Circuit for short detection wanted

[kruland]

Hi all,

Kloudbusters has a really cool ground support setup which features not only continuity test but short detection. How does the short detection circuit work? Anybody have a diagram of this?

Kevin

 

[UhClem]

There was an article on this system in the Feb. 1999 issue of HPR magazine. It mentions an analog amplifier but doesn't have a schematic.

But the method is pretty straightforward. Apply a known current and measure the voltage. Voltages less than some threshold indicates a short.

Not that it is really a short because some igniters had a low enough resistance (Trailing Edge Technology's products) to trigger the circuit.

 

[awseiger]

Check out some op-amp circuits. I don't have time now but it's decently simple to make a circuit that will only illuminate an LED when there is a small resistance at the end of the wire. These things can easily be done with an op-amp and a current mirror circuit. Simply apply about 1mA down the wire, and measure the voltage across the current source. If it's very high, it's an open. If it's very low, it's a short. There should be a value (I say experiment) where the voltage lets you know of a good igniter.

I wish I had some time to draw you out a circuit, these things make my Electrical engineer senses tingle!

EDIT: you could also use some sort of Wheatstone bridge circuit for greater sensitivity. I think my favorite contiunuty checker was someone who bought a bunch of cheapo multimeters (search surplus sites) and actually measured the resistance of the igniter.

 

[kruland]

I found this: https://partsparty.com/beeper-to-find-short-circuits-electronic-circuit-diagram/ which looks close - but has lots of extra junk to drive a speaker. Now to trim it down.

Kevin