Building a Spot Welder from a Microwave Transformer! 

You can control the input voltage with a motor speed controller connected to the primary winding that will give you some control.

nice channel name. I'm a new subscriber im hopefully building one of these with a toroidal transformer. im getting 760amps at 2.7volts from uk 240vac. waiting to fix my lathe so I can get machining things again...

This is nice, I'd make one but I don't trust myself not to get electrocuted somehow in the process lol!

FYI you CAN spot weld aluminium if you use a thin piece of steel between it and the electrodes... Personally I think it might be possible to make this better by using tips with small tungsten carbide insterts on the ends, as it's not a good electrical or thermal conductor (heats up well when current flows through it), but is far more resilient then steel, so it would last a lot longer.

the Fotek ssr that you use has a ‘zero-crossing detection circuit’. This causes the relay to wait until the current it is controlling reaches zero before shutting off.and similarly wait until the mains voltage crosses zero volts before switching on, therefore you can control the pulse duration of your spot welder only with a resolution of 10mS (assuming 50Hz mains ) - there is no point to set times in resolution of 1mS , the welding pulse can be only whole steps of 10mS . e.g. 10 20 30 40 ... mS etc.

I also got a stainles steel table. So basically now i have a solid supply of stainles steeel. MAAAAN that got me :D

Current on the secondary coil is already limited by the battery cable’s diameter. So thick (more diameter than your battery cable has) copper rails are kind of “overkill”. But in general, good explanation and try. Thanks for sharing your design

Nice video.Congratulations

Nice work. I think those copper bars may be just a lil' overkill though..... I can't figure out why not just use the extra couple foot of 2 AWG to run to the electrodes. Then you could've just used wood instead of huge copper bars. At least that's how I built mine. I'm all in on no kill like overkill but damn that huge copper bar ain't cheap! Thanks for the vid.

If people don't already know you can get toroidal transformers on ebay fairly cheap, you don't have to sacrifice a microwave.

Great project and video! Having a pneumatic closer would probably help with constancy because of repeatable pressure. I like the little holes on the copper bars, they totally could be used to add extension cables for welding tabs onto lithium batteries.

Did you remove the shunts? Does removing the shunts do anything more than offer additional room for the secondary?

I'll be nice try DC capacitor discharge spot welder o this mechanical setup

nice video I tried to follow along with it and bought a used MOT, the seller connected ac voltage to the primary winding (thin wire side). And it created humming sound. At home I removed that side and when I connected ac to the secondary side it created smoke and smell and became very hot to touch. Seems like the Secondary was already short? What you say? Also Now can i rewind it using suitable size enameled wire? Will winding it with slightly thinner wire be ok for spot welding?

There's so many people doing this project, if I watch them all... I'm going to get the best info. Yours looks pretty good with machined parts and all... and you cut the primary out "properly" :) To adjust the power, have a look at Alexander Hartdegen's (he's my current "other favourite") ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-MUId45iUrO8.html

I have wanted to make one of these for welding thick nickel strips to batteries for making bat packs.... this was helpful... I might need to make a beefier transformer though.... nice video

Great video & spot welder build, thank you!

This is a good video. FINALLY a MOT spot welder video from a common sense individual. Thanks bro!

you can regulate the output power a few different ways. 1. take another tap off the transformer from the middle of the 2 windings for half the power (same voltage, same resistance, only the current can change) 2. if you want something more variable you can have an IGBT doing PWM on the input (mains), but gotta be careful cuz you're dealing with AC and transistors don't love that so much 3. you can put more windings on it, which will give you a higher output voltage, but rectify it and PWM it with some nice mosfet(s) at a much higher frequency (few khz maybe), it'll be higher voltage but the duty cycle precision will allow you to just make more or less power overall and also, be careful with those few millisecond pulse times, you're still getting the same 50/60hz in the output that you get from mains input, which means 20/16.66ms periods. going bellow that will give inconsistent results depending on what part of the wave you end up catching. also the tabs that connect to the copper rods will likely be the limiting factor on how much current you get since they're likely the more resistive part of the circuit. connecting the copper directly will likely be the wiser solution, or if you have a tig machine just straight welding it. and after that, the limiting factor will still be the minimum thickness in any part of the circuit (assuming all copper), so rods that big aren't necessary unless your thinnest cable is equally as thick. money would better spent on thinner, longer probes that are more versatile. great video tho, surely the best I've seen on the topic. cudos!

nice job can u give the arduino code plz i am in the same priject

This is a great project but I don't think yuo can weld any time shorter than 20ms relyably (assuming your AC voltage has a frequency of 50Hz (european standard)) because you are using a solid state relay and solid state relays just switch off (as far a I know without any extra cuircitry) if the current through the relay is zero, wich only happens in the worst case 20ms after switching on the transformer because the transformer is a highly inductive load. In my project I am planning to use a contactor instead of a solid state relay.

How many volts can be expected from one turn of that heavy gauge wire? like 12v? and would the voltage change with a larger or smaller gauge wire...or does the number of turns determine the voltage? if so would jamming one turn of the largest gauge wire possible give more amps?? or is it only capable of so much amps and becomes a waste to increase gauge size on the secondary? Also rather then have the timer could a 12v solenoid be used on the secondary output on one lead just before the tip as a switch? or would it be better to just add a switch to the transformer main? Thanks for any help...this is all french to me...nice work....

