GPS Synchronizing Clock


All my adult life I've admired watches and timekeeping. Some of my watches consist of Japanese quartz modules with incredible features: solar charging is excellent, however the standout capability is synchronizing time to a source of precision such as the WWVB RF signal, or satellite using GPS. The objective of this project is to improve my electronics and programming skills by building a GPS synchronized clock, writing the code to implement the clock, designing and 3D printing the case.

The clock uses GPS signals to synchronize the time, is daylight savings time aware, uses the system RTC if GPS is unavailable, indicates AM/PM while showing 12-hour time. The clock is powered by an internal LiPo battery, but can also be powered externally via Mini USB, DC 5v adapter, or from a 6v solar panel. While connected to external power the internal battery charges too.

The case I designed is super simple with internal slots for the GPS module, 5v boost module, charging board, Pro Trinket, and 2,500 mAh LiPo cell.

After printing I tapped the case and back plate holes for 2.5mm. The display rests on offsets which I drilled and tapped for 2mm after printing. I didn't want to deal with the extra iterations of modeling LCD backpack mounting holes.

After running for approximately 12 hours the 2,500 mAh LiPo was still reading over 3.7v so I expect the clock will run for a reasonable period of time with no external power. It's my hope it'll run continuously on the internal battery and whatever light the external 6v solar cell can suck up.

Work Product

Here are the designs and code I made while working through the project.

  1. Clock case on Thingiverse (Fusion 360 design)
  2. Arduino sketch (Dependencies: Adafruit GFX, Adafruit LED Backpack, TimeLib, Timezone, )




Project started: 27 December 2015
Project completed: 27 June 2017