I've looked all over and can't find a good answer in the forums on this. I feel like I'm going around in circles. (If only my stepper was...)
I have a 4-phase bifilar stepper on my telescope mount, but I don't have a controller and it's no longer available. I would like to use an Uno, and if necessary a Motor Shield, to control the stepper. I think I understand the logic of needing to pass a switching sequence to the windings and I think I can handle that in the code.
I'm having trouble wrapping my head around what electronics, if any, need to go between the Uno or Shield and the stepper winding inputs. Can I wire the transistor bases directly to a digital out pin, or would the voltage be too high? Do i even need the Motor Shield? (I own both the Uno and Motor Shield already.)
The coils on that stepper are rated for 12V and have 100 Ohms resistance. So, the dirt cheap ULN2003 drivers sold with the popular 28BYJ-48 motors will work without modification. Available on line, for example:
If you want to wire up individual NPN transistors, or N-channel logic level MOSFETs, use 180 to 220 Ohm base resistors between the Arduino I/O pin and each transistor base. Inductive kick diodes are required across each coil, as shown below (built in to the ULN2003 driver):
Thank you for the detailed response! I have a couple of questions.
For your first recommendation of using the ULN2003 driver module, would I need anything else in the circuit? Wire Uno digital out to ULN2003 driver module, and wire output of that module directly to the stepper inputs?
Would the Arduino Motor Shield be able accomplish the same thing? Since I already have it, and would save buying something additional. (I may be completely misunderstanding the uses of the Motor Shield.)
