A PIR sensor, or Passive Infrared sensor, is a type of electronic device that detects infrared (IR) radiation emitted by objects within its field of view. These sensors are commonly used for motion detection and are often found in security systems, lighting controls, and other applications where the detection of human or animal movement is required.
The term “passive” in Passive Infrared refers to the fact that the sensor does not emit its own energy but rather detects the infrared radiation emitted or reflected by objects in its vicinity. PIR sensors are based on the principle that all objects with a temperature above absolute zero emit infrared radiation.
Here’s how a PIR sensor typically works:
- Detection of Infrared Radiation: The PIR sensor consists of multiple infrared-sensitive elements. These elements are arranged in a way that covers a specific area or field of view. When an object with a different temperature moves within this field, it causes a change in the infrared radiation levels detected by the sensor.
- Generating Electrical Signals: The PIR sensor converts the changes in infrared radiation into electrical signals. When there is no motion, the sensor receives a constant level of infrared radiation, resulting in a steady electrical output.
- Triggering Motion Detection: When an object, such as a person or an animal, enters the sensor’s field of view and its temperature is different from the background, it causes a disturbance in the infrared pattern. This disturbance is detected by the sensor, leading to a change in the electrical output.
- Output Signal Activation: The change in electrical output triggers the PIR sensor to send a signal to a connected device or system, such as turning on lights, activating an alarm, or signaling the presence of motion.
PIR sensors are widely used for security purposes, such as in burglar alarm systems, outdoor lighting that activates when motion is detected, and in smart home devices for energy-efficient lighting control. They are valued for their effectiveness, low cost, and low power consumption, making them a popular choice in various applications requiring motion detection.