Firstly I would like to outline my project for you:
The aim is to make a board game (the game of go/baduk/weiqi) recordable via a computer.
For everyone interested this is the game: Go (game) - Wikipedia
Usually the game is played on a wooden board with 19 by 19 intersecting lines. The black and white playing stones are placed on the intersection of the lines. Each turn exactly one stone is placed. Stones can under certain circumstances be removed from the board (captured).
My idea is to use sensors to detect whether a stone has been placed on an intersection. Due to the size of the board, using a sensor for each intersection results in 361 sensors. Having the cost of the whole thing in mind I was thinking about using LDRs for the purpose of detection.
The next thought that came to my mind was that 361 sensors is a lot of input to handle even for an arduino mega with 54 digital I/O pins and 16 analog pins.
Continuing this trail of thought, my next take was to use multiplexers for this. For example the CD74HC4067 http://www.ti.com/lit/ds/symlink/cd74hc4067.pdf.
Hooking up every single ADC pin of the arduino to one of these however only gives 16*16 = 256 inputs. The thought here was to cascade the multiplexers, so that after adding a second layer of 7 multiplexers there are exactly 361 available inputs.
As the selection pins of every layer can be connected and the channel to choose can be controlled using the EN pins of each multiplexer the digital I/O pins of the mega should be sufficient.
However I am pretty inexperienced in designing and building circuits in general and here come my questions:
1.) Could such a design in principle work?
2.) I am very unsure about things like the voltage supply and whether the cascading multiplexers maybe add too much resistance as to effectively read the LDRs. I have a hunch that there is a lot here, which I cannot grasp.
3.) Is the general approach here a useful one? If not could you imagine a better design?
I would be very grateful for any inputs and am more than willing to answer remaining questions.