Setting up my first TIG

[hdonly0]

I found a Miller HF-251D-1 box cheap and plan to use it in conjuction with a Craftsman 230/140 amp ac/dc infinite arc welder. I had read somewhere about a home built foot control for transformer stick welders to use for TIG. Has anyone heard about this ? Do you think the equipment I am wanting to use will work well together? I do have argon and regulator that I bought for my Millermatic 130 mig welder.

[DSW]

Bad things can happen when you try and move the shunt block under power. If you want to fry your machine have at it. The only way to change amps easily with a machine of that design is to manually move the lever, and most machines tell you not to do so under power.

As far as "argon", most migs don't use 100% argon except for alum mig. If you try and use mix for tig, you'll just mess up the tungsten. There's a sticky showing what happens if you try this. It will simply not work.

Good news is you can use what you have to do DC tig. Not the fanciest setup in the world, but fine for basic steel and stainless. It is possible to do AC tig this way as well, but most new guys will not have the skills to do so without a pedal for amp control. You can play if you want, but you will not get good results most likely. A dedicated AC/DC tig is really what you want for alum, not a cobbled together stick machine.

[hdonly0]

I have pure argon for aluminum and co2 for mild steel with my mig welder. Aluminum is just too much trouble without making a rats nest of wire. This was my inspiration for buying the HF box (it was cheap). I found the schematic for the foot controller, but it was designed for a Lincoln Tombstone. I don't know if it will work on my shunt block Craftsman. I understand that this controller works by changing the amperage from near 0 to the max setting the welder is set on. Lots of difference though between the taps on transformer on the Lincoln and the shunt block on my Craftsman. I do understand about not moving the shunt while operating.

[wornoutoldwelder]

Spool gun for mig, then no more rat's nests. This spool gun is the best 200 bucks I ever spent outside a tittzy bar.

If you wanna do the foot pedal tig stuff the easy way, go something like this.

[hdonly0]

I have lots of time and not so much cash and like to make stuff. Got to try to make what I have work. Just my hard-headed nature-Haha. I think I can put the pedal together for about $75 to control the amperage on my stick welder. Talking to an electronics engineer type friend about the differences between the the multi-tap transformer and the shunt controlled transformer. I did come up with a Weldcraft WP-17v tig torch. I figured out that the Miller HF-251 box will control the gas with built in off delay. Onwards and Upwards (or downwards).....

[miller300a]

A few thoughts here.

What you have to figure out is how your welder varries it's output.

The old lever style welders changed the output by PHYSICALLY moving two coils together and apart. I understand this varied the magnetic coupling capacity and therefore the output changed. I don't see how a footpedal would work with this type of source.

Some welders, like mine for example, a miller 300a/bp used a 'map-amp' or variable reluctor system in which varying amounts of dc are introduced into a special coil which satrates in varying amounts to allow different amount of power through. This system is electrical, and is therefore able to be controlled by a footpedal.

Then there are SCR based welders. The power output is controlled by the firing phase angle, and is obviously electrically controlled and foot pedal capable.

Then there are inverters (Some SCR, mosfet, igbt, etc). As per SCR based welders.

So, what do you have?

Even if you don't have a foot pedal capable welder, I find that most times tig welding stainless and carbon steel I don't need the pedal...Get a few scraps to get the heat right and weld.

For AC and aluminum, the pedal is pretty much required unless just spot welding.


You will have a very difficult time getting the spool gun to work on a CC source (they typically use the CV process).

Good luck.

Chay

[hdonly0]

From what I can find out, the foot pedal controller that I am looking at will work on both shunt controlled and multi-tap stick welders. I ordered the electrical parts and will build the foot pedal. Lots of ideas floating around the web. My parts came to about $170 but I ordered some other stuff also.
Here is the schematic I am working from:

[wornoutoldwelder]

I hope you guys don't get it fingered out...For me, the whole foot pedal thing is confusing.....On my tig the pedal controls amps...On my Harley, it controls the rear brake...On my truck it controls road speed....On my trash can it raises the lid.....On my lawn tractor it controls fwd/reverse...On my bicycle it's either go or stop....hmmmmm

Leave it to you to come up with yet ANOTHER foot pedal to 'simplify' my life

[DSW]

Then there's always the clutch pedal if you drive a manual tranny vehicle. Just wait until you have to use one for the tig and one for the positioner at the same time...

[MinnesotaDave]

I've seen pics of a lincoln idealarc 250 with an electric motor hooked to it's crank handle for remote amp control.

But they don't have the locking handle like your craftsman, they are designed to use a crank handle.

In my opinion you are wasting your time, and any money spent, when for the same cash outlay you can buy a used transformer based tig. Prices in the $350-600 range are common.

Good luck on whatever you decide.

[hdonly0]

While we are all headed to the final destination in life, we take many different paths. If not for this, we would still be dragging women around by their hair and whopping each other on the head with sticks. Just saying!

[hdonly0]

Progress so far. I have entirely too many projects going on. Yea this will probably cost more than planned and yes I could buy a dedicated tig weldor but that would take all the fun out of it. I ride a 37 year old motorcycle. I could go buy a new one, but rebuilding this one (twice) is half the fun of owning it.

