8051 Based Temperature Controlled Automatic Air Conditioning System

Hi everyone,today I am gonna share a project entitled  Temperature Controlled Automatic Air Conditioning System.This project was done for Minor Project in which I was a part of the team.As the name implies the main purpose of this project is to devise a system whose sole purpose is to condition or maintain the temperature within the predefined limits.Thus,this system proves to be useful to be used as a Air Conditioning System inside room,offices,departmental stores etc.Apart from that,it can also be used in various industrial applications such as to control the temperature in boilers,refrigerator,AC computers and Laboratories etc.

Now lets look at each element of the design turn by turn.

First lets have a glance at flowchart of the system:

Block diagram:

Above figure  shows the block diagram of the system that we have designed.Basically, it consists of microcontroller  as a central processor of the entire control operation. The temperature sensor gives the analog output voltage based on the temperature of the room.This analog voltage is fed to the A/D converter.The A/D converter then converts the analog input voltage from the temperature sensor into equivalent binary bits.The converted binary data from the A/D converter is applied to microcontroller.The microcontroller reads binary data from A/D converter,convert it to suitable form and performs different operations based on the value of temperature read from A/D converter.

The LCD is used to display the data given by microcontroller.Microcontroller can turn on dc fan through the optocoupler if required.We have used led as prototype model for heater.If appropriate condition is met microcontroller can turn on heater(i.e. LED).

In this system,if the temperature read is in between 20-25 degree celcius,it is considered normal state.In this condition both fan and heater are off but the temperature and status is displayed in LCD.If the temperature of the room is  greater that 25 degree celcius it is considered to be a situation to turn on fan and turn off heater. If the temperature of the room is in between 25-30 degree celcius it is considered as a situation to turn on fan with speed of level one.In this level,appropriate temperature and status is displayed on the LCD. If the temperature of the room is in between 30-35 degree celcius it is considered as a situation to turn on fan with speed of level two.In this level,appropriate temperature and status is displayed on the LCD. If the temperature of the room is greater than 35 degree celcius it is considered as a situation to turn on fan with speed of level three.In this level,appropriate temperature and status is displayed on the LCD. If the temperature of the room is  less that 20 degree celcius it is considered to be a situation to turn on Heater and turn off fan. If the temperature of the room is in between 10-20 it is considered as a situation to turn one heater on with heat of level one.In this level,appropriate temperature and status is displayed on the LCD. If the temperature of the room is in between 0-10 it is considered as a situation to turn two heater  on with heat of level two.In this level,appropriate temperature and status is displayed on the LCD.

Circuit Diagram:

The circuit shown in the figure consists of a microcontroller,LCD,optocoupler,temperature sensor,ADC etc.The microcontroller port one is connected to the data pins of LCD.Likewise port three of the microcontroller is connected to the  data pins of ADC.Pins P2.0 through P2.2 are used to connect to the control pins of LCD.Pins P2.3 through P2.5  are connected to the INTR,WR and RD pins of ADC respectively.Pin 2.6 of the port 2 is use to generate control signal to rotate DC fan.It is obtained using PWM.This pin is connected to the input pin of the optocoupler.The optocoupler is driving the switch to turn the  motor on/off.The pins P0.0 and P0.1 is used to drive LEDs which are used as a prototype model for heater. 

Source Code:

/****************************************************

Programmer: Bikal Adhikari                                                   *

Designation: Student                                                             * 

Compiled on: Keil uVision C51 compiler under Win 8 OS          * 

Program for:Temperature Controlled Automatic                       *

                   Air Conditioning System                                     *  

                   (Appropriate for BEX Minor Project)                   *

*****************************************************/

#include<reg51.h> /*Instructing Preprocessor to add header file reg51.h to use the features of 8051 C Programming*/

#define MYDATA P3 /*Defining Port 3 as "MYDATA" Function:To input the digital data from ADC*/

#define ldata P1  /*Defining Port 1 as data pins for lcd as ldata,Function:To output data to LCD*/

#define FL3i 35   /*Defining set of constants for the temperature limits*/

#define FL2ii 35  /*This approach makes changing the temperature limits very easy*/

#define FL2i 30   /*This prevents from going deeper into the code.*/

#define FL1ii 30

#define FL1i 25

#define NLii 25

#define NLi 20

#define HL1i 20

#define HL1ii 10

#define HL2i 10

#define HL2ii 00

sbit rd=P2^5;   /*Configuring P2.5 with identifier rd,Function:To send read command to ADC*/

sbit wr=P2^4;   /*Configuring P2.4 with identifier wr,Function:To send write command to ADC*/

sbit INTR=P2^3;   /*Configuring P2.3 with identifier INTR,Function:To detect start and end of conversion by ADC*/

sbit rs=P2^0;   /*Configuring P2.0 to give a value to RS register of LCD*/

sbit rw=P2^1;   /*Configuring P2.1 to give a value to RW register of LCD*/

sbit en=P2^2;   /*Configuring P2.2 to give a value to EN register of LCD*/

sbit MTR=P2^6;   /*Configuring P2.6 to give a Pulse width modulated signal to Motor Control Circuitry*/

sbit HTR1=P0^0;   /*Configuring P0.0 as a output line for led which is used as prototype model for heater*/

sbit HTR2=P0^1;   /*Configuring P0.0 as a output line for led which is used as prototype model for heater*/

sbit busy=P1^7;   /*Configuring P1.7,8th bit of ldata or P1 with identifier busy,Function:To know whether */

/*Following are set of functions required by the main routine.

