This is only a preview of the December 1996 issue of Silicon Chip. You can view 28 of the 104 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Items relevant to "Build A Sound Level Meter":
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From the publishers of “SILICON CHIP”
Contents
Vol.9, No.12; December 1996
FEATURES
8 CD Recorders: The Next Add-On For Your PC
Creating your own CD-ROMs is fast and easy with the latest generation
CD recorders. We take a look at what’s involved – by Greg Swain
20 Mitsubishi’s Intelligent Automatic Transmission
This smart new automatic transmission adjusts its shift points to suit the
driving conditions & even provides engine braking – by Julian Edgar
100 Annual Index For Volume 9
CD RECORDERS: THE NEXT ADDON FOR YOUR PC – PAGE 8
All the articles, projects & columns for 1996
PROJECTS TO BUILD
24 Active Filter Cleans Up Weak CW Reception
Build this low-cost filter & dig those weak CW signals out of the noise. It
connects between the receiver & an external speaker – by Leon Williams
38 A Fast Clock For Railway Modellers
Run your trains to a realistic schedule. This circuit interfaces to a low-cost
clock module & runs 4.5-8.5 times faster than normal – by Leo Simpson
58 Build A Laser Pistol & Electronic Target
Hit the bullseye & you’re rewarded with a siren sound. Miss and you get
the sound of a machine gun as the target “shoots” back – by Rick Walters
66 Build A Sound Level Meter
ACTIVE FILTER FOR IMPROVED
CW RECEPTION – PAGE 24
Measures sound pressure levels from below 20 to 120dB with high accuracy & displays the result on a digital multimeter – by John Clarke
80 An 8-Channel Stereo Mixer; Pt.2
Second article has all the constructional and details – by John Clarke
SPECIAL COLUMNS
44 Serviceman’s Log
There’s a long, long trail a’winding – by the TV Serviceman
57 Satellite Watch
The latest news on satellite TV – by Garry Cratt
FAST CLOCK FOR RAILWAY
MODELLERS – PAGE 38
76 Vintage Radio
A new life for a battered Astor – by John Hill
DEPARTMENTS
2
4
19
30
36
94
Publisher’s Letter 98
News & Views 99
Mailbag
102
Bookshelf
103
Circuit Notebook
104
Product Showcase
Ask Silicon Chip
Notes & Errata
Order Form
Market Centre
Advertising Index
BUILD A LASER PISTOL &
ELECTRONIC TARGET – PAGE 58
December 1996 1
Publisher & Editor-in-Chief
Leo Simpson, B.Bus., FAICD
Editor
Greg Swain, B.Sc.(Hons.)
Technical Staff
John Clarke, B.E.(Elec.)
Robert Flynn
Rick Walters
Reader Services
Ann Jenkinson
Advertising Manager
Christopher Wilson
Phone (02) 9979 5644
Mobile 0419 23 9375
Regular Contributors
Brendan Akhurst
Garry Cratt, VK2YBX
Julian Edgar, Dip.T.(Sec.), B.Ed
John Hill
Mike Sheriff, B.Sc, VK2YFK
Philip Watson, MIREE, VK2ZPW
Bob Young
SILICON CHIP is published 12 times
a year by Silicon Chip Publications
Pty Ltd. A.C.N. 003 205 490. All
material copyright ©. No part of
this publication may be reproduced
without the written consent of the
publisher.
Printing: Macquarie Print, Dubbo,
NSW.
Distribution: Network Distribution
Company.
Subscription rates: $54 per year
in Australia. For overseas rates, see
the subscription page in this issue.
Editorial & advertising offices:
Unit 34, 1-3 Jubilee Avenue, Warrie
wood, NSW 2102. Postal address:
PO Box 139, Collaroy Beach, NSW
2097. Phone (02) 9979 5644. Fax
(02) 9979 6503.
PUBLISHER'S LETTER
Going for the big clean-out
Are you reluctant to throw out old electronic components? If you are anything like me,
you are. I hate to see electronic equipment or
components being junked. However, while
this may be a good and worthwhile attitude
and may often save you money in the long run,
there is the other side of the coin to consider.
After a while, you get too much junk.
About a year ago I moved house and there
was a lot of stuff that I didn’t have time to
sort out at the time so it all went into boxes
“to be looked at later”. Now I am slowly wading through it. I have to face up
to the fact that I have “electronic stuff” that I haven’t touched for 20 years or
more. Much of it, and I am talking about all sorts of small components here,
is probably still as good as the day it was made. But I’ll never use it; not ever.
I’ve had to bite the bullet. Some stuff I’m saving and some I’m giving away
but a good deal of it has to go in the bin – there’s just no way that anybody
would use it. Some of the components I’ve had so long that the leads have
corroded; that’s a hazard of where I live, close to the sea. Inevitably too, there
is stuff that I didn’t know I had and some that I thought I’d lost or given away
years ago.
I am sure that there are many readers who are in a far worse situation. Instead of half a dozen boxes of junk, they have a shed, a garage or even rooms
full of it. Like me, they will probably never use it. And sooner or later they
will have to face up to doing something about it, especially if they ever have
to move to a smaller house. If you are one of these people, why not attack the
problem this evening? You will feel a lot happier when it is sorted out. You
will probably find that you have so much more room to move as well and
you will be able to accommodate all that new stuff you want.
You have to be ruthless about it. If you find something that you have had no
use for in the last five years, it probably should be given away or pitched out.
Any components which look corroded or discoloured in any way should be
tossed as well. If you can find an electronics club that wants your electronic
bits, so much the better. In fact, if electronics clubs thought about taking
small classified ads they would probably end up with a lot of good material.
While you’re in clean-up mood, why not sort out all those floppy discs
around your place? Reformat them and put them back into general use. You
can do the same with all your VCR tapes. You’ll probably be amazed at how
many you have lying around.
So have a look around you and see if you’ve been hit by the “hoarding
virus”. It is curable and most people live happily thereafter.
Leo Simpson
ISSN 1030-2662
WARNING!
SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should
be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the
instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with
mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages,
you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed
or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON
CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of
any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government
regulations and by-laws.
Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act
1974 or as subsequently amended and to any governmental regulations which are applicable.
2 Silicon Chip
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Macservice Pty Ltd
News & Views
Home Computers More Popular
Recently the Australian Bureau of Statistics
released the results of a comprehensive
survey on the use of computers in Australian
households. It found a considerable increase in
computer usage but we still lag behind the US
and Britain. Interestingly, most computers are
still used for playing games.
According to the survey, almost two
million Australian households (30%)
used a computer as at February 1996,
compared to 1.5 million (23 percent)
of households in February 1994. Over
the same period, the total number of
computers in use in households had
risen to 2.5 million from 1.9 million.
In February 1996, 23% of households using computer technology had
a modem or external link compared
with 17% two years ago. Desktop or
personal PCs increased from 75% to
81% of the total number of household
computers and use of facsimile machines increased from 4% to 10% of
all households.
The use of peripheral equipment
also increased with CD-ROMs increasing most, from 13% to 41% of
households with computers.
Computer use and modems
Approximately 80% of computers
were owned by a household member.
Married couples with children continued to show the highest percentage use
of computers or 45% of an estimated
2.4 million.
Of the 4.7 million households
without a computer, 41% said they
had no use for a computer and 31%
said that costs were too high. Of the
1.5 million households which have a
computer but do not have a modem,
45% indicated that they were not in-
When the off switch no longer
really means off
Some of the new hifi equipment
now on sale features on/off switches which don’t stay off when you
turn them off. We recently saw a
Denon DCM-27 carousel CD player
which is apparently typical of this
trend. If you turn the set off by
the front panel switch or remote
control it turns off, as you would
expect. But if you then have a
blackout and the power comes back
on, so does the player.
If the power comes back on and
4 Silicon Chip
you have disc in the machine, it
will go straight into play mode –
not very convenient if you happen
to be asleep at 2 o’clock in the
morning!
Apparently the only way you can
be sure of turning these units off is
to switch it off at the power point.
This seems like a backward step.
Maybe the designers had better go
back to the drawing board on this
one and have a think about the
consequences.
terested or would not use a modem and
27% indicated that costs for a modem
were too high.
Computer activities
The most popular use for home computers was playing computer games.
50% of games players were aged 17
years or less. Of the 2.3 million persons
5 years or older who play computer
games on their home computer, 68%
spent one to five hours per week and
12% spent from six to 10 hours per
week playing computer games.
Educational activities were also
highly popular with just over one
The most popular use
for home computers
was playing computer
games.
million home users indicating the use
of mainly educational products.
833,000 thousand persons used
their household computer for doing
work relevant to their employment,
excluding their own businesses.
422,000 thousand persons used it
for doing work for their home-based
businesses, 379,000 used it for doing
work for their own (non-home based)
business and 23,000 used it for other
paid work from home via computer.
There were 1.6 million household
computer users doing work relevant to
studies, with 46% of these aged from
5-17 years.
Expenditure
Households which used a computer spent approximately $3 billion in
the 12 months to February 1996 on
computer related goods and services.
This represents $1500 per household
where a computer is used in Australia.
An estimated $870 million was
spent on desktop or personal com-
Next Year’s Flat-Screen TV
Philips has given its first public
demonstration of large-screen FlatTV at the CeBIT Home exhibition in
Hanover. The Flat-TV has a plasma
display panel with a screen diameter of 107cm (42 inches) and with
a depth of less than 10cm, can be
hung on a wall like a painting or
suspended from a ceiling.
Although the model shown at
CeBIT Home is a first generation
prototype, Philips says it plans to
introduce the Flat-TV onto the market in the first half of next year, at
an expected price of around 22,000
guilders (US$13,000).
Initial demand is expected to
come from businesses wanting to
use the Flat-TV for multimedia displays and from home cinema fans.
Philips expects the total market to
grow to around one million units
a year by 2000. The company will
also sell the system to other suppliers on an OEM basis.
Philips sees increased numbers
of people moving towards large and
wide screen TVs with home cinema
capabilities. At the same time that
they want bigger screen sizes, people also want less bulk in their sets.
puters, $550 million on software and
$680 million on computer peripherals.
Of the 6.6 million households in
Australia, 19% intended to purchase
computer equipment in the 12 months
from February 1996 and a further 11%
intended to spend an amount of money
in the 12 months from February 1997.
Internet
There were 262,000 people (178,000
males and 84,000 females) who indicated that they were using the Internet
from home. People in the 26-40 years
age group were the highest users of
the Internet (38%), followed by those
aged 41-55 years (28%) and 18-25
years (18%).
There were about 141,000 household computer users who used electronic mail and about 116,000 households who accessed other on-line
services/databases. However, when
all households were asked about their
With the largest cathode ray tube
tele
vision sets already weighing
over 100kg, bigger conventional
screens are impractical.
The Flat-TV is capable of receiving PAL, PALplus, Secam and
NTSC signals and offers full VGA
resolution, for use with a PC. The
plasma display technology used
in Flat-TV gives it a 160° viewing
willingness to use other technologies,
78% said “no” to home shopping, 70%
said “no” to home banking and 95%
said “no” to home gambling.
angle, far greater than LCD screens,
which are extremely difficult to
make in such large sizes.
The power supply, electronics
and connections are housed separately in a TV receiver. All connections with external equipment
go through this box, with only one
pair of cables going directly to the
flat display.
BassBox
®
Other technologies
24% of all households owned or
were paying for a mobile phone and
25% of households had an answering
machine. However, 52% of all households do not own or pay for any communication technologies apart from a
telephone connection.
Finally, 3% (200,000) reported
having Pay TV with the majority of
these households being in capital
cities (85%).
Further details and other aspects
of the use of various technologies by
Australian households are contained
in “Household Use of Information
Technology”, February 1996 (Cat No
8128.0), available from ABS bookshops in capital cities.
Design low frequency loudspeaker enclosures
fast and accurately with BassBox® software.
Uses both Thiele-Small and Electro-Mechanical
parameters with equal ease. Includes X. Over
2.03 passive crossover design program.
$299.00
Plus $6.00 postage.
Pay by cheque, Bankcard, Mastercard, Visacard.
EARTHQUAKE AUDIO
PH: (02) 9948 3771 FAX: (02) 9948 8040
PO BOX 226 BALGOWLAH NSW 2093
December 1996 5
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
dicksmith.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
dicksmith.com.au
COMPUTERS
CD Record
The major components of the
COMPRO CD-R kit include: (1) a
CD-R drive, (2) a SCSI interface
card, and (3) Gear pre-mastering
software on a CD-ROM. The kit
also includes two blank CD-ROMs
and a SCSI driver installation disc
for Windows 3.1.
Creating your own CD ROMs is fast and easy
with the latest generation CD recorders. And
the cost is coming down all the time.
Although CD ROM drives have been
the norm in PCs for some years now,
CD recorders have been much more
esoteric devices with price tags to
match. Until now that is – in the last
12 months, CD recorder prices have
plummeted dramatically, placing
them in reach of just about anybody.
For little more than a grand, you
can now choose from a range of CD
recorder kits that you can install
8 Silicon
ilicon C
Chip
hip
yourself or have installed for you.
Alternatively, you can now specify a
CD recorder as one of the options if
you’re buying a new PC.
If you need a reliable method of
archiving and storing (or transferring)
large amounts of data, a CD ROM is
well worth consideration. A CD-ROM
can store up to 650Mb of information
and this can either be added in one
session or, provided the system is ca-
pable of it, in multiple sessions.
But while data archiving is the
biggest application for a CD recorder
(CD-R), there are other applications.
CD-R lets you create your own audio
and video CD titles, for example. Some
systems even have the capability of
copying tracks from an existing audio
CD onto your PC’s hard disc so that
they can then be recorded onto a CDROM. Not all CD-R drives support
By GREG SWAIN
ders:
The next add-on
for your PC
copying audio tracks however, so
check carefully when buying a CD
recorder kit if this particular feature
is important to you.
CD-R drives
A CD-R drive looks exactly the same
as a conventional (read only) CD-ROM
drive and can simply be substituted
for the existing unit. CD-R drives are
invariably SCSI devices (Small Computer Systems Interface) and so a SCSI
interface card is required.
A CD-ROM is not like a floppy or
hard disc drive, so it’s not just simply
a matter of copying files to it. Instead,
you have to use special pre-mastering
software and this is normally supplied
with the kit.
The pre-mastering software is
necessary because CD-ROMs use a
different file format to DOS-formatted
discs – typically the ISO 9660 standard. In practice, the pre-mastering
software is used to create a “virtual
image” file of the CD. A virtual image
file lists all the file names and directories to be copied and contains other
information necessary for writing to
Because it is a SCSI device, the CD-R drive requires a SCSI interface card. This
card is plugged into a spare ISA slot on the motherboard.
a CD-ROM. It does not include the
actual data files, however.
It’s also possible to create what is
known as a “physical image” file on
the hard disc. This is an exact copy
of all the information as it is to be
The CD-R drive is slit into a vacant drive bay from the front
of the computer. We disabled our existing CD-ROM drive to
obtain a spare power connector.
recorded onto the CD-ROM and is
created after the virtual image has
been created.
A physical image file is usually only
necessary if you have a slow hard
disc. That’s because CD recording is a
The free end of the ribbon cable from the SCSI interface card
is plugged into the back of the CD-R drive, along with the
power connector. No audio cable is supplied with the kit.
D
December
ecember 1996 9
Creating A CD-ROM: The Basic Steps Using
1
Fig.2: type in the image filename
in the space provided, then click
the Create button. The image
file is created and the program
returns you to the workbench.
Note that only capital letters, the
numbers 0-9 and the underscore
character (_) are valid characters
for ISO filenames.
2
3
continuous process and there must be
no serious interruptions while record
ing is taking place.
If there is an interruption (eg, because the hard disc can’t keep up and
the data buffer empties), the recording
process will be aborted and the CDROM will be ruined. You can then
either toss it in the garbage or use it
as a drinks coaster.
Because a physical image takes less
10 Silicon Chip
Fig.1: select the CD type
to be created at the Gear
workbench, the click the
Create Image button.
time to read than a virtual image, it
reduces the likelihood of the buffer
running out of data during the recording process. The downside is that you
need lots of space on your hard disc,
since all the files to be written to the
CD are duplicated.
The good news it that a virtual image
file is all that’s required in most cases,
particularly if you have a computer
with a fast hard disc. It pays to de-
Fig.3: click the Edit
Image button to bring
up the Data Editor.
fragment the disc on a regular basis
though, to eliminate any possible
problems.
CD-Recorder Kit
Typical of the equipment now
available in this field is the Compro
CD-Recorder Kit. It comes with an
internal SCSI CD-R drive, a fast SCSI-2
interface card, Gear pre-mastering software (supplied on CD-ROM), a SCSI
g The Gear Pre-Mastering Software
4
Fig.4 (above): edit the virtual
image using the Data editor.
Just select the source drive
and drag the files you want to
the My ISO Track window.
5
Fig.5: click the test button on the
workbench to begin a test write.
Alternatively, you can bypass the
test procedure and write straight to
the disc.
6
driver installation disc (for Windows
3.11 users) and a SCSI interface cable.
Thrown in for good measure are a
couple of blank CD ROMs, plus a user
manual and an installation guide for
the SCSI card.
Our first impressions of this kit were
very favourable, as only good quality
components have been included. The
CD-R drive is a Matsushita CW-7501
Plug and Play unit, while the SCSI card
Fig.6: click Yes to automatically
write the image to the disc if the
test is successful or No for a test
write only.
is an Adaptec AHA-1520B. The SCSI
card features automatic termination
which means that you don’t have to
worry about removing terminat
ing
resistors if a device is plugged into the
external connector.
The CD-R is capable of reading a CDROM at quad-speed (4x) and writing at
double speed (2x). The pre-mastering
software also lets you write at single
speed if you have a computer with a
slow hard disc drive.
Unlike some CD recording kits,
this particular setup supports a wide
range of recording formats. It’s lets you
create multi-session and mixed-mode
discs and it supports CD-ROM Modes
1 & 2 (ISO), CD-ROM XA (extended
architecture), CD-I, CD Enhanced (also
known as CD Plus), and CD digital
audio (Red Book audio).
A multi-session disc is one on which
December 1996 11
Fig.7: a physical image can be created if you have a slow hard disc or for maximum
reliability. It requires a lot more hard disc space than a virtual image however, since
it makes a complete copy of the files to be written to the CD-R.
Fig.8: the “show log” option lists the steps that have been taken in creating a CDROM. This can be handy if you get interrupted during the process.
data has been added during several
different sessions. This is useful for
archiving data or updating a catalog on
a regular basis, for example. When the
disc is read back, the CD-ROM reader
automatically presents all linked sessions as one. You are not aware of the
number of sessions on the disc.
With a multi-session disc, you
can keep on adding data until the
disc is full. Note, however, that each
session introduces a data overhead
of about 15Mb. This data overhead
consists of track lead in and lead out
information.
You can also effectively delete and
update files on a multi-session disc.
This is done by adding (appending)
a new session. During this process,
the software reads back the last session and creates a virtual image of it.
You then edit (update, delete or add)
the file contents of this virtual image
before writing the new image to disc.
Of course, data is not really deleted
from a CD-ROM – it’s just that there’s
no longer any reference to it in the
new table of contents that’s created
12 Silicon Chip
when the new session is added. So as
far as the user is concerned, the file is
no longer there – just as if it had been
deleted.
One variation of the multi-session
format is the CD-En
hanced (or CD
Plus) disc. This is handy when creating
a mixed mode disc containing both
computer data and CD audio. It lets
you “hide” the audio from the data
and vice versa.
Under this format, the audio tracks
are written during the first session
while the data tracks are written during subsequent sessions. An audio
player will then only detect the first
session and so will only play the audio. Conversely, a CD-ROM drive will
show only the data that’s recorded on
the disc.
Installing the hardware
We chose a Pentium machine with
PnP BIOS and Windows 95 as our test
bed for the Compro CD Recorder Kit.
Both the CD-R and the SCSI card are
Plug and Play (PnP) items, so they are
easy to install and get going.
Unfortunately, when we opened
the case, we didn’t have a spare power connector for the new CD-R. We
solved that problem by disabling our
existing quad-speed CD-ROM drive.
Before pulling the power connector
however, we booted Windows 95 and
removed the CD-ROM device driver
(just go to Control Panel, double-click
the System icon, select the CD-ROM
and click Remove).
Of course, there’s nothing to stop
you from keeping your existing CDROM drive if you have enough power
connectors. Indeed, this would be
desirable if your existing drive is an
8x speed (or higher) unit, for example.
The SCSI card plugs into a spare
ISA slot on the mother
board, after
which the SCSI cable is attached to
the internal SCSI connector. This connector is keyed, so the cable can only
be attached one way which is just as
well because the COMPRO Installation
Guide shows the colour stripe on the
wrong side of the cable (the Adaptec
Installation Guide is correct).
The CD-R slides into a spare drive
bay and is secured using the four
screws supplied. It’s then just a matter of plugging in the free end of the
SCSI cable and attaching the power
connector.
A minor niggle here is that no audio
cable is included for attaching the
CD-R to a sound card. This won’t be
missed by most people; an audio cable
is only necessary if you want to play
CD audio discs. You can still copy
audio CD tracks however, since this
data is sent via the SCSI bus.
COMPRO’s excuse is that they don’t
know what kind of sound card you
have but we think that a cable suitable for a Sound Blaster card should
have been included. The installation
guide also incorrectly shows the pin
connections for the audio socket, so be
warned if you intend buying a cable
from your local computer store. Fortunately, the correct pin connections
are clearly labelled on the back of the
drive itself.
When we rebooted the system,
Windows 95 automatically detected
the SCSI card and the new CD-R drive
and installed the appropriate device
drivers. If you don’t have a PnP system, it may be necessary to change
some of the settings for the SCSI card
to avoid a hardware conflict (eg, with
a sound card). You do that by using
the embedded SCSISelect utility. This
Fig.9: the “Multi Session” option must be enabled if you
want to add data to a CD-ROM over several sessions. The
verify and physical image options are also set here.
is accessed by pressing Ctrl-A during
the boot-up procedure, after which
you can change a range of settings,
including the IRQ channel and the
SCSI ID number.
You can also choose from one of
three termination options (Enabled,
Disabled or Automatic) and disable
the host adapter BIOS. In fact, Adaptec
recommend that you disable the BIOS
if the peripherals on the SCSI bus are
all controlled by device drivers and
do not need the BIOS.
By default, the SCSI card uses I/O
port address 340 and IRQ 11 and these
are also typically the default settings
for a SoundBlaster card. If this applies
to your setup, it will be necessary to
change the settings on one card to
avoid problems.
Using the software
The Gear pre-mastering software
comes on a CD-ROM which includes
both Windows 95 and Windows 3.1
versions (versions are also available for
OS/2 and the Mac OS). In addition, the
CD-ROM includes a comprehensive
manual on the Gear pre-mastering
soft
ware in portable document format (pdf) plus a full working copy of
Adobe Acrobat Reader 2.1 (to let you
view pdf files).
The first thing to do after installing
the software is to turn off any screen
savers and anything else that could
interrupt the recording process (eg, a
fax modem). For the same reason, the
manual also instructs you to turn off
the “Auto Insert Notification” option
for the CD-R drive and gives the step-
Fig.10: we initially had problems with buffer under-run.
Ditching the cyclical buffering option and selecting doublebuffering instead solved these problems.
by-step procedure for doing this.
The basic procedure for “burning”
a CD-ROM is clearly set out in the
manual. First, you have to choose the
CD type to be created (eg, CD-ROM)
and create a new image file (Figs.1 &
2) You then open the Gear Data Editor,
select the source drive and drag the
files you want to the My ISO Track
window. If you make a mistake here,
you just delete the track that you don’t
want from the image.
Closing the Data Editor now returns
you to the workbench, at which point
it is a good idea to run a test write. This
useful feature does everything except
actually write to the CD and is used to
confirm that the data throughput from
the hard disc to the CD is high enough.
You can also elect to automatically
write to the disc immediately after a
successful test and there’s a verify after
write option.
Alternatively, you can bypass the
test procedure and write straight to
the CD. A bargraph shows the progress
of the recording and the disc is automatically ejected when the procedure
is completed (as it is at the end of a
successful test run).
The Gear software is easy to use
although the Data Editor is a little
clumsy. First, it’s default window sizes
are too small and although they can
be easily resized, they don’t stay that
way when the Data Editor is closed.
Another problem is that the folders
on the hard disc are not presented
in alphabetical order. That said, both
these criticisms are fairly minor.
Sorting out the wrinkles
Our initial tests with small files
were successful but we quickly ran
into problems when we tried to write
large amounts of data to disc. These
problems centred around the type of
buffering used.
By default, the Gear software installs
with cyclic buffer
ing selected, as
Using Gear For Data Backups
A CD-ROM is useful as a secure
medium for backing up data and
Gear includes various archive setting
options to make the job easy.
By enabling the archives reset feature, the software will automatically
reset the archive bit for each file that
is loaded into the image. Any files
that are then subsequently modified
or created will have their archive bit
set again by DOS.
Provided that the archives only
feature is enabled, you can now simply drag all files across to the image
when writing the next session. However, only those files that have been
modified or created will be loaded
and added to the CD-ROM. Those
files that haven’t been modified remain in the previous session(s), thus
giving a complete backup.
Other options let you choose
whether or not to load hidden and
system files.
December 1996 13
Fig.11 (right): clicking the DiscInfor button on the Gear
workbench toolbar brings up this dialog box. This lets
you select and copy individual tracks (eg, from an audio
CD) to the hard disc.
Fig.12 (below): once the tracks are on the hard disc, the
virtual image for an audio CD is created in the same way
as for a data CD-ROM.
opposed to the alternative double-buffering option. During the recording
process, the buffer stores data from the
hard disc and streams it in a continuous fashion to the CD-R. If the buffer
runs out of data, any interruption to
the data stream from the hard disc
aborts the recording process.
With cyclic buffering selected, we
found that the buffer initially filled
(as indicated by a bargraph) but then
slowly emptied during the first few
minutes of the recording process. After
this, the hard disc really rattled along
as it attempted to keep up with the
demands of the CD-R.
When large amounts of data were
involved, the process inevitably fell
over. Once, we were about two thirds
of the way into writing 600Mb of data
when it crashed, despite a successful
test run. On another occasion, we
didn’t even get to the halfway point.
We tried everything to solve this
problem, including chang
i ng the
buffer size, writing at single speed and
even creating a physical image of the
14 Silicon Chip
files to be written. But no matter what
we did, the buffer still emptied after
just a few minutes and the hard disc
rattled its head off.
Unfortunately, initial test writes
with double buffering selected didn’t
hold much promise. Although the hard
disc now worked at a fairly leisurely
rate, the bargraph always showed an
empty buffer which didn’t even fill
before recording started.
With two dead discs sitting on the
table, it was time to call the local
COMPRO distributor. Their advice:
(1) ditch the cyclic buffering and
use double buffering; (2) create a
physical image of the data; and (3)
record at double speed. And the empty bargraph indicator when double
buffering is selected? Apparently,
that’s normal; it only works for cyclic buffering (it’s just a pity that the
manual doesn’t say that).
And that solved all our problems.
With double-buffering selected, we
successfully recorded large amounts
of data onto six CD-ROMs without
a hitch. In fact, with our setup, it
wasn’t even necessary to create a
physical image file. A virtual image
was sufficient, even when writing at
double speed.
Adding a new session
Adding a new session is quite
straightforward. You just insert the CDROM, click the Append button on the
Gear toolbar, edit the CD-ROM image
and write the data as before. The only
proviso here is that the Multi Session
option must have been selected before
any previous sessions were written to
the CD-ROM.
It’s important to realise here that
only the changes that you make to
the image are written to the disc. If
you want to keep a file, it must not be
deleted from the existing image. If you
do, it will appear as though the file has
been deleted. Of course, you might
want to “delete” files from a previous
session on purpose.
Each new session is added to the
disc using one of several “append”
Writing The Data To Tape
Instead of writing to a CD, you can use the Gear software to write
the data to tape. This tape can then be sent to a CD-ROM mastering
plant so that multiple CDs can be produced.
An unwanted by-product of this feature is that the Gear software
always looks for a SCSI tape drive when it is booting up and if it
doesn’t find one, comes up with the error message “No SCSI tape
units found”. This doesn’t create any problems but can become
annoying if you do a lot of archiving.
Fortunately, it’s easy to disable this feature by editing the gear.
ini file. You can do this is any ASCII text editor such as Notepad –
just look for the line TapeInterface = 1 under the [tape] section and
change it to TapeInterface = 0
options. Normally, for adding or deleting data, the Automatic Append option is used but there are also Manual,
New and Multi-Volume Append modes.
The Manual Append mode lets you select the track
you want to add data to and is useful for recovering data
deleted in a later session. By contrast, the New Append
mode writes an empty track so that all previous sessions
become inaccessible. Accord
ing to the manual, this
feature can be used to recycle a disc that has suffered a
write failure (presumably after a previously successful
session). Finally, the Multi-Volume Append mode is used
for creating multi-volume discs.
Making an audio CD
The procedure for recording an audio CD is slightly
different to making a CD-ROM, since you first have to copy
the tracks to your hard disc. First, you insert an audio CD
in the drive and click the DiscInfor button on the toolbar.
This brings up the dialog box shown in Fig.6, after which
you can select and copy individual files to your hard disc.
A separate dialog box prompts you to name each file just
before it is copied.
