DIY foot pedal TIG conversion

[Taiden]

The amperage control on my 80A DC stick welder is just a potentiometer.

Is there any reason why I cannot hook up an external potentiometer in its place, mount it in a DIY foot pedal?

These guys: http://www.hobartwelders.com/weldtalk/showthread.php?t=5978
are going to great lengths to make the foot pedal control a box wired in series between the welder and the torch on their stick welders. I feel the potentiometer replacement is a better solution, but I'm wondering if there are some shortcomings Im' not aware of. (Or maybe their solution is for a tapped welder instead of an infinitely adjustable welder)

[turbocad6]

from post #14 in the linked thread:

"A potentiometer (or rheostat) is an impractical solution as the wattage involved exceeds the capability of any readily attainable rheostat.

A solid state controller that uses phase control circuit, like a light dimmer works without dissipating as much heat. Look for a schematic for a circuit from Mike W. Keep in mind you are working with dangerous voltages and suitable precautions must be made. I'm just guessing, but you may end up spending more money on this controller than your HF arcone box."

what this means is that the rheostat in the welder itself carries a significant amount of amperage through it & a smaller one isn't going to do it. you would have to remove the actual rheostat from the machine itself & use that, but it will also require heavy wiring for the extended length & it's likely that your dealing with higher voltages too, so what your talking abut could be dangerous if not done correctly, although it could be done I don't know how practical it would be & your machine will always rely on this pedal assy now because it now part of the machine, your basically ripping out one of the components & extending it. .

what they are doing there does seem like the better way to go to do it electrically, but if you want cheap & easy then first thing that comes to my mind is the possibility of devising a mechanical pedal. I would leave the rheostat right where it is, make a cantilever that mounts to the face of the existing welder & replace the knob with a fulcrum arm or maybe even a disc depending on the amount of throw needed, then use bicycle cables to actually push & pull the leaver itself. will require 2 cables to & from the pedal in a loop & must be spring loaded, I've done similar setups to motorize things like drawers & covers & stuff by using a remote mounted motor, only here instead of a remote mounted motor your using a remote mounted lever (pedal)

this works similar to the way a modern car raises & lowers the windows or opens & closes the sunroof, a cable & pulley drive. it will have a cam & pulley system in the pedal assy, sounds like a lot of work but something like this cable drive can be built for dirt cheap & if thought out & done well could work great. you may also be able to add a limit switch & a relay to kill power to the machine when pedal is lifted. will take a little working out of the range of throw & stuff likre that but should be something not too hard to pull off

[DSW]

Taiden, not to discourage you or anything, but you should think this thru first. From your previous posts, it's obvious you are serious about learning, and are new at this. A DIY mod on a cheap machine is not going to help you learn. When you have difficulties ( and you will have them), are they the result of a cheap machine, the result of your DIY mods, or just because you don't know what you are doing yet? Problems resulting from poor machine performance from cheap welders are fairly common here. Guys have issues with cold welds because they are trying to push small machines way beyond their performance envelope, poor feed issues with cheap migs and so on are fairly typical. All this stuff does is make it that much harder for someone trying to learn. Now add to this you are building something that will change the settings on your machine. When you get erratic performance, is it the machine or your mod? Are you doing things different from bead to bead, or does the machine have a mind of it's own?

K.I.S.S. Stick to the basics for now. You already have that small machine as somewhat of a handicap. Learn to use it as is before you go and try to reinvent the wheel. That or save your money and get a real machine designed to do what you want. Yes they are not cheap. Almost all of us have been there at some point. Welding is about patience. You will need patience to learn to do good beads, they won't appear overnight. Same with a good machine. If you save, and be patient and watch CL diligently, you will find a bargain. However you will need to be ready with the cash to grab it fast. You won't have it, if you waste your funds on cheap get it quick schemes for DIY on import machines.

Too many guys think the next newest and greatest machine will "fix" their welding problem and turn them into the greatest welder who's ever lived over night, instead of simply learning to use the tools they have well. There's a lot of guys here with very basic simple "antique" machines doing phenomenal work. It's all about their skill, not the machine they are using.

[pulser]

taiden,
I like the way you think, are you a home brewer?

Are you saying, remove the existing amperage control pot from the front panel of the power supply and extend the wires that connect it to the power supply 12 feet away in a diy foot pedal? Why would this not work? Does the pot or the power supply care if the pot is on the front panel or if it is 12 feet away? Does the power supply allow you to change the current via the pot while welding? I don't see a problem.

