Android control color RGB LED using HC-05 Bluetooth with Arduino (Part I)

Android control color RGB LED using HC-05 Bluetooth with Arduino (Part I)

This time, I am going to show you how to use Android phone to connect to HC-05 Bluetooth module and Arduino.

Hardware needed:

  • Arduino mini pro * 1
  • HC-05 Bluetooth module * 1
  • RGB LED * 2
  • Jump wires * 10

HC-05 Bluetooth Module wiring as follow:

  • TX connect to Arduino Pin 11(RX)
  • RX connect to Arduino Pin 12(TX)
  • Remember to connect TX on the HC-05 to RX on the Arduino and RX on the HC-05 to TX on the Arduino, so Arduino can receive data correctly.
  • VCC connect to 5V power
  • GND connect to Ground

RGB LED wiring as follow:

Warning: You must connect Arduino mini pro, so your PWM Pin can control LED’s color! For example, Arduino mini pro only has 6 PWM pins and they are 3, 5, 6, 9, 10, and 11, other pins do not have PWM.

Refer to Wikipedia for PWM
  • R connect to Arduino Pin 3
  • Common Anode connect to 5V        
    Note: if you bought common anode LED, then this pin must connect to VCC 5V. If you bought common cathode LED, then this pin must connect to GND
  • G connect to Arduino Pin 5
  • B connect to Arduino Pin 6

Arduino wiring as follow:

  • GND connect to Ground
  • VCC connect to 5V
Look at following chart for the wiring and hardware setup:

If you connect all the parts together, it will look like this:

The completed Arduino code is listed here:

#include <softwareserial.h>
#include <wire.h>//Include libraries: SoftwareSerial & Wire
SoftwareSerial BT(11,12); //Define PIN11 & PIN12 as RX and TX pins

//RGB LED Pins
int PIN_RED = 3;
int PIN_GREEN = 5;
int PIN_BLUE = 6;
//RED LED at Pin 13
int RED_LED = 13;
String RGB = ""; //store RGB code from BT
String RGB_Previous = "255.255.255)"; //preserve previous RGB color for LED switch on/off, default White
String ON = "ON"; //Check if ON command is received
String OFF = "OFF"; //Check if OFF command is received
boolean RGB_Completed = false;

void setup() {
  Serial.begin(9600); //Arduino serial port baud rate:9600
  BT.begin(9600);//My HC-05 module default baud rate is 9600

  pinMode(RED_LED, OUTPUT); 
  //Set pin13 as output for LED, 
  // this LED is on Arduino mini pro, not the RGB LED

void loop() {
  // put your main code here, to run repeatedly: 
  //Read each character from Serial Port(Bluetooth)
    char ReadChar = (char)BT.read();

    // Right parentheses ) indicates complet of the string
    if(ReadChar == ')'){
      RGB_Completed = true;
       RGB += ReadChar;
  //When a command code is received completely with ')' ending character
   //Print out debug info at Serial output window
      Serial.print("     PreRGB:");
          RGB = RGB_Previous; //We only receive 'ON', so get previous RGB color back to turn LED on

      }else if(RGB==OFF){
          RGB = "0.0.0)"; //Send OFF string to turn light off
          //Turn the color according the color code from Bluetooth Serial Port
          RGB_Previous = RGB;     
      //Reset RGB String  

      RGB = "";
      RGB_Completed = false;
  } //end if of check if RGB completed
} // end of loop

void Light_RGB_LED(){

  int SP1 = RGB.indexOf('.');
  int SP2 = RGB.indexOf('.', SP1+1);
  int SP3 = RGB.indexOf('.', SP2+1);
  String R = RGB.substring(0, SP1);
  String G = RGB.substring(SP1+1, SP2);
  String B = RGB.substring(SP2+1, SP3);

  //Print out debug info at Serial output window
  Serial.println( constrain(R.toInt(),0,255));
  Serial.println( constrain(B.toInt(),0,255));
  //Light up the LED with color code

//Because these RGB LED are common anode (Common positive)
//So we need to take 255 to minus R,G,B value to get correct RGB color code
  analogWrite(PIN_RED,  (255-R.toInt()));
  analogWrite(PIN_GREEN, (255-G.toInt()));
  analogWrite(PIN_BLUE,  (255-B.toInt()));


