I had to build a blinking device as a Proof of Value (PoV).
The concept is quite simple:
* The device should blink in green during 2 hours,
* After two hours, the device should blink in red,
* After two more hours, the device should stop blinking,
* The time counter can be reset with a magnet near the device.
* The device had to be as small as possible, as it should be wear and visible.
I chose the components, made the PCB layout, write the code, and built the case with my 3D printer.
You can read the full blog post and get the source code here:https://www.iot-experiments.com/blinking-wearable/