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Versatile and mechanical 7-segment display unit — zdjęcie 1
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Versatile and mechanical 7-segment display unit

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Informacje o modelu

Źródło
Printables
Kategoria
Other Gadgets
Licencja
Creative Commons — Attribution — Noncommercial — Share Alike

Note : Improved single digit unit is released. Number of the parts is much reduced. It does not use rubber bands and requires very small force to drive. https://www.thingiverse.com/thing:5066794

Summary

  • A single unit of mechanical 7-segment display driven by a small hobby servo.
  • This unit can be used solely as a kitchen timer, dice, single digit clock, etc.
  • You can make digital clock, score board, counter, etc .. if you make two or more.
  • Two versions are provided. One has digits in ascending-order, and the other is optimized. Latter one has a special order (1 7 4 5 6 0 8 9 3 2) to decrease the load to the servo with less flipping segments between neighboring digits.

Spec

  • Overall size : 10cm (H) x 6cm (W)
  • Digit size : 8cm x 4cm (area in the center lines of segments)

You need additional parts as follows

  • Mini servo* (SG90 type : around 3USD per unit) comes with two screws
  • Control circuit (I use micro:bit and breakout board Ks0360. Codes provided)
  • 4 Screws (M2.5 - M3)
  • Paint
  • Lubricant

*It requires 162degrees rotation to show the all of 0 - 9. I use the servo below. In the spec sheet, rotation angle is limited to 120deg., but actually it can rotate upto 180deg., using PWM output of micro:bit. https://www.amazon.co.jp/gp/product/B07PHFQY6B/

Tools:

  • Soldering iron for plastic welding
  • drill and screw tap (if you do not use tapping screw)
  • files or a fine knife

This thing is a reduced version of "Mechanical 7-segment digital clock", https://www.thingiverse.com/thing:4626956

for ease to make. Since hobby servo is attached to the axis directly, it can show any single number within 0.2sec. It is not necessary to adjust origin at each power on.

I hope you make anything useful or just interesting, using this unit and show your make.

Dec. 19, 2020 : I have added easy to assemble version. It requires support when printing, but all cams are already assembled.

Video

Assembly guide

Optimization of digit order ===========================

Optimization is done with a program to check the all possible patterns of digit order. From 1,814,400 patterns, I selected 1 7 4 5 6 0 8 9 3 2 as a best order. The optimization program written in C programming language is provided.

Misc. =====

Easy to assemble version

Dec. 19, 2020 : I have added STL files as an easy to assemble version. It requires support in printing, but all cams are pre-assembled with corresponding axis. Each cam follower has a hole to insert the hand of segment, so it is easy to assemble and you can confirm the correctness of your assembly before glueing them.

Category: Gadgets

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