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Idea and Concept
Our initial idea was to buy a toy train and modify its wagons by adding two compressing springs with a set and release mechanism. Positioned on each spring would have been a coloured ball that would jump out of the wagon when the mechanism was released.

The reset of the system would have had to be manual and only two balls per time and wagon could have been made jump each time the apparatus was released. We also intended a second surprise mechanism that made it hard to connect the wagons in the first place and to make it somehow difficult to put the balls onto the wagon so it would have been all the more frustrating when the balls flew off. Also the wagons would have automatically separated after a certain time.

What became of the concept you can see here in the video of the final result:


Getting to work and solving the unsolvable

The concept was then split into two Major assignments:

First: Finding a toy-train in the appropriate size with enough space for our modifications and
Second: Finding springs with the required properties (not too hard to draw back (tensile force) but with a good enough take off power) and designing an apparatus that made balls jump with them.

What we did not know at that point: With our final solution of the second assignment came a third major assignment we did not know of while scheduling our time.

After wasting two costly days on solving both major assignments the planned way we decided to solve it by adding work to reduce it:

Instead of buying a toy-train (and wasting precious time looking for it) we decided to built it ourselves as a made-to-measure solution. Using the leftover-stock we took some wood and learned to use Adobe Illustrator for the vector design.

The base for all the measurements was the remote controlled toy-car we had found in the workshop on a coincidence. We designated the chassis to be our towing vehicle. Later followed the self-made chassis and wheels for the wagons. (We could not find any to buy in the required dimensions)

Lesson learned: I am convinced that despite the additional work we put in making it up from zero we did save a lot of time and learned a lot in the process as well. (Using the lasercutter, working with Adobe Illustrator,how to use the tools in the workshop, AND: improvise, improvise, improvise)


The second major assignment turned to the most unexpected result. After focusing days on first finding the perfect spring (which turned out to be a disaster) and make it work SOMEHOW. The solution lay somewhere totally different. A frustration-solving stroll through the workshop brought me to a discarded piece of acrylic glass. It was both: surprisingly flexible and yet dimensionally stable. And immediately a totally new idea took shape. The prototype on the new concept took only a few minutes and worked on the first run. Here a demonstration:

The new concept brought several more advantages: We no longer had to reset the system for every new round. a hacked 360° servo  could keep the springless construction running infinitely. That also meant we were no longer limited to a 1:1 ratio on balls and springs: we now could shoot around a whole load of balls in every wagon.

Lesson learned: Stop trying to reinvent the car when all  need is a wheel.

With the train and the spring-less construction done the day before the presentation, we thought nothing could go wrong now. We thought the electronics would be easy. A mistake that literally cost us our sleep the last night.

Taking up an idea we had had quite in the beginning we used popsicle-sticks with a copper coating to transfer signals plus energy and keep the train able to make turns because the coupling was flexible. It was a rather simple but effective solution. Still it turned out to be very very time consuming and starting a task that requires a focused mind and a still hand after 12 hours of work is not the best idea. Yet we managed it and after 6 more hours everything was working just fine.

The Arduino gets its power from a 9V battery on the first train. From the Arduino emerge 5 cables: A Voltage cable with 5V and a Ground cable that serially connect to every servo. Three seperate Signal cables, so every servo can be controlled autonomosly.

Lesson learned: Do not sleep in the CIP-Pool. You risk freezing to death while asleep. Seriously.
Things that were left out – Ideas for the future

The whole “Trains falling apart just before the balls start jumping out”. We threw the idea aboard after realizing it would require one arduino and a battery per wagon. Plus a strong repellant like an electric stud or electromagnets. Two things that are highly energy consuming. And by adding those the space for the eggs would have been considerably minimzied.

Springs. As mentioned above it didn’t work out. Not only the mechanism was catastrophic, but also aquiring fitting springs… It seems that springs are usually only produced for companies that use them for their tools. The springs we found were all too big or had too much tensile force. Thinking around the corned helped here. A stroll through the lab and we really simply ran into the solution.

