Hello!
I'm wondering if I need a resistor when I connect a led to pin 13 on an Arduino Uno? I know I need one normally, but I was thinking since there already is a LED there must also me a resistor too?
You need the resistor, the pin is directly connected to the headers. The
internal LED has its own private series resistor.
Kalveo:
Hello!
I'm wondering if I need a resistor when I connect a led to pin 13 on an Arduino Uno?
Yes.
Thank you for the quick replies!
The internal LED is not driven directly from the pin - the pin drives an Op-amp, which drives the LED. Not sure which Rev that started at.
VERY early arduinos (pre-Diecimilla) had a resistor built into the D13 signal, so they could connect directly to an LED (which they didn't have on the board, either.) Unless you have one of those, you need to add the resistor. (There are probably still tutorials floating around the net that refer to the built-in resistor. Old documents never die.)