Build Fire-Fighting Robot with Arduino

In this DIY project, we will build a Fire-Fighting Robot that can detect and extinguish fire using flame sensors and a water-spraying mechanism. This robot is an ideal starter project for those interested in robotics, Arduino, and embedded systems.

Overview

This fire-fighting robot uses:

• Two flame sensors to detect fire direction (left or right)
• An ultrasonic sensor to avoid obstacles
• A relay-controlled submersible pump to spray water
• DC motors controlled by L298N motor driver to move the robot

---

Components Required

---

Wiring Connection

Flame Sensors:

• FLAME_LEFT → Digital Pin 2
• FLAME_RIGHT → Digital Pin 3
• (Connect VCC to 5V, GND to GND)

Ultrasonic Sensor (HC-SR04):

• Trig Pin → Digital Pin 8
• Echo Pin → Digital Pin 9
• Connect VCC to 5V, GND to GND)

L298N Motor Driver:

• IN1 → Pin 4
• IN2 → Pin 5
• IN3 → Pin 6
• IN4 → Pin 7
• ENA → Pin 10 (PWM)
• ENB → Pin 11 (PWM)
• Connect motors to OUT1/OUT2 and OUT3/OUT4 respectively
• Power the motor driver with a separate 12V source for motors

Relay and Pump:

• Relay Input → Pin 12
• Pump +ve → Relay Output
• Pump -ve → GND

Note: Make sure to use a flyback diode across the pump terminals for protection.

Flyback Diode Placement (for your setup)

Component	Connected To
Pump +ve	Relay output terminal
Pump −ve	Battery GND
Diode Cathode (stripe end)	Pump +ve (Relay output)
Diode Anode (plain end)	Pump −ve (Battery GND)

---

How It Works

1. Flame Detection
   • The flame sensors detect the presence and direction of fire.
   • LOW signal indicates fire detected.
2. Obstacle Avoidance
   • The ultrasonic sensor checks for obstacles. If something is within 15 cm, the robot stops to avoid collision.
3. Movement Logic
   • If flame is detected on the left: the robot turns left
   • If flame is on the right: it turns right
   • If flame is detected straight ahead: it stops and activates the water pump for 3 seconds
   • If no flame is detected: it stops and turns off the pump
4. Water Pump Activation
   • A relay is used to switch on a 5V/12V submersible pump to extinguish the fire

---

Arduino Code

// --- Pin Definitions ---
#define FLAME_LEFT 2
#define FLAME_RIGHT 3
#define TRIG_PIN 8
#define ECHO_PIN 9
#define RELAY_PIN 12

#define IN1 4
#define IN2 5
#define IN3 6
#define IN4 7
#define ENA 10
#define ENB 11

#define STOP_DISTANCE 15  // cm

void setup() {
  Serial.begin(9600);

  pinMode(FLAME_LEFT, INPUT);
  pinMode(FLAME_RIGHT, INPUT);

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  pinMode(RELAY_PIN, OUTPUT);
  digitalWrite(RELAY_PIN, HIGH);  // Relay off (active LOW)

  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT);
  pinMode(IN4, OUTPUT);
  pinMode(ENA, OUTPUT);
  pinMode(ENB, OUTPUT);

  stopMotors();
}

void loop() {
  int flameL = digitalRead(FLAME_LEFT);
  int flameR = digitalRead(FLAME_RIGHT);
  long distance = getDistance();

  bool flameDetected = (flameL == LOW || flameR == LOW);

  Serial.print("Flame L: "); Serial.print(flameL);
  Serial.print(" | Flame R: "); Serial.print(flameR);
  Serial.print(" | Distance: "); Serial.println(distance);

  if (flameDetected) {
    if (distance > 0 && distance < STOP_DISTANCE) {
      stopMotors();
      digitalWrite(RELAY_PIN, LOW);  // Turn ON pump
      Serial.println("Fire detected & close! Spraying...");
      delay(3000);  // Spray for 3 seconds
      digitalWrite(RELAY_PIN, HIGH); // Turn OFF pump
    } else if (distance >= STOP_DISTANCE) {
      moveForward();
      digitalWrite(RELAY_PIN, HIGH); // Keep pump OFF
      Serial.println("Fire detected, moving closer...");
    }
  } else {
    stopMotors();
    digitalWrite(RELAY_PIN, HIGH); // Pump OFF
    Serial.println("No fire. Standing by...");
  }

  delay(200);
}

// --- Motor Functions ---
void moveForward() {
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, HIGH);
  digitalWrite(IN4, LOW);
  analogWrite(ENA, 150);
  analogWrite(ENB, 150);
}

void stopMotors() {
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, LOW);
  analogWrite(ENA, 0);
  analogWrite(ENB, 0);
}

// --- Ultrasonic Function ---
long getDistance() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  long duration = pulseIn(ECHO_PIN, HIGH, 20000); // Timeout after 20ms
  if (duration == 0) return -1;  // Invalid reading
  return duration * 0.034 / 2;
}

Testing Your Robot

1. Upload the code to your Arduino using the Arduino IDE.
2. Power the Arduino and motor driver.
3. Place a small candle or lighter in front of the robot.
4. Watch it detect the flame, navigate toward it, and spray water!

---

Safety Tips

• Use low flame sources like candles for testing.
• Never test near flammable materials.
• Use protective gloves and goggles while handling fire and water.

---

Future Improvements

• Add camera module for vision-based flame detection.
• Use IR sensors for better obstacle detection.
• Add Bluetooth/Wi-Fi for remote control.
• Incorporate fire extinguisher spray instead of water pump.