guides have a loss
of 1% in 30cm and researchers are
currently trying to reduce that by a
factor of 10, to 1% in three metres. Using current technology, the maximum
effective length of a hollow light guide
carrying sunlight is about 30 metres.
Some hollow light guides are used
to distribute as well as transport the
light. In these designs, the light is
allowed to “leak” at a controlled rate
as it travels along the guide. This
is achieved by lining the pipe with
longitudinal strips of “extractor film”.
In operation, the extractor film
changes the incidence of the light so
that total internal reflection no longer
occurs. If necessary, a uniform light
distribution can be achieved along the
entire length of the guide by varying
the widths of the extractor strips.
Incidentally, hollow light guides
are also a very important part of microwave sulphur lamps, a lighting
Oak Ridge National
Laboratory’s Mike
Cates with a light
pipe. The efficiency
of light pipes needs
further improvement
if their use is to
become widespread,
especially in multistorey buildings.
(Photo: ORNL).
technology that’s currently undergoing major research and development.
Control systems
Electronic systems are used to
automatically control the electric
lighting part of a hybrid installation
(the natural lighting always works at
full power). These systems use light
level sensors and control circuits
with adjustable hysteresis to prevent
the lights from rapidly cycling on
and off due to small or momentary
changes in ambient light conditions.
This can easily occur when clouds
pass overhead, for example.
Some controllers rely on one or
more strategically placed sensors to
operate all the lights within a room,
while others use one sensor per fixture. The latter system is the most
energy efficient. That’s because it only
turns on those lights that are necessary to compensate for natural light
variations (eg, through windows) as
the Sun moves across the sky.
Hybrid lighting systems
In the US, hybrid lighting systems
are now being installed in new buildings. One recent example is the Durant Middle School in Raleigh, North
Carolina. However, instead of using
hollow light guides, this single-sto-
rey building uses special skylights
and carefully orientated windows to
provide daylight illumination of the
classrooms.
The school is built on an east-west
axis and has north and south-facing
solar roof collectors of various sizes.
The collected sunlight is diffused by a
series of baffles within each collector,
so that good-quality natural light is
spread evenly throughout the classrooms. The windows on the north and
south walls allow further light from
the outside to illuminate the rooms.
The electric lighting controls are
equipped with motion and light level
sensors and operate automatically.
Despite adding to the building
cost, the economic benefits of the
new system are impressive. The advanced hybrid lighting system itself
cost around $US230,000, much of this
spent designing and testing the new
systems. This was offset by a reduction of $US115,000 in the cost of the
cooling system (it no longer had to
remove much of the heat generated
by artificial lighting), leaving a net
additional cost of $US115,000.
This extra outlay was recouped in
less than a year by the energy saving,
estimated at around $US165,000 per
annum!
Another recent hybrid lighting
system can be found in the Bay de
Noc Community College in Michigan,
USA. This system uses 14 x 330mm
diameter light pipes in its Extension
Center Building. The sunlight is collected through clear roof-mounted
acrylic domes and is reflected down
mirrored tubes to ceiling-mounted
diffusers.
The light pipes were installed as
part of a complete lighting refit in the
building, which also involved replacing the existing standard fluorescent
luminaires with more energy-efficient
T8 fluorescent bulbs and electronic
ballasts. This new electric lighting
system, on its own, reduced annual
power consumption by 29%, with
consumption subsequently dropping
a further 15% after the installation of
the light pipes.
The efficiency of the system could
be further improved by fitting an
automatic control system to the
fluorescent lights. At present, the
electric lighting is switched off manually when sufficient natural light is
available.
Future goals
The US Government is preparing
to pour a great deal of money into
making hybrid lighting a commercial
success. For example, the Department of Energy’s Oak Ridge National
Laboratory has developed a Hybrid
Lighting Partnership with 10 private
companies which are expected to
contribute some $US5 million for
research. A further $US3-6 million
is expected from the Department of
Energy.
The aims of the Hybrid Lighting
Partnership are as follows:
(1). Successfully deploy a working,
first generation proof-of-concept
hybrid lighting system by the end of
financial year 2001;
(2). Begin introducing commercial
hybrid lighting systems by 2003;
(3). Create a multi-billion dollar industry by 2010;
(4). Reduce electric light energy consumption by about 50 billion kWh
in the year 2020 and save electricity
users $US7 billion annually by 2020.
Although the concept of hybrid
lighting is quite simple, it has the
potential to drastically reduce the
amount of electrical energy used for
lighting! And that can only be good
news for consumers and for the enSC
vironment.
AUGUST 1999 85
PRODUCT SHOWCASE
What’s in a (Jiffy) box?
Everyone knows the ubiquitous Jiffy
Box – after all, they’ve been around for
more than twenty years. And according to Jaycar’s Gary Johnston, that was
half the problem.
“We wanted a modern Jiffy box that
was much more than just a box,” he
said. “Customers were demanding
something that was more user-friendly
but there wasn’t anything available
from our suppliers.”
“So Jaycar designed our own.”
Made from ABS plastic, features
include brand new tooling with pilot
holes (on a 5mm grid) for drilling the
lid, cut-out guidelines on a 10mm
grid, snap-in PC board mounting,
rubber screw hole covers (which
double as feet when the box is used
upside-down) and an overall more
pleasing box.
There are four sizes available in two
colours (black and grey) but custom
colours are available for manufacturers
and others requiring large quantities.
Company names and/or logos can
also be included for bulk quantities
Hioki digital insulation tester with bargraph
The Hioki 3453 digital insulation
tester provides a unique comparator
function with visual and audible
alarms to indicate faults. It provides
testing voltages of 125, 250, 500 and
1000V with respective insulation
scales of 40MΩ, 2000MΩ (250/500V)
and 4000MΩ.
In addition to insulation, the 3453
measures low resistance to 400Ω,
continuity to 30Ω (with beeper) and
AC voltage (0-600V).
The digital display provides both
a moving average digital readout as
well as a bargraph display, combining
the best features of digital and analog
instruments.
For more information, contact
Nilsen Technologies, 150 Oxford St
Collingwood Vic 3066. Phone 1800
623 350; fax 1800 067 263
1/4-inch colour bullet video camera
Intended for surveillance, inspection and machine vision, this compact, water resistant colour video
camera is just 22mm in diameter
and 74mm long. While suitable for
most surveillance purposes, when
fitted with an optional 25mm lens
it can deliver full screen “head and
shoulders” or “cash drawer” images
86 Silicon Chip
from four metres.
Retail price is from $193.00. Contact Allthings Sales & Service. Phone
(08) 9349 9413; fax (08) 9344 5905.
and the boxes are easily silk-screened.
The new Jiffy boxes are priced about
the same as the older style boxes and
are already available in Jaycar Electronics stores.
Manufacturers and others requiring
bulk pricing information should contact Jaycar Electronics head office on
(02) 9743 5222; fax (02) 9743 2066.
Step-down charge
pump delivers 100mA
The industry’s first regulated stepdown charge pumps in 8-lead MSOP
packages have been released by Linear
Technology. The LTC1503-1.8 and LTC1503-2 deliver 100mA of output current
at 1.8V or 2V from a 2.4V to 6V input.
The LTC1503 is up to 40% more efficient than a linear regulator and requires
just four capacitors and no inductor. It’s
ideal for a broad range of space-restricted
devices such as cell phones, handheld
computers and instruments.
For more information contact REC
Electronics, Unit 1, 38 South St, Rydalmere NSW 2116. Phone (02) 9638 1888;
fax (02) 9638 1798. Website is at http://
www.rec.com.au
UTP, STP, coaxial & modular cable tester
Altronics Distributors have
available a cable tester specifically
intended to take the guesswork out
of LAN installation and troubleshooting.
The D3010 LANtest can check
continuity, open, shorted and cross
wired cables and suits 10Base-T/2,
RJ45/11, 258A, TIA 568A/568B and
Token Ring systems.
The tester consists of a main and
remote unit – one plugging in to
each end of a cable under test. The
checks can be done manually or automatically in sequence. For testing
patch leads, both ends of the cable
can be plugged into the main unit.
The main unit measures 62 x
105 x 25mm and the remote 62 x
25 x 30mm. Both are powered by
a 9V battery (not supplied) in the
Subwoofer amp has
infrared control
Jaycar Electronics have released
a new amplifier to augment their
sub-woofer range. Rated at 200W RMS
into 4 ohms, the amplifier includes
infrared remote control for volume
and crossover frequency, high and
low level inputs, speaker output with
built-in crossover network, filtered
line output and auto on/off. It has
a recommended retail price of $399
(Cat. No. AA-0505.)
