Hi DIYers! Some of the most important sensors used with alarm systems are passive infrared (PIR) motion detectors. When installed properly, these devices do an excellent job of detecting any motion that can occur inside a home or business. They are critical for a complete security setup.
But while motion sensors provide many great benefits for alarm systems, they are also some of the most prone to experiencing problems and issues. These problems are usually the result of PIR motion sensors being mounted poorly and/or in unsuitable locations. Problems may also occur if a motion sensor is ever used in an improper application or setting for its intended use.
By obtaining a better understanding of motion sensors and how they operate, a user is less likely to experience reoccurring problems with their PIR motion sensor. Just a few tips and general guidelines need to be followed. It all comes down to installing the motion sensor correctly, selecting a good location for the device and choosing the correct type of PIR sensor. If these three tips are followed, then a motion sensor will be much more likely to work properly.
First, it's a good idea to understand what a motion detector is trying to accomplish and how it works. The goal of a good motion sensor is to detect the motion of a human intruder, while also ignoring unimportant sources of motion, like a ceiling fan, curtains or a pet. But this is easier said than done. If a motion is too sensitive, then false alarms will occur. But if it isn't sensitive enough, then it won't detect intruders.
A PIR motion sensor works by taking a reading of the infrared (IR) energy in a room and detecting any significant changes in IR energy that occur. All people, animals and objects give off some amount of IR energy. When a person, animal or object comes into the field of view of the motion sensor, it causes a change in detected IR energy. Once the motion sensor has detected enough of a change, it will send an alert to the alarm system to let it know that motion is present. The alarm system will then respond accordingly based on the programming settings.
But most users wouldn't want a motion sensor to activate because of very tiny changes in IR energy. This would cause too many false alarms on the system. That is why motion sensors usually have sensitivity levels that can be adjusted through an adjustable pulse count. The pulse count determines how large of an area needs to experience a change in IR energy before the motion will activate. A higher pulse count will mean that a wider change in IR energy is needed to activate the motion detector, thereby making the sensor less sensitive. Likewise, a lower pulse count will increase the sensitivity. Many motion sensors also have lenses that can be swapped out to provide the optimal view for the device.
But it's important to remember that a PIR motion sensor will only work if it can "see" the movement. That is why it is critical that a motion sensor is mounted at a height where it can properly detect a human intruder. A hypothetical scenario is to imagine a motion sensor that is mounted too high up. In that case, a person could just duck down and move below the field of view without setting off the motion sensor.
Most motion sensors are mounted at a height of about 6 to 8 feet high. This should allow the device to detect any human moving in the room. For optimal coverage, we generally recommend mounting motion sensors in the corner of a room. But mounting height becomes even more important for "pet-friendly" motion sensors. The goal of a pet-immune motion sensor is to detect the motion of a human walking upright, while still ignoring the motion of a small animal walking close to the ground.
Users should realize that pets can still set-off pet immune motion sensors, even if the pet is within the suggested weight limit. But the goal is to prevent this from happening. By setting up the motion sensor correctly and by making it impossible for the pet to get within the field of view (FOV) of the motion sensor, false alarms are much less likely to occur because of the activities of pets.
If a user intends on using a PIR motion sensor in a home with pets, they should first make sure their PIR motion detector offers pet-immunity. A pet-immune motion sensor features a lens that is designed to detect the motion of a human walking upright, while ignoring the movement of pets closer to the ground. If a motion does not have this special type of lens, then it will still see a pet moving throughout the room.
Second, a user should make sure that their pet is within the listed weight limit of the motion sensor. The idea here is that pets that weigh more are usually larger in size. So if a dog is 60 pounds, it is estimated that it will be large enough to set off a pet-friendly motion sensor for pets rated for up to 40 pounds. Of course, the pet-immunity values provided from motion sensor manufacturers are rough estimates. But these values should still be taken into account when planning.
Third, the motion sensor should be mounted at a proper height. It will need to be at a height where it can still detect the movement of a human, while ignoring the movement of a pet closer to the ground. Generally speaking, 7.5 feet high is a good height for accomplishing this. But this height can vary for different sensors. Also, the motion sensor should be mounted at a proper angle. If it is facing at too low of an angle, a pet might still set it off.
Finally, the motion sensor should not be facing any "obstacles" that a pet could climb on top of to get within the FOV of the sensor. Even if the motion sensor is mounted at a good height and at a proper angle, a pet can still manage to set it off if it is able to get up high enough. For example, a pet could climb on top of a sofa or walk up the stairs and get within the motion's FOV. For that reason, motion sensors shouldn't be mounted facing furniture or a stairway if pets are present.
There are also a few general guidelines that a person should follow when choosing a location for a PIR Motion. Remember, these devices respond based on changes in infrared energy. By installing a PIR motion near a vent or an air duct, the flow of hot or cold air could result in false alarms. A similar principle can be applied for appliances such as stoves and refrigerators. It is also advised that users do not install motions facing windows, as heavy sunlight could cause the device to activate. Additionally, motion sensors tend to work poorly in environments such as bathrooms, garages and attics, since they tend to feature high levels of humidity and/or dust. A user should also avoid mounting a motion sensor facing a moving ceiling fan or curtains, as this may result in false alarms.
Some users may also overlook the type of PIR motion sensor that is being used. Not all motion sensors are created equal, and there are many types of possible applications. For one, there are residential versus commercial motion sensors. Residential motion sensors are typically less sensitive and better-suited for homes and apartments. Pet-immunity features are usually only found on residential motion sensors. On the other hand, commercial motion sensors are usually more sensitive and feature lower pulse counts. A commercial motion sensor will also typically feature a larger FOV, making it more suitable for commercial settings.
Another common issue is to use an indoor motion sensor in an outdoor setting. Outdoor rated devices feature rugged exterior casings that protect the devices from exposure to rain, wind, dust and extreme temperatures. If a user tries to use an indoor motion sensor in an outdoor setting, then it is very likely that the device will become damaged due to environmental exposure. And while a user can use an outdoor motion sensor indoors, this is usually not recommended because outdoor motions are considerably more expensive. Make sure that the motion you use is suitable for the desired environment.
Following these tips will help ensure that your PIR motion sensor works properly and doesn't cause you problems. When used properly, these are great devices that do an excellent job of keeping homes and businesses secure. You can buy motion sensors of all types on the Alarm Grid website!