Lights are often left on longer than needed, which adds to energy costs. And that’s where occupancy sensors and other lighting controls enter; with occupancy sensors you do not need to switch on or off the lights every time you enter or leave a room.
Occupancy sensors are a flexible option, but they have a problem: the sensor's ability to detect fine motion or heat-emission sources (infrared sensors) or sounds (ultrasonic sensors). A poor quality occupancy sensor can lead to false triggering. The quality and the type of sensor are important features.
Occupancy sensors are largely used in the outdoors, but also in closets and basements and rooms where lights are often left on longer than needed. They may be used in task lighting applications; in this case, lights are turned on by the motion of the people working in a specific area (kitchen counter, for instance).
Some occupancy sensors have timeout options: you can choose, say, 1, 3, 5, 15, 30 minutes timeouts, though the exact options vary with models and manufacturers.
Types & Prices
Occupancy sensors are typically of three types: 1) ultrasonic, 2) infrared and 3) dual ultrasonic-infrared.
Ultrasonic sensors are designed to detect the presence of people by using sound waves, while infrared sensors respond to heat and motion. They are both relatively inexpensive, but prices vary a lot: from about $12 to $80 or more per unit. Dual-technology sensors are the most reliable, but also the pricier.
For customer reviews and prices, you may take a look at the Amazon.com Occupancy Lighting Sensors.
Wireless Occupancy Sensors
Besides the traditional hard-wired occupancy sensors, there are now wireless occupancy sensors (communicating via radio frequency). They do not require any wiring, and are easy to install.
Today’s sensors are very reliable. Just choose the right sensor and install it in the right location. In smaller spaces, the sensors are mostly installed on the walls; in larger areas they are installed on ceilings or high up on walls.
Types of Occupancy Sensors
When choosing an occupancy sensor, pay special attention to its type – passive infrared, ultrasonic and dual technology- and to where they are best suited.
Passive Infrared Sensors work best in small-enclosed spaces. For larger spaces consicer ultrasonic sensors - using high-frequency sound to detect motion; they work better in large spaces with obstructions; anyway, avoid using them in spaces subject to vibration, to prevent false triggering.
Dual technology sensors (Ultrasonic-Passive Infrared combined sensors) are the most reliable occupancy sensors in the market, for large rooms. They combine the Passive Infrared and the Ultrasonic technologies and are less prone to false triggering. They are pricier than simple passive infrared and ultrasonic sensors.