Tomato Cage or Wire Spot Welder Using Microwave Transformer

I have a large garden and grow lots of Veggies that need tomato cages. They really take a beating,get caught in tiller, get bent, Welds break and to use them they get bent more, more welds break etc. And the prices to replace seem to be just getting out of hand.

I try to build all my projects with recycled parts, So this project cost me $0, I build 1 part at a time, then go scavenging for next needed wanted parts, sometimes I get something totally different, Usually for the better.

I got real interested in building one when a site "Homemadetools.net" showed a person in a foreign country that I could not understand the language or comments that followed. Watched several more other related videos, Where have I been? I was really impressed! However trying to spot weld 2 wires balancing on a ground wire was just not going to work, So this one is different as I used real heavy copper lug ends from real big old buss fuse for contacts, Tore apart an old microwave oven and salvaged transformer Modified by removing secondary wires adding welding wires, A power cord and assorted wires. Attached some boards to build base, Added an old push to start power button, Tested made a couple small changes, When repairing the tomato cages you must lightly sand to get good contact or else the wires just get hot without welding.

Please do not ever power up Magnetron

Please do not power transformer before the "LETHEL" secondary coil have been removed

You should wear some kind of glasses

Wear gloves as the welds stay hot longer than one might think.

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Step 1: Modify Transformer

There are two ways to remove secondary, one is by cutting off with hacksaw and drilling inside part out. this leaves the core in original condition, I did not choose this way as one slip with the hacksaw......

The other way is to cut the two opposing welds with a dremel or abrasive blade then pry E and I apart. Remove secondary and primary coil , It took some effort as they are in pretty tight and are shellacked at the factory. Some duct tape was used to insulate the replaced primary coil, My vice and small blocks of wood were used to seat the coil

Then use a short length of welding cable as it is very flexible ( I did not measure as it was what I had). Two wraps around core keeping as tight as reasonable. I used a stainless steel hose clamp to hold the E and I part together. (I will be using some epoxy at a later date to hold the E and I together) Then soldered a bolt lug to each end. Testing with a meter showed 2 volts and 7 amp draw. Now onto the actual welding part.

Step 2:

I needed some sort of heavy copper to make the contacts, so I started hunting my original in my head ideas was the copper bolts from an old starter Solenoid, However on another treasure hunt found an old electrical panel that used to power this place up to see what was there, Picked up two huge old fuses that had escaped scavengers, Perfect..... Took them apart cleaned the copper using salt and vinegar and some stainless steel kitchen scrubbers, Went on to build the levers, roughly drew out pattern I was looking for, cut on band saw, and sanded, Using the thickness of the copper lugs as a guide. Used a sharpie marker to shade part that needed removed then trimmed the inner side and outer of arms so the lugs would match when closed. Then roughly drew out the trimming and drilling that needed done on the copper. Because I was going to be fusing wire I did not want it pointed so used a hacksaw to flatten the top edge. Used a file to form an X shape which didn't work well and had to later file parallel groves so they would bite into the wire. Drilled 1/4 holes at the end of the arms, used a long bolt and two large washers only on each end no center washer (needed no side way play) Attached the copper to the arms, Had to shim the back of one so the tips would line up when clamped shut, Attached two short welding cables with lugs attached ( taken from a battery bank no longer used) I recommend soldering all the lugs as the crimped ones get warmer than the soldered ones. Removed the copper that extended below as there was going to be a base attached later. Used Zip ties to hold cables from moving next to lugs, Assembled all parts as shown in last picture.

Step 3: Final Assembly

Added a 36 inch 1 X 6 for a base, screwed down the electrode assembly, then transformer. Attached a momentary start/stop button, It was taken from an old roller controller that used to operated 3 phase warehouse heavy equipment, It has two buttons one always on the other always off. In testing sometimes the electrodes would stick, The off button removes power while the on button momentarily supply's power. Wired in series fit the bill. Used the original microwave power cord . Attached start button to base, cleaned up the wiring insulated exposed wires with tape and shrink tubing, I was going to put on an antifreeze jug to hide the electrics when Found a 5 gallon bucket that the bottom had froze halfway off, Used the table saw to remove top and bottom ribs from bucket, Took inside to measure how much I needed, cut using table saw then drilled holes and attached cover, Finally as I was cleaning up, the handle from the bucket was screaming "use me"... "use me..." Project now has a handle. Watch the videos at the top with welder being used, they are very short but straight to the point. Figuring how to put videos on you tube was my hardest part. The welder weighs just shy of 20 lbs, is 30 inches long and 7 inches high. Nothing was purchased except the solder, zip ties, tape and shrink tubing. My recycled parts were used throughout. When being used it is heavy enough that it doesn't slide around. I will be adding some sort of removable bolt on regular pointy spot welding like tips at later date So this could be used like a regular spot welder. If I had to build another one I think it would be just like I built it. providing that similar parts were available, Thank you for reading this far, Any tips or suggestions are always welcome . Please consider voting for this.

