An Easy Transparent Edge Lit Display
Displays play a critical role in modern life, appearing ubiquitously in various forms. However, traditional flat-panel LCDs and inexpensive 7-segment LED displays often lack visual appeal. To make time displays more intriguing, hackers frequently turn to unique options like Nixie tubes and edge-lit segmented units. One notable project is by upir, who has developed an edge-lit acrylic 7-segment design, accompanied by a detailed video explanation of the process.
The concept of edge-lit displays is not new, originally using tiny tungsten filament bulbs and complex light paths to illuminate the display’s front. The modern approach replaces these with edge-lit panels and small LEDs positioned beneath each segment, concealed within a casing. This design leverages total internal reflection, a phenomenon where light entering the panel at an angle greater than 42 degrees from normal is completely reflected inside. Small LEDs, due to their wide dispersion angle, effectively guide light into the panel when placed close to the edge. The panel surface is then etched or engraved, disrupting light paths to scatter and direct light sideways to the viewer. Multiple parallel-stacked sheets create each segment of the display, typically seven for a standard 7-segment display, with an option to add more for additional features like a decimal point.
For the lighting arrangement, upir utilizes an ESP32-S3 addressable LED array. Despite its advanced capabilities, this setup is somewhat excessive for a single-digit display. Using basic Arduino code, the array can illuminate a single-segment sheet by setting one display row to white. To form a complete digit, the appropriate combination of sheets is lit. Initially considering laser cutters and CNC machines for engraving, upir opted for a more cost-effective hand-engraving method using 3D printed stencils. They also created a sheet holder and light masking arrangement in Fusion 360, which was extended into an enclosure box for the LED array, all of which could be 3D printed.
Upir’s project showcases an innovative approach to creating visually interesting displays using edge-lit acrylic panels. By documenting the entire process, they provide a valuable resource for others looking to replicate or build upon the design. This project not only highlights the creative potential of using modern LED technology but also demonstrates practical techniques for achieving professional-looking results with accessible tools and materials.
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