Tortun:
So if I go below 3V on a digital pin, the Arduino Uno would not register it as HIGH.
Thank you
Well, I didn't "say" that, but you asked about "0.5V"
In fact there's a point at which a voltage "must be" a HIGH and a similar point where some voltage "must be" a LOW, but there's a window of uncertainty between the two, a sort of no-man's land which should be avoided.