Guest Post: “How Does It Work: Motion Detectors” by Lukas Nicholson

Photo by OSU Valley Library.

I’m sure we’ve all experienced walking up to a business or home and had several lights turn on and illuminate the pathway. It’s very likely that those lights were turned on by motion sensors, meaning that your mere presence triggered the lights to turn on. We know they exist, right? But how do they work? This article explores the different types of motion sensors and how they work.

Radar-Based Motion Detector

These are the type of sensors that are placed above front doors of businesses. The device that sits above the door transmits ultrasonic sound waves (or microwave radio energy­). When no one is near, the energy is bounced back to the box in a consistent pattern. If someone walks up to the door, the energy that is reflected back is disturbed and triggers—in this case—the door to open. Now if they can just figure out a way to keep the flies out without a gust of wind to your face, we’d be in great shape.

Photo Sensor Motion Detectors

These types of detectors only need a couple components to make them work: a laser beam (or any source of direct light) and a light sensor. These two things are usually placed across an entryway. The beam is aimed directly at the light sensor, creating a constant source of light. When someone enters the door, garage door, window, or any other entryway, the beam of light is obstructed. This quick delay in continuous light triggers an alarm; this is usually a chime when used in businesses. However, this type is also very popular in most home alarm systems. In this case, they are programmed to not make a sound immediately, giving the homeowner enough time to type in the security code.

Photo by paxtonlocksmithing.com.

Passive Infrared (PIR) Motion Detectors

This type is what most people think of when talking about motion detection; they are often used in the set of lights I mentioned earlier. The sensors on these devices are designed to recognize infrared energy emitted by body heat. Because there are always changes in energy (usually caused by temperature changes), the sensors only trigger lights and alarms when a rapid change in infrared energy is detected in the field of view.

PIR detectors are also often used in surveillance equipment. When high levels of energy are detected, the device triggers the surveillance cameras to begin recording. This makes it easier when playing back video and it also decreases energy consumption since it is not recording video continuously.

As you can see, there are several different types of motion detectors that are available.  When combined, these motion detectors can provide comprehensive home security. On their own, they provide business owners a simple way to detect customers and provide homeowners with light to guide them through their doors.

Author Bio: Lukas Nicholson is a home security specialist and reviewer. He works hard to provide a security systems review and inform others about what they can do to better protect themselves, their family, and their homes.