Speed measurement project Vedant Amit

 #include <Wire.h>

#include <LiquidCrystal_I2C.h>

// ===== LCD Setup =====

LiquidCrystal_I2C lcd(0x27, 16, 2);  // Change 0x27 to 0x3F if your module uses that address

// ===== Sensor pins =====

const int sensor1Pin = 2;

const int sensor2Pin = 3;

// ===== Variables =====

volatile unsigned long startTime = 0;

volatile unsigned long endTime = 0;

volatile bool firstSensorTriggered = false;

float distance = 0.20;  // distance between sensors in meters (example: 20 cm = 0.20 m)

float speed = 0.0;

void setup() {

  pinMode(sensor1Pin, INPUT);

  pinMode(sensor2Pin, INPUT);

  lcd.init();

  lcd.backlight();

  lcd.setCursor(0,0);

  lcd.print("Vehicle Speed");

  lcd.setCursor(0,1);

  lcd.print("Waiting...");

  Serial.begin(9600);

}

void loop() {

  int sensor1State = digitalRead(sensor1Pin);

  int sensor2State = digitalRead(sensor2Pin);

  // When first sensor detects vehicle

  if (sensor1State == LOW && !firstSensorTriggered) {

    startTime = millis();      // record start time

    firstSensorTriggered = true;

    lcd.clear();

    lcd.setCursor(0,0);

    lcd.print("Vehicle Detected");

  }

  // When second sensor detects vehicle

  if (sensor2State == LOW && firstSensorTriggered) {

    endTime = millis();        // record end time

    unsigned long timeDiff = endTime - startTime; // time in ms

    // Calculate speed

    float timeSec = timeDiff / 1000.0;           // convert ms to seconds

    speed = distance / timeSec;                  // speed in m/s

    float speedKmHr = speed * 3.6;               // convert to km/h

    // Display on LCD

    lcd.clear();

    lcd.setCursor(0,0);

    lcd.print("Speed:");

    lcd.setCursor(0,1);

    lcd.print(speedKmHr);

    lcd.print(" km/h");

    // Print on Serial Monitor

    Serial.print("Time (s): ");

    Serial.print(timeSec);

    Serial.print("  Speed: ");

    Serial.print(speedKmHr);

    Serial.println(" km/h");

    // Reset flag

    firstSensorTriggered = false;

    delay(2000); // pause before next vehicle

    lcd.clear();

    lcd.setCursor(0,0);

    lcd.print("Waiting...");

  }

}