[Insaneride]

Looks like your missing the pot and the diacs?

[hdonly0]

The little blue thingies between the resisters and the capacitors are diacs. The pot will be mounted on the side of the case for access from outside the case. The SCR module is at the top of the board. It will mount on a large heatsink. This enclosed knife-switch rated at 100 amps came in this morning. It will mount in the case with access from the outside to switch between regular stick welding and tig welding. Also bought some cooling fans to keep the SCR cool.

[Insaneride]

I dont see a need for the knife switch but I guess it would save the wear on the weldor power sw. I dont think the 3rd ground wire is needed for the foot pedal either.

If this works on your welder and looks like it will to me, then it should work for controlling motors also. I would like to try it on a drill press. It may lose torque on a drill press tho.

Do you have links for the SCR and parts? Thanks in advance.

BTW, the SCR looks like it is rated for 50 amps but the transformer in BOM doesnt seem to be rated for the 50 amp welder?

[hdonly0]

The knife switch will take the SCR controller completely out of the circuit for normal stick welding. Not sense powering up the parts when they aren't needed.

I don't know how this will work for a motor control. I bought the SCR and most of the electronic parts at Allied Electronics. As I understand it, the small transformer does not see the high amperage of the welder. It only sees the voltage used to control the SCR's. The SCR's are the only components that see the high amps. THis particular SCR that I used is rated for 106 amps. A little overkill, but it was only a couple dollars more than the 50 amp and it adds some buffer to the circuit. Google "SCR welder control for Tig". Lots of people out there that understand how it works much better than I do. ( don't know what "BOM" means)

[Insaneride]

Ok got it, LINE 2 doesnt go thru the small xfmr. LINE 2 goes thru the SCR's so the small xfmr should be ok.

The BOM is Bill Of Material (parts list).

IMO, the ground on the foot pedal isnt needed but that could be debatable.

[hdonly0]

I agree with you on the ground on the pedal. I saw an earlier schematic of this without the transformer. That put 240 volts in the pedal. I believe the ground in this schematic is just a carry-over from the previous one. I also wonder though if when using a HF box, if any high frequency bleeds back into the stick welder and maybe that ground is there to reduce interference with nearby equipment in a shop like a computer or such. Just a thought.

[Insaneride]

I wouldnt want 240V in the pedal but the ground would be needed if 240V was in the pedal.

For noise spikes or HF in the pedal ; my pedal uses two caps. It would work without the caps but I think they filter spurious signals.

I dont know as much about the HF in welders as I would like to but, I think the weld current could bleed into HF circuit before the HF could bleed into the weld circuit. I dont get how HF is coupled to the weld current and not damage the HF circuit. I think its a low current superimposed onto the weld current. Kind of like heterodyne but dont really know. If anyone can explain, please do and thanks in advance.

BTW, have you been able to make any progress and did you find a 4 Watt pot?

[hdonly0]

Spent the last couple of days working on my home brew cooking pot. Converted it to electric instead of propane. Anyway, yes I did find the wirewound pot. Got it from Allied. Ended up with a 1.5k 12.5 watt. Part# RES1K5E OHMITE. Was all I could find at the time. I am sure a 4watt would be cheaper, but I just couldn't find one. I am sure there out their, just got tired of looking. This one was around $30. Pretty sporty.

[hdonly0]

Bye the way, where is Sparks NV? I used to live in Mina NV back in the '60s.

[Insaneride]

Sparks is east Reno about 15 miles from the Cali border on I 80.

If the knife switch doesnt work out, I would use plug and receptacle on the SCR case. You could unplug the welder from the SCR and use the SCR/foot pedal on other buzzbox's this way. I was wondering if a switch on the pedal would help or not do anything

[hdonly0]

I thought about just using a plug and receptacle. I found this switch pretty cheap and since I only have the one stick welder, I thought it would be nice to just flip the switch to change back and forth. Either way would work fine. I too was wondering about a switch on the pedal. All it does is turn the power on and off so the torch is dead until ready to weld. Since the scr controller gives you control of the output, a switch on the pedal doesn't seem to be needed. The HF251 frequency box I have will control the gas automatically with a delay on shut-off, so a foot switch isn't needed for that. What does a foot switch control on a dedicated tig machine?

[Insaneride]

What does a foot switch control on a dedicated tig machine?

On my INVERTEC, the SW on foot pedal is for "LIFT ARC" as opposed to "Scratch Start". I have to be on GTAW tho. SMAW is for scratch start or stick.

Also, the foot sw keeps the weld current off until switched. Your SCR application may not need a switch or switching could interfere until tested I gues.

You could use a ditch box or pendant to proof your remote if the pedal isnt ready yet.

You are probly rite, a SW on your SCR foot pedal wont do anything and may interfere.

[hdonly0]

I have several old computer cases. I am going to use those to build a case for the controller. I am going to start on that tomorrow after I finish with my motorcycle project in the morning. Just too much stuff to do!