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This is only a preview of the November 2000 issue of Silicon Chip. You can view 38 of the 96 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Items relevant to "Santa & Rudolph Christmas Lights Display":
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Milling PC Boards direct from software
SILICON
CHIP
NOVEMBER 2000
6
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Contents
Vol.13, No.11; November 2000
FEATURES
4 Quick Circuit 5000 PC Board Prototyping System
It mills away the copper, drills the holes and makes the cutouts for fast PC
board prototypes – by Peter Smith
10 ShockLog: Monitoring The Things That Go Bump
It rides shotgun with your goods and records the shocks and bumps
72 Tektronix TDS7504 Digital Phosphor Oscilloscope
It’s a computer and a digital oscilloscope all in one package. You can even
plug in an external VGA monitor for a split-screen display – by Leo Simpson
Santa & Rudolph Christmas
Display – Page 13.
PROJECTS TO BUILD
13 Santa & Rudolph Chrissie Display
It’s huge, it’s colourful, it has lights, it has movement: your house will have
the best decoration in the suburb – by John Clarke & TestaRossa
30 2-Channel Guitar Preamplifier
Each channel has bass, mid and treble controls and there’s an optional
digital reverberation unit as well – by John Clarke
60 Message Bank & Missed Call Alert
You’ll never miss another Message Bank call again – by Leo Simpson &
Rick Walters
2-Channel Guitar Preamplifier –
Page 30.
66 Programmable Electronic Thermostat
It’s programmed using a PC and has three relays to control external
equipment – by Michael Jeffery
86 Protoboards: The Easy Way Into Electronics
More circuits based on the 555 timer and how to use the 555 as an audio
amplifier – by Leo Simpson
SPECIAL COLUMNS
Message
Bank &
Missed
Call Alert
– Page 60.
54 Serviceman’s Log
Most customers are reasonable – by the TV Serviceman
78 Vintage Radio
The intriguing Philips “Philetta” – by Rodney Champness
DEPARTMENTS
2
41
42
53
58
Publisher’s Letter
Electronics Showcase
Product Showcase
Subscriptions Form
Mailbag
76
91
93
94
96
Circuit Notebook
Ask Silicon Chip
Notes & Errata
Market Centre
Advertising Index
Programmable Electronic
Thermostat – Page 66.
November 2000 1
PUBLISHER’S LETTER
www.siliconchip.com.au
Publisher & Editor-in-Chief
Leo Simpson, B.Bus., FAICD
Production Manager
Greg Swain, B.Sc.(Hons.)
Technical Staff
John Clarke, B.E.(Elec.)
Peter Smith
Ross Tester
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
Louis Challis
Rodney Champness
Garry Cratt, VK2YBX
Julian Edgar, Dip.T.(Sec.), B.Ed
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Philip Watson, MIREE, VK2ZPW
Bob Young
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ISSN 1030-2662
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2 Silicon Chip
Anyone should be
able to do their own
house wiring
Over the last few months we have had a lot
of correspondence on the subject of whether or
not an electrical licence should be required to do
repairs on electrical equipment or even assemble
a 240VAC mains-powered kit.
Some of the correspondence has been quite
heated, so much so that we have not published
it. Some letters from electricians feel that others
are unfairly attacking them while some corre
spondents have asked that their names not be published because they are
afraid that the official body concerned may victimise them in some way. All
of this is a pretty unhealthy state of affairs.
Up until a week ago I felt that the situation was pretty hopeless. The
official bodies were not likely to review their existing regulations to free
things up and many people would continue to do much as they always have,
disregarding authority and their “petty” rules. Our view was that electricians
should be the only ones to work on fixed mains wiring in buildings and
homes but that assembly and repairs on mains-powered equipment is none
of their business. That was what I wrote in the “Publisher’s Letter” in the
September 2000 issue.
Then a week ago we received a letter from Otto Hoolhorst and this has
blown the lid off the whole topic. You can read his letter on page 59. The
essence of his letter is that anyone in New Zealand can do their own house
wiring and that includes the switchboard! Not only that, they have been
doing it since 1992!
Mr Hoolhorst has been kind enough to send me the relevant NZ legislation
(Electricity Act 1992), their Codes of Practice booklets and so on. It is all laid
out in black and white and is very straightforward. They can do it all - legally.
Now apart from the accent, New Zealand is not a radically different country from Australia and in fact, they use the same electrical fittings and same
electrical standard as we do: AS/NZS3000. So if New Zealanders can do their
own electrical wiring, why can’t we? In fact, our New Zealand readers must
be wondering what all the fuss is about. There they are, happily wiring up
everything within sight and they’re not dying like flies because of hazardous
wiring. No-one, in fact, has died in New Zealand due to hazardous wiring
created by a householder.
So let’s get some common-sense into this whole scene. Let’s lobby the politicians to have most of the regulations scrapped. Let’s make it unnecessary
for electrical licenses for people who repair electrical equipment, assemble
electrical equipment and for anyone who wants to do home wiring.
There will still be just as much work as ever there was for licensed electricians - they won’t be put out of business. There will still be plenty of people
who are capable of doing electrical wiring who will still want it done by a
tradesman. Why fiddle about doing wiring when you don’t have the time or
inclination? But if you want to do it, and can do it, why shouldn’t you have
the right to do it? New Zealanders can and so should we.
Leo Simpson
¢
£
£
£
£
¤
¥ ¥
¥
¥
¡
sales<at>mgram.com.au
info<at>mgram.com.au
Fax: (02) 4389 8388
A u s t r a l i a -W i d e E x p r e s s C o u r i e r . . . $ 1 1 (3kg max.)
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FreeFax 1 800 625 777
Vamtest Pty Ltd trading as MicroGram Computers ACN 003 062 100
Web site:
mgram.com.au
FreeFax 1 800 625 777
Phone: (02) 4389 8444
Looking for a fast way to produce
prototype PC boards? This device lets
you make your own quicker than it
takes to get a courier delivery
from a prototyping bureau.
Quick Circuit 5000
It mills away the copper for fast
PC board prototypes
By PETER SMITH
Traditionally, printed circuit board
manufacture involves both photographic and chemical processes. The
equipment and labour costs in these
processes mean that companies that
design PC boards rarely produce them
in-house. Instead, the designs are
shipped off to speciality manufacturers in electronic format.
How long it takes to get your design
back as a PC board depends on how
much you want to pay. And even if you
pay the top rate, chances are you’ll still
wait for 24 to 48 hours. Even if that’s
fast enough for your needs, a number
of other outstanding features make this
system worth a look.
Manufactured by the US company
4 Silicon Chip
T-Tech, Quick Circuit is a radically
different, although not entirely new
system for circuit board prototyping.
Quick Circuit bypasses the usual
manufacturing processes by engraving
designs directly onto PC board copper.
In other words, it’s a purely mechanical process that does not require
chemical etching.
Quick Circuit is controlled via the
serial port of most Windows-based
PCs. It is supplied with software that
will read the output from any PC board
design package, and includes a num
ber of handy “last minute” checking
and editing features.
Starting with blank PC board material on an X-Y table, a high-speed
spindle motor is fitted with various
drilling, milling and routing bits to
remove the required amount of copper,
drill all the holes and finally “cut out”
the finished product.
Quick Circuit can handle single
and double-sided designs up to 25cm
x 28cm and a variety of options are
available if you need plated-through
holes.
Minimum track width and spacing
is 0.100mm (0.004"), which means it
can handle both surface-mount and
through-hole designs. RF and microwave engineers will be especially
interested in Quick Circuit’s precision
milling capabilities; imagine being
able to fine-tune your designs right
without too much difficulty. The experts at SATCAM are happy to provide
advice if needed, too.
Generating the
engraving pattern
The complete Quick Circuit 5000
system. The black box in the middle
drives the table’s motors and solenoid
under command of a PC running
Windows-based software.
on the desktop!
Odd-shaped boards, irregular internal cutouts and large hole sizes are
all handled with ease using Quick
Circuits profile routing feature.
As a bonus, plastic, aluminium and
other soft metal panels can be drilled,
milled and routed for a super-professional finish. In all my years in this
business, I’ve never managed to get a
“D” connector cutout exactly right –
could this be the answer?
Another day at the office?
Once the word got out that I would
be test driving the Quick Circuit machine, a whole pile of future Silicon
Chip prototype designs appeared on
my desk with an assurance that they
would “really test” the machine! I
waited expectantly for it to arrive.
Rob Leslie from SATCAM set up
the machine and provided about half
a day of hands-on training.
Anyone with a reasonable amount
of technical/mechanical know-how
should be able to drive the machine
Before a design can be transferred
to the Quick Circuit machine, it must
first be manipulated by a stand-alone
software package called IsoPro. IsoPro
reads the standard Gerber and Excell
on files generated by all popular PC
board design packages (we use Protel
99).
As the name suggests, IsoPro allows
you to define the isolation (clearance)
that you would like between tracks,
pads, etc on the finished board.
Isolations are generally performed
in a series of passes with progressively larger mill sizes. For example,
if a design has minimum clearances
of 0.012", then isolations at 0.012",
0.020" and 0.040" would probably be
performed.
Note that although a single isolation
at 0.012" would provide a perfectly
valid result in this case (all nets are
electrically isolated), the board would
be difficult to populate without generating lots of solder bridges. With this
in mind, about 0.030" to 0.040" final
clearance is recommended.
Once isolation is complete, there
will usually be some “dead” (unconnected) copper remaining on the
board. Leaving this copper in place
greatly speeds completion time but if
your design calls for it, a final “rubout”
pass can be performed to remove it.
To save time, IsoPro allows you to
selectively define areas to be cleared
on the rubout pass.
Importing the drilling info
As mentioned above, IsoPro also
reads the drill (Excellon) file output
from your design software. Once loaded, the next step is to ensure that the
drill layer is correctly registered with
the copper layers. If it’s not, IsoPro
provides an excellent function that
snaps them into perfect alignment
with a couple of mouse clicks.
If you’re an old hand at PCB design,
you’ll appreciate the ability to edit
both the drill and aperture tables. If
you don’t know what these are, don’t
worry; there’s a full explanation in the
Users Manual.
Creating notches and cutouts
One of the great features of this
product is the ease with which you
can create notches and cutouts.
Outlines can either be imported
from the mechanical layers of your
design or drawn directly on a new
layer in IsoPro. Once you have the
outline, a simple procedure generates
the necessary information for use with
Quick Circuit’s profile routing tools.
All designs have at least one cutout
that needs to be defined – the board
outline!
Final inspection
In addition to these “special” features, IsoPro is also a general purpose
Gerber editor. In short, this means that
you can examine the final output from
your PC board design software and
make last minute changes if required.
Clearances can be checked, hole sizes
changed, pads and tracks edited, text
added, etc.
Finally, IsoPro provides a graphical
representation of Quick Circuit’s X-Y
table, allowing easy and accurate
placement of the design within the
board material workspace. It also
provides a means of keeping track of
which areas you’ve already used when
making a number of smaller boards
from a larger section of material.
Exporting your work
The last step is to export all the isolation, drilling and routing information
referred to above ready for input to the
Quick Circuit table control software,
QuickCAM.
If you hadn’t already guessed,
IsoPro does not need to be run on
the PC controlling the Quick Circuit
machine. This means that designs can
be prepared in advance, perhaps while
another is on the table. Note, however,
that IsoPro is licensed per PC – you
need a hardware “dongle” plugged
into the parallel port to enable all its
features.
If all that sounds tedious and
time-consuming, it’s not! After a few
practice runs, I was able to get a medium-sized double-sided design in and
out of IsoPro in less than 10 minutes.
Installing the
Quick Circuit table
Setting up the Quick Circuit table
for the first time is quite straightforward. Access to a vacuum source is
required, as Quick Circuit uses this
to clear swarf off the board during all
machining operations. If you don’t
November 2000 5
This assortment of completed boards
shows that no matter how odd the
shape or small the size, Quick Circuit
can handle it. Note the waveguides on
the long PC board.
already have a vacuum source, many
industrial vacuum cleaners are suitable for the task; SATCAM can help
with recommendations here.
Noise levels will be an important
consideration for some businesses. In
practice, we found that the old office
vacuum cleaner made a lot more noise
than the milling and routing!
You need a PC running Windows
95, 98 or NT4 to control the table. The
PC is set up right next to the table and
hooked up via a spare serial port. All
the Quick Circuit table electronics are
housed in a small “black box” which
can also provide switched power to
the vacuum source.
With the PC hooked up, the next step
is to load the table control software,
QuickCAM. Using the information
exported from IsoPro, this software
sends the actual direction and speed
data to the table’s “black box”, where
it is converted to high power drive
signals to move the table’s various
motors and solenoid.
Securing the board material
Quick Circuit uses standard 12 x
18" fibreglass (FR4) board material,
although it is also perfectly capable of
producing designs on more exotic base
materials such as PTFE and ceramics.
Two tooling pins anchor the board
material to the table, so all you have
to do is drill a hole in either side,
drop in the pins and you’re ready to
go. Oops – I almost forgot to mention
that you also need a piece of backing
material underneath so that you don’t
drill into the bed!
OK, so we’ve installed the machinery and mounted the blank board. Now
we can begin the most satisfying part
– exposing the masterpiece!
Crunch time
Fig.1: IsoPro accepts the standard output from PCB design software and
calculates the paths (also called “isolations”) that will need to be milled to
create the desired pattern in the copper. This shot shows a design with .010"
(orange), .020" (yellow) and .040" (pink) milling paths.
6 Silicon Chip
Drilling is usually performed as the
first step. In QuickCAM, the drill file
(exported from IsoPro) is loaded and
with a couple of mouse clicks we’re
under way. QuickCAM prompts for
each drill size in turn and automatically positions the head off the front
of the table for easy (manual) drill
swaps. The only adjustment needed
here is to the drilling depth; we need
to make sure that holes are drilled right
through the board and slightly into the
backing material underneath.
A nice feature allows large holes to
be profile routed rather than drilled.
This means that, say, the .062" routing
tool can be used to “drill” all holes
.070" and larger. This means that there
is no need to stock large drill sizes.
With the drilling done, we can begin the first (smallest) isolation pass.
This is generally performed using a
missile-shaped milling tool. Because
of the tip shape, the depth of the cut
determines the actual width of copper
(or “milling path”) that is removed.
The depth is set with the aid of feeler
gauges and a knob on the head assembly. A fairly simple procedure detailed
in the manual provides a means of
checking the milling path to ensure
that it’s exactly right.
QuickCAM is then loaded with the
relevant file (exported from IsoPro)
and milling can begin.
Subsequent (larger) isolation passes
are performed with end mills. As the
name suggests, these tools are flat on
the end and their size relates directly
to the milling path width. Once again,
feeler gauges are used to set the cutting
depth, which in this case will simply
be the copper thickness.
If it’s a double-sided design, the
board is simply flipped over on the bed
and the isolation processes repeated.
Because of the way the material is
pinned to the bed, layer registration
is spot on every time. If you’ve ever
hand-made double-sided boards yourself, you’ll know that this is one of the
A design takes shape as the first milling pass is performed.
hardest things to get right!
Profile routing is the final step in
the machining process. Any internal
cutouts are routed first, followed by the
board outline to “cut out” the board
from the base material.
A quick clean and coat of solder-through circuit board lacquer to
keep oxidisation at bay completes the
job. Note that as well as the bare copper
type, solder-plated copper board material is also available. We suggest that
even solder-plated boards be protected
with lacquer, as milled edges will be
bare copper.
Double trouble?
Three methods are available if your
double-sided designs require through-
hole connections.
The simplest of the three, from
Harwin, involves inserting “via” pins
for each through-connection using a
special handtool and then soldering
them on both sides. This system is
cheap and simple but does have one
obvious drawback. Holes that must
contain component leads as well as
provide through-connections need to
be soldered on both sides, and this is
not always possible.
The second method, called Copper
set, overcomes this limitation by using
copper tubes for the through-hole
connections. These are provided in
long lengths, pre-filled with solder for
strength and scored at regular intervals
so that they can be easily inserted and
November 2000 7
Above: one of the boards we made during our review. The
results appear similar to any high quality “conventional”
manufacturing technique. Right: this demo PC board shows
the results of each isolation pass, including the optional
dead copper rubout.
snapped off. They are then swaged
over on the top and bottom with a
special tool and the solder removed
from the centre if necessary.
This is an excellent method that
produces results very similar to plated-through holes, although is a little
time-consuming for complex designs.
The final method involves actually
plating the holes with a system called
Quick Plate. Although we didn’t look
at this system during our review, it
seems to be quite easy to use and boasts
very good results.
Quick Plate uses the traditional
method of electrolysis to perform the
plating, which means that it involves
the use of an electrolyte, copper anodes, plating tank and power supply.
According to T-Tech, a 9 x 12" PC
Fig.2: QuickCAM controls the machining table using the milling paths generated
in IsoPro. This shot shows a “zoomed in” view of a design positioned on the table
ready for the first isolation pass.
8 Silicon Chip
board can be plated through in about
35 minutes.
How quick is quick?
It is to be expected, of course, that
any prototyping system will be labour
intensive, and Quick Circuit is no
exception. Despite the preparation
needed in IsoPro and the machine
setup and manual tool changes, we
were able to produce a 12cm x 12cm
single-sided board in about one hour.
And once you know what you’re
doing, the machine can be left unattended during milling runs.
The Quick Circuit system is unquestionably the quickest way of producing
prototype printed circuit boards. Why
doesn’t everyone have one? Well, the
speed comes at a price…
The Model 5000 reviewed here sells
for $17,000, which includes all cables,
software and 10 assorted tools.
Also available is the Model 7000,
which includes a larger table (12 x
18") and sells for $22,000. The Quick
Plate 912 through-hole plating system
for 9 x 12" panels sells for $8750.
Note that these prices do not include
GST and are subject to exchange rate
fluctuations.
Contact SATCAM on (02) 9807 7081
or email satcam<at>ozemail.com.au for
more information. You can also find
more information on these products
on the web. For the Quick Circuit
and Quick Plate systems, check out
www.t-tech.com For the Copperset
through-hole connection system, go
SC
to www.multicore.com
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November 2000 9
ShockLog
monitoring the things
that go bump!
Want to know when and where a valuable
shipment was damaged in transit? This
gadget rides shotgun with your goods and can
indicate whether the damage was due to poor
packaging, rough handling or inappropriate
transport methods.
D
AMAGE PREVENTION special
ists Shockwatch Pty Ltd have
unveiled their latest weapon in the
fight against poor product handling
– a “black box” (well, blue actually)
which quietly sits and logs shocks and
vibrations on an object for periods of
one year or more. Called “ShockLog”
it is a compact “tri-axial monitoring
system” which can be unobtrusively
attached to items in transit or storage
to record bumps, vibration and climatic changes.
Designed to be fitted to vehicles,
10 Silicon Chip
containers or delicate valuable equipment, ShockLog has three piezoelectric accelerometers and a temperature
sensor. These sensors, along with
some low-power electronic circuitry,
are housed in an extruded aluminium
case which is bolted to the object it
is monitoring. An additional sensor
can be attached to record humidity,
pressure (as in air pressure) and temperature, if required (this is known as
an HPT sensor).
Shockwatch’s Jeremy Scott says
the ShockLog is effectively a “spy
in a box” to aid the safe transport of
valuable, hazardous or fragile goods.
It can also be used as an aid to designing cost-effective packaging and
for testing different transport methods
and routes.
For example, you can put a Shock
Log inside different types of packaging, send them on a trial journey and
then examine the event graphs when
the consignments are received. That
way, ShockLog makes it easier to develop the right packaging for the job.
Similarly, you could use a ShockLog monitor in several identical consignments sent by different transport
methods to identify which is the best
one to use.
ShockLog is also an ideal diagnostic
tool for the future development of
low-cost, stick-on “damage indicating labels”, which change colour to
indicate when a product is roughly
handled.
ShockLog is already being used
The optional HPT sensor is attached
to one end of the ShockLog and is
used for recording humidity, air
pressure and external temperature.
by the container industry in Europe
and the United States to monitor the
movement of critical cargos, such as
hazardous chemicals and nuclear
fuel. Other ShockLog users include
museums, art galleries, laboratories,
a major guided-missile manufacturer,
optical equipment manufacturers and
Rolls Royce Engine.
Fig.1: the ShockLog is programmed by attaching it to the serial port of a PC and
running the software. This is the setup screen which, among other things, allows
you to program the starting date and time, the “wake-up” threshold, the run
time, the acceleration range and the parameters to be recorded.
How it works?
ShockLog is powered by a single
1.5V alkaline or lithium C-cell battery and can be user preprogrammed
to monitor a range of conditions. It
then records a summary of the data
recorded over a specified time period in its non-volatile memory – you
can set this from 10 minutes up to 24
hours. ShockLog can record a maxi
mum of 512 “summaries”, so you have
to choose a summary period that will
allow you to cover the full period for
which you wish to record.
If preset handling limits are exceeded, the user will be given a visual
warning via a LED. This “time-triggered” mode is designed to monitor
complete journeys. The peak “G” records in each axis are recorded across
any defined “time slot”, along with the
other parameters such as temperature,
humidity and pressure.
To conserve battery life, the unit
normally operates in “sleep” mode.
Then, if suddenly exposed to conditions which exceed a specified “wake
up” threshold (eg, if the unit it is attached to is dropped), the sensor will
activate itself within 1.5 microseconds
and begin recording the incident. By
using the sleep mode, the unit can
maintain a 500-day battery life.
Once activated, ShockLog can
Fig.2: the setup can be saved to disk as
a file and loaded back in at a later date for downloading to the ShockLog. This
feature allows a number of predefined setups to be stored and quickly recalled.
record up to 4000 samples/second
and the 2MB memory is sufficient
for detailed records of up to 400 significant events. It can handle up to
±250G acceleration and is designed
to function in difficult environments,
operating at temperatures between
-40°C and 85°C.
Programming
Programming the ShockLog is easy.
It connects to the serial port of a PC
(75MHz Pentium or better) via a supplied serial cable and works with Windows-based software that’s installed
from an accompanying CD ROM.
This software allows the operator to
program such things as the starting
date and time, alarm thresholds from
1G to 100G, summary intervals, the
recording length of each event (up to
32K), the parameters to be recorded,
November 2000 11
Fig.3: after downloading data from the ShockLog, the “Examine
Data” window shows the recording sessions, the number of events
and alarms during each session and a host of other data.
Fig.4: double-clicking a session in Fig.3 brings up cascading “Event
data” windows – one for each recorded event. You can view the
data in graphical form as shown here or, by clicking the Data
button, display it in data format as shown below.
Fig.5: the data format shows acceleration figures for each axis (in
this case, X, Y & Z). The data can be printed out and exported to
other applications such as Microsoft Excel.
12 Silicon Chip
The ShockLog is supplied in a large plastic carry
case, complete with software and a serial cable.
the total run time and the maximum number of
events to be recorded.
Once the setup is completed on screen, it is
simply saved to disk and downloaded to the
ShockLog unit. The save to disk feature is particularly handy, as it allows a number of prede
fined setups to be stored on the hard disk. These
setups can then be loaded to the setup screen
and downloaded to the ShockLog with just a few
mouse clicks.
Naturally, the software also allows the recorded
data to be downloaded to the PC, saved to disk
and displayed in text or graphical form. These
reports and graphs may be viewed on-screen,
printed out or exported to other applications
such as MS Excel or Matlab.
The software also features a single-screen report that allows all key data for a journey or test
to be viewed, stored or emailed as a single sheet.
Tamperproof
Because ShockLog has no external switches,
it is virtually tamperproof. In addition, all data
is stored in non-volatile flash memory, ensuring
that information can’t be erased without password
authorisation.
It’s use greatly reduces the risk of damage to
valuable shipments by providing users with a
complete record of an item’s handling and shipping history.
For further information on ShockLog and a
range of related products, contact Jeremy Scott
at Shockwatch Pty Ltd on (07) 5534 3811; fax
(07) 5534 3822; email jeremys<at>onthenet.com.au
Shockwatch markets a broad range of solutions
for product damage prevention and industrial
safety. It is an arm of the Dallas-based Shockwatch Corporation in the USA, which has sold
more than 100 million products during the last 15
years for monitoring impact, tilt and temperature
events in product shipments. You can check out
SC
their website at www.shockwatch.com
It is huge... It has colour... It has light...
It has movement... It is the ultimate
Chrissie Display
You’ll have the best looking house in
the street WORLD this Christmas!
Can you hear it? That faint “Ho Ho Ho” coming from a secret location
far, far away but rumoured to be somewhere near the North Pole?
Yes, Santa is on his way (hey, Christmas is only a few short weeks away!) and
SILICON CHIP is going to help you get right into the Christmas spirit with this
amazing, unique, stupendous, magnificent and original Christmas lights display
Design by the inspired John Clarke
November 2000 13
Words, Music and Artistic Impressions by TestaRossa
J
ust in case you’re thinking this is
one of those tiny little displays
published previously, think again.
At well over a metre wide and
just on a metre high, it’s as big as we
could make it and still be reasonably
easy to transport.
It’s big enough to be seen not just
from the footpath, not just from the
street, not just from a block or so
away but would you believe across a
suburb? (Well OK, you do need lineof-sight).
And if this is not even big enough
for you, it could easily be scaled up to
be a real whopper – if you could find
a piece of backing board big enough,
you could make it metres high and
deep. But more on that anon.
Chevvy Chase, eat your heart out.
Your “National Lampoon Christmas
Vacation” house didn’t have one of
these. Not even the McCallister home
in “Home Alone” could manage one.
In fact, you can bet your last dollar
that your place will be unique – noone else in the world will build one
exactly the same as yours!
Apart from the size, this project has
a couple of other very snazzy features
which we’ll tell you about before we
get down to the nitty gritty (which of
course you want to do!).
First of all, the circuit design borders on genius. As you know, John
Clarke comes up with some pretty
clever projects in SILICON CHIP but
he’s really excelled himself this time.
He’s managed to keep the circuit
amazingly simple while appearing
to be quite complex.
For a start, none of the LEDs in this
project run from pure DC. As you no
doubt know, LEDs need to run from
DC – but here they either run from
rectified (but unfiltered) low voltage
DC or, in many cases, from low voltage AC alone.
What this means to you is a significantly lower cost of components
and, more importantly, lower heat
problems than we might otherwise
expect.
The whole project runs from a 12V
“halogen” transformer which is rated
at 5.25A continuous. Current drain
of our display was around the 1.7A
mark, depending on the number of
LEDs lit at the time, so the transformer
is operating well within its specs.
We tested this all night during
Olympic September (our bemused
neighbours thought we were a bit early
for Christmas or were simply caught
up in the Games euphoria…). The
transformer runs warm but certainly
not as hot as it does running a single
12V halogen lamp. And we’re running
more than 600 high brightness LEDs.
Yes, you read that right – more than
six hundred!
This many LEDs takes a lot of wiring – in fact, that part alone is going
to take you at least a full day or so to
do. But it’s not difficult because we
show you how each section is wired
and you test as you go, to make sure
you haven’t made any mistakes.
