Plasma C Wiring

There isn't any change required really other than to use your new pins for Torch on, arcOK and divided voltage. Remember that the ArcoK expects +24v on one pin and the other pin is connected to an input. I thought your 1k resistor is upgraded to 90 K 10W (or 3 x 270k 5W resistors in parallel). I would still retain that.

Change the divide ratio to 20:1 in the plasma cutter and alter your scaling accordingly in Plasmac. I think thats covered in the Plasmac docs.

Its great to hear my old Everlast got another table up and running to a stage where you are upgrading to a real plasma cutter now like I did! I would have gone with the PM65 except I found a cheap 120 amp Thermal Dynamics.

So time to pass it off to another forum member I think or keep it for the hand torch which would be handy!

rodw wrote: I thought your 1k resistor is upgraded to 90 K 10W (or 3 x 270k 5W resistors in parallel). I would still retain that.

Yeah it is, I didnt want to put too many amps back through the relay but if it is not going to do any harm I guess that I can.

Yeah the Everlast served me well, in the end I got it dialed in and had some very good results with 3,5 and 6mm plate but just wanted to upgrade my capacity.

At the miniute I am not sure what I will do with the machine, may not be out of the question to build another machine in time as I have an old hypertherm 1100 to use as a hand torch. If anyone was interested I would be willing to sell it but am in no rush.

Thanks Rod.

rodw wrote: ............ resistor is upgraded to 90 K 10W (or 3 x 270k 5W resistors in parallel). .......

That would be 90 Ohm and 3x 270 Ohm.

little_sparky wrote:

rodw wrote: I thought your 1k resistor is upgraded to 90 Ohm 10W (or 3 x 270 Ohm 5W resistors in parallel). I would still retain that.

Yeah it is, I didnt want to put too many amps back through the relay but if it is not going to do any harm I guess that I can.

The PM65 internal relay can handle up to 10 amps so the paltry 267 mA passing through the circuit is not of a concern and its well above the minimum 100 mA where issues have been experienced.

Also, in the documentation (attached above) it says that the maximum voltage provided by the divided arc signal is 18V, I’m assuming this is for 20:1 ratio? Or is it 50:1?

I’m trying to work out what ratio will give me the best divider range to use with the THCAD-10

little_sparky wrote: Also, in the documentation (attached above) it says that the maximum voltage provided by the divided arc signal is 18V, I’m assuming this is for 20:1 ratio? Or is it 50:1?

I’m trying to work out what ratio will give me the best divider range to use with the THCAD-10

18V is the max arc voltage output on the CPC connector. The THCAD 10 can handle any over voltages the PMX65 could throw at it (up to 500v indefinitely).

I chose to use 20:1, it will give you the greatest resolution (0-200v). You wont have any cut voltages near 200v, I think the highest in the manual is 148v.

Long answer is here: forum.linuxcnc.org/plasmac/39999-thcad-1...powermax45-xp#181612

Also, even though the cut voltage charts exist for Hypertherm, it's still highly recommended to use auto-volts. It negates all the testing to make sure your voltage readings and their voltage readings align

As per what Snowgoer said

rodw wrote: Change the divide ratio to 20:1 in the plasma cutter and alter your scaling accordingly in Plasmac.

The 18 volts is meaningless for us as the THCAD-10 has a 10 volt maximum scale. As with any A/D converter, the more of the full scale reading the better for accuracy so 20:1 is perfect as it more than covers the cutting range. If volts go >10, it won't matter as the THCAD will show full scale (200 volts) until it falls below that but when its up there, we do not need to sense the arc voltage for any reason.

What is the open circuit (OC) voltage written on the back of the plasma ?

That will be 8.4V at the THACD10 input when plasma is at 140V, soooo that is very good.