My Servo Won't Sweep Smoothly So I've tried this a few times and I always get the same issue. When I try to run the sweep example the servo goes round 180 degrees but only in steps. Anyone know a way to fix this?

The servo I'm using is a Tower Pro Micro Servo 9G SG90

// Sweep
// by BARRAGAN &lt;http://barraganstudio.com&gt; 
// This example code is in the public domain.


#include &lt;Servo.h&gt; 

Servo myservo;  // create servo object to control a servo 
                // a maximum of eight servo objects can be created 

int pos = 0;    // variable to store the servo position 

void setup() 
{ 
  myservo.attach(9);  // attaches the servo on pin 9 to the servo object 
} 


void loop() 
{ 
  for(pos = 0; pos &lt; 180; pos += 1)  // goes from 0 degrees to 180 degrees 
  {                                  // in steps of 1 degree 
    myservo.write(pos);              // tell servo to go to position in variable 'pos' 
    delay(15);                       // waits 15ms for the servo to reach the position 
  } 
  for(pos = 180; pos&gt;=1; pos-=1)     // goes from 180 degrees to 0 degrees 
  {                                
    myservo.write(pos);              // tell servo to go to position in variable 'pos' 
    delay(15);                       // waits 15ms for the servo to reach the position 
  } 
} 


Video: http://vidd.me/A40
In electronics, as usual in situations where a cricuit is misbehaving and we don't understand why, a solution that generally works is to add a decoupling cap between +5V and GND. 

In your case, I would put at least 220uF; that would ensure two things:


the voltage used to control the servo never drops
the voltage brought to Arduino by the USB does not drop either (which would have very bad impact on the Arduino, probably resetting it)


Electrolytic caps are a must-have for every electronics hobbyist (and professional as well, of course).

You can read more about decoupling capacitors on Wikipedia.

Edit:

According to @gwideman comment, it seems that using a decoupling capacitance above 10uF in a USB 2.0 device would violate USB specs and may damage the USB host controller on the computer.

I was not aware of this limitation but I have already used decoupling capacitance up to 100uF in my circuits and never got any issue with my USB computer port.

It might be due to extra electronics on the Arduino board that would "isolate" USB power from Arduino +5V anf d GND pins, I don't know (that should probably be the topic of a specific question); or maybe I have just been lucky all this time...