If you want an article on general 74hc595 shift register usage with detailed explanition on how it works/what it’s doing, you want this article here: http://bildr.org/2011/02/74hc595/ The following code and library are compatible with arduino software 1.0+ ONLY. You can download the newest version of the arduino software here. Earlier this year we did an article on using the 74hc595 shift register with your ...

The 74HC595 is an easy and inexpensive (at about 60 cents apiece) way to increase the number of digital out pins on your Arduino.  In this tutorial I'll show you how to drive up to 16 LEDs with one 74HC595 using a technique called multiplexing.  In the end, all 16 LEDs will require only three of the Arduino's available digital pins. The finished product will look like this: I used the sparkfun button pad pc ...