From there, the process is almost identical to creating
a CD-ROM, the main difference being that you choose
CD-Audio as the CD type before creating and editing
the image file. Another difference is that the recording
bargraph indicates the progress of each individual track
instead of the entire session.
In our case, we successfully created a test CD with 17
tracks. It played back on an audio CD player just like any
other CD, although we did notice a faint click between a
couple of the tracks.
As a point of interest, it is possible to create an audio
CD over several sessions despite the fact that an audio
CD is basically a single-session disc. You might want to
do this if you have limited hard disc space and cannot
load all the wanted tracks in one session, for example.
By now, you will have gathered that the Gear pre-mastering software is extremely versatile, with a host of features
– so many in fact that we didn’t have time to explore them
all. Despite this, it is an easy package to use.
In summary, our impressions of this CD-R kit are very
favourable. The complete package retails for $1295.00
and is available from Rod Irving Electronics, 56 Renver
SC
Rd, Clayton 3168; phone (03) 9543 7877.
MICROWAVE PARTS & REPAIRS
WARNING!: All microwave repairs must be done by a qualified microwave technician. All text
within is to be used as a guideline only. We recommend reading “MICROWAVE OVEN OPERATION
AND SERVICING MANUAL” (code: MAN-MICRO, cost $19.95) for full safety instructions. Shailer
Park Electronics will NOT take liability in any form for safety, health or work done.
MICROWAVE OVEN LAMPS
Hard to Find Range of Microwave Resistant Lamps
Code
Volts
Watts
Baseφϕ
$
CL818
240V
25W
13mm
$8.50
CL819
125V
25W
13mm
$9.50
CL821
240V
20W
15mm
$8.50
CL822
125V
20W
15mm
$9.50
Base φ
MICROWAVE SHORT PROTECTOR
Blowing mains fuse? This short protector may be
blown. It’s located across the high voltage cap which
holds approximately 2300V. This short protector can
be tested by first unplugging mains lead and then discharging the high voltage cap with a 1kΩ resistor.
The short protector can then be safely measured out of circuit. REPLACE SHORT PROTECTOR IF
FOUND DEAD SHORT. Code: 2X062H $14.95
MICROWAVE HIGH
VOLTAGE CAPACITORS
MICROWAVE HIGH VOLTAGE CAPACITORS
Code
Value
Voltage
Cost
Is your microwave oven blowing
the main fuse? The high
voltage capacitor may
be faulty. These
high voltage, low
tolerance capacitors are used in
microwave ovens
to complete a resonance circuit with the magnetron which is inductive.
A faulty capacitor may upset the lead-lag factor of
the resonance circuit and cause the transformer
to labour (hum) or blow short protector and/or
main fuse. The high voltage capacitor, which holds
approximately 2300V, can be tested by unplugging
the mains lead and then discharging the capacitor
with a 1kΩ resistor, after which it can be safely
measured out of circuit. REPLACE CAPACITOR IF
FOUND FAULTY OR DEAD SHORT
MWC65
MWC70
MWC83
MWC85
MWC86
MWC90
MWC95
MWC100
MWC105
MWC110
MWC113
MWC114-6
MWC120
0.65µF
0.70µF
0.83µF
0.85µF
0.86µF
0.90µF
0.95µF
1.00µF
1.05µF
1.10µF
1.13µF
1.14µF
1.20µF
2300V
2300V
2300V
2100V
2100V
2100V
2100V
2100V
2100V
2100V
2100V
2100V
2100V
$35.50
$36.50
$39.50
$36.50
$39.50
$39.50
$39.50
$50.50
$42.50
$44.95
$45.50
$44.95
$44.95
MICROWAVE OVEN ROOF LINING
Does your microwave throw sparks inside cavity? The roof lining may need replacing. This lining
is made of a special material to diffuse the microwave beam for even distribution. You will find the
lining if you open the door and look up inside the cavity; it is a flat sheet held in by screws or clips.
With age, the microwave beam will burn through this lining causing sparks inside. We supply 13cm
x 17cm sheet, simply cut and shape to size.
MICROWAVE OVEN ROOF LINING
Code
Type
Size
13cm
Price
MRL20
Microwave 13cm x 17cm $15.50
MRL50
Microwave 13cm x 17cm $17.95
17cm
MICROWAVE FUSES
Our range of original microwave
fuses are time delayed,
ceramic tube, with brass
nickel plated contact cups
and have a high breaking
capacity of 500A/500V.
Never use conventional
fuses as they may explode and shatter throwing
pieces of glass inside the food cavity, which may
be a health risk.
MICROWAVE FUSES
Code
Rating
Length
Price
AF010P
6.3A
5mm x 20mm
$2.50
AF011P
8A
5mm x 20mm
$2.50
AF012P
10A
5mm x 20mm
$2.50
AF019L
6.3A
6.35mm x 32mm
$2.50
AF020L
8A
6.35mm x 32mm
$2.50
AF021L
10A
6.35mm x 32mm
$2.50
MICROWAVE TURNTABLE BELTS
Code
Dimensions (A x B x C)
Length
Cost
MWB95
95 x 7.0 x 0.6
300
$11.65
MWB100
100 x 7.5 x 0.6
320
$11.75
MWB105
105 x 4.0 x 1.0
330
$11.80
MWB110
110 x 7.0 x 0.6
340
$11.70
MWB165
116 x 4.0 x 1.0
520
$15.65
MWB210
210 x 2.5 square
650
$14.95
MWB260
260 x 3.0 square
800
$14.90
MWB280
280 x 3.0 square
880
$13.30
MWB175
175 x 2.5 round
550
$19.95
MICROWAVE TURNTABLE MOTORS
Postage & Packing $3.50
SHAFT A
2.5 rpm
Code: MWM91
Cost $34.95
SHAFT B
5 rpm
Code: MWM16
Cost $36.95
ORDER HOTLINE: (07)
3209 8648. FREE CALL:
1800 63 8722. FAX: (07)
3806 0119
SHAFT C
2.5 rpm
Code: MWM159
Cost $39.95
SHAILER PARK
ELECTRONICS
KP Centre, Cnr Roselea &
Lyndale St,
Shailer Park, Qld 4128.
December 1996 15
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.altronics.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.altronics.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
www.altronics.com.au
MAILBAG
Dead wrong
on the Internet
I saw your editorial on the Internet
in the October issue. Please take it from
me you are in a goldfish bowl and are
dead wrong. I see my fax bill has gone
down from $US250/month to $US40.
The cost of a web page is not “very”
substantial; I know, since I have set
one up. It runs on my server for free.
The only cost is my time. I can now get
any data sheet within one minute – no
more data books. Wonderful.
Here are two examples to suggest
you are wrong: (1) Most of the electronics magazines in the world now
have web pages so no support for
your position there. Popular Electronics, Electronics Now, Everyday
Practical Electronics, Elektor, Nuts,
all have good pages I look at regularly. Maplin has just started (all
URLs on my web site); (2) Circuit
Specialists (www.cir.com) have reduced their hardcopy catalog from
300,000 per year to 50,000. They now
have the catalog on the web; instant
changes and additions possible.
The USA electronics magazines
generally do not have an editorial/
publisher’s Letter. This may be an idea
for you to adopt for your magazine.
P. Crowcroft,
Hong Kong.
Video transmitter needs
blocking capacitor
I had trouble with the twisted-pair
video transmitter/re
ceiver project
in the October issue. I don’t like RF
stuff (and TV sets in particular – even
though I have managed to repair a
couple in the last 20 years) and the
problem with this project had me
bluffed for about three days. I am
using a small monochrome camera
from Oatley Electronics as the signal
source and direct into the TV video
line this gave an excellent picture.
However, via the twisted pair Tx/
Rx I got a blank screen.
Examining the output of the Tx
unit revealed no signal, so the Tx
must be faulty! Except that I could
find no fault, even with a new IC and
the Maxim data sheet.
I just could not get the system to
work but, out of spite, I eventually
connected a VCR output to the Tx/
Rx and into another TV and presto,
it works. But why?
After carefully studying the waveform from the camera and that from
the VCR on the scope, I realised that
the VCR waveform was AC and the
camera most definitely DC. Obviously
the Tx unit expected an AC input (but
the TV would tolerate either). The
answer is to insert a 100µF tantalum
capacitor in the video signal line from
the camera to the Tx unit.
The article highlighted the situation of using a small monochrome
camera with this project to provide
a remote video system but does not
mention that such cameras may
have a DC output waveform. There
could well be a lot of other people
out there who need “spoon feeding”
when dealing with RF stuff (as I do)
and this may solve their problems
getting this project going.
A. Mott,
Blackburn, Vic.
The UV People
ETCH TANKS
● Bubble Etch ● Circulating
LIGHT BOXES
● Portuvee 4 ● Portuvee 6
● Dual Level
TRIMMER
● Ideal
PCB DRILL
● Toyo HiSpeed
MATERIALS
● PC Board: Riston, Dynachem
● 3M Label/Panel Stock
● Dynamark: Metal, Plastic
✴ AUSTRALIA’S NO.1 STOCKIST ✴
40 Wallis Ave, East Ivanhoe 3079.
Phone (03) 9497 3422, Fax (03) 9499 2381
Waste not, want not
I have read your July 1996 editorial
on the subject of appliance servicing. I
agree that it is wasteful to throw away
appliances when economic repair
is possible. One area which could
improve the situation is dedicating a
section of your magazine to swapping
of major spares for TVs and videos,
as quite a number of readers would
be involved in servicing of these appliances either professionally or as
a hobby. A lot of servicemen have a
large collection of spares from writeoff equipment gathering dust. If these
parts could be sold they could be used
to repair equipment that could not
otherwise be repaired.
I own two VCRs which need
head-drum assembles. One is an
Akai VS-35, the other a Sharp VC682. If anyone has these parts from
writeoffs, I would be grateful as it
would mean an economic repair. I
don’t expect these items for free but
$200+ is more than they’re worth. I
have a writeoff National NV-370 and
an Akai CS-112 for parts, if they’re
of assistance to anyone.
J. Ellis, 15 View St,
Norah Head, NSW.
TRANSFORMERS
• TOROIDAL
• CONVENTIONAL
• POWER • OUTPUT
• CURRENT • INVERTER
• PLUGPACKS
• CHOKES
STOCK RANGE TOROIDALS
BEST PRICES
APPROVED TO AS 3108-1994
SPECIALS DESIGNED & MADE
15VA to 7.5kVA
Tortech Pty Ltd
24/31 Wentworth St, Greenacre 2190
Phone (02) 9642 6003 Fax (02) 9642 6127
December 1996 19
Engine braking from an automatic!
Mitsubishi’s int
automatic tran
Mitsubishi’s smart new automatic
transmission adjusts its shift points to
suit the driver’s style. What's more, it
shifts gear in a much more intelligent
manner than previous automatic
transmissions. Here's how it works.
By JULIAN EDGAR
20 Silicon Chip
Many automatic transmissions are
now at least partially electronically
controlled. Some use a hybrid system
of electronic and hydraulic control,
while others are fully electronic.
The latest innovation is the adaptive
“self-learning” au
tomatic transmission, as fitted to the new TE Magna
from Mitsu
bishi. In this system, a
transmission control unit is used to
constantly monitor the driver’s style.
Depending on what it “learns”, it
then adjusts its control behaviour
accordingly.
With this type of system, the economy/power switch fitted to some transmissions is made redundant. Drive
the car hard and the gear changes will
occur at higher engine speeds; gently
toddle along and the changes will slur
through early. However, there’s more
to adaptive shift control technology
than changing gear shift points, as we
shall see.
Common problems
In most modern automatic transmissions, gear selection is based mainly
on throttle position and vehicle speed.
However, there are many situations
where the gear selected is not appro
priate for the driving conditions – the
control system literally selects the
“wrong” gear.
A good example of this occurs when
driving an automatic car uphill along
a winding road. In this situation, a
slight easing of the throttle prior to
each corner can result in an up-shift,
the transmission then down-shifting
again after the corner has been negotiated.
Obviously, if driving a manual car,
the driver would not change into a
higher gear prior to entering a corner.
Because the automatic transmission
does, it losses engine braking and so
some degree of control is lost.
Fig.1: Mitsubishi’s earlier “Fuzzy Shift Scheduling” system allowed the
transmission control unit to use engine braking and hill-climbing modes.
Self-learning was not incorporated into the system, however.
Downhill driving in a conventional
automatic also results in a lack of
engine braking, unless the driver
manually selects a lower gear. (Incidentally, it is good driving practice
to manually lock a conventional auto
into a single appropriate gear in both
of the above scenarios – lazy drivers
take note!)
Getting back to the TE Magna, Mitsubishi’s research indi
cated that a
conventional automatic transmission
could be in the “wrong” gear for a
given situation up to 60% of the time
telligent
nsmission
– an extraordinarily high figure and
perhaps only possible if the car were
being driven on a racetrack! However,
there are certainly times when the
control system needs more brains.
For Mitsubishi, the first step in
overcoming these problems involved
the development of “Fuzzy Shift
Scheduling” – see Fig.1. In this system,
additional inputs are used to allow
the system to select from three shift
modes: engine braking, standard and
uphill. The current Mitsubishi system
is an extension of this design.
Fig.2 shows the basis of the new
system. The engine Electronic Control Unit (ECU) and the Transmission
Control Unit (TCU) are linked, and
exchange data on engine speed and airflow rate (ie, engine load). In addition,
the TCU receives additional inputs on
the throttle position, brake operation,
steering angle and the transmission
shaft speeds. The throttle opening is
derived from a throttle position sensor,
the frequency and/or duration of brake
operation by monitoring the brake
Fig.2: the new Mitsubishi
adaptive system accepts
additional inputs,
including steering angle
and the frequency and/
or duration of brake
application. This allows
the system to better
calculate appropriate
shift behaviour during
downhill coasting and
to match the style of the
driver.
December 1996 21
Fig.3 (above): if the TCU selects a gear which is too low and thus provides
excessive engine braking, the action of the driver applying throttle will
cause a correction to the downshift. Conversely, applying the brakes
excessively when coasting down a hill – as in Fig.4 (right) – will cause the
TCU to shift to a lower gear, thus increasing engine braking.
light switch, and the steering angle by
a dedicated sensor.
The speed of both the input and
output shafts of the auto transmission
is also measured. This allows the TCU
to monitor road speed and to calculate
the amount slippage occurring through
the transmission. It can then use these
inputs as a feedback mechanism to
reduce “shift shock”. In some versions
of the system, longitudinal and lateral
accelerometers are also employed.
Engine braking
Engine braking is achieved by
calculating an index called “engine
brake applicability”. This is carried
out by a so-called “neural network”
which links together the road gradient,
vehicle speed, braking frequency and
steering angle with varying degrees of
importance.
The influence of these various
factors depends on empirical data
originally gathered by monitoring the
gear-shifting behaviour of experienced
drivers.
The aim here is to approximate the
decision-making process adopted by
a driver in a manual car.
However, while downshift timing
is primarily controlled by the “neural
network” from empirically-collected
data, the calculat
ed timing is not
appropriate for all drivers because
of their individual preferences and
driving styles. A feedback mechanism
dubbed “Learning Control” has therefore been added. This judges the driver’s dissatisfaction with the amount
of engine braking being provided by
the TCU and corrects the downshift
condition until the driver’s preference
is reached.
This judgement is carried out by
monitoring the frequency and/or duration of brake use and by monitoring
throttle variations when the vehicle is
coasting downhill. If throttle needs to
be applied (Fig.3) then the transmission is in too low a gear. Conversely,
if the brake is applied (Fig.4) the gear
selected is too high.
Fig.5 shows how the learning
system changes the ease with which
up-shifts and down-shifts occur in
response to brake and accelerator
movement during downhill coasting.
Variable shift patterns
Fig.5: the self-learning behaviour of the system can be seen here,
where the ease of selection of either a downshift or upshift varies
with the driver’s preference – as sensed by the TCU through brake
or accelerator application while driving downhill.
22 Silicon Chip
A conventionally-controlled transmission has a shift pattern similar to
that shown in Fig.6. An upshift from
second to third, for example, occurs
at a certain combination of throttle
position and vehicle speed. Similarly,
at another precise mix of speed and
throttle, the downshift from third to
second will occur.
It’s this fixed approach which
causes the problem of upshifts before
corners when climbing a hill. To
avoid this, it is necessary to move the
upshift lines to a higher speed range.
Just how much the upshift points are
moved depends on the road gradient,
as derived from the TCU sensors.
Variations in individual driving
styles also require changes to the shift
points. For example, a “sporty” (or
aggressive) style means that the lower
gears need to be held to higher engine
speeds and also selected more readily.
The driving style is evaluated by a
variable that Mitsubishi’s engineers
call the “Sporty Driving Index”.
The “Sporty Driving Index” is calculated by selecting the larger of two
input factors – either the engine load
index or the tyre load index.
On some Mitsubishis (but not on the
Australian Magna), the tyre load index
is calculated by comparing the actual
lateral and longitudinal accelerations
with the maxima of which the tyre is
capable. Similarly, the engine load
index is calculated by measuring the
actual acceleration and comparing
this with the maximum possible acceleration.
How hard the car is being cornered
or accelerated varies the “Sporty Driving Index”, with the shift point maps
then moved as a result. Fig.7 shows a
schematic summary of the complete
TCU system.
Does it work?
According to Mitsubishi, the new
system selects the correct gear for
80% of the time. This represents a
considerable improvement on the 40%
of a conventional auto transmission
and 55% for their second-generation
fuzzy system.
In Australian Government AS2877
fuel economy tests, the V6 automatic
transmission Magna has equal econ
omy to its manual equivalent on the
highway cycle and is only 5% worse
Fig.6: in a conventional shift control system the up and down changes
always occur at a precise combination of speed and throttle position.
in the city cycle. By comparison, the
current model automatic Commodore
is 6% worse than the manual version
on the highway and 9.5% worse on the
city cycle. It would certainly appear
that the more sophisti
cated transmission control system of the Magna
yields economy benefits!
So what’s it like to drive? We took
an automatic TE Magna sedan for a
run to find out.
On the road we found that the
electronic control system had some
noticeable advantages over more traditional transmission control systems.
Most obvious was the transmission
down-changing to provide engine
braking when slowing for a red traffic
light, for example. And on country
roads, the downhill engine braking
was also noticeable.
However, many of the traditional
disadvantages of an automatic transmission appeared to remain. Any
demand for instant power (eg, when
overtaking on a country road) still
results in a relatively slow response,
there being approximately a 1-second
time lag for the transmission to “think”
and then change down a gear.
A quicker response was possible
by manually changing down. Jerky
changes also occurred in some situations – for example, when accelerating
hard away from a standstill and then
suddenly lifting the throttle.
That said, Mitsubishi’s new adaptive control system represents a real
improvement in automatic transmission technology. It matches the
shift points to suit the driver and it
provides superior shift patterns in
certain driving situations. And it does
this unobtrusively.
Certainly it never occurred to me
that the transmission was pre-empting
my decisions or matching its change
SC
patterns to my driving style!
Fig.7: block diagram of the TCU. The shift pattern is calculated from a range of input data.
December 1996 23
By LEON WILLIAMS
VK2DOB
ACTIVE
FILTER cleans up
weak CW reception
Dig out those weak CW signals from the noise
and interference with this simple filter unit. It
easily connects between any receiver and an
external speaker. Unlike other designs that use
a fixed narrow filter this unit has a variable
filter control for obtaining optimum reception.
Most radio receivers are only intended to receive voice signals and are
required to have an audio bandwidth
of several kilohertz.
A typical amateur band receiver
fitted with a SSB filter has an audio
frequency response from 300Hz
to 2700Hz, giving a bandwidth of
2400Hz. By contrast, the frequency
compon
ents of a CW signal only
occupy a bandwidth of 100Hz or so,
depending on the sending speed.
It is quite obvious that there is plenty of room in the receiver bandwidth
24 Silicon Chip
to fit a little CW signal. This situation
is quite OK until another CW signal
or some interfering signal is received
perhaps only a few hundred Hertz
away. We are now in the situation of
trying to decipher a CW signal amongst
a whole lot of other sounds. It’s a bit
like trying to listen to a small voice in
a noisy crowd of people.
The solution is to narrow the audio
frequency response so that the interfering signal is filtered out, leaving the
wanted signal on its own.
There are two main ways of doing
this. First, a narrow crystal filter can
be switched in to the intermediate
frequency (IF) circuits of a superheterodyne receiver. A typical bandwidth
might be 500Hz. When normal voice
signals are to be received, the narrow
filter can be switched out and a wider
(2400Hz) filter switched in.
Filters such as this are quite expensive and you would have to be a
keen CW operator to consider this.
The second alternative is to switch in
and out a narrow audio bandpass filter
somewhere in the audio stages of the
receiver. This technique can be used
in both superheterodyne and direct
conversion receivers.
Direct conversion receivers do not
have IF stages. Once again, the filter
needs to be switched out when voice
signals are received, because the narrow filter would eliminate too many
frequency components of the voice
and probably make it unintelligible.
A recent innovation is the use of out
board DSP processors which digitise
the voice signals and through digital
manipulation result in various filter
responses. These units are expensive,
costing hundreds of dollars.
This Adjustable CW Filter has a
number of advantages over the methods mentioned above.
Firstly, it is self-contained, is
powered from a DC plugpack and
no modifications need to be done to
the receiver. Also it is inexpensive
to build, uses standard parts and it
simply connects between the speaker
socket or audio output of the receiver
and an external speaker.
The front panel has two controls,
Volume and Filter. The filter control
can be adjusted to give any bandwidth
between wide open (no filtering) and a
very narrow band pass response centred on 800Hz. The filter control can
also be used to good effect with voice
signals by acting to reduce the level of
high frequency noise and interference.
If 800Hz is not your favourite frequency this can be changed, as explained
later on.
Fig.2 shows the range of filter responses provided by the unit.
A special feature is a LED on the
front panel that is turned on when
800Hz is detected. This gives an indication that you are tuned correctly
to the CW signal and also it is an
opportunity to learn to “read” CW by
decoding the flashes with the volume
turned down.
Circuit description
The complete circuit is shown in
Fig.1. Audio signals from the receiver
are fed to the 10kΩ trimpot VR1. The
minimum input level that the tone decoder will function correctly is about
70mV RMS or 200mV peak-peak.
Following VR1 is op amp IC1a
which has a gain of two. A 560pF
capacitor connected across the 100kΩ
feedback resistor from pin 2 to pin 1
provides some low pass filtering. As
we are not using separate positive
and negative power supply rails, the
non-inverting input (pin 3) is biased
Fig.1 (right): the circuit is a variable
bandpass filter centred on 800Hz
and includes a tone decoder (IC2) to
indicate when the receiver is correctly
tuned for CW transmissions.
December 1996 25
PARTS LIST
1 metal case, 102 x 62mm x
148mm (W x H x D)
1 PC board, code 06112961, 97
x 68mm
1 9-12V DC plugpack
1 DC panel socket
1 6.5mm mono jack socket
1 RCA panel socket
2 20mm knobs
1 LED bezel clip
1 10kΩ log potentiometer (VR4)
1 10kΩ dual linear potentiometer
(VR2a,VR2b)
2 10kΩ horizontal trimpots
(VR1,VR3)
17 PC pins
Semiconductors
1 TL074, LF347 quad op amp
(IC1)
1 LM567 PLL tone decoder (IC2)
1 LM386 audio amplifier (IC3)
1 1N4004 diode (D1)
1 5.6V 1W zener diode (ZD1)
1 5mm green LED (LED1)
Capacitors
1 1000µF 25VW electrolytic
1 470µF 25VW electrolytic
3 100µF 25V electrolytic
6 2.2µF 63V electrolytic
5 0.1µF MKT polyester
1 .047µF MKT polyester
4 .022µF MKT polyester
2 560pF ceramic
Resistors (0.25W, 1%)
6 100kΩ
2 820Ω
4 47kΩ
1 180Ω
2 10kΩ
1 100Ω
1 5.6kΩ
2 10Ω
1 1kΩ
Miscellaneous
Screws, nuts, spacers, hook-up
wire
to half the supply voltage by two
10kΩ resistors. A 100µF capacitor
helps filter out noise. This half supply
voltage point is also connected to the
non-inverting inputs of the other three
op amps in IC1.
The output of IC1a is split into two
paths. First, it is applied to the input
of an audio bandpass filter using IC1b.
This stage has been designed for a
centre frequency of 800Hz, unity gain
in the passband and a -3dB bandwidth
of 150Hz.
26 Silicon Chip
AUDIO PRECISION SCFREQRE AMPL(dBr) vs FREQ(Hz)
5.0000
01 NOV 96 13:53:59
0.0
-5.000
-10.00
-15.00
-20.00
-25.00
-30.00
-35.00
-40.00
-45.00
20
100
1k
10k
20k
Fig.2: this diagram shows some of the bandpass responses available from a
filter, ranging from a deep notch to quite wide.
When calculations are done for any
audio filter circuit, it’s almost certain
that non-standard value components
will be called for. The components
specified in the parts list are close
enough to the calculated values without greatly affecting the performance.
The output of this stage is connected
to an identical stage using IC1c. The
combination of these two bandpass
stages provides a narrow response
with high attenuation of frequencies
either side of the passband. Fig.3
shows the general filter configuration
and the formulas used in the design
calculations.
The output of IC1c is coupled to
one half of a dual-gang potentiometer
(VR2b) by a 2.2µF capacitor while the
output of IC1a is coupled via another
2.2µF capacitor to the second gang
(VR2a). The mixer stage uses IC1d and
has unity gain.
The wipers of VR2a and VR2b are
each connected to the mixer stage by a
100kΩ resistor and a 0.1µF capacitor in
series. The point to note is that when
VR2 is fully anticlockwise, no signal is
passed from the bandpass filter output
to the mixer, while the full output of
the unfiltered signal from IC1a is fed
through. When VR2 is rotated fully
clockwise, the reverse occurs and
only the output of the bandpass filter
is fed to the mixer. By varying the
position of VR2 we can obtain any
degree of filtering between narrow in
the clockwise position and wide in the
anticlockwise position.
The output of IC1d is coupled to
the Volume control (VR4) via a 2.2µF
capacitor. VR4 varies the signal level
applied to the audio power amplifier
IC3, an LM386. This drives an external
speaker. The 2.2µF capacitor from pin
7 to 0V is included to reduce the level
of hum to an acceptable level when a
plugpack power supply is used. The
10Ω resistor and .047µF capacitor
help keep the amplifier stable at high
frequencies.
800Hz indicator
IC2 is an LM567 tone decoder,
which turns on the LED (LED1) when
800Hz is applied to its input. The
LM567 is actually a phase locked loop
circuit which compares an internal
oscillator to an external signal at pin
3. When they are within a few hundred
Hertz of each other, the open collector
output at pin 8 switches to 0V and
lights LED1.
The frequency of the internal oscillator is determined by the resistance
between pins 5 & 6 and the capacitor
from pin 6 to ground. With the values
shown on the circuit the frequency can
be varied between about 600Hz and
1500Hz by VR3. The capacitors from
pins 1 & 2 to ground provide filtering
for the internal circuits and also affect
Fig.3: the general filter configuration & the
formulas used in the design calculations.
the detection bandwidth. The values
shown on the circuit were arrived at
through experimentation by monitoring LED1 for correct operation under
various signal conditions.
A 180Ω resistor, a 5.6V zener diode
ZD1 and a 100µF capacitor provide
a regulated 5.6V power supply for
IC2. The full circuit is powered by a
9-15V 500mA DC plugpack. Typically
this will be a 12V 500mA plugpack.
Diode D1 provides protection against
the power supply being connected
with reverse polarity. A 10Ω resistor
and a 1000µF capacitor decouple the
power supply line and reduce the
level of hum.
Construction
The prototype Adjustable CW Filter was housed in a standard metal
case measuring 102mm wide, 62mm
high and 148mm deep. The parts are
mounted on a PC board measuring 97
x 68mm and coded 06112961. The
PC component overlay and wiring
diagram is shown in Fig.4.
Start construction by assembling the
Fig.4: the PC component overlay and wiring diagram for the CW filter.
Check your work carefully before applying power.
PC board. Inspect the board for shorts
between tracks and correct hole sizes.
The holes for the trimpots, PC pins
and diodes may need enlarging. Use
the component overlay as a guide and
solder in the resistors, trimpots and
diodes first.
In some cases, a low impedance
termination will be required by the
amplifier in the receiver; eg, 8Ω or
10Ω. If this is the case, an 8Ω or 10Ω
0.5W resistor can be connected across
VR1; provision has been made for this
on the PC board,
Install the PC pins next, followed by
the capacitors. Double check the polarity of the electrolytic capacitors to
make sure they are installed correctly.
Finally, solder in the three integrated
circuits, again checking that they are
in the correct positions. The parts list
details the components associated
with the bandpass filters for a centre
frequency of 800Hz. If you want to
change this, use the equations in Fig.3
to calculate the new values.
When it is complete, put the PC
board aside and mark out and drill
December 1996 27
The completed CW filter
is easy to set up and
adjust, provided you have
access to a multimeter
and an audio signal
generator. Use cable ties
to keep the wiring neat
and tidy.
the holes in the metal case. There are
three holes required on the front and
back panels and four mounting holes
in the base. Install the sockets on the
rear panel and the pots and LED on the
front panel. The LED is held in place
with a plastic bezel clip.
