This is a quick and simple project that uses the same printed circuit board as our MIDI light controller.

https://www.instructables.com/id/MIDI-5V-LED-Strip-Light-Controller-for-the-Spielat/

It uses an Arduino Nano to control 5V tri-colour LED strip lights that can be used to decorate your Christmas tree (our tree is very small!). If you wished to use more LEDs on a bigger tree, you would need to provide external power rather than taking the 5V from the USB connection.

The code provided gives two modes of operation - one that fades in and out of six colours (blue, purple, red, yellow, green and aqua) and the other mode flashes the LEDs half a second on and half a second off for three colours (blue, red, green).

Step 1: CNC Rout the PCB

As stated, this is the same PCB as the MIDI light controller so start by routing the PCB from the dxf file supplied.

nano-leds.dxf
Download

Step 2: Populate the PCB

Solder in all the components as per the schematic provided.

Chritmas tree Led lights board sch.pdf
Download

Step 3: Components to Populate & 3D Mount

The components to populate the board are the same as the MIDI light controller with the addition of two more components.

Four 10K resistors

Three BD681 NPN Darlington pair transistors

One PCB push button switch

And some lengths of single in-line header sockets.

3D print the PCB mount from the stl file provided.

Nano mount std 0.01.stl
Download View in 3D

Step 4: Program the Arduino Nano

Program the Arduino Nano with the code provided.

This is really just a starting point as there would be many options of fading and flashing different colours at different timings and orders. Just use your imagination. The fading is provided using pulse width modulated outputs. There is a single switch that is used to switch between the different modes of operation and the press length of the switch could be used to select from a larger selection of modes.

The present code is not very elegant as we are polling the switch continuously throughout the code. This is because we connected the switch to D12. It would have been better to have connected it to D2 which could have been used as an interrupt - a much better idea. It was an oversight at the time of laying out the board and it would have been very easy to have connected it to D2. Maybe next year :)