Blog - Sketching with Hardware

Team 2 – The Magic Suitcase

Published on: | Author: Florian Lochner | Categories: 2015b, Projects

The Magic Suitcase

Our concept, The Magic Suitcase, was inspired by early 20th century funfair attractions, where magic machines and installations we’re fascinating visitors. We took this concept, but created something that does the magic by using the internet. The Magic Suitcase gives no clue about what it contains or what it does – the only way to find out is to go to a website and press a button on this website. The Magic Suitcase then either opens to fire some water, throws candy, or plays a music box.

Concept Work

One of our original ideas was to create a party game­—however for that we wouldn’t have needed an internet connection. Thanks to some inspiring feedback from our tutors and peers we decided it could also be fun to have some magic box that doesn’t follow the conventions of good interaction design but uses an internet layer to link the user’s interaction with the system (on the web interface) with a physical reaction. By de-coupling the interface and the reaction of the system both physically and through a delay, people should not be able to easily create a mental model of it and hence be confused. (That is basically the opposite of what you try to achieve when creating useful and usable artifacts.)

Once our idea was clear, we searched on ebay Small Ads for some old box and ended up with a nice old suitcase that is a perfect encasing. We then went to some toy shops and found some inspiration by water pistols and other toys that fire other things as well as music boxes.

wp_su

Technical Details

Like with all other teams, the heart of our prototype is an Arduino Mega and a ESP8266 WiFi chip. Our Arduino program regularly checks through HTTP whether the website’s button was pushed and if so,

webinterface

it starts an event routine to trigger some action. We set up a minimalist Node.js web server for the web interface that allows both to have some “random functionality” and also to directly trigger all actions for demo purposes.

Features

Inside the Magic Suitcase are:

  • a mechansim which allows to open the suitcase very fast
    om_2
  • a waterpistol
    wp
  • a sweets catapult
    kp
  • and a musical clock
    su

Issues we ran into and how we solved them

During the development of our project we faced problems in both the physical and digital world.

Like many teams we had problems to extract the information we needed from the HTTP response. Our initial approach was very error-prone—because with the ESP8266 WiFi chip and the open source library we used, you couldn’t tell when the website was fully loaded. It took about one day to find out that this was the main cause of all problems we experienced in this context. Additionally, the WiFi connection was heavily unreliable, probably because there was no shielding and no antenna was used. But restarting the Arduino by pressing its hardware button via USB was no option – The Magic Suitcase had to be fully autonomous. To achieve that, we integrated several checks on different levels to detect whether a TCP connection failed or whether we had to reconnect to the WiFi access point.

To perform the actions of The Magic Suitcase, we rely on servo motors for all actions. Because servo motors built to only rotate by 180 degree, we had to hack one servo so that we could properly play the music box, which is easier than its sounds because the servo was very loud and not only the musical clock used the board as a resonance body. So a construction out of small boards, a wooden adapter and a servo embedded with elastic band was constructed. Another issue we ran into was synchronizing the actions of two servos for the water pistols (because one was not strong/fast enough). However, because the Arduino board doesn’t provide too much flow, one has to make sure that the initial attachment of the servo motors doesen´t happen at the same time because this makes the Arduino shut down.

Because servo motors are quite slow and don’t provide to much force, we had to come up with special mechanisms for both our sweets catapult and opening the suitcase. Our goal was to open the suitcase in a fast manner because only that would surprise people. We decided to build a mechanism with some small boards used as a tension spring. For the opening mechanism and the sweets catapult we used rubber bands that provide spring force and we built a latch snaping in when the lid is closed or the catapult is loaded and tensed. The advantage of this construction was that we needed only one servo motor for releasing the lid or fireing the catapult, because only a small latch had to be moved some millimeters.

The Result – The Magic Suitcase

Bottom Line

The seminar was great fun, we learned a lot and are now looking forward to do more hardware sketching and physical computing in the future.

linked categories 2015b, Projects

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