How Do Motion Sensors Work?Updated August 18, 2022 Home Security
One of the key components in a comprehensive home security system is the set of motion sensors included in your hardware setup. With motion sensors, your home security system can detect movement whenever the system is armed, potentially triggering the alarm and alerting you to a home invasion. Motion sensor technology continues to evolve, and there are several different types of motion sensors that may be included within your system setup. We’ll walk you through each of them so that you fully understand the potential of each type of sensor.
What Are the Different Types of Motion Sensors?
- Passive Infrared (PIR) Motion Sensor
- Microwave Motion Sensor
- Dual-Technology Motion Sensor
- Contact Sensor
- Area Reflective Sensor
- Ultrasonic Motion Sensor
- Tomographic Motion Sensor
- Vibration Motion Sensor
- Camera Motion Sensor
The motion sensors included within your home security system hardware are imperative for your system to work as intended to protect your home and family. When a motion sensor detects movement within your home while the system is armed, it will trigger the alarm and immediately send a signal to you and/or your monitoring center. This makes motion sensors an essential component of your overall home security system. Without them, it would be nearly impossible to know if an intruder were in your home. When a good motion detector system is paired with constant professional home security monitoring, you can rest assured that any attempt at entering your home without permission will be detected and stopped quickly.
Motion Sensors for Home Security
Motion sensors are a key element of the best home security systems and may use a variety of technologies to detect movement within your home and alert you and your monitoring service to a potential threat. Their sole purpose is to register when there is movement within a specific area – such as doors and windows within your home – and to trigger lights, an alarm, or another signal when they do so.
In addition to alerting you of serious threats, motion sensors can be useful in so many other ways – such as turning off lights when there is no motion (like in a hallway). In addition to alerts for package deliveries, you can be notified when your teenager is sneaking in after curfew, or if your pets have wandered into forbidden areas of your home while you are away.
There are several factors to consider when choosing the right type of motion sensors for your home security system.
Consider the components of your existing system. If your home security system came with all necessary sensors as part of your hardware package, then you don’t need to worry about a thing – all of your system elements will be designed to work together. But if you’re purchasing motion sensors separately, be sure to check whether the type of sensor you’re choosing is compatible with your other security system components like smart locks, doorbell cameras, and other smart home elements.
If you’re a pet owner, you may have to adjust the appropriate sensitivity level for your sensors. When the sensors are too sensitive, they may inadvertently pick up the movement of pets within your home and trigger a false alarm. If you have several smart home elements in place, choose motion sensors that can successfully integrate with those elements and the platform you’re using.
You should also make sure that the motion sensors you select are easy to use and controllable via a mobile app. That way you can program your sensors to send alerts to your smartphone or email, no matter where you are in the world.
When shopping for motion sensors, research customer reviews and talk with people who use motion sensors in their homes. You want to get a good value for your money – which means not only getting a reasonable price but a solid, reliable product and good customer service.
Active vs Passive Motion Sensors
Motion sensors come in two basic types: active and passive. A motion detector that is considered passive, like a PIR motion sensor, does not emit any kind of pulse or energy. Instead, passive sensors monitor the area looking for changes in heat and vibrations. In contrast, an active sensor constantly emits light or energy, looking for changes in how the reflection of light travels back to the sensor.
What Are the Different Types of Motion Sensors?
Depending on your specific home security system, several types of motion sensors may be used. Let’s take a closer look now at some of the different types of motion sensors that may be included in your home security system. Each has strengths and weaknesses and is powered by a distinct type of technology, so it’s important to understand their potential and how each can help protect your home.
Passive Infrared (PIR) Motion Sensor
Passive infrared motion sensors are the most common version seen in home security systems. These sensors register infrared energy associated with body heat and detect the resulting change in temperature in the area surrounding the sensor. This type of sensor can detect both heat and movement in its surrounding area, creating a protective “grid.” If the sensor picks up rapidly changing infrared energy levels, it will trigger an alarm. If you have pets in your home, PIR motion sensors can be calibrated to ignore pets up to a certain size.
Since this type of sensor is so sensitive to changes in temperature, it is best used for indoor spaces that are climate controlled.
Microwave Motion Sensor
Microwave motion sensors emit microwave pulses that measure reflections of moving objects. The sensor emits waves that strike nearby objects and then reflect back to the sensor. You may also see these sensors referred to as active motion sensors or radar-based motion sensors.
When an object moves within a microwave motion sensor-controlled area, the sensor detects any frequency shift in the wave when it returns to the sensor. This change in frequency indicates that the wave has made contact with a moving object, and the sensor sends an electrical signal to the alarm system, light, or any other device that is connected to the motion sensor.
