user8167: My code is designed to play a tone when ever pin 3 is high on my Arduino. When I am examine the pins voltage with a multimeter it is always reading below 1 volt. When I examined the voltage off of a osiliscope it is reading the voltage pretty steady at 0.2 to 0.3. 
My multimeter reads at 0.26
:
My code is:
void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
}
void loop() {
  // put your main code here, to run repeatedly:
int input = digitalRead(3);
Serial.println(input);
if(input == 1){
  tone(A5,4000);
  }
}

My board looks like:

The bottom of the board looks like:


user2881: You left pin 3 floating. The multimeter will lower the voltage, resulting the the led lighting. Try enabling the pull-up resistor in pin 3 by adding pinMode(3, INPUT_PULLUP).
PS you might want to add a resistor in series with that led, or it will burn out and/or damage pin 3 on the arduino.

8167: <p>My code is designed to play a tone when ever pin 3 is high on my Arduino. When I am examine the pins voltage with a multimeter it is always reading below 1 volt. When I examined the voltage off of a osiliscope it is reading the voltage pretty steady at 0.2 to 0.3. </p>

<p><strong>My multimeter reads at 0.26</strong></p>

<p><a href="https://i.stack.imgur.com/VDZrq.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VDZrq.jpg" alt=""></a>:</p>

<p><strong>My code is:</strong></p>

<pre><code>void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
}
void loop() {
  // put your main code here, to run repeatedly:
int input = digitalRead(3);
Serial.println(input);
if(input == 1){
  tone(A5,4000);
  }
}
</code></pre>

<p><strong>My board looks like:</strong>
<a href="https://i.stack.imgur.com/WxcKw.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WxcKw.jpg" alt="enter image description here"></a>
<strong>The bottom of the board looks like:</strong>
<a href="https://i.stack.imgur.com/VmlpH.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VmlpH.jpg" alt="enter image description here"></a></p>
 2881: <p>You left pin 3 floating. The multimeter will lower the voltage, resulting the the led lighting. Try enabling the pull-up resistor in pin 3 by adding <code>pinMode(3, INPUT_PULLUP)</code>.</p>

<p>PS you might want to add a resistor in series with that led, or it will burn out and/or damage pin 3 on the arduino.</p>
