DIY Arduino Calculator

OBJECTIVE

To design and simulate a basic calculator using Arduino that performs arithmetic operations through a keypad and displays results on an LCD..

MODULES REQUIRED

Arduino uno
Lcd 16X 2
Keypad
Resistors

SCHEMATIC DIAGRAM

SCHEMATIC CONNECTION

Connect Lcd:

Connect the VS pin of the Lcd to the Gnd pin on the Arduino .

Connect the VDD pin of the Lcd to the 5v pin on the Arduino .

Connect the RS pin of the Lcd to the D12 pin on the Arduino.

Connect the RW pin of the Lcd to the Gnd pin on the Arduino .

Connect the E pin of the Lcd to the D11 pin on the Arduino .

Connect the D4 pin of the Lcd to the D10 pin on the Arduino .

Connect the D5 pin on the Lcd to the D9 pin on the Arduino.

Connect the D6 pin of the Lcd to the D8 pin on the Arduino .

Connect the D7 pin of the Lcd to the D7 pin on the Arduino

connect the A pin to one end of the resistor and the other end of the resistor to the Arduino's 5V pin.

Connect Keypad :

Connect the R1 to R4 pin of the keypad to the D5 to D2 pin on the Arduino .

Connect the C1 to C4 pin of the keypad to the A3 to A0 pin on the Arduino.

To begin your project, click this template link:

Simulate on Wokwi

ARDUINO CODE


#include (LiquidCrystal.h)
#include (Keypad.h)
#include (Servo.h)

/* Display */
LiquidCrystal lcd(12, 11, 10, 9, 8, 7);

/* Keypad setup */
const byte KEYPAD_ROWS = 4;
const byte KEYPAD_COLS = 4;
byte rowPins[KEYPAD_ROWS] = {5, 4, 3, 2};
byte colPins[KEYPAD_COLS] = {A3, A2, A1, A0};
char keys[KEYPAD_ROWS][KEYPAD_COLS] = {
  {'1', '2', '3', '+'},
  {'4', '5', '6', '-'},
  {'7', '8', '9', '*'},
  {'.', '0', '=', '/'}
};

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, KEYPAD_ROWS, KEYPAD_COLS);

uint64_t value = 0;

void showSpalshScreen() {
  lcd.print("GoodArduinoCode");
  lcd.setCursor(3, 1);
  String message = "Calculator";
  for (byte i = 0; i < message.length(); i++) {
    lcd.print(message[i]);
    delay(50);
  }
  delay(500);
}

void updateCursor() {
  if (millis() / 250 % 2 == 0 ) {
    lcd.cursor();
  } else {
    lcd.noCursor();
  }
}

void setup() {
  Serial.begin(115200);
  lcd.begin(16, 2);

  showSpalshScreen();
  lcd.clear();
  lcd.cursor();

  lcd.setCursor(1, 0);
}

char operation = 0;
String memory = "";
String current = "";
uint64_t currentDecimal;
bool decimalPoint = false;

double calculate(char operation, double left, double right) {
  switch (operation) {
    case '+': return left + right;
    case '-': return left - right;
    case '*': return left * right;
    case '/': return left / right;
  }
}

void processInput(char key) {
  if ('-' == key && current == "") {
    current = "-";
    lcd.print("-");
    return;
  }

  switch (key) {
    case '+':
    case '-':
    case '*':
    case '/':
      if (!operation) {
        memory = current;
        current = "";
      }
      operation = key;
      lcd.setCursor(0, 1);
      lcd.print(key);
      lcd.setCursor(current.length() + 1, 1);
      return;

    case '=':
      float leftNum = memory.toDouble();
      float rightNum = current.toDouble();
      memory = String(calculate(operation, leftNum, rightNum));
      current = "";
      lcd.clear();
      lcd.setCursor(1, 0);
      lcd.print(memory);
      lcd.setCursor(0, 1);
      lcd.print(operation);
      return;

  }

  if ('.' == key && current.indexOf('.') >= 0) {
    return;
  }

  if ('.' != key && current == "0") {
    current = String(key);
  } else if (key) {
    current += String(key);
  }

  lcd.print(key);
}

void loop() {
  updateCursor();

  char key = keypad.getKey();
  if (key) {
    processInput(key);
  }
}

INSTRUCTIONS

Assemble the circuit by connecting all components as shown in the schematic diagram.

On the left side of the screen, open sketch.ino and write your Arduino code.

After completing the circuit and writing the code, click the green Play button to start the simulation.

To perform calculations, enter two numbers and select the operator (addition, subtraction, multiplication, or division) to get the result.

WORKING PRINCIPLE

The DIY Arduino calculator takes user input from a keypad, processes the numbers and selected arithmetic operation (addition, subtraction, multiplication, division), and displays the result on an LCD screen.

Project Link

for your reference.