Micro switch question

[ss]

Rating: 15A AC250V Withstand Voltage: AC1,0000V 1 Minute Insulation Resistance: 100M O DC500V Contact Resistance:

[newshound]

Probably a bit OTT. Anything like this should be fine, and probably easier to fit.

[Graham.]

Maybe. Incidentally this is a reed switch, a microswitch is something different. The problem with using this in the application you describe is that the switch is normally closed when the magnet is near, that is when the door is closed in the normal configuration. So the buzzer will sound when the door is closed and stop when the door is opened, the opposite of what you want I think.

You could use a transistor or a relay to make it work correctly, but that might be a hassle for you.

The traditional shop door switch is this

That will do what you want as long as you just need a burst of ringing when the door is opened.

[misterroy]

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[Graham.]

Nice one!

[nemo]

There are reed door switches available with changeover contacts that would do the job directly e.g.:

[Brian Gaff]

I rigged one up on a garage door with a piezo sounder and a pp3 many moons back. I found I needed the sort of switch that had a lever on it to make it easy to mount. You might even be able to buy something like this off the shelf. Beware of using those magnet operated switches, though they work for a while I tened to find them unreliable.

These are the sort of things you often see on windows which are alarmed. Brian

[Dave Liquorice]

Reed switches are fragile, the glass/metal seal particulary so. If that fails so does the switch. IIRC they are not keen on switching very much power either, at least the small ones, contact failure and/or magnetisation of the reeds?

[meow2222]

Yes no problem.

I'd avoid reed switches. They're very fussy and tend to fail when used like this. Also when used as door closed detectors, gusts of wind, warping etc result in false alarms too.

NT

[Dave Plowman (News)]

A reed switch with a 15 amp AC rating?

[Dave Plowman (News)]

I've got reed switches on every window and external door. Fitted years ago. Not ever had a problem. Sound like they weren't correctly installed.

[meow2222]

There are known issues with reed switches. They're no longer used in burglar alarms - they once were - because as well as being electrically issueful there were so many door alignment false alarms. Yours may be fine, but so many were not.

NT

[Bob Eager]

That bit at the top is confusing, and sounds as if the OP read it off something. The actual text says a battery operated buzzer...I wonder which he actually wants?

[Dave Plowman (News)]

It could well be there are problems if they are simply thrown in place. But that can be said for most things.

I can understand pro alarm installers wanting something simpler, though. Most pro alarm house installations I've seen have been terrible - with unprotected wires running everywhere. Often down the side of a fitted carpet - or just tacked to a skirting board. All done in the fastest possible way. With surface mount reed switches all too easily damaged.

I did my own install - and took a lot of time and trouble to conceal all the wiring and switches. And as I've said have had zero problems with them.

[meow2222]

I dont believe that's the problem at all. Doors are prone to move in alignment over time, and gusts of wind can bend them. Both resulted in false alarms.

Indeed. A sample of one system still working does not make it a reliable technology.

NT

[Dave Plowman (News)]

If a gust of wind moves a door enough to trigger a reed switch hardly worth having that door let alone the alarm.

Of course if a door or window no longer closes properly so the reed is 'on', a timely reminder to sort it.

[Dave Liquorice]

Must have crappy doors. our worst (a cheap "hard wood" thing) that was fitted as part of a proch by previous owners only moves 1/4" on it's width between summer and winter. As for gusts none of our doors move more than a mm or two even on the exposed side with an F9 gusting 60 mph hitting 'em.

Never had a problem with the concealled magnets/reed switches on them. Horrible exposed surace ones are more fussy about position of magnet/reed.

[Dave Plowman (News)]

Absolutely. All mine are concealed types. You have to open a sash window about an inch to trigger the reed. Much the same with doors.