# Piezo drive?

R

#### Reg

Jan 1, 1970
0
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

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.

Cheers
Reg

J

#### John Fields

Jan 1, 1970
0
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

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.

R

#### Reg

Jan 1, 1970
0
John Fields said:
If SPL is the issue, then you should drive it at its resonant
frequency. Why don't you want to do that?

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

T

#### Tim Williams

Jan 1, 1970
0
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

R

#### Rich Grise

Jan 1, 1970
0
Thanks John.
I wanted to drive a tune through it at high SPL.

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

R

#### Reg

Jan 1, 1970
0
Rich Grise said:
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

Thanks for the help.
Reg

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