Building a chain driven Plasma table.

Something like this?

www.aliexpress.com/item/1005007245832712...2c-a4a2-79fd969bd58f

or rather one that only uses ceramic capacitors?



 

So it turned out the ohmic sensing was not so reliable. 
while at 25 mm above it started to cut. (False ohmic on when torch is wet) 
My machine is especially sensitive to that. 
I use a hand torch on a steel mounting. 
Distance from mounting to shield is about 3mm. 

so I came up with this experiment. 

I made a break out board. 
with a voltage divider. 

6 30k resistors in parallel so that is 5k ohm.
on the other side 5 5k Ohm resistors in parallel so that is 1k ohm

So I tested with a multimeter when torch is in contact with the negative of the power supply I get 5volt. 
when I put a wet paper in between I get 4.2 volt.  Looks like this helps to get a solid difference between wet contact and real metal to metal contact.

With so many resistors in parallel. I don’t think torch voltage will overload then. 

is it safe to use this kind of  voltage divider. On my Thad.  I was wondering if it would be wise to   add some diodes for safety. Since torch voltage is opposite polarity?

 

5 volt Thad
24 volt power supply.

You mean across positive and negative of the Thad?

What resistor value would you use between positive of the isolated power supply and the positive input of the THCAD ?

Ohmic sensing has been working reliably for the past few days. I would not want to be without it. Makes probing so much faster and more reliable.

So my fifth stepper motor driver arrived and I will soon take the plunge to add a rotational axis.

So I read linuxcnc can only handle 3 axis trajectory planning.

But I need a fourth axis to place the torch above the center of the pipe.
I guess this can be done during homing.

Should I make a new configuration with the rotation axis being the X axis. Change the current X axis to the A axis in order to move the torch to the center of the rotation table?