Are these normal behaviors?

it’s all in the docs/files on github.

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“After upgrading from firmware 0.98 to 0.99. I have notices pulsing when the left motor turns Clockwise. It only happens to the left motor and only clockwise. I downgraded back to 0.98 and the motors do not pules in any directions.”

I’m also seeing this behavior in 0.99… just throwing it out there. Left motor sounds like a helicopter. Still works, but causes a minor ripple effect on the chain.


Are you by any chance using custom PID values or are the custom PID values enabled? I know someone else saw this issue and it was fixed by turning off the custom PID values

0.99 made a significant difference in the PID loops, and so the values need to
be changed. If you had custom PID values before, this will cause problems.

I am actually still having this issue and no i am not using a custom PID values.

The “Enable custom positional PID values” is set to off.


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This is so weird. I’m trying to think of what could be different between the machines of those who are seeing the issue and those who are not but I can’t think of anything that could be different other than that software setting.

Does anyone else have any ideas of what we could test?

different versions of the motor controller card??

Could we re-state the issue(s) we’re chasing? The thread has been running many days with problems from several people.


Let’s start with the basics. Can you re-down load the firmware and Ground Control? Upload the newly downloaded firmware to your Arduino Mega. Go into Ground Control try running test motors and encoders. Please let us know the results.

Thank you

FYI - When I got to test this the other day I did not have any problems related to this.

Thank you

re-downloaded the firmware and GC, Did a Test motors/Encoders and the all passed.

The pulsing is still there when the left motor turns clockwise.



Thank you for the work done so far.

The next step is a bit more involved. You will have to remove the chains. Please swap the Left and Right motors taking the wiring with the motor. That Please us tape to mark the left one A and the right one B. Physically unbolt A and B. Then bolt B to the left side and A to the right. Move the plugs on the shield ports then test again. Did the problem move with the motor?

This will get us closer to an answer of exactly what the issue is.

We are trying to narrow down is it the motor, wire or shield.

Thank you

I am also seeing the same pulsation in my left motor (version 99) not using any custom settings

When i was cutting this weekend, I had some “shudder” as the sled was moving to the right (left motor would be turning clockwise). I attributed it to perhaps having a worn out router bit and now I wonder if its something else. Can someone post a youtube video showing this occurring?

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Swapped the motors and the cable harnesses. The pulsation is still happening at the left motor clockwise.

I also took a video, will post that soon

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That’s what I saw with mine as well… the left chain was bouncing and the sled was shaking a little whenever it was moving to the right.

Now that I know what to look for I will take a look at mine and see if I can notice it on my setup. I’ve been thinking a lot about this issue and I’m completely stumped at what is going on. I can’t figure out what could be different for some machines to show it and some to not.

To reiterate, here’s what we know (correct me if I’m wrong):

  1. The issue only happens with the left motor, and only as it’s moving to the right
  2. The issue only happens with firmware .99 and greater

Would you be willing to try deleting (or just renaming) your settings file? It should be in the users/yourname folder. Renaming that file will give gc the impression that it is the first time it has been installed on the computer and it will use all default settings. Since we’re all using the same hardware the config file is the only place I can think that there could be a difference


I really appreciate you helping us figure this out. Can I ask one last step. Swap the motor cables. At that point if it’s still doing it we know it is in the left Motor, possibly code, when rotating counter clockwise. I’m pretty confident with the information we have but this is being thorough and completing our due diligence.


Would you mind running the same Gcode without a bit to see if it’s reproducible? If so can you up load the Gcode?


Could this have to do with new math in the newer build on this specific port? We know it’s reported on the left possibly in 2 instances, 1 totally reproducible. We have it down to code or a bad port on the shield once we do the last cable swap. If it stays on the left I’d test swapping out the shield, if it’s hardware you could go crazy trying it fix it in code.

To review up to now - we re-downloaded and flashed the firmware for .99 and got fresh copy of Ground Control .99 and swapped the psychical motors and cables and it followed the left side.

What are your thoughts?

Thank you

hmm, it could be that the new pid tuning works with one motor shield revision
and not the other.

didn’t the timer used to control the left motor change between the two