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'[OT:] Chessboard (sensor)'
2004\03\08@184948 by Diego Sierra

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Hi!

I am looking for a (wireless) sensor to be located on each of the chess
pieces in order for a program to know which piece is on any square of a
chessboard.

I do not want a mechanical sensor. I thought on a sort of radio emitter
but it has the problem of the small surface of the squares on a
chessboard. Also there should be a lot of different signals, at least
one for each type of piece of each color.

The chessboards that do know about the pieces on top of them need a
starting position to be typed in some manner, then the program just
remember the movements and knows any time where the pieces are. I would
like not to type that starting position and also the program to be able
to detects if the player is cheating.

Any better idea?, any already made chessboard with this features?

Thanks,
Diego.

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2004\03\08@191303 by M. Adam Davis

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I'd consider RFID.  You can use a simple, low power RFID reader with a
coil under each square.  A switching array can connect any coil to the
reader and read that position.  Lower the output enough so that the only
tag excited enough to respond is directly on the coil being used.

Alternately use a hall effect sensor under each square to detect if a
piece is occupying that square, and a magnet in each piece.  Then put
the entire board on a scale and weigh all the pieces.  Add or remove
weigh from various pieces so erach piece has a distinct weight.

Whenever a hall effect sensor detects a piece removed or added, weigh
the board and compare to the last weighing. Should be able to track
pieces fairly effectively and cheaply.  You'll have to account for the
weight of a hand by waiting until it settles to normal level.

-Adam

Diego Sierra wrote:

{Quote hidden}

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2004\03\08@193000 by Jinx

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> Any better idea?, any already made chessboard with this features?

http://innovexpo.itee.uq.edu.au/2001/projects/s369402/

Now, this might seem to require starting positions. It doesn't say
whether the detection process is refined enough to identify pieces
or whether it simply detects lifting and placing and can therefore
figure out what was moved from where to where. What would it do
for example if you lifted two pieces at once or knocked one over
with another ?

rfID could be one solution, or some sort of bar-code scanning using
IR (assuming the board was made with IR-transparent plastic). Or
maybe a magnet inside each piece, a different value or distance-
from-base for each type, that could be detected with a Hall sensor
under the square. Perhaps even a lump of metal or coil that coupled
with and altered the frequency of an oscillator

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2004\03\08@194451 by 0xDEADBEEF

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Make two small conductive contactplate in two corners of each square and put a
resistor in each figure (with 32 different values, for the 32 differen chess
igures), then measure the resistance at each square to determine what figure
stands on a given square.
You can use square bases for the figures and put conductive plates in each
corner of a field square, this way it doesn't mind if somebody rotates his
figure (This has another advantage, you can use chess figures that already
exist and glue them to your square base, this way you can save the effort of
shaping the figures yourself!).

MfG,

Do.Pe.


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2004\03\08@194907 by Jonathan Johnson

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tag fix

-----Original Message-----
From: pic microcontroller discussion list
[spam_OUTPICLISTTakeThisOuTspamMITVMA.MIT.EDU]On Behalf Of Jonathan Johnson
Sent: Tuesday, 9 March 2004 11:55 AM
To: .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
Subject: Re: ] Chessboard (sensor)


can you make each square IR transparent? then include an ir port under each
one with an ir transceiver in each piece, add a 1wire address part and away
you go. you can then identify each part and where it is on the board. you
will need to connect your board side ir transceivers in a matrix fashion to
getyour location reference, other than this method rfid would work very well
too provided you could contain your read field.

Cheers

JJ

-----Original Message-----
From: pic microcontroller discussion list
[PICLISTspamKILLspamMITVMA.MIT.EDU]On Behalf Of Diego Sierra
Sent: Tuesday, 9 March 2004 10:49 AM
To: .....PICLISTKILLspamspam.....MITVMA.MIT.EDU
Subject: [OT:] Chessboard (sensor)


Hi!

I am looking for a (wireless) sensor to be located on each of the chess
pieces in order for a program to know which piece is on any square of a
chessboard.

