Build a Microwave Transformer Homemade Welder

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Build a Microwave Transformer Homemade Stick/Arc Welderby stasterisk on December 23, 2007

Table of Contents

Build a Microwave Transformer Homemade Stick/Arc Welder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Intro:   Build a Microwave Transformer Homemade Stick/Arc Welder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Step 1:   Dissect the Microwaves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Step 2:   Prepare the Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Step 3:   Get some 24 foot chunks of ten-guage wire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Step 4:   Wind the new transformer secondaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Step 5:   Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Step 6:   Wire your two transformers together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Step 7:   Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Step 8:   Weld . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Step 9:   Thick Rod Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Step 10:   Welding Stainless Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Step 11:   Dimmer Control and Welding Thin Wall Tubing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Step 12:   Other Welders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Related Instructables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Author:stasterisk    author's websiteHi! I'm Star Simpson! I'm a real me! See more at [http://stars.mit.edu stars.mit.edu].

photo by [http://bea.st/ Jeff Lieberman] (http://bea.st)

stasterisk - my name is Star, and when I was 13 I signed my name as "St*r", with the * a five pointed star with the "A" a bit bolder.

I think I once shortened it to "ST*" and my best friend glanced over and said "ST*?" "How am I even supposed to pronounce that, 'st-asterisk'?"

hence stasterisk!

Intro:  Build a Microwave Transformer Homemade Stick/Arc WelderI had no idea making a DIY welder would be so easy to do. And, it's pretty much FREE!

Additionally, the stick welder you get is definitely better than anycheap commercial welder you can buy.Why is this homemade thing better than something you can buy? Because when you factor in shipping and labor and the little bit of retail markup - the companies thatmake typical cheap buzz boxes will skimp on copper as much as possible. Whereas you can use enough copper in this to make something really juicy, and still spendless, to nothing, compared to a store-bought arc welder.

So here's what you need to build a welder:- Two beat up old microwaves- Some 10 gauge wire- Wire nuts

People throw out microwaves all the time, if you keep your eyes on the curbs.Or, you can get microwaves at the local thrift store for $10 each.Try the warehouse that processes donations - they have to pay to get rid of tons of broken ones.

Stuff you need for welding:- Welding helmet ($16 and up)- Welding rods ($6)- Vice grip or purpose-built electrode holder ($6 for either)- C clamp for grounding clamp- Gloves- Thick nonflammable (leather) clothing that will cover your arms

Disclaimer: High Voltage ELECTRICITY and lots of CURRENT! Heat, electrocution, and DANGER! You could die and you could go blind.

That said, try this at home!

See this for a lot of welding safety tips

Here are the really good how-tos that this project is informed by:build a 70 amp welderthe tiny tim welder by tim williamshome made welding machine (via afrigadget)

Dan Hartman's how-to is good for reference, too.

And here's the quickest way to make a DC welder with a bunch of 12 volt batteries.

Image Notes

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

1. sparks! The good kind, from the weld, not the bad kind from the welder.2. me welding3. call me Flashdance.

Step 1: Dissect the MicrowavesInvite your non-hardware oriented pals over to help help dissect your donor appliances.They'll love it. David Grosof donated one of these microwaves under the condition that we take it apart together.

Good safety tip:You'll find a gigantic capacitor inside the microwave. It looks like a metal can with two tabs on top.Short it out to make sure it doesn't have any leftover charge on it, before you poke your hands anywhere near. Just put a screwdriver or something metal you aren'tconnected to, across the two metal terminals shown here.

Image Notes1. microwaves are full of surprises - smelly sneaker surprise!

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Image Notes1. microwave guts!2. transformer: save this and use it!3. front panel electronics: recycle!4. MAGNETRON: coolest name ever!5. AC power cable: save this and use it later!6. fan: recycle!

Image Notes1. Big Cinder: earth after global warming?2. very long screwdriver3. five-bit switcheroo screwdriver4. Star Simpson's dismantling-microwaves face

Image Notes1. magnificent fuse

Image Notes1. waveguide: the magnetron drools its 2.4GHz microwave rays into the ovenarea, through this.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Image Notes1. this is the magnetron. it's good for tronulizing magnetoids. by which I mean, itproduces 2.4GHz radiation.

