[sdiy] touchplate keyboard - works!

[Ian Fritz]

At 01:54 PM 2/5/2005, 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?

Yes, that is correct.