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Thread: DIY TIG Pedal
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16th Oct 2022, 04:38 PM #76Golden Member
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Wiring done. I’m also going to swap out the potentiometers for logarithmic ones as I need less change at the beginning and more at the end as the pedal has more amperage change in the beginning. Also the max amp adjuster goes from 20 to full in about 1/20th of a turn.
The connector block was threaded and is attached from underneath like everything else with countersunk M4 bolts.
Still need to do some cable tidying, but I’ll do that on final assembly after paint.
My bench as I was playing around with potentiometers. Garage is nice and tidy now though.
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17th Oct 2022, 02:17 AM #77
Hi Neevo,
I suspect that the "Max Amp" pot needs to be in series with the bottom end of the 10K pot rather than across slider to one end. I'm assuming that 20 amps is the starting current. Also the way you currently have it wired, it will change the linear law of the 10K pot to a semi log one between the slider and one end.Best Regards:
Baron J.
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17th Oct 2022, 07:07 AM #78Golden Member
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Yeah I did quite a bit of work to get the potentiometer layout correct. Actually just reread the whole thread to understand what I did.
Oddly even without the second potentiometer the pedal goes from 20A to 200A in a very short amount of time. I suspect that there’s a weird relationship between the pedal voltage and how it ramps up the current.
The second potentiometer improves this problem significantly, I suspect because it adds some logarithmic ramp up. So I was hoping a new log pot on the main would improve this even more.
I’ll get some more pots and play around a bit.
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17th Oct 2022, 07:11 AM #79Golden Member
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I’ve also ordered some 1mm music wire to make a new spring for the upper pedal.
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17th Oct 2022, 10:04 AM #80Golden Member
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Testing rig with new potentiometers.
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17th Oct 2022, 05:45 PM #81Golden Member
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The log potentiometers are definitely much better. I’ve also found that a 1K pot is a lot better than the 10k I have been using. Is it possible that the welder is seeing the resistance and using that to adjust the amperage?
I would have assumed it’s a simple voltage regulator but that doesn’t seem to be the case given the 10k and 1k pots are behaving so differently.
The 1k has a much longer low amp ramp up.
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18th Oct 2022, 05:57 AM #82
Hi Neevo,
*. There will almost certainly be a voltage from the welder applied to the pot, you can check this by setting the pot to its maximum value and measuring the voltage across the ends. Also the lower value pot will be able to take more current from the source. This should not result in a lower voltage across it. If the voltage is substantially lower, then the pot resistance is too low.
*. It may be that the voltage source to the pot is not DC ! Which means that you will need an oscilloscope to measure it, if its anything other than DC or a 50 to 100 Hz sine wave your multimeter might tell you lies.
Best Regards:
Baron J.
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20th Oct 2022, 03:51 PM #83Golden Member
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My thinner piano wire came in. I think it’s too light but I’ll give it a go anyway. This time I built a mandrel to form the spring on the lathe. Low speed and back gear.
I was able to create this:
I will make a bushing for it to go on and another stub as the stop for the second leg. Fingers crossed I can get enough tension on it to lift the upper pedal:
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20th Oct 2022, 06:51 PM #84Golden Member
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Nice proof of concept but this spring wire doesn’t stand a snowballs chance in hell of holding up the pedal.
Looks like I’m ordering even more piano wire!
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20th Oct 2022, 06:59 PM #85
Hi Neevo,
I think that I would have just used the thicker wire and made a new spring ! Whatever you use will get compressed with use !Best Regards:
Baron J.
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20th Oct 2022, 07:15 PM #86Golden Member
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23rd Oct 2022, 10:21 AM #87Golden Member
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DIY TIG Pedal
I have all the parts in paint. Hanging up after some machine grey alongside some table legs that are getting a spruce up before they go off to a local charity.
I also bought some 1.5mm piano wire to make the upper pedal return spring. Hopefully that thickness works.
Actually I am trying to spray the tops of the tables too but without a lot of luck. I can easily spray the metal paint (oil based) but the water based stuff for the table tops is more of a challenge. Been spraying it neat but might try and sand back what I have and try and dilute the paint a bit to get it flowing a bit better from the gun.
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26th Oct 2022, 09:15 AM #88Golden Member
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I’ve started the rebuild process. Always a fun time as I get to lay out all the components and start putting them in their place for (hopefully) the final time.
I did go to Bunnings and buy some soft rubber feet and have drilled 4 corner holes to mount those so it doesn’t go skidding around the floor when I try and use it.
The only real part to solve at the moment is making the new pedal lift spring to keep the upper part off the micro switch.
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29th Oct 2022, 09:04 AM #89Golden Member
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I’ve finished up the pedal and it got it’s maiden flight just now. I had to swap out the max amps potentiometer as the 1k one was limiting the max amperage to 130A, put a 10k pot in and now it’s working perfectly.
The pedal all wired up and ready to put the lid on:
Some skateboard grip tape for the top and it’s all done:
Gave it a test run and it’s working perfectly. Not my best weld and I should have dialled the pedal down (max amps set to 130 and forgot to change it) but it’s awesome to have more control:
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1st Dec 2022, 07:46 AM #90New Member
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Hi Neevo,
This is a really nice build. I'm trying to adapt my old pedal to my Unimig Razor 200. As you know, there are only four wires connected to the pedal 7pin plug inside the Razor 200. I'm struggling to understand the five wire set up you have here and what goes where. Would you have a schematic to help me out with the pot wiper?
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