LM35-->A/D Converter-->PIC 16F628

[Pappee]

Hi All!
I woluld like to connect (for example) an LM35 Thermo sensor to a PIC during an A/D converter. Can somebody tell me what kind of A/D converter could I use? Have sombody experience in this?How does PIC process the converted analog sign?
I have a circuit from a Czech web site(**broken link removed**), but the author did use a very-very expensive termistor, what includes A/D converter(SMT160-30).I tought that change it a simple thermistor & a cheap A/D converter. I get any help with pleasure!

http:\\attilapapp.uw.hu

 

[Nigel Goodwin]

Hi All!
I woluld like to connect (for example) an LM35 Thermo sensor to a PIC during an A/D converter. Can somebody tell me what kind of A/D converter could I use? Have sombody experience in this?How does PIC process the converted analog sign?
I have a circuit from a Czech web site(**broken link removed**), but the author did use a very-very expensive termistor, what includes A/D converter(SMT160-30).I tought that change it a simple thermistor & a cheap A/D converter. I get any help with pleasure!

Far easier to choose a PIC with an internal A2D, try the 16F819 or 16F88, both are 18 pin like the 16F628.

 

[Pappee]

Built in A/D

Hello!

If you had read the link I wrote, you would have seen that's a comlett project, and PIC doesn't handle the convertation. I wouldn't change the program, because, I never did the same. But if you can do this, and share the reason with me, I would be very indebted for you.

Special thanx!

 

[densimitre]

Hi

I am a 16F84a working with a ADC0832 A/D converter (8 bits in serial stream output).

MAIn.c


#include <16f84a.h>
#use delay(clock=4000000)
#fuses XT,NOWDT,NOPROTECT
#use RS232(BAUD=9600, BITS=8, PARITY=N, XMIT=PIN_B2, RCV=PIN_B4, RESTART_WDT)
#include "adc0832.c"

float value;
void main() {
   //adc_init();
   set_adc(0);
   read_adc();
   printf("A/D Conversion using ADC0832 Chip\n\r");
   value=(adc_result/51);     // 0-5 volt scale
   putc(13);
   printf("adc_result=%X\n\r",adc_result);
   printf("Channel 0 Voltage = %01.2F\r",value);
}

adc0832.c


#define AD_CS pin_A0   // Chip Select
#define AD_CK pin_A1   // Clock
#define AD_DI pin_A2   // Data In (MUX Channel Selector)
#define AD_DO pin_A3   // Data Out

int adc_result;

void  delay() {
      delay_us(3);
}

void  Clock() {
      output_high(AD_CK);
      delay();
      output_low(AD_CK);
}

