Motion Sensor Switches
Motion sensor switches are in-wall sensors that turn lights on/off when activated. Motion sensors like these are usually placed near doorways and entrances to sense when someone enters the room. Motion light switches normally use passive infrared (PIR) technology to detect motion, but other types of occupancy sensors also perform as well. Different rooms require specific types of sensors, and it's necessary to choose if an occupancy sensor or vacancy sensor would work better. More advanced types of motion sensors can switch between both and combine occupancy/vacancy with dual sensor technology.
Occupancy Sensors vs Vacancy Sensors
Choosing between occupancy sensors and vacancy sensors requires knowing the type of room and how busy it gets. Occupancy sensors are auto on/off sensors can turn the lights on when motion is detected and then turn them off after a time delay once motion stops. Vacancy sensors are auto off sensors that need to be turned on manually but can turn the lights off after a time delay when no motion is detected. Occupancy sensors are more commonly used in bathrooms and storage rooms, while vacancy sensors are more useful in office board rooms and conference rooms. A special type of motion sensor is the dual occupancy/vacancy sensor that can switch between auto on/off and auto off, depending on the room type.
Passive Infrared Motion Sensors
Passive infrared or PIR motion sensors use a body's heat signature to detect motion and activate the light. PIR occupancy sensors detect changes in temperature or the presence of infrared heat when a person walks by within its line of sight, which triggers it to turn on the lights. Passive infrared occupancy sensors are used in bathrooms, restrooms, laundry rooms, storage rooms, small offices and conference rooms. One weakness of using PIR sensors by itself is that they don't work well if the room has large obstructions or partitions that block the sensors immediate line of sight. Large boxes, furniture and cubicle partitions often block the sensor's range so motion behind might not be detected. For a more accurate sensing, PIR sensors are combined with other sensor technologies for larger rooms.
Dual Technology Sensors
Dual technology sensors combine passive infrared technology with another sensor to provide optimal detection and to prevent false triggers. Other types of sensors include ultrasonic technology and microphonics technology. Both ultrasonic and microphonics sensors use sound as a detection mode to reinforce passive infrared detection. The advantage of using sound is that it can be detected even behind large obstructions like walls, furniture and partitions, which is a major weakness of PIR motion sensors. Dual technology sensors prevent false alarms because both PIR and ultrasonic sensors need to be activated before the light is turned on. Moreover, once the light is on, only one sensor needs to detect activity to keep the light on. Dual technology motion sensors are ideal for large offices, bathrooms and shower rooms with stalls, storage rooms and garages.