📡 Bluetooth Based Smart Home Automation System

A low-cost, wireless home automation system using Arduino UNO and HC-05 Bluetooth module to control household appliances via a smartphone.

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📋 Table of Contents

• Project Overview
• Block Diagram
• Components Used
• Circuit Connections
• Working Principle
• Features
• Arduino Code
• Bluetooth Commands
• How to Use
• Project Structure
• Future Scope
• Applications
• Resume Summary
• License

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📌 Project Overview

This mini project demonstrates wireless control of home appliances using the Bluetooth protocol. A smartphone communicates with an HC-05 Bluetooth module interfaced with an Arduino UNO microcontroller. Based on the received character commands, the Arduino toggles a 4-channel relay module that switches connected electrical appliances (bulbs, fans, etc.) ON or OFF.

This project is designed to be affordable, scalable, and easy to implement, making it an ideal starting point for home automation using embedded systems.

Parameter	Details
Microcontroller	Arduino UNO (ATmega328P)
Communication	Bluetooth (HC-05 Module)
Control Unit	4-Channel Relay Module (5V)
Frequency	2.4 GHz ISM Band
Range	Up to 10 metres (Class 2)
Power Supply	5V DC (via USB or adapter)
IDE	Arduino IDE 2.x
Language	C/C++ (Arduino Framework)

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🔷 Block Diagram

+-------------+        Bluetooth         +------------------+
| Smartphone  |  ──────────────────────> |  HC-05 Module    |
| (Control    |       (2.4 GHz)          |  (Slave Mode)    |
|   App)      |                          +--------+---------+
+-------------+                                   |
                                              UART (RX/TX)
                                                   |
                                          +--------v---------+
                                          |   Arduino UNO    |
                                          |  (ATmega328P)    |
                                          +--------+---------+
                                                   |
                                          Digital Output Pins
                                    ______|_____|_____|______
                                   |      |     |     |      |
                                 Relay1 Relay2 Relay3 Relay4
                                   |      |     |     |      |
                                 Bulb1  Bulb2  Fan1  Fan2

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🔩 Components Used

S.No	Component	Quantity	Approximate Cost (INR)
1	Arduino UNO (ATmega328P)	1	₹450 – ₹600
2	HC-05 Bluetooth Module	1	₹180 – ₹250
3	4-Channel Relay Module (5V)	1	₹120 – ₹180
4	Bulbs / CFLs / Fans	4	₹80 – ₹150 each
5	Jumper Wires (M-M, M-F)	1 Set	₹50 – ₹80
6	Breadboard	1	₹60 – ₹100
7	USB Cable (Type-B)	1	₹50 – ₹80
8	5V Power Supply / Adapter	1	₹100 – ₹200
	Estimated Total		₹1,090 – ₹1,640

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🔌 Circuit Connections

HC-05 to Arduino UNO

HC-05 Pin	Arduino Pin
VCC	5V
GND	GND
TXD	Pin 10 (RX)
RXD	Pin 11 (TX)

⚠️ Note: HC-05 RXD operates at 3.3V logic. Use a voltage divider (1kΩ + 2kΩ) on the Arduino TX → HC-05 RX line to prevent module damage.

4-Channel Relay to Arduino UNO

Relay Pin	Arduino Pin
IN1	Pin 2
IN2	Pin 3
IN3	Pin 4
IN4	Pin 5
VCC	5V
GND	GND

The relay module is active-LOW. Sending LOW (0V) to an IN pin energises the relay and closes the circuit.

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⚙️ Working Principle

1. The smartphone runs a Bluetooth terminal application (e.g., Serial Bluetooth Terminal on Android).
2. The app pairs with the HC-05 module (default PIN: 1234 or 0000).
3. Single-character commands are sent from the app to the HC-05 module over the 2.4 GHz ISM band.
4. HC-05 forwards these commands to the Arduino via the UART serial interface (SoftwareSerial on pins 10 & 11).
5. The Arduino reads the incoming character and toggles the corresponding relay channel.
6. The relay acts as an electrically controlled switch, connecting or disconnecting the AC supply to the appliance.

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✨ Features

• ✅ Wireless control up to 10 metres range
• ✅ Controls up to 4 independent appliances
• ✅ Works with any Android Bluetooth terminal app
• ✅ No internet or Wi-Fi required
• ✅ Low-cost implementation (~₹1,200)
• ✅ Status feedback via Serial Monitor
• ✅ Easy to extend to 8-channel or 16-channel relay boards
• ✅ Safe for 220V AC mains appliances through relay isolation

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💻 Arduino Code

The main source code is located at code/smart_home_automation.ino.

