Adding a Foot-Pedal to an Inexpensive TIG welder

About 9 months ago I bought a Chicago Electric 240 Volt Inverter Arc/TIG Welder with Digital Readout, item#98233 from Harbor Freight.  I didn't realize it when I bought the welder, but it is not possible to simply buy a foot pedal separately and plug it in.  I had bought a $75 foot pedal online, and found that while the outlet on the welder had 2 prongs, the pedal's plug had 7.  No matter how hard I pushed, the two would just not connect.

So I dug in.  I'm not embarrassed to say I didn't know much about electronics, just the basics of which I retained from my Welding classes-- AC/DC, Amps-Volts-Watts, and not touch anything with a current going through it.  So I bought some electronics for dummies books, a starter electronics kit, and got to learning.  After a few months of gaining confidence and learning the vocabulary, I searched online for any instructions on how to add a foot pedal to this particular welder, but found very little on the subject, of which was scattered and confusing.  I managed to make some sense of it, and with my newfound background on electronics I made some figures of how to accomplish my goal.

After weeks of looking for the parts I needed online and getting them delivered, I crossed my fingers, opened the welder's cover, and started cutting wires.

My first attempt was promising.  The connections were good, the pedal worked, and when I took it outside to try it, I got some heat.  However, the max amps had dived from 160A to 60A.  It would have worked for me as I'm only working on thin sheet-metal, but I wanted it better! So took it in and tried again.

My beloved Welder

I switched my 22 ga. tinned-copper wires with 18 ga. bare-copper wires, and tried that out.  Didn't work.  After some deductive reasoning, I then switched out the foot-pedal wiring with the 18 ga wires.  It brought the Amps up to 90... for the first 10 seconds, and I lost it.  Testing it with the pedal cover open, I noticed the sliding potentiometer in the pedal was sparking... it couldn't handle the current!  I wanted to get it done so I searched all the electronic shops nearby (Fry's, Radioshack, MarVac), and NONE of them have sliding potentiometers!! I finally found one 45 minutes away, a pot meant for Arduino models.

It works.  The welder now goes up to 150 Amps, and I can switch the welder between foot-controlled and torch-controlled.  If I could find a sliding pot that is not connected to a board and I can verify its Wattage capability, I'm sure I could get that number up...but I'm quite satisfied with 150A out of 160A.

During my frustrating hours, I promised myself that if I could get the welder to work, in gratitude I would post instructions on how to add the foot-pedal online, something people could understand.  So look at my page links to the left to find detailed instructions and diagrams of adding a foot-pedal to the Harbor Freight TIG Welder.