This circuit allows you enough time to reach your bed and lie down before the bedroom lamp switches off automatically. You can find a number of applications for this circuit. The circuit draws almost no power when it is inactive.
Mains power supply is reduced by the capacitive dropper arrangement. A 1F capacitor (C2) handles the timing part. When switch S1 is pushed to 'on' position for a few minutes, bulk capacitor C2 charges and the stored energy drives the internal LED of IC MOC3041 through resistor R4. This IC comprises a GaAs (gallium arsenide) infrared-emitting diode optically coupled to a monolithic silicon detector performing the function of a zero-voltage-crossing bilateral triac driver. 
The working of the circuit is simple. When you press switch S1 for a few minutes, triac BT136 is triggered through its gate terminal. As a result, the lamp glows until the charge ceases out in capacitor C2.
Assemble the circuit on a general-purpose PCB and fit it near the bedroom switchboard. Refer the pin configurations of MOC3041 and BT136 before assembling the components on the PCB.
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