If any mistake please correct me.īut now i’m facing a problem that once when the lamp is switched on at dark and switched off after the preset time at night, it is not turning back on when its dark in next day evening. I’m using a 9v transformer, I used 4x1N4007 diodes along with 1000uF 16v capacitor to make 9vac to DC. R7 and R8 are current limiting resistors.Ĭircuit diagram of automatic night light. ![]() Resistor R1, diode D1, capacitor C1 and Zener D3 forms the power supply section of the circuit. A 9V battery is included in the circuit in order to power the timer circuit during power failures. When output of IC1 goes high transistor Q3 is switched ON which triggers triac T1 and the lamp glows. The output of IC1 remains high for a time determined by resistor R5 and capacitor C4. This automatic triggering is achieved with the help of capacitor C2. NE555 is wired as monostable multivibrator that is automatically triggered at power ON. Base of Q2 is connected to the emitter of Q1 and so Q2 is biased on which in turn powers the IC1. When darkness falls the resistance of LDR increases and so do the voltage across it. ![]() At day time the resistance of the LDR will be low and so do the voltage drop across it, the transistor Q1 will be in the conducting mode. ![]() The working of this night light circuit very simple. ![]() The circuit will automatically switch on the AC lamp when night falls and the lamp will be automatically switched off after a preset time. A cheap and simple automatic night light using few transistors and NE555 timer is shown here.
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