Seco-Larm SM-226L-3Q Overhead Door Magnetic Contact, 2.75-inch Gap, Open/Closed Loop Circuits (3 Wires), 24" Armored Wire Leads, Weatherproof

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.

Use this on a sliding driveway gate. My limit switch system was a gear moving along a threaded rod that pushes a shut off switch. With seasonal changes this requires the limits to the reset. It was a hassle to adjust. When the old limit switch system finally gave after 20 years of service it was going to cost $300 to replace. I've decided to use this instead since I can mount the magnets to the slider gate and the magnetic sensors to the motor brackets. Worked like a charm no adjusting for seasonal changes. I've saved $260 by using this a limit switches.

Works as it should.

Works well when paired with an alarm contact sensor, to detect of a garage door is open or closed. Easy to install.

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 that's because It needs an 1/8" gap on a garage door. On my wobbly old door you're 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.

This is exactly what I needed for my garage door sensor. I had tried a simple reed switch, like one would use on a window, but it just wasn't up to the task. This item is much hardier, and the results are more predictable - meaning no more false readings. I mounted the switch at the top of my overhead door. Because of limited mounting surface on the wall and clearance requirements on the door, I was not able to line up the magnet with the switch. But even with at 50% overlap, it reads correctly. If you are setting up a door sensor that you want to work well for a long time, this is the switch you need.

This seems to be a well made product and there is sufficient flexibility in how the unit can be mounted. I’m particular about how things look and this switch suggests quality.

I bought this to drive a "garage door open" warning light in my residence. The sensor is designed to be installed on a garage floor, but I chose to install above my rolling door. This meant that the supplied magnet bracket didn't fit, so I built a custom bracket out of sheet metal. Combined with a power supply and blinking LED, I got just what I wanted for less than $30. There are lots of mechanical reed switches available for far less, but I wanted something more robust so I'm not replacing it in a year. I'm completely satisfied.