Jaycar have also put this amplifier
into an attractive subwoofer package,
consisting of the amp, a subwoofer
cabinet kit and a 12-inch carbon-fibre
cone speaker, all selling for $669.00.
For more information contact any
Jaycar Electronics store or call the
head office on (02) 9743 5222; fax (02)
9743 2066. Jaycar’s web site is located
at www.jaycar.com.au
main unit. Three adaptor cables
and a BNC male/male adaptor are
included, as is a plastic carry case
which houses all components (but
not, unfortunately, the instruction
booklet).
For more information, contact
Altronic Distributors in Perth (08
9328 2199), Altronics resellers
around Australia or refer to page
112 of the 1999/2000 Altronics
Catalog.
Universal Programmer
Nucleus Computer Services,
the new Australian distributors of
System General programmers, have
introduced the ALLWriter, a universal programmer said to suit the vast
majority of engineering applications
with universal converters for virtually all devices in the one package.
Featuring an embedded CPU
and 32MB RAM, the device supports EPROMs, EEPROMs, Flash
EPROMS. PALs, GALs, PELL,
PALCE, CPLD, EPLD and EEPLD
plus a variety of other devices
including more than 200 microcon-trollers from Motorola, Intel,
Philips, Dallas, Microchip PIC,
Atmel, WSI and more.
The ALLWriter has a Windows
interface and software updates are
free. For further information, contact
Nucleus Computer Services, Phone
(03) 9569 1388; fax (03) 9569 1540.
Email nucleus<at>nucleuscom-puter.
com.au; http://www.nucleus-computer.com.au
Valve tester is
PC-based
Australian Audio Consultants, the
sole Australian distributor for Audio-matica of Florence, Italy, have released a PC-based vacuum tube curve
tracer designed to assist in tube selection and manufacturing processes.
Called “Sofia”, the flexible hardware
performs measurements on diodes,
triodes, tetrodes and pentodes. Parameters such as transconductance, plate
resistance and amplification factor are
shown in real time .
Information on tested tubes can
be stored and retrieved at any time.
Tetrodes and pentodes can be characterized in ultra-linear configuration.
Use of an external PC as the main
controller makes future upgrades easy.
The RS-232 link between Sofia and the
PC enhances compatibility and allows
use of laptops.
For further information contact Australian Audio Consultants by phone/
fax on 08 8528 2201, email aac<at>rbe.
net.au or PO Box 11, Stock-port SA
5410. Audiomatica’s website is at
http://www.mclink.it/com/audiomatSC
ica/products.htm
AUDIO MODULES
broadcast quality
Manufactured in Australia
Harbuch Electronics Pty Ltd
9/40 Leighton Pl. HORNSBY 2077
Ph (02) 9476-5854 Fx (02) 9476-3231
AUGUST 1999 87
Silicon Chip
Back Issues
September 1988: Hands-Free Speakerphone; Electronic Fish Bite
Detector; High Performance AC Millivoltmeter, Pt.2; Build The
Vader Voice.
April 1989: Auxiliary Brake Light Flasher; What You Need to Know
About Capacitors; 32-Band Graphic Equaliser, Pt.2; The Story Of
Amtrak Passenger Services.
May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For
Your PC; Simple Stub Filter For Suppressing TV Interference; The
Burlington Northern Railroad.
July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers;
Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics.
September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024
and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series
20-Band Stereo Equaliser, Pt.2.
October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet
Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2;
A Look At Australian Monorails.
November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY
& Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable
AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The
Pilbara Iron Ore Railways.
January 1990: High Quality Sine/Square Oscillator; Service Tips For
Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit;
Designing UHF Transmitter Stages.
February 1990: A 16-Channel Mixing Desk; Build A High Quality
Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire
Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2.
March 1990: Delay Unit For Automatic Antennas; Workout Timer For
Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906
SLA Battery Charger IC; The Australian VFT Project.
April 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch
(VOX) With Delayed Audio; 16-Channel Mixing Desk, Pt.3; Active CW
Filter; Servicing Your Microwave Oven.
June 1990: Multi-Sector Home Burglar Alarm; Build A Low-Noise
Universal Stereo Preamplifier; Load Protector For Power Supplies;
Speed Alarm For Your Car.
July 1990: Digital Sine/Square Generator, Pt.1 (covers 0-500kHz);
Burglar Alarm Keypad & Combination Lock; Build A Simple Electronic Die; A Low-Cost Dual Power Supply; Inside A Coal Burning
Power Station.
August 1990: High Stability UHF Remote Transmitter; Universal
Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic
Cricket; Digital Sine/Square Generator, Pt.2.
September 1990: A Low-Cost 3-Digit Counter Module; Build A Simple
Shortwave Converter For The 2-Metre Band; The Bose Lifestyle Music
System (Review); The Care & Feeding Of Nicad Battery Packs (Getting
The Most From Nicad Batteries).
October 1990: The Dangers of PCBs; Low-Cost Siren For Burglar
Alarms; Dimming Controls For The Discolight; Surfsound Simulator;
DC Offset For DMMs; NE602 Converter Circuits.
March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch
For Car Radiator Fans; Coping With Damaged Computer Directories; Guide Valve Substitution In Vintage Radios.
April 1992: IR Remote Control For Model Railroads; Differential
Input Buffer For CROs; Understanding Computer Memory; Aligning
Vintage Radio Receivers, Pt.1.
May 1992: Build A Telephone Intercom; Electronic Doorbell;
Battery Eliminator For Personal Players; Infrared Remote Control
For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2.
November 1990: How To Connect Two TV Sets To One VCR;
Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To
9V DC Converter; Introduction To Digital Electronics; Build A
Simple 6-Metre Amateur Band Transmitter.
December 1990: The CD Green Pen Controversy; 100W DC-DC
Converter For Car Amplifiers; Wiper Pulser For Rear Windows;
4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre
Amateur Transmitter; Index To Volume 3.
January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun
With The Fruit Machine; Two-Tone Alarm Module; LCD Readout
For The Capacitance Meter; How Quartz Crystals Work; The
Dangers of Servicing Microwave Ovens.
February 1991: Synthesised Stereo AM Tuner, Pt.1; Three
Low-Cost Inverters For Fluorescent Lights; Low-Cost Sinewave
Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design
Amplifier Output Stages.
March 1991: Remote Controller For Garage Doors, Pt.1;
Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner,
Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal
Wideband RF Preamplifier For Amateur Radio & TV.
April 1991: Steam Sound Simulator For Model Railroads;
Remote Controller For Garage Doors, Pt.2; Simple 12/24V
Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical
Approach To Amplifier Design, Pt.2.
June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher
For Camcorders & VCRs; IR Remote Control For Model Railroads,
Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives.
August 1992: Automatic SLA Battery Charger; Miniature 1.5V To
9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers;
Troubleshooting Vintage Radio Receivers; The MIDI Interface
Explained.
October 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal
Stereos; A Regulated Lead-Acid Battery Charger.
January 1993: Flea-Power AM Radio Transmitter; High Intensity
LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sinewave
Inverter, Pt.4; Speed Controller For Electric Models, Pt.3.
February 1993: Three Projects For Model Railroads; Low Fuel
Indicator For Cars; Audio Level/VU Meter (LED Readout); An Electronic Cockroach; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.5.
March 1993: Solar Charger For 12V Batteries; Alarm-Triggered
Security Camera; Reaction Trainer; Audio Mixer for Camcorders;
A 24-Hour Sidereal Clock For Astronomers.
April 1993: Solar-Powered Electric Fence; Audio Power Meter;
Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up.
May 1993: Nicad Cell Discharger; Build The Woofer Stopper;
Alphanumeric LCD Demonstration Board; The Story of Aluminium.
May 1991: 13.5V 25A Power Supply For Transceivers; Stereo
Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1.
June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer
Stopper; Digital Voltmeter For Cars; Build A Windows-Based
Logic Analyser.
June 1991: A Corner Reflector Antenna For UHF TV; Build A
4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For
Transceivers, Pt.2; Active Filter For CW Reception; Tuning In
To Satellite TV, Pt.1.
July 1993: Single Chip Message Recorder; Light Beam Relay
Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator;
Windows-Based Logic Analyser, Pt.2; Antenna Tuners – Why
They Are Useful.
July 1991: Loudspeaker Protector For Stereo Amplifiers;
4-Channel Lighting Desk, Pt.2; How To Install Multiple TV
Outlets, Pt.2; Tuning In To Satellite TV, Pt.2.
