3D Printed Earth Clock

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Introduction: 3D Printed Earth Clock

About: Hi! I am a French mechanical student, I like to design, build things, and share them here! I'm passionate about Astronomy, especially through the practice of Astrophotography. 3D printing is also one of my hob…

Few years ago, I invented and built a clock showing how the Earth is exposed to the sun in real time.

The Earth Clock: I was happy with the result, however I am now an engineering student and I wanted to put my mechanical knowledge into practice, especially about 3D printing by designing a new version.

This is an unusual clock, it doesn't indicate time as a normal clock would, instead, it shows where your location is, compared to the night. It's a little gadget to put on your desk.

It can be called a "Tellurion" but without the moon, indeed, at this scale the moon is a 13.6mm ball, 1.5 meters away from the Earth. The clock would be far too big! Because I didn't want to make something out of scale, I decided not to include the Moon.

In the following timelapse the the speed is incredibly high, but keep in mind that the Earth's rotation is so slow that the model appears to be motionless!

As the Earth is tilted by 23.4°, it turns on two different axes at different speed rates:

- a “vertical” axis doing one full rotation in 1 year, simulating the movement around the sun, causing seasons and changes in the days length.
- a “tilted” axis doing 1 rotation every day, causing days and nights.

Supplies

  • 3D files
  • 1x Arduino Nano
  • 1x 28BYJ48 5V stepper motor
  • 1x ULN2003 driver board
  • 2x 5mm push buttons Aliexpress
  • 2x 10k Ohms resistors
  • 1x old USB cable
  • wires
  • 3x small screws
  • sandpaper, primer, paint
  • Soldering iron
  • 3D printer

Step 1: 3D PRINTING

Here you can purchase the files on Cults3D

It has been designed with Fusion 360.

Try to avoid the elephant's foot problem, it happens when the first layer is squished against the build plate, it is annoying when printing pieces intended to be put together, particularly when printing gears… so, despite the fact that the bottom surface remains ugly, I used rafts to print the 6 [16]planetary_gear.

Elephant's foot can be reduced by lowering the build plate or its temperature, if it happens anyway, it can be fixed by scratching the surface with a blade.

Here is a table showing how I printed the pieces, no supports needed, nozzle = 0.4mm.

The piece [4]Night_globe has a sacrificial layer improving bed adhesion, it needs to be removed after printing.

NameQuantityMateriallayer height (mm)
[1]Internal_gear1Black PLA0.2
[2]Bottom1Black PLA0.2
[3]Carrier2Black PLA0.2
[4]Night_globe1Black PLA0.12
[5]Night_globe_support1Black PLA0.2
[6]Carrier_plate1Black PLA0.2
[7]Cable_stopper1Black PLA0.2
[8]Sun_gear1Black PLA0.2
[9]Motor_axis1Black PLA0.2
[10]Bevel_gear11Black PLA0.2
[11]Bevel_gear21Black PLA0.2
[12]Spacer1Black PLA0.2
[13]Northern_hemisphere1Dark Grey PLA0.12
[14]southern_hemisphere1Dark Grey PLA0.12
[15]Hemispheres_link1Dark Grey PLA0.2
[16]Planetary_gear6Copper PLA0.2
[17]Year_carrier1Copper PLA0.2
[18]Foot2Copper PLA0.2
[19]Earth_axis1Copper PLA0.2

Step 2: EARTH GLOBE

Once printed, sand down the flat surfaces of the two hemispheres to avoid any gap at the equator.

Put the piece [15] into the southern hemisphere [14] without turning it, align south Africa with north America and rotate the northern hemisphere by 1/3rd of turn. After that, continents should be aligned.

_

Sand the globe with 120grit and 400grit sandpaper to remove the elephant's foot around the equator and to smooth out the surface, then spray 2 coats of primer and finally sand with super fine sandpaper (I used 800).

_

At this point, you can decide the color of your Earth: green and blue, black and white… or “realist” like mine.

To achieve a realistic look, spray blue paint over the entire globe, and paint the continents with acrylic paint according to the colors on google earth.

_

Step 3: ELECTRONICS

You can see here what you will need for the following schematic (wires are ~5cm long).

I started by soldering the two resistors and the wires on the Arduino

_

Then, I soldered these wires to the other components (buttons, ULN2003 board)

Finally, I soldered the USB cable to the ULN2003, but first, don’t forget to pass the cable through the 3D printed piece [2] !

Step 4: ARDUINO

You need to install a library: CheapStepper by Tyler Henry

Here is the code:

// Code by SimonRob and Wallgarden for the 3D Printed Earth Clock 

const uint32_t DELAY = 20979137; //20979.137 ms
#include <CheapStepper.h>

CheapStepper stepper(4, 5, 6, 7);

void setup() {
pinMode(2, INPUT);
pinMode(3, INPUT);
}

void loop() {
if (digitalRead(2) == HIGH){
stepper.step(false);
delayMicroseconds(50);
}
if (digitalRead(3) == HIGH){
stepper.step(true);
delayMicroseconds(50);
}
static uint32_t last_time;
if((digitalRead(2) == LOW)&&(digitalRead(3) == LOW)&&(micros() - last_time >= DELAY)){
last_time += DELAY;
stepper.step(false);
}
}

After uploading it, you can already see if your circuit works, by pressing either buttons, the motor should spin one way or the other. If you are not doing anything, LEDs of the driver board should change every 21s.

