[sdiy] touchplate keyboard - works!

[Roy J. Tellason]

On Saturday 05 February 2005 03:54 pm, Scott Gravenhorst wrote:
> "Roy J. Tellason" <rtellason at blazenet.net> wrote:
> >On Saturday 05 February 2005 02:05 pm, Ian Fritz wrote:
> >> I'm missing something. Could you clarify how you get a pressure output?
> >> It seems to me the piezos just put out a pulse. In fact, it's impossible
> >> to get a dc voltage from a piezoelectric transducer, since they are
> >> capacitive.
> >
> >Eh?  A piezoelectric material is defined as one where,  when you apply a
> >mechanical force you get a voltage,  and vice versa.  Same principle
> > that's used in crystal-controlled oscillators,  too.
> >
> >They may be "capacitive" in the electronic sense,  but that doesn't change
> > the principle of operation...
>
> As far as I understand it, the electrical discharge occurs only while the
> force applied is actively changing.  Once it stops changing, so does the
> current.  Is that correct?

Dunno about "current",  they put out a voltage...

Good question,  though.  I'm not real sure about the answer to it,  but it's a 
good question.  :-)