How does the PIR Motion Sensor Module – SR501 work?

  1. The SR501 PIR Motion Sensor Module works based on the principle of detecting changes in infrared radiation emitted by living organisms. Here’s a simplified explanation of its operation:

  • The module includes a pyroelectric sensor that can detect small changes in infrared radiation.
  • When a human or warm-blooded animal moves within the sensor’s range, it emits infrared radiation that changes the temperature pattern in its surroundings.
  • The Fresnel lens on the module focuses the infrared radiation onto the pyroelectric sensor.
  • The sensor converts the detected changes in infrared radiation into electrical signals.
  • The supporting circuitry amplifies and processes the electrical signals to determine the presence of motion.
  • The module provides a digital output signal that indicates motion detection, which can be used to trigger actions or control other devices.