If you’d like to add your own LED, you can move the built-in LED’s pin to one of the other numbered ones, or leave it at 13, plugging your new LED’s longer leg into whatever pin you choose.

Note: If the /ttyACM* port is not available, here are several reasons why Modem manager is using the port. When the port becomes active, modem manager can claim the port, blocking the IDE's access ...

Here is a simple Arduino Camping Light project. In this design, only one push button switch is used to control the light output (from a bunch of white LEDs) between off, dim, medium, and full ...