What type of sensor does a motion detector switch typically use?

A motion detector switch typically uses infrared sensors to detect motion. These sensors work by sensing the infrared radiation emitted by objects based on their temperature. When a warm object, such as a human body, moves within the detection range, the infrared sensor detects the change in the IR radiation pattern and triggers the switch.

This method is effective because it allows the sensor to detect motion without requiring physical contact and can cover a wide area. Unlike ultrasonic sensors, which analyze sound waves and can be affected by environmental factors, infrared sensors are generally more reliable for detecting movement in most indoor and outdoor conditions. Additionally, while magnetic sensors are helpful in detecting changes in magnetic fields (often used for door or window sensors), and capacitive sensors detect changes in capacitance due to proximity or touch, infrared is the most common choice for motion detection in switches.