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Color distinguished using LDR/Color sensor using LDR

Summary

By: 
Himanshu Choudhary

This circuit can be used to sense and differentiate between different colors. This project demonstrates the principle and operation of a simple color sensor using LDR. The circuit is divided into three parts: Detector (LDR), Comparator and Output. This circuit is based on LM324 IC whose pin diagram has been shown below:

LM324 IC

 

Description

 

In this project, when light of a particular color falls on LDR, its resistance decreases and an output voltage is produced. This voltage is dependent on the intensity and wavelength of different color. For this we need to set reference voltage of comparator according to our requirement.

For Eg., If we set reference voltage at positive pin with 0.38volts, the LDR becomes sensitive to blue light. When blue light falls on the LED, an output of approximate voltage 0.28V is produced, this glows the output LED.But if we use a yellow color light on LDR then input voltage at the comparator is around 0.7 volts at the negative pin of comparator and the output LED doesn’t glow.

Circuit Diagram

Components

Resistor Image
Resistor

Resistor is a passive component used to control current in a circuit. Its resistance is given by the ratio of voltage applied across its terminals to the current passing through it. Thus a particular value of resistor, for fixed voltage, limits the current through it. They are omnipresent in electronic circuits.

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LEDs | Light Emitting Diode
LED
 
Light emitting diodes (LEDs) are semiconductor light sources. The light emitted...
LDR | Light Dependent Resistor
LDR

An LDR (Light dependent resistor), as its name suggests, offers resistance in response to the ambient light. The resistance decreases as the intensity of incident light increases, and vice versa. In the absence of light, LDR exhibits a resistance of the order of mega-ohms which decreases to few hundred ohms in the presence of light. It can act as a sensor, since a varying voltage drop can be obtained...

Presets | Variable Resistors
Preset
 
A preset is a three legged electronic component which can be made to offer varying resistance in a circuit. The resistance is varied by adjusting the rotary control over it. The adjustment can be done by using a small screw driver or...
LM324 | LM324N Datasheet
IC LM324

LM324 is a 14pin IC consisting of four independent operational amplifiers (op-amps) compensated in a single package. Op-amps are high gain...

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