Arduino UNO-Based Smart Home Automation System with Flame and IR Sensors

🔥 Fire Detection

Flame sensor detects IR from fire → triggers buzzer alarm instantly. Active LOW output — fires when sensor reads LOW.

👤 IR Motion Sensing

Dual IR sensors detect human movement and toggle LEDs/appliances on/off automatically for smart lighting control.

🌡️ Climate Monitor

DHT11 reads temperature (°C) and humidity (%) — displayed live on the 128×64 SSD1306 OLED screen via I2C.

⚙️ Appliance Control

L298N motor driver controls fans/pumps. LEDs represent smart light zones. Easily swap for relay modules in real installs.

Project Overview

This project turns an Arduino UNO into a multi-sensor smart home hub that runs continuously, monitoring four distinct home safety and comfort parameters simultaneously. All sensor data is displayed on a 0.96" SSD1306 OLED screen, while automated outputs (buzzer, LEDs, motors) respond in real time to sensor events.

📺

OLED Dashboard

Live 5-line display: Temp · Humidity · Flame status · IR1 motion · IR2 motion.

🔗

I2C Bus

OLED connects via I2C (SDA/SCL) — freeing up digital pins for sensors and outputs.

⚡

Event-Driven

Alarm triggers instantly on sensor input with no delay — 1-second loop refresh for display.

🔧

Expandable

Add ESP8266 for Wi-Fi alerts, GSM for SMS, or relay module to control AC appliances.

Components List

🟦

Arduino UNO R3

ATmega328P

×1

🌡️

DHT11 Sensor

Temp + Humidity

×1

🔥

Flame Sensor

IR fire detector

×1

👀

IR Sensor ×2

Motion detection

×2

🖥️

SSD1306 OLED

0.96″ I2C 128×64

×1

🔔

Buzzer

Active 5V

×1

💡

LEDs ×2

+ 220Ω resistors

×2

⚙️

L298N Driver

Motor / relay ctrl

×1

🔌

Jumper Wires

M-to-F assorted

×15+

📦

Install via Sketch → Manage Libraries: Adafruit GFX Library · Adafruit SSD1306 · DHT sensor library by Adafruit.

Wiring Diagram

Full Pin Reference

Module	Module Pin	Arduino Pin	Notes
SSD1306 OLED	SDA	A4	I2C data
SSD1306 OLED	SCL	A5	I2C clock
SSD1306 OLED	VCC	5V	Addr: 0x3C or 0x3D
DHT11	DATA	D10	Add 10kΩ pull-up to 5V
Flame Sensor	OUT	D9	Active LOW (LOW = fire detected)
Buzzer	+	D8	Active buzzer 5V
LED 1 + 220Ω	Anode	D7	IR Sensor 1 zone
LED 2 + 220Ω	Anode	D6	IR Sensor 2 zone
L298N IN1	IN1	D2	Motor A direction A
L298N IN2	IN2	D3	Motor A direction B
L298N IN3	IN3	D4	Motor B direction A
L298N IN4	IN4	D5	Motor B direction B
IR Sensor 1	OUT	D11	Active LOW on motion
IR Sensor 2	OUT	D12	Active LOW on motion

⚠️

Active LOW sensors: Both the flame sensor and IR sensors output LOW when triggered (fire / motion detected). The code checks == LOW for fire and the ternary irSensorValue ? "No" : "Yes" for display. Always test with Serial Monitor first before trusting LED feedback.

How It Works

🌡️ Temperature & Humidity (DHT11 → D10)

The DHT11 single-wire sensor is polled using the Adafruit DHT library. It returns temperature in °C and relative humidity as a float. Both values are printed to the OLED at row 0 and row 10 (y-pixel coordinates). Read failures return NaN — always check with isnan() in production code.

🔥 Flame Detection (Flame Sensor → D9)

The KY-026 / generic flame sensor outputs LOW when it detects IR radiation from fire. The Arduino reads digitalRead(FLAME_SENSOR_PIN) — if LOW, the buzzer is driven HIGH for an instant alarm. The OLED shows "Flame: Yes". When no fire is present the output stays HIGH (normal).

