This is a Automatic Night Light circuit Without Transformer operated by Light Using Light Sensor LDR (Light dependent resistor). This Transformerless Automatic Light operated Night Light circuit is very simple and easy. At DayThe Bulb is automatic switch off and At night Automatic Switch ON Automatic Night Bulb Switch.
IN this circuit No Any transformer used so it makes this very portable and small. Use 9-12v Relay to connect the Bulb. Capacitor C1 must be 400v Rated . You can use one Rectifier ic MIC DB107 at the place of 4 IN4007 Diode. DB107 is a Small Package of 4 Rectifier diode in single IC. Resistor R1 should be of 1/2w .
The working of this Automatic Night Light Bulb Switch Without transformer is simple. When Light Fall on LDR in day then the resistance of Both LDR is Low and When the resistance is very then the all voltage through passes the R2 Droped with Negative supply and No sufficient voltage goes at Base terminal of transistor. When no voltage goes on Base then transistor Remains turn OFF and Relay Not Activated and bulb is switch off.
At Night time when No Light Fall on LDR then Resistance of LDR is Very High . At Rasistance is high then very Less amount of voltage passes through LDR and droped with negative. And Maximum amount of voltage comes on Base of transistor and it Turns ON. When transistor Turn on then the Relay Get Active and Bulb is switched ON.
So this works Automatically as Night Bulb Switch system. It can be used as Street Light Switching or any other purpose where need to Switch ON and OFF the AC Bulb Automatically.
Please CareFul With High Voltage AC – Use Relay With carefully
Zener Diode 11v 0.5w-1