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Items relevant to "An X-Y Table With Stepper Motor Control; Pt.1":
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A second coil charges the discharge
capacitor to a high voltage before
triggering.
It may be possible to fire the unit
using the reluctor input from the magneto. However, we have not tried this.
A suitable capacitor for C3 should be
0.15µF.
UHF remote control
for car alarm
In your August 1990 issue, you
featured a transmitter which I bought
from Dick Smith Electronics as a kit.
I selected a code to work with my
“commercial” car alarm. It works
fine except that the range is a bit low
(despite tweaking it on a spectrum
analyser).
I haven’t seen the circuit for your
2-channel UHF transmitter (also avail
from Dick Smith Electronics) but can
you tell me:
(1) Does it transmit on the same frequency?
(2) Does it use the same encoder chip?
(3) Does it have a greater range?
(4) Will it therefore work (1-channel
of course) with your old UHF remote
control receiver kit?
(O. W., via email).
• The 2-channel transmitter transmits at 304MHz but does not use the
same encoder. We expect that it has a
similar range to the earlier design but
cannot state whether it could be made
to work with your car alarm.
Enhancing the
class-A amplifier
I have a few questions regarding
the 15 watt class-A amplifier project.
I wish to provide extra inputs for
CD, tuner, stereo VCR and tape in/
out sockets. The plan is to use gold
RCA input sockets on the back panel. These would be selected via two
Notes & Errata
Low Distortion Audio Signal Generator, February & March 1999: on
the circuit diagram on page 28 of
the February issue, trimpot VR4
is incorrectly labelled as 100kΩ
rather than 10kΩ.
Also on the circuit there should
be shown a 10kΩ resistor in
between the 20kΩ resistor connecting to the 330µF capacitors
at the output of IC1b and the pin
2 inverting input of IC4b. The
PC board includes this resistor
and this is shown on the overlay
diagram, on page 63 of the March
issue, as the third 10kΩ resistor
below diode D2.
The overlay diagram also has
transposed the anode and cathodes
(A & K) labelling for LED1 & LED2.
The package outline orientation is
correct. The polarity shown on the
circuit is also correct.
Electric Fence Controller, April
1999: the supply leads to the
battery, as shown on the wiring
diagram on page 28 (Fig.7) are
reversed.
In addition, the transformer
bobbins for T1 & T2 may differ
from those used in our prototype.
The difference will be that the five
rows of pins on each bobbin may be
spaced wider than allowed for on
rotary switches mounted toward the
back of the case and controlled by an
extension shaft to keep the wiring for
the inputs as short as possible.
If I take this approach are the performance figures likely to be degraded?
All other construction details would
be as per the article.
One final question: was the rack
the PC board. You can either bend
the pins on the bobbin inward so
that they will fit into the original
holes or new holes can be drilled
at the wider spacing.
The larger bobbins mean that
the transformers will be easier to
wind and there will be more room
to insert the ferrite cores. A revised
PC board has been produced to
provide for both bobbin types.
Multi-Spark CDI, September 1997:
transistor Q1 in the impulse tachometer circuit on page 30 should
be labelled a BC327 and not BC337
as shown.
LED Ammeter, January 1999: the
circuit diagram on page 55 has an
error. The 10µF capacitor associated with IC1a should have its negative electrode connected to pin 4.
Capacitance Meter, February
1999: the wiring diagram on page
70 has a number of errors. The
100µF capacitor associated with
D1 & D2 is unmarked and is shown
with reverse polarity. Also VR3 &
VR4 are swapped, although their
values are the same.
Bass Cube Subwoofer, April 1999:
the rear panel should be screwed
into place but not glued, although
some sort of sealant should be used
to avoid leaks.
case used in the prototype a commercially available unit or was it built
from scratch to incorporate the two
heatsinks? (J. W., Five Dock, NSW).
• Provided your input switching is
well-shielded, it should not degrade
the amplifier’s performance. Our case
was an obsolete rack case to which we
SC
attached the heatsinks.
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
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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
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MAY 1999 93
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