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Index Pin MK3 flickering unconnected or connected

#1 · 31 December 2025, 16:55

Quote from LogicSpeaks on 31 December 2025, 16:55
Hello,

I'm relatively new here.

CSMIO IPA controller (bought this year)

Drives: Yaskawa Sigma 7 SGD7S-120A00A002

Motors: SGM7J-08A7D61

I’m troubleshooting an issue with the encoder Index (I) input on MotionKit / Encoder Channel 3 of a CSMIO controller and would appreciate your guidance on further diagnostics.

Summary of observations

Encoder Index input on MotionKit 3 shows unstable/flickering state in diagnostics, even when nothing is connected to the I+/I− terminals.

The same encoder wiring, when moved to MotionKit4 / Encoder Channel 4, behaves normally (stable detection).

When the Index wiring is moved back to MotionKit 3, the flickering behavior returns.

Swapping:

DB25 ribbon cables

Terminal breakout boards

Drives

Encoder cables does not change the behavior; it consistently follows MotionKit / Encoder Channel 3.

Encoder A and B channels on MotionKit 3 appear to behave normally when connected; the issue is isolated to the Index input.

With the Index input on MotionKit 3 left completely unconnected, the diagnostics still show activity/flicker, while other MotionKit encoder inputs remain stable when unconnected.

Additional checks performed

Verified grounding and shielding are consistent with other working channels.

Tested with the same wiring and encoder source on other MotionKit channels (no issue observed).

Attempted basic termination / biasing tests on the Index input; behavior on MotionKit 3 remains different from other channels.

No software configuration differences were found between MotionKit channels.

Question

Given that the behavior:

persists with nothing connected,

follows MotionKit / Encoder Channel 3 regardless of wiring or drive used, (i've connected all other functioning drives to the same channel - the flickering continues. Sometimes however there is no detection at all.

and does not appear on other encoder channels under identical conditions,

Is this behavior expected for a floating Index input on this channel, or does it suggest a potential issue specific to the encoder input circuitry of MotionKit 3?

If there are any recommended diagnostic tests, configuration checks, or measurements you suggest to further isolate whether this is normal behavior versus a hardware-related issue, I would be glad to perform them.

Thank you for anyone that can help!

Hello,

I'm relatively new here.

CSMIO IPA controller (bought this year)

Drives: Yaskawa Sigma 7 SGD7S-120A00A002

Motors: SGM7J-08A7D61

I’m troubleshooting an issue with the encoder Index (I) input on MotionKit / Encoder Channel 3 of a CSMIO controller and would appreciate your guidance on further diagnostics.

Summary of observations

Encoder Index input on MotionKit 3 shows unstable/flickering state in diagnostics, even when nothing is connected to the I+/I− terminals.
The same encoder wiring, when moved to MotionKit4 / Encoder Channel 4, behaves normally (stable detection).
When the Index wiring is moved back to MotionKit 3, the flickering behavior returns.
Swapping:
- DB25 ribbon cables
- Terminal breakout boards
- Drives
- Encoder cables does not change the behavior; it consistently follows MotionKit / Encoder Channel 3.
Encoder A and B channels on MotionKit 3 appear to behave normally when connected; the issue is isolated to the Index input.
With the Index input on MotionKit 3 left completely unconnected, the diagnostics still show activity/flicker, while other MotionKit encoder inputs remain stable when unconnected.

Additional checks performed

Verified grounding and shielding are consistent with other working channels.
Tested with the same wiring and encoder source on other MotionKit channels (no issue observed).
Attempted basic termination / biasing tests on the Index input; behavior on MotionKit 3 remains different from other channels.
No software configuration differences were found between MotionKit channels.

Question

Given that the behavior:

persists with nothing connected,
follows MotionKit / Encoder Channel 3 regardless of wiring or drive used, (i've connected all other functioning drives to the same channel - the flickering continues. Sometimes however there is no detection at all.
and does not appear on other encoder channels under identical conditions,

Is this behavior expected for a floating Index input on this channel, or does it suggest a potential issue specific to the encoder input circuitry of MotionKit 3?

If there are any recommended diagnostic tests, configuration checks, or measurements you suggest to further isolate whether this is normal behavior versus a hardware-related issue, I would be glad to perform them.

Thank you for anyone that can help!