NTC thermistor temperature sensing

[pxidr84]

Hi,

I'm somewhat affraid ...


0 < Tb0 < 1024 ... ok ?

1024 - 16170 = ??? - 15146 !!!
so, tb1 is NEGATIVE ...

and PBP do not deal with negative numbers .... but " read " it as 65536 -15146 = ???

a hole in the somewhere ???

Alain

Well, the ADC range is not 0-1024, but 0-65535...
(verified with a display of the raw ADC value).

[mackrackit]

Well, the ADC range is not 0-1024, but 0-65535...
(verified with a display of the raw ADC value).

Alain never said the ADC range was 0 - 65535.
He was telling you how the value would be acted on.

[Acetronics2]

Well, the ADC range is not 0-1024, but 0-65535...
(verified with a display of the raw ADC value).

You should place a patent on this one ...

Hurry up !!!

Alain

PS you do not display Tb0 ( as the ADC result ) , but Tb0 ( after - false - calculations done ! ) ....

[cncmachineguy]

You should place a patent on this one ...

In case you are wondering why, the ADC is 10 bit, so clearly you can't have 16 bit result from the ADC

[pxidr84]

It's weird. I got a 16-bit result. Why? Code :

define OSC 20
DEFINE ADC_BITS 10
DEFINE ADC_CLOCK 3  
DEFINE ADC_SAMPLEUS 10
DEFINE LCD_DREG PORTC
DEFINE LCD_RSREG PORTC
DEFINE LCD_EREG PORTC
DEFINE LCD_EBIT 5 
DEFINE LCD_COMMANDUS 10000'Command delay time in us 
DEFINE LCD_DATAUS 1000 'Data delay time in us
 
ntc VAR WORD

TRISA=%11111111     
ADCON1=%10000010   

PAUSE 4000

lp:

ADCIN 1,ntc
 
PAUSE 100
 
Lcdout $fe,$c0,#ntc

goto lp

you do not display Tb0 ( as the ADC result ) , but Tb0

And what are the differences between Tb0 and Tb0? I didn't understand your answer.

[mackrackit]

Never trust a sim.
Try it in real life and come back.

[Acetronics2]

ADCIN 1,tb0
tb1=tb0-16170
tb1=tb1*tb3
tb2=Div32 634
tb0=tb2/100
tb1=tb2//100

see any difference between Tb0 value @ line 1 and Tb0 Value @ line 5 ???

really no ?

Alain

[pxidr84]

Never trust a sim.
Try it in real life and come back.

In real life with the same code:

see any difference between Tb0 value @ line 1 and Tb0 Value @ line 5 ???

really no ?

Alain

My updated code :

define OSC 20
DEFINE ADC_BITS 10
DEFINE ADC_SAMPLEUS 10
DEFINE LCD_DREG PORTC
DEFINE LCD_RSREG PORTC
DEFINE LCD_EREG PORTC
DEFINE LCD_EBIT 5 

ntc VAR WORD
tb0 VAR WORD
tb1 VAR WORD
tb2 VAR WORD

TRISA=%11111111     
ADCON1=%10000010   

PAUSE 4000

lp:

ADCIN 1,ntc
tb0=ntc
if tb0>=16170 then
tb1=tb0-16170 
ELSE 
tb0=0
ENDIF
tb1=tb1*100                                      
tb2=Div32 634
tb0=tb2/100   
tb1=tb2//100    
           
PAUSE 100

Lcdout $fe,$c0,"ITS: ",DEC (tb0 DIG 1),DEC (tb0 DIG 0),".",DEC (tb1 DIG 1),"°C"

goto lp

I was surprised because the previous code worked good.

[cncmachineguy]

Never trust a sim.

But this time I think the sim is correct. I think you ment to set ADCON2, not ADCON1. ADCON 2 sets right or left justified. Default is left justified.

[pxidr84]

But this time I think the sim is correct. I think you ment to set ADCON2, not ADCON1. ADCON 2 sets right or left justified. Default is left justified.

How do you right-justify bits?
tb0=ntc>>8?

Or there is an another command?

[aratti]

From your code:

ADCIN 1,ntc
tb0=ntc
if tb0>=16170 then
tb1=tb0-16170 
ELSE 
tb0=0
ENDIF

Since ntc could be 0 or 1023 maximum, the condition if tb0>=16170 then is always false so tbo will be always zero and tb1 will be never setted with your required calculation tb1=tb0-16170.

Cheers

Al.

[Acetronics2]

Sorry ...

But my Easy Pic5 outputs " ITS : ...00.00°C " with all the processor settings I gave you in previous code, but 10 bits ADC ... ( Whistle and Bells ... )

I also asked for printing ntc Value ...

comprised between 0 and 1023 ...

try this :

ntc VAR WORD
tb0 VAR WORD
tb1 VAR WORD
tb2 VAR WORD
TRISA=%11111111

PAUSE 700
LCDOUT $fe,1

lp:
ADCIN 1,ntc
tb0 = ntc
if tb0 >= 16170 then
tb1 = tb0-16170
ELSE
tb1 = 0
ENDIF
tb1 = tb1*100
tb2 = Div32 634
tb0 = tb2/100
tb1 = tb2//100

LCDOUT $FE,2,DEC4 ntc
Lcdout $FE,$C0,"ITS: ",DEC3 tb0,".",DEC2 tb1,"°C"
goto lp

so ... take your own conclusions !!!

Alain