Computer fan and supermagnets

[Firnagzen]

Well, here's the rundown: I put a computer fan next to a supermagnet for a few hours, and after I had finished the circuit and wanted to solder in the fan, I realized that it wouldn't run any more! (Yes, it was running fine before.)

So did the supermagnet demagnetize the magnets in the fan or something? Is there any way I can fix it?

Ps. It's a really small 2cm diameter fan, if that's relevant.

 

[JTECH]

Fan and Magnet

Well, here's the rundown: I put a computer fan next to a supermagnet for a few hours, and after I had finished the circuit and wanted to solder in the fan, I realized that it wouldn't run any more! (Yes, it was running fine before.)

So did the supermagnet demagnetize the magnets in the fan or something? Is there any way I can fix it?

Ps. It's a really small 2cm diameter fan, if that's relevant.

It would probably be cheaper to just replace the fan.

 

[dknguyen]

I don't know how strong super magnets are, but I would think it more likley messed up the fan electronics than the fan magnets. If it was strong enough to demagnetize the permanenent magnets in the fan, it would have been strong enough to magnetize everything else in the immediate vicinity.

Where did you get a 2cm fan from? Ive been looking for one.

 

[j m]

It could be because it’s a sleeve bearing fan and the magnet has pulled it out of aliment, most computer fans are like this, using a sleeve bearing and they don’t work very well. I would try pushing or pulling the fan blade [rotating bit] away from the main body? [be careful as will brake it if done to much]
james

 

[Sceadwian]

It takes a lot more than just the presence of a relativly strong magnetic field to de-magnetize a magnet, you more than likley magnetized something else inside the fan assembly. If it's a brushless DC fan with built in control electronics it might have a hall effect sensor which could be reading imporperly from the new magnetic field nearby. Swipeing a strong (but not too strong) magnet back and forth (alternating the poles) will remove this residual magnetism caused by the longer period of time near the bigger magnet.
"Super Magnets" Need to be treated very carefully. Large ones can be attracted to metal so strongly that they're all but impossible to remove once attached, and small ones can actually explode from the impact (they're ususally ceramic) of being allowed to touch another one of it's kind, or a dense metallic object.

 

[Firnagzen]

Oh yes, I know oh-so-well about breaking supermagnets. Darn things...

Thanks for the tips, I'll try all of them...

Hmmm, no luck, I'm afraid. I think that the control electronics are getting a false reading off something inside, when I power it up, the fan twitches ever so slightly.

dkuygen, I got it at my local electronics store, they have all sorts of estoeric parts in there. I even found some UJT's there once!

 

[Sceadwian]

Do you have any extra fans around? Could you duplicate the failure? I'd be cursious to see if this were more than a fluke. Can you kick start the fan by spinning it with your finger? i'd try to pass the whole fan infront of a demagnetizing coil. If you have a modern PC monitor try placeing the fan close to the front or side of the monitor when you engauge it's deguass feature, try a few different places.

 

[Oznog]

How about the possibility that the fan doesn't work for completely unrelated reasons?

It would be hard to imagine magnetizing anything unless it was actually stuck to the magnet.

 

[Hero999]

I would think it more likley messed up the fan electronics than the fan magnets.

Can DC magnetic fields actually damage non-magnetic electronic components?

Will an op-amp really die if exposed to a huge magnetic field?

I have a feeling that it's more likely to have messed up the magnets in the fan than distroyed the electronics.

When I was a kid I placed a wlakie talkie near a large speaker with some music playing so I could listen to is up the other end of the garden. I left it there for a couple of days and when I tried to use it again I noticed the speaker was very quiet. Now I know that the big magnet in the big speaker had demagnetised the small magnet in the small speaker in my walkie talkie.

 

[Sceadwian]

It didn't 'destroy' the fan electronics, but it probably magnetized any metal inside of it. That can effectivly disable any electronics that have hall effect sensors as feedback. Don't know if that applies to PC fans though, not sure how their brushless drivers work.

 

[Hero999]

I didn't think about the hall effect sensors, so yes that could be the problem.