Schaublin 125-CNC retrofit.

I would prefer a single 5V power supply for the Mesa cards.
But maybe this is my thinking this way you could provide the Cards with logic power and test something without having field power.

Thanks. That is how I did it on the Maho, and would do it again. Use a stand alone 5V Din Rail PSU like a MeanWell HDR-05-15 for that task.

I am still wading through options. If I use Lichuan A2 AC Servo drivers, they offer Step/Dir, Analog or RS-485 with Modbus, and seem to have a good manual:
servo.xlichuan.com/Private/ProductFiles/...6753446713131150.pdf

Q1/ Can you daisy chain two drives to a MESA 7i89's single RS-485 port?
If so then it should be possible to use the modbus MB2.HAL component to address the separate drives and output velocity commands to them.

Q2/ I was looking at the MB2.HAL comp documentation, am usure whether whether the drives internal parameters would show up automatically as HAL pins, or whether an addition hal COMP would be required to create the HAL pins necessary to control the drive?

Q3/ Also in the drive itself,

...it is not clear whether it is only able to select one of 16 predefined speeds via modbus, or whether you can do servo control by selecting preset speed 1 (PA_092 = 0) , and then netting PA_150 to the LinuxCNC commanded speed, and thus altering it at theservo thread rate?

Q/4 or is there a good reason to just use a 7i83, and output the linuxCNC velocity commands as analog signals?

If RS-485 speed control works, then drives pass through encoder signals would be wired back to LinuxCNC for it to close the postion loop.
Mark

only a train of thought:

I'm not shure at the moment, but i think that normal modbus (not modbus rtu /ip) is not realtime capable. The mb2hal component you mentiond is an userspace function.
So i don't know if theres an use case for transmit cyclic velocity data for positioning in an servo thread.

I hope that someone else can give an explanation about the implementation with modbus under linuxcnc.

The contact to lichuan is nice, I have them for my lathe conversion and will use them in anlog mode.
I haven’t fired them up yet, so I can‘t tell you much more about them.

Thanks guys. Excellent feedback.

800w 24VDC? CNC welder?
Mark

Hell yeah. As space is not an issue on that build, it is an excellent deal.

If so then it should be possible to use the modbus MB2.HAL component to address the separate drives and output velocity commands to them.

As far as I am aware there have been a few stabs at getting Modbus working in real time space using mesa cards but I don't think anything usable as come out of any of those. In my opinion Modbus is fine for configuration only.
There are some videos out there that seem to be controlling the drives over modbus, altough not with Lcnc, but I'm sceptical.
If I wanted a serial interface to control my drives with Lcnc I would choose EtherCAT (or maybe SSCNET if I already had the drives and motors). That is what has been shown to work.