Dave_Moore

#include <Servo.h>
Servo myservo;

int pos = 0;
int trigger_rpm = 1000;
int val;
long last=0;
int stat=LOW;
int stat2;
int counter=0;
int sens=75;
int milisecs=500;

void open_valve(){

  for (pos = 0; pos <= 180; pos += 1) {
    // in steps of 1 degree
    myservo.write(pos);
    delay(15);
  }
  for (pos = 180; pos >= 0; pos -= 1) {
    myservo.write(pos);
    delay(15);
  }
}

void setup() {

Serial.begin(9600);
pinMode(13,OUTPUT);
myservo.attach(2);
}

void loop() {

 val=analogRead(0);
  if(val<sens)
    stat=LOW;
   else
    stat=HIGH;
   digitalWrite(13,stat);


   if(stat2!=stat){

     counter++;
     stat2=stat;
   }
   if(millis()-last>=milisecs){

     double rpm=((double)counter)/2.0*60000.0/(milisecs);
     Serial.println(rpm);
     if (rpm > trigger_rpm){
         open_valve();
     }

     counter=0;
     last=millis();
   }
}