Step 2: Prepare the TransformersChop and and knock out the secondary (thin wire) windings.Don't nick or damage the primary windings in any way.

If you do, you could create shorts where two windings conduct to each other, allowing electricity to bypass certain parts of the coil, making effectively a smaller coil, andcreating something different than what you expect at the output. Or, you might chop the connection entirely, ruining the primary. So do your best to keep it intact.

Image Notes1. Primary windings - powered by the gods of walljuice. Don't harm these inany way.2. Low-voltage winding for filament current or somesuch thing to feed themagnetron. Remove this.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Image Notes1. use a sharp chisel to cut the copper winding

Image Notes1. after chiseling, pound the wiring out. be really careful to keep the primaryintact, with no nicks.

Image Notes1. the disemboweled remains of the transformer secondary coils. This is at least afew pounds of pure copper. Sell it to the scrap yard for $4.50 a pound and take anice trip.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Step 3: Get some 24 foot chunks of ten-guage wireWe scavenged some heavy wire from an old powerboat the owner was scuttling.We stripped the outer jacket off and separated the inner conductors to wind new secondarieson our transformers.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Image Notes1. Star is skinning the 24 foot anaconda2. this bike innertube creates tension for stripping away the wire jacket. the otherend of the cable is C-clamped to the table.3. Screwdriver pounded into the pavement temporarily.4. Mr. Fireface is mobile now. A cozy glow whereever you're working.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Step 4: Wind the new transformer secondariesWe wound 20 turns of 10-guage wire on each transformer. That's just about how much wire would fit into the available space. It took a little over 20 feet of wire each.

tip: draw tally marks on your table to keep track of the number of windings.

How does a transformer work?The primary winding is an electromagnet connected to alternating current.The humming magnetic field of the primary induces a current to flow in the secondary winding. If both windings have the same number of turns, the output voltage is thesame as the input.(minus a smidgin due to eddy currents, resistance, etc.)If the secondary has more turns than the input, its output voltage is higher. That's the type of transformer you started out with.

OUTPUT VOLTAGE = INPUT VOLTAGE * (NUMBER OF SECONDARY TURNS) / (NUMBER OF PRIMARY TURNS)

Our primary has 100 turns and gets connected to 100 volts AC. We're winding 20 turns on the secondary, so we'll get about 20 volts out.

The available POWER STAYS THE SAME regardless of what the output VOLTAGE is.POWER (WATTS) = AMPS * VOLTS

If the primary is made take 1000 watts (100 volts * 10 amps) out of the wall, we'll be able to take 1000 watts out of the secondary. With 1/5 of the windings, we can draw50 amps out of the secondary.

That's the cartoon version with play numbers anyway.Over here in our shed full of reality we've got two of these beasts in series and plan to short the outputs through a welding rod like Jennifer Beals.

Let's just say we're going to pull a whole lot of amps, which is why we need to wind our secondary with such thick wire.

The copper conductor in ten-guage wire happens to be 1/10" (0.1") in diameter.

Here's a table of conductor diameter, guage, and current rating.

Image Notes1. use a flat bar as a wedge to make space for more windings.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Step 5: SchematicIt's a pretty simple circuit.In fact there's nothing in it except wire!

We'll take two transformers and wind low-voltage secondary windings on them with thick wire.

We'll put the secondaries in series with our welding rod and workpiece.We'll plug the primaries into the wall.

I really like the way aaawelder put it: "do not include yourself in this circuit"

Image Notes1. welding rod2. ground clamp3. workpiece4. New 10 guage low-voltage high current secondary windings5. electrode holder6. To use this unit on 220 volts put the primaries in series rather than parallel as shown here7. existing primary windings

Step 6: Wire your two transformers togetherWhy do we use two transformers?Just one of these isn't big enough to make a really juicy welder.If you happen to find a big enough transformer somewhere, feel free to use that.

