Introduction: Digital Sundial- Ancient Tech in Modern Times

Picture of Digital Sundial- Ancient Tech in Modern Times

The digital sundial speaks to the ancient desire of keeping track of time. A desire probably as old as the concept of time itself; fascination which has lead to very advanced machines. Nonetheless, for thousands of years people relied on the sun (at the time thought) moving around the earth. Some of the first documented time tracking devices date back to Egyptian times where they would raise obelisks and look at the morphing shadow as the day went by.

With this project I wanted to build a simple devise capable of taking us back, appreciating the beauty of time.

Step 1: Math :)

Picture of Math :)

Making a sun dial is not hard but there are a couple of steps one must go through to make it (relatively) accurate.

Location, location, location. Sun dials are very location specific machines (is a sundial a machine??). First you will need to find where you are on the planet. Now a days that can be very easily solved opening google earth and finding yourself, or even looking at your phone's GPS. Take note of the coordinates, you will need them later, in my case they where 37.80, -122.40.

Having this information you can now calculate three things, the angle of your gnomon, the angles for each hour and true north. Sundials are such ancient devices that using modern tech almost feels out of place, nonetheless, if you want to learn more about shadows and the sun, I would really encourage reading about Eratosthenes and how he calculated the circumference of the earth back around the 200BC!

Using AnyCalculator and the numbers recored you can find the angles you need for each hour. In turn, visiting the NGDC (National Geophysical Data Center) you can find the true north which you will need to orient the sundial correctly. To be quite honest, I don't think you need to know where true north is now a days, you could just use another clock to orient the sundial.

Step 2: Modeling & 3D Printing

Picture of Modeling & 3D Printing

Using Autodesk Inventor I first started tracing the angles on a sketch, then I created planes that went through the hour lines and the gnomon line. The hard part is done! Using each plane, extrude the right number out of it.

I modeled it in two parts so I could adjust for daylight savings and for ease of 3DP. Both files are attached, keep in mind that these are both for SF latitudes (about 37°) I attached both the base and the gnomon, be ware of the scale since they might be a little too big.

Step 3: Testing!

Picture of Testing!

Who knew... Sundials don't work that well during the night.

When the print came out of the machine the sun had long been hiding, here a quick video of the initial testings.

Step 4: Outdoor Testing! and Painting

Wouldn't it be amazing to have a huge one built in a park?

In the mean time go build your own!


jRamonGalindo made it! (author)2015-08-29

There are many things you do not say, but still awesome. Thanks a lot, many time ago I wanted make one.

Que onda! El ángulo depende de donde estes, estando en San Francisco toca como a 37.8 grados. En cuanto a las dimensiones puedes hacerlo del tamaño que quieras este era mas o menos como de unos 20 cm. Con respecto a la letra creo que era como Stencil pero la verdad puedes escoger la que tu quieras.


jRamonGalindo (author)2015-08-29

what angle you selected?, and what are the dimensions?

what type of letter is this?

Philippos Trelos (author)2015-07-11

Great idea - i love it !!

Cambenora (author)2015-05-19

I like it. It's a clever idea.

GrfxGawd (author)2015-05-02

It would be interesting to "deform" the physical proportions of the numbers in the dial to compensate for the angle as the light passes through the digit illuminated in the shadow, resulting in the numbers geometric integrity not being compromised. The result would be that the dial may look slightly Dali-esque and potentially artsy, yet the number illuminated in the shadow would be proportionally correct.

wafflemaker878 (author)2015-04-26

Wait how is it digital?

digital = in discrete steps = not continuous.

Nrgdragon (author)wafflemaker8782015-04-26

because the shadow shows the hour.

MichaelG9 (author)2015-04-23

I think the simplest way is to put one up in your back yard and simply go out every hour on the hour and mark the base with the hour.

Do one set of hour marks on the summer solstice and one set of hour marks for the winter solstice and connect them.

Then, make a set of marks between the ends for the months as they pass.

nunolanca (author)MichaelG92015-04-25

Michael, maybe the purpose of this build isn't just to do it the in simplest way. On the contrary, doing it this way makes you live a unique experience and develop skills beyond the ordinary. It brings out the creative human living inside of us! :)

MichaelG9 (author)nunolanca2015-04-25

I see all these neat (OK, neat is an understatement) ideas but rarely have the equipment (most often just the hardware, not software LOL) it takes to complete them. This project did lead me to find some great brass compass sundials of various sizes and shapes.

This is a fantastic idea and I'd love to have a larger one of these for the back yard.

nunolanca (author)2015-04-25

Congratulations! I remember reading Scientific American magazine back in 1988 or 1989, and in this amateur science column there was a challenge to build a digital Sun clock. This marvelous work of yours made it come true. Brilliant!

gabrieltaft (author)2015-04-24

This is cool, nice job sebastian!

Hannahhoo (author)2015-04-24

That's really cool! What a unique idea! Fantastic! :D

martiro7 (author)2015-04-24

Absolutely incredible! When I first started looking at your instructable, I thought you had a stepper rotating the bar - now I realize you use the rotational angle of the sun to select the appropriate digit - Amazing!! Hats off to a mind expanding project.

robolimbo (author)2015-04-24

Double triple awesome.

robolimbo (author)2015-04-24

I have always wanted to make a giant sundial out of a telephone pole. Now perhaps I will find the inspiration! Thanks!!

jellmeister (author)2015-04-24

I've been meaning to do something like this for a long time. Well done for actually doing it!

wdawson3 (author)2015-04-24

You can construct an analemma/equation of time to give you the difference between local time and civil time at any day of the year. In fact you can construct one empirically if you want, but it would take you half a year. You could also just construct one for your latitude. For that matter, one can even make an "analemmatic" sundial that auto corrects., but I digress.

