HC-05 Bluetooth Serial Transceiver Module

Classic Bluetooth 2.0 SPP UART module with master/slave AT-command support; standard for wireless serial links with Arduino.

₹199 + 18% GST

SKU: BOTBIT-IOT-06 · Best for: Wireless serial link between Arduino and an Android phone app

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Overview

About HC-05 Bluetooth Serial Transceiver Module.

The HC-05 is the classic Bluetooth serial (SPP) module that has connected countless Arduino projects to phones and other devices. It uses Bluetooth 2.0 EDR and presents a simple UART interface, so any microcontroller with a serial port can send and receive data wirelessly with almost no code.

What sets the HC-05 apart from the cheaper HC-06 is that it can be configured as either master or slave via AT commands, letting it initiate connections as well as accept them. At around Rs 199 it remains a dependable, well-documented choice for wireless serial links, robot control from a phone, and device-to-device communication.

It is beginner-friendly: pair it from an Android phone, open a Bluetooth terminal app, and you have a wireless serial link to your Arduino. Its long track record means troubleshooting help and tutorials are everywhere.

Key features

Why it stands out.

Bluetooth 2.0 EDR with Serial Port Profile (SPP) over UART

Configurable as master OR slave using AT commands (unlike HC-06)

Simple 4-6 pin UART interface (VCC, GND, TX, RX, EN/KEY, STATE)

Onboard 3.3V regulator allowing 3.6-6V supply, with status LED

Default 9600 baud SPP link, configurable baud/name/PIN via AT mode

Works with Android phones and any UART-capable microcontroller

Specifications

Selection facts.

Bluetooth version	Bluetooth 2.0 + EDR
Profile	Serial Port Profile (SPP) over UART
Chipset	CSR BC417 (typical)
Mode	Master / Slave selectable via AT commands
Operating voltage	3.6-6V (module VCC); 3.3V logic level
Default baud rate	9600 (data mode); 38400 in AT mode
Default pairing PIN	1234 or 0000
Range	Up to ~10m (Class 2)
Frequency	2.4GHz ISM band
Pins	6-pin (VCC, GND, TXD, RXD, EN/KEY, STATE)

Applications

Where it is used.

Wireless serial link between Arduino and an Android phone app
Bluetooth-controlled robots and RC cars
Remote control of relays, lights and home gadgets
Wireless sensor data transmission to a phone terminal
Device-to-device communication using two HC-05s (master + slave)
Replacing a wired USB-serial cable with a wireless link

Buying guide

How to choose.

Buy the HC-05 when you need a simple, reliable wireless serial link and the flexibility to act as master or slave. It is perfect for phone-controlled Arduino robots and any project where you would otherwise run a serial cable. If you only ever need slave mode, the cheaper HC-06 also works.

Mind the logic levels: the module's RX pin is 3.3V, so when connecting a 5V Arduino's TX to the module's RX, use a voltage divider (e.g. 1k/2k resistors) or a level shifter. Powering VCC from 5V is fine thanks to the onboard regulator.

For modern low-energy phone apps and lower power use, consider a BLE module (HC-08, HM-10) or an ESP32 instead, since iPhones do not support the HC-05's Classic SPP for custom apps. But for Android and MCU-to-MCU serial links, the HC-05 is a proven, low-cost workhorse.

FAQ

Common questions.

How do I wire the HC-05 to an Arduino?

Connect module VCC to 5V, GND to GND, module TXD to Arduino RX, and Arduino TX to module RXD. Because the module's RX is 3.3V, put a voltage divider or level shifter on the Arduino-TX-to-module-RX line to avoid damage.

How do I enter AT command mode to change settings?

Hold the EN/KEY pin high (or press its button) while powering on; the LED blinks slowly. Then communicate at 38400 baud and send AT commands like AT+NAME, AT+PSWD, AT+ROLE to change the name, PIN, or master/slave role.

What is the default pairing PIN?

The default pairing code is usually 1234 (sometimes 0000). After pairing from your phone's Bluetooth settings, use a serial Bluetooth terminal app to send and receive data over the SPP link at 9600 baud by default.

Does the HC-05 work with iPhones?

Not for custom app development. The HC-05 uses Bluetooth Classic SPP, which Apple restricts, so it will not connect to a normal iPhone app. It works well with Android and with other microcontrollers. For iPhone projects, use a BLE module or ESP32.

What's the difference between HC-05 and HC-06?

The HC-05 can be configured as master or slave, so it can initiate connections; the HC-06 is slave-only. If you need two modules to talk to each other, or want the module to connect out to another device, choose the HC-05.