How to make a calculator using arduino uno

Overview

A calculator is a device used to solve mathematical problems easily and in a fast way this calculator can Add, Subtract, Multiply, and Divide. 

In this project, we have used a (4*4) keypad to take input and an LCD to show output. A potentiometer is also used to adjust the LCD to show the output. Keys used 

A – Addition

B – Subtract

C – Multiplication

D – Divide

Hardware required 

  1. Arduino Uno R3
  2. Potentiometer
  3. Keypad 4*4
  4. Resistor
  5. LCD
  6. Jumper Wires

Schematic Diagram

Fig 1.  Circuit Diagram

Arduino Code : 

#include <LiquidCrystal.h> 

#include <Keypad.h> 

const byte ROWS = 4; 

const byte COLS = 4; 

char keys[ROWS][COLS] = {

  {‘1′,’2′,’3′,’A’},

  {‘4′,’5′,’6′,’B’},

  {‘7′,’8′,’9′,’C’},

  {‘*’,’0′,’#’,’D’}

};

byte rowPins[ROWS] = { 0, 1, 2, 3 };

byte colPins[COLS] = { 4, 5, 6, 7 }; 

Keypad kpd = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS ); 

const int rs = 8, en = 9, d4 = 10, d5 = 11, d6 = 12, d7 = 13; 

LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

 long Num1,Num2,Number;

 char key,action;

 boolean result = false;

void setup() {

  lcd.begin(16, 2); 

  lcd.print(“Calculator”); 

  lcd.setCursor(0, 1);  

  lcd.print(“-Raghav”);  

   delay(2000); 

    lcd.clear();

}

void loop() {

key = kpd.getKey(); 

if (key!=NO_KEY)

DetectButtons();

if (result==true)

CalculateResult();

DisplayResult();   

}

void DetectButtons()

     lcd.clear();

    if (key==’*’) 

    {Serial.println (“Button Cancel”); Number=Num1=Num2=0; result=false;}

     if (key == ‘1’) 

    {Serial.println (“Button 1”); 

    if (Number==0)

    Number=1;

    else

    Number = (Number*10) + 1; 

    }

     if (key == ‘4’) 

    {Serial.println (“Button 4”); 

    if (Number==0)

    Number=4;

    else

    Number = (Number*10) + 4; 

    }

     if (key == ‘7’) 

    {Serial.println (“Button 7”);

    if (Number==0)

    Number=7;

    else

    Number = (Number*10) + 7; 

    } 

    if (key == ‘0’)

    {Serial.println (“Button 0”);

    if (Number==0)

    Number=0;

    else

    Number = (Number*10) + 0; 

    }

     if (key == ‘2’) 

    {Serial.println (“Button 2”); 

     if (Number==0)

    Number=2;

    else

    Number = (Number*10) + 2; 

    }

     if (key == ‘5’)

    {Serial.println (“Button 5”); 

     if (Number==0)

    Number=5;

    else

    Number = (Number*10) + 5; 

    }

     if (key == ‘8’)

    {Serial.println (“Button 8”); 

     if (Number==0)

    Number=8;

    else

    Number = (Number*10) + 8; 

    }   

    if (key == ‘#’)

    {Serial.println (“Button Equal”); 

    Num2=Number;

    result = true;

    }

     if (key == ‘3’)

    {Serial.println (“Button 3”); 

     if (Number==0)

    Number=3;

    else

    Number = (Number*10) + 3; 

    }

     if (key == ‘6’)

    {Serial.println (“Button 6”); 

    if (Number==0)

    Number=6;

    else

    Number = (Number*10) + 6; 

    }

     if (key == ‘9’)

    {Serial.println (“Button 9”);

    if (Number==0)

    Number=9;

    else

    Number = (Number*10) + 9; 

    }  

      if (key == ‘A’ || key == ‘B’ || key == ‘C’ || key == ‘D’) 

  {

    Num1 = Number;    

    Number =0;

    if (key == ‘A’)

    {Serial.println (“Addition”); action = ‘+’;}

     if (key == ‘B’)

    {Serial.println (“Subtraction”); action = ‘-‘; }

     if (key == ‘C’)

    {Serial.println (“Multiplication”); action = ‘*’;}

     if (key == ‘D’)

    {Serial.println (“Division”); action = ‘/’;}  

    delay(100);

  }

}

void CalculateResult()

{

  if (action==’+’)

    Number = Num1+Num2;

  if (action==’-‘)

    Number = Num1-Num2;

  if (action==’*’)

    Number = Num1*Num2;

  if (action==’/’)

    Number = Num1/Num2; 

}

void DisplayResult()

{

  lcd.setCursor(0, 0);  

  lcd.print(Num1); lcd.print(action); lcd.print(Num2); 

  if (result==true)

  {lcd.print(” =”); lcd.print(Number);} 

  lcd.setCursor(0, 1);   

  lcd.print(Number); 

}

Precautions

  1. Connections should be done properly.
  2. Arduino is case sensitive so code accordingly.
  3. Give different colours to the wires.
  4. Adjust potentiometer to get output on LCD.

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