
3D printed sundial whose precise holes cast a shadow displaying the current time - edward
http://www.mojoptix.com/2015/10/25/mojoptix-001-digital-sundial/
======
gulpahum
Interesting, on the Southern hemisphere, the sundial needs to point to the
South Pole and the design needs to be altered:

"in the Openscad script you can set a flag that will simply rotate upside-down
the whole swiss cheese inside the gnomon, and build a ‘Southern-hemisphere’
version of the gnomon. This way, the ‘roo can simply use this Southern-
hemisphere sundial exactly the same way a cow or a penguin would use their
Northern-hermisphere version the sundial, with just one difference: the ‘roo
will have to point the tip of his sundial toward the _South_ Pole." [1]

[1] [http://www.mojoptix.com/2015/10/25/mojoptix-001-digital-
sund...](http://www.mojoptix.com/2015/10/25/mojoptix-001-digital-sundial/)

~~~
clouddrover
> _a cow or a penguin would use their Northern-hermisphere version the
> sundial_

But penguins live in the southern hemisphere. Conspiracy?! Maybe!

It must be a Galapagos penguin:
[https://en.wikipedia.org/wiki/Galapagos_penguin](https://en.wikipedia.org/wiki/Galapagos_penguin)

~~~
TazeTSchnitzel
A YouTube commenter offered a possibly more plausible explanation:

> Angela Brett 1 month ago

> +Tainer Waynes Maybe he confused the English word penguin with the French
> word pingouin, which means auk (a bird similar to a penguin which lives in
> the Northern Hemisphere.) The French word for penguin is actually manchot.
> :)﻿

[https://www.youtube.com/watch?v=wrsje5It_UU&lc=z13uhf54clysu...](https://www.youtube.com/watch?v=wrsje5It_UU&lc=z13uhf54clysu1keb23pwrmxhryzcrqbt04)

~~~
celticninja
An auk has a black beak, the penguin in the video is of the orange beaked
cartoon type of penguin.

~~~
ArcticCelt
Maybe, but as a french speaker I can confirm that it's easy to confuse. I just
learned that Pingouin and Penguin are not the same. There is even a whole
section explaining more subtleties about why it's often missuses in the french
language.

Confusion habituelle

Par abus de langage, le pingouin est souvent confondu avec les manchots, des
oiseaux de la famille des sphéniscidés qui vivent dans l’hémisphère sud et ne
volent pas. La principale raison de cette confusion est la ressemblance avec
la plus grande des deux espèces de pingouin, le grand pingouin.

Une autre source d’erreur est la parenté étymologique entre le mot français
pingouin et celui désignant les manchots dans les principales langues
européennes comme pinguïn en néerlandais, pingüino en espagnol, Pinguin en
allemand, pinguino en italien, penguin en anglais, пингвин (pingvin) en russe,
ou encore pinguim en portugais.

Dans de nombreuses langues, deux termes différents sont utilisés pour désigner
les deux espèces de pingouin, ce terme n’a donc pas de traduction exacte. En
anglais, le terme Great Auk désigne le grand Pingouin, auk étant un terme
générique désignant le plus souvent l’ensemble des alcidés. Le petit Pingouin
est quant à lui appelé razorbill. En catalan ou en italien, respectivement les
termes de gavot et alca sont en revanche utilisés comme en français pour
désigner les deux espèces.

~~~
clouddrover
The Oxford dictionary has an entry on the origin of the word penguin:
[http://www.oxforddictionaries.com/words/what-is-the-
origin-o...](http://www.oxforddictionaries.com/words/what-is-the-origin-of-
the-word-penguin)

And they made a short video on the same:
[https://www.youtube.com/watch?v=M09oIwSQ6q4](https://www.youtube.com/watch?v=M09oIwSQ6q4)

------
medmunds
On original site: [http://www.mojoptix.com/2015/10/25/mojoptix-001-digital-
sund...](http://www.mojoptix.com/2015/10/25/mojoptix-001-digital-sundial/)

~~~
pen2l
Thanks.

