Another plasma component...

thefabricator03 wrote: Once I get this sorted I want to use my experience to help write a decent step by step guide with the mesa 7i76e outlining my mistakes and how I resolved them.

That would be great...

When you run pncconf you do not need to do anything with the pins for the plasma side of things, the configurator will sort that out. All you need to do is take a note of what pins you physically wired up and input them into the configurator. Needs to be manually put into your machine HAL file before configurator is run as pncconf doesn't know what you are using it for.

You could put it into the machine HAL file in your plasmac config after configurator is run but if you run configurator again later it will lose it.

Clear as mud?

Cheers, Phill.

phillc54 wrote: You could put it into the machine HAL file in your plasmac config after configurator is run but if you run configurator again later it will lose it.

.

Just to be clear it goes into the original machine hal that is in the plasmac created config folder, not one of the hals created for plasmac?

Stefan, its time to throw pncconf away and edit your hal and ini files by hand. To tell you the truth I've never used it

Here is some stuff out of my hal file.

Just ignore the firmware entry in the first line and use what you already have in your file now

I'm not using plasmac to scale the voltage so I guess plasmac will make this connection for you.

I wrote a fair bit about setting up the THCAD last night. I'll share a document with you. Please let me know if it helps or if its incorrect as I wrote it away from a Linuxcnc config so I might have got something wrong.

Just to be clear it goes into the original machine hal that is in the plasmac created config folder, not one of the hals created for plasmac?

The best place is in the HAL file you created for your machine before you ran the configurator. That way you will always have a correct HAL file. The configurator will also make a copy of that in your final plasmac configuration directory.

Cheers, Phill.

@thefabricator03
I had the same heart burn a few weeks ago. I also wound up adding these lines to my hal per that discussion. That is for the 7i96, I don't know if that they are relevant to the 7i76e but I thought I'd share just in case.

I still think it would be nice to have a simple THCAD configuration gui for us rookies, something that could also be used to help with calibration settings / calculations. I've started tinkering with gtk / glade but I honestly doubt I would have time to knock it out anytime soon... Finally just started tacking together my table yesterday!

@rodw
I look forward to seeing your THCAD write up.

Well it goes something like this. Let me know what I got wrong....

Reading Arc Voltage with the Mesa THCAD
The Mesa THCAD board is a remarkably well priced and accurate voltage to frequency converter that is designed for the hostile noisy electrical environment associated with plasma cutting. Internally it has a 0-10 volt range. This range can be simply extended by the addition of some resistors as described in the documentation. This board is available in two versions, the THCAD-10 with a 0-10 volt range and the THCAD-300 which is precalibrated for a 300 volt extended range. Each board is individually calibrated and a sticker is applied to the board that states the frequency at 0 volts and full scale. For use with LinuxCNC, its recommended that the 1/32 divisor be selected by the appropriate link on the board. IN htis case, be sure to also divide the stated frequencies by 32. This is more appropriate for the 1 kHz servo thread and also allows more time for the THCAD to average and smooth the output.

There is a lot of confusion around how to decode the THCAD output so lets consider the THCAD-10 and a Mesa 7i76e for a moment with the following hypothetical calibration data
Full scale 928,000 Hz (1/32 29,000 Hz)
0 volt 121,600 Hz (1/32 3,800 Hz)

Because the full scale is 10 volts, then the frequency change per volt is
(29,000 - 3,800) / 10 = 2,520 Hz per volt
So assuming we have a 5 volt input, the calculated frequency would be:
(2520 * 5) + 3,800 = 16,400

So now it should be fairly clear how to convert the frequency to its voltage equivalent
Volts = (frequency - 3,800) / 2,520

THCAD Connections
On the high voltage side:
Connect the divided or raw arc voltage to IN + and IN-
Connect the interconnect cable shield to the SHield connection.
Connect the other Shield terminal to frame ground.
Assuming its connected.a 7i76e, connect the output to the spindle encoder input
THCAD +5v to TB3 Pin 6 (+5 VP)
THCAD -5v to TB3 Pin 1 (GND)
THCAD FOUT+ to TB3 Pin 7 (ENC A+)
THCAD FOUT- to TB3 Pin 8 (ENC A-)

THCAD initial testing
Make sure you have the following line in your ini file (assuming a Mesa 7i76e):
setp hm2_7i76e.0.encoder.00.scale -1
hm2_7i76e.0.encoder.00.counter-mode 1

Power up your controller and open Halshow (Axis: Show Homing Configuration) Drill down to find the hm2_7i76e.0.encoder.00.velocity pin. With 0 volts applied, it should be hovering around the 0 volt frequency (3,800 in our example). Grab a 9 volt battery and connect it to IN+ and IN-. For a THCAD-10 you can now calculate the expected velocity. (26,480 in our hypothetical example). If you pass this test, then you are ready to configure your LinuxCNC plasma controller.