Understanding how Motion Sensors Work




When you’re looking to increase your home protection, the first step is to purchase reliable equipment that helps you achieve your home security goals.


The next step is crucial to your success - you have to understand how your home security equipment works in order to get the best results out of it. While motion detectors are one of the most common home security purchases, they can also be one of the least understood. Let’s take a closer look at the motion sensor.



A motion detector consists of two parts. The first part is the sensor (also called a transmitter or detector) that is placed either indoors or outdoors and is what “sees” or “captures” motion. The second part is the receiver, sometimes referred to as a chime. The receiver is installed inside and lights up, plays a melody, or both when it receives a signal from your sensor.

For this article, I want to explain how the sensor works since it is often misunderstood, and therefore, not used to it’s full potential.


The Sensor

Almost all motion detectors use passive infrared, or PIR, sensors. PIR sensors are great as motion detectors because they do a great job of picking up human activity while filtering out movement of inanimate objects, they offer a wide field of view, and they are affordable.


So how do they work?  PIR sensors “see” the infrared wavelength.  Basically, objects that are the same temperature give off the same infrared wavelength.  This means that when your sensor is pointed out and no one is passing in front of it, it sees one infrared background.  Nothing is changing in that background, so the sensor will not activate.  Likewise, if a leaf blows past or a branch sways, it will not set off the sensor since it is giving off the same infrared wavelength as the surrounding objects.

However, when a person, or some other warm object passes in front of the sensor, the PIR sensor notices that there is an increase in temperature, followed by a decrease as the person moves past. This triggers the sensor to send out a signal to your receiver which then plays a melody to alert you to this activity.


The second great feature of PIR sensors that is frequently misunderstood is their field of view. Unlike garage door sensors, which are just a single laser beam, PIR sensors have a wide and tall field of view that enables them to keep watch over a large area.  By adjusting the placement and angle of your sensor, you can fully customize the area that you want to cover.


Finally, because PIR sensors are the predominant choice in motion sensor technology, they have become very affordable, allowing you to easily add on additional sensors to increase coverage around your home or business while still staying on or under budget.


To shop our wireless motion detectors, just click here.


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