[Taiden]

good info

Thanks turbocad, lots of good stuff to consider.

wise advice

Thanks DSW, KISS is a really good point... but I am a hacker at heart and I'm always thinking of ways to make things better... :) I will KEEP IT SIMPLE, STUPID!!! but I want to educate myself on my options for this little arc welder.

taiden,
Are you saying, remove the amperage control pot from the front panel of the power supply and extend the wires connecting it with the power supply 12 feet away in a diy foot pedal? Why would this not work? Does the pot or the power supply care if the pot is on the front panel or if it is 12 feet away? Does the power supply allow you to change the current via the pot while welding?, then I don't see a problem.

This is exactly what I'm thinking. I read over that thread again, and supposedly inverter DC welders can be modified exactly like this... so it may be an option.

Thanks all :)

edit: just saw your edit pulser... yes... a homebrewer for sure. It's a big part of my soul!

[pulser]

So, you'll post the results of you're diy foot pedal mod?

Maybe I should have also told you, "it can't be done, you're wasting your time, we've never done it that way, what are doing trying to improve this, you're just a wannabe what do you know, etc, etc, what are you thinking for? That surely would inspire you to prove us all wrong.

[Taiden]

haha. Well what I'm going to do is after I get some practice in i'm going to figure out what type of potentiometer is used... linear.. logarithmic.. exponential etc... the range.. all that good stuff. Then I will put in a switch and a place to plug in the wires extended to the external pot (same specs as the built in one). So I can easily switch between the stock heat knob, and an external heat knob (which will be rigged to a foot pedal)

that way if the whole setup tanks, I can flick a switch and go back to the regular setup

I have no plans to add the foot pedal until I need one. I'd rather learn how to do everything without one, and then enjoy the luxury of having one even though I dont need it. Plus that way I can tell if the foot pedal is screwing me up more than helping me. :)


Edit: the manual does not mention anything about NOT adjusting the knob while welding. It almost sounds like they suggest it while welding, but they dont explicitly specify either way. Good sign I think

[welderShane]

Learn to tig without the foot pedal first. If you can weld like that, high feq, footpedals and such are just luxuries.

[pulser]

Taiden,
have you mastered oxy acetylene, have burned rod in the ditch? If not, you have no business in dreaming of TIG. You're a newbe, and have not earned right to jump ahead of the norm, to think outside the box, it's blasphemy! (spelling?). Do you understand me, young man?

[Taiden]

Learn to tig without the foot pedal first. If you can weld like that, high feq, footpedals and such are just luxuries.

For sure :)

Taiden,
have you mastered oxy acetylene, have burned rod in the ditch? If not, you have no business in dreaming of TIG. You're a newbe, and have not earned right to jump ahead of the norm, to think outside the box, it's blasphemy! (spelling?). Do you understand me, young man?

oh noes! :dizzy: :D


Thanks all for the constructive posts... I appreciate it greatly :)

The basics are coming in the mail tomorrow (so excited!) and i'm getting my regulator and bottle tomorrow as well... that should give me something to do this weekend! I'll be posting up pics of my first tries, and pics of me lighting my garage on fire after going insane from grinding contaminated tungsten 48273984729834 times :D

[turbocad6]

as a beginner I think I get the best results when I set the amperage I want to weld at & then just mash the pedal full, at that point it's almost like there really isn't a pedal & I can get good consistent welds as long as I set the right amperage. point being that the pedal is not absolutely necessary in the beginning to be able to do decent welds, but of course it will eventually come into play as you learn to finesse it a bit too.

part of me also agrees with dsw as far as without a good machine you will always second guess weather the issues you may be struggling with at any given time are from the machine sucking or you sucking. I agree with his statement mainly because this is exactly what I told myself as I decided on what machine to get too & is what pushed me to the point of just going for broke with the dynasty. at least I know when I suck that it is truly just me that sucks, not the welding setup :) on the other hand, like I've said in your other thread, it's intriguing to try & get an adequate setup with budget equipment too so I can fully understand trying what you are trying if spending the $$ for a great unit is just not possible right now too

[Taiden]

It's honestly mostly the 220v issue, and my homebrew nature. :)

At least I'm not trying to do this with microwave oven transformers and backyard casted brass argon regulators!!! :D

[Rick V]

The amperage control on my 80A DC stick welder is just a potentiometer. Is there any reason why I cannot hook up an external potentiometer in its place, mount it in a DIY foot pedal?... i'm going to figure out what type of potentiometer is used... Then I will put in a switch and a place to plug in the wires extended to the external pot (same specs as the built in one). So I can easily switch between the stock heat knob, and an external heat knob (which will be rigged to a foot pedal)
IMO this should work just fine.

