Does a piezzo buzzer needs a protection diode

[rggmiranda]

The question is really simple, i need to drive some piezzo buzzers from a transistor, and i would like to know if they need to use a diode protection like if they where an inductive load, i know they are not, but, even tough i read about it, i am not sure if piezzos cannot generate the same issue, please clarify me on that. Thanks!

[BennVenn]

Is it a buzzer (has the oscillator circuit built in) or just the piezzo element (disc)?

[rggmiranda]

Is it a buzzer (has the oscillator circuit built in) or just the piezzo element (disc)?

I belive it has the oscillator built in, i just connect it to 5v dc

[BennVenn]

then don't bother with a protection diode

[rggmiranda]

then don't bother with a protection diode

Ok, thanks you a lot, anyway, just for further knowledge, in the other case in which i had the piezzo itself, what would happen?

[BennVenn]

Well that is intersting, the piezzo would be capacitive not inductive so you wouldn't get the back EMF that you would with a coil however if you drove it to resonance who knows!! Would be interesting to see on a scope

[rggmiranda]

Well that is intersting, the piezzo would be capacitive not inductive so you wouldn't get the back EMF that you would with a coil however if you drove it to resonance who knows!! Would be interesting to see on a scope

For now, as i need it with the driver i will just avoid the diode, further on i may open one and check it with the scope, who knows maybe it can be harmfull, i will tell you the result, if you do it first tell me!
Thanks for the info

[TheMG]

I've used such buzzers in many projects and have even seen them used in many very expensive pieces of commercial equipment, no diodes on any of them, never been a problem.

[zapta]

You also need to consider what will happen to your circuit if you will hit the piezo and it will generate high voltage exceeding less say Vce. That is the piezo is also a voltage source, not just load.

[Zero999]

A piezo buzzer with built-in driver contains a transistor oscillator and a transducer with a feedback pin which makes building the oscillator easier - it's just an amplifier with the input connected to the transducer's feedback pin.



The only time a piezo buzzer contains a coil is to boost the voltage to get more sound but still no diode is needed as the transducer absorbs the extra voltage.

[zapta]

From Murata:

In order to protect the IC from back electromotive force generated by a piezoelectric sound component, consider connecting a Zener diode in parallel with the piezoelectric sound component and Rp if necessaryFrom

http://www.murata.com/en-us/support/faqs/products/sound/sounder/char/sch0001

[Zero999]

From Murata:

In order to protect the IC from back electromotive force generated by a piezoelectric sound component, consider connecting a Zener diode in parallel with the piezoelectric sound component and Rp if necessaryFrom

http://www.murata.com/en-us/support/faqs/products/sound/sounder/char/sch0001

That only applies to piezo transducers which don't include a built-in oscillator.

[Psi]

Here's a piezo being driven directly from a AtMega I/O pin at 3.5khz
Looks like it will be touching the clamping diodes on switch-off, about -1V