03-09-2008, 10:39 AM | #1 (permalink) |
Junkie
Location: At my daughter's beck and call.
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Hardware question.
Please help settle a question, to wit;
Does turning the power off on your CD, while it is playing, scratch the surface being read? I say no. She says yes, and specifically says "It's like stopping an old record player and having the needle scratch the surface." Now, I do not pretend to be an expert, however I always thought CD's read the data through the use of light (http://electronics.howstuffworks.com/cd.htm). I thought all data corruption would occur through mechanical means, like placing a CD on a rough surface, dust, and the like. Please settle this, as I lack sufficient credibility. If I'm wrong or right, I just want to know the truth. Thanks!
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03-09-2008, 10:49 AM | #2 (permalink) |
Young Crumudgeon
Location: Canada
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You've got it right. The only thingthat physically contacts the cd during playback is the spindle, which goes nowhere near the playing surface. There's nothing to scratch the surface.
However, depending on the design of the individual cd player in question, it is theoretically possible that rotational instability caused by the sudden deceleration could cause the disc to come into contact with any exposed hardware. It's not very likely, though.
__________________
I wake up in the morning more tired than before I slept I get through cryin' and I'm sadder than before I wept I get through thinkin' now, and the thoughts have left my head I get through speakin' and I can't remember, not a word that I said - Ben Harper, Show Me A Little Shame |
03-09-2008, 01:07 PM | #4 (permalink) |
Junkie
Location: At my daughter's beck and call.
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When it comes to the rotational instability, I saw something on
Mythbusters about it. They got the RPMs up to such a degree that the CD's flew apart. Thanks! I'll keep reading for dissenting opinion, though.
__________________
Propaganda is to a democracy what the bludgeon is to a totalitarian state. -Noam Chomsky Love is a verb, not a noun. -My Mom The function of genius is to furnish cretins with ideas twenty years later. -Louis Aragon, "La Porte-plume," Traite du style, 1928 |
03-09-2008, 02:28 PM | #5 (permalink) |
I'm a family man - I run a family business.
Location: Wilson, NC
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You are right. The RPM you are talking about is around 100x read speed - CDs fly apart around that rotational speed. That's why you don't see much past 52x CD-ROMs. They start going unstable past that approximate threshold (warping, etc.)
Turning it off during the middle of an access or whatever will do nothing harmful.
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03-09-2008, 03:56 PM | #6 (permalink) |
has a plan
Location: middle of Whywouldanyonebethere
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It doesn't suddenly stop, either. The mechanics of every *-ROM I have owned (to confess, only four) have gentily slowed down the disc. It wouldn't make sense if it did stop it suddenly, and it certainly doesn't make sense that the motor locks without power. There is a back-EMF in the motor if a closed circuit exists, counter-acting the rotation. In my honest opinion, it would not be strong enough to cause such a deceleration to make a disc warp thus contacting any stray parts in the ROM.
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03-09-2008, 04:17 PM | #7 (permalink) | |
Young Crumudgeon
Location: Canada
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Quote:
__________________
I wake up in the morning more tired than before I slept I get through cryin' and I'm sadder than before I wept I get through thinkin' now, and the thoughts have left my head I get through speakin' and I can't remember, not a word that I said - Ben Harper, Show Me A Little Shame |
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hardware, question |
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