Mesa 7i76e spindle output

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30 Dec 2022 20:37 #260567 by Gorts Revenge
Mesa 7i76e spindle output was created by Gorts Revenge
I'm new to the 7i76e and having some trouble with the spindle output.  Specifically, there isn't any output.  I've checked all the jumpers a dozen times, it's never been connected to anything and I'm getting 0V across TB4s pin 1 and 3 and any other pin on TB4.  Everything else works fine. Does anyone have any ideas?

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30 Dec 2022 20:47 - 30 Dec 2022 20:47 #260568 by PCW
Replied by PCW on topic Mesa 7i76e spindle output
The 7I76/7I76E spindle analog out is a potentiometer replacement device for VFDs.
It expects an external 5 to 15VDC source between TB4 pin 1 and TB4 pin 3 (+ to pin 3)

Normally this 5 to 15VDC source comes from the VFD

Likewise the, direction and enable outputs are simply isolated switches
that can replace mechanical switches, though polarity must be observed.
Last edit: 30 Dec 2022 20:47 by PCW. Reason: format

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30 Dec 2022 22:24 #260582 by Gorts Revenge
Replied by Gorts Revenge on topic Mesa 7i76e spindle output
Thank you.
I've been going bonkers trying to find any kind of stated specifications on the board. I wasn't sure if it was 0+10, -10 to 10 or a variable resistance circuit. You just answered that for me (without my having to risk cratering expensive hardware through the learning process). Your answer has me wondering if what I was planning was the best approach. I'm using a servo that has both digital and analog inputs.
Set-up wise, I figured the analog in a closed loop would be easier and a little more forgiving. Obviously, most VFDs aren't made to work in a closed loop. Is what I'm planning impossible or impractical?

Thanks again.

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30 Dec 2022 22:41 #260588 by PCW
Replied by PCW on topic Mesa 7i76e spindle output
I think its possible to have feedback, but rarely required for spindles
as a few RPM inaccuracy in spindle speed is usually dont-care

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30 Dec 2022 23:24 #260594 by Gorts Revenge
Replied by Gorts Revenge on topic Mesa 7i76e spindle output
I was planning on the capacity for rigid tapping which is why I was trying to close the loop but, as I think on it, it's probably more an exercise in mental self abuse as anything else. I can always double back to it, the required hardware is all there.

Thanks again.

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30 Dec 2022 23:41 - 30 Dec 2022 23:42 #260595 by PCW
Replied by PCW on topic Mesa 7i76e spindle output
Accurately controlled spindle speed is not required by LinuxCNC
for rigid tapping/threading, because LinuxCNC typically uses encoder
feedback and "gears" the Z motion to the actual spindle speed.
Last edit: 30 Dec 2022 23:42 by PCW. Reason: format

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