Peters 7-seg all mechanical display prototype 2

A 3D printed fully mechanical 7 segment display. It can be used without any electronic at all, by turning a gear.

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This is a project i am working on. I now have a working 3D printed 7 segment display prototype, that is fully mechanical, can be used without any electronics. Se my youtube video for best description of it.

The goal is to be able to serially link multiple displays all mechanically, so that one display can count to 9, two can count yo 99, three to 999 and so on.

This is a prototype !
I am already working on prototype 3 so i won't put more time into this one.
But by request i uploaded the current prototype to thingiverse all files ar located there  :-)
And remember its not a polished finished project..

First watch my youtube video about it.

Current status:

It works and can count from 0-9 when turning the gears.
But its is still a prototype and not elegant yet, i want to reduce complexity more and reduce friction. I have a lot of ideas in my head but hard to find time to do make them..

I am working on 10 position indexing gears so that one turn of the input changes display one number. See included file for my current idea regarding that: test_10_pos_index.stl

The reason i did this was the following:
Big led displays draws a lot of power and can be poorly visible in daylight.

The mechanical displays that exist today have one electromagnet for each segment, that requires a lot of wires and electronics.

This display can be used without any electronics att all, for goal keeping, clocks, etc.

And of course i wanted it to be as much 3D printed as possible.

My goal is that when it is finished, multiple display segment will be serially connectable so that if you connect 3 units they will be able to count to 999. That's when one segment switches from 9 to 0 it also switch the display connected to it +1 and so on all mechanically..

The main use of a display like this is that it can be run all mechanical, for goals/points keeping, mechanical clocks, counters, etc where no electronics at all is needed.

To make it electronic just a $2 stepper and driver is needed to drive multiple segments..
Like this one: 28BYJ-48 stepper motor and ULN2003 driver, witch make it very easy to control from a arduino and other controllers.

Great for temperature display and youtube subscription counters and so on, only draws power when switching numbers.


Prototype 2, step file

step - 7.93 MB - 02/04/2019 at 19:12



Prototype 1, step file

step - 6.34 MB - 02/04/2019 at 19:08


Zip Archive - 1.11 MB - 01/18/2019 at 20:38


  • 1 × PLA filament Used for 3d printing
  • 1 × One rubber band Used to return the segments
  • 1 × Superglue Cyanoacrylate

View project log

  • 1

    Print the parts, i have added multiple parts in each stl file so it should be easy to print.
    Use a different color for the digits then the rest. I printed my parts with 0.15 mm layer height.

    Extra parts requred:
    Superglue and one rubber band

  • 2

    First make sure the digits can slide freely in their slots on the bottom part, some filing might be required, but do not file to much so they can twist in the slots.

    When you can move them with minimal friction, then put the corresponding knobs on top, make sure they still can slide but have no play in other directions. Apply some superglue to hold the knobs and digits together.

    The center digit is different, it should be placed in the bottoms center slot with its small top extrusion facing the circle that have the shortest part of the slot. The center digit knob should be placed on the digit extrusion also facing the center of that circle. When done and it moves without friction, then apply some glue.

    Now take the two bottom index wheels, the ones with a box sticking up of them and place on the bottom part. The smaller index wheel with the pointy 7 should be on the circle with the shortest center slot as mention previously.

    Now put both the index wheels with their number 7 towards the center digit knob.
    And keep them in this position when assembling the other index gears, first it might be a good thing to temporary mount the two spur gears, and turn to see it the center digit moves freely, if not some filing might be required.

    Now its time to mount the other index wheels, every wheel is numbered. The numbers represent the current digit being displayed, but also one of the numbers on each index wheel have a arrow on top of one of its number, that number represent what segment it belongs to.

    The segments are numbered from top, left to right, the top segment are 1, the top-left segment are 2, the top-right segment are 3, the center segment are 4, the bottom-left are 5, the bottom-right are 6, and the bottom segment are 7.

    So now its time to add the indexing wheels and match them upp with the segments. And if you have the bottom indexing wheels pointing with 7 to the center, then when you mount lets say number 2 indexing wheel, its number 7 should also point at its segment.

    When all the indexing wheels are mounted, then mount the spur gears on top an put a rubber band around all the digit knobs.

    Now make sure you can turn it and that the display works, here some more filing or sanding might be required, and also some universal oil or lubricant might be helpful.

    Now put the assembly in the front part, and make sure it still works. If everything works, now put some glue to mount the front part, be careful not to glue any segments.

    Final step is to mount the two bottom knobs to the bottom with some glue to secure the index wheels and gears from coming loose.

