Inspired by the Swedish Julkalender of 2016 and the series Trollhunters, I created this amulet - which even glows when there are no trolls around.
I 3D modeled the exterior in Blender and then had it 3D printed in aluminum. Because the initial result didn't look very much like metal, I treated it with a bit of black spray paint and polished it.
To make the circuit inside the amulet, I used an Attiny85 which fades a single Neopixel LED. A small LiPo battery powers the circuit.
The name "Amuletten" is Swedish and means "the amulet".

Code

The code is a slightly modified version of one of the examples in the Adafruit NeoPixel Library.
Download code
Download library

Circuit