It’s also simple because all of the
control of these LEDs is achieved with
just three low-cost ICs.
Having said all that, this is probably not the sort of project you would
undertake as soon as you’ve learnt
to solder.
Additionally, it is not a cheap project. 600+ high brightness LEDs alone
will set you back about three hundred
dollars if bought “off the shelf”.
Incidentally, we must thank Jaycar
This is what the display looks like in fairly subdued light – the LEDs are starting to become quite dominant. What this
photo doesn’t show you is the movement – sled runners, reins and trails chasing, legs moving back and forth and of
course, Rudolph’s red nose flashing away merrily. At right is Fig.1, the circuit diagram. It doesn't show all 606 LEDs but
shows the drivers for each section of LEDs. All other LED sections are simply duplicates of what is shown.
14 Silicon Chip
November 2000 15
A leetle dab here, a leetle splash
there. . . our resident artist, Ferrari
TestaRossa, creating the masterpiece
on which our light show is based.
Do you like our artist’s pallette – an
offcut of PC board, just to keep the
electronics theme going!
Fig.2 (right): you can create your own
work of art, just as good as ours (and
probably much better!) using this 4:1
scale artwork as a base. This file is
also available on the SILICON CHIP
website, www.siliconchip.com.au
Electronics for helping us with the
parts for this project, not the least
being their ability to lay their hands
on 600+ high brightness LEDs at very
short notice! Good one, Jaycar!
The other components, the mounting and backing boards and timber,
the paint and various other bits and
pieces would probably the best part
of a hundred dollars.
So to have the best-looking house
in the street you’re going to have to
invest a bit of the folding stuff. But
once done (and protected from the
weather) you’ll have a display that
your children and grandchildren
will look at in awe, Christmas after
Christmas after Christmas!
And to make it a lot less painful for
you, both Jaycar Electronics and Dick
Smith Electronics have come to the
party with special prices on the complete kit of electronic parts (ie, the PC
board, on-board components, LEDs
and resistors but not the hardware).
It’s significantly less than buying
the components even in bulk packs.
These kits should be available during
early November.
By the way, when we gave this project our test run back in September,
we were simply amazed at the amount
of light it produced.
It was easily enough to read a car
number plate on the other side of a
very dark street – in fact, the whole
front yard lit up like – dare we say
it – a Christmas Tree!
During the day, the LEDs don’t
exactly do much (although you could
see them flashing even in sunlight).
What you do see is a large painting
16 Silicon Chip
of Rudolph, complete with red nose,
pulling good ol’ Saint Nick in his
sleigh full of goodies.
And here is where your display
gets much of its uniqueness: you get
to paint the image.
We’re going to give you a head start
with a really snazzy poster which you
can transfer to the board to use as a
base (and we’ll even show you how
easy that is).
We were going to ask Michaelangelo
to paint our image but he was busy
slapping a coat of paint on his sister’s
chapel or something, so we asked our
resident artist, Ferrari TestaRossa, to
draw and paint Rudi & Nick ready for
the big light job.
As you can see, it’s turned out pretty
neat. No, neat’s the wrong word. In
fact, up close it looks pretty messy
(apologies to my 3A art teacher at
Cowra Primary – you were right).
But move back a couple of metres
or so (or even a couple of hundred
metres or so) and it looks fantastic!
Our point is that you don’t need to
be any sort of artist to produce a
masterpiece. The real impact is not
so much in the image but in the way
it lights up at night.
At night, the coloured LEDs will
animate the display with apparent
motion for the reindeer and the sleigh.
Even the reins move, Rudolph’s red
nose blinks and trails behind the
antlers and sleigh give motion as it
glides through the sky.
We used three different LED colours – red, green and yellow – for
the display. Optional white or blue
LEDs, which actually twinkle, can
be included as separate stars in the
night sky backdrop or as a single star.
How it works
We haven’t tried to show all 600+
LEDs in Fig.1, the circuit diagram –
they simply wouldn’t fit even across
two pages. But that’s no problem
because the circuit can be divided
into sections which duplicate again
and again.
These sections are basically the
steady (looking like they’re constantly
on) LEDs which outline Santa and his
sack, the sleigh body, Rudolph’s body
and antlers; the chasing LEDs – the
reins, the sleigh runners and the trails;
and finally the alternating LEDs – Rudolph’s legs and his red nose.
We mentioned before optional
white LEDs (not included in the Jaycar
or DSE kits) which can be randomly
placed to simulate twinkling stars.
The steady or continuously driven
LEDs (identified on the circuit as LEDs
21-28 – in fact there are 271 of them
in our design but you could have
up to 800 maximum) are powered
directly via the 12VAC supply from
the transformer.
For one cycle or polarity of the AC
waveform, series connected LEDs 2124 are driven via the 180Ω resistor and
the reverse connected LEDs 25-28 are
off. When the AC waveform swings
the opposite way, LEDs 25-28 are
driven and LEDs 21-24 will be off .
Each lit LED will have a nominal
1.8-2V across it so the current applied
to the LEDs will be the supply voltage
(nominally 12V) minus the total LED
voltage drop (say 8V) all divided by
4 x 6 green chasing
6 yellow chasing
6 yellow chasing
19 green steady
(sack)
4-20 white or blue
twinkling (stars)
no positions shown random placementall optional
4 x 6 yellow chasing
November 2000 17
115 yellow chasing
100 red steady
(sleigh)
5 red flashing
(nose)
2 green steady
(eye)
4 x 14 yellow (legs) and
4 x 2 red (hooves) alternate
114 yellow steady
(rudolph)
60 green chasing
(reigns)
4 yellow steady
(beard)
40 red steady
(santa)
1 green steady
(eye)
2 x 6 yellow chasing
6 red steady
(navigation lights)
180Ω, which equals 22mA. Since each LED string is lit for
only half of the time, the average current for an individual
LED will be around 11mA.
The chaser, alternator and twinkle driven LEDs are controlled via the remaining circuitry.
Diodes D1-D4 rectify the 12VAC supply from the transformer to give a pulsating DC voltage to drive the chaser,
alternate and twinkle LEDs. This voltage is isolated by diode
D5 and smoothed by the 470µF capacitor. REG1, a 7812
regulator, provides the fixed 12V output required by
IC1-IC3.
Three oscillators provide the timing pulses required
for (a) the chasers, (b) the alternate switching (legs)
and flashing (nose) LEDs and (c) the optional “twinkling” LEDs (stars).
All are based on IC1, a hex (or six-way) Schmitt
trigger inverter. The inverters can be made to oscillate
by connecting a capacitor between input and ground
and a resistor between the Schmitt output and the
input. Each operates in a similar manner, the main
difference being their speed.
We’ll describe the chaser oscillator, based on IC1a.
The chaser circuits
The photograph of the PC board
above is reproduced same size as the
original, as is the component overlay
(Fig.2, below). Between these two you
should have all the information you
need to successfully complete the PC
board.
Initially, the 4.7µF capacitor is discharged so the
input (pin 1) is low and the output (pin 2) is high. The
capacitor charges via the 5.6kΩ resistor and VR1 until
the capacitor voltage reaches the upper threshold of
the Schmitt trigger input.
The output then goes low and the capacitor discharges via the resistors. The output of IC1a goes high
again when the lower threshold of the Schmitt trigger
input is reached.
Thus oscillation continues. VR1 sets the operating
frequency.
In the case of the chaser, pulses from IC1a trigger the
input of the decade counter IC2. This has ten separate
outputs which go high in succession at each positive
clock. In our case, though, we don’t allow it to count
all the way to ten.
First one ouput goes high, then the next output goes
high with the first output going low. The next output
then goes high and then the final output which resets
the counter immediately so that the first output is
again set high and so on.
4017 ICs are often used to drive a couple of LEDs
direct. But not 260 LEDs!
To drive the LEDs, we use IC3, a ULN2003A. This
contains seven Darlington transistors. Each of these is
capable of driving up to 30 strings (each of 4) of LEDs.
So the three chase outputs are connected to three Darlington drivers in IC3a. The pattern in which the LEDs
are arranged makes them light one after another – the
lights “chase” each other and simulate movement.
The reins, the trails and the runners are all driven
from the chaser outputs.
When pin 4 of IC2 is high, pin 16 of IC3 is pulled
low to turn on the “A” output LEDs (LEDs 1, 4, 7, 10
etc). These are powered from the unfiltered 12V DC
supply via a 390Ω resistor. Then when pin 2 of IC2
goes high, pin 15 of IC3 is pulled low to turn on the
“B” output involving LEDs 2, 5, 8, 11 etc. Finally,
when pin 3 goes high, pin 14 of IC3 turns on the “C”
output, (involving LEDs 3, 6, 9, 12 etc). This process
continues but your eyes do not flick back to the start
– they follow the movement along the strings.
The alternating circuits
The alternating circuits switch the LEDs on and off
on alternate legs, again simulating movement, while
at the same time flashing the red LEDs on Rudolph’s
red nose on and off.
18 Silicon Chip
Operation of the alternating circuits
is somewhat similar to the chasers,
except that there are only two states.
We could use another 4017 and count
to two but we had spare gates available in the 40106 so these were used
instead.
Output from IC1b is fed to the input
of two Schmitt inverter gates, IC1c
and IC1e.
One of these (IC1e) drives one of the
ULN2003A’s inputs direct – when its
output is high, the ULN2003 pin5/12
Darlington turns on. This switches
one of the alternating LED banks. IC1c
also switches high and low in unison
with IC1e but its output is connected
to yet another inverter, IC1d.
Therefore when IC1e’s output is
high, IC1d’s output is low and vice
versa.
IC1d switches the ULN2003 pin4/13
Darlington so the other alternating
LED banks light.
Twinkle twinkle little star(s)
The twinkle circuit itself is included because it requires only four
additional low-cost components – the
IC gates would otherwise be wasted.
The circuit is even simpler – the
oscillator, which runs quite a lot
faster than the other two, drives a
ULN2003A Darlington direct while
the output from that Darlington drives
Fig.3: the simple test jig which you
can lash together to make sure your
PC board is working properly. It’s a
lot easier to troubleshoot the main
display LEDs if you know the
electronics are working!
the input to the last Darlington.
Thus the two strings of LEDs also
light alternately but due to the speed
of operation, appear to twinkle rather
than flash.
The reason this circuit is regarded
as optional is the price of white (or
blue) LEDs. These are quite a lot more
expensive than coloured LEDs – ten
times as much – so to keep the cost
of the kit as low as possible, are not
included. Provision is made for those
who want them.
PC board construction
With the exception of the LEDs
and their current-limiting resistors,
all components mount on a PC board
coded 16111001 and measuring 89 x
60mm.
The LEDs and resistors mount directly onto the hardboard display and
are wired together and connect to the
appropriate PC board terminals.
Begin construction by checking the
PC board for shorts between tracks
and breaks in the copper circuit. Also
check that the hole sizes are correct.
You will need a 3mm hole for the
regulator tab to be bolted down on
the PC board.
Insert all the diodes, links and resistors first – use the accompanying
resistor colour code table as a guide
to the resistor values. Alternatively
you can use a digital multimeter to
select the resistor value required for
each position.
When installing the ICs, ensure
each is placed in the correct position
Parts list
2 1220 x 915 sheets of Masonite WhiteCote or similar
hardboard
1 4.2m length of 50 x 25mm pine
1 PC board coded 16111001, 89 x 60mm
1 12V 5.25A (63VA) or similar enclosed halogen lamp
transformer (eg Jaycar MP-3050)
1 3m length of red medium duty hookup wire
1 3m length of black medium duty hookup wire
1 3m length of green medium duty hookup wire
1 3m length of blue medium duty hookup wire
1 20m length of 0.8mm tinned copper wire
1 length (to suit location) 10A figure-8 cable
1 M3 x 6mm screw and nut
2 2-way terminal blocks
10 PC stakes
Semiconductors
1 74C14, 40106 hex Schmitt trigger (IC1)
1 4017 decade counter (IC2)
1 ULN2003 Darlington driver (IC3)
1 7812 1A 12V 3-terminal regulator (REG1)
5 1N4004 1A diodes (D1-D5)
343 yellow 5mm high brightness LEDs
157 red 5mm high brightness LEDs
106 green 5mm high brightness LEDs
8 white or blue 5mm LEDs (optional)
7 5mm standard LEDs, any colour (for test jig)
Capacitors
1 470µF 25VW PC electrolytic
2 10µF 16VW PC electrolytic
2 4.7µF 16VW PC electrolytic
1 1µF 16VW PC electrolytic
1 0.1µF MKT polyester (coded 104 or 100n)
Resistors (0.25W 1%)
1 10kΩ
(brown-black-black-red-brown)
9 5.6kΩ
(green-blue-black-brown-brown)
1 1kΩ
(brown-black-black-brown-brown)
3 2.2kΩ (for test jig) (red-red-black-brown-brown)
37 390Ω
(orange-white-brown-black-brown)
35 180Ω
(brown-grey-brown-black-brown)
3 220kΩ or 250kΩ horizontal mount trim pots
(VR1-VR3)
(coded 224 or 254)
Miscellaneous
Wood screws, PVA glue, neutral cure silicone sealant,
acrylic paint, wide-point marker pens, carbon paper (if
required)
November 2000 19
Here’s how we transferred the artwork onto our Masonite board. First, we printed the poster out on a laser printer in
“tile” mode and then sticky-taped the whole lot together. Then we stuck this on the Masonite and traced the whole thing
with carbon paper. There are other ways to do this – eg, it’s real simple if you have access to an overhead projector!
and is oriented correctly; likewise the
electrolytic capacitors. PC stakes can
now be inserted as well as the trimpots. REG1 is mounted by bending the
leads to fit into the holes provided,
soldering them in and bolting the
metal tab to the PC board.
Testing
To ensure everything works correctly, we use a special test jig as shown in
Fig.3. Wire up seven LEDs as shown
and apply power. Check that the chaser LEDs (three to the left) move from
right to left and that the alternating
LEDs (next two) flash alternately.
The twinkle LEDs to the right
should also alternate
but the speed may be
too fast to tell.
Adjust the chaser
and alternating trimpots VR1 and VR2
so that the chaser is
slightly faster than the
alternator and at a rate
The LED wiring on the
rear of the display
may look like a dog’s
breakfast but is
actually quite logical.
All LEDs are soldered
leg to leg where possible, then joined with
either tinned copper
wire or insulated wire.
The wiring diagram
overleaf shows this
more clearly. The wood
blocks are pine offcuts
which keep the back
sheet of Masonite away
from the wiring.
20 Silicon Chip
of about two steps per second.
The twinkle trimpot should be adjusted so that the LEDs are flickering
at a fast rate.
If the circuit does not operate check
for shorts on the PC board and power
to IC1 and IC2. There should be 12V
between pins 14 and 7 of IC1 and
between pins 16 and 8 of IC2.
Your masterpiece
Here’s where the real fun part starts.
Even if you’re not a “real” artist, you
can produce a more-than-acceptable
result.
In fact, there are several ways to
do it, depending on your ability, the
equipment you have access to and the
depth of your pockets.
You could, of course, design and
paint your original artwork directly
onto the “whitecote” Masonite. But if
you’re a mere mortal, you may need
to use someone else’s creative genius.
Reproduced herewith is our masterpiece. The JPEG file is also available
for downloading on www.siliconchip.
com.au What can you do with it?
Our original plan was to get a local
computer graphics house to print it
out full size (A0 – 1188 x 840mm).
Then we found that a poster this
size isn’t exactly cheap – we were
quoted about $165 at our local Kinco’s
Steady LED Bank
Fig.4: the “steady”
bank of LEDs (the ones
which are apparently
on the whole time) are
driven from the two
halves of the AC waveform. Wire them as
shown. This layout is
repeated many, many
times!
and scrape it with a straight edge to
remove all the timber swarf. We also
used a very much larger drill, twisted
in the fingers, to remove any swarf
from the front of the board.
With 20/20 hindsight, we don’t
think this step is all that important
because the paint you’re about to
apply hides any rough edges.
Painting
store. Chief bean counter and he who
must be obeyed (CBC & HWMBO)
hasn’t really recovered yet from that
quote. Scratch that idea.
One tried-and-trusted method of
transferring artwork is the “grid”
method. You will note a fine blue grid
printed over the artwork – this grid
is scaled up (4:1) to the 1220 x 915
sheet and used to draw the image on.
Another way, if you have the facilities, is to print out a copy of the
artwork on overhead projector transparency and project the image onto
the Masonite. You then simply trace
over it with a pencil.
The method we finally used was a
bit more creative. We simply printed
the image out as “tiles” on a laser
printer, stuck them all together, then
traced the artwork onto the Masonite
using carbon paper.
Mind you, finding carbon paper at
your local newsagents or stationers
these days is not quite the simple task
you might expect (kids everywhere
are asking “what’s carbon paper?).
We were fortunate in having an A3
printer – that only needed
12 sheets. If you have to
print it out A4, be prepared
to use double that number.
It’s a lot of sticking together
but it works.
for drilling our holes – through both
paper and Masonite.
You need 5mm holes for the LEDs –
this allows them to poke right through
and sit on their collars.
A few tips:
(a) secure the paper artwork to the
board properly so that it doesn’t move
around, allowing your holes to drift
(b) support the board adequately
so that the drill doesn’t flex it when
you apply pressure.
(c) use a drill with a trigger lock. I
didn’t – and that makes it even more
tiring on the hand.
(d) In some ways it’s easier just to
start all the holes with the paper in
place then remove the paper to drill
them out fully.
(e) If you do manage to get a hole
out of position by a few mm or so,
don’t worry. It’ll look alright on the
night (adjust your paintwork to suit.
Whatever you do, don’t try to correct
mistakes – that only makes things
worse!).
When you have drilled all the
holes right out, turn the board over
Having transferred the basic image
to the Masonite and drilled the holes,
it’s time to start painting. We purchased some $2.75 tubes of Acrylic
paint at a local art supplies store –
you’ll need a red, blue, green, yellow,
black, white and brown. Of course you
can mix intermediate colours from
the primaries if you wish to save a
couple of bob.
As far as colours are concerned, we
probably don’t need to remind you
that the jolly fat gent is basically red
and Rudolph is either fawn with grey
or grey with fawn (no, not that sort
of fawn – Rudolph is not that kind of
reindeer. Until he got to pull the sleigh
all the other reindeers used to laugh
and call him names, remember?).
Apart from that, it’s up to you – just
remember the colours of the LEDs
you’re going to get in your kit.
Acrylic paint dries pretty quickly,
even when applied thick. We used
some el-cheapo brushes (in deference
to CBC & HWMBO) so our artwork
didn’t turn out all that smooth. But
as we said before, it matters not one
Fig.5: to make the LEDs chase, you simply arrange them in a particular
flashing pattern. This shows how to do it: 1 to 4, 7 & 10; 2 to 5, 8 & 11; 3 to 6,
9 & 12, and so on. The chasers are driven from rectified but unsmoothed DC.
Drilling the ’oles
Got a spare hour or ten?
You’re gonna need it! Drilling 600+ holes may not seem
like such a tough task but
believe me, my hand ached
something fierce after the
first hundred or two.
I was really glad that the
cordless drill battery was
just as run down as I was
and needed a couple of recharges – just for the breaks
it gave me.
We simply used the paper
layout, still stuck in position
from tracing, as the template
Fig.7: the optional “twinkling”
LEDs are for stars
and these can be
spread around the
board as desired.
Fig.8: the alternating LEDs (the
reindeer legs) are also driven
from pulsating DC. String “D”
is in one leg, string “E” is in the
opposite leg.
November 2000 21
Fig.8: this diagram shows the complete project wired, viewed from the BACK of the the Masonite (ie, the side
you poke the LEDs through and the side on which all the wiring is done). Compare this with the photo one
page back. We have split the project into two sections and turned them on their sides for clarity – otherwise
we would have had LEDs going across the “gutter” between the pages which might make the drawing difficult
to follow.
22 Silicon Chip
November 2000 23
jot nor tittle how good or bad your
artwork is, as long as from a distance
it looks the part.
It’s a good idea to concentrate on
one main colour and leave that to dry
before painting adjacent colours. A
broad-nibbed marker pen is used to
roughly highlight and outline various
sections. It can also be used to smooth
out any rough spots on things like the
runners and reins.
In fact (another 20/20 hindsight) the
reins could be completely done with
the marker pen and look even better.
For the movement trails, we haven’t
shown any artwork – all you need to
do is apply a light “swish” of appropriately coloured paint (grey with a bit
of yellow in it or overprinting it works
well), heaviest at the start and trailing
off towards the end. The photo gives a
good idea of what we mean.
You might also like to look at painting the white Masonite a different colour, especially if you are using white
LEDs as stars. And if you think your
artwork is THAT good, don’t forget to
sign it. Who knows, it could be worth
$$$$ in years to come!
Strengthening the board
As you probably know, 3mm Masonite is not exactly the most rigid
stuff ever invented. It warps badly if
not supported properly.
To prevent warping, we glued a
frame of 50 x 25mm dressed pine right
around the back edge of the frame. As
we planned to place another sheet of
protective Masonite on the back when
the project was complete, we glued
some offcuts of 50 x 25mm pine in
various spots, well clear of any LED
mounting holes.
Wiring up
This wiring job is going to take some
time to do (it took us nearly two days)
so it is recommended that you position
the board in a place where it can be
safely worked on without needing to
move it (eg, to get the car in and out
of the garage!).
Support the board around the edges
so that the LEDs can be inserted easily
without resistance from underneath.
We also recommend testing each block
as it is wired so that the whole circuit
will work when completed and to ensure that if you have made a mistake
this will not be repeated throughout
the whole wiring.
Also the wiring must be kept low
enough so that the rear sheet of
hardboard can be placed on the back
without disturbing any connections.
Our artwork shows the suggested
colour guide for LEDs. Of course the
choices are up to you: for example,
I originally had all yellow LEDs on
the antlers but John said the tips of
the antlers needed red “navigation”
LEDs.
He was right – they look fantastic!
Another tip: keep each of the trail
chasers the same colours. Having a
multi-coloured chaser doesn’t work
well because the eye notices the colour change rather than the chase. Of
course, you could change any of the
6-LED sets to another LED colour if
you wish.
While the PC board is intended to be sandwiched inside
the two pieces of Masonite with the LEDs and resistors,
there will be constructors who wish to place it in an
external case, as shown here.
24 Silicon Chip
The LEDs are all wired up as banks
or blocks. For example the steady
LEDs are connected as a bank of 8
and one resistor. The circuit is simply
duplicated as many times as required
to obtain the necessary number of
connected LEDs.
Use tinned copper wire to interconnect LEDs where the spacing is beyond
the length of the LED leads. This
will be necessary when a particular
outline is finished and the LEDs need
to be wired to another outline on the
drawing.
Additionally, for the last block
where there are less LEDs needed than
required by a block, you can increase
the resistors to keep a more-or-less
equal current flowing through the
LEDs (and therefore much the same
brightness).
A normal block of eight LEDs
(where there are two lots of four LEDs
in series) can be truncated to two or
three LEDs in series. Use two series
connected 390Ω resistors for these to
obtain a similar LED brightness.
The steady LEDs can be wired in
banks of eight as shown in Fig.4.
Wire the LEDs in series as shown by
bending the leads and soldering in a
daisy chain. Most LEDs legs will be
long enough to solder direct to their
neighbours but where the leads will
not reach to the adjacent LED, use
tinned copper wire.
Connect the anode of LED21 to the
cathode of LED28 with tinned copper
wire. The free end of the 180Ω resistor
connects back to the 12VAC(1) terminal. The cathode of LED24 and anode
The PC board is designed to mount inside this commonly
available waterproof case. When completed, the holes under
the terminal strip should be sealed with silicone sealant to
protect the components inside.
of LED25 connect to the 12VAC(2)
terminal (again refer to Fig 4).
The chaser wiring is perhaps most
difficult since the LEDs do not connect
in series to adjacent LEDs but connect
in series to the third LED along (ie,
LED 1, 4, 7, 10, etc connect, LED 2,
5, 8, 11, etc connect; and LEDs 3, 6,
9, 12, etc connect).
The cathode (K) leads for LEDs 10,
11 & 12 connect to the A, B & C PC
board terminals respectively. Follow
this wiring carefully since it is important to obtain the correct direction
effect around the sleigh rails and for
the reins and trails. If some of the
chasers are running backwards this
is easily changed by swapping the
connections to the A, B & C terminals
on the PC board.
Twinkle LEDs, if fitted, are simply
wired as shown in Fig.5. Make sure
the 390Ω resistor goes to the 12VDC
on the PC board, not the 12VAC. The
K leads on LED30 and LED32 go to
the F and G outputs on the PC board.
If you use white (or blue) LEDs anywhere else on the design, remember
they have a higher voltage drop and
resistor values will need to be adjusted accordingly.
When wiring is complete and the
entire circuit is working, you will
need to secure the wiring to the board
using masking tape and some Silicone
sealant.
Some LEDs may be a little sloppy in
their holes: make sure that any loose
LEDs are secured with sealant and
that potential problems with wires
shorting are held apart with the sealant and/or insulation tape.
The PC board is also secured with
sealant and is wired to the 2-way
terminal strip for the 12VAC wiring.
Drill a hole for the wiring to exit
from the rear of the pine strips or
through the rear of the hardboard
backing sheet. Secure the terminal
strip with a wood screw and attach
another 2-way strip to the rear of the
hardboard once secured with wood
screws.
Give it another check to make sure
it works and if all is well, screw the
back on with at least eight small
woodscrews across each edge. The
backing will help prevent warping
so it is essential it is supported well
itself.
Location
Ideally, the display should be used
Fig.9: full-size
artwork for the
PC board. You
can use this to
check for defects
in commercial
boards or if you
want to make
your own board.
(PC board patterns can also
be downloaded
from the SILICON
CHIP website.)
inside – say in a large window or the
fixed panels of sliding doors.
If you must use it outside, we would
apply several coats of clear spray or
even two-part clear polyurethane over
the whole thing – front, back and sides
– to protect it, and the electronics
inside, from the elements.
If you do use it outside, protect it
as much as possible (eg, under an
eave) and make sure the transformer
is run inside with a long figure-8 cable
connecting it to the display.
Remember it draws the best part
of 2A (depending on the number of
LEDs lit at any one time) so heavy
duty cable is essential if you are not
to suffer unacceptable voltage drops
over long cable lengths.
And that’s just about it. But before
we conclude, we mentioned before
the possibility of making the display
even larger.
Realistically, you’re limited by the
size of a mounting board you can get.
2400 x 1200mm is pretty much the
limit from most hardware stores. Of
course, you could always make a frame
which held more than one sheet!
On the circuit, we’ve indicated the
number of LEDs the various circuit
elements will handle – just keep your
design within these limits.
And you could also use giant
(10mm) LEDs on a larger display.
They’re not as easy to get in superbright and you’ll be paying the best
part of $1000 for 700 of these.
