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7-Segments

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 https://cults3d.com/en/3d-model/gadget/reverse-gear-set-for-7-segments

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 file format: PDF and STL

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25 comments

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.

@UhansQkSqj 1.2*13mm would be better

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

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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