#define lidar A0
# define led 2
int analogvalue;
int distance;

void setup() {
  pinMode(lidar, INPUT);
  pinMode(led, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  analogvalue = analogRead(lidar);
  distance = map(analogvalue,0,1023,20000,0);
  Serial.print(distance);
  Serial.println("  mm");
 
   if (distance<=4500)
   {
      digitalWrite(led,HIGH);
   }
 else
 {
  digitalWrite(led,LOW);
 }
}