But if, for instance, you had a corporate budget to play with and really
wanted to impress . . .
SC
WOW! The sky’s the limit.
Wheredyageddit ?
At time of going to press, two kit suppliers had indicated that they planned to release “shortform”
kits (ie, the PC board and electronics but not the hardware (timber, paint etc) for the Christmas Light
Display. In both cases (and, we should add, completely independently) Dick Smith Electronics and
Jaycar Electronics have come up with kit prices which we believe are exceptional value –
especially when compared to retail component prices (see text). Details/availability are as follows:
Dick Smith Electronics:
Kit sells for $148.00 (Cat K3003)
Note: this kit is not available in all Dick Smith
Electronics stores. It should be released 2nd
week November (or soon after), only at Dick
Smith PowerHouse stores or through DSE
Direct Link mail/fax/email/internet order service
(Phone 1800 355 544; fax 02 9395 1155, email
directlink<at>dse.com.au
Jaycar Electronics:
Kit sells for $169.00 (Cat KC5302)
This kit INCLUDES the specified transformer
and 10m figure-8 cable, worth about $30. It
should be available around the end 1st week
November (or soon after) from all Jaycar
stores and through Jaycar TechStore mail/fax/
online order service (Phone 1800 022 888; fax
02 9743 2061, email techstore<at>jaycar.com.au
November 2000 25
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
A 2-channel gui
PART 1: By JOHN CLARKE
This high-quality guitar preamplifier
is easy to build, with all components
and hardware on the PC boards. You
can build it with one, two or more
channels and each channel has input,
bass, mid and treble controls.
30 Silicon Chip
As well as the mandatory tone
controls, this versatile unit has several other desirable features. These
include effects send and return, a
line input socket and a headphone
socket so that you can practice without disturbing others. There’s also an
optional digital reverberation board
(we’ll show you how to build that in
a future issue).
While most people wanting a guitar amplifier would tend to purchase
a commercial unit with an inbuilt
speaker, they often have mediocre
performance, with plenty of hum
and buzz, and even pickup of radio
stations and mobile radios. They of-
itar preamplifier
Main Features
ten have quite a lot of distortion too,
particularly with the unbaffled loud
speaker and modest power output.
Even the headphone outputs are often
noisy and distorted.
By building this S ILICON C HIP
preamplifier and teaming it with,
say, our 175W plastic power module
(described in April 1996), you can
produce a very high quality guitar
amplifier. Why would you bother with
anything else?
This completely new design comprises two PC boards, with the larger
one carrying one channel, the mixing
for both channels and the regulated
power supply. The second, smaller PC
board carries two ICs and four pots,
for the second channel.
Actually, while we are presenting
this design as a 2-channel setup, there
is no reason why you could not add
more channels, just by building the
required number of the smaller PC
boards.
On the main board, the input and
controls are arranged in a logical
manner with the main input located
to the left. Next to it is the level control which adjusts the individual
volume from the guitar. Then there
are the bass, mid range and treble
controls. An effects return level pot
follows this and then the main mixer
•
•
•
•
•
•
•
•
•
Level control.
Bass, Mid and Treble
controls.
Master volume.
Effects return control.
Balanced & unbalanced
line outputs.
Headphone output.
Line and effects return
inputs.
Effects send output.
Optional Digital Reverber
ation in effects loop (to be
described in a later issue).
November 2000 31
Fig.1: block diagram of the Guitar Preamplifier. It has two identical channels (one optional) which are mixed together
and then mixed again with an effects return signal (eg, from a reverberation unit). The resulting signal is then amplified
and fed to the output sockets.
volume control. The headphone socket
is located to the right of the volume
control.
The preamplifier is powered from a
30VAC centre-tapped 5VA transformer. All the rectifier, filter and regulator
components are located on the main
PC board.
Block diagram
Fig.1 shows the block diagram for
the Guitar Preamplifier. As you can
see, it has two identical channels,
both with two gain stages with gains
of 4.9 and 9.3, respectively. Between
the gain stages is a level control (VR1).
This allows the signal level to be ad-
justed so that following stages are not
overloaded.
Following the second gain stage
are the bass, mid and treble controls.
These provide bass boost or cut below
100Hz, mid range boost or cut centred
on 1kHz and treble cut or boost above
10kHz. The graph of Fig.2 shows their
performance.
Both channels are then mixed
together in the first mixer (IC3) and
this is where the additional channels
would be mixed if you wanted them.
The output from the first mixer provides an effects send signal suitable for
reverberation, fuzz, tremolo or other
effects. This mixer output, the effects
SPECIFICATIONS
Frequency response ��������������������������� -3dB at 20Hz & 30kHz (with tone controls at
mid-settings)
Signal to noise ratio ��������������������������� -86dB unweighted (with respect to 1V output
and 50mV input, with input shorted; 20Hz to
20kHz bandwidth); -88dB A-weighted.
Total harmonic distortion ������������������� 0.007% at 1kHz and 10kHz
Input sensitivity ���������������������������������� guitar input, 10.5mV RMS for 1V output; line
and effects return, 1V for 1V out
Maximum signal at guitar input
before overload ................................... 1.8V RMS
Tone controls ....................................... (see graph)
Headphone output ............................... 45mW into 8Ω
32 Silicon Chip
return input and the line input are
combined together in the second mixer
(IC4a). The effects return level is set by
VR6. There is no volume control for
the line input since the signal source
for this would already have a output
level control.
The mixer output connects to a
balanced output driver com
prising
IC4b and IC4c and this makes the
whole system suitable for connection
to a multi-channel audio mixer or a
remote external power amplifier. A lot
of people won’t need this feature but
the extra components and the two op
amps in the quad package don’t add
much cost. If you want good quality
signals over long lines, the balanced
outputs are mandatory.
The master volume output from
the second mixer controls the overall
signal applied to the unbalanced line
output buffer and the headphone amplifier. This amplifier can drive two
sets of stereo headphones. The signal
is paralleled in both the left and right
channels of the headphones to produce a mono signal.
Circuit description
Fig.3 shows a 2-channel version
of the guitar preamplifier. It employs
nine op amps in five IC packages. All
are from the readily available Texas
TL07X series, giving low noise and
(ie, high impedance). So by providing
a low source impedance, we reduce
the hum and buzz.
Apart from anything else, this makes
for a much cleaner sound.
The gain of IC1a is set by the 4.7kΩ
and 1.2kΩ resistors in the feedback
network. This provides a gain of 4.9
(+13.8dB). A 560pF capacitor across
the 4.7kΩ feedback resistor rolls off
high frequencies above 60kHz. The
output signal from pin 7 of IC1a is
AC-coupled via a 2.2µF non-polarised
electrolytic capacitor to the level pot
VR1.
This capacitor prevents any DC
current flow in the pot which would
cause noise every time you adjusted it.
Similarly, the 0.22µF capacitor to the
pin 3 input of IC1b is there to block
DC current. IC1b is set to a gain of 9.33
(+18.4dB) and the 220pF capacitor
across the 10kΩ feedback resistor rolls
off high frequencies above 72kHz.
Tone controls
low distortion.
IC1 is a TL072 dual op amp. The
guitar signal is fed to the non-inverting
input, pin 5, via a 1kΩ stopper resistor
and a 47µF non-polarised capacitor.
The 220kΩ resistor sets the input
impedance so that the guitar pickup
provides a good treble response while
the 10pF shunt capacitor at pin 5
prevents extraneous radio frequency
(RF) pickup.
Readers might wonder why we have
used such a big input coupling capacitor in view of the fact that the input
impedance of the circuit is quite high
at 220kΩ. The reason is that the guitar
pickup is inductive and therefore its
source impedance at low frequencies
is quite low. Now we want the minimum noise to be produced by the
preamplifier and the way to do that
is for it to “see” the lowest possible
source impedance. Ergo, we have a
large input capacitor.
We have taken the same approach
in the past with our low-noise phono
preamplifier designs.
Reduced hum & buzz
However, it turns out that the large
input capacitor and resultant low
source impedance have another bene
fit – reduced hum and buzz. The reason for this is that most of the hum and
buzz on a guitar input is electrostatic
The Baxandall (ie, feedback type)
tone controls are based on op amp
IC2, together with potentiometers VR2,
VR3 & VR4. These pots and their associated resistors and capacitors form
the feedback between the op amp’s
inverting input and its output.
Each of the bass, mid and treble
networks can be considered separately
since they are connected in parallel
between the signal input following
IC1b and the output of IC2 at pin 6.
Furthermore, the wiper of each pot is
effectively connected to the inverting
input (pin 2) which is a virtual ground.
Operation of the bass control is as
follows: with VR2 centred, the value
of resistance connected between the
output from IC1b and pin 2 of IC2 is
the same as that between pin 2 and
pin 6 and this sets the gain to -1. The
.015µF capacitor has no effect since
it is equally balanced across the potentiometer.
If we move the wiper of VR2 fully
clockwise, we get 18kΩ between the
input and pin 2 of IC2 and 118kΩ between pin 2 and pin 6. In addition, the
.015µF capacitor is across the 100kΩ
resistance in the feedback loop.
Without the capacitor the gain
would be -118kΩ/18kΩ or -6.5 at all
frequencies. But with the capacitor, the
gain is high only at around 50Hz and
as the frequency rises it comes back
to 0.1 (ie, overall unity gain). Thus we
have bass boost.
Conversely, when VR2 is wound
fully anticlockwise, the position
is reversed and we get a gain of
18kΩ/118kΩ or -0.15 (-16dB). The
capacitor is now on the input side and
provides less gain at frequencies below
100Hz but with gain increasing to -1 at
AUDIO PRECISION AMP AMPL(dBV) vs FREQ(Hz)
20.000
15.000
13 APR 100 07:25:21
Bass
10.000
Midrange
Treble
5.0000
0.0
-5.000
-10.00
-15.00
-20.00
20
100
1k
10k
20k
Fig.2: this graph shows the response curves for the bass, midrange and treble
controls. The bass boost or cut is mainly below 100Hz, the midrange boost or cut
is centred on 1kHz and the treble boost or cut is mainly above 10kHz.
November 2000 33
34 Silicon Chip
Fig.3: this is the complete circuit
diagram, with the optional second
channel highlighted on a red
background. For each channel, the
incoming signal is amplified by IC1a
& IC1b and then fed to Baxandall
tone control stages based on IC2 and
potentiometers VR2, VR3 & VR4. The
outputs from the tone control stages
are then fed to mixer stages IC3 and
IC4a for mixing with the effects return
signal. Op amp IC5 and transisistors
Q1 & Q2 form the headphone
amplifier.
November 2000 35
frequencies above 100Hz. Thus we have
bass cut. Various settings of VR2 between
these two extremes will provide for less
boost and cut.
The midrange section works in a similar
manner except that there is now a .012µF
capacitor between VR3’s wiper and pin
2. This, along with the .0027µF capacitor across VR3, gives a bandpass filter,
so we either boost or cut the midrange
frequencies.
The treble control operates with no
capacitor across VR4 but with a .0015µF
capacitor between the wiper and pin 2
to produce a high frequency boost or cut
at 10kHz.
The graph of Fig.2 shows the response
of the tone controls, with each one individually set to its maximum or minimum
settings while the other two are centred.
A 39pF capacitor between pins 2 & 6
of IC2 provides a high-frequency rolloff
to prevent oscillation which could otherwise occur when the treble control is set
for maximum boost. Similarly, the 1kΩ
resistor in series with pin 2 is there to
attenuate RF signals; it stops radio breakthrough. The op amp is also provided with
an offset adjustment using VR7 which is
Above: these two photos show the
fully-assembled PC boards. Note that
it is important that the metal contacts
on the input jack sockets face in the
correct direction, as described in the
text.
Fig.4: follow this parts layout diagram to build the main preamplifier
and mixer board for channel 1.
36 Silicon Chip
Fig.5: the parts layout
for the optional
channel 2 PC board.
Note the length of
tinned copper wire
(shown in green) that’s
used to link the pot
bodies together.
set to minimise the DC current flow
in bass pot VR2.
The outputs from IC2 (in channels
1 and 2) are AC-coupled to the first
mixer stage (IC3) via 2.2µF
capacitors and 33kΩ resistors. Note that the channel 2
output is also fed to IC3 via a
150Ω resistor which prevents
any instability which would
otherwise occur with the short
length of shielded cable between
the two boards.
Mixer stages
IC3 combines the two channel signals and provides a gain of about -2. Its
output is coupled to the “effects send”
output via a 47µF capacitor and 150Ω
November 2000 37
Fig.6: this is the fullsize etching pattern
for the channel 2 PC
board. Check all PC
boards carefully for
etching defects before
installing any of the
parts.
resistor. The capacitor blocks the DC
offset at IC2’s output while the 150Ω
resistor isolates the output, preventing
instability which could occur with
shielded (capacitive) leads. The 10kΩ
resistor to ground provides a charging
path for the 47µF capacitor.
IC3’s output is also fed to mixer
amplifier IC4a via a 10kΩ resistor.
The line input is also applied to this
mixer summer via a 2.2µF DC blocking capacitor and 10kΩ resistor. Similarly, the “effects return” signal is
coupled to VR6, the effects level pot,
via a 2.2µF capacitor and the wiper
signal is applied to IC4a via a 10kΩ
resistor. The gain of IC4a is -1 for all
three inputs.
IC4a’s output is AC-coupled to the
main volume control VR5 and to the
balanced output stage involving IC4b
and IC4c. IC4b is a non-inverting buffer
which drives pin 2 of the balanced
output, while IC4c is an inverting
buffer and drives pin 3.
The output from the volume control
(VR5) is coupled to buffer amplifier
IC4d via a 0.22µF capacitor. IC4d provides the unbalanced output which is
suitable for driving an amplifier. IC4d
also drives the headphone amplifier
which comprises IC5 and transistors
Q1 & Q2.
output so that two sets of headphones
can be driven simultaneously. Note
that only one socket is provided on
the PC board.
Power
The op amps for the guitar preamplifier require a ±15V supply and
this is provided using two 3-terminal
regulators. REG1 produces a +15V
regulated supply while REG2 provides
the -15V rail.
Headphone amplifier
Op amp IC5 is combined with a complementary transistor output stage to
drive the headphones. The transistors
are within the feedback network of the
op amp and so the overall distortion
of the stage is low.
The complementary transistors are
operated in class AB and are biased
on via diodes D1 and D2 to reduce
crossover distortion. The overall gain
of the headphone amplifier is set to 3.2
by the 2.2kΩ feedback resistor between
the amplifier output and pin 2 of IC5
and the 1kΩ resistor to ground.
Two 68Ω resistors connect to the
Construction
There may appear to be a lot of
circuitry in the Guitar Preamplifier
but it is easy to build, with all of the
parts on two PC boards. The main PC
board is coded 01111001 and measures 234 x 76mm. It carries all the
parts necessary for a single channel
preamplifier, including the mixer,
output stages and the headphone
amplifier.
The second PC board is coded
Table 1: Resistor Colour Codes
o
No.
o 1
o 3
o 1
o 2
o 1
o 2
o 2
o
14
o 3
o 1
o 2
o 4
o 3
o 2
o 2
38 Silicon Chip
Value
220kΩ
100kΩ
68kΩ
33kΩ
27kΩ
18kΩ
12kΩ
10kΩ
4.7kΩ
2.2kΩ
1.2kΩ
1kΩ
150Ω
68Ω
33Ω
4-Band Code (1%)
red red yellow brown
brown black yellow brown
blue grey orange brown
orange orange orange brown
red violet orange brown
brown grey orange brown
brown red orange brown
brown brown orange brown
yellow violet red brown
red red red brown
brown red red brown
brown black red brown
brown green brown brown
blue grey black brown
orange orange black brown
5-Band Code (1%)
red red black orange brown
brown black black orange brown
blue grey black red brown
orange orange black red brown
red violet black red brown
brown grey black red brown
brown red black red brown
brown brown black red brown
yellow violet black brown brown
red red black brown brown
brown red black brown brown
brown black black brown brown
brown green black black brown
blue grey black gold brown
orange orange black gold brown
Table 2: Capacitor Codes
o
o
o
o
o
o
o
o
o
o
o
Value
IEC Code EIA Code
0.22µF 220n 224
.015µF 15n 153
.012µF 12n 123
.0027µF 2n7 272
.0015µF 1n5 152
560pF 560p 561
220pF 220p 221
150pF 150p 151
39pF 39p 39
10pF 10p 10
01111002 and 142 x 58mm. This
board accommodates only the input
preamplifier and tone control stages
for the second channel. If you require
additional channels, then it’s just a
matter of adding the extra boards.
Before installing any of the parts,
check the PC boards for shorts or
breaks between tracks. You should
also check the holes sizes for the pots
and 6.35mm jack sockets, to make sure
these parts fit correctly – they require
2mm holes.
Figs.4 & 5 shows the assembly details for the two PC boards. Begin by
installing 15 PC stakes at the external
wiring positions on the main PC
board, then install the resistors and
wire links. Table 1 shows the resistor
colour codes but it’s also a good idea
to check their values using a digital
multimeter.
The five ICs can go in next, taking
care to ensure that they are all correctly
orientated (ie, with their notched ends
towards the pots). Also, make sure that
IC1 is a TL072 and that IC2, IC3 & IC5
are all TL071s.
Now for the capacitors. As always,
make sure that the electrolytic types in
the power supply (1000µF and 10µF)
are installed with the correct polarity.
The BP or NP (bipolar or non-polarised) values can be installed either
way around.
Table 2 shows the IEC and EIA marking codes for the smaller capacitors.
Transistors Q1 & Q2 and diodes D1D6 can be installed now. Don’t get the
transistors mixed up – Q1 is a BC337
(NPN), while Q2 is a BC327 (PNP).
Similarly, take care with regulators
REG1 (7815) and REG2 (7915). Each
must be installed in its correct location, with its metal tab facing towards
its adjacent 1000µF filter capacitor.
Next, install trimpot VR7 on the
Fig.7: full-size etching pattern for the main PC board.
November 2000 39
Parts List
Main PC board
1 PC board, code 01111001,
234 x 76mm
1 6.35mm PC-mount stereo jack
socket
1 6.35mm PC-mount switched
mono jack socket
3 grey knobs (bass, mid & treble)
2 yellow knobs (level & volume)
1 blue knob (effects)
1 400mm length of 0.8mm tinned
copper wire
18 PC stakes
Semiconductors
1 TL072, LF353 dual op amp
(IC1)
3 TL071, LF351 op amps
(IC2,IC3,IC5)
1 TL074. LF347 quad op amp
(IC4)
1 7815T 15V regulator (REG1)
1 7915T -15V regulator (REG2)
1 BC337 NPN transistor (Q1)
1 BC327 PNP transistor (Q2)
4 1N4004 1A diodes (D1-D4)
2 1N914, 1N4148 switching
diodes (D5,D6)
Capacitors
2 1000µF 25VW PC electrolytic
5 47µF NP PC electrolytic
7 10µF 63VW PC electrolytic
6 2.2µF NP PC electrolytic
1 1µF NP PC electrolytic
3 0.22µF MKT polyester
1 .015µF MKT polyester
1 .012µF MKT polyester
1 .0027µF MKT polyester
1 .0015µF MKT polyester
1 560pF ceramic
3 220pF ceramic
2 150pF ceramic
2 39pF ceramic
1 10pF ceramic
Potentiometers
3 10kΩ 16mm log pots
(VR1,VR5,VR6)
3 100kΩ 16mm linear pots
(VR2,VR3,VR4)
1 10kΩ horizontal trimpot (VR7)
main board, followed by the 6.35mm
jack sockets (two on the main board,
one on the channel 2 board). Note that
there are two types of 6.35mm jack
sockets – mono and stereo. The mono
40 Silicon Chip
Resistors (0.25W, 1%)
1 220kΩ
3 4.7kΩ
3 100kΩ
1 2.2kΩ
1 68kΩ
2 1.2kΩ
2 33kΩ
4 1kΩ
1 27kΩ
4 150Ω
2 18kΩ
2 68Ω
2 12kΩ
2 33Ω
15 10kΩ
Parts For Second Channel
1 PC board, code 01111002, 142
x 58mm (116 holes)
1 6.35mm PC-mount switched
mono jack socket
3 grey knobs (bass, mid & treble)
1 yellow knob (level)
1 250mm length of 0.8mm tinned
copper wire
6 PC stakes
Semiconductors
1 TL072, LF353 dual op amp
(IC1)
1 TL071, LF351 op amp (IC2)
Capacitors
1 47µF bipolar PC electrolytic
2 10µF 63VW PC electrolytic
3 2.2µF NP PC electrolytic
1 .22µF MKT polyester
1 .015µF MKT polyester
1 .012µF MKT polyester
1 .0027µF MKT polyester
1 .0015µF MKT polyester
1 560pF ceramic
1 220pF ceramic
1 39pF ceramic
1 10pF ceramic
Potentiometers
1 10kΩ 16mm log pot (VR1)
3 100kΩ 16mm linear pots
(VR2,VR3,VR4)
1 10kΩ horizontal trimpot (VR7)
Resistors (0.25W, 1%)
1 220kΩ
3 10kΩ
1 100kΩ
1 4.7kΩ
2 33kΩ
2 1.2kΩ
2 18kΩ
2 1kΩ
2 12kΩ
1 150Ω
version is used for the input socket on
each board and can have either two or
three sets of switched contacts.
Note that the jack plug contacts
should be on the righthand side and
LE
the switch contacts on the left, as
viewed from the front of the board. If
not, they will have to be repositioned
by gently prising the contacts out of
the plastic body and reinserting them
the correct way around. The PC board
photos clearly indicate the orientation
of these contacts.
The stereo socket is used for the
headphone output and has three sets
of switched contacts. Its terminals can
be on either side of the socket body. It
should be installed as shown on Fig.4.
The pots can all be installed now.
Place the 100kΩ linear types (B100k)
in the bass, treble and midrange tone
control positions (VR2, VR3 & VR4)
and install the 10kΩ log (A10kΩ) pots
in the remaining positions. This done,
connect the pot bodies together by soldering each one to a length of tinned
copper wire. You will need to scrape
away some of the passivation coating
on each pot body before soldering the
wire in position, otherwise the solder
won’t “take” to the metal.
The idea here is to prevent hum
pickup by ensuring that the pot bodies are connected to the chassis earth
when the PC boards are installed in a
metal case. This, of course, assumes
that at least one pot makes good contact with the case (it may be neces
sary to scrape away some of the paint
around the holes to ensure this).
Preliminary checks
If you have a power supply with
regulated ±15V rails, you can carry
out a few preliminary checks on the
completed PC boards as described
below. If not, you can leave this step
until after the unit has been fully assembled into the case with its power
supply.
First, apply power and check the
power supply rails on both PC boards.
There should be +15V on pin 8 of IC1,
pin 7 of IC2, IC3 & IC5, and on pin 4
of IC4. Similarly, you should be able
to measure -15V on pin 4 of IC1, IC2,
IC3 & IC5 and on pin 11 of IC4.
If everything checks out, switch off
and connect your multimeter between
TP1 and the 0V supply pin on the main
PC board. This done, set the meter to
the mV range, apply power and adjust
VR7 for a reading of 0V (or as close to
this as possible). Now do the same for
the smaller PC board.
That’s all for this month. Next
month, we’ll describe the digital reSC
verberation board.
ECTRONICSHOWCASELECT
EMC Technologies' internationally
recognised Electromagnetic
Compatibility (EMC) test facilities are fully
accredited for emissions, immunity and
safety standards.
EMC Technologies
Melbourne: (03) 9335 3333
Sydney: (02) 9899 4599
MicroZed Computers
GENUINE STAMP PRODUCTS
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Easy to learn, easy to use, sophisticated
CPU based controllers & peripherals.
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Ph (02) 6772 2777 – may time out to
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Five identical Video and Stereo outputs
plus h/phone & monitor out. S-Video &
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For broadcast, audiovisual and film industries.
Wide bandwidth, high output and unconditional
stability with hum-cancelling circuitry,
front-panel video gain and cable eq
adjustments. 240V AC, 120V AC or 24V DC
High resolution 1in/2out VGA splitter.
Comes with 1.5m HQ cable and 12V
supply. Custom-length HQ VGA
cables also available.
Check our NEW website for latest prices and MONTHLY
SPECIALS
www.questronix.com.au
Email: questav<at>questronix.com.au
Video Processors, Colour Correctors, Stabilisers, TBC’s, Converters, etc.
All mail: PO Box 548, Wahroonga NSW 2076
Ph (02) 9477 3596 Fax (02) 9477 3681
Visitors by appointment only
QUESTRONIX
The
SCIENCE LAB in a PC!
Transform any PC into a complete data acquisition laboratory
It’s so easy with DrDAQ, the low-cost educational data logger distributed exclusively in Australia by Emona Instruments
Simply plug DrDAQ into the parallel port of any PC and run the DrDAQsoftware
EXTERNAL SENSORS
DrDAQ represents a breakthrough in data logging. It is a low cost system
PARALLEL
MICROPHONE
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supplied ready to use with all cables, software and even science experiment
pH
INTERFACE
examples. Plug it into the parallel port of any PC and you’re ready to collect
and display data. No batteries required -- DrDAQ is also
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Measure and store voltage: 0-5V, 5mV res.
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Measure and store light levels: 0-100, 0.1 res.
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Measure and store pH: 0-14, 0.02 res (optional probe).
OUTPUT
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LIGHT LEVEL
TEMPERATURE
USE DrDAQ as an advanced, accurate data logger in its own right . . .
or use DrDAQ to drive or control other experiments . . .
or use DrDAQ as an advanced teaching/learning aid in schools, universities & colleges:
DrDAQ is supplied with a library of science experiments for students and teachers.
Also supplied with PicoScope (oscilloscope software)
and PicoLog (data logging software)
TO PLACE YOUR ORDER,
CALL YOUR NEAREST
EMONA INSTRUMENTS
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PHONE
Fax
NSW
(02) 9519 3933
(02) 9550 1378
VIC
(03) 9889 0427
(03) 9889 0715
email: testinst<at>emona.com.au
QLD
(07) 3367 1744
(07) 3367 1497
WA
(08) 9361 4200
(08) 9361 4300
Website: www.emona.com.au
PRODUCT SHOWCASE
Yes, it's a phone!
Dual display LCR
meter
New from Emona Instruments is this 10,000
count precision LCR meter, intended for professional and trade applications.
The ELC-131D instrument is microprocessor
controlled and features a large dual display,
providing direct and accurate measurements
of inductors, capacitors and resistors with dual
testing frequencies of 120Hz and 1kHz. Ranges
can be selected automatically or manually.
Capacitance ranges are 1000pF to 10µF, inductance 1mH to 10,000H and resistance 10Ω to
10MΩ. Operation is from 9V battery or optional
12V plugpack adaptor.
Each meter is supplied with two clipleads
(although components can be directly
Contact:
plugged in) and a calibration certifiEmona Instruments Pty Ltd
cate. A built-in stand makes it ideal for
Phone: (02) 9519 3933
bench use.
