Easiest MOT Salvage Tutorial Pt.2

Video 2 of a series showing how I disassemble Microwave Oven Transformers (MOTs). This video is an idiot-proof walk-through for any MOT project. It gives you a procedure so you can take your specs and find out: 1 - What core to use, 2 - How many turns to wrap and 3 - What wire size to use. Oh, and you'll also learn how a transformer works. It also introduces multi-MOT projects and E-to-E double core projects.
The cheat sheet is at 10m50s.
Part 1: • Easiest MOT Salvage Tu...
Part 3: • Easiest MOT Salvage Tu...
Perhaps these videos will help you save money on tools or projects, or even make you a little bit of extra money off of the things you make with them. If you live in an underdeveloped country and are looking to start a business but can't afford (or even have anywhere to buy) the tools to startup but have access to junk, this is for you. If you're looking to buy nice tools later, having some trades experience with a cheap one can help you know what features you'll want.
Upcoming Projects: Spot welder, stick (arc) welder, plasma cutter, variac, hydroxy torch, carbon arc torch, arc furnace, battery welder, car (or other) battery charger and more.

[@Bags2723]

There are a lot of people doing videos on the same topics but you seem to explain things in a way that makes it easy for anybody to understand. Fantastic video series. Too bad I wasted so much time on a dozen or more other videos before I found these. Thanks man.

[@MattsAwesomeStuff]

You're welcome. Thank you for the kind words. I'm currently working on some that explain batteries and motors and trying to find that right mix of detail and simplicity. I mean, I haven't released a video in like 6 years but, maybe these ones won't wither and die in editing like the last dozen have.

[@MattsAwesomeStuff]

Thank you, that was very kind of you to take the time to say. I am making other tutorials, but they generally revolve around salvaging and re-purposing things. My actual electronic knowledge is quite amateur so I like to stick to teaching what I know.

[@cyrilpeterlee1]

by far the best tutorial on utube, very painstakingly explained. thanks matts

[@MattsAwesomeStuff]

Very kind of you to say so. I'm far behind on releasing my other vids... part of that is the painstaking approach to wanting them to be quality, not rushed, and I have to be in the right mood to do it.

[@dragan3290]

Bestinstructional video on this topic! Top job young man! Subbed and liked! 🙂👍👍👍

[@MattsAwesomeStuff]

Good question, and you're correct. But there is no such thing as a "thick enough wire' that also has "abnormally high resistance." The resistance of a wire comes from its thickness. The thicker it is, the less resistance. It's inversely linearly proportional, so, wire with double the cross section (double the weight) has half the resistance. This presumes all wire is equal, which it is (tiny details aside). As long as it's the same base metal. Alum wire, like I said, is only 60% as conductive.

[@yannisbio]

Great tutorial,thank you, keep doing it because you really have the gift to share your knowledge with easy steps.

[@MattsAwesomeStuff]

Thank you for the kind words. Life keeps getting in the way, but I have many more videos partially completed.

[@Serostern]

You sir have a GREAT voice, and I am very pleased I found your channel. Would love to throw ideas for MOTrelated projects with you, I have 45MOTs in my closet atm (I actually got 13kV with my MOTstack) =P

[@amiraamir3309]

Great work man. . . . very very informative

[@MattsAwesomeStuff]

You've got me beat. I've got ~25 right now. I've actually put a bunch of time into more videos this week, scripted many of them. I think I can start to crank them out pretty quick once I've got the foundation parts in order.

[@Serostern]

I do not mess around with MOTs to make a transformer that will run for any lenghts of time, I have reliable neon sign transformers for that. The reason I made my MOTstacks was to see how far I could push mots before they released the magic smoke. On the hexamot I have three series-paralell mots, the isolation fails at around 6kV windings to core, I have had some overloads with the hexamot and replaced several mots, the ocotmot never survived more than a few seconds.

