Help on Controlling Air Condition using LM35 interfacing to PIC microcontroller

[Akanbi Ibrahim]

Hi everybody,i am working on a project which i have to switch ON and OFF Air Condition whenever the temperature of the room is above or below certain temperature respectively.I have done my breadboard design and the temperature is displaying properly but the automatic switch ON and OFF is not working as expected instead it will not allow the temperature to go below or beyond my minimum and maxmum temperature respectively.below is my code in MikroC

 

sbit LCD_RS at RC4_bit;

sbit LCD_EN at RC5_bit;

sbit LCD_D4 at RC0_bit;

sbit LCD_D5 at RC1_bit;

sbit LCD_D6 at RC2_bit;

sbit LCD_D7 at RC3_bit;

sbit LCD_RS_Direction at TRISC4_bit;

sbit LCD_EN_Direction at TRISC5_bit;

sbit LCD_D4_Direction at TRISC0_bit;

sbit LCD_D5_Direction at TRISC1_bit;

sbit LCD_D6_Direction at TRISC2_bit;

sbit LCD_D7_Direction at TRISC3_bit;

// End LCD module connections

// Define Messages

char message0[] = “AC Monitoring”;

char message1[] = “Room Temperature”;

// String array to store temperature value to display

char *tempC = “000.0”;

char *tempF = “000.0”;

// Variables to store temperature values

unsigned int tempinF, tempinC,orgtemp;

unsigned long temp_value,maxtemp;

void Display_Temperature() {

 // convert Temp to characters

 if (tempinC/10000)

 // 48 is the decimal character code value for displaying 0 on LCD

 tempC[0] = tempinC/10000 + 48;

 else tempC[0] = ‘ ‘;

 tempC[1] = (tempinC/1000)%10 + 48; // Extract tens digit

 tempC[2] = (tempinC/100)%10 + 48; // Extract ones digit

 // convert temp_fraction to characters

 tempC[4] = (tempinC/10)%10 + 48; // Extract tens digit

 // print temperature on LCD

 Lcd_Out(2, 1, tempC);

 if (tempinF/10000)

 tempF[0] = tempinF/10000 + 48;

 else tempF[0] = ‘ ‘;

 tempF[1] = (tempinF/1000)%10 + 48; // Extract tens digit

 tempF[2] = (tempinF/100)%10 + 48;

 tempF[4] = (tempinF/10)%10 + 48;

 // print temperature on LCD

 Lcd_Out(2, 10, tempF);

}

 

void main()

{

 

 TRISE=1;

 TRISB=0;

 PORTE=1;

 TRISD=0;

 PORTD=0;

// ANSEL = 0b00000100; // RA2/AN2 is analog input

 ADCON0 = 0b01001000; // Connect AN2 to S/H, select Vref=1.19V

// CMCON0 = 0x07 ; // Disbale comparators

 TRISC = 0b00000000; // PORTC All Outputs

 TRISA = 0b00001110; // PORTA All Outputs, Except RA3 and RA2

 Lcd_Init(); // Initialize LCD

 Lcd_Cmd(_LCD_CLEAR); // CLEAR display

 Lcd_Cmd(_LCD_CURSOR_OFF); // Cursor off

 Lcd_Out(1,1,message0);

 Delay_ms(1000);

 Lcd_Out(1,1,message1); // Write message1 in 1st row

 // Print degree character

 Lcd_Chr(2,6,223);

 Lcd_Chr(2,15,223);

 // Different LCD displays have different char code for degree symbol

 // if you see greek alpha letter try typing 178 instead of 223

 Lcd_Chr(2,7,’C’);

 Lcd_Chr(2,16,’F’);

 while(1) 

 {

 temp_value = ADC_Read(2);

 temp_value = temp_value*4882;

 tempinC = temp_value/1000;

 tempinC = tempinC*10;

 tempinF = 9*tempinC/5 + 3200;

}

}

//~ End of main Function

[AJISH ALFRED]

Hi Akanbi,

Air conditioners already have automatic temperature control. It will try to keep the temperature of a room constant, and I guess that is why your project is not working. Please find a way to confirm it first.

 

[Akanbi Ibrahim]

Thanks Mr Aljish,but i tried to test this with a LED to see if the temperature is beyond the normal limit i set the LED will ON instead its prevents the temperature that is displaying on the LCD to reach the limit i set.

[AJISH ALFRED]

Hi Akanbi,

Check whether your circuit is proper. Make sure that you’ve connected the ADC reference pin of the microcontroller to 5V

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