PnCconf and Mesa 7i33

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26 Jul 2022 14:23 - 26 Jul 2022 14:25 #248330 by Roguish
So, I'm checking my hal setup on my new little bench mill.
Figured I'd run PnCconf to see if my current hal setup matches.
Running a 7i80hd-16 and a 7i33ta.
Pretty good comparison, except for one thing.
PnCconf states (in the program and it's docs) that the 7i33 daughter board requires PDM generators.
'The 7i33 requires PDM and a PDM base frequency of 6 mHz'

I have never seen this before.
Is this correct?  and if so, where in any other documentation, either Linuxcnc or Mesa, is this stated?

And what is the effect of not having this in hal?
Little help please....
Last edit: 26 Jul 2022 14:25 by Roguish.

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26 Jul 2022 15:28 #248337 by PCW
Replied by PCW on topic PnCconf and Mesa 7i33
This is mentioned in the 7I33 manual, PDM at 6 MHz gives the bast combination of linearity
and ripple. PWM at 48 KHz is nearly the same (with a tiny bit more ripple)
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01 Aug 2022 20:46 #248806 by Roguish
Replied by Roguish on topic PnCconf and Mesa 7i33
I have run into a problem that I think is encoder, 7i33, and linuxcnc related, together.
please refer to the picture below. spreadsheet with graph.

I have finally tuned my digital drives according to the AMC procedure, for toque and velocity, using their software.  It works pretty good.
My system is setup to for max motor rpm = 1700.  That's actually faster than I ever want it to go.
In Driveware (the AMC software) I have set the analog input signal to 170 volts/krpm.  The drive has a max input of +-10v.

With a 5mm ballscrew and a 3:1 belt reduction, 1700rpm==1.8591 ips travel, so my Output Scale=1.8591 .
On to the problem.  I have a 2500ppr encoder on the motor.  Encoder is full differential.  And an independant tachometer.
I run the system with Lcnc, and monitor with Driveware, and the independant tachometer.
At low speed jogging  below 30ipm all is ok.  All the motor speeds match.

Above 30ipm it's not good.  The motor speed in Lcnc will not go above 550rpm (approx).  So Lcnc jacks the voltage up to max 10v and the motor speeds up to 1450rmp.  But Lcnc reported velocity of travel speed and rpm do not increase.  That's with P=10, and FF1=1 (or 0).
Weird, not good.

So I went to an external and external voltage input, and set P=0, FF2=1, and all others =0.  that should pass through the signal (I questioned andypugh).
Anyway.  Same results. As I increase the drive input voltage, the motor speeds up accordingly, but Lcnc rpm rolls off at about 550ish - see the graph.  The drive's rpm monitor and the independent tachometer agree.
What's up?
      
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01 Aug 2022 20:49 - 01 Aug 2022 20:50 #248807 by PCW
Replied by PCW on topic PnCconf and Mesa 7i33
Can you post your hal and ini files?
Last edit: 01 Aug 2022 20:50 by PCW.
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01 Aug 2022 21:19 #248808 by Roguish
Replied by Roguish on topic PnCconf and Mesa 7i33
thanks for the quick reply.
attached are .hal and .ini files.    at least the important ones.  there are others for the pendant and probe and vfd and stuff.

 
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01 Aug 2022 22:04 - 01 Aug 2022 22:05 #248809 by PCW
Replied by PCW on topic PnCconf and Mesa 7i33
So are you saying that the RPM registered by LinuxCNC is bounded to
550 rpm even though the motor is running much faster?

That sounds like an encoder interface issue of some kind
If these are differential encoder signals, I would verify that:

1. The 7I33 is jumpered for differential encoder signals
2. That you have valid differential signals at the 7I33 encoder pins.
That is, you can measure >2V or <-2V across the A,/A B,/B and Z,/Z
pairs (in all states). Any absolute voltage < 1V indicates a wiring or
hardware issue.
Last edit: 01 Aug 2022 22:05 by PCW.
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01 Aug 2022 22:17 #248810 by Roguish
Replied by Roguish on topic PnCconf and Mesa 7i33
yes. that's what i'm seeing....
the 7i33 is jumpered for differential input.
the motor encoder goes directly to the drive.
the drive has encoder outputs that are going to the 7i33.
I'm not sure of the voltage, but I have been told by AMC that it's a straight pass through. I will ask again for confirmation.
And I will try and put the encoder signal from the drive on a scope.

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01 Aug 2022 22:31 #248811 by PCW
Replied by PCW on topic PnCconf and Mesa 7i33
It often easier to measure these with a voltmeter
(since its a differential measurement)

It does sound a bit like a drive setting issue as an electrical
or signal integrity issue would likely end up with 0 RPM
an some point rather than a cleanly bounded value.
But that makes no sense if the encoder signals are just fed
through
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01 Aug 2022 23:31 #248814 by Roguish
Replied by Roguish on topic PnCconf and Mesa 7i33
I spoke with AMC again. The signal are supposed to be a pass through.
I will try both a scope and a Fluke dvm (with rms).
And check my wiring very carefully.
The encoder is the same brand and type that I have on the spindle and it reads directly into Mesa board and Lcnc fine.
I'll be going over it all very carefully. and post back here.....
Thanks again Peter.

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02 Aug 2022 13:00 #248837 by Todd Zuercher
Replied by Todd Zuercher on topic PnCconf and Mesa 7i33

My system is setup to for max motor rpm = 1700.  That's actually faster than I ever want it to go.
In Driveware (the AMC software) I have set the analog input signal to 170 volts/krpm.  The drive has a max input of +-10v.


Shouldn't that be 170rpm/volt?
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