[@MattsAwesomeStuff]

Mathmatically yes. Contextually, close but not quite. You will get ~60v, and you can draw up to a maximum of 16.6 amps from that 60v line before the transformer saturates and the rest just starts going straight into waste heat. The actual amperage load depends on whatever you hook up to the 60v. You might hook up something small that draws 0.01 amp, you may hook up something that tries to draw 200 amps and then chokes trying. Also, the MOT wastes ~500W just being plugged in with no mods.

[@awesomeguy9573]

Truly amazing video, thumbs up from me :)

[@NEDMInsane]

Ah thanks for explaining that. That is what i had though but again was not really taught about anything like this.

[@pauljordan3064]

Great explanation! Thanks!

[@gortnewton4765]

You've got a great tutorial method. Why don't you try extending this to other things electrical too? You've got a good speaking voice too and the diagrams you make are easy to follow.

[@MattsAwesomeStuff]

You're looking at Grant Thompson's? If you want a furnace, that's the wrong way to go. If you want a spot welder... 1 turn of the thickest wire you can pack together into the gap. Always 1 turn. And yes, you can probably calculate it that way.

[@russellpindar7717]

Very informative video.

[@aaronfael1758]

Thanks a lot for your quick reply. Hope your instructions will be useful for other followers, too. I got 4 additional MOTs, but all different from each other. If I take care to get same output voltage, I should be able to connect two of them in parallel without getting in trouble. Do you agree?

[@MattsAwesomeStuff]

Ahh, I see it now, your previous reply was flagged as spam. This makes more sense now. Sounds like your transformer melted. 65W is gigantic for a charger, especially for just a trimmer. Could lookup part numbers and see, or call manufacturer. I would guess about 4.4V, higher if it has a regulator? (Rectified would be 3V, then up to 4.5 when smoothed). A transformer from a stereo or VCR would work, if rewound. Hard to say, too many unknowns. I'm not really the best person to diagnose it.

[@Hobbywelder617]

For calculating the the amperage and voltage.

[@mrsayao]

Found your videos and they've taught me a lot! I'm pretty sure a transformer in the charging base for my cordless hair clipper has died. On the bottom of the charger it says 120V 60Hz 65W. The battery it charges is 4.5v how would I choose a replacement transformer to match?

[@TheDavelectronic]

I found using a bonding agent interferers with the primary current by an extra amp or so drawn by the primary, so i guess clamping is a better re assemble, bonding agent i used was epoxy.

[@Hobbywelder617]

Yeah, ok thanks for all the help

[@mrsayao]

Hi Matt, thanks for the reply! I have no idea how many windings are on either coil as I haven't cracked the tape on it yet. When I hook up my meter to the secondary, only a few hundred mv are coming out. I want to replace the transformer but I have no idea what kind of voltage the board is looking for. I would probably need to count the coils huh?

[@MattsAwesomeStuff]

@mrsayao : What previous comment? This is about the 10-turn test coil only getting a few hundred mV? Hrm. You powered up your primary to the wall? Your test-coil is using insulated wire right (otherwise would spot weld to the core probably, but would also yield low voltages)? Your multimeter might be screwed or its battery low. Try with a different one, or try connecting a 12v (automotive) lightbulb to the test coil. It should light. Something's fishy.

[@amosbackstrom5366]

Is there something special about the housing? Or could I just make one and rap everything myself?

[@turbo3089]

Thank you

[@Serostern]

The MOT powering MOT experiment failed, but it was indeed a good experiment, I had never seen it done and I was curious as to if it would work, it didn't, 240V 10A in gives 2200V 1.1A out, sadly not enough to saturate the core of the next transformer. I might beat the shunts out of two MOTs and try MOTfeedingMOT again.

[@Serostern]

Btw, sitting here thinking about maybe trying to take two E cores and throw three secondaries in series and one primary on. If that works I might even try to make a monster from two Es and three Is. =P

[@Hobbywelder617]

So, my primary has 137.6 turns, and of I'm doing something like grant thompsons metal melter, and have the secondary wrapped once, I get 137.6:1 ratio, at 127v at the wall, I get .923v correct? How would I calculate the amperage though? If I get 20 amps input @ 127 volts with that ratio I get 2752 amps, but that can't be right. Any ideas?