Here's how to hook up two transformers.First we wire both primary windings in parallel to the wall cord.Then we wire the thick secondaries in series so they both"Push and pull" in the same direction.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Image Notes1. Wire Nut2. Three wires twisted together

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Image Notes1. If the bare part is too long the wire nut won't cover it. If the end is too pointythe threads inside the wire nut might not grip it well. Cut it square if you'reconcerned.

Image Notes1. To everything turn turn turn there is a season turn turn turn and a wirenut forevery purpose such as cover twisted wire ends and shoot through conduit-compressed-air guns at rats.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Step 7: TestGet out yer voltmeter:

Here's the test to make sure the secondaries are both pushing the same direction.Our two secondaries in series produce 38volts AC with no load. That seems about right.If they'd phased wrong it could have been fixed by reversing the wiring to any winding.

Where Tim says "out of phase" in the video, he means "in phase". That is, the center tap should be less than the outer two leads, and if things weren't that way, thetransformers would be fighting each other, or phased wrong.

Image Notes1. Non conducting shoes. Not standing in a puddle of water.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Image Notes1. Electrical safety - keep one hand behind your back or in pocket so you don'taccidentally short across your heart by carelessly grabbing two wires.

Image Notes1. Hi! I'm MR. Baby tongue fun toy!2. Come here often?

Image Notes1. check the heat - these didn't really get warm, which is a great sign!2. Radioshack autoranging multimeter. The best deal I know of for a little meter.Why hasn't progress happened?

Step 8: Weldholy cow, it works!

We wanted to add a series inductor to give the unit more "inertia", but it didn't matter!

Here's Tim welding with some of those.

Built your welder, but not sure how to weld? Check out the instructional videos on youtube - search "how to arc weld". They're very good.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Here's Star striking an arc.It welds great with these thin 1/16" 6013 rods. Even better with 3/32" 6013 rods.

Image Notes1. scratch start technique2. Awesome first weld bead!

Image Notes1. electrical connection, stick, and vice grip to hold it all together (all electricallyactive)

Image Notes1. ground clamp

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Image Notes1. insulated glove for grabbing the electrically active vice grip

Image Notes1. sparks! The good kind, from the weld, not the bad kind from the welder.2. me welding3. call me Flashdance.

Step 9: Thick Rod TestThose skinny 1/16" electrodes cost about twice as much as thicker ones.We wanted to see how our welder works with thicker electrodes.The next size up is 3/32", but we got a box of 1/8" 6011 electrodes.When we pulled one out of the box we both said "wow, that's thick".

We fired up our welder and I welded this bead across the diamond plate with 1/8" rod.The arc was pretty short but it burned in well and felt pretty good once I got used to it.I had to shove it in a bit more than I'm used to to keep the arc going, but sticking wasn't a problem. I welded a long bead and used up more than half the rod withoutstopping.That's the long weld in this photo.

Then I set the "torch" in this plastic tub so it wouldn't short out to anything.I checked the transformers, and they didn't even get warm!3/32" rods are less likeley than 1/8" to blow a circuitbreaker though. For your first welds get 3/32" 6013 rods.6011 rods have thinner flux and make it easier to see what the metal of your weld is doing, but tend to spatter a bit more.

The next picture is for reference, fromhobartwelders.com

Udate 4/16/2008:This is now my favorite welder. I made new leads for it from a pair of jumper cables. I left one alligator clamp on for a ground clamp, and added a $6 electrode holder. I'vetaught a bunch of people to weld using it.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

The next photo is Ita welding for the first time, making an awning frame. That project was welded with this welder by total beginners using 3/32" 6013 rods. As you cansee we have every other kind of welder, but the homemade ones are more fun.

Image Notes1. It burns back into the coating, making it easy to maintain enough distance.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Step 10: Welding Stainless SteelWe needed some brackets for Solara's mizzen mast.So we went to the welding store and bought some 3/32" "Hobart Smootharc+ 316L - 16" stainless welding rods. They're only 12" long because stainless has highelectrical resistance and they get really hot.After much designing and sketching Victor, Kenny, and I cut, drilled, bent and welded these brackets. Very easy. When it cooled the flux went "tik" and fell off the weld.The dark area around the weld is soot from the flux.The welder could have handled much thicker rods due to stainless' high resistance and low thermal conductivity.

