I don't know very much about the Arduino board. Yet I find myself doing a school project that requires me to measure very small flow rates (under a hundredth of a milliliter per second.). There are several designs out there, but they all use the fluid as part of a circuit, and the fluid I'm using is gasoline, which has very poor conductivity. Visual sensors don't seem to work with clear liquid. I've tried setting up a capacitance sensor with the relevant library as well as with the following code:
int i;
unsigned int x, y;
float accum, fout, fval = .07; // these are variables for a simple low-pass (smoothing) filter - fval of 1 = no filter - .001 = max filter
void setup() {
Serial.begin(9600);
DDRB=B101; // DDR is the pin direction register - governs inputs and outputs- 1's are outputs
// Arduino pin 8 output, pin 9 input, pin 10 output for "guard pin"
// preceding line is equivalent to three lines below
// pinMode(8, OUTPUT); // output pin
// pinMode(9, INPUT); // input pin
// pinMode(10, OUTPUT); // guard pin
digitalWrite(10, LOW); //could also be HIGH - don't use this pin for changing output though
}
void loop() {
y = 0; // clear out variables
x = 0;
for (i=0; i < 4 ; i++ ){ // do it four times to build up an average - not really neccessary but takes out some jitter
// LOW-to-HIGH transition
PORTB = PORTB | 1; // Same as line below - shows programmer chops but doesn't really buy any more speed
// digitalWrite(8, HIGH);
// output pin is PortB0 (Arduino 8), sensor pin is PortB1 (Arduinio 9)
while ((PINB & B10) != B10 ) { // while the sense pin is not high
// while (digitalRead(9) != 1) // same as above port manipulation above - only 20 times slower!
x++;
}
delay(1);
// HIGH-to-LOW transition
PORTB = PORTB & 0xFE; // Same as line below - these shows programmer chops but doesn't really buy any more speed
//digitalWrite(8, LOW);
while((PINB & B10) != 0 ){ // while pin is not low -- same as below only 20 times faster
// while(digitalRead(9) != 0 ) // same as above port manipulation - only 20 times slower!
y++;
}
delay(1);
}
fout = (fval * (float)x) + ((1-fval) * accum); // Easy smoothing filter "fval" determines amount of new data in fout
accum = fout;
Serial.print((long)x, DEC); // raw data - Low to High
Serial.print( " ");
Serial.print((long)y, DEC); // raw data - High to Low
Serial.print( " ");
Serial.println( (long)fout, DEC); // Smoothed Low to High
}
As far as I can tell, this doesn't detect drops of anything unless I drop them onto the bare wire that would otherwise have a bit of aluminum foil on it.
Ideas?
Thanks very much.
