Arduino Calculator Using Keypad and LCD

Creating an Arduino calculator using a 4x4 keypad and an LCD in Tinkercad is a great project to combine hardware simulation with basic coding. Here's how you can build and program it.

🧰 Components Needed (in Tinkercad)

🖥️ Circuit Connections

🔌 LCD (16x2) Connections (with potentiometer for contrast)

🎛️ Keypad 4x4 Connections

⚠️ Avoid D0 and D1 if you're using Serial communication. Use D A0–A5 instead.

💾 Arduino Code

#include <Keypad.h>
#include <LiquidCrystal.h>

// LCD setup
LiquidCrystal lcd(7,6,5,4,3,2);

// Keypad setup
const byte ROWS = 4;
const byte COLS = 4;
char keys[ROWS][COLS] = {
  {'1','2','3','+'},
  {'4','5','6','-'},
  {'7','8','9','*'},
  {'C','0','=','/'}
};
byte rowPins[ROWS] = {11, 10, 9, 8};
byte colPins[COLS] = {A1, A2, A3, A4};

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

String input = "";
long num1 = 0, num2 = 0;
char operation;

void setup() {
  lcd.begin(16, 2);
  lcd.print("Calculator:");
}

void loop() {
  char key = keypad.getKey();

  if (key) {
    if (key >= '0' && key <= '9') {
      input += key;
      lcd.setCursor(0,1);
      lcd.print(input);
    } else if (key == '+' || key == '-' || key == '*' || key == '/') {
      num1 = input.toInt();
      operation = key;
      input = "";
      lcd.clear();
      lcd.setCursor(0,1);
      lcd.print(operation);
    } else if (key == '=') {
      num2 = input.toInt();
      long result = 0;
      switch(operation) {
        case '+': result = num1 + num2; break;
        case '-': result = num1 - num2; break;
        case '*': result = num1 * num2; break;
        case '/': result = (num2 != 0) ? num1 / num2 : 0; break;
      }
      lcd.clear();
      lcd.setCursor(0,0);
      lcd.print("Result:");
      lcd.setCursor(0,1);
      lcd.print(result);
      input = "";
    } else if (key == 'C') {
      input = "";
      num1 = num2 = 0;
      lcd.clear();
      lcd.print("Calculator:");
    }
  }
}

🔁 Tinkercad Tips