Room thermometer(using LM35 and microcontroller atmega 8l ) problem

[Akshat Kumar Verma]

guyzzz i need help.........i have made digital room thermometer using LM35 and at-mega 8l micro controller (ADC feature) which shows the value on seven segment.it shows the value initially approx equal to the actual room temperature but after sometime it starts incrementing reach to 60 and 56. i m unable to understand the problem as i touch "ice" to LM35 the value decreases (that means ADC is working and it comes nearer to actual value i.e actual room temperature and but with the increase it starts wandering
i m using code vision avr and serial port programmer.
plzzz help.....:roll:

)

 

[nandhu015]

post your circuit and code, someone could able to solve it

 

[Akshat Kumar Verma]

following is the code made in CVavr and i m posting pcb designed by me as i do not know HOW to use tina pro and other simulators

#include <mega8.h>
#include <delay.h>

// Declare your global variables here
void seven_segmentL(int y)       //function for left seven segment as per pcb design
{
if(y==0)
PORTB=0b01100000;

else if(y==1)
PORTB=0b01111011;

else if(y==2)
PORTB=0b11010000;

else if(y==3)
PORTB=0b01010010;
       
else if(y==4)
PORTB=0b01001011;

else if(y==5)
PORTB=0b01000110;

else if(y==6)
PORTB=0b01000100;

else if(y==7)
PORTB=0b01110011;

else if(y==8)
PORTB=0b01000000;

else if(y==9)
PORTB=0b01000010;

}
void seven_segmentR(int x)        //function for right seven segment as per pcb design
{
if(x==0)
PORTD=0b00010001;

else if(x==1)
PORTD=0b11011101;

else if(x==2)
PORTD=0b10000011;

else if(x==3)
PORTD=0b10001001;
       
else if(x==4)
PORTD=0b01001101;

else if(x==5)
PORTD=0b00101001;

else if(x==6)
PORTD=0b00100001;

else if(x==7)
PORTD=0b10011101;

else if(x==8)
PORTD=0b00000001;

else if(x==9)
PORTD=0b00001001;

}
void main(void)
{  int r,therm,b,d;
// Declare your local variables here

// Input/Output Ports initialization
// Port B initialization
// Func7=Out Func6=Out Func5=Out Func4=Out Func3=Out Func2=Out Func1=Out Func0=Out 
// State7=0 State6=0 State5=0 State4=0 State3=0 State2=0 State1=0 State0=0 
PORTB=0x00;
DDRB=0xFF;

// Port C initialization
// Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In 
// State6=T State5=T State4=T State3=T State2=T State1=T State0=T 
PORTC=0x00;
DDRC=0x00;

// Port D initialization
// Func7=Out Func6=Out Func5=Out Func4=Out Func3=Out Func2=Out Func1=Out Func0=Out 
// State7=0 State6=0 State5=0 State4=0 State3=0 State2=0 State1=0 State0=0 
PORTD=0x00;
DDRD=0xFF;


// ADC initialization

ADCSRA|=(1<<7);// ADC enabled
ADMUX|=(1<<7); //avcc as refernce
ADMUX|=(1<<5);  //reading ADCH
ADCSRA|=(1 << 2); // Prescaler 128
ADCSRA|=(1 << 1); // Prescaler 128
ADCSRA|=(1 << 0); // Prescaler 128




while (1)
      {
    ADCSRA^=(1<<6);
    delay_ms(100); 
    ADCSRA^=(1<<6);
    r=ADCH;
    therm=(r*500)/256;
    b=therm/10;
    d=therm%10;
    seven_segmentL(b);
    seven_segmentR(d);
    delay_ms(1000);

      }
}

 

[Akshat Kumar Verma]

help me ..............