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'[OT] PIC to Pressure Mats'
1999\06\15@183811 by James Cameron

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Summary: looking for cheap sensor mats or alternatives.

There's this team motivational game played on a canvas mat, marked with
squares, six foot by nine foot, each square a foot wide.  The
facilitator holds a beeper and a secret paper map, and makes the beeper
go when a player stands on a square that is marked on the map as bad.

I want to see if I can improve it by adding a bit of automation.

I'd thought of mass/pressure sensitive mats as used for shop doors.  The
only source I've found locally is for a door size, with no indication as
to whether I can cut it up and still make it work.  Do any of you know
sources of such mats?

I'd thought of a set of column and row lasers, but they would require
alignment every time.  I'd thought of the player carrying a metal target
strapped to the shoes and somehow using inductive sensing in the mat,
but I'm afraid I'm a bit clueless on that.  Any ideas?

The area is a touch small for using differential GPS, but can one do
something similar with low power UHF?

The mat has to be reasonably portable and robust, as it is carried to
training classes by the facilitator.

Interface to the PIC will be by a matrix.  Due to the nature of the game
rules; (a) only one person on the mat at any time, (b) must move to
square immediately next to current square (chess: king move), (c) must
enter or leave the mat by the top or bottom edge; the matrix can be
multiplied into six instances of three by three, thus utilising only six
lines on the PIC.

The rest of the game simulation intelligence would be on a laptop
interfaced by serial port to the PIC.  The PIC would be the data
gatherer.

--
James Cameron                                      (spam_OUTquozlTakeThisOuTspamus.netrek.org)

Linux, Firewalls, OpenVMS, Software Engineering, CGI, HTTP, X, C, FORTH,
COBOL, BASIC, DCL, csh, bash, ksh, sh, Electronics, Microcontrollers,
Disability Engineering, Netrek, Bicycles, Pedant, Farming, Home Control,
Remote Area Power, Greek Scholar, Tenor Vocalist, Church Sound, Husband.

"Specialisation is for insects." -- Robert Heinlein.

1999\06\15@185856 by l.allen

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{Quote hidden}

Check out Piezo Co-Polymer sensors or "Kynar" made by AMP.
They come in a wide variety of shapes but most start out in sheet
form, looks and feels like mylar film with printed electrodes on it.
Those silly shoes that flash a led whenever one takes a step uses
these sensors, as does Gottlieb PinBall Machines to sense a contact,
good for millions of operations and fairly cheap.
The only limitation is that they are piezo electric and as such look
like a capacitor in series with a battery, they only sense a change,
cant see that as too much of a problem though.
We have used these sensors to make Hydrophones (in cylindrical form)
and impact sensors. A 2 cm deviation can generate 100 volts in these
sensors... very sensitive.

Lance

1999\06\15@191144 by Des Bromilow

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Talk to an Alarm supply store. There is a "Intrusion mat" which you can by for use in burglar alarms, which measures approx 40cm by 60 cm  This would be more up your alley, OR>>>>>
make it yourself.
To make it yourself, you will need plywood (2 squares) with locating holes drilled in each corner.
then drill several holes through out the ply so it resembles "peg board". then weave a light guage wire through these holes to make up a grid on ONE side of the plywood sheet. (repeat for other sheet)
Then using small "squares" of foam rubber (or styrofoam) build a "sandwich" of ply - foam - ply with the wire grids facing each other. then use "reopenable" cable ties in each "locator hole" to ensure the boards can't shift around and you have a pressure switch mat which will be about 20mm (3/4") thick.
The reasoning of why I specified "reopenable cable ties" is so you can easily open the switch to replace the little foam squares once they wear down and stop acting as springs.

For an "asthetically pleasing appearance" I'd then make up a small "zip up" cover for the switch (viz a cushion cover) so the ply is covered.

Does this help?
Des Bromilow


>>> James Cameron <quozlspamKILLspamUS.NETREK.ORG> 6/16/99 8:24:03 am >>>
Summary: looking for cheap sensor mats or alternatives.

There's this team motivational game played on a canvas mat, marked with
squares, six foot by nine foot, each square a foot wide.  The
facilitator holds a beeper and a secret paper map, and makes the beeper
go when a player stands on a square that is marked on the map as bad.

I want to see if I can improve it by adding a bit of automation.

I'd thought of mass/pressure sensitive mats as used for shop doors.  The
only source I've found locally is for a door size, with no indication as
to whether I can cut it up and still make it work.  Do any of you know
sources of such mats?

