Magnetic contacts explained…
Magnetic contacts are very basic pieces of hardware that simply open and close a circuit. The contact side of the device typically has screw down terminals(like the video above), or they may have 2 leads coming off of them. Each terminal(or lead) has a wire going back to the security system and is wired into the a specific zone and a common input on the security system to make the circuit.
The contact side of the device has a small reed switch installed in it. A magnet is then installed across from the contact side which pulls the reed switch closed and allows current to flow through wired terminals and tells the security system that the contact is closed. Once the magnet is taken away, the reed switch bounces back and the terminals are no longer touching, telling the system that the contact(security system zone) is open.
In this video above, I go over the install of a recessed magnetic contact for a security system. There are a few different sizes, but the recessed contacts I typically install are 3/8 of an inch wide and have screw down terminals on them. These contacts are especially good if the building is unfinished and wiring can be run before the drywall goes up. Like in the video though, if you can remove the trim around the door, these contacts can be used as well.
These 3/8 inch recessed contacts can also be installed on sliding glass doors and windows. Many doors and windows, especially new ones with a couple inches of vinyl around the pane, give you plenty of room to drill a hole in the side and install your magnet. If you use a sharp 3/8 bit and take your time you should be fine. If you’re nervous at all about drilling into the side of these doors or windows though, I’d suggest using a surface mount contact, which I’ll explain more about.
Surface mount contacts
Sometimes if a building is finished, recessed contacts aren’t an option and Surface mounted contacts need to be used. They work the same way, with 2 screw down terminals for the wiring from your security system which open and close the contact by a magnet on the door. These contacts can also come with double sided tape on them so they work well for windows or other applications where glass is being used and the trim size doesn’t allow for screws.
These surface mount contacts typically have a more heavy-duty magnet, making them a good choice for applications where there is a bit more of a gap between the contact and magnet. For commercial doors, these surface mounted contacts are typically the way to go because of the larger magnet and gap allowance.
Overhead door contacts
Overhead door contacts also come in bottom and top of the door styles. For the top, your contact is secured to the back wall while your magnet sites on the top of the door opposite. For the bottom, your contact is secured to the floor while the magnet is attached on the door just above. As the door opens and closes, so does the zone.
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