μWWVB is a watch stand that automatically sets the time on atomic wristwatches where regular WWVB signal isn’t available. The system acquires the correct time via GPS and sets radio-controlled clocks by emulating the amplitude-modulated WWVB time signal.
For more information, see the blog post.
Software is in the src/ directory. If you're using macOS to build the firmware image, use CrossPack.
The board design is in the board/ directory. microwwvb.brd and microwwvb.sch are the Autodesk EAGLE board and schematic. This directory also contains images of the board outline, traces, schematic, and assembled board.
- ATtiny44A microcontroller
- USGlobalSat EM-506 GPS receiver
- 20 MHz crystal oscillator (644-1039-1-ND)
- LEDs
- Red (67-1356-1-ND)
- Green (67-1357-1-ND)
- Blue (732-4989-1-ND)
- Resistors
- 499 Ω (311-499FRCT-ND)
- 1 kΩ, quantity 2 (311-1.00KFRCT-ND)
- 10 kΩ (311-10.0KFRCT-ND)
- Capacitors
- 10 pF, quantity 2 (311-1150-1-ND)
- 1 μF (445-1423-1-ND)
- Mini USB connector (H2961CT-ND)
- JST horizontal 6-Pin connector
- Pin headers
- 4-pin (609-5160-1-ND)
- 6-pin (609-5161-1-ND)
The CAD files for the physical enclosure are in the cad/ directory. The top and bottom pieces of the μWWVB station are 3D-printed, and the sides are laser-cut acrylic.