These guys: http://www.hobartwelders.com/weldtalk/showthread.php?t=5978
are going to great lengths...
The foot controller on the Hobard link is crappy looking - made from a couple cheap electrical boxes and a door hinge! YUK!!!
When you try this, consider spending a few dollars on a decent looking foot pedal!
57100
The above photo is an on/off foot pedal switch for 110 volts but it looks a good condidate for modification to hold a swing arm potentiometer- as long as the potentiometer diameter fits inside the height of the pedal.

I think you have a great idea - go ahead and try it.

[Taiden]

That's a fantastic idea Rick :) Looks perfect, and the price is right too!

[Rick V]

On another post someone mentioned a foot pedal for an electric guitar - likely more $ but why not check it out too? It's probably all set up with a potentiomenter and you'd only have to change it out. Maybe check out Craig List or Kijiji for a used one? Maybe even drop in a music store; they may have a dead one in their junk box.

[Taiden]

On another post someone mentioned a foot pedal for an electric guitar - likely more $ but why not check it out too? It's probably all set up with a potentiomenter and you'd only have to change it out. Maybe check out Craig List or Kijiji for a used one? Maybe even drop in a music store; they may have a dead one in their junk box.

Are you sure you aren't a homebrewer too? You got all sorts of great ideas... I'm going to head over to the local music shops this weekend and do some poking around. :)

[worntorn]

I found the need to add a foot pedal to the mix pretty early on. My early practice was mostly on thin wall SS since my motivation for learning tig was to construct a TIG welded 304 SS Egli-Vincent motorcycle frame (eventually)

Without a foot pedal it was necessary to set the amperage control to about 50 amps on .065 thin wall in order to get a good start to the weld. Much lower on the amperage setting and the start of the weld was too cold. After about one inch of bead at 50 amps the heat starts to build and then becomes too great.
For this reason a foot pedal is essential (for me) in order to control the puddle properly.

Having started with a machine that had a pedal, then gone to one without, then back to one with, I don't think there is any advantage in starting in without the foot pedal. I suppose if you are practising on fairly thick material, say 1/4" or better, then the foot pedal would be less important.
My thought is you might as well get used to controlling the heat in that puddle with your foot as soon as possible because in the end you will be using the pedal most or all of the time.

[Weldordie]

Just in case it might help anyone considering building a pedal, see my thread, "Project Tig Pedal."

[Rick V]

Just in case it might help anyone considering building a pedal, see my thread, "Project Tig Pedal."
That's a nice post; here's a quick link to it.
http://weldingweb.com/showthread.php?t=37489&highlight=Project+Tig+Pedal
The post answers a key question.
I had been wondering, with just a couple inches of vertical travel of the pedal and only say 15 degrees or so of pedal-angle change, how one could turn the potentiometer shaft through its normal 270 degrees of rotation? As shown in the Weldordie photos, it looks like some some form of wire & pulley or gear arrangement will be needed. Another option may be to use a slider-type potentiometer (seen on stereo mixers) and some form of cam level and linkage. If lucky, one could save most this hassle if a suitable used (cheap) electric guitar foot pedal could be found - all the tricky mechanics should be right there.

[jdchmiel]

http://weldingweb.com/showthread.php?t=29020
http://weldingweb.com/showthread.php?t=34235

two different machines, two different methods, same functional end result, though I did read some had issues with the longer wires on the pot picking up noise or something and not working out as expected.

[Taiden]

The cable idea is a great one. So simple, and 100% mechanical which has it's plusses. :)

[turbocad6]

that was my first thought, not saying electrical wouldn't be better just judging the effort vs the investment not to mention the long wire runs WILL change the resistances of the circuits involved without question & resistance is what the potentiometer is based on to begin with, a very long extension could have effects that you won't know about until actually done, where mechanical is more foolproof & guaranteed to function exactly as desired... if built well it can work perfectly long term without having to butcher the machine for unknown results. the single cable with return spring can work or the double cable I spoke about will allow greater range of motion & reliability depending again on throw necessary.

