IoT Home Intruder Detection System Using ESP8266/ESP32 and Blynk

This project uses a PIR motion sensor and an IR sensor with either an ESP8266 NodeMCU or ESP32 development board to detect movement or entry in a monitored area.

When either sensor is triggered, the controller updates the security status in Blynk and sends a remote intrusion notification to the owner’s phone.

The same blog and program can be used for both controllers. The main differences are the Wi-Fi/Blynk libraries, GPIO pin names, and Arduino IDE board selection, which are explained below.

Important: This is an educational IoT security prototype and should not replace a certified alarm or life-safety security system.

Components Required

Component	Quantity
ESP8266 NodeMCU or ESP32 Dev Board	1
PIR Motion Sensor	1
IR Sensor Module	1
Breadboard	1
Jumper Wires	As required
USB Cable / Suitable Power Supply	1

How It Works

PIR Sensor ----\
                \
                 > ESP8266 / ESP32 ---> Wi-Fi ---> Blynk
                /
IR Sensor -----/

The PIR sensor detects movement inside the monitored area.

The IR sensor can be positioned near a door, window, or entry point to detect an object or person passing through its detection area.

PIR triggered OR IR triggered
            ↓
      Intrusion detected
            ↓
     Security Status = ALERT
            ↓
       Blynk Notification

ESP8266 and ESP32 Differences

The project logic is the same for both boards, but a few hardware and software settings are different.

Item	ESP8266	ESP32
Wi-Fi Library	ESP8266WiFi.h	WiFi.h
Blynk Library	BlynkSimpleEsp8266.h	BlynkSimpleEsp32.h
PIR Pin	D5 / GPIO14	GPIO27
IR Pin	D6 / GPIO12	GPIO25
Board Example	NodeMCU 1.0	ESP32 Dev Module

ESP32 normally uses GPIO numbers directly, such as 27 and 25. Do not use NodeMCU labels such as D5 or D6 on a normal ESP32 board.

Circuit Connections

Option A: ESP8266 NodeMCU

Device	ESP8266
PIR OUT	D5 / GPIO14
IR OUT	D6 / GPIO12
PIR GND	GND
IR GND	GND
PIR VCC	Suitable sensor supply
IR VCC	Suitable sensor supply

Option B: ESP32

Device	ESP32
PIR OUT	GPIO27
IR OUT	GPIO25
PIR GND	GND
IR GND	GND
PIR VCC	Suitable sensor supply
IR VCC	Suitable sensor supply

Always connect the sensor grounds and microcontroller ground together.

Before connecting a sensor output to the ESP8266 or ESP32, verify that the sensor output voltage is safe for the 3.3V GPIO input.

Arduino IDE Setup

For ESP8266

Select:

Tools
→ Board
→ ESP8266 Boards
→ NodeMCU 1.0 (ESP-12E Module)

The program will automatically use:

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

and:

PIR -> D5
IR  -> D6

For ESP32

Select:

Tools
→ Board
→ ESP32 Arduino
→ ESP32 Dev Module

The program will automatically use:

#include <WiFi.h>
#include <BlynkSimpleEsp32.h>

and:

PIR -> GPIO27
IR  -> GPIO25

Install the Blynk library from Arduino IDE Library Manager before compiling.

Blynk Setup

Create these Virtual Pin datastreams:

Datastream	Virtual Pin	Purpose
PIR Motion	V0	Shows motion status
IR Entry	V1	Shows IR sensor status
Security Status	V2	Shows normal or alert state

Suggested values:

0 -> Normal
1 -> Detected / Alert

Also create a Blynk Event with this exact event code:

intruder_alert

Enable notification for the event in the Blynk Console.

Code for Both ESP8266 and ESP32

The program below automatically selects the correct library and GPIO configuration depending on whether it is compiled for ESP8266 or ESP32.

#define BLYNK_PRINT Serial

#define BLYNK_TEMPLATE_ID "YOUR_TEMPLATE_ID"
#define BLYNK_TEMPLATE_NAME "Home Intruder Detection"
#define BLYNK_AUTH_TOKEN "YOUR_AUTH_TOKEN"

#if defined(ESP8266)

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

  const int PIR_PIN = D5;   // GPIO14
  const int IR_PIN  = D6;   // GPIO12

#elif defined(ESP32)

  #include <WiFi.h>
  #include <BlynkSimpleEsp32.h>

  const int PIR_PIN = 27;
  const int IR_PIN  = 25;

#else
  #error "Select an ESP8266 or ESP32 board in Arduino IDE."
#endif

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

// Many IR sensor modules are active LOW.
// Change to false if your sensor behaves in the opposite way.
const bool IR_ACTIVE_LOW = true;