August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light
Array; Microprocessor-Based Sidereal Clock; Southern Cross Z80Based Computer; A Look At Satellites & Their Orbits.
September 1991: Digital Altimeter For Gliders & Ultralights;
Ultrasonic Switch For Mains Appliances; The Basics Of A/D
& D/A Conversion; Plotting The Course Of Thunderstorms.
September 1993: Automatic Nicad Battery Charger/Discharger;
Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit
Transistor Tester; +5V to ±15V DC Converter; Remote-Controlled
Cockroach.
October 1991: Build A Talking Voltmeter For Your PC, Pt.1;
SteamSound Simulator For Model Railways Mk.II; Magnetic
Field Strength Meter; Digital Altimeter For Gliders, Pt.2; Military
Applications Of R/C Aircraft.
November 1991: Build A Colour TV Pattern Generator, Pt.1;
A Junkbox 2-Valve Receiver; Flashing Alarm Light For Cars;
Digital Altimeter For Gliders, Pt.3; Build A Talking Voltmeter
For Your PC, Pt.2; Build a Turnstile Antenna For Weather
Satellite Reception.
December 1991: TV Transmitter For VCRs With UHF Modulators;
Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2;
Index To Volume 4.
January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A
Power Supply, Pt.1; Baby Room Monitor/FM Transmitter;
Experiments For Your Games Card.
October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless
Microphone For Musicians; Stereo Preamplifier With IR Remote
Control, Pt.2; Electronic Engine Management, Pt.1.
November 1993: High Efficiency Inverter For Fluorescent Tubes;
Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound
Generator; Engine Management, Pt.2; Experiments For Games
Cards.
December 1993: Remote Controller For Garage Doors; Build A
LED Stroboscope; Build A 25W Audio Amplifier Module; A 1-Chip
Melody Generator; Engine Management, Pt.3; Index To Volume 6.
January 1994: 3A 40V Adjustable Power Supply; Switching
Regulator For Solar Panels; Printer Status Indicator; Mini Drill
Speed Controller; Stepper Motor Controller; Active Filter Design;
Engine Management, Pt.4.
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88 Silicon Chip
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February 1994: Build A 90-Second Message Recorder; 12-240VAC
200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power
Supply; Engine Management, Pt.5; Airbags In Cars – A Look At
How They Work.
February 1996: Three Remote Controls To Build; Woofer Stopper
Mk.2; 10-Minute Kill Switch For Smoke Detectors; Basic Logic
Trainer; Surround Sound Mixer & Decoder, Pt.2; Use your PC
As A Reaction Timer.
March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio
Amplifier Module; Level Crossing Detector For Model Railways;
Voice Activated Switch For FM Microphones; Simple LED Chaser;
Engine Management, Pt.6.
March 1996: Programmable Electronic Ignition System; Zener
Diode Tester For DMMs; Automatic Level Control For PA Systems;
20ms Delay For Surround Sound Decoders; Multi-Channel Radio
Control Transmitter; Pt.2; Cathode Ray Oscilloscopes, Pt.1.
April 1994: Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Universal Stereo Preamplifier;
Digital Water Tank Gauge; Engine Management, Pt.7.
April 1996: Cheap Battery Refills For Mobile Telephones; 125W
Audio Power Amplifier Module; Knock Indicator For Leaded Petrol
Engines; Multi-Channel Radio Control Transmitter; Pt.3; Cathode
Ray Oscilloscopes, Pt.2.
May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal
Locator; Multi-Channel Infrared Remote Control; Dual Electronic
Dice; Simple Servo Driver Circuits; Engine Management, Pt.8.
June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level
Alarm For Your Car; 80-Metre AM/CW Transmitter For Amateurs;
Converting Phono Inputs To Line Inputs; PC-Based Nicad Battery
Monitor; Engine Management, Pt.9.
May 1996: Upgrading The CPU In Your PC; High Voltage Insulation
Tester; Knightrider Bi-Directional LED Chaser; Simple Duplex Intercom Using Fibre Optic Cable; Cathode Ray Oscilloscopes, Pt.3.
June 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo
Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester
For Your DMM; Automatic 10A Battery Charger.
July 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp
2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn
Simulator; Portable 6V SLA Battery Charger; Electronic Engine
Management, Pt.10.
July 1996: Installing a Dual Boot Windows System On Your PC;
Build A VGA Digital Oscilloscope, Pt.1; Remote Control Extender
For VCRs; 2A SLA Battery Charger; 3-Band Parametric Equaliser;
Single Channel 8-bit Data Logger.
August 1994: High-Power Dimmer For Incandescent Lights;
Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For
FM Microphones, Pt.1; Nicad Zapper; Engine Management, Pt.11.
August 1996: Electronics on the Internet; Customising the
Windows Desktop; Introduction to IGBTs; Electronic Starter For
Fluorescent Lamps; VGA Oscilloscope, Pt.2; 350W Amplifier
Module; Masthead Amplifier For TV & FM; Cathode Ray Oscilloscopes, Pt.4.
September 1994: Automatic Discharger For Nicad Battery Packs;
MiniVox Voice Operated Relay; Image Intensified Night Viewer;
AM Radio For Weather Beacons; Dual Diversity Tuner For FM
Microphones, Pt.2; Engine Management, Pt.12.
October 1994: How Dolby Surround Sound Works; Dual Rail Variable
Power Supply; Build A Talking Headlight Reminder; Electronic Ballast
For Fluorescent Lights; Build A Temperature Controlled Soldering
Station; Electronic Engine Management, Pt.13.
November 1994: Dry Cell Battery Rejuvenator; Novel Alphanumeric
Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Discharger (See May 1993); How To Plot Patterns Direct to PC Boards.
September 1996: VGA Oscilloscope, Pt.3; IR Stereo Headphone
Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur
Radio Receiver; Feedback On Prog rammable Ignition (see March
1996); Cathode Ray Oscilloscopes, Pt.5.
October 1996: Send Video Signals Over Twisted Pair Cable;
Power Control With A Light Dimmer; 600W DC-DC Converter
For Car Hifi Systems, Pt.1; IR Stereo Headphone Link, Pt.2;
Build A Multi-Media Sound System, Pt.1; Multi-Channel Radio
Control Transmitter, Pt.8.
December 1994: Dolby Pro-Logic Surround Sound Decoder,
Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion
Sinewave Oscillator; Clifford – A Pesky Electronic Cricket; Remote
Control System for Models, Pt.1; Index to Vol.7.
November 1996: Adding A Parallel Port To Your Computer;
8-Channel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light
Inverter; How To Repair Domestic Light Dimmers; Build A
Multi-Media Sound System, Pt.2; 600W DC-DC Converter For
Car Hifi Systems, Pt.2.
January 1995: Sun Tracker For Solar Panels; Battery Saver For
Torches; Dolby Pro-Logic Surround Sound Decoder, Pt.2; Dual
Channel UHF Remote Control; Stereo Microphone Preamplifier.
December 1996: CD Recorders – The Next Add-On For Your PC;
Active Filter Cleans Up CW Reception; Fast Clock For Railway
Modellers; Laser Pistol & Electronic Target; Build A Sound Level
Meter; 8-Channel Stereo Mixer, Pt.2; Index To Volume 9.
February 1995: 50-Watt/Channel Stereo Amplifier Module; Digital
Effects Unit For Musicians; 6-Channel Thermometer With LCD
Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil Change
Timer For Cars; Remote Control System For Models, Pt.2.
March 1995: 50 Watt Per Channel Stereo Amplifier, Pt.1; Subcarrier
Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers,
Pt.2; IR Illuminator For CCD Cameras; Remote Control System For
Models, Pt.3; Simple CW Filter.
April 1995: FM Radio Trainer, Pt.1; Photographic Timer For Dark
rooms; Balanced Microphone Preamp. & Line Filter; 50W/Channel
Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers,
Pt.3; 8-Channel Decoder For Radio Remote Control.
January 1997: How To Network Your PC; Control Panel For
Multiple Smoke Alarms, Pt.1; Build A Pink Noise Source (For
Sound Level Meter Calibration); Computer Controlled Dual Power
Supply, Pt.1; Digi-Temp Monitors Eight Temperatures.
February 1997: Cathode Ray Oscilloscopes, Pt.6; PC-Controlled
Moving Message Display; Computer Controlled Dual Power
Supply, Pt.2; Alert-A-Phone Loud Sounding Alarm; Control Panel
For Multiple Smoke Alarms, Pt.2.
