Everything You Need to Know About Alarm Door Contact Sensors

Alarm door contact sensors are small sensors that detect if a door is open or closed. They are very commonly used with alarm systems in both homes and businesses. Alarm door contacts help keep your business secure by alerting you any time a door is opened; they can also trigger an alarm if a door opens that isn’t supposed to. 

It’s important to have alarm door contacts synced up with your security system and to have them monitored in real time because they can alert you to intruders in your building. The faster you or law enforcement are able to respond to a potential threat, the more you will be able to protect your assets. 

In addition to being used for alarm and alert purposes, an alarm door contact can also work with other smart features of your business to increase safety and improve energy efficiency. 

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What is an Alarm Door Contact? 

An alarm door contact is a small device installed on an interior or exterior door that can tell if a door is open or closed. The devices can be wireless or hardwired. Batteries on wireless devices usually last about three to five years. If you’re going to use hardwired contacts with a wireless security system, you’ll need to use a converter to connect them to the wireless system. 

Different types of alarm door contacts allow you to install them in different locations; in general, the more out of reach and inconspicuous you can make them, the less likely they’ll be tampered with. Types of alarm door contacts include surface-mount alarm door contacts, recessed alarm door contacts, plunger or roller ball alarm door contacts, overhead contact sensors, and pull-apart contact sensors. Learn more about how each type of sensor works in the section below. 

How Does an Alarm Door Contact Work? 

In general, alarm door contacts sense whether a door is open or closed by detecting whether the two parts of the sensor are together or apart. However, each type of sensor works a bit differently. 

Many door sensors work using magnets and a switch. Because they use magnets, it’s important that the strength of the magnet stays high; steel doors can weaken magnets over time. As the magnet becomes weaker, this can cause false alarms. To prevent this, commercial-grade alarm door contacts with strong magnets are ideal. 

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Surface-Mount Alarm Door Contact 

Surface-mount alarm door contacts are one of the most popular types of alarm door contacts. They consist of two parts: a magnet and a sensor. Typically, the magnet is installed on the door itself and the sensor is installed on the frame. This is because the magnet is able to withstand more abuse than the switch. 

The sensor uses a reed switch to detect if the door is open or closed. Once installed, the sensor and magnet typically need to be aligned within ½ inch, and they should directly touch each other when the door is closed. When the door is opened and the magnet breaks contact, the reed switch is released. This sends a signal to the access control panel that the door has been opened. Depending on the sensitivity of the device, it might sense a closed door when the magnet gets within an inch of the sensor. If needed, you can add spacers to make sure the spacing is right, which helps prevent false alarms. 

Recessed Alarm Door Contact

Recessed alarm door contacts work similarly to surface-mount contacts. The difference is simply where they are placed. Recessed contacts are placed in holes drilled into the door and the frame. This type of contact looks nicer, which is ideal for places where the look of the door is important. They’re also less likely to be tampered with because they’re less visible. 

Plunger and Roller Ball Alarm Door Contacts 

Plunger and roller ball alarm door contacts are one-piece devices. They are installed into a hole in the frame of the door, similar to a recessed door contact. The sensors have small plungers or roller balls that get pushed in when the door closes. This engages the switch and gives the signal that the door is closed. Then, the switch is released when the door is opened. 

Overhead Contact Sensors 

Overhead door contact sensors are typically used for roll-up garage doors. They’re often used in people’s homes as well as at warehouses and other places with roll-up doors. These types of sensors are designed to take more wear and tear and to accommodate a wider gap than you typically have with garage doors. 

Pull-Apart Contact Sensors 

Pull-apart contact sensors consist of a hole and a magnet. The magnet slides into the hole when the door is closed, and it slides out of the hole when the door is opened. This type of sensor is a popular choice for outdoor gates.  

Other Features of Alarm Door Contacts 

Alarm door contacts can do a lot more than simply sound an alarm when the door is open. If you monitor your security system remotely, it can send an alert to you when the door is opened. You can also program the sensors to trigger components of smart devices. 

Rather than alerting you of an intruder, you can program alarm door contacts to play a chime to signify that somebody has entered your business. You can also program your system to turn on lights when a door is opened or adjust the thermostat if a door is left open for a particular amount of time.

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