void  set_adc(short ch) {   //ch corresponde al canal a medir
      if(ch==0){
                            //ch=0 . Seleccionamos canal 0 del ADC
      output_high(AD_CS);   //Inicia transicion de habilitacion del ADC
      delay();              //Retardo necesario para no superar los 200 KHz de frecuencia del ADC
      output_low(AD_CS);    //Activa la linea /CS (chip select) sobre el ADC para iniciar conversion.
		delay();        	    //Debe estar asi durante toda la conversion,
                            //Ahora el chip espera un bit de partida y la palabra de asignacion MUX
      output_high(AD_DI);   //Pone en 1 el bit de partida DI del MUX de seleccion de puerto
      delay();
      Clock();              //Pasamos este bit de start hacia el MUX del ADC0832
                            //El dato DI es pasado al MUX en cada Rising Edge del Clock
      output_high(AD_DI);   //Con DI=SGL/DIF=1 seleccionamos "Single-Ended MUX mode"
      delay();              //Mantenemos en estado High bit DI
      Clock();              //pasamos el SGL/DIF al MUX del ADC0832
      output_low(AD_DI);    //Con DI=ODD/SIGN=0 seleccionamos el Channel 0.
      delay();
      Clock();              //Con este ultimo clock termina la asignacion del canal a conevertir
      }
      else {
                            //ch=1 . Seleccionamos canal 1 del ADC
      output_high(AD_CS);   //Inicia transicion de habilitacion del ADC
      delay();              //Retardo necesario para no superar los 200 KHz de frecuencia del ADC
      output_low(AD_CS);    //Activa la linea /CS (chip select) sobre el ADC para iniciar conversion.
		delay();        	    //Debe estar asi durante toda la conversion,
                            //Ahora el chip espera un bit de partida y la palabra de asignacion MUX
      output_high(AD_DI);   //Pone en 1 el bit de partida DI del MUX de seleccion de puerto
      delay();
      Clock();              //Pasamos este bit de start hacia el MUX del ADC0832
                            //El dato DI es pasado al MUX en cada Rising Edge del Clock
      output_high(AD_DI);   //Con DI=SGL/DIF=1 seleccionamos "Single-Ended MUX mode"
      delay();              //Mantenemos en estado High bit DI
      Clock();              //pasamos el SGL/DIF al MUX del ADC0832
      output_high(AD_DI);   //Con DI=ODD/SIGN=1 seleccionamos el Channel 1.
      delay();
      Clock();              //Con este ultimo clock termina la asignacion del canal a conevertir
      }
}

// Esta funcion debe llamarse despues de seleccionar el canal
// del ADC0832 a ser utilizado para conversion.
// CS debe estar activo (low)
// El ADC0832 entrega dos stream de salida en DO:
// - MSB first
// - LSB first
// Por tanto, leemos el MSB firts, lo desplazamos a la izquierda
// y una vez completado el byte, desechamos el stream LSB y deseleccionamos
// el ADC0832 haciendo CS=1 (high)

void read_adc() {
    int i;
    for (i=0;i<8;i++) {          // Lee el byte resultado de conversion desde el ADC0832
         Clock();                // y lo almacena en adc_result
         shift_left(&adc_result, 1, input(AD_DO));
         delay();
         }
         output_high(AD_CS);     //Despues de leido el byte completo, deseleccionamos el ADC0832
                                 //poninedo CS=1 (high).
                                 //Con esto termina la lectura del conversor A/D
}

Best regards

 

[densimitre]

adc0832.c

// Please first read ADC0832 datasheet

#define AD_CS pin_A0   // Chip Select 
#define AD_CK pin_A1   // Clock 
#define AD_DI pin_A2   // Data In (MUX Channel Selector) 
#define AD_DO pin_A3   // Data Out 

int adc_result;             // Variable that stores the result of the conversion ( 8 bits  ==> int type)

void  delay() {             // Delay rutine
      delay_us(3); 
} 

void  Clock() {             //Signal Clock, to read or put data from/to ADC0832
      output_high(AD_CK); 
      delay(); 
      output_low(AD_CK); 
} 


// Set_adc();   ==> Rutine for set MUX word to send towards ADC0832 (measure mode and channel selected)

void  set_adc(short ch) {   //ch corresponds to the channel to measure, is a "short" data type. (one bit)
      if(ch==0){ 
                            //ch=0. We select channel 0 of the ADC.
      output_high(AD_CS);   //It initiates transition to enable ADC.
      delay();              //Necessary delay to not overcome 200 KHz of frequency of the ADC.
      output_low(AD_CS);    //It activates the line /CS (chip select) on the ADC to initiate conversion 
      delay();              //It must be like that during the whole conversion, 
                            //Now the chip waits for a "Start bit" and the "MUX word setting" bits ( two bits)
      output_high(AD_DI);   //It puts in 1 the bit of game SAY of the MUX of selection of port 
      delay(); 
      Clock();              //We put this start bit towards the MUX of the ADC0832
                            //The bit DI is put into MUX in every Rising Edge of the Clock 
                            
