This is the simple circuit of diagram of a small touch using IC NE 555 . This circuit is ideally useful for making touch operated doorbells, buzzers, toys etc which when touched on the touch plate operates the relay for a preset time and the turns off automatically.
the circuit is realized by utilizing the high input impedance of trigger pin of the IC 555. When the IC is triggered by the induced voltage of human body the output goes high for a time determined by R1 and C1. The transistor is used to drive the relay. The relay contacts can be used to drive the load like bell, motor , lights etc.