On Wed, 17 Jul 2024, Todd Zuercher via Emc-users wrote:
Date: Wed, 17 Jul 2024 16:59:54 +0000
From: Todd Zuercher via Emc-users <emc-users@lists.sourceforge.net>
To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
Cc: Todd Zuercher <to...@pgrahamdunn.com>
Subject: [Emc-users] 5v Encoder Power?
Working on my 8 head machine refitting.
The machine had been previously configured using a Mesa 5i25+7i85s doing
closed loop step/dir control with encoder feedback of 3 servos(xyz).
(Other miscellaneous gpio was handled on an ISA card.) Power for the Mesa
7i85s was through the cable via the 5i25.
With the update, the ISA card was replaced by a Mesa 7i84, and 7 additional
step/dir outputs added using a Mesa 7i88. The new machine configuration is
using 2 of the old servos to control the either end of the Y gantry
(previously only 1 servo), and 8 closed loop steppers have been added for
each of 8 Z spindles.
It appears that adding and powering the 7i88 from the 5i25 has put too much
load on the 5v supply from the 5i25. Now, when the servo drives are not
powered I am having trouble with the encoder feedback running away. I don't
think this was a problem previously. When the drives are powered they add
to the 5v that supplies the encoders and the feedback is steady.
Thats unexpected since the 7I88 should draw only a few 100 ma when fully
loaded. Are you sure the 5I25 and 7I88 cable power jumpers match?
My 1st question is how large of a 5v supply should I add to power the 7i85s
and the encoder feedback? Should I power both the 7i88 and 7i85s using this
supply or keep one powered from the 5i25? Would powering from a USB port be
sufficient?
The 7I85S draws about 250 mA by itself, any encoder power needs to be added
to this
Next question while I setting up and trying to tune the gantry servos, I
found that I was having trouble with the position feedback from the Mesa
stepgen getting out of sync with the feedback from the encoders if the
drives were ever disabled. Then when I am trying to run closed loop using
the encoder feedback, if the drives are disabled, I have trouble with joint
following errors when re-enabling them. Any suggestions for this problem?
I believe the problem is the gantry is going out of alignment when shut down
and there needs to be some provision for resyncing them when they are
re-enabled. But I'm not sure what steps need to be taken to do that.
Rehoming might be an option (but not what I'd prefer), but I can't even turn
the machine back on (F3) without closing and restarting Linuxcnc.
If you are running with encoder feedback, the stepgen position should not be
used (the stepgens would be run in velocity mode and only encoder feedback
used)
Todd Zuercher
P. Graham Dunn Inc.<http://www.pgrahamdunn.com/index.php>
630 Henry Street
Dalton, Ohio 44618
Phone: (330)828-2105ext. 2031
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Peter Wallace
Mesa Electronics
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