Automatic Night Light with IoT Monitoring Using ESP8266 and Blynk

This project uses an ESP8266 and LDR sensor to detect ambient light and automatically control a lamp.

When the surroundings become dark, the ESP8266 turns the light ON through a relay. When enough daylight is available, the light turns OFF.

The current LDR value and light status are also sent to Blynk, where the user can monitor the system and manually override the light when needed.

Components Required

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

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

How It Works

Ambient Light
      |
      v
     LDR
      |
      v
   ESP8266
   /     \
  v       v
Relay    Wi-Fi
  |       |
  v       v
 Light   Blynk

Automatic mode:

Dark environment  -> Light ON
Bright environment -> Light OFF

Manual mode:

Blynk switch -> User controls light directly

Circuit Connections

LDR Sensor to ESP8266

LDR Module	ESP8266
VCC	3.3V
GND	GND
AO	A0

This project uses the analog output (AO) so the ESP8266 can measure different light levels.

Check the supported A0 voltage range of your specific ESP8266 board before connecting an analog signal.

Relay to ESP8266

Relay	ESP8266
IN	D1 / GPIO5
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
LDR Value	V0	Displays light level
Light Status	V1	Shows lamp ON/OFF
Manual Light	V2	Manual lamp control
Automatic Mode	V3	Selects Auto/Manual

Suggested logic:

V3 = 1 -> Automatic Mode
V3 = 0 -> Manual Mode

ESP8266 Code

#define BLYNK_PRINT Serial

#define BLYNK_TEMPLATE_ID "YOUR_TEMPLATE_ID"
#define BLYNK_TEMPLATE_NAME "Automatic Night Light"
#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 LDR_PIN = A0;
const int RELAY_PIN = D1;

const bool RELAY_ACTIVE_LOW = true;

// Adjust this value after testing your LDR.
const int DARK_THRESHOLD = 600;

bool autoMode = true;
bool manualLightRequest = false;
bool lightOn = false;

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 readLight()
{
  int ldrValue = analogRead(LDR_PIN);

  if (autoMode)
  {
    // Change the comparison direction if your LDR module behaves opposite.
    if (ldrValue >= DARK_THRESHOLD)
      setLight(true);
    else
      setLight(false);
  }
  else
  {
    setLight(manualLightRequest);
  }

  if (Blynk.connected())
    Blynk.virtualWrite(V0, ldrValue);

  Serial.print("LDR: ");
  Serial.print(ldrValue);
  Serial.print(" | Mode: ");
  Serial.print(autoMode ? "AUTO" : "MANUAL");
  Serial.print(" | Light: ");
  Serial.println(lightOn ? "ON" : "OFF");
}

BLYNK_WRITE(V2)
{
  manualLightRequest = param.asInt();

  if (!autoMode)
    setLight(manualLightRequest);
}

BLYNK_WRITE(V3)
{
  autoMode = param.asInt();

  if (!autoMode)
    setLight(manualLightRequest);
}

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

  pinMode(RELAY_PIN, OUTPUT);
  setLight(false);

  Blynk.begin(
    BLYNK_AUTH_TOKEN,
    ssid,
    pass
  );

  timer.setInterval(1000L, readLight);

  Serial.println("Automatic Night Light Started");
}

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

Calibration

Open Serial Monitor and observe the LDR reading in:

Bright condition
Dark condition

Then choose a threshold between the two values.

Example:

const int DARK_THRESHOLD = 600;

If your sensor works in the opposite direction, reverse the comparison inside readLight().

Testing

Bright Condition

Expected result:

Light -> OFF
Blynk -> LDR value visible

Dark Condition

Cover the LDR or reduce the surrounding light.

Expected result:

Light -> ON
Blynk -> Light Status = 1

Manual Mode

Set:

Automatic Mode -> OFF

Then use the Manual Light switch in Blynk to turn the lamp ON or OFF.

Common Problems

Light turns ON during daytime

Adjust DARK_THRESHOLD or reverse the comparison logic.

Relay works in reverse

Change:

const bool RELAY_ACTIVE_LOW = true;

to:

const bool RELAY_ACTIVE_LOW = false;

LDR value does not change

Check the A0 connection, sensor power, and Serial Monitor readings.

Blynk does not update

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

Final Result

The completed project provides:

• automatic day/night detection
• automatic light control
• live LDR monitoring
• light-status monitoring
• manual override from Blynk
• Auto/Manual operating modes

Daylight -> Light OFF
Darkness -> Light ON
Blynk -> Monitor + Manual Override

Safety Note

Use a low-voltage DC lamp for 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.