Fax:
(02) 9550 1378
The unit sells for $448.80 including
e-mail
testinst<at>emona.com.au
GST and is available direct from Emona
website: www.emona.com.au
Instruments.
Dick Smith
Electronics has
released a phone
so small that it
fits in the
palm of
your hand.
This unobtrusive
phone comes complete with an earpiece and microphone for hands free
operation and looks great in its translucent blue casing.
With adjustable ringer volume, last
number redial and a visual ringer
indicator, it’s ideal for those who like
to speak on the phone while keeping
their hands free. It is also perfect for
office desks.
The Audioline Petit Mini-Phone is
available from Dick Smith Electronics
for a retail price of $49.86 or via mail
order by calling Dick Smith Electronics Direct Link on 1300 366 644.
Learn On Line with Training OnLine
Have you ever wished you could take a
course in, say, designing Web pages – but
simply don’t have the time nor the inclination to attend a college? Perhaps you’re a
long way from the nearest learning centre
–or maybe your schedule simply doesn’t fit
in with the class timetable?
Of course, you could beg, borrow or buy
a book and try to teach yourself. But the
experts say that’s by far the most inefficient
and least effective way of learning.
With the huge amount of resources on the
world wide web, the information you need
is probably out there somewhere. It’s just a
matter of finding it – and finding it in a state
which you can use, understand and digest.
Well, as far as learning is concerned, the
information is definitely out there. And it’s all
in one place, in easy-to-understand, structured lessons which you can go through
at your own pace and at a time convenient
to you. Simply point your browser to www.
tol.com.au, a site specifically set up for
web-based learning.
No, it’s not free – but neither is it expensive, particularly when you consider
the wealth of courses available. There are
several different subscription rates for the
various types of courses available, with
42 Silicon Chip
prices starting at less than $10 per month.
And they’re not just computer courses
– there are all manner of personal and
business development and finance courses
–including such things as negotiating skills,
motivation, even a course on how to go
about getting a pay increase. Hmm. Must
bookmark that one.
In the computer area there are courses
covering a multitude of popular software,
operating systems, etc and some pretty high
level technical courses including MCSE, web
development, Java and so on. Courses are
interactive and prior skills assessments
means you don’t have to waste time going
over material you already know – you skip
straight to the areas you need.
The benefits to organisations using
on-line training are considerable – not the
least being cost savings over other training
methods. MCSE training, for example, typically costs more than $2000 per session
for each person off site: TOL can do it for
$169 per person per year.
Then there’s the savings in travelling
time and time away from the office, the
ability to pick quite business periods for
training time, 24-hour-per-day availability
and so on. Of course, staff can continue
training (or reviewing) at home with their
own computers – once they have their ID
and password, they can access TOL at any
time from anywhere.
When we said before that the courses
weren’t free that’s not quite true. TOL has
half a dozen or so free courses which you
can use to “try before you buy”, to get the
look and feel of training on line.
Phone and fax enquiries can also be
made to Training OnLine Pty Ltd at the
numbers below.
Contact:
Training OnLine Pty Ltd
Phone: (02) 4389 8800
Fax:
(03) 4389 8389
Website: www.tol.com.au
Jaycar’s “Short Circuits III”: as new as tomorrow
A few years ago, Jaycar Electronics
produced a book of electronics projects
called “Short Circuits”. It featured 20
or so easy-to-build electronics projects
suitable for absolute beginners in electronics. Short Circuits very quickly
became a best seller, used by countless
thousands of electronics hobbyists not
just here in Australia but around the
world.
More importantly, due to its structured approach and ease of understanding, Short Circuits also rapidly
found its way into the
science and technology
curriculums in schools
and colleges. It has now
become the textbook
of choice in many educational institutions,
replacing books written
in the 1980s and now
showing their age (think
how far technology has
come in 20 years!).
Now there is a brand
new “Short Circuits”
which is just as certain
to find its way into the
education arena and
also be just as popular
with hobby-ists. Perhaps curiously called “Short Circuits
Vol III”, this 128-page, full colour book
is crammed with more than 30 projects
which, while easy to build and get going, actually “do things” – they make
lights flash, buzzers sound, they can
transmit messages, amplify Walkmans,
add sound effects to models and music
and much more.
Gary Johnston, Managing Director of
Jaycar Electronics, explained why the
book is called Short Circuits III, not II:
“For some time we’ve been planning
to release a sequel to Short Circuits,”
he said. “But when this one started to
come together, I realised it was just so
much more advanced in every way,
involving concepts as modern as tomorrow, that it wasn’t just a sequel, it
was another step ahead again.”
“So I decided that we should make
this Short Circuits III and then sometime in the future, hopefully not too far
away, we’ll ‘fill the gap’ and produce
another book, Short Circuits II.”
All projects use components soldered to PC boards and, with one
exception, all of the projects in Short
Circuits can operate from batteries,
making them extremely safe. The one
exception is a mains-operated power supply which is also capable of
powering most of the other projects.
And before anyone should think that
it’s unwise to let children use mains
power, this kit uses a fully enclosed,
pre-wired mains transformer which
simply plugs in to the supply PC board.
It is impossible for anyone to access the
“bitey” 240V power without literally
smashing apart the transformer.
In addition to the 30+ projects there
are fully illustrated, major features
including how to
use a multimeter,
how to solder, the
tools needed to
build projects and
even how to recognise the components used. There’s
also extremely useful data spread right
through the book
–such as component
operation, how various circuits work,
basic electrical and
electronic principles and an extensive
glossary.
It’s printed on high
quality paper with every project
photographed in colour and each project has the familiar “Tech Talk” panels
(as in Short Circuits I) which explain
exactly how each project works. And
every project has a “What to do next”
section which explains how you can
put your completed project to even
more uses.
Considering the number of projects and the exceptional quality of
production, Short Circuits III is very
good value for money at $24.95. It
would make a superb gift for a young,
enquiring mind this Christmas! The
book (and kits of parts for the projects)
are available from all Jaycar Electronics stores, dealers and through Jaycar
Techstore online.
Contact:
Jaycar Electronics
PO Box 185
Concord NSW 2137
Phone: (02) 9743 5222
Fax:
(02) 9743 2066
Email:
techstore<at>jaycar.com.au
Website: www.jaycar.com.au
TOROIDAL POWER
TRANSFORMERS
Manufactured in Australia
Comprehensive data available
Harbuch Electronics Pty Ltd
9/40 Leighton Pl. HORNSBY 2077
Ph (02) 9476-5854 Fx (02) 9476-3231
RF Chemical
Technology Guide
The new RF Chemical Technology
brochure, recently released by Richard Foot Pty Ltd, includes a wide
range of service aid products for
the electronics industry, including
electro-chemical aerosols, thermal
protection, contact lubricants and
cleaning solutions.
The brochure, which is available
free of charge, includes descriptions
of the products and also typical applications.
Contact:
Richard Foot Pty Ltd
PO Box 245, Terrey Hills NSW 2084
Phone: (02) 9979 8311
Fax:
(02) 9979 8098
e-mail
rfoot<at>hotkey.com.au
NOW YOU CAN
TRAIN ON LINE
]
]
]
]
]
]
]
learn at your own pace
at times to suit you
stop & start as you like
400+ courses available
focus on what you need
24 hours/7 days a week
anywhere, anytime
Huge range of computer software & hardware
courses, business, finance and personal development courses and much, much more
FOR FREE TRIAL LOG ONTO
www.tol.com.au
Training OnLine Pty Ltd
Phone (02) 4389 8800 Fax (02) 4389 8389
November 2000 43
Step up, step down ICs from Linear Technology
Two new ICs from Linear
Technology address two
power supply problems in
modern equipment – that
is, where higher or lower
voltages are required than
that delivered by the batteries, without wasting a
lot of power.
The LTC1612 is a synchronous 800kHz stepdown DC/DC converter
which is ideal for use in
any portable device operating from a lithium-ion or 2-cell
alkaline battery.
It operates from a 2V to 5.5V supply
and features internal 700mA synchronous switches. Output voltages can be
set as low as 620mV. The LT1612’s 1µA
shutdown current virtually eliminates
battery drain during shutdown, extending battery life. It is available in 8-lead
SOT and MSOP packages.
Conversely, the LTC1619
is a current-mode step-up
DC/DC controller.
Operating at 300kHz and
accepting a wide 1.8V to 20V
input voltage range, it is ideal
for applications such as flyback, conversion to 5V, 12V
or 15V output in distributed
power and 5V to -48V telecom applications, as well as
automotive power supplies.
It is available in 8-lead MSOP
and SOIC packages.
Linear Technology semiconductors
are distributed in Australia and New
Zealand by REC Electronics.
Contact:
REC Electronics
Unit 1, 38 South St Rydalmere 2116
Phone: (02) 9638 1888
Fax:
(02) 9638 1798
website: www.rec.com.au
805 SMD resistors in
reusable pack
With surface mount devices becoming the
“norm” rather than the exception, Jaycar Electronics have released a comprehensive SMD resistor
pack, ideal for service work, design labs or even
for the advanced hobbyist wishing to experiment
with and use these components.
The reusable plastic case contains
Contact:
805 5% resistors in 72 values from
Jaycar Electronics
2.4Ω to 10MΩ, with each value
PO Box 185 Concord NSW 2137
packaged in strips of 50 with values
Phone: (02) 9743 5222
printed on the back of the strips.
Fax:
(02) 9743 2066
The pack sells for $69.95 (Cat No
Email:
techstore<at>jaycar.com.au
KK2060) and is available from all
Website: www.jaycar.com.au
Jaycar stores.
Marantz CD changers are CD-R/W compatible
The new CC-3000, 4000 and 4000
OSE five-disc carousel CD changers
are claimed to be amongst the first to
offer CD-RW playback capability for
total compatibility with all recordable
audio media.
Of special note is the new $799
top-of-the-range 4000 Original Special Edition (OSE) model which has
performance rivalling that of premium
single-disc players. It also has a number of editing features which make
it ideal for use with CD-recorders
(including fade-in and fade-out capability), 30-track programming and a
coaxial digital output for connection
to an A/V receiver, preamp/processor,
CD recorder or output D/A converter.
It also has a full function remote control compatible with other Marantz
components.
Marantz hifi is distributed by Jamo
Australia and is available at selected
hifi specialist stores.
Contact:
Jamo Australia
Phone: 03 9543 1522
email:
info<at>marantz.com.au
44 Silicon Chip
William Tell?
No, it’s
NATA’s new
directory
No company wants
defective goods or
materials to reach its
markets, which is
why professional testing, calibration
or inspection by an accredited facility
has become an essential part of the
production process.
Because companies may be uncertain about which facilities are independently accredited, the National
Association of Testing Authorities
(NATA) has released a comprehensive
new 2000/2001 directory of accredited
laboratories.
Over 2500 labs are listed, covering
the full range of services – acoustic,
chemical, electrical, heat and temperature, construction and engineering
materials, information technology,
medical, biological, verterinary and
even forensic testing labs.
Copies of the A4-format directory
are available from NATA with discounts for NATA members and for
standing orders.
Contact:
NATA
7 Leeds Street, Rhodes NSW 2138
Phone: (02) 9736 8222
Fax:
(02) 9743 5311
Email:
cfratti<at>nata.asn.au
New DAQ & I/O cards
Novatech has relased several new
“ComputerBoards” data aquisition
and digital I/O boards.
First is a “plug’n’play”, auto calibrating 20MHz, PCI-bus board with
four analog input channels, each with
12-bit, 20MHz A/D, 24-bit digital I/O
and two 12-bit D/A functions.
A new series of PCMCIA DAQ cards
is also available. These have ruggedised edge connectors for security
and longest possible life and the range
includes a 16 analog channel board
with digital I/O. Many other models
are also available.
Contact:
Novatech Controls
309 Reserve Rd, Cheltenham Vic 3192
Phone: 03 9585 2833
Fax:
03 9585 2844
email:
roger<at>novatech.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.jaycar.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.jaycar.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.jaycar.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.jaycar.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.jaycar.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.jaycar.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.jaycar.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.jaycar.com.au
Order Form/Tax Invoice
Silicon Chip Publications Pty Ltd
ABN 49 003 205 490
PRICE GUIDE- Subscriptions
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(all subscription prices INCLUDE P&P and GST)
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11-00
SERVICEMAN'S LOG
Most customers are reasonable
Servicing produces a wide variety of customer
personalities. Most are easy to get along with
and some are even apologetic for the “trouble
they are causing”. But at the other extreme is
the odd one who is aggressive right from the
start; convinced that all servicemen are rip-off
merchants.
My first story involves a typical customer type; easy to get along with and
prepared to pay what was necessary
to solve any awkward problems. The
set was a Masuda MGV28AV, bought
from the now defunct Brashs chain
of shops.
The Masuda was a Chinese-made
set and I explained to Mr Bull that
there could be problems obtaining
parts or service information. However, he was eager for me to try; as I
said, he was easy to get on with and
prepared to pay.
The problem was a very annoying
intermittent brightness variation – it
sometimes became brighter when the
set got hot. Well, the first thing was
to confirm that the set was exhibiting
this fault and so I put it to one side
where I could monitor the picture.
Nothing happened for the first two
days but on the third day, towards
closing time, the fault began to show,
the picture gradually becoming
brighter and brighter. I couldn’t do
anything about it just then, although
I did remove the back and set it up
on the workbench so that it would be
ready for me to tackle the next day.
The next morning, while waiting
for it to misbehave again, I tried accelerating matters by covering it with
a blanket. And I rummaged among my
circuits to see if I had a diagram that
might match. As luck would have it,
I found a circuit for a 1993 Teac CTM715B, which is very similar.
Where does one start? I needed
to make measurements consistent
with the symptoms so I started by
measuring the screen voltage to the
picture tube (pin 7) to see if it varied
when the fault occurred. When it did
occur some hours later, the voltage
was rock steady, so I wasn’t looking
at an EHT fault.
Eventually, I determined that it was
some kind of video fault, because the
tube cathode voltages were drifting
lower when the problem occurred. I
even went so far as to trace this drift
back to IC304, a TDA3504 which is
well known for causing problems
(usually resulting in loss of picture).
This was encouraging but the job was
still proving to be extremely frustrating because it took so long for the
fault to show.
Calculated gamble
As a result, I took a calculated gamble and plumped for replacing IC304.
Unfortunately, it wasn’t meant to be,
so I spent yet another day leaving a
meter connected to pin 17 of IC304,
the brightness control input. This was
normally at about 2V but under fault
conditions it was all over the place.
Where to from here? I followed the
beam limiting signal path from pin
17 via R355 (56kΩ) to R433 (150kΩ),
then to the 143V rail and R403, C425
& D406, but these all measured OK.
I also checked D302 which links the
contrast DC tracking, before going on
to check R322 and transistor Q302.
Once again, I drew a blank.
That left the brightness control
circuit itself which comes out of pin
54 Silicon Chip
Items Covered This Month
• Masuda MGV28AV TV set.
• Blaupunkt IS70-33VCT TV set
• Mitsubishi CT-29ATS(A)TY TV set
3 of microprocessor IC601 and also
involves pin 25, the mute line, which
controls transistor Q302.
I wasn’t getting anywhere – I knew I
was in the right area but I couldn’t isolate the exact cause. Finally, I decided
to check the sub-brightness control
circuit involving VR301 but initially
couldn’t find its location. The reason
was that it was, rather ridiculously,
situated under a large resistor which
in this instance had been bent down
so that it was literally touching the
plastic former of the control.
Naturally, the heat from the resistor had distorted the control former,
resulting in its function being intermittent when hot. A new control
fixed the problem completely and
I also relocated the resistor so that
it wouldn’t happen again. The only
tricky part now was telling Mr Bull
how much all this cost – plus the GST!
But he didn’t baulk.
Crook Blaupunkt
My next customer, Bill Strong, is
another reasonable bloke; not the sort
to whinge for no reason. He brought
in his Blaupunkt IS70-33VCT complaining about the sound – or lack of
it. He was very apologetic in admitting
it was extremely intermittent.
He wasn’t wrong. I put it on the
soak bench with the sound on low
while I hunted up a circuit. This set
used an FM310.32 chassis with part
No. 7663 700. The nearest I had was
for IS70-31VT with part No. 7660 800
but it would have to do.
The fault didn’t occur for the first
couple of days but did on the third
day and continued to give trouble.
Unfortunately, I couldn’t do anything
about it because I had my hands full
with other more pressing jobs.
On the fourth day, I transferred the
set to the main bench and took the
back off. But much to my frustration,
it worked perfectly all day. By the
fifth day, I was losing patience with
the set – I needed something I could
work with but it refused to play up. In
the end, I switched it off and pulled
the chassis out, looking for bad connections and faulty joints but could
find none.
I switched it back on and tapped
the chassis with a screwdriver handle, then tried heating and freezing
it. Nothing I did made any difference
at all. Fed up, I decided to put it back
on the soak bench and switched the
set off to do this. But – you’ve guessed
it – as soon as it was back on the soak
bench, it started playing up again.
By now, I was beginning to notice
that, at times, the fault would occur almost from the moment I switched it on
until I switched it off. At other times,
when I switched it on, it would come
good and stay good until I switched
it off. Bells were beginning to ring.
Perhaps it was the way I switched
it on and off. I was using the master
switch on the soak bench but perhaps
it was the set’s switch itself?
I tried switching it on and off many
times and it did seem that there was
something about the switch that was
causing the problem. But what was
it and more importantly, why did it
only affect the sound?
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November 2000 55
I removed the switch (S601) and
checked the contacts. The main AC
power contacts were fine but the
standby or “Temp contact” (as Blau
punkt calls it) was intermittently
sticking on. This momentary switch
controls T801 (BC548C) and the U
WISC line P1.0 to pin 15 of the microprocessor I811 and, if left permanent
ly on, mutes the sound!
A new switch fixed the problem
completely.
An overbearing customer
And now for a change of scene.
Mrs Ruddock did not strike me as a
reasonable type and the screaming
and demanding children she brought
with her only made matters worse.
Anyway, she arrived with her Mit
subishi TV set in the back of the station wagon. She said that it wouldn’t
56 Silicon Chip
come on and asked if I could fix it.
I said that I was sure I could – not
realising that she meant immediately.
But having lifted the 68cm 46kg TV
set into the workshop, all by myself, I
wasn’t in the mood to return it to the
car when she made that point obvious.
And she reinforced this idea by closely following me into the workshop
and standing there expectantly.
Somehow or other, I had allowed
myself to be painted into a corner –
almost literally. For lots of reasons
(including safety), I regard it as an
unwritten rule that clients do not to
come into the workshop. Yet here I
was plugging the set in and switching
it on. And before I knew it, I had the
back off and was making measurements.
This Mrs Ruddock had powers
beyond my understanding. Indeed,
I felt as though I was part of some
Greek mythology, where I was being
controlled by one of the Gorgons –
probably Medusa. I even tried to avoid
Mrs Ruddock’s gaze; after all, I didn’t
want to be turned to stone!
Anyway, this was a 1993 Mitsubishi
CT-29ATS(A)TY with an ATMT691
chassis. This set employs a lot of advanced features and is a real bells and
whistles job. It even had a motorised
swivel stand so one could rotate it by
remote control.
Apparently, the fault had been
intermittent but had pro
gressively
become worse until now it was completely dead. I had never come across
this model before and didn’t have a
circuit. However, I did have a few
notes from a trade meeting I attended,
at which this type of dual switchmode
power supply had been discussed
although not in great detail.
I could measure voltages all over
the place and all the fuses were OK,
so I knew this wasn’t going to be easy.
But Mrs Ruddock was still pressurising me to fix it now.
I located the standby switch transistor (Q9132) and was trying to measure
the voltage on its base when suddenly
the set came on. At the time, I didn’t
have a clue why and could only conclude that my shaking hands had accidentally shorted something. What’s
more, the set now came on perfectly
each time it was switched on, with
all functions working (including the
power/on/off/standby). And nothing
I could do would recreate the fault.
Mrs Ruddock was initially pleased
that it was working but wanted more
– basically, a lifetime guarantee was
the kind of thing she had in mind.
However, her slight sign of pleasure
released the psychological hold she
had over me; the image of Medusa
instantly vanished and she was now
just plain Mrs Ruddock. The spell
had been broken and I took full advantage of it.
Emboldened, I told her that whatever I had done could only be considered temporary and that, sooner
or later, the set would give trouble
again. I also told her that the only
way to fix the problem was to leave
the set on test while I acquired the
correct service manual (which costs
$60), so that the real fault could be
tracked down.
She immediately tried to reassert
control but failed. I had won; well,
sort of. In any event, I was happy
to replace the back of the set
and put it back into her car.
But I wouldn’t budge from
my position and I didn’t
charge her.
That was the last I heard of
the set until some nine months
later, when the set suddenly
reappeared with the same
fault. The lady’s attitude had
improved a little. She said that the
fault had recurred within a few days
(just as I had predicted) and so she
had taken it to a Mitsubishi agent. She
also complained that they had kept it
for eight weeks before they fixed it.
I am also a Mitsubishi agent but I
resisted the temptation to ask her why
she had taken it elsewhere. Nor did I
ask her why she hadn’t taken the set
back there now. But I insisted on my
basic ground rules – I must have a
circuit, time and space!
This agreed to, I proceeded to connect the set and see what was cooking.
Well, to begin with, the set came on
straight away with severe hum and
picture distortion and with the picture
jumping. Mrs Ruddock thought I was
splitting hairs when I mentioned these
faults, pointing out that it came good
after five minutes.
I then asked her what the other
Mitsubishi agent had done. Their bill
was produced, which showed they
had changed micropro
cessor IC701
(M50436-566SP) but, in fact, they had
done more. I discovered this when
checking the -30V rail on the power
supply – capacitors C9F1 and C9E9
had both been changed.
My insistence on getting the correct
service manual had paid off but it was
irritating to find different voltages
marked along the same supply rail.
This makes it difficult to be sure of
the correct value. In the end, I found
that the 12V rail was significantly
low, with the CRO showing significant
ripple on it. The culprit turned out to
be C9E5, a 470µF 25VW electrolytic
that was leaking badly.
Because I had to take the board
out to change this capacitor, I took
the opportunity to examine the rest
of them. C9E1, another 470µF 25V
electrolytic was also leaking badly
and I could see that most of the other
electrolytics were in poor condition.
Before changing all 25 or so, I thought
that I would confirm that the two I
had just replaced were the significant
ones. I was gratified to see that they
were, the set coming on immediately
with picture and sound.
I then set about replacing all the
remaining capacitors and cleaning
up the damage caused by the leaking
electrolyte from the C9E1 and C9E5.
These had even corroded the heatsink
a few centimetres away.
Finally, when it was ready, I replaced the board and checked the
six main voltage rails (130V, 33V,
15V, 12V, 9V and -30V), all of which
were OK. With soak testing I had the
set turned around within one week
but received only moderate praise
from Mrs Ruddock. I guess there is
no pleasing some people but maybe
she learnt something. Who knows, she
might even call on me the next time
SC
something fails!
November 2000 57
MAILBAG
Alarm about pool alarm
I have no quibble with your electronics capabilities but your front
cover story in the September 2000
edition raises an alarm. Have a good
look at the two photos of Georgia.
In both you can see that the gate is
unlatched! The photos show the end
of the gate at least 100 mm from the
latching post.
Primary safety (locking the gate)
must be the first line of defence.
Brian Wilson,
Curtin, ACT.
Comment: blame the photographer.
He lured Georgia through the gate.
But her grandmother was standing
poised, just out of the picture, ready
to swoop. And she did!
CD Compressor should have
had dual detectors
It was great to see the CD Compressor in the June 2000 issue of the magazine. However, I have some comments
regarding the design.
John Clarke talks about the VCAs
being “hifi laser trimmed units” but
has only included one DC detector/
control unit for both channels. It
seems strange that he has not taken
the better approach and kept the two
channels completely separate.
By having two DC controllers for
the VCAs, the signal of one channel
does not modulate the other, if little
or no signal is present. John’s single
approach is as per the old dbx 117 and
119 units. Later units, from the model
128, I believe, had twin controllers.
The 3bx went the whole hog and
had stereo 3-band active crossovers
with separate DC controllers and VCA
processing on each band. Having had
experience in modifying 117 and 119
units to provide separate controllers
for each channel, I can attest to the
benefits of dual DC controllers. Getting these to track can be a bit of a
fiddle when you have a compansion
range of - infinity compression to +3
expansion on the 119, but as John’s
design only has a range of -3 compression to 0 this shouldn’t be a major
problem.
I should mention that the NE571
“compander in a chip” is still avail58 Silicon Chip
able and its small size would be
beneficial in today’s cars where you
have to shoehorn yourself in, let
alone a box the size of John’s project.
I know the VCAs of the 571 are not
“laser trimmed” but for automotive
or elevator music they might be an
alternative.
Brad Sheargold,
Collaroy, NSW.
Comment: the idea behind this design was twofold and to some extent
these conflicted. First, we wanted a
better compressor than we had done
in the past but we also wanted a very
compact design which would work in
cars. The latter criterion mean that
we had to keep the parts count as low
as possible and that meant only one
detector. As it was, the requirement
to use so many op amps was a real
problem.
Electrical licencing debate
Well, I’ve read enough emotive
“sparkie bashing” in the Mailbag to
force me to put my five cents worth
in. I’ll say first up that I detect a lot
of sour grapes and venting of spleens
arising from what was initially an issue regarding kits with mains wiring
involved. I’ll also say that I believe
some are using what they think is the
“Parliamentary Privilege” of an electronics magazine to unfairly knock
those in the electrical trade.
I am a sparkie myself, having enjoyed the huge window of opportunity such a trade offers for about 10
years now but before that, I was an
electronics technician employed in
the industrial electronics field. While
I enjoyed many of the challenges
in the game, and still miss some of
those, I’m glad I had the persistence
to pester my boss into taking me on
as an apprentice electrician.
I was also cocky enough to think
those four years of the apprenticeship would be unnecessary given my
technical knowledge but I soon learnt
there was a huge amount to absorb and
take in regarding rules, regulations
and safety. In short, it was a whole
new world, ever changing and dynamic and it has been a constant effort
to try and keep up with the changes.
I currently work at a remote mining
site in the north-west of Australia
where the electrical staff have to be
up to speed on everything from domestic wiring to process control of
plant to power generation to Austel
Licensed communications work to
radio communications work to high
voltage work (up to 33kV here), all
without killing ourselves or others or
causing damage to the plant.
While I believe there is an issue
with the mains-powered kit situation,
I think the spillover into the attacks
on the electrical trades in general is
an example of very misguided and
deluded elitism.
Peter Cairns,
Alice Springs, NT.
Health card is a silly idea
Your editorial in the October 2000
issue discussing a smartcard that
stores the whole of a person’s medical
record is a silly idea, for three reasons:
(a) there is no technology available
which could reasonably be developed
in the near future to make it possible
and even if there was, the people in
that industry would be wary;
(b) there are a lot of people who
wouldn’t reasonably want it, and
(c) there are a lot more people who
simply couldn’t do what they had to
do if that were the way things were
done.
