Trying to squeeze some new life out of the tried-and-true clock paradigm can be a frustrating design challenge. Likewise, creating a clock from the absolute minimal number of parts (e.g., no more than 6 components) can lead to some sleepless nights. Finally, trying to shoehorn everything into an itty-bitty space (roughly 2-x3-inches) and making it a portable, battery-powered clock can make even a seasoned project builder scream “Uncle!” Getting everything to work like, err, clockwork, priceless.

The Dot • Watch is a new spin on the classic microcontroller clock project. It’s small, portable, low cost, and sports a unique timekeeping function. If this method of timekeeping interests you, you can purchase a more “refined” watch with a similar time display function from Tokyo Flash.

Driven by an Arduino microcontroller clone, called Freeduino, Dot • Watch forces you to do some fast number cypherin’ to tell the current time. Rather than displaying numbers on a screen, Dot • Watch uses an 8x8 LED matrix to depict the current time. In this context four columns of “dots” are used for displaying time in a 24-hour format. For example:

• Columns 1 & 3 are used for hours.
  • Column 1 represents 5 hour increments
  • Column 3 uses 1 hour increments
• Columns 6 & 7 are used for the minutes.
  • Column 6 shows minutes in 10-minute increments
  • Column 7 flashes the minutes in 2-minute increments

So how do you drive a 24-pin 8x8 LED matrix with just one Freeduino? Very carefully; seriously, there are more than enough I/O pins on the Freeduino for handling this unorthodox time display. On the next page, the point-to-point wiring schedule for Dot • Watch.