STEM

On past projects, when I needed multiple LEDs, I just connected each to its own GPIO pin. I knew the current only worked in one direction, but I didn’t think to take advantage of that fact. Charlieplexing is a method for arranging multiple LEDs so as to use the minimal number of pins possible.

Last summer, I found this “Smithsonian Motor-Works” set at a garage sale. Once built, it models a 4-stroke internal combustion engine. I’d shelved it for a rainy day and rediscovered it last weekend while cleaning the basement. The girls were out - time for a little father/son bonding!