telephase - a simple voltage detector

telephase elektor november 1984 F. Pipitone At last, here is a small unit that provides a quick, safe, and simple way of checking the presence or absence of a voltage in an electrical line without the necessity of physical access to the conductor. And, what"s more, it"s really cheap to build. Telephase will enable the detection of a break in any normal, non- shielded, "live" electric cable or wire. It is suitable for use with a.c. voltages from about 60 V to 250 000 V. With a little practice, it should be possible to gauge the voltage level from the distance between the detector and the wire at which the indicator LED extinguishes. telephase a simple voltage detector Circuit description The circuit is based on a type 4049UB hex inverter. The sensor is formed by a small piece of thin (about 0.2 mm) tin plate. The electro-magnetic field surrounding the live conductor or source induces a very small voltage in the sensor. This voltage is suf- ficient to start a low-frequency oscillato...