Reed switch failings - Page 1
Forum section: electronics / projects

author: oskimac
author_rank: Contributor
timestamp: February 15, 2022, 09:12:43 pm
content: Just that. I had replacer both endstop reed switches on my garage door like 3 times each. They seem to fail being closed or not making a connection. You can hear it clicking if you get a magnet close but no continuity.I didn't bent the legs so no cracks on the glas. Any guess?

author: TheMG
author_rank: Frequent Contributor
timestamp: February 16, 2022, 12:00:37 am
content: Are the reed switches just carrying small control signals back to the opener/controller, at low voltage and negligible current?Reed switches normally last a very very long time (easily the life of the equipment and then some) but can fail prematurely if they are carrying substantial current. You really don't want more than a handful of mA if you want them to last a good long time.

author: thm_w
author_rank: Super Contributor
timestamp: February 16, 2022, 12:29:56 am
content: Sounds odd.What are you replacing them with, just the reed or the entire assembly? What was the part number of the replacement?Can you look at it under a microscope maybe.https://electronics.stackexchange.com/questions/80886/reed-switch-sticks-until-tapped

author: IDEngineer
author_rank: Super Contributor
timestamp: February 16, 2022, 08:02:34 am
content: The earlier respondent is correct about too much current. I try very hard to design reed switch circuits to dry switch the contacts (meaning zero current during make and break). The spec sheets and app notes specifically point out the benefits of doing so. With dry switching, reed switches have lifetimes rated in the 100's of millions of actuations, one of the most robust electromechanical devices out there.

author: Zipdox
author_rank: Regular Contributor
timestamp: February 16, 2022, 08:03:08 am
content: Bridge them yourself and see if that gets registered. If it does, and they really are just failing, maybe you could replace them with hall effect sensors and a MOSFET.

author: Psi
author_rank: Super Contributor
timestamp: February 16, 2022, 08:22:46 am
content: hm.. yeah.Only things I can think of are- Too much current (arcing/welding damage happening inside)- Too much voltage (arcing/welding damage happening inside)- Junk/cheap/reject reed switches (aliexpress/ebay)- Using them with crazy powerful neodymium magnets that permanently bend the moving parts.

author: jonpaul
author_rank: Super Contributor
timestamp: February 16, 2022, 11:16:23 am
content: Reed switches are very ux reliable but need proper specificationsDoor sense has vibration and weather exposureWe uses Sentrol wide gap rolling door magnet and switches for 30 years, never had a failure.Available from sécurité dealers and distribution in USA.Unprotected glass reeds fail due to stress fractures in the glass end seals.Bon courageJon

author: Renate
author_rank: Super Contributor
timestamp: February 16, 2022, 07:03:12 pm
content: Just put your milliampmeter across it and see what the current is.If it's anything more than a couple of milliamps then it could be switching relays without any diode protection.That might cause arcing and burn out.Probably not your problem, but if you use a mondo powerful magnet on a reed switch it can get magnetized and be "stuck".You can just use your cassette recorder degauser and degauss it.You do have a degausser for your cassette player?

author: Psi
author_rank: Super Contributor
timestamp: February 17, 2022, 06:42:00 am
content: Also watch out for big capacitors. it may be low voltage and low current but if you have big low ESR caps you can still get huge inrush current that may exceed the reed switch ratings.

author: oskimac
author_rank: Contributor
timestamp: February 24, 2022, 01:21:47 pm
content: I don't think it was to much current becouse is a comercial producto not a homemade. I was thinking more about factory failures like moisture inside them making it faul in the short time or craking on the glass. I can hear them ticking but not passing any voltage. Anyway we decided to replace the whole assembly for big "industrial" one.The one with a wheel. I post a picture later. Thanks to all the comments

author: jonpaul
author_rank: Super Contributor
timestamp: February 24, 2022, 02:01:10 pm
content: BonjourHard to comment without Photos of your switches and installation.Generally alarms system for rollup and garage doors, use wide gap industrial switches rated for dry circuit, with strong mating magnets.We use only Sentrol, Ademco,and Honeywell switches and magnets, with no failures in 30 years.The switch has a metal jacketed cable and strong flat aluminum cast housing.Jon