I'm having a weird problem: my Arduino seems (in my far-from-expert interpretation) to be getting supply voltage from a digital pin.
This is my setup:
Arduino is using external supply voltage. I've connected the power supply's GND and positive outputs to Arduino's GND and Vin inputs, respectively.
I have a simple program using digital pin 3 as an input. I read the value on pin 3 and use it to set the value on pin 13, which then powers on or off an external LED.
Now, I thought that if I unplugged the Vin pin, the LED would go off, but it doesn't. Am I missing something?