Buying a toy train. Looking for something extremly specific (exact measurments, size, material) is really hard. If you have any talent in “do it yourself” then do just that. No point in fearing failure. Just do it. At the very least you will learn a lesson.

Acoustics: At one point we intended the train to make some funny childisch train sounds, time killed the idea rather soon, but we still liked it

Light effects: Blue subfloor illumination. Again time was the killer but this would be the simplest of all to add as we have already designed the wagons with extra space for an additional battery and space left for some LEDs.

A stronger towing vehicle: Altough we tested the admissable total weight of the toy car to be 1,5 kg it still had trouble towing the wagons. Either the last wagon has to go, or the towing vehicle needs a stronger engine.

A remote controlled starter: We still have to start the arduino manually. Adding a remote would certainly improve the effect.


Things that were added

Easter Eggs instead of balls (spontanously)

Selfmade train + wheels

10 Eggs rather than two balls. The more eggs the more the fun


Final words by the author

Despite the batch of chaos in the final 24 hours I really really enjoyed the course. The project with all its ups and downs was really cool, the learning curve amazing and the people were not only helpful but especially the lunchtimes were real fun. For every stressful moment (including having to sleep on the CIP-Pool floor): it was worth it.

Day 4 – Work in Progress

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Being the first day of pure project development, day 4 had a very special feeling to itself. The groups dedicated themselves to the advancement of their projects, aided by the always needed help of the tutors. The Arduino platform begins to feel natural, its workings are more and more understood, and the first deeper insights are made (who knew that an output set to HIGH still differs to the permanent 5v output?).

Transistors make their first appearance, almost every group makes use of them, as they prove quite useful to close circuits when needed. The poor labeling on the transistors-box makes it more fun, as it is necessary to search for specs online to see if they are n or p switches.

Some groups have first minor or major breakthroughs, solving problems they had in a different way than previously planned.

Group 1

The Rescute team is well on their way. Solved is the problem of the spraying of the pepper spray, the LEDs are also working as planned, thanks to the additional power now used. A bit of frustration about the limited range of arduino servo motors came up, therefore effectively limiting the range of the bear’s neck. Originally it was planned for the bear to turn its head a creepy 180° on each side, now it looks like he will have to be able to turn its head 180° on one side only. Maybe hacking a servo motor will help.




Group 2

The second group works hard on its project. It proved to be more challenging than previously anticipated, as seemingly simple tasks like the compressing of a spring prove difficult to realize with the resources at hand. Thankfully, being the creative people they are, team 2 members can compensate these problems through ingenious alternatives or workarounds. For the construction of their toy train, they make use of the laser cutter upstairs, and the result is very satisfying. Nonetheless, all of this requires lots of energy and concentration from the team 2 members, leading to part of them to almost fall asleep during the lunch break.




Group 3

The togebear has seen some progress as well. The knit-work (yes, you read well, this bear is 100% handmade, something a soul-less laser cutter could never achieve) is almost done, meaning that the outside of the bear is almost ready. The inside of the bear proves more challenging than expected: when receiving an email from a loved one, the bear should spray some perfume. Using a hacked airwick system proved to be tricky, as reversing the motor rotation (it needs to go in both directions) proved an impossible task. Building an h-bridge did not solve the issue, maybe some of the used mosfet transistors where not suited for the used voltage. An hacked servo motor (not limited to 180° rotations) was used instead.




Group 4

The Looping Louie team moved to the laboratory upstairs, as they need the space and tools it offers. Probably one of the most complicated projects hardware-wise, it makes sense for them to be close the equipment. Being physically removed from the rest of the other groups makes it more difficult to judge their progress, but whenever one needed something from upstairs, she or he would hear a small Eureka shout, signaling a further success of group 4, approaching the end goal step by step.




Group 5

Today post arrived for the Madlab group, it was the game they are going to hack. Finally having the game, they were quickly able to make some progress. Surely it did help, that they didn’t lose time the previous days, thinking ahead of what and how to do it. Servomotors were quickly attached to the game, LEDs were tested, boards altered. Group 5 may have had a delayed start due to the late arrival of the game board, but they managed to make up for the time lost, and then some. If they keep up with this pace, they will be out of work by monday.