    Good Luck, have fun !

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kmatch98 wrote 07/17/2020 at 20:52 point

After being inspired by your project, it took me year and a half, but I finally got a working display:
I haven’t been able to get it as compact as yours though. 

Thanks for posting your project, it is a really great one that inspired me to learn about designing mechanisms.

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fwacer wrote 03/31/2020 at 03:14 point

What a fantastic take on 7-segment mechanical displays. Love it! 

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seilerjacinda925 wrote 11/19/2019 at 15:24 point


Nice to meet you after viewing your profile i am Jacinda, from (jakarta) indonesia,

i have a project discussion with you please email me on: (

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matthewkleinmann wrote 03/28/2019 at 17:02 point

This is a neat project.  I built a totally manual 7 segment display for our food pantry.  I think I like my design a bit better for "public" use as there is very little to go wrong with it.  I like yours a lot because I love mechanical things and yours tickles that in me.  But still, I like the drop dead simplicity of my project.  Check out my page here for details.

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dg wrote 03/01/2019 at 12:54 point

Brilliant. You maybe missed a trick by not patenting it. A lot of petrol stations have signs for the price of their fuels. Some use LEDs which are not always visible in sunlight. In the UK we have a lot of cricket scoreboards too. Imagine wireless control using ESP8266 using these.  The low power and simplicity are good features of the design. Well done!

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Sophi Kravitz wrote 02/21/2019 at 21:49 point

This is so freaking cool! I love the planes behind your head in the video ;)

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Alexander wrote 01/29/2019 at 17:39 point

Wow. I am definitely not a mechanical engineer, so trying to fathom how things like this work baffles me! The diagrams and explanation helped a lot. I can't wait to see how version 3 works out!

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kmatch98 wrote 01/24/2019 at 10:15 point

Your concept for the mechanical display is inspiring. Can’t wait to see how you find ways to improve this.

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SephenDeVos wrote 01/24/2019 at 07:52 point

These are the things that get me all warm and fuzzy inside :) Really Cool and interesting!

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Gene wrote 01/24/2019 at 02:08 point

I think this is great! Would you be willing to also release the CAD files? Thanks for sharing this!

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Peter Lehnér wrote 02/04/2019 at 19:15 point

Sure, i have now uploaded prototype 1 and prototype 2 in step format. But since its not a finished project, the files are a bit messy with parts spread all over the place.. :-) 

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Gene wrote 02/04/2019 at 19:29 point

Thank you, Peter!

Would adding simple fillets to the edges of the segment sections that follow the cogs reduce friction also?

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donaldpapp wrote 01/23/2019 at 23:00 point

Holy crap, this is some amazing work. Well done!

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Peter Lehnér wrote 01/23/2019 at 23:22 point

Thank you ! 

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umurri wrote 01/23/2019 at 21:47 point

I find this your project very interesting. The final result is certainly not new, nor would it be retro art or retro technique. The thing that I find interesting is the originality of the solution, of the realization. Moreover, contrary to what I read in the comments, it seems to me that it is applicable to both huge displays and tiny displays. I think this idea could even go beyond the scope of conventional displays.

It should be emphasized that the system used for this type of display, requires power only in the short time when the data changes.
It could also be added that the mechanism could be moved by small pneumatic systems and not exclusively electric / electronic ones, which instead could limit themselves to the check of what should be visualized and which actuators to use (the coding).
Congratulations, but ..... do not stop surprising us.

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Peter Lehnér wrote 01/23/2019 at 23:21 point

Thanks ! I will keep up my work, trying to make it better.. 

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Milan wrote 01/23/2019 at 18:03 point

this looks amazing! very creative (well, retro actually) way to manipulate the segments.

I would love to see this working with a 28BYJ-48. 

Too bad it is just a tad too big for my kossel mini; i'm afraid that simply sizing it down will mess up the  tolerances. would make a nice clock.

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Peter Lehnér wrote 01/23/2019 at 22:52 point

Thanks ! I hope to reduce friction more in the design before putting a stepper on it, or it would need a bit of gearing down..  The biggest in this prototype is 15x10 cm.

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Mike Szczys wrote 01/21/2019 at 17:45 point

Oooh, you've got my number with this one. I'm huge fan of flip-dot and flip-segment displays. This one feels way cooler than the eletro-magnet since you ganged all of the segment changes into the singe mechanical design. Spectacular project!

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Peter Lehnér wrote 01/23/2019 at 22:43 point

Thanks !  A all mechanical flip-dot display, could be made using punch cards i think :-)

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