@abbesnabb it is equally true that the led strip is being powered from two sources: one of your buck converters and the 5V pin of the Nano. No two 5V sources are exactly 5V or exactly equal to each other. There is no way to know which of the two sources will provide what portion of the current that the strip demands, so more could be drawn from the Nano 5V pin than it can withstand. This could be why your Nano burned out. Removing that wire @TomGeorge indicates could have prevented the burn-out.
2 Likes