everlast 82i ohmic sensing

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68rscamaro
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everlast 82i ohmic sensing

Post by 68rscamaro » Mon Nov 16, 2020 4:42 pm

Is anybody using ohmic sensing with an 82i? I've done a fair amount of searching and can't seem to find shielded consumables.
Any help or a link to what I need would be much appreciated!

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Re: everlast 82i ohmic sensing

Post by adbuch » Tue Nov 17, 2020 2:52 am

68rscamaro wrote:
Mon Nov 16, 2020 4:42 pm
Is anybody using ohmic sensing with an 82i? I've done a fair amount of searching and can't seem to find shielded consumables.
Any help or a link to what I need would be much appreciated!
You can rig up your own - I have seen it done several different ways. The main thing is that you want to attach the sense wire to make electrical contact with the shield. The Hypertherm version looks like this. You could even use a small hose clamp to attach a metal spade lug to emulate this setup for your machine.
David
Ohmic Sensing Retaining Cap.jpg

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68rscamaro
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Re: everlast 82i ohmic sensing

Post by 68rscamaro » Tue Nov 17, 2020 8:16 pm

That's exactly what I would do if my torch looked anything like that! This is what I have, just wondering what I need to get to make it work

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Re: everlast 82i ohmic sensing

Post by adbuch » Tue Nov 17, 2020 8:35 pm

You could use a small hose clamp and attach a copper wire directly to your nozzle.
David

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Re: everlast 82i ohmic sensing

Post by djreiswig » Tue Nov 17, 2020 10:56 pm

Check and make sure your nozzle is electrically isolated from your work lead. This is not the case on some plasma cutters. I know the topic has come up here before. If there is continuity between the nozzle and the work lead with an ohm meter then an ohmic setup won't work.
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Re: everlast 82i ohmic sensing

Post by adbuch » Tue Nov 17, 2020 11:46 pm

djreiswig wrote:
Tue Nov 17, 2020 10:56 pm
Check and make sure your nozzle is electrically isolated from your work lead. This is not the case on some plasma cutters. I know the topic has come up here before. If there is continuity between the nozzle and the work lead with an ohm meter then an ohmic setup won't work.
In that case, perhaps a shield could be added that is isolated, or even a separate "probe" mounted to the side of the retaining cap. This could be a piece of copper rod which protrudes to the same height as the tip of the nozzle.
David

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Re: everlast 82i ohmic sensing

Post by Rodw » Wed Nov 18, 2020 5:18 am

Be very careful here. When you have an exposed tip like that, as soon as you start cutting your ohmic circuit will take the full brunt from the arc voltage. So the whole circuit and any isolating relays etc need to be able to handle around 500 volts and in your case at up to 80 amps! A meltdown is almost inevitable. I was part way through setting something up for my Everlast 50s before I realised this and stopped!

I have not tested it but if you were willing to move to linuxcnc, the hypersensing circuit with a $69 Mesa THCAD-5 I developed in conjunction with Mesa, should manage it. It is certainly been well tested to prove its impervious to torch voltage as my and my recollections of using an Everlast, I think it should work. Provided you use the recommended isolated power supply, everything is capable of withstanding overvoltage to 500 volts.

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Re: everlast 82i ohmic sensing

Post by adbuch » Wed Nov 18, 2020 6:01 am

Rodw,
Please put on your Electrical Engineering "hat" here and talk to me. How is a copper probe in close proximity to the nozzle/cap any different than having the ohmic sensing wire connected directly to the shield (if one were available for his torch)? In both cases, the shield (or probe) would be exposed to the same voltage levels while cutting. These are both essentially the same thing, and would serve the same purpose. Please tell me what I am missing here. Of course, the prerequitite for the adaptation of ohmic sensing with the OP's system will hinge on his processing circuitry (if any) which may very well include relays or solid circuit relays for isolation.
David

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Re: everlast 82i ohmic sensing

Post by adbuch » Wed Nov 18, 2020 6:31 am

Rodw wrote:
Wed Nov 18, 2020 5:18 am
Be very careful here. When you have an exposed tip like that, as soon as you start cutting your ohmic circuit will take the full brunt from the arc voltage. So the whole circuit and any isolating relays etc need to be able to handle around 500 volts and in your case at up to 80 amps! A meltdown is almost inevitable. I was part way through setting something up for my Everlast 50s before I realised this and stopped!

If you have the relays in place that can handle the "500 volts" and up to 80 amps, then a meltdown is not inevitable. But your point is well taken.
David

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Re: everlast 82i ohmic sensing

Post by adbuch » Wed Nov 18, 2020 6:34 am

Rodw wrote:
Wed Nov 18, 2020 5:18 am

I have not tested it but if you were willing to move to linuxcnc, the hypersensing circuit with a $69 Mesa THCAD-5 I developed in conjunction with Mesa, should manage it.
I'm not sure the OP needs to switch to linuxcnc to solve his problem. While this is an option, there are probably much simpler solutions.
David

68rscamaro
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Re: everlast 82i ohmic sensing

Post by 68rscamaro » Thu Nov 19, 2020 8:58 pm

Thanks for the input guys! I did find (and ordered) some shielded consumables that I'm going to try. A guy on one of the Facebook groups has the same system (myplasm) and said it's working well. This is what he did.

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Re: everlast 82i ohmic sensing

Post by djreiswig » Thu Nov 19, 2020 11:03 pm

Looks like it should work. I've seen people modify a non ohmic Hypertherm retaining cap with a tab and a hose clamp.
2014 Bulltear (StarLab) 4x8
C&CNC EtherCut
Mach3, SheetCam, Draftsight
Hypertherm PM65
Oxy/Acetylene Flame Torch
Pneumatic Plate Marker, Ohmic, 10 inch Rotary Chuck (in progress)

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Re: everlast 82i ohmic sensing

Post by adbuch » Thu Nov 19, 2020 11:11 pm

68rscamaro wrote:
Thu Nov 19, 2020 8:58 pm
Thanks for the input guys! I did find (and ordered) some shielded consumables that I'm going to try. A guy on one of the Facebook groups has the same system (myplasm) and said it's working well. This is what he did.
That looks good! Thanks for the update.
David

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