Trouble with PIC16F877 and LM35DZ ( Stabilizing Temp)

[Amaal]

lm35dz

Hi All,

I'm having trouble stablizing the temperature.
It's fluctuating between 21 and 48 Deg C

I used the same code in http://www.rentron.com/PicBasic/LM34.htm

But with a help of a friend here. He told me to change it to this code.

I'm still having trouble. VREF is not becoming +5V on my pin 5 (AN3)

Can Anyone help me please.

I'm using Picbasic


DEFINE loader_used 1 ' Boot loader is being used
DEFINE debug_mode 0 ' Debug sending True serial data
DEFINE debug_reg portc ' Debug Port = PortC
DEFINE debug_bit 6 ' Debug.bit = PortC.6
DEFINE debug_baud 9600 ' Default baud rate = 9600
DEFINE osc 4 ' We're using a 4 MHz oscillator
DEFINE ADC_BITS 10 ' Set A/D for 10-bit operation
DEFINE ADC_CLOCK 1 ' Set A/D clock Fosc/8
DEFINE ADC_SAMPLEUS 50 ' Set A/D sampling time @ 50 uS

samples VAR WORD ' Multiple A/D sample accumulator
sample VAR word ' Holds number of samples to take
temp VAR word ' Temperature storage
samples = 0 ' Clear samples accumulator on power-up

TRISA = %11111111 ' Set PORTA to all input
ADCON1 = %10000000


PAUSE 500 ' Wait .5 second

loop:
FOR sample = 1 TO 20 ' Take 20 samples
ADCIN 0, temp ' Read channel 0 into temp variable
samples = samples + temp ' Accumulate 20 samples
PAUSE 250 ' Wait approximately 1/4 seconds per loop
NEXT sample

temp = samples/40
DEBUG "Temperature is: ",DEC temp," Deg C",10,13
samples = 0 ' Clear old sample accumulator
GOTO loop ' Do it forever

END




Thanks

 

[Medtronic]

stable power supply for pic 16f877

Hi My Friend
check your power supplay capacitor if the dc have more ripple the temprature may be flactuated

Regards

 

[garg29]

lm35dz pic16f877

i'm not familiar with picbasic but still are you sure for the line

 temp = samples/40

i think it should be

temp = samples/20

because you are taking 20 samples & not 40 samples.

 

[Prabakaran]

pic16f decoupling

Dear,
Put the Decoupling Capacitor in the PIC Microcontroller section. Then in POwer Supply section also put the capacitor so as to reomove the ripples in that. Else use the SMPS and test ur code.

 

[Amaal]

pic16f87x decoupling capacitor

Thank you all.

I changed my power supply and its more stable now.

What decoupling capacitor do i use though?