Short circuits or broken pcb tracks can be easily recognized by means of a Multimeter, but this tool can give wrong results when testing the...

A Battery-status Indicator circuit can be useful, mainly to monitor portable Test-gear instruments and similar devices. Parts: R1,R7________...

This circuit uses two 741s or equivalent op amp to form a beeper that is used to detect short circuits. This design offers a way to trace re...

This circuit, enclosed in a small plastic box, can be placed into a bag or handbag. A small magnet is placed close to the reed switch and co...

This lovely circuit is a real gem! Easy to assemble and more sensitive than many commercial devices available. It's based around an LF35...