I do not want a mechanical sensor. I thought on a sort of radio emitter
but it has the problem of the small surface of the squares on a
chessboard. Also there should be a lot of different signals, at least
one for each type of piece of each color.

The chessboards that do know about the pieces on top of them need a
starting position to be typed in some manner, then the program just
remember the movements and knows any time where the pieces are. I would
like not to type that starting position and also the program to be able
to detects if the player is cheating.

Any better idea?, any already made chessboard with this features?

Thanks,
Diego.

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2004\03\08@235056 by THE NELSONS

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So how would you handle the confusion of capturing apiece. For example
you move a white bishop across the board to capture a black rook.  You
remove the
black rook and set the white bishop in its place.

Being a chess players and computer nut for years an engineering friend
and I thought this out back in the days of the Commodore PET. For it to
go beyond having
entering the data manually. you would have to as a minimum have 12
unique peices identified. for the white side: pawn, rook, knight,
bishop, queen & king. and the
same for black side.  We did some experiments with the resister idea but
had some problems with the resistance of the conection.

What about these micro ID chips they  inject into dogs and other pets to
ID them?

Bob


Jonathan Johnson wrote:

>tag fix
>
>{Original Message removed}

2004\03\09@001914 by 0xDEADBEEF

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Am Dienstag, 9. März 2004 05:46 schrieben Sie:
> So how would you handle the confusion of capturing apiece. For example
> you move a white bishop across the board to capture a black rook.  You
> remove the
> black rook and set the white bishop in its place.
>
> Being a chess players and computer nut for years an engineering friend
> and I thought this out back in the days of the Commodore PET. For it to
> go beyond having
> entering the data manually. you would have to as a minimum have 12
> unique peices identified. for the white side: pawn, rook, knight,
> bishop, queen & king. and the
> same for black side.  We did some experiments with the resister idea but
> had some problems with the resistance of the conection.

Well it's still the easiest and cheapest solution!!! If you choose the resistance of each resistor the way that even with small mistakes in the connection resistance the controller could still detect it reliable!
I think about building a potential divider with the chess figures as a par of it. The controler then detects the potentials and dicides what figure is on the scanned field (therefore the potential must be within a given range, that could surely be achieved even with these connection resistance problems!)

>
> What about these micro ID chips they  inject into dogs and other pets to
> ID them?
>

This might be the most elegant solution, but the most expensive, too.

> Bob
>


MfG,

Do.Pe.

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2004\03\09@031642 by Robert Rolf

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0xDEADBEEF wrote:
{Quote hidden}

What Jinx suggested, a resonant coil under each square
whose frequency is changed by the loading of the piece, is elegant and inexpensive. If you used RFID you'd have the coils
and multiplexer anyway.

You could drill the bases of existing pieces and insert a
varying length of iron rod to get N discrete frequencies
corresponding to the type of piece. Or possibly various types
of metals in a couple of thicknesses. Their eddy current
decay profiles are all different (hence metal detectors
that can discriminate between brass and iron).

And the idea of using hall effect and having different
field strengths for the pieces is also cheap and simple.
Black would be one polarity. White the other.
This avoids the problem of contact resistance and oxidation.

One could also use an IR transparent base and a reflective
patch with discrete reflectances (not bar code although
a varying duty cycle grid (halftone) would give you something that
is easy to print).

What I don't understand is why you need to know the 'starting
position'. I thought all chess games start with the pieces
in the same position, so all you need to detect is which
squares have activity, assuming that the humans know the movement rules for the pieces.

Do let us know what you discover works best.
My bet is hall effect with enough variance in the magnet strengths that position error is within the
12 quantizing levels you'd need. Or IR.

Robert

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2004\03\09@080802 by Jonathan Johnson

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you give the dog a bloody good whack! (and a laxative if your game enough:-)
or find a way to trace the 'presence' of each piece and not just
disappearing and then reappearing. or another option may be to have a timer,
if a piece doesn't reappear after a preset time expires then presume it a
has been taken(with an extra long timer for the dog incident).

hmmm, reminds me of a scene from gone in 60 seconds......ewwww.

