I want to build this -- it's a quick and dirty little device to test the shutter speed of some of the cheaper film cameras I have. The precision I'm after kind of stands in contrast to the whole lo-fi photography trend, but humor me. If nothing else, it will be a fun project for my son (the wannabe roboticist) and me to work on. I'm no electrician and the instructions are sketchy, so I need some help picking the right parts. Here they are with my questions: phototransistor (will infrared work?) 5K ohm resistor (half watt or quarter watt? 4.7K seems standard.) mono plug switch battery holder (2 AA? What about 9V? How do I know which type will work?) project case Also, do I need a particular gauge solder? Thanks for the help!