Category Archives: How Things Work

There is definitely some mystery surrounding motion sensors. They are a core element of most alarm systems and a standard feature ion our Smart, Safe Home package. So, let’s dig into what they really do.

Motion sensors detect and report motion – in most cases when nobody is home (Armed-Away). That’s why they are not “awake” when you arm your system for the night (Armed-Stay) . It’s usually not practical to put a sensor on every window, and you usually don’t need to, since you can use motion sensors and glass break detectors to get the protection you need more affordably. Plus, motion sensors have come a long way from the original models – much more reliable, and less prone to false alarms.

How do they work?

The early motion sensors were considered “active” devices, because they emitted energy (microwave or ultrasonic) to see what was happening around them. There are some still some microwave sensors being installed in commercial spaces. Today the most common motion sensor uses Passive Infra-Red energy to detect heat given off by people (and animals!) – hence the name “PIR” given to the device. The smart detectors look for objects warmer than the normal background temperature, using a special lens to create “beams” of passive energy, and then look for motion: when the sensor detects a “warm” object moving across several beams within a specified time frame – that trips the alarm.

Where do you use them?

The standard range is 30-35 feet, and the coverage area is shaped like a large water droplet, with the skinny part at the detector. The ideal spot for a motion sensor is in a high-traffic area that an intruder would cross if moving about in your home or business: think hallways, living rooms with big-screen TV, etc. The sensors work better when people move across the beams, as opposed to approaching the sensor directly. The beams project out and down, to pick up anyone trying to avoid detection by crawling.

Motion sensors and pets

Today’s sensors are usually “pet-friendly” up to 40 pounds, which means they “ignore” cats and small dogs – unless your Siamese is downright acrobatic! That means that large dogs with the run of the house all day and night make it harder to use motion sensors – unless you kennel them!

 Things to Remember

Manufacturers recommend careful placement of their products to prevent false (non-intruder caused) alarms. They suggest mounting the PIDs in such a way that the PIR cannot ‘see’ out of a window. Although the wavelength of infrared radiation to which the chips are sensitive does not penetrate glass very well, a strong infrared source such as from a vehicle headlight or sunlight reflecting from a vehicle window can overload the chip with enough infrared energy to fool the electronics and cause a false alarm. A person moving on the other side of the glass however would not be ‘seen’ by the PIR.

They also recommended that the PIR not be placed in such a position that an heating and air conditioning vent would blow hot or cold air onto the surface of the plastic which covers the housing’s window. Although air emits very small amounts of infrared energy, the air blowing on the plastic window cover could change the plastic’s temperature enough to, once again, fool the electronic

Specifications

For more information on this exciting product call us at 302-656-5110 or visit our website at http://www.burnsandmcbride. Finally you might want to follow our blog at http://www.burnsandmcbrideblog.com. Just as Smartphones are adding applications and changing every day so to with the technology behind our Smart, Safe home system. Our blog explains some of the constantly changing things that are happening in the industry and we hope that you find it informative.