Interface between Mesa 7i77 and Granite Devices VSD-E servo amplifier

You cannot separate the output voltage from the input threshold on a 7I77
I suspect the easiest way to sense 5V is what Andy suggested, use the analog inputs for 5V sensing
and run the outputs at 24V for your relays

We do have some experimental firmware for the 7I84 which could be ported to the 7I77
that separates the input thresholds from the output voltage by making the input thresholds
settable from LinuxCNC but we don't have a time frame for porting this yet

Good thing I ran out of time and hadn't started to research the separating input from output thing.

The analog input idea is something I was never even aware I could do. I glossed over that part of the manual because it (at the time) didn't seem relevant to what I was trying to accomplish. As I really only need 3 inputs, I am happy to dedicate IN0, IN1, IN2 to my X, Y and Z fault inbound lines (7i77 perspective). If I'm reading it all correctly, I would want Mode 3 because I do want to have an MPG on my control panel. I don't quite know what "field voltage analog in" means in the context of the manual's description though. Mode 2, 3 spells that out explicitly...

Somewhere in the system (HAL or LinuxCNC configuration), the 5V value from the servo drive will how to be converted to a TRUE or FALSE. I don't quite know where that is accomplished yet but it seems reasonable to assume that such an ability exists....

Your comments on the MPG have made me question whether or not I have a looming problem there though... If I have a 24V field, is that going to be a problem for me? I'm guess not, but confirmation is always a good thing

DeckelHead wrote: Somewhere in the system (HAL or LinuxCNC configuration), the 5V value from the servo drive will how to be converted to a TRUE or FALSE. I don't quite know where that is accomplished yet but it seems reasonable to assume that such an ability exists....

Yes, you would use something like linuxcnc.org/docs/2.7/html/man/man9/comp.9.html
linuxcnc.org/docs/2.7/html/man/man9/motion.9.html

Your comments on the MPG have made me question whether or not I have a looming problem there though... If I have a 24V field, is that going to be a problem for me? I'm guess not, but confirmation is always a good thing

You can power the MPG from the encoder 5V (or any other 5V sharing the same GND)

Awesome...

Thank you both for all of the help. I have some reading, tinkering, and additional wiring to complete now, but I think I'm well on my way to having a viable solution.

Best regards and happy holidays,
Alan

I have a documented implementation of a 7i77 with a Granite servo drive.

wiki.eusurplus.com/

Fantastic! Thank you emcPT. I'm pretty close to being done with my conversion, but there are a few areas that still need to be tidy'd up and such. I was good about drawing schematics and once everything is up and running, I'll document things here as well. I like your approach of using a Wiki. I hadn't really considered that, but as I perused everything very briefly, I think I may follow suit.

I'll be going through all of your site over the next few days. I may have some questions for you and I'm hopeful that this is OK with you. Either way, however, I am very appreciative that you have take the time to send me the link to conversion.

Best regards,
Alan