What are low energy Bluetooth modules? Complete Guide

2021-10-09/ By Admin

low energy Bluetooth modules

Introduction of low energy Bluetooth modules

The Arduino has been widely common in projects where you have to make the communication without wire sensors, controllers and processors. Low energy Bluetooth modules communication is already popular and common in several devices:

  • Smartphones
  •  Tablets
  • Headsets
  • notebooks and others

 It is one of the best options to implement wireless networks with Arduino.

Furthermore, the HC05 and HC06 are the main Bluetooth modules for interfacing with Arduino. In addition to being easy to common and prototype, they are cheap and easily found at any electronics distributor that works with Arduino.

 In this post you will learn a little more about low energy Bluetooth modules, about the HC05 and HC06 modules, and you will learn how to make your Arduino talk to your Smartphone through a Bluetooth network.

Low energy Bluetooth modules networks are the heart of IoT

Bluetooth technology is a protocol for radio communication for personal common, that is, it is a wireless network specification classified as PAN (Personal Area Network). It developed in 1994 by Ericsson as a wireless alternative to the RS-232 protocol. The frequency range common by Bluetooth is 2.4 to 2485 GHz.

A group of companies and development centers called the Bluetooth Special Interest Group is responsible for writing the protocol specifications and releasing updated versions and new features.

Protocols of low energy Bluetooth modules

The protocol comes under low energy Bluetooth modules communication emblem it must comply with all protocol specifications. However, for each Bluetooth version there are qualification tests that a product must pass in order to be certified as a device using Bluetooth communication.

Why adruino is popular as low energy Bluetooth modules?

Arduino has been widely common in projects that require wireless communication of sensors, controllers and processors. Bluetooth communication already popularized and common in various devices such as Smartphones, tablets, Headsets, notebooks and others, is one of the best options for implementing wireless networks with Arduino.

The HC05 and HC06 are the main low energy Bluetooth modules for interfacing with Arduino. In addition to being easy to common and prototype, they are cheap and easily found at any electronics distributor that works with Arduino.

The main versions of the protocol already released are:

The Bluetooth modules available on the market are divided into three classes, depending on the range and maximum power, they are:

  • Bluetooth  classes according to maximum power and range

Currently there are several manufacturers and Bluetooth modules, as well as software and applications available for free that allow the integration of this technology in your electronic projects.

Applications modules HC05 and HC06

The HC-05 low energy Bluetooth modules can work in both master mode (make and accept pairing with other devices) and slave mode (only accept pairing). The HC-06 module can only work in slave mode.

Communication voltage on the low energy Bluetooth modules

It is important to note that the communication voltage on the modules is 3.3V, that is, despite the power supply being 5V, the RX and TX pins common 3.3V signals to communicate. Thus, it is necessary to common a voltage divider to obtain 3.3 V from the 5V output of the Arduino TX.

Among the applications of these two modules are:

  • Transmission of sensor data;
  • Communication between two Arduino boards for data exchange;
  • Furthermore, data transmission to actuators;
  • Also, Arduino communication with Smartphone and other mobile devices;

Now that you know the main concepts behind Bluetooth and the HC-05 and HC-06 modules common with arduino, lets implement our first project using low energy Bluetooth modules communication.

Project Description of low energy Bluetooth modules

In this project we will show you how to interface an Arduino Uno R3 with your Android smartphone. Through the Bluetooth connection between the arduino and the smartphone. We will inform the status of a key monitored by Arduino on the cell phone screen.

Thus, there are three main dimensions of the project:

  • Establish Bluetooth  communication between the Arduino and the cell phone/tablet through an HC-05 or HC-06 module ;
  • Read the status of a key with Arduino and send it to the cell phone to be shown on the screen;
  • Send cell phone commands to Arduino so that it activates and deactivates a led;

    low energy Bluetooth modules 2021

Hardware Aspects of low energy Bluetooth modules

First of all, let's go to our list of components. You will need all of them to make this montage:

  • Arduino UNO R3 + USB cable ;
  • low energy Bluetooth  modules HC-05/HC-06 ;
  • A push button or protoboard retentive switch;
  • Also, Properly sized resistors for a 5V to 3.3V voltage divider;
  • Protoboard ;
  • Moreover, Cables for prototyping ;
  • A Smartphone android Bluetooth  SPP application installed;
  • 1 LED.

If you common an HC-05, the Bluetooth connection can be established either from the module or from the cell phone. If you choose the HC-06, you will have to make the pairing from the cell phone, as this module only operates in slave mode, and does not perform search and pairing operations by itself.

Hardware connections of low energy Bluetooth modules

 For this project we are going to common the HC-05 module, which can be connected either in master or slave mode. The 6 pins of the HC-05 are well identified on the low energy Bluetooth modules and consist of the following:

  • State
  • Moreover, RX
  • TX
  • GND
  • +5V
  • Similarly, EN

The RX and TX pins are the module's communication channels. Furthermore, the module's RX must connect to the arduino's TX through the voltage divider.

Commands for low energy Bluetooth modules

The +5V pin is the power pin and the GND is the power reference, which must be the same as the Arduino. However, EN pin is common to enable the AT command mode of the low energy Bluetooth modules.

AT commands are a set of commands that can be sent to the module through a serial terminal. These commands are common to configure the module and be able to talk to it.


For our assembly, we will use the RX and TX, +5V and GND pins. Now that the assembly is ready and the SPP Bluetooth tools pro app is installed on your mobile device, it's time to program the Arduino to talk to the low energy Bluetooth modules and pair the phone with our hardware.