5v to 3.3v potential divider

You could use a pot, but personally, I'd just go with a voltage divider. 1K ohm and 2K ohm works for 5V, and it'll pass 1.7mA. If you need .17mA, go with 10K/20K, if you need 17mA, go with 100/200. They make 2K resistors, but 2.2K is much more common. That should do, but some other combinations using common values include 5.1K/10K, 3.3K/6.8K, 2.2K/4.7K. It all depends on how accurate you need the voltage to be, and how much current you need to pass. Sure, we could just use trimmer pots everywhere a resistor is needed to set values more accurately, but that would get cumbersome and expensive in a hurry. I don't really suggest using potentiometers/trimmers where voltage dividers will suffice, unless adjustment or really fine tuning are a must-have feature.

Sorry pot was for demonstration purposes only