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@tommylight
Sorry for the questions, but I'd like to get it right the first time. I'm not yet that good with various electrical components at a detailed level.
I've read through your other threads and I think I found the right info, thank you very much!!
Are the following components suitable for making a voltage divider? My plasma has a 1:1 arc output.
I'm using a TH-CAD2 in combination with two resistors in series and a 0.1uF capacitor to absorb the voltage spikes. Am I doing this correctly?
What happens if a voltage spike does occur? Will the capacitor fail?
 

I have another question.
Can I connect the start arc and arc OK signals directly to the Mesa board, or is it better to use a relay to protect the mesa board?
Can I route these signals to the plasma cutter through the same cable as the THC?
 

For now, I think I'll test it this way.
Later, I can make a support from cut aluminum plates.

I've also ordered the plasma source.
Any other tips and tricks? 

 

 

I've decided to immediately apply a 1:3 reduction ratio, which translates to 25mm (15T) or 20mm (12T) of displacement per revolution.

I want to listen to the advice of  rodw and  tommylight

This will change the design somewhat. I think I'll place the linear guide directly on the underside of the tubes to reduce contamination.

Slowly, all the parts are arriving, and I've started welding the table. Unfortunately, I have limited time

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. 

The resistor(s) go in series with the plasma voltage  to the negative THCAD input
Safety wise the resistors should be in the plasma source itself.

Thanks a lot for your replies.

The stahlwerk-plasmacutters look good.
 
I already have a THCAD10 that I use for my hypertherm powermax 1000g3, but the cut quality on the hyptherm is not the best because there is a thermal dynamics-torch mounted on the machine and it doesn't cut without an angle at 10mm steel (2mm bevel to the other side). I already changed most of the parts exept the starter cartrigde, and if I can't get it to work properly I need to buy another plasma-machine. 

So I could change the Plasmacutter and still use the THCAD-10 if I add series resistors.
Maybe you can explain which exact resistor(s) I need and how exactly the resistors should be added to the plasma-cutter ? I
Somewhere I read that the THCAD should not be placed inside the controller-box ? Is that right ? So where should I put the THCAD 10 and the resistors ? 

Thanks

You can use a THCAD2 or  THCAD-10 with a series resistor
or resistors, for example  2.4M will give a 250V full scale range.

Mesa has a set of three .4W  1M .1% resistors for this purpose, when used
with a THCAD-10  or a THCAD2 set for 10V you get:

1 = 110V full scale
2 in series  210V full scale
3 in series  310V full scale

Note that lower voltage ranges improve resolution so the 210 V range is fine for most
plasma systems as it will accept continuous inputs over 1000V without damage
and voltages over 200V are not typically useful when cutting.

www.stahlwerk-schweissgeraete.de/Plasmas...ider-CUT-50-SThtml_1
www.stahlwerk-schweissgeraete.de/Plasmas...er-CUT-60-Pilot-IGBT
www.stahlwerk-schweissgeraete.de/plasma-schneidbrenner-p60
-
www.stahlwerk-schweissgeraete.de/plasmas...-cut70-pilotzuendung
www.stahlwerk-schweissgeraete.de/zubehoe...r-p-80-cnc-edelstahl
Kein divider, und kein ARC_OK, aber
noch 2 mal die 1MOhm/2W resistors und ein "reed switch/reed relay" ist alles notig, etwa 5 Euro total
dan die THCAD2 von Mesa
www.welectron.com/Mesa-Electronics-THCAD...n-A-D-Accessory-Card
sehe
linuxcnc.org/docs/devel/html/plasma/plas....html#_arc_ok_signal
forum.linuxcnc.org/plasma-laser/52203-th...able?start=30#299935
forum.linuxcnc.org/plasma-laser/52203-th...able?start=30#299958
linuxcnc.org/docs/2.8/html/plasma/plasma...ide.html#reed-arc-ok
-
forum.linuxcnc.org/plasma-laser/35349-op...ea-and-a-lot-of-info

That should pretty much cover everything... i hope!

Hi,

i'm looking for a good plasmacutter that works with plasmac.

What if the plasmacutter doesn't have an internal voltage divider ? Then the THCAD 300 would be good, but its out of stock everywhere. What is the alternative if I want to use THAD 5 oder 10 ? 

To buy a Proma voltage-divider or is there another professional-looking alternative ?
And maybe you can recommend a plasmacutter for plasmaC ?

Thanks.

Master is 2.10

So you would need to build from source or get a snapshot from the buildbot
to update to master.

BUT... you should be able to just replace the current pncconf pieces with these:

forum.linuxcnc.org/39-pncconf/56464-mesa...thcad-pncconf-screen

( Thanks kworm )


Another option is MesaCT which has had 7I95/7I95T support for a long time.

 

possible solution

forum.linuxcnc.org/39-pncconf/56464-mesa...thcad-pncconf-screen    

thnx kworm

after editing the PNCCONF according to kworm - update 
forum.linuxcnc.org/39-pncconf/56464-mesa...thcad-pncconf-screen

is possible to configure the step-dir spindle in 7i95T

I'm afraid ChatGPT will just be a time-sink here.

I suspect the easiest current path would be to make a pncconf  QTPlasmac/THCAD configuration
for a 7I95T (This requires updating to the very latest LinuxCNC master as 7I95T support was just added
about 1 week ago) This configuration will match as far as encoders, inputs, and outputs go (though will show
more inputs than the 7I97T has, so just don't use any inputs beyond input 15)

When creating the 7I95T configuration, setup step/dir axis.  and encoder feedback. This will create the
basic PID loop structure  required for changing over to the 7I97T PWM/analog axis configuration.

When this is done, you will have a step/dir configuration for a 7I95T and QTPlasmac/THCAD.
Next you will need to change the card name in the ini file to "7i97".

then the created hal file will need to be edited to change the PID feedback input from stepgen
position to encoder position and the PID output from stepgen velocity to PWM value.

There are also enables and some PWM setup needed. I can help with these when you get a basic
hal file setup. 

You can use this example of basic 7I97/7I97T PWM hal file setup:

 



 

Thank you, the wiring is making much more sense and less challenging now.  

Im using linuxcnc_2.9.4-amd64.hybrid.iso that I downloaded here.  It installed qtplasmac 2.9.  Is it recommended to install 2.10?

What is the easiest way to configure a 7i97t and a couple thcad2 for plasma?  I dont see 7i97t as an option in pncconf and in mesact there isnt an option for qtplasmac.

I asked chatgpt to create a quick ini for qtplasmac and a 7i97t and it came up with this pretty quick: