[Andrew] lives in Hawaii where the climate usually doesn’t necessitate heating and cooling systems. Usually, some open windows and doors will cool the house down enough. This relies on the breeze though, and that isn’t always there. [Andrew] came up with the solution of automating an attic fan to circulate air depending on outside temperature. Sure, he could have just installed a fan with a switch, but he wanted it to do all the work itself. He used a PIC16F877 as the brains and made the pretty control panel shown above.