Opamp LM324 as comparator using LDR

This project based on op amp comparator circuit demonstrates the principle of operation of op amp (operational amplifier) as comparator. A comparator compares two voltages fed to it and gives output correspondingly. This circuit finds application as intermediate circuit in numerous circuits where there is need to compare two voltages. This circuit uses a LM324 IC, whose pin diagram has been shown in the image below:

[[wysiwyg_imageupload:7744:]]

This Op amp comparator circuit project uses opamp (IC LM324) as comparator. The output of the comparator is high if voltage at positive end is more than voltage at negative end and gives low output if voltage at positive end is lesser than negative end. Here in this circuit if LDR1 is covered and LDR2 is in light. The resistance of LDR1 increases and the entire voltage drop takes place across it, thus positive input pin of opamp becomes high while resistance of LDR2 becomes low and entire voltage drop takes place across 10K resistor, making negative input pin low. On comparing these voltages comparator gives high output. If the situation is reversed then positive pin becomes low and negative pin becomes high and comparator gives low output. At output end two LEDs are connected in opposite fashion one gets forward biased at high output and other at low output. Led’s are connected through 330? resistor to regulate the current flowing through them. The circuit operates at 5V DC.