A good source for cheap magnets and magnet wire

[MagnetJuice]

I have found out that one of the cheapest ways to get magnets and magnet wire is microwave ovens.

A few years ago, I thought about building a permanent magnet alternator. I placed an ad on Craigslist and offered to pick up old and broken microwave ovens. I got responses from 5 people, so I got 5 free ovens.

That was just before Summer, so I decided to start going to garage and yard sales to see if I could find more ovens. By the end of that summer I had 12 microwave ovens.

The next year I did the same thing. I ended up with 30 ovens all together.

I never paid more than $5 for an oven. I used to go to the sales in the afternoon. By that time the sale was almost over, and if they had a microwave, I made them an offer, $2 or $3. Most of the time they sold it cheap because they didn’t want to take it back in the house.

Here is a picture of 44 matching magnets. Those magnets are C8 grade. Ferrite or Ceramic C8 is one of the strongest ceramic magnets. I need a total of 48, so I still need 4 more magnets of the same size so I can have 2 rotors with 12 double magnets per rotor. I found out that the size of the magnets varies a little from oven to oven. I want all the magnets that I want to use for the alternator to be close to the same size.



Here are some pictures of the first 12 ovens that I took apart and how to get the parts out.



Each transformer has 2 nice coils, one is the primary winding that has thick wire and the other is the secondary with thin wire. I have 30 of these transformers. Each coil weights about 1 Lb. That is about 60 pounds (27 kilos) of magnet wire for a few dollar$.

The transformers can also be used to make a welder or a very powerful battery charger.

These transformers are easy to take apart. The laminations in the transformer are held together by a thin welding that can be easily cut.

Here are the steps to get the coils out.



more to come...

[MagnetJuice]

Each magnetron tube has 2 magnets

It is believed that the magnetron tube insulators contain beryllium oxide. They are those little pink cylinders that you see in the picture. Be very careful not to brake those during disassembly. If they brake, they could produce a dust that is very toxic. It might be a good idea to wear a dust mask just in case. Also make sure that the leftover parts are disposed according to local environmental regulations.

There is a lot of aluminum fins in the magnetrons. That could be useful for some people.

Here are some tips on how to take the magnets out.





more to come...

[MagnetJuice]

I saved the largest microwave oven cabinet to be used as a Faraday cage. That type of cage protects electronics from getting fried by electromagnetic waves (EMP). I made sure that all the openings into the cabinet internal compartment were completely covered with some kind of sheet metal.



For many years there has been a concern about an enemy nation detonating a nuclear bomb high in the atmosphere. If that were to happen, the detonation would create electromagnetic waves that would destroy unprotected electronic components for hundreds of miles on the land below the explosion. That means that phones, computers, and most automobiles will stop working. The electric grid too, including the electronics in homemade power, wind and solar.

Inside the Faraday cage, I keep a small laptop, and an additional hard drive with digital copies of all my important documents. I also, from time to time, place a protected thumb drive in the cage with up to date documents. I also keep a small battery powered AM/FM radio, 2 sets of Two-Way Radios (walkie talkies) and a short wave radio. That way, If the worse ever happens, I still have access to news and some way to communicate with others.

For those that have wind or solar power, it is a good idea to store some of the electronic components that would be needed to repair the system if it gets knocked-out.

The steel microwave cabinet is not enough to protect the electronics. For full protection they have to be wrapped in plastic, cloth or paper, then 2 layers of aluminum foil. Then plastic, cloth or paper again followed by another 2 layers of foil. And then, it needs to be wrapped one more time in cloth or paper before placing it inside the microwave cabinet.

Since all those radios need batteries, I keep plenty of rechargeable batteries and a way to charge them using a human powered generator/charger.

It is good to be prepared. We live in crazy times with some nations being ruled by unstable leaders.

There are other parts of the microwave oven that are useful.

The front panel timer has a relay good for over 12 amperes. It can be used as a timer to power just about anything from a few minutes to more than an hour.

Most ovens have a nice electromagnetic interference filter (EMI) that is fused and good for about 15 amps. I installed some of those filters inside some of my power bars where I plug some of my sensitive electronics gear.

[noneyabussiness]

Awsome write up.. Thank you

[tanner0441]

Hi

All those microwave ovens appear to be piled up in your kitchen. You must have a very toerant wife.

You mentioned wearing gloves, I have stripped a few microwave transformers and the coating the coils are impregnated with when you wind another coil straight from the transformer windings the coating will rip skin from your fingers. I have not so far found anything to disolve it without also damaging the laquer on the wire. So if you find a way please let us know.