Important:Use a fresh grinding wheel on stainless, or one that you only use on stainless.You'll get rust if you use any abrasives that have been used on non-stainless steel. Same for the wrong wire brush. It will smear rustable iron on the stainless, and due togalvanic effects it'll rust quick if it gets damp.

Hooray! Where did I get the idea you needed TIG for stainless? Stick welds on stainless are just great!

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Step 11: Dimmer Control and Welding Thin Wall TubingThe welder was too hot for thin-walled tubing frames, I kept melting holes even with the 1/16" 6013 rods. So I plugged the welder into a variac dimmer and turned thepower down about 30%.That gave me very fine control over power. Marc Lander and I did some very nice welds as seen here. After a few we got good enough to do the same welds with 3/32"6013 rods and no dimmer and not burn holes.More tricks - I used my left hand to feed a piece of mig welding wire into the weld to add more metal in and soak up the heat. Here's Marc doing that. Any wire is fine forthis, coathangers are traditional for muffler work. Sand off the paint first if you don't like fumes.Stopping to eat lunch helped a lot also. Your welds won't be good when you're shaky and tired.

I got my variac for free, don't buy one for this, they cost as much as a welder.A solid-state dimmer that's rated for inductive loads does the same thing and costs a lot less.

If you're feeling particularly fancy, you can add in your own scr-based switching circuitry to vary the power, like this guy did.

Image Notes1. Darth Vader doing crafts with his lightsaber on the weekend

Image Notes1. Nice Weld2. automobile jumper cable ground clamp

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Image Notes1. Mr. Variac a.k.a variable center-tapped autotransformer2. Jumper cables3. jumper cables. How many times in your life can you pull apart a zip-cord thisbig?4. handy welding magnet5. Handy non-vicegrip electrode holder should bring great joy to safety loverseverywhere6. rewound microwave transformers7. Your pal ms. Wire Brush. Brush rust away before welding, brush flux away afterchipping.8. Your pal ms. Hammer. Use to chip flux and peen the weld to reduce stress fromweld freeze contraction

Step 12: Other WeldersFolks have sent me a few photos and videos of welders they've built off of this instructable. I want you to be able to see them too, so here they are!

Here's a video I got from Paul du Buf, of the Netherlands (nice case, Paul!)

'

Cheyyne said:

Hey there, here's my welder based on your instructabletion. It outputs 35.5v, because the transformers were a little smaller than yours I think (couldn't wind a single more turn). So far I have managed to lay down gobs of metal on various steel objects in my garage, but I still suckat welding. Luckily I rented a nice welding video from Smartflix that had good reviews, hopefully that'll give me some insight into the process. I did manage to lay down a 1" bead though! The whole thing is going into a tacklebox housing.Props for a great instructable. Thanks for it!

llamafur followed with:

Heres another one, same basic welder, but its housed in a .50 cal ammo can. Looks pretty sweet. Its relay controlled ( two 15 amp HVAC control board relays wired in parallel) , I measured 24 volts ac across the output wires.its also sorta heavy, 30 pounds.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

Image Notes1. llamafur's welder

Image Notes1. llamafur's welder

Image Notes1. this case is metal, so it should be connected to ground.2. llamafur's welder

Image Notes1. llamafur's welder

Image Notes1. Cheyyne's welder

Image Notes1. Cheyyne's welder

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

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Comments

50 comments Add Comment view all 567 comments

 efdaitsiomna says:  Mar 12, 2011. 10:33 AM  REPLYhey! this is cool! not to doubt, but thus this really work and is safe to use? or is thier a danger that if done wrong, the voltage can arc through u or somethingcan go boom. not sure if im asking the right question, i dont know much about high voltage stuffs. just curious...

