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Seven segment displays have been around for more than a century ( and form the familiar shape of the numbers in digital watches, instrument panels and many other numerical displays. They’ve been replaced in many cases by screens, but from an efficiency standpoint it’s hard to argue with the brevity of encoding the state of a numerical display in only 7 bits of information (each segment on or off)

Most seven-segment displays are monochrome, so this edge-lit version adds visual interest by using the full color capabilities of cheap RGB LED strips to illuminate each digit and even each segment (or even half-segment) of the display in a different color. Embedding the clear acrylic segments in a larger acrylic frame allows you to see completely through the entire display, which another unique aspect of this project.

This build combines small dozens of small laser-cut acrylic pieces which fit together with very tight tolerances. It uses skinny (4mm wide) LED strips which must be soldered, bent, and then slotted in between those acrylic pieces. When assembling the parts you must be willing to force pieces into place, even though it feels like you are stressing the brittle acrylic. You must also be willing to remove and re-seat said pieces and LED strips when it turns out they can’t actually be forced into place. At some point during the assembly there is a strong likelihood that you will have to remove everything and re-solder your LED strip when you realize that forcing everything into place broke one of the wires away from your LED strip or created a short circuit.

With all of that said, this is a rewarding project if you are patient and willing to rework the alignment until everything slots into place.

This write up describes the build of the 6-digit display. It’s a bit easier to build the 4-digit display, and the steps are basically the same for both, so it’s probably best to start with the 4 segment display unless you feel very confident.

The quantities required depend on whether you’re building the 4-digit or 6-digit display.

1/8″ thick sheet wood for laser cutting
1/16″ clear acrylic for laser cutting
1/4″ clear acrylic for laser cutting
Skinny (4mm wide) SK6812 3535 RGB LED strip with 60 LEDs/m (like this one)
Adhesive vinyl foil THAT IS NOT CONDUCTIVE (I used this Cricut adhesive foil)
26 AWG solid hookup wire with white insulation
30 AWG stranded wire with white insulation
A tiny amount of scotch tape
5 or 7 x 12mm M2 screws and M2 nuts
MicroController capable of controlling the LED strip
Power supply for MicroController and LED strip.
Wood glue
JB Weld (or similar) glue that can attach acrylic to wood
3-4 x M3 Screws and M3 nuts (optional but useful)
Soldering iron/solder
Wire cutter/stripper
Laser cutter (or an online service like Ponoko)”

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