ADC output conversion problem

[ecaits]

Dear All,

I am facing problem in below code. Please refer below.

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Code C - [expand]
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void main()
{
    int data[4];
    unsigned int b,c,d,z=0,e,i,f,a,x,p=0,g,h,j,k,l,o,q;
    unsigned int v;
    float t=0;
    long long m,n;
 
    PORTD=0x00;
    PORTC=0x00;
    PORTB=0x00;
    TRISD = 0x00;
        TRISB = 0x00;
        TRISC = 0x00;
    ADC_Init();
    
    f = ADC_Read(0);
 
    a = f;
    t=a/6.82;

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In above code, I am getting output of ADC say 193 in f and same in variable a.

Now I want to devide a by 6.82 to reduce the range from 0-1023 t0 0.00 to 150.00 to display on LCD. But I am not getting the output as per my expectation. What may the problem or how can i divide the variable a by 6.82???

This is part of the whole program code. I am working on PIC16F877 using Hitech C Compiler.

 

[milan.rajik]

Add LCD code.

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Code C - [expand]
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unsigned char strADCVal[23];
float fAdcVal = 0.0;
 
void main()
{
     
    TRISA = 0x01;
    PORTA = 0x00;
    //ADCON1 register have to be configured
          
    while(1) {
    
        fAdcVal = ADC_Read(0) / 6.82;
        //if adc value is 1023 then 1023 / 6.82 = 150 (LM35 max o/p)
        //1023 should represent 150 that is Vref+ should be 1.5V
        FloatToStr(fAdcVal, strADCVal);
        LCD_Out(2,1,strADCVal);     
    }
}

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[ecaits]

Add LCD code.

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Code C - [expand]
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unsigned char strADCVal[23];
float fAdcVal = 0.0;
 
void main()
{
     
    TRISA = 0x01;
    PORTA = 0x00;
    //ADCON1 register have to be configured
          
    while(1) {
    
        fAdcVal = ADC_Read(0) / 6.82;
        //if adc value is 1023 then 1023 / 6.82 = 150 (LM35 max o/p)
        //1023 should represent 150 that is Vref+ should be 1.5V
        FloatToStr(fAdcVal, strADCVal);
        LCD_Out(2,1,strADCVal);     
    }
}

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But I require LCD output in 150.00 range and I want to keep Vref+ as 5V.

 

[milan.rajik]

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Code C - [expand]
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unsigned char strADCVal[23];
float fAdcVal = 0.0;
 
void main()
{
     
    TRISA = 0x01;
    PORTA = 0x00;
    //ADCON1 register have to be configured
    //Configure CMCON here (disable Comparators)
     
    while(1) {
    
        fAdcVal = ADC_Read(0) / 2.046;
        
        FloatToStr(fAdcVal, strADCVal);
        LCD_Out(2,1,strADCVal);     
    }
}

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//5V = 1023
//1.5V = 306.9

//306.9 * x = 150

//x = 0.4887585532746823

//1/x = 2.046

//Temperature = fADCVal / 2.046

//If AD value is 306.9 then 306.9 / 2.046 = 150 (150 degree C)

//If your Vref+ is 5V then your max adc value for 150 deg C will be 306.9 (less resolution)
//If your Vref+ is 1.5V then max adc value for 150 deg C will be 1023 (more resolution)