Hello. I'm a college student majoring in EE, and unfortunately, so far I've never worked with sensors of any kind, really, aside from the mic as an acoustic sensor. I'm wishing to take a toy piano and modify it for velocity-sensing (possibly via some kind of light sensors) and for MIDI functionality. However, first and foremost I would like to know just what kind of sensors are there? I hear names like "light sensors", "IR sensors" but I've never really seen them or used them yet. I'd like to look them up, see their pictures for sizes and read their datasheets for information. Could someone please give me a decent list? Are there IC-packaged sensors? Could I get some names of them too?