How Motion Detectors work

07-03-2020

We all love the idea that when you walk into a room the lights automatically turn on. Or when you wave your hand by the paper towel dispenser and it automatically spits out a paper towel. These things are made possible by motion sensors or detectors. The same technology is used to trigger an alarm when a burglar gets into your home. How do these almost magical devices work?

There are two general types of motion detectors. Some use ultrasonic technology and others use IR technology. Ultrasonic detectors, also known as active sensors, send out ultrasonic waves that are bounced back to the detector, much like radar or prenatal ultrasound, and very similar to how bats navigate through the dark. The term ultrasonic refers to the use of ultra-high-frequency sound waves, which are outside of the hearing range of most people and animals. The device constantly sends out ultrasonic waves and constantly listens for the reflected waves that bounce back. In an empty room, this will stay constant. When something or someone moves in the room, the reflected waves will change and the device will recognize this and spit out a paper towel or trigger an alarm, or whatever it is designed to do.

IR technology, also known as passive technology uses Infrared light, which is normally not visible to humans, though some animals can see it. If you have ever watched a ghost hunting TV show, you may have seen them using FLIR cameras that detect infrared light, that apparently some ghosts emit. IR light is constantly being emitted by humans and most other warm-blooded animals it is produced by heat. Basically, an IR detector is looking for heat signatures. In an empty room, most things will be at a constant temperature and will not be putting off much heat, but when a human walks by, suddenly there will be a big warm mass that is easily detected by the sensor. These are the most common kind of motion detectors found in home security systems.

Some of the more sophisticated security systems will combine IR technology with a security camera and an alarm trigger so that when motion is detected, the camera turns on and records whatever is happening. An alarm may also be triggered that emits a loud obnoxious sound or turn on bright lights that will hopefully scare off any burglars. Many of these systems will also send out a text or email message to the homeowner and/or an alarm monitoring company notifying them of the situation. This will allow you or your alarm company to determine if it’s really a burglar or if it’s just your cat chasing a moth around your living room.  If it’s a burglar the police can be immediately notified and hopefully, the culprit can be arrested.

Even more sophisticated systems will allow you to watch the video on your cell phone and even talk directly to the burglar (or your teenager who is supposed to be at school) tell them that you are calling the police and you have their pictures and video so they better leave immediately without stealing anything.

If you’re wondering how you can get such a cool high-tech home security system installed in your home, just click here to get a free quote and let Affordable Home Security take it from there.