Who needs a Fluke high voltage detector when you’ve got one of these things?
Actually, we still recommend a professional high voltage detector for serious work, but you’ve got to like this electric field detector that [Alessandro] recently put together.
The detector works by using a JFET to detect the high impedance electric fields that are generated by high voltage lines. The JFET amplifies the signal while dropping the impedance in order to drive a pair of NPN transistors which are used as a threshold amplifier. Once the voltage hits 3V, an LED is lit, indicating the presence of high voltage near the detector’s probe. A wire-wrapped resistor does double-duty serving as the probe while providing a high impedance path to ground, ensuring that stray charge does not accumulate on the JFET’s gate, causing false readings.
It’s a neat project, and something that can be constructed in no time, making it perfect for beginner electronics classes.
Keep reading to see a quick video of the HV detector in action.