What are Motion Sensor Lights?

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  • Written By: Britt Archer
  • Edited By: Bronwyn Harris
  • Last Modified Date: 12 October 2019
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When designing a security system or finding new ways to cut energy consumption, many individuals choose to add motion sensor lighting to their setup. Motion sensor lights are not only a cost-effective, easy way to alert the occupants of the house to a potential intruder, but also a way to turn off lights in rooms that are unoccupied. In security applications, motion sensor outdoor lights of the past may have turned on for every leaf, rabbit or neighborhood cat, causing undue stress to homeowners, but as technology progresses, motion sensor lights are becoming both increasingly sensitive and easier to customize. Motion sensors are comprised of fairly basic components, which sense a change in surroundings, and then activate a light accordingly.

The motion light sensor is composed of a small lens that detects changes in heat, and sometimes movement, in a given area. When the motion sensor switch is activated by a very rapid change in heat or light conditions, the switch activates the lighting. Because motion sensor lights are built to detect rapid changes in heat or movement within a specified area, they deactivate when there is no change to conditions for a period of time. The automatic shut-off feature of motion sensor technology makes motion sensor lighting a practical way to conserve on energy costs when used in indoor, household applications.


Motion sensor lights operate with what is known as a passive infrared detector. The difference between passive detectors and active detectors is that active detectors add something to the surrounding environment, such as microwaves, sound waves or light waves, while passive detectors do not. A person's proximity to the motion sensor detection system also determines how effective it is. The farther away a person is from the system, the harder their infrared heat becomes to detect. This may present a problem to homeowners investing in lower-end makes and models, as basic motion sensor lighting is only sensitive to the relative temperature of the human body.

Motion sensor lights are available from a variety of sources, including home improvement stores, department stores and specialty security stores. Prices range from about $10 US Dollars (USD) to $100 USD or more. Models are available for purchase that utilize LED lighting, as well as more traditional incandescent lighting. There is a wide range of styles to choose from, including decorative and utilitarian models, as well as kits to convert already existing lighting into motion sensor lighting.


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Post 9

What type of sensor doesn't react to rain, snow and moving branches?

Post 8

I want a sensor switch which is activated by my automobile's headlight, i.e., incandescent bulb light impinging on the sensor enclosed by a tube blackened inside to prevent the seepage of ambient light.

If such a sensor is possible, it will help me register the presence of vehicle (the distance of the vehicle from the sensor to actuate the switch being (a) 200mm max. and (2) 2.30 metres minimum) through electrical circuitry.

In nutshell, I am looking for a sensor switch to actuate i.e. change contact, when the auto headlights are switched on.

Post 7

@whiteplane – That sounds like an excellent plan! I wonder why more businesses don't have systems like this?

I would think that any large building could benefit from motion sensor lighting. There is one discount store that sells overstocked merchandise in my town that is huge, and they recently switched to lower wattage lighting.

This makes it harder to see details of items, though, and I think a much better plan would be to use motion sensor lighting. That way, even the low lights wouldn't run all the time, and people would be able to see the products better when the lights did come on, because the store would be able to afford brighter lighting.

Post 6

I found motion sensor lights to be very creepy as a kid. I had already been traumatized by ghost stories and horror movies, so any time the outdoor light came on, I instantly felt a chill.

It was so sensitive that it would actually come on if the wind blew very hard. To me, the fact that no one was there was creepy, though I'm sure my parents were relieved. I thought it meant there were ghosts in my backyard.

The motion sensor light quit working for years. Then one day, it suddenly came on when I walked by. It instantly gave me flashbacks to my childhood, and I felt as if there must be a ghost nearby, until I realized it had come on because of me!

Post 5

I have both interior and exterior motion sensor lights. The lights on the outside are around the garage area, and really are helpful when it is dark outside.

The worst part about those is they come on every time the dog or cat run by, but the advantages are far better than the disadvantages.

I also have motion sensor lights installed along side the steps going down to my basement. As soon as you begin going down those steps, the lights come on so you can see where you are going.

This is a nice feature to have anytime, but especially so if it is dark and your hands are full. I never have to worry about turning on a light before I go up or down these stairs.

Post 4

I was looking at different kinds of flood lights to install on a walkway to our front door.

I really liked the idea of solar powered motion sensor lights, but we don't have very many sunny days where we live.

I don't think they would be able to soak up enough sun during the day to really make much difference at night. I think they were more for a pleasing look than providing any real light.

Because of this, I ended up buying some motion sensor flood lights. This way they come on as soon as someone walks by, and really do a good job of lighting up the pathway.

Post 3

We have an outside motion sensor light installed right above our side garage door. There are many times when this has been a life saver.

We live in the country and don't have any street lights or overhead lights to give us illumination at night.

If I need to unlock the side door at night, the motion sensor light automatically senses the motion and comes on.

It is so much easier to find the right key and insert it into the lock when you can see. If the light needs to be replaced and doesn't come on, I find myself fumbling around in the dark to get the key in the lock.

Post 2

My apartment building has outdoor motion sensor lights in the backyard. Its annoying because I go outside to smoke and every time I open the door about 4 bright spotlights come on and I feel like a police raid is about to happen. Sometimes I wish I could just step out back and enjoy the night but it has to turn into a three ring circus.

But I can understand why they have them there. I do not live in the best neighborhood and break ins have been a problem in the past. I guess I would rather smoke in a spotlight than worry about whether or not I'm safe.

Post 1

I work in a library and we have motion sensor lights everywhere. This is to cut down on energy costs and to help preserve the books.

Libraries tend to have lots of floor space in them and require lots of bright light for reading and browsing. But if there is no one on a give floor or in a given aisle than that light is just wasted and it fades the books. So all of our lights are dim until someone steps into an aisle. Then they rise to full strength as long as someone remains in the aisle.

After we installed this system our energy costs dropped by over %40. Its a great idea for any business or even your home. Why light up a space where no one needs any light?

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