#define TRIG 3
#define ECHO 2
#define distance 40 //change this value to change how far to open. in cm

#include <Servo.h>

Servo Signal;

void setup() {
  Serial.begin(115200);
  Signal.attach(9);
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
}

void loop() {
  // v these things measure.
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);

  int duration = pulseIn(ECHO, HIGH);
  int cm = duration / 58; //change 58 to 148 if you wanna make it inch
  
  if(cm <= distance) {
  Signal.write(180); //change to 90 if you want
  } else {
  Signal.write(0);
  }
}