Do battery reconditioners work?
I saw an advert in a 4WD magazine for a car battery
reconditioner which brings batteries back to life. It goes in line with the
battery and charges it, restoring the battery. What do you think about it? (L.
S., via email).
There may well be
some truth in this product and it may be along the same lines as the battery
desulphator circuit we published in the Circuit Notebook pages in February 2003.
Note that we have yet to try such a circuit.
NTSC version of TV Pattern Generator
I am purchasing two Programmable TV Pattern Generator kits
(SILICON CHIP, June & July 1997) from
the local Altronics store. I wish to adapt the design to provide RGB & sync
outputs (I presume I can use the signals applied to the AD722) and also wish to
have an NTSC video signal option. I only have data for the AD723/724/725 devices
so in regard to the AD722, can I simply change crystals to achieve this? (W. A.,
Pin 11 selects the
NTSC or PAL operation. Set pin 11 high for NTSC. Also change the crystal to
Replacement for Hall Effect sensor
Could you tell where can I get the HKZ101 and MJH10012 required
to build the High Energy Ignition – I don’t want to buy the kit, I have been
offered alternatives, UGN3503U and MJ10012 respectively. Are they
Finally, how do you connect the Programmable Ignition Timing
module to the Multi-Spark CDI?(D. S., Bandung, Indonesia).
The HKZ101 is
obsolete and no longer available. Unfortunately, the UGN3503 is not the same and
You can use the Honeywell 4AV16F Hall Effect Vane sensor but
note that a rotating soft iron vane is also required to pass through this
sensor. The Hall sensor is available from Farnell Electronics – www.farnellinone.com
The MJH10012 is available from Jaycar – contact firstname.lastname@example.org
Interfacing the Programmable Ignition to the Capacitor
Discharge Ignition requires two connections as follows: (1) connect the output
of the trigger circuit to the points input of the Programmable Ignition; and (2)
connect the Programmable Ignition output to the main circuit at the point marked
"To Trigger Circuit"; ie, to the 10kΩ base resistor for Q4.
Using the Remote Extender with Foxtel
I purchased one of your Remote Control Extenders (from
SILICON CHIP, July 1996) and have been
very happy with it. However, I recently changed to a Foxtel Digital box and the
Remote Extender will not work with this unit. I have tried adjusting the carrier
oscillator with no success.
Can you tell me what to do next? (P. W., via
We’re not aware of
the infrared protocol or carrier frequency used by the Foxtel infrared remotes
so cannot be certain why the Extender is not working. However, some constructors
have been able to get their kits working by subsituting a different IR receiver
module (eg, Altronics Z 1611).
These is also another possible solution. A learning remote
could be used to store the recalcitrant remote codes and this then used with the
Remote Extender. Give it a try.
Studio 350 amplifier for a car
I am considering starting work on the Studio 350 power
amplifier module (SILICON CHIP, January & February
2004) but would like to adapt it for use in a car. I’m sure I could use a power
inverter for this but would rather do it as part of the amplifier itself. How
would I go about doing this? Is it possible? (D. T., via email).
You need a massive
inverter to run the Studio 350 power amplifier – about 600W.
It just so happens that we described a 600W DC-DC inverter in
the October & November 1996 issues. However, it would be expensive to build
and it would be far more practical and cheaper to buy a ready-made car
amplifier. We would love you to build the two kits but the expense would be
Midrange boost for guitar
I have a Champ audio amplifier kit (SILICON
CHIP, February 1994) that I’d like to use in my guitar as an onboard mid
boost. What modifications would you suggest I make to it? (B. D., via
The Champ is not
really suitable for guitar mid boost. It does not have a high input impedance or
any mid-range band-pass filtering.
The DI Box published in the August 2001 issue would be more
useful. It has a 3-band equaliser and so the midrange can be boosted.
