hi. Many of us face problem when try to connect more sensors and output devices in arduino. Because there is no enough ports to connect.To overcome this some may go to arduino Mega.We need not go to Arduino Mega to have extended ports.Here is a solution to extend the ports of Arduino Uno. We extend the ports of arduino using IC 74HC595N which is ashift Register for Serial in and Parallel out.This register IC takes 3 pin input and gives output at 8 Pins. Thus this extends 3 pins to 8 pins.The extended pins are used only as output port to connect output devices such as LED,LCD,Bar Graph Display,Piezo Buzzer etc.
Step 1: Components Required :
- Arduino Uno
- LED --------------------- 8
- Resistor 100ohm ---- 8
- IC 74HC595N Shift Register
Step 2: Operation of IC74HC595N
How does it extends ports?
Arduino combines the data to be sent to output devices in serial format and transmit the serial data to IC 74HC595N.The IC shifts the serial data and make its available at the parallel output pins of IC 74HC595N.The serial formatting of data to various output device is done by shiftwrite function given in the coading.
For example
10101100 these numbers represents 8 bit data.Each number in 8 bit represents the status of eight LED'S.
One(1) indicates LED is ON.
Zero(0) inducates LED is OFF.
So there are 8 LED'S connected to the output data pins of IC74HC595N.So each bit in 8 bit data has to be available at the output pins of IC74HC595N.To get the 8 bit data available at output pins.The 8 bit data has to be shifted 8 times so that each bit will be available at 8 output pins of IC74HC595N.So eight clock pulses are required to shift 8 bit.In order to get data without error the shifting has to be done in nano Seconds(ns).So high frequency clock is requied.This clock is generated by arduino code itself.The communication between electronic devices is called as Digital Communication.Arduino is also a digital device because it deals with digital data that is Zeros and Ones.So in digital communication every data has to be sent in frame format.So this 8 bit data is to be sent in frame format.This is also done by arduino code itself.So with the proper coading you can connect output devices at the parallel pins of IC74HC595N.The diagram explanation is given above.I have also attached diagram explanation in zip format.
DOWNLOAD
EmoticonEmoticon