SN74HC595 is a great way to extending your Arduino devices. This is SIPO: Serial In Parallel Out. What does that mean? You can connect 3 wires back to your Arduino device and get 8 outputs. You can even daisy chain them together to expand from 8 to 16, 24, 32 outputs. The benefit of shift registers is you can expand your devices to more input and output ports. I will be discussing SN74HC165 PISO Parallel In Serial Out chip for dip switches to control the 8 LEDs.
8-Bit
Serial-In,Parallel-Out
Pin 14: Data
Pin 12: Latch
Pin 11: Clock
Output: QA to QH
Pin 16: VCC: 5V
Pin 8 and 13: Ground
Wide operating voltage range of 2 V to 6 V
Arduino pin out:
int latchPin = 8; // SR Latch Pin 12 Digital pin
int dataPin = 11; // SR Pin 14 PWM pin
int clockPin = 12; // SR Clock Pin 11 Digital pin
Cascading SR:
Pin 9 cascades to Pin 13 on next SR (Data)
Pin 11 to Pin 11 (Clock)
Pin 12 to Pin 12 (Latch)
All must share common ground and 5V