int runtime = 0;
int Ptime = 0;
int PSenRead = 1;
int CSenRead = 0;
 int count = 0;
const int range = 1000;
const int RPtime = 1000;
int RPS = 0;
int sensor;
void setup() {
 
  // put your setup code here, to run once:
pinMode(A0, INPUT);
Serial.begin(11500);

}
void loop() {
runtime = millis();
sensor = digitalRead(A0);
// Serial.println(runtime);
if(PSenRead != sensor)
  { 
    CSenRead = sensor ;
    if (CSenRead ==0) 
    {
      count++;
    }
  PSenRead = CSenRead;
  }
  // Serial.print(count);
  // Serial.println(digitalRead(A0));
if(runtime-Ptime>range){
  RPS =  count;
  Serial.print("RPS =");
  Serial.println(RPS);
  count = 0;
  Ptime = runtime;
}



}