JJ

{Original Message removed}

2004\03\09@081839 by Jonathan Johnson

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some of the initially simpler methods still have a downside,labour.
the inductance method sounds really nice but it would require a fair bit of
calibration.
the resistance idea would require quite a bit less calibration but the you
need to worry about making proper contact, this applies with any contact
method.
RFID would be pretty effective I think but it presents a major problem in
reliably containing the scan field (try holding your wallet up to a prox
card reader with your card buried under 26 layers of cards and other crap
etc, most often it will still work. it penetrates pretty damn well, which,
in its normal situation is perfect.

Which leaves us with a lot of creative methods of contact id or IR.

Has anyone actually tried shielding the RFID stuff? or directing the field
possibly?
I'd be interested to know how effective it could be done in a 'low cost'
manner.

Cheers,

JJ

{Original Message removed}

2004\03\09@101817 by Bob Ammerman

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Perhaps make each square out of bulk resistive material with electrodes on
two edges.

Place a circle of conductive material on the bottom of each piece.

The size of the circle will determine the effect that piece will have on the
measured resistance of the square when the piece is placed on it.

Orientation of the pieces on the squares will not matter because you are
using a circular shaped conductor.

You would need to be able to discriminate 12 different sizes of circles.


Bob Ammerman
RAm Systems


{Original Message removed}

2004\03\09@120225 by 0xDEADBEEF

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>
> Has anyone actually tried shielding the RFID stuff? or directing the field
> possibly?

Shielding is easily done with a grounded metal plate. There are two methods of
directing the field. First you could use an electromagnetic mirror (like a
sattelite dish, but smaller in this case) to concentrate the field in one
point. The second method is more complex and deals with electromagnetic
lenses. The second method is based on the fact, that you can influence the
direction of an EM field with the help of another EM (or only E or only M)
field.

MfG,

Do.Pe.

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2004\03\09@121517 by Howard Winter

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On Wed, 10 Mar 2004 00:27:31 +1100, Jonathan Johnson
wrote:

> RFID would be pretty effective I think but it presents
a major problem in reliably containing the scan field
(try holding your wallet up to a prox card reader with
your card buried under 26 layers of cards and other crap
etc, most often it will still work. it penetrates pretty
damn well, which, in its normal situation is perfect.

That's because it's designed like that - it has an
effective field about 6" to 12" in diameter to make it
easier and more reliable to use for door-opening.  If
you built something yourself you'd use much less power
and much smaller coils to pick up the signal, limiting
it to, say 1" diameter or less.  The RFID device really
has to be "inside" the reader's coil to pick up its
activation power, so there shouldn't be much problem
with cross-reading, especially if you activate the
"scan" one square at a time.

Cheers,

Howard Winter
St.Albans, England

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2004\03\09@142953 by Mike Hord

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>Has anyone actually tried shielding the RFID stuff? or directing the field
>possibly?
>I'd be interested to know how effective it could be done in a 'low cost'
>manner.

Look in last month's Circuit Cellar.  There's an article about low cost RFID
implementation.  You wouldn't necessarily need to shield it, just use
REALLY low power, with only a few windings, and poll the squares one
at a time.  Orientation in low power RFID becomes very important: I
have an RFID door key which will open the lock if it is parallel to the
wall,
but I can touch the pad with no effect holding it perpendicular to the
wall.  Short answer, I would be thinking RFID, since the RFID interface
can be an 8-pin PIC, 6 inches of wire, two caps, one inductor and a NPN
transistor, and that's if you get kind of fancy.  Again, see the Circuit
Cellar article about cheap RFID.  Very informative.

Mike H.

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2004\03\09@160959 by Diego Sierra

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Hi!

Thank you all your this nice thread and ideas.

If I end up with something I will tell you, even if it doesn't work :-)

Cheers,
Diego.