I'd thought of a set of column and row lasers, but they would require
alignment every time.  I'd thought of the player carrying a metal target
strapped to the shoes and somehow using inductive sensing in the mat,
but I'm afraid I'm a bit clueless on that.  Any ideas?

The area is a touch small for using differential GPS, but can one do
something similar with low power UHF?

The mat has to be reasonably portable and robust, as it is carried to
training classes by the facilitator.

Interface to the PIC will be by a matrix.  Due to the nature of the game
rules; (a) only one person on the mat at any time, (b) must move to
square immediately next to current square (chess: king move), (c) must
enter or leave the mat by the top or bottom edge; the matrix can be
multiplied into six instances of three by three, thus utilising only six
lines on the PIC.

The rest of the game simulation intelligence would be on a laptop
interfaced by serial port to the PIC.  The PIC would be the data
gatherer.

--
James Cameron                                      (.....quozlKILLspamspam.....us.netrek.org)

Linux, Firewalls, OpenVMS, Software Engineering, CGI, HTTP, X, C, FORTH,
COBOL, BASIC, DCL, csh, bash, ksh, sh, Electronics, Microcontrollers,
Disability Engineering, Netrek, Bicycles, Pedant, Farming, Home Control,
Remote Area Power, Greek Scholar, Tenor Vocalist, Church Sound, Husband.

"Specialisation is for insects." -- Robert Heinlein.

1999\06\15@210422 by William Chops Westfield

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>> To make it yourself, [horrific sounding construction details]

I think you'd be better off finding a bunch of the conductive foam that IC
chips are stuck in for shipping samples, or some of the conductive work mats
or floor tiles designed for antistatic environments.  They ought to change
resistance depending on how much weight is on them...  Not particularly
CHEAP, IIRC, but likely to hold up much better.

BillW

1999\06\15@214554 by Eric Oliver
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Check out http://www.qprox.com.  They sell one chip proximity sensors.  You might
be able to embed a sensor wire in the square and detect when someone steps
in it.

Eric

{Quote hidden}

1999\06\15@223039 by Mark Willis

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Possibly, you could try their QT60320 Matrix Scanning IC, this sounds
maybe IDEAL for that job.  (See http://interquant.com/qt60320ic.htm) I
don't have a .PDF file yet - they're nice folks from my talking to them
so far, and their circuit looks decent.  Also look at the QT9701 (Ask
them - they know their line well, Technical Sales folks not salespeople
from what I gather <G>)  Their QT110 might do it ($1.95 ea in quantity),
I have samples but need to get around to 'em still.  (Looking forward to
that!)

 Tons of other ways to do this, of course - If it works, it's good <G>

 Mark

Eric Oliver wrote:
{Quote hidden}

1999\06\15@224315 by Eric Oliver

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Jameco all sells a flex sensor. It doesn't say how long it is, but it might coul
d be placed diagonally in the square.


On Tuesday, June 15, 1999 8:03 PM, William Chops Westfield [SMTP:RemoveMEbillwTakeThisOuTspamCISCO.COM
] wrote:
{Quote hidden}

1999\06\16@093426 by paulb

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James Cameron wrote:

> Summary: looking for cheap sensor mats or alternatives.

> and makes the beeper go when a player stands on a square that is
> marked on the map as bad.

 I'd go for the proximity sensors.  The Qprox or similar ones sound
fine, but you have to get them (here!).  I very much suspect (am banking
on it in fact) that a PIC will do this very well, and I'd look at using
one PIC at the intersection of each four squares (shortest connections -
they are a problem, if shielded, extra capacitance, if not, spurious
tripping).

 Sensors would be foil, probably under a plastic sheet to protect the
connections as much as for electrical isolation.  Protection resistors
maybe 10 k ohm with diodes to supply rails etc.  Another challenge in
PCB protection.
--
 Cheers,
       Paul B.

1999\06\22@143216 by Alice Campbell

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Hello james,

> Summary: looking for cheap sensor mats or alternatives.

A while ago there was a reference to MITs wearable computers page.
One picture was a keypad embroidered to a denim jacket.  I checked
with the local fabric store and a local DVM and found a brand of
metallic thread that conducts (you need the meter--some of them dont
conduct, some kind of mylar, i think).  A fabric with a horizontal
metallic stripe, something for a spacer with a hole in it (a nonwoven
fabric like felt) and the ziz-zag foot of a sewing machine would
probably do ya.  if you need a sketch email me.

alice

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