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Hypersensing questions

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18 Apr 2020 12:17 #164446 by Uthayne
Replied by Uthayne on topic Hypersensing questions

I'm wondering now if the relay system would work with a short in the torch from water. Certainly the relays I used had on and off points well below the off threshold.

I wonder if its worth trying a 48 volt power supply and changing the THCAD scaling? Would that increase the on/off threshold. Maybe PCW could chime in here with his thoughts.


Are we having this issue because the thcad is too sensitive? Would F/64 smooth things out or would it be too slow?

For me, I'm going to try increasing the debounce value but also try changing the comp to add a band to the threshold. Since my on voltage only fluctuates about 0.03V when touching, I think I can add logic to cap it off say threshold + 0.05v. This is not an elegant solution but maybe it will work until we figure out the hardware side.

Another idea I've been thinking about is if plasmac triggers an ohmic trip prior to reaching probe height, maybe send a torch pulse signal for 0.1 seconds. It's enough to turn the air on but not actually fire the torch. Could help clear water out.

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18 Apr 2020 12:39 #164449 by rodw
Replied by rodw on topic Hypersensing questions
I don't think the issue is unique to the THCAD bud rather water tables in general as there are other similar reports about issues with water tables where the solution was to stop and clean out the torch. Non Linuxcnc...

Take a opto22 relay which turns on at 18 volts and off at 1 volts. It can never turn off.

But I think we have the opportunity to come up with something better.

One thing I noticed is I don't use encoder filtering. I wonder if you disabled it if you got a larger variance?

Also I wondered if we might be able to have a Mcode that pulsed the torch? It might be able to be called at the beginning oaf a job...

Anyway, its good to have some feedback... I gotta think through a different algorithm for ohmic2.comp...

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18 Apr 2020 12:45 - 18 Apr 2020 15:19 #164451 by tommylight
Replied by tommylight on topic Hypersensing questions
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Last edit: 18 Apr 2020 15:19 by tommylight.

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18 Apr 2020 15:21 #164470 by tommylight
Replied by tommylight on topic Hypersensing questions
Above post deleted due to some new information, will report back after sifting through it.

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18 Apr 2020 18:02 - 18 Apr 2020 18:04 #164478 by snowgoer540
Replied by snowgoer540 on topic Hypersensing questions

Above post deleted due to some new information, will report back after sifting through it.


Well i guess i can put the 4 resistors away then? :laugh:

Patiently waiting in suspense...
Last edit: 18 Apr 2020 18:04 by snowgoer540.

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18 Apr 2020 18:15 #164480 by Uthayne
Replied by Uthayne on topic Hypersensing questions

Above post deleted due to some new information, will report back after sifting through it.


Well i guess i can put the 4 resistors away then? :laugh:

Patiently waiting in suspense...


Haha I had mine out as well! Eager to try anything, but don't want to ruin anything

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18 Apr 2020 19:10 #164485 by tommylight
Replied by tommylight on topic Hypersensing questions

Above post deleted due to some new information, will report back after sifting through it.


Well i guess i can put the 4 resistors away then? :laugh:

Patiently waiting in suspense...

As i mentioned before somewhere, i have 4 o the THCAD on the way to me, so i can not test anything for now, but PCW reminded me that the ohmic sensing is not disconnected after probing, and that is a bit of a doodle as it can catch the wrath of the HV/HF start from the plasma and cause all kinds of havoc.
For now i have to wait, and even when i get them i have to find a plasma cutter with a shielded nozzle, all i have use no shields for that.
Then again, those THCAD can withstand quite a lot, so thinking differently for now.

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18 Apr 2020 20:35 #164508 by rodw
Replied by rodw on topic Hypersensing questions
So I think we need to explore what can be done in software before we give up. It would be good if Uthayne could disable the encoder filter and see if the voltage difference between on and off increase or not as I have never had it enabled.

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18 Apr 2020 21:32 - 18 Apr 2020 21:33 #164522 by Uthayne
Replied by Uthayne on topic Hypersensing questions
I tried disabling the encoder filter, did not see any change.

Here's some plots of a "wet torch" condition. Both touching the plate and not. The data was taken right after a pulse command, which had no real effect on lowering the voltage.

My low voltage is 23.8v and high is set at 23.9v

The noise seen on the floating picture is about 0.5v, maybe more, just eyeballing. Sometimes it gets as high as 24.5V, which is above what the PSU is set at (exactly 24.00V)

SHIELD on THCAD-5 is connected to frame ground.
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Last edit: 18 Apr 2020 21:33 by Uthayne.

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18 Apr 2020 22:13 #164530 by snowgoer540
Replied by snowgoer540 on topic Hypersensing questions

Above post deleted due to some new information, will report back after sifting through it.


Well i guess i can put the 4 resistors away then? :laugh:

Patiently waiting in suspense...

As i mentioned before somewhere, i have 4 o the THCAD on the way to me, so i can not test anything for now, but PCW reminded me that the ohmic sensing is not disconnected after probing, and that is a bit of a doodle as it can catch the wrath of the HV/HF start from the plasma and cause all kinds of havoc.
For now i have to wait, and even when i get them i have to find a plasma cutter with a shielded nozzle, all i have use no shields for that.
Then again, those THCAD can withstand quite a lot, so thinking differently for now.


Well, the nice thing is you have at least two guys who are stuck inside due to this pandemic stuffs, and willing to do tests. So you can live vicariously through us :)
The following user(s) said Thank You: tommylight

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