Magnetic Reed Switch MC-32 NC Surface Mount Wired Security Window Door Contact Sensor Alarm Magnetic Reed Switch White - (6 Sets)

I had a sensor fall off a window bought these and it works perfectly. Having the wire attached was a huge plus because the wire coming out of the wall was too short.

Good product and reliable service!

They work!

Reed switches are pretty simple devices, and these are no different. I ordered these to use in some Arduino projects to monitor the state of my garage and cellar doors, and they function just as I'd expect. In a few weeks of use they haven't gotten stuck open or closed, and have no problem with the wild temperature swings of an unheated garage. The included adhesive backing works fine, but it doesn't look like anything fancy so I'd still suggest using small screws when installing in a permanent location.

So I almost gave this 4 stars (subtracted one star for price) until I read the description saying distance less than 25mm at which point I subtracted another. The magnets used allow for roughly a 19cm (or 3/4") sensing distance, not the 25mm the description makes you believe (your results may differ depending on alignment and batch differences though). So either their claim is exaggerated or there is enough of a batch difference that some get 25mm and some only 19mm. Either way it isn't good. It also says it can handle 0.5A and up to 100V DC (neither I tested). Personally these types of switches should only have small currents going through them just to test for continuity. Basically they make great switches for various projects using a microcontroller (i.e. like Arduino). These won't have any problems with voltage and amperage in these use cases. In case you want to know I measured the closed resistance at 2.73 ohms (open is obviously infinite).This is just a basic reed switch housed in a plastic enclosure so price is obviously a selling point which is why I subtracted a star for price alone (being on the high side compared to others). The MC-38 is about half the size, half the price...but I don't think it can sense as great of a distance as these. So if you have some alignment mishmash it may be worth it to get the MC-32 version. But, just make sure whatever price this is at the time you go to purchase it...it is competitive with others.