I need an advice on making electromagnet/solenoid from bare copper coil/other option

I have in my lab room thick tinted copper wire. I planned using them to make some electromagnet, but fail to find a solution on how to insulated them. At first I thought using those acrylic/enamel can spray, but I am not sure if it would fully insulated them. Would the acrylic/enamel penetrate between the contact gap and insulated them or will it just fail to do so?

In fact, I am not even sure if it's a good idea to begin with, because I don't want to actually waste the copper.

As an alternate option I thought using those magnet wire from the Microwave Oven transformer, the one with really thick diameter. I would uncoil them, and manually turn them. 

I thought I could use some of your advice. Actually, I dont mind if the process takes time, I am just looking a convenient way.


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richardphat (author) 1 year ago

Hi, here is an update.

Attached are the three pictures I manage to take. Notice in the 2 first MOT, the welding assembly is on the lower part, and the third one on the top. Further as mentionned earlier, there is some sort of epoxy between the paper and the iron framing. So I guess some heat/freezing will manage to remove them.

I may also add some sort of top plate, rather than re-use the one freshly cut from the MOT; because aesthetic ;)

Further,does anyone haave some suggestions for that thin (secondary coil?).

I just don't want to throw them away, and I am looking for some application.


Is the tinted copper anodized or is it already insulated?

Have you done a continuity test?

Most magnetic wire made today has up to four layers of polymer film as insulation.

Although I salvage magnetic wire:


I also make a polymer coating I call plastic coat:


This stuff dries in seconds and takes about an hour to fully set, it makes a very good flexible insulator.

richardphat (author)  Josehf Murchison1 year ago

Unfortunately they are not insulated, I just checked with the contiuity test.

OK so it is most likely anodized.

That can make the wire hard to solder or coat with an insulation, anodizing is made to prevent things from sticking and oxidation.

Try a lacquer on a section of the wire and let it dry. Once the lacquer is dry rub it with a cloth if the dry lacquer comes off with rubbing chances are you will be hard pressed to get something that will stick to the wire.

richardphat (author)  Josehf Murchison1 year ago

I will check in my lab tomorrow. I haven't paid attention to that detail.

We first thought it was some lead/tint meant for soldering and we put them together. Until we realize it was copper. For one thing sure, we did have to scratch it in order to see the red/orange copper colour.

richardphat (author) 1 year ago


After giving some thought about it, I saw some electromagnet on Amazon claimed to be able to lift 400N. Technically it would solve my problem right off the bat, but I feel it is cheating, since it doesn't require any challenge.

Therefore, there's 2 viable solution; buying magnet wire and customize my own electromagnet. Or heck, should I just use the directly the coil in the plastic roll and insert some iron core.

Second, based on Rick, I may want to try out the MOT oven and mod it. This guy manage to pull 50 pounds, which is quite interesting, considering the fact it has been powered by AA battery.

Further I wonder, if you can actually change the "rectangular" magnetic field into a "circular" by using any particular mean? Say if I put a round plate under that microwave oven electromagnet, will I end up having "circular" magnetic field?

Thanks for linking to that video. It is a good demo, and I think I have most of the parts needed to reproduce this experiment. If can find the time to do this, I will snap some pictures, and up those, and my observations, to this thread.

For now I just wanted to give you some advice on the disassembly of microwave oven transformers (MOTs), because in my experience taking apart the MOT is somewhat tricky, especially if you want to do it without destroying the windings.

The best Youtube tutorial I have seen for doing this, so far, is this one:

The thing that makes this surgery so complicated is the fact the windings are glued into place, so it is necessary to weaken, or break, this glue, without breaking the windings. IIRC the author of this video uses heat to soften the glue, specifically by energizing the transformer, and just letting it sit, and cook itself, for some length of time. Note that the transformer is dangerous to touch in this condition, so if you want to get a feel for how hot is the MOT is getting, turning off the power first should keep you from getting electrocuted.

I have also read rumors of baking the MOT in an oven, or toaster oven, to heat the glue.

I myself, tried cooking a MOT in water, in a pressure cooker, for like an hour, but the results were disappointing. This treatment did not have much of an effect on the glue. Maybe this did not get it hot enough?

I found that an oscillating mult-tool saw, one capable of making plunge cuts, could be used to make narrow cuts in between the windings and core, in some places. But there were also some places where this saw could not reach.