Mount the PC board in the case with
3mm screws and nuts and 6mm spacers. This done, connect the sockets,
pots and LED to the PC board with
hook-up wire. The prototype used
separated cores from rainbow ribbon
cable which makes the job of tracing
wires easy. If you have trouble identi
fying the tags of the DC socket, plug
the plugpack into the socket, turn on
the power and check the voltage and
polarity with a multimeter.
Finally, fit the two knobs and adjust them so that when the pointer is
vertical the pots are at mid-position.
Fig.5: actual size artwork for the PC board.
Testing
To test and adjust the filter you
should have a multimeter and an audio
generator. If you don’t have an audio
generator, try to borrow one as it makes
the setting up process easy.
Turn the filter and volume pots fully
anticlockwise and the input trimpot
VR1 and the decoder trimpot VR3
fully clockwise. Plug a speaker into the
speaker socket, connect the DC plug
pack and connect the audio generator
to the receiver socket.
Power up the CW filter and measure
the voltage between pin 6 of IC3 and
0V. If you are using a 12V plugpack
28 Silicon Chip
Fig.6: actual size artwork for the front panel.
this reading will probably be around +14V. Most plugpacks
are unregulated and only really get to their rated voltage
at full load, so don’t get too alarmed if the reading seems
high. If the reading is 0V or close to 0V, check to see if the
plugpack polarity is reversed or that diode D1 is around
the wrong way.
If these check out OK there may be a short circuit in
the PC board. Turn off the power straight away and check
the PC board for problems. There could be a component
in the wrong way, shorts between tracks or a wiring error.
If everything appears OK, set the audio generator to
800Hz (or the alternate frequency chosen for the bandpass
filters) with an output of around 100mV RMS. Adjust the
volume pot so that you can hear the tone in the speaker.
Now, using a small screwdriver, turn the decoder trimpot
VR4 until the CW LED turns on and note VR4’s position.
Keep rotating VR4 until the CW LED turns off, again noting
the position. This done, return VR4 to the midpoint between these two positions, disconnect the audio generator
and check that the CW LED turns off.
That’s all there is to setting up the CW filter. The lid can
now be fitted to the base using four self-tapping screws.
Using the filter
The CW filter is designed to sit alongside your receiver
and be permanently connected. The method of connection to the receiver will depend on the specific receiver.
Probably it will have an external speaker socket. When
using this option you will need to check that the internal
speaker is disconnected otherwise you will hear both the
unfiltered and filtered signal at the same time.
Some receivers have an output that is not directly from
the speaker but from a low level audio signal point before
the speaker. If you use this option you will need to once
again make sure the speaker in the receiver is turned off.
As mentioned previously, if the output of your receiver
overdrives the CW filter, adjust the input trimpot VR1 until
the sound from the speaker is undistorted.
If you don’t have an external speaker for your receiver,
now is the time to get one. There are commercially available speaker boxes specifically suited for this purpose or
you could buy yourself a cheap speaker and build a box
to mount it in. The cheapest solution could be to use a
small speaker box from a discarded mini stereo system.
In any event, the sound from an external speaker will
almost always be better than that obtained from the little
speakers found in most receivers.
To operate the CW filter, turn the filter control to the
wide position and adjust the volume control to suit. Tune
in a CW signal on the receiver and watch the CW LED
until it flashes in time with the bursts of tone. Turn the
filter control clockwise until the CW signal is clear of any
interference and easy to listen to.
If the interfering signal is wideband it won’t be possible
to completely filter it out as some of it will lie in the filter
passband but a significant improvement will be heard
anyway. You will be amazed how effective the CW filter
can be when listening to a noisy crowded band. A small
CW signal can sometimes hardly be heard but when the
filter control is turned to narrow, the CW signal seems to
jump out from the noise.
Of course, if the band conditions are good the filter con
SC
trol can be left in the wide position.
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.winradio.com/
December 1996 29
BOOKSHELF
Understanding & Servicing
Compact Disc Players
Understanding and
Servicing CD Players
by Ken Clements.
Published September
1994 by Newnes.
ISBN 0 7506 0934 6,
255 x 195mm, hard
covers, 202 pages.
R.R.P. $69.95.
To most of us, the compact disc
player is still a black box into which
we place our discs, press a button and
music issues forth. It is only when the
music doesn’t play that we wish we
knew more about them. This book,
written by the former technical training manager of Pioneer in the UK, will
certainly fill the gap in knowledge.
The Author begins with an introduction to the principles of CD
playback, goes on to discuss optical
assemblies and servo systems, then
analyses the various types of circuits
used to control and decode the disc
information.
Further chapters cover test modes
and adjustments, system control and
fault diagnosis. There is also one
chapter covering the similarities and
differences between domestic and car
players.
For anyone to successfully service
any electronic equipment, it is necessary to have a reasonable understanding of the theory behind that product.
To this end the Author begins in chapter 1 by giving some technical details
on the playback of compact discs.
Unlike vinyl records which rotate
30 Silicon Chip
at a constant 331/3 RPM from outside
to inside (constant angular velocity),
the CD starts playing from near the
centre at a speed of around 500 RPM
and finishes at around 200 RPM at the
edge. This is done to retain a constant
linear velocity which allows a lot more
music to be recorded on the disc.
Clements explains how the original audio is processed, with error
correction bits and synchronising
words added, before the digital data is
encoded on the disc. This description
is helpful for, if you are unaware of the
encoding process, when the decoding
processes are described, they will not
make much sense.
Chapter two gets down to the actual
details of the CD player itself. The
optical assembly, which recovers the
data from the disc, is obviously one
of the most important assemblies in
the unit. Being a mechanical system
which has to track the data across the
disc, it can be expected to be one of
the more troublesome areas as well.
Once the information is recovered
from the disc it is fed to an RF amplifier to increase the signal level. This
high level signal is then fed to a focus
servo, a tracking servo and a decoder
to recover the audio.
The optical system needs to be
focused precisely on the compact
disc pits to ensure that the recovered
information is as accurate as possible.
As well as focusing, the optics need
to move from centre to edge, to track
the “groove” as the disc rotates. These
functions are carried out by servo amplifiers and servo motors.
Chapter 3 covers the various types
of optical assemblies. These can be a
single beam device with radial tracking, or single or 3-beam devices with
linear/straight line tracking. Philips
CD players are typical of those using
the first system. The second type is
found in Technics models, although
Pioneer used this system in its early
car players. The 3-beam system is used
by Akai, JVC and Kenwood among
others.
The chapter explains how 4-diode
and 6-diode tracking and focus sensors
are affected by misalignment between
the laser and the disc. It also describes
the various methods used to drive the
tracking amplifier.
Chapter 4 delves into the servo systems used to keep the beam in focus
on the disc and to drive the optical
system across the disc. The tracking
servo drives a tracking coil (similar
to a tiny loudspeaker), which has a
range of around 2mm, as well as the
tracking servo motor. This lets small
adjustments to the tracking be carried
out by the coil and the larger movements by the motor.
The spindle motor, which spins the
disc at a continuously varying speed,
is controlled by another servo which
compares the motor speed with the
reference sync frequency of 7.35kHz
from the disc. The spindle speed does
not have to be stable; in fact it can be
varied up and down to ensure that
the data read from the disc does not
overflow the digital storage area.
The virtually immeasurable wow
and flutter of CD players is obtained
by clocking the data out of the storage
area under crystal oscillator control,
the stability of a crystal oscillator being
typically a few parts per million.
Early players used a large range of
discrete components, which made
them expensive to build. The latest
units use just a few large scale integrated (LSI) circuits specifically designed
for the task.
The fifth chapter describes the
operation of some of these integrated
circuits and lists the part numbers of
those used for the RF processing, servo
operation and decoding. Most players
use a selection of either Philips or
Sony chips.
The 36 pages of this chapter discuss,
using block diagrams, the following
circuits; focus error, focus OK, EFM
comparator, disc defect, radial error
processor, spindle, VCO and data
decoders.
We now come to the chapter which
tells us how to locate and (hopefully)
repair faults. The main instruments
needed, apart from a few basic tools,
are a multimeter and an oscilloscope.
Some players such as the Philips and
Pioneer have a built-in service mode
whereby you can test functions like the
focus and tracking. This mode is enabled by holding down a combination
of front panel buttons before turning
on the mains power.
Naturally, someone unfamiliar with
CD players should not attempt any
repairs without the service manual,
as “twiddling” adjustments without
fully understanding the outcome can
only cause further problems.
For optical alignment a suitable
test disc is really necessary. These are
made by various companies including
Philips, Sony and Technics. As many
of the circuits in a CD player are DC
(direct coupled), it is necessary to
ensure that all oscilloscope measurements are made with the input coupling set to DC and preferably using
a 10:1 probe.
Many service people are used to
leaving the input coupling on AC.
With AC coupling any DC offset adjustments to the player may appear
to work, as the trace will move up or
down, but eventually it will return to
the original position, probably causing
a search for a non-existent fault.
The Author recommends that electrical adjustments be carried out in the
following order: focus offset, tracking
offset, RF offset, laser power, tracking
balance, focus balance, focus bias,
photodiode balance, RF level, focus
gain, tracking gain and VCO frequency.
If mechanical adjustments are need
ed, the recommended sequence is as
follows: turntable height, tangential
adjustment, lateral adjustment and
diffraction grating adjustment. This
chapter covers both the electrical and
mechanical procedures for a variety of
different brands of players.
The next chapter briefly covers
system control, which is the interface
between the buttons on the front panel
or remote control and the electronics,
usually via a microprocessor.
Chapter 8 is a summary of car
CD players with emphasis on the
multi-disc variety and their start-up
procedures, as well as the differing
power supply requirements of car
systems, which must operate from a
12V battery.
The final chapter, titled fault diagnosis, contains a number of block diagrams which give a step-by-step guide
to checking the various functions in a
logical sequence, with advice on the
adjustment to be made if the test fails.
Obviously, the initial checks should be
for cleanliness of the lens system and
correct operating voltages.
The 28 pages of this chapter cover tests on a number of proprietary
players as well as general tests. It
also shows a number of typical oscilloscope waveforms to be expected at
various points in the circuits.
I believe this is an ideal book for
any person who is not already into
CD service and is thinking of doing
so, or for the inquiring mind that likes
to keep up with the theory and operation of modern electronic equipment.
However, it was published in 1994
and while the principles remain the
same, most current CD players will
probably not use the ICs referred to
in the text.
Our copy was supplied by Butter
worth-Heinemann, West Chatswood,
SC
NSW. (R.J.W.)
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December 1996 31
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
dicksmith.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
dicksmith.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
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dicksmith.com.au
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
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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.
Overload protected
power supply
Many regulated power supplies
make use of LM78xx or LM317 series
devices which are cheap and perform
well. These ICs are protected from
overloading but under short circuit
conditions they allow a small yet
significant current to flow. This can
be enough to damage the device connected to the power supply.
By contrast, this circuit employs
a series transistor to shut off current
when an overload condition occurs.
Power is not restored until a reset
button is pressed.
The circuit consists of three func36 Silicon Chip
tional blocks: current sensing circuits
based on Q1 & Q2, a bistable protection
circuit (Q3 & Q4), and positive and
negative 3-terminal regulators (REG1
& REG2). Q1 turns on when a current
of more than 1A flows through current
sensing resistor R1.
The RC network at the base of Q1
provides filtering to prevent transients from triggering the protection
circuit. When an overload does occur, the bistable protection circuit is
triggered and Q4 turns on. A 2N3904
was chosen here due to its low VCES
of about 0.2V.
When Q4’s collector goes low, Q5 &
Q6 are turned off, as are Q7, Q8 & Q9;
ie, both supply rails shut down.
Similarly, R2 and Q2 provide current sensing for the negative supply
rail and they turn Q3 off in the bistable
protection circuit when an overload
occurs. This then turns Q4 on and so
Q5, Q6, Q7, Q8 & Q9 off to shut down
the supply rails, as before. Switch S2
is used to reset the bistable protection
circuit after the cause of the overload
has been removed.
The regulator section uses LM317
and LM337 adjustable regulators, with
a 2-pole, 6-position switch providing
output voltages of 3, 5, 6, 9, 12 and
15V. Note that both regulators should
be mounted on a heatsink.
B. Low,
Gwynneville, NSW. ($35)
Adding 1/4 stops to
the Phototimer
The Phototimer published in
the April 1995 issue provides a
range of exposure times with the
individual range steps increasing
by a factor of 1.414; ie, the square
root of 2. Thus, each switched
increase in exposure is equivalent
to opening the enlarger aperture
by a half-stop.
However, one of our readers
has pointed out that this ratio between switch steps is still a little
too coarse for photographic work
and that an ability to provide for
quarter stops would be better. Ac-
cordingly, this circuit modification
involving an extra switch (S3)
provides that facility. In the upper
setting, S3 provides an exposure
increase equivalent to a quarter
stop while the lower setting provides a quarter stop decrease in
exposure time.
S3 and the associated two resistors act to shift the threshold
voltage at pin 5 by approximately
+1.2:1 and -0.85:1; ie, roughly
quarter stop ratios. The precise
factors are 1.189 and 0.84. S3 is a
centre-off switch.
SILICON CHIP
VCO has constant
mark/space ratio
The standard 555 astable circuit
can be made into a VCO by varying
the capacitor charging voltage. However, the discharge period is fixed by
the resistor between the discharge
and threshold pins (2 & 6), limiting
the range of frequencies available. In
addition, the charge time must always
be greater than the discharge time,
limiting further the range available.
In this circuit, the capacitor discharge time of IC1 is controlled by op
amp IC2. The DC voltage at pin 3 of IC1
is compared to a reference and the op
amp adjusts its output to maintain a
constant mark-space ratio. This gives
a much greater range of control and,
as a bonus, a greater control range of
the mark space ratio if desired.
The circuit operates as follows.
When charging the capaci
t or the
output is high and Q1 is off, so that
the charge period is determined by
R1/C1. When the capacitor reaches
2/3Vcc, the output switches low, Q1
turns on and the capacitor is discharged by the op amp until 1/3Vcc
is reached and pin 3 of IC1 switches
high.
R3 and C3 average the output to provide the mark-space ratio feedback for
the op amp (IC2). The time constant
of this network should be at least 100
times the period of one output cycle
at the lowest frequency of operation.
This time constant determines the
settling time for the output after a
control input change. A voltage reference for the op amp is provided by
voltage divider R5 & R6; equal values
provide an output mark-space ratio of
about 50%.
By running the 555 from a split
supply the circuit can be used to drive
a transformer directly to ground. In
this case, if the op amp reference is
connected to ground, no DC will flow
through the transformer primary.
D. Timmins,
St Peters, NSW. ($35)
Especially For Model
Railway Enthusiasts
THE PROJECTS: LED Flasher; Railpower Walkaround Throttle; SteamSound Simulator;
Diesel Sound Generator; Fluorescent Light Simulator; IR Remote Controlled Throttle;
Track Tester; Single Chip Sound Recorder; Three Simple Projects (Train Controller,
Traffic Lights Simulator & Points Controller); Level Crossing Detector; Sound & Lights
For Level Crossings; Diesel Sound Simulator.
PRICE: $7.95 (plus $3 for postage). 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.
December 1996 37
Fast clocks running at six to eight times
actual speed are desirable for model
railways which run a 24-hour schedule in
a compressed time of three to four hours.
A fast clock for
railway modellers
Are you a keen railway modeller? Do you run
your trains to a schedule? If so, you will want to
build this fast clock which can be set to run at
between 4.5 and 8.5 times faster than normal.
By LEO SIMPSON
Why would anyone ever want a
fast clock? Surely time passes rapidly
enough as it is, except, of course, in
the afternoons at school or work. But
there is a sound reason and it has to
do with running trains to a schedule
on a model railway layout.
Because model railway layouts are
always much smaller with respect to
scale than the real thing, the times
taken to run a train from one point
to another are ridiculously small, in
real time.
38 Silicon Chip
For example, while the distances
on real railways can be hundreds of
kilometres and the trains can take
many hours or even days to get to their
destination, a typical large model railway would be unlikely to have more
than 50 metres of track. For HO scale
(1:87), this equates to 4.3 scale kilometres; for N scale (1:160) it equates
to 8 scale kilometres. Even on these
large layouts, the time for a train to
make several circuits will be measured
in minutes rather than hours.
So to inject a little more realism
into a model railway train schedule, it
makes sense to use a “fast clock”. But
there is another more practical reason
which has nothing to do with scale
factors and this has more to do with the
number of spare hours in an evening.
Typically, a model railway club will
have a running session which lasts
around three hours in an evening but
a “realistic” operating session should
last at least one day, or 24 hours.
So the club needs to squeeze 24
hours of operation into a real time
of three hours or so. The reason for
the fast clock now becomes clear – it
needs to run about 6 to 8 times faster
than normal.
The question is, how do you make
a clock run this fast? Our approach
was to take a typical crystal controlled
clock movement which is more or less
Fig.1: this is a typical circuit for
a 1.5V crystal controlled clock
movement. It uses a 32kHz crystal
and drives the clock stepper motor
coil with pulses at 1-second intervals.
typical in zillions of battery operated
clocks. Fig.1 shows a typical circuit
using a Samsung chip. It uses a single
CMOS IC operating from a 1.5V AA
cell and controlled by a 32kHz crystal.
The IC has an internal divider chain
which produces complementary pulses to drive a stepping motor.
Fig.2 shows the oscilloscope waveforms from the clock movement used
in this article. As can be seen, there
are two pulse trains, each with pulses
about 30ms long and exactly two seconds apart. The pulse trains are staggered by one second. What actually
happens is that the IC applies a pulse
to the clock coil (the stepper motor)
in one direction and then one second
later, applies the same pulse in the
opposite direction. This operates the
escapement which makes the ticking
sound and drives the clock hands.
Our first approach was to see if we
could make the chip operate six to
eight times faster than normal. The
simplest way to do this would be to
Fig.2: this digital oscilloscope printout shows the waveforms from the
circuit of Fig.1. In effect, there are two pulse trains with pulses two
seconds apart. A pulse is applied to the coil in direction (upper trace)
and then a pulse in the opposite direction is applied to the coil (lower
trace). The oscilloscope timebase for these waveforms is 500ms/div; the
printout is five seconds long!
replace the 32kHz crystal with one
of 192kHz but such crystals are not
readily available. Hence, we decided
to remove the 32kHz crystal and to
drive one of the oscillator pins of the
chip with an external oscillator based
on a 7555 CMOS timer.
The first hurdle with this approach
is that a 7555 will not operate at 1.5V.
It will operate with a 3V supply so we
cobbled together a suitable circuit with
a voltage divider at the output, to make
the signal compatible with the 1.5V
clock chip. Fig.3 shows this approach.
Did it work? Well, yes and no. It
would work up to about 100kHz or
so but higher than that and the clock
mechanism itself refused to work. The
reason appears to be the length of the
Fig.3: our first attempt at a speed-up circuit involved using a 7555 CMOS chip
driving one of the crystal input pins on the clock chip. The circuit conked out if
we attempted a speed-up of more than four times.
pulses applied to the clock stepper
motor.
In the standard clock, the pulses
are typically 30ms or 46ms long and
their length is a fixed relationship to
the 32kHz crystal. At an oscillator
frequency of, say, 128kHz, the clock
pulses would only be one quarter as
long (ie, 7.5 or 11.5ms) and this appears to be insufficient to operate the
motor reliably. We tried a number of
circuit variations, such as operating
the clock chip from 3V which is in
excess of the ratings but it still did
not work.
Final circuit
The next approach was to scrap the
crystal controlled circuit and develop
a new circuit to drive the clock stepper
motor directly. This is shown in Fig.4.
Again it is based on a 7555 CMOS
timer, IC1.
This operates at a frequency of
between 4.5Hz and 8.5Hz, as set by
the components at pins 2, 6 & 7. The
fre
quency is adjustable by trimpot
VR1. The output of IC1 can be varied
between 4.5Hz and 8.5Hz and thus the
speed-up factor can be varied between
4.5 and 8.5 times by trimpot VR1.
The output from pin 3 is inverted
and buffered by NAND gate IC2a and
then applied to IC3, a 74HC76 flipflop.
This divides the output by two and
produces complementary outputs at
pins 14 and 15. These are gated toDecember 1996 39
PARTS LIST
1 1.5V crystal controlled clock
movement
1 PC board, code 09112961, 67
x 38mm
2 1.5V AA cells
1 double-AA cell holder and
battery snap connector
1 1MΩ trimpot (VR1)
Fig.4: our final circuit for the Fast Clock Driver uses three ICs: a 7555 CMOS
timer, a 74HC76 flipflop and a 74HC00 NAND gate chip. The circuit drives the
clock coil directly, dispensing with the internal clock circuitry.
gether with the pulses from pin 11 of
IC2a to provide complementary pulses
from pins 3 & 6 and of IC2. Fig.5 &
Fig.6 shows the output waveforms at
two different clock speeds, six times
and eight times.
Fig.5 shows the waveforms when
the clock is operating at six times
normal speed while Fig.6 shows
it operating at eight times normal
speed. Considering Fig.5, the upper
trace (Ch1) is the waveform at pin 3
of IC2b while the lower trace (Ch2) is
the waveform at pin 6 of IC2c.
In effect, while the period of both
waveforms in Fig.5 is 333ms, the clock
coil receives stepping pulses 166.5ms
apart which is six times faster than
the normal stepping rate of one per
second. A similar situation applies
in Fig.6 except that the period of both
waveforms is 250ms and the speed-up
is eight times.
Notice that the pulse width applied
to the motor is between 15 and 16ms
which is half that applied to the clock
in normal operation and as shown in
Fig.2. There are two reasons for this.
First, the clock motor itself is designed
to run from a circuit powered with a
1.5V cell whereas our circuit uses 3V.
We have used 3V because the CMOS
chips specified will not run reliably
below 2V.
This means that the pulses delivered from the modified circuit were
twice the voltage they should be.
Paradoxically, because the clock coil
was being driven so hard, its operation became unreliable at the higher
speeds. We could correct that problem
by inserting a 330Ω resistor in series
with the clock coil but then the effective battery life would be reduced;
as the battery voltage dropped, the
pulse drive was unduly reduced by
the series resistor.
Our final version, presented in Fig.4,
Fig.5: waveforms from the circuit of Fig.4, taken at pins
3 & 6 of IC2. The speed-up factor is six times. The oscillo
scope timebase is 50ms/div.
40 Silicon Chip
Semiconductors
1 7555, LMC555 CMOS timer
(IC1)
1 74HC00 quad 2-input NAND
gate (IC2)
1 74HC76 dual JK flipflop (IC3)
Capacitors
1 100µF 16VW electrolytic
capacitor
3 0.1µF MKT polyester
1 .01µF MKT polyester
Resistors (0.25W, 1%)
1 820kΩ 0.25W resistor
1 150kΩ 0.25W resistor
compensates for the higher pulse amplitude by halving the pulse width and
eliminating the series 330Ω resistor.
This has the benefit of allowing the
circuit to work reliably down to below
2V which means that the batteries last
longer.
PC board
We designed a small PC board to
take the circuit of Fig.4. It measures
67 x 38mm and is coded 09112961. Its
component layout is shown in Fig.7.
Fig.6: waveforms from the circuit of Fig.4, taken at pins 3
& 6 of IC2. The speed-up factor is eight times. The oscillo
scope timebase is 50ms/div.
Left: when you pull the back off the clock movement, it will
look like this. Be careful not to scatter the parts. If you lift off
the two top gears, you will be able to remove the PC board and
coil assembly. The photo above shows how we made two cuts
to the PC tracks and then connected two fine gauge enamelled
copper wires direct to the clock coil terminals.
Fig.7: follow this parts layout to build the
Fast Clock Driver circuit of Fig.4.
When assembling it, make sure that
all three ICs are correctly oriented and
that the 100µF electrolytic capacitor is
correctly polarised.
You will need four PC stakes, two
for the battery connections and two for
the clock coil connections.
Assembling the PC board and get-
Fig.8: this is the actual size artwork for the
PC board. Check your board carefully before
installing any of the parts.
ting it going is the easy part. Pulling
the clock apart and making the connections to the clock coil are a little
trickier but it just takes a little care.
Essentially what must be done is to
remove the hands and time-setting
knob, undo one screw and unclip the
clock case. Then, while the clock is
This photo shows
the assembled Fast
Clock Driver. Two
wires connect it to
the clock movement.
face down, lift out two gears and then
the internal PC board.
In practice, you will find that the
PC board actually supports the coil so
it cannot be removed and discarded.
Instead, you must cut the PC tracks
where they connect to the coil. Then
you need two fine wire connections
to the coil which can be brought out
through the side of the clock case. You
can then reassemble the clock and
connect it to the new driver board.
When power is applied the clock
should immediately start running
and the speed-up factor should be
variable between about four and nine
times, depending on the setting of
trimpot VR1.
We suggest that you leave the
second-hand off the clock; it will go
around so fast that the effect will be
SC
ludicrous.
December 1996 41
Silicon Chip
Back Issues
September 1988: Hands-Free Speakerphone; Electronic Fish
Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build
The Vader Voice.
April 1989: Auxiliary Brake Light Flasher; What You Need to
Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; The
Story Of Amtrak Passenger Services.
May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor
For Your PC; Simple Stub Filter For Suppressing TV Interference;
The Burlington Northern Railroad.
July 1989: Exhaust Gas Monitor; Experimental Mains Hum
Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class
Electrics.
September 1989: 2-Chip Portable AM Stereo Radio (Uses
MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector;
Studio Series 20-Band Stereo Equaliser, Pt.2.
October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet
Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio,
Pt.2; A Look At Australian Monorails.
November 1989: Radfax Decoder For Your PC (Displays Fax,
RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip
Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats &
Options; The Pilbara Iron Ore Railways.
December 1989: Digital Voice Board; UHF Remote Switch;
Balanced Input & Output Stages; Operating an R/C transmitter;
Index to Volume 2.
January 1990: High Quality Sine/Square Oscillator; Service
Tips For Your VCR; Phone Patch For Radio Amateurs; Active
Antenna Kit; Designing UHF Transmitter Stages; A Look At
Very Fast Trains.
9V DC Converter; Introduction To Digital Electronics; Build A
Simple 6-Metre Amateur Band Transmitter.
December 1990: The CD Green Pen Controversy; 100W DC-DC
Converter For Car Amplifiers; Wiper Pulser For Rear Windows;
4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre
Amateur Transmitter; Index To Volume 3.
January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun
With The Fruit Machine; Two-Tone Alarm Module; LCD Readout
For The Capacitance Meter; How Quartz Crystals Work; The
Dangers of Servicing Microwave Ovens.
February 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.
February 1991: Synthesised Stereo AM Tuner, Pt.1; Three
Inverters For Fluorescent Lights; Low-Cost Sinewave Oscillator;
Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier
Output Stages.
March 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.
March 1991: Remote Controller For Garage Doors, Pt.1;
Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner,
Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal
Wideband RF Preamplifier For Amateur Radio & TV.
April 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.
April 1991: Steam Sound Simulator For Model Railroads; Remote
Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser;
Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To
Amplifier Design, Pt.2.
June 1990: Multi-Sector Home Burglar Alarm; Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies;
Speed Alarm For Your Car; Fitting A Fax Card To A Computer.
July 1990: Digital Sine/Square Generator, Pt.1 (Covers
0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple
Electronic Die; Low-Cost Dual Power Supply; Inside A Coal
Burning Power Station.
August 1990: High Stability UHF Remote Transmitter; Universal
Safety Timer For Mains Appliances (9 Minutes); Horace The
Electronic Cricket; Digital Sine/Square Generator, Pt.2.
September 1990: Low-Cost 3-Digit Counter Module; Simple
Shortwave Converter For The 2-Metre Band; the Bose Lifestyle
Music System.
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: How To Connect Two TV Sets To One VCR;
Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To
May 1991: 13.5V 25A Power Supply For Transceivers; Stereo
Audio Expander; Fluorescent Light Simulator For Model Railways;
How To Install Multiple TV Outlets, Pt.1.
June 1991: A Corner Reflector Antenna For UHF TV; 4-Channel
Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers,
Pt.2; Active Filter For CW Reception; Tuning In To Satellite TV.
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; The Snowy Mountains
Hydro Scheme.
August 1991: Build A Digital Tachometer; Masthead Amplifier
For TV & FM; PC Voice Recorder; Tuning In To Satellite TV, Pt.3;
Step-By-Step Vintage Radio Repairs.
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.
October 1991: Build A Talking Voltmeter For Your PC, Pt.1;
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42 Silicon Chip
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Detach and mail to:
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Or call (02) 9979 5644 & quote your credit card
details or fax the details to (02) 9979 6503.
✂
v
SteamSound Simulator Mk.II; Magnetic Field Strength Meter;
Digital Altimeter For Gliders, Pt.2; Military Applications Of
R/C Aircraft.
December 1993: Remote Controller For Garage Doors; LED
Stroboscope; 25W Amplifier Module; 1-Chip Melody Generator;
Engine Management, Pt.3; Index To Volume 6.
July 1995: Electric Fence Controller; How To Run Two Trains
On A Single Track (Incl. Lights & Sound); Setting Up A Satellite
TV Ground Station; Door Minder; Adding RAM To A Computer.
November 1991: Build A Colour TV Pattern Generator, Pt.1;
Junkbox 2-valve receiver; Flashing Alarm Light For Cars;
Digital Altimeter For Gliders, Pt.3; A Talking Voltmeter For
Your PC, Pt.2.
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.
