Infrared Sensor/Detector Circuit

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4 Working Explanation of InfraRed Sensor

Introduction

As electronic students, we have always heard that IR technology is used extensively in the Industrial sector for making different devices and products. For example, the television we used in our homes uses an InfraRed sensor to determine the signal coming from the remote which is not apparent to human sight. But what is an IR sensor? A sensor that detects infrared radiation. The infrared sensor contains IR LED and IR photodiode. The LEDs in the sensor are almost similar to the standard LED.

There are two types of InfraRed sensors, the active sensor which includes both transmitter and receiver, and the passive sensor which only includes the receiver/detector and has no transmitter. To avoid supplementary reflections of the environment both the transmitter and the receiver should be enclosed appropriately with plastic and painted black enclosure. In this project, we are going to make an IR circuit sensor.

Hardware Required

S.no	Component	Value	Qty
1.	Breadboard	–	1
2.	IC	NE555 Timer	1
3.	Dual Operational Amplifier IC	LM358
4.	Regulator IC	7812
5	Diode IR LED, IR Photodiode, LED	–	1, 1, 1
6.	Diode	1N4148	2
7.	Diode	1N4002	1
8.	PNP Transistor	BC558	1
9.	Capacitors	1uf/63V, 100uf/25V, 47pf/63V	2, 3, 1
10.	Resistor	10K/4W, 1K/4W, 33K/4W, 22K/4W, 1M/4W	1, 4, 1, 2, 1
11.	Trimmer cermet	10K	1

Circuit Diagram

Working Explanation of InfraRed Sensor

The Infrared LED is driven by the IC NE555 which is wired with a frequency of around 120Hz and 300mA peak current and for a duty cycle of 0.8msec. The diode D1 gives the IR output to diode D2. The signal is then given to the inverting pin of op-amp IC LM358 which gets amplified and given to D4 and C4. The diode D4 produced the forward voltage which is offset by D3, R5, and R6. A DC voltage is provided to the inverting terminal of IC2 LM358. The LED gets ON and OFF by the outcome of the comparator. The comparator output is set by the potentiometer in the circuit. The comparator output is given to Q1 which drives the relay or load of the circuit.