Another idea for a piece-tracking chess board Answered
RFID-based chess boards have their merits of course, but would be pretty expensive and could potentially suffer from antenna cross-talk. Furthermore, the relatively immense amount of information carried compared to what's required makes RFID sort of overkill. Reed switches have the opposite problem, only carrying a single bit of information per square (piece present y/n). It seems that what you want is something in-between (six kinds of pieces, two colors, so you only need four bits of entropy per square/piece).
My idea is the following:
- Each square is a circuit containing a signal generator connected to four bandpass filters at frequencies f1,f2,f3,f4 (multiplexed of course, so that we only need a few signal generators/filters)
- Each piece has a RLC circuit in the foot (with fairly large inductance)
- The circuit in each piece is tuned to resonate at frequency f1, f2, f3 or f4, or any combination of the four
- To poll a square for information, we mux to the square's circuit and generate sin(f1) + sin(f2) + sin(f3) + sin(f4). Now we should be able to discern which piece is on the square based on the frequency response observed at the output of the bandpass filters
If I'm not completely missing something, the resulting PCB should be comparatively cheap to construct. But I'd love to hear if this is a less elegant solution than I think. Are there any problems with this idea?