Hi guys

I have been trying to connect my laptop to my chinese servos via rs485 for
ages to get the tuning software working and am not having any luck.

In the mean time I am just wondering what the best way to tune the servos
is?  Can I hook up a oscilloscope to something?  I am lost how that would
work but have one I can use if needed.

I can manually change the pid parameters in the drive easily  I just can't
measure it very well.  other than listening for noise.

Now once I get it shipped here I should have a mesa 7i89 for allow me to
close the feedback loop right back to linuxcnc.  I am using step and
direction drives.  I am just a little confused about how tuning would
work.  If I was using 0-10v analog control I can understand how I could
just set all pid settings in the drive to zero and tune everything from
halscope.  but with step and direction drives I assume i kind of need to
tune the servo first.  And I don't want to have to feedback loops fighting
each other.

Now one last idea is I haven't yet used the 7i76 spindle encoder input yet
on my cnc mill and maybe while I am waiting for the mesa cards to arrive I
could connect up to the feedback from the x axis to the encoder input.
that way I could use halscope to see the error.  But to change the pid
settings maybe if I only changed them in the servo drive and didn't
actually connect the pid to the step Gens, once it was good I could remove
the encoder input and re use it for the next axis and so on.  maybe that
would work ok.  bearing in mind that I will close the loop with the 7i89 in
the end anyway.  I just want something I can do now.  and I have jobs
waiting that need better accuracy than I currently can get with the tuning
I have now.  (I just did a quick guess while the servos were off the
machine and got them to roughly folllow commands)

let me know what you think

regards

Andrew

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