How are you measuring the strength of the magnets?

Brian

[Mary B]

Yes the pink IS beryllium! Handle with care! Wear an N95 mask minimum, a respirator would be better with an appropriate filter for super fine particles. Berylliosis is a nasty lung disease caused by beryllium dust.

[Mary B]

Hi

All those microwave ovens appear to be piled up in your kitchen. You must have a very toerant wife.

You mentioned wearing gloves, I have stripped a few microwave transformers and the coating the coils are impregnated with when you wind another coil straight from the transformer windings the coating will rip skin from your fingers. I have not so far found anything to disolve it without also damaging the laquer on the wire. So if you find a way please let us know.

How are you measuring the strength of the magnets?

Brian

I can't remember who but someone made a wind turbine using microwave oven magnets. Performance was decent if my bad memory serves me.

[Bruce S]

Ed from Windstuffnow did a build about the size of a box fan.
Here's a link if you wish to look over his post on his website.
https://www.windstuffnow.com/main/microwave_wind_generator.htm

IF you do a search for round ceramic magnets you should get a lot of info from the early days when NEO's weren't all the rage and post price hike when they did get noticed by people like the Dan's , Ed, Scourgwind, etc.

Please note: Ed is no longer with us , his website is still up and can very helpful with tons of info. I still use it for some references.


Hope this helps
Bruce S

[MagnetJuice]

All those microwave ovens appear to be piled up in your kitchen. You must have a very toerant wife.

I have a very tolerant wife, but if I would pile up all those microwaves in the kitchen, I would have to sleep in the basement for a few days. 

The microwaves were in my unfinished basement/shop. That is where I do all my tinkering in the winter.

I don’t have a way to measure the strength of these magnets but sometime ago I saw somewhere on the WEB that microwave ovens used C8 in their magnetron tubes.

The BrMax for C8 is 3850 gauss, and for the most powerful Ceramic C10, the BrMax is 4000. That compares with a BrMax of 13200 for an N42 Neodymium magnet.

I have a lot of speaker magnets, since speaker design is one of my main hobbies. I have done some crude tests and the magnets from the microwaves appear to be stronger that the average speaker magnets.

Mary, you are right, beryllium dust is very nasty, but as long as the pink insulators remain intact, there is little chance of dust.

The guy that made the turbine a few years ago was Pedro from Portugal. He built an alternator using the same type of magnets. According to Hugh Piggott, it was capable of producing 400 watts. He had sets of 3 magnets per pole, but I think he found out that the third magnet didn’t help much and added a lot of weight to the rotors so he went back to using 2 magnets per pole. That is 2 rotors with 12 poles and 24 magnets each.

Here is the thread:

https://www.fieldlines.com/index.php?topic=145661.0

Brian, I have never taken the time to unwind and clean any of these coils. I am going to clean one and see how it goes.

I started to work with one of the coils from one of the above pictures, the one that is 16 Ga. (1.3 mm). I started by removing most of the paper and tape that was stuck to it. Then, while holding it on top of a rubber mat, I gently hit it with a rubber hammer all the way around the edges. Then I washed it with warm soapy water to clean the dust. That is as far as I got today. Tomorrow I am going to unwind it and wind it back on a spool and see how it goes.

Here are some pictures:

The last picture is after I washed it. It looks OK, we'll see how it turns out.



Ed

[MagnetJuice]

After I unwound and cleaned the coil, I wound it on a spool. This is the result.



There is nearly 2 layers of wire in that spool, 107 feet total. I measured the resistance using my milliohm meter, it is .435 ohms.

All the wire insulation stayed intact, there was no bear spots anywhere on the wire. Some of the yellow tape that was on the coil didn't come off, but I think that is not a problem.

These are some of the tools that I used to clean the coil and to straighten out the wire.



The scrubbing sponge that you see there was the main cleaning tool. That is how it looked after I was done with it.
I used a cheap pair of felt gloves from the $ store and rubber gloves over them. I used the rubber gloves because I soaked the sponge in soapy water. I think that it could be possible to clean the wire with just a dry sponge. In that case, the rubber gloves will not be necessary. Using just a good pair of cotton or leather gloves would be just fine.

I used the nut driver to straighten out the wire after it was cleaned. It doesn't have to be a nut driver. Any smooth round tool could do the job.

Unwinding, cleaning and rewinding that coil in my cramped up basement was not easy. It took a total of 27 minutes.

If the work could be done outdoors, it would be a lot easier and faster. I think that it could be done in about 10 minutes
outdoors.

