LED Retrofit

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Warning Warning: Please note that this page has been depreciated. Current control interface is on control.fixme.ch, documentation here.

What are LED Strips?

The idea with the LED Retrofit is to provide the HS with an effective yet sleek lighting solution, by using color-changeable LED strips which are controllable via the network.

Here is an exhaustive explanation and tutorial from laydyada. In essence, there are 3 SMD (Surface Mount Technology) RGB (Red Green Blue) LEDs (Light Emitting Diodes) on a segment with 3 resistors which allow the ~3 v LEDs to be drivven using a 12v power supply. These 'segments' are continuously joined together to form spools 5 meters each. Sometimes you can buy them in smaller bits (1 meter, 50 cm, 1 foot, etc), but sticking to a 5 meter spool is the best.

Currently there are 5x5m of 5050 RGB LED Strips @ 60 LEDs/m placed on the ledge just under the ceiling. Each 5 meter segment is individually connected to the Arduino-based controller via repurposed 230v cables. The Arduino is connected to the local network via an ethernet shield, and it controls the LEDs by PWMing a signal to 3 mosfets (1 for each color) which switches the 12vdc from the modded 400w ATX PSU.

How to control them?

You can get the code from git:

git clone ssh://gitolite@foo.fixme.ch:1337/led-strip.git

Or you can use a basic online interface found here (accessible only via internal network).

How to compile ?

  • There is a library problem which need to be adresse, but since then, there's a chroot on foo with the correct settings to compile/upload the code
ssh foo.fixme.ch
sudo su
cd /root/led-strip/LedStripDriver
# Put the USB cable from foo to the leds
make upload
# Remove the USB cable


  • Figure out a way to fix brightness issue I think we should feed each 5m segment from multiple sides, or even split it into smaller pieces (it is suspected that the pcb traces aren't thick enough for the current). Maybe use individual power supplies every couple of meters coupled with their own (more basic) control circuitry that get commands from central Arduino? I suspect that there is a significant voltage loss along the connecting cable because of the low voltage and long distance, using 230v AC could help. We could also experiment in raising the voltage as long as it does not bypass the specified wattage, and that no single LED gets more than its designed voltage. Maybe the mosfets are the wrong kind?
  • Better control options maybe a nicer web-interface with more options (See Uses below), as well as an android app.
  • Moar LED strips place LED strips in other places, e.g. to replace the crappy CFL in the middle of the room (maybe use pure white LED strips instead of RGB ones), electronics bench, inside fridge, foyer, inside thermibel :) ?


  • Control remotly using a script (netcat)
    • Web server running on an Arduino board to control the LEDs: http://leds.fixme.ch/rgb
    • Little scripts for the current implementation inside the repository
  • Controled by the music (color, intensity)
  • Special program: Burger time, etc
  • Philips ambilight-like for projected videos
  • Time dependent light (i.e. automatically dimming)




Project Leader