Question on Mesa board best suited for what i need to do.

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28 May 2020 04:23 #169188 by machinedude
what i have at the moment is a gantry mill build and what i want to do is a dual loop feed back with a linear encoder and some DYN4 DMM servo motors and drives. i have 4 drives and motors and the 4th could very well end up on the spindle for a drive motor. the cables for the scales are not really super long and the longest is 8 meters long.

my question would be around the Mesa boards. i was thinking the 7i76E would be a good fit for my needs but seen that a 7i76ED also sold. the interface for the encoders would need another Mesa board and i'm not sure which combination would be best to use with the DMM motors and drives? 7i85 or a 7i85S ? which combination of these would work best with the DMM motors and drives?

the linear scales and readers use RS422 from what i gathered. but here is a picture of the specs for those just to keep things clear.
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28 May 2020 04:34 #169189 by machinedude
this might be helpful too. the pins on the scale are shown.

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28 May 2020 05:41 #169194 by bbsr_5a
as of servos you shoudt go for a 7i92 +7i77 setup
this will fit the need you ask

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28 May 2020 06:04 #169196 by machinedude
i will have to look into those. i have no experience with the Mesa boards so any insight is helpful.

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28 May 2020 12:09 #169218 by machinedude
from what i gathered the DYN4 drives can do analog in all the modes of operation. and from what i can tell as of now speed mode is the easiest to tune and torque mode might preform a little better but is more difficult tune in. i'm guessing the +/- 10 VDC is supplied from the controls side of things?

servo systems are a bit new to me so it's a learning process for me. i built the cabinet but mostly played around with the step and direction mode of the drives and only started to scratch the surface of the +/- 10 VDC with a servo as a spindle motor.

i'm trying to sort out the pieces of the puzzle :) so the linear scales interface with the 7i77 but one thing that i am not sure of is how the rotary encoders tie into things? do they have connections to the 7i77 or just the drives? i was thinking just the drives or am i wrong in my thinking? i have yet to find any information that gets into specifics.

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28 May 2020 12:21 #169219 by tommylight
How many motors/drives ?
7i77 has 6 encoder inputs, but one is for the spindle.
Anyway you look at it, you might have to go with the 7i77 and 7i85, so that would make 6 +-10V outputs, 4 step/dir outputs and 10 encoder inputs. That to me seems like the most versatile choice, as you can use step/dit and scale feedback till you get a better understanding of how things function, and later go to analog and dual feedback, without the need of changing anything on the controller side.

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28 May 2020 12:27 #169222 by machinedude
i have 4 750 watt motors and 4 drives one of them i will probably use as a spindle drive motor.

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28 May 2020 12:37 #169225 by machinedude
DMM drives can do anything just as long as you configure them to what your doing with them. so it sounds like the rotary encoders from the servos also have to tie into the Mesa hardware, so if that is case i would take a guess the the output on the DMM drive gets used to do this?

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28 May 2020 15:09 #169236 by PCW
Typically on modern drives, the rotary encoders go only to the drives
(they often have a proprietary protocol) but the drive can synthesize
quadrature or other industry standard protocol feedback data to go back
to the controller

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28 May 2020 19:08 #169240 by machinedude
the DMM drives have a DB9 output on the drive for the encoder signals. the rotary encoders plugs directly into the drives from the motors so if you need the signals from the rotary encoders this is the point where you can access them.This sounds like what you just described.

so the big question about dual loop feedback with LInux CNC and Mesa is do you need 3 interfaces or 6 for a 3 axis machine? and what is the best combination of boards to work with the DMM servo system?

i'm not even getting into the DB25 pin out side of things yet. this is the point on the drive where the step and direction connections are accessed but if you go analog that's going to be different i am assuming so i have not had a chance to look into that side of things to much. like i said before i have mostly just bench tested the step and direction mode and barely scratched the surface of the +/- 10 VDC for use as a spindle drive motor. this was my first time using servo's. it's just new to me so understanding how every thing ties together is a process for me :)

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