On Mon, 15 Apr 2024, Todd Zuercher wrote:
Date: Mon, 15 Apr 2024 20:22:03 +0000
From: Todd Zuercher <to...@pgrahamdunn.com>
To: Peter Wallace <p...@mesanet.com>,
Todd Zuercher via Emc-users <emc-users@lists.sourceforge.net>
Subject: RE: [Emc-users] Mesa Card Stepgens?
Thanks Peter,
We've had this 7i85s for quite a while, and it must be one of the early ones
because I see DS34C87TM chips on it.
I'm not sure I like the idea of using them single ended. But is a +5v-0v
single ended signal actually any better or even much different than a +/-3v
differential signal? How hard would it be to move the last steepen over to
the 7i88 and have all 8 of these stepgens on one card? I am not planning on
using the Smart Serial output on the 7i88. The 3 servos have been working
on the 7i85S for years and can stay there.
Differential is needed and advised for servo drives with line receiver inputs,
however, with optocoupled input step/dir drives, there is little advantage to
differential mode. With optocoupled input step/dir drives the input will only
see ~3V drive in differential mode with the DS34C87 driver, so its better to
run in single ended mode with the 7I85S sinking so you get full 5V drive.
I am using the Smart Serial connection on the 7i85s to connect a 7i84.
If all else fails I can simply set all of the other steppers the same as the
slow one and leave it be. Even the slow one is working as fast or faster
than I was hoping it would, but a little more safety margin would be nice.
The drives are likely not rated for 3V input so you would probably be better
off if you ran single ended.
Todd Zuercher
P. Graham Dunn Inc.
630 Henry Street
Dalton, Ohio 44618
Phone: (330)828-2105ext. 2031
-----Original Message-----
From: Peter Wallace <p...@mesanet.com>
Sent: Monday, April 15, 2024 3:41 PM
To: Todd Zuercher via Emc-users <emc-users@lists.sourceforge.net>
Cc: Todd Zuercher <to...@pgrahamdunn.com>
Subject: Re: [Emc-users] Mesa Card Stepgens?
[EXTERNAL EMAIL] Be sure links are safe.
On Mon, 15 Apr 2024, Todd Zuercher via Emc-users wrote:
Date: Mon, 15 Apr 2024 19:27:19 +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] Mesa Card Stepgens?
I was working on this machine where I need a whole bunch of extra stepgens. I
am using a Mesa 7i85S and a 7i88 connected to a 5i25 card. I was testing some
of the stepper drives and I noticed that with one of the drive/motor
combinations I am needing to use slightly longer step timing and lower max
velocity. I thought that this was odd, because all of the drives, motors, and
mechanicals are the same for all of the ones I was testing. The only
difference is that the slower one was connected to a stepgen on the 7i85S and
all of the others are on the 7i88. So just for curiosity sake I checked the
voltage at the input terminals of step/dir signals of the drive. On the
terminals connected to the 7i88 I found +/-5v, and on the one connected to the
7i85S there is only +/-3v. This is the only difference I've been able to find
between the different joints in question.
Does it make sense that the voltages would be different on the step/dir outputs
between the 7i85s and the 7i88? Does it make sense that the difference would
cause a difference in the required step timing? Why might there be a
difference between the output voltage on the two cards?
Both cards are getting their 5v from the 5i25. The 7i85S is also connected to
3 step/gen servo drives and their encoder's feedbacks. Is it possible that the
5v drain from the encoders might be causing the lower voltage on the 7i85S's
outputs?
I would check the 5V rail at the 7I85S card, and if its low, power the 7I85S
directly from 5V rather the through the parallel cable. ALso the very first lot
(many years ago) of 7I85S cards were built with DS34C87 drivers which do not
have full 5V drive. If you have this card, you can get 5V drive by using single
ended sinking outputs and 5V+ to drive step+ and 7i85s step- to drive
step-
Todd Zuercher
P. Graham Dunn
Inc.<https://nam04.safelinks.protection.outlook.com/?url=http%3A%2F%2F
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Phone: (330)828-2105ext. 2031
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Peter Wallace
Mesa Electronics
Peter Wallace
Mesa Electronics
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