7i85 encoder question

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28 Jul 2019 21:33 #140844 by Timmyag
I have been redoing my machine electronics, as it turns out that you learn things the first time you do something.

I’ve added a 7i85 to my 7i76e, as I want to have real feedback to linuxcnc even though I have position drives “CNCdrive 16035’s”

My encoders rod426’s expect a minimum load resistance of 100ohm but if I connect both the 7i85 and drives I’m going to have ~60 ohm. This might work I assume I’ll have low V’s and that sounds like a reliability problem.

Is there a standard way of managing this, can I get a simulated encoder output? disconnect the termination resistors from 7i85? trick a position drive to behave like a velocity drive by changing the pid to have only P and fake encoder inputs?

A side question is a 7i85 and a 7i85s the same bar firmware? I ordered the “s” but the card is marked 7i85. I didn’t care but want to know my options.
Thanks
Tim

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28 Jul 2019 22:36 - 28 Jul 2019 22:39 #140848 by PCW
Replied by PCW on topic 7i85 encoder question
Most fancier drives have a simulated encoder output so there is no need to wire the
encoder output to multiple destinations. If the CNCDrive 16035 does not have this feature,
it may not be the best idea to tap onto the drives encoder for noise/EMI reasons.

The 7I85 and 7I85S use the same circuit card with different assembly options
so the top side card markings are the same on both

(If in doubt there is a sticker on the back of the card the has the model number)
Last edit: 28 Jul 2019 22:39 by PCW.

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