Why Have Seven Segments When You Can Have 21?

IO user [monte] was pointed towards an 1898 display patent issued to a [George Mason] and liked the look of the ‘creepy’ font it defined. The layout used no less than 21 discrete segments to display the complete roman alphabet and numerals, which is definitely not possible with the mere seven segments we are all familiar with. [monte] then did the decent thing and created a demonstration digit using modern parts.

For the implementation, [monte] created a simple PCB by hand (with an obvious mistake) and 3D-printed an enclosure and diffuser to match. After a little debugging, a better PCB was ordered from one of the usual overseas factories. There isn’t a schematic yet, but they mention using a CH32V003 Risc-V micro, which can be seen sitting on the rear of the PCB.

Maximum flexibility is ensured by storing every glyph as a 32-bit integer, with each LED corresponding to a single bit. It’s interesting to note the display incorporates serifs, which are definitely optional, although you could display sans-serif style glyphs if you wanted to. There is now a bit of a job to work out how to map character codes to glyph codes, but you can have a go at that yourself here. It’s still early doors on this project, but it has some real potential for a unique-looking display.

We love displays—every kind. Here’s a layout reminiscent of a VFD digit but done purely mechanically. And if you must limit yourself to seven digits, what about this unique thing?

35 thoughts on “Why Have Seven Segments When You Can Have 21?

    1. I thought of this instantly as well. My dad loved his HP41C.
      However the crazy serifs on this one are kinda neat. Not sure about using 32 bits but hey 🤷🏼‍♂️, if you’ve got them.

      I’m sure there are some bitwise operations that could compact the storage as this is essentially has 4 identical quadrants. So maybe store every permutation of one quad, and then call each quad separately? I’m not great at that.

  1. I’ve seen a vintage photo of such a display. It was in “Electricity In Every-Day Life”, published 1903 if I recall. It was a 3-volume set, of which I had 2 volumes. The application in the photo was a large advertising display on top of a multistory building, taken at dusk, displaying a message that I recall as “THE AMPICO PLAYS YOUR PIANOS”.
    I have lost track of the books over the decades, so I can’t supply additional details.

    1. and the bitmap font is rectangular, which is important for packaging. personally i think 21 segments is inefficent in terms of pin addressing. the most efficient would be a square number of parallel pins. in this instance the closest square is 25, so you end up with 4 unused spaces for led. that is to say add the pins 3+7=10 so then divide 10/2=5 5×5=25.

    2. I like that 3×3, needs a tiny bit of refinement though. The A is wrong, should be an upside-down V (maybe add the middle pixel). G needs the middle pixel removed. R needs a pixel at middle-right.

      Gets you twice as many rows on your LCD, why spend the cash on a 16×2 when a 16×1 will work!

      The 5×3 reminds me of the 8-bit days trying to cram as much as possible into a tiny display.

  2. I like this design, it’d be from a Britisch cyberpunk history which never was. I frequently encounter alternative segment displays on YT. Either with more, or fewer digits. Not too long ago Pekero released a video demonstrating his 38 segment display, as it enables some other alphabets as well. The simulation of his full display with date and time in Japanese wouldn’t be too out of place in a universe like Dues Ex.

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