I wanted to post a quick update about the chessboard. I have tested using several Hall sensors simultaneously using a multiplexer (MUX). The multiplexing chip I chose allows for the controlling of 16 sensors while using only 7 pins on the Arduino. Since there are 64 squares on a chessboard, I will need 4 MUX chips. Adding additional chips only requires 5 additional pins per MUX, bringing the grand total to 22 pins, 20 of which needs to need to be I/O. This is approaching the number of pins on my Arduino UNO and I still have to drive three motors to move the chess pieces. I have two simple options at this point, buy an Arduino Mega, which has a near infinite number of pins (54 digital I/O and 16 analog inputs) compared to the UNO (14 I/O, 6 analog), or I can use a fifth MUX to offload some of the pins. Thankfully, the MUX chips I bought are I/O and therefore will allow me to switch through the 16 pins on each of the other 4 chips. Since I already have 5 MUX chips and I don't want to spend the $60 on the Mega, I'll give this a try first. I might try offloading the sensor work to the Raspberry Pi and use the Arduino for only motor control in the end. I haven't tried using sensors with the Pi yet so I don't know how well that will work. Anyway, I made a little video where I'm driving four Hall sensors with the Arduino through a MUX. Everything seems to be working fine. I didn't do all 16 because it would have been a wiring mess on the tiny breadboard and the sensors would be close enough to for multiple to be tripped a once when the magnet is near by. On the chessboard, they will be far enough to avoid magnetic bleeding (a term that might not describe what I mean, but I like it enough to keep it) away and there will be more space to wire everything correctly. The next step is to start wiring together the sensor array, which I will work on this weekend.
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