motors and lights?
I have three radios that use an
LM386 for the audio output. This chip
tends to be noisy. (It produces audio
hiss.) Are there any circuit
modifications that can be applied to
this chip to make it less noisy?
#7041 John Morgan
I have been looking for years for a
circuit to sense cars in my driveway. I
know that the traffic lights use a
single wire loop in the pavement and
I assume that it is some kind of tank
circuit tied to a PLL. I would
appreciate any information on the
I work at an electronics repair
depot. There are times when we do
not have documentation or even a
parts list for the equipment that we
repair. This isn't too much of a
problem until it comes time to identify
SMT devices (like the SOT- 23 style)
that have only a device code — like
“R2C.” Is there some universal
standard for these codes and if so,
where can I find them? Sometimes,
we can guess what the device is by
where it resides in the circuit and
search manufacturers’ websites until
we find that device code, but this is
very time consuming.
#7043 Dean Hutsell
What is the easiest way to allow
my computer to operate 120 VAC
I have several ultrasonic units
(Branson 303) with many variable
outputs, frequency adjustments, coil
attachments, etc. Are there any
books on applying this unit as a
treasure finder to search for coins,
jewelry, etc.? I assume it has the
power to search that deep, although I
expect I would have to build the right
kind of search coil.
I am looking for an I/O board that
could control the pan and tilt, zoom,
focus, and iris controls on a camera.
Ideally, I’d like a PCI board that I could
plug into a computer that would have
relays to control the functions.
#7046 Ron Ross
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Can anyone suggest a good
transistor driver or other circuit that
could PWM control halogen lamps
(up to 12 amps) at 13. 8 V? I will be
controlling this driver with a pin on a
[3047 — March 2004]
Does anyone have a simple
circuit that can be used to count the
number of times a bird goes in and
out of a birdhouse?
NUTS & VOLTS
A very easy way to build an event
counter is to use any cheap calculator
you are willing to dispose of that is in
working condition. It must be able to
do "constant" calculations, in which a
constant number is added to several
different numbers. I believe that all
cheap calculators can do this.
Remove the cover and attach
wires to the "equals" button contacts.
Connect the wires to a switch that is
placed to record the bird's
movements, such as a microswitch
on the floor of the birdhouse near the
entrance. When everything is ready,
set up the calculator in the "constant"