13. hall_effect

#define ledPin 13

#define hall_effect 2

unsigned long time;

int pulse = 0;

int rpm;

void setup() {

pinMode(ledPin, OUTPUT);

pinMode(hall_effect, INPUT);

attachInterrupt(0, count_pulse, RISING);

Serial.begin(9600);

}

void loop(){

if(millis() - time > 1000){

time = millis() ;

rpm = pulse*60/2;

Serial.print(rpm);

Serial.println(" RPM");

pulse=0;

}

}

void count_pulse(){

pulse++;

}