Measuring RPM using Hall sensor A3144

Projects Programming
3

Hi PaulS,

I got that from here.

http://forum.arduino.cc/index.php?topic=92624.0

I think the point of him putting the two is for the debounce mechanism. In my case, if I use FALLING would a code like this work?

byte revolutions;
unsigned int rpmilli;
float speed;
unsigned long timeold;
float wheel_circ = 1.634;

void setup()
{
  Serial.begin(9600);
  attachInterrupt(0, rpm_fun, FALLING);

  revolutions = 0;
  rpmilli = 0;
  timeold = 0;
}

void loop()
{
  if (revolutions >= 10) { 
    //Update RPM every 10 counts

    // calculate the revolutions per milli(second)
    rpmilli = revolutions/(millis() - timeold);

    timeold = millis();
    revolutions = 0;
    speed = rpmilli * wheel_circ/ 1000;      // speed in meters per second
    speed = 2.237*speed;                    // speed in miles per hour

    Serial.print(" Speed:");
    Serial.print(speed,DEC);
    Serial.println(" mph");
  }
}

void rpm_fun()
{
  revolutions++;
}

For now I don't have a wheel or rotating object which I can attach my magnet to, but I tried periodically bringing the magnet close to the hall sensor and it keeps showing me 0.0000000000 mph in my COM port :~