Group 6

The Ghostcamera team had some important hardware arrival as well, now having a functioning printer for their project. The idea is to have a camera take a picture of you and then print it, but with one twist: the printed picture will have some sort of monster on it, be it a ghost or zombie, or whatever. This surely has to be the most complicated project from a software point of view, but the team members are concentrated and seem very confident about the outcome.




All in all it was a very productive day. Each team was able to make significant progress, each team already faced problems, some of them are already solved. Creative thinking seems to be the key here. The lesson learned today seems to be not to give up immediately, but also not to fixate on one approach. If something does not work after scrupulous researching and trying, then it is time to think of a different solution to the same problem.

Another important aspect of today, was the fact that we really got our hands dirty, and quite quickly. Almost every group used power tools like power drills, dremel or power saws, as well as special machinery like the laser cutter. These are tool that some of us used for the first time. It became quite clear, that this course would not be completed by simply putting some lego together, but that custom work is necessary.

Even the components used in our electrical circuits became more sophisticated. If there was the idea that sketching with hardware could be completed by simply putting some pre-made components on a bread-board, after today the reality became clear: it is much more than that. We finally understood the importance of transistors and switches. It is one thing to read about them in a chapter of some lecture where they are mentioned briefly, but it is a totally different thing to understand how they work in order to use them in our projects. If we want to power some LEDs with an additional power source, how can we control this source? Transistors! If we want to make a motor rotate in 2 different directions, without physically switching cables, how do we do that? Transistors! Thankfully the tutors were there to answer our questions, an we all had some, ranging from where can i find xyz to more technical ones.

This was a very long day, but thankfully the weekend awaits, and monday the show will go on!

Day 3 – From Concept to Implementation

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On the third day, we needed to further develop our concepts that were come up with yesterday. So in the morning we were busy optimizing the ideas and consulted with Bernhard and Felix on technical problems.




At around 10 o’clcok, we started presenting the concepts in turn with the help of posters on the wall. It is evident that  many groups had made much progress after careful and thorough analysis.

Group 1

When it comes to the concept “Rescute”, a more detailed explanation was given about the 3 steps to scare the attackers. As the first step, a kind of scaring light comes from the eyes and the bear turns the head. If it does not work, the police siren goes off as the 2. step. The last step will be sound like dogs’  frightening snarl.




Group 2 

The determination of final concepts seems to be a bit complicated for group 2 due to the technical difficulties encountered before.

However, the primary concept about toy railway was picked up again in the end. Some improvement was done such as the self-making shell of the toy train using laser cutter instead of refitment of an existing one, and oval Easter egg instead of round shaped Ping-Pong ball etc.



Group 3

The conccept “Togebear” of group 3 kept almost the same as one day before, The so-called Togebear can smell, listen, spreak and give light to interact with the person one speaks to.



Group 4

Group 4 had already done a lot so far, the emphasis was put on the technical aspect while the idea kept unchanged. Details on functions, challenges to be overcome were explained.



Group 5



Group 6

Group 6 decided for the concept “Ghost Polaroid”. Except for showing some ghost-related effects mentioned on the second day, group 6 were concentrated on the technical aspects including the  transfer of photos from the camera to the computer, image processing program, a print-out program and establishment of a big shell.




After the lunch break Felix made an introduction to the laboratory and laser cutter, during which we got familiar with the electronics and tools for prototyping, as well. Then some groups begun directly with the implementation. Other groups might be inspired by the inconspicuous but fairly useful tools and improved their ideas accordingly. The whole afternoon was really very flexible for all groups to arrange themselves. Group 5 went to the shop on the Türkenstraße in search of springs which are not available in the lab.

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Some interesting experiments to test the feasibility implemented by Group 2.

Paper prototype made by Group 2:


Day 2 – Arduino and Brainstorming

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The day started with Arduino. It is the heart of our projects. With Arduino we can control lamps, movements and much more. This is possible through a programming interface on the notebook. It is a mixture of programming with C or Java. Afterwards the notebook transfers the final function to the Arduino. After we examined a few examples from Arduino Playground the first function we tried to control was to let a lamp blink. It was our first feeling of success with Arduino. The rest of the morning we made experiences with Potentiometer and Servo.