      output_high(AD_DI);   //DI=SGL/DIF=1 we select "Single-Ended MUX mode" 
      delay();              //We stay DI in high state (DI=1)
      Clock();              //we put SGL/DIF into MUX of ADC0832 
      output_low(AD_DI);    //With DI=ODD/SIGN=0 we select Channel 0. 
      delay(); 
      Clock();              //With the latter clock it finishes the allocation of the channel to convert
      } 
      else { 
                            //ch=1. we select channel 1 of ADC 
      output_high(AD_CS);   //It initiates transition to enable ADC
      delay();              //Necessary delay to not overcome 200 KHz of frequency of the ADC.
      output_low(AD_CS);    //It activates the line /CS (chip select) on the ADC to initiate conversion 
      delay();              //It must be like that during the whole conversion, 
                            //Now the chip waits for a "Start bit" and the "MUX word Setting" bits ( two bits)
      output_high(AD_DI);   //It puts in 1 the bit of game SAY of the MUX of selection of port 
      delay(); 
      Clock();              //We put this start bit towards the MUX of the ADC0832 
                            //The bit DI is put into MUX in every Rising Edge of the Clock 
      output_high(AD_DI);   //With DI=SGL/DIF=1 we select "Single-Ended MUX mode" 
      delay();              //We stay DI in high state (DI=1)
      Clock();              //we put SGL/DIF into MUX of ADC0832
      output_high(AD_DI);   //With DI=ODD/SIGN=1 we select Channel 1.  
      delay(); 
      Clock();              //With the last clock it finishes the allocation of the channel to convert 
      } 
} 

// This function must be called after selecting the channel 
// of the ADC0832 to be used for conversion. 
// CS must be active (low) 
// The ADC0832 delivers two stream out in DO: 
// - MSB first 
// - LSB first 
// Therefore, we read the MSB firts, shift it to the left side of adc_result
// and as soon as the byte was completed, we reject the stream LSB and disable
// the ADC0832 doing CS=1 (high)

void read_adc() { 
    int i; 
    for (i=0;i<8;i++) {          // Read the result buyte of ADC0832 conversion.
         Clock();                // and store it into adc_result 

         shift_left(&adc_result, 1, input(AD_DO)); 
         delay(); 
         } 
         output_high(AD_CS);     //After read the finished byte,disable ADC0832 
                                 //doing CS=1 (high). 
                                 //With this it finishes the reading of the ADC0832 out stream, 
                                 //and we can process the result in main.c 
}

 

[dinesh_aurum]

Hi All!
I woluld like to connect (for example) an LM35 Thermo sensor to a PIC during an A/D converter. Can somebody tell me what kind of A/D converter could I use? Have sombody experience in this?How does PIC process the converted analog sign?
I have a circuit from a Czech web site(**broken link removed**), but the author did use a very-very expensive termistor, what includes A/D converter(SMT160-30).I tought that change it a simple thermistor & a cheap A/D converter. I get any help with pleasure!

http:\\attilapapp.uw.hu

hi,
the easiest and best way is to use inbuilt A/D convertor of pic
if you you are facing the problem you mail your project and i will do the coding for your aplication our i will suggest some more circuits and codes
for your application

dinesh_aurum@yahoo.com

 

[candz12]

NEED a circuit and program

can any one help me in my project? i have a project which is controlling the temperature and humidity. My problem what IC to be used in humidity. and also how can i build a circuit and program of temperature and humidity.

I hope any one can help me with my project..

here' s my email add.. please send me.

anaviso_candido@yahoo.com

 

[blueroomelectronics]

can any one help me in my project? i have a project which is controlling the temperature and humidity. My problem what IC to be used in humidity. and also how can i build a circuit and program of temperature and humidity.

I hope any one can help me with my project..

here' s my email add.. please send me.

anaviso_candido@yahoo.com

Don't hijack posts, start a new thread instead.

The humirel hs1101 has a schematic in its datasheet for a humidity sensor using a CMOS 555.