Simple continuity tester

Posted on Jul 3, 2012

This tester is for tracing wiring on Printed Circuit Boards. Resistors below 50 ohms act as a short circuit; above 100 ohms as an open circuit. The circuit is a simple multivibrator switched on by transistor T3. The components in the base of T3 are Dl, Rl, R2, and the test resistance.

Simple continuity tester
Click here to download the full size of the above Circuit.

With a 1,5 volt supply, there is insufficient voltage to turn on a semiconductor connected to the test terminals.

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