ArduinoCode.ino

// only 1 sensor to test
const int led = 8;
const int echo = 3;
const int trig = 2;

const long wait = 1000; //cooldown time for the sensor
unsigned long last = 0;


int spots = 4; // the number im trying to update each time the sensors are triggered

int distance;
long duration;

void setup() {
  Serial.begin (9600);
  pinMode(trig, OUTPUT); // Sets the trigPin as an Output
  pinMode(echo, INPUT); // Sets the echoPin as an Input
  pinMode(led, OUTPUT);
}

void loop() {
  
  unsigned long timePassed = millis();
  
  // Write a pulse to the HC-SR04 Trigger Pin

  digitalWrite(trig, LOW);
  delayMicroseconds(2);
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);

  // Measure the response from the HC-SR04 Echo Pin

  duration = pulseIn(echo, HIGH);

  // Determine distance from duration
  // Use 343 metres per second as speed of sound

  distance = (duration / 2) * 0.0343;

  // Send results to Serial Monitor

  if (distance <= 20) {
    if (timePassed - last >= wait){ // im trying to have a 1 second delay here without using the delay function soo that 2 sensors could be triggered at once
    Serial.print(distance);
    Serial.println(" cm");
    digitalWrite (led, HIGH);
    last = timePassed;
    spots += 1;
  Serial.print(spots);
     Serial.println(" Spots Left");
   }
  }
  else {
    digitalWrite (led, LOW);
  }
}