Also, I encourage everyone to donate to the guy, which you can do here:
[http://www.mojoptix.com/donations-page/](http://www.mojoptix.com/donations-
page/)

What he is doing is just so wonderful and inspiring in so many ways, and to
top it all off, he's doing it without muddling up his content with ads and
other gimmicks. Please repay him for what he is so selflessly giving out for
free and without strings attached. (He is sharing all files, all 3d designs
etc... of such complicated things, a lot of people don't do that, so this guy
is just super brilliant). I don't make a lot of money but I'll be giving him
$50. I hope you can give even more. :)

------
ant6n
Skip the intro and see it in action:
[https://youtu.be/wrsje5It_UU?t=12m58s](https://youtu.be/wrsje5It_UU?t=12m58s)

~~~
Beltiras
I found the explanation of the technical challenges well done and worth the
time.

------
edejong
Probably just as impressive is this (patent just expired) digital sundial:
[http://www.digitalsundial.com/](http://www.digitalsundial.com/)

------
tyingq
Very, very, cool. This got me searching for other implementations of a digital
display sundial.

This one is interesting...uses a mask of slits
[http://www.fransmaes.nl/genk/welcome-e.htm](http://www.fransmaes.nl/genk/welcome-e.htm)
(iframes, ugh...click #8 in the left sidebar)

Edit: Another cool implementation [http://www.voshart.com/SUN-CUBE-
prototype](http://www.voshart.com/SUN-CUBE-prototype)

~~~
kilovoltaire
I bought one of those a while ago, very clever.

They are sold at
[http://www.digitalsundial.com/](http://www.digitalsundial.com/)

------
StavrosK
Can anyone tell me how OpenSCAD compares to something like SolidWorks for
designing objects? I'd much prefer to learn something open and programmable,
but if SolidWorks is much easier to use for common cases, then I'd go with
that.

I've never used any 3D designing program other than SketchUp.

~~~
IshKebab
Yeah they're not remotely comparable. For 99% of CAD stuff SolidWorks is _far_
superior. It is only with occasional tasks that are generative or highly
repetitive that you would sanely want to use OpenSCAD.

Examples of when you'd use OpenSCAD:

* Computational art (e.g. convert a photo into some 3D model, print a sound wave, etc.)

* Gears, sprockets, etc.

* Fasteners (nuts, bolts, screws, etc.)

Examples of things you would be insane to use OpenSCAD for, and should
definitely use something like SolidWorks:

* Motorbike

* Cordless drill

* CNC machine

* Well pretty much everything except the stuff I listed above

~~~
LeifCarrotson
There's also the point that SokidWorks costs $4000 minimum! (Excluding the
student license).

For many purposes, such as the author sharing his designs with random viewers,
that makes it a non-starter.

~~~
justinclift
An alternative commercial program (not OSS), but free for Hobbyists is
Autodesk Fusion 360.

It does have significant drawbacks... but if you're just getting into CNC
stuff, it has fairly decent CAM functionality in built, making it a reasonable
intro thing. :)

~~~
StavrosK
Hmm, it looks like that's only free for 30 days?

~~~
justinclift
It shouldn't be. It's supposed to be for 1 year, and be renewable. I've been
using it on and off for a few months now, without issue, if that helps. :)

~~~
StavrosK
You're right, they mention somewhere you open up the trial and select "I'm a
hobbyist" and it becomes free, thanks!

------
IvyMike
This older one is pretty neat, too. I've owned it for a while and still can't
really figure it out--the shadow mask is incredibly thin, and as far as I can
tell it works on magic.
[http://www.digitalsundial.com/product.html](http://www.digitalsundial.com/product.html)

~~~
emptybits
Here is the patent for that product. Perhaps this will shed some light on how
it works. I'll see myself out.
[http://www.google.com/patents/US5590093](http://www.google.com/patents/US5590093)

------
deutronium
Very cool!

Also apparently a 'digital' sundial was patented at one point -
[https://en.wikipedia.org/wiki/Digital_sundial](https://en.wikipedia.org/wiki/Digital_sundial)

[http://www.hineslab.com/digital-sundial/](http://www.hineslab.com/digital-
sundial/) \- The notebook drawings are cool

