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Piezo drive?

Have a simple Piezo in a helmholz housing. Would like to make a huge amount of noise with it but...

I only have a three volt battery supply, and would like to deviate from the resonant frequency a bit - to be a bit more creative than just square wave warbling.

I have seen the following arrangements:

1) A choke (say 10mH) in series with a diode and the both in parallel with the Piezo, then one junction (Piezo and choke) to an NPN and the other (Piezo and diode) to +V

2) An NPN to the centre tap of a 10:1 transformer in a 'T' arrangement with the outer connections to either end of the Piezo then where the 'primary' joins the Piezo to +V

3) An NPN to the centre tap of a 10:1 transformer in a 'T' arrangement but one end goes to the Piezo which is connected to 0v and the other end is connected to +V

Can anybody enlighten me as to the advantages/disadvantages of such different configurations and what is the most efficient way to get 50+ volts p-p into the Piezo?

Obviously there will be a resonant frequency but if I can get sufficient voltage the 'off resonant' won't matter much.

Are there better ways to drive them i.e half/full bridge.

Component cost is not really an issue, but volume is.

Thanks for any advice. Cheers Reg

Reply to
Reg
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If SPL is the issue, then you should drive it at its resonant
frequency.  Why don\'t you want to do that?
Reply to
John Fields

Thanks John. I wanted to drive a tune through it at high SPL. Reg

Reply to
Reg

You can't really "drive a tune" when you've got a Q > 5 resonator. The bandwidth is pretty narrow on most piezos to begin with, and an acoustic resonator is only going to make that narrower. You might as well add a parallel inductor, tuned for the piezo's capacitance and resonant frequency, to make it a triply tuned system. A little negative resistance amplifier and you have a buzzer of probably quite reasonable electrical-acoustic efficiency and stable frequency.

Tim

-- Deep Fryer: A very philosophical monk. Website @

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Reply to
Tim Williams

Well, you've got two strikes against you right off the bat - both the piezo and the resonator have a resonant frequency. Trying to drive the system off resonance to some "high" SPL would probably break the crystal.

Good Luck! Rich

Reply to
Rich Grise

Thanks for the help. Reg

Reply to
Reg

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