 dan says:  Dec 25, 2007. 2:15 AM  REPLYreferring to your 'one hand behind the back' electrical safety position - for high voltage work you can't just put either hand behind your back - it must be theLEFT hand behind your back. the reason is that if you are prodding at some high voltage gear with your right hand and get zapped - the primary current flowis the shortest path to ground: through your right arm, down your torso on the right side, down your legs and into the ground. now if you use your left handinstead - then unfortunately your heart is in your left side torso and is now part of the predominant current path. high voltage electrical work is unfortunatelynot a good career choice for lefties. now, as shown (with either hand behind back) it is usually ok for 120vac work, because if your shoes are dry and havedecent rubber soles then 120vac isn't enough to go through that.

 tashammer says:  Dec 27, 2007. 2:19 PM  REPLYThe heart being on the left hand side is not always true speaking as one who's heart has been moved over to the middle right due to having a lung out.

 xl5rob says:  Mar 8, 2011. 5:04 PM  REPLYThere's always one! Lol

 stumppuller71 says:  Mar 5, 2009. 9:32 PM  REPLYOk but for the majority of people this applies correct?

 everlastwelders says:  Feb 28, 2011. 9:40 AM  REPLYAs a welder I will surely try this out.

 ARJOON says:  Feb 28, 2011. 2:50 AM  REPLYi just made mine. with 2 1000w mots. but when i use it. my rod becomes red hot and do not fuse. can anyone tells me what is the problem

 larze says:  Apr 25, 2009. 7:39 PM  REPLYSo if you connect two transformers primaries in series (for 220V) then wouldn't it just be all the same use just one transformer? Because, with 2 x windingson both sides it makes the ratio equal to 1 x windings, for example 2:20 = 1:10. Right?

 stayputnik says:  Aug 5, 2009. 1:28 PM  REPLYthe primaries aren't actually connected in series. the 2 primaries are separate circuits since they're plugged into separate outlets and aren't connected atall. you connect the *secondaries* in series to double the voltage going through the weld. if each transformer with a power of 1,000 watts (total of 2,000watts) outputs 20 volts at 50 amps individually (for the sake of argument), you won't get a decent arc unless you put the secondaries in series to give you40 volts with 50 amps. using just one transformer won't give you high enough voltage to arc well (which usually requires 30+ volts)... nor would it giveyou sufficient amperage to sustain the arc. in short, one transformer couldn't supply enough power... and if you tried, you'd probably melt the insulationon your secondary and end up frying the whole transformer.

 lenny25 says:  Aug 12, 2009. 4:34 AM  REPLYAaaaaaaaaaah....*lightbulb* .Thanks so much that answers a lot of my questions. So it's not just high amps that you need you also need a fairamount of volts. I tired it with one. I thought i had blown my wall plug, cos it didnt want to work, but then i just reset my earth leakage and now itsback to normal, I got another transformer, so i will give it a bash now. So the way to wire it is: Primaries in parallel and secondaries in series.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

 agb6 says:  Jun 23, 2010. 8:04 AM  REPLYNo . The reason being welding demands high current and low voltage . The primaries need to be wound in series considering that you are havinga 220 V wall socket . The secondary here needs to be connected in parallel , since by doing so you'll be able to supply a greater value of currentinto the welding joint at a much lower voltage which you wpouldn't be able to achieve when the secondaries are connected in series

 ac-dc says:  Feb 19, 2011. 11:27 PM  REPLYIf you are in an area where wall outlets are 220V, odds are any microwave transformer you find will also have a primary meant for 220V. Ifthat is the case, and you can tell easily enough by what power cord plug is on the microwave, then you would still wire the primaries inparallel, and still wire the secondaries in series.

Whether the secondaries are in series or parallel depends on how many wraps around the transformer you can get, it will vary based on howlarge the transformer was. I had a microwave like the one pictured which had a much larger transformer than what you find today in the sub-$100 models even if the newer one is rated similarly like 1200W.

