Introduction: Strong Electromagnet From an Old Transformer

Picture of Strong Electromagnet From an Old Transformer
This is a very strong electromagnet made out of an old transformer.
The materials used are recycled from transformers and motors.
This magnet can lift over 30lbs (14kg)

Step 1: Parts & Tools

Picture of Parts & Tools

1 Transformer
Enough magnet wire to fill the core.

Box Knife
Slotted Screwdriver
Small Hammer

Step 2: Disassemble the Core

Picture of Disassemble the Core

The transformer core is made of layers of "E" shaped & "I" shaped pieces which are held together with varnish.
To separate the layers use a box knife to break apart the first layer, then beat the piece out with a hammer and screwdriver. Once it breaks free it can be pulled out with the pliers.
Once you get the first couple of layers out, put the transformer on a hard surface and hit all sides of the core with the hammer to help break the varnish loose. Then you should be able to get the rest of the pieces out with the knife easily.

Step 3: Wind the Coil

Picture of Wind the Coil

I wound this coil by hand so I didn't get any pictures in the process.
I used wire that I collected from other transformers and motors.
So I ended up twisting together about 15 strands with a drill to make about 50ft (15m) of 22awg wire.

The coil form has a divider between the coils that needs to be cut out in order to wind one big coil.

This coil has 5 layers of wire in it.
The layers must all be wound in the same direction and should be wound as neatly as possible .

This coil will run at 5 volts. For a higher voltage use more turns of a thinner wire.

When using DC to run the magnet, you can estimate the current using a wire resistance chart & ohms law.

Step 4: Put the Core Back In

Picture of Put the Core Back In

For this to work as an electromagnet we will only use the "E" core pieces.
To reassemble the core, the easiest way to put it back together is to put all but a few pieces in at once. Then put the rest in on at a time, and pound them in with a hammer.
The core should stay in from friction alone, but you could use more varnish or super glue to hold them together.

Step 5: Using the Magnet

Picture of Using the Magnet

These magnets work best when a piece of metal comes in contact with all 3 parts of the core.
I find them the most useful for lifting thick, flat pieces of metal. They have very little pull with sheet metal.
The core will heat up fairly quick and should only be used for intermittent use .


Pandita100 (author)2016-05-25

Do you know the formula to calculate electromagnetic in the middle of E shaped ?

InfinityHex (author)2016-01-31

I really need to know how to make it repel because I'm doing a project where I need it to launch metal or a magnet I already hooked it up to AC and DC and tried various metals. HELP!!!!!

NojoTurkie (author)InfinityHex2016-05-11

try using a paramagnetic material. magnetic material (iron) attracts. paramagnetic (aluminum) is not usually magnetic yet under high magnetic fields is repulsed

rocketman221 (author)InfinityHex2016-01-31

This won't work very well for launching something. You could build a ring launcher though, they are pretty easy to make and a lot of fun to mess around with.

InfinityHex (author)InfinityHex2016-01-31

I just need to repel anything

HunterL23 (author)2016-05-09

if you are interested in this kind of stuff, check out this video of how Colon Furze walks on the celing by ways of electromagnets made from old microwave MOT transformers.

HunterL23 (author)2016-05-09

if you are interested in this kind of stuff, check out this video of how Colon Furze walks on the celing by ways of electromagnets made from old microwave MOT transformers.

Sammbo (author)2016-01-23

I wonder how strong a magnet made from a microwave oven transformer
could actually be? If you had enough of them side by side, could you
make one of these sheet metal benders?

lesphoto (author)Sammbo2016-03-07

I'd like to build the same thing....seams like a no brainer. Wire in parallel and find a good DC power source. Big I beam and some welding to hold it together.

rocketman221 (author)Sammbo2016-01-23

You could probably use 3 or 4 of them for that. They are quite strong when stuck to thick steel. It will take a lot of power to run them though.

SamK57 (author)2016-02-01

How effective would an electromagnet made from a transformer be at moving a small magnetic ball/neodynium spherical magnet 1and a half inches away? 39cm round abouts. Most electromagnets i have made so far using an iron nail and 36awg wire(wound maybe a thousand or 2 turns around a straw that fit around it) would be able to move the magnet successfully half an inch away, but not any further.

rocketman221 (author)SamK572016-02-01

I didn't have a spherical magnet, but I tried a half inch cylindrical one and the smaller electromagnets pull it in from 2 inches away, my biggest one pulls it in from 2.5 inches away.

