Unsure if I'm stating the question correctly, but I know there are warnings against quickly unplugging projectors suddenly because of the damage it can cause to the projector bulb. Is this applicable as well to laptop and desktop power cords assuming that the unplugging is done after powering off the computer?
asked May 9, 2012 at 3:46
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3possible duplicate of laptop: Should one plug the AC first or to the laptop first. And, to restate what I said as a comment in that question: It makes no difference. The AC/DC transformation is a one-way deal, so it literally doesn't matter (both circuits are electrically isolated from eachother - or at least they should be!).– BreakthroughMay 9, 2012 at 3:47
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I don't think this is the same. I also think it does matter. You should connect the cord to the unit first, then plug it in to the outlet. Plugging a live cord into the unit is risky, although admittedly there's not much chance of a problem. But there's a right way and a wrong way to do everything, regardless of how much or how little risk there is of doing it wrong. Anyway, I don't see what difference the AC/DC transformation makes; you can shock yourself or cause a short circuit with either one, I know from experience during my electronic repair days long ago.– Marty FriedMay 9, 2012 at 4:04
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@MartyFried are you seriously telling me there's a difference between the action of "connect the cord to the unit first" versus "plugging a live cord into the unit"? Unless you're using a cable with exposed conductors (in which case, you shouldn't be using it at all), there's no difference. Yes, there's a difference between shutting the device off (in which case, graceful termination is always best), but when you're plugging it in, no, there's no difference.– BreakthroughMay 9, 2012 at 4:13
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@MartyFried define right way and wrong way, its a matter of opinion for everyone what is right or wrong. I suppose if you cannot pay attention you should not use electrical devices, or drive a car for that matter, that's my opinion.– MoabMay 9, 2012 at 15:11
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8 years late to the party, but I have some relevant info. The reason you werent supposed to pull the power on old projectors was not for electrical reasons, but heat. Bulbs used in projectors back then got extremely hot. The internal fans were required to keep air flowing through the internal electronics and bulb. If the bulb was not cooled, this could damage the electronics and significantly reduce the lifespan of the very expensive bulbs.– KeltariMar 1, 2020 at 16:20
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3 Answers
For any device, it is certainly best to power it down before removing power, as you stated. But once this is done, it really doesn't matter how quickly you remove the plug, only that you pull it straight out to avoid bending the prongs.
When you remove the plug, there is going to be a point where the connection is broken. No matter how slowly you remove the plug, when it hits that point, there is no more power, unless you have a high enough voltage to arc across the air gap.
As for projector bulbs, they might benefit from a gradual reduction in power, but you won't get that from removing the plug slowly; you get that from some special circuitry that can vary the power on power down or power up.
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3With the projector, the "don't unplug it suddenly" warning tends to be more due to needing to run a correct power down cycle to cool the stupidly hot bulb to a safe temp from memory. If deprived of power, you get a very hot bulb and no active cooling - which could fry/melt/make bad whatever is near the blub (particularly if you put it back in the carrying case) May 9, 2012 at 13:40
For my ThinkPad, Lenovo recommends connecting the cord from the charger to the laptop first, then plugging the charger into the power socket, and using the reverse procedure on disconnection. My feeling is that this may be more important if you are connecting or disconnecting the power cord while the laptop is in use, i.e. the laptop is switching from being on mains power to battery power or visa versa without powering down.
There are no such issues with typical laptop or desktop computers.
answered May 9, 2012 at 3:49
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It's basically just because these are smart power supplies, not dumb things like light bulbs. They have circuitry that controls the flow of power to their sensitive components. Jul 15, 2012 at 18:02
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True, light bulbs are flimsy and have no smart circuitry. But the thing you have to remember is that human error can trump smart power supplies and cause issues. Oct 9, 2012 at 22:47