I sped watched this so idk if you said it but a foot pedal switch is the way to go you can either buy one premade or like I did at first make one Which worked great but I did wind up buying a Tig welder footpedal for 20 bucks online Which has a power control knob on it and the one I made was just from a light dimmer switch but it Has to be the kind that you turn on and off by pushing it in and out not having to turn it all the way to the left to turn it off then I built it into a nice little case took the original knob off put about a inch and Half extension on the little nub that the knob goes on drilled a hole so it’s stuck out Like 3/8 of an inch but it cannot have any play The extension can only be able to move up and down and be spun so if you step on it add an awkward angle you’re not gonna snap it off and fix on your foot pedal Are used plexiglass so I could see through it put a red line move it in 8th inch increments with a multimeter attached And marked out the readings underneath the footpedal which I could see through turned it all the way to its lowest point and put a red line on the plexiglass that would lineup with my markings underneath. Longest RU-vid comment I’ve ever left

For the 5v PSU, I'd recommend the HLK-PM01. It's a really good PSU for the cost. There's a teardown and test on this page: lygte-info.dk/review/Power%20Mains%20to%205V%200.6A%20Hi-Link%20HLK-PM01%20UK.html

it all looks great but shouldn't you be concerned about cooling more space is a great way to start with your cooling system then a fan,, really great job thanks for sharing

DOES IT WORK IN THIK METAL SUCH STRUCTURES OF CAR OR THE THIN LAYER CARS? WHAT I MEAN UPTO 2mm OR 3mm TWO PCS TO JOIN THEM BETTER THAN MIG WELDING?

sir really a great video one of my favourite youtube channel . sir i also made by watching your steps but had one query can you please tell me what is the input voltage and current to operate this spot welder (according to input voltage is 220v but what is the required current ). please sir tell me as i cannot move forward untill my doubt is cleared. please sir a big fan of your channel

So, I don't want to be 'That guy' but what would happen if you accidentally shorted the two big copper bars with you in the middle? I notice how you hold down the top one, so maybe a stray piece of metal was touching the bottom bar and you brushed your hand against it during the weld? If that would do what I think it would, and that would be give you a very nasty shock, wouldn't it be worth two delrin sleeves to make it all a lot safer? Let me know if I'm missing something :)

You didn't show that you connected the green (ground) wire of the power cord to the case. You probably did, but I mention it in case some of your viewers don't know to do that. It's an important safety thing.

Oh, btw....that's dope haha

Good timing

Nice job, the controller looks quite professional. How thick have you managed to weld successfully? I had a dodgy attempt a while back, was doing well on two pieces of 0.9mm sheet but anything thicker was breaking the weld before tearing the parent metal. I wonder if cramming as much copper into the transformer as possible will reduce power losses?

Awesome

where can I buy a bushing like that please answer

Is there a formula for determine the thickness of the delrin bushing?

Thanks. Great metal work. They look exactly like a Military design. Perhaps, a strong handle on top would look good.

Where Can I get the scetch for arduino?

Well hello there! Excellent timing, let me grab something to drink and relax in the morning summer sun with this video Again a project I've been looking at myself and has been pushed forward way too many times. Are you sure that you haven't seen my "idea's sketchbook" and "to-do list" ?

“Any code I write isn’t worth any money “ lmao same dude

Cool project! The Auto White Balance is a little distracting early in the video but I didn't notice it as much at the end so I don't know if that was just an artifact of that one set up.

What is the thickness of the copper bars? Both the arms and the tips...

I would have been the same, lets see how much spot welding i can do!! Nice channel, subbed!!!

Harbor freight sells a spot welder for $127.99 USD. I am not saying i wouldnt build one myself but is this one you made superior? The spot timing is a cool feature.

damn thats a lot of thick copper. all that must add up on the cost.

Lock the white balance for god sake

If you want sheet metal enclosure will not get a press/brake etc

That's sick. The unit looks quite professional.

It freaks me out when you hold the copper rod with your hand while welding.

You could limit current with a large resistor on the primary side of the transformer

How could you modify this to be able to weld tabs onto batteries? Seems like another good application.

Great video! My microwave just died and I'm going to give this a try with the salvaged transformer. I was thinking -- if you attached the heavy leads out closer to the tips, you could get away with just a few inches of copper rod. To get the length of jaws you wanted, you could press fit the copper ends into something like 1" EMT tubing. Your construction looks great, but I'm basically cheap (and copper is pricey). Nice job!

nice!! 💪 👷🏻

the best ELI5 of how transformers work.

Well done!

How are you holding it and not getting shocked?

could you not operate that solid state replay with pwm to give you some control over the power

Does the SSR have zero crossing and if so does that effect timing?

One way you might be able to adjust the power is adding multiple taps to the primary winding, and have each tap run through a selector switch. It's pretty analogue but it could work.

OK vid, but the rest of the parts are already from a spot welder! OK I guess if it broke and you're subbing the transformer. However, this design will not get the full current of a manufactured spot welder. Interesting tip: Big industrial spot welders have controllers that set weld time plus multiple "pre-welds" fast weld pulses intended to blow platings off parts so the main weld with longer time creates a true weld between the base metals of the parts - otherwise parts can look welded but snap apart later!

Lmfao "I made a sailboat" "flapping in the breeze" Lmao dude we would get along so well 😂 Holding it with your thumb and welding, well that looks and sounds sketchy lmao I'd make something that looks safer to touch haha I got two microwave transformers sitting in my tool box for a similar project. I'm thinking an industrial induction foundry, one of my friends was working on one for jewelry casting and it really got me interested in it. You have convinced me, I am sending you a care package 😆 Also, email me the electronics you are using, part numbers and boards, etc. I'm alright with code, but I have friends that are engineers that legitimately love doing it and are very good. I'll make sure it's coded right:)

Can you give a link to the arduino controller, i cant find it... nice welder! Good job!