I've been running an uno with two strands of adafruit led strips for 8 months. The sketch I've been using creates a slow moving rainbow that's been working great until the last month. Lately after turning on the project the lights will sort of strobe and flash in random colors not at all like it should. After a few minutes it will begin to run normal again. Occasionally it will flash back to the strange strobe pattern but then return to normal. Could there be some sort of corruption in the memory of the uno that would make it act like this? I've tried different sketches and some will get this strange strobing error that lasts for a short time while others will work perfectly. The leds can't program themselves and the sketches are the same ones that I've been using for 8 months so that leads me to think it's some sort of corruption with the arduino itself.
I see nothing wrong with the code and circuit diagram that you have posted.
Leds on the strips are on a bus - so any "fatigue" to the bus or the power supply can drive weird patterns. that's what I would look at first....
Update: I've tried a new arduino, rewired my circuit board to clean up some connections and get rid of the Bluetooth input just in case it was causing some trouble, and started with some very basic sketches. Using the fastled library examples I'm just trying to get a steady one color light. It works for about 30 seconds then goes to a white pulsing light with occasional other colors flashing randomly. Too weird. I'm convinced it's not the arduino or the sketches because I've used several different examples and they all last about 30 seconds. Is it possible for a power supply to cause something like this? I'd hate to replace the led strips as they were the most expensive part of the project. I've got a 1000uF capacitor between the pos and neg power lines and a 470ohm resistor on the data line. The power supply is 5v 4A which should be more than enough to power 60 neopixels. I think the next thing I'll try is replacing the capacitor and resistor then check if there is a difference in output from the power supply after it starts the weird behavior.
See reply #1
Occasionally it will flash back to the strange strobe pattern but then return to normal.
Something is making an intermittent connection, try and trace it down. And yes read reply#1 again.