Ryan Micallef and friends put together a backyard luge challenge that they call the Mario Cup, but were having trouble making accurate measurements of participant’s tract times. Fortunately, they are also hackers, so they threw together an automatic race timing system to help make precise measurements.

Their system consists of two parts: A countdown timer/control unit at the starting line to kick off the race, and a sensor at the finishing line to end the race. A pair of Arduinos with attached xBee radios were used for communication, and a photocell buried under the snow detected when riders passed over it. [via NYC Resistor]