In this article, you will learn how to make an automatic night light using LDR. This circuit senses the darkness and turns ON the lights. Before getting started, you must know how a light dependent resistor works.
Light Dependent Resistor is also know as LDR. It changes its resistance according to the light intensity. When there is high light intensity the resistance of LDR increases resulting conductivity decreases. When there is low light intensity, it mean darkness, the resistance of LDR decreases, resulting conductivity increases. By using this phenomenon of sensing darkness, we build this project.
LDR – 1 [ Amazon India ]
Resistor 1K -1 [ Amazon India ]
Resistor 330 Ohm – 1
Diode 1n4007 – 1 [ Amazon India ]
Transistor BC547 – 2 [ Amazon India ]
Relay 5V – 1 [ Amazon India ]
Power Supply 9V
LDR SWITCH CIRCUIT
Below we can find the circuit of dark sensor switch
Working of LDR circuit
This circuit is operated with 9V power supply. The LDR is used to sense the darkness. When there is a darkness, the resistance is decreases and it is able to drive the base of the transistor. Here transistor Q1 acts as switch. When there is high at base of Q1, it will turn ON. The transistor Q1 will drive the transistor Q2 to turn ON the relay. When there is light on the LDR, the resistance increases, then there will be low at base of the transistor Q1, then the transistor acts as OFF switch and turns OFF the relay.
DOWNLOAD LDR SWITCH CIRCUIT AND GERBER FILES
If you have any queries, please feel free to comment below, we will respond you soon.