Stepper motor spinning in random directions

[CMF]

Our set up consists of a PCI-7334 connected to a UMI-7764.  One axis is wired to a MCB15081 Bipolar Microstep Driver driving a 200 step Lin Eng. motor.

When trying the 1-D interactive move via MAX, I am sending it a command to perform a relative move 5000 counts.  The motor responds by moving some amount (not sure if it is the correct amount yet) in a given direction.  If I repeatedly hit the start button, over and over, sometimes the motr moves, clockwise, sometimes counter-clockwise.  On occasion it will stutter back and forth without really rotating.

Any thoughts?

Chris

[CMF]

I should also mention that we are checking the signal coming out of the UMI-7764 and it goes high/low appropriately .  That is a command of 5000 always generates a high signal and a command of -5000 always generates a low signal but the direction the motor spins is seemingly random.

Chris

[Bill_5335]

I thought there was a radio button on Max that specified absolute or relative positioning.

How many steps per revolution is set up in Max?  Does this match your motor?

Good Luck.

[Jochen]

Do you receive any error messages? What about the axis' status in 1D interactive in MAX? Do you see any red LEDs? Which? Is your motor configured in open loop mode or closed loop mode?

Best regards,

Jochen Klier
National Instruments Germany

[CMF]

We found the problem yesterday.  It was a wiring issue between the stepper controller and the motor.

We are currently running the motor in open loop mode so I assume that is the reason there were no error messages.

Thanks,

Chris

[Buechsenschuetz]

I was thinking of the same reason when I read your first posting. If only one winding of the motor is connected properly to the driver it will perform random moves, depending on whether the impact of the activated winding is sufficient to make it move more than 1 full step. Sometimes you can check it by trying to turn the motor shaft manually, it will continue to move in the same direction for a short time and then move randomly again.

[CMF]

That was exactly the wiring error.

Thanks.

Chris