LM35 interfacing with 89S52 using adc0808

[fazeelat]

I am using ADC0808, microcontroller 89S52, and 16X2 Alpha-numeric LCD to display the sensed data using sensor (LM35) connected to ADC0808.
my step size is 10mV by keeping Vref=2.56 but can't obtain accurate temperature on LCD please help me in conversion of binary output of ADC into ASCII data for LCD
here is the C code written in keil ..... plz someone help me

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Code C - [expand]
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#include<reg52.h>
sbit ale=P1^0;  //address latch enable
sbit oe=P1^3;  //output enable
sbit sc=P1^1;  //start conversion
sbit eoc=P1^2;  //end of conversion
sbit clk=P1^7;  // clock
sbit ADD_A=P1^4;  // Address pins for selecting input channels.
sbit ADD_B=P1^5;
sbit ADD_C=P1^6;
sfr lcd_data_pin=0xA0;  //P2 port
sbit rs=P3^5;
sbit rw=P3^6;
sbit en=P3^7;
sbit led=P3^4;
sfr input_port=0x80;  //P0 port
unsigned int value;
void timer0() interrupt 1  // Function to generate clock of frequency 500KHZ using Timer 0 interrupt.
{
clk=~clk;
}
void delay(unsigned int count)  // Function to provide time delay in msec.
{
int i,j;
for(i=0;i<count;i++)
for(j=0;j<1275;j++);
}
 
void lcd_command(unsigned char comm)  //Function to send command to LCD.
{
lcd_data_pin=comm;
en=1;
rs=0;
rw=0;
delay(5);
en=0;
}
 
void lcd_data(unsigned char disp)  //Function to send data to LCD.
{
lcd_data_pin=disp;
en=1;
rs=1;
rw=0;
delay(5);
en=0;
}
 
lcd_dataa(unsigned char *disp)  //Function to send string data to LCD.
{
int i=0;
while(disp[i]!='\0')
    {
        lcd_data(disp[i]);
        i++;
        delay(10);
    }
    return;
}
 
void lcd_ini()  //Function to inisialize the LCD
{
lcd_command(0x38); 
delay(2);
lcd_command(0x0F); 
delay(2);
lcd_command(0x80);  //Force cursor to blink at line 1 positon 0
delay(2);
}
  void BCD(unsigned char value)  // Binary to decimal conversion to send the data to LCD
{
 unsigned char x,d1,d2,d3,d4,d5,d6;
x=value/10;
d1=value%10;
d2=x%10;
d3=x/10;
d4=d1+48;
d5=d2+48;
lcd_command(0x01);
lcd_dataa("TEMP :");
lcd_data(d5);
lcd_command(0x87);
lcd_data(d4);
lcd_command(0x88);
lcd_data(223);
delay(10);
lcd_data('C');
delay(10);
led=0;
} 
 
void adc()  //Function to drive ADC
{
while(1)
{
  ADD_C=0;  // Selecting input channel 2 using address lines
  ADD_B=0;
  ADD_A=1;
  delay(2);
  ale=1;
  delay(2);
  sc=1;
  delay(1);
  ale=0;
  delay(1);
  sc=0;
  while(eoc==1);
  while(eoc==0);
  oe=1;
  value=input_port;
  BCD(value);                                                                    
  lcd_command(0x85);
  delay(2);                                                                     
  oe=0;
}
}
 
void main()
{
input_port=0xFF;
eoc=1;
ale=0;
oe=0;
sc=0;
TMOD=0x02;  //timer0 setting for generating clock of 500KHz using interrupt enable mode.
TH0=0xFD;
IE=0x82;
TR0=1;
lcd_ini();
adc();
}

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[basade.abdul]

**broken link removed**

//Program to display temperature in Celsius and Farenheit scale.