👤 IR Motion Sensing (IR1 → D11, IR2 → D12)

Two IR proximity/motion modules are placed in different rooms or zones. Each outputs LOW when motion is detected. The Arduino immediately turns on the corresponding LED (zone light) using a ternary expression. The OLED shows live motion status for both sensors.

⚙️ Motor / Appliance Control (L298N → D2–D5)

The L298N H-bridge is wired to D2–D5. In the example code both motors run forward continuously. In a real smart home you'd tie motor activation to sensor conditions — for example, run a fan when temperature exceeds a threshold, or activate a door lock motor when an intruder is detected.

📺 OLED Display Layout

Y Pixel	Content	Source
0	Temp: 28.5 C	DHT11
10	Humidity: 65 %	DHT11
20	Flame: No / Yes	Flame sensor (LOW = Yes)
30	IR1: No / Yes	IR Sensor 1 (LOW = Yes)
40	IR2: No / Yes	IR Sensor 2 (LOW = Yes)

Interactive OLED Preview

🖥️ Live OLED Simulator — toggle events below

Temp: 28.5 C

Humidity: 65 %

Flame: No

IR1: No

IR2: No

🔥 Fire Detected

👤 IR Sensor 1 Motion

👥 IR Sensor 2 Motion

🔕 Buzzer: OFF

Full Arduino Code

Arduino / C++

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <DHT.h>

// ── OLED Settings ──
#define SCREEN_WIDTH  128
#define SCREEN_HEIGHT  64
#define OLED_RESET     -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// ── DHT11 ──
#define DHTPIN  10
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);

// ── Sensor & Output Pins ──
#define FLAME_SENSOR_PIN 9   // Active LOW
#define BUZZER_PIN       8
#define LED1_PIN         7   // Zone 1 light
#define LED2_PIN         6   // Zone 2 light
#define IN1_PIN          2   // L298N Motor A
#define IN2_PIN          3
#define IN3_PIN          4   // L298N Motor B
#define IN4_PIN          5
#define IR_SENSOR1_PIN  11   // Active LOW
#define IR_SENSOR2_PIN  12   // Active LOW

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

  // OLED init
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for (;;);   // halt
  }
  display.display();
  delay(2000);
  display.clearDisplay();

  dht.begin();

  pinMode(FLAME_SENSOR_PIN, INPUT);
  pinMode(BUZZER_PIN,  OUTPUT);
  pinMode(LED1_PIN,    OUTPUT);
  pinMode(LED2_PIN,    OUTPUT);
  pinMode(IN1_PIN,     OUTPUT);
  pinMode(IN2_PIN,     OUTPUT);
  pinMode(IN3_PIN,     OUTPUT);
  pinMode(IN4_PIN,     OUTPUT);
  pinMode(IR_SENSOR1_PIN, INPUT);
  pinMode(IR_SENSOR2_PIN, INPUT);
}

void loop() {
  // ── Read sensors ──
  float humidity    = dht.readHumidity();
  float temperature = dht.readTemperature();
  int flameSensor   = digitalRead(FLAME_SENSOR_PIN);
  int irSensor1     = digitalRead(IR_SENSOR1_PIN);
  int irSensor2     = digitalRead(IR_SENSOR2_PIN);

  // ── OLED Display ──
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);

  display.setCursor(0, 0);
  display.print("Temp: ");
  display.print(temperature);
  display.print(" C");

  display.setCursor(0, 10);
  display.print("Humidity: ");
  display.print(humidity);
  display.print(" %");

  display.setCursor(0, 20);
  display.print("Flame: ");
  display.print(flameSensor == LOW ? "YES!" : "No");

  display.setCursor(0, 30);
  display.print("IR1: ");
  display.print(irSensor1 == LOW ? "Motion" : "Clear");

  display.setCursor(0, 40);
  display.print("IR2: ");
  display.print(irSensor2 == LOW ? "Motion" : "Clear");

  display.display();

