What Is a Motion Sensor Alarm?

A motion sensor alarm is a device that uses an optical, microwave, or acoustic sensor to detect motion around your home or workspace. Its normal use, within physical security, is to detect intruders within a facility and trigger an alarm.

A complete motion sensor alarm system has a few main components. The first is a motion detector, which is the most outwardly evident part of it (that’s why the whole motion sensor alarm system is sometimes only known as a motion detector). This motion detector is generally composed of a component that emits either infrared radiations, microwave radiations, or ultrasonic waves, and a receiver that captures these waves/radiations.

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The third component of a motion sensor alarm is the electronic control panel. This is usually an integrated panel that controls multiple sensors, and interprets the signals from the motion sensors, and translates them into usable signals.

Finally, this is all managed from a mobile or a desktop app. The best modern systems are cloud-based, or at the very least integrated with some sort of online platform, which is the layer that you will interact with when looking at the data from your motion sensor alarm.

A complete motion alarm system can also be connected to a motion sensor camera. The camera sets off when the alarm is activated to send a visual message to the responder. The responder can consequently take the most appropriate action for each specific intrusion. Although motion sensors’ main purpose is to warn the business owner or admin of unwelcome “visitors”, such as burglars or thieves, they are also used for other situations where motion is the kickoff event, such as the automatic opening of doors, or the automatic turning on of lights.

Motion detectors either provide safety or create an easier lifestyle. Typical alternative applications of motion sensors are smart lighting, detection of poaching animals, and activation of door locks and automatic gates in residential and commercial premises. You can use your smartphone to implement affordable motion detectors that cover up to 15 feet of distance. Advanced and more expensive motion sensor models extend to larger surfaces and can keep you feel safe on large-scale properties and spacious business buildings.

How Does A Motion Sensor Alarm Work?

Motion sensor alarms work in different ways depending on the type of sensor. If the sensor is a microwave motion sensor or an ultrasonic motion sensor, the functioning is often pretty similar. It starts with the emission from the device, of microwave radiations or ultrasonic waves that hit the surfaces in the room and then bounce back into the receiver in the same device. By doing so, the machine can realize when there are interferences in the signal and trigger the alarm. This happens in case there is an object that interferes with these radiations/waves and this is normally when an intruder is present. This works similarly with the active infrared sensor alarms for which the only difference is the emission of infrared radiations instead of microwave/ultrasonic waves.

A different scenario is one of the passive infrared sensors (or PIR sensors) that, instead of emitting radiations, only capture the temperature radiations of a room and get triggered when there is an interference or anomaly in the radiations received by the device. If the receiver notices suspect movements, the alarm will be triggered.

Other options of motion sensors are tomographic motion sensors and gesture detectors. Ultrasonic motion detectors use both modes: active and passive. They use high-frequency sound waves that go back to the transmitter and remain uninterrupted unless there is an intrusion. This is when the alarm gets activated by buzzing a sound.

Gesture detectors use elements from infrared light technology and photodetectors to enable a digital screen to observe hand gestures by applying machine learning technology. They work with smartphones.

Why Is It Important to Have a Motion Sensor Alarm?

Motion sensor alarms are the principal guards of perimeter security, forming the outer layer of protection. Motion sensors can warn you to act before things get out of hand. For example, you’ll be able to call the police before there is greater property damage or, even worse, a bigger risk to yours, or to the lives of your loved ones.

Motion sensors are resourceful and easily installed. They can be placed at vulnerable points of your office or house and help you sleep safe and sound. Since they are small and not as detectable as video surveillance systems, intruders are less capable of locating and disabling them.

When a motion sensor is programmed to activate a motion sensor camera, the camera keeps a video record of the event. Activating lights to scare off intruders is the least a motion sensor alarm can do. While you are waiting for the police, the combination of light, a siren, and an irretrievable door lock can disempower impostors keeping them under lockdown.

What Are the Various Types of Motion Sensors?

A conventional way to categorize motion sensors is by using the receiving and emission detection mechanisms as criteria.

Passive motion sensor alarms are based on infrared technology and only observe movements by passive heat detection.

Active motion sensors are based on radar technology. They work by transmitting, as well as by receiving radio waves that boomerang when hitting a moving object.

Combined motion sensor alarms use several technologies, but are not applicable to all areas. Some work better outside than others, and vice versa. Many access control systems use a couple of them to provide better protection.

