Noise hunting

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TomKerekes
Posts: 2951
Joined: Mon Dec 04, 2017 1:49 am

Re: Noise hunting

Post by TomKerekes » Wed Jul 01, 2026 5:19 pm

There are RJ45 or similar footprints on the Kanalog for encoder inputs. Not sure I will use them, but curious if those are usable and tied to encoders 0-3? If so, is there a pinout detail somewhere?
We don't support their use. I think the chips are too big and close to make it difficult or impossible to plug connectors into them when installed. We also don't recommend Users to solder onto the boards.

But yes they are for Encoder inputs 0-3 and also each have an additional encoder input for index pulses plus 5V and Gnd.

RJ.png
GND and 5v terminals for the encoders... There are GND terminals near the analog I/O on JP6 & JP11, and 5V on JP8. These seem kinda far with trying to keep noise from Snapamp above from dropping in. Are these the best points to use for the encoder supply and cable shield connections?
I think so.

I will use encoder 0-3 for my 4 axis motors. For the index signals, can two different axis index inputs connect to both encoder 4 and 5 or do I have to limit one index input per encoder channel?
Yes. Index pulses are handled in software so any input may be used.

This is a tough one. While testing earth ground and looking for loops, I find under 2 ohms from all parts of my 3 axis gantry router back to the quasi star point. I am still digging for hidden ground straps, but it appears the mechanics, probably ball screws and bearings, are working as a ground all the way to the the cutter. The original wiring had a ground line running from limit switches at both ends of travel for XY and Z. Plus the DC servo motor shield to earth at the drive and motor housing at other. This seems like a lot of loops. I was thinking maybe running an insulated earth ground line in my new shielded motor power cables that would terminate at the motor housing for good earth ground on each carriage and attach those cable shields to earth ground at the snapamp end only. I think that would be a quasi-star approach except the mechanics still creating loops. Any suggestions?
I'm not sure I follow that. Where are you referring to earth ground vs DC GND? I think the main issue is with DC GND. Limit switches and such should be opto isolated and not involve DC GND. My thinking is Motor shields (and noise generating signals) should have shields connected to earth GND. Encoder shields should be connected to DC GND at the Kanalog end only.

Side note... when I searched in the forum for my user name to remind me where I left this thread, it does not find this here in the "Noise, Grounding" section.
It seems our search only includes subject and body of posts. Here you didn't put your User name in the body so it won't be found here.

HTH
Regards,

Tom Kerekes
Dynomotion, Inc.

MadTooler
Posts: 91
Joined: Thu Nov 08, 2018 11:57 pm

Re: Noise hunting

Post by MadTooler » Wed Jul 01, 2026 10:24 pm

Thank you again!
TomKerekes wrote:
Wed Jul 01, 2026 5:19 pm
We don't support their use. I think the chips are too big and close to make it difficult or impossible to plug connectors into them when installed. We also don't recommend Users to solder onto the boards.
I thought that may be the case. It is very convenient that all the connections are together, but I will steer clear since you do not like them as much.
TomKerekes wrote:
Wed Jul 01, 2026 5:19 pm
Yes. Index pulses are handled in software so any input may be used.
I also saw you have added the cool ability to use the diff inputs with a latch with the latest software release which I may apply to the index as well for homing. Too bad I can't have it real time comparing index to position to confirm noise hasn't misled kflop: viewtopic.php?f=8&t=1915&p=8418&hilit=index#p8418
TomKerekes wrote:
Wed Jul 01, 2026 5:19 pm
I'm not sure I follow that. Where are you referring to earth ground vs DC GND? I think the main issue is with DC GND. Limit switches and such should be opto isolated and not involve DC GND. My thinking is Motor shields (and noise generating signals) should have shields connected to earth GND. Encoder shields should be connected to DC GND at the Kanalog end only.
I was referring mostly to earth ground. The original builder used the shield of the limit switches to connect to earth gnd at both ends. Not sure why. I do have them connected to opto inputs on kanalog. The original builder also had the motor shields attached to earth gnd (chassis) at both ends, but I had massive noise that devastated the encoder feedback when in that configuration. I found I had to remove the motor shield connection at the motor end from earth gnd/chassis/motor housing, and connect the shield at the snapamp end to motor DC gnd instead of earth. Not good, but what it took to make it work then. I hope to do as you suggested with this new wiring.

Another side note, I just now learned Autodesk decided to cripple standalone perpetual licenses a while back by not allowing online generation of authorization codes when reinstalling my seat of Autocad after a hard drive crash. Straight up thievery. Instead of fighting through getting it up and running again just for schematics right now, I will be making them in inkscape since I use that for a lot of other projects. Would you have any interest in the native SVG files to share with others?

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TomKerekes
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Re: Noise hunting

Post by TomKerekes » Wed Jul 01, 2026 11:15 pm

Yes you might post your schematics. They might be useful to someone. Thanks.
Regards,

Tom Kerekes
Dynomotion, Inc.

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