You can use an external one or use the one soldered on the board (pin 13). Turn ON an LED Sketch This is a very simple arduino project where a led is turned on by setting the pin 13 as output, then ...

The Julia programming language is a horrible fit for a no-frills microcontroller like the ATMega328p that lies within the classic Arduino, but that didn’t stop [Sukera] from trying, and succe… ...

As a perfect example, these LED “blinking eyes” were created by [Will Moser]. Using nothing more exotic than some bare LEDs, an Arduino, and a cardboard box, ...