Instructables

Microwave Oven Transformer Stack

This is my Microwave Oven Transformer stack. It is currently current limited using a heater.

There is approximately 10 36 watt 4' fluorescent tubes in a string around my garage that I am lighting with the MOT stack .

My MOT stack contains 4 Microwave Oven Transformers connected with their outputs in series and their inputs in parallel. They are mounted on plastic cutting boards. I am using threaded rod to hold the layers in place while the PVC pipe covers the threaded rod and it also supports some of the weight.

The output of this is approximately 8800VAC at 350mA The Input voltage is 240VAC

Thanks for looking, Please comment and remember to rate if you like it!

Just say if you want any pics of a certain thing, e.g. the MOT stack arcing to wood/metal etc. (I will try to get more pics of it arcing soon but it is hard to use a camera that has like a second delay before it takes the actual pic from when you press the button, stupid camera) ********************************************************************************************************** Edit The new pictures are of an arc between two carbon electrodes. The other pictures are of 12 fluorescent tubes connected in series but arranged in parallel so you can see them all

100_3224.JPG
100_3220.JPG
100_3202.JPG
100_3203.JPG
100_3204.JPG
100_3206.JPG
Could you please make a step by step
Plasmana4 years ago
Man you did a good job! I wish I had more microwaves to salvage for their transformers.. :P
thermoelectric (author)  Plasmana4 years ago
Thanks Plas, I will hopefully be submerging them in oil so I can run them with a bigger ballast, so I can get sparks like yours :-) It took about 4 trips to the tip (dump/waste disposal etc.) shop (they put things that people might want that was sorta in the garbage up for sale. I had mostly one each time, but sometimes I scored good and got 2 microwaves. (I have 5 MOT's all up), one that is going to be a ballast.)
Nice, I only use one transformer for voltage and the other as an ballast. Those huge arcs I got in the end was completely unexpected, I never knew why those arcs are huge. Until some helpful guy told me why...

Quoted by HighVoltageScience
The burned out sparkler make bigger arks cause
the burned part is a insulator and the wire is a
conductor that makes a capacitor and make's
bigger arks.

I don't know how to describe it in non technical form, so you will have to figure it out.. :P

I am (hopefully) going to the car boot sale in about a week, I might find microwaves there :-D
thermoelectric (author)  Plasmana4 years ago
Wow, The sparklers are capacitive? You might have been achieving near resonance with the MOT's, Because that can give you monster arcs
Yeah, I thought so... :-D When i get a chance, I am going to add two microwave oven capacitors to the circuit to get the transformer to it's resonance to make big arcs. BTW the link you gave me is blocked.. (I am at collage) So I won't be able to see it untill I get home which will be about a week. :-( I might forget it by then, lol
Use HTTPS
thermoelectric (author)  Plasmana4 years ago
Have you tried using a proxy to get onto the sites? Have a look at the list here and try inputting that link I gave you. Look out though, because if your collage techies will probably start to block them, if they haven't already done so
That is also blocked, lmao Is there some kind of code that I can download onto my usb key back at home and take it to the collage computers to get some sites unblocked?
thermoelectric (author)  Plasmana4 years ago
Hmm, I don't know if there is some kind of code to do that, sounds like your collage has some tight filtering. How about a forum topic?
It is pretty tight, and some features on college computers are locked by admin, which prevents me to play my browser game 'darkorbit', so I came back to Instructables instead :P
thermoelectric (author)  Plasmana4 years ago
Are you using a laptop? If so why not try to make an antenna to pickup a signal from a nearby household?
How do I make an antenna for my mac laptop? My computer is picking up something, but it is too weak to use, lol
thermoelectric (author)  Plasmana4 years ago
You can just searcl Instructables for it...
Also, the blocker is called: MessageLabs Look it up on goolge, its popular, I think, lol
Oh, if I used that circuit, would it make for a better MOT based welder?
thermoelectric (author)  The Ideanator4 years ago
Maybe, But it would be harder to get caps rated for the amperage, Idon't think it would be worth it, but that is just my 2 cents
Nice work with the MOT building Thermo. Hope to see it connected to the telsa coil at your building. I also like the pics of all of the light s connected together. GOOD JOB!
thermoelectric (author)  Hydroelectric4 years ago
Haha, Thanks. I hope to have a Tesla Coil built by the end of the holidays, But wether or not it will happen is a mystery. I know my MOT stack is tough, because after I took it to school, I felt like taking it down teh steps, on the trolley thing, It fell off. and fell about 10 steps (concrete), And I didn't notice any damage at all.
How was the reaction of your class when you showed them? Dam , that must be pretty tough.
thermoelectric (author)  Hydroelectric4 years ago
They were pretty amazed... After that, our science teacher showed us a vandegraff generator, really puny sparks compared to my MOT's...
Lol, your's compared to the vandegraff generator, I think that your's would win by a long shot. By that I mean in spark disposal ofcourse.
Holy zombie jesus! Its a thing of beauty! 8800vac?? OMG!
thermoelectric (author)  The Ideanator4 years ago
Thanks :-) Yep, Sure is 8800VAC. Tis a bit less than what comes from a NST or a OBIT, But the current is sure a lot higher than those other whimpy transformers... (Gotta be careful not to let the spark touch me and make my heart do the dance of death...)
Yeah, that would not be the best thing in the world, I wanna see more HV coolness
thermoelectric (author)  The Ideanator4 years ago
I'm trying to get some transformer oil to submerge the stack in, so I can run it at a higher current, and not be as worried about burning out the MOT's.

