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Home Automation using Bluetooth and Mobile App

Ligo George

Contents

Technology is a never ending process. To be able to design a product using the current technology that will be beneficial to the lives of others is a huge contribution to the community.

Generally in today’s modern world human beings are addicted to using modern equipment. So here we can perform home automation by using an Android App and Bluetooth as a wireless communication medium. Home automation not only refers to reduce human efforts but also energy efficiency and time saving.  Home Automation System has been designed using PIC 16F876A microcontroller and HC-06 bluetooth module. It can control a number of home appliances like lights, fans, bulbs and many more using electro-mechanical relay.

Components Required

Hardware

Circuit Diagram

Home Automation using Bluetooth and Mobile App – Circuit Diagram

Hope you can easily understand the circuit. PIC 16F876A is the heart of this circuit. Two voltage regulators are used in this circuit. 7812 for providing 12V supply for the operation of relays and 7805 for the operation of the rest of the circuit. ULN2803 driver IC is used to driver relays. HC-05 is operating at 3.3V, but the module which we are using here is having built in 3.3V regulator. Thus we can provider 5V to it. R11 (4.7K) and R12 (10K) are used to reduce the 5V TX output of PIC microcontroller to 3.3V as HC-05 module inputs are not 5V tolerant. 3.3V TX output of HC-05 is directly connected to the RX input of PIC microcontroller. As 3.3V will be taken as LOGIC HIGH as per 5V TTL specifications.

HC-05 Bluetooth Transceiver Module

HC-05 Bluetooth Transceiver Module
Pin Name Details
KEY AT Command Mode
VCC 3.3V to 5V
GND Ground
TXD Serial Port Transmit Data
RXD Serial Port Receive Data
STATE Not Connected

Software

PIC Microcontroller Program

int cnt,t,st;
void interrupt()  
{
  if(UART1_Data_Ready())      // If data received
  {
    RCIE_bit = 0;
    if(cnt == 0)              //If it is the first character
    {
      if(UART1_Read() == 'A') // Check whether it is the valid character
      {
        cnt = 1;
        TMR1L = 0;
        TMR1H = 0;
        TMR1ON_bit = 1;       // Start the timer for timing out
      }
    }
    else if(cnt == 1)         // If second character
    {
      t = UART1_Read() - 48;
      cnt++;
    }
    else if(cnt == 2)         // If third character
    {
      st = UART1_Read() - 48;
      cnt++;
    }
    else if(cnt >= 3)         // Clear if count is greater than 2
    {
      cnt = 0;
      TMR1ON_bit = 0;
      TMR1L = 0;
      TMR1H = 0;
    }
    RCIE_bit = 1;
  }
  else if(TMR1IF_bit == 1)   // UART Timeout
  {
    TMR1IE_bit = 0;
    TMR1IF_bit = 0;
    TMR1H = 0;
    TMR1L = 0;
    cnt = 0;
    TMR1IE_bit = 1;
  }
}

void main()
{
  TRISB = 0x00;   // Make all PORTB pins output
  PORTB = 0x00;   // Turn off All relays

  GIE_bit = 1;    // Global Interrupt Enable
  PEIE_bit = 1;   // Peripheral Interrupt Enable
  RCIE_bit = 1;   // UART Interrupt Enable
  T1CON = 0x30;   // Configure Timer 1
  TMR1IE_bit = 1; // Enable Timer1 Interrupt

  cnt = 0;
  UART1_Init(9600);

  while(1)  
  {
    if(st == 1)    // Relay Status Flag is 1
    {
      if(t != 0)   // t = 0, to control all realys, master switch
        PORTB = PORTB | (0xFF & (1<<(t-1))); // Turn ON individual relay
      else
        PORTB = 0xFF; // Turn ON All
    }
    else           // Relay status flag is 0
    {
      if(t != 0)   // t = 0, to control all realys, master switch
        PORTB = PORTB & (0xFF & ~(1<<(t-1))); // Turn OFF individual relay
      else
        PORTB = 0; // Turn OFF all
    }
  }
}

Hope you can easily understand the program as it is well commented. The main program handles the relay status and interrupt section handles UART communication with the Bluetooth module. Two global variables (t and st) are used to pass value from interrupt service routine to main program.

Microcontroller needs to get 3 sequential characters to update the status of relays. That is
1. Start character (A)
2. Relay ID ( 0 to 8)
3. ON OFF Status (1 or 0)

When the microcontroller receives ‘A’ it will start a timer and wait for next two characters. It will update ‘t’ and ‘st’ global variables depending on next two characters. So the main program will update relay status depending on it.

If the microcontroller not receiving next two characters.. timer will overflow and timer interrupt will get generated. This will reset the counter and microcontroller again waits for next start character.

Android App

Below table indicates the commands sent via Bluetooth.

Commands Operations
A00 All OFF
A01 All ON
A10 Relay 1 OFF
A11 Relay 1 ON
A20 Relay 2 OFF
A21 Relay 2 ON
A30 Relay 3 OFF
A31 Relay 3 ON
A40 Relay 4 OFF
A41 Relay 4 ON
A50 Relay 5 OFF
A51 Relay 5 ON
A60 Relay 6 OFF
A61 Relay 6 ON
A70 Relay 7 OFF
A71 Relay 7 ON
A80 Relay 8 OFF
A81 Relay 8 ON

Practical Implementation of  Circuit

Home Automation using Bluetooth and Mobile App – Practical Implementation

Working

The home automation circuit is built around PIC 16F876A Microcontroller, Android App, Bluetooth module HC-05 and a 8-channel relay board. Bluetooth has a range of 10-15 meters, so that you can switch ON and OFF any electronic appliance within the range.

First install the app, it will automatically ask permission to switch on the Bluetooth of mobile phone and connect that to Bluetooth module HC 05 which located with appliance controlling part.

Here Bluetooth App operates in Control Mode and HC-05 module operates as a receiver. App Passes the commands to HC-05 RX module  in order to control the home appliances.

Commands are sent to PIC 16F876A microcontroller via HC-05 Bluetooth module. PIC 16F876A microcontroller  analyses the received commands from HC-05 and generates outputs at output port.

Output of PIC 16F876A microcontroller is connected load unit i.e., home appliances via driver IC 2803 and relay unit. Driver drives the respective load for the respective received command via relay as a switching unit.

Software used: MikroC compiler
Language: Embedded C

Advantages

 PCB

Bottom Layer

Home Automation using Bluetooth and Mobile App – PCB Bottom

Component Layout – Top

Home Automation using Bluetooth and Mobile App – Component Layout

Video

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