Design and build an animated LED sign for the engineering department. We have a very crude one that we use for the “Departmental Fair” during orientation, but it is possible to build a much fancier one (with scrolling, animations, color?) that is easily programmable. This entails hardware, low level software (to drive the LED’s) and some higher level software (web-based?) to create messages and animations.
People might be encouraged to save water if they could see how much they are using. Build an in-line water meter that measures flow – and to make it easier to hook up, have it powered by the flow of water. Can it be wireless too?
Build an oven with programmable temperature profiles for soldering surface mount parts.
If you want to do a project with wireless communication and don’t mind writing the communications software at a low level (or want to learn how to do this) check out the development system from TI. Note: this is much less capable than something like wifi, but much lower power (both Watts and processing power).
A description of the PID algorithme w/o a lot of math.
Articles with background on AC Power measurement