Step 5: ASSEMBLY

First, the motor shaft must be shortened by 4mm.

_

The assembly is detailed step by step in this video:

TIP: at 3:15, when you place the [17]year_carrier above the [1]Internal_gear, try to align the triangle of the internal gear with the beginning of the current month, it will be useful when setting the time.

Step 6: SET THE TIME

Now it should work 😊!

To set the time, you need to start at the beginning of the current month and place your country in the night, then press the button that turns the Earth counterclockwise and count the days until you reach the current day, finally go to this website and fine tune the position to match reality.

Step 7: CALCULATIONS

This step is here just if you are curious to know how I designed it and where the values are coming from (you don't need to understand this step to successfully make your own Earth Clock)

The real difficulty of the design was to find a gear combination linking the day rotation and the year rotation and to keep it compact.

Because the Earth’s axis is attached to the piece turning at 1rev/year and by knowing the ways of motions of the Earth, I had to achieve a 367.25:1 ratio.

To keep the gearbox small enough, I divided this ratio into three identical planetary gear sets with an aimed ratio of 7.1612:1 for each one. I found a gear combination giving 7.1666:1 which is:

Sun gear (Z1) =12 teeth

Planetary gears (Z2) =31 teeth

Internal Gear (Z3) =74 teeth

(Z1+Z3)/Z1 = (12+74)/12 = 7.1666…

With 3 of them in a row, the ratio is: ((12+74)/12) ^3 = 368.087963:1

In theory, 365.25 rotations of the Earth should induce one full rotation of the year carrier, but using this gear ratio, the year carrier will achieve 99.77% of this rotation (It has an error of around 20h/year which I find acceptable for a 3D printed model).

The gear ratio isn’t perfect, so I coded the Arduino according to the day’s rotation,

The speed rate of the motor must be calculated with the real gear ratio for the earth to achieve 360°/24h (solar day),

Motor speed rate: X°/24h

X = 360 / (1 - 2/368.087963) = 361.96674° (this formula results from the design itself)

Motor speed rate: 361.96674°/24h

360° => 4096 steps

361.96674° => ?? steps

361.96674 * 4096 / 360 = 4118.37713 steps/24h

24h = 86 400 000ms

86 400 000 / 4118.37713 = 20 979.1375 ms/step

Thank you for following my instructables! :D

And Thank you for the Grand prize in the Clocks speed challenge 2021!

Clocks Speed Challenge

Grand Prize in the
Clocks Speed Challenge

6 People Made This Project!

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121 Comments

0
amonphi
amonphi

2 months ago

Hi SimonRob,

Meanwhile, I congratulate you for the beautiful project, it's fantastic.
Having said that, I printed and tried the functioning of the circuit before assembling everything, and the buttons rotate the stepper motor both clockwise and counterclockwise and if they touch nothing, the LEDs change every 21s as it should.

Despite this, I have some problems, first of all a overheating of the stepper motor. If I measure the temperature arrives almost 50°C and the printed piece [2]Bottom swell slightly in the part below (if it were normal I think I'll print that piece in PETG, much more resistant to high temperatures than the PLA) ...

What is described happens by providing power supply with a Samsung charger 5V 2A smartphone but, trying to provide power supply from a USB socket on the PC, the temperature remains unfortunately unchanged, so I wanted to know if this is normal or not or what it can depend on.

For now I stop here

thanks for now

Pierluigi

0
amonphi
amonphi

Reply 2 months ago

Update:
I just realized that the overheating of the Stepper Motor also deformed me the [8] Sun_gear, as a photo attached unfortunately.

[8]Sun_gear.jpg
0
SimonRob
SimonRob

Reply 2 months ago

Hi Pierluigi

This stepper motor generate a lot of heat, that is normal, however PLA shouldn't deform below 60°C, maybe when everything is closed it may reaches 60+°C
you could try with another USB port delivering less current or print the affected pieces with PETG as you mentionned,
I am so sorry this problem happened, you are the first one repporting it.
Also I have to say that your printing quality is amazing!
Hope you'll find a way to reduce the heat
Simon ROBERT

0
amonphi
amonphi

Reply 2 months ago

Hello in the meantime thanks for your availability and for having appreciated the 3d print.

Now I will do a test with the PETG but, I am already thinking of creating a hole in the piece [2]Bottom, right in the part of the stepper motor, to be able to put a heatsink, naturally creating feet to raise [2]Bottom, then I will show you anyway.

The other thing that I have not managed to do is synchronize the time following the link https://www.timeanddate.com/worldclock/sunearth.h... Let me explain:

Once the timetable is set according to my location, in the image that is shown (which I attached as an example), a side (right or left) of the piece [4]Night_globe, with which shadow should it coincide?

