I'm on Debian (Jessie) using KDE 4.14.2 nothing really stood out to me in the System Settings on how to trigger a lock screen and after doing a bunch of research I ended up binding Ctrl+L to run the following command:
qdbus org.freedesktop.ScreenSaver /ScreenSaver Lock && xset dpms force off
which will trigger the lock screen and turn off my monitors. The prob is if someone bumps into my desk (which is often) the monitors turn on but they don't turn off again.
What can I do to have my monitors automatically turn off after X minutes?