title: Arduino input fluctuates
body: <p>With the following code I get a log like the one below. Why is that?</p>
  
  <pre><code>int analogPin = 5;
  int val = 0;
  
  void setup(void) {
     Serial.begin(9600);
  }
  
  void loop(void) {
     val = analogRead(analogPin);
     Serial.print("Analog reading = ");
     Serial.println(val);   
  }
  </code></pre>
  
  <p>Result:</p>
  
  <pre><code>Analog reading = 998
  Analog reading = 981
  Analog reading = 511
  Analog reading = 159
  Analog reading = 24
  Analog reading = 108
  Analog reading = 439
  Analog reading = 946
  Analog reading = 1023
  Analog reading = 420
  Analog reading = 116
  Analog reading = 25
  Analog reading = 151
  Analog reading = 542
  Analog reading = 997
  Analog reading = 982
  Analog reading = 513
  Analog reading = 161
  Analog reading = 25
  Analog reading = 107
  Analog reading = 437
  Analog reading = 945
  Analog reading = 1023
  Analog reading = 421
  Analog reading = 117
  Analog reading = 25
  Analog reading = 150
  Analog reading = 541
  Analog reading = 997
  Analog reading = 983
  Analog reading = 515
  Analog reading = 162
  Analog reading = 25
  Analog reading = 107
  Analog reading = 437
  Analog reading = 945
  Analog reading = 1023
  Analog reading = 422
  Analog reading = 117
  Analog reading = 25
  Analog reading = 149
  Analog reading = 540
  Analog reading = 997
  Analog reading = 983
  Analog reading = 516
  Analog reading = 162
  Analog reading = 25
  Analog reading = 107
  Analog reading = 436
  Analog reading = 945
  Analog reading = 1023
  Analog reading = 422
  Analog reading = 117
  Analog reading = 25
  Analog reading = 150
  Analog reading = 540
  Analog reading = 998
  Analog reading = 982
  Analog reading = 516
  Analog reading = 162
  Analog reading = 25
  Analog reading = 108
  Analog reading = 437
  </code></pre>
  
  <p>Is the result just noise?</p>
  
  <p>And as soon as I plug in a cable I see the following pattern:</p>
  
  <pre><code>Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 72
  Analog reading = 447
  Analog reading = 1023
  Analog reading = 1023
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 118
  Analog reading = 849
  Analog reading = 1023
  Analog reading = 835
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 40
  Analog reading = 401
  Analog reading = 1023
  Analog reading = 1023
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 0
  Analog reading = 89
  Analog reading = 475
  Analog reading = 1023
  Analog reading = 1023
  </code></pre>
  
  <p>Is that my heartbeat or so??? No idea what can have such an influence on a empty pin.</p>