= Civil Twilight (Lightst Shade)
= Nautical Twilight
= Astronomical Twilight
= Night, No Twilight (Darkest Shade)

I tried with "Night, no Twilight (Darkest Shade)" but, having tried in the afternoon and checked in the evening when it was dark, my country was not hidden in the piece [4]Night_globe.

Where is I wrong?

Time.jpg
0
SimonRob
SimonRob

Reply 2 months ago

Hi yes I would love to see the result of your work!
you need to fit to the civil twilight because it is the moment when the sun cross the horizon which is considered as "night" in my model because earth is separated 50%-50% day-night :)

0
amonphi
amonphi

Reply 2 months ago

Hi SimonRob,
I finally finished reorganizing everything and I make you a summary of what I did:

1) at [2]Bottom I practiced a hole at the base to add an aluminum heatsink with thermal adhesive heat transfer pad for the steppe motor, plus I had to close the hits for 18]foot and created 4 feet directly at the base, seen the thickness of the heatsink.
2) at [1]Internal_gear, almost certainly due to the tolerances of my 3D Printer compared to yours, in the part where the [17]Year_carrier_impoved must be positioned, since there was too much friction, I created a ring reduction of 0.9mm and 5.66mm high to rotate without forcing. Initially I tried to use thin glass paper to streamline the internal wall where the months are engraved but, it broke and detached.
3) The pieces [1]Internal_gear, [2]Bottom, [8]Sun_gear, [9]Motor_axis, [12]Spacer, [17]Year_carrier_impred I printed them in PETG for the reasons previously explained.

Now it's turned on, and I have synchronized the time following your indications and I hope this time I can.
Just to confirm, if in my Country the local hour are 11am, on the website https://www.timeanddate.com/worldclock/sunearth.h... is shown UTC time, then 09am right?

Last thing, at "step 6: set the time", when you say "Place your Country in the night", exactly where it must end/coincide in [4] Night_globe?
Maybe it's precisely this passage that I'm wrong.

I am attaching some photos in the meantime.

01.jpg02.jpg03.jpg04.jpg05.jpg06.jpg
0
fsinato
fsinato

Question 6 months ago

hi! it's an awesome project, very happy to start printing. i just have some problems getting it moving, I tried connecting everything first on a breadboard and can't get the motor to turn maybe there is some error on my part. also, can I replace the buttons with two simple ones? and in that case should I change the resistors? thank you!

0
SimonRob
SimonRob

Answer 6 months ago

Hi, thanks for printing it! First, you have to know that the rotation isn't visible, the only clue is the LEDs on the driver board changing every 21s, if it does so, it means it is working. If it's not, double-check the wiring or send me a picture of your breadboard. Also, what do you mean by simple buttons? The resistors can remain the same ;) I hope to see the result once finished :D

0
fsinato
fsinato

Reply 6 months ago

I just figured it out, it was the input not giving 5v Jej , ill try fixing that. and by simple buttons I mean the one on the connection picture, with four legs I'm using those instead, should I change the 1k resistor or it doesn't matter? thank you! I enjoy your work!

0
SimonRob
SimonRob

Reply 6 months ago

Thanks! The resistors can remain the same

0
Don9999
Don9999

Question 7 months ago

Hi
I am just starting to make the earth clock and have 2 questions for you.
The code above is it the new modified version or the original ?
Are the files available in other than stl format as I run windows 10 and my printer does not see stl files ?
My printer wants gx files
Great project and I am looking forward to completing it soon
Regards
Gordon

0
SimonRob
SimonRob

Answer 7 months ago

Hi Gordon,
The code above is the latest version :)
It is normal that your printer does not see stl files you need to use a slicer first (Cura, Simplify 3D, ...)

0
GianR1
GianR1

8 months ago

nice! but.... not easy. where can i buy one of that already done?

0
SimonRob
SimonRob

Reply 7 months ago

Sorry you can't buy one, it is not that complicated and I am here to help you if you decide to make one :)

0
pguncheon
pguncheon

8 months ago

NIce. I would love to see a larger inverted ceiling mount version with the moon added.

0
SimonRob
SimonRob

Reply 7 months ago

What a great idea indeed!

0
kjellgnilsson.kn
kjellgnilsson.kn

9 months ago

Sorry to say, my clock was also at least 37 min/day too slow even if I have use the latest updated code downloaded from SimonRob. What I did, I used the modified code by SimonRob and Wallgarden, then it work perfectly. Thank you

0
SimonRob
SimonRob

Reply 9 months ago

Glad to hear it's working now :)

0
Wallgarden
Wallgarden

10 months ago

The Earth-Clock has been adorning my desk for some time now.
The time, days and seasons are reflected on my desk. It's a jewel on my desk.
Very glad I made it. As a result, I read and learned a lot about the movements of the sun and earth. It made me more aware of how special it actually is.
I would recommend building this project to anyone.

0
SimonRob
SimonRob

Reply 9 months ago

It's a pleasure to hear that, thank you for your involvement in the project :)