InfinityHex (author)2016-01-31

How would I make it repel???

John_Singleton_ (author)2016-01-31

The core takes hours!

Miles426 (author)2016-01-31

If I have an iron core electromagnet being fed a constant power in the same direction would an air core electromagnet attract and repel when introduced to the iron core magnet if I change the polarity of the air core magnet?

rocketman221 (author)Miles4262016-01-31

Yes, it will repel the air core electromagnet is they are the same polarity.

Benjamni_lee (author)2015-12-15

Where did you get your transformer. And also, what were you using as a power source and on/off switch

The transformers were taken out of some old chargers in my junk bin.
The power supply I used is a modified ATX computer power supply. I didn't use a switch, I was connecting some wires with banana jacks to the power supply.

aloving95 (author)2011-12-15

Immagine if you did this with a MOT (microvave oven transformer)

rocketman221 (author)aloving952011-12-15

I was thinking about that, but I have never taken one apart. I don't know if it would come apart very easily.
The small electromagnets are hard enough to pull off of something. I would like to seen what a mot would do.

G-dawg7 (author)rocketman2212015-06-25

Taking apart a MOT is much easier than taking apart one of these smaller more fiddly transformers. This video from Grant Thompson shows the easiest way to do it. ( go to 1:15)

I have found that microwave ovens are a very good source for copper wire, the main problem is the varnish that that is used on the coils when they are made is very tough leaving sharp fragments stuck to the copper wire as it is unwound, which can act like a saw if pulled over unprotected hands.
Never the less around 1/2 a kilo of copper magnet wire from an old microwave oven destined for the garbage bin can't be all that bad, and if any one knows of a way to soften the varnish that is used to hold the coils together 'with out damaging the wire's insulation' ........

Wrap the wire around a metal rod or a screwdriver and pull it tight over it. It will straighten the wire and break extra bits of varnish loose.

50-50 (author)rocketman2212012-02-08

please don't try this with a MOT
I alredy have and it killed preaty much evrything electronic around it when I hooked it up to my electric fence power supply.(10 000 volts)
It also sucked the ring I was waring to it and I started getting zapped by the current.ouch.

aloving95 (author)rocketman2212012-01-21

I Found a MOT that was messed up and the lamanations were bolted together. ill try and post a pic when i finish winding the giant bobin

bhry (author)2014-11-16

Hello , Mr rocketman221 you done a good Job thanks for share information
I need a help if you would please help me in this
I am working at an electric magnatic for water the pipe diameter is 50 mm and another pipe 65 mm
the volt I use 24 V " transformer from 220 v to 24 v and its AC Voltage "
the pipe is plastic the water well pass throw
and the magnatic well run for 6 hours daily
I need to know how much wire long and diameter and how much layer I need and many layer
and how many turns for layer
realy I Am THANKFUl for your Answer and Information
ANd its my first magnatic project
with thankful

jbrown146 (author)bhry2015-04-04

This won't work because AC can't generate a magnetic field.

rocketman221 (author)bhry2014-11-18

This probably won't work very well for what you are doing. It sounds like you are trying to trap metal particles flowing through a pipe. These magnets are great for lifting large pieces of metal, but not very good for small pieces.
I haven't been able to make any that will run for long periods of time and still perform well.

lam (author)2015-02-07

Hi rocketman221

Please could you help me to know:
My old solenoid coil has 100 meters of 28 gauge (0.32 mm) . Now I want to build an other but I have only 34 gauge magnet wire (0.16mm) . So Please could you help me to know:
Can I use 2X 100m of 34 gauge magnet wire and 2 wire must twisting together or not need to do(twisting) that ? Thank you so much

jbrown146 (author)lam2015-04-04

If you were to do that you would need to twist it. I wouldn't worry about the gauge if your making another one. 34 gauge should work just fine.

rocketman221 (author)lam2015-02-07

That would work, but you need 4 pieces of 34awg wire to replace one piece of 28awg. The wire should be twisted, that will be fun with such a long piece of wire.

dmalamas (author)2015-03-10

Hi, could you tell me if this electromagnet works with AC (50 - 100 Hz) input?

jbrown146 (author)dmalamas2015-04-04

Nope, only DC. Cell phone chargers can do the trick. I'm not responsible for you hurting yourself.

cjhynum (author)2014-12-24

Could i hook the magnet up to a 12v plug in a vehicle i got the transformer out of a microwave

rocketman221 (author)cjhynum2014-12-24

As long as you wound the magnet suitably for 12v you can. The 12V socket will typically have a fuse around 10-15A so your magnet will have to use less current than that. Keep in mind the socket may supply up to 14V.

