Gallery, Projects and General > How to's

Electrical Demagnetizer

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websterz:
You'd be surprised at how difficult a micro tranny is to actually FIND these days! I spent a half hour looking for that little gift for ya'.  :lol:

ScroungerLee:
Bernd,  any idea how many ohms that coil measures?

Thankee

Lee

Bernd:

--- Quote from: ScroungerLee on March 22, 2010, 11:16:20 AM ---Bernd,  any idea how many ohms that coil measures?

Thankee

Lee


--- End quote ---

Yup, 62.7 ohms

Bernd

John Hill:
I have a bulk tape eraser from the time when we used 1" wide magnetic tapes.  As far as I can see the eraser is a single coil wound around a 'E' shaped stack of laminations.  I know the core of a transformer is usually made of laminations of shapes 'E' and 'I' stacked alternately so if you can get one apart you could reassemble with just the 'E's.

If you have a stable load, like a coil, which does not have enough resistance/reactance to limit current flow you could use a resistor (or a light bulb) to limit the current flow  but you can also use a mains rated capacitor in series, the smaller the capacitor the lower the current.

madjackghengis:
Hi ya'all, I just wanted to say there is an even easier, and safer way, which is probably also cheaper, which is to take any of the kind of small ac motors, such as a phonograph motor or small fan motor, which has a shunted "stator", which you will see as a thick copper wire wrapped around the stator in a couple of places, remove the bearings and the rotor, and cut a slot wide enough for the biggest thing you want to demagnetize, either put a switch in the circuit, or unplug it to turn it off.  To use, plug it in, take what is magnetized, and put it between the two poles you left, and slowly draw it away from the motor stator until it is a couple feet away, and then turn it off or unplug it.  If you do exactly the same thing, but unplug or turn off the stator while the piece of steel is between the poles, you will very effectively magnetize it most of the time, unless by luck you switch it off while the coil was in a null of the a/c wave.  I worry about microwave transformers, because if you don't do something with the small wire side, which is the high voltage side, it can easily reach above a thousand volts on "flyback", as it is made to drive a magnetron to make microwaves, like radar.  They are great for making the primary power supply for a really powerful Tesla Coil if that is what you're into though.  My demagatizer has a stator that's about an inch and a quarter thick, and will demagnetize a six or eight pound chunk of steel easily, and I haven't bothered to be safe, I just plug it in, and un-plug it.  Opening up where the rotor goes, and leaving two poles which are a fair distance apart makes the shunted motors very efficient for magnetizing and demagnetizing, and they need no current control, which is what the light bulb effectively does.  Mad Jack

shaded pole fan motor with cord

another view, showing the hack saw cuts, to provide good poles.

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