Color distinguished using LDR/Color sensor using LDR


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




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


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