August 1995: Fuel Injector Monitor For Cars; Gain Controlled
Microphone Preamp; Audio Lab PC Controlled Test Instrument,
Pt.1; Mighty-Mite Powered Loudspeaker; How To Identify IDE
Hard Disc Drive Parameters.
December 1991: TV Transmitter For VCRs With UHF Modulators;
Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2;
Index To Volume 4.
February 1994: 90-Second Message Recorder; 12-240VAC
200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power
Supply; Engine Management, Pt.5; Airbags - How They Work.
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 1994: Intelligent IR Remote Controller; 50W (LM3876)
Audio Amplifier Module; Level Crossing Detector For Model
Railways; Voice Activated Switch For FM Microphones; Simple
LED Chaser; Engine Management, Pt.6.
September 1995: Keypad Combination Lock; The Incredible
Vader Voice; Railpower Mk.2 Walkaround Throttle For Model
Railways, Pt.1; Jacob’s Ladder Display; The Audio Lab PC
Controlled Test Instrument, Pt.2.
March 1992: TV Transmitter For VHF VCRs; Thermostatic
Switch For Car Radiator Fans; Telephone Call Timer; Coping
With Damaged Computer Directories; Valve Substitution In
Vintage Radios.
April 1992: IR Remote Control For Model Railroads; Differential
Input Buffer For CROs; Understanding Computer Memory;
Aligning Vintage Radio Receivers, Pt.1.
May 1992: Build A Telephone Intercom; Electronic Doorbell;
Battery Eliminator For Personal Players; Infrared Remote
Control For Model Railroads, Pt.2; Aligning Vintage Radio
Receivers, Pt.2.
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.
July 1992: Build A Nicad Battery Discharger; 8-Station Automatic
Sprinkler Timer; Portable 12V SLA Battery Charger; Multi-Station
Headset Intercom, Pt.2.
August 1992: An Automatic SLA Battery Charger; Miniature 1.5V
To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers;
Troubleshooting Vintage Radio Receivers; MIDI Explained.
October 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal
Stereos; A Regulated Lead-Acid Battery Charger.
January 1993: Flea-Power AM Radio Transmitter; High Intensity
LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sinewave
Inverter, Pt.4; Speed Controller For Electric Models, Pt.3.
February 1993: Three Projects For Model Railroads; Low
Fuel Indicator For Cars; Audio Level/VU Meter (LED Readout);
An Electronic Cockroach; 2kW 24VDC To 240VAC Sinewave
Inverter, Pt.5.
March 1993: Solar Charger For 12V Batteries; Alarm-Triggered
Security Camera; Reaction Trainer; Audio Mixer for Camcorders;
A 24-Hour Sidereal Clock For Astronomers.
April 1993: Solar-Powered Electric Fence; Audio Power Meter;
Three-Function Home Weather Station; 12VDC To 70VDC
Converter; Digital Clock With Battery Back-Up.
May 1993: Nicad Cell Discharger; Build The Woofer Stopper;
Alphanumeric LCD Demonstration Board; The Microsoft Windows Sound System; The Story of Aluminium.
June 1993: AM Radio Trainer, Pt.1; Remote Control For The
Woofer Stopper; Digital Voltmeter For Cars; 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.
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; A +5V to ±15V DC Converter; Remote-Controlled Cockroach.
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; Passive Rebroadcasting For TV Signals.
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; Portable 6V SLA Battery Charger; Electronic Engine
Management, Pt.10.
August 1994: High-Power Dimmer For Incandescent Lights;
Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner
For FM Microphones, Pt.1; Build a Nicad Zapper; 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: Dolby Surround Sound - How It Works; Dual Rail
Variable Power Supply; Talking Headlight Reminder; Electronic
Ballast For Fluorescent Lights; Temperature Controlled Soldering
Station; 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); Anti-Lock Braking Systems;
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; Cruise
Control - How It Works; Remote Control System for Models,
Pt.1; Index to Vol.7.
January 1995: Sun Tracker For Solar Panels; Battery Saver For
Torches; Dolby Pro-Logic Surround Sound Decoder, Pt.2; Dual
Channel UHF Remote Control; Stereo Microphone Preamplifier;The Latest Trends In Car Sound; Pt.1.
February 1995: 50-Watt/Channel Stereo Amplifier Module;
Digital Effects Unit For Musicians; 6-Channel Thermometer With
LCD Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil
Change Timer For Cars; The Latest Trends In Car Sound; Pt.2;
Remote Control System For Models, Pt.2.
March 1995: 50W/Channel Stereo Amplifier, Pt.1; Subcarrier Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers,
Pt.2; IR Illuminator For CCD Cameras; Remote Control System
For Models, Pt.3; Simple CW Filter.
April 1995: Build An FM Radio Trainer, Pt.1; A Photographic
Timer For Darkrooms; Balanced Microphone Preamplifier &
Line Filter; 50-Watt Per Channel Stereo Amplifier, Pt.2; Wide
Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder
For Radio Remote Control.
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.
May 1995: What To Do When the Battery On Your PC’s Mother
board Goes Flat; Build A Guitar Headphone Amplifier; FM Radio
Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; 16-Channel
Decoder For Radio Remote Control; Introduction to Satellite TV.
November 1993: Jumbo Digital Clock; 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.
June 1995: Build A Satellite TV Receiver; Train Detector For
Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video
Security System; Multi-Channel Radio Control Transmitter For
Models, Pt.1; Build A $30 Digital Multimeter.
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
Transverter 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.
February 1996: Three Remote Controls To Build; Woofer Stopper
Mk.2; 10-Minute Kill Switch For Smoke Detectors; Basic Logic
Trainer; Surround Sound Mixer & Decoder, Pt.2; Use your PC
As A Reaction Timer.
March 1996: Programmable Electronic Ignition System; Zener
Tester For DMMs; Automatic Level Control For PA Systems;
20ms Delay For Surround Sound Decoders; Multi-Channel Radio
Control Transmitter; Pt.2; Cathode Ray Oscilloscopes, Pt.1.
April 1996: Cheap Battery Refills For Mobile Telephones; 125W
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; Duplex Intercom Using Fibre Optic Cable; Cathode Ray Oscilloscopes, Pt.3.
June 1996: BassBox CAD Loudspeaker Software Reviewed;
Stereo Simulator (uses delay chip); Rope Light Chaser; Low
Ohms Tester For Your DMM; Automatic 10A Battery Charger.
July 1996: Installing a Dual Boot Windows System On Your PC;
Build A VGA Digital Oscilloscope, Pt.1; Remote Control Extender
For VCRs; 2A SLA Battery Charger; 3-Band Parametric Equaliser;
Single Channel 8-bit Data Logger.
August 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;
September 1996: Making Prototype Parts By Laser; VGA Oscilloscope, Pt.3; Infrared Stereo Headphone Link, Pt.1; High Quality
PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Feedback
On Programmable Ignition (see March 1996).
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; Infrared Stereo Headphone Link, Pt.2;
Build A Multi-Media Sound System, Pt.1; Multi-Channel Radio
Control Transmitter, Pt.8.
November 1996: Adding An Extra 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.
PLEASE NOTE: November 1987 to August 1988, October 1988
to March 1989, June 1989, August 1989, May 1990, February
1992, September 1992, November 1992 and December 1992 are
now sold out. All other issues are presently in stock. For readers
wanting articles from sold-out issues, we can supply photostat
copies (or tear sheets) at $7.00 per article (includes p&p). When
supplying photostat articles or back copies, we automatically
supply any relevant notes & errata at no extra charge. A complete
index to all articles published to date is available on floppy disc
at $10 including packing & postage.
December 1996 43
SERVICEMAN'S LOG
There’s a long, long trail a’winding
Well, in the words of the popular song, that’s
what it seemed like; a long, long trail through
circuits and PC boards in search of the most
elusive combination of intermittent faults that has
been my misfortune to encounter for many years.
It is a story about an Akai video
cassette recorder, model VS-35 and
the problem was an intermittent sound
fault. Not just any intermittent sound
fault, mind you. This was an intermittent sound fault the like of which
I have never seen before – and I hope
I never see again.
The machine came to me from a
colleague, who felt that he could no
longer cope with the problem. And
so it landed on my bench along with
a “best of British luck” attitude.
While there was some history of the
problem, I suspected that there
had been more than one finger in the
pie before it reached me.
Anyway, I was saddled with it. The
gist of the problem was faulty sound
on playback although, as far as I could
determine, the sound always recorded
normally. To test this theory, my first
step was as to make a test recording
on the machine immediately after
observing the sound problem. This
tape subsequently played perfectly
on another machine, which seemed
to clarify this point.
But putting such doubts aside, the
extent and nature of the faulty sound
was the real problem. Sometimes, at
switch on, the sound would be perfect for a few minutes, then become
intermittent. And when it went intermittent, the whole machine became
mechanically sensitive; the lightest
tap anywhere could turn the sound
on or off, as the case may be.
Initially, I couldn’t believe what I
was observing. It seemed impossible
that there would not be some variation
in sensitivity which, in turn, would
give a clue as to the general location
of the fault. But no; touching anything
– boards, leads, the deck itself – produced an equal response.
Making a start
The setup consists of a large mother
board, a small chroma board, a power
supply board and a preamp
lifier/
audio board. Initially, to the extent
that there was any particular sensitivity anywhere, I sensed that the
area around the preamplifier/audio
board might be marginally more sensitive. I even reached the stage where
I could achieve a response by flexing
or tapping the board, without it being
supported in any way but simply connected by the various leads.
I was convinced that this was where
the trouble lay. And I wasn’t particularly impressed by the soldering on
the underside. There had been some
work done on it but there was still a
large number of original joints which
were, at least, suspect.
I set to and checked every suspicious joint and remade anything which
looked even remotely suspect. I spent
a lot of time on it and by the time I
had finished was prepared to bet my
reputation on it.
Initially, it appeared that the fault
44 Silicon Chip
had been cured. But not for long. After
a few minutes it was back just as it was
before. Well, not quite; the equipment
as a whole seemed just as sensitive as
before but it now appeared that the
area of sensitivity had moved to the
motherboard. To the extent, that is,
that I could be sure of anything.
But if it was on the motherboard
the implication was that I was chasing
two faults; one which I might have
found on the preamplifier board and
one still to be found. So was it a case
of two faults producing essentially
identical symptoms? It seemed like an
impossible long shot but I was ready
to believe anything.
Assuming that there had been a fault
in the preamplifier board, and that it
had been fixed, the next logical step
was to investigate the motherboard.
Parts of the underside of this had
also obviously been worked on, while
other untouched areas needed closer
scrutiny.
The upshot of this was a major
overhaul of this board. Any suspect
connection, whether it had already
been reworked or not, was tackled. It
was a long process but when I finished
I felt reasonably confident that I had
done a thorough job.
And so it seemed. When I replaced
the board and set everything working
the machine came good. There was
no sign of the sound fault and the
machine was seemingly immune from
its previous mechanical sensitivity. I
let it run for about half an hour or so,
giving it an occasional prod or bash,
and all seemed well.
Or at least it was until I put
everything back into place and prepared to fit the cover. Then it was back
into fault condition, exactly as it was
before. I won’t bore the reader with all
the emotions and rude words which
resulted from that discovery. Suffice it
to say that it was back to taws.
The methodical approach
By now it appeared that the mass
soldering approach had served its
purpose. If it had done any good at all,
it wasn’t good enough. What was now
needed was a methodical approach.
A major problem here is how best to
convey all the circuit ramifications to
the reader. We are talking about several A3 sheets, covering both circuit
and PC board patterns. Obviously,
reproducing these is out of the question and the best I can do is present a
Fig.1: part of the audio preamplifier board in the Akai VS-35. Audio from
the A/C head (top, right) goes to pins 3, 4 & 5 of IC700, comes out on pin
16, and then goes to the motherboard via pin 12 of connector WF10.
word picture which I hope will help
the reader follow the story.
First, it is it necessary to visualise
the audio signal paths where a fault
is likely to be. And there are, initially, two sources of audio signal. One
comes from the audio track on the tape,
feeding the Audio/Control (A/C) head
on the deck. These signals are fed to
the preamplifier board, on pins 3, 4 &
5 of IC700, come out on pin 16, and
go to the motherboard via pin 12 of
connectors WF10 (“A.OUT”).
The other source comes from the
tuner and the IF system on the motherboard, which demodulates the sound
IF and delivers an audio signal. These
signals involve a longer path but
eventually find their way back to the
preamplifier board, where the two audio signals are combined into a single
audio path which then reappears on
the motherboard.
This path eventually goes to the
modulator but, on the way, connects to
an RCA socket, designated as A.OUT,
December 1996 45
Serviceman’s Log – continued
on the rear of the chassis. This provides a convenient audio check point
and the first thing I did was to organise
an external amplifier to monitor the
audio at this point, which is close to
the end of the combined audio line.
At the same time I arranged things so
that the output from the VCR was fed
into a TV set.
This simple test confirmed that the
fault was present at both the RCA
A.OUT socket and the TV set.
At this point I had to choose between
the two audio paths. I was convinced
that, whatever I did, it would be wrong
(Murphy would see to that) but I had
to start somewhere. So, for better or
for worse, I elected to check the line
coming from the IF system.
The signal from the tuner is pro-
cessed to IF level, designated on the
circuit as VIF, and applied to pins 4
& 5 of IC1 (M51496P) – see Fig.2. The
audio signal then comes out on pin
11 of IC1, which was where I started
tracing the signal.
For this purpose, I used a simple
audio probe which I have mentioned
in previous notes. This confirmed
that the signal was intact out of the IF
system at pin 11 of IC1, even though
the fault was evident at both the TV
monitor and the A.OUT socket. Well,
that was a good start.
From here, via a long path on the
circuit, I traced the audio signal to pin
5 of IC201 and then out again on pin
4. It then went to the base of transistor
TR213, the signal from the emitter then
going to line “SELECT.A” and thence
to pin 11 of a 12-pin connector WF10.
And the audio signal was still fault free
at this point.
Now, from pin 11 of connector
WF10 on the motherboard, the circuit
goes to a similar WF10 connector on
the preamplifier board, then into pin
13 of IC700 and out on pin 16.
And, as mentioned earlier, the audio
signal from the A/C head on the deck
also appears at pin 16. In short, the two
signals are combined at this point and
the combined signal goes to pin 12 of
WF10 and then back to pin 12 of WF10
on the motherboard. And I still had a
clean signal at this last point.
I was getting close now because
there was not much circuitry left between this point and the A.OUT RCA
socket where the fault was obvious.
But where was it?
From pin 12 the signal goes direct-
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46 Silicon Chip
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Fig.2: IF signals are applied to pins 4 & 5 of IC1 on the mother board (Akai
VS-35) and appear as demodulated audio on pin 11. From there, the signal
eventually goes to pin 11 of connector WF10 and then to the preamplifier
board where it is combined with the audio from the A/C head.
ly to a 680Ω resistor, R276, which is
mounted alongside the WF10 connector. There was a clean signal on both
sides of R276 so I traced the copper
track to the next convenient point, a
jumper link about 12cm away, near
the edge of the board.
And bingo! – there was a faulty
signal at this point. The fault was
somewhere along that 12cm of track.
I pulled the motherboard out and
examined that length of track in the
minutest detail, using my most powerful glass. I couldn’t pick it so I resorted
to cleaning away small areas of lacquer
on the track, allowing the probe to
make contact, until I narrowed the
fault to a small length near resistor
R270 and transistor TR214.
It was then that I noticed a hole in
the board through which a mounting
screw was fitted. Suppose someone
had been a mite too heavy handed in
fitting that screw; could it have cracked
the track?
Now that the search area had been
narrowed to within a couple of centimetres I took a long hard with the glass.
And, yes, there was no doubt about it;
the finest and faintest of cracks could
be discerned but only because I knew
where to look.
As usual, once a fault is found, the
whole thing becomes something of an
anticlimax; a spot of solder was all that
was needed to bridge the gap. Then,
just to be on the safe side, I fitted a
wire link anyway.
That fixed it. No amount of bashing,
prodding, or soak testing produced any
sign of the fault. I progressively put
everything back in place and there was
no sign of trouble. Finally, I phoned
the customer and told him to collect
it. He indicated that he would come
around immediately.
The unbelievable
Now you’re not going to believe
this. No sooner had I hung up than
the machine went into its act again. It
is not enough to say that words failed
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December 1996 47
me; no, that wouldn’t be anywhere
near strong enough.
Unfortunately, no amount of wailing and gnashing of teeth was going
to solve the problem. I just had to
get stuck into the monster and start
all over again. Nor was it any help to
know that the customer was on his way
and that I would be under pressure to
either come up with a quick fix or some
kind of an excuse, although I couldn’t
imagine what it would be.
As it transpired, I had a reprieve.
The customer had been delayed and
rang back after a short time to say that
he couldn’t make until the next day.
But a reprieve was all it was; I still had
to start all over again.
By the time I had delved back to
where I started I was shocked to
find that the fault now appeared to
have shifted back to the preamplifier
board. Indeed, I quickly found that by
flexing it at one corner I could create
the fault.
After seeking desperately for some
kind of inspiration, I finally decided
to look more closely at a number of
surface mounted components on this
board. I was clutching at straws but it
was all I could think of.
To tell the truth, surface mount
components do not usually cause
problems – at least not in my experience. Of course, there are a lot of
factors that must be considered at the
manufacturing level but, provided due
care is taken, a surface mount assembly
is extremely reliable.
So had I overlooked something? As
I said, I was clutching at straws but,
after going over this part of the board
and re-soldering everything yet again,
it did appear that the problem was
fixed. Mind you, I could be pardoned
for being sceptical.
Anyway, all seemed well for a while
until I started to put everything back
together again. Then the fault reappeared only this time it was pretty
clear that it was on the motherboard.
What was more, after more prodding
and flexing, it appeared that the sensitive area was now back near where
I had found the original crack.
I fished out the audio probe and
began tracing the audio path as before.
But this time there was a difference.
Originally, the audio signal had appeared as a clean signal on pin 11 of
socket WF10 on the mother board, having originated from IC201. And, after
its journey to the preamplifier board,
it was still clean when it reappeared
on pin 12 of WF10.
But not this time – the fault was now
obvious on pin 11 of WF10. Now the
important point about this is that the
copper track running from pin 11 runs
parallel to the track from pin 12 –the
very track containing the fault which
I had originally repaired.
Another crack
It didn’t take Sherlock Holmes to
suspect that there might be another
crack in the adjacent track. And so it
was; this crack was even more difficult
to see and the audio probe gave the
only positive indication. Anyway, I
bridged it as before and tried again.
And this time the job held in spite
of all I could do it. I even finished the
job before the customer turned up.
Considering everything, I would have
preferred to give the machine a much
longer test but the customer wanted it
back as soon as he could get it.
Yes, I thought the worst every time
the phone rang for the next few days
but there was no sign of a bounce. A
phone call to the customer several
weeks later confirmed that the machine hadn’t missed a beat. Still, I’m
SC
keeping my fingers crossed!
48 Silicon Chip
SILICON
CHIP
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SATELLITE
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Compiled by GARRY CRATT*
Gorizont 42-142.5°E longitude: Papua
New Guinea broadcaster EM TV has
commenced limited encryption using
a UK-designed Videocrypt scrambling
system, for several “premium” USA
programs, to protect the original copyright holder.
Initially, the decoders will be operate
without a subscriber “smart card” but
that initial familiarisation period will
expire within a month or so. EM TV
regularly run an advisory screen explaining these changes. Subscriptions
are available only to residents of PNG.
Elsewhere on this satellite, Asia Music continues to operate at 1470MHz
and RAJ TV, seen until mid-October
on the neighbouring Gorizont 41 satellite at 130°E, has moved temporarily
to this satellite at IF 1420MHz. RAJ
TV will eventually move to an Intelsat satellite over the Indian Ocean.
Meanwhile, India’s first adult channel
“PLUS 21” has yet to commence regular operations, despite a publicised
start-up date of October 1st.
Gorizont 41 (130°E) now has only
one occupant, “Laos TV”, operating
at IF 1375MHz. The satellite has been
sold by the Russian Space Agency
“Intersputnik, to the Philippine Agila
Satellite Corpora
tion. To be called
“Agila 1”, the satellite will be moved
to either 148°E or 153°E and placed in
an inclined orbit.
The reason for the purchase is the
requirement for coverage of the Asia
Pacific Economic Cooperation Forum,
held in the Philippines during November. Earlier, Agila had expressed
interest in acquiring Intelsat 505, in
return for Intelsat dropping their objection to Agila’s application for the
orbital location of 161°E. Intelsat 505
is currently located at 69.7°E.
Another Philippines broadcaster,
RPN, operating on Gorizont 42 has
changed to MPEG format. The broadcaster has adopted the Scientific Atlanta PowerVu platform, limiting the
type of receiver that can be used to the
S/A D9223.
Palapa C2M-113°E longitude: there
has been only one recent change to
this satellite: Star TV’s “Channel V”
has changed to MPEG digital format.
Now appearing at 1300MHz IF, the
transmission uses a Symbol rate of
26.85 and an FEC of 7/8. Presently,
subscriptions are not available to Australian residents, although this could
change after deregulation in July 1997.
All other transponders remain unchanged in frequency and a spectral
analysis of transponders shows equal
power distribution, after several
months of adjustment by the satellite
operator, Satelindo. This means that
CFI, ABN, ATVI, SCTV, Anteve, TVI,
TPI, GMA and RCTI can now all be received quite well along the east coast.
However, reports from Perth indicate
signal levels are well down in the west.
One additional signal now carried
on Palapa C2 is TVSN, the TV shopping network, also carried on Panamsat
PAS-2 and Asiasat 2. In late October,
the signal appeared on the transponder
utilised by ATVI, the international
Australian ABC channel. TVSN now
appears there for several hours each
morning, prior to commencement of
regular ATVI broadcasts. The TVSN
signal on Asiasat 2 has dropped dramatically in power and now requires
a 3m dish for good results.
Intelsat 703 177°E longitude: in addition to the AFRTS (US Armed Forces
TV) B-MAC signal at IF 968MHz (radio
service 7.4MHz), a Korean broadcaster
has been regularly using this satellite
on IF 984MHz. AFRTS utilises LHCP,
while the Korean signal uses RHCP
(righthand circular polarisation).
This is the new logo of French broadcaster RFO, indicating that a new
channel may commence soon.
A Korean channel using righthand
circular polarisation is now available
on Intelsat 703 at 177°E longitude.
Intelsat 511 180°E longitude: primary
channels of interest on this satellite
continue to be Worldnet (1175MHz IF)
and French channel RFO. For many
months a rumour has persisted that
the French broadcaster will soon commence operation of a second channel.
That rumour seems confirmed now
that RFO have changed their logo to
“RFO 1”. Elsewhere, vidiplexed feeds
for Network 7 are still carried on this
satellite (984MHz IF) and there are
several itinerant feeds each day. SC
*Garry Cratt is Managing Director of
Av-Comm Pty Ltd, suppliers of satellite TV
reception systems.
December 1996 57
A game to
improve your
hand/eye
coordination
Build a laser pistol
& electronic target
Most people can’t legally own guns any more so
if you have a yen for target shooting, this project
will fit the bill. It uses a visible LED laser in the
pistol & a bullseye target which responds visibly
& audibly when you score a direct hit.
By RICK WALTERS
Most people are attracted to the
idea of target shooting even if they
have no wish to own a gun. With this
project, you can indulge that whim in
a completely harmless way and have
a lot of fun in the process.
The game consists of a laser pistol
and an electronic target. The pistol is
a readily available plastic toy which
has been modified to hold a battery, a
switch for the trigger and a 5mW red
laser. Each time it is fired, the laser
58 Silicon Chip
emits a brief pulse. Holding down the
trigger does nothing; you must pull the
trigger fully each time to fire it.
The target is quite different from
anything you might have experienced
in the past. It is active rather than
passive and it gives you immediate
feedback, if you hit the bullseye or if
you miss. While it uses the “Official
100-yard small bore rifle target”, as
produced by the National Rifle Association of the USA, we have mod-
ified it with quite a bit of electronic
circuitry.
Around the outer ring of the target
are 24 evenly spaced LEDs which
chase around the circle for a random
period while a siren sounds. Then
all LEDs go out and you must fire the
pistol within one second and hit the
bullseye. If you miss, you get the sound
of a machine gun which means you
have been SHOT.
If you hit the target, you get one of
three different sound effects which can
be a police siren, ambulance or fire-engine. These are selected randomly by
the circuit as your reward for hitting
the bullseye.
At the bullseye is a PIN diode which
is matched to the gun’s laser. If the
laser beam hits this diode at the appropriate time, the police siren or one of
the other reward sounds will indicate
that you hit your target.
PARTS LIST
(TARGET BOARD)
Fig.1: the circuit
of the laser pistol.
Each time switch
S1 is closed, the
laser circuit dis
charges the 100µF
capacitor to give
a brief pulse.
The target’s electronics is powered
by a 9V DC plugpack.
How it works
Let’s start with the pistol circuit
shown in Fig.1. The 100µF capacitor
is always charged by the battery to
3V via the 1.5kΩ resistor. When the
trigger is pulled, the switch closes,
rapidly discharging the capacitor
through the laser diode and associated circuit.
The current drawn is such that the
laser only emits one pulse of light before the voltage drop across the 1.5kΩ
resistor causes it to turn off. Therefore
you can’t cheat by holding the trigger
down and pointing the barrel at the
bullseye.
The laser diode assembly consists of
a near infrared emitter optically cou-
pled to a detector diode. This is used
to monitor the light output from the
IR emitter and keep it constant, even
while the battery voltage is falling.
Q2 monitors the voltage across the
330kΩ resistor, this voltage being
proportional to the light output from
the diode. The voltage across LED1 is
used as a reference for Q2’s emitter.
The difference between its base and
emitter voltages cause just enough
collector current to flow through the
10kΩ resistor to turn Q1 on to give the
required light output. The 4.7µF and
0.47µF capacitors slow the rate of rise
of the current to ensure that there is
no overshoot, which could damage
the IR diode.
WARNING: the pulse of light from
the pistol, while of short duration, is
dangerous. It should never be point-
PARTS LIST (PISTOL)
1 toy pistol, Toys-R-Us Power
Ranger Dart 099236 or equiv.
1 PC board, code 08112961,
43mm x 16mm
1 momentary contact toggle
switch C&K 7109 or equivalent
(S1)
2 AAA 1.5V batteries
1 AAA or AA battery holder
1 BC338 NPN transistor (Q1)
1 BC328 PNP transistor (Q2)
1 3mm red LED (LED1)
Semiconductors
1 660nm 5mW laser diode and
lens assembly, Oatley Electron
ics 660-5I or equivalent
Resistors (0.25W, 1%)
1 330kΩ
1 470Ω
1 10kΩ
1 1.5Ω
1 1.5kΩ
Capacitors
1 100µF 16WV electrolytic
1 4.7µF 16WV electrolytic
1 0.47µF MKT 63VW or monolithic ceramic
1 PC board, code 08112962,
140mm x 80mm
1 38mm 8-ohm loudspeaker
1 National Target Co target,
TQ-4(T) or equivalent
1 sheet of white perspex to suit
target, 355 x 355mm
1 9V DC plugpack
2 10mm x 3mm tapped spacers
2 3mm x 5mm countersunk
screws
2 3mm x 5mm screws
24 5mm LED bezels
11 PC stakes
Semiconductors
1 40106 hex Schmitt trigger
(IC1)
1 555 timer (IC2)
2 4017 counter (IC3, IC5)
1 4093 quad 2-input NAND
Schmitt trigger (IC4)
1 4016 or 4066 quad bilateral
switch (IC6)
1 UM3561A sound effects
generator DSE Z-6203 (IC7)
1 LM311 comparator (IC8)
1 BC338 NPN transistor (Q1)
8 BC328 PNP transistor
(Q2-Q9)
1 PIN diode (PD1) Oatley
Electronics 04PC2 or
equivalent
1 3.3V 500mW zener diode
(ZD1)
8 1N914 signal diodes
(D1-D8)
1 1N4004 rectifier diode (D9)
24 5mm red LEDs
(LED1-LED24)
Capacitors
1 100µF 16WV electrolytic
2 10µF 16WV electrolytic
4 4.7µF 16WV electrolytic
3 1µF 16WV electrolytic
3 0.1µF MKT polyester
1 .022µF MKT
1 .01µF MKT
Resistors (0.25W 1%)
1 4.7MΩ
1 220kΩ
1 3.9MΩ
1 150kΩ
1 2.7MΩ
4 100kΩ
1 1.8MΩ
5 10kΩ
1 1.5MΩ
1 1.8kΩ
1 1.2MΩ
1 1.5kΩ
3 1MΩ
6 820Ω
1 470kΩ
December 1996 59
60 Silicon Chip
Fig.2: the target circuit has a LED chaser driven by IC3, a sound effects circuit based on IC5 & IC7, and a random timer based on IC1a, IC1b & IC1c.
ed at anyone’s eyes as damage could
result.
Target circuit
Now let’s have a look at the target
circuit in Fig.2. We’ll start with the
chaser circuit which is based on IC3, a
4017 decade counter. We are using just
six of its outputs. As it counts, each of
the six outputs will go high (+V) while
the rest are low (0V). IC3 is clocked by
a Schmitt trigger oscillator based on
IC1e together with the 1.5MΩ resistor
and the 0.1µF capacitor.
Since five of the outputs of IC3 will
always be low, five of the six groups of
four LEDs will always be turned on by
the emitter followers Q4-Q9.
