A simple timer built around the popular 555 Integrated Circuit. The timer enables the output when the power is applied to the circuit and disables it after the preset time interval. You can adjust the timer from a few seconds to a maximum of about 20 minutes. The circuit provides a 9 to 12V DC / 50 mA output (depending on the supply voltage used) that can be directly connected to a 9V or 12V DC relay to switch more power.