Command mapping:

Command Sent	Action
1	Appliance 1 ON
2	Appliance 2 ON
3	Appliance 3 ON
4	Appliance 4 ON
5	Appliance 1 OFF
6	Appliance 2 OFF
7	Appliance 3 OFF
8	Appliance 4 OFF
A	ALL Appliances ON
Z	ALL Appliances OFF

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📱 Bluetooth Commands

Full command reference is available in code/bluetooth_commands.md.

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🚀 How to Use

Step 1 – Hardware Setup

1. Assemble the circuit as per the wiring diagram in circuit-diagram/wiring_connections.md.
2. Connect the relay module outputs to AC appliances through proper insulated wiring.

Step 2 – Upload the Code

1. Install Arduino IDE.
2. Open code/smart_home_automation.ino in Arduino IDE.
3. Connect Arduino UNO to your PC via USB.
4. Select Board: Arduino UNO and correct COM Port.
5. Click Upload.

Step 3 – Pair the Bluetooth Module

1. Power on the circuit.
2. On your Android phone, go to Settings → Bluetooth → Scan.
3. Pair with HC-05 (PIN: 1234).

Step 4 – Control Appliances

1. Open Serial Bluetooth Terminal (or any Bluetooth terminal app).
2. Connect to HC-05.
3. Send commands (1–8, A, Z) to control appliances.

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📁 Project Structure

Bluetooth-Smart-Home-Automation/
│
├── README.md                        ← Project overview (this file)
├── LICENSE                          ← MIT License
│
├── circuit-diagram/
│   ├── circuit.png                  ← Schematic diagram
│   ├── block_diagram.png            ← System block diagram
│   └── wiring_connections.md        ← Detailed pin connections
│
├── code/
│   ├── smart_home_automation.ino    ← Main Arduino source code
│   ├── bluetooth_commands.md        ← Command reference sheet
│   └── code_explanation.md         ← Line-by-line code walkthrough
│
├── images/
│   ├── setup.jpg                    ← Hardware setup photo
│   ├── working.jpg                  ← Live working photo
│   ├── components.jpg               ← All components laid out
│   └── output_demo.jpg              ← Output demonstration
│
├── report/
│   └── mini_project_report.pdf      ← Full project report (B.Tech)
│
├── docs/
│   ├── abstract.md
│   ├── introduction.md
│   ├── objectives.md
│   ├── methodology.md
│   ├── working_principle.md
│   ├── experimental_procedure.md
│   ├── pin_configuration.md
│   ├── components.md
│   ├── advantages.md
│   ├── applications.md
│   ├── future_scope.md
│   └── conclusion.md
│
├── videos/
│   └── demo_link.txt                ← Link to demo video
│
└── requirements/
    └── required_components.txt      ← Bill of Materials

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🔭 Future Scope

• 🌐 Wi-Fi Integration – Replace HC-05 with ESP8266/ESP32 for internet-based control
• 🗣️ Voice Control – Integrate Google Assistant or Amazon Alexa
• 📱 Custom Android App – Build a dedicated MIT App Inventor / Flutter control app
• 📊 Energy Monitoring – Add ACS712 current sensor to track power consumption
• 🔐 Security – Add PIN-based authentication for Bluetooth pairing
• ⏰ Scheduling – Add RTC module (DS3231) to automate appliance timers
• 🌡️ Smart Sensing – Integrate PIR / temperature sensors for automatic control

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🏠 Applications

• Residential home automation
• Hostel and dormitory room control
• Office lighting automation
• Industrial equipment switching (low-voltage signalling)
• Prototype for larger IoT-based smart systems

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📄 Resume Summary

Bluetooth Based Smart Home Automation System | B.Tech Mini Project – ECE
Designed and implemented a wireless home automation system using Arduino UNO and HC-05 Bluetooth module. Interfaced a 4-channel relay module to control AC appliances via smartphone. Programmed in C/C++ using the Arduino framework with SoftwareSerial library. Demonstrated wireless communication over 2.4 GHz Bluetooth with a range of up to 10 metres.

Skills demonstrated: Embedded C, Arduino IDE, UART communication, relay interfacing, circuit design, hardware debugging

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🏷️ GitHub Topics

arduino  bluetooth  hc-05  relay  home-automation  embedded-systems
arduino-uno  iot  smart-home  softwareserial  ece-project  btech-project
mini-project  wireless-control  uart  c-cpp  microcontroller

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📜 License

This project is licensed under the MIT License – see the LICENSE file for details.

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🙋 Author

B.Tech ECE Student
Department of Electronics and Communication Engineering

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