Temperature Sensor (LM35 + PIC16F877A)

[Mr.Khiros]

Hi ;
i'm using PIC16F877A with temperature sensor LM35 . I refered to this work
https://forum.allaboutcircuits.com/blog.php?b=513
but i'm not able to unterstand those instructions :
ADRead = (ADC_Get_Sample(0) * 500) >> 10;
vDisp[0] = ADRead / 100;
vDisp[1] = (ADRead / 10) % 10;
vDisp[2] = ADRead % 10;
Display[1] = vDisp[0] + 48;
Display[2] = vDisp[1] + 48;
Display[3] = vDisp[2] + 48;
NEED YOUR HELP.

 

[pinout]

ADRead = (ADC_Get_Sample(0) * 500) >> 10;

// consider and ADRead value of 123
vDisp[0] = ADRead / 100; // vDisp[0] will become 1. i.e. integer left dividing 123/100 = 1 (most significant digit)

vDisp[1] = (ADRead / 10) % 10; // vDisp[1] will become 7. i.e. 123/10 = 12, and 12 % 10 is the remained times i.e. 2 (middle digit)

vDisp[2] = ADRead % 10; // vDisp[2] will become remainder of 567/10 i.e. 567/10 = 16 and the remainder is 7 (least significant digit)

The following converts the numbers to ASCII for display on a serial terminal etc. So for 123 above
Display[1] = vDisp[0] + 48; // = 49
Display[2] = vDisp[1] + 48; // = 50
Display[3] = vDisp[2] + 48; // = 51

For ASCII look at https://www.asciitable.com/ and you will see decimal 48 displays character '0'

Hope that helps with the understanding of integer division, remainders and ASCII. Nice question.

 

[jayanth.devarayanadurga]

Max value of adc is 1023 for 5V input. Max o/p of LM35 is 1.5V. So, max adc value will be 306.9

0 to 306.9 is multiplied by 500

eg:

306.9 * 500 = 153450

153450 >> 10 = 149

149 is approx 150 max temperature of LM35.

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Code C - [expand]
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vDisp[0] = ADRead / 100;
vDisp[1] = (ADRead / 10) % 10;
vDisp[2] = ADRead % 10;
Display[1] = vDisp[0] + 48;
Display[2] = vDisp[1] + 48;
Display[3] = vDisp[2] + 48;

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These are for extracting digits of the number

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Code C - [expand]
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vDisp[0] = ADRead / 100;
vDisp[1] = (ADRead / 10) % 10;
vDisp[2] = ADRead % 10;

---

149/100 = 1 //hundredths digit
149/10 = 14
14%10 = 4 //tens digit
149%10 = 9 //units digit

Converting int value to ascii charcaters by adding 48 or 0x30

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Code C - [expand]
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Display[1] = vDisp[0] + 48;
Display[2] = vDisp[1] + 48;
Display[3] = vDisp[2] + 48;

---

1 + 0x30 = 0x31 = '1'
4 + 0x30 = 0x34 = '4'
9 + 0x30 = 0x39 = '9'

Display[] = "149"

You can replace the above with

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Code C - [expand]
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Display[1] = ADRead / 100 + 48;
Display[2] = (ADRead / 10) % 10 + 48;
Display[3] = ADRead % 10 + 48;

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or

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Code C - [expand]
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IntToStr(ADRead, strADRead); //strADRead is a string (unsigned char strADRead[23];

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[Mr.Khiros]

It's work know ... but there is a little prob , after the conversion to string

IntToStr(ADRead, strADRead); //strADRead is a string (unsigned char strADRead[23];

the LCD shows the digit far of it's place ?

 

[jayanth.devarayanadurga]

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Code C - [expand]
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strADRead[8] = '\0';
LCD_Out(1,7,strADRead);
LCD_Chr(1,15,'223');
LCD_Chr(1,15,'C');

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[sreepss]

Try WordToStr command instead of IntToStr

 

[forforum]

This code change integer to string:
- number 0 is referred to character '0' in ASCII table ('0' has index is 48).