If the pin 13 LED was driven by a transistor instead of directly, pin 13 could be used as a high impedance input. Today I wanted to use 13 as an input and connect it to a sensor whose output is only rated to source 2mA. The presence of the LED circuit makes this a bad idea. Yes, I used a different p…

UNO: add transistor to remove LED drive current from pin 13

westfw February 27, 2015, 9:33am 3

(This was one of the changes made in between the original Uno, and the Uno Rev3.)

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