Path: utzoo!utgpu!water!watmath!clyde!att-cb!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!mit-eddie!uw-beaver!cornell!rochester!ritcv!ritcsh!sic
From: sic@ritcsh.UUCP (Eric A. Neulight)
Newsgroups: sci.electronics
Subject: Re: Pressure sensing
Keywords: transducer, pressure, sensor, circuit
Message-ID: <1740@ritcsh.UUCP>
Date: 16 Apr 88 06:35:39 GMT
References: <1368@PT.CS.CMU.EDU>
Reply-To: sic@ritcsh.UUCP (Eric A. Neulight)
Organization: Computer Science House @ RIT, Rochester, NY
Lines: 21

In article <1368@PT.CS.CMU.EDU> pedmond@A.GP.CS.CMU.EDU (Patrick Edmond) writes:
>I want to build a circuit that senses the pressure someone's foot is exerting 
>on a surface, without using springs, rheostats etc, because it has to be small
>& simple. Is there such a thing as a small (e.g. < 0.5" tall) transducer or
>some such component whose resistance/capacitance/whatever varies with the
>pressure exerted on it? (The weight would range, I guess, from 0 up to ~ 200
>pounds).

   About two years ago I helped my little brother assemble a Heathkit
digital bathroom scale.  It sounds like what you want is a simple scale.
The transducer they used was a relatively long, thin (5"x1/4"x1/4"??)
metalic strain gauge with a few leads coming off the tail.  I suppose it
was piezo-electric or capacitive (redundant?).  You would most likely
need to situate a hefty platform centered on the end of the gauge
just like the scale.  How big an area does the sensor you have in mind
have to cover?
   If you call Heathkit I'm sure you could order the part.  Check out
their catalog.

   I wish I had the old schematics to talk more intelligently.
Alas, I am 300 miles away.

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CLAIMER:  Well -- I wrote it!                      Eric Alan Neulight
                                                 Electrical Engineering
"INSANITY is just a state of mine."              Computer Science House
                                            Rochester Institute of Technology
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