Introduction

In today’s age of automation, controlling devices remotely has become increasingly popular. One of the most common applications is controlling electrical appliances using a smartphone. This can be achieved using a variety of methods, but one of the most cost-effective and versatile solutions is the ESP32 microcontroller paired with a Bluetooth module.

In this blog post, we’ll delve into the process of building a Bluetooth-controlled relay using an ESP32 board. This project allows you to remotely switch on or off any electrical appliance connected to the relay.

What You’ll Need:

• ESP32 Development Board
• Bluetooth Module (HC-05 or similar)
• Relay Module
• Jumper Wires
• Power Supply (5V DC)
• Smartphone with Bluetooth
• Basic Electronics Knowledge

Circuit Diagram:

How It Works:

1. ESP32 Setup:
   • Programming: Use Arduino IDE or other development environments to program the ESP32.
   • Bluetooth Pairing: Pair the ESP32 with your smartphone via Bluetooth.
   • Relay Control: Write code to control the relay’s state based on commands received from the smartphone.
2. Smartphone App:
   • App Development: Create a simple app using platforms like MIT App Inventor or Thunkable to send commands to the ESP32.
   • Command Sending: The app will send specific commands (e.g., “ON” or “OFF”) to the ESP32 via Bluetooth.
3. Relay Operation:
   • Command Reception: The ESP32 receives the command from the smartphone.
   • Relay Actuation: Based on the received command, the ESP32 controls the relay module to switch the connected appliance on or off.

Code Example (Arduino IDE):

C++

#include "BluetoothSerial.h"

String data;
 int fan = 25;
 int bulb = 26;
BluetoothSerial SerialBT;

void setup() {

  pinMode(fan,OUTPUT);
  pinMode(bulb,OUTPUT);
  Serial.begin(9600);
  SerialBT.begin("abhishek");

}

void loop() {
  if (SerialBT.available()) {
   
     String x=SerialBT.readString();
       data=x;
      data.trim();
      Serial.println(data);
       }
    
    if (data=="B"){
     digitalWrite(bulb,HIGH);
    }
    
   if (data=="F"){
     digitalWrite(fan,HIGH);
     }

    if (data=="O"){
   digitalWrite(bulb,LOW);
    digitalWrite(fan,LOW);
    }
    
   if (data=="B1"){
     digitalWrite(bulb,LOW);
     }

     if (data=="F1"){
     digitalWrite(fan,LOW);
  }

}

Applications:

• Home Automation: Control lights, fans, and other appliances.
• Remote Control: Switch on/off devices from anywhere within Bluetooth range.
• Security Systems: Trigger alarms or activate security cameras.
• Industrial Automation: Monitor and control machinery.

Conclusion:

By following this guide, you can create a versatile and affordable Bluetooth-controlled relay system. With a bit of creativity and experimentation, you can extend its functionality to various applications. Remember to prioritize safety when working with electrical components and ensure proper wiring.

Additional Tips:

• Power Supply: Use a stable 5V DC power supply to avoid fluctuations.
• Relay Module: Choose a relay module with appropriate voltage and current ratings for your load.
• Bluetooth Range: Consider the range of your Bluetooth module and use a suitable antenna for better coverage.
• Security: Implement security measures to protect your device from unauthorized access.

By following these tips and the provided code, you can easily build your own ESP32 Bluetooth control relay and enjoy the convenience of remote control.