  // ── Fire Alarm ──
  digitalWrite(BUZZER_PIN, flameSensor == LOW ? HIGH : LOW);

  // ── Smart Lighting (IR-triggered) ──
  digitalWrite(LED1_PIN, irSensor1 == LOW ? HIGH : LOW);
  digitalWrite(LED2_PIN, irSensor2 == LOW ? HIGH : LOW);

  // ── Motor Control (example: forward) ──
  // Change to sensor-conditional for automation
  digitalWrite(IN1_PIN, HIGH);
  digitalWrite(IN2_PIN, LOW);
  digitalWrite(IN3_PIN, HIGH);
  digitalWrite(IN4_PIN, LOW);

  // Serial debug output
  Serial.print("T:"); Serial.print(temperature);
  Serial.print(" H:"); Serial.print(humidity);
  Serial.print(" Flame:"); Serial.print(flameSensor);
  Serial.print(" IR1:"); Serial.print(irSensor1);
  Serial.print(" IR2:"); Serial.println(irSensor2);

  delay(1000);
}

💡

The original code had a small typo: display.begin(SSD1306_I2C_ADDRESS, OLED_RESET) — this has been corrected to display.begin(SSD1306_SWITCHCAPVCC, 0x3C) which matches the current Adafruit SSD1306 library API.

How to Upload the Code

Install Arduino IDE

Download from arduino.cc/en/software and install for your OS.

Connect Arduino UNO via USB

Use a USB-A to USB-B cable. The power LED on the board should light up.

Install Required Libraries

Go to Sketch → Include Library → Manage Libraries. Search and install: Adafruit GFX Library, Adafruit SSD1306, DHT sensor library.

Paste Code & Select Board

Create a new sketch (File → New), paste the code. Go to Tools → Board → Arduino UNO. Go to Tools → Port and select the COM port (Windows) or /dev/tty... (Mac/Linux).

Upload

Click the → Upload button. Wait for "Done uploading". The OLED will display sensor data after 2 seconds.

Monitor & Debug

Open Tools → Serial Monitor, set baud to 9600. You'll see T/H/Flame/IR values every second for debugging.

Online Simulation

▶ Simulate Online — No Hardware Needed

Test flame detection, IR motion and DHT readings in your browser before building the real circuit.

Open Wokwi CirkitDesigner

Simulation Steps

#	Step
1	Open Wokwi, create new Arduino UNO project, paste `diagram.json` above.
2	Paste the code into `sketch.ino`. Install libraries via Wokwi's Library Manager.
3	Click ▶ Start Simulation. The OLED will show live sensor readings.
4	Click the Flame Sensor component — toggle it active. Watch buzzer activate and OLED show "Flame: YES!"
5	Click IR Sensor 1 — toggle active. LED1 (D7) lights up. OLED shows "IR1: Motion".
6	Click IR Sensor 2 — LED2 (D6) lights up. OLED shows "IR2: Motion".
7	Adjust DHT slider temperature above 35°C — observe OLED temp value change. Add conditional motor logic for fan automation.
8	Open Serial Monitor to see real-time debug output from all sensors simultaneously.

Applications & Upgrades

🏠Smart home security

🔥Fire prevention

💡Auto lighting

🏢Office monitoring

🏭Warehouse safety

🏥Hospital alerts

🎓Engineering projects

🌆Smart city demos

Possible Upgrades

📱

GSM Fire Alert

Add SIM800 to send an SMS when flame is detected — instant notification to homeowner anywhere.

📶

ESP8266 Wi-Fi

Push temp/humidity and alerts to Blynk or ThingSpeak for a live IoT dashboard on your phone.

🔌

Relay Module

Replace L298N with a 4-channel relay to control real AC appliances (fans, lights, alarms).

📷

Camera Module

Add ESP32-CAM for live video feed triggered by IR motion detection — full security system.

ROBOTICS

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