LED Brightness Control using Light Dependent Resistors (LDR)

Components Required:

1) Breadboard

2) 1N4007 Diode

3) 470 ohm resistor

4) 15 Kilo ohm Light Dependent Resistor (LDR)

5) LED (Any Color)

6) 9Volt Battery

7) Digital Multimeter 

Procedure:

• Connect the 1N4007 diode and 470Ω resistor to one terminal of 15 Kilo ohm Light Dependent Resistor (LDR) in series. Connect the other terminal of LDR to the LED in series in a breadboard. 

• Connect the 9V battery's positive end to the anode of 1N4007 diode and negative end to the cathode of the LED as shown in the circuit diagram below.

• Measure the voltage across various points by altering the Light input on the LDR using a digital multimeter and note the change in brightness of the LED accordingly.

• Observe the change in LED brightness in a dark room and in a bright light. Here I have used a cap to cover the surface of the LDR to observe the change in LED brightness.

• Also observe the change in resistance value of the LDR using a digital multimeter which is the cause for the alteration in LED brightness.

• The resistance of LDR is low in bright light and high in darkness.

Circuit Diagram:

Figure 1: LED Brightness Control using Light Dependent Resistor (LDR) (LDR in Room Light)

 

Figure 2: LED Brightness Control using Light Dependent Resistor (LDR) (LDR covered with a cap)