Each time the oscillator clocks the
counter, the “off” group will step,
giving the appearance of rotation.
The oscillator resistor and capacitor
values are selected to make the target
LEDs appear to rotate at a suitable
speed.
Pin 5 of IC3 (the seventh output)
is connected to the reset terminal, so
each time the 4017 steps to this output
it will reset itself and start over again.
Switching another resistor in parallel
with the 1.5MΩ resistor using IC6a
increases the speed of rotation, as we
will see later on.
Random timer
Schmitt triggers IC1a, IC1b and
IC1c, together with their resistors and
capacitors, are three oscillators running at slightly different frequencies.
Fig.3: dimensions of the bracket for
mounting the trigger switch.
Their outputs are fed to an AND gate
formed by diodes D1-D3. When all
three oscillator outputs are low, the
voltage across the associated 100kΩ
resistor will also go low.
The diode AND gate is connected to
the input of IC1f via a .01µF capacitor
and so when the AND gate output
goes low, IC1f’s input will be pulled
momentarily low. This causes pin 12
of IC1f to go high and this will rapidly
charge the 10µF capacitor at pins 2 &
6 of IC2, via diode D6.
IC2 is a 555 timer but the way in
which it is connected is not conventional. In effect, it is a monostable and
when pins 2 & 6 are taken high via
diode D6, the output at pin 3 goes low
for a period set by the 100kΩ resistor
and 10µF capacitor on pins 2 & 6; ie,
around one second.
IC2’s output is normally high and
when it goes low it affects four functions. First, the oscillator formed by
IC1a will stop as D5 will hold its input
pin near 0V.
Second, the monostable formed by
IC4a and IC4b will be triggered, taking
pin 4 of IC4 high. This will hold the
voltage across the 100kΩ resistor high
through D4, preventing any further
pulses being applied to IC1f for around
four seconds.
The third consequence will be for all
the chaser LEDs to extinguish, as the
output pin of IC2 is the supply voltage
for them. The LEDs going out is the
signal to shoot at the target.
The fourth effect is that pin 3 of IC4
will go low and will take pin 1 of IC8
low, thereby grounding the emitter of
an inter
nal transistor which allows
its output (pin 7) to go low. If the PIN
diode (PD1) is now illuminated by the
laser pistol, its current will increase,
pulling pin 2 of comparator IC8 below
its pin 3. This causes pin 7 of IC8 to go
RESISTOR COLOUR CODES
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
No.
1
1
1
1
1
1
3
1
1
1
1
4
6
1
2
6
1
1
Value
4.7MΩ
3.9MΩ
2.7MΩ
1.8MΩ
1.5MΩ
1.2MΩ
1MΩ
470kΩ
330kΩ
220kΩ
150kΩ
100kΩ
10kΩ
1.8kΩ
1.5kΩ
820Ω
470Ω
1.5Ω
4-Band Code (1%)
yellow violet green brown
orange white green brown
red violet green brown
brown grey green brown
brown green green brown
brown red green brown
brown black green brown
yellow violet yellow brown
orange orange yellow brown
red red yellow brown
brown green yellow brown
brown black yellow brown
brown black orange brown
brown grey red brown
brown green red brown
grey red brown brown
yellow violet brown brown
brown green gold brown
5-Band Code (1%)
yellow violet black yellow brown
orange white black yellow brown
red violet black yellow brown
brown grey black yellow brown
brown green black yellow brown
brown red black yellow brown
brown black black yellow brown
yellow violet black orange brown
orange orange black orange brown
red red black orange brown
brown green black orange brown
brown black black orange brown
brown black black red brown
brown grey black brown brown
brown green black brown brown
grey red black black brown
yellow violet black black brown
brown green black silver brown
December 1996 61
This is what the pistol looks like after
being disassembled and having the
electronics installed. The spring-loaded
switch is operated by the existing pistol
trigger.
low, discharging the 1µF capacitor on
pin 13 of IC4 via D7. Phew!
But we’re not finished yet, as this
convoluted circuit has more tricks up
its sleeve. We will now talk about the
functions of gates IC1d, IC4c & IC4d,
counter chip IC5, quad analog switch
IC6 and IC7, the sound effects chip.
If PD1 is illuminated while pin 1 of
IC8 is high, the output will not change.
This prevents anyone cheating by
continuously shooting at the target,
hoping to hit the bull just before the
LEDs go out.
When pin 3 of IC2 goes high after
its 1s period, it pulls pins 8, 9 & 12 of
IC4 high via the 1µF capacitor. Pin 10
will always go low, turning on Q2, thus
applying power to the sound effects
chip IC7 and to pin 13 of IC6a via a
10kΩ resistor. This causes the LED
flasher to speed up.
There will be two different outcomes from the sound effects chip,
depending on whether the bullseye
was hit or not.
IC7 is a low-cost sound effects chip.
If pin 1 is taken to the chip’s supply
voltage (+3.3V), a machine gun sound
is generated, regardless of the voltage
on pin 6. If pin 1 is left floating (ie,
open circuit), three additional sounds
can be generated. If pin 6 is high, a fire
engine sound is generated; if low, an
ambulance sound; and if left floating, a
police siren sound will be heard from
the speaker.
If the bullseye is missed, both inputs
of IC4d go high and its output goes
low to turn on Q3. Q3’s collector going
high will take pin 12 of switch IC6d
high, to connect pin 11 to pin 10. This
generates the machine gun sound and
YOU ARE DEAD! At the same time,
pin 13 of IC6a will be pulled low
via D8, switching out the additional
1MΩ feedback resistor for IC1a, thus
returning the chaser speed to normal.
Conversely, if the photodiode is
illuminated while the LEDs are off
(IC2, pin 3 low), then D7 will discharge
the 1µF capacitor. When pin 3 of IC2
goes high again after one second, Q2
will apply power to the sound chip
as previously. As both inputs of IC4d
are not high, its output will stay high
and Q3 will stay off. This leaves pin 1
of IC7 floating; (ie, IC6d open-circuit).
IC1d with its associated resistor and
capacitor form an oscillator which
clocks IC5, another 4017 decade counter. This time we only use three outputs, resetting it on the fourth. When
pin 3 of IC5 is high, the SEL1 input
of IC7 is connected to ground and the
output sound will be an ambulance.
If pin 4 of IC5 is high, the SEL1 input
will be high and the sound will be a
fire engine. When pin 2 of IC5 (the Q1
output) is high, both IC6b and IC6c are
open circuit and therefore the SEL1
input will be floating and the sound
will be a police siren.
Note that pin 2 of IC5 is not connected in the circuit and therefore is
not shown.
When Q2 turns on it takes the Clock
Enable (pin 13) of IC5 high, effectively
freezing the selected output. This prevents the selected siren sound from
changing halfway through. Thus, IC1d
and IC5 together randomly select the
siren “reward” sound heard each time
the bullseye has been hit.
In both the above cases (ie, bullseye or no bullseye), after the 2.7MΩ
resistor on IC4 pin 12 has discharged
the 1µF capacitor, the outputs of IC4c
and IC4d will go high again, turning
off the siren and returning the chaser
to normal speed.
The 4-second inhibit monostable
(IC4a & IC4b) operating via diode D4
Fig.4: this diagram shows the wiring
details of the laser pistol. Make sure the
IR1 (the laser diode) is wired correctly
and take care to ensure that Q1 (BC338)
and Q2 (BC328) are the correct type
numbers.
62 Silicon Chip
Fig.5: the parts
layout for the target
PC board. Note that
IC3 & IC5 face in the
opposite direction to
the other ICs.
prevents the random timer (IC1a, 1b &
1c) from almost immediately starting
the “fire” sequence again, which could
be the case from time to time.
Pistol assembly
Our prototype pistol was purchased
from Toys R Us. The red plastic pieces
on the handle were prised apart with
a knife blade, giving access to three
small Phillips head screws which hold
the main body together. Once the pistol
is apart the black pillar on each half
near the trigger must be cut off to make
room for the spring-loaded switch.
The type of switch we specified
springs back to the off position and
is actuated by the existing plastic
trigger of the pistol. We made a small
metal bracket (see Fig.3) to mount
the switch and positioned it so that
it operated smoothly with the plastic
trigger. When the trigger is released
the switch pushes it back to the rest
position. The elastic bands which
previously restored the trigger can
be discarded.
Most of the laser circuit of Fig.1
was supplied assembled and tested by
Oatley Electronics, as a laser pointer.
While it could have been used like
this, we still required the 1.5kΩ resistor and the 100µF electrolytic to be
mounted somewhere. As the parts can
be supplied in kit form, we elected to
make another small PC board which
would accept all the components and
be a better fit inside the pistol barrel.
Its component layout is shown in
Fig.4. Having so few parts it should
only take a few minutes to build. Just
ensure that the electrolytic capacitors
are inserted with the correct polarity
and make doubly sure that the wires
to the laser diode are connected to the
correct pins.
The pistol wiring is straightforward
and should cause no problems. An
AAA battery holder is not readily
available so we used an AA holder.
If the batteries are loose, stretch the
springs a little until they are held
firmly.
The pistol barrel comes with a white
plastic tubular insert which was used
to hold the dart. The dart is discarded
and the tube trimmed 10mm from the
end. This piece is used to hold the laser
diode in the end of the barrel.
Test your work before re-assembling
the pistol by pointing the laser at a wall
and pulling the trigger. A brief pulse
of red light should be seen. The lens
will also need to be focused before
final assembly.
Stand at about the distance you
intend to be from the target and, with
the 1.5kΩ resistor shorted out, hold
the trigger down and rotate the end
of the lens until the spot of light is as
small as you can get it. Remove the
short and assemble the pis
tol. The
red barrel needs to be superglued to
the black butt on both pieces before
assembly.
Target PC board
The component layout for the target
This close-up view shows the assembled target PC board. Note how the infrared
diode sits directly behind a small hole which is drilled through the bullseye.
December 1996 63
Fig.6: this diagram shows how the LEDs are wired around the target.
PC board is shown in Fig.5. After checking the PC board for open or shorted
tracks and undrilled holes, the first step
is to fit and solder the 13 links and 11
PC stakes. Fit the resistors, diodes, ICs
and other low-profile components first,
then move on to the taller components.
Be sure to double-check the diode
and electrolytic capacitor polarities.
You should also carefully check the
orientation of the various ICs and that
the single BC338 transistor (Q1) is in
64 Silicon Chip
the correct place.
Testing
This board can be tested now, before
you wire up the target LEDs. Solder
the cathodes of each of six LEDs onto
the six PC stakes near the 820Ω resistors, with all six anodes connected
in parallel to the LED common pin.
Connect the speaker to its terminals
and connect the DC plugpack or a
power supply to the +9V and 0V pins.
Apply power and five of the six LEDs
should light.
After a short time each of the six
LEDs should have turned off, but not
in sequence, then they should all go
out and a second later a burst of machine gun fire should be heard from
the speaker. If all is OK so far, ground
pin 7 of IC8. Over a period you should
hear the three different sirens.
If the board is working, continue
with the target wiring, as shown in
Fig.6.
Fault finding
If the LEDs don’t light, check that
their polarity is correct by reversing
one of them. Pin 3 of IC2 should
measure around 11V or thereabouts,
depending on the actual output voltage
of the 9V DC plugpack. If pin 3 of IC2
is at 0V, look for shorts or a faulty chip.
If the LEDs don’t step, check around
IC3 or IC1e for faulty or incorrect components or perhaps a blob of solder
shorting two pins.
If the three siren sounds are not
produced (after a number of tries) suspect IC5 or IC1d and its components
or a solder bridge. To force a burst of
machine gun fire, use a jumper lead
from pins 8 & 9 of IC4 to Vcc. If pin
13 is then grounded the other sirens
should be heard.
Target wiring
The cardboard target specified is
available from most gun shops. We
mounted ours on a piece of white perspex. Before drilling the 24 LED holes,
we drilled a hole at the bullseye and
two holes to mount the pillars which
support the target PC board. These
were positioned so that the PIN diode
sat behind the bullseye.
The LEDs are wired in series in
groups of four, one in each quadrant as
shown in Fig.6. If you use a different
coloured wire for each group it will
help you to keep track of them.
All the anodes in the first quadrant
are commoned and connected to the
LED common PC stake. The last LED
We used a sheet of white perspex to hold the target. The loudspeaker and PC
board mount on the back, with the PIN diode behind the bullseye hole.
in the first group should be connected
to Q4’s 820Ω resistor, the last LED in
the second group to Q5’s 820Ω resistor
and so on, until the sixth group LED
is connected to Q9’s resistor.
You will have to follow the PC overlay of Fig.5 carefully, as the transistors
are not in sequence.
Now power up the target and check
that all functions are working. You will
need to carefully “sight” the pistol so
that it shoots straight and then you
will find that you need a fair amount of
practice to hit the target consistently.
Have fun.
SC
Fig.7: here are the fullsize etching patterns for
the laser pistol (above)
and the target board
(right).
December 1996 65
Build This
Sound Level
This Sound Level Meter adaptor will
measure sound pressure levels from
below 20dB up to 120dB with high
accuracy. It connects to any standard
digital multimeter and has inbuilt
filters for A and C-weighting.
Noise can have a huge affect on the quality of our lives. A
reliable measuring instrument is a must for those interested
in finding out just how much noise is in their environment.
Just how much noise is present at any time is very
subjective. If you are confined to a soundproof room for
a period of time, even the sound of a pin dropping will
seem quite loud. But if you are in a normal home or office
environment, the dropping of a pin is likely to be completely inaudible. And even the sounds of people on
the telephone or using computers may be completely
drowned out if a semi-trailer passes down your street
or a jet flies overhead.
The above examples show just how exceptional
our ears are in responding to the possible range of
sounds in our environment. In fact, we could expect
to experience a sound pressure range of about three
million to one. Because of this huge range of values sound pressure levels are usually expressed in
decibels, a logarithmic ratio where 20dB (decibels)
is equivalent to 10:1; 40dB is 100:1 and 60dB is
1000:1, all compared to a reference level. The
overall 3,000,000 to 1 range can then be expressed
as 130dB (20 log 3,000,000).
Since the dB is a ratio it must be referenced to
•
•
•
•
66 Silicon Chip
66 Silicon Chip
Main Features
Connects to any digital multimeter
Calibration method uses loudspeaker & pink noise source
A and C weighting plus flat (unweighted) filters
Slow, Fast and Peak response
By JOHN CLARKE
Meter
a particular pressure level of 20.4µPa
(micro Pascals). Usually sound pressure levels are quoted as so many dBSPL, indicating that the 0dB reference
is 20.4µPa.
On the dBSPL scale, 0dB is virtually inaudible, 30dB might be the
sound level in a quiet rural area with
no wind while a noisy home kitchen
might be 80dB or more. Heavy traffic
can easily be 80-90dB while a suburban train in a tunnel can produce
100dB. Electric power tools or pneumatic drills can easily run at 110dB
and some can go into the pain level
at 120dB.
Measuring SPL
The S ILICON C HIP Sound Level
Meter is designed to produce accurate
readings of sound pressure which are
displayed on a digital multimeter. It
Fig.1: this graph shows the differences between A and C-weighting and flat
(unweighted) responses in the Sound Level Meter.
comprises a handheld case with a
short tube supporting the microphone
at one end of the unit. Flying leads
with banana plugs connect to the
multimeter.
A slide switch provides A-weighting
and C-weighting filters to tailor the
measurement readings. A-weighting
is called for in many measurements to
Australian standards although it is not
really appropriate for louder sounds
where C-weighting or a flat response
(unweighted) can give more meaningful results. Fig.1 shows the differences
between A and C-weighting and flat
(unweighted) responses in the Sound
Level Meter.
Slow and fast response times are
provided as well, so that sudden noise
can be filtered out, if need be.
A “peak detect” facility has also been
included which will give an indication
Fig.2: the block diagram of the Sound
Level Meter. IC4b controls the gain
of IC2 so that the output from the
full-wave rectifier is constant. IC4b’s
output is attenuated by IC3b and fed
to an external multimeter.
December 1996 67
Fig.3: apart from the use of a VCA (IC2), an unusual feature of the circuit is
the use of IC5 to evenly split the 18V supply. This has been done because the
negative rail is subjected to a higher current drain than the negative rail, which
would shorten the life of battery B2.
of the noise waveform shape. If there
is no or little difference between the
peak and the fast reading then the noise
waveform can be assumed to be relatively sinusoidal. If, however, the peak
level is greater than the fast reading,
then the noise waveform has a lot of
transient bursts. These may result in a
low average value as shown on the slow
68 Silicon Chip
or fast response settings but are easily
captured by the peak detect circuitry.
The cost of the Sound Level Meter
has been kept low by using a multi
meter as the display.
Logarithmic conversion
As already noted, the Sound Level
Meter will read from below 20dBSPL
to 120dBSPL, a range of 100dB. That’s
a pretty stiff requirement. The circuit
has to provide a direct logarith
mic
conversion over 100dB, producing an
output of 10mV per dB.
In practice, the signal fed to the multimeter ranges from 200mV at 20dB
to 1.2V at 120dB. This means that all
readings can be made on the 2V range
of the multimeter; there is no need to
switch ranges.
Fig.2 shows the block diagram of
our sound level meter. Signal from
the microphone is amplified by op
amp IC1a and then fed to either the A
or C-weighting filters which involve
switch S2 and op amp IC1b.
IC2 is a voltage-controlled amplifier
(VCA) which can either amplify or attenuate the signal from IC1b, depending on the voltage at its control input.
This input operates in a logarithmic
fashion so that small control voltage
changes can produce large variations
in the output signal.
IC2’s output is full wave rectified
by IC3a & IC4a and the rectified signal
fed to the Slow, Fast or Peak filters
involving switch S3. The resulting
DC voltage is compared in error amplifier IC4b against a 20mV reference.
IC4b’s output then controls the VCA
so that it produces a constant output
regardless of changes in the microphone signal.
As well as driving the control input
of the VCA, IC4b drives op amp IC3b
which modifies the signal so that it
provides the required 10mV per dB,
to drive the external multimeter.
Circuit description
Fig.3 shows the complete circuit
for the Sound Level Meter. It uses five
ICs, three of which are dual op amps
(IC1, IC3 & IC4). IC2 is the VCA, which
can be considered as an op amp with
a DC gain control. IC5, a TL071 single
op amp, is used to accurately split the
18V battery supply; more of that later.
The microphone is an electret type
which is biased via a 10kΩ resistor
from the +9V supply. Its signal is coupled to op amp IC1a which has a gain
of 7.9 (+18dB), as set by the 68kΩ and
10kΩ feedback resistors. This gain has
been selected for the specified microphone and will need to be altered if
other types are used.
IC1a drives both the C and A-weighting filters. These are selected at positions 1 and 2 of switch S2a respectively. Position 3 selects IC1a’s output
directly for the flat or unweighted
signal mode. IC1b is simply a unity
gain amplifier to buffer the filters and
prevent loading of the filter signal.
IC1b’s output is fed to IC2 via switch
S2b and a 10µF coupling capacitor.
Note that in positions 1 and 3 of S2b,
the 4.7kΩ and 12kΩ resistors are connected in series while for position 2,
the 4.7kΩ resistor is bypassed. This
allows a 3dB higher gain for IC2 when
A-weighting is selected. The gain adjustment is necessary to maintain the
Fig.4: waveforms from the precision full-wave rectifier. The top trace (Ch1)
shows the input sinewave while the lower trace (Ch 2) is the rectified version.
Note that the RMS values are slightly different due to small offsets in the op
amps.
same 1kHz signal level applied to IC2
for all positions of switch S2.
IC2 is an Analog Devices voltage-controlled amplifier (VCA). It
has a dynamic range of 117dB, .006%
distortion at 1kHz and unity gain, and
a gain control range of 140dB. The DC
control input operates at -30mV per
dB gain change. IC2’s gain is set by
the voltage at pin 11 and the ratio of
resistance between pins 3 and 14 and
the input at pins 4 & 6.
The 100kΩ resistor between pin 12
and the +9V rail sets the bias level for
the output at pin 14. This bias can be
selected for class A or B operation.
Class A gives lower distortion but
slightly higher noise. We opted for
class B bias for best noise performance. A .001µF capacitor between
pins 5 & 8 compensates the gain control circuitry.
Precision rectifier
IC2 is AC-coupled to the precision
full wave rectifier formed by op amps
IC3a & IC4a. For positive signals the
output of IC3a goes low to reverse bias
diode D1. Positive-going signals are
then summed in inverter IC4a via the
20kΩ resistor R1 to produce a negative
output at pin 7. The gain is -1. Diode
D2 and the 20kΩ series resistor limit
the op amp’s negative excursion.
For negative signals D1 conducts
and IC3a acts as an inverting amplifier
with a gain of -1 to sum into IC4a via
R5. Negative-going signals are also
summed in IC4a via R1. Since the
voltages across R1 and R5 are equal
but opposite and the value of R5 is
exactly half R1, the net result of the
sum into IC4a is a negative output with
an overall gain of 1.
So for positive signals applied to
the full wave rectifier the gain is -1
and for negative signals the gain is 1.
Thus IC3a and IC4a form a precision
full wave rectifier. The 10kΩ and
5.6kΩ resistors at IC3a’s and IC4a’s
non-inverting inputs minimise any
offset voltages in the op amps.
Fig.4 shows the oscilloscope waveform of the precision full wave rectifier. The top trace shows the input
sinewave while the lower trace is the
rectified version. Note that the RMS
values are slightly different due to
small offsets in the op amps.
The switched feedback across IC4a
provides filtering of the rectified signal
as well as gain control. In the ‘slow’
setting of S3a, the 20kΩ resistor sets
the gain and the 470µF capacitor
controls the response. Similarly, for
the ‘fast’ setting of S3a, the 100µF capacitor sets the response. In the ‘peak’
position of S3, diode D3 charges the
10µF capacitor to the peak value of the
waveform while the 12kΩ resistor sets
December 1996 69
Fig.5: follow this diagram
when installing the parts on
the PC board and take care to
ensure that all polarised parts
are correctly oriented. Note
that REF1 and a number of
capacitors must be laid flat on
the PC board (see text).
the gain. This is lower than the 20kΩ
value used in the other S3 positions
so that the output at the wiper of S3b
is the same as for the slow and fast
settings when a sinewave is applied.
VR1 allows precise adjustment of
this calibration, providing a divide
by 4.6 to 1.8 range. VR2 is the offset
adjustment.
Error amplifier
If, after reading the circuit description so far, you are unclear about its
operation, do not despair. Let’s summarise what really happens. Op amp
IC4b, the error amplifier, is really the
The filter signal at the wiper of
S3b is monitored with error amplifier
IC4b. This has a gain of -100 (ie, it is
an inverting amplifier) and compares
the rectified signal from switch S3b
against the -20mV reference at the
non-inverting input, pin 3. IC4b’s
output drives pin 11 of IC2.
The -20mV reference is derived
from the 2.49V reference REF1 via
560kΩ and 4.7kΩ resistors. REF1 is
an LM336-2.5 preci
sion reference
diode which has facility for a small
amount of adjustment although it is
not used here.
REF1 is also used to provide a calibration offset for op amp IC3b. IC3b
attenuates the logarithmic DC control
voltage for IC2 to convert its nominal
30mV/dB calibration to 10mV/dB.
70 Silicon Chip
The big picture
CAPACITOR CODES
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
Value
0.56µF
0.22µF
0.18µF
0.15µF
.047µF
.0027µF
.001µF
100pF
33pF
12pF
IEC
EIA
560n
564
220n
224
180n
184
150n
154
47n
473
2n7
272
1n
102
100p
101
33p 33
12p 12
heart of the circuit. It continually adjusts the control voltage fed to IC2 so
that the negative DC voltage fed from
the wiper of S3b to its pin 2 is always
very close to the -20mV at its pin 3.
In fact, VCA IC2 does not really
operate as an amplifier for most of the
time. For example, when a signal of
120dBSPL is fed to the microphone,
the output of IC1a and IC1b is close to
clipping; ie, around 14V peak-to-peak
or 5V RMS. This is heavily attenuated
by IC2 so that around 30mV RMS (see
Fig.4) is applied to the input of the
precision rectifier, IC3a.
Actually, it is only for signals of
around 20mV or less from IC1b that
the circuit involving IC2 has any gain;
the rest of the time it is attenuating
and the actual degree of attenuation
depends on the size of the signal coming from IC1a. Typically, the control
voltage delivered by IC4b ranges from
about +3V, corresponding to maximum
attenuation in this circuit, to about
-1V, corresponding to maximum gain.
Hence, IC4b makes sure that its two
inputs are very similar, and in doing
so, it produces a control voltage which
happens to be 30mV/dB. This is then
further attenuated by IC3b to produce
an output of 10mV/dB which can be
read out as a measure of the sound
pressure level. Looked at this way, the
output voltage read by the external
multimeter is almost just a byproduct
of the overall circuit operation.
The assembled PC board
is secured to the base of
the case using four small
self-tapping screws.
Battery supply
Two 9V batteries in series provide an
18V supply. The 18V is divided using
two series connected 10kΩ resistors,
to produce a 0V reference and this is
buffered by op amp IC5. IC5’s output
feeds a 100Ω resistor and two 100µF
capacitors. These decouple the op
amp’s output and ensure that it has
a very low output impedance at all
frequencies of interest. The result is a
dual-tracking supply which is nominally ±9V.
Now why go to all that trouble when
we could have used the midpoint of
the two 9V batteries to do the same
thing? The reason is that there is more
current drain from the negative rail
in this circuit and so the negative 9V
battery would normally be discharged
faster than the positive 9V battery.
This would be a problem because the
circuit require more negative output
swing.
By using the op amp split supply
RESISTOR COLOUR CODES
❏
No.
❏ 1
❏ 1
❏ 1
❏ 3
❏ 1
❏ 1
❏ 1
❏ 1
❏ 6
❏ 1
❏ 2
❏ 9
❏ 1
❏ 1
❏ 1
❏ 2
❏ 2
❏ 2
❏ 1
Value
2.2MΩ
560kΩ
180kΩ
100kΩ
68kΩ
33kΩ
22kΩ
24kΩ
20kΩ
18kΩ
12kΩ
10kΩ
8.2kΩ
6.8kΩ
5.6kΩ
4.7kΩ
3.9kΩ
150Ω
100Ω
4-Band Code (1%)
red red green brown
green blue yellow brown
brown grey yellow brown
brown black yellow brown
blue grey orange brown
orange orange orange brown
red red orange brown
red yellow orange brown
red black orange brown
brown grey orange brown
brown red orange brown
brown black orange brown
grey red red brown
blue grey red brown
green blue red brown
yellow violet red brown
orange white red brown
brown green brown brown
brown black brown brown
5-Band Code (1%)
red red black yellow brown
green blue black orange brown
brown grey black orange brown
brown black black orange brown
blue grey black red brown
orange orange black red brown
red red black red brown
red yellow black red brown
red black black red brown
brown grey black red brown
brown red black red brown
brown black black red brown
grey red black brown brown
blue grey black brown brown
green blue black brown brown
yellow violet black brown brown
orange white black brown brown
brown green black black brown
brown black black black brown
December 1996 71
shown in Fig.5, to allow room for
the battery to lie on top of the PC
board. For the same reason, the
.001µF capacitor near IC2, the
0.18µF capacitor near VR2 and
the 100pF capacitor near VR1
should be inserted so that they
lie flat on the board.
The electrolytic capacitors
must be oriented as shown.
Insert and solder LED1 at the
end of its leads to allow it to
protrude through the front panel
when assembled. Insert trimpots
VR1 and VR2 and cut the ‘A’
PC stakes slightly higher than
the trimpot height. This will
prevent the batteries pressing
on the trimpots and altering the
set values.
Now fit the assembled PC
This battery holder was made by soldering several pieces of double-sided PC board
board into the base of the case
material together. The three smaller pieces fit into the integral slots moulded into the
and secure it with four small
lid of the plastic case.
self-tapping screws. Wire up the
9V battery clips and multimeter
method, the current drain from the
assembly of components. Begin by leads as shown. Prepare the two wires
two 9V batteries must always be the
inserting the two links and all the for switch S1.
same and the battery life will be exresis
tors. The accompanying table
Fit the Dynamark adhesive label to
tended. For the same reason, LED1 is
can be used as a guide for the resistor
the lid of the case and drill and file
connected across the full 18V supply
colour codes. Alternatively, use your
out the holes for the switches and
via a 10kΩ resistor.
multimeter to check each resistor as
LED. Attach S1 with the screws and
it is installed.
connect its wiring.
Construction
Next, insert and solder in the PC
The rear end panel can be drilled
stakes. These are located at all external
The SILICON CHIP Sound Level Meto accept a small grommet. Pass the
wiring points, the ‘A’ positions and for
ter is housed in a plastic case measmultimeter leads through the gromuring 150 x 80 x 30mm and uses a PC the eight switch terminal locations for metted hole and attach the banana
S2 and S3.
board coded 04312961 and measuring
plugs to it.
67 x 120mm. The microphone is held
Next, the ICs can be inserted and
Microphone mounting
inside a copper tube which protrudes soldered in. Take care with the orifrom the front of the case. This is done entation of each and make sure that
An 80mm length of 12.7mm copper
to prevent sound reflections from the
IC5 is the TL071 (or LF351). Diodes tube is soldered to a 12 x 30mm piece
case from upsetting the reading.
