This kind of sensor switch is suitable for making touch operated bells, buzzers of small toys which operate for a small time and then switch off automatically. The input impedance of the trigger is very high and the touch sensor switch can be triggered by the voltage induced in the human body. The relay is a 12 V DC relay operating at currents les
s than 200 mA. i tried a breadboard prototype of above circuit but not working relay energises without touch when powered on and keeps on even when capacitor is full charges.