Using HC-05 Bluetooth Module - Control an LED with an Android phone [ARDUINO]

So, you saw how we used a PIR motion sensor to create a simple motion detecting mechanism within a short span of time. We also saw how to use simple sensors like HC-SR04, HC-SR501 and DHT11. We even controlled LCD and 7-segment display. But, the major inconvenience was - wiring. Just think of it. You make a motion detector, wire up all the components and then what, connect an LED in your room with around 5 to 6 meters to the setup on your staircase? Oh, hell no! In situations like these, the word: "wireless" comes to our mind, and why shouldn't it? Everything around us is more or less, wireless! Our phones, wifi, etc are major examples. You can even lock your car with a tiny wireless remote. We all know stuff like these.

But, to make your arduino project wireless, you have a lot of technologies at your disposal.
Major wireless techniques, that could be used with arduino projects and let you go wireless:
1. Bluetooth
2. FM transceiver
3. Infrared
4. WiFi

Now, let's briefly discuss these technologies:

1. Bluetooth: 

    Simple, elegant, cheap. Has a pretty good range. Less complicated. Easy to connect. A large spectrum of devices use Bluetooth.

2. FM transceiver:

    Excessively cheap. Pretty great range (90 meters). Requires two standalone arduinos(One for receiving, One for transferring data)
    But, huge chances for interference. Legal issues.

3. Infrared:

   Cheap, short range. Less effective, not secure. Can't send different signals.

4. WiFi:

   A bit expensive. Good range. A bit complex. But, convenient.

Don't worry, slowly but steadily, we'll use all of those, but first, lemme take a selfie! Just, kidding.
But first, let's use bluetooth in our projects.

Let's know the basics:

Pinouts of my HC-05 module

HC-05 module is an easy to use Bluetooth SPP (Serial Port Protocol) module, designed for
transparent wireless serial connection setup.
Serial port Bluetooth module is fully qualified Bluetooth V2.0+EDR (Enhanced Data Rate) 3Mbps
Modulation with complete 2.4GHz radio transceiver and baseband. It uses CSR Bluecore
04-External single chip Bluetooth system with CMOS technology and with AFH(Adaptive
Frequency Hopping Feature). It has the footprint as small as 12.7mmx27mm. Hope it will simplify
your overall design/development cycle.

The HC-06 module is similar in design to the HC-05, but, it can't act as a master device. The HC-05 can behave both as master and slave.

We'll also use this library: Software serial

What this project does?
Demonstates the simple use of HC-05 bluetooth module. With this, you can simply use your android phone to turn an LED ON or OFF, via an android app.

Materials Required:

Click for clarity

1. An HC-05 or HC-06 Bluetooth Module
2. Arduino
3. Jumpers
4. One LED
5. One 220OHM resistor for LED
6. Breadboard
7. and of course, a PC with Arduino IDE installed.
8. Oh yes, an Android phone too!


Procedure:

1. Upload the sketch given below.
2. Then remove the arduino and wire up the components as shown below.

NOTE: PLEASE REMEMBER TO CONNECT THE RX OF HC-05 TO SOFT TX[PIN 11] ON ARDUINO AND VICE VERSA.

3. Power on the Arduino.
4. Download and install the app on your phone: [DOWNLOAD THE APP]
5. Turn on the BLUETOOTH in your phone and tap on Scan.
6. You'll notice your HC-05 or HC-06 name on the list of found devices.
7. Tap on the module's name and pair with it. The default pairing code is 1234 or 0000
8. Now, open the HC05_ARDUINO_LED app.
9. Tap :"Connect to Module"
10. You'll get a screen, where the nearby bluetooth devices' names and addresses will be listed.
11. Tap on the device(HC-05 or HC-06)
12. You'll notice that the led on HC-05 will stop blinking randomly and will blink once in every 4 seconds
13. Now, tap on ON to turn on the LED or tap on OFF to turn it off.
14. Done. Simple. :)

Sketch:

/* 
 * ON PUBLIC DOMAIN
 * Author         : Nitish Dash
 * Name           : LED control with HC-05 and android
 * Created        : 1/10/2015
 * Webpage        : http://goo.gl/u2d0Cv
 * Author Email   : nitishdash95@gmail.com
 * Author Website : http://www.nitishdash.com/
 **** DONOT COPY AND PLAGIARATE WITHOUT THE AUTHOR'S PERMISSIONS ****
 */

#include 
SoftwareSerial electro(10, 11); // RX, TX
int l1=12; 
int flag=0;
String bdata="";
char c=' ';

void setup()
{
  electro.begin(9600);
  pinMode(l1, OUTPUT);
}
void loop()
{
  while (electro.available()){
    c=electro.read();
    bdata+=c;
if (bdata=="on")
    {
      flag=1;
    }
    if (bdata=="off")
    {
      flag=0;
    }  
}
  digitalWrite(l1, flag);
  delay(500);
  bdata="";
}

NOTE: Please remove the line 42 before uploading the sketch.

How this works (Algorithm):

We used Software Serial library, which converts any digital pins into serial pins RX and TX. That means, your 0 and 1 digital pins are free to be used. Now, I created the android app in such a way that, when you press the ON button, it will send a string value "on" to the HC-05 module. Same is the case of "off" button. Now, using if-else, I turn the LED on and off. At the end, the string is cleared for next iteration. 

Video:
Coming soon.....


Downloads:
1. sketch.ino
2. HC-05 datasheet
3. HC-06 datasheet
4. HC-05_ARDUINO_LED  app 

Something for you!

Try these ideas to enhance your knowledge and test yourself:

1. Replace the LED with a buzzer.
2. Try adding 3 different colored LEDs.

In the upcoming tutorials, we'll get more advanced and shift up our level! The HC-05 is a wonderfully good device, which will surprise you till the end. Just think of the possibilities! Controlling any device in your home, for example, you could easily automate your TV, A/C, XBOX, etc from the comfort of your couch!