D1-D4 can now be inserted, taking care
of 1mm thick copper sheet (or PC
to ensure that they are also correctly board). The copper sheet becomes a
Fig.5 shows the component layout
oriented. Switches S2 and S3 can be flange for easy attachment to the front
for the PC board. You can start construction by checking the PC board mounted by soldering their pins to the end piece of the box. Drill holes in
top of the PC stakes.
for any shorts or breaks in the copthe flange and front end plate to allow
per tracks. Repair any faults before
REF1 is mounted on its side as it to be secured with two screws and
Fig.6: this is the set up
used for calibrating
the Sound Level Meter.
It relies on using a
speaker of known
sensitivity. Most
manufacturers quote
sensitivity figures for
their loudspeakers.
72 Silicon Chip
nuts. Also drill a hole central to the
flange and end plate for the shielded
cable to pass through the tube. The
tube and flange can be painted if
desired.
Connect the microphone using
shielded cable and attach some heat
shrink tubing around its body. Shrink
the tubing down with a hot air gun
and insert the wire and microphone
into the tube.
Leave the microphone flush with
the end of the tube. The flange can be
attached to the end plate of the case
with the screws and nuts. The shielded cable is clamped with a solder lug
attached to one of the screws.
The batteries are held in place on
the lid of the case using three pieces
of double-sided PC board (73 x 5mm)
which are inserted in the integral
slots. Two pieces of double sided PC
board, measuring 30 x 15mm, are soldered in place between the transverse
pieces so that they provide a snug fit
for the battery and clip assemblies.
Check that the lid will fit onto the
base of the case.
Voltage checks
Switch on and connect the red
multimeter lead from the Sound Level Meter to the common input of the
multimeter and then measure voltages
on the circuit with the other lead of the
multimeter. Check that there is +9V at
pin 8 of IC1, IC3 and IC4; at pin 7 of
IC5; and at pin 2 of IC2. There should
be -9V at pin 4 of IC1, IC3, IC4 & IC5
and at pins 10 & 16 of IC2.
REF1 should have -2.49V at its
anode and pin 3 of IC4b should be
-20mV. LED1 should also be lit.
Connect both output leads from the
sound level meter to the multimeter.
Performance
‘A’ response .......................................... -18dB at 100Hz, -10dB at 20kHz (see Fig.1)
‘C’ response ......................................... -5dB at 20Hz, -13dB at 20kHz (see Fig.1)
Overall flat response (input
versus multimeter reading) .................. -3dB at 28Hz and 50kHz
Log conversion accuracy at
multimeter output ................................ <0.5dB over a 100dB range from 0.550V
RMS to 5.5µV input level
Temperature stability ............................ <10mV (1dB) change per 30°C
Slow response time constant ............... 9.4 seconds
Fast response time constant ................ 2 seconds
Peak response ...................................... 1.5ms attack; 120ms decay
Power ................................................... 12-18V at 32mA
Microphone Performance (ECM-60P A version)
Sensitivity �������������������������������������������� -56dB ±3dB with respect to 0dB+1V/µbar <at>
1kHz
Microphone response .......................... within ±3dB from 50Hz to 3kHz and ±6dB
from 3kHz to 8kHz. Above 8kHz and below
50Hz unspecified.
Maximum SPL ..................................... 120dB
Note: filter responses measured at VCA output with control input (pin 11) grounded.
it is greater than 400mV, rotate VR1
slightly clockwise.
Conversely, if the multimeter reading is less than 400mV, rotate VR1
slightly anticlockwise. Now measure
the difference again with the 0dB/
-60dB switch. You will note that the
reading will now not be 1V for the 0dB
setting. However, what we are look-
ing for is a 600mV change between
the 0dB and -60dB pink noise level
settings (ie, 10mV per dB). After some
repeat adjustments of VR1 it should
be possible to obtain close to 600mV
variation between the 0dB and -60dB
settings.
Calibration now only requires the
offset adjustment trimpot VR2 to be
Calibration
Calibration is done in two steps and
a pink noise source is required for both
steps. We will describe a suitable pink
noise source in next month’s issue of
SILICON CHIP and we assume that you
will also build that or have access to
an equivalent source.
First, connect the pink noise source
to the electret microphone input of
the sound level meter. Select 0dB on
the pink noise source (equivalent to
60mV RMS) and adjust trimpot VR2
for a reading on the multimeter of
1V DC. Now switch to -60dB on the
pink noise source and check that
the multimeter reading is 400mV. If
Fig.7: check your etched PC board against this full-size artwork before installing
any of the parts.
December 1996 73
PARTS LIST
1 plastic case, 150 x 80 x 30mm
1 PC board, code 04312961, 67 x
120mm
1 front panel label, 75 x 144mm
1 ECM-60P type A electret
microphone (sens. -56dB with
respect to 1V/1µbar at 1kHz)
3 pieces of double sided PC
board, 73 x 5mm
2 pieces of double sided PC
board, 30 x 15mm
1 DPDT slider switch and mounting screws (S1)
2 DP3P slider switches (S2,S3)
1 50kΩ horizontal trimpot (VR1)
1 100kΩ horizontal trimpot (VR2)
2 9V battery snaps
2 9V batteries
1 black banana plug
1 red banana plug
1 250mm length of shielded cable
1 500mm length of black hookup
wire
1 500mm length of red hookup
wire
1 50mm length of 0.8mm tinned
copper wire
30 PC stakes
2 3mm x 10 screws and nuts
4 small self-tapping screws (to
secure PC board)
1 solder lug
1 small rubber grommet
1 small cable tie
1 SSM2018P voltage controlled
amplifier (IC2)
1 TL071, LF351 op amp (IC5)
4 1N914 signal diodes (D1-D4)
1 LM336-2.5 2.5V reference
(REF1)
1 3mm red LED (LED1)
Semiconductors
3 LM833 dual op amps
(IC1,IC3,IC4)
Miscellaneous
12mm diameter heatshrink tubing,
solder.
Capacitors
1 470µF 16VW PC electrolytic
5 100µF 25VW PC electrolytic
1 47µF 16VW PC electrolytic
3 10µF 16VW PC electrolytic
1 0.56µF MKT polyester
1 0.22µF MKT polyester
1 0.18µF MKT polyester
2 0.15µF MKT polyester
1 .047µF MKT polyester
2 .0027µF MKT polyester
1 .001µF MKT polyester
1 100pF ceramic
1 33pF ceramic
1 12pF ceramic
Resistors (0.25W 1%)
1 2.2MΩ
2 12kΩ
1 560kΩ
9 10kΩ
1 180kΩ
1 8.2kΩ
3 100kΩ
1 6.8kΩ
1 68kΩ
1 5.6kΩ
1 33kΩ
2 4.7kΩ
1 24kΩ
2 3.9kΩ
1 22kΩ
2 150Ω
6 20kΩ
1 100Ω
1 18kΩ
set. This is done using the setup shown
in Fig.6.
You will need an amplifier, the pink
noise source and a woofer or tweeter
with known sensitivity. All manufacturers of loudspeakers provide a sensitivity rating for their units and these
are specified as a dBSPL when driven
at 1W and at 1m on axis. Note that if
you use a tweeter, the manufacturer’s
specified filter should be used when
making the measurement.
For example, a loudspeaker may be
rated at 88dB when mounted on a baffle and driven from a 2.828V AC source
at a distance of 1m. The loudspeaker
impedance is 8Ω. Note that 2.828V
into 8Ω is equivalent to 1W.
Use your multimeter to measure the
voltage applied to the loudspeaker and
set the amplifier’s volume control to
deliver 2.828V AC for an 8Ω system
and 2V AC for a 4Ω speaker. Be sure
to set your amplifier’s tone controls to
the flat settings (ie, centred or switched
off) and make sure that the loudness
switch is off.
Now connect the multimeter to the
sound level meter (with the unweight
ed and slow settings selected) and
with the microphone at 1-metre and
on axis to the speaker. Adjust trimpot VR2 to obtain the loudspeaker
sensitivity. For our 88dB example,
the multimeter should read 0.88V or
880mV DC.
Alternatively, if you have a calibrat
ed sound level meter, adjust VR2 for
the same readings. Make sure that both
sound level meters are set with the
same filtering and responses.
SC
74 Silicon Chip
(10mV/dB)
CONNECT TO
MULTIMETER
FILTER
C-WEIGHTING
A-WEIGHTING
UNWEIGHTED
+
SOUND
LEVEL
METER
RESPONSE
SLOW
FAST
PEAK
+
OFF
+
ON
+
Fig.8: this is the
actual size artwork
for the front panel.
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$18 Ea. ...12V SLA BATTERY CHARGERS: INTELLIGENT “PLUGPACK” 240V-12V GEL BATTERY
CHARGERS, 13.8V / 650mA, proper “switching”
design with LED status indicator: $8.80 ...LASER
POINTER KIT: A special purchase of some
660nM/5mW laser diode means that we can reduce
the price of our Laser Pointer kit, includes everything
except the batteries: $29 ...SPECIAL BATTERY AND
CHARGER OFFER: When our 7AHr/12V SLA battery
($30) is bought with the SLA battery charger the
total price for both is: $33 ...USED BRUSHLESS DC
FANS: 4"/12V/0.25A: $8, 24V/6"/17W: $12
...100,000uF ELECTROLYTIC CAPACITORS:
30V/40Vsurge, used but in exc. cond.:$10 ...12Hr.
MECHANICAL TIMERS: 55X48X40mm, 5mm shaft
(Knob not supplied), two hours timing per 45deg.
rotation, two 25V/16A SPST switches which close at
the end of the timing period: $5 ...USED IEC LEADS:
Used Australian IEC leads: $2.50 ...STANDARD
PIEZO TWEETERS: Square, 85X85mm, 4-40KHz, 35V
RMS: $8, Wide dispersion, 67X143mm, 3-30KHz,
35V RMS: $9 ...COMPUTER POWER SUPPLY:
Standard large supply as used in large computer
towers, +5V/22A, +12V/8.5A, -5V/0.5A, -12V/0.5A,
used but in excellent condition, guaranteed: $30
...MAGNIFIERS: Small eyepiece: $3, 30mm Loupe:
$8, 75mm Loupe: $12, 110mm Loupe: $15, a set of
one of each of these magnifiers (4): $30 ... NEW
NICAD BATTERY BARGAIN: 6 PACK (7.2V) OF 1.2V
/ 800 mAHr. AA NICAD BATT’s plus 1 X thermal switch,
easy to seperate: $4 per pack or 5 packs for $16,
FLAT RECTANGULAR 1.2V, 400mAh NI-CAD BATTERIES with thermal switch, easy to seperate, (Each
batt: 48x17x6 mm): $4 per pack or 5 packs for $16
...UV MONEY DETECTOR: Small complete unit with
cold cathode UV tube, works from 2 X AA batteries
( Not supplied), Inverter used can dimly light a 4W
white fluoro tube: $5Ea. or 5 for $19 ...MISCELLANEOUS USED LENS ASSEMBLIES: Unusual lens
assemblies out of industrial equipment: 3 for $22
...USED PIR MOVEMENT DETECTORS: Commercial
quality 10-15M range, used but tested and guaranteed, have O/C transistor (BD139) output and a
tamper switch, 12V operation, circuit provided: $10
Ea. or 4 for $32 ...CCD CAMERA WITH BONUS: Tiny
(32X32X27mm) CCD camera, 0.1lux, IR responsive
(Works in total dark with IR illumination), connects
to any standard video input (Eg VCR) or via a modulator to aerial input: $125, BONUS: With each
camera you can buy the following at reduced prices:
COMMERCIAL UHF TRANSMITTER for $15 (Normally $25), IR ILLUMINATOR KIT with 42 X 880nM LED’s
for $25 (Normally $35), REGULATED 10.4V PLUGPACK for $10 (Normally $25) ...PIR CASE FOR CCD
CAMERA: Used PIR cases of normal appearance, use
to hide the CCD camera, plenty of room inside: $2.50
Ea. or 4 for $8 ...CAMERA-TIME LAPSE VCR RECORDING SYSTEM: Includes PIR movement detector and interface control kit, plus a learning remote
control, combination can trigger any VCR to start
recording with movement and stop recording a few
minutes after the last movement has stops: $90
...GEIGER COUNTER KIT: Based on a Russian tube,
has traditional “click” to indicate each count. Kit includes PCB, all on-board components, a speaker and
Yes, the geiger counter tube is included: $30 ...RARE
EARTH MAGNETS: Very strong! 7X3mm $2, 10X3mm
$4, Torroidal 50mm outer, 35mm inner, 5mm thick:
$10 ...IR TESTER: Kit includes a blemished IR
converter tube as used in night vision and an EHT
power supply kit, excellent for seeing IR sources,
price depends on blemishes: $30 / $40 ...ARGON-ION
HEADS: Used Argon-Ion heads with 30-100mW
output in the blue-green spectrum, power supply
circuit provided, size: 350X160X160mm, weight 6Kg,
needs 1KW transformer available elsewhere for about
$170, head only for: $350 ...DIGITAL RECORDING
MODULES: Small digital voice recording modules as
used in greeting cards, microphone and a speaker
included, 6 sec. recording time: $9 ...WIRED IR
REPEATER KIT: Extend the range of existing IR remote
controls by up to 15M and/or control equipment in
other rooms: $18 ...12V-2.5W SOLAR PANEL KIT:
US amorphous glass solar panels, 305X228mm, Vo-c
18-20V, Is/c 200mA: $22 Ea. or 4 for $70 ...MIDI
KEYBOARDS: Quality midi keyboard with 49 keys, 2
digit LED display, MIDI out jack, Size: 655115X35mm,
computer software included, see review in Feb. 97
EA: $80, 9V DC plugpack: $10, also available is a
larger model which has mor features and has touch
sensitive response keys: $200 ...STEREO FM TRANSMITTER KIT: 88-108MHz, 6-12V DC supply, 8mA <at>
9V, 25X65mm PCB size, PCB plus all on-board
comp’s, plus battery connector and 2 electret mic’s:
$25, plastic case to suit: $4 ...WOOFER STOPPER
KIT: Stop that dog bark, also works on most animals,
refer SC Feb. 96, Kit includes PCB and all on board
comp’s, wound transformer, electret mic., and a horn
piezo tweeter: $39, extra horn piezo tweeters (drives
up to 4) $6 Ea. ...ALCOHOL BREATH TESTER KIT:
Based on a thick film alcohol sensor. The kit includes
a PCB, all on board comp’s and a meter : $30 ...CENTRAL LOCKING KIT (NEW): A complete central
locking kit for a vehicle. The kit is of good quality and
actuators are well made, the kit includes 4 actuators,
electronic control box, wiring harness, screws, nuts,
and other mechanical parts: $60, The actuators only:
$9 Ea. ...CODE HOPPING UHF CENTRAL LOCKING
KIT PLUS A ONE CHANNEL UHF REMOTE CONTROL:
Similar to above but this one is wireless, includes
code hoping Tx’s with two buttons (Lock-unlock), an
extra relay in the receiver can be used to immobilise
the engine, etc., kit includes 4 actuators, control box,
two Tx’s, wiring harness, screws, nuts, and other
mechanical parts: $109 ...ELECTROCARDIOGRAM
PCB + DISK: The software disk and a silk screened
and solder masked PCB (PCB size: 105 x 53mm) for
the ECG kit published in EA July 95. No further
components supplied: $10 ...SECURE IR SWITCH:
IR remote controlled switch, both Rx and Tx have
Dip switches for coding, kit includes commercial 1
Tx, Rx PCB and parts to operate a relay (not supplied):
$22 8A/4KV relay $3 ...FLUORESCENT TAPE: High
quality Mitsubishi brand all weather 50mm wide Red
reflective tape with self adhesive backing: 3 meters
for $5 ...LOW COST IR ILLUMINATOR: Illuminates
night viewers or CCD cameras using 42 of our 880nm
/ 30mW / 12 degrees IR LEDs. Power output is
varied using a trimpot., operates from 10 to 15V,
current is 5-600mA ...IR LASER DIODE KIT: Barely
visible 780nM/5mW (Sharp LT026) laser diode plus
constant current driver kit plus collimator lens plus
housing plus a suitable detector Pin diode, for medical use, perimeter protection, data transmission,
experimentation: $32 ...WIRELESS IR EXTENDER:
Converts the output from any IR remote control into
a UHF transmission, Tx is self contained and attaches with Velcro strap under the IR transmitter, receiver has 2 IR Led’s and is place near the appliance
being controlled, kit includes two PCB’s all components, two plastic boxes, Velcro strap, 9V transmitter
battery is not supplied: $35, suitable plugpack for
the receiver: $10 ...NEW - LOW COST 2 CHANNEL
UHF REMOTE CONTROL: Two channel encoded UHF
remote control has a small keyring style assembled
transmitter, kit receiver has 5A relay contact output,
can be arranged for toggle or momentary operation:
$35 for one Tx and one Rx, additional Tx’s $12 Ea.
OATLEY ELECTRONICS
PO Box 89
Oatley NSW 2223
Phone (02) 9584 3563
Fax (02) 9584 3561
orders by e-mail:
branko<at>oatleyelectronics.com
major cards with phone and fax orders,
P&P typically $6.
December 1996 75
VINTAGE RADIO
By JOHN HILL
A new life for a battered Astor
Not all vintage radios are highly sought after
items. A mid-1950s 4-valve Astor can often be
picked up for just a few dollars and is usually
quite easy to repair and get going again.
Vintage radio receivers vary from
those rare relics from the 1920s to
the mass-produced plastic mantel
models of the 1950s and 1960s, with
a multitude of makes and models in
between. Although some collectors
specialise in a particular era or brand
name, many collect whatever comes
their way, regardless of age or whether
it is housed in a timber, bakelite or
plastic cabinet.
From a writing point of view, I like
to produce a similar variety in my
monthly column and endeavour to
give my readers a mixed bag of stories
about the many and varied aspects of
vintage radio. It appears that a restoration story on a relatively late-model
valve receiver is just as interesting, in
its way, as a similar story on an older
and rarer set that few of us are ever
likely to own. In fact, far more readers can relate to a late-model receiver
because that is what most people are
likely to collect.
It so happened that a particular
repair came my way recently and it
seemed to be a good one to write about
for the simple reason the receiver is so
ordinary and unspectacular. It was a
mid-1950s 4-valve Astor mantel with
odd control knobs and a smashed
speaker grille – the sort of wreck that
can be picked up at a garage sale for
$10 or less.
Apart from the broken cabinet, the
receiver was in poor condition and
although it supposedly “worked”
when purchased, it made no sound
other than a badly distorted whimper.
The first step with the grille repair was to make up a plastic louvre to replace
the missing one. The handle of a plastic knife was used for this purpose.
76 Silicon Chip
In fact, it was the type of set that one
would normally buy for spare parts.
In this instance, however, the
receiver was brought to me to be
repaired. As the woman who owns
it is a friend of the family, I really
couldn’t say no.
Of course, she realised when she
bought the set that it needed a lot
doing to it but thought that it would
be no trouble for me to fix it because
my magic wand can mend just about
anything. Oh – such faith!
Grille repairs
I decided to attempt the broken
grille repair first and it was fortunate
that the damage was not as bad as it
could have been. One broken piece
had already been glued back in place
while the other piece was missing.
This meant that a new section had to
be made and glued into position.
Finding something suitable from
which to make a new grille part was
the problem. Eventually, the handle
of a takeaway plastic knife supplied
the necessary material. It was shaped
with a file until it wedged firmly into
position, then it was glued in place.
A couple of smaller fragments were
then used elsewhere to fill in a few
missing chips.
Although the broken grille louvres
had been successfully replaced, the
stark white plastic replacements
stood out like a neon sign compared
to the rest of the speaker grille. The
repair area needed a touch up with
a matching paint but obtaining the
correct colour match was a near impossible task.
So instead of a match, a contrast was
used, and the whole grille area was
painted an off-white. The result was
pleasing enough and at the same time
disguised the repair area reasonably
well. With the grille reconstruction
completed, the circuitry was next on
the agenda.
Speaker repairs
In order to work on the speaker
grille, the speaker had to be removed
from the cabinet. This should have
been a simple operation requiring the
removal of four spring steel clips from
the plastic studs they fit onto. Alas,
two of the studs snapped off!
Removing the speaker revealed
that whatever smashed the grille also
damaged the speaker cone – it was torn
from rim to centre. Repairing the split
with silicone rubber (Silastic®) cured
the problem and while such cone
patch-ups aren’t always the neatest
looking repairs, they are effective and
long lasting.
The speaker, by the way, is unusual in that it is a very small oval type
measuring 125 x 75mm (5 x 3 inches),
so replacement was not an option.
As an aside, most 4-valve receivers
from the 1950s used 125mm (5-inch)
speakers so it appeared that the little
Astor might be at a disadvantage as far
as a good sound reproduction was concerned. However, after the restoration
had been completed, the midget Rola
performed really well and the set’s
tonal quality was excellent.
A close-up view of the finished grille repair. The whole louvre area was painted
off-white to disguise the repaired section. Although not a totally invisible repair,
there were no complaints from the owner.
Original parts
Checking out the chassis revealed
everything to be original and the state
of the 40-year old Ducon paper capacitors was not good. They appeared to
have been overheated, having bulged
ends and droplets of solidified wax
hanging from their undersides. Naturally, they were replaced and that,
in itself, would have au
tomatically
solved a number of problems.
The valves were checked next and
the valve tester’s neon quickly indicated an intermittent short in the 6BE6.
These valves often flash the shorts/
leakage neon on my valve tester but,
despite this, they usually function
Spring-steel clips are used to hold the
loudspeaker in place. As is often the
case, the plastic stud breaks off when
the clip is removed.
This is the miniature (125 x 75mm) Rola loudspeaker that was used in the old
Astor. Note the missing retaining clips and the repaired cone areas at 12 o’clock
and 2 o’clock. The cone repair was completely satisfactory.
quite normally. The rest of the valves
checked OK.
Numerous other items needed attention. The 200Ω back-bias resistor
had split, a noisy volume control
required cleaning, a new power cord
was needed, the dial cord was about
to let go, both dial lamps were burnt
These two spring retaining clips are
all that hold the cabinet together.
This view shows how the clips are
fitted to the underside of the cabinet.
December 1996 77
The two odd knobs at left were replaced with a pair of Radiola knobs which
matched the maroon colour of the Astor cabinet perfectly.
out, and the chassis was just floating
around loose inside the cabinet.
An ohmmeter check on other resistor values cleared them all as being
well within tolerance. The intermediate frequency, power, and output
transformers also passed inspection,
as did the aerial and oscillator coils.
Testing
After replacing all the necessary
parts it was time for a tryout. While
the receiver worked, there was very
little volume and an incredible amount
of distortion.
Distortion in a valve radio can often
be caused by a leaky coupling capacitor from the plate of the driver stage
to the grid of the output valve. This
allows the plate voltage to be applied
to the control grid of the output valve,
thus biasing the grid positive instead
of negative. As the little Astor had just
had all of its old capacitors replaced,
a faulty coupling capacitor seemed
unlikely.
However, a voltmeter check of the
output valve’s control grid revealed a
high positive potential. The coupling
capacitor was replaced but the situa-
The little Astor is of simple construction
and is a very basic 4-valve receiver. It was
straightforward to repair and get going.
78 Silicon Chip
tion remained the same – the control
grid was still positive!
Studying the circuitry more closely
revealed a 100pF silvered mica capacitor connected between the plate of
the 6AQ5 output valve and its control
grid, via a 47kΩ stopper resistor. This
capacitor is designed to apply a small
amount of negative feedback to the
control grid of the output valve, to
improve the audio frequency response
of the receiver. It was reasonable to
assume that this mica capacitor was
faulty and it was!
Removing the capacitor immediately cured the distortion problem and
the set sounded normal – but not for
long. After about a minute or two, the
distortion returned and the volume
faded to almost nothing.
At this stage, I recalled the short
indication when testing the 6BE6.
The valve was replaced and that fixed
that problem – no more distortion
and stable volume. A new 100pF capacitor was also fitted in place of the
faulty one and repairs were nearing
completion.
There was still one remaining problem with the receiver – it was full of
whistles. The 6AD8 IF (intermediate
frequency) amplifier valve was replaced and that eliminated the birdies, so the valve obviously had some
sort of an internal fault or a shielding
problem.
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The finished Astor mantel receiver looked quite presentable. It’s not the sort of
receiver that collectors would fight over but its owner was very pleased to have
it restored to working order.
An alignment session peaked the
IF transformers and aligned the aerial
and oscillator circuits. That completed
the restoration except for a few minor
details. One of these details was the
mounting of the loudspeaker. It has
already been stated that two of the
mounting lugs broke off when removing the speaker’s retaining clips. This
is not an uncommon happening with
this method of mounting and can make
remounting the speaker difficult.
Perhaps the easiest way out of
this situation is to glue the speaker
back in place but this should be
done with care. Some modern glues
can be rather tenacious, so use them
sparingly in case the speaker has to
be removed some time in the future.
Also, it is advisable to fit a grille cloth
to minimise the accumulation of dust
and fluff that builds up between the
bottom of the speaker cone and the
speaker baffle.
Checking mica capacitors
A megohmmeter test on the suspect
mica capacitor revealed a serious
leakage problem. Capacitors which
work at high voltages should be tested
at high voltages.
Perhaps some comment should
also be made regarding that leaky
mica capacitor. The faulty capacitor
was the only silvered mica capacitor
in the receiver. As time progresses,
more and more of these capacitors
give trouble and need replacing but
it is not always easy to detect faults
in mica capacitors.
When checking the suspect capacitor with a multimeter set to the ohms
x 1000 scale, the meter needle showed
not the slightest deflection. To many
vintage repairers this would indicate
that the capacitor was not leaking or
shorted and not the cause of the problem. Not necessarily so!
When the same suspect capacitor
Send SSAE for Catalogue
Visit our Showroom at
242 Chapel Street (PO Box 2029),
PRAHRAN, VIC 3181.
Phone: (03) 9510 4486; Fax (03) 9529 5639
was checked at 500V using a megohm
meter, the meter reading was about
0.5MΩ and that sort of leakage is quite
unacceptable under the conditions in
which the capacitor operates.
Leakage and resistance might be
regarded as two different effects. A
good component will measure the
same whether checked on a multimeter at 3V or a megohmmeter at 500V.
But leakage in a faulty component
can increase with voltage. Which is
why capacitors that work under high
voltage conditions should be checked
for leakage at high voltages.
In conclusion, this somewhat undesirable wreck of a radio was brought
back from the dead and is once more
an operative and useful receiver.
With its repaired and painted speaker grille it has little appeal to serious
collectors but its owner was absolutely
thrilled with the transformation. The
little Astor now has pride of place in
her bedroom and is looked on as a
treasured possession.
This only goes to prove that beauty
is in the eye of the beholder. What
may not appeal to some can be simply
SC
wonderful to others.
December 1996 79
Build an 8-cha
stereo mixer;
Building the new 8-Channel Stereo Mixer is
straightforward since nearly all the parts are
mounted on one large PC board. A second,
much smaller board takes care of the power
supply components.
By JOHN CLARKE
80 Silicon Chip
The general arrangement of the new
mixer can be quickly gleaned from the
accompanying photos. As shown, the
main board mounts on the back of the
front panel, while the power supply
board mounts on the base of the case.
The main board is coded 01210961
and measures 400 x 290mm, while
the power supply board is coded
01210962 and measures 105 x 67mm.
Begin construction by checking the
PC boards for shorted or broken tracks
annel
Pt.2
and by checking the hole sizes. All
holes for the pots should be just large
enough to accept the threaded section,
while the holes for the 6.35mm stereo
sockets should be 11mm in diameter
(to accept the stub at the end of each
socket).
Rotary switch S9 is mounted directly on the main board and should be
test fitted to ensure that its mounting
holes are large enough to accept the
switch pins. The eight toggle switches
(S1-S8), the 6.35mm socket contact
points and the three power supply
inputs are all soldered to PC stakes.
Check that the relevant holes are
large enough to accept the PC stakes
supplied.
The holes for the XLR sockets and
plugs should also be tested for correct
size. In addition, there should be a
12mm hole directly below S9 and in
line with the Effects pots. This hole
allows the relevant leads to pass
through the PC board on their way
to the mains switch (S10) and to an
adjacent earth solder lug bolted to the
front panel.
Finally, there are 11 mounting holes
for attaching the PC board to the front
panel (via 3mm screws and 25mm
standoffs). Check that all these holes
are drilled to 3mm.
Fig.4 shows the assembly details
for the main PC board. Begin by inserting the PC stakes, wire links and
resistors. The PC stakes are installed
at the S1-S8 switch positions (three
for each switch), at the 6.35mm socket connection points (tip, ring and
ground), and at the +15V, GND and
-15V power supply points located
near LED1.
Table 2 shows the resistor colour
codes but we also suggest that you
check each value using a digital
multimeter, just to make sure. That’s
because some colours can be difficult
to decipher and it’s easy to make a
mistake when there are lots of resistors
to be installed.
The next step is to install the ICs.
Be sure to install the correct op amp
in each location and with the correct
orientation. In particular, note that IC6
and IC8 are oriented differently to the
remaining ICs. Once the ICs are in,
install the two signal diodes (D1 and
D2) and transistors Q1 and Q2. Don’t
get these two transistors mixed up –
Q1 is a BC338 NPN type, while Q2 is
a BC328 PNP type.
The capacitors are next. Note that
the electrolytics with 10µF and 100µF
markings are polarised and must
be oriented as shown on Fig.4. The
remaining electrolytics are NP (nonpolarised) and can be oriented either
way around. Table 1 shows the codes
used for the ceramic and polyester
capacitors.