~~~
cfcef
So would OP be the 'fractal sundial'?

~~~
deckar01
I would consider it a holographic sundial.

A fractal is "any of various extremely irregular curves or shapes for which
any suitably chosen part is similar in shape to a given larger or smaller part
when magnified or reduced to the same size"[0].

A hologram is "a three-dimensional image reproduced from a pattern of
interference produced by a split coherent beam of radiation"[1].

The 3rd dimensional component of the hologram is modulated by the position of
the sun instead of the observer.

[0] [http://www.merriam-webster.com/dictionary/fractal](http://www.merriam-
webster.com/dictionary/fractal)

[1] [http://www.merriam-webster.com/dictionary/hologram](http://www.merriam-
webster.com/dictionary/hologram)

------
theoh
There's a high profile public digital sundial in Paris, installed in 1989:

[http://www.cadrans-solaires.fr/cadran-halles-paris.html](http://www.cadrans-
solaires.fr/cadran-halles-paris.html)

~~~
kweks
Unsure this is still there, Les Halles has been under major works for the last
4 years - haven't seen the sun dial for years.

------
bdg
I doubts the claim about only being able to produce with a 3d printer. I can
imagine easily making the layers in mass out of wood and sliding them through
bandsaws to mass produce these.

~~~
hop
That sounds orders of magnitude more difficult. You might as well 5-axis
machine them.

~~~
DannyBee
You don't need 5 axes to machine what he machined. It looks like you can do it
with 3 (at least, my CNC seems to think it will do it). 4 at the worst if you
want to spin it for some reason.

Truthfully, the problem they have is that it's still cheaper, easier, and more
accurate to do this with a subtractive CNC machine.

Plus you aren't material limited.

~~~
jessewmc
This can't be done in a single setup on a 3-axis, its not xy-monotonic (there
are overhangs). Theoretically you could do it on a 3 axis by manually
remounting the piece at different angles, but it would be hundreds if not
thousands of setups. 4 axis is definitely the practical minimum to machine it.

~~~
DannyBee
It looked like the the overhangs can be machined with a small rabbeting bit
(remember that we can use more than just end mills :P), and like i said, both
my pieces of HSM software seemed to think it wasn't trouble (IE the simulated
finished piece is within 0.001).

You are right that in practice, you would likely want a 4th axis rather than
messing around, but a 4 axis setup is just not a big deal (the 4th axis on my
woodworking CNC cost < 4k)

------
DickingAround
This kind of creativity is really something special to the 21st century; not
just that people can make things but that they can make things which are so
complex and otherwise would have been cost prohibitive before CNC technologies
like 3d printing.

~~~
lvs
You're serious? There are a few centuries of history in amazing timekeeping
engineering -- long before, guffaw, CNC. Just a random link to a Breguet, for
instance:

[http://www.breguet.com/en/house-breguet/manufacture/marie-
an...](http://www.breguet.com/en/house-breguet/manufacture/marie-antoinette-
pocket-watch)

------
rahul286
Amazing!

I am wondering how much extra time it will take for 3D printing as we add
support for 10 minute time interval, 1 minute interval and then seconds (extra
set of digits HH:MM:SS).

Also will it be practically possible to have second-level granularity?

~~~
skykooler
The width of the Sun in the sky is wide enough that it takes about 1 minute
and ten seconds to cross its own diameter. So optically speaking, it would be
pretty much impossible to have any resolution finer than a minute, no matter
how small the holes are.

~~~
Someone
I cannot see how to do it, but one way to beat that limit might be the use of
diffraction gratings. It might be possible to have the light from two opposing
edges of the solar disk interfere and produce a darker spot, thus allowing one
to draw the time in darker text on a light background.

If that can work, I guess both the design (I can't see how to design one
object that shows a number for say 5 seconds; now fit thousands in a single
object) and the engineering challenge would be quite a bit higher (at
submicrometer scales), and that the resulting contrast of the display would be
a lot lower.

