Infrared Sensor: Working Principle and Applications

This page explains the basic function and workings of an infrared (IR) sensor. Infrared is radiant energy that is invisible to the human eye. It has a longer wavelength compared to visible light.

The wavelength of infrared waves ranges from 700 nm to 1 mm, corresponding to 430 THz to 300 GHz in the electromagnetic spectrum. Infrared sensors are devices that emit and detect infrared waves to detect distant objects.

Applications of Infrared Sensors

There are numerous applications for IR sensors, including:

• Target acquisition and surveillance in military operations.
• Tracking systems.
• Night vision equipment.
• Infrared spectroscopy.
• Thermal efficiency analysis.
• Industrial facility inspections.
• Environment monitoring and weather forecasting.
• Wireless communication, such as IR TV remotes.
• Remote temperature sensing.

How Infrared Sensors Work

An infrared sensor typically consists of two main components:

• Transmitter: Usually an IR LED that emits infrared waves when voltage is applied. The IR transmitter sends these waves over a short distance.
• Receiver: Detects reflected infrared waves and generates a voltage accordingly.

Here’s the process:

1. When voltage is applied to the IR LED in the transmitter, it generates infrared waves.
2. The transmitter emits these IR waves.
3. If an object is in the vicinity of the sensor, the IR waves will be reflected.
4. The receiver detects these reflected waves and produces a corresponding voltage.

If there is no object nearby, there will be no reflected IR waves, and the receiver will produce no voltage output.

The voltage levels produced by the receiver are then compared using comparators or microcontrollers for further processing. This is how an infrared sensor works to detect the presence of an object.