Electro Lab: Light and Dark Sensor - LDR Project

Light and Dark Sensor is a basic electronic project. It also helpful for Robotics project. The principle of this project is to detect light and dark. This can be done by a simple way.
We will take a light(LED) for output. If there is dark the led will turn on and if there is light the led will turn off.

Required Equipment:

1.LDR : LDR - Light Dependent Resistor is a Transducer. That means it converts light intensity into resistance. It is one kind of variable resistance depend on light intensity. If the light intensity increased the resistivity of LDR is decreased and vice verse.

LDR-Light Dependent Resistor

2. LM741 Op Amp:
 It is an operational amplifier IC, including 8 pin. Pin no 2 and 3 are input and pin no 6 is the output in this op amp. There are various op amp in market, but LM741 is very easy to use and also available.

LM741 opamp

3. Others:
 - a Bread Board.
- Resistance - 100K(x2).
- Resistance - 4.7 K (x1) - you can use a potentiometer if you cant find 4.7 K resistor.
- Jumping wires.
- 9v Battery.
- LED

Connection:
 Put the parts on the breadboard like the digram shown below.

Circuit Diagram of Light/Dark Sensor

Now you are done. Make the plate of LDR dark and see the LED(LED shown in figure as L1) automatically turn on and if the plate of LDR get light the LED turn off. Now your project is ready.