Hello all, first off--I'd like to thank you for all the great suggestions! Some clarifications on what I'm trying to achieve; I'm not planning to use it as a camera trigger but as a target at a gun range which keeps score via the Arduino everytime a bullet is accurately fired into a given target area covered by the IR sensors (1 foot square or so).
@jackrae: I contemplated the sound sensor as well, however, I only want the device to trigger only IF the projectile passes within a defined target area. Also, if there are other people shooting in the area as well, there may be false triggers. What do you think?
@Krupski: I plan on having the sensors be placed at least 5-10+ yards/meters away from the muzzle; so we should be able to rule out muzzle flash. Was that the only thing that made your first attempt (with the IR LED and detector) fail?
@dc42: The bullet path will be predictable but within a square foot box/ring if you will. Great suggestions! The IR emitters in the link you sent are much cheaper and have an even faster rise and fall time than what I originally found! I think you're right that I should have multiple emitters to provide as much IR illumination as possible since the projectile is travelling so fast and is a relatively small object. Perhaps multiple detectors would further help as well? Would you suggest this photodetector: http://www.newark.com/jsp/search/productdetail.jsp?SKU=32C9136
@kg4wsv: very interesting that all your chrono needed was to watch for a drop in light. I'm wondering how far above the sensors the bullet can be as still be detected.