Strong Electromagnet From an Old Transformer





Introduction: Strong Electromagnet From an Old Transformer

About: 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 like to play with high voltage power suppli...
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

1 Transformer
Enough magnet wire to fill the core.

Box Knife
Slotted Screwdriver
Small Hammer

Step 2: 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

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

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

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 .



    • Oil Contest

      Oil Contest
    • Clocks Contest

      Clocks Contest
    • Water Contest

      Water Contest

    118 Discussions

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

    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!!!!!

    3 replies

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

    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.

    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.

    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.

    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?

    2 replies

    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.

    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.


    2 years ago

    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.

    1 reply

    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.

    How would I make it repel???

    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?

    1 reply

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

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

    1 reply

    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.

    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.