DIY Home Automation: Control LED with Android App and ESP32

Welcome to YaranaIoT Guru’s ESP32 tutorial! In this guide, we’ll show you how to control an LED remotely using an Android app via Bluetooth.

ESP32 is a powerful microcontroller that comes with built-in Bluetooth and Wi-Fi. By using its Bluetooth capabilities, we can create a DIY home automation system to control devices such as LEDs, relays, or small appliances without any internet connection.

🔹 Why Bluetooth Control?

Works offline, no Wi-Fi required
Ideal for home automation in apartments or remote locations
Simple to implement and perfect for learning Bluetooth communication
Can be extended to control multiple devices like fans, motors, and relays

🔹 Project Goals

Set up ESP32 Bluetooth communication
Create a simple Android app (via MIT App Inventor / Blynk / custom)
Control LED ON/OFF remotely
Display status feedback in the app
Lay the foundation for smart home automation projects

🔹 Applications

Control LEDs, relays, and small appliances
Smart lighting in homes or offices
DIY home automation and IoT workshops
Educational Bluetooth communication projects

🔹 Required Components

Component	Quantity	Description
ESP32 Dev Board	1	Microcontroller with Bluetooth
LED	1	Output indicator
220Ω Resistor	1	Current limiting for LED
Breadboard & Jumper Wires	As needed	Circuit setup
USB Cable	1	ESP32 programming
Android Phone	1	App to control LED
Arduino IDE	1	Development environment

🔹 Circuit Overview

Connections:

LED → GPIO2
220Ω Resistor in series → GND
ESP32 powered via USB

This simple hardware setup is enough to test Bluetooth control, and additional LEDs or relays can be added later.

🔹 How It Works

ESP32 starts a Bluetooth server using Serial Bluetooth
Android app connects to ESP32 via Bluetooth
Commands from the app (ON or OFF) are received by ESP32
ESP32 toggles the LED accordingly
Feedback can be sent back to the app to indicate current LED status

🔹 Step 1: Arduino IDE Setup for ESP32

Install the latest Arduino IDE from https://www.arduino.cc/en/software
Add ESP32 board support:
- Go to File → Preferences → Additional Board Manager URLs
- Add: https://dl.espressif.com/dl/package_esp32_index.json
- Go to Tools → Board → Board Manager, search ESP32, and install
Select your ESP32 board:
- Tools → Board → ESP32 Dev Module
- Select the correct COM port

🔹 Step 2: Initialize Bluetooth Serial on ESP32

ESP32 has built-in Bluetooth. We can use BluetoothSerial library to create a Bluetooth server:

#include "BluetoothSerial.h"

BluetoothSerial SerialBT;  // Create Bluetooth Serial object

const int ledPin = 2;  // LED GPIO pin

void setup() {
  Serial.begin(115200);
  pinMode(ledPin, OUTPUT);

  // Start Bluetooth with device name
  SerialBT.begin("ESP32_LED_Control");
  Serial.println("Bluetooth device started, connect from your Android phone");
}

void loop() {
  if (SerialBT.available()) {  // Check if data received
    char command = SerialBT.read();  // Read command

    if (command == '1') {  // Turn LED ON
      digitalWrite(ledPin, HIGH);
      SerialBT.println("LED ON");  // Send feedback
    } else if (command == '0') {  // Turn LED OFF
      digitalWrite(ledPin, LOW);
      SerialBT.println("LED OFF");  // Send feedback
    }
  }
}

✅ This code allows LED control using Bluetooth commands:

Send 1 → LED ON
Send 0 → LED OFF
Feedback sent back to the Android app

🔹 Step 3: Connect Android App to ESP32

You can use any Bluetooth terminal app (like Serial Bluetooth Terminal) or custom Android app:

Open Bluetooth on your phone
Scan for devices → connect to ESP32_LED_Control
Send commands: 1 or 0
LED should turn ON/OFF, and feedback will appear in the app

🔹 Step 4: Optional Enhancements

Multiple LEDs
- Add additional GPIO pins and commands (2 for LED2, 3 for LED3, etc.)
Visual feedback on ESP32
- Use onboard LED (GPIO 2) to show device activity
Serial Monitor Debug
- Monitor commands received and feedback sent

🔹 Step 5: Testing & Troubleshooting

Ensure Bluetooth on ESP32 is started before connecting
Check correct COM port in Arduino IDE
Use simple commands (1 or 0) to avoid issues
Ensure LED + resistor is connected properly

🔹 1. Tools for Creating the Android App

You can use:

MIT App Inventor (Free, web-based) → drag-and-drop interface
- https://appinventor.mit.edu
Blynk App (Optional) → IoT app for controlling devices
- https://blynk.io

For simplicity, we’ll use MIT App Inventor.

