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# 25-Hour Digital Myst Clock/Chronometer

Tells the time in both our "surface" system and in the "D'ni" time system used in the Myst games. Featuring custom 25-segment displays

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My wall clock in my house recently died, and with there being a running joke that I’m a time traveller thanks to my DeLorean, I thought I might as well build a replacement clock myself so it could be extra unique. Here’s what I came up with: a self-setting, self-correcting, self-adjusting wall clock/chronometer that tells time both in our timekeeping system and in the 25-hour D’ni timekeeping system used in the Myst series of video games. This's actually pretty handy if you want to know if it’s the right time to log in for certain events in Myst Online: Uru Live.

Technically it’s more a “chronometer” than a “clock” – the main difference is that chronometers have far higher accuracy & precision, to the point that they can be used for scientific experiments. For this one, it’s generally safe to assume it shouldn’t read outside 0.003s of the actual time, but in practice it’s under 0.001s

First up, a little primer – the digits used in the Myst games, aka D’ni digits, are a base-25 numbering system. This means they count up using symbols like [1], [2], [3], [4] … [22], [23], [24], [1][0]. That is, what they call “10”, we call “25” – the same way that in hexadecimal “10” represents what we call “16”. The numbers themselves are based on the numbers 0-4, which are then rotated anticlockwise 90° to represent 5/10/15/20. Here's an example, showing how you add the row & column header symbols together to get the final number symbol:

Each D'ni "day", or "yahr", is roughly 30 hours, 14 minutes long and each D'ni "second", or "prorahn", is roughly 1.4 seconds. The Guild of Archivists has more details on how the actual D’ni timekeeping system works if that interests you. There’s nothing like these digits anywhere out there on the market, aside from something crazy like using LCD displays, but that didn’t interest me much and would be a bit pricey. This whole project was designed to be as cheap, low-tech, skill-free, and expensive-tool-free as possible. So I had to come up with my own solution… And here’s how that turned out!

There’s so many places I could start with describing how this project was made so I’m gonna pick the one that probably interests most people reading this – the custom D’ni digit 25-segment displays! These are basically like my own custom 7-segment displays, but they’re easier to read with much higher contrast than store-bought 7-segs. I couldn’t find any instructions or guides out there on how to make your own (I’m sure there has to be some out there somewhere), so I had to work it all out myself from trial and error. The design itself was all made in Inkscape. Laser cutting holes in sheet acrylic and filling them with translucent resin was the way to go. The trickiest part is to have even light diffusion throughout an entire cell. The black parts are made from laser-cut 4.5mm black acrylic.

(Laser-cutting D'ni digits out of acrylic)

To help bounce light around inside each cell as much as possible, I airbrushed them with a thin white paint before filling them with resin. For the side that was to be the “front”, aka the good-quality side, I wanted the poured resin cells to be smooth & flush with the surface of the acrylic, which is tricky. I placed a piece of clear packing tape on a table with the sticky side up, stretched it out as far as I could, then carefully placed the front of the acrylic piece on the stretched tape. This kept the packing tape under constant tension, so that the resin cured against a smooth flat surface. The empty cells were filled with a 7:1 mixture of clear resin with super fine plaster of paris (mixed before pouring, obviously), which was the best-looking diffusing medium I tried. If you try this, sift the plaster into the resin while stirring to make it as evenly distributed as possible and to reduce plaster clumps in the resin. Use a needle to break up the remaining clumps and to remove any air bubbles that might be stuck in the corners. I recommend carefully picking up the cured acrylic blocks and looking at them from underneath to check for any plaster clumps or bubbles too. A vacuum chamber would be great if you’ve got one to remove the bubbles, but I didn’t have one. Once the resin was cured I carefully removed the packing tape and the segments were ready.

At 4.5mm thick, a single layer of diffusion from this material is likely good enough for most people, but just to make the light segments look extra smooth I used two layers of resin-filled acrylic. However, in this video you can see that there’s a lot of light bleeding from one cell to another, so to seal the edges well, I laser-cut some cardboard gaskets out of 2mm thick black cardboard backing board. I painted the interior edges with a silver pen to increase reflection. I used these gaskets between the two layers...

