The PIR Motion Sensor Detector Module HC-SR501 allows you to sense motion. It is almost always used to detect the motion of a human body within the sensor’s range. It is often referred to using “PIR”, “Pyroelectric”, “Passive Infrared” and “IR Motion” sensor. The module has an onboard pyroelectric sensor, conditioning circuitry, and a dome-shaped Fresnel lens. It has a delay time adjustment Potentiometer and sensitivity adjustment Potentiometer. Repeat Trigger Selection Jumper is also available.