Ash Small wrote ...

If I understand your question correctly, any cheap buzzbox for arc welding will have a current control knob.

As for the starter circuit, you can superimpose an HV signal onto the welding current using an air core transformer, Tesla coil style.

You'll want to prevent the HV getting back into the buzzbox, but this can be achieved using a capacitor accross the buzzbox output, and maybe a choke.

This is basically how an HF TIG welder circuit works.

I used a flyback and 2N3055 for my TIG welder circuit below:





You'll only need a pulse to start it though, but the above circuit shows how to superimpose the HV onto the output from the buzzbox. You also won't need the rectifier, unless you want DC.

Meatball wrote ...

So in your circuit, your buzzbox is the rectified variac output, and the rest of the circuit is the trigger which begins with a wall wart and ends with an LC network... is that correct?

So the whole bottom portion of your circuit is the HV superimposed onto the output terminals of any TIG PSU? Just to make sure I've got this straight..

Thanks for the replies guys, I appreciate the info.

Ash Small wrote ...

The buzzbox (arc welder) is connected to the rectifier. There is no variac. The symbol is supposed to represent a variable current transformer (buzzbox).


Then there is the choke circuit, consisting of two capacitors and HF choke. Apperently, from what others on this site have said, only one capacitor is required here. I just like 'overkill'.

The part from the wall wart to the air core transformer is the HF circuit, using the 2N3055 flyback driver circuit, and basic SGTC circuit.

The air core transformer, which in this case consists of ten turns primary and ten turns secondary, wound on an effervescent vitamin C tube (because these are made from polypropylene) superimposes the HF HV onto the welding current (the secondary is the welder cable itself).

This circuit converts an arc welding buzzbox into an HF DC TIG welder.

What you will need is a cheap arc welding buzzbox (you mentioned an 80 amp one), and a means of supplying an HV pulse. If you use a ferrite rod instead of the air core transformer I used, just wind the welder cable around it to form the secondary, and the primary will be from the pulse transformer, or capacitor and SCR, or whatever you decide to use (you could use a flyback or ignition coil, I expect).

(I don't think an air core transformer would work with just one pulse, due to the 'loose' coupling)

I'd advise putting a capacitor accross the output from your buzzbox, to keep the HV pulse out of the buzzbox. There is probably no need for the choke and second capacitor.

EDIT: Some adverts describe arc welder buzzboxes as being suitable for TIG welding. You can use them for 'scratch start' Tig Welding, but this contaminates the workpiece with tungsten. (unless you clamp a piece of scrap to the workpiece, and scratch start on that, but as you end up welding it onto the workpiece you then have to grind it off. Scratch start TIG welding using this method is only used on long distance gas pipelines as far as I'm aware, to eliminate the possibility of stray HF HV causing an explosion elsewhere in the pipeline)

Meatball wrote ...


Ah ok. So I'll need some beefy 150A diodes for the rectifier (probably have to heatsink/cool these), a choke with large gauge wire to handle the current, a capacitor with around 3X the breakdown voltage as the HV trigger arc, I'll need a fairly large ferrite core (do you recommend cylindrical? Or a closed square?) to wind a simple SGTC driven by a rectified flyback. The 3055n circuit self resonates and the ferrite TC is basically an isolation transformer.

The cap across the buzzbox with have to have a HV breakdown rating also yes? The larger the capacitance the better? Something on the order of uF then?

I've found this arc welder:

It says 100% duty cycle is ok, and for up to 100A I can't go wrong, right?

Oh, and as for the bulb, I plan on keeping it well contained and away from me while its connected.

I've been around some unbelievable laser beams (YAG, eximer) and tesla coils (DRSSTCs), but for some reason I am actually afraid of this project most. I feel it is the most dangerous I've ever attempted.

75A @ 26V is nothing to just mess around with.

Thanks for your advice so far, you are very helpful.

-Tyler