Sunday, March 03, 2013

DIY 110 V Portable Arc Welder - with DC!




I needed a more portable arc welder so I built this unit 110 V unit that weighs 40 lbs. It is made entirely of scrap parts. The frame is wood, the welding and power cables are from appliances, and the transformers/wiring are from microwaves ovens.


It is made form 3./4" plywood scraps. It uses a piece of EMT tubing as a handle. It is easy to pick up with one hand to tote around. I can not say the same for my other welder.

 

Schematic:




The unit has infinite welding current control and can do around 60 amps max. It uses a massive light dimmer type circuit to control the welding current. The circuit controls a triac which varies the input power to the transformers.

 

The transformer primaries are put in parallel so both are energized with 110 volt. If welding too long at max power it will pop the breaker on a 20 amp circuit. Running slightly lower output works great. The transformer secondaries have been cut off and rewound with 12 gauge copper wire, and then put in series to generate approximately 50 volts AC. This then goes to the bridge rectifier.


 The bridge rectifier is rated at 60 amps and converts the AC to DC, multiplying it up to 75 VDC open circuit, which goes to the filter choke. Another microwave transformer core that was completely rewound with 12 gauge wire (50 turns) serves as the choke to smooth the welding current before it goes to the electrode.


The ground clamp is a battery charging alligator clip. The rod holder or "stinger" is a standard model that cost $10.  The ground and electrode welding cables are made from 3-conductor, 12-gauge appliance cables with the conductors in parallel to give 60 amps + capability and minimize voltage drop. Also this makes the cables very flexible.

I was able to weld with 1/8" rod without trouble, you can see my first test bead above. Both 1/16" and 3/32 rods also would work. Due to the high OCV of the welder, I am able to start the arc very easily.

28 comments:

Spike said...

"...it's actually starting to melt..."
Heh, my kinda guy. Sweet project, good presentation.

Anonymous said...

Thank you for sharing your DIY project. I just want to ask questions:

1. How many turns of wire is the secondary of main transformer?

2. What's the purpose of using 2 transformer? Can I use just 1 transformer?

Thanks!

raymundo mayote said...

thanks for your post,but i discovered
that not only mot transformer canbe used for this project,but also ordinary EI core

Anonymous said...

I watched all your youtube videos on the 110 welder and I got so exiceted that I bought a used scr on ebay, semikron. Your chicken shack auto door is also on point, thanks for the link!

Sam Rosenstein said...

Awesome project! You wouldn't happen to have schematics for the traic and SCR setup, as well as the windings on the transformers. It's a lot to ask, but I figured I might as well before I start messing with my own transformers.
Thanks!

Kellie Taylor said...

This is one epic DIY project! It seems all of the parts were second-hand. Perhaps someone figured if one had some busted appliances with workable parts, then it could be made into something that's useful. Good thing you showed us how to do this one. Anyway, thanks for sharing!

Kellie Taylor @ Aim Dynamics

Gregory Rideout said...

I would also like the full schematics to either have an electrical engineer make it for me or if is easy enough to give it a try making the homemade welding machine with my knowledge which is a little more than basic knowledge

Lucas Bila said...

I was wondering if you had a schematic for how you wired your 220v welder? DId you wire 3 of the transformers with 1 leg of the 110 and the neutral and then the other 3 with the other 110 and the neutral?
Awesome build by the weight. looking forward to staring my own!

Anonymous said...

It looks like you've got a pretty beefy cap wired in parallel with the output as well. Which makes sense since the rectified DC output would be choppy.

How many turns did you use for your secondaries?

Jude Perera said...

thanks i got the idea now how to make a arc welding plant by using micro wave txfmrs good work

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ibrahim ┼čahin said...

Can you explane easy start circuit transformer

ibrahim ┼čahin said...

Can you explane easy start circuit transformer

Anonymous said...

Depending on size of wire you use, and size of transformer your looking at about 25' of #10 on one transformer. That's about 35 to 40 turns I believe. #12 will use about 35' to 40' of wire yielding about 55 to 60 turns. Do it in feet and wrap til you can't wrap no more!!! Lol

As for the second transformer. Depends on the size of transformer first off. If you can get one 2 or 3 times bigger than a microwaves yes you can use just one. It has to do with amperage and how much your secondary can pump out at a smooth and steady flow.

Gary C. said...

I am confused about the easy start circuit. There is no transformer in the diagram, yet you describe using a transformer with a single turn of wire in the secondary. Your diagram shows a diode rectifier bridge and capacitor used to convert AC to DC and smooth the DC output which is sent to the relay. What size transformer do you use? Where is the primary powered from? What wire runs through the secondary? How does the circuit "know" when you strike an arc? How is the welding circuit incorporated into the easy start circuit? What are the "pigtail" things on the AC terminals of the diode bridge? Do you have an alternate diagram of the easy start circuit?

Gary C. said...

Answered my own questions by doing some more investigating. The easy start transformer is a small transformer (such as found on the control board of one of the microwave ovens) with it's secondary winding(s) removed. A loop of wire from the secondary of one of the MOTs is passed through the secondary of the small transformer and becomes the primary coil of the small transformer. The original primary of the small transformer becomes the secondary in this new arrangement. The new secondary is connected to the second bridge rectifier with variable resistor, capacitor, and relay. I will post a schematic later when I figure out how - or maybe on my own blog - I'll let y'all know.

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Aquz Pewe said...

do you have the scheme of power control..?

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Anonymous said...

Wouldn't going to 220v allow more range and less wire heat?
(Power=Volts*Current) so the more voltage the less current (heat)


If you ever need to weld thicker items and decide to build a 220v
AC/DC rig ..p lease post it.

I did enjoy your post
Thanks

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