user41672: Okay probably not the first time this has been asked, but really, I search all over the internet and was not able to find this.
I want to drive LEDs on the output on some of my pins. Is it required to put a pull-up resistor or current limiter resistor on these? or can I just plug the LED into the output, and the other end of the LED to +vcc? Are there example schematics someplace that will show this?
thoughts? suggestions?
thanks.

user31105: You always should use a resistor.
Simply the following schematic should be used.
The resistor value can be calculated as follows:
(V + Vfwd = I * R) => R = (V + Vfwd) / I
V is 5.0 V
Vfwd is the forward voltage of the LED (this differs per type/color/brand)
I is normally max. around 20 mA (but can be briefly more if the LED does not continuously lights)
Normally R is between 100 and 500 R, but can differ if you want to add multiple LEDs.

simulate this circuit – Schematic created using CircuitLab

41672: <p>Okay probably not the first time this has been asked, but really, I search all over the internet and was not able to find this.
I want to drive LEDs on the output on some of my pins. Is it required to put a pull-up resistor or current limiter resistor on these? or can I just plug the LED into the output, and the other end of the LED to +vcc? Are there example schematics someplace that will show this?
thoughts? suggestions?
thanks.</p>
 31105: <p>You always should use a resistor.</p>

<p>Simply the following schematic should be used.</p>

<p>The resistor value can be calculated as follows:</p>

<p>(V + Vfwd = I * R) => R = (V + Vfwd) / I</p>

<p>V is 5.0 V
Vfwd is the forward voltage of the LED (this differs per type/color/brand)
I is normally max. around 20 mA (but can be briefly more if the LED does not continuously lights)</p>

<p>Normally R is between 100 and 500 R, but can differ if you want to add multiple LEDs.</p>



<p><img src="https://i.stack.imgur.com/iEF1Q.png" alt="schematic"></p>



<p><sup><a href="/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fiEF1Q.png">simulate this circuit</a> &ndash; Schematic created using <a href="https://www.circuitlab.com/" rel="nofollow">CircuitLab</a></sup></p>
