Encoder question
- tommylight
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06 Sep 2026 21:41 #349402
by tommylight
Replied by tommylight on topic Encoder question
forum.linuxcnc.org/10-advanced-configura...to-example-mesa-7i77
Skip to the part about wiring and tuning.
Skip to the part about wiring and tuning.
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- Tinker
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07 Sep 2026 00:11 #349408
by Tinker
Replied by Tinker on topic Encoder question
I think i might have a drive issue, the encoder counts are working but it just runs as soon as i enable it. The drive for the 4th is from another machine and i thing i need to break my oscilliscope out and actually tune it per their directions. Im going to get that squared away and then start messing with the software side of it.
Thank you again for all your help!!!!
Thank you again for all your help!!!!
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07 Sep 2026 00:31 #349409
by tommylight
If the drive and motor are a set, do not try to tune them before making sure that is the issue, for this:
-disconnect the analog drive input from Mesa
-connect those two wires together
-power on the drive
-enable the drive
>>>does the motor turn slowly ?
-If yes = move on the drive is fine
-If no = first thing to check is Tacho wiring and brushes, then check motor brushes (if any).
>also check the commutator state for both, if there are signs of sparking on tacho = change tacho and check the drive output to tacho for whatever signal it should output. Rarely an issue, very rarely.
-Use compressed air to blow the brush holes and do not breathe near it
-And VERY important, return the brushes in the same hole you got them from, in the same direction and orientation.
Replied by tommylight on topic Encoder question
Does it run slowly or at full speed?...but it just runs as soon as i enable it.
If the drive and motor are a set, do not try to tune them before making sure that is the issue, for this:
-disconnect the analog drive input from Mesa
-connect those two wires together
-power on the drive
-enable the drive
>>>does the motor turn slowly ?
-If yes = move on the drive is fine
-If no = first thing to check is Tacho wiring and brushes, then check motor brushes (if any).
>also check the commutator state for both, if there are signs of sparking on tacho = change tacho and check the drive output to tacho for whatever signal it should output. Rarely an issue, very rarely.
-Use compressed air to blow the brush holes and do not breathe near it
-And VERY important, return the brushes in the same hole you got them from, in the same direction and orientation.
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07 Sep 2026 19:41 #349432
by Tinker
Replied by Tinker on topic Encoder question
So the DC servo is like new, but coupled to a second hand drive that i had to replace the mosfets on. I bench tested the drive and it works very nicely with my power supply to control the servo. When i disconnect the +-10V from the mesa card it holds position and is what im assuming is waiting on a +-10v signal. When i hook the +-10v back to the Mesa card it just starts running until i get a following error. It is unresponsive when i try to command a jog signal, it just runs and then errors out.
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07 Sep 2026 19:42 - 07 Sep 2026 19:51 #349433
by Tinker
Replied by Tinker on topic Encoder question
I did inspect the tack and servo and the brushes and both commutators look like they were never used. Also, my pid settings are now in a usable state, not perfect but better than the all zeros that were in place before. They didn't transfer over for some reason and i missed that one.
Last edit: 07 Sep 2026 19:51 by Tinker.
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- PCW
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07 Sep 2026 23:26 #349439
by PCW
Replied by PCW on topic Encoder question
Is it possible you have the feedback reversed?
(check by changing the sign of the PWM scale)
(check by changing the sign of the PWM scale)
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08 Sep 2026 01:25 #349443
by tommylight
Can you move it by hand? Does it kick back in place when released? Or does it actively refuse to move?
Replied by tommylight on topic Encoder question
Analog servos should turn slowly when there is no input signal.When i disconnect the +-10V from the mesa card it holds position and is what im assuming is waiting on a +-10v signal.
Can you move it by hand? Does it kick back in place when released? Or does it actively refuse to move?
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08 Sep 2026 01:32 - 08 Sep 2026 01:39 #349445
by Tinker
Replied by Tinker on topic Encoder question
So i tried changing the sign of the scale via Mesa CT with no change, also tried changing the analog scale so they were backwards with no change.. should i try changing something in my hal file or ini? I also tried swapping the +- leads going to the drive and that didn't work, i had to change some +- signs with the scale and encoder and basically gave me the same result but now in reverse...
Last edit: 08 Sep 2026 01:39 by Tinker.
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08 Sep 2026 01:46 - 08 Sep 2026 01:48 #349447
by Tinker
Replied by Tinker on topic Encoder question
I have tuned the servo driver to be totally still via the pots when no input is present. Its the balance (RV8) pot. I did this per the manuals instructions. I am unable to even try to do the mentioned tests because the servo has a mechanical advantage of a 90/1 worm drive and just runs... i would not dare to try to stop that thing.. LOL!!!
Last edit: 08 Sep 2026 01:48 by Tinker.
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08 Sep 2026 02:41 - 08 Sep 2026 03:22 #349449
by PCW
Replied by PCW on topic Encoder question
1. Please post your hal and ini files
2. Measure the output voltage of the 7I97T to see that it changes with position error.
I also tried swapping the +- leads going to the drive and that didn't work,
Note that this usually ends up shorting out the analog output
2. Measure the output voltage of the 7I97T to see that it changes with position error.
I also tried swapping the +- leads going to the drive and that didn't work,
Note that this usually ends up shorting out the analog output
Last edit: 08 Sep 2026 03:22 by PCW.
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