The pretty-good 12V-5V DC-DC converter

I put the power supply on a board and wired it all up. I figure I’m getting around 60-65% efficiency — far better than the 42% efficiency of using a linear regulator. In other words, if my lighting stuff (the motivation for the 5-volt supply in the first place) outputs 1 watt, the battery will be hit with 1.5 watts whereas if I had used a linear regulator, it’d see 2.4 watts — the 84 watt-hour battery could run for 56 hours instead of 35 hours. Heck, it’s almost half as much time as I put into making the fucking thing!