This is a timer that blinks green for a set amount of time, then yellow, then red when you push a recessed button. The face of the timer has the total time printed into it. (You can use the STL, or go into openscad and substitute the number/text of your choosing). It uses a lithium 3v coin cell and should be good for a few hundred cycles (deep sleep between activations).The timer program uses the internal clock of the ATTiny85 chip, which is not that accurate (but pretty repeatable) so you will have to adjust the delay numbers to get your version most accurate. You can also print a new faceplate and program for a different time. Also included: a Fritzing file for the connections and for making a PCB should you choose to. (I am planning an order from Osh Park because soldering the perfboard version is a pain.)