//https://en.wikipedia.org/wiki/Servomotor
#include <Servo.h> //including the servo library
#define SERVO_PIN 3 //define as a constant the SERVO PIN
// global variables
bool positive = 1;
int angle= 0;
Servo Servo1; // declare a new variable of type Servo

void setup() {
  pinMode(SERVO_PIN, OUTPUT); //setup the pin as output
  Servo1.attach(SERVO_PIN);    
}

// we move the servo from 0 to 180 and back, min and max angle
void loop() {
   //managing the rotation inversion
    if (angle > 180){
      positive = 0;
      angle = 180;
    } else if (angle < 0){
      positive = 1;
      angle = 0;
    }
    //Start position of the servo
    Servo1.write(angle);
    if (positive) angle= angle+10; //increase or decrease the angle
    else angle= angle-10;
    delay(30); //Choose the right delay: the motor need time to reach the position
}