There are 4 essential types of motion detectors that are usually integrated in LED ceiling lights and are activated by different mechanisms, as detailed below: Passive infrared (PIR) motion sensors. This type of sensor reacts to heat, i.e. it causes the light to come on when it detects heat from a body within its range. Microwave motion sensors. They are triggered when the signal they emit is interrupted by a person or object. High frequency radar motion sensors. These luminaires are activated when they detect a variation in the frequency of the electromagnetic wave it sends out caused by a moving object. Twilight movement sensors. These elements detect the amount of light and are activated when the light falls below a certain programmed threshold.