As someone mentioned already, if you are below 30V or so you will need to wire secondaries in series. It is not really true that welding"demands" low voltage, it is simply that it does demand fairly high current. Higher voltage is more dangerous, and to have both high voltageAND high current would raise the cost quite a bit, but if you make the voltage too low not only will it not arc, but the impedance of certainmetals will in itself limit how much current you can pass unless the clamp is nearer the working area.

Easiest would be to just wind the transformers, do connect the primaries in series for a moment, and measure the output from eachtransformer's secondary with them not connected, to determine what the voltage is of each.

It is important to note that you do not want to connect the secondaries in parallel if they are not VERY near the same voltage, otherwise youhave power going from the one which is higher voltage to the one which is lower.

 NAILS1978 says:  Feb 19, 2011. 10:49 PM  REPLYBy all means correct me if im wrong, i could take my little comercial stick welder apart and re wind with bigger and more wire ??

 doityoureself says:  Jan 9, 2011. 1:17 AM  REPLYI am getting ready to rewire my transformers, I have a ton of 6ga copper wire but it has no insulation on the wire, any ideas on what to use, other thatelectrical tape?

 stasterisk says:  Jan 9, 2011. 5:55 PM  REPLYAre you sure it is uninsulated, or is it enamel coated? i.e., If you take a small piece of it and nick it with a blade, does the copper seem to be of a differentcolor than it is on the surface? (this would suggest enamel insulation, in which case you are ready to go.)

Also, do NOT insulate bare copper with electrical tape to make it insulated: your inductors will be vibrating and getting knocked about (no matter howcareful you are) and the tape will eventually slip and create a short somewhere.

 evjim says:  Jan 24, 2011. 1:19 PM  REPLYEnamel coating is not enough for the welding environment. Enamel can easily be scratched off when working around metal and it will be hard to tell ifthe coating is still there since it is a similar color.

Be safe and buy some heat shrink tubing or buy new wire. It really won't cost much.

 ac-dc says:  Feb 19, 2011. 7:58 PM  REPLYThat is false, the wire already on the transformer is enamel coated, besides which you aren't going to be attacking the welder with pieces of metal- which could be pretty dangerous to do to ANYTHING plugged into an AC outlet.

Further, "new wire" for transformer windings IS enamel coated. There is a catch though, when you are winding wire on an existing welded-together E core transformer it is very easy to scrape the wire against the metal core which could scrape off the enamel (or other *painted on*insulation).

Also, don't step on cracks or cross a black cat's path. ;)

 jkinrade says:  Feb 2, 2011. 2:51 PM  REPLYAs this is an AC welder, does anybody know if this will work for aluminum? I don't like the electronics involved in a homemade TIG....

 doityoureself says:  Feb 10, 2011. 11:49 PM  REPLYI have the tig gun and hose-cables-argon-CO2 setup and I actually tried it and it does not work, tungsten electrode just sticks to the aluminum. I also donot know all the electronics involved in TIG welding but I am going to try to get this to work, if anyone has any ideas feel free to jump in and let me know.A higher frequency 120 or 240vac seems to be needed as emihackr97 stated because it did spark or hum at about 1-2 times a second (60hz , 120 timesa minuite, sparks both top and bottom of the sine wave) but it would not hold the arc. I feel that if the voltage was higher(I have about 50vac max) and athigher frequency(maybe in the 300 to 400 range, it would work.

 emihackr97 says:  Feb 3, 2011. 10:43 AM  REPLYI dont think it'll wrk 'cause that needs high frequency AC, not only 50 or 60 Hz.

Not sure.

