Arduino Home Automation (Bluetooth)




Posted in TechnologyArduino

Introduction: Arduino Home Automation (Bluetooth)

About: Student studying Electronic and Information Engineering at Imperial College London

Hello All!

Now I don't know about you, but to me it seems an awful lot of effort to get up and flick a switch on an appliance. Let's say a lamp. Wouldn't it be marvellous, I ask myself, if I could just speak to my phone......YES IT WOULD.

So in this 'Instructable' I will attempt to show how to connect an Arduino to your android phone via Bluetooth and then use voice commands to control high voltage devices using relays.

Source code is available at:

Electricity is dangerous so please be careful!!!!

So without further ado let's charge in!

Step 1: Things You Will Need!

Step 2: Relay Test

So first of all we want to check if the relay is switching.

Wire up the relay as shown in the diagram, make sure that the JD-VCC and VCC pins are bridged if you are powering the relay from your arduino. If they are not bridged you will see the LED turning on and off every 2 seconds but there will not be the clicking sound of the relay switching.


#define relay 2    //attaches the relay to pin 2

void setup()
  pinMode(relay, OUTPUT);    //sets the relay as an output
void loop()
  digitalWrite(relay, HIGH);    //relay open
  delay(2000);                  //wait 2 seconds
  digitalWrite(relay, LOW);     //relay closed
  delay(2000);                  //wait 2 seconds

Step 3: Bluetooth Test

First off wire up the circuit as shown above. I have used a breadboard and made one rail positive and one negative. Annoyingly I found that the TXD and RXD pins on the Bluetooth module don't work when connected to the same pins on the arduino itself. The TXD pin on the Bluetooth module I have connected to the RXD pin on the arduino (pin 0), and the RXD pin on the Bluetooth module is connected to the TXD pin on the arduino (pin 1). The Bluetooth Module will run off 3.3v but the relay needs 5v to work, hence I have used 5 volts on the arduino.

Here is the code I have written for this 2 switch relay. As an example I have it controlling a kettle and lamp.

String voice;
#define relay1 2    //Connect relay1 to pin 2
#define relay2 3    //Connect relay2 to pin 3
void setup()
  Serial.begin(9600);            //Set rate for communicating with phone
  pinMode(relay1, OUTPUT);       //Set relay1 as an output
  pinMode(relay2, OUTPUT);       //Set relay2 as an output
  digitalWrite(relay1, LOW);     //Switch relay1 off
  digitalWrite(relay2, LOW);     //Swtich relay2 off
void loop()
  while(Serial.available())    //Check if there are available bytes to read
    delay(10);                 //Delay to make it stable
    char c =;    //Conduct a serial read
    if (c == '#'){
      break;                   //Stop the loop once # is detected after a word
    voice += c;                //Means voice = voice + c
    if (voice.length() >0)
      if(voice == "*switch on"){
      }               //Initiate function switchon if voice is switch on
      else if(voice == "*switch off"){
      }               //Initiate function switchoff if voice is switch off
      else if(voice == "*lamp on"){   
//You can replace 'lamp on' with anything you want...same applies to others
        digitalWrite(relay1, HIGH);
      else if(voice == "*lamp off"){
        digitalWrite(relay1, LOW);
      else if(voice == "*kettle on"){
        digitalWrite(relay2, HIGH);
      else if(voice == "*kettle off"){
        digitalWrite(relay2, LOW);
void switchon()               //Function for turning on relays
  digitalWrite(relay1, HIGH);
  digitalWrite(relay2, HIGH);
void switchoff()              //Function for turning on relays
  digitalWrite(relay1, LOW);
  digitalWrite(relay2, LOW);


You can add any function you want depending on how many devices you have hooked up.
For example you could have a function called 'cinema' which would dim the lights and
turn the TV on. You can have as many as you have pins on your arduino.
For my relay 'LOW' turns off and 'HIGH' turns on
The outline to follow is this:
   void ......()
     digitalWrite(...., LOW/HIGH);
     digitalWrite(...., LOW/HIGH);

When you upload the code to your Arduino, make sure you unplug pins 0 and 1 otherwise you will probably get this error:

avrdude: stk500_getsync(): not in sync: resp=0x00

Now on your android phone download this brilliant app by SimpleLabs!

Connect to the Bluetooth module it will probably be called something like 'HC-06'

The first time it will ask you for a password which is usually 1234.

Once you have connected say the commands you have chosen in the code and hopefully the relay will switch on and off!

Step 4: Adding the Appliances

To quote Brick from Anchorman 'I love Lamp!'

So the first thing to do is find and old lamp or other appliance as we are going to be cutting the lead.

Now remove the outer rubber sleeving making sure not to cut the sleeving of the wires inside, we don't want any live wire showing! Next cut the positive wire (the red one) and remove a few millimetres of sleeving on each end. Insert the exposed wire in the correct ports of the relay as shown in the diagram and pictures above. MAKE SURE THERE IS NO WIRE VISIBLE! For safety wrap the wires in electrical tape, and cover any of the places that could be live on the relay, such as the screws.

I am not responsible for your safety, do this at your own risk!

Once this is done we are ready to power on the lamp and test the system. XD

Step 5: Conclusion

Hope that was informative and you were successful.

Electricity is dangerous so please be careful!!!!

The possibilities for this I feel are endless you can add loads of devices and then create functions in order to control several at once.

Here is a video of the lamp working:

Thank You :)

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2 Questions


I got the problem with the relay that the led is blinking for 2 seconds in which you have mentioned above at the relay test.Also u have said that this problem will occur because of the connection between jd-vcc and vcc. please help me to avoid this problem.

Relay wont turn on when I use the app, is there something wrong with the code?


my relay is not working

Relay wont turn on when I use the app, I followed the instructions step by step & my relay has two led lights on as showed in your picture, any help?

I tried to review the code. the second relay voice command will be found in the codes.

Any one knows that this codes works? Thanks

1 reply

Hi Kiani1,

this really works, this helps me a lot.. just follow his clear instruction.. thanks for Doug Brion..

how to connect relay with light ...i have some doubt about connection between lamp and relay ...i made it nearly 75% ...but because of having dilemma about that i can finish it ..plz help me to complete it....

i getting trouble in connection between relay 12V and light lamp and i need button type app not voice command

may i use HC05, will there any changes occur in the programming....
pls any1 rply fast...its urjnt...
and I'm using 4 chnnl 12V relay board

can i get code for a 8 relay module plz?

Is the power outlet connected to the relay with the lamp? i don't think i'm fully understanding that part.

im telling to amr voice "Включи свет", in programm i wrote "Включи свет", but relay module does nothing, im stock at step#3 can u help me plz


send me the code.

Hope it is working well for you.

Small problem the device it will switch on and off every now again without any reason ???? please help

sir pls give me codes for just copy padt for 2 channel

It not success