// Prevent continuous notification while a sensor remains triggered.
const unsigned long ALERT_COOLDOWN = 30000;

unsigned long lastAlertTime = 0;

BlynkTimer timer;

bool readIR()
{
  int state = digitalRead(IR_PIN);

  if (IR_ACTIVE_LOW)
    return state == LOW;

  return state == HIGH;
}

void checkSecurity()
{
  bool motionDetected = digitalRead(PIR_PIN) == HIGH;
  bool entryDetected = readIR();

  bool intrusion = motionDetected || entryDetected;

  if (Blynk.connected())
  {
    Blynk.virtualWrite(V0, motionDetected ? 1 : 0);
    Blynk.virtualWrite(V1, entryDetected ? 1 : 0);
    Blynk.virtualWrite(V2, intrusion ? 1 : 0);
  }

  Serial.print("PIR: ");
  Serial.print(motionDetected ? "DETECTED" : "NORMAL");

  Serial.print(" | IR: ");
  Serial.print(entryDetected ? "DETECTED" : "NORMAL");

  Serial.print(" | Security: ");
  Serial.println(intrusion ? "ALERT" : "NORMAL");

  if (intrusion)
  {
    if (lastAlertTime == 0 ||
        millis() - lastAlertTime >= ALERT_COOLDOWN)
    {
      if (Blynk.connected())
      {
        Blynk.logEvent(
          "intruder_alert",
          "Movement or entry detected by the security system."
        );
      }

      lastAlertTime = millis();
    }
  }
}

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

  pinMode(PIR_PIN, INPUT);
  pinMode(IR_PIN, INPUT);

  Blynk.begin(
    BLYNK_AUTH_TOKEN,
    ssid,
    pass
  );

  timer.setInterval(500L, checkSecurity);

  Serial.println();
  Serial.println("IoT Intruder Detection System Started");

#if defined(ESP8266)
  Serial.println("Controller: ESP8266");
#elif defined(ESP32)
  Serial.println("Controller: ESP32");
#endif
}

void loop()
{
  Blynk.run();
  timer.run();
}

Why the Same Code Works on Both Boards

This part:

#if defined(ESP8266)

is compiled only when an ESP8266 board is selected.

This part:

#elif defined(ESP32)

is compiled only when an ESP32 board is selected.

Therefore the correct:

• Wi-Fi library
• Blynk library
• PIR GPIO
• IR GPIO

are selected automatically.

You only need to choose the correct board in Arduino IDE before uploading.

Testing

Test 1: PIR Motion

Move in front of the PIR sensor.

Expected result:

PIR Motion -> 1
Security Status -> ALERT
Blynk notification -> sent

Test 2: IR Entry

Trigger the IR sensor.

Expected result:

IR Entry -> 1
Security Status -> ALERT
Blynk notification -> sent

Test 3: Normal Condition

When neither sensor is triggered:

PIR Motion -> 0
IR Entry -> 0
Security Status -> NORMAL

Notification Cooldown

The program uses:

const unsigned long ALERT_COOLDOWN = 30000;

This means another notification will not be sent for approximately 30 seconds after an alert.

This prevents the owner’s phone from receiving continuous notifications while a person remains in front of the sensor.

Common Problems

PIR Always Shows Motion

PIR sensors may need a short stabilization period after power-up.

Wait for the sensor to stabilize and adjust its sensitivity controls if available.

IR Sensor Works in Reverse

Change:

const bool IR_ACTIVE_LOW = true;

to:

const bool IR_ACTIVE_LOW = false;

ESP32 Compilation Error

Make sure an ESP32 board is selected in Arduino IDE and that the ESP32 board package is installed.

The ESP32 version uses:

#include <WiFi.h>
#include <BlynkSimpleEsp32.h>

ESP8266 Compilation Error

Make sure an ESP8266 NodeMCU board is selected and the ESP8266 board package is installed.

The ESP8266 version uses:

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

Blynk Notification Does Not Arrive

Check:

• Wi-Fi SSID and password
• Blynk Template ID
• Blynk Auth Token
• intruder_alert event code
• event notification settings in Blynk

Final Result

The same project can now be built using either microcontroller:

ESP8266 NodeMCU
       OR
ESP32 Dev Board
       ↓
PIR + IR Sensors
       ↓
Intrusion Detection
       ↓
Blynk Monitoring
       ↓
Remote Notification

Students learn how the same IoT application can be implemented on two different microcontroller platforms while adapting the required libraries and GPIO configuration.

Safety and Privacy Note

Install the system only in locations where you have permission to monitor activity.

For real home or commercial security, use properly designed alarm equipment with reliable backup power and communication methods.