[nmcclana] wrote out this very detailed instructible on building Mr. Burns, a sun burn alarm.  Enter your skin type, sunscreen type, and UV levels for the day and Mr. Burns will let you know when it is time to go seek shelter or re-apply that sunscreen. Built on a Propeller platform, he's using a blue LED as the UV sensor. He mentions that the device is fairly accurate, however people tend to put … [Read more...]