It’s now time to install the switches. The toggle switches (S1-S8) are
simply soldered to the tops of their
corresponding PC stakes. Take care
to ensure that each switch is centred
over its PC stakes and that it is at right
angles to the PC board before soldering
all the connections.
Rotary switch S9 is mounted directly on the PC board. Push this switch
all the way down onto the board before
soldering its pins. This done, remove
and discard the locking ring that’s
located under the mounting nut and
star washer.
The 6.35mm sockets are mounted
with their rear stubs inserted into the
PC board holes. Note that it is necessary to bend the Tip (end terminal)
outwards and the GND terminal (front)
inwards so that they contact their corresponding PC stakes. The Ring (centre
terminal) is left unchanged.
The Tip and Ring terminals can
now be soldered directly to the Tip
and Ring PC stakes. The connection
from the GND terminal to the GND PC
stake requires a short length of tinned
copper wire to bridge the gap.
Note that only the Tip and GND terminals are used in some cases, and the
Ring terminal is left unconnected. For
the headphone socket, however, the
Tip and Ring terminals are connected
together, so that the sound is fed to
both sides of the headphones.
Potentiometers
There are 54 potentiometers to be
mounted on the board, so installing
them all will take some time. The main
thing to watch out for here is that their
values differ, so be sure to install the
correct pot at each location.
As shown, the pots are all mounted
from the underside of the PC board.
Before doing this however, it is necessary to fit a 10.5mm ID x 2mm thick
plastic washer to the threaded bush
of each pot.
This is to prevent the pot bodies
from shorting the copper tracks on the
PC board. In addition, the locating tag
on the side of each pot must be bent
sideways (to clear the PC board), while
the centre terminal must be bent at
right angles, towards the shaft.
This done, secure each pot to the
PC board in turn and solder its centre
terminal directly to its PC board pad.
The outer pot terminals are wired
using short lengths of tinned copper
wire. Once all the pots are in, trim the
plastic shaft of switch S9 to the same
height as the pot shafts.
The XLR sockets and plugs can
now all be soldered in place, making
December 1996 81
82 Silicon Chip
December 1996 83
Fig.4: follow the order suggested in the text when installing the parts on the PC board and note that the pots are fitted
with an insulating washer (see text) and installed from the copper side. Take care to ensure that all polarised parts are
correctly oriented and that the IC type numbers are correct.
Repeated from last month’s issue, this photo shows the fully-assembled PC
board. Note that a few changes were made to the board after this photo was
taken and so it will differ slightly from the layout shown in Fig.4.
sure that they sit square with the PC
board. This done, insert the two LED
bar
graphs. Note that, in each case,
the anode (longer) lead goes towards
switch S9. Similarly, install LED21 but
do not solder this LED or the bargraphs
just yet; first, we have to temporarily
fit the front panel.
The front panel is straightforward
to fit. Begin by fitting the 25mm
spacers to the PC board,. There are
11 spacers in all and these should
be firmly secured using 3mm machine screws. Once the spacers are
in place, fit the front panel over the
top of the PC board, so that it sits on
the standoffs.
The toggle switches (S1-S8) and
6.35mm socket securing threads
should protrude through the panel,
although you may need to slightly
adjust the toggle switches for correct alignment. Check also that the
XLR sockets and plugs sit flush with
the underside of the panel. When
everything fits correctly, secure the
84 Silicon Chip
panel from the top using 3mm screws
into the spacers.
The LED bargraph displays and
LED21 can now be pushed into their
respective holes in the front panel
and their leads soldered. This done,
remove the front panel and fit the
mains toggle switch (S10). In addition,
an earth solder lug should be securely
bolted to the back of the front panel,
immediately to the left of the mains
switch. Be sure to scrape away the
paint around the mounting point to
ensure a good earth contact.
Power supply
It’s now time to build the power
supply and this can begin with the PC
board assembly – see Fig.5. The four
diodes (D3-D6) can go in first, followed
by PC stakes at the six external wiring
points.
The two 1000µF electrolytic capacitors are mounted side-on, which
means that the leads must be bent at
right angles to go through the PC board.
Take care to ensure that they and the
smaller 10µF capacitors are mounted
with the correct polarity. It’s a good
idea to glue the bodies of the 1000µF
capacitors to the PC board, so that
they cannot move and place stress on
their leads.
The two 3-terminal regulators are
fitted with small heat
sinks and the
assemblies secured to the PC board
using 3mm screws and nuts. There’s
no need to isolate their tabs from the
heatsinks but note that REG1 is a 7815
while REG2 is a 7915, so don’t get them
mixed up. Bend the regulator leads at
right angles so that they go through
the holes in the board and trim off any
excess after soldering.
The remaining power supply items
are mounted on the chassis – see Fig.6.
If you are making your own metalwork, you will need to drill holes for
the fuseholder, cordgrip grommet,
transformer mounting screw, earth
screw and the mains terminal block.
Four mounting holes are also required
for the power supply board. The board
can then be mounted on 6mm standoffs and the other major hardware
items installed.
Note that the earth solder lugs must
be securely bolted to the case using a
screw, nut and starwasher. A second
nut can then be used to lock the first,
so that there is no chance of it coming
loose. As before, scrape away the paint
from around the mounting hole before
installing this assembly, to ensure a
good earth contact.
Follow the layout shown in Fig.6
exactly when installing the mains
wiring. The mains cord enters the case
through the cordgrip grommet and
must be securely clamped (check this
carefully). The Neutral (blue) lead goes
directly to the main terminal block,
while the Active (brown) lead goes to
the fuseholder. A mains-rated lead is
then run from the other terminal on
the fuseholder to the terminal block.
Slip a short length of heatshrink
tubing over the leads before soldering
them to the fuseholder. This done, solder the leads, then push the heatshrink
tubing over the fuseholder and shrink
it down using a hot-air gun. Do not
neglect this step – it is an important
safety measure to prevent accidental
contact with the mains.
The Earth lead (green/yellow) from
the mains cord must be securely
soldered to the earth lug. Leave this
lead longer than the others, so that it
will be the last lead to break should
the mains cord ever come adrift due
to some brute force. After making the
Fig.5: this is the parts layout for the power supply PC board. Use PC stakes
at the external wiring connections and make sure that you don’t get the
positive and negative 3-terminal regulators mixed up
connection, use a multimeter to confirm that there is zero ohms resistance
between the earth pin of the mains
plug and the case.
The remaining connections to the
terminal block involve the transformer primary leads plus a 3-wire
mains-rated cable that runs to switch
S10 on the front panel and to the adjacent earth solder lug. Note the .001µF
2kV capacitor that’s connected to the
terminal block in parallel with these
leads. The leads are fed through the
12mm hole in the PC board below S9,
before being connected to the power
switch.
As with the fuseholder, be sure the
shroud the switch body with heat
shrink tubing – ie, slip heatshrink
tubing over the leads before soldering
them to the switch terminals, then
Below: the view from the rear of the
PC board, with all the pots in place.
The two outer terminals of each pot
are soldered directly to the copper
pads, while the centre terminals are
connected via a wire link.
December 1996 85
Fig.6: install the power supply wiring as
shown in this diagram. Note that the leads
to power switch S10 must be mains rated,
as must the Earth lead to the adjacent
solder lug.
push the tubing over the switch body
and shrink it down.
The transformer secondary leads
can now be connected to the power
supply board but don’t connect the
supply leads to the main (mixer) PC
board at this stage. That step comes
later, after the power supply has been
tested. Use cable ties to secure the
mains wiring and transformer leads.
Testing
When the wiring is complete, go
86 Silicon Chip
back over your work and check carefully for any wiring errors. In particular, check that the mains wiring
is correct and that all exposed switch
and fuseholder terminals have been
shrouded with heatshrink tubing. Now
carry out the following test procedure:
(1). Disconnect both power switch
leads and the .001µF capacitor from
the mains terminal block and connect
an insulated link across the vacant terminals (this disconnects and bypasses
the mains switch).
(2). Install the fuse, apply power
and check that the +15V and -15V
supply rails are present on the power
supply board.
(3). Switch off and run the supply
leads (+15V, GND, -15V) from the
power supply board to the main
board (immediately below the left
bargraph). These leads can be run
using medium-duty hookup wire.
Twist the leads together to keep them
neat and tidy and make sure you don’t
get them mixed up; ie make sure that
The power transformer and the power supply board are mounted on the base of
the chassis. Make sure that the mains cord is securely anchored via its cordgrip
grommet and be sure to cover all exposed terminals with heatshrink tubing.
+15V goes to +15V, GND to GND, and
-15V to -15V.
(4). Reapply power and check that
the power LED lights. If it doesn’t,
check the LED orientation. Check each
LM833 IC for +15V on pin 8 and -15V
on pin 4. The SSM2017 and OP27GP
ICs should have +15V on pin 7 and
-15V on pin 4, while the LM3915s
(IC6 & IC8) should have +15V on pins
3 and 9.
(5). Connect a signal source to one
of the inputs and check that the LED
bargraph displays operate correctly.
The headphone output can be checked
by plugging in a set of headphones.
(6). Check that the corresponding
pan control shifts the signal from left
to right, as indicated by the displays
and the headphone output. Do this
for each of the eight main channels,
then test the Auxiliary input and its
pan control.
(7). Check for signal at the left, right,
monitor and effects outputs using an
oscilloscope or a multimeter set to
read AC volts.
All that remains now is the final
assembly. First, check that the mains
plug has been pulled out of the wall
TABLE 1: CAPACITOR CODES
❏
❏
❏
❏
❏
❏
❏
❏
Value
.01µF
.0047µF
.001µF
270pF
180pF
27pF
10pF
IEC
10n
4n7
1n0
270p
180p
27p
10p
EIA
103
472
102
271
181
27
10
socket, then remove the insulated link
from the terminal block and reconnect
the switch leads and the .001µF 2kV
capacitor.
TABLE 2: RESISTOR COLOUR CODES
❏
No.
❏ 5
❏
47
❏
36
❏
46
❏
19
❏
25
❏
44
❏
10
❏ 2
❏ 7
❏ 3
❏ 2
❏
23
Value
68kΩ
22kΩ
15kΩ
10kΩ
6.8kΩ
4.7kΩ
2.2kΩ
330Ω
270Ω
100Ω
68Ω
33Ω
10Ω
4-Band Code (1%)
blue grey orange brown
red red orange brown
brown green orange brown
brown black orange brown
blue grey red brown
yellow violet red brown
red red red brown
orange orange brown brown
red violet brown brown
brown black brown brown
blue grey black brown
orange orange black brown
brown black black brown
5-Band Code (1%)
blue grey black red brown
red red black red brown
brown green black red brown
brown black black red brown
blue grey black brown brown
yellow violet black brown brown
red red black brown brown
orange orange black black brown
red violet black black brown
brown black black black brown
blue grey black gold brown
orange orange black gold brown
brown black black gold brown
December 1996 87
PARTS LIST
1 metal case, 430 x 300 x 132mm
1 front panel (484 x 309mm) with
screen printed artwork plus
securing screws
1 PC board, code 01210961, 400
x 290mm
1 PC board, code 01210962, 105
x 67mm
1 20VA 2 x 15VAC toroidal transformer (T1) (Jaycar
MT-2086)
1 2AG panel mount fuse holder
1 2AG fuse (F1)
8 SPDT toggle switches (S1-S8)
1 single pole 12-way rotary switch
(S9)
1 SPST mains rocker switch
(S10)
12 6.35mm stereo sockets (Altronics P-0075 or equiv.)
8 straight pin PC mount XLR panel
sockets (Altronics P- 0883)
2 straight pin PC mount XLR panel
plugs (Altronics P-0881)
29 10kΩ log pots with 38mm long
shaft (VR1, VR2, VR5, VR7-10,
VR12-14, VR17, VR19, VR20,
VR23, VR25, VR26, VR29,
VR31, VR32, VR35, VR37,
VR38, VR41, VR43, VR44,
VR47, VR49, VR50, VR53)
9 10kΩ lin. pots with 38mm long
shaft (VR6, VR11, VR18, VR24,
VR30, VR36, VR42, VR48,
VR54)
8 100kΩ lin. pots with 38mm long
shaft (VR3, VR15, VR21, VR27,
VR33, VR39, VR45, VR51)
8 20kΩ lin. pots with 38mm long
shaft (VR4, VR16, VR22, VR28,
VR34, VR40, VR46, VR52)
9 red knobs
10 blue knobs
16 grey knobs
10 green knobs
The front panel can now be refitted.
Check that the LED displays and power
LED fit their respective holes before
securing the panel to the standoffs
using 3mm screws.
The front panel is further secured by
fitting the nuts to the 6.35mm sockets
and to the toggle switches, and by
fitting the self-tapping screws that
come with the XLR plugs and sockets.
This done, the entire assembly can be
fitted to the case and secured using the
88 Silicon Chip
10 black knobs
1 mains cord and plug
1 cord grip grommet
3 solder lugs
1 3-way mains terminal block
2 heatsinks, 29 x 30 x 12mm
4 6mm standoffs
10 25mm tapped standoffs
59 PC stakes
4 rubber feet
30 3mm dia. x 6mm long screws
1 3mm dia. x 9mm screw, nut and
star washer
2 3mm dia. x 12mm screws and
nuts
2 3mm nuts
20 self-tapping screws for XLR
sockets and plugs
54 10.5mm ID x 2mm high plastic
spacers for pots (Farnell 3 x
582-591 or similar)
1 6m length of 0.8mm tinned copper wire
1 300mm length of sheathed twin
mains wire
1 300mm length of red hookup
wire
1 300mm length of green hookup
wire
1 300mm length of black hookup
wire
Semiconductors
8 SSM2017P balanced microphone preamplifier ICs (IC1,
IC13, IC16, IC19, IC22, IC25,
IC28, IC31)
8 OP27GP op amps (IC3, IC15,
IC18, IC21, IC24, IC27, IC30,
IC33)
14 LM833 op amps (IC2, IC4, IC5,
IC7, IC9, IC10, IC11, IC14,
IC17, IC20, IC23, IC26, IC29,
IC32)
1 TL071 op amp (IC12)
self-tapping screws supplied.
It’s now simply a matter of fitting the
push-on knobs to the potentiometer
and switch shafts. We suggest that red
knobs be used for the Monitor controls,
black for Effects and Auxiliary, red for
Pan, grey for Treble, green for Bass and
blue for Main.
The final testing is best done using
all inputs with microphones and instruments. Note that the mixer is intended to operate with the signal GND
2 LM3915 log LED bargraph drivers (IC6, IC8)
1 BC337 NPN transistor (Q1)
1 BC327 PNP transistor (Q2)
2 1N914, 1N4148 diodes (D1,D2)
4 1N4004 diodes (D3-D6)
1 15V positive regulator (REG1)
1 15V negative regulator (REG2)
4 5-segment LED bargraph displays (LEDs 1-20) (Altronics Z
0179)
1 3mm LED (LED21)
Capacitors
2 1000µF 25VW PC electrolytic
2 100µF 16VW PC electrolytic
6 47µF 50V non-polarised PC
electrolytic
35 10µF 35VW PC electrolytic
8 6.8µF 50V non-polarised PC
electrolytic
40 2.2µF 50V non-polarised PC
electrolytic
4 1µF 50V non-polarised PC electrolytic
8 .01µF MKT polyester
16 .0047µF MKT polyester
2 .001µF MKT polyester
27 270pF ceramic
2 180pF ceramic
5 27pF ceramic
8 10pF ceramic
1 .001µF 2kV ceramic
Resistors (0.25W, 1%)
5 68kΩ
10 330Ω
47 22kΩ
2 270Ω 1W
36 15kΩ
7 100Ω
46 10kΩ
3 68Ω
19 6.8kΩ
2 33Ω
25 4.7kΩ
23 10Ω
44 2.2kΩ
Miscellaneous
Solder, heatshrink tubing.
earthed at one point. This is usually
done at the power amplifier. If this is
not the case, then earth the signal GND
to chassis at the mixer.
Finally, note that the maximum
input levels before clipping were incorrectly listed in the specifications
panel on page 23 of the November
issue. The correct levels are 260mV
RMS on the Low setting and 3V RMS
on the High setting (not 2.9V and 9V,
SC
as shown).
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Rod Irving Electronics Pty Ltd
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
Rod Irving Electronics Pty Ltd
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Rod Irving Electronics Pty Ltd
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Please feel free to visit the advertiser’s website:
Rod Irving Electronics Pty Ltd
SILICON
CHIP
If you are seeing a blank page here, it is
more than likely that it contained advertising
which is now out of date and the advertiser
has requested that the page be removed to
prevent misunderstandings.
Rod Irving Electronics Pty Ltd
PRODUCT SHOWCASE
200MHz TekScope from Tektronix
Tektronix has announced
the THS730A, the top of
the range oscilloscope/
DMM in its TekScope family
of products. The THS730A
model operates at 200MHz,
with 1Gs/s sampling rate
and features the Tektronix
exclusive Isolated Channel
Architecture for user and
circuit safety as well as wide
bandwidth.
Developed for electronics design
and test engineers, as well as for field
troubleshooting, the THS730A offers
high speed dual channel/dual digitiser
measurement and triggering capabili
ties for quick timing error detection.
The THS730A utilises the TekScope
graphical user interface (GUI).
Other features of this oscilloscope
include comprehensive and advance
triggering, glitch capture, dB and dBm
measurements.
Other members of the THS700
oscilloscope family include the THS
STEPDOWN
TRANSFORMERS
60VA to 3KVA encased toroids
Harbuch Electronics Pty Ltd
9/40 Leighton Pl. HORNSBY 2077
Ph (02) 9476-5854 Fx (02) 9476-3231
94 Silicon Chip
710A, THS720A and THS720P. The
THS720P, designed for electrical
service and power electronics testing,
can make measurements to 1kV RMS.
For further information, contact
Tektronix Australia Pty Ltd, 80 Waterloo Rd, North Ryde, NSW 2113. Phone
(02) 9888 0100; fax (02) 9888 0125.
Thingamebobs
& Douvres
MicroZed Computers has released
two kits for making prototypes. Intended for use with BASIC Stamp
control computers, these kits are designed to minimise soldering, speed
prototyping time and allow reuse of
prototypes.
Stamp boards, like most other small
computers, come with a 0.1-inch matrix of plated through holes. Soldering
and unsolder
ing more than a few
times deteriorates the prototype area
of the board. MicroZed’s Thingamebob
wiring kit is a low-cost, ready-made
solution to match the Stamp’s header
strip connections.
The basic wiring kit has 20 x 150mm
coloured wires, two each of the 10
colours used for resistor values. Each
wire is terminated with a single pin
plastic housed socket for slipping
onto a header pin. A feature of the
Thingamebob kit is that a selection of
multiple pin housings are supplied, so
that a multi-pin socket can be made.
A 40-pin single row header strip
is supplied, so that the idea may be
interfaced to “breadboard” style proto
typing kits, used to connect to other
circuits, or to “daisy chain” Thinga
mebob wires, where multiple power,
common or communication lines are
needed.
Five spare header connecting
sockets are supplied, to use
on your own wires. Recommended maximum current
capacity for Thinga
mebob
wires is 1000mA. Warning:
Thingamebobs are not suit
able for use on 240V mains
wiring.
Douvres for Stamps is a
small kit of simple circuits,
already wired and ready for
attachment to the header
pins. Each Douvre kit contains seven circuits: a piezo
sounder, a thermistor circuit,
a potentiometer circuit, a
pushbutton circuit and three
LED circuits (red, green and
orange).
Purchasing a Douvres kit
allows a novice user to learn
and use Stamp commands
within an hour of opening
a kit. Professional users, on
the other hand, will find that
they eliminate the tedium
of search
ing for parts and
making up mundane circuits.
Packed in a small reusable
plastic box, Thingamebobs
are priced at $24.00 and Douvres $34.00, including sales
tax. Quantity and tax exempt
prices are available.
Contact MicroZed Computers (067) 722 777 (or see the
advertisement in the Market
Place of this issue).
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.emona.com.au/
Component
counting scales
Manual component counting for batching or stock-take
is one of the big time-wasters
in the electronics industry.
Fortunately, most electronic
components are very nearly
identical in weight, allowing
them to be easily counted by weight.
The PS1015 is a high resolution,
portable counting scale. A rechargeable battery is installed to allow a
full day’s work, before overnight
recharging with the power pack supplied. An internal resolution of 40mg
ensures accurate counting of small
components and pins used in many
products. The maximum capacity of
1.5kg allows counting of some of the
larger components, including electrolytic capacitors, or the large quantities
found in some bulk packs.
The three panel display shows
total weight, unit weight and current
count simultaneously. Back lighting
provides for easy viewing, even in the
dim back corners of some stores. When
not in use, the display can be folded
down for storage and transport.
The measuring tray is 230 x 280mm,
large enough to accommodate a wide
range of containers. The one-touch
Tare button returns the display to zero
for counting after a new container is
placed on the platform.
For further information, contact
Computronics International Pty Ltd,
31 Kensington St, East Perth 6004.
Phone (09) 221 2121; fax (09) 325 6686.
December 1996 95
PIC development
tool kit
The universal and affordable ICEPIC
tool kit, for the Microchip range of PIC
microcontrollers, includes 20MHz
in-circuit emulation, a simulator, a
programmer and an assembler. The
package presents emulation data by
their symbolic names, allows assembling and automatic back notation of
edited error-report files, and generates
extensive assembly warnings to prevent those pitfalls.
The tool kit runs on an IBM compatible PC. System requirements are
386+, DOS, mouse, printer port and
a small amount of extended memory
under himem.sys or equivalent.
The user-screen presents all information required for emulation and
simulation and provides immediate
access to the accompanying PICASM
assembler and user-supplied editor.
A multi-function oscillator is included. The user can select the clock
source to be a user-supplied crystal
or oscillator, a special clock signal located on the target board, or the stable
(5kHz- 20MHz) VFO on the ICE card.
The VFO frequency is selected in four
Programmable video
generator
Leader Instruments has released a
new programmable video generator,
the LT 1610. The unit can drive a
wide range of displays from LCD to
CRT and can be easily controlled
from an external personal computer
through an RS232C interface.
The LT 1610 is provides full digital 8-bit 120MHz output of dot clock
and analog RGB 150MHz output of
dot clock. It enables easy programming of the following functions
under the Windows environment:
horizontal timing, vertical timing,
output conditions and output patdecades and can be fine adjusted, with
the ICEPIC screen acting as an accurate
digital frequency meter.
An on-board switching power
supply generates all the re
quired
voltages from an external 12-24VDC
or AC power source. The ICE card
communicates bi-directionally with
a printer port on the user’s PC. This
link transfers operational code, target
ICEPIC - In Circuit Emulation for Microchip PIC
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multiple windows. User-friendly 8051-type source code instruction
option. Microchip & Parallax syntax compatible assembler. Single step,
run to breakpoint, or run continuously. Edit errors in listing file & back
notate to source. Realtime & transparent emulator with no register
loss. Full source code debugging with register & bit symbolic names.
Change a register, value, or port in decimal, hex, binary, ASCII. Easy
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( Shipped direct to you, import levies are not included ) Includes:-
Simulator, Emulator, 16/17Cxx Assembler, 16C5x ICE pod.
1 year’s FREE software upgrades! Unconditional 30 day refund!
96 Silicon Chip
terns. It is also possible to draw
patterns using a graphics function.
For further information, contact
Stantron Australia Pty Ltd, Suite 1,
Unit 27, 7 Anella Ave, Castle Hill,
NSW 2154. Phone (02) 9894 2377;
fax (02) 9894 2386.
emulation code and emulation information back and forth. Downloading
the ICE operational code from the PC
to the ICE card ensures easy upgrading
in the field as further enhancements
become available.
For further information, contact Neil
Kirkness, 29 Pacific Sands, Poinciana
Road, Holloways Beach, Qld 4878.
Phone (070) 55 0242; fax (070) 55 9077.
KITS-R-US
RF Products
FMTX1 Kit $49
Single transistor 2.5 Watt Tx free
running 12v-24V DC. FM band
88-108MHz. 500mV RMS audio
sensitivity.
FMTX2A Kit $49
A digital stereo coder using
discrete components. XTAL
locked subcarrier. Compatible
with all our transmitters.
FMTX2B Kit $49
3 stage XTAL locked 100MHz
FM band 30mW output. Aust
pre-emphasis. Quality specs.
Optional 50mW upgrade $5.
FMTX5 Kit $98
Both a FMTX2A & FMTX2B on 1
PCB. Pwt & audio routed.
FME500 Kit $499
Broadcast specs. PLL 0.5 to 1
watt output narrowcast TX kit.
Frequency set with Dip Switch.
220 Linear Amp Kit $499
2-15 watt output linear amp
for FM band 50mW input.
Simple design uses hybrid.
SG1 Kit $399
Broadcast quality FM stereo
coder. Uses op amps with
selectable pre-emphasis.
Other linear amps and kits
available for broadcasters.
PO Box 314 Blackwood SA 5051
Ph 0414 323099 Fax 088 270 3175
AWA FM721 FM-Tx board $19
Modify them as a 1 watt op
Narrowcast Tx. Lots of good RF
bits on PCB.
AWA FM721 FM-Rx board $10
The complementary receiver
for the above Tx. Full circuits
provided for Rx or Tx. Xtals
have been disabled.
MAX Kit for PCs $169
Talk to the real world from a
PC. 7 relays, ADC, DAC 8 TTL
inputs & stepper driver with
sample basic programs.
ETI 1623 kit for PCs $69
24 lines as inputs or outputs
DS-PTH-PCB and all parts. Easy
to build, low cost.
ETI DIGI-200 Watt Amp Kit $39
200W/2 125W/4 70W/8 from
±33 volt supply. 27,000 built
since 1987. Easy to build.
ROLA Digital Audio Software
Call for full information about
our range of digital cart players & multitrack recorders.
ALL POSTAGE $6.80 Per Order
FREE Steam Boat
For every order over $100 receive
FREE a PUTT-PUTT steam boat kit.
Available separately for $19.95,
this is one of the greatest educational toys ever sold.
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.oatleyelectronics.com/
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.
Torch dimmer
wanted
Have you designed a dimmer for
torches? I’ve searched through your
floppy index files but can find no
mention of a suitable circuit. I think
a 555 could be made to do the job. (A.
K., Belmont, Vic).
• The closest we can come to nominating a suitable circuit is the Mini
PCB Drill Speed Controller featured in
the January 1994 issue of SILICON CHIP.
It uses a 7555 and a BDY79 Darlington
transistor but it was designed to run
from voltages in the region of 12V or
more whereas torches typically run
from 3V or 4.5V.
This does not present a problem for
the 7555 which will run down to 2V
but the BD679 is another matter. Since
it is a Darlington transistor, there will
always be a loss of 1V or more across
it. This is immaterial in a 12V speed
control circuit but it’s a big problem
in a torch dimmer; 1V lost in a 3V
circuit amounts to a large permanent
reduction in brightness.
You could overcome this problem
Dolby ProLogic kit
is motor-boating
I have a problem with the Dolby
ProLogic kit regarding beat effects.
On effects mode with surround
selected I am finding the unit is
very unstable and will break into
low frequency motor boating. This
does not occur in the other two
positions. In the ProLogic position,
the sound output is very distorted
and significantly down in volume
from the surround speakers. When
noise mode is selected in either
effects or ProLogic position, similar motorboating is experienced
except in the stereo position of S4.
All voltages are correct or very
close to those specified. I have
checked and rechecked the wiring
98 Silicon Chip
by using an IRF540 FET instead,
as used in our Torch Battery Saver
circuit featured in the January 1995
issue. At 4.5V supply, it will typically have a voltage loss (Drain-Source
voltage) of 0.2V which is acceptably
low. Note that you would have to twist
the leads of the IRF540 to match the
PC board.
Other modifications which would
be desirable would be to omit the
9.1V zener and its 220Ω resistor.
You could also omit the heatsink
for the transistor and the protection
diode D1.
Queries on
power supply
I am writing in reference to the
circuit for the 100Hz Tone Burst
Generator published in the “Circuit
Notebook” pages of the August edition
of SILICON CHIP. After reading the article I was a little bewildered by the
description for the power supply. The
article states: “power is derived from
a 15V transformer. D1-D4 rectify the
AC, while a 7815 regulator provides
to S3, S4 & S2 and believe these to
be correct and all other functions
of the unit work as per spec.
If you can short circuit my agony
and tell me I’m an idiot for having
a wire out of place I will thank you
very much. If you can point me in
a direction of changing bits and
what to check I also have access
to a scope but the readings have
been somewhat obscure without
some form of reference. (N. R.,
Melbourne, Vic).
• After checking power supply
voltages, compare the PC board
around IC1 against the published
pattern. You possibly have a short
between tracks or IC pads. This
could be with a large solder bridge
or slither of solder. Scrape between
tracks and pads with a sharp knife.
the circuit with a 15V supply”.
This doesn’t seem to work, for the
following reason: 15V is being supplied to the rectifier circuit D1-D4.
Assuming a 600mV drop for each
diode, that would leave 13.8V peak,
less if you take the filtered voltage,
available to the input of the regulator.
The 7815 regulators have a dropout
voltage of 2V and a minimum input
voltage to maintain line regulation of
17.7V (National Semiconductor Voltage Regulator Handbook).
