GitHub

Simple numitron iv-9 desk clock using 4 shift registers, Arduino Uno(or equivalent) and ds3231 RTC clock

According to documentation, the first iv-9 leg is common, second is indication dot. You need to connect common(first) to GND then every single leg to outputs of your ...
Hackaday

Parts: ChronoDot RTC Module (DS3231)

Macetech’s ChronoDot is a Real Time Clock module for projects requiring highly accurate time keeping and measurement. The ChronoDot uses the DS3231 chip, which features a TCXO to compensate for ...