Chronio – Low power Arduino based (smart)watch

Chronio is an Arduino-based 3D-printed Watch. By not including fancy Wi-Fi and BLE connectivity, it gets several months of run time out of a 160mAh button cell. The display is an always-on 96×96 pixel Sharp Memory LCD. If telling the time is not enough, you can play a simplified version of Flappy Bird on it.
DIY watches often consist of a PCB and screen wrapped in duct tape. I wanted to change that by designing a 3D-printed case. It is closely oriented on the Pebble Time.


  • Microcontroller: Atmega328p with Arduino boot loader
  • Real Time Clock: Maxim DS3231 (<2min per year deviation)
  • Display: 96×96 pixel Sharp Memory LCD (LS013B4DN04)
  • Battery: CR2025 160mAh coin cell


  • The AT mega is in Sleep mode for most of the time and only runs once a minute to update the time or if a button is pressed. This reduces the current consumption to 2uA. Sady the display needs a certain pulse every second, which requires a complicated additional circuit. Because of this the current consumption is around 20uA. This still makes for around half a year of battery life.
  • User Interface controllable with three side buttons. Buttons are 3D-printed and activate switches on the PCB
  • Tells time, date, temperature and battery voltage on the main screen. No additional temperature sensor is needed, because the DS3231 already has one integrated for temperature compensation.
  • Stopwatch
  • Flappy Bird clone (“That would have been cool in 2013″)
  • The case consists of four 3D-printed parts. It has a thickness of only 10.8mm, which is thinner than the Apple Watch. Unfortunately it lacks screen protection.
  • Fits any 22mm Watchband

Starting with the battery life, the watch has now been running since August 7. In a previous project log I showed that the calculated run-time would be up to 6 months, which has been achieved now. The voltage has dropped to about 2.8 V, so it might last for a couple more weeks.
Additionally the source code is now online on GitHub:
As the PCB and 3d printing files have already been released, there is nothing more you need if you want to build your own copy of the watch.
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