Guide on flow sensor application

[tacbanon]

Hi everyone, I have G1'1/4 Water Flow sensor from (http://www.seeedstudio.com/wiki/inde...er_Flow_sensor). As I understand I have to count the output pulse using RA4/TOCK1 using PIC16F877A(20Mz).
My question are as follow:
1. RA4/TOCK1 is using TIMER0 can I use TIMER1 to count up to 65535?
2. What is the best hardware setup to read pulses of 4 water flow sensors...is it possible 4 sensors in 1 pic16F877A?

Sorry if my question are not too clear, I really appreciate any help and guide on this..

Regards,
tacbanon

[HenrikOlsson]

Hi,

1) Sure, configure TMR1 as a counter and feed the signal to the T1CKI (Timer 1 Clock Input) pin instead of T0CKI.
2) It's possible for sure but how to do it "the best way" depends on the frequency of the incoming pulses from the sensors and on what else the PIC needs to do. For example, use TMR0 and TMR1 to count pulses from two of the sensors and use two IOC-pins for the other two. Another option is to use four IOC-pins, one for each sensor. Another is to use four external F/V converter chips and feed the output voltage from each to the ADC of the PIC. Yet another is to use the count command on four pins in sequence.

/Henrik.

EDIT: OK, just saw that the output frequency is fairly low. ~45Hz at full flow, dutycycle of 40-60%. So, as long as you poll the inputs at at least ~120Hz (timer interrupt for example) you should be able to count pulses in software.

[tacbanon]

Hello Henrik,

Another option is to use four IOC-pins, one for each sensor.

Is this mean that I can use similar approach like in this link? (http://www.picbasic.co.uk/forum/show...519#post117519)

Regards,
tacbanon

[HenrikOlsson]

Not sure.
In that thread it looks like you're using the external interrupts (INT0-INT2) but the 877A only has one "normal" external interrupt (INT0). However it does have four Interrupt on change pins (PortB.4-7) which you could use.

Or, like I said, you might get away with simply polling the inputs in a loop. As long as you read the inputs atleast ~120 times per second you shouldn't miss any pulses.

/Henrik.

[tacbanon]

Thank you Henrik, I will try to work on it and post here in case I have some inquiries.

Regards,
tacbanon

[tacbanon]

Hi I'm back...My first attempt for 1 flow sensor is I tried to count the pulse similar to a switch button....but still not really sure if I'm doing it right. If its fine how do I get flow rate?...kindly check the code I'm using.

INCLUDE "MODEDEFS.BAS"       ' Include Shiftin/out modes
INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"  ' Include if using PBP interrupts
 
;-- Define LCD connections -- (change these to match your hardware) ------------
DEFINE LCD_DREG PORTB
DEFINE LCD_DBIT 0
DEFINE LCD_EREG PORTB
DEFINE LCD_EBIT 5
DEFINE LCD_RSREG PORTB
DEFINE LCD_RSBIT 4
DEFINE LCD_BITS 4
DEFINE LCD_LINES 2
DEFINE LCD_COMMANDUS 2000
DEFINE LCD_DATAUS 50
PAUSE 100

TRISA = %00000000               ; set PORTA to output pins
PortA = %00000000               ; set to PORTA low
TRISB = %10000000               ; set PORTB to B7 input pin rest output pins
PortB = %00000000               ; set to PORTB low
TRISC = %10000000               ; set PORTD to output pins
PORTC = %00000000 
TRISD = %10000000               ; set PORTD to output pins
PORTD = %00000000               ; set to PORTD low
LCDOUT  $FE,1                   ; Initialize the LCD
pause 200                       ; pause 2 milisec

OPTION_REG = $7f  'enable pull offs
'--variables init
flag1 var bit
flag1 = 0
c var byte
c = 0
cnt1 var word
cnt1 = 0
StatLed var PORTA.0
StatLed = 0

But0 var PortB.7
But0 = 0
'--LCD line
ln1 con $80
ln2 con $C0
CS  con 1 

SerialInput var byte[50]  
Serialdata var byte  

; setup serial port line for transmition   

DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 20h ' Enable transmit, BRGH = 1
DEFINE HSER_BAUD 9600
DEFINE HSER_CLROERR 1 ' Clear overflow automatically    
RCIF       VAR     PIR1.5     ' Receive  interrupt flag (1=full , 0=empty)
TXIF       VAR     PIR1.4     ' Transmit interrupt flag (1=empty, 0=full)
'------------------------------------------------------Transmition-------------

; create the transmition interrupt
        '((((((((((((((((((((((((((((((((((((((()))))))))))))))))))))))))))))))))))))))
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,  _ToggleLED1,   PBP,  yes
        INT_Handler   RX_INT,    _Getbytes,    PBP,  no
         endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM
;
T1CON = $31                ; Prescaler = 8, TMR1ON
@ INT_ENABLE  TMR1_INT     ; enable Timer 1 interrupts
@ INT_ENABLE  RX_INT
'((((((((((((((((((((((((((((((((((((((()))))))))))))))))))))))))))))))))))))))
;------------------------------------------------------------------------



Hserout ["Flow Sensor Test",13]
pause 1000

Main:
PortB.7 = 0 
LCDOUT $FE,ln1,"Flow Sensor Test"
LCDOUT $FE,ln2 ,"Cnt: ",dec3 cnt1
Pause 25
IF But0 = 0 then
cnt1 = cnt1+1
   While But0 = 0:Wend   
   If flag1 = 0 then
    HSEROUT ["Counter:",Dec3 cnt1,13]
    flag1 = 1
    else
    flag1 = 0
   Endif
else
endif
Goto main


'(((((((((((((((((((((((((This is a preparation for PC interface))))))))))))))))

Getbytes:  
        
       While RCIF = 1     ' clear the buffer
       c = c + 1
       Hserin [Serialdata]
       select case Serialdata          ' What to do with that data???
                                
           case "A"            ' User selection 
                HSEROUT ["Option A",13] ' take it out 
           case "B"
                HSEROUT ["Option B",13] ' take it out 
           case "C"
                HSEROUT ["Option C",13] ' take it out            
           case "*"
                'HSEROUT ["This is it! > ",13] ' take it out
                SerialInput[c] =" "  
           case else                       
               SerialInput[c] = Serialdata          
         End select            
            
       Wend

@ INT_RETURN
'*******************************************************************************


ToggleLED1:

'Toggle statLed 

@ INT_RETURN

I also attached some pics about my hardware setup..
Appreciate any input and time...

Regards,
tacbanon