[SOLVED] Flow meter code not working

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baileychic

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My flow meter code is not working properly. I have to multiply the count of the TMR1 register by 2 to get correct value. Why is it ?

This is my code. PIC18F26K22 is running at XT 4 MHz.

Code C - [expand]
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#include "float2ascii.h"
 
// LCD module connections
sbit LCD_RS at LATB4_bit;
sbit LCD_EN at LATB5_bit;
sbit LCD_D4 at LATB0_bit;
sbit LCD_D5 at LATB1_bit;
sbit LCD_D6 at LATB2_bit;
sbit LCD_D7 at LATB3_bit;
 
sbit LCD_RS_Direction at TRISB4_bit;
sbit LCD_EN_Direction at TRISB5_bit;
sbit LCD_D4_Direction at TRISB0_bit;
sbit LCD_D5_Direction at TRISB1_bit;
sbit LCD_D6_Direction at TRISB2_bit;
sbit LCD_D7_Direction at TRISB3_bit;
// End LCD module connections
 
// strings
const code char txt1[] = "   Flow Meter   ";
const code char txt2[] = "dL/ds: ";
char txt[32];
 
typedef struct {
    unsigned long pulses_per_sec;
    unsigned char one_sec_delay_counter;
    unsigned char one_second_delay_count;
    double liters_per_sec;
    double scaling_factor;
} FLOW_METER_TYPE;
 
FLOW_METER_TYPE my_flow_meter;
 
//Timer0
//Prescaler 1:8; TMR0 Preload = 3036; Actual Interrupt Time : 500 ms
void InitTimer0() {
    T0CON = 0x82;
    TMR0H = 0x0B;
    TMR0L = 0xDC;
    GIE_bit = 1;
    TMR0IE_bit = 1;
}
 
void Interrupt(){
    if((TMR0IE_bit) && (TMR0IF_bit)) {
       TMR0IF_bit = 0;
       TMR0H = 0x0B;
       TMR0L = 0xDC;
       //Enter your code here
       if(++my_flow_meter.one_sec_delay_counter >= my_flow_meter.one_second_delay_count) {
            TMR1ON_bit = 0;
            my_flow_meter.one_sec_delay_counter = 0;
            TMR0IE_bit = 0;
       }
    }
 
    if((TMR1IE_bit) && (TMR1IF_bit)) {
        TMR1IF_bit = 0;
    }
}
 
 
char *CopyConst2Ram(char * dest, const code char *src) {
    char *d;
 
    d = dest;
 
    for(;*dest++ = *src++;);
 
    return d;
}
 
void main(void) {
 
    CM1CON0 = 0x00;
    CM2CON0 = 0x00;
 
    ANSELA = 0x00;
    ANSELB = 0x00;
    ANSELC = 0x00;
 
    TRISA = 0x00;
    TRISB = 0x00;
    TRISC = 0x01;
 
    PORTA = 0x00;
    PORTB = 0x00;
    PORTC = 0x00;
 
    LATA = 0x00;
    LATB = 0x00;
    LATC = 0x00;
 
    Delay_ms(200);
 
    Lcd_Init();
    Lcd_Cmd(_LCD_CURSOR_OFF);
    Lcd_Cmd(_LCD_CLEAR);
 
    //Lcd_Out(1,1,CopyConst2Ram(txt, txt1));
    Lcd_Out(2,1,CopyConst2Ram(txt, txt2));
 
    T1CON = 0b10000100;
    T1GCON = 0x00;
 
    my_flow_meter.scaling_factor = 1.70068e-4;
    
    PWM1_Init(588);
    PWM1_Set_Duty(127);
    PWM1_Start();
 
    while (1) {
 
           TMR1H = 0;
           TMR1L = 0;
           InitTimer0();
           TMR1ON_bit = 1;
           while(TMR1ON_bit);
           my_flow_meter.pulses_per_sec = (unsigned long)(((unsigned int)(TMR1H << 8) + TMR1L) * 2);
           my_flow_meter.liters_per_sec = (double)my_flow_meter.pulses_per_sec * my_flow_meter.scaling_factor;
           Float2Ascii(my_flow_meter.liters_per_sec, txt, 5);
           strcat(txt,"   ");
           Lcd_Out(2,8,txt);
           Float2Ascii((double)my_flow_meter.pulses_per_sec, txt, 2);
           strcat(txt,"   ");
           Lcd_Out(1,1,txt);
    }
}


This is the screenshot of simulation.
 

