Smart Home Light Control Using ESP32 and Blynk App

Project Overview

This project demonstrates how to control a light (or any appliance) wirelessly using the Blynk IoT platform and an ESP32 microcontroller. It’s the first step toward building a full-fledged smart home automation system.

So far, I’ve successfully:
✅Controlled a bulb using a relay and ESP32
✅ Used the Blynk app to switch it ON/OFF
✅ Tested reliability and responsiveness
✅ Ready to expand to multiple lights for full room automation

This project aims to:

• Save energy
• Allow centralized control
• Enable remote switching
• Automate operations in the future

Components Used

Software & Tools

Blynk IoT App (Play Store / App Store)

Blynk Web Console (https://blynk.cloud)

Arduino IDE

USB cable (for uploading code)

Blynk Auth Token, Wi-Fi SSID, and password

ESP32 to Relay Connections

ESP32 Pins → Relay Pins
🟢 5V → VCC
🟤 GND → GND
🟠 GPIO 5 → IN

Note:

• You must connect the relay’s VCC and GND to 5V and GND of ESP32
• The IN pin on the relay receives a HIGH or LOW signal from GPIO 5

AC Mains:

• Live (Phase) from wall → Relay COM
• Relay NC → Live to bulb(s)
• Neutral from wall → directly to bulb(s)

Set Up the Blynk Mobile App for Wi-Fi Light Control

1: Install the Blynk IoT App

• On Android: Google Play Store link
• On iPhone: App Store link

Search for “Blynk IoT” — not the old Blynk Legacy app.

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2: Create a Free Blynk Account

1. Open the app after installing
2. Click Sign Up
3. Enter your email and password
4. Click Create Account
5. You’ll be taken to the Blynk dashboard

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3: Create a New Project

1. Tap the “+ Template” button
2. Tap “New Device Template”
3. Fill in:
   • Template Name: Light Control
   • Hardware: Choose ESP32 Dev Board
   • Connection Type: Wi-Fi
4. Click Done

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4: Add a Datastream (Virtual Pin V1)

1. Tap the template you just created
2. Go to Datastreams tab
3. Tap “+ New Datastream” → Choose Virtual Pin
4. Set:
   • Name: Relay Control
   • Virtual Pin: V1
   • Data Type: Integer
   • Min: 0
   • Max: 1
5. Tap Create

This datastream is how your app will communicate with the ESP32.

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5: Create a Device from the Template

1. Go back to home screen
2. Tap “+ Add Device”
3. Choose From Template
4. Select your Light Control template
5. Tap Create Device

Now your phone is linked to this project.

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6: Add a Button Widget to Control Relay

1. Open your device dashboard (from Home)
2. Tap the “Edit” pencil icon (top right)
3. Tap + Widget → Choose Button
4. Drag it onto the canvas

Then tap the button to configure:

• Datastream: Select V1 (Relay Control)
• Mode: Switch (toggle)
• Label it something like “Corridor Light”

📌 This button now sends ON (1) and OFF (0) to ESP32 when pressed.

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7: Get Your Blynk Auth Token

1. From your Blynk Web Dashboard: https://blynk.cloud
   • Log in with same email/password
2. Go to Devices → Click your device
3. You’ll see the Auth Token (copy it)

OR

4. On your phone, open the device → Click Device Info → Copy Auth Token

You’ll paste this token into the Arduino code later.

Arduino Code

Required Libraries in Arduino IDE

Before uploading the code to ESP32, install these libraries:

1. Open Arduino IDE
2. Go to: Tools → Manage Libraries
3. Search & install the following:

✅ WiFi
✅ Blynk (Official)

• Search for: Blynk
• Install: Blynk (by Volodymyr Shymanskyy)
• Version: Blynk 1.0.1 or latest

4. Install ESP32 board support:

• Go to: File → Preferences
• Add this URL in “Additional Board URLs”:
  https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json
• Then go to: Tools → Board → Board Manager
• Search “ESP32”
• Click Install for “esp32 by Espressif Systems”

Now restart Arduino IDE.

Arduino Code

#define BLYNK_TEMPLATE_ID "YourTemplateID"
#define BLYNK_TEMPLATE_NAME "LightControl"
#define BLYNK_AUTH_TOKEN "YourAuthToken"  // ← Paste from Blynk email

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

char ssid[] = "YourWiFiName";         // ← Your Wi-Fi name
char pass[] = "YourWiFiPassword";     // ← Your Wi-Fi password

#define RELAY_PIN 5  // GPIO5 connected to Relay IN

BLYNK_WRITE(V1) {
  int value = param.asInt();  // Get button state
  digitalWrite(RELAY_PIN, value);
}

void setup() {
  Serial.begin(115200);
  pinMode(RELAY_PIN, OUTPUT);
  digitalWrite(RELAY_PIN, LOW);  // Relay off at start
  Blynk.begin(BLYNK_AUTH_TOKEN, ssid, pass);
}

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

📝 Replace:

• BLYNK_AUTH_TOKEN: with your blynk auth token
• ssid & pass: your actual Wi-Fi credentials

Testing

Upload code to ESP32

Open Serial Monitor (115200 baud)

When ESP32 connects to Wi-Fi, your Blynk button will control the relay

Clicking the button will turn ON/OFF the connected bulb

Final Tips for Blynk App

You can log in on another phone with the same Blynk account

Only one user per project in free plan (share login if needed)

You must keep the ESP32 powered at all times

Internet is required for the Blynk app to send the command

Conclusion

Through this project, I was able to build a simple and effective smart lighting system for the corridor lights at Vigyan Ashram. The main goal was to avoid manually switching on and off multiple lights from different switches across the building. By using an ESP32 microcontroller, a relay, and the Blynk mobile app, I created a system where all six lights can now be controlled from one place — a smartphone.

I’ve tested the setup successfully using a breadboard and a single relay. It works reliably, and with a proper power supply and enclosure, it can be permanently installed. The only part left is combining all the light wires into one switch point, which can be done with the help of an electrician.

This project has not only helped solve a real problem at the ashram, but also taught me a lot about basic IoT, working with hardware, and how to bring an idea into reality. I hope this documentation helps anyone who wants to take it further — whether it’s installing it, maintaining it, or even building something more advanced using this as a base.