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Would this work for a simple 0.1 - 2.0 A micro tig welder circuit?

microtig welders typically run from 0.1A or less to 2.0A, constant current. Unfortunately machines that can do this are very expensive.

These use (I think) squarewave DC to acheive a tight arc.

If I were to make a simple constant current circuit and drive it with a benchtop function generator through a power mosfet or some other switching device, would you foresee any problems?

Now also, apparently any sort of current surges during arc-start is bad as it can blow a hole in the material being welded. I haven't the foggiest idea what to do to prevent that, maybe some sort of capacitor or something to buffer surges?

I know only a tiny bit about electronics, so forgive me if I am asking something obvious or stupid.

Reply to
greedware
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Plus $95 for shipping to the CONUS. Ouch.

I'm not too sure what to make of 'Unable to test no Power Cord' either. If I was selling a $300 delivered-price doodad, I'd sure as heck find a way to plug it in and check for functionality.

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Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

Without going into a lot of detail, you want something like shown below. This is an adjustable current source that flows constantly and is shunted around the work piece or not to pulse current into it. Diodes in series with load ensure the shunting action.

View in a fixed-width font such as Courier.

. . . V+ . . | Rc . +------------/\\/\\--+--------------. . | | | . +--------. | PFET| . | | | | S . | | | (-) ||-+ . _|_/ / POT +----|\\ ||>- . // \\ \\ | >----||-+ . --- / |-|>|---. . +--------' | | . | OFF | | . / --- | D | . Rbz | | ||-+ | . / ON | | ON >-----||

Reply to
Fred Bloggs

More details on arc starting please.

I have a 0-16V 0-40A regulated supply that I've been wanting to convert into a *mini*tig welder. Something for welding thin aluminum boxes together.

My experience with macrotig has been horrible. I can't do ANYTHING without turning on the "buzz-box" RF generator.

It's not obvious how you get big RF volts to start the arc without blowing up the regulated supply.

Then there's handpiece design and the plumbing to get the argon flowing. thanks, mike

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Reply to
mike

Hi Fred, this looks great!

Thanks so much. I have most of these parts floating around, I'll try wiring this up today.

Regards

Fred Bloggs wrote:

Reply to
greedware

View in a fixed-width font such as Courier.

. . . . V+ . | Rc . +------------/\\/\\--+--------------. . | | | . +--------. | PFET| . | | | | S . | | | (-) ||-+ . _|_/ / POT +----|\\ ||>- . // \\ \\ | >----||-+ . --- / |-|>|---. . / | | . \\ OFF | | . | --- | D | . | | | ||-+ | . | ON | | ON >-----||

Reply to
Fred Bloggs

One last time- this one makes more sense if you're pulsing with an external generator- CMOS voltage levels will work:

View in a fixed-width font such as Courier.

. . . . V+ . | Rc . .------+------------/\\/\\--+--------------. . | | | | . | +--------. | PFET| . | | | | | S . | | | | (-) ||-+ . / _|_/ / POT +----|\\ ||>- . Rpu1 // \\ \\ | >----||-+ . / --- / |-|>|---. . | | | | | | . | | | D | | | . / / ||-+ | | D | . Rpu2 Rbz +---||

Reply to
Fred Bloggs

On 18 Jun 2005 11:14:29 -0700, snipped-for-privacy@gmail.com wroth:

You can buy 60 volt, 17 amp power supplies for around $200 from surplus dealers on eBay. Those supplies have adjustable voltage and current outputs. Then all you would have to build is the high frequency, low power, arc starting circuit.

Here's a link:

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Jim

Reply to
James Meyer

Hmmm- if you have jittery hands then it would be a good idea to add a compliance clamp- this ensures that the current source remains in regulation at all times: View in a fixed-width font such as Courier.

. . . . V+ . | Rc . .------+------------/\\/\\--+--------------. . | | | | . | +--------. | PFET| . | | | | | S . | | | | (-) ||-+ . / _|_/ / POT +----|\\ ||>- . Rpu1 // \\ \\ | >----||-+ . / --- / |-|>|--. . | | | | | | | . | | | D | NFET| +---+ | . / / ||-+ | | zener|_/ | | . Rpu2 Rbz +---||

Reply to
Fred Bloggs

For *micro* TIG? You can't be serious.

You would think.

DC touchstart is suitable for microTIG.

Reply to
Fred Bloggs

This microTIG stuff requires only a few volts to keep the arc going once started , I am guessing something less than 5V, but this pulsating stuff is not an on/off action, it is an alternation between the set current and a "background" current ( needed to keep the arc going?). Lincoln has some patents on what they claim to be a low voltage current limited high frequency starter, Micro-Start. It would be worth taking a look if you can find it. I don't know why an inductor in series with drain of current regulator PFET shouldn't work as a touchstart arc.

View in a fixed-width font such as Courier.

. . . .-----------------------------------. . V+ | | . | | Rc | . .------+--------+---/\\/\\--+--------------. | . | | | | | . | +--------. | PFET| | . | | | | | S / . | | | | (-) ||-+ Rback . / _|_/ / POT +----|\\ ||>- / . Rpu1 // \\ \\ | >----||-+ \\ . / --- / |-|>|--+----. . | | | | | | . | | | D | | | . / / ||-+ | | D | . Rpu2 Rbz +---||

Reply to
Fred Bloggs

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