#include <Servo.h>

const int trig = 9;
const int echo = 8;

const int servo = 11;

Servo gServo;

long duration;
int distance;

void setup() {
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);

  gServo.attach(servo);

  gServo.write(0);

  Serial.begin(9600);

}

void loop() {

  digitalWrite(trig,LOW);
  delayMicroseconds(3);
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);

  duration = pulseIn(echo, HIGH);

  distance = duration * 0.034 /2;

  Serial.print("Расстояние: ");
  Serial.print(distance);
  Serial.print(" см \n");

  if (distance < 20){
    Serial.println("Шлагбаум открыт \n");
    gServo.write(90);
    delay(10000);
    gServo.write(0);
    delay(1000);
  }
  delay(500);
}