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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FooPlinger wrote 10/12/2022 at 14:50 point

Is there a file to load onto the attiny 84s, and what is the other (white) board in the photographs?  I would love to make this, but not sure what code is driving the steppers, or if it is purely mechanical

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ekaggrat singh kalsi wrote 10/13/2022 at 22:56 point

it is a arduino code. U can use any arduino for this. The white board is a custom pcb. The reason i didnt upload it is because it had a error on the track and i didnt get time to fix it. I will do it soon. 

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FooPlinger wrote 10/14/2022 at 14:21 point

is that code available?   Working on printing parts now.  Also, It looks like the Drum, and the Top and Bottom connectors are missing.

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brickstuff wrote 10/10/2022 at 16:51 point

Fantastic work!  I'm working to print the parts and see if I can make one per your instructions.  Looking at the 3D files, some seem to be missing?  The drum itself, for example.  And the pieces to hold the motor (bottom) and drivers?  Would it be possible to add these to the Thingiverse collection?  Thank you again.

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ekaggrat singh kalsi wrote 10/11/2022 at 08:25 point

i added them . thingiverse keeps eating parts on first upload . damn. 

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brickstuff wrote 10/11/2022 at 11:42 point

Hmm just checked-- they're still not showing up.  Only 16 files total. :-(

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Ken Yap wrote 10/10/2022 at 02:41 point

This is cute. Time display comes full circle. Next thing you know someone will make an electronic display that shows the mechanical changes this clock undergoes. 🤣

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ekaggrat singh kalsi wrote 10/10/2022 at 03:00 point

hahaha that would be fun. As such clocks have become a novelty. We have lived past the race to make the most accurate/functional piece long time back. Simple clocks are so boring.

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Dr. Cockroach wrote 10/09/2022 at 18:32 point

There is something so satisfying in watching the segments in motion. The movements are so smooth and fluid. Almost seems alive. Well done :-)

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ekaggrat singh kalsi wrote 10/10/2022 at 02:28 point

thanks a lot 

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evanhelene wrote 10/09/2022 at 13:00 point

Amazing! What specific steppers will fit the printed parts without modification?

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ekaggrat singh kalsi wrote 10/10/2022 at 02:28 point

any 15 mm geared steppers. they are usually 1:100 ratio. I found a rejected lot which had a ratio of 1:99 and got them really cheap. If you want to experiment i have a larger set at double the scale which works with any cheap 25by stepper motor. I could send you the model

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FooPlinger wrote 10/18/2022 at 15:49 point

so the ratio doesn't matter?  What about the shaft size?   You have part numbers for yours so I can get the same size/ratio/shaft?

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Conrad Parker wrote 10/21/2022 at 03:37 point

model plz

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Gregory Sanders wrote 10/09/2022 at 12:31 point

Very nice! 

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ekaggrat singh kalsi wrote 10/10/2022 at 02:31 point


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Wojciech Sielski wrote 10/09/2022 at 08:48 point

Fantastic project, waiting for "metallized" Steam Punk version  :) or even hand watch ;) 

I wonder, what is the limitation in segment size?
If 9-segment or 16-segment would be even possible to make mechanically - for having alphabet ;)

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fhunter wrote 10/09/2022 at 14:19 point

cam size will be a limitation - you need cams big enough so that they can reliably turn the segments, and every alphabet combination must be on them. - more symbols - bigger cam diameter

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RunnerPack wrote 10/14/2022 at 19:36 point

You could use multiple camshafts in parallel, like the intake and exhaust on an engine.

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ekaggrat singh kalsi wrote 10/10/2022 at 02:30 point

my final version I intend to make even smaller in brass or 3d printed metal. but I lack the funding to do that . Right now the segment size is limited by the support rod which can be only printed so thin and the smallest screw usable in plastic being m2. 

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Dan Maloney wrote 10/08/2022 at 16:39 point

Very nice job! Such smooth operation, too, and shockingly small when you see it at scale. I wrote this up for the blog, should publish soon. Thanks for the tip!

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ekaggrat singh kalsi wrote 10/09/2022 at 02:42 point

thanks a lot . will look forward to it

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