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How Do Motion Detectors Work?

Jun 07, 2022|

Motion detectors are a central part of any home security system. They let you know when potential intruders are near your property or inside your home.

Having motion detectors in your home can go a long way in bringing you and your family peace of mind, but how do they work to keep you safe?

This guide tells you all about how motion detectors work and explores the most common types of motion sensing detectors. We’ll let you know what to consider when choosing the right detectors for your home and provide tips on where to place your sensors for maximum effectiveness.

Young girl playing with her dog near a motion detector.

Which sensor is used for motion detection?

There are different types of technologies to choose from when it comes to motion detection. The most common types of motion sensors use either ultrasonic or passive infrared (PIR) technology.

We’ll tell you about both types of sensor technology and explain how they operate in the next few sections. We’ll also go over a few less common technologies used in motion detectors.

How active ultrasonic sensors work

Active ultrasonic sensors shoot ultrasonic sound waves at objects around your home to detect active motion. The sensor uses waves that bounce back to measure the distance of an object.

You don’t have to worry about these sound waves being too loud. Ultrasonic waves are too high to be heard by the human ear.

Here’s how the process works:

  1. A transducer inside the sensor sends out an ultrasonic sound wave.
  2. The wave then reverberates back to the transducer. When this happens, the transducer measures how long it took for the wave to get back.
  3. The sensor uses this measurement to judge how far away an object is. When the distance between the transducer and an object changes, the sensor knows there’s a moving object.

When the ultrasonic sensor notices motion in a specific area, it may send you notifications or set off a motion sensor alarm. It’s best to use active ultrasonic motion sensors indoors around entry points to your home, like doors and windows.

These types of active sensors aren’t great for outdoor security. Things like small animals and insects can set them off. Be aware that furniture and other obstructions can affect an ultrasonic sensor’s ability to gauge motion.

How passive infrared (PIR) sensors work

Passive infrared sensors (or PIR motion sensors) measure the heat (or infrared radiation) given off by humans, animals, and objects to detect motion in an area. When they detect a change in the temperature of an environment, they can deduce that someone or something is moving.

PIR sensors are usually used indoors, but they can sometimes be used in devices that monitor the outside of your home. For example, some security cameras are equipped with PIR sensors. The camera starts recording whenever the PIR sensor detects a rise in infrared energy.

Because PIR sensors measure changes in temperature instead of distance, they’re less likely than ultrasonic sensors to be impeded by objects in a room (like home furniture or walls).

Other sensor types

Here are a few other types of sensors that can be used to power motion detectors.

  • Microwave sensors gauge distance by shooting out microwave pulses and measuring how long the pulses take to reflect back. They cover a bigger area than PIR sensors but are pricier and can experience electrical issues.
  • Dual-technology sensors unite different motion-detecting systems. For example, a sensor might use both PIR and active ultrasonic tech to sense intruders. Both sensor types must be activated for an alarm to sound. Using two different methods for motion detection helps lower instances of false security alarms.
  • Vibration sensors read vibrations caused by people moving throughout a room.
  • Area reflective sensors send out light-emitting diode (LED) rays to detect motion.

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Where should you mount motion detector sensors?

Sensor placement is crucial if you want your motion detectors to work their best. Your sensors need to be in the right location to have the best chance of sensing disturbances in your home. You should also place sensors in areas where they’re less likely to produce false alarms.

Sensors typically come with instructions for proper placement. Here are some general tips that can help you determine the best places to put your sensors.

  • The best places to put motion sensors are at choke points in your home. Choke points are places that people must walk through in your home. Some examples of choke points include central hallways and entrances to stairwells.
  • Place PIR sensors about 10 to 15 feet away from areas and appliances that produce heat. The heat caused by stoves, heating vents, and windows can confuse PIR sensors and cause false alarms.
  • Place sensors in areas where you have valuable belongings. The master bedroom is a common room that burglars target. Make sure yours is protected by installing security sensors.
  • Take some time to examine your home. Identify rooms that are particularly vulnerable to intruders and place security sensors in these areas. For example, many thieves will attempt to enter your home through the garage door.
  • Security sensors work better when thieves walk beside them. Try placing sensors in your hallways to make sure criminals walk parallel to them rather than directly toward them.

With your family’s safety on the line, it’s advisable to employ a trained professional who will ensure your motion-sensing devices are installed properly and efficiently. If you purchase a Vivint motion detector, one of our certified Smart Home Pros will assess your home, determine the most effective placement for each of your sensors, and provide custom installation to make sure the job is done right. You won’t have to worry about sensor placement, and you won’t have to lift a finger.

How far can motion detectors sense movement?

The distance that motion detectors can cover depends on the type, quality, and placement of the sensor. On average, however, motion sensors have a detection range of around 50 to 80 feet.

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How to choose the best motion detector

There are a lot of different factors to take into account when deciding which motion sensors to buy for your home. Here are a few questions to help you make a smart decision.

  • Do you want wireless or wired sensors? Wired sensors need to be tied into your home’s electrical system, which may not be an option if you rent your place. Wireless motion sensors are less intrusive, easier to DIY install, and can work in conjunction with the rest of your security system using Wi-Fi internet.
  • Do you want to record footage of your home? For example, your indoor security camera might have built-in PIR sensors that activate the camera whenever they detect motion in your living room.
  • Do you have pets? Some sensors are pet immune. For example, the sensors offered by Vivint have functionality that lets them recognize your pets, so you don’t get a false alarm every time your cat runs across your living room.
  • Do your sensors have connectivity with the rest of the devices in your security alarm system? You’ll likely want to choose sensors that can integrate with other smart appliances in your home.

Vivint motion sensor.

How motion detectors work together with home security systems

With a smart security system, all the devices can communicate. Having motion detectors that integrate with your larger security system gives you the ability to control your entire system using a central panel or smartphone.

Having an integrated smart security system lets you do things like schedule your sensors to work at specific times, like when you go to work or after you go to bed.

You can also program your sensors to work with other programs in your home. For example, you can program Vivint’s smart LED light bulbs to turn off whenever your sensors are activated at night.

Vivint offers smart motion sensors and other smart security equipment for a seamless security experience that you can control from anywhere using a mobile app.

Discover Vivint motion sensors with smart integration

If you’re looking for security sensors that will work smoothly with the rest of your home automation devices, explore the motion sensors offered by Vivint. Our motion detectors are reliable, pet friendly, have a large field of view, and have a battery life of up to five years.

We’ll also put you in touch with an expert who can determine the perfect spots in your home to place your sensors.

A Vivint professional can help you find all the smart security devices you need to design your ideal smart home setup. Vivint devices even have integrations with smart assistant software like Google Home and Amazon Alexa.

Call us today at 855.822.1220 to see how a smart home setup from Vivint can make your home more efficient, valuable, and comfortable.

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