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After the break we got our topic for the final projects. The topic is “Gute Miene, Böses Spiel(zeug)”. In the afternoon we had time to do a brainstorming. So, each group thought about an appropriate project to do. Here are the following findings:


Group 1

The name of group one’s project is ‘Rescute’. It is about a teddy bear wich turns out to be a life safer. In this teddy bear several functions will help persons to safe their life from attackers. First step of defense will be barking sound. The next one will be blue light and noise of the police which comes out of the bears’ head. When the attacker is not yet scared the next step will be pepperspray which comes out of the teddy bear’s mouth. Optional the last step would be an emergency call to the police. The teddy bear will be small and fits in each bag.



Group 2

The centric toy of group two’s project is the toy railway. On this railway there are several balls loaded. When the single trains get connected to a railway it starts. After a few meters the balls will start to fall apart and jump around.



Group 3

Group three uses a teddy bear as well for their project. The sense is to connect two persons which have a long-distance relationship. The teddy bear has a blinking heart on it and the lover’s fragrance bottle in it. Every time one person receive an email from the other one the bear’s heart will blink. Additionally, fragrance bottle starts to spray. By clicking on the off button the functions will stop.



Group 4

Looping Louie is the chosen toy from group four. It is called “grantiger Alois”. The sense is to attack one special player and to spare the others. This is achieved by using high sensors, a regulated motor, position and hit detection.



Group 5

Group five will work with the ball labyrinth. By inverting axes, attaching a latency, a vibration, magnetics to deflect the ball or moving walls the game will be manipulated.



Group 6

Group six has still two options not sure which one to take. The first option is to manipulate a polaroid camera. When someone takes a photo there will be ghosts  in the background of photo or the camera won’t take a picture and instead makes crazy other things like pup sounds. The second option is the mole game known from amusement parks. Normally you have to hit these moles with an hammer. Group six wants to come out a hammer from the mole’s mouth to hit the player.



Melody Bakery

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This project, “Melody Bakery”, was made from an old toaster. We equipped it with an Arduino Mega, took advantage of the toaster’s convenient, useful physique and transformed it into something totally different with completely new functionalities: A MIDI sequencer loop station, aka. “Melody Bakery”. This device can read a set of eight notes, making up two four-four times at the range of seven notes adding up to one whole octave. Furthermore, you can feed the toaster with a set of an instrument which the notes are to be played with and a background beat to make the produced music loop more enjoyable and usable for playing along with e.g. the bass or the guitar. The notes, instrument, and background loop can then be sent to an audio program on a connected PC.



The idea for this project came into existence when we found this old, non-functioning toaster. Since it didn’t toast bread properly any more, it could no longer be used for its original purpose. However, we agreed that it would have been a pity to throw it out. Therefore, we decided to bring back some live to this toaster again. The motto of this year’s course “reuse, reduce, recycle” supported our idea: To disassemble the toaster and rebuild it as something completely new. Since both our team members play several instruments as amateur musicians, we decided to create a device that has something to do with music and can be used, for example for practicing playing the guitar. In the end, we came up with a midi sequencer loop station that can read notes written on the toaster’s crumb tray.

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From the beginning on, we tried to keep the basic concept of the toaster, where you put something into the toaster’s slots and then start a process by pressing down the handle.


Instead of putting bread into the toaster’s slots, we defined one slot as input for the instrument that the notes should be played with, the other slot was destined to serve as input for the background loop sound. For the notes themselves to be recorded, we used the crumb tray at the bottom of the toaster as a note sheet, and magnets on top of the crumb tray as notes. This way, we have a removable note sheet where notes can easily be added, removed, or modified by moving the magnets on the trays top surface. To scan the notes on top of the note sheet, the crumb tray simply has to be pushed into the toaster.

