How to make light sensor circuit using LDR

Introduction:-

In this post we are going to use a LDR to build a darkness sensing circuit.

What is a LDR?

A LDR(light dependent resistor) is a electric component that has variable resistance that changes with the intensity of light falling on it. It is also known as photo-resistor.

The resistance of a LDR decreases with increase in the intensity of light and the resistance increases with decrease in the intensity.

Components required-

1. A LDR.

2. 50k Ohm resistor - 1

3. 220 Ohm resistor - 1

4. BC547 transistor - 1

5. Power supply (5v to 10v)

The circuit-

BC547 Transistor-

BC547 is a NPN bi-polar junction transistor.

It is commonly used to amplify current. A small current at the base of the transistor controls the current at collector and emitter which is much larger.