Formulas and calculators > Coil winding
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
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