SIK_circuit14_shiftRegister by SparkFun SIK Examples

Use a shift register to turn three pins into eight (or more!) outputs!

An integrated circuit ("IC"), or "chip", is a self-contained circuit built into a small plastic package. (If you look closely at your Arduino board you'll see a number of ICs.) There are thousands of different types of ICs available that you can use to perform many useful functions. The **74HC595** shift register in your kit is an IC that has eight digital outputs. To use these outputs, we'll use a new interface called SPI (Serial Peripheral Interface). It's like the TX and RX you're used to, but has an additional "clock" line that controls the speed of the data transfer. Many parts use SPI for communications, so the Arduino offers simple commands called shiftIn() and shiftOut() to access these parts. This IC lets you use three digital pins on your Arduino to control eight digital outputs on the chip. And if you need even more outputs, you can daisy-chain multiple shift registers together, allowing an almost unlimited number of outputs from the same three Arduino pins! See the shift register datasheet for details: [http://www.sparkfun.com/datasheets/IC/SN74HC595.pdf](http://www.sparkfun.com/datasheets/IC/SN74HC595.pdf) ###Hardware connections: ####Shift register: Plug in the chip so it bridges the center "canyon" on the breadboard. The shift register has 16 pins. They are numbered counterclockwise starting at the pin 1 mark (notch in the end of the chip). See the datasheet above for a diagram. 74HC595 pin LED pin / Arduino pin 1 (QB) LED 2 + 2 (QC) LED 3 + 3 (QD) LED 4 + 4 (QE) LED 5 + 5 (QF) LED 6 + 6 (QG) LED 7 + 7 (QH) LED 8 + 8 (GND) GND 9 (QH*) No Connection 10 (SRCLR*) 5V 11 (SRCLK) Arduino Digital 3 12 (RCLK) Arduino Digital 4 13 (OE*) GND 14 (SER) Arduino Digital 2 15 (QA) LED 1 + 16 (VCC) 5V ####LEDs: After making the above connections to the positive (longer) legs of the LEDs, connect the negative side (short lead) of each LED to a 330 Ohm resistor, and connect the other side of each resistor to GND.