I have a 5V DC signal coming from an external device, which is there permanently, even when my Arduino is powered down. I need to be able to monitor this signal, to see if it ever goes low (to ground), and also be able to short it to ground myself. What is the best way of connecting this to my Ard…

Prevent Arduino taking power from input pin.

ted June 15, 2018, 1:55am 4

The inputs have high resistance, I think the leakage current is in range 5uA @ 5V

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