A digital, 3D printed sundial whose precise holes cast a shadow displaying the current time

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Surely this will need adjusting every week or so as the sun’s zenith rises and falls? Also, I’m not sure how the seasonal lengthening and shortening of the day factors into the accuracy.

I don’t think it ought to matter, if the holes are designed right. In simplistic terms, the “vertical” angle will change throughout the year, but the “horizontal” angle won’t. So long as those numeral holes aren’t round holes, but are more like slots, then this should work even with a changing vertical angle. Much like a sundial’s shadow will still hit the hour lines, even though the shadow itself becomes longer and shorter.

More precisely, the hour lines aren’t straight lines but make an analemma, but I don’t know whether this is significant enough in a small sundial that it needs to be factored in to the shape of the holes, or if the holes can just be a little bigger to allow for some wiggle room.

If it’s precise enough, it could actually be more accurate than a regular sundial, because if the pin holes can account for the analemma then that takes care of the Equation of time inaccuracy. But thinking about it, maybe we can’t account for that just in the hole’s shape, and that needs to involve marking the locations of the numbers on the base.

Without fancy adjustment, it’s still fairly accurate throughout the year, just as a regular sun dial is.


Is there a reason you didn’t embed the English version of the video?

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to make people practice their french?


Thank you! Didn’t know about it!


dayton ( ohio ) metro library has 3d printers at some locations ( printrbot metal plus , i think ) , bring them a dot stl file on a flash/thumb/usb drive/dongle and they only charge like TEN CENTS a gram !! groovey as all get out !! alas , cura ( 3d slicer software ) says that the main part of this is about a 17 hour run ( with .2 mm layers ) , which exceeds the generous maximum of a 6 hour run ~ hmmm , but if i take Gnomon_Northen_Half_1_of_2.stl and print with a .3 mm layer , which i am not sure that the machine will do , it gets awfully close to 6 hours , ahhhh , hmmmm ~
did i mention that 3d printing in pla ( only ( at this time ) ) in your choice of about 8 colours is only
TEN CENTS a gram at some dayton area libraries ??

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Awesome. Brilliant. Genius.


PRANK IDEA: Find someone who has one of these and replace it with an identical-looking version that just flashes “12:00” all day. Then tell them that they have to reset the time due to a recent solar eclipse.


And the plastic used to fab this is… UV-stabilized?

Our Texas sun here just destroys plastics.

Those questions are addressed in the comments on the mojopttix site. Basically they made the holes in the gnomon wide enough that it works with only one adjustment every six months.


PRANK IDEA: Replace the Earth with one that doesn’t spin. Then all the sundials will be stopped. Tell people that they have to unplug the Earth and plug it back in again. When it doesn’t work, tell them that they didn’t wait the full 60 seconds.



My favorite sundial (in this case, “multi-faceted”) is in the Rawlings Conservatory in Baltimore:

But sundials of any sort are fascinating to me.

As do some public libraries in my area. And let me add: Hooray for public libraries!

EDIT: That video–so metal.


I have just been running the files through the makerbot application to try to fit it to our local library’s 3d printer time slots. I think i am going to go with a 50% scaled down size size of the half gnomon with .1 at less infill than suggested to get it into the 1hr 30 min slot to see what i will get and if it will be functional before I try to book on of the longer slots to make it closer to the recommended print settings and size.


We charge ten cents a gram canadian, and have no time limits on print runs.

As such, we are the official unofficial provider of 3D printed PipBoy 3000s in the greater Edmonton area :wink:

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Too bad it looks like an excited dong.

Hunting for an on-line copy of Ian Stewart’s article on digital sundials (Sci.Am., 1991) led me to the Whackyweedia article

which in turn links to a number of instantiations of the concept.

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404 dead end.

I ordered mine last Friday and got it Tuesday! It was perfect,It came fully assembled and even had a nice set of instructions on how to set it up to get the best view. I highly recommend them! The quality is amazing!

You’re the owner of that Etsy shop (3Dexpression)… so you ordered a Digital Sundial from yourself (??). I guess it’s good that you received it only 4 days later.
(Just following the breadcrumbs: waternut131434 … https://twitter.com/waternut13134 … https://www.instagram.com/3dexpressions/ )

Anyhow, I am just teasing you :wink: I really don’t mind, quite the opposite even: I think it’s pretty cool that you’re 3D printing and selling my design !! Keep it up !
( maybe please just mention somewhere on your page my name and website )

I open-sourced all the 3D files for my Digital Sundial on Thingiverse under a CC-Attribution licence (instead of a non-commercial CC-SA or CC-NC licence, which is more typical on Thingiverse) specifically for that purpose : so that other makers could make some pocket money with it, if they ever wanted to. It is one of the most permissive licence: you can not only print your own digital sundial, but also modify it, and even sell it. The only thing you “have to do” is mention the author ( me ! ).
The underlying idea is that “Makers” (people that can make things) can potentially make unique things that “Geeks” (people that like cool stuff) might be interested in buying (such as a Digital Sundial).

Julldozer (from Mojoptix)

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