Interference from Fan Magnets?

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Interference from Fan Magnets?

Postposted on Tue Jul 03, 2012 8:11 am

I just recieved a new 120mm Enermax fan in the mail which I intend to use on my tower-style CPU heatsink. This fan has a magnetic bearing (which I was aware of at time of purchase) but I didn't think the magnet would be so strong. This magnetic bearing can suspend the fan on the side panel of my case and even upside down. I know that having strong magnets near a computer (and specifically near a mechanical hdd) can cause data corruption/loss and other problems, but I have to assume that Enermax has thought of this; considering that these "case fans" could end up right in front of and nearly touching a hdd if used in the front of a case. My case is such that the CPU fan sits pretty close behind the hard drive cage, such that I have to use 90 degree power and SATA cables to attach them. Granted, the magnet is on the side facing the heatsink... Should I be worried, or am I overreacting?
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Re: Interference from Fan Magnets?

Postposted on Tue Jul 03, 2012 8:16 am

You need a pretty strong magnet to degauss a hard drive, and floppies are a thing of the past. I wouldn't worry overmuch, but you won't see me buy one of those things! :D
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Re: Interference from Fan Magnets?

Postposted on Tue Jul 03, 2012 8:20 am

I wouldn't worry about it. The HDD itself contains magnets that are a lot stronger than that (in the head actuator).

Only way I could see it being a problem would be if you have an old school CRT, and the PC is located right next to the CRT.
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Re: Interference from Fan Magnets?

Postposted on Tue Jul 03, 2012 9:22 am

I've been using two fans with the same magnetic structure in this machine for over a year and haven't seen any problems. Error counts on the drives are normal. As JBI said, the magnets in the actuator are much stronger, as are the fields created by the motor that spins the platters themselves.
This problem was caused by Windows, which was created by Microsoft Corporation.
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Re: Interference from Fan Magnets?

Postposted on Tue Jul 03, 2012 9:24 am

The only interference that case fans may create in a desktop system is " EM noise" on your front-panel audio connectors if the cables run near the fan itself.
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Re: Interference from Fan Magnets?

Postposted on Tue Jul 03, 2012 10:47 am

Thanks for all the quick replies! I am aware of the rediculus strength of the magnets inside the hdd, but wasn't sure if that was a "controlled" magnetic field that could be disturbed or not. All possible cables are neatly tucked behind the motherboard tray so the only cables that would be even remotely close to this new CPU fan would be the power and SATA cables from my SSD. Sounds like I'm in the clear, this was good peace of mind. Thank you everyone.

If anyone cares, I'm very impressed with this fan. I hooked it up to my "open air" case to test it out and it pushes lots of air while also being very quiet. Unfortunately I don't have a smoke machine (or a nice rack) to create any cool videos about fan airflow patterns but that's what youtube is for. The only noise I hear is the woosh of air. The "halo frame" seems more of an aesthetic/marketing gimic than anything, but it definetly makes the fan look unique and cuts some weight without sacrificing rigidity (for what it's worth). The fan blade does pop off with a gentle tug for cleaning, though I've never not been able to clean a fan sufficiently with just compressed air. Great fan with a relatively low price of $12 shipped.
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Re: Interference from Fan Magnets?

Postposted on Tue Jul 03, 2012 1:32 pm

Magnetic fields diminish according to r². Not only are the rare-earth magnets in the drive heads vastly stronger, they are vastly, vastly, nearer. I wouldn't stick it directly atop the HD, HD cooler style (among other things, that might affect the head actuator) but sitting several inches away in your case isn't going to have any effect on the HDs.
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Re: Interference from Fan Magnets?

Postposted on Thu Aug 09, 2012 4:17 am

All fans have magnets in them, creating rapidly oscillating magnetic fields all over your PC.
Granted, yours sounds stronger than most in the grand scheme of things it's not even in the same ballpark as something that could cause your PC any problems.
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Re: Interference from Fan Magnets?

Postposted on Thu Aug 09, 2012 5:14 am

I just made a little test with a dismantled HDD. While there are strong magnets in the actuator, their magnetic field is strictly confined by the surrounding steel plates. Any part of these plates barely attracts a screwdriver from a small (say 5 mm) distance. That's undestandable - in the opposite case the HDD would erase half of its data in no time.
I have some experience with loudspeaker magnets, cassette tapes, and close distances. I'd keep any magnet, even a "plain" black ferrite one, at least a centimeter away from the HDD case. Three times as much for a rare earth magnet - if it were completely unshieded, but fortunately it never is.
The side with connectors is safe anyway because it's farther away from the platters.
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Re: Interference from Fan Magnets?

Postposted on Thu Aug 09, 2012 8:30 am

Also, the top side of the HDD case (which is closest to the platters) is usually made of steel. This will provide some protection since the magnetic field will tend to spread out as it passes through the steel, preventing it from being concentrated in a small spot.
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Re: Interference from Fan Magnets?

Postposted on Thu Aug 09, 2012 11:04 am

Wirko wrote:I just made a little test with a dismantled HDD. While there are strong magnets in the actuator, their magnetic field is strictly confined by the surrounding steel plates. Any part of these plates barely attracts a screwdriver from a small (say 5 mm) distance. That's undestandable - in the opposite case the HDD would erase half of its data in no time.
I have some experience with loudspeaker magnets, cassette tapes, and close distances. I'd keep any magnet, even a "plain" black ferrite one, at least a centimeter away from the HDD case. Three times as much for a rare earth magnet - if it were completely unshieded, but fortunately it never is.

I wouldn't install a loudspeaker magnet anywhere near a hard drive, either, but as you just demonstrated, magnetic field lines decrease in strength exponentially with distance. Too many people have gotten their magnet physics from the movies. The problems people had with old-school CRTs was mainly a function of the extreme electromagnetic sensitivity of the electron beam that illuminated the phosphors.
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