THC Controller Polabs.com - PlasmaSensOut on LinuxCNC v2.8 connection

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15 Aug 2020 19:49 #178319 by hermann1976
Dear LinuxCNC Forum,

I'm a beginner in LinuxCNC and I have a problem.

I am in the process of building a plasma machine and have converted a basic machine into a plasma machine with the Plasmac Configutator.
So far everything has worked.
With ARC Ok and THC I use mode 2.
With the THC up or down connection, I connected 7i76e.0.encoder.00.input-a and 7i76e.0.encoder.00.input-b to the encoder input for up and down movement.
THC worked well. When the cutting voltage changed, the Z axis moved up or down during the cutting process.

During the final assembly, I changed the cable routing for the ground connection of the thc controller and then accidentally took the 24V + connection instead of ground. (stupidly....)
Unfortunately the hardware encoder chip is broken.
But everything else works fine.

My question to you is: is it possible to use a different connection for the THC up and down command?

A repair request is already out.
Repair Request

I still had one mor problem (before the mistake): The THC Active LED did not light up. Though THC worked up and down.
Does this have to do with the middle port on the THC controller? How should this be connected? (No. 2 Arc OK signal?)

I ask you for help with my problem.
Many thanks
(Answers could be also in German)
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15 Aug 2020 20:40 #178323 by tommylight
That type of THC does not go to encoder inputs, they are to be wired to normal inputs, or in your case they should be wired to normal inputs on the 7i76. Where did you get the idea of wiring it to the encoder inputs? I would like to know so we can avoid further miss information.
You can use any of the 32 inputs on the 7i76E, TB5 from pin 1 to pin 16 and TB6 from pin 1 to pin 16, for the up/down and arcok, you need to have arcok connected, it will not work without it.

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15 Aug 2020 22:06 #178329 by hermann1976
Thank you for your fast answer.

That was my first attempt to use an input connector.
I tried it, but in the HALshow I couldn't see any change in the input pins.
I am not an electrician but if I understand it correctly then the input pins are switched with connected to 24 V +.
But according to the description, pin 4 is connected to ground.
If I measure the voltage at Pin1 or Pin3 against ground, then this is approx. 8-10V with no up or down switching. Then when a movement request comes the voltage drops to zero.
In any case, it worked with the encoder inputs. At first ist was only a test with the encoder connection.
Unfortunately there is not really anything useful on the web for connecting the Polabs.com THC controller for LinuxCNC.
The ARC Ok Signal will comes direktly from the Tewin Plasma 100 Generator if the arc was buildet (picture). So in my understanding the ARC Ok from the THC Controller should be the THC Active Status.
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15 Aug 2020 23:32 #178334 by PCW
It would be possible to use the serial expansion port RX pins as a differential input for the THCAD, with modified firmware

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16 Aug 2020 06:19 #178356 by tommylight

I am not an electrician but if I understand it correctly then the input pins are switched with connected to 24 V +.
But according to the description, pin 4 is connected to ground.

The easiest solution would be to use 2.2k to 4.7k pullup resistors on the inputs.

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16 Aug 2020 08:23 - 16 Aug 2020 08:34 #178365 by hermann1976
Thank you tommylight,
i tested your solution and it works perfectly.

One more Question: Whats up with the "THC active" Led. It doesn´t do anything. THC is working (the leds also too) but no reaction on led THC active. Is there a separate connection for it?

Many thanks,
Hermann
Last edit: 16 Aug 2020 08:34 by hermann1976.

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16 Aug 2020 09:23 #178373 by tommylight
Do you have the THC enabled on the RUN panel?
If yes, then there is something with the feed speeds as the THC will not activate if the speed is lower than the one set in gcode.

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16 Aug 2020 10:48 #178380 by hermann1976
Speed for cutting comes from the Material Selection.
THC is enabled and working (see attachments). But the THC active is not lightning.
Sometimes in the corners ist blinking the THC Velocity Lock, when the feedrate ist sinking under the settings from the material.
Is also working correctly. (i think this was the point what you meant)
Attachments:
The following user(s) said Thank You: tommylight

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16 Aug 2020 10:56 #178383 by phillc54
Looks like it might be a bug. It seems the THC Active LED only works for modes 0 & 1.
Is your THC actually working correctly apart from the THC Active LED.

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16 Aug 2020 11:19 #178386 by tommylight
If the THC Velocity lock is working, that is another good sign that the THC is working correctly.
Nicely done, and thanks to Phill the issue will be fixed very fast.

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