This is how I would do it outdoors;

After I break the coil loose with a rubber hammer or a piece of wood, I would put a plastic pipe or wood dowel through the coil. I would attach one end of the wire to a fence pole or a tree. Then I would slowly start walking back unwinding the coil.

Then I would go to the beginning and start scrubbing the wire with the sponge.

After that, I would use the nut driver to straighten out the wire. Keep the wire taught while doing that and make sure there are no kinks on the wire.

There are other ways to straighten out the wire. One way is to secure one end of the wire to a solid wall or a vise and the other end to vise-grips and pull on the wire. I have used that method to straighten out the nichrome wire from hair dryer heating elements. It works well. If you do that, make sure that you use eye protection in case that the wire breaks or come loose.

That's it. All that remains now is to wipe the wire with a damp rag and wind it on a spool.

The price of new magnet wire is $15 a pound or more (in 2020) if you buy a large spool. And it costs a lot more than that in some countries, if you can find it. Anyone who has access to old microwave ovens can save a lot of money on wire and build a nice permanent magnet generator.

Ed

[SparWeb]

Great work, Ed.  The other Ed would be proud!

Would you like to test the insulation to see if it has been damaged by your separation and cleaning of the coil?  Even though I'm sure you used a lot of care in unwinding the transformer coil, cleaning it, and rewinding the spool, I would still wonder if the varnish was still intact, if it was me.  Just thinking out loud here:  A way to test the integrity of the varnish would be with a "hipot" tester.  If you wanted to make your own hipot testing device, you would need to step up voltage, yet have a high resistance to keep the current low.  I wonder... 

The only thing I've made with microwave transformers is a de-magnetizer (degauss).  After a few years experimenting with magnets and alternators, all my screwdrivers, rulers, wrenches, and stuff was magnetized.  There are a lot of youtube videos about that.

[MagnetJuice]

Would you like to test the insulation to see if it has been damaged by your separation and cleaning of the coil?

Hipot testers are expensive. I could build one if I wanted to, but I would have very limited use of it.

In the case of this wire, it most likely be use for 12 or 24 volt alternators. That voltage would be low enough that even if there were a few small bare spots in the insulation, it would not cause problems.

Anybody thinking about building a 48-volt system or higher, would want to use new magnet wire anyways.

But you are welcome to pay me a visit and bring your hipot tester if you want to. 

Ed

[electrondady1]

good work. nice recycle project

[GreenTeam]

Wow.,that is some nicely wound spool of enamelled copper wire. Im still mostly using recycled wires myself.
I try my best to clean the wire, but, I dont wash it. I just pretty much try to stretch it in my hands to straighten it out.
I just learned how to get all three phases out from the hoverboard motors. I didn't know that the hall sensors are epoxied or super glued in
the slots, not the pole. Also, the motor manufacturer for some reason seems to tangle the windings. They are often having one tooth with the bifilar windings
with one wire overlapped, so you sometimes have to break a wire, and than pry it loose. Sometimes, im lucky and get all three phases out undamaged.
I get one of these spools per hoverboard motor. On my winder, I think its close to 700 turns on the plastic spools. Its a real pain to unwind the bifilar wire, untwist them,
separate them, solder into one continuous strand. The wire is wound very poorly in the motors. They are made by AMK

[SparWeb]

MJ,

I just remembered that the front panel keypad and timer can be saved and used, too.  It's got pre-programmed countdowns, and at the very least you can set a clock on the display.  If you want to use it as a countdown timer for some device you just have to find the switched relay or SCR contacts to power whatever you want - 500W to 1000W depending on the microwave you tore apart.

[Scruff]

That pink bittov the magnetron..kill ya stone dead if it goes airborne and you breath it. Beryllium oxide..nasty stuff. I wrap it in tape when I'm breaking them.
Good neo magnets and all sorts of goodies in rowing machines too.

You can make very powerful electromagnets with the microwave transformer, great for machine clamps. Spot welders too.

[Bruce S]

Don't remember seeing it yet, but don't forget that little turntable motor. Those wires are likely to be tiny, but they can be useful .

Cheers
Bruce S

[MagnetJuice]

Yea Bruce, the turntable motor can be used for all kinds of projects. They turn about 10 RPM and run on 120 volts ac. Some people use them to spin a little disk with holes in it for lights displays. The imagination is the limit.

Here is a video of a guy that used one as a generator to power an LED. He built what he calls a gravity light.

https://www.youtube.com/watch?v=6vwcIO9M-uE