How about a problem to design a multiplexed moving led-matrix display? Offer the capacitor discharge method as a "hint", but make the display large enough that a basic approach will only barely work. I assume we can specify some of the components ...

It doesn't have to be an outdoor type, which taxes the available technology in a number of ways, but, it does have to be properly timed, properly multiplexed, properly adjusted for brightness, and, in the event the designer wishes, it has to have the proper time constant in the capacitor's charge path and discharge path to allow the LED to attain proper brightness, yet allow for long-term survival of the LED's and NPN's.

This can be approached in a number of ways, some requiring considerable ingenuity, and some requiring considerable facility with the associated arithmetic. No serious mathematics are required, however. Since it does require study and comprehension of datasheets, and how various parameters interact, as well as some understanding of retinal persistence and LED behavior, and how they interact, a thorough and complete treatment of the problem should earn any student a better-than-just-passing grade.

The problem probably will turn out to be quite straightforward for serious engineers in a serious engineering curriculum, yet still comprehensible to students in a technical course more focused on practical implementation than on theory. Since there are MANY variables, it will turn out to be more of a "linear programming" (optimization) type of problem than a math problem with only one discrete solution, and will challenge nearly anyone at that level.

Naturally, we won't provide the solution.

RE