help with how to use signal from motorcycle hall effect sensor.

#include <LiquidCrystal.h>
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);

 

// Specify the pins for the two counter reset buttons and indicator LED
byte resetButtonA = 11;
byte resetButtonB = 12;
byte statusLed = 13;

 

byte sensorInterrupt = 0; // 0 = pin 2; 1 = pin 3
byte sensorPin = 2;

 

// 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 totalMilliLitresA;
unsigned long totalMilliLitresB;

 

unsigned long oldTime;

 

void setup()
{
lcd.begin(16, 2);
lcd.setCursor(0, 0);
lcd.print(" ");
lcd.setCursor(0, 1);
lcd.print(" ");

 

// 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);
digitalWrite(statusLed, HIGH); // We have an active-low LED attached

 

// Set up the pair of counter reset buttons and activate internal pull-up resistors
pinMode(resetButtonA, INPUT);
digitalWrite(resetButtonA, HIGH);
pinMode(resetButtonB, INPUT);
digitalWrite(resetButtonB, HIGH);

 

pinMode(sensorPin, INPUT);
digitalWrite(sensorPin, HIGH);

 

pulseCount = 0;
flowRate = 0.0;
flowMilliLitres = 0;
totalMilliLitresA = 0;
totalMilliLitresB = 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()
{
if(digitalRead(resetButtonA) == LOW)
{
totalMilliLitresA = 0;
lcd.setCursor(0, 1);
lcd.print("0L ");
}
if(digitalRead(resetButtonB) == LOW)
{
totalMilliLitresB = 0;
lcd.setCursor(8, 1);
lcd.print("0L ");
}

 

if( (digitalRead(resetButtonA) == LOW) || (digitalRead(resetButtonB) == LOW) )
{
digitalWrite(statusLed, LOW);
} else {
digitalWrite(statusLed, HIGH);
}

 

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);
//lcd.setCursor(15, 0);
//lcd.print("*");

 

// 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
totalMilliLitresA += flowMilliLitres;
totalMilliLitresB += flowMilliLitres;

 

// During testing it can be useful to output the literal pulse count value so you
// can compare that and the calculated flow rate against the data sheets for the
// flow sensor. Uncomment the following two lines to display the count value.
//Serial.print(pulseCount, DEC);
//Serial.print(" ");

 

// Write the calculated value to the serial port. Because we want to output a
// floating point value and print() can't handle floats we have to do some trickery
// to output the whole number part, then a decimal point, then the fractional part.
unsigned int frac;

 

// Print the flow rate for this second in litres / minute
Serial.print(int(flowRate)); // Print the integer part of the variable
Serial.print("."); // Print the decimal point
// 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

 

// Print the number of litres flowed in this second
Serial.print(" "); // Output separator
Serial.print(flowMilliLitres);

 

// Print the cumulative total of litres flowed since starting
Serial.print(" "); // Output separator
Serial.print(totalMilliLitresA);
Serial.print(" "); // Output separator
Serial.println(totalMilliLitresB);

 

lcd.setCursor(0, 0);
lcd.print(" ");
lcd.setCursor(0, 0);
lcd.print("Flow: ");
if(int(flowRate) < 10)
{
lcd.print(" ");
}
lcd.print((int)flowRate); // Print the integer part of the variable
lcd.print('.'); // Print the decimal point
lcd.print(frac, DEC) ; // Print the fractional part of the variable
lcd.print(" L");
lcd.print("/min");

 

lcd.setCursor(0, 1);
lcd.print(int(totalMilliLitresA / 1000));
lcd.print("L");
lcd.setCursor(8, 1);
lcd.print(int(totalMilliLitresB / 1000));
lcd.print("L");

 

// 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++;
}