There simply isn’t any card that
can store that much info. Think about
how few kilobytes are on a smartcard
versus how many megabytes it would
take to store scanned-in x-rays, with
the high-capacity alternatives having
to be reprinted in full each time there’s
an addition. The closest we’d come
today is a multi-session writeable
DVD-ROM and who’s going to carry
that around. And what if they lost it,
or required emergency medical treatment in a situation where they didn’t
have their records with them, like
being taken unconscious to hospital
after a car crash, or even were well
away from home when they got sick?
There are a zillion reasons why
anyone who has had to provide access to significant quantities of data
at various locations but at the same
time secure it and guarantee that it
wasn’t lost would laugh at the idea
of the customer carrying it around
with them.
Sure, put certain vital or shortterm info on a card or make it easily
accessible by some other means but
that’s all. I don’t mean to be negative,
just realistic, so let me suggest an
alternative:
(a) Connect all doctors, pharmacies
and hospitals to the Internet, preferably by broadband or the fastest
practicable other means;
(b) Encourage doctors and hospitals
to store as much as possible of their
records in computerised form accessible from the Internet, keyed not by
name but by a private encryption key;
(c) Provide off-site managed data
stores for doctors too small to operate
their own data servers and managed
backup;
(d) Allow access only to the data
either by production of the person’s
Medicare card, by a nominated family
doctor or by authorised emergency
medical personnel. There would
also need to be penalties for doing
it without good reason as is the case
with criminal records.
Gordon Drennan,
Ultimo, NSW.
Comment: the health card is already
possible and has been demonstrated.
Credit card-size CD-ROMs are now
available and DVD-ROMs in credit
card size are equally possible.
Anyone in New Zealand
can do electrical wiring
I feel compelled to write concerning
the electrical safety debacle that the
members of the electricians’ cartel in
Australia have ruthlessly perpetrated
on their cousins in the electrical and
electronics industries.
It may interest those in the electronics industry to know that anyone
in New Zealand can legally do their
own house wiring and house wiring
repairs and modifications, as well as
appliance repairs. This has been the
case since 1992. Current legislation
in New Zealand reflects the reality
prior to its introduction of widespread
do-it-yourself house wiring and appliance repairs.
There were no problems in legalising DIY electrical work in NZ
because many New Zealanders have
done their own house wiring and
appliance repairs over so many years
that they either know what to do or
they can conveniently get the detailed
information they need from relatives,
neighbours, DIY books, etc.
The crucial aspect of the NZ system
as it relates to prospects for reform of
the Australian system is the number
of electrical fatalities. The extremely
low level of fatalities and the fact that
none of the fatalities are related to
incompetent house wiring or appliance repairs by householders makes
the claims of the electricians’ lobby
in Australia look ridiculous.
Safety is not the issue and never has
been. The bigwigs in the electricians’
lobby know that ordinary people have
done their own house wiring and appliance repairs in the United Kingdom
and elsewhere for many decades but
they persist with their propaganda
about extreme dangers.
For the past year or so in Queensland there has been a blitz of expensive television “scare campaign”
advertising by Energex, warning
people that they are not allowed to
do electrical work.
In Australia, on average, at least 100
people die as a result of rail accidents
each year. Similarly, at least 500 die
as a result of road accidents in each
state in each year. The official figures
from the AMA are that approximately
19,000 people die each year in Australia as a result of cigarette smoking
and smoking-related diseases.
The New Zealand experience clear
ly demonstrates that the prospects of
deaths due to electrical accidents do
not warrant the ridiculously stringent
regime that exists in Australia.
In Queensland, even electrical engineers who design complete power
distribution and protection systems
for multi-storey city buildings are not
allowed to pull the wiring through the
conduit in their own homes. When
I checked with a number of large
Brisbane electrical contracting firms
I discovered that unskilled labourers
pull the wiring through the conduits,
ostensibly under the “supervision” of
an electrician!
I am now retired but a little over
a decade ago, just before I moved to
Brisbane, I began the Associate Diploma in Electrical Engineering at St.
George college of TAFE. I already had
the Electronics and Communications
Certificate from North Sydney TAFE
but I was willing to do the electrical
associate diploma because an electrician at building services told me that
with the electrical associate diploma
and a 13-week wiring course, I could
get an electrician’s licence. I worked
hard academically and came top of
St. George tech for the first two stages
of the four-stage electrical associated
diploma course.
Luckily, one of my lecturers at St
George tech, who was an electrical
engineer for the electrical supply
authority in NSW, alerted me to the
reality that I could only get a restricted
licence and I discontinued the course
at the end of stage two.
The fact that I was a technical
officer designing and building data
acquisition and control hardware at
Sydney University (for minicomputer
automation of psychological and
physiologi
cal research), including
the design and construction of power
supplies, etc, meant nothing to the
electricians at building services in
NSW, and the situation is even worse
in Queensland.
I am a member of Mensa but obviously neither a Mensa intellect nor
proven knowledge and mechanical
ability are enough to allow me to just
pull the wiring through the conduit
in my own home in Queensland, let
alone wire up power points, etc. How
long are engineers, technical officers
and electronics service people going
to stand by and allow this ludicrous
situation to continue?
If engineers, technical officers and
service persons effectively unite, we
can put an end to these inequitable
and totally unjustified restrictions on
the performance of “electrical work”.
Otto S. Hoolhorst,
Brisbane, Qld.
November 2000 59
Message Bank
Alert
Do you have Telstra or Optus
Message Bank on your phone? Do
you forget to check for messages?
Have you found an important
message a day (or more) after
you should have got it? Solve this
problem with our Message Bank
Alert. If you get a call while you
are out, the Message Bank Alert
will flash to remind to check your
messages – or just to tell you that
someone has called you.
By RICK WALTERS & LEO SIMPSON
M
any people now don’t bother
with phone answering machines now that Optus and Telstra have their message bank service
available.
You do have to pay for it but it
avoids the problem of having to turn
the machine on, erase the messages
and so on. If you do get messages, the
dial tone changes to indicate that fact.
However, if you are not in the habit
of picking up your phone to check for
messages each time you return from
a trip, you can easily miss important
calls. This is especially the case if you
have two phone lines and they both
have Message Bank installed. Who is
going check both lines, maybe several
times a day, after each trip away from
home?
Now you don’t have to. With our
Message Bank Alert installed in the
line to one of your phones, it will register the fact that someone has called
in and was not answered. It will then
flash a LED to remind to check your
Message Bank service. If there was a
message, you can phone the caller. If
60 Silicon Chip
not, and you still want to know who
called, you can dial “*10#” to find
out the number (on Telstra, at least).
Note that Message Bank and dialling
“*10#” do cost money.
The SILICON CHIP Message Bank
Alert is designed along the same lines
as the Off-Hook Indicator described
in the January 2000 issue. It uses the
same board shape, the same plastic
case and rechargeable NiCd AA cell
and the same RJ telephone connectors
to enable to be connected in line with
a telephone handset. That’s where the
similarity ends because the circuit is
quite different.
Circuit description
What does the circuit do? In essence, it detects the presence of the
“ring voltage” when the phone starts
ringing. Once the ring voltage is detected, the LED begins to flash. It then
continues to flash until the handset is
picked up.
In designing the circuit we decided that we could use the flasher IC
circuitry used in the Off-Hook Alert
together with a sensing circuit to detect the AC ring voltage. Then all we
had to do was to figure out how to turn
the flashing LED off when the handset
was picked up. A flipflop with a SET
and RESET seemed the logical answer.
But where do you get flipflops that
operate at voltages down 1V?
Believe it or not the “old faithful”
555 CMOS timer will typically work
down to 1V and it typically only
consumes 50µA at this supply voltage. But can it be used as a flipflop?
The circuit of the Message Bank Alert
shown in Fig.1 shows that it can.
If you look at Fig.2 which is a block
and connection diagram for the CMOS
555 (variously known as a 7555 or
LMC555) you can see that it does contain an RS flipflop. The Qbar output
of the flipflop is inverted (which effectively makes it the Q output) at pin
3. Going to the main circuit of Fig.1,
pin 3 of IC1, the 7555, is connected to
pin 4 of IC2, the LM3909 LED flasher.
If the voltage at pin 3 of the 555 or
pin 4 of the LM3905) is high (ie, above
1V) the flasher will not operate, if it
& Missed Call
is low (0V) then the LED will flash. If
the internal flipflop in the 555 is reset
(output pin low) the LED will flash,
if it is set (output high) the LED will
be extinguished.
If we bias pin 6 so that it is normally
low and pin 2 so that it is normally
high, we have the conditions we
require.
If we can detect the phone’s ring
and pull pin 6 high the internal flipflop will be reset, the output at pin 3
will go low and the LED will flash. If,
when the handset is lifted we can take
pin 2 low, the flipflop will be set, the
output at pin 3 will go high and the
LED will cease flashing. Fig.1 makes
this explanation a little clearer.
Ring voltage detection
When a call comes in the phone
rings because there is a large AC signal (typically 75VAC) applied to the
lines. This signal is coupled via the
bridge rectifier, the 0.1µF capacitor
and 330kΩ resistor to pin 6 of IC1.
The three diodes protect this input
from excessive voltages.
On the first positive cycle of the
ring voltage, pin 6 is pulled to about
1.3V which resets the flipflop. This
causes the output at pin 3 to go low,
enabling the flasher.
When the receiver is ‘on hook’ ie,
1
8
V+
GROUND
LMC555
2
7
TRIGGER
DISCHARGE
R
3
OUTPUT
_
Q R
6
+
_
THRESHOLD
R
_
R S
RESET
+
_
4
R
R=100k
the LED to flash again. The diodes on
pins 2 and 6 of IC1 are there to prevent
any spikes which may be on the incoming telephone line (eg, lightning)
from damaging the ICs.
Now let’s have a look at the operation of IC2, the LM3909.
5
CONTROL
VOLTAGE
Fig.2: this block diagram of a 7555
shows that it contains a flipflop. This
is the crucial part of the 7555 which is
used in the Message Bank Alert circuit.
hung up, there is around 48V DC
across the lines. As pin 2 of IC1 is fed
from a voltage divider, it will be held
high. When the handset is lifted the
line voltage drops to below 12V.
With the voltage divider consisting
of the 1MΩ and the 56kΩ resistors,
pin 2 is now well below the switching
threshold (about half of the battery
voltage of 1.2V) thus setting the flipflop, pulling pin 3 high and preventing
the LED from flashing.
The 3.3µF capacitor on pin 6 is
to prevent transient voltages, which
occur as you replace the handpiece,
from resetting the flipflop and causing
LM3909 flasher operation
The flasher circuit is a standard
arrangement of the LM3909 which is
designed to flash a LED from a supply
of between 1V and 1.5V even though
the typical turn-on voltage for a LED
is around 1.8V.
It manages this trick by charging an
electrolytic capacitor and then connecting that capacitor in series with
the 1.2V supply, to effectively double
the voltage which is then dumped
across the LED to briefly flash it.
Previously we said that the pin 3
of the 7555 enabled the LM3909 by
pulling its pin 4 low. That’s one way of
looking at it but what really happens
is that the 7555 provides the negative
supply connection to the LM3909, so
that it turns the LED flasher circuit
on and off.
A 470µF capacitor is connected
across the supply connections (pins
5 & 4) to smooth out fluctuations due
to the LED flashing. This capacitor
must be charged each time pin 3 of IC1
Fig.1: the Message Bank Alert uses a 7555 as the
ring voltage detector and flipflop and it controls
the power to the LM3909 LED flasher.
November 2000 61
goes low and since this causes quite
a high peak current, a 10Ω resistor is
connected in series with pin 3 to limit
the current and protect IC1.
Battery power
Readers may wonder why the circuit includes a 1.2V cell.
Having the NiCd cell means that
there are no pulses of current drawn
from the phone line as the LED is
flashing. Instead, the current drawn
from the phone line is very low and
constant; around 370µA and less than
100µA when the phone line is in use.
By taking this approach, the Message Bank Alert will have no effect on
any phone equipment and it will be
invisible to the system.
By the way, we said before that
the Message Bank Alert was to be
connected in line with one of your
phone extensions. But that does not
mean that it is actually connected “in
series” with the phone. In practice, it
is connected in parallel.
In fact, the two RJ sockets in the
Message Bank Alert are connected in
parallel so that they merely loop in
and out of the box. The Message Bank
Alert then connects in parallel with
the phone line and causes negligible
loading on it.
As noted before, the circuit is
connected to the line via a bridge
rectifier consisting of diodes D1 to
D4. This is included because the line
polarity does vary, each time you use
the phone in fact.
Following the diode bridge, the
1.2V NiCd cell is charged via the
150kΩ resistor although some of the
current via this resistor is “robbed”
by the 7555. This results in a nominal
trickle charge of about 220µA when
the phone line voltage is at 50V.
The cell can be isolated from the
circuit by removing a shorting plug on
the PC board. This is provided so that
the cell can disconnected if the Message Bank Alert is not connected to
the phone line. If the cell is allowed to
completely discharge there is a strong
chance that it will fail completely.
Construction
The Message Bank Alert is constructed onto a PC board which
measures 50 x 79mm and is coded
12111001. This is designed to fit into a
standard plastic case which measures
83 x 54 x 31mm (Jaycar Cat HB-6025).
The component overlay for the PC
board is shown in Fig.3.
You can begin construction by
checking the PC board for shorts and
possible breaks in the copper tracks.
The four corners of the PC board need
to be cut to shape to clear the integral
pillars in the case. The outline is
shown on the copper side of the PC
board.
You will also need to drill holes
for the integral mounting pins on
the 6P6C sockets so that they clip in
correctly to the PC board.
The Altronics socket (Cat P-1405)
differs slightly to the one sold by
Jaycar (Cat PS-1474), so we have provided hole positions for both.
The plastic case has integral slots
in the case sides and these need to
be removed so that the PC board can
slide into place. You can remove these
with a sharp chisel or Stanley knife.
Check that the PC board fits into the
case without fouling.
Insert and
solder the
diodes and
resistors.
Check each
resistor
value with
Fig.3: compare the component overlay above with the
photograph at right when assembling the PC board.
62 Silicon Chip
your multimeter before it is installed.
The two ICs and the capacitors can installed next. Both ICs must be oriented
as shown and the electrolytic capacitors positioned with the positive lead
where indicated.
The 470µF and 6.8µF capacitors
will need to be laid over on their sides
otherwise they will be too tall for the
box lid to go on.
LED1 is a high brightness type and it
is mounted so that the top of its dome
is 19mm above the PC board, which
allows it to poke through a hole in
the lid. It is oriented with the cathode
toward the adjacent RJ socket.
The US modular 6P6C (also known
as RJ12) sockets can be installed next.
Also insert and solder the PC stakes
for the solder terminals on the AA
cell. We used a standard NiCd cell
and soldered tags to its end electrodes.
However, cells with solder tag types
are readily available and are preferable. These tags solder to the PC stakes
on the board. Make sure you solder
the cell in with the correct polarity
otherwise the circuit won’t work.
Insert and solder the 2-way pin
header but do not fit the shorting
plug yet.
Now you need to cut the case so
that there is a neat cutout in each end
to clear the modular phone sockets.
Place the PC board over the case and
mark out the cutout positions for the
sockets.
We cut the box with a fine-toothed
hacksaw and broke off the pieces with
pliers. The cutout was then filed to
shape. Test the PC board for fit into
the case and adjust any of the cutout
sides accordingly. The lid will require
a hole for the LED and also the flanges
above the sockets will need to be filed
flat so that the lid sits flush on the case.
Fit the label to the lid and cut out
the LED hole with a sharp knife.
Measure the cell voltage with a multimeter. It should be at least 1.2V. If it
is lower than this it will require charging before you can use the circuit.
You can let the phone line do this
for you by plugging the line into the
socket. Charging via the phone line
will require the shorting plug to be
connected to the pin header. The
telephone connects to the second
socket using a 6P2C (or 6P4C or 6P6C)
extension lead.
Testing
To test the circuit, you need to have
it connected to the phone line and the
phone must be connected as well. You
can do a quick test of the circuit by
shorting out the 680kΩ resistor with
a pair of long nosed pliers.
The LED should begin to flash
after a second or so, and continue to
flash at around one second intervals.
This depends on the actual value of
the 100µF capacitor. When you lift
the handpiece the LED should stop
flashing.
The final test is to use a mobile
phone to dial in and again confirm that
the LED begins flashing after the ring
is heard. Lifting the receiver should
stop the LED flashing.
If, when you hang up, the LED begins flashing again it means that you
need a larger capacitor in place of the
The PC board is designed to suit this particular plastic case (Jaycar HB-6025).
The electrolytic capacitors are laid over on their sides to allow the lid to fit on.
It connects in line with your phone via a pair of RJ-12 modular connectors (the
same type used to connect a modem to a phone line).
6.8µF. This will depend to some extent on the distance between you and
the telephone exchange, as the cable
capacity will vary with the distance.
On the other hand, if the circuit
does not trigger when the phone rings,
the 6.8µF capacitor may be a little
too large and you should try 4.7µF
or 3.3µF.
If the circuit refuses to work at all,
you can check the LM3909 operation
separately. Remove IC1 and connect
Parts list: Message Bank Alert
1 PC board 50 x 79mm, code 12111001
1 panel label 50 x 77mm
1 plastic case 83 x 54 x 31mm (Jaycar HB-6025)
2 6P6C PC-mount sockets (Jaycar PS-1474, Altronics P-1425)
1 6P2C (or 6P4C) extension lead
1 AA Nicad (or NiMh) cell with solder terminals
1 2-way header with shorting plug
2 8 pin IC sockets
Semiconductors
1 LMC555 CMOS timer (IC1)
1 LM3909 LED flasher (IC2)
1 5mm high brightness red LED (LED1)
4 1N4004 1A diodes (D1-D4)
5 1N914 small signal diodes (D5-D9)
Capacitors
1 470µF 16VW PC electrolytic
1 100µF 6.3V PC electrolytic
1 6.8µF 6.3V PC electrolytic
1 0.1µF monolithic or MKT polyester
This photo shows how we modified
the plastic case to accept the RJ phone
sockets. Note that the integral slots in
the sides of the case must be removed
to allow the PC board to fit properly.
Also note the bevelled inside edges of
the cutouts.
Resistors (0.25W, 1%)
1 1MΩ
(brown black black yellow brown
1 680kΩ (blue grey black orange brown
2 330kΩ (orange orange black orange brown
1 150kΩ (brown green black orange brown
1 56kΩ
(green blue black red brown
1 10Ω
(brown black black gold brown
DISCLAIMER
Please note that the Message
Bank Alert is NOT an Austelapproved device.
The penalty for using a nonapproved device, if detected
and subsequent prosecution
took place, could be a heavy
fine, up to $10,000.
or
or
or
or
or
or
brown black green brown)
blue grey yellow brown)
orange orange yellow brown)
brown green yellow brown)
green blue orange brown)
brown black black brown)
November 2000 63
Fig.4: the actual size artwork for the PC board. Note
that the corners must be
removed to allow it to fit
around the pillars of the
case. At right is the samesize artwork for the front
panel.
MESSAGE BANK ALERT
IC1’s pin 3 to pin 1. The LED should
flash. If it doesn’t most likely the LED
(or the IC) is in backwards. Once the
LED does begin flashing remove the
short and plug IC1 in. Check your
diode and electrolytic capacitor polarities again. Shorting the 680kΩ should
cause the LED to flash; shorting pin 2
to pin 1 should inhibit it.
might like to use different colour for
the high brightness LED in each unit.
We also recommend that you do
not place a total of more than three
Off-hook and Message Bank Alerts
on the same phone line, including
extensions. This is to make sure that
the extra loading on the line does not
cause any operational problems.
Message Bank and Off-Hook
Alerts
No time limit
If you built the Off-Hook Indicator
described in the January 2000 issue,
you can use it in conjunction with
the Message Bank Alert although you
IRECT
OMPONENTS
COMPONENT
1-9 PRICE
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AXIAL ELECTROLYTIC
CAPACITORS
10uF <at> 450 volt
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22uF <at> 50 volt
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AXIAL POLYESTER
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0.01uF
$0.38
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64 Silicon Chip
While the Off-Hook Indicator did
have a time limit on its operation
because the battery would discharge
while the LED was flashing, this limitation does not apply to the Message
0.022uF
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330uF
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Bank Alert because when it is flashing
it is always fully powered from the
phone line (via the charging circuit).
So even if you are away from home
for weeks or months at a time, the
Message Bank Alert will flash if an
incoming phone call has been detectSC
ed (and not answered).
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ABN: 70-032-497-512
Looking for an
electronic thermostat
that’s easy to build
and is programmed
using Windowsbased software?
This unit interfaces
with a DS1620
Thermometer/
Thermostat IC and
has three relays to
control external
equipment.
T
HIS PROJECT IS based on the
“PC-Controlled Thermometer/
Thermostat” described by
Mark Roberts in the June 1997 issue
of SILICON CHIP. That design used a
DS1620 Digital Thermometer/Thermostat from Dallas Semiconductor
as the sensor and interfaced to the
parallel port of a PC. An accompanying Windows-based software program
allowed the user to set the high and
low switching points of the device
so that external equipment could be
controlled via relays.
In the original design, the DS1620
plugged into an 8-pin header socket
and was connected to the pins of a
DB25 connector via flying leads. Two
other components – a 1N4148 diode
and a 1kΩ resistor – were housed in
the backshell of the DB26 connector.
Fig.1 shows the software interface
66 Silicon Chip
By MICHAEL JEFFERY
that was used for programming, while
Fig.2 shows a block diagram of the
DS1620.
The original design also showed
how the outputs of the IC could be
used to drive three 5V relay circuits.
However, no con
structional details
were given for these. Similarly, no
details were given showing how the
device could be made to operate inde
pendently of the PC after programming (although this is fairly simple
as we shall see).
The software allowed the user to
set the high (THIGH) and low (TLOW)
points for the thermostat just by clicking a few buttons. It also featured a
bargraph and a digital readout that
showed the current temperature.
In operation, THIGH switches high
when the temperature exceeds a programmed upper limit but immediately
switches low again when the temperature falls below that limit. Conversely,
TLOW switches high when the temperature falls below a programmed lower
limit but is low when the temperature
goes above that limit.
A third output from the DS1620,
TCOM, switches high when the upper
preset is exceeded and remains high
until the temperature goes below the
lower preset. TCOM could, for example, be used to control a fan which
would come on when the temperature
exceeded THIGH and stay on until the
temperature dropped below TLOW.
Making it independent
It’s quite easy to make the device
operate independently of the PC. All
we have to do is provide a regulated
+5V supply rail and the necessary
clock signals to pin 2 of the DS1620
Fig.1 (above): the software lets you set the THIGH and TLOW trip points of the
DS1620 Thermometer/Thermostat IC by clicking the Min and Max up/down
buttons. Fig.2 at right shows the block diagram for the DS1620. It covers a
temperature range from -55°C to +125°C.
– two functions that were previously
provided by the PC’s parallel port. We
also have to ground pin 3 (reset)
All these functions are provided
here and the circuitry is built on a
PC board, along with the relay output
stages. The DS1620 is mounted on a
separate PC board, with spare pads to
make it easy to connect flying leads to
its pins (supply, clock, outputs, etc).
Fig.3 shows the circuit configuration for the DS1620 after programming.
Actually, there are two small PC
boards for the thermostat IC – one
for mounting a single DS1620 and
the other for mounting two DS1620s
(eg, to provide two independent thermostats with different trip points).
Both boards carry machined-pin IC
sockets. That way, a DS1620 IC can
be easily removed and plugged into
the pin header for programming, then
transferred back to its PC board again.
The thermostat board is connected
to the relay board via flying leads.
Basically, it’s a 2-way street – the
DS1620 drives the relay board and at
the same time, the relay board provides the DS1620 with clock signals
and a regulated +5V rail.
used as a control output. Just imagine
switching a refrigeration compressor
motor on and off at around 2-3 Hz for
even a few seconds at a time. Do that
on a regular basis and you will end
up with a very hot motor that could
eventually burn out.
The answer to this problem is to
clock the DS1620 chip with a brief
pulse at preset intervals. This means
that the THIGH and TLOW outputs are
only updated at widely-spaced intervals which, in this circuit, can be set
by the user.
TCOM, on the other hand, has a
certain amount of switching hysteresis built in, depending on the
programmed upper and lower limits.
For example, if the upper limit is 60°C
and the lower limit is 30°C, then the
hysteresis is 30°C.
In practice, this means that TCOM
can toggle rapidly in response to
temperature changes only if it has a
very narrow hysteresis range.
In this circuit, there are 10 preset
clock intervals to choose from, ranging
from 6.7 seconds to 1.9 hours. So, if
you wish, you can have the DS1620
update every 1.9 hours, although in
most cases you will want a time interval that’s much less than this (eg,
a few minutes).
Circuit details
Refer now to Fig.4 for the circuit
details. The final clock circuit is very
simple and uses a 4060 14-bit binary
counter (IC1) with an inbuilt clock
oscillator. It has 10 binary outputs, one
of which is selected to drive a 74C14
(or 40106) Schmitt inverter to give a
brief logic low timing pulse.
The external RC network on pins
9 & 10 of IC1 (C7 & VR1) sets the
oscillator frequency and this can be
adjusted using VR1. When VR1 is set
to maximum (200kΩ), IC1 is clocked
Clocking the DS1620
The DS1620 toggles its relevant
output (THIGH or TLOW) fairly rapidly
(2-3 times a second) when the temperature is very close to a programmed
set point. When used as a freestanding
thermostat, this toggling effect can
cause problems if THIGH or TLOW is
Fig.3: this circuit shows how the DS1620 is configured after
programming. The programming circuit is shown on page 11 of
the June 1997 issue.
November 2000 67
Fig.4: the complete circuit for the temperature controller relay board. It has
three relay output stages, a clock circuit (IC1, D1 & IC2a) and a power supply
(BR1, REG1 & REG2).
at a nominal 0.42Hz. Its 10 binary
outputs divide this down (by 16, 32,
64, 128, 256, 512, 1024, 4096, 8192 &
16,384) to give time durations ranging
from about 6.7 seconds to 1.9 hours.
Any one of these 10 outputs can be
selected on the circuit board. If you
want longer periods, increase VR1 to
1MΩ. Conversely, for shorter periods,
reduce the value of C7.
When the selected output from IC1
goes high, a brief positive-going pulse
is fed to pin 13 of IC2a via C8 and
diode D1. Resistor R2 discharges C8
after each pulse, while D1 prevents
pin 13 of IC2a from being pulled
negative each time the selected output
from IC1 switches low, as this could
damage the IC.
68 Silicon Chip
Schmitt trigger IC2a inverts and
squares up the signal on its pin 13 input. The resulting clock signal appears
on pin 12 and is used to clock pin 2
of the DS1620. Pulldown resistor R4
is there to prevent pin 13 of IC2a from
floating when D1 is not conducting.
