IR Sensor Circuit, Connection Diagram, Project

Inferred Or IR sensor is a very useful electronic sensing device used in so many electronic projects, devices, circuits for detection, automation, counting, etc. Generally, the inferred sensor works on the principle of measuring and detecting the inferred radiation surrounding or focused on it. You can see the applications of inferred or IR sensors in your daily life. For example, your TV or DVD remote control system uses the inferred technology. The remote contains the IR rays emitter whereas the TV or DVD contains the IR light detector or receiver.

In this article, we are going to see the Active IR sensor circuit diagram, its terminals. Also, we will see the IR sensor connection diagram. Here also you will get an example of IR sensor projects with making procedures and applications.

The IR sensor is divided into two different types,

1. Active IR Sensor
2. Passive IR Sensor or PIR Sensor

A passive IR sensor circuit is built with only a photodetector or photodiode. It only can sense or detect a light source. It provides an output when a light focused on it. Passive IR sensors mainly used for detection circuit. In television sets, passive IR sensors are used. Here, one way communication is happened. Here, measurement of the shape and distance of object is very difficult. A passive IR sensor does not required any external power supply for its operation.

The active IR sensor circuit is built with both a photodetector and a light emitter. The light emitter or LED continuously remains on when the circuit is connected to a DC supply(generally 5V). So when any object put in front of the IR sensor, the light generated by the emitter hits that object and falls upon the light detector reflected by the object, so the sensor gives the output signal. Active IR sensors are used in traffic counter system, thief control, and many more applications.

So you can understand, the passive IR sensor can detect light only, but the Active IR sensor can detect any object placed in front of it. Active IR sensor has more advantages than a passive IR sensor such as it can count, measure distance, displacement, obstacle, etc.

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Components and Terminals of a conventional IR Sensor

In the above figure, you can see an Active Sensor Module that has both IR Transmitter and IR Receiver LEDs. Here, you can see the IR sensor has a total of three terminals,

1. Vcc
2. Ground
3. Output

You can see it also has a distance adjustment potentiometer, we can vary the sensitivity of the IR sensor at different distances between the sensor and object. We need to rotate the potentiometer knob to vary the sensitivity.

The IR sensor circuit also has two indicating LEDs - 1. Power LED, 2. Obstacle LED

The power LED(Light Emitting Diode) will glow when the Sensor is connected to a 5V DC power supply and it indicates either the sensor is connected to the power supply or not. To provide the power supply to the IR sensor, its Vcc terminal is to be connected to the positive and the Ground terminal is to be connected to the negative.

The obstacle LED will glow when the sensor senses any object and it indicates the sensor giving output.

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IR Sensor Circuit Diagram

Here, you can see the internal circuit diagram of IR sensor module below.

You can see the above circuit consists of a photodetector or photodiode, IR LED, Normal LED, operational amplifier IC and Potentiometer.

The IR LED emits the inferred light and the photodiode detects the light. Here the operational amplifier or OpAmp used as a voltage comparator. The one input terminal of OpAmp is connected to the Vcc through the potentiometer and another terminal is connected with the Photodiode.

So when the light emitted by the IR LED got reflected by any object and falls on the photodiode, its resistance will decrease and it starts to conduct current. Due to that, a voltage drop occurs across the series resistor to the photodiode. By varying the potentiometer we can adjust the threshold voltage of the OpAmp. So once the voltage drop across the series resistor to photodiode goes above the threshold voltage, the output of the OpAmp will be high, as a result, the circuit will produce an output voltage.

The potentiometer helps to vary the threshold voltage, so we can vary the potentiometer to set the distance between the IR sensor and object to make the IR sensor more sensitive.

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IR Sensor Connection Diagram and Project

Here we have taken a very simple IR Sensor project, which is automatic fan control. You can see the connection of IR sensor and other electronic components to make this project.

Basically, the main objective of this project is, when anyone comes in front of the fan, the fan will be turned on automatically. When no one is there in front of the fan, the fan will be in off condition.

Generally, the IR sensor is placed in such a way that it can sense when anyone comes in front of the fan, and it creates the output voltage which will operate the Solid State Relay(SSR). Once the SSR got a voltage from the IR sensor, it will be turned on and will connect the fan to the main power supply. Remember that here we have used an Active IR sensor.

Components required:

You can make this circuit very easily by using the following components,

• 230V SSR(Solid State Relay)
• 6V battery
• 5V IR sensor
• Table Fan

Also, you can make so many different types of electronic projects using IR sensors. But before that, you must know and understand the working principle of IR Sensor and its connection procedure properly.

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