What it boils down to is you can’t
get something for nothing. 13.8V in
(or less) and 15V out? Am I missing
something or what? (C. B., Sale, Vic).
• The circuit description of the power
supply is correct. The 15V transformer
delivers a sinewave which will have a
peak-to-peak voltage of 42.4V or 21.2V
peak. After allowing for the voltage
drop in the diodes, this will produce
a filtered DC voltage of about +20V.
This is then regulated by the 7815 to
produce 15V DC.
Measuring insulation
resistance
I wish to congratulate you on the
superb performance of the Insulation
Tester published in the May 1996
issue. I have used it to measure the
insulation resistance between tracks
on Veroboard and was surprised that
when heated, the insulation resistance
dropped below 1GΩ. The same effect
occurred with many complete white
goods appliances.
This brings me to a question. Is
there an Australian Standard (or other
standards) regarding insulation resistance of components and of completed
hardware?
I have an outstanding washing
machine which uses the latest technology and yet measures only 20MΩ.
I presume that it must have a mains
filter with capacitors and discharge
resistors to prevent mains-borne interference.
I have always assumed that we
measure the insulation resistance at
working voltages because the “tracking” carbon has a negative resistance
coefficient and therefore, only becomes visible at higher voltages, and
hence higher dissipation, when the
tracking resistance drops substantially.
(V. E., Highett, Vic).
• Australian Insulation standards for
household appliances are available
from Standards Australia – phone (02)
9746 4700 or fax (02) 9746 8450.
An insulation resistance of around
20MΩ for a washing machine is fairly
typical. The low resistance is unlikely
to be due to any mains filter but is due
to the insulation of the heating element
(if it has one) or the insulation of the
various timer switching contacts, solenoids and the motors.
In fact, washing machines with
heating elements often cause nuisance
tripping with core-balance safety
switches and it is a good idea to have
them protected separately from other
household circuits.
Smoking inductor
in power supply
We are having difficulties with the
40V/8A power supply meeting the
specifications outlined in your January/February 1992 issues. The unit is
smoking the inductor L1 which is the
17-745-22 powdered iron core wound
with 10 turns of 1.2mm enamelled
copper wire. This is heating up to the
point of it being a fire hazard if left to
draw more than about 4.5A for more
than a few minutes. (P. S., Perth, WA).
• It does seem strange that this problem is appearing after four and a half
years. However, the Neosid 17-745-22
core is not ideal for the job. The 17745-23 is better. Also reducing the
turns to four or five rather than six
will reduce core saturation.
Similarly, using a few 0.8mm wires
in parallel rather than 1 x 1.2mm
wire for winding should reduce resistive losses. Alter
natively, use an
ETD49 transformer core as per the
Nicad Charger in October 1995. Use
the 0.5mm gap and 10 turns of 4 x
0.8mm wire as shown on page 59 of
this issue. The secondary winding is
not required.
Notes & Errata
Woofer Stopper MkII; February 1996:
depending on which type of piezo
loudspeakers are used, they can pro-
Fence controller
needs more output
I would like to make some comments about two of your projects I
constructed. The first is the Electric
Fence Controller described in the
July 1995 issue. It was constructed
correctly and all components, including the ignition coil work OK.
Unlike electric fences on different
properties that I have been to, the
output of this device has very little
bite. I made changes to replace the
timing resistors so as to give a 0.1
second pulse every second and
increase the wattage of the 6.8Ω
resistor.
I also built the Engine Immobiliser described in December 1995
– a great idea. However, the 75V
zener diodes shorted after testing
and driving my car. This may be an
isolated incident but to make sure
I placed a 560Ω 0.5W resistor in
series with the new 75V zeners and
placed a 0.22µF 630VW capacitor
across the collector and emitter of
Q1. There has been no trouble since.
(D. C., Narangba, Qld).
• We should point out that Notes
duce audible clicking at the rate the
signal bursts to a high and low level.
This can be cured by adding a 47µF
16VW electrolytic capacitor between
the base and emitter of transistor Q3.
The positive side of the capacitor
connects to the base. The capacitor
effectively slows down the rate that the
burst signal rises and falls to eliminate
any audible noise in the speaker.
We should also point out that if
the tweeter drive level control (VR2)
is set too high, it can cause the same
symptom.
Minivox Voice Operated Relay; September 1994: diode D1 is shown with
the incorrect polarity on the overlay
diagram on page 33.
LPATS: Striking A Blow Against Lightning; November 1996: the text on page
8 and in Fig.1 on page 6 refers to parabolas as the paths of possible lightning
strikes. The term used should have
been “hyperbola”.
Engine Immobiliser; December 1995:
there have been reports of the zener
diodes in this circuit failing. In line
& Errata were published on the
Electric Fence Controller in the December 1995 issue. These noted that
Australian Standard AS/NZS 3129:
1993 now specifies a maximum
output voltage of 10kV instead of
5kV. In order to increase the output
voltage by the required amount, the
6.8Ω 1W resistor should be changed
to 1.2Ω 0.5W.
While the coil on-time for the
electric fence may need some minor
adjustment for different coils we
are inclined to the view that if the
coil does not give a good output
it is probably defective. We have
seen one kit version of our electric
fence controller where the circuit
was working correctly but the HT
output was non-existent. It turned
out that the coil was a dud.
As far as adding a resistor in
series with the zeners for the engine immobiliser, this cannot be
recommended as it will prevent the
zeners from protecting the MJ10012
transistor. Howev
er, in line with
our circuit practice for high energy ignition systems, the specified
zener diodes should be rated at 5W
instead of 1W.
with our circuit practice for high energy ignition systems, the specified
zener diodes should be rated at 5W
instead of 1W.
Video Transmitter/Receiver; October
1996: it has been pointed out that
some video camera modules have a DC
output instead of AC. If these are used
with the Video Transmitter it will not
work. The cure is to connect a 100µF
non-polarised electrolytic capacitor
in series with the input socket. This
can be wired directly between the
RCA input socket and the input on
the PC board.
Fuel Injector Monitor; August 1995:
we have recently seen a fuel injector
monitor in which only eight of the
LEDs would light instead of the full 16.
The problem is that differing switching
thresholds on the 4053 (IC2) can cause
faulty switching of the LM3914 dot/
bar modes.
If this occurs, the cure is to replace
zener diode ZD1 with a 1µF electrolytic capacitor, with its negative lead
SC
connected to pin 3 of IC5.
December 1996 99
Index to Volume 9:
January-December 1996
Features
01/96 4 Living With Engine-Managed
Cars
01/96 10 Recharging Nicad Batteries
For Long Life
01/96 53 Satellite Watch
02/96 4 Fluke 98 Automotive
ScopeMeter
02/96 26 Germany's New MagLev Train
03/96 4 Traction Control: The Latest In
Car Technology
03/96 12 Cathode Ray Oscilloscopes,
Pt.1
03/96 77 Satellite Watch
04/96 4 Refill Your Dead Mobile Phone
Battery With Standard AA
Rechargeable Cells
04/96 14 Traction Control In Motor
Racing, Pt.2
04/96 12 Cathode Ray Oscilloscopes,
Pt.2
05/96 6 Cathode Ray Oscilloscopes,
Pt.3
05/96 22 Upgrade Your PC In 10
Minutes
06/96 4 Review: BassBox 5.1 Design
Software For Loudspeaker
Enclosures
06/96 26 'MV Oriana' – Luxury And
Technology Afloat
06/96 53 Satellite Watch
07/96 4 Installing A Dual-Boot System
On Your PC
07/96 10 Fuel Injection In Economy
Cars
07/96 82 Review: The Tektronix THS720
Tekscope
08/96 4 Electronics On The Internet
08/96 38 Satellite Watch
08/96 64 Cathode Ray Oscilloscopes,
Pt.4
08/96 76 An Introduction To IGBTs
09/96 10 Making Prototypes By Laser
09/96 53 Neville Thiele Awarded IREE
Medal Of Honour
09/96 68 Cathode Ray Oscilloscopes,
Pt.5
10/96 4 An Introduction To Smart
Cards
10/96 25 Snappy: Capturing High
Quality Video Images On A
Personal Computer
10/96 75 Satellite Watch
11/96 4 LPATS: Striking A Blow Against
Lightning
11/96 82 Adding An Extra Parallel Port
To Your Computer
12/96 8 CD Recorders: The Next AddOn For Your PC
100 Silicon Chip
12/96 20 Mitsubishi's Intelligent
Automatic Transmission
12/96 57 Satellite Watch
Serviceman’s Log
01/96 80 Sanyo 6627-79P; Telefunken
ICC4
02/96 54 Pye 48SL1; NEC N-3450
03/96 48 NEC N-4830 C500; Philips
20CT6750/75Z CTO-S
04/96 38 Superstar 1401R Remote
Colour TV; Toshiba 207E9A
05/96 40 National Panasonic TC-68A61/
M16M
06/96 54 National Panasonic TC-1407
M12H; Mitsubishi VS-405R
07/96 40 National Panasonic RX-DT610
Portable Stereo CD Player;
Akai VS-8 VCR
08/96 40 Teac CT-M515S; Sanyo
CTP6626 80P; Sanyo CCC3000 80P
09/96 40 General CG187; Sharp DC1600X
10/96 40 Grundig Receiver 3000 (GB);
National NV-180 Portable
Video Recorder
11/96 38 Tascam Ministudio Cassette
Deck; Marantz 740A VCR;
GC181 TV; Philips Trakka
KA212
12/96 44 Akai VS-35 VCR
Computer Bits
01/96 32 Upgrading Your PC: Is It
Worthwhile?
02/96 85 Use Your Personal Computer
As A Reaction Timer
03/96 74 Electronic Organisers And Your
Personal Computer
05/96 22 Upgrade Your Personal
Computer In 10 Minutes
05/96 74 Create Your Own Home Page
On The World Wide Web
06/96 10 Overcoming The 528Mb Hard
Disc Barrier In Older PCs
07/96 4 Installing A Dual-Boot
Windows 95/Windows 3.1x
System On Your PC
07/96 22 Dressing Up The Screen In
Basic
08/96 82 Customising The Win95
Desktop & Start Menus
Radio Control
03/96 54 A Multi-Channel Radio Control
Transmitter For Models, Pt.2
04/96 65 A Multi-Channel Radio Control
Transmitter For Models, Pt.3
05/96 53 A Multi-Channel Radio Control
Transmitter For Models, Pt.4
06/96 60 A Multi-Channel Radio Control
Transmitter For Models, Pt.5
07/96 77 A Multi-Channel Radio Control
Transmitter For Models, Pt.6
08/96 72 A Multi-Channel Radio Control
Transmitter For Models, Pt.7
10/96 82 A Multi-Channel Radio Control
Transmitter For Models, Pt.8
11/96 54 AM Vs FM: The Real Facts In
The Argument
Vintage Radio
01/96 86 Converting From Anode Bend
To Diode Detection
02/96 88 Reflex Receiver Basics
03/96 86 A Look At A 1948 Model
4-Valve Peter Pan
04/96 84 Early Transistor Radios
05/96 88 A Look At Early Radiograms
06/96 86 Testing Capacitors At High
Voltages
07/96 86 Making A Few Odd Repairs
08/96 86 A Rummage Through My Junk
09/96 84 Vintage Radio And Collecting
10/96 88 A New Life For An Old Hotpoint
11/96 88 A Pair Of Astor Valve Radios
12/96 76 New Life For A Battered Astor
Circuit Notebook
01/96 16 Automatic Level Control For
Line Signals
01/96 16 Bilge Pump Timer Uses A
Mercury Switch
01/96 17 PWM Speed Controller
01/96 17 Pot Plant Moisture Monitor
01/96 17 DC Amplifier For A CentreZero Meter
02/96 32 Reluctor Circuit For High
Energy Ignition
02/96 32 Intercom Uses Surplus
Telephones
02/96 33 4-Channel Mixer Modifications
03/96 40 Model Railway Level Crossing
Control
03/96 40 Binary Counting Demonstrator
03/96 40 Charge Controller For A
Transceiver
03/96 41 Precision Timer Uses Cheap
Crystal
03/96 41 Brake Pedal Alarm Circuit
04/96 80 Body Filler Depth Detector
04/96 80 Micropower Low-Voltage
Indicator
04/96 81 RS232 Modem Switcher
Projects to Build
04/96 72 Knock Indicator For LeadedPetrol Engines
05/96 14 Duplex Intercom Using FibreOptic Cable
05/96 30 High Voltage Insulation Tester
05/96 53 A Multi-Channel Radio Control
Transmitter For Models, Pt.4
05/96 57 Motorised Laser Lightshow
05/96 80 Knightrider Mk.2 LED Chaser
06/96 14 High Performance Stereo
Simulator
06/96 22 Party Rope Light
06/96 31 Build A Laser Pointer From A
Kit
06/96 40 A Low Ohms Tester For Your
Digital Multimeter
06/96 60 A Multi-Channel Radio Control
Transmitter For Models, Pt.5
06/96 70 Automatic 10-Amp Battery
Charger
07/96 26 VGA Digital Oscilloscope, Pt.1
07/96 31 Remote Control Extender For
VCRs
07/96 54 2A SLA Battery Charger
07/96 60 Minilog: An 8-Bit SingleChannel Data Logger
07/96 70 3-Band Parametric Equaliser
07/96 77 A Multi-Channel Radio Control
Transmitter For Models, Pt.6
08/96 14 Electronic Starter For
Fluorescent Lights
08/96 20 VGA Digital Oscilloscope, Pt.2
08/96 30 A 350-Watt Audio Amplifier
Module
08/96 54 Portable Masthead Amplifier
For TV & FM
08/96 72 Multi-Channel Radio Control
Transmitter For Models, Pt.7
08/96 75 6-12V Alarm Screamer Module
09/96 16 VGA Digital Oscilloscope,
Pt.3
09/96 28 3-Band HF Amateur Receiver
09/96 54 Infrared Stereo Headphone
Link, Pt.1
09/96 60 High Quality PA Loudspeaker
09/96 80 Feedback On The
Programmable Ignition System
10/96 12 Send Video Signals Over
Twisted Pair Cable
10/96 22 Power Control With A Light
Dimmer
10/96 32 600W DC-DC Converter For
Car Hifi Systems, Pt.1
10/96 53 Infrared Stereo Headphone
Link, Pt.2
10/96 66 Build A Multimedia Sound
System, Pt. 1
10/96 82 A Multi-Channel Radio Control
Transmitter For Models, Pt.8
11/96 20 8-Channel Stereo Mixer, Pt.1
11/96 30 Low-Cost Fluorescent Light
Inverter
11/96 42 How To Repair Domestic Light
Dimmers
11/96 59 Build A Multimedia Sound
System, Pt. 2
11/96 79 Digital Speedometer & Fuel
Gauge For Cars, Pt.2
11/96 66 600W DC-DC Converter For
Car Hifi Systems, Pt.2
12/96 24 Active Filter For Improved CW
Reception
12/96 38 Fast Clock For Railway
Modellers
12/96 58 Laser Pistol & Electronic
Target
12/96 66 Sound Level Meter
12/96 80 8-Channel Stereo Mixer, Pt.2
04/96 81 Single Rail Operation For The
TDA1514
05/96 38 Reluctor Version Of
Programmable Ignition
05/96 38 Larger Search Coils For The
Metal Locator
05/96 39 0-18V Power Supply With
Current Limiting
05/96 39 Electrolytic PC Board Etcher
06/96 32 Bridge Operation For LM3886
Stereo Module
06/96 33 Stereo Preamplifier With
Selectable Gain
06/96 33 Novel Modulator For Signal
Generators
07/96 16 Multi-Cell Charging With The
TEA1100
07/96 16 Random Number Generator
07/96 17 0-16V 15A Power Supply With
Current Limiting
08/96 8 Tone Burst Source For
Loudspeaker Testing
08/96 9 Cordless Telephone Ring Tone
Booster
09/96 8 Low Cost Monitor Amplifier For
32Ω Headphones
09/96 8 Pulse Stretcher For Printer
Signals
09/96 9 A Digital Display For The
Geiger Counter
10/96 8 Muting The LM3886 Module
10/96 8 Printer Port Zero Voltage
Detector
10/96 9 6V Motor Speed/Direction
Controller
11/96 16 Swimming Pool Lap Counter
11/96 16 Obtaining Balanced & Isolated
9V Supply Rails
11/96 17 Thermostatic Fan Controller
11/96 17 9V Nicad Battery Saver/Reg.
12/96 36 Overload Protected Power
Supply
12/96 37 Quiet Line/Buzzer Alert For
Communications Handset
12/96 37 VCO With Constant Mark/
Space Ratio
02/96 94 Subwoofer Controller,
December 1995
04/96 93 Radio Control 8-Channel
Encoder, March 1996
06/96 93 Insulation Tester, May 1996
07/96 94 Digital Voltmeter For Cars,
June 1993
09/96 94 Stereo Simulator, June 1996
09/96 94 16V 15A Power Supply, Circuit
Notebook, July 1996
10/96 94 2-Amp SLA Battery Charger,
July 1996
10/96 94 Fluorescent Lamp Starter,
August 1996
11/96 94 Photographic Timer, April 1995
11/96 94 175W Power Amplifier, April
1996
12/96 99 Minivox, September 1994
12/96 99 Fuel Injector Monitor, August
1995
12/96 99 Engine Immobiliser, December
1995
12/96 99 Woofer Stopper, MkII,
February 1996
12/96 99 Video Transmitter/Receiver,
October 1996
12/96 99 LPATS: Striking A Blow Against
Lightning, November 1996
01/96 22 Surround Sound Mixer &
Decoder
01/96 40 Magnetic Card Reader &
Display
01/96 54 The Rain Brain Automatic
Sprinkler Controller
01/96 56 IR Remote Control For The
Railpower Mk.2
02/96 8 Fit A Kill Switch To Your Smoke
Detector
02/96 12 Build A Basic Logic Trainer
02/96 22 Low-Cost Multi-Tone
Dashboard Alarm
02/96 36 Woofer Stopper Mk.2
02/96 60 Surround Sound Mixer &
Decoder, Pt.2
02/96 76 Three Remote Controls To
Build
03/96 22 Programmable Electronic
Ignition System For Cars
03/96 32 A Zener Diode Tester For Your
DMM
03/96 42 Automatic Level Control For PA
Systems
03/96 54 A Multi-Channel Radio Control
Transmitter For Models, Pt.2
03/96 60 A 20ms Delay For Surround
Sound Decoders
03/96 84 Simple Battery Tester For
Around $3.00
04/96 22 A High-Power Hifi Amplifier
Module
04/96 53 Replacement Module For
The SL486 & MV601 Remote
Control Receiver ICs
04/96 65 A Multi-Channel Radio Control
Transmitter For Models, Pt.3
Notes & Errata
01/96 94 Dolby Pro Logic Surround
Sound Decoder, Mk.2,
November & December 1995
01/96 94 Five-Band Equaliser,
December 1995
02/96 94 Dolby Pro Logic Surround
Sound Decoder, Mk.2,
November & December 1995
December 1996 101
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MICROCRAFT PRESENTS: Dunfield
(DDS) products are now available exstock at a new low price; please ask for
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LARGE 7 SEGMENT DISPLAYS:
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Tube Stereo Amplifiers 150W & 300W
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December 1996 103
New stamp instruction book version 1.7. 280 pages BS1, BS2 & app. notes. Special for December $30 plus $8 post.
MicroZed Computers
Scott Edwards Electronics
Microchip
OPTO 22
NEW Micro
Micro Engineering Labs (PICBASIC)
MICROMINT
PicStic
DOMINO
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Advertising Index
Allmedia Electronics..................104
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Altronics................................. 16-18
http://www.microzed.com.au
Av-Comm.....................................47
Specialising in easy-to-get-going hard/software
kits.
Send 2 x 45c stamps for information package
Stamp kits now have a compiler for 16C58
Your next project will be easy, fast and satisfying with a development kit
Dick Smith Electronics.... 6-7, 32-35
Earthquake Audio..........................5
EDA Solutions.............................31
Emona.........................................95
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1Mbx9 – 70ns
$15
30-pin Simms
For Quality Assembly On Time Every Time
356 Gilbert Rd.
West Preston
Victoria 3072
PCB Assembly
PCB Design
Prototyping
Wiring Looms
OEM Manufacture
Mobile 018 378750
SATELLITE TV confidential newsletter
“Coops Technology Digest” covers the
latest activities by satellite operators,
broadcasters and programmers, covering free to air and pay broadcasts.
Issued 10 times per year. For those who
need to know. One year subscription
A$175. Send for your free sample issue.
Av-Comm Pty Ltd, 198 Condamine St
(PO Box 225), Balgowlah, NSW 2093.
Tel (02) 9949 7417 or fax (02) 9949
7095.
MicroZed WEB PAGE always changing.
http://www.microzed.com.au
68HC705 Development System:
Oztechnics, PO Box 38, Illawong NSW
2234. Phone (02) 9541 0310. Fax (02)
9541 0734.
http://www.oztechnics.com.au/
BUSINESS FOR SALE: if you are
interested in valve equipment and
particularly vintage radio, this is the
business for you. Technical skill is not
essential. Established in 1987 and
with a huge stock of rare parts, valves
and test equipment, this is a suitable
operation for a sole proprietor or partnership. A secure lease in Melbourne’s
premier shopping strip and with an
Australia-wide customer base, there is
opportunity for expansion and growth.
104 Silicon Chip
SIMMS
(Parity/No Parity)
4Mb 30 PIN-70
$45
$38
4Mb 72 PIN-70
$43
$29
8Mb 72 PIN-70
$83
$56
16Mb 72 PIN-70 $190 $140
32Mb 72 PIN-70 $342 $288
EDO SIMMS
8Mb (1Mbx32) – 60ns $56
16Mb (2Mbx32) – 60ns $144
32Mb (4Mbx32) – 60ns $280
MAC MEMORY
8/16Mb DIMMS $69/125
32/64Mb DIMMS $288/594
16Mb P’BOOK 520/540 $257
LASER PRINTER MEMORY
4Mb HP 4&5
$52
COMPAQ
8Mb CONTURA AERO
$147
All other models available $Call
TOSHIBA
8Mb Portege/ Sat EDO
$133
16Mb Portege/ Sat EDO
$229
16Mb Tecra 500/610 Sat $229
All other models available $Call
CACHE
256Kb PIPELINE BURST
$25
256Kb 7200/8500
$93
VIDEO MEMORY
256K x 16 70ns (SOJ)
$17
1Mb 7200/7500/9500
$83
SO DIMMS
8Mb/16Mb
$92/180
Ex Tax Pricing – Delivery $8. Pricing as at 31/10/96. Phone for latest.
Sales Tax 22%.
Credit Cards Welcome. We Also Buy And Trade-In Memory.
PELHAM
Memory Pty Ltd
Suite 6, 2 Hillcrest Rd,
Ph: (02) 9980 6988
Pennant Hills, 2120.
Fax: (02) 9980 6991
Email: pelham1<at>ozemail.com.au
Genuine enquiries to Arthur Courtney,
Resurrection Radio (03) 9510 4486.
MicroZed have 16C84 at $8, 16C58A
at $5. Discounts start at 10 pieces. Add
$5 post on IC orders.
RAIN BRAIN 8-STATION SPRINKLER
KIT: Z8 smart temp sensor, LED display,
RS232 to PC. Uses 1 to 8 DALLAS
DS1820. Call Mantis Micro Products,
38 Garnet Street, Niddrie, 3042. P/F/A
(03) 9337 1917.
mantismp<at>c031.aone.net.au
Freedman Electronics..................46
Harbuch Electronics....................94
Instant PCBs..............................104
Jaycar ................................... 49-56
Kalex............................................19
Kits-R-US.....................................96
Macservice....................................3
MicroZed Computers.................104
Neil Kirkness...............................96
Oatley Electronics...................75,97
Pelham......................................104
RCS Radio ................................103
Resurrection Radio......................79
Rod Irving Electronics .......... 89-93
Rosetta Laboratories...................29
Shailer Park Electronics..............15
Silicon Chip Bookshop...............IBC
Silicon Chip Back Issues....... 42-43
Silicon Chip Car Projects.........OBC
HOMEMADE GENERATORS: how to
instructions. Eight pages free text and
colour photos on the Internet at http:/
www.onekw.co.nz/
Zoom Magazine.........................IFC
_________________________________
Microprocessor For
Digital Effects Unit
Printed circuit boards for SILICON
CHIP projects are made by:
This is the 68HC705-C8P programm
ed microprocessor IC for the Digital
Effects Unit (see Feb. 1995).
Price: $45 + $6 p+p
Payment by cheque, money order or
credit card to: Silicon Chip Publica
tions. Phone (02) 9979 5644; Fax (02)
9979 6503.
• RCS Radio Pty Ltd, 651 Forest
Rd, Bexley, NSW 2207. Phone (02)
9587 3491.
Tortech.........................................19
PC Boards
• Marday Services, PO Box 19-189,
Avondale, Auckland, NZ. Phone (09)
828 5730.
electronic design, and applications.
The sixth edition has been expanded
to include chapters on surface mount
technology, hardware & software
design, semicustom electronics &
data communications. 63 chapters,
in hard cover at $120.00.
Silicon Chip Bookshop
Radio Frequency
Transistors
Newnes Guide
to Satellite TV
Installation, Reception & Repair.
By Derek J. Stephenson. First
published 1991, reprinted 1994
(3rd edition).
This is a practical guide on the
installation and servicing of
satellite television equipment. The
coverage of the subject is extensive, without excessive theory or
mathematics. 371 pages, in hard
cover at $55.95.
Guide to TV & Video
Technology
By Eugene Trundle. First publish-
ed 1988. Second edition 1996.
Eugene Trundle has written for
many years in Television magazine
and his latest book is right up date
on TV and video technology. 382
pages, in paperback, at $39.95.
Servicing Personal
Computers
By Michael Tooley. First published 1985. 4th edition 1994.
Computers are prone to failure
from a number of common causes
& some that are not so common.
This book sets out the principles
& practice of computer servicing
(including disc drives, printers &
monitors), describes some of the
latest software diagnostic routines
& includes program listings. 387
pages in hard cover at $59.95.
format and R-DAT. If you want to
understand digital audio, you need
this reference book. 305 pages, in
paperback at $55.95.
The Art of Linear
Electronics
By John Linsley Hood. Published
1993.
This is a practical handbook from
one of the world’s most prolific
audio designers, with many of his
designs having been published in
English technical magazines over
the years. A great many practical
circuits are featured – a must for
anyone interested in audio design.
336 pages, in paperback at $49.95.
Components, Circuits & Applica
tions, by F. F. Mazda. Published
1990.
Previously a neglected field, power
electronics has come into its own,
particularly in the areas of traction
and electric vehicles. F. F. Mazda
is an acknowledged authority on
the subject and he writes mainly
on the many uses of thyristors &
Triacs in single and three phase
circuits. 417 pages, in soft cover
at $59.95.
Digital Audio & Compact
Disc Technology
Electronics Engineer’s
Reference Book
Hard cove
Produced by the Sony Service
Centre (Europe). 3rd edition,
published 1995.
Prepared by Sony’s technical
staff, this is the best book on
compact disc technology that we
have ever come across. It covers
digital audio in depth, including
PCM adapters, the Video8 PCM
Power Electronics
Handbook
Your Name__________________________________________________
PLEASE PRINT
Address____________________________________________________
_____________________________________Postcode_____________
Daytime Phone No.______________________Total Price $A _________
❏ Cheque/Money Order
r
Edited by F. F. Mazda. version now
available
First published 1989.
6th edition.
This just has to be the best refer
ence book available for electronics
engineers. Provides expert coverage
of all aspects of electronics in five
parts: techniques, physical phenomena, material & components,
❏ Bankcard ❏ Visa Card ❏ MasterCard
Card No.
Signature_________________________ Card expiry date_____/______
Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097.
Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503.
Principles & Practical Applications. By Norm Dye & Helge
Granberg. Published 1993.
This book strips away the mysteries of RF circuit design. Written
by two Motorola engineers, it
looks at RF transistor fundamentals before moving on to specific
design examples; eg, amplifiers,
oscillators and pulsed power systems. Also included are chapters
on filtering, impedance matching
& CAD. 235 pages, in hard cover
at $85.00.
Surface Mount Technology
By Rudolph Strauss. First pub
lished 1994.
This book will provide informative
reading for anyone considering
the assembly of PC boards with
surface mounted devices. Includes
chapters on wave soldering, reflow
soldering, component placement,
cleaning & quality control. 361
pages, in hard cover at $99.00.
Audio Electronics
By John Linsley Hood. Published
1995.
This book is for anyone involved
in designing, adapting and using
analog and digital audio equipment. Covers tape recording,
tuners & radio receivers, preamplifiers, voltage amplifiers, power
amplifiers, the compact disc &
digital audio, test & measurement,
loudspeaker crossover systems
and power supplies. 351 pages, in
soft cover at $52.95.
Title
Newnes Guide to Satellite TV
Guide to TV & Video Technology
Servicing Personal Computers
The Art Of Linear Electronics
Digital Audio & Compact Disc Technology
Power Electronics Handbook
Electronic Engineer's Reference Book
Radio Frequency Transistors
Surface Mount Technology
Audio Electronics
Price
$55.95
$39.95
$59.95
$49.95
$55.95
$59.95
$120.00
$85.00
$99.00
$52.95
Postage: add $5.00 per book. Orders over $100
are post free within Australia. NZ & PNG add
$10.00 per book, elsewhere add $15 per book.
TOTAL $A
December 1996 105
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