THCAD-10 configuration, QtPlasmaC

Hi,

First off I have enjoyed the last few days spending time getting my plasma CNC project working somewhat with linuxcnc.

I have been spending a few hours now trying to figure out how to configure the THCAD properly and been reading on the forum. I seem to have it functioning but it does not seem to matter what values I put in the configuration tool. I am using a 7i76e and THCAD-10 with 1 Meg resistors on IN+ and IN-. I try with a DC-voltage to test of 0-60V. The max voltage of 60V produce about 2.8V into the THCAD-10 which gives values on the arc voltage around 110000.

Where do I find the divider ratio and voltage offset in the files? I can't seem to find it anywhere.

I have calculated,
Scale: 0.00789993
Offset: 3718.7500

Here is the first cuts on the 1250x2500mm plasma build


This is from before I went with QtPlasmaC instead,

Wow, how did I miss that? I was looking everywhere except in the GUI itself.

Thanks, will try tomorrow.

Put in the new values and it seem to work perfectly!

What are reasonable PID values to start with on the THC?

The default of P:10, I:0, D:0 is quite common.

I seem to be missing something fundamental when it comes to the THC. It measures the voltage all OK. I have set it to 110V just to see if it regulates but it does not show THC Enabled LED lit up, so I must be missing something. I tried to add M65 P2 in the G-code but without luck.

I also noticed that having any of the cables from the computer near the plasma torch is a bad idea, luckily it survived fine

You have IGNORE ARC OK set, that disables THC.

linuxcnc.org/docs/devel/html/plasma/qtplasmac.html#qt_ignore-ok

Yes, that solved that issue. However the reason I disabled it is because I don't have any ARC OK signal and use Mode 0 for that reason. But when I have IGNORE ARC off it just triggers for a split second and alarms that ARC is not OK.

Probably something more I have overlooked I guess I should probably try to get a reed relay and fix an ARC OK signal as well, but eager to get it working

sm2wmv wrote:

I guess I should probably try to get a reed relay and fix an ARC OK signal as well, but eager to get it working

Some plasma cutters just don't work with the soft arc ok, the reed is very reliable.

I've ordered some reed relays and I will try it again.

Thanks for all the help, I must say I am really impressed with LinuxCNC. I managed to get most of it up and running without asking for help.

I have an Morbidelli Author 400 CNC that I have used to mill all parts for this plasma table and I have intentions to convert that one later to use LinuxCNC as well.