What is an Occupancy Sensor?

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  • Written By: Malcolm Tatum
  • Edited By: Bronwyn Harris
  • Last Modified Date: 02 April 2020
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Occupancy sensors are simple devices that are found in many lighting systems. The sensor is capable of identifying when a particular space within a building is occupied, and adjusts the lighting, heating and cooling, and other appliances accordingly. In recent years, the installation of an occupancy sensor has become an important part of creating an environmentally responsible control system within a home or public building.

There are two common forms of use associated with an occupancy sensor. One is a means of lowering utility costs. When no one is currently occupying a given area of the building, the sensors note this and will turn off unnecessary lights as well as adjust temperature controls slightly. This helps to minimize the use of electricity during those periods when the space is not in active use. As someone enters the space, the occupancy motion sensor recognizes the movement and automatically brings up the lights and adjusts the climate control equipment, allowing the individual to be comfortable while in the room.


However, an occupancy sensor can also be used as a security measure. With this application, occupancy motion sensors are located in every area of the building. At any given time, it is possible to consult the security system and determine where there is movement or activity taking place. With some monitoring systems, the occupancy sensor is configured to trigger surveillance cameras to display images of the area, making it possible for security personnel to view whomever has entered a given chamber or space.

While many people think of an occupancy sensor as controlling lights along with heating and cooling equipment, sensors of this type can do a lot more. For example, occupant sensors can be used to open and close doors as someone enters or leaves an area. In like manner, the sensors can power up equipment when anyone enters the space, then power down that same equipment when the space is unoccupied.

The simplest type of occupancy sensor focuses on shutting down lights and equipment when no one is in the room. With these sensors, it is necessary for someone to manually turn on lights and equipment upon entering the space. However, once the space is vacated for a fixed amount of time, the occupancy sensor triggers a shutdown of the lights and any other equipment that is routed through the sensor. Sensors of this type are relatively inexpensive and can be added to an existing residential power system with little effort.


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Post 6

How do automatic doors work? The article mentions occupancy sensors can make doors open, but I always thought they were controlled by extra weight from a person being put on the space in front of the door. Maybe both of these systems exist. Does anyone know?

Post 5

I remember watching a news story or reading a magazine or something several years ago about Bill Gates building a new house. In it, every person had a special card they carried with them that was programmed to their temperature and lighting preferences. Whenever they walked into a room, there were occupancy sensors that would recognize the card and customize the room to that person's settings. It sounded really neat. That was a while ago, so maybe those types of things are getting closer to a reality in normal homes.

I know a lot of people now have installed lighting control units so that they can adjust settings through the house using a special remote or even a cell


Does anyone have any idea how much it would cost to have motion light sensors installed in your house? How much energy does it usually end up saving in a year? What kind of companies do this kind of work?

Post 4

I knew occupancy sensors were common in schools and offices, but I didn't realize they were becoming more common in homes.

I seems like it would be a very wise decision to have them installed if you were building a new house, especially since the article mentions them not being that expensive. For a house, the best kind would probably be the last example where you manually turn on the lights, but they turn themselves off.

I don't think I would want the lights coming on every single time I walked through a room. It would be really bad if the lights came on every time you moved while you were sleeping!

Post 3

I know that when I was still in high school, our hallways had occupancy sensors. Once you think about it, it makes sense because there are rarely people walking through the halls in between classes, so there is no need to have the lights on all of the time. I would be curious to know how much this saved the school every year.

I have noticed occupancy light sensors in certain office buildings, as well. I think it would be a beneficial system any time you have a scenario where people might be in the building at all time of the day, but there would still be long periods where people are not in certain areas.

I have

been in situations where a room has occupancy sensors, but the people in the room are not moving enough for the sensor to register they are there, so the lights would shut off when they were really needed. This doesn't happen very often, though.
Post 1

provide the associated circuit diagrams with the theory.

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