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Creation's quality: 4.7/5 (54 votes)
Evaluation of members on the printability, utility, level of detail, etc.

3D model description

A mechanical 7 segment counter

A kit to build a mechanical display that cycles through the numbers 0-9 by turning a crank.
Do you love building mechanical contraptions? Complicated looking gear trains that perform some task?
Then this kit is for you !

However, beware. It is not for the faint-hearted. The assembly instructions are 26 pages long. The counter comprises of well over 100 parts.

If you want to take it even further you can install a motor and drive it automatically.

NB: The counter only counts in one direction, up. It cannot be wound backwards. If you'd like it to count down instead, grab the reverse gear set

3D printing settings

I printed my units with a 0.2mm layer height on an Ender 3 with the standard 0.4mm nozzle in normal PLA. My printers are tuned for accuracy, well leveled to avoid elephant foot type artifacts and minimum stringing.

3D printer file information

  • 3D design format: PDF and STL Folder details Close
    • BevGearA.stl
    • BevGearB.stl
    • Case_with_crank.stl
    • Case_without_crank.stl
    • ConnectA1_m.stl
    • ConnectA2_m.stl
    • ConnectB1_m.stl
    • ConnectB2_m.stl
    • ConnectC.stl
    • ConnectC_m.stl
    • Corner.stl
    • Gear1A.stl
    • Gear1B.stl
    • Gear2A.stl
    • Gear2B.stl
    • Gear3A.stl
    • Gear3B.stl
    • Gear4A.stl
    • Gear4B.stl
    • Gear5A.stl
    • Gear5B.stl
    • Gear6A.stl
    • Gear6B.stl
    • Gear7A.stl
    • Gear7B.stl
    • Iconnect.stl
    • MMspacer.stl
    • PCB_spacer.stl
    • Pinion.stl
    • Segment.stl
    • Segment4.stl
    • Spacer.stl
    • assembly_instructions5.pdf
    • back_panel.stl
    • back_panel_e.stl
    • base.stl
    • base4.stl
    • base_m.stl
    • connectA1.stl
    • connectA2.stl
    • connectB1.stl
    • connectB2.stl
    • connectBD.stl
    • cover.stl
    • cover_m.stl
    • crankA.stl
    • crankB.stl
    • crankC.stl
    • crank_collar.stl
    • crank_gear.stl
    • earA.stl
    • earB.stl
    • hinge_arm.stl
    • motor_mount.stl
    • pivot_arm.stl
    • rest_arm.stl
    • shaftH.stl
    • shaftV.stl
    • shaftX.stl
    • slider.stl
    • slider_m.stl
    • spring.stl
    • t_connect.stl
    • tjuncA.stl
    • tjuncB.stl

    Learn more about the formats

  • Last update: 2020/06/24 at 03:09
  • Publication date: 2019/10/01 at 09:52





I am an artist and maker with a love for engineering

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@3DWP Nicely spotted. Thanks for the heads up! Will be fixed in v6.

Printing parts now, in V5 of the manual Gear 6B is mentioned twice (no big problem of course).

Heh, that's actually what I was doing to debug. I had actually written out a long response, and in describing the problem in detail, I found my bug.

The initial assembled digit is 0 not 8. I kept trying to make the dots line up to make 8 and was failing. Now I'm just chasing teeth alignment with the vertical axis gears to make everything change exactly when I want it to.

Thanks for the great design!

Hey @PDUKES3, yes, in theory all the dots should be aligned the same way as a starting point. However, it's quite easy for them to get out of alignment during the assembly. When aligning the segments to each other I'd recommend to sync up the middle segments first and do the outer segments next. You can shift the timing of the horizontal segments by sliding the drive gears (connectC, connectBD, etc.) up/down the shaft to disengage them and then rotate the mechanism before re-engaging them. Before you can do that, you need to loosen the slider (slider_m, slider), the easiest way to do that is to remove the nail to disconnect the slider from the hinge_arm and flip it up and out of the way. Sounds more complicated than it is.

I've gotten everything printed and assembled and I understand how it works for the most part. I've got a problem though, the side bars are all correct when I turn the crank, but I can't seem to get the right synchronization between the 3 horizontal layers. For these, the dots should all be aligned the same as the other units? Is there a chance you can share a picture of all three of those units at once so I could try to make the pegs match up?

