I have a situation where I need to power an Arduino Uno R3 from a ~16V power supply.
The problem is I have no idea of the implications of voltage dropping. I think I just need a 100 Ohm resistor.
So, in case I am right, my actual question turns into: When is it better to complicate a circuit with a Zener diode?
I will also attach a photo since I understand it is easier to read from it.
Edit 1: A neighbor suggested a 4V LED that would also indicate it's working.