You need to go to Google Play Store and download "BT LED Controller"; you need to use it with this tutorial. You may download APP here

This is what Android BT LED Controller App can do:

1.     Connect to Bluetooth
2.     Wireless control LED on/off
3.     Wireless control LED to change the color

The screen of Android APP is below and you can use it easily:

  • Click the ”BT-List” button (The red dot next to it means BT not connected)

  • Next select the Bluetooth you want to connect from the list, after it connected successfully, the APP will jump back to the main screen

  • On the main screen says BT connected (The green dot indicates BT connected)
  • Click LED on / LED off button, you can turn LED on/off
  • Click any color block on the App, the RGB color code will be sent to HC-05 and HC-05 will send the RGB color code to Arduino. RGB code is composed 3 numbers of 1~255 with “)” as the ending character, such as “255.20.10)”. Arduino receives a character at a time from the serial port and it combines all characters together. When a “)” is received, the RGB code is completed.
  • Arduino then decompose RGB code string into 3 sets of numbers for R, G, B, and then send the code to RGB LED to display the color indicated.
  • As shown below (RGB code 255.51.255 will make RGB LED to show magenta)
  • Click Disconnect to cut the connection between Android and Arduino.

You also learn how to use this APP by watching the video below:

Android 藍芽連線控制彩色 RGB LED (Part I)

本次教學將如何用 Android 程式以藍芽方式連線到HC-05藍芽模組及Arduino.

  1. Arduino mini pro * 1
  2. HC-05 Bluetooth module * 1
  3. RGB LED * 2
  4. Jump wires * 10

HC-05 Module 接法:

  • TX接到 Arduino Pin 11 (RX)
  • RX接到 Arduino Pin 12 (TX)
    就是發射端與接收端要反接到Arduino, 這樣 Arduino 才收的到訊號
  • VCC 接 5V 電源
  • GND 接地


注意: 一定要接 Arduino mini pro  有 PWM 的腳位才能控制LED的顏色!
以 Arduino mini pro PWM 腳位只有 : 3, 5, 6, 9, 10, and 11,其它沒有 PWM.
  • R 接 Arduino Pin 3
  • Common Anode 接 5V
    (我買的是共陽的 LED, 所以這支腳要接 5V,若你買的是共陰的 Cathode, 則要接 GND)
  • G  接 Arduino Pin 5
  • B 接 Arduino Pin 6

Arduino 接法:

  • GND 接地
  • VCC 接 5V
 Arduino, HC-05 module, & RGB LED 電路圖如下:


Arduino 的程式碼請參考上方!

請由 Google Play Store 下載 BT_LED_Controller V1.0 與這個程式搭配這個教學使用.
由此下載 APP
Android BT_LED_Controller V1.0 有下列功能:

  1. 藍芽連線
  2. 無線遙控 LED 開/關
  3. 無線遙控 LED 改變它的顏色

Android App 畫面如下,使用方法很簡單:
  • 點選上方 "BT-LIST" 鈕 (右方的小紅點表示藍芽尚未連線)

  • 接下來點選你要搭配的藍芽 HC-05 模組,連線完成後,程式會跳回到主畫面

      • 主畫面上顯示 BT Connected (小綠點表示已藍芽連線成功)
      • 按下 LED Turn on / LED Turn Off 可以打開/關閉 LED

      • 點選 App 上的任一顏色方塊,App 會把那個方塊的 RGB code 送到 HC-05,再由 HC-05傳給 Arduino,  RGB code 由3組 1~255的數字組成, 再加上右括號尚作是結束符號, 如 255.20.10), 當 Arduino 由 serial port 一個字元一個字元接收, 一直收到 ) 時,才當作是一個完整的 RGB code。
      • Arduino 把 RGB code 字串解析後,再送給 RGB LED 顯示指定的顏色
        如下圖 (RGB code: 255.51.255 會傳到到 Arduino 顯示出紫紅色)
      • 點選 Disconnect 則關閉 Android 和 Arduino 的連線
      • 完成測試