[sdiy] Piezo body sensors?

[harrybissell]

Hiya Michael  (inline)

WeAreAs1 at aol.com wrote:

> Hello guys n' gals,
>
> Since we're talking about piezo sensors, I'll bring this up:   Someone
> has asked me to help him build a triggering system with trigger
> sensors that will be mounted on or in his clothing -- his pants, his
> shirt, etc.  I can't imagine that he's the first to think of doing
> this, so I'm wondering if any of you have experience with this, or
> know someone who has -- or know of any web references on the subject.
>
> I'm assuming that we'll use piezo sensors, unless someone comes up
> with a better idea (unfortunately, FSR's are not readily available to
> DIY'ers).

Actually the FSRs are available as a demo kit (assorted) although it is
NOT cheap
(about $100 US, shipped). It has some decent size pads (2" x 2") and
some
resistive strip sensors... and a bunch of really tiny stuff you can't
work with unless
you want to tap with your fingertips.

Piezos are good.  I use encased piezos... and I glue a weight to the
middle of them
to add mass and lower the resonant frequency way down.  I use a
"wadcutter .177
lead pellet which has a flat nose, and exopy it face down on the brass
disk.  It protrudes
from a thinner case piezo, but is enclosed in a larger one.

Then I add some load resistance across the leads. You might want to
include a diode
to make it more sensitive in one direction, depends on the trigger
input. Usually, no
preamp is needed.

> He wants to play the sensors with his bare hands, which should
> probably work OK with piezos.  It's probably a pretty straightforward
> thing to do, but I would like to see how others might have approached
> mounting the sensors to clothing or to arms and legs, and hear about
> potential problems that we might face.  I was thinking that we might
> hot-glue them onto some thin but stiff sheets of plastic or rubber,
> then sew the sheets into some pockets on the clothing.  Any better
> ideas?

Piezos attached to stiff rubber or plastic will have the resonant
frequency increased
(and damped). Might be OK with a stick, but you'd beat yourself silly
with your hands
(which might be entertaining as well...)

I'd try what I mentioned, and put them in pockets like you said. Maybe
you could
mount them in thin plastic boxes to give mechanical protection.

> These sensors will most likely be wired up to the electronics from a
> Roland SPD-S sampling drum pad unit, which has inputs for up to 11
> trigger sensors.  It will be part of a very interesting and fun
> portable electronic performance rig that's mounted onto a, umm, one of
> those, umm... well, one of these:
> http://urbanscooters.com/cgi-bin/urbanscooters/QELECCHA.html

have yet to look, bet its wild :^P

H^) harry