When everything is set, the toaster’s handle can be pressed down, which starts the MIDI-transfer of the notes, instrument, and background loop to an audio program on a PC connected via USB.

Let’s get technical!

The note sheet & note scanner

Let’s start with the feature of our “Midi Toaster” that required by far the most effort.

We decided to read the notes by taking advantage of the fact that white surfaces reflect light a lot better than black ones. Therefore, we painted the toaster’s crumb tray black to serve as the note sheet. Then we put a matrix of white spots on the top of the black tray, where each spot represents one note. One dimension (vertical) serves as the tone pitch and the other one (horizontal) for the temporal distance of the notes. While the first seven light sensors’ job is to read the notes, the eighth light sensor is to read the music’s beat. To make the notes easy to modify, we used small magnets that we covered with white duct tape instead of directly painting the notes onto the tray. This way, you can create a new melody simply by sliding the magnets on top of the tray’s surface.

With a distance of about 1-2 cm above the crumb tray, we attached eight light sensors and eight LEDs inside the tray’s slot. Each light sensor is being backlit by its own LED, which is positioned right next to the sensor. Whenever a white magnet note is positioned right underneath a sensor while slowly pushing the crumb tray into the toaster, the light reflected is a lot higher compared to the light reflected by the dark crumb tray. This way, it was possible to recognize a note as such to be recorded. It was necessary to measure and find the light threshold, above which a spot underneath a light sensor can be recognized as being white.

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While pushing the tray into the toaster, the key to getting good results for the note detection was finding the best possible threshold for each individual light sensor. Different light situations forced us to find a more flexible solution than manually calibrating each light sensor in the source code. Therefore, we decided to implement a calibrate button in our toaster, which measures the brightness of the black tray without any white spots underneath. This helped a lot for our goal of making the scanner accurate enough not to skip any notes or not to see notes where there actually are none (e.g. when the light sensor on position three measures a value, it is influenced by the light reflected from neighboring notes on position two and four. In this case, light sensor number three should not deliver a false positive value).


Inside our toaster, an Arduino microcontroller functions as its heart and brain. Every LED, sensor and button is connected to one of its pins. Due to the high number of required analog pins for our project, we had to use Arduino Uno’s bigger brother, an Arduino Mega.

12The logic the Arduino Mega runs is declared in our program written in C, which turned out to be around 600 lines of code. One of our program’s responsibility is to transfer the recognized notes, instrument, and loop sound into MIDI signals and send them to an audio program on a PC connected via USB.

Instruments and background loops:

13The realization of adding different instruments and background loops was relatively straight forward. We used some card board toasts that we designed in Adobe Illustrator and cut with a laser, and attached some copper bands at different positions at the bottom. When inserted into the toaster’s slots, each toast closes different contacts with their copper bands and therefore can be recognized as different instruments and loop sounds.

Some of our problems and how we solved them:

Finding the right threshold for the light sensors:

Finding the best threshold for every light sensor for recognizing the notes was by far the hardest part of our project.

In the beginning, we planned on making it possible to scan 16 notes on the note sheet. This lead to several misinterpretations of notes by the light sensors. Some notes were skipped and others were read where there actually was just a note on its neighboring position. We then decided to half the number of notes on the note sheet to only eight notes. This lead to much better scanning results. An auto calibration button on the toaster, which we implemented during our testing period, helped a lot for detecting the right note values. Another measure we took in order to get better results while reading the notes was to increase the amount of LEDs lighting up the crumb tray. We doubled the amount from originally four to eight LEDs, so that in the end each light sensor had its own LED.

The toaster’s handle:

When pressing down the handle of the toaster to start the recording, it has to be held down by a magnet until the recording is done. To do so, we had to replace the original magnet which operated with 220 Volts by a magnet that can function with only 5 Volts, as this is the maximum current we can receive from our PC’s USB slot.

This step was unexpected for us and turned out to be quite time-consuming until the magnet held the handle in place just right.


Unfortunately, we had to find out that the Arduino can not directly send MIDI-signals via USB. Therefore, we had to order a MIDI-to-USB-adapter online. Luckily, this adapter cable could be purchased pretty cheap and the delivery only took less than a day..