### 25_segment_dni_chronometer_normal_digits.zip

Gerber file of the normal digit shift register PCB

x-zip-compressed - 370.26 kB - 01/23/2020 at 14:04

### 25_segment_dni_display_gerber.zip

Gerber file of the 25-Segment D'ni Digit PCB

x-zip-compressed - 99.33 kB - 01/23/2020 at 14:04

### 25-segment-myst-display.svg

Layered SVG of the 25-Segment D'ni Digits including segment numbers

svg+xml - 59.93 kB - 01/23/2020 at 14:03

• ### Slow-motion digit video

RIUM+ (Mike Ando)01/26/2020 at 12:13 0 comments

Since the other videos of my Chronometer were only recorded at 30fps, I thought I'd share a video taken of its display in slow motion using my friend's camera. My friend couldn't remember off the top of their head what maximum framerate their camera supported, but by looking at the video, it's clearly 24 frames per 100ms - which means it was recorded at 240fps. The advantages of having those extra digits flashing away!

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## Discussions

Starhawk wrote 01/29/2020 at 17:53 point

Far be it from me to question the legendary RIUM+ -- but as I understand it, the particular numbering system you show here, was introduced in the Riven game and strongly implied if not explicitly described as being that of the Rivenese -- particularly since that game also points out, in a similar context IIRC, that the D'ni system is base *six*... but, do please correct me if I am wrong!

Also, obligatory: I would LOVE to have that MYST Book of yours someday :D not that I have any money... eh, maybe eventually I'll finish getting the stuff I need to build my own version. I *did* plan that out... ;) (Books: PM me if you want to chat!)

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RIUM+ (Mike Ando) wrote 01/30/2020 at 02:05 point

They were first introduced to us in Riven, but it was D'ni's numbering system that Gehn was imposing on the Rivenese people, in a similar way to how Cho tries to speak D'ni at you because Gehn was trying to make them speak D'ni too. The numerals make their appearances many times in the later games, including in the D'ni cavern itself in places like Kadish's gallery, so they're definitely D'ni in origin.

My Myst book build was pretty crazy build back in the day, but the good news is that what I said above at the end of my build log about electronics getting cheaper & easier all the time is true! Myst/Riven/Exile are now supported by ScummVM so an ARM-based Raspberry Pi could run them, and x86-based compute sticks are also now a thing too that are probably fast enough (if not a NUC  style system probably would be) if you want to go down the road of playing the native binaries. You can even get a start with one of the #myst25 25th anniversary book boxes to save time getting the book part right. These days you could do it for literally a fraction of both the time and the cost of my one! :)

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Starhawk wrote 01/30/2020 at 02:55 point

Ah :D I sit corrected! I *knew* you were correct -- you do have that reputation, you know ;) -- but I was interested to see exactly how that worked out... very cool. You really are THE expert!

By the way... I have a similar-but-not-exactly-identical Harper's "book" -- I was going to just have it do the Myst Island animation from the beginning of the game, and make the Link sound if you touched the panel... alas, I lost interest when a particular needed component was stolen by an employee of the shipping company (FedEx's USPS-partner service... I live in NC, it "disappeared" in Charlotte... I called FedEx and they did an "investigation"... when they said they couldn't find it, I said, "well, I hope whoever took it home, enjoys it" and hung up... the seller was an incredible idiot and kept insisting that I wait for it to arrive... I didn't even get my money back :( ) and even though it was a sub-\$10 part, I couldn't replace it that month... maybe someday I'll get back to it, but not today.

Oh, one other thing... computer hardware is my thing, way more than electronics -- I can usually beat a computer into working, electronics projects are generally um less successful -- around the time you were building that book, a company named VIA had created a new motherboard size called PicoITX that is the size of a really tall 2.5" notebook drive -- I bet one of those would've worked perfectly without being a custom PCB ;) VIA's CPUs are never powerful and never have been (in fact, they're absolutely horrible) but for stuff like this they're actually more than good enough. I have an early 1990s (1993 IIRC) CD of the original MYST, and although I haven't installed it on my Toshiba T3400CT (486SX-33 / 20mb RAM / 420mb HDD / DOS6.22 + WFW3.11) just yet, I have every reason to imagine that it would work fine ;) even something like a Wyse C-series client with a drive and XP would be overkill... and it's about on par with the early PicoITX boards.

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RIUM+ (Mike Ando) wrote 01/30/2020 at 11:38 point

My memory's a bit fuzzy, but from what I recall, VIA's offerings back then weren't anywhere near fast enough, particularly in the graphics department. Keep in mind that my original book didn't just play the original Myst, but ALL the games in the series - including the later 3D ones too. And I didn't want it to be a "bare minimum" playing them at the lowest graphics settings at low fps, I wanted it to play the games well too. The rough computing power equivalent that I used to use as a comparison is that it had to be fast enough to play Half-Life 2 at a consistent 30+ fps. I think there might have even been a hard limit on a specific DirectX extension that VIA's options back then didn't offer or VIA's CPUs weren't supported by the original higher-quality DVD edition of Exile I was using or something like that; I can't quite remember. Such a long time ago!

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