This circuit is an automatic street light controller. Sensors used to detect changes in light is LDR (Light dependent resistor), the working principle of Light dependent resistor is exposed to light when the resistance value of LDR great, but if not exposed to light or dark then the resistance value of LDR. This circuit when the dark conditions (night) or the resistance value of LDR, a small electric current is passing, because the non-inverting reference voltage is greater than the inverting input voltage. So that the LM741 IC output value “1″, the transistor switches in the ON condition, the relay is also in the ON condition, so that the light is on. Here is a schematic drawing of automatic street light controller:
When light conditions (daylight) or LDR resistance value is small, a large electric current is passing. This is due to the inverting input voltage is greater than the non-inverting reference voltage, the LM741 IC output value “0″, the transistor in the OFF condition, the relay is also in the OFF state, so the lights went out. To light using AC Lamp 220V 20watt. To source voltage of this circuit using a battery 9Volt. LDR (Light dependent resistor) should be placed on the affected light directly. here I also include a PCB (printed circuit board) of the automatic street light controller and you can also download it.
Download PCB Download Now