Attachments

  • flow meter 03.png
    56 KB · Views: 219
Last edited:

Hi,

multiply with what value?
A random calibration value?

Klaus
 

Unless you have posted the question just to show this project, in other words you are just asking "why a physical quantity liters_per_sec is not exactly the same value of the current timer pulses_ per_ sec ?"
 

Here is the datasheet of the flow sensor.

Calculation is like this.

Max flow is 6Ltr/min = 6Ltr/60sec and so for 1 sec max flow is 0.1Ltr.

For 1 Ltr max pulses is 5880.

So, for 0.1 Ltr max pulses is 588.

max 0.1 Ltr flows in 1 sec and so to convert 588 to 0.1 the magic number is

588 * x = 0.1

x = 0.1 / 588 = 1.70068e-4

PIC18F26K22 is used. Why there is a need to multiply the value (count value) in TMR1 register with 2 to get correct reading ?

I have attached the flow meter mikroC PRO PIC project.

Edit:

Found the bug and fixed it and it is working fine now.

Had to initialize this variable.

Code: 
my_flow_meter.one_second_delay_count = 2;

Thank you all for helping.
 

Attachments

  • flow sensor.pdf
    167.1 KB · Views: 163
  • PIC18F26K22 - Flow Meter.rar
    27.4 KB · Views: 147
Last edited:

@KlausST

I already fixed it. It was mentioned in my previous post. Here is the final project.

Code C - [expand]
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#include "float2ascii.h"
 
// LCD module connections
sbit LCD_RS at RB0_bit;
sbit LCD_EN at RB1_bit;
sbit LCD_D4 at RD0_bit;
sbit LCD_D5 at RD1_bit;
sbit LCD_D6 at RD2_bit;
sbit LCD_D7 at RD3_bit;
 
sbit LCD_RS_Direction at TRISB0_bit;
sbit LCD_EN_Direction at TRISB1_bit;
sbit LCD_D4_Direction at TRISD0_bit;
sbit LCD_D5_Direction at TRISD1_bit;
sbit LCD_D6_Direction at TRISD2_bit;
sbit LCD_D7_Direction at TRISD3_bit;
// End LCD module connections
 
// strings
const code char txt1[] = "     Flow Meter";
const code char txt2[] = "dL/ds  : ";
const code char txt3[] = "dL/dm  : ";
const code char txt4[] = "Pulse/s: ";
char txt[32];
 
typedef struct {
    double pulses_per_sec;
    unsigned char one_sec_delay_counter;
    unsigned char one_second_delay_count;
    double liters_per_sec;
    double liters_per_min;
    double scaling_factor;
    double previous_pulses_per_sec;
} FLOW_METER_TYPE;
 
FLOW_METER_TYPE my_flow_meter;
 
//Timer0
//Prescaler 1:256; TMR0 Preload = 61; Actual Interrupt Time : 49.92 ms
void InitTimer0() {
    OPTION_REG = 0x87;
    TMR0 = 61;
    INTCON = 0xA0;
}
 
void Interrupt() {
    if((TMR0IE_bit) && (TMR0IF_bit)) {
       TMR0IF_bit = 0;
       TMR0 = 61;
       //Enter your code here
       if(++my_flow_meter.one_sec_delay_counter >= my_flow_meter.one_second_delay_count) {
            TMR1ON_bit = 0;
            my_flow_meter.one_sec_delay_counter = 0;
            TMR0IE_bit = 0;
       }
    }
    
    if((TMR1IE_bit) && (TMR1IF_bit)) {
        TMR1IF_bit = 0;
    }
}
 
 
char *CopyConst2Ram(char * dest, const code char *src) {
    char *d;
 
    d = dest;
 
    for(;*dest++ = *src++;);
 
    return d;
}
 
void main(void) {
 
    CMCON = 0x07;
 
