Do I need to put a diode on the 5v or can I just not connect the 5v to my 12v led strip? The Arduino nano is being powered by USB. I have a common ground from the LED strip to the nano.
You only need the common ground between everything. Your nano can be powered by USB and your 12V strip can be powered by a separate 12V source.
Would be similar to the bottom connection here:
Thank you much. For some reason I had forgotten that the nano was also 12v capable; and I ended up doing it like the bottom image. Only I used the spare pos wire on my strip to run power back the the nano.
Thank you again.
12v strips, I’m jaelous 