#include <Servo.h>
Servo servo1;
int pos = 90;
void setup()
{
  servo1.attach(12);
  servo1.write(pos);
  delay(2000);
}

void loop()

{
  for (pos = 90; pos >= 0; pos -= 1)
  {
    servo1.write(pos);
    delay(15);
  }
  delay(3000);
  for (pos = 0; pos <= 90; pos += 1)
  {
    servo1.write(pos);
    delay(15);
  }
  delay(3000);
}