@DRIESTONE You may have to double check your printing parameters. Make sure the gears move easily on each segment.

I'm having a really hard time driving with a stepper motor. I can spin gears by hand, but it takes too much torque to spin using the recommended stepper motor. Any suggestions?

@timgood827 sure thing

Or maybe I can open an issue on Github and we can work through that?

Can we do Instagram? I do not have a Facebook account.

Can you provide any guidance with programming the mainboard? I am using Atmel AVRStudio and it appears to compile correctly. I see the LED on the board flash during loading and that reports as successful. I have the fuses set to 0xFF which I believe is correct. But the board doesn't seem to be working. I believe I have the ESP8266 programmed correctly as I see that blink about every 5 seconds. I did update the SSID & password and set the proper time zone. But the mainboard doesn't blink and the stepper never moves. All voltages appear to be correct on the board. Any guidance you can provide would be most welcome.

Thank you!


Having fun putting this together with a few hiccups. You mention in the guide the circuit board is a "stripped down Arduino" - as someone without access to a circuit board printer, but has an Arduino Uno - is there a way to hook this up to that?

@grmi91: Not without major modifications. At least not while driving it mechanically.
When driving it with a motor this is not an issue.

@timgood827, Thanks for the corrections regarding the manual, I've updated it to v5 now. You should be able to get the latest by just downloading the files again. I originally had a spacer on the main shaft, but I never needed it in any of my prints so I removed it. If your bevel gear slides up on the shaft easily, adding a spacer on the shaft is a good solution. Glue will work too, but it makes it harder to disassemble later.
The distance of the hall sensor isn't crucial. Mine is about 1mm away from the underside of the board. You don't want it to stick out too far and get in the way of the gears below.

can we put 4 boxes side by side to go up to 9999 without the cranks getting in the way?
Thanks a lot for your answer

For the PCB I see it now. I doing the V2.1 PCB ( I had boards made before you did the new release). The Hall Effect sends is bent over and lays flat against the PCB.

Great! Where can we get the updated manual?

I have also noticed another minor typo unfortunately. On Page 7 the MM_spacer is shown as 1x but it should be 2x and the Pcb_spacer is also shown as 1x but should be 3x. I would also advise people that on Page 8, buy the 2.5mm self-tapping screws in 8mm length as the blind hole in the Tconnect part won't take anything deeper unless you want to drill it out.

I am almost finished my first digit. I'm having a little problem with bevel_gearA riding up the shaft and skipping teeth. I'm guessing I might have a little too much friction in the system? I did work each segment assembly to be as free as possible without being too loose. I think I might need a spacer between connectBD and bevel_gearA to keep it in mesh with the other bevel gear. Or I suppose I could glue it in place. There's no direction regarding that in Step 16 on Page 22.

Also with the PCB assembly, how far out should the Hall Effect sensor sit from the board? Do you have it very close to the gear face that has the magnet in it?

Hi @TIMGOOD827, you're right the labels were switched in the manual v3. I have updated the manual to v4 now.

I also just noticed that in the STL ConnectB2-m has the round hole but in the manual it is showing the hexagonal hole.

I'm working through assembling my first digit. I am on Part 2 Connecting the segments Step 2. I am looking at the ConnectA2-m and ConnectB2-m and if I compare them to the STL files, it looks to me like they are reversed. The alignment dots in the manual images do not match the STL files. Can you verify please?

all of my segments are out of sync and are not making anything close to numbers. I followed the guide very closely. any ideas?

Hi. it's really great but I have a question, can we put 4 boxes side by side to go up to 9999 without the cranks getting in the way?
Thanks a lot for your answer

@Kyletal Hey, the mechanism works best when the parts fit together with minimal friction but being not so loose that they rattle around. I find, when I make sure the holes are a good size by pushing a drill bit with just the right diameter for my nails through them and make sure there are no blobby printing artifacts inside the gear holes and on the shafts, everything works very reliably.
Thanks @wsadasdasdddd for your tips as well.

