Chess board and detecting chess pieces.

I am planning out a wedding present for my brother and his fiancé. I was thinking of making a 64 element (8x8) RGB chess board, with a diffused glass top. The LED would change the cell colour based on the chess piece on top of the cell. An example might be that under all the black pieces would be a red glow, and under the white pieces might be a blue glow. I have given thought that I could just have two sets of LEDs and two sets of switches turning on the appropriate colour but it still I would like to have the options that using a microcontroller presents.

I am trying to consider all the ways a person could detect the presence of the chess pieces. My problem is that, while capacitance and IR could be used to show something is on the chess board, it can’t show the colour of the piece (black or white). I am considering Hall Effect sensors using North and South Pole magnets in the base of the chess pieces. I have found several Hall Effect sensors which will produce a voltage depending on magnet polarity but the idea of needing 64 ADC is a bit scary. I know MAXIM makes 16 inputs 12bit ADC with SPI interface but even then I would still need four chips.

I suppose what I am asking here is 1) does anyone have any other ideas for a way to detect which piece is on the glass and 2) does anyone know of a hall effect sensor that detects north and south polarity but expresses it with two separate outputs. I was thinking that might be easier to multiplex digital signals then convert 64 analog signals.

Any ideas?

There is a good write up of a project like this but it is in German. Still the schematics are a universal language:- http://www.andreadrian.de/schach/#Selbstbau_Schachcomputer_SHAH

a hackishly cool soultion would be to put an LED in each piece and power them by wireless power. Then the pieces could even be powered by other sources like door beeper things as a party trick :D

Just to detect the colour you could do something like this:

Put an IR emitting LED under each square. Also a couple of IR detectors. On the black pieces have a white circle underneath, and on the white pieces entirely white (or silver or something).

Then the IR emitter reflects back into both detectors if you have the filled circle underneath, and only into one detector with a "rim" circle. And no piece at all means no reflection.

Another idea: Put a magnet into the bottom of each piece and have a reed switch operate if the piece is close enough.

Another idea: Some sort of RFID detection, where you have a different pattern on the bottom of each piece. Now 64 RFID detectors would be pretty expensive, but maybe the idea could be adapted so that you have one transmitter "powering" them, and small receivers under each square. Maybe, for example, a coil built under each piece which resonates at a slightly different frequency.

Another idea (this one might work!) - build into the bottom of each piece a 1-wire "button". These are specifically sold for this sort of purpose (well, not exactly chess). The DS18B20 temperature sensors are an example of this. Now the bulk of the chess board could be metallic (or partly anyway) which is your ground return. And in the middle of each square is the 1-wire contact. Maybe you need a magnet as well to make good contact. These could be wired into a matrix. Now when a piece is placed down you detect its presence, query the 1-wire device for its serial number, and look up a table to see which piece it is. Then by working out the matrix position you know where the piece is. The 1-wire devices are used, amongst other things, for tracking parcels, where you briefly make contact with the button to see the serial number of it. (Google "1-wire button").