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.

Very durable. Utilized for double garage doors to detect (open/close) positions. Connected reed switches in series to controller to operate and monitor garage door utilizing WiFi.

Works great if you do better than me and wire it correctly the first time. Thanks to whoever put the following out there: When the door is closed, there is continuity between Black/Green When the door is open, there is continuity between Black/Red

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.

So, 5 stars for quality, but yikes, $20 for a magnet sensor, so 4 stars for value. Anyway, I bought a Nexx garage door wifi control which is just a repurposed $5 Sonoff control with a very cheap magnetic sensor for reporting door position, but it also has a fairly good app (so you pay for the app I guess). Read the reviews on the Nexx, a large number talk about it working and then not, becaue the position sensor stops reporting correctly. and thats because It needs an 1/8 gap on a garage door. On my wobbly old door youre never going to get that consistency; so Sentrol to the rescue with their 2 inch gap. This sensor is industrial quality. Buy a LeMotech ABS Plastic Dustproof Waterproof IP55 Junction Box, cut the cord on the cheap magnet, and splice it into the Sentrol inside this box. Two day shipping, problem solved. Oh, and use the black and green wires from the Sentrol for this application.

works good

Used it to replace my ADT floor switch that went out. Was nice having the option to use as NO or NC as I didnt know what my existing switch was. Easy to install and work good. I wasnt going to replace the magnet but this one was a lot nicer so I opted to use it.

Had one installed, but it split in half from winter weather freezing it

This is a great switch. The switch part is both lightweight and extremely tough; the magnet part is easy to mount and also light. The activation distance is around two inches that makes for finding a nice mount point easy. Additionally, the magnet can be reversed on the mount if you need a little more distance for a weird mounting spot. The armored cable protects the signal wires, so if you run over it with the car it will still work. Since it has normally open and normally closed outputs, it will work in any wired alarm application. Really nice device.

Perfect. Using for my Insteon home automation....they used to include this exact item in their garage door kits but have since cheaped out. I ordered this to match the one Ive had for several years when I wanted to add HA control to my second door.