wdawson3 (author)2015-04-24

It's very easy to find true North, mimicking one of the ancient methods. Erect a stick or rod where your gnomen will be, use a plumb-bob (pretend you don't own a square level) to ensure it is at right angle to the horizon (I.e is true vertical). Before noon (local time - which is when the shadow is the shortest), observe the shadow it casts, and put a rock at the end of the shadow. Tie a rope to the rod and stretch it out taut to where you put the rock. Tie a nail (or something sharp) I'm the string where the rock is. Scribe an arc from the rock in the direction the shadow will move (yes you could just scribe a circle with the distance from the rod to the rock as the radius). Then you just have to wait. The shadow will shrink away from the arc you scribed until local noon, and then grow back towards the arc. Just when it touches the arc again, put another rock at that location. Now just use your rope and nail to bisect the angle between the two rocks and the rod. That is true north. (If your thinking it will be the opposite of local noon's shadow direction, you'd be right, but practically it's difficult to tell when the sun's shadow stops sharing and begins to grow.) of course, one can scribe a few circles at different times as protection against a cloudy afternoon.

barancanaydin (author)2015-04-23


lourens01 (author)2015-04-23

Nice, very nice!

Kiteman (author)2015-04-23

This is awesome, but...

What about seasonal changes in the sun's elevation? What about daylight saving time?

Two real problems. Right now you can turn the gnomon to shift the hour, this however is not a real solution since it will make the reading inaccurate. The problem being that the angles for each hour are not uniform increments.

As for seasonal elevations, the sundial could be designed to allow more light to come through the top and bottom of each number.

Laral (author)Sebastian Morales2015-04-23

Actually, rotating the gnomon should work well. Here's why. You are really projecting the shapes of the numbers onto an imaginary cylinder, much as the gnomon's shadow is projected onto a real cylinder with an armillary sundial. The spacings of the hour planes IS uniform. The projection onto the imaginary cylinder is intercepted by the horizontal cutting plane of the ground or table. The spacings on the plane are not uniform because it is tilted WRT the axis of the gnomon, but that does not matter. The plane is 'catching' the number's shape on its way to the cylinder.

perhaps you can create separate gnomons for each season.

pc1975 (author)Kiteman2015-04-23

This thought occurred to me as well. I imagine as with modern clocks, some maintenance & repositioning could be required. Time is most likely approximate from day to day, but for daylight saving, a second numbered shaft would have to be made.

Zakafarious (author)2015-04-23

Where is the 6? Is it just me or does it jump from 5 to 7?

ianheavy (author)2015-04-23

I think this is one of the neatest things I've seen, I congratulate you on your design.

Laral (author)2015-04-23

Nice job. When I first saw the title and the thumbnail, I thought this would include a digital watch or something. I see it really is 'digital' and even 'solid state' (I just couldn't resist). :) So you projected the numbers, centered on each hour plane, from the gnomon axis to the cylinder wall, and extruded them to both surfaces. Elegantly simple. The Kiteman does make a valid point. Any solar declination, except at the equinoxes, will cut off parts of the numbers, especially at the solstices. A conical or prism-shaped cavity below the number would eliminate that. For DST you can just add a note (a.k.a. 'furniture') to add an hour and the ~dates, just as in a traditional sundial.

warpling (author)2015-04-23

Great instructable! You *should* get a huge one built in a park!

gpart (author)2015-04-23

With what did you paint it, and how?

blanchae (author)2015-04-23

What a great idea!

crickleymal (author)2015-04-23

That is brilliant. If only I had access to a printer

You have access to thousands of printers. Check out shapeways 3dHubs, you can even click on .STL files on instructables to outsource a print.

art.scottIII (author)2015-04-23

3 maybe 4 times a year depending on weather, I can found here ---

Latitude: 37° 42' NLongitude: 122° 16' W

Maybe I'll see you there Vernal equinox is especially fun.

Designer Ronald Bracewell used an oculus, a disk with a central hole, standing 8 cm in front of the dial face. The disk casts a shadow with a bright sunlight dot to indicate both time and season. Hour lines include longitude correction.

mgalyean (author)2015-04-23

An interesting take on an old device. I've always found revisiting "archaic" ideas with new insights fascinating. I do think that in this case having the numerals on the surface the shadow falls on the simplest solution, but major points for going after it from a new angle!

dorybob (author)2015-04-23

very nice work.

tcblack (author)2015-04-23

This. Is. Awesome!

rkrishnan7 (author)2015-04-23

Cool melding of ancient and modern science! Aristarchus will be prod of you!

Kdemon (author)2015-04-23

A massive one in a park would be nice, I think a prism in each numbered hole could scatter the time all over the park.

pc1975 (author)Kdemon2015-04-23

Great idea! Functional, and appealing to look at!

schmitta (author)2015-04-23

Very Good Instructable.

pc1975 (author)2015-04-23

This is one of the coolest projects I've seen in a long time! Great job!

magiceye (author)2015-04-23

Do you have to calculate the Equation Of Time on this sundial.

zappenfusen (author)2015-04-23

Pretty sharp, Left Coast!

nanoBorg88 (author)2015-04-23

Very clever. Tbh when I read digital sundial I thought you had put a GPS compass accelerometer gyro in it with a micro controller and servos to automatically position the stick in the right place. This is much better.

mosix (author)2015-04-22

very nice!!

About This Instructable




Bio: Mechanical Engineer who loves merging science and art.
More by Sebastian Morales:Capture 3D Models From Google Maps or EarthCNC Light DrawingOlas Flotadoras
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