I'm having some trouble with my Arduino/WS2812 LED project- When I initially wired everything, it worked great. Then I added some connectors. I'm sending the output from 2 12v to 5v transformers along with the data output from the Arduino to the WS2812 LEDs via Cat6 cable and connectors. I also have 12V going directly to the Arduino via the DC in jack. The set up worked fine, until I removed the USB cable from the Arduino, then the WS2812s started acting oddly- like flashing random colors and patterns. IT looked like there was some logic to it, but nothing I programmed. When I stuck the USB back in, it worked fine again. I then tried bypassing the Cat6 cable and connector, jumpering the data wire on the LEDS to another PIN on the Arduino, and it worked fine again.
My suspect is possibly noise on the lines, or a crossed wire somewhere. Would the data signal really be that susceptible to line noise running alongside 5V power lines? Any other thoughts?