That homebrew contact sensor I saw at the Phoenix job site made me rethink everything

I watched a guy in Tempe wire a reed switch to a Raspberry Pi instead of using a proper DSC contact, and he claimed it saved $12 per zone. Has anyone else tested a DIY sensor that actually held up longer than 3 months without false alarms?

3 comments

3 Comments

brian_smith623d ago

I remember a guy in Scottsdale who tried a DIY sensor with a hall effect sensor and a magnet, and it actually worked for 6 months with zero false alarms. He had it on a garage door, and the trick was using a ferrite bead on the signal wire to kill interference from the opener motor. The big problem I've seen with the reed switch approach is that the cheap glass reed switches crack after a few hundred cycles, especially in Phoenix heat where the plastic housing expands and contracts. If you use a proper hermetically sealed reed switch like a Coto 9000 series, they usually last years, but then you are paying almost as much as a DSC contact anyway. The Pi setup is fun for tinkerers, but for reliability on a real job site I'd still want something with UL certification and a known failure rate.

nancycooper23d ago

Oh yeah, I saw that same story in a security forum a few months back, someone posted about their hall effect sensor setup lasting through an Arizona summer. They mentioned using a ferrite bead too and said it was key for cutting out the RF noise from the opener. I actually tried a similar thing on my own shed door with one of those little Hall sensors from an old hard drive, and it worked for about four months. But then the heat got to it and the signal started getting flaky. The Coto 9000 series reed switch is a good call though, I heard those things are built like tanks. But yeah, for a real install you just can't beat a proper alarm contact that's been tested to death.

robert_bell23d ago

Haha, classic "six months in Arizona" success story, I caught that one too from @nancycooper's forum mention. The ferrite bead trick is solid, but my own attempt at a hall sensor rig ended with the magnet falling off and the sensor roasting like a potato on a dash during a Phoenix summer. Until I stop forgetting to buy a proper enclosure, I'll stick with the cheap reed switches and just swap them out every season.