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What kind of THC are you using?

John

I'm still researching, I thought about buying a brand PROMA THC, my intention is to use along with Hypertherm PM65 or 1650. But if you have a suggestion of a different type of THC can show me.

gois wrote:

I'm still researching, I thought about buying a brand PROMA THC,

This one: www.ebay.com/itm/321088257230 ?

It looks quite nice. An alternative is the $69 THCAD from Mesa. The Mesa device sends out a pulse train (which LinuxCNC can count with an encoder HAL module) this puts all the control in HAL (where you can see it).

Look at the bottom of the "AnythingIO Daughter boards" section at www.mesanet.com

Where do I find information for this HAL module, how to configure to have all control alert by LinuxCNC

gnipsel.com/shop/plasma/plasma.xhtml

gois wrote:

Where do I find information for this HAL module, how to configure to have all control alert by LinuxCNC

That rather depends on whether you end up with an up/down THC or an analogue arc-voltage THC.

gois wrote:

Where do I find information for this HAL module, how to configure to have all control alert by LinuxCNC

If you use the Mesa THCAD card the thc component information and connection is part of the man page .

This can also be viewed on the computer you installed LinuxCNC on by opening up a terminal and type in:
John

Can I hook up a Mesa THCAD card to a 5I25-7I76 combo for a good Torch height control? Would I have to modify the Plasma-5i20 configuration very much to get it to work? I don't have a lot of experience with Linuxcnc. I do have touch-off working with a floating torch head. I was able to get it working after looking at your touchoff subroutine John. Thanks.

yes their would be a few changes to your configuration mostly just in gpio pin allocations , the actual program it's self will work
dont worry if your not up to it , their is plenty of help to assist you available , your not alone with linuxcnc

once you are to the point of connections post your hal and ini files and let us know what pins you have allocated to the thc , and
we can guide you through the changes needed

I don't have access to my plasma computer till I get the memory stick in a few days but I believe this to be a current config for my plasma with the 5i20 7i76.

John

Ok. Thanks for the info.

Right now I am just using the pc's parallel port with a cheap C10 breakout board from Keiling and everything is working very well. How well would it work just hooking up the THCAD card to one of the C10's inputs and using a software encoder (velocity pin) to get arc voltage? Would this cause problems at fast cut speeds because of slow response? Would it possibly work?

I do know the THCAD card has dividers for the pulse to work with a parallel port but I don't know much about the C10 even though I used one on my plasma when I first started. At one time I used the parallel port directly I think with the THCAD...

John

It will work but the response time will be slower than when counted in hardware,
since a low pass filter is needed to get sufficient resolution.
At a 1 ms servo thread the THCADs ~1MHz count rate gives about
10 bit resolution or about 1/3 V resolution at 300V full scale

With a software counter, if you have a 50 KHz base thread you only get about 4-5 bits
of resolution at 1 ms update rate, so you need to use the low pass filter with about a
20 ms time constant to get to a useful amount of resolution.

Thanks guys. That is very helpful information. I will probably order the 5i25, 7i76, and THCAD and try to get it working in another computer.

Ok. Got my 5i25 installed in another computer. I was able to get John's 'plamsa-5i25' configuration to start up in linuxcnc after removing some lines in the ini and hal files. I have an adjustable power supply connected to the THCAD-10 voltage input to simulate an arc voltage. I have a couple questions.

1) For some reason I am getting a negative 'thc-encoder.vel'. I am able to correct this with negative values for 'thc-vel.scale' and 'thc-scale.offset'. Just wondering why it is negative value. All connections to the THCAD and 7i76 appear to be correct. I tried both single ended and differential connections to the incoder inputs on the 7i76 with same results.

my hal settings:

# Set up the Encoder for the THC
setp hm2_5i25.0.encoder.00.counter-mode 1
net thc-vel-in hm2_5i25.0.encoder.00.velocity => thc.encoder-vel
setp thc.scale-offset -119500
#setp thc.scale-offset 0
setp thc.vel-scale -0.00037866834
# this might need to be adjusted
setp thc.correction-vel 0.000075
# I added
setp thc.voltage-tol 1.0

question 2) I have to set 'thc.voltage-tol' manually in the hal file. The 'Voltage tolerance' setting in the pyvcp panel doesn't seem to be working or connected.

#net thc-volts-tol pyvcp.volts-tolerance thc.voltage-tol

If I remove the '#' Linuxcnc won't start up.

Also Arc 'Under' 'OK' and 'Over' lights don't seem to work or be connected in the postgui.hal file.

postgui.hal:

# THC connections
net thc-enable pyvcp.thc-enable thc.enable
net thc-voltmeter pyvcp.actual-volts thc.volts
net thc-voltset pyvcp.volts-requested thc.volts-requested
net thc-req-vel thc.requested-vel <= motion.requested-vel
net thc-cur-vel thc.current-vel <= motion.current-vel
net thc-vel-status pyvcp.vel-status thc.vel-status
net thc-vel-tol pyvcp.vel-tol thc.vel-tol

# connect the arc ok indicator
net start-motion-input => pyvcp.arc-ok

#net thc-volts-tol pyvcp.volts-tolerance thc.voltage-tol

# MDI commands
# rapid to home button
net remote-rapid-home halui.mdi-command-00 <= pyvcp.rapid-to-home

Appreciate any info.