Motion Activated Smart Room Light Using ESP8266/ESP32 and Blynk

This project uses a PIR motion sensor with an ESP8266 or ESP32 to automatically control a room light.

When motion is detected, the controller turns the light ON through a relay. If no new motion is detected for a fixed timeout period, the light turns OFF automatically.

The motion status and light status can also be monitored using Blynk.

Components Required

Component	Quantity
ESP8266 NodeMCU or ESP32	1
PIR Motion Sensor	1
Relay Module	1
Low-voltage Bulb / Lamp	1
Suitable Power Supply	1
Breadboard	1
Jumper Wires	As required

For classroom practicals, use a low-voltage DC lamp instead of exposed AC mains wiring.

How It Works

Motion Detected
      |
      v
  PIR Sensor
      |
      v
ESP8266 / ESP32
   /        \
  v          v
Relay       Wi-Fi
  |          |
  v          v
Light       Blynk

Control logic:

Motion detected -> Light ON

No new motion
for timeout period -> Light OFF

Circuit Connections

PIR Sensor

For ESP8266:

PIR	ESP8266
VCC	VIN / suitable supply
GND	GND
OUT	D5 / GPIO14

For ESP32:

PIR	ESP32
VCC	5V / suitable supply
GND	GND
OUT	GPIO27

Relay

For ESP8266:

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

For ESP32:

Relay	ESP32
IN	GPIO26
GND	GND
VCC	According to relay module

Connect the lamp through the relay’s COM and NO terminals.

Blynk Setup

Create these Virtual Pin datastreams:

Datastream	Virtual Pin	Purpose
Motion Status	V0	Shows motion detection
Light Status	V1	Shows whether light is ON/OFF

Suggested values:

0 -> No Motion / Light OFF
1 -> Motion Detected / Light ON

ESP8266 / ESP32 Code

#define BLYNK_PRINT Serial

#define BLYNK_TEMPLATE_ID "YOUR_TEMPLATE_ID"
#define BLYNK_TEMPLATE_NAME "Smart Room Light"
#define BLYNK_AUTH_TOKEN "YOUR_AUTH_TOKEN"

#ifdef ESP8266
  #include <ESP8266WiFi.h>
  #include <BlynkSimpleEsp8266.h>

  const int PIR_PIN = D5;
  const int RELAY_PIN = D1;
#else
  #include <WiFi.h>
  #include <BlynkSimpleEsp32.h>

  const int PIR_PIN = 27;
  const int RELAY_PIN = 26;
#endif

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

const bool RELAY_ACTIVE_LOW = true;

// Light remains ON for 30 seconds after the latest motion.
const unsigned long LIGHT_TIMEOUT = 30000;

bool lightOn = false;
unsigned long lastMotionTime = 0;

BlynkTimer timer;

void setLight(bool state)
{
  lightOn = state;

  if (RELAY_ACTIVE_LOW)
    digitalWrite(RELAY_PIN, state ? LOW : HIGH);
  else
    digitalWrite(RELAY_PIN, state ? HIGH : LOW);

  if (Blynk.connected())
    Blynk.virtualWrite(V1, lightOn ? 1 : 0);
}

void checkMotion()
{
  bool motion = digitalRead(PIR_PIN);

  if (motion)
  {
    lastMotionTime = millis();

    if (!lightOn)
      setLight(true);
  }

  if (lightOn && (millis() - lastMotionTime >= LIGHT_TIMEOUT))
  {
    setLight(false);
  }

  if (Blynk.connected())
    Blynk.virtualWrite(V0, motion ? 1 : 0);

  Serial.print("Motion: ");
  Serial.print(motion ? "YES" : "NO");
  Serial.print(" | Light: ");
  Serial.println(lightOn ? "ON" : "OFF");
}

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

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

  setLight(false);

  Blynk.begin(
    BLYNK_AUTH_TOKEN,
    ssid,
    pass
  );

  timer.setInterval(200L, checkMotion);

  Serial.println("Motion Activated Smart Light Started");
}

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

Adjusting the Timeout

The example keeps the light ON for:

const unsigned long LIGHT_TIMEOUT = 30000;

This means:

30000 ms = 30 seconds

For a 1-minute timeout:

const unsigned long LIGHT_TIMEOUT = 60000;

Every new motion detection resets the timeout.

Testing

Motion Detected

Walk in front of the PIR sensor.

Expected result:

Motion Status -> 1
Light -> ON

No Motion

Stop moving and wait for the timeout.

Expected result:

Motion Status -> 0
Light -> OFF after timeout

Common Problems

PIR always shows motion

Allow the PIR sensor some startup time and adjust its sensitivity/delay controls if available.

Light turns OFF too quickly

Increase LIGHT_TIMEOUT.

Relay works in reverse

Change:

const bool RELAY_ACTIVE_LOW = true;

to:

const bool RELAY_ACTIVE_LOW = false;

Blynk does not update

Check Wi-Fi credentials, Blynk credentials, and Virtual Pin configuration.

Final Result

The completed project provides:

• motion detection
• automatic room-light control
• timeout-based light OFF
• automatic timeout reset when new motion is detected
• Blynk motion monitoring
• Blynk light-status monitoring

Motion -> Light ON
No Motion -> Wait
Timeout Complete -> Light OFF

Safety Note

Use a low-voltage DC lamp for normal student practical work.

If an AC mains lamp is used in a future installation, the mains wiring must be properly enclosed and handled only by a qualified person.