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    8 Discussions

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    spiritburner

    Tip 7 months ago on Introduction

    Dont mess with microwave ovens unless you know what you are doing, at least 6 people a year are killed taking out the windings and magnetron, always discharge the Capacitor as Bert says with a heavy insulated electrical screwdriver first, never take apart a oven thats just been plugged in and used, they normally have a discharge diode in them to make the Super Capacitor safe but still it can take several weeks for the Capacitor which acts like a battery to bleed off its 2000plus volts. Play safe and if you dont know how to do it leave it to a professional. It will kill and you won't even know it, it is that fast!!! The picture below shows what they look like and they are normally on their sides with wires coming out of them. Don't even touch the wires. Please believe me I suffered an electrical shock at 380 volts and it put me in hospital for a week, someone had wired in a house network before the meter so when the fuses were removed the house was still live. I should have tested the cables first but you dont think to check after the fuses are removed. It taught me a valuable lesson. NEVER play with live electrics or even ones that dont appear to be live unless you have checked first there is no current in the cables.

    51DOlwaPtPL._SX425_.jpg
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    spiritburner

    7 months ago

    Spot welders work on the basis of an electric charge going through the metal between two poles, its fuses the same metals together, thats how cars are mainly made, there is no flux needed as you are just melting the metal as one, flux is used when you need to solder something or weld something and it prevents oxidisation and cleans as you weld allowing for a clean joint, for example you cannot weld galvanised metal successfully without removing the coating, one its dangerous and two it doesn't work. you need a flux to weld it or just spot weld and fuse the metals together at melting point. stick welders have a flux coating encased around the metal rod, gas welders use flux and bring the metals to near molten and apply a filling material of the same metal , brazing is normally done with flux and brass or copper and copper piped are soldered or brazed with a tin alloy flux solder mix temperature based, for example water pipes use a lower melting point solder where as gas have a higher melting point to prevent them from melting in small fires. A Sprinkler system would use steel tubing all welded to prevent it melting under the high temperature of fires. I personally feel all houses nowadays should be fitted with sprinklers to prevent these awful fire deaths we here about, it would not add more than 1/2 % to the cost of a house and should be done everywhere especially if most of the house is wood, failing that you should have Smoke and Co2 alarms and fire extinguishers as a minimum. The use of candles from places like IKEA is now causing more fires in properties than before. There are now small fire extinguishers 1 to 3 kilos that you can buy for your house that come with a sprinkler type head and activate at 73 degree C and will fill the area with an inert Gas. they cost about 50 GBP each for a 1KG model.

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    spiritburner

    7 months ago

    Well Bert, I managed to do a deal with the local tip and have about 5 magnetrons and the copper winding, i going to have a try on the biggest one first as it has so much copper in it, I also did a deal with my local scrap metal dealer and she took a load of old lead of me from jobs i had done in houses over here and replaced the lead plumbing, I got a credit note rather than cash as its worth more money that way and I need copper pipe all the time for my hobbies, so I got a couple of copper slabs from her and now just need to get a few more bits and pieces and I'm ready to start. the fuse could be an issue but I'm sure I can find one, what voltage are you running through it 110Volts?

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    neilscott100

    7 months ago

    I guess the wire is galvanised which is why you needed to sand it to get a good earth and phase contact, its a nice welder, i actually might make one for some ideas i have in mind, microwaves are abundant at the tip, fuses and switches not sadly! but i do have some 8mm copper bar i got from the metal scrap yard i could use, i will give it a go i think, what voltage are you putting into it? I missed it somewhere please

    1 reply
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    bertssatneilscott100

    Reply 7 months ago

    Thanks for comment, Speaking about galvanised metal fumes are bad. I was sanding with sandpaper at first, but found my Dremel wheel did better and faster The MOT is 120 volt, 2 volt out. If you are welding small diameter wire a wide base works fine,And much easier to position the wires. However if you wanted to spot weld two pieces of flat metal , Tips must be pointed so the energy is concentrated in a tiny spot.
    Bert

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    bertssat

    7 months ago

    Hi
    No nothing at all else needed, I have stick welded for years, acetylene a little , I tried my stick welder several times turning heat way down to weld wire , and just failed miserably. When I saw the video posted on home made tools showing a Russian I assume) doing it with just a very basic homemade spot welder, using no flux, no wire like the wire feed, no nothing. The spot welder just sends high current, low voltage thru pieces being fused. When you watch the video of tomato cage watch carefully as soon as it starts getting hot the leg starts to drop, and that it, welded , well fused. If you leave it on too long sometimes it just burns in half. I was using small diameter coat hanger wire, and sanded tomato cages, I tried this morning spot welding copper rings for a rain chain and it just gets hot I assume too conductive as current was going around as well as thru. I will be looking for a larger transformer to accomplish that.
    Sorry for long answer
    Bert

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    nickton

    7 months ago on Step 3

    Awesome. Just wish I understood it... So you don't need to use any welding rods or mig wires? I never knew how spot welders worked.

    1 reply
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    bertssatnickton

    Reply 7 months ago

    Hi
    No nothing at all else needed, I have stick welded for years, acetylene a little , I tried my stick welder several times turning heat way down to weld wire , and just failed miserably. When I saw the video posted on home made tools showing a Russian I assume) doing it with just a very basic homemade spot welder, using no flux, no wire like the wire feed, no nothing. The spot welder just sends high current, low voltage thru pieces being fused. When you watch the video of tomato cage watch carefully as soon as it starts getting hot the leg starts to drop, and that it, welded , well fused. If you leave it on too long sometimes it just burns in half. I was using small diameter coat hanger wire, and sanded tomato cages, I tried this morning spot welding copper rings for a rain chain and it just gets hot I assume too conductive as current was going around as well as thru. I will be looking for a larger transformer to accomplish that.
    Sorry for long answer
    Bert