Hi, I am able to drive my motor with a L298n using 12v . I power my arduino with the same 12v and it is easy to make the L298n and arduino share ground (which is required). However I want to connect the L298n to 14v (because there is a 2v drop in the L298n and I want max speed for my 12v motor). I don't see how I can power 14v to the L298n and a maximum of 12v to the arduino (limit of the Vin) while sharing the same ground. I am new to electronic; I am sure there is a simple solution but I can't find it. Can you help? Thanks!
The voltage regulator on the Arduino is inefficient and tends to overheat.
So, rather than supply power to Arduino Vin, buy a separate, more efficient voltage regulator that can take 14V or higher, and provide 5V directly to the Arduino (to the 5V pin).
This one is perfect, but will require soldering the connections.
Consider also using a modern, more efficient motor driver than the ancient L298. Pololu has a great selection of those as well.