I needed a way to power a Raspberry Pi and a 7inch display in my car, a way to sense ignition key and power On/Off the screen and, in turn, cleanly shutdown the Pi and the buck converter.

Being it a Dash/CarPc I needed to keep startup times reasonable and avoid continuosly power on/off the Pi (thinking of a normal car usage, start in the morning, go to work, get back and stop at the mall and so on)...

I made a tiny board with a 12v->5v buck converter rated 3a@5v, an Attiny85, a separate linear voltage reg for the Attiny, an RTC DS3231, a backup battery (for RTC), and a 25mm fan.

The board is actually funded on a kickstarter campaign, but as a true diy project, my intent is to give them away in kit or let you all build your ones!

Kickstarter link is here, just give it a look, there are some other infos!