Sunset Lamp

The circuit uses popular timer IC NE555 as a Schmitt trigger to give the bistable action. The set and reset functions of the comparators within the NE555 are used to give the instantaneous action. The upper threshold comparator of IC1 trips at 2/3Vcc, while the lower trigger comparator trips at 1/3Vcc.The inputs of both the threshold and the trigger of NE555 are tied together and connected to the voltage divider formed by LDR1 and VR1. The voltage across LDR1 depends on the light intensity. In daylight, LDR1 has low resistance and the input voltage to the threshold comparator goes above 2/3Vcc and its output becomes zero, and the lamp remains off. At sunset, the resistance of LDR1 increases, and the voltage at the input of the threshold comparator decreases below 2/3Vcc and that of the trigger comparator goes below 1/3Vcc. As a result, the outputs of threshold and trigger comparators go high. Thus it completes the power supply to the lamp through triac1. LED1 glows to indicate the high output state. Application of NE555 in bi stable mode. Concepts related to the working of Light Dependent Resistors. Application of TRIAC BT136. Application of Zener Diode. Brand: Kits'n'spares, Marketed by: Kits'n'spares