Driving a piezo sounder

[Martin Griffith]

I've just got back to thinking how to drive piezo sounder, and was
wondering if something like the Natsemi LM4908 headphone amp working
in bridge mode would be ok.
The piezo has a 18nF capacitance
The lm4908 seems a lot easier and smaller than brewing my own

Any potential gotcha's?


martin

 

[Eeyore]

The piezo has a 18nF capacitance

So what's the Z at the f of interest ?

Don't forget it's reactive either.

Graham

 

[Martin Griffith]

So what's the Z at the f of interest ?

Don't forget it's reactive either.

Graham

Nowt on the data sheet, just says 3KHz, and a max current of 10mA just
wondering where the 3uS slew rate op the amp comes in to the Eq. I'm
doing an Olimex run in a couple of days, so I'll see if if I can
squeeze a quick test pcb onto the gerbers

Maybe a few R in series will be needed


martin

 

[Eeyore]

Nowt on the data sheet, just says 3KHz,

that's -j2707 ohms

and a max current of 10mA

When driven from a fairly high voltage obviously such as 27V.

just wondering where the 3uS slew rate op the amp comes in to the Eq.

V/us ? Hardly sounds a problem for 3kHz. What are the supplies ?

I'm doing an Olimex run in a couple of days, so I'll see if if I can
squeeze a quick test pcb onto the gerbers
Ok.


Maybe a few R in series will be needed

Wouldn't hurt.

Graham

 

[Scott Seidman]

I've just got back to thinking how to drive piezo sounder, and was
wondering if something like the Natsemi LM4908 headphone amp working
in bridge mode would be ok.
The piezo has a 18nF capacitance
The lm4908 seems a lot easier and smaller than brewing my own

Any potential gotcha's?


martin

Can you pass on the spec sheet for your piezo buzzer?? Many of these have
on-board stuff that works just fine with a TTL signal.

 

[Martin Griffith]

Can you pass on the spec sheet for your piezo buzzer?? Many of these have
on-board stuff that works just fine with a TTL signal.

It's this, the kpe130
http://www.farnell.com/datasheets/23964.pdf

I'm just trying to make it a bit louder with a push pull drive


martin

 

[Mike Harrison]

It's this, the kpe130
http://www.farnell.com/datasheets/23964.pdf

I'm just trying to make it a bit louder with a push pull drive


martin

If you want louder, put an inductor across it ( 10-100mH - yes milli, not micro) and drive it with
an open-collector transistor at the sounder's resonant peak. Use a HV transistor (e.g. MPSA42) if
there is any risk of the piezo getting disconnected as it will swing over 100V off-load.

Bourns do some nice cheap axial inductors that work a treat.

 

[Martin Griffith]

If you want louder, put an inductor across it ( 10-100mH - yes milli, not micro) and drive it with
an open-collector transistor at the sounder's resonant peak. Use a HV transistor (e.g. MPSA42) if
there is any risk of the piezo getting disconnected as it will swing over 100V off-load.

Bourns do some nice cheap axial inductors that work a treat.

Great, thanks for that tip, I have a go when I put the scope back
together, (fuzzy focus)


martin