Note also that the remaining unused Schmitt inputs are tied to the
ground rail. This is done to prevent
them from oscillating due to stray
electrical noise. R3 and C9 provide
a brief positive-going pulse to pin 12
(reset) of IC1 at power on, so that it
automatically resets.
Power for the circuit is derived from
a 16V AC plugpack supply. Its output
is rectified by diode bridge BR1 and
then fed to 3-terminal regulator REG1
which provides a +12V rail. REG1
also drives REG2 which delivers a
regulated +5V rail.
Relay options
One application I use this circuit for
is to switch a 30A solid state relay, to
turn a heater on and off during winter.
This involves using an onboard relay
on the Temperature Con
troller PC
board to switch the solid state relay at
low voltage. By using a timing cycle
of 3.5 minutes from IC1 (ie, one clock
pulse every 3.5 minutes), the room
temperature stays within 1°C of the
programmed set point.
There are a few options for the
relays and the power supplies:
(1) If you are using 5V relays and
switching 5V, omit REG2, C4, C5, C6
and use a 7805 for REG1. Resistors
R7, R10 & R13 should be reduced to
Fig.5: the parts
layout for the relay
driver board. Note
that the linking
options and resistor
values shown here
are for 12V relays.
You can also use 5V
relays by making a
few simple changes
– see text & Fig.4.
Fig.6(a): this diagram
shows how the
DS1620 is installed
on its PC board.
Fig.6(b) below shows
the dual DS1620
board.
470Ω and you have to link points B
to D and B to C. The relay(s) are then
used to switch between the +5V rail
at point B and ground (+5V to NO;
ground to NC).
(2) If you are using 5V relays and
switching 12V, install both regulators
and use 470Ω resistors for R7, R10 and
R13. Link point A to C and point C to
D. As before, connect point B (now
at +12V) to the NO relay contact and
ground to the NC contact.
(3) Finally, if you are using 12V relays
and switching 12V, use 1kΩ resistors
for R7, R10 and R13. Link points A to
C and B to D and connect point B and
ground to the relay NO & NC contacts
respectively (if you want to switch 5V,
connect point A to NO instead).
Note that 12V relays will be supplied in the kit (along with both
regulators), so most people will want
to use option 3. What ever you do,
make sure that the DS1620 is powered
from a +5V rail, otherwise it will be
destroyed.
One option is to use mini DIL PCB
relays (which require only low current), especially is you want to run the
unit from solar power. These relays are
available in both 5V and 12V versions
and can handle 1A at 30V DC.
The PC board can accommodate
both conventional and mini DIL PCB
relays (see Fig.5).
Stand-alone timer
By the way, you don’t have to use
this design to switch the outputs of
a DS1620 chip. If you wish, it could
be used as a stand-alone relay driver
board with various timed outputs.
You could even use a rotary switch to
select between the outputs of IC1. The
selected output could then be used to
drive one of the relay circuits.
Construction
Fig.5 shows the assembly details for
the PC board. The first thing to do is to
decide how you want to configure the
power supply (see above). The links
shown in blue on Fig.4 are for option
3 described above (ie, 12V relays). It’s
up to you to install the relevant links
to switch +12V or +5V.
Begin construction by installing all
the wire links, followed by the resistors, trimpot VR1, the capacitors and
diodes. Make sure that all polarised
parts are installed the correct way
around.
Next, install the bridge rectifier
(BR1), the transistors, regulators and
LEDs. The two ICs can then be installed, along with the relays and the
fuseholder clips. Be careful with the
fuseclips; these have a small spigot
at one end and this must go to the
outside. Put them in the wrong way
round, and you won’t be able to install
the fuse.
Don’t worry about installing a wire
link between the selected output of
IC1 and the track adjacent to pin 16
(which links across to C8) at this stage;
that step comes later, after testing.
The two smaller boards will only
take a few minutes to assemble. In
Resistor Codes
No.
1
2
1
3
3
3
3
Value
1MΩ
100kΩ
47kΩ
2.2kΩ
1kΩ
1kΩ
470Ω
4-Band Code (1%)
brown black green brown
brown black yellow brown
yellow violet orange brown
red red red brown
brown black red brown
brown black red brown
yellow violet brown brown
5-Band Code (1%)
brown black black yellow brown
brown black black orange brown
yellow violet black red brown
red red black brown brown
brown black black brown brown
brown black black brown brown
yellow violet black black brown
November 2000 69
TABLE 1
ivision
Pin No. DR
atio
7
16
5
The prototype used 0Ω resistors instead of wire links but you can simply use
tinned copper wire. A cable gland is now recommended instead of the 6-way
barrier strip at top.
either case, you simply install a machined-pin IC socket (8-pin or 16-pin,
depending on which board you use).
The larger of these two boards also
carries a 0.1µF capacitor to provide
extra supply line decoupling.
Finally, complete the construction
by linking the appropriate pins on the
DS1620 board back to the relay board
(ie, to THIGH, TLOW & TCOM, +5V, 0V
and clock). This can be done using
6-way telephone cable.
Setting up
After you have checked the PC
board thoroughly for correct compo-
WARNING!
This design is intended for switching low voltages only. Do not attempt
to use it to switch 240V AC mains voltages or any other high voltages.
The track spacings between the relay pins are too close for 240V use and
also the external barrier terminal strip is not suitably protected.
If you wish to switch mains voltages, you can use the on-board relays to
switch suitably isolated (and rated) external relays at low voltage (either 12V
or 5V). The external relays then do the mains switching. Do not attempt this
unless you are experienced and know exactly what you are doing.
It’s a good idea to use a zero switching solid state relay if you are switching
inductive loads, such as a motors, fluorescent lighting and compressors, etc.
In that case, the on-board relays are used to simply activate the internal LED
of the solid state relay via a suitable resistor.
70 Silicon Chip
32
4
64
6
128
14
256
13
512
15
1024
1
4096
2
8192
3
16,384
nent positioning and polarity, apply
power and check that you have +5V
between point A and ground and +12V
between point B and ground.
If all is OK, disconnect the power
then link point A to C and point B to
D. Now reapply the power and place
a test LED in series with a 1kΩ resistor
between pin 7 of IC1 and ground (0V).
Adjust VR1 until the test LED flashes
at 3.5-second intervals (ie, the LED
should light for 3.5 seconds, then go
off for 3.5 seconds and so on).
Once you have set the oscillator
speed, temporarily link pin 7 of the
4060 to C8. Now place the test LED
and its series resistor between pin 12
(clock out) of IC2a and ground. The
test LED should now briefly flicker
every 7 seconds.
Assuming it all checks out, remove
the link on pin 7 of IC1 and connect
a link between pin 13 and X2 for a
3.5-minute clock or between pin 15
and X2 for a period of 7 minutes.
Altern
ative
ly, you can link to any
of the other output pins for shorter
Where To Buy The Parts
Parts List
Parts for this design are available as follows:
(1). Main Relay Driver PC Board ....................................................... $16.50
1 DS1620 Thermometer/Pro
grammer software (see panel)
1 or 2 DS1620 Thermometer/
Thermostat ICs
1 relay-driver PC board
1 PC board for DS1620 (single
or dual)
1 TO-220 heatsink
3 1A DPDT mini DIL PC-mount
relays (RLY1-3); Altronics Cat.
S4128 (5V) or S4130 (12V); or
3 10A SPDT PC-mount relays
2 M205 PC-mount fuseclips
1 1A M205 fuse
1 200kΩ 5mm horizontal mount
trimpot (VR1)
1 test LED and 1kΩ resistor
1 6mm cable gland (replaces
6-way barrier strip in prototype)
1 8-way barrier terminal strip
8 3mm x 20mm metal screws
4 12mm spacers.
4 3mm nuts and washers.
1 plastic electrical case, 170 x
120 x 90 (L x W x H)
1 16V 1A AC plugpack supply.
(2). PC Boards For DS1620 (both types) ............................................ $9.50
(3). DS1620 Thermometer/Thermostat IC ......................................... $13.50
(4). DS1620 Thermometer/Thermostat with programmed
THIGH & TLOW (you specify) ........................................................ $15.50
(5). 16VAC 1A Plugpack Supply ........................................................ $23.50
(6). Complete kit (does not include DS1620 chip, software or
plugpack supply) ......................................................................... $76.00
(7). Basic Kit including Relay Driver PC Board, DS1620 Boards
& all components for Relay Driver PC Board .............................. $54.00
Please add $3.95 for p&p if ordering the PC boards only, or $9.95 p&p for the
complete kit (Australia only). Payment by cheque or money order to: Michael
Jeffery, Clinch Security Systems, R.M.B. 5811, Myrtleford, Vic 3737. Ph: (03)
5756 2424. Email michael.jeffery<at>porepunkahps.vic.edu.au
Note: this design is copyright to Clinch Security Systems. All prices include
GST.
Software availability: the programming software for the DS1620 is available
from Softmark, PO Box 1609, Hornsby, NSW 2077. Ph/fax: (02) 9482 1565.
Price: $25 plus $5 p&p (includes GST).
or longer periods. Table 1 shows the
division ratios for IC1’s outputs.
The three relays can be tested by
connecting the +5V rail to each of the
RET inputs in turn. Warning: do not
attempt this while a DS1620 chip is
connected.
Now place a programmed DS1620
into the socket on its board. The
DS1620 will now sample and hold
every 3.5 or every 7 minutes (or at
some other interval, depending on the
output from IC1 that’s used). If a relay
is tripped, it should remain in that
state at least until the next clock pulse
comes along. Even then, it will only
change state if the output from the
DS1620 also changes state in response
to changing temperature conditions.
The prototype relay board was installed in a plastic electrical case with
a clear lid. The four mounting holes
in the board mate with integral pillars
inside the case, so it’s easily secured
using spacers and 3mm machine
screws (the screws make their own
thread in the plastic pillars).
An 8-way barrier terminal strip
is mounted on one side of the case
adjacent to the relays, while (on the
prototype) a 6-way barrier strip was
mounted on the opposite side. The
8-way strip accepts the relay outputs
Semiconductors
1 4060 14-bit binary counter (IC1)
1 74C14 hex Schmitt inverter
1 W04 bridge rectifier (BR1)
1 7812 12V regulator (REG1)*
1 7805 5V regulator (REG2)
3 BC337 NPN transistors (Q1-Q3)
1 1N4148 signal diode (D1)
3 1N4004 silicon diodes (D2-D4)
3 5mm red LEDs (LED1-3)
A couple of pin headers were install
ed at the X2 position in the prototype,
to make is easy to select between two
different timing outputs from IC1.
and the 16VAC power supply leads
from the plugpack.
The 6-way strip was used to terminate the three outputs from the
DS1620 (RET1, RET2 & RET3), the
clock output signal and the +5V & 0V
rails (for the DS1620).
Alternatively, you could simply run
the 6-way telephone cable through a
6mm cable gland and terminate the
leads directly to the PC board, thus
eliminating the 6-way barrier strip.
Note that kits will be supplied with
the 6mm cable gland (not the 6-way
barrier strip).
Capacitors
1 1000µF 25VW electrolytic (C1)
1 100µF 25VW electrolytic (C4)*
1 1µF 25VW electrolytic (C7)
1 0.22µF monolithic (C8)
7 0.1µF monolithic (C2, C3, C5*,
C6*, C9, C10, C11)
Resistors (0.25W, 1%)
1 1MΩ (R1)
2 100kΩ (R3,R4)
1 47kΩ R2
3 2.2kΩ (R5,R8,R11)
3 1kΩ (R6,R9,R12)
3 1kΩ or 470Ω (R7,R10,R13)*
* Omit or change to suit 12V or
5V version.*
Finally, don’t overtighten the screws
when you’re attaching the lid, otherwise it may crack. Just lightly nip them
SC
up so that it seals properly.
November 2000 71
It’s a computer &
digital oscilloscope
all in one package!
You can control the TDS 7054 with the
touch screen, the front panel controls
or via the mouse. The scope operates
under Windows 98 and any Windows
software can be run on it at the same
time as the scope is being used.
Tektronix TDS7504 Digital
Phosphor Oscilloscope
While many people tend to be blase about
the march of technology, it is difficult not to
be impressed by the latest offering from
Tektronix, the TDS7000 range. These are
Tek’s Digital Phosphor Oscilloscopes, based
on a colour LCD display and having very
high sampling rates.
By LEO SIMPSON
Our review machine was the Tektronix TDS7000, a 500MHz, 5 Gigasample/second, 4-channel oscilloscope
with an amazing range of facilities.
In fact, it is almost possible to ignore
the oscilloscope’s performance while
you familiarise yourself with the com72 Silicon Chip
puter facilities. Did we say computer?
Well, yes. This machine is more of a
computer than oscilloscope.
In fact, the TDS 7000 series can be
regarded as a Windows-based computer which happens to have a very high
performance digital oscilloscope built
into the same box. And rather a big
and heavy box it is, measuring 277mm
high, 483mm wide and 425mm deep
and weighing in at 19kg, which includes the accessory pouch on the top.
It is a Pentium Celeron 500MHz
computer, with a 6GB hard drive, 128
megabytes of RAM, a 3.5-inch 1.44MB
floppy drive and a CD-ROM drive
(rear-mounted). It also has approximately 100KB of non-volatile RAM for
waveform storage (up to two 50,000
point waveforms can be stored).
The TDS 7054 comes loaded with
Windows-98 and virtually any Windows based program can be run on the
machine. The front panel display is
an active-matrix liquid crystal display
(LCD), measur
ing 211mm wide by
158mm high and its display resolution is 640 x 480 pixels. Its contrast
Fig.1: this is a typical screen of the TDS 7054 with two
traces displayed and running at the default sampling rate,
as defined by the timebase setting. Here the timebase is
quite slow at 1ms/div and the sampling rate is relatively
slow too, at 50kS/sec. This defines the resolution of the
waveforms.
Fig.3: Again, same waveforms as in Fig.2 but now all the
amplitude measurement options are shown in the lower
half of the screen. Note that some measurement options
have been selected for both traces.
ratio is 150:1 and the refresh rate is
60Hz. It runs in Windows SVGA highcolor mode (16-bit).
What else has it got? A Creative
SoundBlaster PCI 64V sound card
and a huge array of sockets on the rear
panel. These include two PS-2 sockets
for a keyboard and mouse, a USB (uni
versal serial bus) socket for a mouse,
two video out sockets (SVGA & VGA),
a GPIB (general purpose instrument
bus) socket, a PCMCIA card slot, a
parallel printer port, an RJ-45 ethernet socket (supports 10base-T and
100base-T) and sound card inputs.
The oscilloscope is a 4-channel,
500MHz 5 Gigasample/second digital
Fig.2: Here are the same waveforms as in Fig.1 but now
the sampling rate has been wound up to 5MS/sec and this
shows a lot more resolution. Notice the overshoots on the
lower trace. Also present on this screen are horizontal
cursors and their voltage settings. Note that this shows
buttons at the top instead of the Windows menu bar.
Fig.4: If you don’t want to go through the process of
selecting measurement options for a waveform, you can
do it via the “snap-shot” mode, as shown here for channel
2.
storage Digital Phosphor Oscilloscope
(DPO). DPO is a Tektronix patented
system for showing trace intensity
modulation similar to that inherent
in the CRT phosphor of conventional
analog scopes.
Let’s make a comment on DPO right
at the start. We think it is an awkward
name and one which does not really
do justice to the scope. Sure, it does
show intensity modulation but it is
still not the same as an analog scope
because the traces still show the
quantisation jitter or noise inherent in
any digital scope. At the same time,
it has all the advantages of a very fast
digital scope.
Having criticised the DPO name, we
must say that the real benefit of this
scope is that the sampling rate is not
locked to the timebase as it is in most
other digital scopes. This normally
means that waveforms captured at low
timebase speeds are limited to very
low sample rates. However, we are
getting ahead of matters. Let’s have a
look at the control panel.
Here again, there are major differences between the Tektronix TDS 7000
series and other digital scopes.
For a start, each of the four input
channels has its own vertical sensitivity and position controls, as well as a
button to select an input impedance of
November 2000 73
Fig.5: Same waveforms as in Fig.4 but the timebase and
vertical settings have been changed. This is the snapshot
for channel 1. Note that the timebase is twice as long as
Fig.4 and so the sampling rate is halved.
1MΩ or 50Ω, the latter being selected
when active probes are in use.
Second, the horizontal input also
has its own knobs for timebase, delay
and resolution. Triggering is controlled by an array of buttons plus the
level control. All of these controls are
backed up by indicator lights, so that
no matter what happens, you should
be able to work out the scope settings
by looking at the indicator lights and
the various settings shown on the
LCD screen.
All of this is very important because all functions are settable via the
scope’s touch screen. And when you
touch the screen or use the mouse,
say to change a trigger setting, not
only does it register on the screen
but it also shows on the panel lights,
where applicable. That is a big advance in scope usability. It means that
by looking at the screen readings for
sensitivity, etc and the front panel
lights, you can always get a picture
of what the scope is doing.
On-screen help
Not only that, the TDS 7000 series
has also dispensed with multi-level
on-screen menus. Hooray to that because multi-level menus are hard to
use, particularly if you don’t use the
scope on a regular basis.
Even better, you have on-screen help
for any function selectable on screen,
which means virtually everything.
Better still, you can read the on-screen
help while you use the scope. How? By
using an external SVGA monitor (Ah,
so that’s what the extra VGA socket is
74 Silicon Chip
Fig.6: There are range of options in the display mode,
enabling you to select different coloured traces for each
channel, traditional green, gray, temperature distribution
or spectral distribution.
for). Well actually, as already noted,
there are two video sockets. One is a
VGA socket and it is only used for the
scope display. The SVGA socket, on
the other hand, can be used to display
any Windows application you might
run, such as Word, Excel, Internet
Explorer etc.
For example, when I started doing
this review I used Wordpad on the
second screen, using the keyboard and
mouse in the normal way and then,
if I wanted to change a setting on the
scope, I could move the mouse from
the SVGA screen to the scope screen,
make the setting on a drop-down
menu or button, and then flick back
to the word processor to continue
writing.
Want to write some commentary on
the scope screen to annotate a waveform? Sure, just use the on-screen
keyboard directly, or move the cursor
with the mouse and then type on the
keyboard. Want to save a waveform?
Easy. Decide whether you want the
full screen or just the graticule, hit
Control C and then paste it into
whatever program you want. Or you
can drop it into Windows Paint and
save it as bitmap (.bmp) file. That’s
how all the waveforms shown here
were saved.
Back to the scope now. You can operate it like a Windows program, with
drop-down menus from the task bar at
the top or you can use menu buttons
along the top. Either way, you can
make all settings via the touch screen
or use the mouse, as noted above.
Having used both, I found myself
preferring the mouse at it seems to be
faster and easier, particularly when
selecting from the drop-down menus.
Measurement options
Measurements are easy and highly
flexible. Here, when you touch the
“Measure”, the scope graticule is
vertically compressed so that half
the screen now shows measurement
options. For example, for amplitude
measurements there are 12 options
such as peak-peak, RMS, positive and
negative undershoot.
You can also select which of the
four channels you want to measure
and a total of eight different measurements, enable statistics calculations
on any of the measurements (mean &
standard deviation etc; after all, they
do vary all the time) set up reference
levels, gating and so on. Fig.3 shows
the Measurement screen and you can
see that measurements have been
selected for both channels.
Another screen gives nine time
measurement options such as frequency, period and duty cycle, while
yet another gives another four measurement options and a third screen
gives 12 histogram options.
Maybe you don’t want to go
through all the business of selecting
measurements for each channel. In
that case you simply select “snapshot” and it gives a bunch of measurements for Ch1 or any of the other
three. Fig.5 shows a snapshot group
for Channel 1, while Fig.4 shows a
snapshot group for a similar signal
but on Channel 2.
Fig.7: Quite a few mathematical functions are possible:
Shown here are the four predefined expressions but you
can also define your own as well as the spectral analyses.
We’ve selected Ch1 multiplied by Ch2.
The TDS 7000 also has a mathematics (MATH) mode. This enables you
to display the result of a mathematics
calculation as another trace on the
screen. Four predefined expressions
are available: Ch1 - Ch2, Ch3 - Ch4,
Ch1 x Ch2 and Ch3 x Ch4. You can
also do spectral analyses of waveforms
in both frequency and time domains.
Again, this is where this scope excels
because while the FFT functions are
locked to the sampling rate, they are
not locked to the timebase. So you
can do a more detailed analysis than
would otherwise be possible.
Time did not permit us to delve into
these functions at all but clearly there a
large number of options available and
you can use as many as four different
Fig.8: And here is the result of the Ch1 x Ch2 expression
selected on Fig.7, shown here as the red trace. This can
be very useful when monitoring instantaneous power in a
circuit.
spectral analysers simultaneously.
Nor could we really do justice to all
the other features of this multifaceted
machine. We only had the machine for
a few days and in that time you can
really only gain a brief acquaintance
- you would need weeks to learn and
be really adept with all the functions
and features.
However, in the brief time that we
had the Tektronix TDS 7054 we continually found ourselves being impressed
with its many features and its general
ease of use. This is high praise for the
designers because it is very difficult
to combine very high performance, a
vast range of operating features and
most of all, ease of use.
Still, we’re not sure whether to
regard it as high performance scope
with a Windows computer built in or
a Windows computer which just happens to contain a high performance
scope. Tek
tronix would no doubt
prefer to think of it as the former.
And whether you are in the market for a costly machine such as this
or whether you are just interested
in oscilloscopes, we think the TDS
7000 range is the precursor for digital
scopes of the future - one day they
will all operate under a Windows (or
similar) environment. But the TDS
7000 series does it now!
For further information on product
availability and prices, contact Tek
tronix on (02) 9888 0100 or see their
website at www.tektronix.com SC
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November 2000 75
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.
Water level
indicator
This water level indicator
was designed after a recent
mishap with the pump in a
water tank on a rural property. It went unnoticed that the
water supply had fallen below
the level at which the pump
could operate properly, with
the result that it burned out
and had to be replaced.
This circuit depends on
the fact that there is a fairly
low and constant resistance
between a pair of electrodes
in a tank of water, irrespective
of the distance between them.
The circuit is based on the
LM3914 linear LED bar/dot
driv
e r. It drives five green
LEDs to indicate level, with
the added feature of displaying
a red LED when the water falls
below the lowest sensing point;
ie, when all the green LEDs are
extinguished.
To give a clear on/off indication, the red LED is driven by a
555 with the control voltage on
pin 5 pulled towards the supply voltage by a 1kΩ resistor.
This causes the 555 to switch
at 0.46 and 0.92 of the supply
voltage instead of the usual 1/3Vcc and
2/3Vcc thresholds.
A BC548 transistor (Q1) is used as
a buffer to provide a reasonably low
impedance drive into pin 5 of the LM3914 (SIG) while keeping the current
through the water sensors below the
level at which electrolysis could become a problem.
The sensor assembly is made by
threading six lengths of 1mm enamelled copper wire through an 8mm
OD clear PVC tubing, long enough to
reach the bottom of the tank and with
sufficient additional length to fasten
the top end securely. The reason for
using 1mm wire is primarily to make
it easy to thread it through the plastic
tube.
76 Silicon Chip
The top sensor (S6) is about 10
to 15cm below the overflow outlet
at the top of the tank and the other
sensors are spaced evenly down the
tube. Using a 1.2mm drill, holes are
made through the tube wall at the
appropriate points, including that for
the bottom contact (S1) to hold it in
place more securely.
The cut end of the wire should be
smoothed to make it easier to push
it through the tube and to avoid any
danger of scratching the enamel of the
wires already in the tube. The wire
goes in more easily if the PVC tube is
bent more or less at a right angle so
that the drilled hole is in line with the
bore of the tube.
About 15cm of wire is left outside
the tube at each point, scraped clean
of enamel and close-wound firmly
around the outside of the tube. A
30mm length of 12.5mm copper water
pipe can be pushed over S1 to add
weight and increase the surface area
if desired.
On no account should solder be
used on the submersible part because
corrosion will result from galvanic
action.
At the top end of the assembly,
the resistors are soldered to their
respec
tive wires (double checking
is recommended!), with insulating
sleeving over each join, This is then
covered with heatshrink tubing after
attaching the two leads to run to the
indicator unit.
A. March,
North Turramurra, NSW. ($35)
Do-it-youself car
battery charger
You can easily buy a charger for
your car’s battery but some people
like to “roll their own” and may
have some or all the necessary parts
on hand.
I found that a 12V halogen lamp
transformer was ideal, as it’s fully
enclosed with thermal protection
and needs only a 35A bridge rectifier on a small heatsink to function
as a charger.
I fitted a voltage indicator in the
form of a red LED, 10V zener and
100Ω resistor across the battery connections. The in-line 10A blade fuse
in the positive output lead will blow
if the battery leads are reversed.
The transformer I used was rated
at 63VA (Jaycar MP-3050) but other
similar ones should be just as suitable. Do NOT use the electronic
switchmode or toroidal types. The
rectified DC current is about 3A
average.
P. King,
Croydon, NSW. ($20)
Hi/Lo pulse indicator
uses a 7-segment display
A common cathode 7-segment display and a single NPN transistor can
be used as a pulse polarity indicator.
As shown in this circuit, Q1 is used
to invert low signals and its collector
drives diodes D1, D2 and D3 which
are connected to segments d,e & f.
Hence, when the input signal is low,
the collector of Q1 will be high (Q1
is off) and so the display will indicate “L”.
When the input signal is high,
diodes D4-D8 drive all segments of
the display except a & d, to indicate
“H”.
Note that the circuit loading is quite
low, as set by the 1kΩ input resistor.
WANTED!
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idea but there are a few conditions:
• It must be your own work
• It must not have been published or submitted elsewhere
• It must be something other SILICON CHIP
readers would find interesting.
Send to: The Publisher, SILICON CHIP,
PO Box 139, Collaroy, NSW 2097.
email: silchip<at>siliconchip.com.au
Phone: (02) 9979 5644
This is a compromise between circuit
loading and segment brightness.
Raj K. Gorkali,
Kathmandu, Nepal. ($20)
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UX
A collection of computer features from the pages of SILICON
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November 2000 77
VINTAGE RADIO
By RODNEY CHAMPNESS, VK3UG
The Intriguing Philips “Philetta”
Every so often, a radio appears that is quite
different from the usual fare of vintage radio
receivers. The Philips “Philetta” is one such
set. It was not only a multi-band AM receiver
but also came complete with an FM band.
The Philips Philetta fits into the
mantle set category but it’s the inclusion of FM that really got my
attention. It is not a large set and has
only four valves but despite this, it
still delivers good performance on
FM (more on that later).
Unfortunately, I don’t own this set;
Geoff, its owner lent it to me so that I
could share this story with you.
I first saw this set playing at a
vintage radio club meeting and was
immediately attracted to it. But what
really impressed me was that it was
receiving the local FM stations on just
a few metres of wire – and it used only
four valves! I just had to have a much
closer look at this set and Geoff agreed
that I could take it home for a couple
of weeks so that I could examine it
at my leisure.
