Stepper motor driver

[Beryl]

I'm running a 17HS4401S motor with an MA860H(https://www.oyostepper.com/goods-118-St ... 10VDC.html) motor driver. It's based pretty much on this circuit here, but I've got a dpdt switches that pull the direction pin high and low to be able to control the direction of the motor. its maybe 5-200 rpm or so is my rmp range.

All is well, and im also using the same swtich to pull the enable pin low and high to disable the motor while the switch is in the middle position, since it would leave the direction pin floating otherwise. Does this have anything to do with my problem?

My problem is that i cannot get the motor to start when my pots are set such that the motor is at max rpm. If i switch the motor on at middle range, it starts no problem, and i can crank the pots and bring the motor up to full speed no problem.

but if i leave the pots cranked to the max rpm value (lowest resistance), and then throw the switch, the motor will not start, it just buzzes and cannot get going. and never will settle and start going, it just buzzes, clearly recieving steps, but it does not turn in either direction.

I have to turn the pots down to a mid or low range, and then bring it back up to full speed if i want it at full speed.
I'll almost always be using it in a low to moderate range, but there are times i will want to jog the motor at full speed.

What might my problem be?

[Dieselman]

Go back to the manufacturer and ask them whether this controller is suitable to start at full speed.
I assume you are using either a 2, or 4 pole motor.
It could be the full speed operation uses only single phase, so is 180 degree phase shift, so the motor fails to start and if it did the direction would be random.