This code is to introduce the 74HC595 to drive 8 LED lights and turn them on from 0 to 8 one by one while keeping each LED on. In Project 5: Adjusting delay of each digit using a potentiometer To learn better or to have fun, I have added a potentiometer (or variable resistor) to the project so we can adjust the delay time between each digit (multiplexing) so we can see how each digit is turned on. For example, when we want to display 876, we first see 8, then a delay, then 7 with a delay, and then 6 with a delay, which can be adjusted using the variable resistor.