Bluetooth Module HC-05

The HC-05 Bluetooth Serial Module is one of the most popular and widely used wireless communication modules in the maker, hobbyist, and engineering communities. Based on the proven Bluetooth Specification v2.0 + EDR (Enhanced Data Rate) standard, it acts as a transparent wireless serial (UART) bridge, allowing any device with a TX/RX serial interface to communicate wirelessly over Bluetooth — essentially turning your Arduino, microcontroller, or computer into a Bluetooth-enabled device.

Unlike the simpler HC-06 which only operates as a Slave, the HC-05 module can be configured as either a Master or a Slave, giving it significantly more flexibility. As a Slave, it can pair with smartphones, tablets, PCs, and PDAs to receive commands and send data. As a Master, it can actively search for and connect to other Bluetooth devices, making it ideal for module-to-module wireless communication in robotics and automation projects.

The module supports a wide range of baud rates from 9600 up to 115200 bps, ensuring compatibility with most serial communication setups. It operates on a +3.3V DC supply with around 50mA current consumption, but all signal pins are 3V–6V tolerant, allowing direct connection to both 3.3V and 5V microcontrollers like Arduino UNO, Mega, and Nano without requiring an additional level shifter. Important: Do not connect the module directly to a computer's RS232 serial port; you must use a USB-to-TTL converter or an Arduino-based interface.

With features like authentication and encryption, the HC-05 ensures secure wireless connections. Its compact dimensions of just 15.2 × 35.7 × 5.6 mm and wide working temperature range of -20°C to +75°C make it suitable for a vast array of applications, including Bluetooth-controlled robots, home automation systems, IoT projects, wireless sensor networks, mobile-controlled devices, data logging, and DIY electronics. It works seamlessly with Arduino, Raspberry Pi, ESP32, STM32, PIC, and most other microcontroller platforms, and can communicate with Android phones, iOS devices, Windows PCs, and Mac computers running a Bluetooth serial terminal app.

Specifications

• Module Name: HC-05 Bluetooth Serial Module
• Bluetooth Protocol: Bluetooth Specification v2.0 + EDR
• Operating Frequency: 2.4 GHz ISM Band
• Modulation: GFSK (Gaussian Frequency Shift Keying)
• Emission Power: ≤ 4 dBm (Class 2)
• Sensitivity: ≤ -84 dBm at 0.1% BER
• Asynchronous Speed: 2.1 Mbps (Max) / 160 kbps
• Synchronous Speed: 1 Mbps / 1 Mbps
• Supported Baud Rates: 9600, 19200, 38400, 57600, 115200 bps
• Security: Authentication and Encryption
• Profiles Supported: Bluetooth Serial Port (SPP)
• Operating Modes: Master / Slave (configurable)
• Power Supply: +3.3V DC, 50 mA
• Signal Pin Tolerance: 3.3V – 6V tolerant
• Working Temperature: -20°C to +75°C
• Dimensions: 15.2 × 35.7 × 5.6 mm
• Default Pairing Code: 1234 or 0000
• Connection: 6-pin interface (VCC, GND, TXD, RXD, KEY, STATE)

Applications

• Arduino Bluetooth Projects – wireless control and data transmission
• Bluetooth-Controlled Robots – control robots via smartphone or PC
• Home Automation Systems – wirelessly control lights, fans, and appliances
• Wireless Sensor Networks – transmit sensor data without cables
• IoT and Smart Devices – add Bluetooth connectivity to embedded systems
• DIY Mobile-Controlled Devices – build apps to control hardware via Android/iOS
• Wireless Data Logging – send logged data from microcontrollers to PCs
• Smart Home Switches – remotely control electrical devices
• Educational STEM Projects – great for teaching wireless communication
• PC to Microcontroller Communication – replace USB cables with wireless link
• Module-to-Module Communication – pair two HC-05s for wireless serial link
• Remote Monitoring Systems – monitor sensors from a phone or computer