I've decided I want to try to make most of my future projects capable of 7-32v or so operation. I like the eBay switcher modules. They are fairly efficient but I think there was a bad batch that was rated at 42v but only used 30v input capacitors one time so I choose versions where you can see the rating on the input capacitor in the picture. New ones say 50v which should be perfectly good for 30v use.