[David Hopkins] built a seven segment clock, but not in a way you ... The easy part consists of Neopixels, an Arduino Nano and a DS3231 Real Time Clock. The hard part consists of Plasticard ...

His clever solution is to use an Arduino Uno R4 and take advantage of the onboard DAC. To turn on a segment, he connects a segment to a GPIO pin set high while sending 3.5 volts out of the DAC ...