Originally I wanted to build my own watch rather than getting a regular smartwatch. But as the price of the Pebble Time dropped over the past months, I couldn't resist buying one. Even if it was only to see how it compares to my watch.

The Pebble Time was without a doubt the main inspiration for this project. The case is almost the exact width and length, only the thickness was not doable. Chronio's screen has a much lower pixel density and is only black/white. Then again it is 24% larger than the Pebble's, reducing the bezel size noticeably. In terms of processing power and features, the watches are not really comparable. The ATmega328 is no match against a Cortex M4, which can handle color graphics and animations but has a high power consumption. This is where Chronio has its biggest advantage: battery life. It can display the time for several months until the battery needs to be replaced. The current prototype has been running for 6 weeks now. However the Pebble Time lasts a week on a charge, which is still a lot compared to Android Wear or Apple devices. Disabling Bluetooth extends its battery life to about a month.

Chronio Pebble Time Dimensions 40.3 × 37 × 10.8 mm 40.5 × 37.5 × 9.5 mm Screen 96 × 96 px white/reflective 144 × 168 px 64-color Screen size 24.2 × 24.2 mm 20.1 × 23.44 mm Battery 3 V 165 mAh

CR2025 coin cell 3.7 V 130 mAh

Li-Ion (rechargeable) Battery life ~ 6 months ~ 1 month (airplane mode) Processor 16 MHz ATmega328P 100 MHz ARM Cortex-M4 Additional features Temperature sensor Bluetooth, Microphone,

Compass, Accelerometer,

Backlight, Vibration motor,

Apps/Watchfaces

In conclusion, the project was a great way to learn about low power electronics. It may not be the best watch to wear on a daily basis, but building it was a lot of fun and I would definitely consider the project a success as I already exceeded the month of planned battery life.