[Rick V]

jdchmiel, thanks for that 2nd post - who'd a thought of that simple solution?
http://weldingweb.com/showthread.php?t=34235
57115
Looks like hell - a real MacGyver Solution! But it works!

Nice thing here is that no change in the potentiometer is required - just replace the knob!
Now, if one can figure a way to avoid drilling the two small holes in the case... :laugh:

[Matt_Maguire]

jdchmiel, thanks for that 2nd post - who'd a thought of that simple solution?
(snip picture)
Looks like hell - a real MacGyver Solution! But it works!

Nice thing here is that no change in the potentiometer is required - just replace the knob!
Now, if one can figure a way to avoid drilling the two small holes in the case... :laugh:

Hmmmm... Rick did you just get caught bringing more home from Tractor Supply than the Oxy/Acet bottles you went to buy???? Maybe hid the Argon in the trunk???

Matt :drinkup:

[Rick V]

Hmmmm... Rick did you just get caught bringing more home from Tractor Supply than the Oxy/Acet bottles you went to buy???? Maybe hid the Argon in the trunk??? Matt :drinkup:
Now Matt, let's not confuse people by mixing up posts - I didn't buy any argon.:(
{Besides the only 'gas' some 'faster' folks than me have in their trunks is Nitrous Oxide (Laughing Gas)}. :laugh:

However, I will admit that I did have a look at my TIG welder and I did rotate the amperage knob back and forth.:D
The trick is to come up with a means of getting the required 270 degree rotation of the knob.

In his post, soflokustomz came up with the idea of turning the knob by friction - using a flexible steel bike cable travelling over a rubber drum (air tool sander drum). The cable acts like a moving rack, turning the knob.
I pondered the idea of a hidden spring, using a coiled spring underneath a replacement knob that would automatically rotate the knob back to zero position when released. One could then use either soflokustomz's friction cable/rubber-drum-knob or a cable/string wound around a pulley-knob.

[turbocad6]

it would not be too difficult to get 360* rotation at all, I'll draw up a sketch of a straight forward way to do this when I get a chance. basically you would run a cable in a big loop with the cable wound a few times on either end for friction, & then where the cable connects to itself would be spring loaded to keep the tension. a threaded bolt is great to use as the drum because the threads become the cable guide. the drum inside the foot pedal could be adjustable even for the amount of desired throw, use a large drum in the foot pedal & a small drum at the knob so ~1/4 turn at the drum in the pedal gives full 360* turn at the knob. this could be done in a way that won't require any modification at all at the welder, not even any tiny holes... I've done similar before with perfect results, just not on a welding knob :)

[turbocad6]

ok, heres a quick sketch, I didn't show the pedal return spring but obviously it would be set up to return the pedal to up which will return the knob to rest position which will be fully ccw.

also the tension spring is not shown to scale or in the right place but basically it's there to keep tension in the whole cable loop so the cable can't slip on either drum changing the position, just 3 or 4 winds will be enough friction that the cable will not slip on the drums. an alternative to the tension spring being at the cable junction would be for the cable to be attached to itself solid & then keeping tension by pulling one of the cable sleeves at it's junction

[Rick V]

Good sketch turbocad6...
Two cables? That really complicates things plus you're now adding a bracket on the welder.
Could we not just stick with one cable? That should eliminate the bracket and be simpler inside the foot pedal.

[turbocad6]

to do it with one cable then the return spring will need to be on the welder at the knob & it will still need a drum type setup to wrap the cable to be able to get the 360* rotation. the 2 cables are just 2 separate internal sleeves but they could be joined/taped or sleeved together to look act & be handled like it's one cable.

the 2 cables are so it can push & pull, where one cable can only pull. I'm sure it can be done with one cable but a push pull loop seems better to me. the bracket is so no modification is done to the welder itself. one way or another there will be a "bracket" needed unless you drill a hole in the welder as the "bracket". either way even with 2 cables it's still much easier than electrically extending the knob & way more fool proof & sure to work well.

[greenbuggy]

The usual banter about safety applies, BUT

I am one of those "nutjobs" that built their own setup to put a pedal on. I put pics up on sft but don't have them on this machine so sorry for the offsite linkage: http://shopfloortalk.com/forums/showthread.php?t=25420

On "tapped" machines like the one I added a pedal to the reason you can't switch under load is that the switch on the front is actually a mechanical slide-type contact switch, in a lincoln buzzbox there's as large as #4 wires running to some of the contacts (which are 1/2" thick copper lugs) and switching under load would cause massive arcing that would surely destroy the switch if not the transformer in no time flat.

