In sci.electronics.repair on Wed, 30 Mar 2005 07:10:59 -0500 "Art"
posted:

Agreed: Much easier to actually frabricate the inductor with zig-zag traces
rather than have a descrete coil inserted in the pcb.
"Michael A. Terrell" wrote in message
...
meirman wrote:

I have a little power supply module, made in 1983, for a burglar
alarm, but I've seen the same thing on other printed circuit boards:

One of the metal traces on the non-parts side of the PCB has, in place
of the 1/10" and 1/16" wide traces used elsewhere on the board that go
to their destinations as quickly as possible, using straight lines, a
half inch of one trace is zig-zag, sort of.It's really not a zig-sag
since all of the angles are right angles, and none from Z's. Here it
is:

___ ___ ___
|___| |__| like this, except smaller segments, 2 or 3mm. Not

even in a critical spot, afaict. It's the lead from a resistor, it
looks like, that comes from an AC 12v transformer connection, to one
of the 4 diodes in a bridge rectifier setup.** The first inch of
this trace is straight for an inch, with a right angle and straight
for another half inch.

Why don't they just use a straight line for the rest also?

Thanks.

**(FWIW, the bridge is followed by a filter cap and I think a voltage
limiting transistor with a heat sink)


Meirman


It is an inductor to filter RF and spikes from inputs in an attempt
to prevent false alarms. I was involved i starting an alarm company in
the late '70s when alarms were going from relays to electronics and the
manufacturers were more than willing to explain what they were doing to
push the newer, and more expensive equipment.

--
?

Michael A. Terrell
Central Florida

Thanks to all of you. In this case I think it is a filter, a
flattened coil. I'll keep my eyes open for other instances of this
and see if I can find the other uses too.



Meirman
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