piezo electronics question

[STORM 2 0]

OK folks, can someone explain piezo-electric sounders/buzzers to me?

I have several flat round 12v alarm buzzers but when connected directly up to the 12V power source all I get is a crackling - so what am I doing wrong?????

Is there some wee magic box of sprites that I need to connect in betwixt the power and the buzzer?

[yalan 0]

piezo needs a signal to generate a sound.

The crackle is just the sounder acting as a speaker.

[STORM 2 0]

thanks yalan, so where do I manufacture a signal?

[coolrado 0]

what sounders are they (make and model)?

 

if they are 12v that usually means they simply need 12v applied to them and they will have an in built tone generator.

 

are you sure they are 12vdc or could they be 12vac, a lot of industrial control gear is 12v ac, although most well known industrial sounders will work on ac or dc.

 

 

piezo crystals emit electrical charge when squeezed or struck as in the ignitors for gas hobs or electric spark cigarette lighters (the ones that click).

but if you apply a charge to them they will expand, they are commonly used for cheap high frequency tweeters in crappy stereos or for the sounder on the backs of digital watches.

sounders usually consist of a metalic disk coated with a thin layer of piezo ceramic with a conductive coating over its surface with an electrical connection to the metalic disk and another to the conductive coating on the piezo ceramic.

 

you can actually get sound out of a barbeque lighter to prove it.

[STORM 2 0]

Hi coolrado, thanks for the reply I knew there would be an expert around sooner or later.

Its a 12VDC - I have several flat round things - some are supposed to buzz some are supposed to chime. Most were bought from Maplins.

However simply applying 12V to them only results in crackles.

 

Is there supposed to be some sort of additional circuitry or maybe a cone funnel or something attached to the thing?

Many thanks

[coolrado 0]

which ones are they?maplin piezo sounders

some come with a driver built in some dont, but if they say they produce certain tones they should have the driver built in.

 

are you sure maplin supplied the correct ones? the staff there arent allways the sharpest tools in the shed :lol:

[STORM 2 0]

Theyve definately got the driver built in - and two terminal ends :?:

[coolrado 0]

i dont mean the driver as in speaker driver, i meant driver circuitry that produces the tone.

the first one on that list needs an external driver circuit.

[STORM 2 0]

AAAAhhh

 

By George I think you've got it!

An External Driver Circuit.!! Whats one of those by the way?

 

Can I get one ready made from Maplin or does it have to be made up?

cheers matey

[yalan 0]

on that maplin link, the ones labelled piezo transducers are the raw sounders & will only crackle unless supplied with a signal.

 

If it is labelled as a buzzer it'll have a plastic case around it which contains the circuitry.

 

If you want a buzz - just buy a buzzer! They're so cheap its just not worth the hassle of trying to get a separate sound generator though I'm sure yoou'd find one at maplin in their velleman range.

[STORM 2 0]

yalan - I wanted a bong /chime sound thats easier on the ears.

It also sounds more authentic.

 

If anyone can knock up a wiring diagram of a piezo mated to the light switch I'd be grateful