PlasmaC Voltage Divider

Much better.
 

Thanks.

I soldered both resistors in the + und - Line inside the plasma source and also connected the 2 torch-start pins of the plasma-source with the Spindle enable + and Spindle enable - -Pin of the Mesa 7i76e-board.

When I power up the plasmacutter it instantly fires although the torch is not activated in plasmac. When I remove the 2 wires from spindle enable +- then the plasmacutter doesn't start when powered up.

When I measure between s-en+ and e-en- with a multimeter there is no connection but the plasma fires when started. Maybe somebody has an idea ? Do I need an additional relays ? With the hypertherm powermax 1000 G3 on the same mesa-card this didn't happen ?

Maybe sb has an Idea?

Sounds like you may have the spindle ENA polarity backwards.
 

I tried it again without changing anything and the plasmacutter started without firing at startup. Then I loaded the materal and tried to make a cut through 10mm mild steel. The torch fired, but the machine didn't move. And the torch went on and of a few times.
Why does that happen ? And why doesn't the machine move ?

Sounds like it did not get an Arc OK signal.  

The criteria is different depending what Mode you are using:

linuxcnc.org/docs/devel/html/plasma/qtplasmac.html#plasma:modes

I use mode 0.
I connected the divided arc voltage to the thcad and now the machine moves when it cuts, but it also goes on and of very often. You can see it here:



Could it also be a grounding-problem as the part is very small and I attached the ground clamp to the aluminium box where a steel grid is inside.

And why does it dive down in the middle of the part ? It seems to stop when the float switch is activated.