To interface LCD we need six digital pins from Arduino. To save your Arduino pins and easy interfacing

IC 74HC595N Shift Register is used.Using this shift register we can interface LCD using 3 pins.

Step 1: Components Required

  • LCD 16x2
  • Arduino Uno
  • IC 74HC595N
  • 1K Potentiometer

Step 2: Operation of IC74HC595N

IC 74HC595N shift Register accepts serial input data and converts into parallel output.This shift Register contains 3 input pins and 8 output pins.By updating LiquidCrystal libraries the arduino generates serial data in single pin and give it to input data pin of IC74HC595N and the shift Register converts these serial data into parallel output and these parallel data is given to LCD.

IC 74HC595N contains 3 input pins

  • Data pin: Data is sent in serial mode.
  • Clock Pin: A clock runs on this pin
  • Latch Pin: This pin is used to toggle so that shift register shows 8 bit data on output.

Step 3: Updating Libraries

To interface LCD using 3 pins you need to Update the ARDUINOLiquidCrystal libraries.Which is located at the following location

Local Disk(C)-->Program Files-->Arduino-->libraries-->LiquidCrystal.

Open the LiquidCrystal folder and there are some files inside that folder.Cut and paste these files Some where on your pc. Because you need to use these files when you interface LCD using 6 pins.

Now Download and Extract the following libraries.Which is an updated Liquid Crystal libraries to use LCD with 3 pins.Copy the extracted files and paste it in the following Location

Local Disk(C)-->Program Files-->Arduino-->libraries-->LiquidCrystal.

Note: open the folder of Liquid Crystal and paste it.
Now you have updated your Arduino Liquid Crystal libraries

Step 4: Schematic Diagram

I have also attached Schematic in RaR format.

Step 5: Program Code

#include <Wire.h>

#include <LiquidCrystal_SR.h>

// Defining LCD and Pins for interfacing.

LiquidCrystal_SR lcd(6, 5, 9); // Pin 6 - Data Enable/ SER, Pin 5 - Clock/SCL, Pin 9 -SCK

void setup(){

lcd.begin(16,2); // Initializing LCD

lcd.home (); // Setting Cursor at Home i.e. 0,0


void loop(){

lcd.print("3 Pin LCD"); // Print Something on LCD

delay(2000); // Waiting for a while

lcd.clear(); // Clearing LCD





Step 6: Download Program Code

I have attached program in RaR format

Download and extract it and open it in Arduino IDE

Step 7: Video

<p>I have tried it in past project, it works great, Latest development is you can get I2C board cheaply with LCD that takes care of hassle (just sharing info)</p>
I2C is costly when compare to 74HC595N.You can get the IC 74HC595N cheaper in cost
<p>no doubt about that, 595 costs around 8/Pkr while I2C 64/Pkr. </p>
I think 10k pot should also work flawlessly.
<p>10K potentiometer is more common, than 1K. I have also made this project;)</p>
Yes you can also use 10K pot to have wide range of contrast levels
<p>Very helpful to me </p>

About This Instructable




Bio: iam a student studying B.E Electronics and Communication Engineering. Iam a final year student.I have great interest on electronics.I love my college ... More »
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