7 segment clock

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This project was inspired by another similar project that I saw a few years back. I mostly rebuilt it completely and challenged myself to print it as small as possible on a standard 3d printer using a standard nozzle. The size was determined by the smallest screw hole that was possible. The clock consists of 4 modules which work in a pair to display the time. The mechanism is quite simple using a set of cams and followers. The stepper motor turns one module and the second one is driven by a carry over mechanism. The right side pair displays the minutes and the left side displays the hours.

The clock consists of 7 segments which are driven by seven cams. The cam push the followers which in turn lift the segments at the right moment to display the digit needed. The modules work in pairs. The entire clock is driven by a attiny 84 and two a4988 stepper drivers. The first module is driven by a 15mm geared stepper motor which turns it every 1 minute. After a full circle of the module the second module is driven by a carryover gear. The third module is again driven by a stepper motor which turns every one hour and then carry overs to the forth module at 10  and 12 o clock.

The modules run in pairs making it easier to adjust the time. The time is adjusted by two buttons present in the center of the clock. The over all dimensions of the clock are 191 X 52 X 84 mm Or 7.5 x 2 x 3.3 inches

Circuit board:

Note the scale : 

Adjusting the time :

  • 1 × attiny 84
  • 2 × a4988 Power Management ICs / Motion, Motor and Servo Control
  • 2 × 15mm geared stepper motor
  • 3 × a3144 hall sensor

  • prototype #1

    ekaggrat singh kalsi10/08/2022 at 09:49 0 comments

    This prototype used 4 modules with a complex carryover mechanism so that the entire clock could be run with just one motor and one motor driver making the electronics simple and compact. But this made adjusting the time very slow and tedious. Hence this method was dropped for the more simpler approach of using 2 motors and 2 drivers.

  • module #2 carry over

    ekaggrat singh kalsi10/08/2022 at 09:41 0 comments

    The second module was to make it really small and to test the carry over mechanism

  • module 1 big

    ekaggrat singh kalsi10/08/2022 at 09:36 0 comments

    This was the first module I made but It was a lot larger . I used this to just study the mechanism.

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Maty wrote 10/20/2023 at 00:13 point

What PCB board did you use? Do you have an electrical schematic of the circuit?

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ZjcNB wrote 09/24/2023 at 08:26 point

How is the cam part designed?

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ktewell wrote 03/13/2023 at 15:56 point

How do you know what cam goes where?

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jeffrey sorom wrote 03/01/2023 at 20:52 point

like a few other people, im wondering if you will post the full file for the full clock, be it just releasing it or selling them. are you still going to do that? or is this only a single cell module indefinitly?

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Jozerworx wrote 01/14/2023 at 14:50 point

It has been 3 months since there has been any activity on the github, and there are still no plans for a complete clock.  Are you planning on releasing/selling the complete plans at some point, or is this project abandoned?

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Adam Mills wrote 11/29/2022 at 20:57 point

I am new to the world of Arduino. so sorry if this is a dumb question. Would an Arduino with an attiny85 or attiny88 work instead of the attiny84?

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ekaggrat singh kalsi wrote 11/29/2022 at 23:26 point

yes any arduino will work. a attiny wont work as it doesn't have sufficient pins

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Russ Turner wrote 11/18/2022 at 22:11 point

The PDF says on the diagram that the hook wire should be  .2mm but in the text below it says .4 mm.  Which is it.?

The spring is really .2mm wire?

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ekaggrat singh kalsi wrote 11/29/2022 at 23:28 point

0.4 mm for the hooks and 0.2-0.3 mm for  the springs . yes the springs are tiny

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dg wrote 11/17/2022 at 11:46 point

Brilliant idea, well thought out and superbly engineered. I don't have a use for one but I may make one anyway.

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Jozerworx wrote 11/16/2022 at 12:06 point

Have the complete set of 3D parts/code been posted to the GitHub?  I'd love to build one of these clocks, but I want to make sure all the design files are available. 

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Pentizuki wrote 11/04/2022 at 20:41 point

do you have a link to those motors? I don´t find any cheap ones

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Eliza wrote 11/04/2022 at 02:14 point

WOW! I have to say that your program is so wonderful. I LOVE IT SOOOOO much. And in the next days i think i will try to do it with your instructions. Thank your for your share. Have a googd day!

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jon wrote 11/03/2022 at 14:32 point

It might be useful for the STL files to include one or more "plate" STLs which contain all of the parts necessary for a single module, in the correct orientations for printing, and in the correct quantities.  I probably spent 15 minutes trying to get this right.  In the long run, doing this once and sharing would be helpful

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jon wrote 11/03/2022 at 13:06 point

Very amusing!  My thought would be to make the thing larger, not smaller.  Can you see any problem just making everything 2x or 4x?

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beamer wrote 10/26/2022 at 23:33 point

Great project! I really would like to build such a clock. When looking at the stl-files, I see the ones for one single module, but I am missing the items that shift the movement from one module to the next and the parts coupling the modules together? Also the very left module seems to have special cams because it only displays 0, 1 an d 2 that are also missing in the stl's?

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edgar hurlbatt wrote 10/26/2022 at 12:26 point

Hi ekaggrat, I have printed all the parts, but cannot identify which cams are which. You said 1 to 7 as per your earlier reply, but the numbers are not showing on the instructions. Are there more than 10 pages?

I’m really happy with the quality of the prints and the fit is really good but a little tight on the cams and drum, quite possibly a result of shrinkage. I’ve printed with PLA as a prototype run and as I said I’m very happy. Great job. 

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FooPlinger wrote 10/18/2022 at 15:50 point

I don't see anything referencing buttons (in the middle to set time) nor hall effect sensors.   Are there instructions including them?

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angelvash88 wrote 10/17/2022 at 06:53 point

which attiny84 board did you use? thanks great project

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domooooo wrote 10/16/2022 at 07:54 point

not found drive gear STL at Thingverse ?

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ekaggrat singh kalsi wrote 10/17/2022 at 05:45 point

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FooPlinger wrote 10/17/2022 at 15:07 point

Thank you!

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Lee wrote 10/15/2022 at 05:56 point

I downloaded again from Thingiverse, still broken with missing files, can you attach the zip to Hackaday?


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ekaggrat singh kalsi wrote 10/17/2022 at 05:45 point

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Tim McNerney wrote 10/14/2022 at 17:29 point

I love it!

Question about the 3D models at Thingverse: If I want to fab a complete set of parts for 2 digits, do I need to request that any of the STL files be printed twice (or more)?  Shipping can get expensive, so I want to get it right the first time.

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ekaggrat singh kalsi wrote 10/14/2022 at 22:56 point

no currently it is only one digit. the other digits have different cams. I will put the other digits later. it is only for experimentation currently.

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