Help needed: Retrofitting a CNC plasma table with new drivers and controller

for linking in the Plasma torch you need a THC Interface ( torch height controller ) if your going to use Mesa interfaces as has been suggested then a mesa thc interface would be the logical choice THCAD-10 , THCAD-300

frecel wrote: I've been reading a lot on controllers trying to educate myself more on the subject what I can't figure out is how to hook up the the actual plasma power source to it.

The plasma we are thinking of getting has contacts that are normally open and close when the torch switches from the pilot arc to cutting arc.

I'm not sure how to make sure I'm selecting the right controller to take advantage of that.

If its like my as yet unhooked up plasma cutter, the machine torch simply requires a switch to replace the switch on the hand torch.. On my Mesa hardware, I have yet to wire this in but I have a 24 volt relay to replace the switch. The relay coil will be wired to a 7i76e Output pin on one side and earth on the other. Then the wires to the plasma cutter go to the other side of the relay. I have not followed it right though yet, but I think the output to use is configured is Spindle on. This will light up the output which triggers the relay.


For Arc OK, my instructions say this is a dry mechanical contact at the plasma end (eg. a relay). So run 24 volt power to one side of the ArcOk switch and the other side to a 7i76 input. I think this is configured as the Spindle at speed signal.

I have seen an external THC that ran 24 volt internally but the logic levels on a parallel port breakout board were 5 volts. In this case, they used a 24 V relay to switch constant 5 volt to a BOB input.

Time for another one of my stupid questions
What's the difference between a Mesa 5i25 board and something like this? www.omc-stepperonline.com/5-axis-cnc-bre...iver-stv2-p-197.html

MESA 5I25 is a very fast FPGA that can do a lot of procesing and can be programed to do a lot of things.
The link you posted is a simple break out board used as isolation between the computer and the machine, it just repeats the same signals from the computer parallel port. So nothing programable and no logic circuitry. it has 12 outputs and 5 inputs, same as parallel port, Mesa has 34 on its own and can be programed to have hundreds of inputs and outputs using add on cards, can do step generation, drive servo drives, count encoders and much much more.