I plan to power some WS2812 NeoPixel LEDs via an external 5 V wall adapter and use an Arduino Nano for data only, but Adafruit (NeoPixel vendor) mentions:
If powering the pixels with a separate supply, apply power to the pixels before applying power to the microcontroller. Otherwise they’ll try to power “parasitically” through the data line, which could spell trouble for the microcontroller.
They also suggest a 300 - 500 Ω resistor on the Arduino's data pin and the data input on the first LED to help prevent voltage spikes.
How do I work around this constraint so that I don't always have to remember to first plug in my 5V and then plug in the USB to the Arduino? I would like to be able to plug in the Arduino before the 5V.