Let me know how well the magnet works with a MOT. I have wanted to make one, but never gotten around to it. You could probably lift over 100kg with a magnet that size.

cjhynum (author)rocketman2212014-12-25

I seen a guy do it on youtube and tried it i wanted to pick metal up out of a field with it but it wasnt strong enough do u have any ideas im not thinking of

AmakW (author)2014-12-15

hello @rocketman221.. It is possible to use this electromagnet in the water? If can? How can I make it waterproof?

rocketman221 (author)AmakW2014-12-15

You could dip the whole magnet in varnish a couple of times to seal it.

m.amir.456 (author)2014-12-12

Hello @rocketman221 i want to make an electromagnet that can move a 10kg object in To and Fro... how can i make it... which wire, its length and no of turns and how many volts (dc)....

rocketman221 (author)m.amir.4562014-12-15

The magnet shown in this instructable will work for what you need. It runs from 5V DC. As long as the object you have has iron or steel that's flat and over 10mm thick, it will lift it.

The magnet has 50 feet of 22awg wire on its core and about 125 turns.

reidintransit (author)2014-10-09

what about adding a resistor in series with the coil for cases where the source voltage is too high or coils are too small?

You could, but you will need a high wattage resistor and it will get hot.

avwerosuo (author)2013-10-15

Hello rocketman, it's a nice job you are doing keep it up! I am not a professional in this field so I'll need your help. I've a neodymium magnet of 4''diameter x 1.5''long and i want to make an electromagnet of if possible equal force for repelling purpose. I want use a larger core of 3''diameter x3'' long and the electromagnet will operate continuously. Please kindly guide me on the wire size, the number of turns and length of wire that will not generate heat and also operate at low current. Please i need a very strong electromagnet with equal force as the neodymium magnet. I'll be very grateful if you or anyone can give me any useful advice. THANKS!

rocketman221 (author)avwerosuo2013-10-15

Unfortunately you won't be able to make an electromagnet capable of repelling that super magnet using a transformer core. If you were to use an iron core, the neodymium magnet would just stick to it and be very difficult to remove.
You could try using an air core electromagnet, that would be able to attract and repel the neodymium magnet, but won't be nearly as strong as the neodymium magnet.
Be careful with those super magnets, they will crush anything that comes between them and a piece of iron or another magnet.

avwerosuo (author)rocketman2212013-10-15

Thanks for your reply!
But yes i actually wants it to stick together when the electromagnet is switched off and when the electromagnet is connected (switch On), the North pole of the electromagnet and the North pole of the Neodymium magnet will cause them to repel from each other, and when switch off again they stick together.
I don't know if am correct, but i want to know if this is possible.
Thanks for your reply!

barry92 (author)2013-08-07

if DC power supply is used on E-shaped ferrite core electromagnet, will the performance of the electromagnet the same as the one usign AC power supply?
How to differentiate the poles of the transformer, as i want to repel another identical transformer?
Do the armatures of the E-shaped electromagnet exert forces on the other identical one when current is supplied?

rocketman221 (author)barry922013-08-07

The magnets are much stronger on DC. On AC the magnet's polarity is constantly changing and they will vibrate strongly when brought near metal. They will draw less current on AC and the current will decrease when stuck to a piece of metal.
The inner part of the E core is one pole and the outer parts are the other pole.
Two magnets will repel each other when the polarity is different, but they don't like to stay centered on each other. The inner core will stick to the outer core on the other magnet unless something prevents them from moving side to side.

sdhavle (author)2013-07-31

which wire did you use?

rocketman221 (author)sdhavle2013-08-01

I have used 22awg wire on my 5v magnets and 28awg wire on my 12v magnets.

ankit pundir (author)2013-07-27

Hello rocketman, I have few questions in my mind.
I am working on 12V magnet and using the 'E' shaped core having dimensions (40x26x17) mm. So can you please suggest me the diameter(or gauge no.) and the length of the copper insulated wire needed.

About This Instructable




Bio: I enjoy building electronics & robots. I like building computers as well as writing programs & web sites. I like to build and launch rockets. I especially ... More »
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