Walkman Remote

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Reuse, Reduce, Recycle → Upcycle

This year’s workshop theme was “Reuse, Reduce, Recycle”. So basically the idea is to create new devices that use parts of or consist of electronic scrap. Another interesting idea is to upcycle things. Upcycling takes old items and enhances them in some way, either by improving purpose or by getting it all in a whole new context. So we searched basements, drawers, boxes, flea markets and the internet to find stuff that could be fun hacking.


The idea we have chosen for our project started with a walkman: many of us have one at home and it is hard to throw it away, because it often has good childhood memories attached to it. On the other side a walkman has all controls that are needed to control a music player (Play/Pause, Next/Previous Song, etc.) so our plan was set: let’s build a remote for your computer’s music player that is inside an old walkman. It should contain all the basic functions needed for that: play/pause a song, switch between songs and adjust the volume.

Initial Idea.

Initial Idea.

Our basic idea impressed the participants and the persons in charge the most among all of our ideas we presented on Day 3. So in the brainstorming session we refined our expectations on the prototype and developed further ideas that could be implemented within the small case of the walkman. Some of these creative new facts were to turn the remote in a music streaming device, adding a sleep time or even fitting the whole setup in a cassette (this idea is further explained in the last section of the post). After the creative part of the brainstorming and the presentation of our poster we got to the point of considering technical issues and what can be realised within such a small box casing.

Results of our first brainstorming.

Results of our first brainstorming.

After we first wanted to create our own infrared sender to copy the signals sent out by an Apple remote, the other participants hinted that a wireless connection can be done by hacking yet another keyboard, but this time with a bluetooth sender. More technical issues were discussed like what kind of buttons could be used to trigger commands, how the device could be supplied with power and if the connection between the remote and the computer should be uni- or bi-directional. Having clarified the technical setup we had to obtain all parts we needed. Our shopping list contained a bluetooth keyboard and a bluetooth adapter for headphones. We found the most important part, our walkman, on eBay. A very friendly old man was giving it away for free and as he was located within a half an hour bike ride, we had everything we needed for the project ready.

Getting Started

Similar to the exercise of Day 1 we decided to hack a keyboard controller. As our remote should be wireless we got a bluetooth keyboard and disassembled its controller. Our next objective was to find out the pin combinations for all the keys we needed. We used a systematic approach so that we could easily remember and note pin combinations.

Approaching pin combinations systematically.

Approaching pin combinations systematically.

In the progress of our project a major issue of the keyboard hack was that the media keys of the keyboard and the shortcuts to control the computer’s music player can only be fired by connecting a combination of key-pairs (e.g. Fn + F8). One way to achieve this would be to permanently activate the Fn key. This solution was however not satisfying to us as it would mean that the bluetooth controller permanently fires this key, possibly reducing battery life. Our second approach was to connect the pin combinations for both keys simultaneously via transistors. After some unsuccessful attempts we found out that this approach works, but requires good timing: if the time interval between both keys was a bit to big, the combination was not triggered. Firing the function key a bit longer than the modifier key (as you do with a real keyboard) worked perfectly.

First steps: speaking to Spotify through an Arduino.

First steps: speaking to Spotify through an Arduino.

Stripping the Walkman

When we first opened the case of our walkman, we were pretty impressed. It contained a board with loads of capacitors, switches, resistors and mainly everything that is need for radio reception. The soldering joints looked crafted. There was a lot of manpower involved when the device was built back in the last century. Under that board a lot of mechanics revealed that we needed to dismount in most parts. After a session of screwing, cutting and removing parts the case was finally stripped to its bare minimum.

First looks at the walkman's inside.

First looks at the walkman’s interior.

How does it work?

Our device contains a bluetooth keyboard controller that can trigger certain keys when the right pins are connected through a power circuit. In some cases (like the play/pause key) we could directly close the power circuit by mechanical movement of the walkman’s buttons. In other cases where key combinations and software logic were needed (like the text-to-speech feature) we used the Arduino to close the circuits programatically by setting transistors to high and low.

