[SOLVED] Is this setup alright?

I am somewhat afraid of breaking something. Is the way i wired my project up alright or could i possibly break something this way?

Instructions are from this site: Tweaking4All.com - Ambient TV lighting with XBMC Boblight, OpenElec and WS2811/WS2812 LEDs

And I don't really get why they would also wire GND of the Arduino to the power-supply, as the Arduino gets its power via USB..

Apart from the crappy drawing (breadboard view is just crap) and the fact you don't want to run this through a breadboard it looks semi-okay. Is that 5V from a separate supply? And one main thing, add a resistor (470R - 1k) in the data line to protect the first led.

Linsane:
And I don't really get why they would also wire GND of the Arduino to the power-supply, as the Arduino gets its power via USB..

Because EVERY connection needs a return path (electricity only flows in a loop). And without a GND connection, what is the return path back to the Arduino of the data line? :wink:

Thank you very much!

Of course you may also be able to power the Arduino from that 5V source though the 5V pins of the Arduino, or (if it doesn't take too much power) the device sketched to the right using the Arduino's 5V pins.