While microwave motion sensors can cover a larger area of your home than infrared sensors, they do have some limitations. First, they are generally more expensive than PIR sensors, and they are also more vulnerable to electrical interference. Microwave motion sensors aren’t recommended for outdoor use since the movement of random objects like windblown items, small animals, and even large insects can trigger a false alarm.
Dual-Technology Motion Sensor
To provide redundancy and decrease the chances of false alarms, some systems combine PIR technology with microwave motion sensors. This allows each sensor to operate simultaneously within a different portion of the electromagnetic spectrum and combines both active and passive monitoring.
You may also see these types of motion sensors referred to as hybrid motion sensors or combined motion sensors. With dual-technology motion sensors, an alarm system is less likely to generate a false alarm since both sensors must detect motion in order to trigger the system. This can be especially helpful in households with large pets that may inadvertently trigger an alarm.
A contact sensor uses a magnet to detect the movement of a door or window. When the sensor and its corresponding magnet move apart as a door or window opens, the sensor triggers an alarm as long as the security system is armed.
Area Reflective Sensor
Much like PIR motion sensors, area reflective sensors use infrared light to detect motion. But while PIR detectors are passively collecting infrared light readings, area reflective sensors are active, much like microwave or ultrasonic detectors. These active sensors constantly emit pulses of infrared light from a light-emitting diode and then use the reflection from these rays to measure the distance to a person or object. This type of sensor can detect motion when a person or object moves within a predetermined area.
Ultrasonic Motion Sensor
An ultrasonic motion sensor sends out high-frequency sound waves that are then reflected back to the motion detector. If the sensor picks up any interruption in the sound waves, the active ultrasonic sensor will trigger the alarm system. It’s similar to the technology used in a microwave motion sensor. The only difference is that an ultrasonic motion sensor constantly emits ultrasonic waves instead of microwave energy.
Tomographic Motion Sensor
Tomographic motion sensors are fairly new to home security technology. Instead of relying on a single sensor, tomographic motion detectors employ several distinct nodes placed throughout a given space. These nodes constantly communicate with one another. When a person or object enters the field between nodes, this communication link is disturbed and the system can detect movement.
Tomographic sensors can be completely hidden since they don’t depend on a clear line of sight as many other sensors do. Since they use radio waves, tomographic motion sensors can also detect motion through walls. Because of this, they can detect motion within large spaces and can be hidden behind walls or objects.
Vibration Motion Sensor
A vibration motion sensor can detect the minute vibrations people cause when they move through a room. If the sensor picks up a vibration, it will trigger the alarm system.
Camera Motion Sensor
Most security cameras use advanced signal processing to begin recording when they detect motion within the camera’s immediate area. Home security cameras with motion sensor capability can help save memory storage by only recording when activity is detected. This can prevent your storage device from filling up quickly with unimportant footage.
Most of the software included in home security cameras (and even cheap webcams) include motion detection, but this is considered a fairly unsophisticated type of motion detection that simply compares changes in light and shadow from frame to frame.
Tips for Installing Security Motion Sensors
Motion sensors are typically wireless, which makes them extremely easy to install. Once paired with your system, motion sensors can communicate with one another and your central monitoring unit via your home’s Wi-Fi.
If you’re installing your motion sensors yourself, there are a few key tips to keep in mind to make sure your sensors are keeping you as safe as possible.
First, always read the installation instructions that come with your motion sensors. They will often contain valuable information about how your particular sensors work and how to properly install them to maximize the coverage area that is monitored.
Next, make sure you’re placing your sensors – especially PIR sensors – away from heat sources. This can include radiators, sunny windows, heating vents, or any other source of significant heat within your home. Since PIR sensors detect quick changes in the temperature around the sensor, having a heat source too close can lead to false alarms triggered by your sensors.
Place your sensors at points an intruder would have to pass through in order to enter your home, regardless of the final destination. Think about points like entryways, stairwells, and windows that must be crossed to gain access to your home. In addition, think about the rooms in your home where an intruder is most likely to go.
Studies show that most thieves go straight to the master bedroom of a home, so make sure you have sensors leading to that area. If you have a study or other room with a safe, it’s a good idea to track motion there as well. Think about the path a burglar would take through your home – likely entering through a front door, back door, garage door, or patio door – and place sensors along that path.
Motion sensors work best when someone is moving in parallel to them, instead of toward them, so it’s also smart to place sensors along hallways that any intruder would have to use to access key areas of your home. Security motion sensors are vital when it comes to effectively detecting an intruder in your home. You’re wise to take the time to research the number of sensors you need and to make sure they are installed effectively.