Bubble LED Clock with AC5948N Chip
As CuriousMarc's video below shows, in 1976 Texas Instruments premiered their LED watch, taking such technology from an expensive oddity to something that could be widely implemented. Per the limited electronics of the day, the technology behind the actual LED display unit is quite interesting, featuring small LEDs, with a “bubble” magnifying lens over each digit and segments formed with tiny light pipes.
After finding the chip that powered this watch, the TI AC5948N, during a repair, Marc got to work setting up a timepiece with it and a bubble LED display. Rather than carefully designing some sort of watch housing, he simply soldered components together directly.
The chip itself is used as the base of the design, with a coin-cell battery glued to the bottom. For user interface, pushbuttons straddle the chip, and attachments are made with a combination of wire wrapping and soldering. The resulting timepiece looks great with his collection of other oddball clocks.
While it’s fairly simple connections-wise, the big challenge was getting the voltage levels correct. As it turns out, the CR2032 battery supplies too much voltage for chip-happiness. After some experimentation, Marc was able to get it functioning properly by adding a diode in series with the set pin, dropping the voltage to the proper range. It's a fun build and something to keep in mind if you find an AC5948N in the wild!