Wedding Clock

Designing for pragmatic manufacture with limited toolset.

I wanted to do something special for my marriage to the love of my life. Since I have a big love of quantitizing and visualizing raw data, I thoguht something spirited in this way would be fun, geeky, and interesting. For the design considerations, I wanted to make sure it would always work at home, and would recover if it ever was powered down for any period of time. Interestingly enough, if you need an electronic device which can keep decently accurate time, you really only have four (practical) options:

• 1.) A precision oscillator and an uninteruptable power supply
• 2.) A GPS communicator (GPS Satellites send the current time as part of their data package)
• 3. A radio time signal reciever (usually synced to an atomic clock)
• 4.) Access to the internet

I ordered two large 4 digit 7-segment display, and a Raspberry Pi Zero W. Raspberry pi's have three nice features which fit this project quite nicely. First, it has a very generous GPIO selection for communicating with other devices. Second, it has a built in wifi chip. Lastly, it offers the easy to use python language for coding everything up in. I wrote up some code to get the latest time from the system clock (which is updated by NIST at regular intervals), compare it with the original date when the doorbell had been pressed (at our wedding) and then subtract the two, convert that time to hours, and send that information via I2C to the displays. With 8 digits available, the clock had space for a little over 11 thousand years. Since I think we'll still be married, but very long gone from this world by then, I decided to use two far left digits to display the number of minutes to the next hour. This brought the total possible time displayed to 114 years -- far more realistic than the previous 11 thousand. In the future at some point, I'm thinking about adding a feature which posts our anniversary to twitter or facebook. But for now, it's nice to be able to tell people how many thousands of hours I've been married off the top of my head.