The Arduino can just increment the counter up to the appropriate LED. The Arduino then controls the state of the LED using the active high enable line from the column multiplexer chip.

This part number (and ofcourse the LED type) is not very critical. If you want to use a bi-polar transistor, don’t forget to add a resistor (~1KΩ ) between Arduino D10 and the base terminal of the ...

The Arduino-powered display is built from a strip of 35 RGB LEDs. Now, that’s four pins per LED but one of is ground, leaving just 105 pins that need to be addressable.

A case will protect your Arduino and ensure your sweater has the chance to light up the room for many holidays to come.