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From: wli@fornax.UUCP (William Li)
Newsgroups: sci.electronics,comp.robotics
Subject: Re: Pressure sensitive plastic
Message-ID: <2525@fornax.UUCP>
Date: 18 Apr 91 05:25:27 GMT
References: <14978@life.ai.mit.edu>
Organization: School of Computing Science, SFU, Burnaby, B.C. Canada
Lines: 29

In article <14978@life.ai.mit.edu>, bellutta@ai.mit.edu (Paolo Bellutta) writes:
> I need to find the makers of those pressure sensitive sandwiches which are
> used for example in drum machines. This sandwich should have a layer of
> semiconductive plastic on a conductive layer and between them is a plastic
> insulator, then when pressure is applied, it is possible to measure the
> position, and possibly the applied pressure. The use would be as a person
> counter, under a carpet. Do any one of you know of such kind of product?

Offhand, I can think of a couple of different products.  One is Kynar's
piezoelectric film, based on TPFE.  Kynar is based out of Pennsylvania
in the U.S.  Unfortunately, I've lost their address (sorry!).
Interlink (Montecito California, (805) 684-2100) is based around a
pressure-sensitive resistor product.  By putting intermeshing
silver fingers on top of a sheet of the pressure-sensitive resistor,
one can get linear position.  Two crossed linear potentiometers,
as they're called, give an "XYZ pad".

The question, though, is how big of an area you want to rig up.
Interlink's stock product XYZ pads hover around 4"x4".  How much sensitivity
do you need in your positions?  You might be able to get away with
rigging up a regularly-spaced grid of strain gauges (I believe Omega
makes a line of strain gauges).

- William Li
School of Engineering Science
Simon Fraser University
Burnaby BC  Canada V5A 1S6
Tel: (604) 291-4451
Fax: (604) 291-4951