multiple sensors that can read multiple objects

Using Arduino Sensors
#1

I am trying to expand on a simple Hall Effect (Magnetic) sensor idea I had. I would like to have multiple sensors detect multiple objects.

For example, lets say I want to make a puzzle where someone needs to place 3 chess pieces on a chess board.
The Queen on C3
The Bishop on A8
The Rook on D1

I could easily add magnets to the bottom of each piece and then put magnetic sensors below those spots on the board. However, they could change the order of the pieces in the correct spots and it would still trigger.

I thought about NFC tags but I think it would work from anywhere close by.

Anyone have an idea or what might work that can distinguish the different pieces from each other, and still require the pieces to be set on the board in the correct spots?

#2

Color sensor (with LED) and different colors on the bottom of the chess pieces.

#3

pylon:
Color sensor (with LED) and different colors on the bottom of the chess pieces.

Yes, I thought about that and will keep that as a possible solution. I am not to keen on this because I would have to drill holes in the center of each square. was hoping for something that would work with a wooden chess board (classic looking board).

thanks,

#4

mgrosh:
was hoping for something that would work with a wooden chess board (classic looking board).

Near field magnetic communication. A coil under each square and a coil under each chess piece.
For inspiration look at the way wireless phone chargers talk to handsets.

#5

Is it only 3 pieces or the whole set?

For 3 pieces, have one with the north end of the magnet down, two with south down but make one much stronger (super magnet or just two stacked) and put that sensor further away so it is only triggered by the stronger magnet.

#6