The Philetta is a small-to-medium
The Philetta is housed in an attractive veneered plywood cabinet and is very
nicely made. There’s just one problem – it isn’t mine!
78 Silicon Chip
sized set in an attractive veneered
plywood cabinet. It features a recessed front panel and escutcheon,
which means that it can be tipped
onto its front without damaging the
controls. It really is quite attractive
and the wooden cabinet would have
been considered unusual in Australia
at the time, as most of our sets were
residing in plastic cabinets. However,
this set is a quality receiver with lots
of worthwhile features.
Having admired it, I proceeded to
put it through its paces. The front panel escutcheon is labelled in German,
as is the back panel, but the function
of each control is still quite apparent.
This leads me to suspect that it was
brought into Australia by a migrant
during the 1960s. Eventually, it was
sold to a secondhand dealer because
it didn’t work at times. Geoff bought
it from the dealer and quickly found a
dry solder joint on the mains switch.
The various radio bands that the set
operates on are selected using a bank
of piano-style switches in the lower
centre of the front panel. These are as
follows: LW (Long Wave) 150-270kHz;
MW (Medium Wave), 515-1630kHz;
KW (Short Wave) 5.8-12.4MHz; and
UKW (Frequency Modulation) 88107MHz. However, the dial calibrations show slightly different tuning
ranges, indicating that it was probably
tweaked to work on our bands out
here, particularly the FM band which
shows 88-104MHz.
The last switch is marked AUS
which means power off. Pressing LW
and KW at the same time actuates the
record player terminals.
The two front panel rotary controls
are actually dual concentric controls.
The lefthand one is for volume and
tone, while the one on the right
consists of two tuning controls –
one for the AM bands and the other
P.C.B. Makers !
•
•
•
•
•
•
•
•
The rear panel is well-labelled – even if it is in German! Fortunately, the
symbols make it easy to work out what’s what. The back is removed by undoing
just two screws, while another four screws underneath release the chassis.
exclusively for the FM band. This
means that it is possible to set both a
favourite AM station and a favourite
FM station and just switch between
them by pressing the appropriate
band change switch. Nifty!
Performance
Having worked out the function
of each control, I soon had it up and
running on the AM broadcast band.
On local stations, I found that it work
ed quite satisfactorily using only its
ferrite rod antenna.
When an external antenna and
earth were connected, it proved to be
quite a performer, with 10µV signals
being heard. On the long-wave band,
the set was just as sensitive with an
external antenna connected but didn’t
pick up much using just the ferrite rod
antenna. A number of non-directional
beacons (NDBs) were heard over quite
some distance with the antenna connected but unless you are able to read
Morse code, it is difficult to determine
what the callsigns are or where the
stations are located.
On the shortwave band, the results
were not as impressive, the sensitivity varying between 30µV and
300µV across the band. Perhaps the
alignment was out on this band but
it wasn’t my set, so I didn’t have the
right to fiddle. Still, the band provided some worthwhile listening – Radio
Australia booms in here, being only
10km away, just north of Shepparton.
FM performance
Now to the FM band. I was curious
to find out how well a 4-valve FM
receiver would work.
For the FM band, there are two
sockets for a balanced antenna of 240
ohms – not 300 ohms as generally
specified in Australia. The difference
in impedance is not important and an
FM antenna with a 300-ohm twin lead
will work very well with the set. The
receiver was connected to just a few
metres of wire initially and later to
my outside FM antenna. It proved to
be quite sensitive on the FM band and
all the local stations were received at
good strength, along with a few more
distant stations.
One handy little item at the
lefthand end of the escutcheon is
a bar-type magic eye valve. This is
used for tuning the set for maximum
signal strength and works on both
AM and FM.
I was most impressed with the
audio quality of the set, this being
noticeably better than from Australian-made plastic mantle sets of the
same era. The speaker was around 150
x 100mm and remarkably well baffled for such a small set. The output
transformer uses “C” core construction and is obviously a good-quality
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November 2000 79
There’s quite a lot of circuitry built onto the chassis – not surprising considering
the AM & FM bands that the set covers. Most of the parts, including all the
valves and the tuning gang, are mounted on a large PC board.
unit, as there is plenty of bass and
treble in the audio output. In short,
it sounded good.
A look inside
My next step was to take the back
off and remove the chassis, so that
I could get a really good look at the
works. Undoing two screws allows
the back to be removed and this reveals a chassis with a PC board that
holds most of the parts. The chassis is
then released by undoing four screws
underneath the cabinet, after which it
can be removed by tilting the back up
and sliding it out. It comes out with
all the controls and the escutcheon
attached.
Good one Mr Philips – it’s a pity
that a lot more sets aren’t like this
as it make alignment so much easier. Another nice feature is that the
speaker remains in the cabinet but the
red and white leads running to it are
long enough to permit the removal of
the chassis while leaving the speaker
connected so that the set can still be
operated.
Because the set is able to tune three
AM bands and one FM band, there’s
quite a lot of circuitry. As a result, it
wouldn’t be easy to service without
80 Silicon Chip
a circuit diagram but unfortunately,
this isn’t included with the set.
As shown in the photos, the parts
are all mounted on pheno
l ic PC
board. One drawback with this board
is that you cannot see the tracks from
the component side when you hold it
up to the light. This makes it harder
to trace circuit paths, although the
board appears to be of good quality.
On a similar theme, the wave-change
switches are all enclosed, so it’s not
easy to work out the switch connections from the copper side of the PC
board.
Circuit technicalities
A quick look around the set soon
revealed the valve complement. For
the AM bands, there’s a 6AJ8/ECH81
converter (arguably the best AM
converter of its type), a 6DC8/EBF89
460 kHz IF amplifier and detector,
and a 6GW8/ECL86 2-stage audio
amplifier. The tuning indicator is an
6FG6/EM84 and is used on both the
AM and FM bands.
The FM section uses an ECC85/6AQ8 twin triode in the front
end, the first triode wired as an
RF amplifier and the second as a
self-oscillating converter. The output
from the converter is nominally on
10.7MHz.
By the way, the much higher IF
used for FM as compared to AM
(455kHz) serves two purposes: (1) it
means that “double-spotting” is unlikely to occur, as the image is 21.4
MHz away (compared to just 910kHz
in an AM receiver); and (2) it provides
the necessary bandwidth (180kHz) to
receive the FM signal without clipping the higher amplitude (ie, louder)
audio signals.
Following the 6AQ8, the signal is
applied to the 6AJ8 converter valve.
In this case, however, it is configured to act purely as a 10.7MHz IF
amplifier and its output is applied
to the 6DC8 which acts as the second
IF amplifier. From there, it goes to a
pair of germanium diodes connected
in a frequency discriminator circuit.
Finally, the detected audio is fed
to the 6GW8 audio output stages, as
in the AM mode.
The FM IF has no limiting circuitry
and there is no inter-station muting –
two features that are commonly found
on later sets with FM tuners.
Power supply
The power supply is quite conventional and uses a transformer with
a tapped primary for 110-127V and
220V AC. In Australia, the receiver
has 240V AC applied to it, so it is
being operated above its rated mains
voltage. Despite that, it has worked
well for many years without any
problems or signs of overheating, so it
can obviously tolerate this situation.
The high-voltage AC output from
the transformer is fed to a block selenium rectifier which uses the chassis
as a heatsink. This gives an output
voltage of about 245V DC, so with
220V AC mains the output would be
about 225V DC.
Ancillary circuits
The tuning indicator is mounted
upside down at the left front of the set
and is held in place with a close-fitting metal sleeve. As a result, the
valve socket that the indicator plugs
into is “floating”, with the leads running away to the PC board. It’s quite
safe but is rather unusual since we
are used to valve sockets being firmly
attached to the receiver chassis.
On the back of the chassis are two
DIN sockets, one for a record player
input and the other an output for a
tape recorder. Certainly very little has
been left to chance in this little set.
Safety blemish
From all the foregoing, it might be
thought that I think this set is without
blemish. Not so! European receivers
often have mains wiring exposed
when the chassis is removed from the
cabinet, often just where you might
be tempted to place your hand to turn
the set over! This set is not as bad
as some but the power transformer
terminals are exposed along one edge
of the chassis.
Repositioning these deadly termi-
The PC board assembly is quite well-made, although it is rather difficult to
determine which tracks go to the components mounted on the top of the board.
This makes signal tracing rather difficult and this would not be an easy set to
service without a circuit diagram.
nals or at least putting a cover over
them would not have been all that
difficult.
Another small problem is the effect
that the heat from the output valve has
on the cabinet above it. It has caused
the veneer to split slightly. Including
some method to dissipate the heat
above the audio valve would have
eliminated this problem.
Summary
As you will have gathered, I was
very impressed with this little mantle
receiver. In my opinion, it’s the best
European-made set that I have seen.
That’s not to say that it has the best
performance, looks the most elegant
or has the most features. It was, after
all, designed as a medium-quality
receiver that could be sold for a relatively low price.
It has a nice cabinet, is easy to disassemble, works well and has most of
the frequency ranges that were (and
still are) used in Europe. However,
at the time this set was brought to
Australia, we did not use the FM band
for domestic radio broadcasting. The
same goes for the long-wave band.
What failings does the set have?
Well, we mentioned the lack of a
circuit diagram, the exposed mains
terminals and the heat damage to the
top of the cabinet. That said, I have
been quite picky about the faults and
had to look hard to find any.
The only real problem I have with
this set is that it isn’t mine. If you see
one, grab it; it’s worth collecting. SC
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November 2000 81
REFERENCE
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AUDIO ELECTRONICS
Satellite & Cable TV by Graf & Sheets
Edition 1998
$
By John Linsley Hood. First published 1995.
Second edition 1999.
65
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This book is for anyone involved in designing,
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radio receivers, preamplifiers, voltage amplifiers, audio power amplifiers, compact disc
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power supplies and noise reduction systems.
375 pages in soft cover.
By Philip Miller. Published 1997.
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By Tim Williams. First published 1991
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ELECTRIC MOTORS AND DRIVES
By John E. McNamara. 2nd edition 1996.
By Austin Hughes. Second edition
published 1993 (reprinted 1997).
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Widely regarded as the standard text on EMC,
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DIGITAL ELECTRONICS – A PRACTICAL APPROACH
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Silicon Chip
Back Issues
April 1989: Auxiliary Brake Light Flasher; What You Need to Know About
Capacitors; 32-Band Graphic Equaliser, Pt.2; 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.
April 1993: Solar-Powered Electric Fence; Audio Power Meter;
Three-Function Home Weather Station; 12VDC To 70VDC Converter;
Digital Clock With Battery Back-Up.
June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer
Stopper; Digital Voltmeter For Cars; Build A Windows-Based Logic
Analyser.
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.
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.
July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers;
Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics.
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.
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.
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.
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.
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.
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.
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.
January 1990: High Quality Sine/Square Oscillator; Service Tips For
Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit;
Designing UHF Transmitter Stages.
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.
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.
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.
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; Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies; Car Speed Alarm.
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.
November 1990: Connecting 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; 6-Metre Amateur Transmitter.
December 1990: 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.
ORDER FORM
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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.
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.
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.
August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array;
Microprocessor-Based Sidereal Clock; Southern Cross Z80-Based
Computer; A Look At Satellites & Their Orbits.
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 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.
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 – How They Work.
March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio
Amplifier Module; Level Crossing Detector For Model Railways; Voice
Activated Switch For FM Microphones; Engine Management, Pt.6.
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.
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.
July 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor
Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Po
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.
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.
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.
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details or fax the details to (02) 9979 6503.
Email: silchip<at>siliconchip.com.au
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.
April 1997: 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.
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.
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.
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.
June 1997: 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; Cathode Ray Oscilloscopes, Pt.10.
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.
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.
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.
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 Hexapod Robot.
May 1995: 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.
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.
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.
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.
August 1999: Remote Modem Controller; Daytime Running Lights
For Cars; Build A PC Monitor Checker; Switching Temperature Controller; XYZ Table With Stepper Motor Control, Pt.4; Electric Lighting,
Pt.14; DOS & Windows Utilities For Reversing Protel PC Board Files.
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; How To Identify IDE Hard Disk 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.
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 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.
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.
December 1997: 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.
November 1999: USB – Hassle-Free Connections TO Your PC; Electric
Lighting, Pt.15; Setting Up An Email Server; Speed Alarm For Cars,
Pt.1; Multi-Colour LED Christmas Tree; Build An Intercom Station
Expander; Foldback Loudspeaker System For Musicians; Railpower
Model Train Controller, Pt.2.
January 2000: Spring Reverberation Module; An Audio-Video Test
Generator; Build The Picman Programmable Robot; A Parallel Port
Interface Card; Off-Hook Indicator For Telephone Lines; B&W Nautilus
801 Monitor Loudspeakers (Review).
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.
February 2000: Build A Multi-Sector Sprinkler Controller; A Digital
Voltmeter For Your Car; An Ultrasonic Parking Radar; Build A Safety
Switch Checker; A Sine/Square Wave Oscillator For Your Workbench;
Marantz SR-18 Home Theatre Receiver (Review); The “Hot Chip”
Starter Kit (Review).
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.
August 1998: Troubleshooting Your PC, Pt.4 (Adding Extra Memory);
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.
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 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.
September 1996: VGA Oscilloscope, Pt.3; IR Stereo Headphone
Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio
Receiver; Cathode Ray Oscilloscopes, Pt.5.
October 1998: CPU Upgrades & Overclocking; Lab Quality AC
Millivoltmeter, Pt.1; PC-Controlled Stress-O-Meter; Electronic Guitar
Limiter; 12V Trickle Charger For Float Conditions; Add An External
Battery To Your Flashgun.
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.
October 1999: Sharing A Modem For Internet & Email Access
(WinGate); Build The Railpower Model Train Controller, Pt.1;
Semiconductor Curve Tracer; Autonomouse The Robot, Pt.2; XYZ
Table With Stepper Motor Control, Pt.6; Introducing Home Theatre.
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; Build Your Own
4-Channel Lightshow, Pt.2; Understanding Electric Lighting, Pt.4.
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.
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 Alarm; Control Panel For Multiple
Smoke Alarms, Pt.2.
September 1999: Automatic Addressing On TCP/IP Networks;
Wireless Networking Without The Hassles; Autonomouse The Robot,
Pt.1; Voice Direct Speech Recognition Module; Digital Electrolytic
Capacitance Meter; XYZ Table With Stepper Motor Control, Pt.5;
Peltier-Powered Can Cooler.
December 1999: Internet Connection Sharing Using Hardware;
Electric Lighting, Pt.16; Index To Volume 12; Build A Solar Panel
Regulator; The PC Powerhouse (gives fixed +12V, +9V, +6V & +5V
rails); The Fortune Finder Metal Locator; Speed Alarm For Cars, Pt.2;
Railpower Model Train Controller, 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.
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.
December 1996: 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.
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.
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.
July 1998: Troubleshooting Your PC, Pt.3 (Installing A Modem
And Sorting Out 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.
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.
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.
November 1998: The Christmas Star; A Turbo Timer For Cars; Build
A Poker Machine, Pt.1; FM Transmitter For Musicians; Lab Quality AC
Millivoltmeter, Pt.2; 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; Improving AM Radio Reception,
Pt.2; Mixer Module For F3B Glider Operations.
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
February 1999: Installing A Computer Network (Network Types,
Hubs, Switches & Routers); Making Panels For Your Projects; Low
Distortion Audio Signal Generator, Pt.1; Command Control Decoder
For Model Railways; Digital Capacitance Meter; Remote Control
Tester; Electric Lighting, Pt.11.
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.
March 2000: Doing A Lazarus On An Old Computer; Ultra Low
Distortion 100W Amplifier Module, Pt.1; Electronic Wind Vane
With 16-LED Display; Glowplug Driver For Powered Models; The
OzTrip Car Computer, Pt.1; Multisim Circuit Design & Simulation
Package (Review).
April 2000: A Digital Tachometer For Your Car; RoomGuard – A LowCost Intruder Alarm; Build A Hot wire Cutter; The OzTrip Car Computer,
Pt.2; Build A Temperature Logger; Atmel’s ICE 200 In-Circuit Emulator;
How To Run A 3-Phase Induction Motor From 240VAC.
May 2000: Building the Ultra-LD Stereo Amplifier, Pt.2; Build A LED
Dice (With PIC Microcontroller); A Low-Cost AT Keyboard Translator
(Converts IBM Scan-Codes To ASCII); 50A Motor Speed Controller
For Models; Dolby Headphone – Five Channels Of Surround Sound;
What’s Inside A Furby.
June 2000: Automatic Rain Gauge With Digital Readout; Parallel
Port VHF FM Receiver; Li’l Powerhouse Switchmode Power Supply
(1.23V to 40V) Pt.1; CD Compressor For Cars Or The Home; Sony’s
New Digital Handycam (Review).
July 2000: A Moving Message Display; Compact Fluorescent
Lamp Driver; El-Cheapo Musicians’ Lead Tester; Li’l Powerhouse
Switchmode Power Supply (1.23V to 40V) Pt.2; Say Bye-Bye To
Your 12V Car Battery.
August 2000: Build A Theremin For Really Eeerie Sounds; Come In
Spinner (writes messages in “thin-air”); Loudspeaker Protector &
Fan Controller For The Ultra-LD Stereo Amplifier; Proximity Switch
For 240VAC Lamps; Structured Cabling For Computer Networks.
September 2000: Build A Swimming Pool Alarm; An 8-Channel PC
Relay Board; Fuel Mixture Display For Cars, Pt.1; Protoboards – The
Easy Way Into Electronics; Cybug The Solar Fly; Network Troubleshooting With Fluke’s NetTool.
October 2000: Guitar Jammer For Practive & Jam Sessions; Booze
Buster Breath Tester; I Spy With My Little Eye (Wand-Mounted Inspection Camera); Installing A Free-Air Subwoofer In Your Car; Fuel
Mixture Display For Cars, Pt.2; Structured Data Cabling For The Home.
PLEASE NOTE: November 1987 to March 1989, June 1989, August
1989, December 1989, May 1990, February 1991, June 1991, August
1991, February 1992, July 1992, September 1992, November 1992,
December 1992, May 1993, February 1996 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 $7.70 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 disk for $11 including p&p, or can be
downloaded free from our web site: www.siliconchip.com.au
November 2000 85
The easy way into electronics Pt.3
This month we feature a few more circuits based on the 555
timer. As we shall see, this chip can be used in more than just
timer and oscillator circuits. You can even use as an audio
amplifier and in pulse width modulation circuits.
By LEO SIMPSON
B
UT FIRST, AS THEY say in the
news programs, we have some
corrections to make on last
month’s circuit. Red faces all around
here because the circuits published
on page 61 both had the same mistake: the 1kΩ and 10kΩ resistors
were swapped for both IC1 and IC2.
Both circuits will still work but the
negative pulse widths will be about
10 times narrower than those shown
on the oscillo
scope waveforms on
page 63.
That error was bad enough but we
also made a mistake with the Proto
board wiring layout shown on page
62. In this case the connection of
potentiometers VR1 and VR2 is different from the circuits on page 61
and to compound the misery, the pot
values were actually 50kΩ instead
of 100kΩ. Again, the circuits still
work but the pulse width is variable
instead of being fixed and the range of
frequencies is not as large with 50kΩ
as it would be with 100kΩ.
Why did these mistakes happen?
Put it down to old age, poor eyesight, Olympic Games’ distractions
or straight out incompetence – we’ll
own up to all of those and will now
try to make amends.
In fact, these mistakes demonstrate
how easy it is easy to make changes
to circuits when you are using Proto
boards and at the same time, how easy
it is to make mistakes. You have to
keep your wits about you and carefully
check that what you think you’ve done
is actually what you should have done!
It is also very easy to push a wire into
the row or column next to the one you
really want. So look before you jab!
OK. Fig.1 shows the high frequency
part of the Siren circuit as it should
have been on Fig.1, page 61, of last
month’s article. Fig.2 shows the circuit
actually depicted in the Protoboard
layout on page 62 of last month’s issue.
If you wired up your version along
the same lines, you will find that the
This photo features all
the components shown
in the diagram of Fig.3.
You can use this layout
to demonstrate how a
555 timer can be used
as an amplifier for
the signal from a CD
player.
86 Silicon Chip
frequency and negative pulse width
are variable.
If you haven’t tried the circuit, wire
it up now on your Protoboard. The
wiring layout is shown in Fig.3. This
has extra parts associated with pin 5
and these should be omitted for the
time being. The scope waveforms of
Figs.4 & 5 demonstrate the circuit’s
performance.
Fig.1: this 555
oscillator circuit
has a fixed resistor
between pin 6 & 7 and
this results in a fixed
negative pulse width
as the frequency is
varied over a wider
range.
Square waves not possible
Two things are demonstrated by
the waveforms of Figs.4 & Fig.5. First,
when the resistance between pins 7
and 6,2 is variable, as it is in Fig.2, the
negative pulse width is also variable;
when the resistance between pins 7
& 6,2 is fixed, as shown in Fig.1, the
negative pulse width is fixed. This is
be
cause the aforementioned resistance determines the discharge time
for the capacitor at pin 6.
But the other consequence of this
is that this 555 circuit cannot ever
deliver a perfect square wave; ie, a
waveform with 50% duty cycle or to
put it another way, where the positive
and negative pulse widths are equal.
You might get close to 50% at one
particular frequency (as shown in the
waveform of Fig.5) but as soon as you
change the frequency, the duty cycle
goes far off that for a square wave.
So is it impossible to get a square
wave from a 555? No. It can be done
Fig.2: this version of the 555 circuit uses exactly the same components but now
the resistance between pins 6 & 7 is variable and this results in variable negative
pulse width over the entire frequency range.
Fig.3: use this diagram to wire up the circuit of Fig.2 but leave out VR2 and the components associated with pin 5 for
the time being.
November 2000 87
Fig.4: this waveform demonstrates the fixed negative pulse
width produced by the circuit of Fig.1. This is determined
by the time constant of the 1kΩ resistor and 0.1µF capacitor.
but the circuit has to be changed so
that the internal transistor at pin 7
no longer does the discharging of the
capacitor.
The circuit of Fig.6 shows how it
can be done. Instead of charging the
capacitor from the positive supply
and then discharging via pin 7, the
charging and discharging of the capacitor at pins 2 & 6 is done from
pin 3. So pin 7 has no connection in
this circuit.
Square wave circuit
To change your Protoboard circuit
from that shown in Fig.2 to that of
Fig.6, remove the 10kΩ resistor connecting pin 7 to the +12V line and
move the pot lead that connects to
pin 7 so that it now goes to pin 3.
And leave the speaker disconnected
for the moment.
Fig.5: this waveform looks much the same as in Fig.4 but
now the negative pulse width is variable as well as the
frequency, as per the circuit of Fig.2.
The scope waveforms of Figs.7 &
8 show that the output waveform at
pin 3 (Ch2 – lower trace) now has
a duty cycle of close to 50%. Fig.7
shows the circuit oscillating at around
138Hz with pot VR1 set for maximum
resistance while Fig.8 shows it running at around 6.8kHz, with VR1 set
for minimum resistance.
Two things can be noted about the
“square” waves of Figs.7 & 8. First,
the duty cycle is not exactly 50%, in
spite of what we said above. Second,
in Fig.8 the tops of the square wave
are sloping rather than dead square.
Both of these effects are caused by the
output stage of the 555.
If we had a “perfect” output stage in
the 555, it would switch between the
full supply voltage (12V nominal) and
0V. But it doesn’t. Depending on the
current it has to “source” or “sink”,
Fig.6: by charging and discharging the capacitor at pin 6 from a variable
resistance connected to pin 3, the 555 can be made to deliver a square
wave regardless of its frequency of operation.
88 Silicon Chip
it typically won’t quite get to 0V and
it will do worse in switching up to
the positive supply. In our circuit for
example, it will switch down to about
0.1V but will only switch up to within
about 0.4V of the positive supply rail.
Furthermore, if we make the 555
drive the speaker via a 68Ω resistor
and 100µF capacitor, it will have to
source and sink substantially more
current (around 110mA) and so it will
do considerably worse.
In fact, Fig.9 shows how bad it
is. The output waveform is considerably reduced in amplitude, with
the negative excursion now being
about 1V (instead of close to 0V) but
the positive excursion is only about
+8.5V. Clearly, the output stage of the
555 is far from perfect and nor is it
symmetrical.
The result of this is that the output
waveform from pin 3 is now nothing
like “square” as the positive excursions of the waveform are now more
than double the negative excursions.
Because the output at pin 3 is not
switching as high as it should, it is
taking that much longer to charge the
capacitor at pins 2 & 6.
OK. So if we want a near perfect
square wave from a 555 we can use the
circuit of Fig.6 but we have to maintain the minimum possible loading on
the output at pin 3. In other words,
don’t connect the speaker.
You might ask why most 555 circuits do not use the configu
ration
of Fig.6 since it gives a more ideal
square wave. The answer is that the
conventional circuits of Fig.1 & Fig.2
are normally preferred because they
give much better frequency stability.
Fig.7: this shows that the 555 can produce a near ideal
square wave, using the circuit of Fig.6. In this case, the
circuit is set to oscillate at 138Hz and the loading on pin
3 is minimal.
The frequency is less affected by
circuit loading at pin 3 and is almost
entirely independent of supply voltage variations. So, for example, for
a given setting of VR1 in Fig.2 and
with the speaker disconnected, the
frequency will be substantially the
same, regardless of whether the supply voltage is 3V or 15V.
That’s a pretty good result for an
oscillator.
Fig.8: when set for the maximum frequency, the circuit
of Fig.6 still delivers a duty cycle of close to 50% but the
higher loading on pin 3 means that the tops of the pulse
waveform are no longer square.
Fig.9: with the
speaker connected,
there is high
loading on pin 3
and so the output
is much reduced
and no longer can
be called a square
wave.
Frequency modulation
While most oscillator circuits using
555s tend to be along the lines we
have discussed so far, few make any
use of pin 5 which is usually referred
to as the CV or Control Voltage input.
In most circuits, it is not connected
at all or it might be connected to the
0V line via a capacitor. However, it
can be used to produce pulse width
modulation or looking at it another
way, frequency modulation.
To demonstrate this effect, let’s
change the circuit to that of Fig.10.
The Protoboard can
be mounted on a
simple folded
aluminium
baseplate, with the
pots and DC power
socket mounted on
the front panel.
November 2000 89
Fig.10: used to
demonstrate pulse width
modulation, this circuit
is similar to that of Fig.2
except that we have
another 50kΩ pot, VR2,
connected between the
positive and negative
supply and its wiper
goes to pin 5 via a 10kΩ
resistor. Ignore the
components shown in
red for the moment. Note
that the capacitor value
at pins 2 & 6 is now
.01µF instead of 0.1µF.
