This is a tool for field use, cared for but not babied. Should be weatherproof against rain and dust and 'sandstorm'. Able to withstand being dropped or banged to reasonable degree. Again, I will more than likely take care of final packaging and only desire students to bear in mind robustness is a typical failing of electronics for the consumer. Good 'warm-up' project if students ever do military design work.
Portability requires battery operation.
Components will dictate voltage. Operating time on contained power source should be several hours. Last year Dr. Hess recommended another sensor placed sufficiently in front of target frame to 'wake up' the circuitry when a shot was coming. Typically velocity will be nearer 1100-2000 fps. This would allow shooter to not worry about turning off unit during slack time.