Celtic Christmas

A Celtic Knot-shaped PCB, populated with charlieplexed LEDs, controlled by an ATtiny13A

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I have a tiny apartment and it needed a matching Christmas tree.


The Celtic Christmas kit is 4 PCBs built on a single board which break appart and are soldered into a 3D celtic knot shapped like a christmas tree. 

Each of the 4 PCBs contain the same circut. Actually, it is the same circut and program as the heart, dragonfly and shamrock. Specifically, there are 4 Attinys wich each controll 20 LEDs which blink independantly. The LEDs are controlled by charlieplexing.

For more information on charlieplexing watch this video:


How it was Designed:

  • 80 × 0603 LEDs 80 0603 LEDs: 32 of one color, 48 in another.
  • 20 × 0603 110 ohm resistors
  • 4 × 4 Attiny13As
  • 2 × 0603 resistors for the star (optional)
  • 4 × 0603 capacitors

View all 7 components

  • 1
    Break the PCB into 3 parts: 2, 5 by 10 cm triangles; 1, 10 x 10 cm triangle.
  • 2
    Solder all the 0603 components on one side of the PCB before beginning with the other. This makes it easier to flip the board over and solder the other side.
    • The lower 5 balls get resistors,
    • The bow has a capacitor on it
    • The horizontal pad pairs get LEDs
    • The vertical pad pairs get the other color of LEDs.
    • For the titled pads look at the figure
  • 3
    Solder the 0603 components on other side of each PCB

View all 8 instructions

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siddacious wrote 12/18/2018 at 19:03 point

Just saw this posted and felt compelled to say how awesome that PCB design is. Great work!

Hope to see more detail soon!

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hammeshacks wrote 12/24/2018 at 01:04 point

Thanks! I am currently editing a build video for this (youtube under hammeshacks) and updating my web page at . Also, I will be discussing the design process for this PCB at 35C3 (day 1, 11:30 Dijkstra). I have a limited number of them, and I will be selling them there. Afterward, I plan on putting them on tindie.

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