user23120: I would like to connect a headphone jack to my Arduino and make it as an output. I mean I would simply send some simple beeps.
I know that there is a breadboard friendly headphone jack, but I don't know how to wire it. I really don't know if I can simply connect the Arduino to the headphone jack, or I will need some resistors, etc. Will I need some voltage measurements? 
Also, can I do this simply by connecting the parts of the jack ( right, left, GND) to the Arduino?
So could you please help me with this?

user20245: This project connects the headphones directly to a digital pin.  Here is the schematic:

I would, however, be more cautious and add a limiting resistor.  The output of an Arduino pin should be limited to 20mA as stated here. So, using 

V=I*R 
5 = 0.02 * R 
R = 5 / 0.02 
R = 250ohms

So I would add a ~250ohm resistor in series with the head phone.  Especially if I were debugging my code.  That is, in case I accidentally left the output pin high for an extended period of time.
The head phones should have some DC resistance.  If the sound is not loud enough you might measure that DC resistance of the head phones and subtract it from the 250 ohm resistance calculated above and use a limiting resistor of that value instead.

23120: <p>I would like to connect a headphone jack to my Arduino and make it as an output. I mean I would simply send some simple beeps.</p>

<p>I know that there is a breadboard friendly headphone jack, but I don't know how to wire it. I really don't know if I can simply connect the Arduino to the headphone jack, or I will need some resistors, etc. Will I need some voltage measurements? </p>

<p>Also, can I do this simply by connecting the parts of the jack ( right, left, GND) to the Arduino?</p>

<p>So could you please help me with this?</p>
 20245: <p><a href="http://www.echanter.com/home/howto-build" rel="nofollow noreferrer">This</a> project connects the headphones directly to a digital pin.  Here is the schematic:</p>

<p><a href="https://i.stack.imgur.com/oWNwS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/oWNwS.png" alt="enter image description here"></a></p>

<p>I would, however, be more cautious and add a limiting resistor.  The output of an Arduino pin should be limited to 20mA as stated <a href="https://www.arduino.cc/en/Main/ArduinoBoardUno" rel="nofollow noreferrer">here</a>. So, using </p>

<blockquote>
  <p>V=I*R </p>
  
  <p>5 = 0.02 * R </p>
  
  <p>R = 5 / 0.02 </p>
  
  <p>R = 250ohms</p>
</blockquote>

<p>So I would add a ~250ohm resistor in series with the head phone.  Especially if I were debugging my code.  That is, in case I accidentally left the output pin high for an extended period of time.</p>

<p>The head phones should have some DC resistance.  If the sound is not loud enough you might measure that DC resistance of the head phones and subtract it from the 250 ohm resistance calculated above and use a limiting resistor of that value instead.</p>