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Code C - [expand]
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#include<reg51.h>
#define port P3
#define adc_input P1
#define dataport P0
#define sec 100
sbit rs = port^0;
sbit rw = port^1;
sbit e = port^2;
 
sbit wr= port^3;
sbit rd= port^4;
sbit intr= port^5;
 
int test_intermediate3=0, test_final=0,test_intermediate1[10],test_intermediate2[3]={0,0,0};
 
void delay(unsigned int msec )
{
    int i ,j ;
    for(i=0;i<msec;i++)
        for(j=0; j<1275; j++);
}
 
void lcd_cmd(unsigned char item)    // Function to send commands to LCD
{
    dataport = item;
    rs= 0;
    rw=0;
    e=1;
    delay(1);
    e=0;
    return;
}
 
void lcd_data(unsigned char item)    // Function to send data to LCD
{
    dataport = item;
    rs= 1;
    rw=0;
    e=1;
    delay(1);
    e=0;
    return;
}
 
void lcd_data_string(unsigned char *str)  // Function to string to LCD
{
    int i=0;
    while(str[i]!='\0')
    {
        lcd_data(str[i]);
        i++;
        delay(10);
    }
    return;
}
 
void shape()        // Function to make the shape of degree symbol
{
    lcd_cmd(64);
    lcd_data(2);
    lcd_data(5);
    lcd_data(2);
    lcd_data(0);
    lcd_data(0);
    lcd_data(0);
    lcd_data(0);
    lcd_data(0);
}
       
void convert()     // Function to convert the values of ADC into numeric value to be sent to LCD
{
    int    s;
    lcd_cmd(0x81);      
    delay(2);
    lcd_data_string("TEMP:");
    test_final=(((9*test_intermediate3)/5)+32);
    s=test_final/100;
    test_final=test_final%100;
    lcd_cmd(0x88);
    if(s!=0)
    lcd_data(s+48);
    else
    lcd_cmd(0x06);
    s=test_final/10;
    test_final=test_final%10;
    lcd_data(s+48);
    lcd_data(test_final+48);
    lcd_data(0);
    lcd_data('F');
    lcd_data(' ');
 
    test_final=test_intermediate3;
    lcd_cmd(0xc1);        //Setting  cursor to first position of first line
    delay(2);
    lcd_data_string("TEMP:");
    s=test_final/100;
    test_final=test_final%100;
    lcd_cmd(0xc8);
    if(s!=0)
    lcd_data(s+48);
    else
    lcd_cmd(0x06);
    s=test_final/10;
    test_final=test_final%10;
    lcd_data(s+48);
    lcd_data(test_final+48);
    lcd_data(0);
    lcd_data('c');
    lcd_data(' ');
    delay(2);
}
 
void main()
{
    int i,j;
    adc_input=0xff;
    lcd_cmd(0x38);        //2 Line, 5X7 Matrix display
    lcd_cmd(0x0c);        //Display On, Cursor blinking
    delay(2);
    lcd_cmd(0x01);        // clear screen
    delay(2);
 
    while(1)
    {
        for(j=0;j<3;j++)
        {
            for(i=0;i<10;i++)
            {
                delay(1);
                rd=1;
                wr=0;
                delay(1);
                wr=1;
                while(intr==1);
                rd=0;
                lcd_cmd(0x88);
                test_intermediate1[i]=adc_input/10;
                delay(1);
                intr=1;
            }
            for(i=0;i<10;i++)
            test_intermediate2[j]=test_intermediate1[i]+test_intermediate2[j];
        }
 
        test_intermediate2[0]=test_intermediate2[0]/3;
        test_intermediate2[1]=test_intermediate2[1]/3;
        test_intermediate2[2]=test_intermediate2[2]/3;
        test_intermediate3=test_intermediate2[0]+test_intermediate2[1]+test_intermediate2[2];
        shape();
        convert();
    }
}

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[fazeelat]

thanx basade.abdul
but above code is for adc 0804 and i m using adc0808.... i think there is some difference in case of conversion in case of adc0808
help me plz

 

[:pH]

you said you are not getting accurate temperature on LCD , please describe what are you getting giving an example

 

[fazeelat]

temperature variation is so random
that is if i get 25 degree C on LCD for 25 degree temperature then on increasing this temp to 26 degree C
i got 88degree C on LCD

 

[:pH]

Alright , are you using an amplifier at the output of lm35 ? like lm324 ?

 

[fazeelat]

no i m nt using any amplifier

 

[:pH]

Lm35 gives output in terms of fraction of 1V meanining , 0.32v for 32 degree celsius . . So generally people use an amplifier of gain 10 , for making the output variation coarse

 

[fazeelat]

check out my schematic
https://obrazki.elektroda.pl/46_1336758164.png
i have connected an amplifier but my output remains constant now
wats the problem with it kindly figure it out