---

#define TRIG 3
#define ECHO 2
#define LED 5

unsigned long t = 0;
bool state = 0;

void setup() {
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
  pinMode(LED, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);

  int d = pulseIn(ECHO, HIGH) / 58;
  Serial.print("Расстояние = ");
  Serial.println(d);

  int pause;
  if (d < 50) pause = 200;
  else if (d < 100) pause = 500;
  else pause = 1000;

  if (millis() - t >= pause) {
    t = millis();
    state = !state;
    digitalWrite(LED, state);
  }
}