Jean-Michel
Tapeswitch is exactly what you need.
http://www.tapeswitch.com/
Go to their web site, and look at "ribbon switch"  or "safety mats" in their
products section.  I really think the ribbon switch would work best because
of the weight involved, mats are for heavier items I think.
I called them and they sent me a sample.

Malcolm


----- Original Message -----
From: Jean-Michel Howland <vege@VMAPA.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Sunday, April 01, 2001 8:49 AM
Subject: Re: [EE] Pressure/Mass sensor pad/mats


> >> I need to to measure weight or to be more precise, measure if weight is
>  >> present or not in the rangeo of 0 to 100kgs.  I really need some sort
of
>  >> flexible mat/pad that can be slipped under a cushion.
>  >
>  >
>  >With the intent of keeping it cheap and sensible I
>  >suggest buying a digital bathroom scales, quite common
>  >now, and they have all the hardware needed to measure
>  >weight in that range. You could interface to the PIC
>  >with little hassle.
>  >
>  >"slipping under a cushion" sounds difficult as it is
>  >hard to measure weight unless the person is stationary
>  >and above the sensor. If they are on a lounge or chair
>  >(you said cushion) they may have weight on their feet
>  >or arms.
>  >
>  >I'm sure if you explained more about the exact thing
>  >you want to achieve there would be some helpful answers.
>  >-Roman
>
> OK, good point about explaining more.
>
> Last night I had an accident in my electric wheelchair, I was driving
> around and ended up with my front in stuck in a drain hole, I fell
forward,
> barely able to breathe and was stuck like that for 40 minutes.  I never
> want to go through that again so I need a solution.
>
> I thought of of 2 possible solutions:
>
> #1. Build some sort of pendant to wear around my neck that would contain a
> tilt sensor, RF transmitter and a timer.  However this would be bulky to
> wear because I couldn't build it small enough, battery life would be a
> problem and the range would be very small.  In my opinion this is not
workable.
>
> #2. Slip a pressure transducer under my cushion and one behind my back,
> hook them into a PIC.  If I'm sitting in the chair the unit is activated,
> if I fall forward for more than a minute the PIC timesout and activates
one
> of those 110db alerts which will be heard by the people around my
> house.  The advantage is everything can be mounted on and powered from the
> chair.
>
> The reason I want to find a mat/pad type of sensor is I'm reluctant to
> drill/cut or modify an $8000 chair that I don't own.
>
> Oh and before someone mentions the obvious, a seatbelt, well it's not an
> option. :o)
>
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>

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