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Introduction 

In this tutorial we will show you how to use the 2-Digit seven segment display with the Arduino UNO board. We will use the countUP() and countDown() functions to count from 0 to 'number' (variable) and from 'number' to 0. We can change this 'number' with a value from 0 to 99.

​Let's get started!

What you will need - Hardware


​For this tutorial you will need:

The Circuit

The connections are easy :
4-Digit  Seven Segment connection:
  • Vcc to Arduino 5V Pin
  • GND to Arduino GND
  • SDI to Arduino pin 2
  • CLK to Arduino pin 3
  • LOAD to Arduino pin 4

The code

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/* 
 *  2 Digitl 7 segment display PCB board with (2) 74HC595 shift register ICs
 *  Arduino Tutorial - www.Ardumotive.com
 *  Dev: Michalis Vasilakis // Date: 31/1/2018 // Ver:1.0
 */
#include <ShiftRegister74HC595.h>
// create shift register object (number of shift registers, data pin, clock pin, latch pin)
ShiftRegister74HC595 sr (2, 2, 3, 4); 

int number=99; // <--- Change it from 0 to 99

int value,digit1,digit2,digit3,digit4; 
uint8_t  numberB[] = {B11000000, //0
                      B11111001, //1 
                      B10100100, //2
                      B10110000, //3 
                      B10011001, //4
                      B10010010, //5
                      B10000011, //6
                      B11111000, //7
                      B10000000, //8
                      B10011000 //9
                     };
                        
void setup() {
  //Count from 0 to 'number' 
  countUp();
  //Count from 'number' to 0
  //countDown();  // <--- Comment countUp and uncomment countDown
  //Blink 4 times all on and all off.
  blink();  
}

void loop() {

}

void countUp(){
  for (int i = 0; i<=number; i++){
    //Split number to digits:
    digit2=i % 10 ;
    digit1=(i / 10) % 10 ;
    //Send them to 7 segment displays
    uint8_t numberToPrint[]= {numberB[digit2],numberB[digit1]};
    sr.setAll(numberToPrint); 
    //Reset them for next time
    digit1=0;
    digit2=0;
    delay(1000); // Repeat every 1 sec
  }
}

void countDown(){
  for (number; number>=0; number--){
    //Split number to digits:
    digit2=number % 10 ;
    digit1=(number / 10) % 10 ;
    //Send them to 7 segment displays
    uint8_t numberToPrint[]= {numberB[digit2],numberB[digit1]};
    sr.setAll(numberToPrint); 
    //Reset them for next time
    digit1=0;
    digit2=0;
    delay(1000); // Repeat every 1 sec
  }
}

//Blink
void blink(){
  for(int i = 0; i<4; i++){
    sr.setAllLow(); // set all pins Low (off)
    delay(1000);
    sr.setAllHigh(); // set all pins High (on)
    delay(1000);
  }
}
Download the code from here and open it with Arduino IDE. Inside you will also find and the DHT.h library.
twodigit7seg595.zip
File Size: 2 kb
File Type: zip
Download File

Well done!

You have successfully completed one more Arduino "How to" tutorial and you learned how to use the 2-Digit 7 Segment Display 74HC595 module.
​
I hope you liked this, let me know in the comments.
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