[@RobotUnderground]

I know in audio inductors you can use other materials in the core to increase the EMF. Steel laminate being the cheapest. Then ferrite and the top being neodymium as used in hybrid cars and windmills. I have access to a bunch of ferrite, can I make my own massive E?

[@nerfinator6]

A block of ferrite or individual sheets? Because if it's a block, you might run into some magnetic issues, these things are built with plates for a reason

[@NEDMInsane]

Just had a question here. i know a bit about electricity and everything but am not totally sure how transformers work so im sorry if this is a dumb question. But what about resistance on certain cables. Lets say you accidentally pick up a thick enough wire but has an abnormally high resistance. Wont that higher resistance cable meltdown faster if you are trying to push more current through than it can handle. Only asking because i want to learn more.

[@mindhormone]

Nice.

[@Hobbywelder617]

I should first ask: do you know the calculation for calculating the amperage output at the secondary?

[@MattsAwesomeStuff]

You'll need 4 I-pieces, if you're thinking of making a triple-tall with an inserted middle section. Also, high voltage is no joke. The voltage you're playing with is *instantly lethal*. Instantly. As in, you won't even feel "Ouch" and go to the hospital and die later. Zero warning. Zero pain. Zero regrets. Just one moment you're alive, the next moment you're dead. MOTs aren't anything specially dangerous, except the way you're doing it. Powering up those 2000 turn secondaries is kinda dumb.

[@Hobbywelder617]

So, (10:29) using that formula, if I have a 1000 watt trans, at 120v, I should get 8.3333 amps correct? And if I have 2:1 ratio (prim:seco) I should get 60v at 16.6666 amps correct?

[@liljoey112]

Hello again quick question does it matter how neat or sloppy your coil is besides how much space it takes up?

[@MattsAwesomeStuff]

liljoey112 Hrm... it'll be noisier if loose, it will vibrate and abrade more and eventually short out. But short-term? Nope, it'll work.

[@Hobbywelder617]

What is the formula for this, and how do I know what size of transformer I have, should it say so?

[@greenalyd]

hola, primero que nada revisa si no hay algun corto en tus tranformadores revisa las bobinas primarias y secundarias, si todo esta bien sera algo en tu instalacion electrica o tendras que hacer algun cambio, dime que tipo de instalacion electrica tienes para poder ayudarte. saludos!!!

[@aaronfael1758]

I'm currently developing two rewound MOT based projects, but experiencing some troubles. 1. Spot Welder: 220 Volts in, 1 turn - 2 gauge secondary, 2,5 Volts, 660 A out. With this device I'm only able to weld up to 2x19 gauge thick steel plates. What can I do in order to get more power, allowing me to join two 14 gauge plates? What about using two series connected MOTs? If the answer is yes, may I use two different MOTs? 2. Arc Furnace (stick welder used in a very small closed chamber getting high temperature). Using the same MOT of the spot welder, nothing happens. Only a very weak spark and overheated wire, obviously. Is it a matter of too low voltage? Should I rewind another MOT with more turns? How many Ampere and Volts should I measure on the secondary wire? I've seen something on youtube using 8 gauge cable and 18 turns, but no idea which voltage and current it gets (kzbin.info/www/bejne/jIXdfHypZp6YkKc) Thanks in advance

[@MattsAwesomeStuff]

Montaldo Selvaggia 1 - For more power, more amps. Thicker secondary, or, add another MOT in parallel. Or, shorter wires, short as possible. 2 - Spot welder MOT will not work. To "arc" you need ~15-20v minimum. Then an arc (plasma at 50,000'C) will form that melts. I would aim for 24 volts and as thick of wire as possible. This can be used for an arc welder , mig welder and others. ... Yes, I've seen Grant Tompson's videos, he learned how to do those MOT projects from me 4 years ago :)

[@MattsAwesomeStuff]