That's kind of a long story I guess. All I'm really trying to say here is it this MOT surgery is maybe not super-easy.

I will try to up some pictures of what I've got for cut-open MOTs, and using these as electromagnet, in the next day or two.

Hey, it occurred to me: if you have the freedom to just leave the MOT's existing windings in place, that will simplify things considerably.

I tried pushing a 1.0 ampere constant current through the primary winding of an old MOT-with-top-cut-off, and this does a pretty good job of magnetically holding the cut-off-top in place.

A picture of this mojo is attached.

The red meter is showing the voltage across this winding, in millivolts: 800 mV = 0.8 V. The yellow meter is showing the current through this winding, in amperes: 1.0 A.

Thus the DC resistance of this winding is about 0.8 ohm.

Not sure how much force would be required to pull the top loose. It is more pulling force than I can produce with my arms, although I can't seem to get a good grip on it, really.

50 pounds force, which is about 220 N, this seems believable. I am inclined to believe Dorian McIntire's video demo, the one you linked to, is legit. I mean, I don't think he's hoaxing you.

Note that in the picture I am showing you, the force pulling on the two pieces is just the weight of the bottom section of the transformer, which is only about 5 pounds, or 22 N.

Oh, the other pic I upped, the detail of the top piece of the MOT, is to show you an example of what not to do. I cut too deeply on this MOT, on the welds on both sides. The welds were only about 3 mm, or 1/8 inch, deep, but I overshot that by a factor of about 3, on both sides.

The reason I cut too deeply is because, even after I had sawn through the welds completely, the glue was still holding the transformer together. I thought the steel welds were still holding, but it was actually the glue.

I have since learned, gentle prying with a screwdriver, is the technique needed to break the glue loose, in this first step of removing the top (I-shape) from the bottom (E-shape) of the transformer core.

richardphat (author)  Jack A Lopez1 year ago

I had the opportunity to scavenge some MOT in the past few months, some of their shape are quite different. I had assume they would be the same since there has to be the same manufacturer.

I'll try to get some pic for tomorrow, if I got some spare time.

Any magnetic field is essentially spherical no matter what the shape of the producing magnet.

The Magnetic field radiates out from the core of the magnet and will return to the other pole.

richardphat (author)  rickharris1 year ago

Good to know!

iceng1 year ago

First make certain it is bare wire. Magnet wire looks bare to a untrained eye.

If you have a ohmeter it is easy to touch two parts of the wire an inch apart.

Otherwise use a file or dull knife to scratch the end of the wire to see real copper.

iceng iceng1 year ago

On of the problems in small electromagnets is I^2xR heating.. The below picture depicts how to run a cooler magnet by reducing current with the addition of a NIB magnet...

The penalty for a cooler or stronger magnet is the requirement of a negative current flow to zero the flux ( turn the magnet off )...

As usual click the picture to see the whole self explanatory image.

Kiteman1 year ago

1. Wrap your core in plastic, paper or adhesive tape (an insulator).

2. Wind the wire around the core, with each turn not touching the next.

3. When you get to the end of the core, re-wrap the core, covering all the turns.

4. Wind back along the core.

5. Repeat steps 3-4 until you run out of wire or get bored.

6. Wrap the outside of the coil to hold everything in place.

rickharris1 year ago

Copper magnet wire is usually insulated with a coat or 2 of lacquer, I think at home it would be very hard to be totally sure it was insulated all over.

magnet wire isn't all that costly to buy. and you will need a few hundred turns round an iron core to make a decent electromagnet.

For advice you need to specify some things:

the voltages & current your going to use.

The level of magnetic field you need (if it matters)

The size you need the thing to be.

richardphat (author)  rickharris1 year ago

Hi Rick,

I mainly consider anything from 5 to 12V, I have some server power supply that can provide a high current, or anything powered with battery.

My aim would be making electromagnet that can lift 10 to 20kg objects (100 to 200N). I have some steel core of 1" core, that I plan to turn.

Further, the number of turns isn't an issue to be honest, I have hand turn several tesla coil and I find it quite relaxing to do. However, these wire seems innapropriate for my use.

Ok then this should tell you all you need to know


Good luck.

For that you might want to consider a pot magnet as used by car wreckers and in the steel industry.
It's basically a coil inside a "pot" - like those strong ring magnets with a hoock for the fridge.