🔹 2. Design Your App

App Components:

Component	Purpose
ListPicker	Select Bluetooth device
Button ON	Send command to turn LED ON
Button OFF	Send command to turn LED OFF
Label	Display LED status feedback
BluetoothClient	ESP32 communication

Steps:

Drag ListPicker → Rename to SelectDevice
Drag Two Buttons → Rename LED_ON and LED_OFF
Drag Label → Rename StatusLabel
Add BluetoothClient from Connectivity palette

🔹 3. Blocks Logic in MIT App Inventor

Step 1: Connect to ESP32

When SelectDevice clicked → show list of Bluetooth devices
On selection → call BluetoothClient.Connect

Step 2: Send Commands

When LED_ON.Click
  call BluetoothClient.SendText("1")
  set StatusLabel.Text to "LED ON"

When LED_OFF.Click
  call BluetoothClient.SendText("0")
  set StatusLabel.Text to "LED OFF"

Command "1" → LED ON
Command "0" → LED OFF

Step 3: Receive Feedback (Optional)

ESP32 sends "LED ON" or "LED OFF" over Bluetooth
Display feedback in StatusLabel

When BluetoothClient.BytesReceived
  set StatusLabel.Text to BluetoothClient.ReceiveText()

🔹 4. Real-Time Control

Buttons in the app send immediate commands
Feedback from ESP32 shows current LED status
Works offline, no internet needed

🔹 5. Optional Enhancements

Multiple LEDs / Devices
- Add more buttons → send 2, 3, etc.
RGB LED Control
- Use commands like R255,G0,B0 for color control
Smart Automation
- Schedule LED ON/OFF from the app
Use a Slider
- Control brightness via PWM

🔹 6. Testing & Troubleshooting

Ensure ESP32 Bluetooth is ON and visible
Check app connects to the correct device
Use Serial Monitor to debug commands received
Verify LED pin and resistor connections

🔹 1. Multiple LED Control

You can control several LEDs using unique commands from your Android app.

ESP32 Example Code:

const int led1 = 2;
const int led2 = 4;
const int led3 = 5;

void loop() {
  if (SerialBT.available()) {
    char command = SerialBT.read();
    switch(command) {
      case '1': digitalWrite(led1, HIGH); SerialBT.println("LED1 ON"); break;
      case '2': digitalWrite(led1, LOW); SerialBT.println("LED1 OFF"); break;
      case '3': digitalWrite(led2, HIGH); SerialBT.println("LED2 ON"); break;
      case '4': digitalWrite(led2, LOW); SerialBT.println("LED2 OFF"); break;
      case '5': digitalWrite(led3, HIGH); SerialBT.println("LED3 ON"); break;
      case '6': digitalWrite(led3, LOW); SerialBT.println("LED3 OFF"); break;
    }
  }
}

App sends 1-6 to control 3 LEDs
Feedback confirms LED status in real-time

🔹 2. PWM LED Brightness Control

Control LED brightness using PWM:

const int ledPin = 2;
int brightness = 0;

void loop() {
  if(SerialBT.available()){
    brightness = SerialBT.read();  // Expect 0-255
    analogWrite(ledPin, brightness);
    SerialBT.print("Brightness: ");
    SerialBT.println(brightness);
  }
}

App can use a slider to send 0–255 values
LED brightness changes dynamically

🔹 3. Timer-Based Automation

You can automate LED control with timers:

unsigned long previousMillis = 0;
const long interval = 5000; // 5 seconds

void loop() {
  unsigned long currentMillis = millis();
  if(currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
    digitalWrite(led1, !digitalRead(led1)); // Toggle LED every 5 seconds
  }
}

Perfect for scheduled lighting or night lamps
Can integrate multiple devices

🔹 4. Expand to Full Smart Home Automation

Add Relays to control AC devices
Integrate Sensors: Motion, temperature, humidity
Group multiple ESP32 devices controlled via Bluetooth app
Offline home automation: works without internet

🔹 5. Optional Advanced Features

RGB LED Control: Control color with 3 PWM channels
Scene Management: Turn on multiple LEDs in patterns
Energy Saving Automation: Auto OFF if no activity detected
Voice Assistant Integration: Use Bluetooth + Google Assistant / Alexa

🔹 6. Testing & Deployment

Test LED commands on single and multiple devices
Verify feedback on the app
Test timers and PWM sliders
Expand app UI to control more devices
Ensure Bluetooth connectivity is stable for continuous operation

🔹 Conclusion

By completing this tutorial, you have learned to:

Build an ESP32 Bluetooth server
Control LEDs remotely using an Android app
Add multiple devices and PWM brightness control
Automate devices using timers
Lay the foundation for advanced smart home automation projects

“With ESP32 and Bluetooth, you can create a full-featured DIY home automation system that’s offline, secure, and highly customizable.”
— YaranaIoT Guru

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