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This is the document of making assignment work for “Building automata with micro:bit workshop” which is organized by FabLabSENDAI – FLAT.
It’s written by Tomohiro Tsuchita who is the maker of this mechanical 7-seg display in Japanese, and translated into English by FabLab SENDAIFLAT.

About workshop
In the workshop, I’ve learned basic programming skill with micro:bit, some mechanical structures and movements for building automata and also famous artists who build automata.

Assignment : Make something beautiful but totally useless.

After the lecture, I decided my theme that “Turning a utility to useless by changing its structure.”

And I thought like “How about 7-segment display as my target ?”. The 7-segment display is a well-design method showing one number from 0 to 9 with 7 tiny segments. The Display changes its state depending on received bits data which is decoded number to control segments. For the assignment, I made it by not digitally but mechanically.

My automata is made by following rules of the workshop below…

(1)The automata should be driven by a servo motor.
(2)The servo motor should be controlled by micro:bit.
(3)The power source is 3 AA batteries.
(4)Rotary motion of a motor should be converted to another motion by cam mechanism or other mechanical motion mechanism.
(5)Speed of motor should be changed by input like value of sensors or time course.

Most of existed 7-segment displays flip each segments because it fast and can control each segments separately. But in this case, I have to do 7 different control at same time. I couldn’t come up any idea to do so and could be pointless if it become utility. So I skip flipping system.

For me, It was first time to make such a mechanical structure so I prefer simple structure rather than technical challenge. Cam mechanism was chosen as the core of my automata.
The mechanism will show from 0 to 9 per one revolution.(Its reason will be described below.)

About finish, I’d like to make is very analog looking with brass plates and wire in the beginning. As result, I made it with laser-cut acrylic due to short fabrication time and precision. But still I couldn’t give up with my favorite style so axis and belts are made of brass and 7-segments parts are made of tinplate.”

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