The timer circuit can be used to turn off a particular device after approximately 35 minutes. The circuit can be used to turn off appliances such as radio, television, fan, pump etc after a preset time of 35 minutes. Such a circuit can certainly save a lot of power. The circuit is based on quad 2-input CMOS IC 4011 (U1). The resistor R1 and capacitor C1 occurs along time required. When push button S2 is depressed, the capacitor C1 is discharged and the input of the four NAND gates are pulled to zero. The four outputs short-circuit U1 to go high and transistor Q1 to activate the drive over. The equipment connected via the relay is energized. When S2 is released from the C1 begins charging and the voltage at its positive pin becomes equal to the half of the supply voltage U1 output becomes zero and the transistor is turned off. This makes the relay deactivated and the unit connected via the relay is switched off. The timer can be done to stop if necessary by pressing the switch S1. Schematic diagram with list of electronic parts:
