Color-Cycling Glowing Heart Pendant

This pendant project embeds a color-cycling LED inside laser-cut semi-opaque acrylic, sold as "engraving plastic". Unlike edge-lit acrylic, where the light is brightest at the acrylic edges and at etched patterns on the surface, illuminating engraving plastic produces a lovely diffuse glow throughout the entire acrylic piece. Sandwiching the glowing acrylic between two layers of laser-cut wood allows the colors to shine through patterns of holes in the wood pieces. This Instructable contains design files for two different heart pattern pendants. If you are good with CAD, the design can be adapted to many other different shapes as well.

Materials:

• 1/8″ Sheet of Rowmark Colorhues Phantom Engraving Plastic
• 1/8″ Sheet of wood for laser cutting (single sided veneer is fine as only one side of the wood will show)
• 2 x 12mm M2 Screws and Nuts
• 2x3x4mm rectangular LEDs (available in solid colors or slow-flash color changing patterns)
• CR2032 battery
• Cord for hanging your pendant

Tools:

• Laser cutter or laser cutting service like Ponoko
• Flush cutters
• Fine-nosed pliers
• Screwdriver

Download the vector files for the wood and acrylic pieces for the shape you'd like to make. Design files for a pendant with a single heart design or intersecting hearts are attached to this step. In each file, the blue lines are for cutting and the teal lines are for etching. Each pendant has two wooden outer pieces and one acrylic inner piece. Don’t resize the pieces before cutting as they are scaled to fit around the battery. Once cut, peel any protective paper off of the all pieces.

The legs of the LED must be bent at the right position to fit through in the tiny centered holes in the wood pieces. That keeps them from moving around when the battery is inserted.

Take the two screws and insert them through the smaller set of holes in one of the wooden pieces as shown, then lay that piece down on a table so that the screws point upwards. Place the acrylic piece over the wood so that the screws pass through the corresponding holes in both layers.

Now take the LED, and place it sideways so that the LED fits into the rectangular hole in the acrylic. To figure out where the bend in the legs should be, place the 2x3x4mm LED in the slot in the acrylic and note where the small hole in the wood falls along the LED legs. That is where the bends go. Using pliers, bend the legs outward 90 degrees at that position. The bent legs should point directly away from each other.

Slightly separate the LED legs so they make a narrow “V” shape then place the LED back in the acrylic so the bent end of one leg slots into the tiny hole in the bottom wooden piece.

Take the last wooden piece and carefully lay it over the acrylic so that the tiny hole slots over the top leg of the LED and the screws pass through the correct holes in the wood. Now add the nuts and tighten them to hold everything together.

If the ends of the LEDs extend beyond the wood, cut the protruding parts off with a flush cutter so you don’t get poked when you wear your pendant.

The next step is to thread the cord through the holes in one of the wooden pieces from the outside and pull it up and away from the pendant. Tie the cord into a tight knot as close to the end as possible, and pull the cord back so that the knot is seated firmly between the two wooden pieces.

Insert the battery into the slot in the top of the pendant. It may be hard to insert the first time, but it will get easier once the LED legs settle into place. As long as the ends of the legs are seated in the holes in the wood, they should stay in place while you insert and remove the battery. You can store the battery inside the pendant by turning it around and placing it back in the battery slot so that it won’t get lost.

Your color-changing LED heart pendant is ready to wear!