It boggles my mind why some people are making ghetto pedals out of things like repurposed electrical boxes when you can get a cheap pedal for some chinese machine off ebay for $39 shipped (thats what I paid for mine from ebay, new). Added bonus: when you don't like the value of the pot in the pedal, its something radio shack will probably have in stock (make sure to get linear taper, not audio taper)

All told I put 39 into a pedal from ebay, 5 for a replacement pot, 29 for 4 matched antiparallel SCR modules, stole a couple fans and a heatsink from some junk equipment at work. Of course I have more money in the tig torch, cooler and the HF generator to be able to weld aluminum, but you won't be able to do that with a DC CC machine anyways.

I only wish I had the ability to control arc balance, but for what I've got into it I can't complain. Sure beats the hell out of the price of an esab Heliarc 252, which is what I eventually want to replace this machine.

[Rick V]

Thinking over the electrical versus mechanical approach, I'd prefer electrical because of freedom to position the foot pedal anywhere without having to worry about a mechanical linkage. The ability to simply unplug the pedal appeals to me as well.
e.g. Mechanical brake cables work fine on bicycles - because they are fixed in position relative to the brake-handle/frame/brake. The intended use here is not a fixed welder-pedal arrangement.

It boggles my mind why some people are making ghetto pedals... when you can get a cheap pedal for some chinese machine off ebay for $39 shipped (thats what I paid for mine from ebay, new).
I just did a quick look on ebay...I saw three pedals in the $40 price range:

USA $45 + $100.98 shipping to my location (Why so much for USA-Can shipping? :gunsfirin)
China $42.42 + $56.35 shipping
China $40.98 + $42.04 shipping

In my case, you can add another $30-$40 for border-crossing brokerage fees. The reality for me is that I would be looking at a China import at ~$120. I think I'd rather modify a $16 foot switch.
On the other hand, for USA folks the $45 USA pedal looks a good deal.

[turbocad6]

if it works easily by extending it electrically then I'd agree no doubt that's the best option

[3 weelin geezer]

Rick V, what brand is this thing? Has anyone tried this on one of those 80 amp Harbor freight dc welders? Does it damage the circuits if you change the amperage while welding?

[Raul]

taiden,
I like the way you think, are you a home brewer?

Are you saying, remove the existing amperage control pot from the front panel of the power supply and extend the wires that connect it to the power supply 12 feet away in a diy foot pedal? Why would this not work? Does the pot or the power supply care if the pot is on the front panel or if it is 12 feet away? Does the power supply allow you to change the current via the pot while welding? I don't see a problem.

I see what may be an issue.

If I understand the operation of the foot pedal:
The foot pedal is like the low voltage relay that send a signal to a high voltage switch thereby protecting the operator from handling high energies at the low voltage end.
The energy in the foot pedal is small and it controls VIA electronics the higher energies that do the welding.

However I have a question about the welding machine:
How does the OP know it is merely a potentiometer? Has he disassembled the thing?
Wouldn't that be a really - really big pot and wouldn't it be terribly inefficient? I say this because in order to attenuate the energy one does not want at the weld it would have to dissipate a boat load of power. This would mean lots of heat dissipated and lots of electrical usage.

Pots don't regulate energy so much as they waste it in the form of heat: thus transferring attenuated amounts to the work.

[Rick V]

Hi there 3 weelin geezer... are you aware that you resurrected a 2.5 year old post?

Since Oct 2010... maybe a year ago, Everlast Canada had a clear out - selling off some discontinued model of footpedal for $40, so I bought one (real rugged metal beast) and put it away for future possible application.

Raul, in my view the application for the foot pedal is for controlling a DC inverter welder. On such welders, current selection is usually continuous by rotating a small wattage potentiometer - not a high wattage reostat as found on some older & simpler transformer machines.

[acourtjester]

The foot pedal shown needs other circuit components for work as a speed controller on a motor. Or for tig the correct valve used for the potentiometer for controlling the welder.

http://www.youtube.com/watch?v=283PgFZbHAA

have fun
Tom:jester:

[B_C]

My friend made his own foot pedal out of Radio Shack parts and it worked kinda good

http://cbssacramento.files.wordpress.com/2012/11/fire4.jpg?w=420