Thursday, August 30, 2012

How To Prevent Your Computer From Waking Up Accidentally

If you find your Windows computer waking from sleep for no apparent reason, your computer is either being woken up by a hardware device – such as your mouse — or scheduled task set to wake your computer.
In some cases, the cause may not be obvious. For example, if your laptop occasionally wakes up for no apparent reason, it’s possible that the floor is shaking a bit, causing the mouse to vibrate slightly and wake the computer.

Determining Why Your Computer Last Woke Up

If you’re not sure why your computer just woke up, you can run a command which will tell you. To run this command, you’ll need to use the Command Prompt application, which you can find in your Start menu – press the Windows key, type Command, and press Enter to launch it.
Type the following command into the Command Prompt window and press Enter:
powercfg -lastwake
The output below tells us that a USB device woke the computer. I know my mouse is plugged into a USB port, so it’s clear that my mouse recently woke the computer. To prevent your mouse from waking the computer, consult this article or see below.

Controlling Hardware Devices That Can Wake Your Computer

To view a list of the hardware devices that can wake your computer, run the following command:
powercfg -devicequery wake_armed
You can stop these devices from waking your computer in the Device Manager. Open it by pressing the Windows key, typing Device Manager, and pressing Enter.
In the Device Manager, locate the device you want to prevent from waking your computer (it will have the same name as it does in the output of the command above). Right-click the device and select Properties.
On the Power Management tab, uncheck the Allow this device to wake the computer check box and click OK.

Wake Timers & Scheduled Tasks

Programs – scheduled tasks, for example – can ask Windows to automatically wake the computer at a specific time. If a scheduled task sets a “wake timer” for a specific time, your computer will automatically wake up at that time to run the task. This can be useful – for example, you could have your computer automatically wake up in the middle of the night to perform system maintenance tasks.
To see a list of wake timers set on your computer, you can run the following command. Note that this command must be run as Administrator. You’ll have to right-click the Command Prompt shortcut in your Start menu and select Run as Administrator before running this command.
powercfg -waketimers
If a specific program is causing your computer to wake, you can uninstall it or adjust the scheduled task’s settings in the Windows task scheduler.
However, if you don’t want any programs waking your computer up automatically, you can disable wake timers entirely. To do so, use the Power Options control panel – open it by pressing the Windows key, typing Power Options, and pressing Enter.
Click the Change plan settings link in the Power Options window.
In the next window, click Change advanced power settings.
Expand the Sleep section, expand the Allow wake timers section, and ensure that wake timers are set to Disabled.

These are the two ways your computer can automatically wake from sleep – after adjusting these settings, your computer should stay asleep when it’s told to do so.