This pendant measures 1.5” tall, 1.75” across, and weighs 9 grams. The circuit board (PCB) is OSHPark purple with a white silkscreen snowflake design. A CR2032 coin cell battery powers an ATtiny85 microcontroller, which flashes six blue LED’s (one at each of the points) in a couple of different patterns at random time intervals. The surface mount electronics on the front are protected by a clear, domed jewelry resin.

It comes hanging by a jump-ring on an 18" silicon necklace cord. However, the pendant could be used in many different ways, including as a Christmas tree decoration.

Battery life

A single battery will last about a month of continuous use. There is a power switch on the back so the battery won't need changing often.

Open source and programmable

The circuit board design, schematic, BOM, and Arduino code are open-source and can be found in the links on this page.

The programming port on the back can be used to upload your own Arduino code if you wish. A Tag-Connect Cable along with something like Sparkfun's Tiny AVR Programmer would be needed.