Sensors enabled lighting fixtures are used very often in commercial and industrial applications, and some residentials outdoor lighting applications.
With sensor enabled fixtures, it will detect the occupancy in the area and lighting condition of the area to better control the light on/off with a lighting schedule control ,or dimming down light when ambient light is good enough to save energy at area with good natural light .
let us get an overview what type of sensors are typical used in an integrated LED lighting fixtures.
there are 3 categories of sensors:
1) motion sensor is typically used for occupancy detection. the technology used in sensor from traditional Passive Infrared ( PIR ), Microwave, and ultrasonic .
PIR is the most used technology in motion and occupancy sensor. It detects the heat and movement in the areas with infrared waves. Most PIR sensor have a multiple facets Fresnel lens in front of the pyroelectric sensor. The Fresnel lens help focusing the infrared energy to the sensor. Most effective range for PIR is at 30ft or 10 meters.
Both Microwave and ultrasonic are active sensors, they both actively emit signal pulse or waveform and listen to the echo pulse /waveforms from environment to tell whether there is object movement in the area. It is good for large areas.
Microwave sensor is using some high frequency (10GHz, 24G Hz) electromagnetic wave, while ultrasonic is using sound waves. Microwave sensor can even detect whether the moving object is moving close or away from the fixtures. Generally microwave sensor has a higher sensitivity than PIR sensor. The other benefits of microwave sensor is that it can operate under a much larger temperature range (-30c to 80c) than PIR sensor( 0c-55c). It also tends to have a longer lifetime and higher cost than PIR Sensors.
Ultrasonic motion sensor functional similar like Doppler radar. One drawback for ultrasonic sensor is false triggers coming from unwanted areas due to the soundwave bounce around surfaces in the space.
2) photo sensor , it is gaining a lot traction due to daylighting and daylight harvesting. Due to local energy code such as California Title 24 ,there are more requirements of fixture integrated photo sensor. The photo sensor includes a photocell that produce voltage/current output when light shine on it.
Photo sensor can work with led driver /fixture ballast to control light fixture on/off or dimming up/down light for better daylight harvesting purpose.
3) combined sensor with hybrid technologies.
There are a lot modern motion detectors use combinations of different technologies such as combing PIR with Ultrasonic technologies. In using the two technologies, in order to detect movement both PIR and Ultrasonic triggers have to be detected, which could help reducing false detection. Ultrasonic can see around obstacles that would normally overlook by PIR sensor. With ultrasonic sensor not affected by temperature and air flows, the overall occupancy detect accuracy is greatly improved.
We also see combine motion detection with photocell into one sensor and also can work with dimming of led drivers. these type of sensors is used in outdoor that can be automatically switch light off during the day or used indoor where to facilitate daylight harvesting by dimming the light.
what are some of the new trends in lighting control sensor ?
1) the size goes smaller for indoor integrated fixture type sensor.
2) wired and wireless connectivity build into sensors to create a network control system ,such as communication protocols, Power over Ethernet, DALI, Bluetooth, ZigBee, WIFI protocols.
3)multiple functions ,combined multiple technologies ( PIR, Ultrasonic, Microwave, Photocell ,smoke ,CO detector)
4)focus on integrate lighting sensor network into overall Building management control system.
5) easy filed installation and configuration via wireless or Visible light programming.
