Motion detector wiring is usually included as part of the prewire for all hardwired home security systems. Passive infrared motion detectors, or PIR’s, are your best “second line of defense” after the magnetic door and window contacts.
If you’re considering a DIY home security system, you should consider wiring for a motion detector or two to protect the interior of the house. If you have a home alarm company doing the wiring, they will likely include at least one PIR sensor in their standard prewire.
Motion detector wiring should always be home-run from each sensor back
to the alarm panel, without looping. This makes it easy to put each
detector on its own separate zone, and makes troubleshooting faster if
there’s a problem.
Sensors using passive infrared technology are most sensitive to movement across their field of view, and are very effective in small to medium sized rooms. Every motion detector comes with an installation sheet showing recommended mounting heights, coverage patterns, and adjustments. Amazingly enough, I recommend that you follow these instructions;-)
If you have PIR sensors without any paperwork, here are some general wiring and mounting guidelines:
For most rooms, run wiring for each motion detector to a corner of the desired room, at a height of 6-8 feet. Corner mounting will give the best coverage of most square or rectangular rooms, without being an eyesore.
In hallways, a PIR sensor will be slightly less sensitive. Movement directly toward or away from the unit will not be picked up as quickly, but will still be detected. Route motion wiring at 6-8 feet high, or near the hallway ceiling if it’s lower than this.
Locate motion detectors so that they divide or break up the house into sections, rather than trying to cover every square foot. This usually means wiring a detector along each major traffic path. Hallways, entryways, kitchen areas, and family rooms are good locations. For most homes of 3,000 square feet or less, a detector in two or three areas will provide good coverage.
Run motion detector wiring to the corners of rooms for best coverage. A passive IR detector is most sensitive to movement across its field of view. Wiring for a corner-mounted motion detector gives you good coverage of the area, and also helps the detector “disappear” into a corner of the room for less visual clutter.
Install wiring for a motion detector in any area where you feel you need
extra security. Wiring for an additional detector is smart, and will
give you added protection for a master bedroom closet, gun or jewelry
safe, computer room, etc.
For many of us, dogs, cats, and other pets are considered members of our family. This means we need to take them into consideration when planning our home security systems.
After years of helping people, pets, and alarm systems coexist together, I have some suggestions.
In my experience, meeting the requirements for a pet immune detector is difficult in the average home. For instance, some manufacturers stipulate that you position the detector such that a pet cannot approach within 6 feet of the unit.
Since dogs and cats can trip most motion detectors, the best solution is to keep them in an area without motions when you leave the house. There are ways around this inconvenience, but one of the easiest is to use a pet alley.
This trick is often done with motion detectors in hallways. The idea is to invert a standard motion detector and mount it 3 to 4 feet above the floor. This creates a so-called “pet alley”, allowing average-sized dogs or cats to pass under the detection zone. Wiring for a pet alley means animals can roam the house freely while you’re away, and don’t have to be restricted to a laundry room or other non-motion protected area.
Visonic, a leader in motion detector technology, has taken this to the
next level with its Spy motion detector. The Spy is a small cylindrical
motion sensor designed to work well in a pet alley application.
Wiring for Spy motion sensors should be done in hallways for the best capture of motion, without risking false alarms due to your favorite pets.
Be careful to use pet alleys mostly in hallways. They don’t work well in regular room spaces, because pets climbing on furniture can still trigger the motion sensor.
Regardless of how you create a pet alley, always walk test the area during installation of the detector. Coax your pet(s) to walk through the protected area a few times, and watch for the detector to trip. If your pet is uncooperative, you can always crawl through the area yourself.
If the unit does trigger for motion, adjust the viewing angle or pattern, or use masking to keep the detector from "seeing" the pet. Most manufacturers include tips for doing this in the included instructions.
Most motion detectors are designed to be surface-mounted. Bring motion detector wires out of the wall framing onto a nail driven partially into a stud, and wrap the wire around the nail. After drywall is installed, the motion sensor can be attached to the stud or drywall with screws and plastic anchors.
Motion detectors use 22-gauge, 4-conductor wiring. As with all alarm system wiring, solid or stranded types are both acceptable.
Two wires, usually color-coded red and black are used for 12-volts DC
power from the main alarm panel. The other 2 wires, green and yellow (or
white) are used for the burglar alarm loop.