Motion Sensor Guide

Motion Sensor Guide

Burglars Beware, my Infrared Sights are Set on You

Heat wave infrared sensors, or more commonly known 'Motion Sensors' catch anything 35 lbs and up (typically).  There are motion lights that can come on when you get close to the front pouch or when criminal approaches providing you with ample lighting to get in while serving as a deterrent to criminals.  There are also motion detectors that take pictures of anything within a certain range when it is triggered (like the Canary or Piper product).

ten different motion sensors displayed

They come in all shapes, sizes and colors. 

What Exactly is a Motion Sensor?

Motion sensors are gadgets that utilize different technologies to detect when a person or thing has entered into its area of reach. Put differently, a motion detector is a gadget that detects motion. A motion detector can be combined with other gadgets and appliance to further enhance its function for example, motion activated lighting that comes on when someone is detected around its perimeter thereby reducing power consumption etc. Another very common use is in home security systems, a motion detector triggers an alarm when it detects motion in its perimeter. Other uses for motion sensor abounds and more are being introduced.

Most security systems such as ADT, Vivint or Protect America all come with 1 to 2 motion detectors per package.  Most are now wireless and will sound a beeping noise before the battery dies in years to come.  If it is wired, it is most likely a 2-in-1 security camera + motion sensor.  These are part of the standard security system package along with a control panel (usually a 2gig or Honeywell), window and door sensors and security stickers.

How Does Motion Sensor Work?

Utilizing varied technologies, a motion sensor working within a particular range of distance would trigger its function when it detects motion within its perimeter.  Once it detects a large heat wave (typically 30-45 lbs) it will trigger the alarm system and sound the siren off.  If being monitored by a company you will be notified and the dispatch called.

heat wave on body shown via infared

This is how a motion sensor sees humans - as bursts of heat waves.

This brings up a common issue with motion detectors which is, dogs.  If you have a pet over 30 lbs that stays in the home while you are gone (or want the alarm system set) you are better off with glass break sensors and not motion detectors.  Otherwise this will result in a lot of false alarms throughout the day.

Types of Motion Sensors

The technology by which a motion sensor works differs from one to another, this is because the various methods are available to serve as a trigger for a motion detector.

These technologies include:

PIR Motion detector (most common).  Image from Adafruit

  • PIR: otherwise known as the passive infrared technology, this technology is sensitive to change in temperatures, it detects a slight change in body temperature through emitted black body radiation at mid-infrared wavelengths (source), it finds use in motion activated light bulb and security systems. When a moving object sets off multiple zones in an activated motion sensor area, the trigger is set off and it carries out its function of turning on the light or setting off an alarm.

occupy sensor

  • Microwave Occupy Sensor: Microwave technology is an active technology compared with passive infrared technology discussed above. This sensor is regarded as active sensors because it emits and utilizes energy. The microwave active sensor continually emits microwave and gets triggered when a body reflects the wave back to it. The microwave technology finds use in automatic doors.  Not common with home alarm system providers.  Users would have to go out of their way to use one of these.

A Dual tech occupy sensor shown by

  • Dual technology: A new technology in modern motion sensor, the dual technology makes use of both the passive infrared and the active microwave technologies. It works best when both systems are activated reducing false triggering but at the expense of greater vulnerability.


Other technologies in use include:

  • Ultrasonic
  • Tomographic sensors
  • Vibration
  • Gesture sensors
  • Security camera integration + smartphone software (shown below courtesy of

Features to Consider When Purchasing a Motion Sensor

The following features should be considered when purchasing a motion sensor:

  1. Motion detection area determined by angle and range. Outdoor motion detector has longer range than indoor motion detector whose range is limited by walls.
  2. Indoor motion detector lighting functions either by occupancy or vacancy or both. This means in occupancy, the light comes on when a person enters a room, the individual is expected to turn the light off when living the room, in vacancy functionality, the light goes off when it detects that the room is empty, this means the individual is supposed to turn on the switch. Newer models of motion sensor lighting's utilize both functionalities. This means that the lighting comes on when a person enters the room and goes off if it deters that the person has left after some time. Be sure of what you need and are getting.
  3.  Ease of installation.  Will you be doing it yourself or have a professional company come and put them into corners of wall?
  4. Mounting positions: Motion sensor can be installed on the wall, ceiling etc. some manufacturer offer either one or both positions.  Living room and hallways are most common so they cover a lot of ground.  Motion sensors have a 20-40' range and detect heat waves of 30 pounds or more.  *Notice, each motion sensor can vary on these statistics based on manufacturer.
  5. Sensor technology: Understanding the technology a particular sensor utilizes would help in deciding of it works well for you.


Wrap up of this Motion Detector Guide

While a motion sensor finds use in a different scenario like security, lighting, doors etc. it’s important to understand how it works in order to get a system that suits your specific needs. Looking to use a motion sensor or intending to purchase a unit? Let us know your thoughts in the comment section.

[Total: 1    Average: 2/5]
3 User Reviews
  1. Lora
    08/16/2018 at 16:54

    The motion sensors available today are really awesome and some of them pack the best features and are super effective. I've been utilizing motion sensors at home so I would vouch that they really are worth the purchase. I think installation is fairly easy if you just follow the instructions!

  2. Carl
    05/22/2017 at 16:49

    Motion censors are fantastic and a lot better than they were in the 90's! I owned my first home in the 90's and then lost my job. I had to relocate back closer to family and rebuild my life again. Several years later I am a home owner again and I am blown away by the technology advancements that have been made!

    • Vickie Holmes
      05/30/2017 at 15:55

      Oh I had a few motion to light sensors in the 80's want to talk about an upgrade! I recently bought some and had no idea what I was in for. I wish I seen this guide first. I got some that are VERY powerful and I didn't have to pay this much haha My son is going to buy them off of me and use them at his cabin.

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