Motion Sensors Guide

If your motion sensor knowledge comes purely from sci-fi novels and heist movies, you’ve come to the right place. We’re about to explain what motion sensors are, how they work, whether you need them, and how you can get them.

Ready? Let’s jump into this motion sensor guide.

These sensors sound like the stuff of fiction, but they’re not.  Detectors are commonly used for security purposes because they’re a great way to know if someone is somewhere they shouldn’t be. They work by sensing the movement of humans and sometimes animals. 

Broadly speaking, motion detectors are easier to use than cameras because you don’t have to monitor them to see if anything’s going wrong. However, you can combine a motion detector and a camera for the ultimate security experience.

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Home security motion sensors use different types of radiation and light emission to sense human and animal movement.

There are several different types of motion sensors floating around. Some types show up more in home security than others.

A passive infrared sensor (PIR sensor) is one of the most common types of motion detectors. This sensor detects body heat AKA infrared radiation.¹

View a passive infrared sensor from Arduino.

An active infrared sensor has two pieces. Infrared light emitted from one piece reflects onto the other. When the beam is interrupted, the alarm goes off.²

Infrared light is usually invisible, so active infrared sensors can slip by unnoticed.

View an active infrared sensor from Angshi.

Despite what it sounds like, microwave motion sensors aren’t motion detector–oven combos that can heat up your pizza rolls while detecting intruders. Instead, they use electromagnetic radiation to look for moving objects.³

One nice thing about microwave motion sensors? They can be calibrated to be more or less sensitive, which is especially useful if you have roaming pets.

Ultrasonic and tomographic sensors are similar to microwave sensors, but they use high-frequency sound waves and radio waves instead of electromagnetic waves.⁴

Dual sensors use two different technologies. For instance, this sensor from Napco uses both microwave and passive infrared detection.

Now that you know all about motion sensors, the next question is, do you need them?

Motion sensors aren't necessarily a requirement, but if you’re going back and forth on whether the expense is worth it, here are a few situations in which you probably do want sensors.

Most people who use motion sensors use them as part of a security system. They put them in highly trafficked locations or valuable-filled rooms. In those cases, the users usually only arm the motion detectors when they’re out of the house. 

Motion sensors can be found in baby monitor cameras as well. For example, the Lollipop baby monitor has "crossing detection" that will notify users of any movement in the room.

That sounds sinister, but it doesn’t have to be. You might get a motion sensor purely to keep your roommate out of your minifridge or your teen in their room at night.

You can also use a motion detector in a gun closet, a liquor cabinet, or the front room that your kid and your cat aren’t allowed in.

Some motion sensors can send you notifications without triggering an alarm. These kinds of sensors can be useful if you want to know where your kids or pets are while you’re gone or busy in another room.

In these cases, you generally want to put the sensors in most rooms to track movement throughout the house.

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You have two choices when it comes to obtaining motion sensors. You can buy some standalone sensors and jury-rig a piecemeal security system. Or you can buy a preassembled home security kit that includes at least one motion detector.

Most national security providers offer both standalones and kits.

You can usually buy your motion sensors online, but every now and again, you’ll run into a provider that requires you to call in to order.

In the past, motion sensors tended to have wires. Now they’re usually wireless—easy for anyone to install.

If you order a motion sensor from a company that does professional installation (ADT comes to mind), a technician will usually install it. Otherwise, it’s all you.

Installing a motion sensor generally goes something like the following:

1. Find a place to put the motion detector. Many providers recommend placing the detector in a corner, six to eight feet above floor level.
2. Follow the manufacturer’s instructions to fasten your motion detector in place. Many DIY motion sensors are peel-and-stick, so you don’t need any brackets or tools.
3. Follow the manufacturer’s instructions to activate the detector. This usually involves some kind of app.

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We love telling a smart assistant to arm home security devices. It’s easy to do as you run out the door or settle down for a good night’s rest.

You can get the convenience of a voice assistant for some, but not all, motion sensors. We’ve put together a list of compatibility for some of the most popular motion detector brands.

Motion sensors that work with Amazon Alexa*:

• SimpliSafe sensors
• Frontpoint sensors
• Link Interactive sensors
• Ring sensors
• ADT sensors
• ADT Self Setup sensors
• Google Nest sensors
• Cove sensors
• Scout sensors
• Abode sensors

Motion sensors that work with Google Assistant*:

• SimpliSafe sensors
• Frontpoint sensors
• Link Interactive sensors
• Abode sensors
• Ring sensors
• ADT sensors
• Self Setup sensors
• Google Nest sensors
• Cove sensors
• Scout sensors

Motion sensors that work with Apple HomeKit*:

• SimpliSafe sensors
• Abode sensors

Some motion sensors can also be linked directly to other smart equipment, like lights, locks, or plugs. These connections are usually made through Z-Wave or Zigbee protocols.

Now that you know the facts about motion sensors, buying one may have sparked your interest. Let’s quickly walk through the process you’ll need to follow to decide.

Determine whether you need a motion sensor: It makes more sense for some people to buy a motion sensor than others. If you need to keep an eye on certain parts of your house, or you have security concerns, a motion detector is probably a good fit.

Choose a sensor: You can select either a standalone sensor or a sensor associated with a home security system.

Install your sensor: Some sensors are professionally installed, while others are DIY. In today’s world, most DIY sensors are relatively easy to install.

Connect the sensor to your smart home: If you want a fully automated home, take advantage of your sensor compatibility to link it up to some other equipment.

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