I usually leave my laptop running overnight to download torrents. Because my Vaio-E laptop doesnt have a button to turn off the LCD, I use the following command to turn off the LCD:
xset dpms force off
After you hit enter, the monitor will be turned off. To turn it on, you just need to move the mouse or hit a key. Another way to auto turn on the monitor is to use the following command with crontab:
xset dpms force on
It means that you just need set the time to run the turn-on command with crontab first then turn off the monitor. This trick is quite handy to use as an alarm clock. The monitor will be automatically turned on to wake you up.
Note: If you use the above command and your monitor isnt turned off, it means that DPMS ( Display Power Management Signaling) isnt enabled in your system. To enable DPMS, just use the following command: