A very interesting and simple project of a highly sensitive static electricity detector circuit, it can also be used as ion detector, electric field detector etc. The circuit is able to detect static charge in any substance from 2 to 3 feet away, it can also be used to test your room ionizer and also detect electric
field in a wire from a foot away. Also you can do a variety of experiments with this little project. The circuit is using only four components.
The heart of the circuit is a FET (Field Effect Transistor) 2N3819. The 1K variable resistor is used to increase or decrease the sensitivity of the circuit. An LED is used as an indicator of detection.
A 5 inches antenna is connected at the gate terminal of the transistor. The antenna will detect any charge around and send it at the gate of the transistor and the transistor will activate the LED.