Subject: Re: Short Circuit Detector
Date: Fri, 11 Oct 2002 17:40:37 -0700
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There was a similar sounding one published in EDN 4/3/95.
I never built it because it used +/- 12V supplies. It used 100mA drive
current and hogged a lot of supply current.
I'd be interested in seeing your schematic.
Bunch of stuff For Sale and Wanted at the link below.
Tek 2465, TFT projector, Transoceanic, ham radio, 30pS pulser
Tektronix Concept Books...
Tom Bruhns wrote:
> I have one I've used for years (and happen to be in the process of
> re-vamping to use more readily available components). It's very
> simple. In the configuration I _normally_ use, it injects a current
> from a 1.5v cell through a 1k resistor and a diode, so the
> short-circuit current is about 1mA. The voltage across the "short"
> converts to a current to drive an oscillator, so the higher the pitch
> the shorter the short. With it I can hear the difference between 1
> ohm and a dead short, about 1mV delta. BUT...if you inject a current
> from an external source, you can use it to find where in the circuit
> the drop is the lowest: the point of the short. So with an amp
> excitation, you can hear milliohm changes. The circuit is currently
> an A77 watch cell (or similar 1.5V), 2 pnp transistors, 2 npn's, a
> tiny audio transformer (Mouser TC001), and as tiny an 8-ohm speaker as
> you can find, and a very few R's and a couple C's. When not
> connected, the current drain is less than a microamp, so no on-off
> switch. The one I've had a long time draws a lot more "off" current,
> and even so the AAA cell lasts over five years.
> I'm planning to make the circuit available through the Wenzel web site
> (where there are a few other neat little test circuits) eventually,
> but could perhaps give it limited distribution before that.
> "red rover" wrote in message news:...
> > Does anyone have link to a design for
> > short circuit detector? I recall that Bob
> > Pease had a design for one in his Analog
> > Troubleshooting book. I believe it was
> > basically a micro ohmeter with an audio
> > output and you worked your way around
> > the pcb homing in on the fault.
> > Anybody here made one? Any good success?
> > Steve