Blog - Sketching with Hardware

Snails

Published on: | Author: Miriam Mayer | Categories: 2016a, Best Projects, Projects

Wednesday

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In the morning we all presented our first ideas. Due to the complexity of the mechanism, we had to skip the idea to make ’Pac-Man’ an analogue game. We finally decided to convert the game ‘Tempo, kleine Schnecke’. One of the most popular games in Germany for young children. By rolling two coloured dice you lead the six different coloured snails to the finish line.

During the day we had our first meeting and discussed how we could realise our ideas.

We decided to use servomotors, moving the wooden snails using a flat belt drive and magnets. For that we needed a motor that drove the servos to the right track and one servo to place another one in contact with the track by changing its angle. A wheel would be attached to this last servo so it could move the track. We were in luck and found the driving unit of a printer in the facilities of the course that was perfect for our needs. Now we already had a motor that could steer a little cart up and down a track.

For the dice we first thought about some sort of colour sensor below an area where you would roll the dice. But these sensors are not sensitive enough to make out two colors on a large area and it was not possible to perfectly place a rolled die in some sort of cone without some extra positioning work which would be annoying during the game.

So our control became a turning wheel, similar to the ‘Wheel of Fortune’. With a contact control and pattern of binary numbers called ‘Gray Code’ it is easy to check the current status of the wheel in the software. Gray code is a form of binary code where only one digit at a time changes. See the Github repository for more information about this code and why and how we used it. As we needed at least 6 colors for 6 snails we decided to go for a code with three digits, so for 8 ( = 2^3 ) possible combinations. This way we also had two extra fields that we could fill with other functions that would make the game a bit more interesting.

After all this planning we finally were able to really get started. First we bought the original game and some magnets that would later move the snails. We did not want to build the field or the snails ourselves as we liked the idea that the original setting would trigger some nostalgic feelings in our players.

In the final hours of the day we planned a wooden box for the game and its interior. Also first code snippets for the servos were written and tested in small circuits.

Thursday

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After attending to all plate materials, we cut the box on a table saw. All compounds of course in mitred construction.

In order to make the motor not only go in both directions but also adjust its speed we did a lot of research how this would best be realised. With the help of Bernhard we found an H-Bridge in an old project we could use to solve this problem.

So after that there was still some coding and testing to do so that motor and both servos did what they were supposed to do and the development of the game’s logic began.

Friday

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After assembling our box, the next topic was the production of rolling mechanisms for the snails. With the help of pot drills we could easily customise our special wheels for carrying the rubber belts on which our magnets were mounted.
At the end of the day, our mechanical components were ready for assembly with our printer driving unit and the servomotors.

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In the meantime the software grew further and further including the game’s logic and also including the contact mechanism for the turning wheel and the motor- steps: For the motor we needed a way to ‘tell’ it where to stop for which snail. So we planned on placing a copper wire on the cart that would have contact with a copper tape in certain intervals. Therefore we needed to check whether there was electricity flowing at four pins (three for the wheel, one for the motor position) or not.

Monday

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Since we produced the mechanical components and the software with its circuits rather independently, we planned to finally combine them this day.

Assembling our mechanical components with our hardware and software took a lot more time than expected. The production and alignment of engine mounts took ages.

Also the turning wheel with its coded contacts still needed to be laser-cut and its contacts positioned.

After all this time-consuming work a longer night shift was ahead of us, during which we had to merge the individual pieces.

Tuesday

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The final day of the presentation was an exciting one. We still had three hours to eliminate the remaining malfunctions.

First of all we printed the last elements for the game: The top of the wheel and a blue triangle for the corner which read “Schneckenburger” in order to show our close collaboration with a locally known boardgames manufacturer.

For the turning wheel we decided to use our two extra fields as ‘return fields’. So if this is rolled, a random snail is picked and set back one field -except when it still sits on its pole position.

After a bit of stress when nothing seemed to work anymore, the wheel colours were coded correctly in the software, the wires of the circuit were sealed and a last minute servo and power source change was accomplished.

The whole game actually never worked better than during the presentation — a positively reversed demonstration effect. All servos, the motor and wheels colluded

perfectly and let the magnets shift the snails across the board. Only ‘drawback’: we somehow ended up with turbo snails. We guess they must have felt so comfortable in our game they were just super motivated.

Any additional information you might need to recreate our game (circuit, documented source code and the patterns we used for laser-cutting) is published on Github.

linked categories 2016a, Best Projects, Projects

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