I am exploring the idea of using touch screen and controller to operate a number of input relays. The process will be regularly powered down so I am considering DTDP bistable relays, therefore I will need two output pins per relay; i.e. one pin to switch and another to reset each relay. Assuming I use this type of relay I would need a minimum of 4 relays (8 switching pins) with future developments potentially needing 18 (or ultimately 32) pins. I have seen people switching 16 relays but without a screen connected. Is my kind of application possible with an Arduino, is there a better solution?
At this stage I have two problems, the first being that I have no experience to draw from and am thinking I need to get a board to experiment with (possibly a mega 2560). Unfortunately this brings me to the second problem, being which model should I get? The board selection issue is simply that I don’t know how many pins are available once a touch screen is connected. I have seen some “intelligent” screens that can connect via 4 wires (+5V, TX, RX, GND) e.g. https://www.youtube.com/watch?v=D-zgtylBKUc https://nextion.itead.cc/index.html#home Then there are the normal style of board to screen connectors that appear to use a significant number of a boards IO pins.
I know I am not the first to think about using an Arduino as a switching controller, and I doubt I am the first to want to use the board with a large number of output/switching pins in conjunction with a touch screen, but I don’t know the limits and am unsure how to attempt/investigate this. Any thoughts and/or ideas are appreciated and questions are welcome.