Fig.11: these wave
forms demonstrate
pulse width
modulation with the
555. The top trace is
the 500Hz sinewave
applied to pin 5
while the lower
trace is the pulse
width modulated
waveform which is
running at around
5kHz.
This is similar to that of Fig.2 except
that we have another 50kΩ pot, VR2,
connected between the positive and
negative supply and its wiper goes to
pin 5 via a 10kΩ resistor.
Note that the capacitor value at pins
2 & 6 is now .01µF instead of 0.1µF.
Now by leaving the setting of VR1
constant and varying VR2, we can
vary the frequency and pulse width
over a very wide range.
To demonstrate the effect, connect
the speaker (if not already connected)
and wind VR2 over its full range. If
VR1 is already set for a reasonably
high frequency (say 3kHz) you will
find that VR2 will vary the frequency over a range from 3kHz to above
20kHz (ie, supersonic).
But not only do we vary the frequency, we are varying the pulse
width. This can be seen on a scope
if you have one but if you don’t you
can still demonstrate that the pulse
width is varying. How? By using your
multimeter to measure the average DC
90 Silicon Chip
voltage at pin 3. If you go through the
same exercise in varying VR2, you
will find that the DC voltage at pin 3
varies from about 2V to 10V.
This principle is widely used in
pulse width modulation circuits to
vary the average DC or power level
to a load.
PWM amplifier
Finally, we can use this pulse width
modulation principle to make the 555
function as an audio amplifier. To do
this, we connect the positive electrode of a 10µF electrolytic capacitor
to the wiper of VR2 and the negative
lead of the capacitor is connected to
0V via a 4.7kΩ resistor.
These extra components are shown
in red on Fig.10. VR2 and these extra
components are included in the Protoboard layout of Fig.3 and you can
plug them in now.
We now connect an audio signal
to the 4.7kΩ resistor. In our case,
we applied a 500Hz sinewave signal
of about 2V RMS and the result can
be seen in the scope waveforms of
Fig.11. The top trace is the 500Hz
sinewave while the lower trace is the
pulse width modulated waveform
which is running at around 5kHz or
thereabouts. Note that the wide pulses
correspond to the positive peaks of
the sinewave modulation signal and
the narrow pulse correspond to the
negative peaks.
If you listen to the speaker it won’t
sound too pleasant but if you wind
up VR1 or VR2 so that the “carrier”
frequency becomes supersonic, you
will then hear a clear 500Hz tone.
You can play around with the settings of VR1, VR2 and the input signal
level to get the loudest and clearest
signal from the speaker. So there you
are – it works as an amplifier.
If you don’t have an audio oscillator, don’t worry. You can feed in the
signal from a standard CD player.
Go ahead and try it. It won’t be high
fidelity but you can listen to it – a
555 does work as an audio amplifier.
What is happening here is that we
are pulse width modulating a carrier
frequency of say 30kHz with an audio
signal. The speaker cannot respond to
the 30kHz signal but it can respond
to the average DC level and this is
the audio signal we feed in from the
CD player.
Feedback wanted
Finally, we’d like some feedback
about these Protoboard articles.
Do you like them? Do they explain
enough? And would you like a particular circuit demonstrated and
explained? Please email your comments to leo<at>siliconchip.com.au SC
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.
Back-to-back
capacitors explained
I am building the Model Train Controller from the April 1997 issue and
I came across the Notes & Errata for
this project in the August 1999 issue.
In that note it said that the 4700µF capacitor connected between switch S1
and the -12V rail needs to be replaced
with “two back-to-back 4700µF 25VW
capacitors connected between switch
S1 and the 0V rail”. What I want to
know is what does “back-to-back”
mean? Are the capacitors connected
in parallel, series or what? (G. M.,
Caringbah, NSW).
• Hmm. Perhaps we should have explained that better. The background to
the change was explained in an answer
to a letter on the train controller on
page 91 of the August 1999 issue. In
the original circuit (April 1997), the
4700µF inertia capacitor connected
to S1 and the -12V rail could never
be reverse-biased but it did cause an
initial lurch in the train because it was
discharged.
One solution to that problem is to
connect the negative side of the capacitor to the 0V rail. That fixes the
Voltage regulator
for motorbike
I own some older motorcycles
that have permanent magnet, single phase alternators. These have
very simple shunt regulators that
“waste” surplus power. I’ve heard
that a better way to regulate is with
a DC-DC converter. I didn’t get more
detailed info but am wondering if
something along the lines of your
2A SLA battery charger described
in July 1996 could be used? (J. P.,
via email).
• Normal alternator regulators
work by switching the field current
on an off but clearly this is not
possible with a permanent magnet
alternator and so a shunt regulator
initial lurch but it does means that
the 4700µF capacitor will be reversebiased when the throttle potentiometer
is wound down for reverse operation
of the loco. Clearly, this cannot be
allowed to happen and the simple
solution would be to use a non-polarised electrolytic 4700µF capacitor.
Non-polarised electrolytics can be
operated with a positive or negative
bias voltage or with none at all. The
problem is that the non-polarised
electros are not readily available in
large values.
So we specified the next best thing
which is two capacitors “back-toback”. In effect, you connect the two
capacitors in series but with their
negative leads connected together (ie,
back-to-back). One positive capacitor
electrode goes to S1 and the other
positive capacitor electrode goes to 0V.
Electric fence output
voltage uncontrollable
I have built the Electric Fence kit
from April 1999 and when I try to set
the capacitor charging voltage via VR1
(to 340V) I find that it shoots all over
the place (starting from about 56V,
is used. A DC-DC converter is not
the solution but a switchmode series regulator could be. We doubt
whether the 2A SLA battery charger
would be suitable as its current and
voltage ratings are unlikely to be
anywhere near adequate.
None of our existing circuits
could be easily adapted. However,
even if they could, it would not
make any more charging current
available from your alternator
and the amount of power that is
“wasted” is probably quite small
relative to the power developed by
the engine.
So we doubt that there is any real
advantage to be gained by using a
switchmode charging circuit with
your existing alternator.
up to 1000+ and off the scale of my
meter) with very small changes in the
pot position. I’d be grateful if someone
could suggest what might be wrong. (J.
N., via email).
• Check the components around VR1.
Check that you have 4.7V across ZD1.
Also check that you do not have high
resistance in the wiper of VR1. Our
tip is that the bottom leg of VR1 is
open circuit.
Data logger for
pH readings
I have made the pH meter for swimming pools described in the April
1988 issue and it all checked out OK.
I would now like to connect the pH
meter to an ADC so the readings could
be timed and stored using a computer.
I have searched the web for a circuit
which could read microamps using
an ADC but with no success. (J. R.,
via email).
• Have a look at the Mini-log, an 8-bit
data logger published in the July 1996
issue. It has an ADC and is based on
the Basic Stamp II.
Capacitors for SLA
battery charger
I refer to the July 1996 Silicon Chip
article “Charge SLA Batteries Away
From Mains”. The circuit requires
two 0.68µF 250VDC polyester caps.
I’m having trouble obtaining same.
However, I can get suitable electrolytics. Can I use these, paying attention
to polarity?
The instructions suggest that the
circuit is suitable for 12V 6.5Ah and
greater capacity SLA batteries. Is it
suitable to fast charge a 12V 2.4Ah
Nicad battery pack? (J. P., Wirrabara,
SA).
• The 0.68µF 250VDC capacitor is
difficult to obtain but you can use a
1µF 250VDC instead. These are available from Jaycar or Altronics.
This charger is only suitable for
SLA batteries. It is not suitable for
Nicads.
November 2000 91
Feedback on the
Ultra-LD amplifier
I’ve just finished assembling the
100W Ultra-LD stereo amplifier
(March & May 2000). I must say
that I’m pretty im
pressed with
the sound – the clarity and stereo
imaging especially.
I have some feedback on the
construction process. The Jaycar
kits were well done. The power
and audio wiring was diffi
cult
using the 1mm PC pins. I ended up
using PC-mount spade pins with
Utilux connectors on the wires. I
used shielded cable that was quite
stiff and it would have eventually
twisted the pins out of their pads
when moving things around during assembly.
I noticed that the bias setting
was a very sensitive proce
dure.
Once set at 4.4V, it would drift
around aimlessly between 4.3V
and 4.6V. If you blew on the TO220 heatsinks in the middle of the
PC board, the bias would shoot up
Questions on the
fast charger
I recently built the “Fast Battery
Charger” as described in the February
& March 1998 issues. When I tested
the charger according to the test procedure, I could not get the 200mV
across the two 0.1Ω resistors. The
most I could get was about 87mV. I
also measured the DC current; 1.6A DC
into a 12V 1.8A cordless drill battery.
A few minutes after it started to
charge the battery the charger started to
buzz and continues until the time out
period ends and then the buzz changes
slightly but does not stop.
I also tried charging a 6V battery
and the same thing happens (the buzz
is louder). All the other voltages I was
supposed to check seem to be OK.
Could you tell me how to stop the
buzzing and what might be wrong with
the charge current?
There is one other problem I would
like you to explain and that is the
number of turns on the inductor. It
specifies 10 turns bifilar wound. Is that
10 turns for each winding for a total of
20 turns or 5 turns for each winding
for a total of 10 turns? When I wound
92 Silicon Chip
to 4.65V. It’s just a bit too sensitive
for my liking.
I don’t know how it will affect
the sound but it’s something you
may want to look into.
I used the 35V-0-35V plus 55V-055V transformers from Har
buch
Electronics (who offered great service by the way). However, hooking up the 12V fans presents a bit
of a problem in this configuration. I
have the speaker protector kit (described in August 2000) on order
from Jaycar which will allow me
to hook it up but in the meantime,
I have to be careful how long I run
the amplifier without overheating
it. (M. D., via email).
• Thanks for the feedback. The
bias on any class AB amplifier
does tend to wander about so it’s
not a worry. Also you can run the
amplifier without a fan as long as
you don’t consistently drive it to
high power. However, we really
don’t understand why you have
not used the fan hook-up described
in the May issue.
on the total of 20 turns I could only
wind 19 coils with the 20th coil above
the 19th coil.
Also, why do you need the spacer
between the E cores and how precise
does it have to be? (E. L., Midvale,
WA).
• The actual current which charges
the battery is both switching at high
speed and also following a pulsating
DC waveform shape at the mains frequency. This makes it difficult to measure with a standard digital voltmeter.
Measurement of the current can
only be made with a true RMS meter
or by calculating the current via the
waveform on an oscil
loscope. The
value of current read from a standard
multimeter will be erroneous. Perhaps
the best way to tell if the current is
correct is to check if the heatsink gets
quite hot during charge and if a battery
charges in the expected time.
The squeal in the transformer is
normal. It can be quietened by potting
the windings in epoxy. The number
of turns on the transformer should be
two lots of 20 turns. In other words,
wind the two lengths of wire together
for 20 turns. The windings will go to
at least two layers.
The gap between the cores sets the
inductance of the transformer and its
saturation characteristic. Therefore it
should be the 1mm as specified, within
± 0.15mm.
Headlight pinouts and
tacho interfacing
I am looking for the pinout details
for a car headlamp, preferably with
Low/High beam. The reason is that my
car’s headlights are fine on high beam
(practically cook a rabbit at 10 yards)
but low beam is awful. It seems that
the power is earthing out via the high
beam filaments.
Also, on the Speed Alert published
in November & December 1999, is it
possible to use a Hall Effect device
instead of the coil sensor? I don’t fancy
having to wind the coil. Can you please
help? (W. S., via email).
• Have a look at the choice of input
arrangements used in the Tacho published in the April 2000 issue. You
could modify the input op amp along
the same lines.
We don’t have info on car headlight
pinouts but generally one side of
both filaments connects to a common
terminal.
Problems with
3A train controller
As a member of the “Logan District
Model Railway Club Inc.”, I have been
asked to write to you to seek some
advice concerning the 3A Train Controller featured in the February 1993
issue. We realise that this is a fairly old
circuit but still hope that you may be
able to help us with our problem. The
circuit has all the features we need for
our large “HO” club layout which has
six “plug in” positions to connect our
controllers.
We wanted to build some new
controllers for the club. After looking
around at numerous circuit diagrams,
by sheer coinci
dence our secretary,
Darren Lee, and myself both came up
with the same circuit. All the club
members agreed that this circuit appeared to represent all the features we
wanted. Following this, Darren built
one and so did I.
This is where the problems started!
He built the circuit exactly as shown
in the article. However, I modified my
unit by replacing the two trimpots with
linear potentiometers mounted on the
box sides. This gives the operator the
ability to adjust the inertia and braking
to suit his own requirements.
Unfortunately, both units failed to
operate. The test supply is from an
old Triang Controller claiming to be
15VAC but on testing is 17VAC. The
unit was connected to this supply but
not connected to the track. Our know
ledge of electronics then limits us from
checking much further. I know that on
the output side of the bridge rectifier
the voltage is DC and the output is
1.414 times the input. This makes
the feed to the circuit approximately
24VDC. This checks out as correct.
Both our units have been assembled on
Veroboard. These have been carefully
checked numerous times to ensure that
no error exists in the circuit.
Our questions are as follows:
(1). Could the input VAC be too high,
thus damaging some of the components?
(2). A silly thought, but was an error
discovered after the article was published and rectified in a later issue of
the magazine? (No insult intended!)
(3). Nobody can tell us the handling
capacity of the Veroboard strips; ie,
can one strip carry 3A?
(4). Is it acceptable to change the trimpots as mentioned above?
(M. B., Logan City, Qld).
• The most likely reason for the
malfunction in your train controller
circuits is mistakes in the Veroboard
layouts. From bitter experience we
know how easy it is to make mistakes.
Your best approach is to obtain
the PC board as it is much easier to
assemble. You can purchase it from
RCS Radio Pty Ltd, 41 Arlewis Street,
Chester Hill, NSW 2162; phone (02)
9738 0330. The board is type number
02102931 and is $12.65 plus $3.30 for
postage and packing.
You can change the trimpots to pots,
as you have done.
Basic Stamp2
Xout function
I have been doing some programming on the Basic Stamp2 module
and am interested in using the Xout
function. This provides remote
control functions via the reticulated mains power lines within a
building. Special 110V interface
modules are available in USA for
this purpose.
Is this facility available for the
Australian 240VAC power system?
Are there approved “control via
mains” systems in use here and if
so, are the interface units available
Coil failure in
ignition system
I have built the High Energy Ignition system as described in the June
1998 issue and the unit has worked
well. But the other day my ignition
coil failed and I think this caused the
output transistor to fail as well.
I checked for continuity from the
transistor’s heatsink to case and there
was a short (it was still connected
up to my car, with power off when I
checked it). I can find no reference to
this transistor in either the Dick Smith
Electronics or Jaycar catalog.
Is there a higher-rated substitute
I can put in? By the way, is there a
simple go/nogo test for the output
transistor? I think it was a Darlington
type. (M. K., via email).
• The coil probably failed because
the transistor’s collector became short
circuited to the case. This would have
meant that the full battery voltage was
connected across the coil which would
burn it out fairly quickly.
This short from the transistor to case
for purchase? (K. M., via email).
• We referred your question to
Microzed Computes, the Australian
agents for The Basic Stamp2. Their
answer is as follows:
Our understanding is that X10 is
being discouraged in Australia by
power supply authorities because
of developments in power line
accessing of meter readings, using
a protocol that would collide with
X10.
A more reliable option is CE BUS
from Clipsal. This uses a separate
2-wire, low tension bidirectional
bus. CE Bus has more features and
should interface with the Stamp.
would suggest that it is the insulating
washer between the transistor and case
or the bush which has failed. Check
that there are no sharp edges around
the mounting hole for the transistor
as this will give a starting point for
any arc-over between the transistor
and case.
Use either a new silicone washer or
two mica washers.
You can check the output transistor
(it is a Darlington type, by the way) by
using your multimeter to measure the
resistance between base and emitter,
between base and collector and collector to emitter. The 1999/2000 Dick
Smith Electronics catalog shows how
it is done on page 236.
Notes & Errata
Opto-Electronic Ignition, October
2000: the circuit featured in Circuit
Notebook on page 58 shows a 470Ω
resistor connected to the collector of
Q2 via a .01µF capacitor. This resistor
SC
should be 470kΩ.
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.
November 2000 93
MARKET CENTRE
Cash in your surplus gear. Advertise it here in Silicon Chip.
FRWEEBE
YES!
Place your classified advertisement in
SILICON CHIP Market Centre and your
advert will also appear FREE in the
Classifieds-on-the-Web page of the
SILICON CHIP website,
www.siliconchip.com.au
And if you include an email address or
your website URL in you classified advert, the
links will be LIVE in your classified-on-the-web!
S!
D
E
I
F
I
S
C LAS
EXCLUSIVE TO SILICON CHIP!
CLASSIFIED ADVERTISING RATES
Advertising rates for this page: Classified ads: $11.00 (incl. GST) for up to 12
words plus 55 cents for each additional word. Display ads: $27.50 (incl. GST) per
column centimetre (max. 10cm). Closing date: five weeks prior to month of sale.
To run your classified ad, print it clearly in the space below or on a separate
sheet of paper, fill out the form & send it with your cheque or credit card details
to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details
to (02) 9979 6503.
Taxation Invoice ABN 49 003 205 490
_____________ _____________ _____________ _____________ _____________
_____________ _____________ _____________ _____________ _____________
_____________ _____________ _____________ _____________ _____________
_____________ _____________ _____________ _____________ _____________
_____________ _____________ _____________ _____________ _____________
Enclosed is my cheque/money order for $__________ or please debit my
❏ Bankcard ❏
Visa Card ❏ Master Card
Card No.
Signature ________________________ Card expiry date______/______
Name _____________________________________________________
Street _____________________________________________________
Suburb/town _________________________ Postcode______________
94 Silicon Chip
FOR SALE
COLOUR Bullet Cameras 440 Line
SONY CCD from $178 * Time-Lapse
VCRs from $699 ! TWO YEAR WARRANTY ! National Service Centres
! Multinational Manufacturer. VIDEO
CAMERAS DOME COLOUR from $75
! Mono from $52 ! BULLET from $94
TWO YEAR WARRANTY * DOME 480
Line 0.05 Lux with SONY CCD & ChipSet from $79 * COLOUR DOME: 400
Line DSP from $134 * 600 + Line DSP
from $159 * COLOUR DSP PIN in PIR
CASE from $148 * MINI CAMS from
$67 * DSP COLOUR from $133 * 4 Ch
Switcher from $82 * QUAD 1024 H-Pixels from $168 * COLOUR QUAD from
$301 * PC DIGITAL VIDEO RECORDER
SYSTEM from $179 * MULTIPLEXER 4
Ch from $609 * PC REMOTE DIAL-UP,
PAGING, WEB-CAM, DVR System 768
x 576 from $199 * DIY PLUG-IN 20
metre AV Cables from $19 ! BLEMISH
FREE & LOW BLEMISH CCDs * UP
TO 5 YEARS WARRANTY
* OVERNIGHT DELIVERY * www.
allthings.com.au
RAIN BRAIN AND DIGI-TEMP KITS:
8-station sprinkler controllers. New
Digi-temp and Moni-temp use DS1820
sensors. Feature PC data logging, 60
channels over 500 metres.
www.mantismicroproducts.com.au
COVERT VIDEO SURVEILLANCE Tiny
Sub-Matchbox size Wireless Video &
Audio TRANSMITTERS from $77 *
Pinhole Cameras from $59. Easily
concealed in: Mobile Phone Case,
Clock, VCR Cassette, Toys, Teddy Bear
(Nanny-Cam), Smoke Detector, Ornament, Cap, Cigarette Pack, etc. www.
allthings.com.au
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.
HOME CCTV Mono / Colour PAKS
Only! $111 / $138 DIY Plug-In to TV
/ VCR 20 metre Cable, Plug Pack &
Camera www.allthings.com.au
RAINBOW POWER COMPANY: Solar
Panels 80W $660, Batteries, Inverters,
Regulators, Rebates available – call
(02) 6689 1430.
FUNCTION GENERATORS BWD 160A
2MHz max, sin, tri, sq, pulse, TTL, offset, 20Vp/p o/c lin VCO, C/W manual,
schematic, no exotic parts. Six only <at>
$80.00 ea. jcd<at>c031.aone.net.au A/H
Melb. 9836 6494.
WEATHER STATIONS: Windspeed &
direction, inside temperature, outside
temperature & windchill. Records highs
& lows with time and date as they occur.
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 phone:
(03) 5968 4863; fax: (03) 5968 5810,
PO Box 18, Emerald, Vic., 3782. ACN
006 399 480.
KITS KITS AND MORE KITS! Check
‘em out at www.ozitronics.com
C COMPILERS: everything you need
to develop C and ASM software for
68HC08, 6809, 68HC11, 68HC12, 68
HC16, 8051/52, 8080/85, 8086, 8096
or AVR: $170.50 each. Macro Cross
Assemblers and Disassemblers for
above CPUs + 6800/01/03/05, 6502
and 68HC12 for $88. Debug monitors:
$88 for 6 CPUs. All compilers, XASMs
and monitors: $5280. 8051/52 Simulator (fast, now incl. 80C320): $88. Try
the C-FLEA Virtual Machine for small
CPUs, build a “C-Stamp”. Demo desk:
FREE. All prices + $5.50 p&p.
Atmel Flash CPU Programmer: Handles the 89Cx051, 89C5x and 89Sxx
series, and some AVRs in both DIP
and PLCC44. Also does most 8-pin
EEPROMs. Includes socket for serial
ISP cable. $220 $11 p&p. SOIC adaptors: 20-pin $99, 14-pin $93.50, 8-pin
$88. Credit cards accepted. GRAN
ROLA AUSTRALIA
PH/FAX (08) 8270 3175
WEB SITE WWW.BETTANET.NET.AU/GTD
CHECK OUR WEBSITE FOR DETAILS ON KITS AND
COMPONENTS
•
•
•
•
Silvertone’s RC Receiver
Still the best little performer available!
TRANSMITTER KITS AND MODULES
AUDIO MODULES
COMPUTER INTERFACE KITS
RADIO STATION AUDIO SOFTWARE
NEW: Our MP3-CD player in short form for $169 inc GST.
Includes the following: processor board, front panel display
and tactile keypad; just add a case, cables, 12V power supply
and a CD-ROM drive. Play CDs and up to 2600 MP3’s from a
CDR. Great for car or home.
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°.
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
AV-COMM P/L, 24/9 Powells Rd,
Brookvale, NSW 2100.
Tel: 02 9939 4377 or 9939 4378.
Fax: 9939 4376; www.avcomm.com.au
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.
TRONICS PTY LTD, PO Box 275,
Wentworthville 2145. Ph (02) 9896
7150 or Internet:
http://www.grantronics.com.au
RCS HAS MOVED to 41 Arlewis St,
Chester Hill 2162 and is now open, with
full production soon. Tel (02) 9738 0330;
Fax 9738 0334. rcsradio<at>cia.com.au;
www.cia.com.au/rcsradio
HOME CCTV Mono / Colour PAKS
Only! $113 / $140 DIY Plug-In to TV
/ VCR 20 metre Cable, Plug Pack &
Camera www.allthings.com.au
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.
Time-Lapse VCR $699 with CCTV
Systems 2 Year Warranty !
MORE at: www.allthings.com.au
Fully Plug-In DIY Paks with all Cables
& Power Supplies ALSO PC Digital
Motion / Sound detection & activated
Video / Audio Recording systems 08
9349 9413.
KIT ASSEMBLY
TELEPHONE EXCHANGE SIMULATOR, SC February 1998. Test equipment without the cost of telephone lines.
Melbourne 9806 0110.
ANY KITS assembled/repaired:
professional, speedy service. Phone
Neville Walker (07) 3857 2752 or email
flashdog<at>optusnet.com.au
DIY CCTV PAKS
4 Cameras & Switcher ............... $341
as above COLOUR ................... $449
4 Cams, Switcher/Monitor .......... $479
as above 14" Monitor ............... $511
4 Cams, QUAD & Monitor .......... $677
4 COLOUR & QUAD .................. $707
WANTED
PERSON WITH EXPERIENCE / APTITUDE able to fault find & repair PCBs
– without diagrams. GENEROUS PKG
NEG. Tel John<at>AER (03) 9482 4958
0415 305 470.
November 2000 95
Silicon Chip Binders
Keep your copies safe, secure and
always available with SILICON CHIP
binders: they’re cheap insurance!
Advertising Index
Av-Comm Pty Ltd.........................95
REAL
VALUE
AT
$12.95
PLUS P
&P
Heavy board covers with
2-tone green vinyl covering
EMC Technologies.......................41
4D Systems...................................9
Harbuch Electronics....................43
SILICON CHIP logo printed
in gold-coloured lettering on
spine & cover
Instant PCBs................................95
Investment Technology..............IBC
Price: $12.95 (includes GST)
plus $5.50 p&p each (available
Aust. only). Price includes GST.
Jaycar ................................... 45-52
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.
Do you feel left behind by the latest
advances in computer technology? Don’t
miss the bus: get the ’bus!
Includes articles on troubleshooting your
PC, installing and setting up computer
networks, hard disk drive upgrades,
clean installing Windows 98, CPU
upgrades, a basic introduction to Linux
plus much more.
Direct Components......................64
Evatco............................................9
Each binder holds up to 14
issues so that you can include
catalogs
DON’T MISS
THE ’BUS
Dick Smith Electronics........... 26-29
Kalex............................................79
Mass Technology.........................41
Microgram Computers.....3,43,OBC
MicroZed Computers...................41
Printed Electronics...................... 95
Questronix...................................41
www.siliconchip.com.au
SILICON
CHIP’S
132 Pages
$ 95 *
9
Rall Electronics............................41
ISBN 0 95852291 X
9780958522910 09
09
9
780958
522910
COMPUTER
OMNIBUS
INC
LUD
ES
FEA
TUR
E
LIN
UX
A collection of computer features from the pages of SILICON
CHIP magazine
Rola Australia..............................95
R.T.N..............................................7
Silicon Chip Back Issues....... 84-85
Silicon Chip Binders....................96
Silicon Chip Bookshop........... 82-83
SC Computer Omnibus...............96
Hints o Tips o Upgrades o Fixes
Covers DOS, Windows 3.1, 95, 98, NT
o
SC Electronics Testbench............65
RT
Price: $12.50 (incl. GST) Order now by using the handy order form in this issue or
call (02) 9979 5644, 8.30-5.30 Mon-Fri with your credit card details.
Special subscription offer available only while stocks last.
Silicon Chip Subscriptions...........53
Silvertone Electronics..................95
Smart Fastchargers.....................55
Solar Flair/Ecowatch....................95
Tektronix....................................IFC
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
Telephone Technical Services.....55
Truscotts Electronics....................79
_____________________________
PC Boards
Printed circuit boards for SILICON
CHIP projects are made by:
• RCS Radio Pty Ltd. Phone (02)
9738 0330. Fax (02) 9738 0334.
• Marday Services, PO Box 19-189,
Avondale, Auckland, NZ. Phone (09)
828 5730.
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