[sdiy] touchplate keyboard - works!

[Scott Stites]

> What was explained to me some two years ago from the manufacturer, inside
> these specific switches is a crystal.  the harder you press, the more the
> aluminum face of the button (SLIGHTLY)  deforms,  the more of whatever it
is
> you put through the switch passes out

Absolutely no expert on the subject, but I imagine the term that would
clarify this would be 'piezoresistive'?

I bought some Motorola pressure sensors off of Ebay a while back (I think I
even mentioned them to you once, Ian, in context of using them as breath
controllers) that are piezoresistive and work pretty much like Peter
describes here.  There are four leads to these sensors, one goes to Vcc, one
goes to ground, and two are + and - connections that carry the voltage out,
which in the datasheet examples go to instrumentation amplifiers.  Works
pretty well for a breath controller, though, as usual, I moved on before I
really did a whole lot with them (with the usual thought of 'I'll get back
to that later').  I might add that the output voltage range is pretty small,
too, just as Peter mentioned.

Google for MXP10D and that'll get anyone who interested a datasheet
somewhere.  Can't quite remember which one's I have right now.....

BTW, IIRC, Electronic Goldmine has these things for sale, too.

So, Peter, grab one of these and some rubber hose and add a nice little
Piezo breath controller to your cool touch controller.  Just make sure no
one mistakes it for a hookah =0).

Cheers,
Scott