    ADCON0 = 0x40;
    ADCON1 = 0x8F;
 
    TRISA = 0x00;
    TRISB = 0x00;
    TRISC = 0x01;
    TRISD = 0x00;
    TRISE = 0x00;
 
    PORTA = 0x00;
    PORTB = 0x00;
    PORTC = 0x00;
    PORTD = 0x00;
    PORTE = 0x00;
    
    Delay_ms(200);
 
    Lcd_Init();
    Lcd_Cmd(_LCD_CURSOR_OFF);
    Lcd_Cmd(_LCD_CLEAR);
 
    Lcd_Out(1,1,CopyConst2Ram(txt, txt1));
    Lcd_Out(2,1,CopyConst2Ram(txt, txt2));
    Lcd_Out(3,1,CopyConst2Ram(txt, txt3));
    Lcd_Out(4,1,CopyConst2Ram(txt, txt4));
    
    Float2Ascii(my_flow_meter.liters_per_sec, txt, 3);
    strcat(txt," Lt/s ");
    Lcd_Out(2,10,txt);
    Float2Ascii(my_flow_meter.liters_per_min, txt, 3);
    strcat(txt," Lt/m ");
    Lcd_Out(3,10,txt);
    Float2Ascii((double)my_flow_meter.pulses_per_sec, txt, 1);
    strcat(txt,"  ");
    Lcd_Out(4,10,txt);
    
    T1CON = 0x06;
    
    my_flow_meter.previous_pulses_per_sec = 0xFFFFFFFF;
    my_flow_meter.one_second_delay_count = 20;
    my_flow_meter.scaling_factor = 1.700680e-4;
    
    InitTimer0();
    
    while (1) {
           TMR1H = 0;
           TMR1L = 0;
           TMR0 = 61;
           TMR0IE_bit = 1;
           TMR1ON_bit = 1;
           while(TMR1ON_bit);
           my_flow_meter.pulses_per_sec = (double)((double)((unsigned int)(TMR1H << 8) + TMR1L) * 1.0);
           
           if(my_flow_meter.previous_pulses_per_sec != my_flow_meter.pulses_per_sec) {
               my_flow_meter.liters_per_sec = (double)my_flow_meter.pulses_per_sec * my_flow_meter.scaling_factor;
               my_flow_meter.liters_per_min = my_flow_meter.liters_per_sec * 60.0;
               Float2Ascii(my_flow_meter.liters_per_sec, txt, 3);
               strcat(txt," Lt/s ");
               Lcd_Out(2,10,txt);
               Float2Ascii(my_flow_meter.liters_per_min, txt, 3);
               strcat(txt," Lt/m ");
               Lcd_Out(3,10,txt);
               Float2Ascii((double)my_flow_meter.pulses_per_sec, txt, 1);
               strcat(txt,"  ");
               Lcd_Out(4,10,txt);
               
               my_flow_meter.previous_pulses_per_sec = my_flow_meter.pulses_per_sec;
           }
    }
}
 

Attachments

  • Flow Meter.rar
    21.7 KB · Views: 137
  • flow meter 06.png
    44.6 KB · Views: 229

Here is my Flow Meter updated project with my Proteus Flow Sensor VSM model. This VSM model is made by me. I am not posting any copy righted material here.
 

Attachments

  • Flow Meter + Flow Sensor Proteus VSM Model.rar
    207 KB · Views: 153
  • Flow Meter.png
    51.4 KB · Views: 224

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