#define Vr A0
#define Relay 8

int val,map_val;
void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(Relay, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  val = analogRead(Vr);
  map_val=map(val,0,1023,0,100);
  Serial.println(map_val);
  if(map_val>=50)
    digitalWrite(Relay,1);
  else
    digitalWrite(Relay,0);
  
  delay(100);
}