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James, order one of these to be safe. There isn't any need to go with 12 volt on a plasma cutter.
au.element14.com/mean-well/mdr-60-24/pow...gKi9I4hoCco4QAvD_BwE

Also if it really is hitting a limit switch, use a HOME_OFFSET in your ini file to move the sensor off the limit switch when homing.

Hi All, 

Not a major issue, but my spindle speed is varying significantly under contant load. Sometimes during a cut and sometimes when it's just sitting and spinning up under no load and should be at constant speed. I'm not sure how much it varies because if I try to probe the pin the variance disappears, but audibly it slows down as if I ploughed it into a slightly too heavy cut that wasn't enough to stall the motor but enough to bog it down noticably. 
My VFD (AT4 Aliexpress job) is driving a 3 Phase induction motor, 2.2kW, 2 pole. 

The VFD has a 24v output but takes a 10v analog input, so I've just wired the 24v out to a simple voltage divider resistor pair (<5k total resistance) and I'm using that to feed the high side of the digipot on my 7i76e with 7v or therabouts. I tried using my 24v rail that supplies the limit switch, e-stop etc  originally but the spindle speed was varying a lot (under constant load) so I assumed the VFD reference voltage and 24v rail might be too de-coupled and switched to using the VFD output thinking that would be a more consistent Vref for the VFD, but the spindle speed is still varying a lot.

My .ini file has got the SPINDLE_SCALE set to 8000 (It's an 8k RPM spindle), so I used M3 S8000 and then adjusted the vfd paramaters (P73) to get 60Hz, then checked at M3 S4000 and got roughtly 30Hz showing on the VFD screen so it seems to be working OK at max rpm and  linear to within a few hundred RPM at 50%. 

If I try to probe the voltage on the pin the impedance of the multimeter is enough to pull the VFD back to max RPM as soon as I probe it so I can't tell what the VFD vout or analog signal from the 7i76 is when a dip occurrs. My instinct is that the multimeter has some huge resistance in voltage mode and that a weak pullup / pulldown (1Meg?) would help, but I'm not sure so want to check to see if this is typical behaviour, I'm surprised that it doesn't 'just work'

On a separate (but potentially related?) note, I've got a significant AC voltage leakage to the machine frame ground, I'm not sure if this is the VFD itself or the SMPS which feed 72v to the stepper drivers, I need to do some un-plugging and checking. It's enough that you get a tingle if you touch the frame and you're grounded. I'm getting no DC voltage from machine frame to protective earth in the garage, but 20-60v AC showing on the multimeter. If I use current mode and check leakage current from machine frame to ground it immediately trips the RCD, so >>30mA. Not sure if this is an independant thing or if this leakage could be messing with the analog voltage signals. 

Thoughs? Next steps? Independant things or related? What would you do next....

I've neve used qtplasmac but can you describe what is / is not happening as expected?

after a long struggle to get a debian system working together with wifi, network, linuxcnc and rt kernel on a newer n100 intel nuc-like computer, im finally at the get linuxcnc woking with my setup phase. i havent tinkered in linux for about 10 years, after linuxmint that is not really needed anymore for basic use cases.
i downloaded this configuration for linuxcnc and mr1. github.com/alexphredorg/mr1. i can't get it to work it errors out and quits, i don't know enough to figure out what is missing or broken. ill get a log later when im back with it.

my current software setup is
base 2.9.4 iso, added driver for usb wifi, installed software listed on the readme.txt in the home folder and mods from the intall guide found in the github link above relating to mesa. nothing more kept it as close to stock as possible before swapping to newer kernel etc.
hardware is a 7i96s. i can ping it and setup the most basic axis config with only xyz and spindle and can run the included g-code(no i/o hooked up).
most of the sims work, the ones from installing from the list in the home folder do not work.
im not sure if i need to sent something to the mesa card, i have not found any instructions or mention of this, or if something needed is missing from the enviroment.
as for the electrical end i should be good maybee ssome questions on specifics when i get there.

Stuck with joint errors

thinking the 12v field power isnt enough......

You could also copy the macros directly from the gmoccapy sim config (untested):

That way you do not need to have duplicate gmoccapy specific files in the pncconf sources.

I think it's time to update the first post of this thread, It's not working straight forward anymore even with 2.9.3, I had to jump on the last post to find a way to let it work. Also tried 2.9.4 and it's not working. Thanks for your time, when it works It's so satisfying

Yeah, sounds like it's a 5V PWM input.
 
There is 5I25 +7I76 firmware that replaces one stepgen (stepgen4)
with a PWMGen:

 

Which should work to drive the motor driver

No clicking the screen button with a mouse.