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

 bferland says:  Jan 3, 2011. 10:07 AM  REPLYWhat rods are used? I have my welder working, but I can not lay a beed, does rod size make a difference, or is my voltage to low?

 doityoureself says:  Feb 10, 2011. 7:18 PM  REPLYI found unless you have at least 35 to 40 volts its not enough. I had to put 3 transformers wired in series to get enough voltage. I used 8ga stranded wirewith 12 to 15 turns on each transformer. at first I tried the 6011 electrodes at 1/8 inch diameter and it would not bead good at all. I switched to 6013electrodes at 3/32 and wow, it lays great beads, I have welded 1/4inch steel no problem, great penetration, 1/8 inch with good results too, just have tomove a little faster. Also I use three extension cords, plug each transformer to an extension cord and plug the extension cord to an outlet that is on adifferent curcuit breakers. you may be able to plug 2 transformers in on the same cord if it is on a 20 amp curcuit. any more will probably trip breakerswhen running long beads. also I use a small room fan on a low speed and aim it right at the transformers and they stay nice and cool even under heavyloads. Good luck and let me know if I can help or maybe let me know how your progress is going I would be interested.

 stasterisk says:  Jan 9, 2011. 5:55 PM  REPLYThank you to all the instructables users who are answering questions in the comments here.

 doityoureself says:  Jan 9, 2011. 1:50 AM  REPLYI really like the clean look but one problem, no way to get any cooling, no vents or fan

 jackie46 says:  Aug 14, 2010. 4:56 AM  REPLYjust question wondering if u could put air regulater and plasma cutter head on here make it work

 oddelyodd says:  Dec 21, 2010. 3:04 PM  REPLYSorryI dont think so; there isn't enough voltage to ionize the gas, here is why:the voltage coming out of the transformer...the amperage is there but the voltage isn't; you would need a bigger core to wrap the same sized wire to getthe right voltage/amp outputalso, the output of the transformer is ac (you need dc to use as a plasma cutter) unless you could rectify the ac into dc with a REALLY BIG rectifier or lotsof medium sized rectifiers to supply the needed amperage without blowing up the rectifier (quite literally)and last but not least: you would need some sort of high voltage pulse to start the arc between the electrode and the thing to be cut

 arkfusion says:  Sep 6, 2009. 6:03 PM  REPLYI used 12 gauge. is this going to make a difference?

 bferland says:  Dec 6, 2010. 6:35 PM  REPLYI used 12 wire 10 was two thick to get enough windings. Idid melt one coil when my rod stuck rewound and it added a fan to my enclosure and pay a littlemore attention and no problems. 12 wire makes for less of a "duty cycle".

 timmy300 says:  Nov 8, 2009. 2:00 PM  REPLYHi guys. im from the uk. i want to use two MOT's for my welder, but i dont undeerstand how to wire them up correctly and safely. Ok so in everyones elsesMOT arc welder are the transformers with in series to each other or in parralel? How to i connect all the primary wires into a 13amp three pin UK wallsocket?I havent got my MOT's yet but does anyone know what kind of current i can get out of 10 turns of thick wire on both transformers with an input of 230v @50hz? Also i heard that somone used 10awg wire and it melted can anyone recomend a good thickness and a supplier?

THANKS

 clayfigur says:  Nov 27, 2010. 4:16 PM  REPLYif you have a 3 pin wall socket... the third one must be a ground wire... connect the earth wire/ground wire to the casing of your MOT welder....

Its better to make a welder, using thicker wires on the secondary, even with lesser turns.You just need to add another transformer..

I tried 2 transformers, 10AWG 10 turns each... secondaries in series, primary in parallel.

then 3 transformers 8AWG 7 turns each... secondaries in series, primary in parallel. (this works better)

I'm also thinking of making a 4 transformer welder, as soon as I find one more...

Anyway, as added cooling, i used the fan found in the microwave, to cool of the unit from heat. a little aluminum heat sink would also help..

 charlieb000 says:  Sep 16, 2010. 3:08 AM  REPLYwhy is there no DC rectifier in your circuit? (do note you will need a large number of diodes to cope with the current, and will drop the output power by a bit), ithought it was better to DC weld...

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

 evza134 says:  Nov 26, 2010. 6:45 PM  REPLYfrom what i understand and have been told by my boilermaking teacher, its almost always better to stick weld AC that way you avoid arc blow.

 natcrazz says:  Jul 29, 2010. 12:26 AM  REPLYCan I use only one transformer if I intend to weld only thin metal for small jobs and artistic purposes?

 clayfigur says:  Nov 24, 2010. 4:38 AM  REPLYmake a spot welder, use bigger wire, lesser turns... its ideal for thin sheet metal..use a copper or carbon rod instead of welding rod...

