Piezo amp

[Imbanon]

Hiya everyone!

Does anyone have any simple schematic or any ideas how to amplify the sound of a 2 pin piezo?
For now I drive it simply from a controller pin, but the sound is somewhat quiet for an alarm clock, so I'm looking for something different.

Thanks! :)

[Adam Jacobs]

Make sure that you are driving the piezo at the frequency that the
datasheet specifies. Piezo buzzers are resonant in a specific frequency
range. If you are outside of that range, they will under perform.

-Adam

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[Mike Harrison]

Put a 10-100millihenry Inductor across piezo ( you can get some very cheap axial ones), and drive
withan open collector transistor, Note that disconnecting the piezo will produce a high voltage
that may kill the transistor unless you use a HV transistor like MPSA42,. if the piezo is solidly
connected you can usually use a bog-standard NPN as the piezo will limit the voltage.
Also remember that piezos are sharply resonant so tweaking the frequency for loudest output makes a
big difference, regardless of how you drive them.

[H. Carl Ott]

One simple thing you can do is drive it from two mcu pins out of phase. You get twice the peak to peak voltage that way. 

As mentioned, it helps a lot to dive at resonance.

carl
--------------------------------------------------------
Henry Carl Ott   N2RVQ    hcar...@gmail.com

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[Imbanon]

Also, is there any need to protect the controller pin from the voltage spikes? And what about current draw, should I put a resistor because of the inductor, or can I expect small currents?
Thanks a lot guys :)

[Mike Harrison]

On Tue, 15 Jan 2013 09:59:46 -0800 (PST), you wrote:

>Also, is there any need to protect the controller pin from the voltage
>spikes? And what about current draw, should I put a resistor because of the
>inductor, or can I expect small currents?

No - the small high-value inductors have typically hundreds of ohms of series resistance so no smoke
if the transistor turns on continuously

the transistor base resistor won't pass enough current to damage the MCU.

[Imbanon]

Thanks!