Faced with the situation to control the time that the light is turned on, engineer Radu Preda from Romania has started experimenting with different circuits to save money spent on electricity. He has designed 2 energy saving lighting circuits, the first one uses a relay and the second one uses a optoisolator triac MOC3041 and a normal triac like BTA06-600 and both using the 555 one-shot timer.
Note that the circuit is coupled directly to AC mains using the existing system in the building. A switch is used to start the timing and light one or more bulbs. The relay is powered from 12V and its contacts must outstand up to 1kW at 220V.
The LM555 IC is in a monostable configuration. The timing period is set with R4 and C3 and can be calculated with the formula:
T = 1.1 x C3 x R4
With the values from the schematic the working time of the lighting circuit is around 4 minutes. Power is applied through R1, C1, R2 and the voltage is stabilized at a value of 15V with the zener diode PL16Z.
The second schematic uses the same timing block but the control element is the BTA06-600 triac. Please be careful in constructing and utilizing these circuit because there is danger of electrical shock. Assemble it in plastic or metal box and place it in places inaccessible to children or animals. Obviously, must be protected from rain and solar radiation that adversely affect the proper functioning.