I'd like to add someting like the ringer on a cell phone ringer to a project, something small and LOUD to make some beeps and boop noises. I've tried a few small piezo speakers but they are very quiet, need to be right up on your ear to hear. I need something you can hear across the room.

Any ideas? Thanks
Posted on 2004-02-23 09:35:04 by Ernie
Are you sure that you are sending the right voltages to piezzo speakers?

Some piezzo can get you out of the room :grin: with pain in your ears
But they have to be comanded by high voltages (and low curents)

Unless you are needing HiFi low frequence... piezzo speakers are the best performers IMHO
ie with regards to dimensions and audible sound intensity
Posted on 2004-02-23 09:48:27 by BogdanOntanu
Connect an inductor across the speaker. The speaker looks mostly capacitive (about 2~10 nF, depending on diameter, etc.). Try to make the resulting LC tank resonate at a few kHz.
Posted on 2004-02-23 11:41:13 by VVV
The piezo I'm using now is getting about 5 volts peak-peak across it, checked on a scope. I've also tried a small (< 1" or 2.5 cm) speaker I got at Radio Shack, it is also pretty quiet.
Posted on 2004-02-23 12:39:08 by Ernie
5 volts is much too small for a piezzo speaker....
Posted on 2004-02-23 17:40:49 by BogdanOntanu
What voltage would be about right?
Posted on 2004-02-24 16:12:20 by Ernie
Already has high impeadance but if you are usinf a low voltage than you want to convert you power to mostly current. You can do this with a emitter follower or even better a Darlinton pair configuration straight into speaker.
Posted on 2004-02-24 16:39:58 by mrgone
What's the bet he'll get hooked on basic amplifier circuits now :)
If you're going to hook two transistors together in a Darlington configuration, you may as well buy 4 instead of 2, and make a Push-Pull amplifier, it's still going to cost under 2 bucks :)
Posted on 2004-02-24 22:47:19 by Homer
Piezo speakers require tens of volts across them.

The solution I suggested earlier , with the inductor in parallel with the speaker, driven by an open collector will double your voltage across the speaker, about 10Vpp. They used this approach in the alarm watches.

I would also try driving the speaker with two gates, the outputs of which should be 180 deg out of phase, again to double the voltage across the speaker, much like a bridge amplifier.

These are simple things. If not satisfactory, you would have to step up the voltage and use an amplifier to drive the piezo.
Check out this link, too. http://www.amroh-electronics.de/amp.pdf .

Hope this helps.
Posted on 2004-02-25 11:12:10 by VVV
That's a lot of expensive silicon (just counting the ICs) to run a cheap piezo.

Guess I'll need to set one up in the lab and make some tests.

(I sure haste comps without spec sheets.)

Thanks all
Posted on 2004-02-28 11:40:31 by Ernie