IoT Flame and Fire Detection System Using ESP8266 and Blynk

A flame sensor can be used with the ESP8266 to detect the presence of a nearby flame and automatically activate a warning output.

In this project, the ESP8266 reads a flame sensor, switches a warning light through a relay, and sends a fire alert through Blynk.

The local warning works directly from the ESP8266, while Blynk provides remote monitoring and notification.

Important: This is an educational prototype and should not be used as a replacement for a certified fire alarm or life-safety system.

Components Required

Component	Quantity
ESP8266 NodeMCU	1
Flame Sensor Module	1
Relay Module	1
Low-voltage Warning Light / Bulb	1
Suitable DC Power Supply	1
Breadboard	1
Jumper Wires	As required

For classroom testing, use a low-voltage DC warning light rather than exposed AC mains wiring.

System Working

Flame Detected
      |
      v
Flame Sensor
      |
      v
   ESP8266
   /     \
  v       v
Relay    Wi-Fi
  |       |
  v       v
Warning  Blynk
 Light   Notification

When flame is detected:

Flame detected → Warning light ON → Blynk fire alert

When no flame is detected:

No flame → Warning light OFF

Circuit Connections

Flame Sensor

Flame Sensor	ESP8266
VCC	3.3V
GND	GND
DO	D5 / GPIO14

This project uses the sensor’s digital output (DO).

Most flame sensor modules include a small potentiometer that can be used to adjust the detection threshold.

Relay Module

Relay	ESP8266
IN	D1 / GPIO5
GND	GND
VCC	According to relay module

Use a relay module that can be reliably triggered from a 3.3V ESP8266 GPIO signal.

The warning light is connected through the relay’s COM and NO contacts.

Blynk Setup

Create a Blynk Template and Device and obtain:

BLYNK_TEMPLATE_ID
BLYNK_TEMPLATE_NAME
BLYNK_AUTH_TOKEN

Create one Virtual Pin:

V0 → Flame Status

Suggested values:

0 → Normal
1 → Flame Detected

Also create a Blynk Event with the event code:

fire_alert

The ESP8266 can trigger the event using Blynk.logEvent().

ESP8266 Program

#define BLYNK_PRINT Serial

#define BLYNK_TEMPLATE_ID "YOUR_TEMPLATE_ID"
#define BLYNK_TEMPLATE_NAME "Fire Detection"
#define BLYNK_AUTH_TOKEN "YOUR_AUTH_TOKEN"

#include <ESP8266WiFi.h>
#include <BlynkSimpleEsp8266.h>

char ssid[] = "YOUR_WIFI_NAME";
char pass[] = "YOUR_WIFI_PASSWORD";

const int FLAME_PIN = D5;
const int RELAY_PIN = D1;

const bool FLAME_ACTIVE_LOW = true;
const bool RELAY_ACTIVE_LOW = true;

bool previousFlameState = false;

void setWarning(bool state)
{
  if (RELAY_ACTIVE_LOW)
    digitalWrite(RELAY_PIN, state ? LOW : HIGH);
  else
    digitalWrite(RELAY_PIN, state ? HIGH : LOW);
}

bool flameDetected()
{
  int sensorState = digitalRead(FLAME_PIN);

  if (FLAME_ACTIVE_LOW)
    return sensorState == LOW;

  return sensorState == HIGH;
}

void checkFlame()
{
  bool flame = flameDetected();

  setWarning(flame);

  if (Blynk.connected())
  {
    Blynk.virtualWrite(V0, flame ? 1 : 0);
  }

  if (flame && !previousFlameState)
  {
    Serial.println("WARNING: Flame detected!");

    if (Blynk.connected())
    {
      Blynk.logEvent("fire_alert", "Flame detected by ESP8266 sensor.");
    }
  }

  if (!flame && previousFlameState)
  {
    Serial.println("Flame no longer detected.");
  }

  previousFlameState = flame;
}

void setup()
{
  Serial.begin(115200);

  pinMode(FLAME_PIN, INPUT);
  pinMode(RELAY_PIN, OUTPUT);

  setWarning(false);

  Blynk.begin(
    BLYNK_AUTH_TOKEN,
    ssid,
    pass
  );

  Serial.println("Flame Detection System Started");
}

void loop()
{
  Blynk.run();
  checkFlame();

  delay(200);
}

Testing

Normal Condition

Keep the flame away from the sensor.

Expected result:

Flame Status → 0
Warning Light → OFF

Flame Detection

Carefully bring a small controlled flame near the sensor.

Expected result:

Flame Status → 1
Warning Light → ON
Blynk Event → fire_alert
Remote notification → triggered

Remove the flame.

Expected result:

Flame Status → 0
Warning Light → OFF

If the sensor behaves in reverse, change:

const bool FLAME_ACTIVE_LOW = true;

to:

const bool FLAME_ACTIVE_LOW = false;

If the relay behaves in reverse, change:

const bool RELAY_ACTIVE_LOW = true;

to:

const bool RELAY_ACTIVE_LOW = false;

Common Problems

Sensor always detects flame

Adjust the potentiometer on the flame sensor and check the digital output using Serial Monitor.

Relay works in reverse

Change the RELAY_ACTIVE_LOW setting.

Blynk alert does not arrive

Check the Wi-Fi connection, Blynk credentials, Event Code, and notification settings.

ESP8266 resets when relay switches

Use a stable power supply and keep relay/load switching noise away from the ESP8266 supply.

Final Result

The completed system provides:

• flame detection
• automatic warning-light activation
• local alarm operation
• flame status monitoring through Blynk
• remote fire-event notification

Flame
  ↓
Sensor
  ↓
ESP8266
  ├──→ Relay → Warning Light
  │
  └──→ Wi-Fi → Blynk → Remote Alert

Safety Note

This project is intended for education and prototyping only.

Do not depend on a hobby flame sensor, ESP8266, Wi-Fi, Blynk, or a breadboard circuit as the only protection against fire.

For real buildings or safety-critical installations, use properly designed and certified fire detection and alarm equipment.