~~~
05
Sun isn't a coherent light source, so no interference of light from different
sides..

------
zeristor
I loved this. Then I thought how about if you could use words which appear in
the shadow over the day.

As ever someone had already had the same idea written the code to produce the
OpenSCAD files for different wordings and put it on Github:

[https://github.com/roipoussiere/Customizable-Shadow-
Display](https://github.com/roipoussiere/Customizable-Shadow-Display)

------
mitchtbaum
Cool! Perhaps someone could cast a piece like this with concrete or baked clay
inside a larger, sturdy building to display an alphanumeric message to future
generations, only during specific alignments. I can see one potential benefit
compared to hieroglyphs, tablets, pillars[0], and other megalithic messages
that some of our ancestors left us; it would take different skills to warp its
message than simply a chisel or spray paint. One fictional story that comes to
mind, Indiana Jones' Staff of Ra[1], makes this seem like even if only for a
treasure hunt game, it would make for a fun story later on.

0:
[https://en.wikipedia.org/wiki/Ashoka_Pillars](https://en.wikipedia.org/wiki/Ashoka_Pillars)

1:
[http://indianajones.wikia.com/wiki/Headpiece_to_the_Staff_of...](http://indianajones.wikia.com/wiki/Headpiece_to_the_Staff_of_Ra)

~~~
nbohra
[http://longnow.org/clock/](http://longnow.org/clock/)

------
jhallenworld
It should display the time with Roman Numerals... then ancient Romans could
use it.

This is very cool, I'm going to have to play with OpenSCAD.

------
soheil
This is just incredible, would love to see a version with milliseconds
support:) It'd also be nice if the numbers didn't fade in/out but had a sharp
cut off point where they'd quickly switch.

~~~
periodontal
While theoretically possible, it'll be very difficult to realize physically.
If you allow fractal constructions, purely unrectifiable sets can fit the
bill. For example, here's an example in 2-dimensional space that casts a solid
shadow when the light source is along one axis but not from any other:
[https://books.google.com/books?id=usjNBQAAQBAJ&lpg=PP1&dq=&p...](https://books.google.com/books?id=usjNBQAAQBAJ&lpg=PP1&dq=&pg=PA34#v=onepage&q&f=false)

~~~
nightcracker
With millisecond precision I think it's even theoretically impossible as the
slits would become so small it destroys the shadow in an effect seen in the
double slit experiment.

But that's just a gut feeling.

~~~
Const-me
You'll have to make 500 meters thick clock, but theoretically it's possible.

~~~
meric
And practically, too, perhaps not politically or economically possible.

------
wetmore
Something like this came up on hn a while back:
[https://news.ycombinator.com/item?id=8042673](https://news.ycombinator.com/item?id=8042673)

------
tobr
Very clever! Is there any reason why you couldn't just carve out tunnels
shaped like the numbers, using a stencil typeface?

~~~
soheil
You'd need a lot more carvings.

------
supahfly_remix
How does the error vary with how far you are from the edge of the time zone?

~~~
madaxe_again
As much as local solar time differs from your time zone. This would be of
limited use in China, for instance, where the entire country is on a single
timezone, despite solar time having a four and a bit hour spread.

~~~
ansible
It would be relatively easy to modify the script for your own location in
China to display the correct time. So that it is not displaying 12:00 when the
sun is directly overhead.

------
techlover14159
Wow. This is amazing!

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dominotw
finally a killer app for 3d printing. Future is here.

------
MrBra
so this proves that time really exists ;)

~~~
mitchtbaum
If you see that when it casts these shadows, then you could call it real,
sure. You could also look at it as celestial bodies aligning and their
patterns of shades of light.

Accuracy helps a lot when using understanding of some things' existence to
find another thing and its attributes (incomplete understatement). Proof
making and checking helps a lot for someone to stay true to their beliefs and
maintain a consistently accurate path.

------
JoeAltmaier
Seems cool. But a 15-minute video? Pictures or it didn't happen.

