I'm trying to build a relatively precise timer for track and field using the Arduino (hundredth of second precision). For reference, I have an Arduino Duemilanove.
Essentially, I want the Arduino to emit a sound, and I want to be able to detect when an individual crosses a laser far away, probably 100M. Ideally, I could then calculate the difference, and display it on one of these: 7-Segment Display - 4-Digit (Red) - COM-09483 - SparkFun Electronics.
However, there a couple of problems. First of all, what is the response time of a photocell, such as this one: Mini Photocell - SEN-09088 - SparkFun Electronics ? On the data sheet, it simply says "quick response". I would need a response of the order of the millisecond, or potentially 10 milliseconds in the worst case scenario.
Secondly, the wiring seems to be problematic. Indeed, it doesn't seem simple to have a photocell 100M away from the Arduino. Furthermore, I'd be great to have the display at the end of the race as well; nevertheless, I would be able to do without that. Is this extended wiring feasible ? Are there any performance drawbacks to doing things this way ?
I've seen small examples that work great on Youtube: I just don't know how those translate to real life scenarios. Do you have any suggestions on how to implement such a system ?