Raspberry Pi GPIO pins are NOT 5-volt tolerant, so connecting an LED tied to +5v will make the Pi unhappy.

? Please explain why a 5V power pin is "NOT 5-volt tolerant"? He wasn't using a GPIO pin but a power pin. Is PI designed for 3.3V IO?

 

The Pi has 3.3v I/O pins, which are not 5 volt tolerant. If you connect an LED + resistor between +5 and the I/O pin, the I/O pin may see > 3.3v when the LED is off.

 

Thanks! That explains a lot.

 

I am sure they are addressable LEDs like WS2812B or similar. NeoPixel type which uses say 5V for all parallel powered LEDs and current based on LED string length, color, and brightness of each LED in the string.