Arduino Bluetooth Basic Tutorial


In this tutorial a serial Bluetooth module is used to create a connection between Arduino Uno and an Android app. You can use any android app to create a serial link between your MCU and Bluetooth.

Arduino listens for commands to light some LED’s or show its status. In addition, a timer interrupt makes it check for temperature via a TMP36 sensor: if temperature is greater than a threshold a LED is lit; every n seconds (where n is a parameter set through the app) a status report is sent to the app. A simple command structure enables the app to send parameters and values to Arduino and the other way round.


  1. Arduino Uno
  2. LED’s
  3. Bluetooth Module HC-05 or HC-06
  4. Resistors-100R or 330R
  5. Android Phone


  1. Arduino IDE
  2. Blynk App (I am using Blynk app for my tutorial but you can use any which perform the same operation as my app does.)

Let’s Start Building

There is only few connection to be made.

Arduino Pins           Bluetooth Pins

RX (Pin 0)     ———->      TX

TX (Pin 1)      ———->      RX

5V                ———->      VCC

GND             ———->      GND

Connect a LED negative to GND of arduino and positive to pin 13 with a resistance valued between 220Ω – 1KΩ. And your done with the circuit

hc-05-LED blink Circuit (2)

Note : Don’t  Connect RX to RX and TX to TX of Bluetooth to arduinoyou will receive no data , Here TX means Transmit and RX means Receive

Note : While uploading your program in your Arduino Uno make sure you plug out RX and TX pins connections from Arduino board otherwise your program will start showing error while uploading.

How Does it Works?

HC 05/06 works on serial the android app is designed sending serial data to the Bluetooth module when certain button is pressed. The Bluetooth module at other end receive the data and send to ardunio through the TX pin of Bluetooth module(RX pin of arduino). The Code fed to arduino check the received data and compares.If received data is 1 the LED turns on turns OFF when received data is 0

Open the serial monitor and watch the received data

How to use the App ?

Watch in video how to pair to Bluetooth module

  • Download the Application from here .
  • Pair your device with HC 05/06 Bluetooth module1) Turn ON HC 05/06 Bluetooth module2) Scan for available device3) Pair to HC 05/06 by entering default password 1234 OR 0000
  • Install  LED application on your android device
  • Open the Application

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