December 1997: A Heart Transplant For An Aging Computer;
Build A Speed Alarm For Your Car; Two-Axis Robot With Gripper;
Loudness Control For Car Hifi Systems; Stepper Motor Driver
With Onboard Buffer; Power Supply For Stepper Motor Cards;
Understanding Electric Lighting Pt.2; Index To Volume 10.
January 1998: Build Your Own 4-Channel Lightshow, Pt.1 (runs off
12VDC or 12VAC); Command Control System For Model Railways,
Pt.1; Pan Controller For CCD Cameras; Build A One Or Two-Lamp
Flasher; Understanding Electric Lighting, Pt.3.
February 1998: Hot Web Sites For Surplus Bits; Multi-Purpose Fast
Battery Charger, Pt.1; Telephone Exchange Simulator For Testing;
Command Control System For Model Railways, Pt.2; Demonstration
Board For Liquid Crystal Displays; Build Your Own 4-Channel Lightshow, Pt.2; Understanding Electric Lighting, Pt.4.
April 1998: Automatic Garage Door Opener, Pt.1; 40V 8A Adjustable
Power Supply, Pt.1; PC-Controlled 0-30kHz Sinewave Generator;
Build A Laser Light Show; Understanding Electric Lighting; Pt.6;
Jet Engines In Model Aircraft.
May 1998: Troubleshooting Your PC, Pt.1; Build A 3-LED Logic Probe;
Automatic Garage Door Opener, Pt.2; Command Control For Model
Railways, Pt.4; 40V 8A Adjustable Power Supply, Pt.2.
June 1998: Troubleshooting Your PC, Pt.2; Understanding Electric
Lighting, Pt.7; Universal High Energy Ignition System; The Roadies’
Friend Cable Tester; Universal Stepper Motor Controller; Command
Control For Model Railways, Pt.5.
July 1998: Troubleshooting Your PC, Pt.3 (Installing A Modem
And Sorting Out Any Problems); Build A Heat Controller; 15-Watt
Class-A Audio Amplifier Module; Simple Charger For 6V & 12V
SLA Batteries; Automatic Semiconductor Analyser; Understanding
Electric Lighting, Pt.8.
August 1998: Troubleshooting Your PC, Pt.4 (Adding Extra Memory
To Your PC); Build The Opus One Loudspeaker System; Simple I/O
Card With Automatic Data Logging; Build A Beat Triggered Strobe;
A 15-Watt Per Channel Class-A Stereo Amplifier.
September 1998: Troubleshooting Your PC, Pt.5 (Software Problems
& DOS Games); A Blocked Air-Filter Alarm; A Waa-Waa Pedal For
Your Guitar; Build A Plasma Display Or Jacob’s Ladder; Gear Change
Indicator For Cars; Capacity Indicator For Rechargeable Batteries.
October 1998: CPU Upgrades & Overclocking; Lab Quality AC Millivoltmeter, Pt.1; PC-Controlled Stress-O-Meter; Versatile Electronic
Guitar Limiter; 12V Trickle Charger For Float Conditions; Adding An
External Battery Pack To Your Flashgun.
November 1998: Silicon Chip On The World Wide Web; The Christmas
Star (Microprocessor-Controlled Christmas Decoration); A Turbo
Timer For Cars; Build Your Own Poker Machine, Pt.1; FM Transmitter
For Musicians; Lab Quality AC Millivoltmeter, Pt.2; Beyond The Basic
Network (Setting Up A LAN Using TCP/IP); Understanding Electric
Lighting, Pt.9; Improving AM Radio Reception, Pt.1.
December 1998: Protect Your Car With The Engine Immobiliser Mk.2;
Thermocouple Adaptor For DMMs; A Regulated 12V DC Plugpack;
Build Your Own Poker Machine, Pt.2; GM’s Advanced Technology
Vehicles; Improving AM Radio Reception, Pt.2; Mixer Module For
F3B Glider Operations.
March 1997: Driving A Computer By Remote Control; Plastic
Power PA Amplifier (175W); Signalling & Lighting For Model Railways; Build A Jumbo LED Clock; Cathode Ray Oscilloscopes, Pt.7.
January 1999: The Y2K Bug & A Few Other Worries; High-Voltage
Megohm Tester; Getting Going With BASIC Stamp; LED Bargraph
Ammeter For Cars; Keypad Engine Immobiliser; Improving AM Radio
Reception, Pt.3; Electric Lighting, Pt.10
May 1995: What To Do When the Battery On Your PC’s Motherboard
Goes Flat; Build A Guitar Headphone Amplifier; FM Radio Trainer,
Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder
For Radio Remote Control; Introduction to Satellite TV.
April 1997: Avoiding Win95 Hassles With Motherboard Upgrades;
Simple Timer With No ICs; Digital Voltmeter For Cars; Loudspeaker
Protector For Stereo Amplifiers; Model Train Controller; A Look At
Signal Tracing; Pt.1; Cathode Ray Oscilloscopes, Pt.8.
June 1995: Build A Satellite TV Receiver; Train Detector For Model
Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security
System; Multi-Channel Radio Control Transmitter For Models, Pt.1;
Build A $30 Digital Multimeter.
May 1997: Teletext Decoder For PCs; Build An NTSC-PAL
Converter; Neon Tube Modulator For Light Systems; Traffic
Lights For A Model Intersection; The Spacewriter – It Writes
Messages In Thin Air; A Look At Signal Tracing; Pt.2; Cathode
Ray Oscilloscopes, Pt.9.
February 1999: Installing A Computer Network (Network Types, Hubs,
Switches & Routers); Making Front Panels For Your Projects; Low
Distortion Audio Signal Generator, Pt.1; Command Control Decoder
For Model Railways; Build A Digital Capacitance Meter; Remote
Control Tester; Electric Lighting, Pt.11.
July 1995: Electric Fence Controller; How To Run Two Trains On
A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV
Ground Station; Build A Reliable Door Minder.
August 1995: Fuel Injector Monitor For Cars; Gain Controlled
Microphone Preamp; Audio Lab PC-Controlled Test Instrument,
Pt.1; Mighty-Mite Powered Loudspeaker; How To Identify IDE Hard
Disc Drive Parameters.
September 1995: Railpower Mk.2 Walkaround Throttle For Model
Railways, Pt.1; Keypad Combination Lock; The Vader Voice; Jacob’s
Ladder Display; Audio Lab PC-Controlled Test Instrument, Pt.2.
October 1995: Geiger Counter; 3-Way Bass Reflex Loudspeaker
System; Railpower Mk.2 Walkaround Throttle For Model Railways,
Pt.2; Fast Charger For Nicad Batteries; Digital Speedometer & Fuel
Gauge For Cars, Pt.1.
November 1995: Mixture Display For Fuel Injected Cars; CB Trans
verter For The 80M Amateur Band, Pt.1; PIR Movement Detector;
Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.1; Digital
Speedometer & Fuel Gauge For Cars, Pt.2.
December 1995: Engine Immobiliser; 5-Band Equaliser; CB Transverter For The 80M Amateur Band, Pt.2; Subwoofer Controller; Dolby
Pro Logic Surround Sound Decoder Mk.2, Pt.2; Knock Sensing In
Cars; Index To Volume 8.
January 1996: Surround Sound Mixer & Decoder, Pt.1; Magnetic
Card Reader; Build An Automatic Sprinkler Controller; IR Remote
Control For The Railpower Mk.2; Recharging Nicad Batteries For
Long Life.
June 1997: Tuning Up Your Hard Disc Drive; PC-Controlled
Thermometer/Thermostat; Colour TV Pattern Generator, Pt.1;
Build An Audio/RF Signal Tracer; High-Current Speed Controller
For 12V/24V Motors; Manual Control Circuit For A Stepper
Motor; Fail-Safe Module For The Throttle Servo; Cathode Ray
Oscilloscopes, Pt.10.
July 1997: Infrared Remote Volume Control; A Flexible Interface
Card For PCs; Points Controller For Model Railways; Simple
Square/Triangle Waveform Generator; Colour TV Pattern Generator, Pt.2; An In-Line Mixer For Radio Control Receivers; How
Holden’s Electronic Control Unit works, Pt.1.
August 1997: The Bass Barrel Subwoofer; 500 Watt Audio Power
Amplifier Module; A TENs Unit For Pain Relief; Addressable PC
Card For Stepper Motor Control; Remote Controlled Gates For
Your Home; How Holden’s Electronic Control Unit Works, Pt.2.
