Mechanical 7-segment displays

Mechanical display clock. Each display is comprised of 7 decagons controlled by one stepper motor
17h 10m
3× print file
0.25 mm
0.40 mm
203.00 g
In the contest Timekeepers
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2482
updated June 13, 2021

Description

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This design is a clock built with 4 mechanical displays. Each display is comprised of 7 segments controlled by one stepper motor. Every tick the stepper rotates 36 degrees (1/10 of full rotation) and the movement is distributed across all gears.

It includes an opto-interrupter to detect position of the zero; when the circuitry is turned on there is no way to know the last digit, so the stepper turns until it reaches the zero and then it can start from there.

Each segment of each gear has to be spray or hand painted to show the corresponding digit correctly. I'm working on markers to help with this process. Assembly of all pieces requires gluing (hot glue or Loctite).

Stepper can be controlled with an Arduino and the corresponding driver. I'm using a ESP8266 along to get time from the network and display it on the clock (work in progress).

I have printed and tested one so far, cover picture is a montage of the one I have depicting the final desired result. I designed it from scratch, I found some designs made with servos controlling each segment, but that's quite expensive and I wanted a low budget version using only one stepper. 

It just fits to be printed in the Mini (which is the one I have), it takes at least 3 trays to accommodate all pieces (gcode attached) for a total of 200 g and a little over 17 hours of print time (0.25mm layer height). Stepper motor on the model is 28BYJ-48 and opto-interrupter IRT9608-F.

I set the gears standing, that causes one of the sides to have blurred reference letters but the top side gets printed clearly and the teeth are not affected. If anyone can come up with a better angle or way of printing, please let me know :)

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