The sort of smallish round sounder you get in myriads of things that bleep. Just fed with DC and produce that bleep.
Are they susceptible to damp in the air? My guess would be they were designed not to be, since they're common on kitchen appliances. or perhaps once were.
Mallory 'Sonalert' were the originals - robustly made with encapsulated electronics - quite pricey. I've just replaced one on my Benford single drum vibrating roller with an eBay £2.50 jobby that seems to do all that is asked of it and has the exact same mounting requirements as the Mallory type which I've been familiar with since the late 1960's
Andrew
Dave Plowman (News) brought next idea :
The ones which work on a DC supply, have a built in oscillator, some are just the sounder, needing an external oscillator.
Yes. The one in question has that built in oscillator, so works from plain DC.
Basically, it's gone intermittent for no apparent reason I can find. Sometimes bleeps, sometimes just clicks. Could be a dry joint in the electronics, but does seem to depend on the weather.
A quick google suggests that Rochelle salt piezo crystals can be affected by moisture. They can even be used as humidity sensors.
Owain
Some tend to die for no apparent reason. Most are a pietzo device in the main I think. Very cheap as chips, but you need the right voltage one. Often find them in old computers. Brian
Dry joints can be weather sensitive. Seen with phone street cables.
I've brought sounders that have a bit of tape over then that you remove after soldering and washing (for automated process). I don;t think there's an officail technical differnce for whether an device can be referred to as a buzzer or sounder, then there's Piezo transducers that we use either to make sound or used as a simple microphone to sense vibrations.
on 05/06/2018, whisky-dave supposed :
I would call a buzzer one of those electro mechanical devices, with contacts which make and break, like an old fashioned bell, but lacking the dome/ bell.
they can indeed. Of course no piezo disc uses rochelle salt.
NT
I don't think that is how they are classified.
but that isn't how piezo devices work and the vast majority of them are called buzzers.
Are speakers electro-mechanical . when a student asks me for a buzzer, sounder, speaker, or piezo or transducer I always ask them what they want it for before I'll supply one to them. Unless it;s on their list of parts then I order what they have asked for usually.
what do HGVs use as reversing warnings ?. They are exposed to all manner of weather, salt and crap.
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