The full-wave diode bridge delivers pulsed-dc voltage to the load, making the circuit suitable for dc-control applications such as dimming. (The circuit can handle ac power if you substitute a triac ...

This is a very simple touch sensor switch that is build with the 555 timer IC ... induced in the human body. The relay is a 12 V DC relay operating at currents less than 200 mA. I love all about ...

The shots you see above are an enclosed relay ... the full control scheme that he uses, but it takes care of the bulk of the hardware. He uses a triggering circuit based on a 555 timer (PDF).