Hi,
In stage 3 you need to connect the gnd of both arduino and LED supply.
The supplies will still be independent but the gnd reference will be the same, very important for the control signal to the LED strip.
Tom... 
Hi,
In stage 3 you need to connect the gnd of both arduino and LED supply.
The supplies will still be independent but the gnd reference will be the same, very important for the control signal to the LED strip.
Tom...