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 ...

Used in a variety of timer, pulse generation, and oscillator applications, the 555 was designed in 1971 by Hans Camenzind. A favorite for many engineers, the 555 is still in widespread use due to its ...