Master preamplifier connection
I’d like to connect four power amplifiers to one master
preamplifier. What precautions should I take in terms of the reduced impedance
load of the power amplifiers as seen by the preamp?(P. S., via
It largely depends
on the input impedance of the power amplifiers and to a lesser extent, on the
minimum load impedance that the preamp can drive. In general though, if the
combined input load of the power amplifiers is more than say, 10k, then there
should not be any problems.
If it is less, you might consider providing a buffer for the
preamplifier, along the lines of the audio stage in the Video/Audio Distribution
Amplifier featured in the November 2001 issue. Note: if you do use this buffer
(based on an LM833), the individual 47kΩ output resistors should each be changed
Speed Control kit for RC boat
I have purchased a 10A DC Speed Control which was published in
the June 1997 issue. I’m wanting to connect a receiver to it for use on an RC
boat. I was wondering if you could point me in the right direction for a guide
on how to achieve this. (N. R., via email).
The 10A circuit is
not suitable for radio control. Have a look at the 50A speed controller in the
May 2000 issue. It is designed to work in an RC system.
Level meter for digital camera
I want to monitor an analog audio signal (something like a VU
meter) as it passes through a microphone and into a digital camera; preferably
something mobile that’s easy to move around with. I wonder if the Loudspeaker
Level Meter featured in the April 2004 issue would be appropriate. (P. M., via
You can use the
Level Meter but the gain of IC1 may need adjusting. IC3 would be best replaced
with a log version (LM3915; Dick Smith Cat Z-6297). The scale on the display
will then be 3dB per LED.
Intercom for aircraft wanted
Do you have any duplex intercom kits? This is for an aircraft
application. I want to be able to talk to other passengers as well as hear
myself while we are wearing our headsets. Do you have anything suitable? (A. M.,
Have a look at the
Multi-Station Headset Intercom from the June & July 1992 issues.
Connecting a VCR to a PC
My son was given a Panasonic NV-SJ400 VCR in excellent
condition. Unfortunately, we do not have the instruction manual and we cannot
find the channel that will let it speak to the computer so we can set it up. Can
you help? (B. K., via email).
All you have to do
is connect the A/V output from your VCR to the VIVO (video-in/video-out) socket
on your PC’s video card. There is no need to know the RF channel of the VCR’s
modulator. If your video card doesn’t have a VIVO socket (and a lot don’t), then
you will either have to replace it or purchase a separate video capture card.
Roof blower control wanted
I am looking for a circuit which is used to activate a blower
to blow hot air from the roof space into several rooms if the temperature in the
roof space is higher than the temperature in the room or rooms and only if a
master switch is activated for the heating action.
A similar circuit may have been described which switches on a
pump to circulate water from the solar panels to a tank below only when the
temperature in the panels is higher than the temperature in the tank. (D. W.,
We published a
circuit to do this in the Circuit Notebook section of the March 2002 issue of
SILICON CHIP. It comprised two
temperature sensors (LM335Z) and an LM393 comparator. This drove a Mosfet to
power a pump motor for a solar hot water system. It could equally be used for an
air pump fan in the roof cavity. The master switch you require can either switch
power on and off for the circuit or for the fan motor directly.
Note that an air filter system would be required to remove dust
and fibre glass (when insulation is used in the roof space) from the roof
Higher power for bridged modules
Since the upgrade model of the ETI-480 amplifier can only drive
8-ohm loads under bridging, I was wondering if it was possible to add another
push-pull output transistor pair to increase the power output of these modules
or are there other limiting components, or will it mess up the biasing? (R. G.,
We assume you are
referring to the SC480 presented in January & February 2003. If so, it is
possible to add parallel output transistors to increase the current capability
of the output stages (for two modules) but the whole project becomes uneconomic
and very bulky. You would be better off going for a higher-rated module such as
the Plastic Power amplifier described in April 1996. It can deliver 175 watts
RMS into a 4-ohm loads and up to 230 watts music power, and at lower
Jacobs Ladder to drive spark plugs
I am looking for a kit for an automotive project that I am
building. The requirement is to continually ignite from one to four spark plugs
at the flick of a switch. I was going to use the Jacobs Ladder kit
(SILICON CHIP, September 1995) but I’m
not sure it would work if I replaced the wires with spark plug leads and added
spark plugs to the end of them. What do you think? (F. S., via
You should be able
to use the Jacobs Ladder circuit to drive the spark plugs without problems.
