DIY amp control for TIG

[Burkeee]

My second hand tig machine didn't come with a remote, and I tried a few welds scratch starting it and running a constant amperage, but I'm spoiled by using foot and hand amp remotes at work and school. I'm not too excited about spending a couple hundred for a new one, so I cobbled together a DIY unit.

http://myweb.dal.ca/burkep/welder/DSC01575.JPG

The pedal was a 115V on/off switch to use with grinders etc, but all it was was a switch and a spring. I gutted the insides and mounted a 10k pot from radio shack which has a bobbin on it and the torsion spring from a toy pull back car. The big spring in the middle forces the treddle up, which pulls on the string and winds out the pot to full off. As you step on the pedal the torsion spring on the pot winds the string in and cranks up the amps. The switch on the outside turns on the gas and current as soon as you step on the pedal.

http://myweb.dal.ca/burkep/welder/DSC01574.JPG

I wired it up and tested it tonight, and it worked great. I used to do some practice beads on some 1/16" aluminum sheet. I've done a bit of steel tig before, but not much Al.

http://myweb.dal.ca/burkep/welder/DSC01578.jpg

I don't know about the longevity of the pedal with the 2 springs fighting each other, but at a total cost of less than $20, I'll just keep building new ones.


Paul

[guidolyons]

Looks a sewing machine pedal.

[Wicked_S10]

I made a similar pedal and a hand control for my miller CST 250. Here is a snip from my thread posted elsewhere:

I made my hand controler with a 5k linear pot and it works great, I also built a tig pedal. It is not real pretty, but I mostly wanted to see if my mechanics would work before I built it out of more than scrap around the shop. I am happy to say it works flawlessly. I built it useing one of the ideas metioned in one of the previous threads that were sugested above. Basically a little spool I made out of two brass things I found in a drawer in my grampas old shop, I drilled them to fit the pot shaft and tapped them for a set screw. The "linkage" is all 30lb Stainless Steel Fishing wire, and the springs are from my local Home Depot. All and all includeing the radio shack pot it cost me about $15. There is no contactor control because my CST doesn't use it, but for someone needing contactor as well, Radio shack sells a SPST switch that piggybacks their pots. I am not sure if it will handle the current needed for contactor control, but I assume it would since the contactor is basically a small solenoid...

http://www.rollmeover.com/jeepboard/low_tigpedal_001.jpg
http://www.rollmeover.com/jeepboard/low_tigpedal_002.jpg
http://www.rollmeover.com/jeepboard/low_tigpedal_003.jpg
http://www.rollmeover.com/jeepboard/low_tigpedal_004.jpg
http://www.rollmeover.com/jeepboard/low_tigpedal_005.jpg

It worked great for the inverter CST 250, but when I traded off my CST for a big dialarc, and hooked up the pedal to that I smoked it. Evidently the potentiometers are only good for the inverter machines control circuit. They wont handle the current needed to run the Mag-Amp current controls on bigger transformer machines. Turns out you need a linear wound high current pot, capable of at least handling 10-15 amps. I ordered a pot from miller, but it does not include the brush assembly, so I back burnered the thing for a while. My only point is that although it is a cheap, and will work just as well as a miller pedal, it wont work for just any machine. I have a hard time believing that for how simple the damn pedals are, that the manufacturers can justify charging so much for one. I mean, $250 for a damn variable resistor, housing, and chunk of cord is freaking ridiculous! I applaud your creation though, looks a hell of a lot better than mine!

Later,
Jason

[jeepnmatt]

how do you determine which pot to use?

i have a PowCon 130SS and can no longer get pedals or finger controls for it since Miller bought PowCon. i did some research and found a place in CA that would build a custom for me for around $400...no thanks.

i have access to an old foot pedal from a potters wheel. i'll just need to put the correct pot, wiring, and connector to hook it up to the PowCon.

thanks!
Matt

[Burkeee]

Mine is a mosterous ESAB transformer and the 0.5 watt pot works fine for me. Maybe the older transformer machines run the current straight through the pot? I know I'm supposed to have a 2 watt for mine, but it still works with 0.5, just probably for 100,000 cycles instead of 1,000,000.
I found the owners manual for the pedal that my machine is supposed to use off the ESAB website. Had a circuit diagram and socket pinout, and a parts list. Everything I needed to know to copy it.
If you cant find a manual for your PowCon, take the panel off and check which pins in the socket are hooked up. There is usually 2 that go to the contactor switch, and 3 that go to the pot. Take a pot with a high value, say 100K and hook it up. Turn it up slowly until the current doesn't go up anymore. Measure the resistant off the pot at that setting.

Paul

[Wicked_S10]

your machine is probably still solid state control, the dial arc is mag drive, it sends a percentage of the current through the control, not all of it, but it still much higher than any of the solid state machines. As for a pot, you can use almost any linear pot on an inverter, the higher the resistance it goes to though the more coarse the control will be because what it actually does is reduse a reference voltage as a signal and the machine translates that to amount of current output. The best bet is to try to find a manual for the pedal your machine had available, in the parts list, they will typically list the size of the variable resistor.

[jasonmt]

your machine is probably still solid state control, the dial arc is mag drive, it sends a percentage of the current through the control, not all of it, but it still much higher than any of the solid state machines. As for a pot, you can use almost any linear pot on an inverter, the higher the resistance it goes to though the more coarse the control will be because what it actually does is reduse a reference voltage as a signal and the machine translates that to amount of current output. The best bet is to try to find a manual for the pedal your machine had available, in the parts list, they will typically list the size of the variable resistor.

There is a reason why the Dial-Arc has a 3 blade twist-lok plug for the remote instead of a little 5, 6 or 14 pin plug, I have a hand control for mine and the pot looks more like a light dimmer than anything else.

[Wicked_S10]

There is a reason why the Dial-Arc has a 3 blade twist-lok plug for the remote instead of a little 5, 6 or 14 pin plug, I have a hand control for mine and the pot looks more like a light dimmer than anything else.

Yeah, it never crossed my mind when I hooked it up... I actually considered using a light dimmer to build a control for the dial arc. The wall I ran into their, is for about the last 15 years or so light dimmers have used triacs instead of resistance dimmers. Basically switching power on and off very quickly to reduce the light output. If I could find a old school rheostat light dimmer, I would probably be in business...

[Urban Wheeler]

I was searching DIY tig welder stuff on the Hobart board and found some circuits that would help some of you, I remember they used a pot to control some SCRs and I think they were in the line in circuit.