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DPChallenge Forums >> Tips, Tricks, and Q&A >> Do magnets affect digital cameras?
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 10/07/2003 06:31:34 PM · #1
i want to take some macro shots of this cool levitating magnet toy i have, but i'm not sure if magnets are safe around digital cameras
 10/07/2003 07:21:28 PM · #2
i bet it would be ok

Originally posted by eswik:
i want to take some macro shots of this cool levitating magnet toy i have, but i'm not sure if magnets are safe around digital cameras

 10/07/2003 07:28:34 PM · #3
Minimum focal distance for most cameras is > 1" which is probably beyond the range of most magnet toys. I'd not let them touch, and keep the media card as far away as possible.

Hmmm ... would taking the media card and waving it over a strong magnet to jumble the data constitute use of an illegal filter? (Besides destroying the card, I mean.)
 10/07/2003 07:36:59 PM · #4
Originally posted by GeneralE:

Hmmm ... would taking the media card and waving it over a strong magnet to jumble the data constitute use of an illegal filter? (Besides destroying the card, I mean.)


Btw, these aren't ordinary magnets. They're neodymium iron boron magnets, the strongest known permanent magnet on earth. they can attract objects up to 6 inches away. So, yeah, would my camera be affected? or only the memory card?

I have a Sony Memorystick. For those that have one, aren't those flash memory sticks? which shouldn't be affected by magnets?
 10/07/2003 07:42:49 PM · #5
The data on them is stored magnetically. I'd keep everything outside the range where it could be significantly affected (at least 8-12" from the way you describe it). Whether the CCD or any of the chips in the camera could be affected is a question more suited to the manufacturer ....
 10/07/2003 07:43:58 PM · #6
Memory sticks and compact flash and whatnot aren't magnetic storage devices. Magnets don't affect them. That's why there are USB flash drives that have magnets on them, and PDA and camera cases with magnetic closures.

Caveat: Microdrives ARE magnetic, like other hard drives, not flash memory. No magnets if you use those!
 10/07/2003 07:51:27 PM · #7
What are they using if it's not magnetic? I thought they were essentially like non-volitile RAM chips.
 10/07/2003 07:57:56 PM · #8
This should answer your question.
 10/07/2003 08:23:03 PM · #9
Originally posted by vonautsch:
This should answer your question.

That's a terrific link, but it seems to reinforce what I first thought -- that flash memory is electromagnetic media, and should be kept away from magnetic fields strong enough to induce a current.
 10/07/2003 08:33:22 PM · #10
Originally posted by GeneralE:
Originally posted by vonautsch:
This should answer your question.

That's a terrific link, but it seems to reinforce what I first thought -- that flash memory is electromagnetic media, and should be kept away from magnetic fields strong enough to induce a current.


But remember that in order to induce a current, there has to be relative movement between the conductor and the field lines. You'd need a pretty powerful moving field, such as induced by AC current, to have any effect.
 10/07/2003 08:42:36 PM · #11
Originally posted by kirbic:

But remember that in order to induce a current, there has to be relative movement between the conductor and the field lines. You'd need a pretty powerful moving field, such as induced by AC current, to have any effect.

Read the description of the magnets. Moving the media around within a few inches could probably induce sufficient current to affect those transistor gates. Either element can be in motion.
 10/07/2003 11:46:39 PM · #12
I sent this question to my brother, a computer hardware engineer at Intel, and he explained it thusly:

Flash memory uses basically the cheaper equivalent of EEPROM technology
(Electrically Erasable Programmable Read Only Memory). Long acronym, but
the key words in here are erasable and programmable, meaning you can
change the values stored in the various bit locations (as opposed to
PROM...1 time programmable), and "electrical" (as opposed to magnetic or
UV erasable) meaning you do it with electricity, not with UV light
(EPROM) or magnets (DISKS) :)

So first off, they use transistors to store information...A MOSFET
transistor is just basically a switch.. 3 terminals in a "T"
formation... If the center terminal has a positive voltage applied to
it, it attracts electrons to it, and that "bridges the gap" between the
other two terminals (input and output, or source and drain), allowing
electrons to flow through unimpeded...thusly "on" or "1"... Take away
the voltage and there's no more tunnel, so that would be a "0", or
off...

So basically (this dovetails into the ret of it, bear with me here...)
its like a gate on a normal road.. Open the gate, cars can go through,
close the gate and cars stop. Easy.

So for Flash Memory, it becomes a 4 terminal device...Now think of it as
a drawbridge with a gate. if the bridge is down, the gate controls
whether traffic (electrons) can go across or not (so that represents a
stored 1...) If the cell is selected (open the gate) you just read it
and if you get electrons (a voltage), you take that as "1".

If the drawbridge is up, the gate doesn't do anything.. Cars (electrons)
still can't get across even when the cell is selected (the gate is up).
Read that as a 0.

So to set the state of the drawbridge, it gets a little complicated.
There is another terminal put down directly on top of the "gate" (it
actually is called a gate) that puts a much higher voltage into the
device. Whereas the relatively low voltage of the 1st gate just draws
electrons up to temporarily form a channel between the input and output
terminals, and releases those electrons back into the silicon when
turned off, the much higher voltage that is applied to this 2nd gate
causes electrons to "Migrate" and permanently move into, or out of the
channel region.

So, if you apply a large negative voltage, you drive the electrons
permanently away from the channel region (like charges repel), they
migrate out, and no matter how much you turn on the 1st gate, it doesn't
have enough power anymore to create a channel, because there aren't
enough electrons. Apply a large positive voltage to the 2nd gate and it
causes the electrons to migrate back into the region, so they are then
controllable by the 1st gate.

That make sense? So the end result is that it takes a large voltage (I
think like 10 volts, which is huge nowadays when the 1st gate operates
at like 1.5) to change the 1/0 of the device. Magnetic fields wont
attract electrons in the same way. Perhaps if the magnetic field were
HUGE (and I mean way bigger than any kitchen magnet) it might disrupt
something in there, but there's no way it would do the same thing as it
does to a floppy disk or the like (which stores magnetic charge on a
piece of Mylar in a grid pattern...)

It also explains why flash memory is so slooooow. You have to migrate
the electrons up into the region instead of just write and move on as
you do in a disk... But the fact that its silicon and integrated makes
it CHEAP.
 10/08/2003 02:12:08 AM · #13
kostia, do you build rockets too?
 10/08/2003 02:55:07 AM · #14
Originally posted by eswik:
i want to take some macro shots of this cool levitating magnet toy i have, but i'm not sure if magnets are safe around digital cameras

I have taken my digital camera into an MRI scanner room with no ill effects, however I did leave the memory card in the reception area.
 10/08/2003 10:11:23 AM · #15
Originally posted by kostia:
I sent this question to my brother, a computer hardware engineer at Intel, and he explained it thusly:

That's very well-done by both of you -- thanks. I think I'll still keep my cards as far from known magnets as I can just to be sure, although I have a couple of 8mb ones I might "sacrifice."
 10/08/2003 10:12:49 AM · #16
He was so excited to be asked something about his job that I couldn't bear not to share his response. He's my *younger* brother and he's so cute when he's enthusiastic about something.

Personally I build books, not rockets or computer chips, but I'm the weirdo in the family. :)
 10/08/2003 10:19:29 AM · #17
Originally posted by kostia:
He was so excited to be asked something about his job that I couldn't bear not to share his response. He's my *younger* brother and he's so cute when he's enthusiastic about something.

Personally I build books, not rockets or computer chips, but I'm the weirdo in the family. :)

That's not weird -- So do I.
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