Repairing a talking radio
I have a talking clock radio that I am quite attached to.
Unfortunately, when I recently dismantled it to clean the switch contacts, the
LCD screen removed itself from the circuit board and the attaching strip. Being
attached by this rubber strip with micro conductors has caused me great distress
considering how I will repair the connection.
Is my only solution to get out the microscope and some
conductive epoxy glue and try and repair it? Or am I able to purchase a
replacement LCD mounted on a board that I can solder?(D. V., Newcastle,
Just reassemble the
unit so that the LCD is sandwiched against the elastomeric conductor strips on
the PC board. It should work.
Correct connection for HEI system
I have just assembled the High Energy Ignition system and
installed it on the car. There is a problem that I do not know how to solve and
where to start. I built the kit from the diagram for ignition with points and
although the car won’t run, the problem seems to be at the distributor. I have
power to the HEI and power at the negative side of the coil.
I connected a plug lead to an external spark plug and cranked
the engine over. The plug fired only once. I put a test lamp on the wire to the
distributor from the HEI and there is power there the moment the starter is
tuned on, then nothing. Any ideas on what to look for? (R. M., via
Power for the High
Energy Ignition system must be obtained from a switched 12V supply via the fuse
box. This connection must apply 12V when ever the ignition is on and not only
when the starter motor is running.
Also note that only one points input is normally required.
Remove the diode associated with the points input that is not used.
Programming PICAXE via USB
I was wondering if it is possible to program PICAXEs using a
USB-serial converter module from DLP design, based on the FTDI FT232BM IC. The
device only has 5V logic levels on the serial lines – not true RS232. Do I need
to modify the programming circuit or change the two resistor values? (L. W., via
programming system will work with certain types of USB-to-serial port adapters.
Go to www.rev-ed.co.uk and search for "USB" to find out more.
Circuit for the Cylon Voice
I am after an old kit from "Electronics Australia" or ETI which
was called the "Cylon Voice". I am not sure whether it used a XR2206 IC or not
and if the IC it used is still available.(R. M., via email).
The Cylon Voice was
described in the January 1981 issue of "Electronics Australia" and did use an
XR2206 which was rather heavy on batteries. We don’t know of a current source
for the XR2206.
We published an equivalent circuit, the Vader Voice, in the
September 1995 issue of SILICON CHIP. Its
current consumption was much less than the Cylon Voice.
Subwoofer controller times out
I have built one of the subwoofer controllers (SILICON
CHIP, December 1995) and all is working OK except it has problems with low
signal levels; the timer times out whilst in use. I was wondering if it would be
possible to adjust the sensitivity of the VOX circuit to cope with lower levels
of input to the controller to enable switching. High efficiency speakers are
being used and the unit is OK just above normal listening levels.
I use the 15W Class-A circuit (SILICON
CHIP, July & August 1998) and it is very sweet indeed. Any chance of a 30
watter in the future? (W. C., via email).
To reduce the
incidence of dropout try increasing the value of R40 to 330kΩ. This reduces the
feedback around IC2b.
We may do another class-A amplifier but it would have to be
more than 30W to make it a worthwhile increase over the 15 watter.
Backup for cordless phones
Some years ago you described a construction article on a
gel-cell backup for telephones. Can you please tell me the project/kit number,
board number and if any of the kitset suppliers produced same? (E. R., Cobram,
The project was entitled "Backup
Battery for Cordless Phones" in October 1999. The PC board number was 12510991.
