I'm building a 5-phase stepper motor driver with 5 of these half-bridge circuits, one for each stepper motor coil:
I'm using TIP111 darlington for the NPN and TIP116 darlington for the PNP. I have them hooked up as shown, but I don't know what resistors, if any, that I need to use on the bases of the transistors so that I can hook up my arduino pin and have it work. To be honest I don't understand why I need resistors at all, because it seems like switching both transistors "on" completely would be the goal.
Also, it seems that I will have to drive the base of the PNP tranistor all the way up to 5V in order to turn it off. If I'm running my motor on 5V, that is, if my positive rail is 5V, can I switch this setup with the 5V output of the Arduino satisfactorily? What if I want to run my motor on 12V; is there some way I can make it work?