September 1997: Multi-Spark Capacitor Discharge Ignition; 500W
Audio Power Amplifier, Pt.2; A Video Security System For Your
Home; PC Card For Controlling Two Stepper Motors; HiFi On A
Budget; Win95, MSDOS.SYS & The Registry.
October 1997: Build A 5-Digit Tachometer; Add Central Locking
To Your Car; PC-Controlled 6-Channel Voltmeter; 500W Audio
Power Amplifier, Pt.3; Customising The Windows 95 Start Menu.
November 1997: Heavy Duty 10A 240VAC Motor Speed Controller;
Easy-To-Use Cable & Wiring Tester; Build A Musical Doorbell;
Relocating Your CD-ROM Drive; Replacing Foam Speaker Surrounds; Understanding Electric Lighting Pt.1.
March 1999: Getting Started With Linux; Pt.1; Build A Digital
Anemometer; 3-Channel Current Monitor With Data Logging;
Simple DIY PIC Programmer; Easy-To-Build Audio Compressor;
Low Distortion Audio Signal Generator, Pt.2; Electric Lighting, Pt.12.
April 1999: Getting Started With Linux; Pt.2; High-Power Electric
Fence Controller; Bass Cube Subwoofer; Programmable Thermostat/
Thermometer; Build An Infrared Sentry; Rev Limiter For Cars; Electric
Lighting, Pt.13; Autopilots For Radio-Controlled Model Aircraft.
May 1999: The Line Dancer Robot; An X-Y Table With Stepper Motor
Control, Pt.1; Three Electric Fence Testers; Heart Of LEDs; Build A
Carbon Monoxide Alarm; Getting Started With Linux; Pt.3.
June 1999: FM Radio Tuner Card For PCs; X-Y Table With Stepper
Motor Control, Pt.2; Programmable Ignition Timing Module For
Cars, Pt.1; Hard Disk Drive Upgrades Without Reinstalling Software;
What Is A Groundplane Antenna?; Getting Started With Linux; Pt.4.
July 1999: Build The Dog Silencer; A 10µH to 19.99mH Inductance
Meter; Build An Audio-Video Transmitter; Programmable Ignition
Timing Module For Cars, Pt.2; XYZ Table With Stepper Motor Control,
Pt.3; The Heapod Robot.
PLEASE NOTE: November 1987 to August 1988, October 1988 to
March 1989, June 1989, August 1989, December 1989, May 1990,
August 1991, February 1992, July 1992, September 1992, November
1992, December 1992 and March 1998 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 tear sheets) at
$7.00 per article (includes p&p). When supplying photostat articles
or back copies, we automatically supply any relevant notes & errata
at no extra charge. A complete index to all articles published to date is
available on floppy disc for $10 including p&p, or can be downloaded
free from our web site: www.siliconchip.com.au
AUGUST 1999 89
ASK SILICON CHIP
Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line
and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097.
CD repair
kit available
In answer to a recent request concerning repairing scratches on CDs, a
CD repair kit is available from Verbatim. Its reorder code is 38630. The kit
contains one bottle of scratch repair
solution and two lint free cloths. (M.
A., via email).
Preamplifier for
bass guitars
While many projects have been dedicated to lead guitars, bass guitars have
their own special needs. They don’t
need bass cut but bass boost. Would it
be possible to produce a preamplifier
especially for bass guitars to build in
front of one of the many fine power
amplifiers that you have produced.
(D. T., via email)
• We could do a bass guitar preamplifier but it would really only be a
slight modification of the preamplifier
featured in the January 1992 issue. It
is still available as kit from a number
of suppliers. Making the tone control
provide boost only would be simple
Driving stepper
motors with a Pentium
I am trying to develop a project
using stepper motors as a learning
exercise. I built the stepper motor
driver with buffer kit with a YM
2750 motor and tried to run it
from a Pentium 166 and 300 but
the motor does not step properly! I
then built the January 1994 design
as I thought it was a simpler system
but the motor still does not step
properly!
It appears the computer is too
fast and the motor doesn’t have
time to step. Can I control this or
can you suggest another possible
cause? (A. P., via email).
• The stepper motor card with
onboard buffer published in the
90 Silicon Chip
but the circuit would have the same
number of parts and we would not
provide any more boost because of the
danger of overload.
Can the “engine immobiliser described in the December 1998 issue
of SILICON CHIP be used with a diesel
engine? (J. B., via email).
• The immobiliser won’t work on
a diesel motor. You need to stop the
fuel pump or the injectors and the
immobiliser will not do that in its
existing form.
you have any info or advice? (P. M.,
via email).
• The W20NA50 comes in a TO-247
package which is pin-for-pin compatible with the TO-218 package of
the BUK436 Mosfets. Howev
er, we
cannot recommend using it since it
has an RDS-on of 0.27Ω and its current
rating is only 20A. By comparison, the
BUK436 has an RDS-on of .065Ω and a
current rating of 31A. Consequently,
the dissipation would be much higher
for the W20NA50 device and it is more
likely to be damaged in circuit. You
can try using them but we suspect that
they will run hot, particularly at the
higher currents.
Dead Mosfets in the
40V power supply
Ignition noise in
car sound system
I have just completed the 40V 8A
Power Supply described in April &
May 1998 but I blew up the BUK436s.
These are over $12 each. I have some
W20NA50 500V 20A Mosfets which
come in a slightly larger package and
I don’t know if the pin connections
are the same and whether your drivers
in this circuit will work with it. Do
I am writing in regards to the 100W
DC-DC Converter for car audio amplifiers, as published in the December 1990
issue. The unit was built from scratch
about two years ago and was teamed
up with the 50W stereo amplifier
featured in the February 1995 issue. I
have had the complete unit installed
in two cars so far, a 1980 Suzuki Stockman and a 1979 Ford Falcon XD. In
both cars they performed brilliantly
with the exception of a small amount
of engine noise.
However, in my latest car, a 1993
Holden Barina, I am getting an unacceptable amount of ignition noise
coming through the speakers; ie, I
can hear the engine revving through
the speakers. I have wired the unit up
directly to the battery terminals with
heavy duty cable and use the “remote
amp switch” wire in the back of my
CD player to switch a heavy duty
automotive relay to turn the unit on.
I had hooked up a noise suppression
unit which came with an old car CD
player (which is now dead) and this
unit worked well (about 70% reduction in noise) but it was only rated at
about 5A and it didn’t take long to
melt the windings in the inductor at
full power. An auto electrician friend
allowed me to try an inductive noise
Immobiliser for
diesel engine wanted
December 1997 issue does not rely
on the speed of the computer to
step the motor. The stepping speed
is set by VR1 and VR2. You say the
motor doesn’t step properly but
you have not elaborated on this.
The fact that you have used the
motor unsuccessfully on two different projects makes us wonder
if there is something wrong with
it. We have no knowledge of the
YM2750 stepper. Does it require
12V or is its voltage higher?
For the January 1994 design,
have you followed the test procedure on page 86? It is possible with
this card that the computer is too
fast. Use the TEST.BAS file on the
disk and put a delay loop in if it
is necessary to slow it down even
further.
Surge problem with
train controller
I have some questions regarding
the train controller published in
the April 1997 issue of SILICON
CHIP. We purchased two kits recently and have been wiring up
our new layout.
Firstly, when the power is turned
on, the train surges in reverse for
about 30cm. Slowing down from
this surge appears to involve the
inertia; ie, it is gradual, not sudden.
If the brake switch is set to “brake”,
the surge still occurs, though is
only about 15cm in travel. No matter which way the direction control
is set, the surge is in reverse. Why
does this happen?
Secondly, and perhaps more
complex, is a question regarding
modification. Is it possible to connect, via a 4-pole switch (rotary
break before make), both “ends” of
the resistance of the throttle VR1,
the “selector” connector for brake
switch S1 and the “brake” position
suppressor unit but it wasn’t very effective at all. I have seen other similar
units in the Altronics catalog but at $80
I’m sure I can build something similar
for a lot less. Can you give any circuit
diagrams or suggestions for a noise
suppressor? Any help with the above
subject would be greatly appreciated.
(L. T., via email).
• We are concerned that your Barina’s
electrical system may need some suppression components for the ignition
and alternator. Is any engine noise
noticeable in the standard car radio?
If so, you should have some components fitted.
If not, perhaps you should try using
a 20A choke in series with the power
lead. These can be obtained from Jaycar at $24.95 (see their 1998 catalog,
page 69, Cat AA-3078). These are
superseded components but are still
in stock at Jaycar stores.
