We can’t see magnetic flux lines but with an inexpensive piece of Magnetic Viewing Paper we can easily visualize what we are missing. I took the motor magnet out of an old 5 1/4 floppy drive and was amazed at the complex magnetic pattern that emerged. It looks like the outer ring of the magnet has magnetic notches that are read by the electronic circuit. I imagine this is used for speed control, although this seems like a very complex method of regulating motor speed. You can also “watch” a relay energize by holding the viewing paper beside a normal relay while energizing the coil. Thanks to Edmund Scientific for providing the cool magnet viewer.
There is a video after the jump of the Magnetic Viewing Paper being swiped across the floppy drive motor magnet.
“Millions of tiny metal particles are suspended in oil within a 20 x 50mm laminated sheet of plastic. When a magnet is placed next to this “viewing paper”, the particles become magnetized.
This paper is so intriguing because it enables you to view the varying magnetic patterns of individual magnets. Take the obscure and begint “viewing” it like it’s magic. Great for educational demonstrations.”
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This is so cool, I went to the vendor to try to buy some, but they’re out of stock 🙁 Guess I wasn’t the only one who had that in mind!
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I love stuff like this… Is there a practical app. for this?
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Bill: Damn D:
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I can think of a few… finding optimal placement of magnets in
things like generators, motors or electric guitar pickups. Also,
if you’re the type to make your own amps or cabents, you can
find if they’ve been properly sheilded.
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The looking for proper shielding is definitely an application, the relay that I tested to see if I could “see” it energize was an automotive type and I was thinking that it may have the spray on shielding inside. Turns out I could detect it energize so there is no shielding.
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I was just thinking, it may also be very useful for all of those DIY electro-magnet makers out there, you could probably make your home-made designs more efficient.
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Yeah, I agree with Joven, this would be great for working with guitar pickups.
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cool!!! that looks sweetTt!!!!!!
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Looks like it’s back in stock. 🙂
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“It looks like the outer ring of the magnet has magnetic notches that are read by the electronic circuit. I imagine this is used for speed control, although this seems like a very complex method of regulating motor speed. ”
Actually, the motor is a many-poled permanent magnet rotor (the disk you’re looking at) working against a “coil” formed by the rectangular pattern on the printed circuit board. By pulsing the current through the coil pattern, the poles on the disk are advanced. It’s like the linear motors sugegsted for mag-lev trains, bent into a circle…
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Here is another place to get magnetic viewing paper:
http://www.kjmagnetics.com/proddetail.asp?prod=MV43
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Man I had some of this YEARS ago. Also the logo in the middle of the video is way annoying.