Montaldo Selvaggia 1 - For more power, more amps. Thicker secondary, or, add another MOT in parallel. Or, shorter wires, short as possible. 2 - Spot welder MOT will not work. To "arc" you need ~15-20v minimum. Then an arc (plasma at 50,000'C) will form that melts. I would aim for 24 volts and as thick of wire as possible. This can be used for an arc welder , mig welder and others. ... Yes, I've seen Grant Tompson's videos, he learned how to do those MOT projects from me 4 years ago :)

[@MattsAwesomeStuff]

@TreeMyzer : If you knew what I was doing, you wouldn't need to be watching a tutorial on it, would you? Or maybe my personality is magnetic enough for you to sit through the most boring video I'll ever have to create. Either way, keep watching, then go build something awesome! :)

[@fredcdobbs823]

At 7:00, where did you get the 24 volt number? I thought you were usung 120 volts which should have been 12 volts instead

[@MattsAwesomeStuff]

Fred C Dobbs You are not incorrect, but are confused. Look at 5:09 or a bit before. We're trying to figure out how many turns the secondary requires to get 24v for our imaginary project specs. We know secondary volts (our target), primary volts (the outlet), and the last piece we need to tell us how many secondary turns, is to know how many primary turns there are which is mystery. Just prior to 7:00 we figure out via the 10-turn test coil method, that the primary has 120.1 turns. There is no 12v. There is 117v/9.8 which is ~12, but it's then multiplied by 10 back up to 120 as the number of Primary Turns. The rest of the test-coil doesn't matter, because that's not the voltage or coil we're using. Then we insert the Primary Turns as the missing piece from back from 5:34. Note that during the test-coil the thing we're calculating is Primary Turns, but, then at 7:00 we switch back to what we really want which is Secondary Turns. Make sense?

[@familyguyrofl]

When using two E's is it necessary to use two primaries or could you just use one of the primaries?

[@MattsAwesomeStuff]

It is not necessary. You can just use one primary. It will work almost exactly the same as on a single core (slightly worse coupling and slightly larger iron loss, but that is the same regardless). Although... since you have all that extra room, you could improve the efficiency a lot by connecting both primaries in series (head to tail), and then wrapping your secondary (keep in mind the primary now has 2x as many turns, so your secondary will need 2x what it would have before too). But, I dunno what your application is, so, that may or may not be advantageous to you.

[@Heulerado]

I'm not sure I understand. Does using just one primary decrease the efficiency? Does that translate to a larger electricity bill or to a worse weld? I was thinking that with all the extra room I could use extra-thick cable to minimize the risk of overheating. Is that a bad idea?

[@Hobbywelder617]

So, if I make an electric metal melter, which requires 500-1000 amps. So, by using the math to calculate the output amperage, would that work (let me rephrase that)

[@MattsAwesomeStuff]

Not sure. What part are you referring to as the "housing"?

[@travers114]

Do you mean the E looking thing? If so, no, you probably can't make one yourself, but you can make something for it all to fit into so it looks prettier.

[@matthewheyse8205]

Its a Lamination core, meaning its made from lots of thin sheets, and are insulated from each other. A core takes electrical current, changes it to Magnetic energy (Flux) and then back again. During operation the Core will create electric current in itself, this current literally rotates inside the block of iron (called eddy currents). This is Bad for two reasons, one it wastes power, and two the waste becomes heat getting things hot. The Lamination break the core in to thin electrically separated parts, that all but eliminated eddy currents, and Magnetically still look like a solid core. Making a well insulated, tight laminated core by hand is mostly a waist of effort.

[@liljoey112]

Hello, What would i do if my Transformer needs a center tap?