I am also thinking of making one my self... already have 3 stick welder and a migwelder.. I need to make a spot welder for thin sheets...

 Bob_144 says:  Nov 15, 2010. 5:51 PM  REPLYwould you be able to help with some tips for making this transformer work for a welder??? its from an old master-craft battery charger.

 bferland says:  Nov 15, 2010. 7:20 AM  REPLYWould a standard light dimmer on the 120 v in wire work for power control?

 Styki says:  Oct 23, 2010. 9:37 AM  REPLYOK so if you do Nick a primary winding, would it be correct to think that you can repair it with carefully placed solder ?

 gigavolt says:  Nov 14, 2010. 11:04 AM  REPLYDON'T SOLDER IT!! YOU WILL BURN THE ENAMEL OFF THE SURROUNDING WIRES!!! THAT IS REALLY BAD!! Seriously, if you nick the primarywiring too bad, its better to just get another MOT! A small nick can be taped up with electrical tape, or covered in glue, though.

 h3x_your_nightmare says:  Nov 12, 2010. 11:25 PM  REPLYthat's a cool instructable :) my grandpa,here in romania, has a home made welder but it's 50 times bigger and heavy than this:D oh, and it's eating too manykWh :)) and because of heat i need to repair the wall sockets every 2months :D

 sakimoto says:  Aug 24, 2010. 6:45 AM  REPLYhow can you tell which side of the transformer is positive or negative using a multimeter?

 tinstructable says:  Nov 11, 2010. 2:50 PM  REPLYmy multimeter will tell you a negative voltage if the polarity is incorrect... and analog multimeters the needle will move backwards from the starting point.

 Computothought says:  Nov 11, 2010. 1:22 PM  REPLYGotta try this.

 Opcom says:  Nov 11, 2010. 9:26 AM  REPLY

This is a great project and also re-uses transformers that would otherwise be pitched. The saved copper from the secondary is valuable too. If high techcontrols like a dimmer or tapped choke is not available, a bucket of strong salt water solution can be used on the primary. Have a 2x4 above it with two (ormore in parallel) heavy steel electrodes coming down thorugh it, and as the assembly is lowered so that the electrodes are more immersed in the solution, itwill pass more current. It can limit the current yet keep the open circuit voltage high. bubbling vats of electrolyte are not for the faint of heart but neither is thisinstructable.  We're fortunate here to have enough 'junk' to make great things from. Here's another very low-buck home made welder, similar in some waysbut it's seen an awful lot of use, which is the interesting part. http://www.bunkerofdoom.com/00_misc/welder/index.html

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/

 breinhardt says:  Nov 9, 2010. 5:11 PM  REPLYstick welding on stainless releases chrome 6. if you're going to stick weld stainless, wear a respirator.

 thelmer44 says:  Nov 9, 2010. 11:02 AM  REPLYThis seems somewhat dangerous... But cool nonetheless.

 PaulMakesThings says:  Nov 9, 2010. 1:52 PM  REPLYYeah, but there are lot's of sites for safe kids projects. I like that instructables allows stuff that assumes some level of caution and maturity, or at leastacceptance of liability.

 fgleich says:  Oct 21, 2010. 8:13 PM  REPLYI have first hand knowledge of a guy getting killed by one of these capacitors because he did not short out the terminals and drain the charge out of it. Thesecaps contain a lethal charge and can KILL.

 Bob_144 says:  Oct 16, 2010. 9:18 PM  REPLYI scavenged a transformer weighing in at about 25-30lbs for the core weight, would someone be able to tell me what AWG and the turns to make this into awelder?

 fishnfreak18 says:  Oct 7, 2010. 3:11 PM  REPLYwould the transformer out of a golfcart charger be enough to use by itself for a welder? and how would u wire it?

 xz586 says:  Sep 24, 2010. 6:21 AM  REPLY???

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