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# Screen Brightness controls not working

The sven keyboard daemon, which displays its icons in the [panel](panel-icons.md), calls a couple of scripts to control the screen brightness. Unfortunately this varies a bit between computers. There are a couple things that can go wrong with this.  
**1)** Sven might not be configured to use the correct keys for your computer.  
**2)** The two scripts that Sven calls (/usr/bin/brightness-up and /usr/bin/brightness-down) could be using the wrong file in /sys  
So the first thing to do is open a terminal and type: *brightness-up* and then press Enter.  
If it changes the screen brightness then it's probably problem 1, and you need to right-click on the sven panel icon and select Preferences. If you get an error about file not found , then it's probably problem 2.  
The brightness-up script looks like this:  


``` 
#!/bin/ash
DEVICE= #radeon_bl0, acpi_video0, etc
DEVPATH=/sys/class/backlight

[ -z $DEVICE ] && DEVICE=$(ls $DEVPATH | head -n 1)
[ -z $DEVICE ] && exit 1

CURRENT=$(cat $DEVPATH/$DEVICE/actual_brightness)
MAX=$(cat $DEVPATH/$DEVICE/max_brightness)
STEP=$((MAX/10))
CURRENT=$(( CURRENT + STEP ))
if [ "$CURRENT" -gt "$MAX" ]; then CURRENT=$MAX; fi
echo $CURRENT > $DEVPATH/$DEVICE/brightness
      
```


For problem 2, you'll need to replace the **DEVICE** with the correct filename. You'll also need to make the corresponding changes to **/usr/bin/brightness-down**.  
For problem 1, you'll need to edit the Brightness down and Brightness up properties in Sven (right click and select Preferences).  


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