Do you need to display the flowrate? If not, you don't need all this code.
The OP's code auto formatted.:
/*
Liquid flow rate sensor -DIYhacking.com Arvind Sanjeev Measure the liquid/water flow rate using this code. Connect Vcc
and Gnd of sensor to arduino, and the signal line to arduino digital pin 2.
*/
byte statusLed = 13;
byte sensorInterrupt = 0;
// 0 = digital pin 2
byte sensorPin = 2;
int val = 0;
// put your button on pin 4
const int startpin = 4;
int buttonState = 0;
// The hall-effect flow sensor outputs approximately 4.5 pulses per second per
// litre/minute of flow.
float calibrationFactor = 4.5;
volatile byte pulseCount;
float flowRate;
unsigned int flowMilliLitres;
unsigned long totalMilliLitres;
unsigned long oldTime;
void setup() {
// Initialize a serial connection for reporting values to the host
Serial.begin(38400);
// Set up the status LED line as an output
pinMode(statusLed, OUTPUT);
// put your relay on pin 5
pinMode(5, OUTPUT);
pinMode(startpin, INPUT_PULLUP);
digitalWrite(statusLed, HIGH);
// We have an active-low LED attached
pinMode(sensorPin, INPUT);
digitalWrite(sensorPin, HIGH);
pulseCount = 0;
flowRate = 0.0;
flowMilliLitres = 0;
totalMilliLitres = 0;
oldTime = 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()
{
// read the input pin:
int buttonState = digitalRead(startpin);
// fill button start if relay turn off
if (digitalRead(5) == LOW)
{ val = digitalRead(startpin);
digitalWrite(5, val);
}
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. We also apply the calibrationFactor to scale the output
// based on the number of pulses per second per units of measure (litres/minute in
// this case) coming from the sensor.
flowRate = ((1000.0 / (millis() - oldTime)) * pulseCount) / calibrationFactor;
// Note the time this processing pass was executed. Note that because we’ve
// disabled interrupts the millis() function won’t actually be incrementing right
// at this point, but it will still return the value it was set to just before
// interrupts went away.
oldTime = millis();
// Divide the flow rate in litres/minute by 60 to determine how many litres have
// passed through the sensor in this 1 second interval, then multiply by 1000 to
// convert to millilitres.
flowMilliLitres = (flowRate / 60) * 1000;
// Add the millilitres passed in this second to the cumulative total
totalMilliLitres += flowMilliLitres;
unsigned int frac;
Serial.print(buttonstate)
// Print the flow rate for this second in litres / minute
Serial.print("Flow rate: ");
Serial.print(int(flowRate));
// Print the integer part of the variable
Serial.print(".");
// Print the decimal point
// turn on pin 3 if flowrate is greater than 4
// Determine the fractional part. The 10 multiplier gives us 1 decimal place.
frac = (flowRate - int(flowRate)) * 10;
Serial.print(frac, DEC) ;
// Print the fractional part of the variable
Serial.print("L/min");
// Print the number of litres flowed in this second
Serial.print(" Current Liquid Flowing: ");
// Output separator
Serial.print(flowMilliLitres);
Serial.print("mL/Sec");
// Print the cumulative total of litres flowed since starting
Serial.print(" Output Liquid Quantity: ");
// Output separator
Serial.print(totalMilliLitres);
Serial.println("mL");
// check if flow volume is > 1 litres
if (totalMilliLitres > 1000)
{ digitalWrite(5, LOW);
delay(5000);
// reset volume to zero
totalMilliLitres = 0;
}
// Reset the pulse counter so we can start incrementing again
pulseCount = 0;
// Enable the interrupt again now that we’ve finished sending output
}
if digitalRead(
attachInterrupt(sensorInterrupt, pulseCounter, FALLING);
}
}
/* Insterrupt
Service Routine
*/
void pulseCounter()
{
// Increment the pulse counter
pulseCount++;
}