On 4/15/24 17:09, Peter Wallace wrote:
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.
I'm running into the same problem in 3d printers, Peter. I am currently
rebuilding an Ender5+ using the new stepper/servo drives from hanpose,
that are rated for up to 90 volts for the nema 17 motors used on most
printers. Most of the big tree tech controller boards use 1.5 micro-sec
step pulses, but I am finding I need to stretch that to 2 micro-secs if
I don't want an occasional miss, this while driving the lc42 driver.
These drivers all have opto inputs, and need a little longer step on the
less than 5 volt signals.
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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