Here is a great collection of touch switch circuits. A touch switch is an electronic device that enables us to control a circuit by simply touching a sensor. Simple touch switch circuit with 4011 – ...

This is a very simple touch sensor switch that is build with the 555 timer IC. You just need to touch the metal plate and the relay gets energised and is kept in this state for about 100 seconds, then ...

This PLL-based circuit implements a touch-switch circuit using the PC board or small metal pads as sensors; it is radiometric and thus insensitive to changes in temperature and supply voltage.

There seems to be nothing a 555 can’t do. We’ve seen it before, but [electronzapdotcom] reminds us you can use a 555 and a few parts to make a reasonable touch switch in this video, embedded below.