Major components: 9V battery, Arduino Uno, soldered board with transistors, bluetooth controller.

Major components: 9V battery, Arduino Uno, soldered board with transistors, bluetooth controller.

Bluetooth controller with first wires soldered onto it.

Bluetooth controller with first wires soldered onto it.

Arduino Uno hooked up to bluetooth controller, buttons and transistors.

Arduino Uno hooked up to bluetooth controller, buttons and transistors.

The power supply is a 9V block battery that is connected to a switch which closes the circuit to the Arduino. With the Arduino being powered we could also supply the keyboard controller with its 3,3 V output. The bluetooth adapter for the headphones can be connected by turning it on in the cassette case.

On the software side of the project we needed Arduino code to evaluate control input values and to trigger key combinations by controlling transistors. Furthermore some scripts on the computer enable us to define the output of the key combinations sent from the walkman’s bluetooth. Thus the project is not fixed to controlling a certain music player, like Spotify, as we can change the commands with our script. Additionally we created AppleScripts which allow to change the computer’s audio output device (between line-out and bluetooth headset) and to parse the currently playing song for text-to-speech.

AppleScript which parses and speaks the current song.

AppleScript which parses and speaks the current song.


The biggest challenge for the project was to always keep an eye on the limited space the walkman offers. The very first step was to get rid of all unnecessary parts inside. Then we had to plan, where to place the bluetooth keyboard controller, the Arduino and the bluetooth headset adapter. Available space was further constrained by our wish to have an all wireless self-contained prototype which meant that place for a relatively big 9V battery was needed. Even though it was dimensioned for two AA batteries, we fortunately managed to fit our 9V block into the original walkman battery slot with some force and a rather big saw.

One solution to save space would have been to switch form our Arduino Uno to a smaller version, the Arduino Mini. This one has no USB connection so it can only be programmed via an additional programmer module. In our considerations we got to the point that the Arduino Uno could perfectly fit at a certain spot in the Walkman’s case and so we decided to focus on getting the rest of our work done first.

Another challenge was to tell apart all the different wires. As we expected to have a big chaotic bundle of wires packed in the small box casing in the end, we started to colour-code each wire depending on its function early on. That way it was relatively easy to connect the correct wires in the final phase.

Final Prototype

Final Prototype

Going one step further

An ongoing idea from this project is to scale down all of the functional parts of the device so that it could fit in a simple audio cassette. That way every unused cassette player could be upcycled to a music player remote simply by inserting the cassette.