How to eliminate
hum loops
I’ve lately become interested in constructing hifi equipment and recently
built up a pair of the 125W amplifier
modules described in the April 1996
of that switch, to a second control
panel incorporating the throttle pot
VR1 and switch S1, with the wiper of VR1 connected to the “run”
connector of S1 via a 470Ω resistor.
Assuming that the brake is
applied when changing between
control locations, would this also
cause the surge as experienced on
power-up?
If I had two train controllers
(with the track broken into power
blocks and switches allocating the
blocks to cab A or cab B), would it
be possible to have a 4-pole switch
at the small remote control panel
(as described above) to allow the
extra controls to connect into either
of the two cabs? In other words,
from either of the two controllers,
you could apply the brake, switch
to the “auxiliary” controls, then
walk there, then select either A or
B, depending which control you
came from, then control that cab
from there.
Note that our track is broken
into power blocks and each block
edition. I installed them in a case in a
dual-mono configuration, with a separate power supply for each channel.
I constructed the power supplies as
indicated in the schematic.
My problem has been in eliminating
ground hum. I am running a CD player
with standalone DAC, preamplifier
and power amplifier. The schematic
connects the power supply/signal
ground (0V DC) to the chassis ground/
earth.
The only way I have been able to
cure the hum is by lifting the signal
ground from the chassis grounds in
all the equipment except one (the
preamplifier). I emphasise that in
all the equipment, the metal chassis
are correctly grounded to earth. All
signal connectors are insulated from
the chassis. So the signal ground
reaches chassis ground only in the
preamplifier.
This solution is totally successful
in terms of noise reduction. But is it
safe? I’d appreciate your opinions and
alternative suggestions. By the way,
the amplifier modules sound fantastic
in my rig. (P. H., via email).
• Your solution to hum elimination
is the correct one. You must have the
is switched to either A or B. (C. F.,
via email).
• You are the first person to bring
this surging problem to our attention which is surprising because
quite a few have been built over
the period since April 1997.
The problem is caused by the
4700µF capacitor being initially
discharged. It could be avoided by
connecting the negative terminal
of the 4700µF capacitor to the 0V
(earth) line instead of the -12V
line but that would mean that the
capacitor would be reverse-biased
whenever the controller was set
for reverse operation. One solution
is to use two 4700µF capacitors
connected back-to-back between
the common terminal of switch S1
and the 0V line.
Alternatively, wire a switch in
series with the output so that the
track is not connected when power
is first applied to the controller.
Your proposed switching method for the two controllers should
work in principle.
signal earth isolated from the chassis
earth in all units except one, usually
the preamplifier/control unit.
Gain required
after compressor
Having recently constructed a high
power amplifier for my son to use in
his band, there was a need to include
some form of preamplifier to allow for
the direct connection of an electric
guitar. It was at this time that your
Audio Compressor project appeared
and it seemed like a good idea to build
this into the amplifier. In addition to
providing preamplification of the guitar, it promised to be a useful device to
limit the input into the amplifier and
hence prevent unwanted overdriving,
with the added bonus of providing a
sustain effect.
Careful reading of the text revealed
that “It can provide extra gain, ranging
from 0dB (x1) up to 20dB (x100)”.
A gain of x100 seemed just perfect
for what I needed to bring the guitar
signal of about 10 or 20mV up to that
required to meet the input sensitivity
of the main amplifier.
Unfortunately that was not to be.
AUGUST 1999 91
Questions on electric
fence output
I was hoping that the article on
testing electric fences in the May
1999 issue would provide the answer to a question which I have.
But it didn’t, so I thought I’d write
and ask. The Low Power Electric
Fence described in July 1995 should
produce around 5kV across a 1MΩ
load while a subsequent modification raised this to 10kV. The high
power unit described in April 1999
should produce a peak voltage of
around 3.6kV but is supposed to
power a longer fence.
Speedrite give a ratio of 1 joule
per 10km, while Daken information
shows a linear relationship between
fence length, output voltage and
work done. So why work and not
power? Because of pulse length I
presume? Could pulse length relate
to fence length?
I am trying to quantify the ratio of
the output of the unit to the length
of fence and the answer doesn’t
seem to be in volts. Either I need to
add some more information and do
some mathematical manipulations
or else find a method of measuring
After constructing and installing the
Audio Compressor into the 300W
power amplifier and plugging the guitar directly into the audio compressor,
the resulting noise (er, I mean music)
was only a little louder than my son’s
15W practice amplifier.
Measurement of the output from
the compressor gave a result of barely
150mV with maximum gain setting
(at 1:1 compression). It was then that
I decided to look up the definition for
decibels and found that 20dB equates
to x100 power gain but only x10 voltage gain (The Radio Amateur’s Handbook 1983). I believe that voltage gain
is the more relevant parameter for a
circuit of this type.
Later on in the article is the statement that “The buffer amplifier has a
gain of -1, as set by two 10kΩ feedback
resis
tors.” In fact, for this feedback
arrangement the gain is +2 (or 6dB).
Fortunately the specification sheet
for the SSM2166 in
tegrated circuit
was readily available from the Analog
Devices web site at:
92 Silicon Chip
the work done. The Maxi fence
tester described in May 1999 may be
close to what I need but how would
you convert the energy stored in the
capacitor to joules? (T. U., Georgica,
NSW).
• Electric fences are rated in terms
of energy delivered, not work output. More specifically, the energy
output is related to the capacitance
and DC voltage across the main
dump capacitor.
The actual energy delivered to the
fence line depends on the losses in
the SCR and the pulse transformer
and also on the load presented by
the fence line itself. The energy
rating is actually measured with
a load of 500Ω and is obtained by
integrating the power delivered
over the time of the pulse.
The Australian & New Zealand
standard for electric fence energisers specifies a maximum output
voltage of 10kV so regardless of the
fence length, the peak voltage is
limited to 10kV.
If you want to calculate the energy stored in the capaci
tor, the
formula is:
E (joules) = ½CV2
where C is in Farads and V is volts.
http://www.analog.com/product/
Product_Center.html
From this I found that I could
configure the buffer amplifier to give
a further gain of 20dB (or x10) by
changing one of the feedback resistors
to 1.1kΩ. This will give a total gain of
40dB (or x100) which is made up of
20dB for the buffer amplifier plus 20dB
for the voltage controlled amplifier
(at 1:1 compression) of the SSM1266
integrated circuit. I have yet to try
this modification. (K. C., Strathfield,
NSW).
• Increasing the gain of the buffer
will not solve your problem. Normally
the compressor would be followed by
more stages of gain, bass and treble
controls and so on, before the signal
was fed to a power amplifier. If you
want more gain, you might like to
consider building the 4-Channel Guitar
Mixer published in the January 1992
issue. This provides gain and bass,
treble and mid controls.
As far as gain figures in decibels
are concerned, 20dB in voltage gain
is exactly the same as 20dB in power
gain. This is because power is a voltage-squared function. Therefore, if
you increase the voltage by 10 times,
the power increases by a factor of 100.
This point confuses a lot of people.
Just remember that gain expressed in
decibels is always the same amount,
regardless of whether it refers to voltage, current or power.
Darkroom supply
blows lamps
I built the “Regulated Supply for
Darkroom Lamps” described in the
November 1997 issue of SILICON CHIP
but it blows the rather expensive EFP
12V, 100W enlarger lamps used in an
“Opemus” enlarger colour head. This
occurs within seconds of switching on
and even at reduced voltage output.
However, other 12V, 100W halogen
lamps are not affected under similar
controlled conditions. Could this be
due to a resonance effect with the
induc
tance of those particular filaments? Would a change in the TL494
oscillator frequency help? (D. S., Torrens Park, SA).
• There are two possibilities for the
failure of your enlarger lamp. First,
the soft-start facility is not working
and coupled with that, the supply may
be giving excessive output voltage for
a short time. We suggest you check
both possibilities using a cheap halogen lamp. Ideally, for this test, you
should measure the output voltage
with an analog meter as this should
show whether there is a brief surge at
switch-on. If the soft-start facility is not
working, check the components in the
slow-start circuit.
Subwoofer with
auto power-on
Many active subwoofers contain
auto power on circuits and I was wondering if you have at any stage published a project to make such a circuit
using audio levels to switch a relay.
In September 1994 you published
the MiniVox project. Could the microphone be replaced with a line or
speaker level input to accomplish the
same thing, as I would like to install
motorised surround sound speakers
in my ceiling and need a circuit to
automatically switch on when I turn
on the Audio/Video system. (G. A.,
via email).
