Presence and ambient light sensors

There are a few types of sensor available in the market and each has particular attributes, which mean they work optimally under different circumstances.
Occupancy sensors turn lights on when they detect motion and they turn the lights back off when there has been no motion for a while. Light harvesting sensors measure the ambient light levels in a room and dim the lights up and down to achieve a pre-determined level of illumination.

When the occupancy sensor is matched with a lighting control system featuring in-built daylight sensors and light harvesting, they can both determine which areas of e.g. a warehouse or car park are in active use and determine what light level is required.

There are two main types of occupancy sensors

• Active sensors e.g. microwave, and
• Passive sensors e.g. passive infrared (PIR).

PIR sensors

The most common sensors used in the building sector are passive infrared (PIR) sensors. These passive sensors react to variations of infrared radiation due to the movement of objects by detecting heat and light in their field of view.

• Activated by heat and light
• Do not function well in temperatures >35 degrees Celsius
• Cannot penetrate plastic or glass, so the detector is positioned externally to a light fitting
• Lenses can age due to exposure to the atmosphere, which may result in reduced performance over time
• Life span of around 20,000 hours

microwave sensor

Microwave sensors detect motion through the principle of Doppler radar. They monitor reflections from walls or objects in the room irrespective of heat or light.

• Activated by motion – speed and size
• Unaffected by background temperature
• Can safely penetrate non-metallic objects such as glass and plastic
• Dust and smoke proof as they are inside the fitting
• Life span of around 100,000 hours

lux level sensor

Lux level sensors are presence detectors that automatically control lighting levels by measuring the level of ambient light in a room. As the level of ambient light  increases, the sensor will dim or turn off the lights.

• Provide a constant light level, supporting occupant comfort and productivity
• Help to conserve energy by dimming/turning off lights when not needed and lowering a building’s internal heat gain
• Extend bulb life by reducing kilowatt hours of use
• Save money on electricity bills