If you need a digital watch, you can of course just buy one, but what’s the fun in that? David Johnson-Davies at Technoblogy decided that he needed his own custom timepiece, and made one that takes the form of a bare PCB with components attached, including 12 APA102 RGB LEDs arranged like an analog display. Since all 12 can be powered by one output, this saves precious IO space on the ATtiny85 chip controlling the device.
When he needs to check the time, he turns it on with the press of a button, which wakes the processor and turns on the display. After 15 seconds, it’s back to sleep, allowing it to run one month on its CR2032 battery. Importantly, since the ATtiny85 is clocked via a crystal, it stays accurate without the use of an RTC module.
If this geek chic gadget looks familiar, it’s actually Johnson-Davies’ third try at an LED-based watch design. We featured the Tiny Time 2 Watch here, which distinguishes between hours and minutes by flashing LEDs instead of the colorful face of this version. If that wasn’t enough, he even made a similar design with a tiny OLED face. It goes to show that you really never know if a project is actually done!