I'm using a Dell Inspiron N5110 laptop with Ubuntu 13 and I find that every time I plug the power in to charge, the screen brightness dims. If I go into the brightness settings window the brightness immediately goes back to full brightness (as they are set) without me changing anything. In order to keep the screen brightness on full I have to keep the brightness settings window open in the background. As soon as the battery is charged the brightness drops again until I unplug the power again. This happens every time and now I know how to get round it it's not a huge problem but still quite annoying. Any advice would be gratefully received. Let me know if you need any more info.

I'm quite new to Ubuntu so if you can give me nice simple instructions that would be great :)

  • Can't you turn the brightness up using Fn+F5 (I think that is Brightness Control Up key on that laptop)? If not, can't you set a Keyboard shortcut to do so? – Wilf Oct 30 '13 at 22:50
  • How about disabling screen dimming in the Power Manager? Also, do you use 13.04 or 13.10? – mikewhatever Oct 30 '13 at 23:01
  • I have Dell v131 laptop. This issue finally disappeared after upgrade to Ubuntu 16.10. – azurkin Oct 16 '16 at 15:42

Until someone comes up with an answer, here is at least a partial workaround that I use for the same problem (Dell Insprion 1525, 13.10).

I use "Indicator Brightness" http://www.omgubuntu.co.uk/2013/04/brightness-control-ubuntu which allows you to simply mouse over the indicator and roll the scroll wheel to increase the brightness. If I am in a situation that makes it difficult to even see the indicator I will move the mouse, plug in the adapter, roll the wheel up, and bang you're back in business.

As explained in the article...

sudo add-apt-repository ppa:indicator-brightness/ppa

sudo apt-get update && sudo apt-get install indicator-brightness
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I'm experiencing this issue with my Dell Inspiron 15. Monitoring /sys/class/backlight/*/brightness shows that on these occasions, the brightness goes down to 0.

(By the way, for me, it's not COMPLETELY dark - I can still see shadows - but it's dark enough to be useless, and I can't brighten it).

The workaround I'm using is: I wrote this little script, which monitors the brightness and keeps it from going below a certain threshold. As long as this script runs, I'm protected.

Pro: It solves the problem. With this, I could always turn the brightness back up. Con: Also prevents extreme manual dimming. (But doesn't prevent turning the monitor off, so doesn't break ACPI).

I put this in ~/bin/prevent_dimming.sh and then, in a terminal/screen/initialization script, keep this program running (as root!):

$ sudo ~/bin/prevent_dimming.sh

while [ 1 == 1 ]; do
    ME=$(cat /sys/class/backlight/intel_backlight/brightness)
    if [ "$ME" -lt "$THRESH" ]; then
        echo $THRESH > /sys/class/backlight/intel_backlight/brightness
    sleep 5
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I had a similar problem with a Dell Inspiron 1420, but was able to brighten the display using the Function key plus the up arrow (Fn+Up).

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