Encoder polarity

[vt92]

Hello,

I'm using a  MXI controller card to a PXI 7344 motion controller and a NI MID-7654 servo drive.

The servo works, but the encoder counts in the negative direction.  I can changed "line A" to active high and the encoder counts positive, but the motor moves too far and I get following errors.  I have tried different combinations of lineA/LineB/index active high/low, but the current setting is the only way that I have found to avoid the errors.  Any suggestions?

Message Edited by vt92 on 03-12-2009 03:46 PM

[AnalogKid2DigitalMan]

My initial guess is that you have the A and B channels mixed up in wiring from the encoder to the controller.

-AK2DM

[Jochen]

I agree with AK2DM. There is no standard that defines which is phase A and B of the encoder, so you typically have a 50% chance to find the correct setting right from the start. In older NI-Motion versions you would have had to change the wiring, but in newer versions you just need to adjust the settings in MAX.

If your motor still doesn't move correctly, this sounds like a tuning issue. Please visit the Understanding Servo Tune tutorial for more information about this topic.

Regards,

Jochen Klier

National Instruments