•
A subwoofer controller with auto
power on was published in the December 1995 issue of SILICON CHIP
and it was available as a kit from Altronics in Perth. The MiniVox could
also be modified as you suggest but
the relay must have adequate ratings
to switch the motor current.
Kit availability for
FM Radio Intercom
I am interested in the FM Radio
Intercom for motorbikes, published
in about 1990 I think. Just wondering
would you still know if this kit is
available or another is made to replace
it? (J. E., via email).
• The kit is no longer available and
the LM381 stereo output stage chip
is now obsolete. If you wanted to
substitute another output stage you
can still get all the other bits. It was
described in October and November
1989. We can supply the relevant back
issues at $7 each, including postage.
Charging a 4.8V
NiCd battery
I recently constructed the Fast Battery Charger which appeared in the
February and March 1998 issues of
SILICON CHIP from a kit. The charger
project provides for five nicad battery
types to be charged. In a modification
published in SILICON CHIP in June
1998, you suggested using a 12kΩ and
an 18kΩ resistor in parallel to provide
for a 4.8V battery.
It was suggested that this replace
the 14.4V provision. As switch S5 has
six positions I would like to add the
4.8V modification as an extra value to
other five. However, when I added the
two resistors between the switch and
the PC board the output voltage appears too high and the “Fast” charge
Notes & Errata
Line Dancer, May 1999: diode D10
on the circuit diagram on page 18
is shown the wrong way around.
Its cathode should connect to pin
2 of IC2.
and the 0V rail.
Alternatively, wire a switch in
series with the output so that the
track is not connected when power
is first applied to the controller.
Model Train Controller, April 1997:
to avoid a problem with the loco
moving backwards for a short distance when power is first applied,
the 4700µF capacitor connected
between switch S1 and the -12V rail
needs to be modified. Instead, two
back-to-back 4700µF 25VW capacitors should be connected between
the common terminal of switch S1
FM Radio Tuner Card, June 1999:
the board numbers and “SC” logo
on the PC artworks (page 26) will
short out unused pins in the ISA
slot on the motherboard if left intact.
To avoid this problem, remove the
board numbers and logo from the
artwork before etching the board.
Suitably modified patterns have
been posted on our web site.
LED lights instead of the “No Battery”
LED as with the other values.
Could you please advise whether
the 18kΩ and 12kΩ resistors are
correct for 4.8V and whether any
additional modification needs to be
done. (D. M., Auckland, NZ).
• Unfortunately, the modification
published in June 1998 to use 12kΩ
and 18kΩ resistors in parallel to allow
charging of 4.8V batteries is incorrect.
In order to charge 4.8V batteries a
resistance of 28kΩ should be used for
the extra switch position. This value
can be obtained using two 56kΩ resistors in parallel, a 27kΩ resistor in
series with a 1kΩ or an 18kΩ resistor
in series with 10kΩ.
SINAD measurements
explained
I would like to know if there has
been an article that explains the difference between S/N (signal-to-noise)
and SINAD measurements? (R. S.,
via email).
•
SINAD stands for “signal plus
noise and distortion” and is a measure
of signal quality in a communications
receiver or link. We published an article on the subject in the November
1988 issue. We can supply a photocopy of this article for $7 including
postage.
Engine immobiliser
transistor needed
Where can I buy the MJH10012
transistor used in the Engine Immobiliser Mk.2 featured in the December
1998 issue. I can only find the metal
version. (D. L., via email).
• If you have built a kit and the
transistor has failed, you should be
able to buy it as spare part from the
retailer who sold you the kit.
Failing that, Oatley Electronics has
a plastic TV line output transistor
which will probably do the job. It is
the 2SD1554 and they have them at
around $3. Phone them on (02) 9584
SC
3563.
WARNING!
SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should
be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to
the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact
with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high
voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone
be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in
SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing
or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant
government regulations and by-laws.
Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices
Act 1974 or as subsequently amended and to any governmental regulations which are applicable.
AUGUST 1999 93
MARKET CENTRE
Cash in your surplus gear. Advertise it here in Silicon Chip.
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To run your classified ad, print it clearly in the space below or on a separate
sheet of paper, fill out the form & send it with your cheque or credit card details
to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details
to (02) 9979 6503.
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94 Silicon Chip
FOR SALE
WEATHER STATIONS: Windspeed &
direction, inside temperature, outside
temperature & windchill. Records highs
& lows with time and date as they occur.
$420.00 complete plus sales tax if appli
cable. Optional rainfall and PC interface.
Used by Government Departments,
farmers, pilots, and weather enthusiasts.
Other models with barometric pressure,
humidity, dew point, solar radiation, UV,
leaf wetness, etc. Just phone, fax or
write for our FREE catalogue and price
list. Solar Flair/Ecowatch ph: (03) 5968
4863 fax: (03) 5968 5810, PO Box 18,
Emerald, Vic., 3782. ACN 006 399 480.
TELEPHONE EXCHANGE SIMULATOR, SC Feb. 1998. Test equipment
without the cost of telephone lines. $190.
MAGNETIC CARD READER, SC Jan.
1996. Holds up to 8 cards. Use as a door
lock. $65. Melbourne 9806 0110.
ELECTRONIC/MECHANICAL DESIGN AND CONSTRUCTION: We
offer a complete design service for
electronic and mechanical devices.
Most work is done in house and you
deal directly with the designers. No job
is too small and can be to prototype or
“turn key” stage, in one offs or for future
production. Simply send us an email at
vladimir<at>u030.aone.net.au with your
questions or requirements and we will
get back to you.
RAIN BRAIN AND DIGI-TEMP KITS: 8
station sprinkler controllers, 60 channel
temp monitor uses DS1820s over 500
metres. Has PC Data logging. Mantis
Micro Products,
http://www.home.aone.net.au/mantismp
A NEW address for Acetronics
http://www.acetronics.com.au
On-line PCB quotes, free software, DIY
PCB supplies plus many other items &
services. 02 9743 9235.
1A LASER DIODE DRIVER, 3W head
laser power monitor, IR laser diode with
housing, greatly reduced price, e-mail
CCTV * Modules from $85 PINHOLE
On-Board MICROPHONE 32 x 32 *
PIR MOVEMENT DETECTOR with
inbuilt concealed PINHOLE Mono or
DSP COLOUR Camera, Microphone
& Timer/Controller for VCR - Lights
- Etc from $139 * BULLET Camera
22mm dia 480 Line 0.05 lux SONY
CCD or DSP COLOUR from $132 *
COLOUR DSP 32 x 32 Pinhole Module
with MICROPHONE from $155 * MINI
36 x 36 Cameras from $85 - SONY
CCD $102 - COLOUR DSP $162 *
DOME Cameras from $88 - SONY
CCD $105 - COLOUR DSP $164 *
SINGLE-CABLE-SOLUTIONS 5mm
dia for Video, Audio & Power Supply
from 40 c/m * BALUNS use Telephone
or LAN cable for Video & Power
Supply from $11 * DIY PAKS: FOUR
Cameras, Switcher & Power Supply
from $499 - with 14 Inch Monitor
from $601 with MULTIPLEXER for
FULL-FRAME FULL-RESOLUTION
RECORDING from $1209 * FOUR
COLOUR CAMERAS, SWITCHER &
POWER SUPPLY from $807 - with
COLOUR QUAD 4 Pix 1 Screen from
$1211 * With MULTIPLEXER $2033 *
HIGH RESOLUTION QUADS (Near
SUPER-VHS Quality) from $256
* COLOUR QUADS from $512 *
COLOUR DUPLEX MULTIPLEXERS
from $1329 * 14 Inch MONITORS from
$218 - with Inbuilt 4 Ch SWITCHER
from $256 * SEE-in-the-DARK with
our Combination CAMERA INFRARED
ILLUMINATOR Kit from $160 * 50 LED
DIY Infra Red Kits only $19 * Plus full
range of ANCILLARY EQUIPMENT
* DISCOUNTS: Based on ORDER
VALUE, BUYING HISTORY, for CASH
/ CHEQUE & NZ BUYERS ! BEFORE
YOU BUY Ask about New Enquiry Offer
& visit our Web Site at:
www.allthings.com.au Allthings S &
S. Tel 08 9349 9413; Fax 08 9344 5905
PC-CONTROLS: Frequency Meter
(2GHz), Temperature Recorder, Audio
Generators, I/O Cards, Data Logging,
plus ActiveX. SOFTMARK Ph/Fax 02
9482 1565 www.ar.com.au/~softmark
C COMPILERS: everything you need
to develop C and ASM software for
68HC08, 6809, 68HC11, 68HC12,
68HC16, 8051/52, 8080/85, 8086,
8096 or AVR: $155.00 each. Macro
Cross Assemblers and Disassemblers
Need prototype PC boards?
