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I do not want my laptop to change brightness when my laptop power is plugged in or unplugged. I set my brightness based on how bright my surroundings are. If I am in a dark room, I set my brightness very low and when I plug my laptop in the brightness gets set to maximum which feels like sticking my eyes in boiling lava.

In System SettingsBrightness and Lock the Dim screen to save power checkbox is unchecked.

My laptop is an HP Mini 110

In case it is an acpi issue I have put my acpi-support file here
http://paste.ubuntu.com/1008244/

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Are you still using ACPI events? –  pschmidt May 16 '12 at 22:31
    
How can I check? –  user63985 May 26 '12 at 15:18

3 Answers 3

Under "brightness and lock" in the system settings, remove the checkbox from "Dim screen to save power".

This will keep your screen at the same brightness all the time, instead of dimming it when running on battery power and making it brighter when it's on mains power.

You should still be able to adjust the screen brightness manually as you desire in order to save power or when you need more light.

If your "brightness and lock" settings do not have this option, then you have a different issue, so let us know.

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The checkbox "Dim screen to save power" is not checked. –  user63985 May 24 '12 at 14:24
    
In that case you may want to add this information to your question, as well as information about which laptop you have. –  neon_overload May 24 '12 at 23:26
    
Thanks, information has been added. –  user63985 May 26 '12 at 15:18

I tested a solution that works fine for me. One solution is to add a script file in /etc/pm/power.d/

Just creates a file

sudo vi /etc/pm/power.d/run_after_pwrmanagmt.sh

Then writes this code into this file :

case "${1}" in
    true) #battery_mode
        xinput set-int-prop 12 277 8 2 3 0 0 1 3 2
        echo 4000 > /sys/class/backlight/intel_backlight/brightness
;;
    false) #ac_mode
        xinput set-int-prop 12 277 8 2 3 0 0 1 3 2
        echo 4000 > /sys/class/backlight/intel_backlight/brightness
esac

Now, you need to give execution rights to this file by typing

sudo chmod +x /etc/pm/power.d/run_after_pwrmanagmt.sh

Now it should work fine, just test to plug/unplug your computer. Note that you can do similar things after a suspend (/etc/pm/sleep.d/run_after_sleep.sh), that's how I found out this solution... You will find information on the web...

Note that xinput is just a command for my trackpad to set the middle button working... You should skip the two lines xinput if not needed (or adapt ). For the value 4000, it may be diffrent for each screen, you should first see what is your max value with the command cat /sys/class/backlight/intel_backlight/max_brightness

Hope this helps, and that the moderator will not delete this post since this is an answer and not a question. Thanks

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This is a super-complicated answer for such a simple question! Try looking at the other answers for a something simpler. –  Chris Nash Jun 8 at 20:12

What worked for me was:

  1. Click the battery icon on the bottom right side of the desktop.
  2. Click more power options.
  3. Click change plan settings.
  4. Click on change advanced power settings.
  5. Scroll down to display.
  6. Click on enable adaptive brightness.
  7. Change them to the off position.

Now you can have complete control over the brightness.

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I like this answer, it's simple. I didn't see a "adaptive brightness" setting on my Windows 8 laptop, but there were options about dimming percentages. That worked. –  Chris Nash Jun 8 at 20:07

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