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Why doesn't my optical mouse's red LED turn off after I shut down my PC?

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Because it is still powered. Your computer, when shut down, does not shut down power completely. –  slhck Jul 21 '11 at 21:20
    
should i always switch off surge protector to get rid of that light?? Or is there any other way?? –  DrStrangeLove Jul 21 '11 at 21:23
    
Does it really annoy you? You should be able to change that in BIOS, but I have no clue how exactly. –  slhck Jul 21 '11 at 21:24
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It's scared of the dark ;-) –  Linker3000 Jul 21 '11 at 21:33
    
The answers are assuming that this is a wired mouse. But is that the case? Is this a wireless mouse, or one with a USB cable? –  Kaz Apr 7 '13 at 5:41
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5 Answers

up vote 7 down vote accepted

The optical mouse's LED stays on because the mouse itself is still being powered.

Just because the computer is turned off it doesn't necessarily mean the USB power is turned off. This is done so that the Power key on some keyboards can be used to turn the computer on.

And why does it stay red? Simple. It is red. Why does the grass stay green...?

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I would add that it's OKAY. Don't bother shutting off the mains power or anything like that. –  Shinrai Jul 21 '11 at 21:43
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@Shinrai, unless, of course, you're interested in not wasting energy -- the amount we waste on ambient computer and electronic equipment really adds up. –  thursdaysgeek Jul 21 '11 at 22:15
    
@thursdaysgeek - True, of course (although sufficiently modern stuff draws next to nothing, every little bit helps). My point is that it's not a bad thing in the context of your equipment. –  Shinrai Jul 21 '11 at 22:37
    
@Shinrai, I agree with your original point: it does no harm. However I've read that the little bit of energy used on the sleeping computer, the laptop, the DVD player, the TV, and all those other electronics is actually adding up to a huge power drain that can be noticeable in even a single household. Perhaps most of us don't have sufficiently modern stuff, and many don't turn their electronics off at all. I have coins on the lights on the keyboard for my (turned-off) computer because the light it generates at night is enough to light up the room. (Guess I should turn it off at the strip!) –  thursdaysgeek Jul 22 '11 at 0:27
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A lot of computers these days leave power to the usb devices. This is one way for the computer to know it needs to wake up.

Two, there is no standard on how much power is necessary to determine that the device be "lit". For example, on my USB ports, if I plug in speakers that power themselves through USB, the speaker power light stays on when my computer goes to sleep.

If I plug in a Logitech MX Revolution to that port, it stays off. If I plug my wireless keyboard into that front port, the receiver's LED flashes . . .

By definition, this is insanity and thus there is little reason to believe there is an actual deliberate pattern.

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I have ran across this problem in other people's computers and have come to this one simple conclusion. The problem doesn't reside in your computer, but rather in the mouse. I have found that changing out the USB mouse fixes this. I like to refer to this problem as "Mouse Insomnia".

~Avalanche5150~

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The LED is able to stay on because the mouse is powered, yes. But that's not a good answer why it is on. After all, the mouse can't be used when the computer is powered off. The LED being on provides no benefit, and can be a nuisance at night.

The mouse is a little computer in itself. It contains a little microcontroller which coordinates all of its functions, including USB communication with the host.

So the mouse should be able to notice that it has not been polled by the host for some time, and shut down the LED. (There may even be other ways in the USB protocol to infer that the host is down.)

This feature could have diagnostic value also. The LED being on would confirm that the host is interacting with the mouse, not only providing power. (A really useful behavior would be, when the mouse is powered up, to flash the LED several times to indicate "I have power and have started up!" and then turn it off if there is no communication with a host.)

So in other words your mouse isn't sophisticated enough to implement the behavior of shutting down the LED when it's not in use.

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All you need to do is change the setting in the BIOS, under USB devices change the idle (different on every motherboard) power settings to disabled. It is typically a feature of higher end motherboards.

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