In an effort to free up some pins on my Uno, I’ve come up with a multiplexing schematic for the three stepper motors. This hopefully allows me to free up 5 pins, drive all three motors from one ULN2004a, and drop one of the control IC’s. The idea is to drive all three motors with the same ULN2004a outputs, but control via NPN transistors which of the motors motor actually have 5v provided in order to actually obey those outputs. I understand that the trade off is that I’d be only able to control one motor at a time, which if acceptable for this project.
I’d like some input if what I’ve built drawn out is practical before I start pulling apart my breadboard and re-writing code.
Two drawings attached - before and after the multiplexing.