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Old 06-13-2021, 11:54 AM   #1
MMente81
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Magnetic cover is safe ?

I'm thinking buying a magnetic cover but I saw some reports that may give a problem on screen, is true ?
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Old 06-13-2021, 12:51 PM   #2
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Only if it's rubbish?
No problem here on PW3 for years.

Don't cut it open and eat the magnet. Magnets are bad things to eat.
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Old 06-13-2021, 03:13 PM   #3
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No problem I have always used them
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Old 06-13-2021, 03:46 PM   #4
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My PW3 has a sleep cover. So does my Kobo Aura H2O (6 years 7 months).
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Old 06-14-2021, 04:00 PM   #5
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Actually, it depends how strong the magnet is! The screen is, after all, electromagnetically driven... big enough fields will interfere with the display process, though I'm not sure how strong that field needs to be: pretty strong, given that the voltage used to drive the thing is 15V over a very short distance. Don't try to read in an active MRI machine, since that is probably strong enough to rupture some of the spheres that implement the light/dark patterns on the display. (Well, actually, since a Kindle contains metal, it would basically turn into a sharp-edged flying brick if you did that, so... don't).

Obviously, if an MRI machine is bad, bigger fields are worse! Don't try to read near a magnetar, though if you did that you'd be in way bigger trouble on account of chemistry basically stopping working due to all your electron clouds and even nuclei deforming under the pressure of the monstrous magnetic field. But... the field close enough to a magnetar is so strong it polarizes spacetime, and a bit of back-of-the-envelope calculation suggests that this would be enough, at a normal reading distance, to make a typical monochrome e-ink display appear to be in (rainbow) colour! See? Colour e-ink using existing hardware! It is possible! (Caveat: there may be certain minor technical difficulties, such as that the nearest known magnetar is 9000 light years away, the Kindle is not vacuum-rated, and that field would *certainly* rupture the screen and definitely turn the Kindle into something less like a flying brick and more like a hypersonic blob of metallic plasma. Also you'd die in seconds. But, colour!)
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Old 06-14-2021, 04:42 PM   #6
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It's rare to see a non Smart Cover for most tablets and e-readers now-a-days. They won't hurt your device.
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Old 06-14-2021, 05:02 PM   #7
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Quote:
Originally Posted by NullNix View Post
Actually, it depends how strong the magnet is! The screen is, after all, electromagnetically driven... big enough fields will interfere with the display process, though I'm not sure how strong that field needs to be: pretty strong, given that the voltage used to drive the thing is 15V over a very short distance. Don't try to read in an active MRI machine, since that is probably strong enough to rupture some of the spheres that implement the light/dark patterns on the display. (Well, actually, since a Kindle contains metal, it would basically turn into a sharp-edged flying brick if you did that, so... don't).
Minor nit, the display is electrostatically driven. No magnetic fields involved other than the very minor ones caused by micro-amp currents. Short of the type of fields involved in a EMP event, the type of magnetic field strength found outside of physics labs is unlikely to cause any issues for the display.

Last edited by DNSB; 06-14-2021 at 06:55 PM.
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Old 06-14-2021, 06:21 PM   #8
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Minor nit, the display is electrostatically driven. No magnetic fields involved other than the very minor ones caused by micro-amp currents. Short of the type of fields involved in a EMP event, the type of magnetic field strength found outside of physics labs is unlikely to cause any issues for the display.
You're quite right, of course, which explains why I was getting stupid figures when I tried to work out magnetic field strengths: it's the electric field doing the work, not the magnetic component.

I'd recommend not putting your Kindle at ground zero of an EMP-enhanced nuclear explosion too, though it is true that it is not known for certain that a Kindle would not survive this because it has not to my knowledge been tested

(I'm not sure what the amperage of the currents is. I was only able to find voltage figures: 15V.)
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Old 06-14-2021, 07:17 PM   #9
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I wish there were a way to turn off the magnetic wake sensor, when you are not using a sleep cover (or no cover, as in my case). I’m often setting it down on top of my iPad mini and it tends to get triggered by its sleep cover magnet.
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Old 06-15-2021, 05:40 AM   #10
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@tomsem,
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Old 06-15-2021, 08:38 AM   #11
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Quote:
Originally Posted by NullNix View Post
Actually, it depends how strong the magnet is! The screen is, after all, electromagnetically driven... big enough fields will interfere with the display process, though I'm not sure how strong that field needs to be: pretty strong, given that the voltage used to drive the thing is 15V over a very short distance. Don't try to read in an active MRI machine, since that is probably strong enough to rupture some of the spheres that implement the light/dark patterns on the display. (Well, actually, since a Kindle contains metal, it would basically turn into a sharp-edged flying brick if you did that, so... don't).

Obviously, if an MRI machine is bad, bigger fields are worse! Don't try to read near a magnetar, though if you did that you'd be in way bigger trouble ......Also you'd die in seconds. But, colour!)
Your post is the funniest thing I've read here in weeks.
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Old 06-15-2021, 09:04 AM   #12
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I'm on a "sewing" group on Facebook. It has 165k members from all over the globe. A frequent comment and question concerns small magnetic guides that can be used on the metal presser foot plate that help you keep the fabric straight when sewing.

A popular accessory for many sewists are magnetic pin holders. Some are like smallish saucers, some are designed to be on a strip of fabric that holds them on the front of the sewing machine.

Every time someone asks about them, there is a chorus of warnings about them messing up computerized machines. Which of course they won't. But there is no convincing some folks.
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Old 06-15-2021, 10:13 AM   #13
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I have an after-market cover for the Kobo Clara that causes rapid battery drain. Remove the cover, and the problem stops. The cover uses several magnets, including one that holds a kick stand closed on the back.

I cannot prove that a poorly placed magnet was interfering with the Clara's auto-sleep function. But I can't think of another explanation, either.
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Old 06-15-2021, 10:38 AM   #14
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Every time someone asks about them, there is a chorus of warnings about them messing up computerized machines. Which of course they won't. But there is no convincing some folks.
Going back a few years, one company I did some IT work for had a issue with one of the staff losing their backup file copies. When I dropped by, he showed me the backup on two 5.25" floppy disks—carefully stuck to the side of a file cabinet with a magnet.

I suspect most IT types from that era would have a similar story.
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Old 06-15-2021, 12:45 PM   #15
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Every time someone asks about them, there is a chorus of warnings about them messing up computerized machines. Which of course they won't. But there is no convincing some folks.
Of course, the thing is that they *did*, and people assume that since computers these days are much smaller and pack more stuff in more tightly, that they are more vulnerable to magnetic fields than they were. But this is not true: they are *less* vulnerable.

The actual electronics can still be affected (though it takes pretty damn strong fields, as in nearby lightning strike or major power surge, and that would take out both old and new machines) -- but spinning-rust data storage these days uses much smaller magnetic domains than it used to, which means the material needs to be much less easily magnetizable, needing a much stronger magnet to do the job. This means external fields need to be impractically strong to affect it (and some modern disks these days use materials that don't allow remagnetization at all, even by the drive head, unless the drive surface is heated, usually with a laser, or blasted with microwaves). Fridge magnets won't hurt hard disks even if applied directly to the disk surface, let alone the outer casing of the drive: or, rather, only the dust and debris deposited would hurt it. It's far too weak a magnet to affect the actual data stored. Probably even crane electromagnets wouldn't hurt it (except that if you are in the habit of getting your hard drives near active crane electromagnets you should probably re-examine your life choices). Hard drive heads are *really* strong electromagnets.
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