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box sides. This gives the operator the
ability to adjust the inertia and braking
to suit his own requirements.
Unfortunately, both units failed to
operate. The test supply is from an
old Triang Controller claiming to be
15VAC but on testing is 17VAC. The
unit was connected to this supply but
not connected to the track. Our know
ledge of electronics then limits us from
checking much further. I know that on
the output side of the bridge rectifier
the voltage is DC and the output is
1.414 times the input. This makes
the feed to the circuit approximately
24VDC. This checks out as correct.
Both our units have been assembled on
Veroboard. These have been carefully
checked numerous times to ensure that
no error exists in the circuit.
Our questions are as follows:
(1). Could the input VAC be too high,
thus damaging some of the components?
(2). A silly thought, but was an error
discovered after the article was published and rectified in a later issue of
the magazine? (No insult intended!)
(3). Nobody can tell us the handling
capacity of the Veroboard strips; ie,
can one strip carry 3A?
(4). Is it acceptable to change the trimpots as mentioned above?
(M. B., Logan City, Qld).
• The most likely reason for the
malfunction in your train controller
circuits is mistakes in the Veroboard
layouts. From bitter experience we
know how easy it is to make mistakes.
Your best approach is to obtain
the PC board as it is much easier to
assemble. You can purchase it from
RCS Radio Pty Ltd, 41 Arlewis Street,
Chester Hill, NSW 2162; phone (02)
9738 0330. The board is type number
02102931 and is $12.65 plus $3.30 for
postage and packing.
You can change the trimpots to pots,
as you have done.
Basic Stamp2
Xout function
I have been doing some programming on the Basic Stamp2 module
and am interested in using the Xout
function. This provides remote
control functions via the reticulated mains power lines within a
building. Special 110V interface
modules are available in USA for
this purpose.
Is this facility available for the
Australian 240VAC power system?
Are there approved “control via
mains” systems in use here and if
so, are the interface units available
Coil failure in
ignition system
I have built the High Energy Ignition system as described in the June
1998 issue and the unit has worked
well. But the other day my ignition
coil failed and I think this caused the
output transistor to fail as well.
I checked for continuity from the
transistor’s heatsink to case and there
was a short (it was still connected
up to my car, with power off when I
checked it). I can find no reference to
this transistor in either the Dick Smith
Electronics or Jaycar catalog.
Is there a higher-rated substitute
I can put in? By the way, is there a
simple go/nogo test for the output
transistor? I think it was a Darlington
type. (M. K., via email).
• The coil probably failed because
the transistor’s collector became short
circuited to the case. This would have
meant that the full battery voltage was
connected across the coil which would
burn it out fairly quickly.
This short from the transistor to case
for purchase? (K. M., via email).
• We referred your question to
Microzed Computes, the Australian
agents for The Basic Stamp2. Their
answer is as follows:
Our understanding is that X10 is
being discouraged in Australia by
power supply authorities because
of developments in power line
accessing of meter readings, using
a protocol that would collide with
X10.
A more reliable option is CE BUS
from Clipsal. This uses a separate
2-wire, low tension bidirectional
bus. CE Bus has more features and
should interface with the Stamp.
would suggest that it is the insulating
washer between the transistor and case
or the bush which has failed. Check
that there are no sharp edges around
the mounting hole for the transistor
as this will give a starting point for
any arc-over between the transistor
and case.
Use either a new silicone washer or
two mica washers.
You can check the output transistor
(it is a Darlington type, by the way) by
using your multimeter to measure the
resistance between base and emitter,
between base and collector and collector to emitter. The 1999/2000 Dick
Smith Electronics catalog shows how
it is done on page 236.
Notes & Errata
Opto-Electronic Ignition, October
2000: the circuit featured in Circuit
Notebook on page 58 shows a 470Ω
resistor connected to the collector of
Q2 via a .01µF capacitor. This resistor
SC
should be 470kΩ.
WARNING!
SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such
projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be
carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do
not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects
employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd
disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of
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November 2000 93
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