Random arc signal lost

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04 Sep 2020 09:27 #180634 by Clive S
Replied by Clive S on topic Random arc signal lost

Edited and added more info to the above post, sorry had to attend installing the roofing on the "hut" or "tent" or whatever that thing outside my shop is called. :)


Fridge in the winter and Sauna in the summer
The following user(s) said Thank You: tommylight

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04 Sep 2020 09:43 #180636 by tommylight
Replied by tommylight on topic Random arc signal lost

Edited and added more info to the above post, sorry had to attend installing the roofing on the "hut" or "tent" or whatever that thing outside my shop is called. :)


Fridge in the winter and Sauna in the summer

LOL, that is so true. :)

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04 Sep 2020 09:48 #180637 by rodw
Replied by rodw on topic Random arc signal lost
I'm sorry guys, I personally think you are off on a tangent debouncing your ArcOK. Show me the halscope plots showing signal bounce on ArcOK! I've never seen any evidence of that!

Please do not clutter Plasmac with unnecessary performance reducing crap! Leave that for the user to add if he needs it! I for one want the ArcOK to be taken in its raw state without any delays which software debounce inevitably adds. I don't want the pierce delay to be extended which will happen if a software debounce is added.. I want the plasma cutter to obey the cut parameters so that a 0.2 second delay is actually a 0.2 second delay not 0.22 seconds.

Don't you think Hypertherm, Thermal Dynamics ESAB et. al. have electronics engineers that might be smart enough to ensure there is no signal bounce on ArcOK which is a critical system parameter?

Please refer to the Plasma Primer which contains this halscope plot which dates back to my Everlast plasma cutter..


Zoom in and locate the pink ArcOK signal (hint, its near the arc voltage). Can you see any evidence of signal bounce? I can't.

I'm sorry Snowgoer. The fault I had with my Everlast ArcOK was correctly diagnosed by a panel of two silver haired experts in analog circuits. Your feedback just confirms that today, nobody understands the issue of relay contact oxidisation. Its not something that occurs in digital circuits. I had no clue either!

It might not be the issue causing your problem, but you should be aware of it and the fact there is a 25 cent fix for it.

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04 Sep 2020 10:06 #180641 by phillc54
Replied by phillc54 on topic Random arc signal lost
If you are looking for contact bounce I think you would require a much faster sampling rate than 200Hz.

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04 Sep 2020 10:07 #180642 by rodw
Replied by rodw on topic Random arc signal lost

If you are looking for contact bounce I think you would require a much faster sampling rate than 200Hz.


Show me an example from halscope then.

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04 Sep 2020 10:08 #180643 by phillc54
Replied by phillc54 on topic Random arc signal lost
I don't have that issue.

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04 Sep 2020 10:21 #180645 by rodw
Replied by rodw on topic Random arc signal lost

I don't have that issue.


Neither do I, don't make assumptions about plasma behaviour and force it on users without clear evidence its required. By all means discuss the possible issue in the docs though.

Few people have studied as many plots as I have. I've never seen evidence that ArcOK needs debouncing and I've drilled down a lot further than 200 Hz which is a function of the number of signals plotted in that example. Yet you choose to listen to somebody who has not even done one Halscope plot!

Don't get me wrong, I am full of admiration for what you've achieved with Plasmac but if I see you going down the wrong path I will call it out. And if its a Friday night after a busy day, a nice steak and some matching red grape juice, I may call it out rather bluntly.

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04 Sep 2020 10:27 #180646 by tommylight
Replied by tommylight on topic Random arc signal lost
@Rod,
To late, you should have backed me up when i was makig noise about this, but i never blame Phill, he just wants to please everyone and he likes challenges. :)

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04 Sep 2020 10:33 #180647 by phillc54
Replied by phillc54 on topic Random arc signal lost
Well I can only act on the feedback I get.

Just because you have not experienced contact bounce doesn't mean that it does not exist. I have never experienced contact wetting issues but I do agree that it does exist.

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04 Sep 2020 10:34 #180648 by snowgoer540
Replied by snowgoer540 on topic Random arc signal lost

I'm sorry guys, I personally think you are off on a tangent debouncing your ArcOK. Show me the halscope plots showing signal bounce on ArcOK! I've never seen any evidence of that!

I would wonder if I actually have to use an oscilloscope, and whether or not halscope can catch it. Talking to an electrical engineer friend of mine, it can happen quite fast.


Please do not clutter Plasmac with unnecessary performance reducing crap! Leave that for the user to add if he needs it! I for one want the ArcOK to be taken in its raw state without any delays which software debounce inevitably adds. I don't want the pierce delay to be extended which will happen if a software debounce is added.. I want the plasma cutter to obey the cut parameters so that a 0.2 second delay is actually a 0.2 second delay not 0.22 seconds.

Currently, what fixed Cody's table is 5 periods on the 1000000ns servo thread, or 5ms. 5 milliseconds is .005s. So, as it is currently, it would bump your pierce delay from 0.2 seconds to 0.205 seconds. I am hard pressed to believe you can tell the difference a 0.005s debounce has on your pierce. However, without the debounce, the table, as I said, is unusable. But aside from all of that, if you dont want it, just don't add it to your config, or comment it out if it ends up there B)


Don't you think Hypertherm, Thermal Dynamics ESAB et. al. have electronics engineers that might be smart enough to ensure there is no signal bounce on ArcOK which is a critical system parameter?

I don't think it really has anything to do with their intelligence. It probably either has to do with industry standard, or cost. They're dry contact relays. They have mechanical bounce, and as such electrical noise. By your same logic, you could say "If minimum current fixes this problem, don't you think the engineers would be smart enough to mention it in their manual?"


Please refer to the Plasma Primer which contains this halscope plot which dates back to my Everlast plasma cutter..

I'm curious A if your halplot is shown with your resistor in place, and B if halscope is fast enough to catch it and C what it looks like when you zoom in much further (with halscope, not on a grainy picture).


Zoom in and locate the pink ArcOK signal (hint, its near the arc voltage). Can you see any evidence of signal bounce? I can't.

I would expect to have to zoom in MUCH further to see it. The time period of this plot is far too coarse to see the electrical noise from contact bounce.


I'm sorry Snowgoer. The fault I had with my Everlast ArcOK was correctly diagnosed by a panel of two silver haired experts in analog circuits. Your feedback just confirms that today, nobody understands the issue of relay contact oxidisation. Its not something that occurs in digital circuits. I had no clue either!


No need to be sorry bud. As I stated, the table wouldn't cut metal before, and it cuts metal now :) I would propose that by the same logic you apply to oxidation, perhaps the "silver hair" folks you mention aren't aware of digital computers fast enough to be effected by the switch bounce present in analog circuits. As stated, I suspect the resistor reduces the hysteresis present. Bounce when mechanical switches, buttons, relays, etc. is an electrical fact. In fact, that's why a debounce module exists in the first place.


It might not be the issue causing your problem, but you should be aware of it and the fact there is a 25 cent fix for it.

Table seems to work fine so far now (knock on wood?). I'd be remiss if I didn't point out that adding debounce to the arc-ok signal is ... free, and there's no chance of wiping out a ~$200 Mesa card due to a misplaced resistor. :)

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