Don:
When I feed it my square wave, at the resonant frequency I see some
oscillation at each edge, but very low voltage, seems nothing to worry
about.  I did notice that at one or two other frequencies I saw a spike of a
half a volt or so at the edge, which I could eliminate with a series
resistor.  Is this what you were referring to?
Thanks,

Bruce Cannon            Style Management Systems
bcannon@jps.net         http://www.jps.net/bcannon
(510) 787-6870          1228 Ceres ST Crockett CA 94525

Remember: electronics is changing your world...for good!

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Donald Riedinger
> Sent: Sunday, July 25, 1999 5:04 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: piezo audio transducer driving
>
>
> Bruce,
>
> Have you looked at it with a scope?  You'll see what they're talking
> about.
>
> Don
>
> Bruce Cannon wrote:
> >
> > Hello all:
> > I've been developing a device which includes a piezo element driven
> > differentially by two IO lines, no other components.  It works great and
> > draws very little power for so much sound.  Too easy, I wonder?
>  I've looked
> > over past PICLIST discussions of driving piezo elements with
> the PIC (and
> > have searched the web for other info as well to no avail), and have seen
> > mention of a series resistor, annd occasionally external
> protection diodes.
> > 1. Can anyone give me a nutshell explanation of why these
> elements might be
> > neccessary?  I understand that there is an average current at the given
> > frequency, but is there also an instantaneous (or do I mean periodic?
> > inrush?) current and/or voltage which I must consider as well
> (and which is
> > dangerously higher)?
> > 2. Can anyone recommend a source for additional reading to help
> reduce my
> > ignorance?
> > Thanks,
> >
> > Bruce Cannon            Style Management Systems
> > bcannon@jps.net         http://www.jps.net/bcannon
> > (510) 787-6870          1228 Ceres ST Crockett CA 94525
> >
> > Remember: electronics is changing your world...for good!
>