It was intended to provide backup power for the phone/base station of a cordless
phone system. A kit was produced at the time but it is no longer
Preamplifier for projector photocell pickup
I am currently updating a pair of RCA 1018-F 35mm film sound
heads. I think they were made around the 1935 mark. They are in good condition
but need to be converted to SVA (Stereo Variable Area) pickup. This involves
removing the old photocell and replacing it with a split solar cell, one side
per soundtrack half.
As I have very little money to spend on the project, I cannot
afford to buy a commercial split cell so I improvised by purchasing a "hobby
cell" from Dick Smith and modified that. Bingo! Instant stereo cells.
My question refers to the preamp I am using to interface the
cells and power amplifier. I have built the "Universal Stereo Preamplifier"
published in SILICON CHIP in April 1994 and am very happy with the
performance of the unit but I need advice on a design modification.
Testing with the projector running and the solar cell installed
exhibit an "RIAA-like" frequency response, ie, bass boost and treble cut. What
components should I change, and which values, in order to flatten the response
of the design? If possible, some treble boost with a flat bass response will be
the ideal as cutting treble is simply a matter of de-
The preamplifier you’ve built is not suitable as it
stands – you do need treble boost, etc. The best way to work out what you need
would be to have a look at the Optical/Magnetic Preamp for projectors, produced
by Jim Rowe way back in October 1975 in "Electronics Australia" magazine. You
can then modify your existing preamp to do the same function
focussing the sound
lens; otherwise a flat response is perfectly OK. The version of the preamp I
built is the microphone version. Should I have built the "Tape" version instead?
(I. P, Imbil, Qld.)
Weather satellite receiver is noisy
My son-in-law, a medical electronics technician, has made a
good job of Weather Satellite receiver (SILICON CHIP, December 2003) and it
seems to be properly tuned according to the instructions, yet its performance is
very poor. No satisfactory pictures have been received.
Compared with an old kit receiver, sold by SciSat products in
Queensland about eight years ago, the new unit is much noisier. With the same
antenna and masthead preamp used on both receivers, the Sci Sat receiver gives
good pictures, while the new kit either fails to lock on or produces a screen
full of snow with no picture detail.
Could you please help?(T. B., via email).
It sounds as if either your IF chip or RF
stage is "taking off". Have you checked the RSSI voltage (across the 390kΩ
resistor), when the RF control is turned fully anticlockwise? It should be below
0.27V if the IF chip isn’t oscillating.
Turning up the RF control shouldn’t make the voltage rise much,
if there’s no signal input to the receiver. If it does, the RF stage may be
A small number of these receivers have needed a small earthed
shield plate over the top of the IF chip, to keep it from taking off. Similarly
one or two have needed additional bypass capacitors from the source of the RF
amplifier to ground, to keep it stable. We suggest 47nF SMD capacitors for this
if they’re needed, as these have extremely low self-inductance.
Radon detector wanted
With the ever-increasing growth of dense city housing, the
design of houses is becoming more and more restrictive to the flow of air
through the buildings.
Radon is a documented (second highest) cause of adeno-carcinoma
of the lung in non-smokers and smokers (cigarettes) alike. It would be very
useful to be able to detect the radon levels in the household via continuous
I have seen some Electronic Radon Detectors on the market. An
example of an EPA (US) approved model is: www.testproducts.com
There are no products available in Australia that cater for the
home/office environment. I am proposing that your gifted technical staff design
a homemade kit using a radon detecting transducer. Is this feasible? (G. S., via
While a solid state alpha scintillation
counter is relatively easy to design, it does not necessarily give an indication
of radon or its daughter elements with their short half lives.
We think that if you are concerned about a possible build-up of radon in your
house, you should consider installing an under-floor fan. If the underside of
your house is well-ventilated, or it is built on a concrete slab, it is highly
unlikely that there is any problem with radon build-up. It is mainly a problem
in cold countries where houses are well-sealed against air leakage.
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