I'm currently working on a flow meter, which measures in GPH. I'm trying to set it up so it displays the current gph usage and two resettable total gallon used counters. The sketch counts the number of pulses from the sensor every second or so. I then take the flow measurement( which is pulses * gals per pulse) and add it to totalgallonsA.
TotalgallonsA += flowgal; // both are float
The problem I'm having is totalgallonsA instead of increasing always goes back to zero?
I can post the complete code if needed, I have it on my other computer
I'm very new to programming, and don't know where to begin??
Matt
Floating point doesn't seem like a good bet for that sort of thing - you're going to be getting unpredictable rounding errors that could get quite large. Better IMO to define the resolution you're going to measure at (tenths of gallons, hundredths, thousandths etc) and store your counters as fixed point integer numbers.
I agree. A flow meter that generating pulses per unit of material flowed is best dealt with using integer math. it's rather straight forward counting of pulses in a fixed time interval and of course updating the total flow value, I see no advantages to using floating point math and several disadvantages.
Here is my code so far. Im pretty new to the language, any help would be great
Matt
#include <LiquidCrystal.h>
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12,11,10,9,8,7);
byte sensorInterrupt = 0; // 0 = pin 2; 1 = pin 3
byte sensorPin = 2;
// The hall-effect flow sensor outputs aproximatly one pulse per .00038L
volatile byte pulseCount;
float flowRate;
unsigned int flowGallons;
float totalGallonsA;
unsigned int totalGallonsB;
int pulseCounttot;
unsigned long oldTime;
void setup()
{
Serial.begin(9600);
lcd.begin(16, 2);
lcd.setCursor(0, 0);
lcd.print("BRADSHAW ");
lcd.setCursor(0, 1);
lcd.print("INDUSTRIES ");
delay(3000);
lcd.clear();
pinMode(sensorPin, INPUT);
digitalWrite(sensorPin, HIGH);
pulseCount = 0;
flowRate = 0.0;
flowGallons = 0;
totalGallonsA = 0;
totalGallonsB = 0;
oldTime = 0;
pulseCounttot = 0;
// The Hall-effect sensor is connected to pin 2 which uses interrupt 0.
// Configured to trigger on a FALLING state change (transition from HIGH
// state to LOW state)
attachInterrupt(sensorInterrupt, pulseCounter, FALLING);
}
/**
* Main program loop
*/
void loop()
{
if((millis() - oldTime) >= 1000) // Only process counters once per second
{
// Disable the interrupt while calculating flow rate and sending the value to
// the host
detachInterrupt(sensorInterrupt);
// Because this loop may not complete in exactly 1 second intervals we calculate
// the number of milliseconds that have passed since the last execution and use
// that to scale the output.
unsigned long time = millis() - oldTime;
float time_in_sec = time / 1000;
float impuls = pulseCount * time_in_sec; //scale pulse number
float flowG = impuls * .00010; // amount of gals
float GPH = flowG * 120 ; // convert to gph
totalGallonsA =+ flowG ;
oldTime = millis();
{
}
lcd.setCursor(0,0);
lcd.print(GPH);
lcd.setCursor(6,0);
lcd.print("GPH"); // Print the integer part of the variable
lcd.setCursor(0,1);
lcd.print(totalGallonsA,4);
// Reset the pulse counter so we can start incrementing again
pulseCount = 0;
// Enable the interrupt again now that we've finished sending output
attachInterrupt(sensorInterrupt, pulseCounter, FALLING);
}
}
/**
* Invoked by interrupt0 once per rotation of the hall-effect sensor. Interrupt
* handlers should be kept as small as possible so they return quickly.
*/
void pulseCounter()
{
// Increment the pulse counter
pulseCount++;
}
Disabling global interrupts is a single bit manipulation, attach/detach interrupt are not as efficient.
The operation could be done before detachInterrupt even returns.