Touch Sensor Circuit

The touch sensor circuit is built with three components such as a resistor, a transistor and a light emitting diode.Here, both the resistor and LED connected in series with the positive supply to the collector terminal of the transistor. Select a resistor to set the current of the LED to around 20mA. Now give the connections at the two exposed ends, one connection goes to the +ve supply and another goes to the base terminal of the transistor. Now touch these two wires with your finger. Touch these wires with a finger, then the LED lights up!