The Retro Binary Watch is a project by Lee Hart started way back in 1985. It uses three generic 4000-series CMOS chips to display the time in binary on four LEDs for hours (8-4-2-1), and six LEDs for minutes (32-16-8-4-2-1). But with 1980s LEDs, he couldn’t get enough brightness without excessively short battery life; so he set it aside.
Flash forward to 2025 and modern LEDs easily solve the brightness and battery life problems. It is small, cheap, and *very* vintage! Depending on your skill level, it takes about an hour to build.
