“In this Instructable I’ll show you how you can build a non contact voltage detector for checking of live power wires.
A transistor is a device that can be used in two basic operations, as an electronic switch or as an amplifier. Depending on the current we apply to it’s base, it can control a much larger current through the collector and emitter path with a typical multiplication of around 200 times. This is called the transistor gain.
By connecting the output of one transistor to the base of another, we can multiply this gain to now get an amplification of 40 000 times. By building a circuit with three such stages we can create a device that is capable of detecting even the tiniest charges and movement of electricity.”