Here is how are motion sensors commonly categorized:

  • Passive infrared sensors (PIR). These motion sensor alarms sit with a bird’s eye view of the room and detect changes in the IR signature of a room over time.
  • Active infrared sensors. Also known as tripwires, these emit an IR beam from one side of the room to the other, that detects an intruder when it gets interrupted. Active infrared sensors, while still being used for security purposes, are especially used in robotics and for proximity detection.
  • Ultrasonic motion detectors. A different paradigm, these work by emitting ultrasonic sound waves to detect motion.
  • Tomographic motion detectors. One of the coolest innovations in motion sensor technology, these are comprised of a mesh of radio detectors around a room that detect changes in the ‘fabric’ of the mesh caused by people moving through them.
  • Gesture detectors. These are a subcategory of IR or camera motion sensor alarms that detect specific motions.

Hybrid motion sensors apply several technologies. Case in point, a motion sensor camera can be integrated into inside and outside access control systems, and the technology in use will depend on whether it is dark or light.

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Hardwired vs Wireless Motion Sensors

If you are in the process of purchasing a motion sensor for your business, you will surely face the choice of going for hardwired or wireless. Let's see what the main differences are for the two types of alarms.

Hardwired motion sensors require a higher upfront cost as it generally requires an installer to come to the facility. This is definitely something you should keep in consideration in terms of timeline and costs when planning your project.

These solutions are more indicated for business facilities rather than homes because the cables are often considered non very esthetically pleasing.

The great advantage of hardwired motion sensors and systems, more in general, is that there is a lower risk of interference and malfunctioning (even if wireless systems are also extremely efficient). Furthermore, the overall maintenance cost for this type of solution is also lower due to the lack of batteries. As a matter of fact, wireless detectors work with batteries and this means you will have to make sure that the batteries are charged and pay for their price.

Wireless motion sensors are the exact opposite when it comes to pros and cons. They are more esthetically pleasing and do not require any type of installation. Often they even work outside of the box with little to no setup required.

The downside is that the admin will have to make sure that the batteries are always charged and pay for them once they are not anymore.

Modern solutions of both hardwired and wireless types work extremely well and the deciding factor is often personal taste. If we have to choose one solution, especially for businesses, it would be hardwired cables as they are less prone to malfunctioning, maintenance is basically not required and it is easier to incorporate in a bigger security ecosystem (pair them to cameras or access control).

Motion Sensors Manufacturers

To help you navigate through the enormous motion sensors product offering, we have created a small overview of the most looked-for brands for motion detection.

Ring Motion Sensors

Ring is very widespread as a security solution for businesses and, mainly, privates. Their starting kits also incorporate motion detectors with a 90° angle range. Their motion detectors are a perfect addition if you are already using Ring products as they work seamlessly and out of the box.

Some concerns from the customers usually revolve around the quality of the materials used and the difficulties in getting the adhesive part to work on the first trial when setting the solution up.

Overall the solution works pretty great and we recommend it for very small offices or home and residential security. If you are working in a bigger office or even need to secure a warehouse, we would suggest looking into solutions that have a broader range of detection and are better-integrated overall security systems.

Lutron Motion Sensors

Lutron motion sensors are some of the most looked for motion sensors on the internet. However, their use is mostly relegated to create a smart home environment and not really focused on the security use case. For this reason, we will not indulge in further reviewing.

In general, finding a great motion sensor should not be an intimidating process. Most security companies offer their own motion sensors, just like Kisi does. The advantage is having a seamlessly-working security system with compatible products working together to reduce the number of false alarms and facilitate the admins' lives.

Motion Sensors and Access Control

Now that we've seen what motion sensors are and how they work, we can see what are their uses in the access control market.

Access control companies, like Kisi, integrate with motion sensors to grant an extra level of security to businesses. If a motion sensor is installed in a room, the signal that is triggered by a security breach will be sent to the access control panel and translated into an alert by the access control dashboard. By doing this, owners can receive real-time alerts and make sure to contact the police if it's the case.

Kisi offers this integration with the name of Kisi Intrusion Detection. You can learn more about the feature and its benefits on our product page. In case you have more specific questions, feel free to contact us.

If, instead, you want to learn more about intrusion alarms check out our overview page.

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How many doors or entry points do you want to secure?

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