The 74HC595 shift register provides 8 outputs from the use of only three digital pins on an Arduino. Multiple 74HC595 shift registers can be chained together, and still only consume three digital pins ...

Arduino 74hc595 Shift Register | 16 Led Chaser With 18 Effects Hello again, I am thinking about how to control more than 20 led with Arduino Uno because Arduino Uno only has 13 digital pins.