Christmas is not the same without a Christmas tree; but ass I live in a dorm room, I don't have the space to put a real one. So that's why I decided to make my own Christmas tree instead!

I've wanted to experiment with edge lit acrylic for a while now, and this seemed a good project to try it out.

The idea is that you shine light on the edge, and that it refracts on any imperfections (scratches or engravings) in the acrylic; thus lighting up the plexi.
I wanted to go one step further and make it dual color: a green tree, with a red star on top!

Let's get building!

Step 1: Parts & Tools

Parts

Acrilic (PMMA / Plexiglas) sheet
Green LED 5 mm x4
82 Ohm resistor x4
Red LASER pointer
Micro USB breakout board or USB cable
Prototyping board

Tools

Soldering Iron
Drill
Sandpaper (coarse grid)
3D printer (for the base)
Laser cutter (for the acrylic)

Step 2: Electronics

To light up the acrylic, we'll need some - you guessed it - lights!
We'll use both green LEDs and a red LASER module for the dual color effect.

The idea is that the LEDs will light up the bottom part of the tree, while the laser will cover the top part, since the beam is more focused.

Start by cutting a piece of perfboard of 13x13 pads and drill a 12 mm hole in the center. Then insert 4 LEDs into the holes and solder them in place. They should not touch the perfboard, but hover about 2 mm above it.

It's now time to add the current limiting resistors to the LEDs, which can be calculated by Ohms law:

R = U/I
R = (USB voltage - LED voltage)/LED current
R = (5V - 2.5V)/30mA
R = 82 Ohm

Solder the resistor to the negative side of the LED, and connect the other leads of the resistor in a circle.

Take apart a cheap laser pointer and take out the LASER module itself (this also includes the lens). Mine had a metal casing, which happened to be the positive terminal.
We can now insert the LASER module into the hole and bend the positive leads of the LEDs onto it.

Finish off by connecting the positive and negative leads to the micro USB breakout board. Also test if everything lights up as expected.

Step 3: Mechanical Build

Now that we have the electronics out of the way, we will make the piece that will actually light up.

Cut the pieces out of 3 mm acrylic. If you have access to mat acrylic, that's the easiest way to go. Otherwise, take clear acrylic and sand the surface such that it becomes mat and will refract the light.

Slide both pieces into one another and fit them over the LEDs. This is most easily done with a twisting motion. Wrap some black electrical tape around the LEDs to contain the light.

The next step is assembling the base. Print out both parts; be careful: they are mirrored versions of each other, don't print the same one twice. Now insert the assembly we made before into the base.

That's all there is to it!