Multiple steppers question

Hi all, I have a few queries regarding driving multiple stepper motors (11 of them) with individual pololu a4988 drivers and an arduino mega. Excuse my ignorance as I am novice in this area.

1/ My stepper motors are far enough apart that the wires out of them would not all run to a single point where the drivers would be. What cabling should I use to extend the stepper motor wiring? The run length would be about 40cm (total). Should I use shielded twisted pair cabling (as I have seen suggested in another thread)?

2/ Would the 5V supply from the arduino be sufficient for the logic power supply for all the stepper drivers? If not, how is it best to provide the 5V logic power supply whilst keeping the ground separate from the motor supply? (I have read that the two should be kept separate to avoid ?interference?)

Kind regards.

  1. Yes. That sounds possible. Twisted is OK - it doesn't need any extra shield beyond that. Clamp a long pair of wires in a vise and a drill and run the drill until the twist looks right. Then cut that up to use for your motor wires.

  2. Probably not. Measure the current that one requires and multiply by the number of controllers. Get a 5V power supply from Polou which will deliver this current, plus extra.

  1. Make sure you are only providing Arduino 5V to the logic supply of the drivers, not the motor supply, then its fine - its a logic supply running from another logic supply... You can measure the logic supply current to the A4988 or look it up in the datasheet to check the total load on your 5V bus.

The motor supply wiring should be entirely separate from the logic supply - common the grounds only at each driver board, there will be significant voltage drop on the motor supply wiring (make sure to use thicker wires to keep this under control). Never run motor supply or motor leads alongside logic or sensor cables, that's a recipe for heavy interference. The motor supply will be 12V or 24V, or similar, not 5V. At the very least motor wiring to a bipolar stepper will be two twisted pairs, one for each winding. Normally these pairs are then twisted together in the opposite direction to keep things tidy.

The point about twisted pair is that the induced interference (magnetic radiation) cancels out well over each turn - shielding works better at high frequencies and for capacitive coupling, shielded twisted pair is the best of both.