[sdiy] touchplate keyboard - works!

[Ian Fritz]

At 07:32 PM 2/5/2005, Scott Stites wrote:

> > 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.


Yes, but Peter's device only has two leads.


>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).


Well, I thought of that, but the description of the part says it puts out a 
pulse, so I assume it is piezoelectric.  Maybe it *is* piezoresistive.  I'm 
still totally baffled by this part.

   Ian