@Kyletal, initially I had the same problem. Check out my make / print guide I put in a few hints on how to avoid that. For your, to make it short, test the spring mechanism of EACH segment by itself before assembly of the digit. What I do is:
Step 1: Widen the hinges and the spring with a 1.2mm drill, make sure the pins rotate freely in them before doing anything else
Step 2: Assemble one segment but DO NOT assemble the hinges and the actual segment (yellow part)
Step 3: Hook up the middle hinge to the base including the spring
Step 4: Make sure the hinge freefalls when you move it (e.g. hold it upside down, it has to move freely without touching)
Step 5: Test for free and easy movement, if the spring doesn't snap into both ends rework the base with a sharp knive and widen the slots
Step 6: Hook up the segment to the centre hinge and test the mechanism it should snap easily into place. If not: Rework the segments as in Step 6 with a knive and widen the slots
Step 7: Attach the 2 other hinges and make sure they move freely as described above
Step 8: Connect
Step 9: If it doesn't work, I will make a youtube video explaining it

Additional note: I have now assembled 5 segments and before even starting I widen all the orange (see my Make) parts with the drill and test-fit the pins to see if they move freely. Then I proceed as above.

I have now printed this in PLA at a .2mm layer height with a .4mm nozzle. Same issue, can’t get the segment to “snap” in the open or closed position. It mostly closes, but the opening action only opens it about half way. Moving the lever with my fingers shows that the action works, it’s just that the gears only push it part way and the spring isn’t powerful enough to bring it the rest of the way. any idea what may be happening?

I printed this in PETG and I think the spring action doesn't like that. Have you had any luck with PETG? It will move the segments a small amount, but they don't snap into their open or closed position.

Awesome design! When I get some time I hope to succesfully build one of these.

Are the model files for the motorization included? (like in your youtubevideo)

@TOMSTER The + and - are just differentiating the two gears from each other, so you'll have a pair of 1+ and 1- for example. It's not important. Looking at the dots on top or the direction of the arcs to the pins works just as well to identify what gear goes where. Plus and minus doesn't look so good in a filename so instead of Gear1- I called the objects Gear1A, etc.
You are right about page 15. A and B are swapped in the labels. I'll update the docs, but at this point in the build I doubt anybody looks at the names of the parts anymore. Well spotted though.

I really like the segment and is was great fun to build it. I'm going to build a watch out of four of them, driven by an arduino. However, I have a couple of questions / comments:

What are the plus (+) and minus (-) signs on the back of the segment gears 1 - 7 for? The assembly instructions don't mention them, while the video shows them. I assume, the + one is the one that lifts the segment while the - one lays the segment down. Nonetheless, before I took notice of the plus and minus, I have built it with the two-dotted gear always being the one that lifts the segment, ignoring plus and minus and it works.

There is an error in the manual: page 15, step 2: I think, connect_A and connect_B are probably swapped. In the stl files connect_A is the one with the hexagonal hole.

Absolutely great design. Goal is 5 digits showing my current flight hours. I posted my make a couple of minutes ago. Some things were not 100% clear for me in the manual, in my make I added a few hints that might be useful for others.

Really great design! Is it possible to use it as a clock? Maybe 4 motors connected to one esp and control all of them. But what about hour and minutes separator? Would you think to design it?

@GRIMALDI you won't be able to fit the case on a 150x150mm build plate. Everything else should be fine.

Can I print this on printer with a 15cm x 15cm x 20 cm build volume?

@martincollar Thanks for your notes. I have updated the manual with the fixes. (Also, great print!)

Thanks man for awesome model. I’ve just posted my make. Btw there are few issues in the manual including issues with part list... you can contact me if you’re interested in fixing them I have it noted in the printed manual.

Is the PCB for motor control part of this package?

Commercial versions of this display are still in use for Sport Timing and you can still buy them new. Look at Alge Timing.

They use magnetics to switch the elements. Very very low energy to drive the display.

Can You put sources for the parts we need!!!

@UhansQkSqj 1.2*13mm would be better

Would 1.2*13mm or 1.2*15mm be better to purchase?

@shirokuma not sure this helps but I got my nails from this Etsy seller:
From looking at the specs I'd say 18ga could work but may be a little loose, 16ga will work but you probably have to slightly enlarge the holes with a drill.
Lengthwise, 3/4" is indeed a little long. You'll be able to fit most of them but some would have to be cut.

Could use a little help sourcing the nails. The closest I can get is 16ga 3/4in or 18ga .5in. I think shorter is better but the difference is nearly .2mm in the diameter. Cutting is my only option.

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