#include <Servo.h>

Servo myServo;

const int servoPin = 9; // the pin the servo is connected to

int val = 0;    // a value accumulated from data on the serial port
int angle = 60; // the current angle of the servo



void setup()
{
  Serial.begin(9600);
  myServo.attach(servoPin);
  myServo.write(angle);  // center the servo
}


void loop()
{
  if ( Serial.available())
  {
    char ch = Serial.read();

    if(ch >= '0' && ch <= '9')        // is ch a number?
   val = val * 10 + ch - '0';        // yes, accumulate the value
    else if(ch == '-') // is this the minus sign?
    {
   angle = angle - val;
   if(angle < 60)
      angle = 60;
   myServo.write(angle);      // write the new angle
   val = 0;
    }
    else if(ch == '+') // is this the plus sign?
    {
   angle = angle + val;
   if(angle > 145)
      angle = 145;
   myServo.write(angle);      // write the new angle
   val = 0;
    }
  }
}