Project idea
An interesting project might be that of an electronic control system that monitors the position of a weight suspended in a large tube (to block any wind effect) on an elastic cord. The system could monitor the position of the weight from the bottom and top with a transmitting led and a led receiver, thus creating a null bridge between top sensors and bottom sensors. Any movement of the weight is a shift due to outside forces and so this system is able to maintain a highly sensitive position reference. Use similar simple systems to monitor each of the three axis, and you have created a very sensitive seismograph. Any displacement can be tracked in 3-D on a video monitor (as well as recorded digitally), and allow you to generate a visual picture of that displacement for use in locating direction, angle of approach, and intensity of any seismic event. Usable in anything from a state of the art seismograph for serious field work, to the heart of a truly critical performance alarm system for a high tech, high-security application.
Led sensors, null bridges, signal conditioning, digital position to analog output, (and use a basic stamp for the CPU, and a small laptop for the visual signal imaging.) None of these sub-systems is difficult, yet the marriage of all of these into a working system with actual real world potential will be a test of your electronics skills and your imagination.