We have the solutions – we print electronics!
Four-day turnaround, less if urgent; Artwork from your own
positive or file; Through hole plating; Prompt postal service; 29
years technical experience; Inexpensive; Superb quality.
Printed Electronics, 12A Aristoc Rd,
Glen Waverley, Vic 3150.
Phone: (03) 9545 3722; Fax: (03) 9545 3561
Call Mike Lynch and check us out!
We are the best for low cost, small runs.
Satellite TV Reception
International satellite TV reception in
your home is now
affordable. Send for
your free info pack
containing equipment
catalog, satellite lists, etc or call for
appointment to view. We can display
all satellites from 76.5° to 180°.
Positions At Jaycar
We are often looking for enthusiastic staff
for positions in our retail stores and head
office at Rhodes in Sydney. A genuine
interest in electronics is a necessity. Phone
02 9743 5222 for current vacancies.
KITS-R-US
PO Box 314 Blackwood S.A.
Ph/fax 08 8270 3175
FMTX2A Universal Stereo Coder $49
FMTX2B 30mW Xtal Locked 100MHz Transmitter $49
FMTX1 1-3 Watt Free Running Transmitter $49
FMX1 200mW Full Broadcast Transmitter, built & tested $499
FM220 10-18 Watt FM BGY133 Philips Linear $499
FM1525 25 Watt Discrete Linear FM Band $499
FM2100 110 Watt Discrete Linear FM Band $699
FM3000 300 Watt Discrete Linear FM Band $1499
Philips 828E/A VHF Receiver Boards (6 metres) $9
AWA 721 VHF Receiver Boards (2 metres) $9
AWA 721 VHF transmitter boards 1 watt (2 metres) $19
Philips 323 UHF transmitter boards 500mW (70cm) $19
AEM 35 Watt Little Brick Audio Power Amp $15
Digi-125 200W RMS Audio Power Amp $39
CA Clipper Compiler, new in box $49
6dBd Gain Colinear FM Band Antenna $999
Roll Smart-1 FM Station Audio Processor $999
Free catalog on disk of discounted surplus components
Same day shipping, credit cards OK, circuits supplied.
SPECIAL STEAM
BOAT KITS $14
lmatthee<at>perthpcug.org.au for details and pictures
AV-COMM P/L, 198 Condamine St,
Balgowlah, NSW 2093.
Tel: 02 9949 7417 or 9948 2667.
Fax: 9949 7095; www.avcomm.com.au
Silvertone’s RC Receiver
Still the best little performer available!
Ph: (03) 98306288 Fax: (03) 98306481
for above CPUs + 6800/01/03/05, 6502
and 68HC12 for $78. Debug monitors:
$78 for 6 CPUs. All compilers, XASMs
and monitors: $480. 8051/52 Simulator
(fast, now incl. 80C320): $78. Try the
C-FLEA Virtual Machine for small CPUs,
build a “C-Stamp”. Demo desk: FREE.
All prices + $5 p&p.
Atmel Flash CPU Programmer:
Handles the 89Cx051, the 89C5x and
89Sxx series, and the new AVRs in
both DIP and PLCC44. Also does most
8-pin EEPROMs. Includes socket for
serial ISP cable. $199, $37 tax, $10
p&p. SOIC adaptors: 20-pin $90, 14-pin
$85, 8-pin $80. Credit cards accepted.
GRANTRONICS PTY LTD, PO Box 275,
Wentworthville 2145. Ph (02) 9896 7150;
Fax (02) 9631 1236; or Internet:
http://www.grantronics.com.au
Win $500USD cash dontronics.com
PRINTED CIRCUIT BOARDS for all
magazine projects, then go to http://
www.cia.com.au/rcsradio
RCS Radio – Bexley (+61 2) 9587 3491.
Still only $129.50 AM or $149.50 FM.
May be used with most ppm transmitters.
This and many other radio control
products available from:
Silvertone Electronics, PO Box 580,
Riverwood 2210.
Phone/Fax (02) 9533 3517.
www.silvertone.com.au
RTN Australia Parallax distributor:
Basic Stamps BS1, BS2, BS2-SX all ex
stock. Chipsets also available for high
volume applications. SX development
tools and chips also available. New super
BS1/2 development board Oz made now
available. Custom I/O extender chips
for the Basic Stamps. Serial Led driver
kits, a/d kits, temperature kits, etc.
FerretTronics servo and stepper motor
chips. TiePie HandyScope HS2, Dos
AUGUST 1999 95
Silicon Chip Binders
Keep your copies safe, secure and
always available with SILICON CHIP
binders: they’re cheap insurance!
REAL
VALUE
AT
$12.95
PLUS P
&P
Heavy board covers with
2-tone green vinyl covering
Advertising Index
Aust. Audio Consultants...............81
Av-Comm Pty Ltd.........................95
Clarke & Severne........................81
Coffs Harbour Electronics............81
Computronics Corporation..........80
Each binder holds up to 14
issues so that you can include
catalogs
Dick Smith Electronics........... 12-15
EMC Technologies.......................80
SILICON CHIP logo printed
in gold-coloured lettering on
spine & cover
Emona Instruments...................IFC
Harbuch Electronics....................87
Price: $12.95 plus $5 p&p each
(available Aust. only)
Instant PCBs................................95
Order by phoning (02) 9979 5644 & quoting your credit card number;
or fax the details to (02) 9979 6503; or mail your order with cheque or
credit card details to Silicon Chip Publications, PO Box 139, Collaroy,
NSW 2097.
Jaycar .............................. 45-52,95
Kalex............................................67
Kits-R-Us.....................................95
Microgram Computers..............3,81
$110.00 (12V 140W). High quality pure
sine wave inverters from $390.00. Call
with your requirements.
WIND GENERATORS: wide variety
available, call with requirements.
TASMAN ENERGY Free call 1800
226626.
and Win software included. Ph/Fax (03)
9338 3306.
Email: nollet<at>mail.enternet.com.au
http://people.enternet.com.au/~nollet
SOLAR PANELS: buy by mail and save!
75 watt from $590.00, unbreakable s/
steel 64 watt $555.00. Largest manufactured: 120 watt $995.00, flexible 32
watt $475.00. All other sizes available,
top brands, lowest prices.
INVERTERS: budget inverters from
KIT ASSEMBLY
ANY KITS assembled/repaired: professional, speedy service. Phone Neville
Walker (07) 3857 2752.
WANTED
SERVICE MANUAL. Restoring Uher
Royal R/R tape recorder 784E serial
287509. Arthur Grebert, 145 Golden
Ponds, Forster, NSW 2428. 02 6555
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MicroZed Computers...................80
Oatley Electronics........................31
Premier Batteries.........................79
Printed Electronics...................... 95
Procon Technology......................95
Questronix...................................80
RobotOz......................................80
R.T.N............................................80
Silicon Chip Binders/Wallcht....OBC
Silicon Chip Bookshop........... 72-73
Silicon Chip Subscriptions...........53
Silvertone Electronics..................95
Solar Flair/Ecowatch....................94
Truscott’s Electronic World...........67
Vass Electronics..........................55
HELP SAVE THE NIGHT SKY!
We are losing our heritage of starry night skies. Poor, inefficient
outdoor lighting is causing glare and “light pollution”. This wastes
energy and increases greenhouse gas emissions.
You can help by joining SYDNEY OUTDOOR LIGHTING IMPROVEMENT SOCIETY (SOLIS). SOLIS aims to educate and inform about
quality outdoor lighting and its benefits. We also lobby councils, government and other bodies to promote good lighting practice. SOLIS meetings
are held third Monday night of each month at Sydney Observatory.
Individual membership is $20 pa. Donations are also welcome. Cheques payable
to “SOLIS c/- NSAS”, PO Box 214, West Ryde 2114.
Email: tpeters<at>pip.elm.mq.edu.au
96 Silicon Chip
Zoom EFI Special......................IBC
_____________________________
PC Boards
Printed circuit boards for SILICON
CHIP projects are made by:
• RCS Radio Pty Ltd, 651 Forest
Rd, Bexley, NSW 2207. Phone (02)
9587 3491.
• Marday Services, PO Box 19-189,
Avondale, Auckland, NZ. Phone (09)
828 5730.
Own an EFI car?
Want to get the
best from it?
Youll find all you
need to know in
this publication
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