Retro Clock

I’ve had this 7 segment display for as long as I can remember, but never did anything with it until now.  I wanted to learn how to interface with real time clock chips and so this was a perfect excuse to finally use it.

It’s only breadboarded at the moment; soon I’ll etch a custom board as well as fabricate a nice case for it.




The clock chip isn’t shown in this photo.  I’m using an Arduino Nano and a Charlieplexed interface to the display.


The display doesn’t ‘know’ how to represent characters such as ‘4’ or ‘8’ and so in my program I define the numeric and time seperator characters I need.

The clock chip benefits from a watch battery (what a surprise) to prevent it from losing the time when the main unit is unplugged.