Dark and Light Indicator Circuit

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In this tutorial, we are going to make a dark and light indicator circuit. This project indicates whether there is darkness or light in the surroundings. Automatic day and light indicator systems have great importance in daily life. The circuit has a sensor that works in response to ambient light conditions. The main component of the circuit is an operational amplifier IC.

This project uses LM358 IC which comprises two opamps in a single chip. It is a general-purpose opamp that operates in several modes like comparator, summer, integrator, amplifier, differentiator, etc. Another main component of the project is a light sensor which is LDR.

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Hardware Components

The following components are required to make a Dark and Light Indicator Circuit

S. No	Component	Value	Qty
1.	Breadboard	–	1
2.	Battery	9v	1
3.	Connecting Wires	–	1
4.	Op-Amp IC	LM358	2
5.	POT	10k ohm	2
6.	Resistor	150 ohms	2
7.	LDR	–	1
8.	LED	5mm	2

LM358 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of LM358

Working Explanation

The Dark and light indicator circuit contains two LM358 dual comparators ICs for comparing voltages coming from a variable resistor and an LDR. LDR is a light-dependent resistor that changes its resistance according to the light. So the output of the sensor is compared to set the reference value. As the light conditions change from dark to light or light to dark, an output of a comparator goes high.

When the light intensity decreases the threshold resistance of an LDR becomes maximum. This automatically switches the LED ON which acts as a dark sensor. Whereas when the light intensity increases the threshold resistance of an LDR becomes minimum. And the circuit now turns ON the LED which acts as a light sensor.