Modular Watch

Created: 2023-02-10

A follow up to my Bubble LED Watch. Using the same model of Feather M0 dev board. There is one button installed sideways on the main board. The display is on a spearate board this time. It has headers that go into matching female headers on the microcontroller board. The bottom of the case is screwed to the microcontroller board, and the top of the case is screwed to the display board. This lets me make and easily swap other display options.

Having two boards connected with standard-size headers required shaving off as much height as possible to keep the watch from being taller than the old one. The battery fits in-between the boards. The bottom case is printed in matte black PLA, the button is silver PLA. There is a gray TPU cover that plugs into the case to cover the USB port.

Pressing the button once displays the time for a few seconds. Pressing it again switches to date, and once more goes into sync mode and displays the battery voltage.

Green Wood Matrix Display

The first display is a green 15x7 LED matrix, the Charliewing from Adafruit. It displays time by lighting up points on a grid. The left two columns are the hour. They count from 1 to 12 up from the bottom. The left column is am and the column to the right of it is pm. The larger grid on the right is the minutes. It counts single minutes from left to right, and 5's of minutes from top to bottom. In date mode, the month is displayed in the hours column, and the day in the minutes column. The day of the week is displayed in a separate area at the top.

The case for this module is wood PLA stained with golden oak stain and sealed with polyurethane. The grid is printed in black on normal white printer paper, with a green gel over it. I thought the gel might help filter out ambient light, but it mostly just looks cool. It looks strangely luminescent in some lighting! It also protects the paper underneath.

Bubble Display

The second display is a recreation of the Bubble LED Watch using a spare display. To save height, the resistors are soldered on the bottom, and everything is connected point-to-point with wirewrap wire. The time, day of week, and day of month are displayed the same as the old watch. I had to add two extra resistors to pull up the i2c lines. The watch detects which display is attached by polling for the matrix dirver on the other module, and floating i2c lines can cause false positives and delay.

To Be Continued...

More displays to come! I'm currently planning other colors of the matrix display to coordinate with different outfits. I'm also brainstorming different ways to tell time that could fit on a Feather Wing without too much height.