  It is to be noted that function protoype are not used.

  Instead functions are directly implemented along with their definitions.

  While doing so proper function ordering should be made otherwise compiler 

  will generate error.For example:Most of the functions in program calls msDelay() function 

  ,and if msDealy() function is kept below the one calling it,compiler will generate error.*/

void msDelay(unsigned int value){ /*Provides delay in Miliseconds equal to the argument provided.Note that the choice of loop parameter 1275 is 

                                   completely determined by the inernal design of Compiler and may vary from Compiler to Compiler.*/

unsigned int x,y;

for(x=0;x<value;x++)

    for(y=0;y<1275;y++);  /*; is kept because second for loop is written as a single line statement*/

}

void lcdReady(){  /*Checks if LCD controller is busy or not and waits till not busy if it is busy*/

busy=1;

rs=0;

rw=1;

while(busy==1)

{

en=0;

en=1;

}

return;

}

void lcdCmd(unsigned char value){ /*Gives command to LCD*/

lcdReady();/*Calls to check for busy flag*/

ldata=value;

rs=0;

rw=0;/*To appreciate why these values are enforced,one needs to have basic understanding*/

en=1;/*of LCD controller internal operations for read,write etc.*/

en=0;

return;

}

void lcdInit(){ /*Initializes LCD.Whenever initialization is necessary this function is called.*/

lcdCmd(0x38);

lcdCmd(0x0c);

lcdCmd(0x01);

lcdCmd(0x80);

return;

}

void lcdData(char value){ /*To give data to LCD controller for display.*/

ldata=value;

rs=1;

rw=0;

en=1;

en=0;

return;

}

void display(char d1,char d2){

    lcdData(d2);

msDelay(30);

msDelay(30);

lcdData(d1);

msDelay(30);

msDelay(' ');

msDelay(30);

lcdData('C');

}

void convert(char value){/*Converts data from binary to ASCII code.*/

    char y,d1,d2,d3;

y=value/10;

d1=value%10;

d2=y%10;

d3=y/10;

d1=d1|0x30;

d2=d2|0x30;

d3=d3|0x30;

display(d1,d2);/*d3 will be needed only if temperature exceeds 100 degree celcius.

                         If needed it can be added in this call and in function definition

                         as well as body of display().Here it is not included so as to 

                         eliminate redundant digit in the display.*/

 }

 void update(char value){/*Updates the data in lcd if data is changed and is within the range.*/

    char y,d1,d2,d3;     /*Other method would also apply to update data*/

y=value/10;      /*But I thought this to be the easy and elegant approach.*/

d1=value%10;

d2=y%10;

d3=y/10;

d1=d1|0x30;

d2=d2|0x30;

d3=d3|0x30;

lcdData(d2);

msDelay(30);

msDelay(30);

lcdData(d1);

msDelay(30);

lcdCmd(0xc0);

 }

char adcRead(){/*Reads data from ADC and returns a value in binary format.*/

char value;

wr=0;/*Gives LO-HI pulse to ADC to Start the conversion process.*/

wr=1;

while(INTR==1);/*Waits till data has been converted by ADC.*/

rd=0;/*Gives LO-HI pulse to ADC to read the data converted by ADC*/

value=MYDATA;/*Receiving the converted data into the port 3 of uC*/ 

rd=1;/*End of LO-HI transition.*/

return value;

}

void motorcontrol(){

         unsigned char i;

 unsigned char value;

 unsigned char x[6]="TEMPR:";/*This Section consists Set of Strings defined for purpose of display in LCD*/

 unsigned char x1[5]="FANON";/*TEMPR: means Temperature,HTRON means Heater On*/

 unsigned char x2[5]="HTRON";/*HTRON meansHeater on.*/

 unsigned char y[12]="SPEED:LEVEL";

 unsigned char z[11]="HEAT:LEVEL";

 unsigned char u1[5]="NORM.";/*NORM. means Normal.*/

 unsigned char u2[11]="FAN,HTR OFF";/*FAN,HTR OFF means FAN and Heater both off.*/

 

while(1){  /*Infinite loop is made because of the absence of Operating System.

