My current thought that would probably be the most robust is to use a linear voltage regulator like a
7805. These are extremely common chips. The one I linked to can handle up to 35V. I would need to go to one that puts out 5V though due to how they work. That means I would also need to get a 5V to 15V dc-dc converter instead of my 12V to 15V converter. However, this would pretty much ensure nothing would fry. That being said, there is one of these built into an arduino which is the programmable micro controller that I'll be using for phase two anyways. So, I wouldn't even need one if I got the new dc-dc converter.