Thomas Burghart and Maximilian Walker

The Workout Orb

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General description The Workout Orb (formerly: Weather Orb Muscle Cool Trainer) is a device that allows you to keep track of the progress in your workout (such as lifting weights) as well as to improve its quality. It consists of a wristband worn near the elbow that measures the rotation and muscle activity of ones arm. It then sends this data to the Arduino and thus triggers the feedback in the second component, the actual orb. This component cosists of a translucent orb that is filled with water, which, when turned on, is nebulized to form mist. It is then illuminated by LEDs to give visual feedback. The orb also harbors a small piezo element that additionally allows feedback in the form of sounds an melodies. input deviceThe Workout Orb Ideation process The concept for The Workout Orb is based on two of our original ideas, first a wearable gesture interface and second a weather simulator orb. Having originally decided on the weather simulator we then used brainstorming techniques to further elaborate on this idea. ideation processIdeation process – from ideas to final concept During this process we decided that having an output device would not be satisfactory. To create a direct interaction we were looking for an interesting input device. The decision to use the orb as a tool to improve ones workout was made by being inspired by another group that tried to utilize a workout stepper as in input device. Since this device was not available for our group, we thought about an alternative way measuring workout / muscle activity. Through further brainstorming and lots of trial and error the exact details for our project formed very much on the go and in response to problems that we found. Functionality Inside the wristband three contacts that are part of an Electromyography (EMG) sensor that connect to ones skin to measure muscle activity. A gyroscope, to measure xyz movement of the arm, is also implemented. These sensors in combination give access to information on when your arm moves in which direction and most importantly with what kind of intensity and effort. The built wristband is comparable with the MYO (https://www.thalmic.com/myo/) input device, which will be hopefully released in the near future. 😉 input deviceThe wristband – our input device Analyzing this data, meaning the timing, duration and direction of ones lifting weights is assessed and then visualized via coloured LEDs inside the Orb. After successfully finishing the workout session a set of lifts a short jingle and a light pattern are played to indicate the completion. To optimize performance The Workout Orb also evaluates the positioning of the lifting arm and thus can detect whether the exercise is performed in a way that is beneficial or warns with an acoustic signal when you start making movements that may have a negative effect on your training of even health. Components and inner workings Hardware Input The wristband as actually a recycled headband that is shortened to half size. As already stated, the input interface consist of two different kinds of sensors, an EMG sensor and a Gyroscope (not shown on the picture below). Compared to the upcoming MYO our wristband was not wireless and required a special power-supply with a positive and a negative voltage. Thus of a lack of money we utilized two ordinary 12V supplies to also create a negative potential. Armband Internal ComponentsComponents of the armband. There are two actual sensors, which are attached on a particular muscle that has to be measured and a third sensor (the reference sensor), attached to a bony part of the arm to calculate the relative change. Output The Orb is build from a plastic sphere mounted onto the base of a former lava lamp (the remains of which are used as weight for testing). Inside a laser-cut piece of acrylic holds the LEDs and the vaporizer. Orb - InsidesThe insides of the orb Since both of the components, LEDs and vaporizer, require more than the 5V the Arduino offers, they are connected to transistors on the breadboard to use an external power supply. Those transistors are then controlled by the Arduino which, for reasons of water-proofness is located outside (and preferably far away from the orb). The Arduino connections furthermore contains resistors with the intend of preventing voltage leakage from the transistor that might give the LEDs unwanted colours (which happened a lot during early testing). Next to the breadboard there is also a piezo element inside the base to provide audio-feedback slightly amplified by the metal casing as a resonating body. Circuit layout - Output DeviceCircuit layout of the output device. Software Input The event that triggers a successfully performed movement is detected by a deflection of the delta value in muscle activity. Additionally the delta values of a gyroscope are used to detect if the movement is also performed in the right direction. The sensor processing is taking place on the Arduino micro controller itself. Furthermore the sensor raw data and the sensors delta values are transmitted via USB to the computer, where our own software visualizes these in graphs. This software also allows the user to set their own arm and hand gestures to a free chose able function. The setup is simple: The user can assign a key to a desired gesture, that he is able to record. After saving it, the computer tries to find the recorded pattern in the current sensor data. sensor dataRepresentation of the sensor data, later to be processed and visualized in the orb. Output To assess the progress of the workout the Arduino internally differentiates 256 states of training process which in turn also provide (with a little math) the the LEDs brightness to form red light at the beginning gradually turning yellow and then green upon completion. To control how many exercises have to be made to complete one workout set, the speed, i.e. the value added per exercise, can be varied. The so generated colour is then flashed every time the motion is detected, gradually fading away in a simple loop. Upon reaching state 255 (or more) the piezo element is triggered using the already existing code for playing sounds´which we modified to play something that seemed slightly more appropriate than Happy Birthday or Super Mario music. Encountered problems Two occurences can be counted as the major challenges faced troughout the construction of The Workout Orb. The first being the matter of sensor data classification. This describes the process of taking the raw sensor data, identifying  the desired patterns and consistently responding to them. The second challenge was that of regulating the power supply for all components. Since all elements (except for the piezo acutator and the Arduino itself) required at least 12 V, some 24 V, extensive use of transistors had to be made. However these proved to be unreliable and often didn’t cut power entirely when they were supposed to. Varying designs using resistors were tested that ultimately provided satisfactory but not optimal results. Another minor challenge in this field was the fact that some transistors died on us due to the heat while soldering.

We however mastered all these challenges and were able to present a working prototype that not only proved to be a good learning experience but might also be a glimpse into the future and the possible uses for the MYO released end of this year and other gesture interfaces.

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