Problem in display correct values of the temperature sensor

[caramelz]

hi I'm using Pic18f4520, the temperature sensor doesnt give the correct values. the values isnt consistent at all too.

Temperature sensor is connect to AN12 of the IC
I display the ADC reading into the LCD, the values kept jumping from 50 , 70, 100 back to 50.
Can anyone tell me whats wrong with it. thanks

 

[jayanth.devarayanadurga]

ADCON1 configured properly? Post the code.

 

[caramelz]

I'm using a LM35 sensor.

ADCON2=0b10001010;

void temperature(void)
{
	unsigned int temp;
	char degree[4]="   ";
	unsigned int me;
	temp=ADCRead(12);
	me=temp;
	Init_LCD();
	itoa(me,degree);						
		i=0;  
		W_ctr_8bit(0x80);		
		while (degree[i]){              	
			W_data_8bit(degree[i]); 	
			i++;
		}              		
	
}
unsigned int ADCRead(unsigned int ch)
{
	if(ch>13)return 0; 	
	ADCON0=0x00;
	ADCON0=(ch<<2);
	ADCON0bits.ADON=1;
	Delay10TCYx(5);	
	ADCON0bits.GO = 1;	
	while(ADCON0bits.DONE);	
	ADCON0bits.ADON=0;
	return (ADRESH*256+ADRESL);
}

 

[jayanth.devarayanadurga]

Where is ADCON1 settings?

TRISBbits.TRISB0 = 1;
ADCON1 = 0b00000001;
//or
ADCON1 = 0b00000010;
//or
ADCON1 = 0b00000000;


Mention Fosc used so that ADCON2 value can be calculated. Put Init_LCD(); in main() before while(1) loop.

 

[caramelz]

I'm using 20Mhz crystal
ADCON0=0b00000001;
ADCON1=0b00000111;
ADCON2=0b10001010;
the sensor is connected in RB0 CH12.
Sensor Connection: 5V, GND, RB0.

 

[jayanth.devarayanadurga]

Your ADCON1 settings is wrong. See datasheet. Your settings make AN12 as digital I/O. Use ADCON1 = 0b00000010. AN12 should be analog input. Also set TRISBbits.TRISB0 = 1;

 

[caramelz]

I just changed the sensor to CH8(RB2) as to minimize the port usage cos i have 8 other ADC CH for measuring the batteries.
yeah I had set the trisB to Input for RB2

 

[jayanth.devarayanadurga]

Zip and post your project files and also Proteus file if any.