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TIG pedal build

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TIG pedal build

Postby DennisCA » Wed Nov 23, 2016 4:12 am

I've come to the conclusion I want a pedal for my TIG welder. I'm used to not being able to change the current when welding but I just can't get to grips (ha ha) with this torch style that my machine has:
http://arweld.net/userfiles/image/008.JPG

I see americans use much slimmer handles and with much more flexible torch hoses and I think, that looks nice. But I don't have a pedal, I couldn't use such a torch unless I mounted a trigger on it, which kinda brings me back to square one doesn't it? i looked up what a pedal for a kemppi would cost and it said 800 euros!!!!??? I found some 3rd party from the UK for 250, still too steep for my shallow pockets.

Only one way to go, build my own. Which turned out to be more difficult than I thought for this welder. It doesn't work like most of you are used to, you set the max current on the welder and that's it. Any remote, hand or foot (I have a hand remote, meant for stick welding) takes over completely. So Kemppi pedals have a min and max adjustment on the pedal itself. I would have to replicate this and I have no electronics skill or experience. Fortunately I was able to get a schematic from Kemppi, and with the help of some electronics forums I was able to start building:

Started out with a scrap u-beam I cut to shape with the portaband
Image

Bottom plate from scraps:
Image

Potentiometers for min and max mounted on the front, copying the kemppi design here. I found some sprockets that fit on the pots, thought they looked cool as knobs:
Image

I then made the circuit I had designed in kicad:
Image

Electronics installed:
Image

This is where I am now, not yet completely finished, I lack a 4-pin amphenol connector for the microswitch which has a separate connector, but the pedals current adjustment worked correctly when I tested it so all I need is that part (in the mail).

I might redesign it yet, it might make more sense to put the electronics and the min and max adjustment in a separate box on the welder itself and just have the switch and main pot in the pedal, it wold be easier to adjust that way instead of reaching down the front of the pedal.

I've really learned a lot from doing this project, about electronics, PCB design and just how this whole setup works, if it breaks I know I can fix it myself.
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Re: TIG pedal build

Postby Artie F. Emm » Wed Nov 23, 2016 6:09 am

Good morning! Very impressive build. To start with zero electronics experience and a schematic means you learned it all the hard way. Good on ya!
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Re: TIG pedal build

Postby RamboBaby » Wed Nov 23, 2016 10:59 am

Holy crap dude,
That's the cat's nuts! Big, hairy, swaggering nuts made out of brass that clang together like a bell when the cat walks!!!
#AWESOMENESS
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Re: TIG pedal build

Postby exnailpounder » Wed Nov 23, 2016 11:11 am

Wow! Very impressive. Great job!
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Re: TIG pedal build

Postby AndersK » Wed Nov 23, 2016 4:39 pm

That is a sturdy build indeed 8-)
Like the gears as pot knobs :mrgreen:

What will the pcb do?
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Re: TIG pedal build

Postby MosquitoMoto » Wed Nov 23, 2016 5:59 pm

Impressive and also kinda Steampunk - I like it.

Dennis, I will say this - the torch that came standard with my machine was also one of those bloody awful, bulky 'Euro style' (Trafimet?) torches with the switch.

I absolutely hated it.

I purchased a lightweight tube-style torch online and attached a cheap paddle switch. Trust me, if you ever need the option of a more nimble torch with a switch on it, this setup is MUCH better.

If I ever found the person responsible for designing those awful Euro style torches, the next person to see his torch would be his Proctologist.


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Re: TIG pedal build

Postby kiwi2wheels » Wed Nov 23, 2016 8:40 pm

MosquitoMoto wrote:Impressive and also kinda Steampunk - I like it.

Dennis, I will say this - the torch that came standard with my machine was also one of those bloody awful, bulky 'Euro style' (Trafimet?) ..................................

If I ever found the person responsible for designing those awful Euro style torches, the next person to see his torch would be his Proctologist.

Kym


:D :D :D

Right on Kym !
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Re: TIG pedal build

Postby DennisCA » Thu Nov 24, 2016 12:41 am

Thanks guys!

AndersK wrote:That is a sturdy build indeed 8-)
Like the gears as pot knobs :mrgreen:

What will the pcb do?


Well based on what I've found out how these things work I believe it modifies the range of the 10k pot that adjusts the current. Without the PCB and the two other pots doing their thing, the potentiometer alone would just be a 10k pot and if you hooked that up alone it would change the amperage between 0-300A (range of this machine). That's basically how the hand remote that I got with the machine works, just a 10K pot in a plastic housing is all it is.

So the PCB is all about modifying the resistance range of the potentiometer, while maintaining it's full physical "throw". I can see this being useful, if you want a narrow range with lots of "resolution" in your pedal for some reason, then you could set it say 50-100A and get a 50A range on your pedal, or less.
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Re: TIG pedal build

Postby MosquitoMoto » Thu Nov 24, 2016 12:57 am

Just one thing;

I love the knobs on the front of the pedal but they wouldn't work for me. Your setup and technique might be different but while welding I am forever moving that pedal around, generally with a haphazard push of the foot, as I reposition myself to tackle another part of the project I'm on.

You are probably way tidier than I am (most people are...) and won't have any such problems, but if I had knobs on the front of my pedal I'm sure they'd get moved about as I accidentally shoved the pedal into whatever was on the floor at the time.

Perhaps I should just tidy up...



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Re: TIG pedal build

Postby DennisCA » Thu Nov 24, 2016 1:58 am

I try to keep it tidy as I get frustrated when things are in disarray, though in a project things just happen to get like that until it's over. It's a constant battle. But you are right, I might in the future move the PCB and min & max pots into their own control box and attach it permanently on top of the welder or perhaps on the side.

This is my welder, old school slow frequency inverter, squeals in use, made in '94 I think, a sticker on it says serviced in 2011:
Image

What you see there is my attempt to add a dust cover. The intake under has a filter too, it's a solid old unit.
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