#include <SoftwareSerial.h>

// Define pins
const int irSensorPin = 4;  // Pin connected to IR sensor output
const int buzzerPin = 5;     // Pin connected to buzzer
SoftwareSerial hc05(11, 10);  // RX, TX pins for HC-05 communication

void setup() {
  // Initialize serial communication for Arduino <-> PC (Serial Monitor)
  Serial.begin(9600);
  
  // Initialize communication between Arduino and HC-05 at 9600 baud
  hc05.begin(9600);  // Baud rate for HC-05
  
  // Initialize the IR sensor pin and buzzer pin
  pinMode(irSensorPin, INPUT);   // Set IR sensor pin as input
  pinMode(buzzerPin, OUTPUT);    // Set buzzer pin as output
  
  // Print message to Serial Monitor for user
  Serial.println("Baby Alert System Initialized");
}

void loop() {
  int sensorState = digitalRead(irSensorPin);  // Read the IR sensor state
  
  if (sensorState == HIGH) {  // If obstacle detected
    // Print to Serial Monitor (optional)
    Serial.println("Obstacle Detected - ON");

    // Send message to HC-05 via Bluetooth
    hc05.println("ON");  // This will be sent to the paired device
    
    // Activate buzzer for 3 seconds
    tone(buzzerPin, 1000);  // Play buzzer at 1000Hz frequency
    delay(3000);             // Buzzer rings for 3 seconds
    noTone(buzzerPin);       // Stop buzzer sound after 3 seconds
    
    // Optional: Add a delay between obstacle detections
    delay(1000);  // Adjust this to control how frequently you detect obstacles
  }
}

Board 1

#include <SoftwareSerial.h>

SoftwareSerial hc05(2, 3); // HC-05 TX to pin 2, RX to pin 3
int motorPin = 7; // Connect to MOSFET Gate

void setup() {
  pinMode(motorPin, OUTPUT);
  digitalWrite(motorPin, LOW); // Ensure motor is off
  hc05.begin(9600);  // Bluetooth baud rate
  Serial.begin(9600); // Serial Monitor
  Serial.println("Waiting for Bluetooth command...");
}

void loop() {
  if (hc05.available()) {
    String command = hc05.readString(); // Read Bluetooth command
    command.trim();  // Trim whitespace and newline characters from the string
    Serial.println("Received: " + command); // Print received message to Serial Monitor
    
    if (command == "ON") { // Compare the trimmed command
      Serial.println("Activating motor!"); // Print when activating motor
      digitalWrite(motorPin, HIGH); // Turn on motor
      delay(3000); // Run motor for 3 seconds
      digitalWrite(motorPin, LOW); // Turn off motor
      Serial.println("Motor turned off."); // Print when motor is turned off
    }
  }
}

Board 2

Code Test