How to Connect Wire a RGB LED Strip 12V - YouTube Feb 22, 2015How to Connect Wire a RGB LED Strip 12V SUGARSTARR feat. Sandra Huff - Get Up (REMIX-ME SUGARSTARR) How to Build a Common Cathode RGB LED circuit The diagram at the following link shows the internal layout of the RGB LED: Internal Diagram of a Common Cathode RGB. So with common cathode RGB LEDs, we connect pin 2 to ground. This grounds all of the LED grounds. And then we connect all of the toggle switches to positive voltage and ground, so that we can turn off or on whichever LED.