Stepper motor control issue.

[RichieP]

Hi,

I have set up a Geckodrive G201X stepper motor drive, to drive a small 8 lead bipolar stepper motor (1.8 degree, 5v/phase) I have supplied a simple pulse generator to the unit, and the motor turns completely. But it moves much slower than I anticipated, it only seems to move on every 4th pulse supplied. The motor twitches on the three intermediate pulses, but never moves until the 4th.

I am happy that I've identified the cables correctly, and I have tried wiring it in both series and parallel, and it still has the same effect. The power supply I am using is well rated for the motor set up. (supplies 35V at 5A)

If anybody has any ideas/suggestions I can try, I would appreciate the help.

Cheers, Richie.

 

[kellys_eye]

Show a diagram of the connections being used.

 

[RichieP]

Hopefully this is clear enough!

 

[kellys_eye]

That's not a diagram..... that's a list of the connections.



If you haven't got the 'polarity' of the windings correct then you get problems. Do you have the datasheet for the specific stepper motor you're using?

 

[RichieP]

I don't have a data sheet for this particular motor, it has no information on the body.. It's one I have found on the shelf covered in dust!

I currently have it wired in 8 wire series, and I have also tried it in 8 wire parallel but have the same fault. The motor connections are listed on the photo I uploaded, with the black/white and red/white connected together and white/green + white yellow connected.

Do you think it could be a polarity issue? If so I could spend some time playing around with some trial and error?

 

[kellys_eye]

It's undoubtedly a polarity issue - given the number of combinations of connection it could take a while....!

Start by identifying the individual windings. Then parallel two windings on the same phase and try spinning the shaft with your fingers.

Reverse the connections and try spinning the shaft again. The connection that offers the highest 'resistance' to turning is the correct one to use. This will get the phases correct on the individual windings.

You should end up with two pairs of wires.

You can then connect the stepper to the driver. If it fails to move properly then reverse the connections of one pair of wires.

 

[RichieP]

Ok, thanks for the help! I will put some time aside for testing in the morning.

 

[RichieP]

Hi Kellys_eye,

I have worked out the polarities of the phases this morning using my oscilloscope, the results can be seen in the attachment.

Because of how they coloured the cables, I happened to have the motor wired correctly for the serial arrangement before I started testing.

I have wired the motor up correctly in parallel today, but it still has the same effect, where the motor twitches for three steps and has the correct angle of movement for the fourth.

Could I have the wrong drive? I am new to stepper motors (obviously!) and I'm unsure if the drive is correct because it says "micro stepping controller" on the casing.

 

[RichieP]

Sorry, here are my results.

 

[kellys_eye]

Try grounding or taking the direction pin to logic 1. Don't leave it floating.

With the motor disconnected apply a single pulse to the input (step) and measure the status of the motor drive output terminals. Do this repeatedly for subsequent pulses to determine the step outputs are being driven correctly.

If you bought the unit as 'used' it may just be a faulty drive module.