Project Hub /IoT & Connected Devices/Telemetry & Remote Logging/Arduino to Arduino Bluetooth Communication using Master Slave Configuration

Intermediate

ARDUINO

₹500 – ₹1,500

3 – 6 Hours

Complete Kit

Arduino to Arduino Bluetooth Communication using Master Slave Configuration

Learn how to establish wireless communication between two Arduino boards using HC-05 Bluetooth modules configured in Master and Slave modes.

Originally published on CircuitDigest

View original tutorial

Parts You'll Need

This project is sourced from another site, not written by us — this list is our best match of their components against what we stock, not a verified bill of materials. Always check the original blog (linked above) for the actual parts list before buying.

Arduino UNO R3 Board (Compatible) – ATmega328P Microcontroller with USB Cable Rs. 999.00
Arduino Nano C Type V3 ATMEGA328 with Soldered Headers Rs. 608.00
ESP32 WiFi+Bluetooth CP2102 Development Board Rs. 520.00
MB102 Adjustable Breadboard Power Supply Module (3.3V & 5V) for Arduino & Raspberry Pi Rs. 139.00
Jumper Wire 10 Pin Male To Male 20cm Rs. 45.00
10pcs - 220 ohm 1/4 W Resistor Set Rs. 39.00
400 Points Mini Solderless Prototype PCB Breadboard High Quality Rs. 89.00
Jumper Wire 10 Pin Male To Female 20cm Rs. 45.00

Selected: Rs. 0.00

This list includes a generic resistor set as a placeholder — it is not matched to the exact value or part number this circuit needs. The correct one is specified on the original source page linked above; check it before buying.

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How It Works

This project establishes a wireless serial link between two Arduino boards (such as an Arduino Uno and an Arduino Nano) using a pair of HC-05 Bluetooth modules configured respectively as a Master and a Slave. The microcontroller communicates with its local Bluetooth module via asynchronous serial communication (UART), using transmit (TX) and receive (RX) pins. Because Arduino boards operate on 5V logic while HC-05 modules operate on 3.3V logic, a voltage divider circuit made from 1kΩ and 2.2kΩ resistors is implemented on the Arduino-to-HC-05 RX data line to safely step down the voltage. Once powered, the Master HC-05 module actively searches for and pairs with the specific MAC address of the Slave HC-05 module. After the connection is successfully established, any data sent from the first Arduino through its serial port is transmitted wirelessly over the 2.4GHz Bluetooth radio frequency by the Master module. The Slave module receives this data stream and passes it along to the second Arduino via its own serial RX pin, allowing the two microcontrollers to exchange sensor readings, control commands, or telemetry logs in real time without being physically tethered by USB or jumper cables.

Why Build This

Design and deploy wireless sensor networks for distributed multi-microcontroller data acquisition.

Implement cable-free industrial automation and remote telemetry systems using standard UART protocols.

Master advanced peripheral configuration by pairing and linking discrete Bluetooth modules in Master-Slave topologies.

Real-World Application

Wireless sensor networks, remote telemetry, multi-microcontroller data logging, and cable-free industrial automation.

Skills You'll Learn

UART serial communication

Bluetooth module AT command configuration

voltage level shifting

master-slave network topologies

wireless telemetry data logging

Safety Precautions

Ensure correct voltage division using resistors to reduce the 5V Arduino output to 3.3V on the HC-05 RX pin to prevent damaging the module.

Technology Tags

ARDUINO

BLUETOOTH

HC-05

WIRELESS COMMUNICATION

MASTER-SLAVE

AT COMMANDS

SOFTWARESERIAL

Frequently Asked Questions

Why is a voltage divider required between the Arduino and the HC-05 module?

Arduinos typically use 5V logic levels, whereas the HC-05 Bluetooth module's RX pin is only rated for 3.3V. Using 1kΩ and 2.2kΩ resistors drops the 5V output down to a safe 3.3V to prevent permanent damage to the module.

Can I use two HC-05 modules right out of the box without changing settings?

No. By default, most HC-05 modules are manufactured in Slave mode. To create a working link, one module must be manually reconfigured into Master mode using AT commands so it knows which Slave device to search for and connect to.

Can I substitute an Arduino Uno for the Arduino Nano in this setup?

Yes, any combination of Arduino boards that feature hardware or software serial capabilities (such as the Arduino Uno R3 and Arduino Nano) can be used, provided the wiring and voltage division are correctly replicated.

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This page is part of Kitkraft's Project Hub — a curated collection of electronics & robotics projects gathered from the maker community to help students and hobbyists discover and learn to build. Kitkraft does not claim authorship of the original project, and makes no representation as to the accuracy, completeness or safety of third-party source material. The summary and "How It Works" explanation above are AI-generated, rewritten with reference to the original tutorial — not a reproduction of it. Full credit and a direct link to the original source are provided above. If you're the original creator and have a concern about how your work is represented here, please contact us and we'll address it promptly.

Kitkraft Project Hub — curated from the maker community, credited at the source.

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