#include<Servo.h> 

Servo myServo; 

int btn = 8; 
int pos = 0; 
int relay = 4; 

void setup() {
  myServo.attach(9); 
  pinMode(btn, INPUT); 
  pinMode(relay, OUTPUT); 
  myServo.write(0);
  Serial.begin(9600); 
}

void loop() {
  if (digitalRead(btn)==HIGH) {
    pos+=20;  
    myServo.write(pos);
    delay(100);
    if (pos == 180) {
      digitalWrite(relay, HIGH);
    } else if (pos==200) {
      pos = 0; 
      myServo.write(pos);
      digitalWrite(relay, LOW);
    }
  } 
}