[@MattsAwesomeStuff]

+liljoey112 Ahh, good question. Easy answer. A center tap transformer is where the output coil has an extra "tap" at the mid-point. A "tap" is an electrically accessible point. Easy example: Say your secondary was 10 turns, and you wanted it center tapped? You'd coil 5 turns, drag the wire out and away from the core, double it back on itself, and then continue coiling in the same direction. When you're done you can strip the wire at the fold and use that as an electrical connection. So your taps would be 0 turns (start of the coil), 5 turns (half way), and 10 turns (end of the coil). You could also coil two separate 5 turn coils and then just connect the head of one to the tail of the other. You can do as many taps as you want, and they don't have to be in the middle. You could tap at 5v, 12v, 24v, and 50v if you wanted, so you have access to a variety of voltages off the same coil. However, for "center-tapped" usage, usually the circuit depends on the coils being balanced around the mid-point. Make sense?

[@liljoey112]

MattsAwesomeStuff Yes it does :) Thanks for the awesomely quick reply!

[@Serostern]

I am quite aware of the dangers, at 13.25kV measured with my HV probe. Close to 4000VA in gives roughly 300mA out, enough to kill ten persons, or just kill one person ten times over. This is assuming a perfect system with cos phi = 1, clearly my system is not this effective, I probably lose a few milliamps due to the fact they hum so much they are practically jumping up and down. There are no mistakes with MOTs, no matter if you use one or twenty.

[@JohnECurtis]

Hey this may sound like a dumb question but what is the purpose and or what does it accomplish to put two transformers together making one with two primaries and one secondary?

[@MattsAwesomeStuff]

Double the power. It's basically like one bigger transformer.

[@JohnECurtis]

@@MattsAwesomeStuff good for a welder?

[@MattsAwesomeStuff]

@@JohnECurtis - a welder almost certainly needs two, yes.

[@JohnECurtis]

@@MattsAwesomeStuff so two primaries at 120 turns each and one secondary at 48 turns?

[@JohnECurtis]

@@MattsAwesomeStuff and should i make two of those?

[@mrsayao]

Re my previous comment: When I took a reading off the secondary coil I got only a few hundred mV. I have no idea what the its original output was!

[@Hobbywelder617]

Sorry, if I'm so confusing, I'm not exactly the best descriptor.

[@MattsAwesomeStuff]

I don't speak Spanish. Something about putting 2 transformers into one outlet? I am making a video that will explain that in more detail, it will probably be compete in one month. It will be very detailed. Sorry I'm not more helpful.

[@SuperDinesh95]

whitch is transformer used for arc welding

[@Willeexd1337]

Dinesh Jha a like 50volts and 90+ amps transformer

[@MattsAwesomeStuff]

Why can't that be right? You math checks out. You'll get somewhere around 2752 amps on that output. That's why you need for spot welding, massive, massive, massive amounts of current to generate the heat. In normal welding you create a plasma arc which melts the metal, but spot welding has no arc. In practical terms, your transformer will have many loses and you won't actually get 2752 amps out, but, probably 1500-2000 is reasonable, yep. Have more faith in yourself :)

[@conservativemacro80]

Maybe its because i'm only 15 but i am good in math but i didnt understand any of that math, maybe cause i learn hands on but great vids

[@manesantosh05]

WHAT IS THE MEANING OF M O T

[@fredcdobbs823]

Santosh Mane Microwave Oven Transformer

[@MrAutocristales]

hola me podria decir comooma puedo poner los 2 tranformadores en una sola toma de corriente si que se voten los fucivles se lo agradeceria mucho [e-mail]

[@MattsAwesomeStuff]

"For this"? What part? I gave you the info you need in the tutorial. MOTs are roughly 100W/lb. A 10lb MOT is roughly 1000W. The actual math to calculate the physics is long and ugly and I don't even know it myself.

[@mitropoulosilias]

:-)

[@TreeMyzer]

heh, why am i watching this. I have no idea what your doing

[@Serostern]

I do not mess around with MOTs to make a transformer that will run for any lenghts of time, I have reliable neon sign transformers for that. The reason I made my MOTstacks was to see how far I could push mots before they released the magic smoke. On the hexamot I have three series-paralell mots, the isolation fails at around 6kV windings to core, I have had some overloads with the hexamot and replaced several mots, the ocotmot never survived more than a few seconds.