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2004\03\09@161332 by Peter L. Peres

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An easy way is to use reed relays or hall sensors in each square (and
small magnets in each piece). You tell the players they need to place the
pieces in the standard start position and then move them *one by one* (as
in normal play). When striking a piece both can be moved simultaneously.
The computer can trace all the pieces from the moment they are placed in
the standard position. Even if the player cheats and places f.ex. a third
bishop where a pawn should be initially, the computer will refer to this
piece as a pawn by position, and make cheating impossible. If the player
lifts two pieces off the board, and both are put back (no matter where)
then he cheats. If a game position is set up then pieces will be moved
from the standard position to the setup positions (one by one) or taken
off the board (one by one). Any attempt to move two pieces at once and put
them back will be flagged as a cheat.

This corresponds to playing rules and you can set up any position just as
long as you start with all the pieces in standard positions, and then move
them one by one only. The setup in standard positions is customary anyway,
if for nothing else, then to ascertain that all the pieces made it in the
storage box, and that none are lost.

Peter

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2004\03\10@221541 by M. Adam Davis

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Another RF method that might be a bit simpler to realize is to do what
most graphic pad input devices do.  One long coil for each row, and
another long coil below for each column.

Excite the row, and the columns will respond according to the pieces on
them.

The graphics pads have overlapping coils, and sense the pen/mouse (coil
and capacitors with switches to change the resonant frequency of the
coil on button presses) in several coils at varying strengths.  The pen
can be found with somewhere around 1000dpi for some designs.

The chessboard would be much simpler.

But if you want a conceptually easy design, which may be expensive/labor
intensive, then color the bottom of each piece according to three color
shading.  Each color needs 3 levels of shading.  Mix them together to
get one solid color.  Then use a CMOS camera underneath for nearly
trivial detection.  Could even be done with a TV camera and a PIC (with
an composite to RGB decoder).  Need to provide good even lighting, and
take into account dark squares.  Use glass, for instance.

Make sure the colors have a good black border around the base of the
device and you can fairly easily find which squares are occupied and
which can be ignored (which will help with falsely detecting hands,
overhead lighting, etc).  Use oblique lighting so the reflection of the
glass does not affect the camera.

To make it uber cool, use infrared paints (12 levels, or give each piece
two spots of color and 4 levels each), infrared undertable lighting, and
use infrared transparent black paint to mark the black squares.  Use an
infrared filter on the camera (which, at this point, can be monochrome)
to avoid some external light.  If you're using a computer, take a number
of shots without the internal light on, then several with the light on.
Average the two sets and subtract one from teh other to get a fairly
decent picture without external lighting interference.  Alternate the
shots to get a better average.

Do proof of concept with color and visible spectrum first (webcam,
paints, and visual basic), then search out the not so common infrared
materials (paints, etc) which you'd need to do the infrared version.

Good luck!

-Adam

Diego Sierra wrote:

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2004\03\11@090053 by THE NELSONS

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Mike Harrison wrote:

{Quote hidden}

A camera under the board requires a special table or stand with some
depth, the special transparent board and the bottom of each piece to be
marked in some way.

bob

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2004\03\11@190253 by Diego Sierra

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Alexander Rice wrote:

> If we have a ring devided into sectors, we can detect the number of 1's,
> and we can also detect some patterns eg, alternating sectors. My my

Alex, nice approach, have to read it twice although ;-)

Cheers,
Diego.

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2004\03\11@212425 by Alexander Rice

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On Fri, 12 Mar 2004 00:02:43 +0000, Diego Sierra <RemoveMEdsierraTakeThisOuTspamTELEFONICA.NET>
wrote:

> Alexander Rice wrote:
>
>> If we have a ring devided into sectors, we can detect the number of 1's,
>> and we can also detect some patterns eg, alternating sectors. My my
>
> Alex, nice approach, have to read it twice although ;-)
>
> Cheers,
> Diego.
>

Sorry, it was getting late and i had an essay to write so i just hit send
: we poor engineering student have to work sometime ;-)

regards

alex

ps - whoever tries this should probably knock toegether a little program
to search for other possible abiguous situations.

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