Making a great LED triangle
Making a great LED triangle

Triangles are cheap these days. Your mobile phone can draw ten million of them in a second, and they'll be quite alright. I wanted to build something different. A triangle capable of being very dim or very bright. A triangle with tangible edges, a precise geometric lattice around soft pats of warm light.

In early 2013, I was prototyping techniques for building LED light sculptures with a very geometric look. I wanted to achieve a very uniform surface with very hard edges. This Instructable documents a technique I found for achieving this look using stacked laser-cut parts.

The project I prototyped this technique with is a 16-pixel equilateral triangle. It's made to match the spacing of commonly available WS2812B addressable LED strips with 60 pixels per meter. Several stacked layers form a painted diffusion cavity that extends all the way through the piece, completely separating the light emitted by each pixel. The top surface of each pixel is a precisely laser-cut inlay of white lighting acrylic, held in by stainless steel hardware.

Skills and tools you'll need for this technique:

  • Some variety of CAD skill. (In a pinch, you could do it all in Illustrator)
  • Basic soldering
  • Some programming skills
  • Spray adhesive (Super 77)
  • Access to a laser cutter
  • Paintbrush

    Materials:

  • Opaque acrylic (I used a nice P95 black)
  • "Lighting white" acrylic (I used 60% transmissive)
  • Thin chipboard (in the book binding section at the art supply store)
  • Titanium Dioxide White latex paint
  • Stainless steel hardware. I'm partial to "button-head socket cap screws", M3 size
  • LED strip, WS2812B "NeoPixel", 16 pixels with 60 pixels/meter spacing
  • Hookup wire (22 gauge stranded is best)
  • LED driver of choice (Fadecandy works great with this!)

    Note that the particular bolts you pick should be sized according to the thickness of the actual materials you're working with. Measure your chipboard, acrylic, etc. with calipers. When stacking materials, small deviations in thickness can add up quickly. I usually try to have a range of bolt sizes on hand, and acorn nuts give a very finished look to the back side even if it's hard to predict exactly how much bolt will poke through.

    Step 1: Laser cutting

    Making a great LED triangle
    Making a great LED triangle
    Making a great LED triangle
    Making a great LED triangle

    This approach involves many laser-cut layers. From the front to the back:

  • Bezel + Pixels (Acrylic)
  • The translucent pixels fit snugly in the corresponding holes in the bezel layer.
  • The bezel layer on its own is fragile and thin.
  • The bezel blocks light from crossing between pixels, allowing for hard edges.
  • First spacer layer (Acrylic)
  • Sits directly behind the bezel
  • Holds pixels from behind
  • More spacer layers (Acrylic or chipboard)
  • Precision is less critical for these layers
  • They open up a space large enough in each pixel for the light to thoroughly diffuse
  • In this design, about 1" of spacing was necessary
  • Try creating thicker or thinner stacks: the laser-cut parts are modular!
  • LED form layer (Chipboard)
  • This marks the best location for each LED strip, and provides some room for wiring
  • Base layer (Acrylic)
  • Mechanical support

    The design files provided are for one part of each type. You'll need to cut bezels and at least one spacer out of nice acrylic (I used a black that's matte one one side and glossy on the other). The backing and other spacers can be whatever material you like. I use acrylic for the base, for strength. The LED form works well in chipboard, so it's a little thinner. This will give you a smaller gap between pixels where the LED strip passes under the spacer layers.

    Try your design in paper first! You'll see how well it lines up with your LED strip before cutting any expensive acrylic.

    Making a great LED triangle
    triangle-prototype-pattern.ai294 KB
    Making a great LED triangle
    triangle-prototype-pattern.pdf334 KB

    Step 2: Mount and wire LEDs

    Making a great LED triangle
    Making a great LED triangle
    Making a great LED triangle
    Making a great LED triangle
    Making a great LED triangle

    I like to attach the LED form permanently to the base using Super 77 spray adhesive. Now the LED strips, cut into lengths of 1, 3, 5, and 7, can zig-zag up the triangle. The strip changes directions at each row. Mind the arrows that indicate data flow direction. You'll need to splice the strips across each bend. Due to the narrow space, creative wiring may help. Sometimes it's easier to reach a capacitor's pad than the intended +5 or Ground pads.

    The data and power input can come from anywhere you like. I use a Fadecandy controller. With 16 LEDs, it's just barely low enough power that I can power it from the USB bus. Any larger and it would need a separate power supply.

    Step 3: Stack and paint layers

    Making a great LED triangle
    Making a great LED triangle

    Stack the laser-cut layers to a height you like. You can test early and often, to make sure everything looks good with the lights on.

    When you have a layer stack you like, temporarily bolt it into place without the topmost layer and paint the inside of each pixel. You want to cover everything except the LED itself with white paint. This will increase brightness efficiency and diffuse the light even more.

    After the paint dries, you can bolt it together fully, with the diffuse white acrylic inlay in place. Success! This completes the diffuser portion of the design. You can combine this with techniques for powering, animating, and interacting with the LEDs.

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