Do you have a URL of this online chess service as you have to connect to it somehow. what protocols are available?Bonus: do you intend to use a chess clock?
In the same way that a keypad senses which button is pressed, you could use 8 pins for the "rows" and 8 pins for the "columns" and quickly scan the row/column values that have a piece on them.
A simple solution for (#4) would be to have a red/green LED in each square. Light up the red one for where the piece should leave, and the green one for where the piece should go to. A fantasy solution for (#4) would be to build a stepper-motor powered miniature gantry crane that would actually grab the piece, lift it, move to the new spot, and lower it. Of course, it would probably count against your time and is impractical for at least that reason.A simple solution for (#5) would be to have a magnet in the bottom of each piece and a reed switch or a hall magnetic sensor in each square. Then you can scan all 8 rows and 8 columns (as PaulS described) to see which piece was picked up and where it went.A fantasy solution for (#5) would be to use one of those schemes that uses a bunch of rods in a big array. By pushing up certain rods to certain heights, you could make a modern abstract representation of each piece. Then by programming, you could represent any piece in any square. You can use translucent plastic rods and colored LEDs underneath to represent pieces of opposing sides.
QuoteHow will you know which chess piece is on each square?The starting lineup is known. Whenever a piece is picked up, you know which one it was by were it was. And if you put it back down, it seems like a safe assumption it is the same piece that was just picked up seconds ago.
How will you know which chess piece is on each square?
Have you seen this project:-http://www.andreadrian.de/schach/#Selbstbau_Schachcomputer_SHAHIt's in German but the circuits are in schematic.
Are 140 resistors good for both the buttons and LEDs?
Input Voltage (recommended) 7-12V
R=V/I , but i'm not sure what values to use in this formula?