I want to run 2 identical steppers (5V, 0.45A short circuit current, 10.6 ohms motor resistance ) at the same constant speed (via AccelStepper) - can I use 1 EasyDriver board with the same coils from each connected to the same terminals on the board, or do I have to have one for each? I do not need individual control of the steppers.
Hi Ross,
Theoretically, you could so long as you make sure the wire pairs for each motor are securely connected to the Big Easy Driver. That would be the most important point since a loose connection to the motors will quickly damage the Big Easy Driver and usually results in a nice puff of smoke. The Big Easy Driver is rated for 2A/phase so two motors with a 0.45A stall current should work fine. I would recommend setting the current adjustment potentiometer to “0” and then slowly turn it until both motors are running smoothly. After that, leave the potentiometer alone unless you are trying to really dial it in while monitoring the current to each motor.
I hope this helps! Let us know if you have any other questions about the Big Easy Driver and we would be happy to help as much as we can.
Thanks TS-Mark! Appreciate your info. I am a little worried about accidentally disconnecting the motors while it’s running, but I’ll keep a fire extinguisher handy 
As to your comment re: setting the current adj pot to “0”, is that the same as the “MIN” marked on the board? If you mean to measure the output of the pot with a DMM, what contacts do I use?
Hi again Ross,
It’s a little weird to describe but if you splice the wires together with some solder for the two motors, you can then add in a single-wire output for each “pair” to the motor pins on the Big Easy Driver. Soldering screw terminals to those pins also works well to create a solid connection.
You are correct. I just wrote that without referring to the board itself. By “0” I meant the MIN position. Start there and slowly turn it up until you get both motors moving smoothly.
Fantastic, thanks again TS-Mark!
I’ve got 1 motor hooked up to play with constant speed using non-blocking code (i.e. Accelstepper library) and I notice that it doesn’t matter what MS1/MS2 are set to, the stepper always rotates at the same speed - I had thought that with the 1/8 stepping mode [MS1/MS2 connected directly to +5V] it would run differently. Is the Easy Driver set to run at 1/8 by default (i.e. MS1/MS2 left unconnected)? Or should I be connecting MS1/MS2 to something else to set it too HIGH?
// ConstantSpeed.pde
// -*- mode: C++ -*-
//
// Shows how to run AccelStepper in the simplest,
// fixed speed mode with no accelerations
/// \author Mike McCauley (mikem@airspayce.com)
// Copyright (C) 2009 Mike McCauley
// $Id: ConstantSpeed.pde,v 1.1 2011/01/05 01:51:01 mikem Exp mikem $
#include <AccelStepper.h>
int motorDirPin = 3;
int motorStepPin = 2;
//set up the accelStepper intance
AccelStepper stepper(AccelStepper::DRIVER, motorStepPin, motorDirPin);
//AccelStepper stepper; // Defaults to AccelStepper::FULL4WIRE (4 pins) on 2, 3, 4, 5
void setup()
{
stepper.setMaxSpeed(30000);
stepper.setSpeed(9000);
}
void loop()
{
stepper.runSpeed();
}
Hi Ross.
MS1 and MS2 are pulled high on the board by a pair of 10K resistors and are always high even if disconnected. If you want to change the state of either, you need to connect them to a pin and do a digital write LOW to pull them to ground.
If you’re not going to need to change the pins on the fly while the board is running you can skip connecting them to digital pins and connect them directly to ground.
Thanks TS-Chris. That tells me that by default the board is configured for 1/8 step (i.e. MS1/MS2 left floating) and that I’d need to connect them to GND to get full step, right?
That tells me that by default the board is configured for 1/8 step (i.e. MS1/MS2 left floating) and that I’d need to connect them to GND to get full step, right?
Yes, you’re correct, although MS1 and MS2 aren’t technically floating since there are pullups built into the board the pull both pins high. If you need a low on either pin, you’d need to connect that pin to ground. Pulling both to ground will give you full steps. 
Thanks!