Ultrasonic sensor as a counter to change leds

Projects Programming
1

I am trying to design a "gate" using an ultrasonic sensor and count the number of times an object it passed in front of the sensor. I am using a HC-SR94 and some WS2818B RGB Leds. The lights will start on red, and change colors as the counter is increased to a set number and then reset to red.
I will use the FastLED library as well as the ]asted code:

int trigPin = 4;  //Define the pins that you will work with
int echoPin = 2;
int LEDR = 3;
int LEDV = 5;
float Speed = 0.0343;  // Sound speed at cm/us
long duration, distance;

void setup()
{
   pinMode(trigPin, OUTPUT);  //Define digital pin 7 as an output
   pinMode(echoPin, INPUT);   //Define digital pin 8 as an input
   pinMode(LEDR, OUTPUT);   //Define digital pin 10 as an output
   pinMode(LEDV, OUTPUT);   //Define digital pin 11 as an output
   digitalWrite (LEDR , LOW);  // Define digital pin 10 in a low status
   digitalWrite (LEDV , LOW);  //Define digital pin 11 in a low status
}
void loop()
 {   
   digitalWrite(trigPin, LOW);        // Make sure that the TRIG is deactivated
   delayMicroseconds(2);              // Make sure that the TRIG is in LOW
   digitalWrite(trigPin, HIGH);       // Activate the output pulse 
   delayMicroseconds(10);             // Wait for 10µs, the pulse remains active during this time
   digitalWrite(trigPin, LOW);        //Stop the pulse and wait for ECHO 
   duration = pulseIn(echoPin, HIGH) ; // pulseIn measures the time since the defined pin (echoPin) changes its status from low to high (from 0 to 1)
   distance = Speed* duration / 2;   //Divide by 2 because we want to have only the “go” time, not the “go and back” time
                                       // and divide by 29,1 because 1 is divided by the sound speed (1/SpeedSound) at cm/us
   if ( distance < 20){
       digitalWrite (LEDR , HIGH);     //If the sensor detects a distances less than 20 cm the red LED turns on
       digitalWrite (LEDV , LOW);      //and turns off the green LED
   }
   else{       // otherwise
       digitalWrite (LEDR , LOW);    // turn off the red LED
       digitalWrite (LEDV , HIGH);   //turn on the green LED }
 }
 }

Any help would be greatly appreciated.

2

If you are counting objects passing the sonar, you should add State Change Detection. Without it, an object sitting in front of the sensor will be counted multiple times.

   boolean detected = distance < 20 && distance != 0;
   if (detected != WasDetected)  // WasDetected is a global boolean variable
  {
    // The state has changed!
    WasDetected = detected;  // Remember the new state
    if (detected)
    {
      counter++; // Detector was just triggered
    }
  }
3

There's no good reason for that code, and there's no good reason for "duration" and "distance" to have global scope.

Pin numbers can be of "const byte" type.

4

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