I have a power line that will switch between 0 and 14 volts. I want to read it as a digital input into an atmega328. Can I simply join the grounds of the 14v system and my atmega and use a resistor between the 14v line and my atmega input pin? If so, how do I calculate the resistor value and wattage? The only way I know how to calculate resistance for voltage drop is with LEDs but how do I know how much current to calculate for?
Thanks
Thanks