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How Occupancy Sensors Work - Motion Detection Lighting

If you want to know how occupancy sensors work, you've come to the right place.  We've been using motion detection lighting and it seems to work well to save energy and provide a little security.  If you want to only have the lights on when they need to be turned on, you may want  consider installing occupancy sensors.  Occupancy sensors allow the lights to turn on when someone enters the room and turns the lights off after it senses no one is left in the room.

Occupancy sensors are used for motion-activated lighting control. The two ways they do this, that I am familiar with, is through the use of passive infrared (PIR) or Ultrasonic Technology (US), or a combination of the two. Regardless of which one you use, the field of view for the sensor must be selected and adjusted so that it responds only to motion in the space served by the controlled lighting.

Ultrasonic  works a certain area by sending out ultrasonic soundwaves.  The outbound US sound waves first emit throughout the room / area then reflect back off of objects after "striking" them.  The US is able to measure these frequencies.  When it senses a change between the emission (going out) of the wave's frequency and when it reflects (return) it turns the lights on.

Passive Infrared technology is different.  It can tell if someone (or something) is in the room based on heat.  PIR  basically looks at the heat being generated in various spaces throughout an area.  The various spaces are not random. PIR basically subdivides the area using special lens.  When the emission of heat differs from one space to the next, it can be presumed that someone is walking through that area. This would turn on the lights.

Combinations of both technologies can be used to exploit the benefits of both.  PIR is great for 'big' movement such as running down a hall, whereas US is better suited for subtle movement (such as things you'd do while sitting at a desk).  PIR reliability is reduced if there is something blocking the space. US is not affected by obstructions (thought I admit, I'm not sure why).

That is a simple overview and, honestly, the total extent of my knowledge on this subject. I found it interesting and hope you do to. Feel free to comment.

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1 comment:

  1. Occupancy sensors are sensing devices that are normally connected to the lighting of a room. In many homes, occupancy sensors are also connected to heating or ventilation. When the space is unoccupied, these sensors shut down the heating or ventilation or lighting services of the room.