            Because there is no operating system to return to*/

value=adcRead(); /*read data from adc*/

    if(value<20){ /*Heater on logic ,confirms to turn on the heater*/   

     lcdCmd(0x01);   /*clear display*/

 for(i=0;i<6;i++) /*display string TEMPR: */

     {

     msDelay(50);

     lcdData(x[i]);

     }

 convert(value); /*convert data and display*/

 lcdCmd(0x8b);  

 for(i=0;i<5;i++){ /*display HTRON message*/

 msDelay(30);

 lcdData(x2[i]);

 }

 

     while(value>HL1ii && value<HL1i){ /*level 1 heat for heater*/

       MTR=1;  

   HTR2=1;

   HTR1=0;

   msDelay(1);

   z[10]='1';

   lcdCmd(0xc0);

   for(i=0;i<11;i++){

    msDelay(30);

    lcdData(z[i]);

    }

   bkl5:

   value=adcRead();

   if(value>HL1ii && value<HL1i){

    lcdCmd(0x86);

    update(value);

   goto bkl5;

   }

   else

   break;

   } /*While closed*/

 

    while(value>=HL2ii && value<=HL2i){ /*level 2 heat for heater*/

      MTR=1;

  HTR1=0;

  msDelay(30);

  HTR2=0;

  msDelay(1);

  lcdCmd(0xc0);

  z[10]='2';

  for(i=0;i<11;i++){

    msDelay(30);

    lcdData(z[i]);

    }

  bkl6:

  value=adcRead();

  if(value>=HL2ii && value<=HL2i){

    lcdCmd(0x86);

    update(value);

    goto bkl6;

   }

  else

  break;

  } /*While closed*/

   

   } /*Heater on logic closed*/

   

   

   while(value>=NLi&&value<NLii){ /*Normal state logic*/

     HTR1=1;

 HTR2=1;

 MTR=1;

 lcdCmd(0x01); /*clear display*/

 for(i=0;i<6;i++){ /*display TEMPR:*/

     msDelay(50);

     lcdData(x[i]);

      }

 convert(value); /*convert data and display*/

 for(i=0;i<5;i++){

 msDelay(30);

 lcdData(u1[i]);

 }

     lcdCmd(0xc0);

 for(i=0;i<11;i++){

 msDelay(30);

 lcdData(u2[i]);

 }

 bklbkl:

 value=adcRead();

 if(value>=NLi&&value<NLii){

  lcdCmd(0x86);

  update(value);

  goto bklbkl;

  }

     else

 break;

   }

    

    

if(value>=25) /*fan on logic,first confirms the situation to turn on fan*/

{

 HTR1=1;

 HTR2=1;

 lcdCmd(0x01); /*clear display*/

 for(i=0;i<6;i++) /*display TEMPR:*/

     {

     msDelay(50);

     lcdData(x[i]);

     }

 convert(value); /*convert data and display*/

 lcdCmd(0x8b);

 for(i=0;i<5;i++)

 {

 msDelay(30);

 lcdData(x1[i]);

 }

 

     while(value>=FL1i && value<FL1ii){ /*level 1 speed for fan*/

  lcdCmd(0xc0);

  y[11]='1';

  for(i=0;i<12;i++){

    msDelay(30);

    lcdData(y[i]);

   }

  bkl1:

  MTR=0;

      msDelay(50);

      MTR=1;

      msDelay(50);

  value=adcRead();

  if(value>=FL1i && value<FL1ii){   

  lcdCmd(0x86);

  update(value);

  goto bkl1;

  }

  else

  break;

   

  } /*level 1 speed logic closed*/

 

     while(value>=FL2i && value<FL2ii){ /*level 2 speed for fan*/

  y[11]='2';

  lcdCmd(0xc0);

  for(i=0;i<12;i++){

    msDelay(30);

    lcdData(y[i]);

   }

  bkl2:

  MTR=0;

      msDelay(75);

      MTR=1;

      msDelay(25);

      value=adcRead();

  if(value>=FL2i && value<FL2ii){

    lcdCmd(0x86);

    update(value);

    goto bkl2;

   }

  else

  break;

  } /*level 2 speed logic closed*/

   

 while(value>=FL3i){ /*level 3 speed for fan*/

  y[11]='3';

  lcdCmd(0xc0);

  for(i=0;i<12;i++){

    msDelay(30);

    lcdData(y[i]);

   }

  bkl3:

  MTR=0;

  value=adcRead();

  if(value>=FL3i){

    lcdCmd(0x86);

    update(value);

    goto bkl3;

   }

  else

  break;

  } /*level 3 speed logic closed*/

   

     } /*if statement closed i.e fan on logic closed*/

   }  

}  

  void main(){ /*Main function starts.Execution begins from here.*/

   P0=0xff;  /*Setting all pins of P0 to 1s to make it as output port in negative logic*/

   MYDATA=0xff; /*Setting all pins of P3 to 1s to make it as input port in positive logic*/

   INTR=1;/*Active low signal therefore initialized as high.*/

   rd=1;/*Active low signal therefore initialized as high.*/

   wr=1;/*Active low signal therefore initialized as high.*/

   MTR=1;/*Active low is required to drive optocoupler,so initialized as high.*/

   HTR1=0;/*To give a blink effect during a startup to show they are functioning and*/

   HTR2=0;/*leds are used as prototype for heater and are connected in active low configuration.*/

   msDelay(50);

   HTR1=1;/*After 50ms of delay Leds are turned off by high output.*/

   HTR2=1;

   lcdInit();/*Initializes LCD with appropriate Display Setting*/

   motorcontrol();/*Calls motorcontrol() subroutine*/

   } /*main function closed*/

You can request the download to the source code,keil and proteus project files and other files through this link
Also the arduino version of this same project can  be requested through this link