It will sure look more awesome when I start using a secondary shorted MOT to current limit it!
thermoelectric (author)  The Ideanator4 years ago
You got it! More pics were just uploaded!
Sweeeeeet!
thermoelectric (author)  The Ideanator4 years ago
Sure is!
i just realized, you should burn some stuff with this >=D
thermoelectric (author)  The 4th Doctor4 years ago
What type of stuff? I'll be more than willing to do it...
Sandisk1duo4 years ago
cool! i probably wouldn't keep such a deadly device in my house
thermoelectric (author)  Sandisk1duo4 years ago
Haha, It sure is cool! It is only deadly when it is plugged in, lol. Anyways there are many things that are just as deadly as that in your household, you have a microwave don't you, probably a TV too, they are all dangerous...
yes, but my TV doesn't have it's HV coil exposed i usually mess around with 300V flash circuits, they have lots of voltage, but very low current
thermoelectric (author)  Sandisk1duo4 years ago
That is true.

What happens if you accidentally charge a small (or large) cap bank? This happens! Let me introduce you to Project Thumper!


i have a 300v 2000uf capacitor made form 30 flash caps
Lol nice, I got one made from 20 flash caps, I use it to blow up stuff and coilgun experments. :-)
i let the magic smoke out of my charger circuits, so i have to go get more... i'll probably add another 10 or 20 caps to the circuit
thermoelectric (author)  Sandisk1duo4 years ago
I seem to let the magic smoke out of alot of my circuits too. Why not charge them with the mains (try the 220/240 outlet, current limit it with a light bulb in series ithe the rectifier, rectify it and you can charee a bank hell quick.
i have only 120v outlets
thermoelectric (author)  Sandisk1duo4 years ago
No 220v outlets for a dryer?
oh, yes there are 220v outlets
thermoelectric (author)  Sandisk1duo4 years ago
So if you put a light bulb in series with the rectifier and the rectifier charging the caps it will work.

light _ connection between cap bank and -
---()----------| - |-----------|

AC Rectifier cap bank
thermoelectric (author)  thermoelectric4 years ago
Dang, It didn't work I don't think the light is necessary though
yeah i suppose it siphoned off too much power, if your capacitor bank isent too large there shouldent be that bad of a current surge when you charge it up
thermoelectric (author)  The 4th Doctor4 years ago
I'm gonna try it again thisarvo. I hopw it works this time.
you'll need the light as a ballast, so your capacitors charge slower
thermoelectric (author)  Sandisk1duo4 years ago
Ah, okay
lol and the mini chargers take too long to charge the cap bank too.. So I use the MAINS for instant charging. :P Also the way I have desinged my cap bank, I can charge it up to 600v safely... Muahahah!
thermoelectric (author)  Plasmana4 years ago
I'm gonna set up a mains charger tonight, I'm just worried that i'll over voltage the 330V photo flash caps.
I one time accadently over charged one up to 350v on 330v limmit flash cap, but it still works fine. :-) If they begin to swell or making faint popping noise, (inside the cap) then it is bad.
check out these caps
http://www.bgmicro.com/index.asp?PageAction=VIEWPROD&ProdID=12865

i just got 8 of them! two freaking kilojoules! equivalent to around 400 photoflash caps!
those have a higher internal resistance, so it would take longer to discharge
meh there not so bad, got a pretty nice can crushing effect, thompson disk shooter, i hooked it up to a small coil and it freaking exploded, and im sure thell make a nice railgun but they certainly arent the fastest
Yeah, I seen those caps, I can get em cos Im in the freaking UK! :-(
thermoelectric (author)  Plasmana4 years ago
Did you see Project Thumper Plas?
I'll link in an introduction, it has a MASSIVE cap bank
Yeah, i saw it :P Danm, just about all the good stuff on the internet is blocked. Even instructables, I went through a lot of trouble to get instructables unblocked for me :-D
thermoelectric (author)  Plasmana4 years ago
That's unfortunate, Tell me how the proxy sites go, they used to work for me until my school blocked all of them :-/
thermoelectric (author)  Sandisk1duo4 years ago
That's easily enough to kill you
yes, but the voltage is less then 8800VAC
thermoelectric (author)  Sandisk1duo4 years ago
Still, It can still kill you so it is considered dangerous, although I admit having something where you don't have to touch it to strat the arc is a bit more dangerous.
if you convert the AC to DC, you will get 13200V DC
well your still getting that peak voltage before you rectifier it, but loosing half of the power unless you have a full wave rectifier and with the caps and diodes needed for that you could make a voltage quadrupler
quite right
thermoelectric (author)  Sandisk1duo4 years ago
Wow, That sure is a lot more voltage, I wish that TC's were suited for DC...
you rectify the output voltage
thermoelectric (author)  Sandisk1duo4 years ago
Oh
guyfrom7up4 years ago
NICE MOT STACK You are running those in anti parralel, right? As in it's +-4400 vac around earth ground? if not, you should do that immediateley, 8800 is very hard on the insulation. I'm jealous :P Also, for those of you that are looking for microwave transformers on the cheap, your county might have a bulk waste day where people throw out stuff that normally the garbage men won't take, ie couches, MICROWAVES, furniture, etc. Over the summer I picked up 6 MOTs for free, turns out one was broken, so i turned it into a 12 volt 60 amp power supply for a 1.5 farad capacitor to cut metal through a huge IGBT.
thermoelectric (author)  guyfrom7up4 years ago
Thanks :-) Yes, it is 4400VAC on wither side of the dround, you can see the ground wire linking the two bottom (middle) cores in one of the pics.
Pro

Get More Out of Instructables

Already have an Account?

close

PDF Downloads
As a Pro member, you will gain access to download any Instructable in the PDF format. You also have the ability to customize your PDF download.

Upgrade to Pro today!