Automatic Light Operated Switch using LDR and IC741

Along with modernization, people are more prone to the comfort zone. Several inventions have been made to meet this requirement. Following the same trend, here we have presented a simple circuit; automatic light operated switch using LDR and IC741. People are busy, every second has a vital role in our busy schedule.

Why shall we waste our valuable time turning on every switch in the building? The situation turns more troublesome when one needs to reach the ground floor just because it’s getting dark and s/he needs to turn on the light. The importance of this circuit; the automatic light operated switch is much felt in such traumatic situations.

Who will stay calm being victimized when the solution is right in front of us? To overcome such problems, you don’t need to throw a hefty sum of your hard-earned money. What you need to do is just connect the electric appliances you want to operate automatically with the circuit of an automatic light-operated switch. Then the switch will automatically turn on, LDR will serve its purpose and you will get your surroundings lightened without pressing the switch.

Circuit description of automatic light operated switch using LDR and IC741

The circuit presented here is a light-operated circuit using LDR. LDR is a semiconductor component whose value of resistance is changed according to the intensity of light falling on it i.e. more the light falls on the LDR, the less the resistance is and vice-versa.

The heart of the circuit is a very common operation amplifier IC 741(IC₁) and is used herein inverting mode. The LDR is used here as a light sensor and variable resistor; VR₁ is used to adjust the sensitivity of LDR. Capacitor C₁ behaves as a feedback capacitor. The output from PIN 6 of IC₁ (IC 741)is given to the base of transistor T₁ through resistor R₅, which is used here as a relay driver circuit. Diode D₁ is used as a protector and protects the relay from surge current. The load to be controlled is connected to the output pin of the relay.

Hurry up! Reduce your worries and enjoy what the technical world has to offer.

Check out other interesting projects using LDR posted in bestengineeringprojects.com

1. Photoelectric switch using ne555
2. Self Resetting LDR Alarm using Timer IC 555
3. Automatic Light Operated Switch using LDR and IC741
4. Automatic Fence Lighting with Alarm
5. IC 555 Based Automatic evening lamp

PARTS LIST OF LIGHT OPERATED SWITCH USING LDR AND 741

Resistor (all ¼-watt, ± 5% Carbon)

R1 = 1 KΩ R2 = 1KΩ, ½ W R3 = 10 KΩ, ½ W R4 = 10 KΩ R5 = 2.2 KΩ, ½W R6 = 330 Ω, 1/2W VR1 = 470 KΩ

Capacitor

C1 = 0.1 µF, 30V (Electrolytic Capacitor)

Semiconductors

IC1 = 741 (Operational Amplifier) T1 = SL100 or BC148B (Medium Power Silicon Transistor) D1 = 1N4001 (Rectifier Diode)

Miscellaneous

RL1 = 400 Ω, 9V relay SW1 = Double Pole Double Through (DPDT) LDR