Tom Mooijman
New Member
- Messages
- 19
- Location
- The Netherlands - Rotterdam
My welder (XMT 350) is a multi process welder, although it is mostly used as a MIG machine, I've always been interested in learning some TIG welding. Now the XMT doesn't require a foot pedal, I figured that learning TIG welding doesn't but make a lot of sense without a foot controller. I was looking at foot pedals and thought it would be a fun project to build myself; no it probably is not worth the trouble since SCC makes good, (somewhat) affordable foot pedals. However, I had an idea and some parts laying around that would make for good distraction in between studying.
The idea of a pedal is easy enough, typically it requires two features; a switch to tell the welder to start an arc, and a voltage divider to tell the welder how much heat you want coming from the pointy end. I wanted to keep it as simple and robust as possible, since it will spend a lot of time on a dirty floor, being stepped on, kicked and yelled at.
A voltage divider can be as simple as a potentiometer (10k rotary potentiometer in this case), but these pots can typically rotate 300° for their full range. Which is not very useful since our feet are not designed to make similar movements. Most DIY pedals use pulleys, strings/belts and springs to get the full range of the pots. But I didn't like the idea of fiddling with strings or belts. My idea was to make a gear reduction to 'drive' the pot, I had some small gears from an old uni project so I gave it a try just to see if it would work.
Now potentiometers can rotate ~300°, the gears I had could make a 5:1 reduction, so 60° of pedal rotation.. Good enough for a proof of concept. I had some scrap pieces of square tubing that would make the body of the pedal and some 5mm stainless steel rod to make a torsion spring. A few years ago I made a quick jig to make springs and was happy to find it in the scrap pile for this project.
I added two potentiometers, one for the foot amperage control, the other controls the upper limit of the foot control (in case I am too lazy to reach for the dial on the welder, but mostly because why not), they're both 10k Ohm pots but the dial on the front should probably be 2k or 4k Ohm (because of some weird nonlinearities).
There is a small limit switch wired normally closed in the pedal that will activate lift arc on my welder when the foot pedal is depressed.
This pedal functioned properly and was pretty easy to build with basic tools, the first iteration is shown in the first picture. But the 60° rotation of the pedal was HORRIBLE, but I knew that already and figured 30° would be a comfortable action. I got some other gears and hot blued them to add some corrosion resistance but mostly because I was curious how that process works. The gears I got now made a 10:1 reduction and the pedal actually runs very smooth. I added a bolt to act as a stop since the geometry was for a 60° rotation rather than 30°, and added a lip to activate the switch from the new position and changed some other small things on the internals. It is not the neatest pedal ever but it works really well, and will do for a long time I suppose.
I just realized I didn't take a proper picture of the assembled pedal, but will do that another day if people are interested.
The idea of a pedal is easy enough, typically it requires two features; a switch to tell the welder to start an arc, and a voltage divider to tell the welder how much heat you want coming from the pointy end. I wanted to keep it as simple and robust as possible, since it will spend a lot of time on a dirty floor, being stepped on, kicked and yelled at.
A voltage divider can be as simple as a potentiometer (10k rotary potentiometer in this case), but these pots can typically rotate 300° for their full range. Which is not very useful since our feet are not designed to make similar movements. Most DIY pedals use pulleys, strings/belts and springs to get the full range of the pots. But I didn't like the idea of fiddling with strings or belts. My idea was to make a gear reduction to 'drive' the pot, I had some small gears from an old uni project so I gave it a try just to see if it would work.
Now potentiometers can rotate ~300°, the gears I had could make a 5:1 reduction, so 60° of pedal rotation.. Good enough for a proof of concept. I had some scrap pieces of square tubing that would make the body of the pedal and some 5mm stainless steel rod to make a torsion spring. A few years ago I made a quick jig to make springs and was happy to find it in the scrap pile for this project.
I added two potentiometers, one for the foot amperage control, the other controls the upper limit of the foot control (in case I am too lazy to reach for the dial on the welder, but mostly because why not), they're both 10k Ohm pots but the dial on the front should probably be 2k or 4k Ohm (because of some weird nonlinearities).
There is a small limit switch wired normally closed in the pedal that will activate lift arc on my welder when the foot pedal is depressed.
This pedal functioned properly and was pretty easy to build with basic tools, the first iteration is shown in the first picture. But the 60° rotation of the pedal was HORRIBLE, but I knew that already and figured 30° would be a comfortable action. I got some other gears and hot blued them to add some corrosion resistance but mostly because I was curious how that process works. The gears I got now made a 10:1 reduction and the pedal actually runs very smooth. I added a bolt to act as a stop since the geometry was for a 60° rotation rather than 30°, and added a lip to activate the switch from the new position and changed some other small things on the internals. It is not the neatest pedal ever but it works really well, and will do for a long time I suppose.
I just realized I didn't take a proper picture of the assembled pedal, but will do that another day if people are interested.