SM-226L-3Q Seco-Larm Overhead Door Mount N.C. Magnetic Contact w/ 3 Wires for N.O./N.C. Applications (One Pack)

This sensor was the perfect choice for sensing when my roll up garage door is completely secured. What I like the most is that this model supports both Normally Closed and Normally Open systems; There are three wires, red/black/green. When the door is closed, there is continuity between Black/Green When the door is open, there is continuity between Black/Red In my application I discarded the red wire and have a raspberry pi send a text notification when the door is opened unexpectedly. The activation range is very good, over two inches. This prevents false alarms when the wind blows against the overheard door and it moves slightly.

I wish I had found this years ago. This works perfectly on the top edge of my garage door

Does what I needed. Has both normally open and normally closed contacts making it perfect for residential/commercial applications as well as automotive security applications.

I have 2 of these installed on garage doors, unheated space for many years and they have never failed in harsh MN weather, that is why I purchased 2 more for barn doors on a new building.

Item as listed Worked great.

Works as expected. Used it to automate my garage door with a Raspberry Pi. Now garage door knows position when I give the command to open or close vs just actuate.

Magnet bracket works fine on probably 90% of garage doors. Mine, unfortunately was in the 10%. Had to rig up a method to attach the bracket. Would be nice if the bracket was more a of C shape rather than an L shape.

Buy this one instead of the Honeywell Contacts because this one have contacts for both Normally Open (NO) and Normally Closed (NC) circuits so I use one for my alarm and another circuit for indicator for the garage doors are open or closed. There are no label the wires so you need to test it with test meter. Need to connect to a relay if pull more amperage or volts. The distances apart can be up to 2 inches.

Was actually a NC contactor for an old school buzzer using 12v. Many others come NO without the three wires.

Using as a sensor with a Raspberry Pi. Working perfectly so far. Straightforward install.