PIR sensor

PIR detection stands for Passive Infrared Detection. It is a method used by PIR sensors to detect motion by measuring changes in infrared (heat) radiation in their surroundings.

What Is a PIR Sensor?

A PIR sensor (Passive Infrared Sensor) is an electronic sensor that detects movement of people, animals, or objects based on their body heat. It does not emit infrared radiation—hence the term “passive.”

How PIR Detection Works

1. Infrared Sensing: All warm bodies (like humans or animals) emit infrared radiation.

2. Sensor Lenses: A PIR sensor has a lens (often Fresnel-type) that focuses infrared signals onto a sensor element.

3. Detection: When a warm object (like a human) moves across the sensor's field of view, it causes a sudden change in infrared levels.

4. Signal Output: The sensor detects this change and outputs a signal that can trigger an alarm, turn on a light, or activate a camera.

Where PIR Sensors Are Used

Home security systems – To detect intruders

Automatic lighting – To turn lights on when someone enters a room

Smart home devices – For presence or motion sensing

Energy-saving systems – To control HVAC or lights based on occupancy

Advantages of PIR Detection

Low power consumption

Reliable for indoor motion detection

Cost-effective

Easy to install