What this blog is about :-)

Posted: 19. August 2014 in Allgemein

myrijam-01Hello everyone!!

At first I’ll tell you who I am and why do I guide this page…

My name is Myrijam Stoetzer, I’m 16 years old and I’m in the 10th class… 😉

I like swimming and climbing, and I love hanging out with friends, soldering and programming.

DSC06110I want to show you all my technical projects, I did since the 3rd class. So I won’t forget what I did as yet…
The most of my projects I did in the robotic- club after schools end.

Here is my e-mail adress to contact me: myrijam.stoetzer@gmail.com


MAG3D – Update!

Posted: 5. March 2017 in Allgemein

Finja and I developed our scanner for vectorfield analysis of magnetic flux further: We have built a new design with a linear 3-axis delta approach – now we can truly scan a 3d-space mapping the magnetic flux as a 6dimensional vectorfield! And we have added some fine mathematics to cheat – eh, improve performance and/or resolution 😉


Design of the Linear Delta for moving Sensorplattform

I am still not satisfied with this design because the ratio of the arms and the radius is not optimal and therefore you can only measure a very small area of 3x3cm because the sensor plate is raised at the edges of the measuring surface. I know this could be simulated e.g. with Geogebra, but I have no clue at the moment how to do simulations in this software…

New scans – examples

Here is a vectorfield plot of a round magnet from above:


And, of course, we have taken the traditional electric-current-in-a-wire magnetfic field to the next level: How do strange or funny shaped-wires produce magnetic fields? Have a look:

heart_vectorfield heart_surface

It is the shape of a heard with about 10amps going through it – but apart from the “girlish” attitude of showing a heart, there is real-world application for it. Think about the complex magnetic field necessary in fusion reactors… they need odd-shaped coils to produce them 😉

Constructing the linear delta

Coming back to the new mechanical design we have chosen: Delta printers have a parallel kinematics, since the positions of the motors are not interdependent, so one motor does not move the other. On the other hand, the positioning becomes more complex, because, in the case of a positional change in one plane, all three motors must always run at different speeds but start and end at the same time. The mathematics behind the delta design, for the precise control of the stepping motors, is derived from the theorem of Pythagoras itself – ignoring acceleration and deceleration. We 3d-printed the carriages and motor attachments and first used an Arduino Mega, 2 motorshields Bluetooth-Dongle and a smartphone to control the scanner. In the meantime we have started on porting this to the Raspberry Pi using Python and Matplotlib to visualize the scans.

How to cheat nicely with math 😉

In the case of different measurements it is noticeable that the visualization of the vector field can show “jumps”. This is why we asked ourselves which mathematical algorithms we can use to improve the measurement results, since we cannot change the sensor itself to reduce noise.

One way to increase the measuring accuracy or to reduce the “noise” is to carry out several measurements and calculate the average. The sensor itself allows an average value formation and transmits to the micro-controller the average formed by 2-fold, 4-fold or 8-fold measurements. We have also implemented this accordingly and have the sensor now always perform an 8-fold measurement at each individual measuring point. This way only the mean variation at a given point is reduced.

Nevertheless, a clear noise remains in the further pictures. We have therefore researched how noise can be reduced in a vector field and found a contribution in a scientific journal describing a corresponding filter for geophysical investigations: a so-called vector-median filter. Median is exactly in the middle of an ascending sorting series. MATLAB has the possibility to calculate a vector median filter. The specific characteristics of the field are preserved. We’ll combine that with another mathematical improvement:

A further mathematical optimization in measurement is the interpolation of data. Some of the measurements take quite a long time when a large measuring field is set – because a doubling of the resolution or the measuring field on two axes leads to a fourfold higher data volume and scan duration (quadratic relationship). If this is transferred to the z-axis, the time for an overall measurement is doubled (cubic correlation). Since the individual measuring points lie at a very small distance from each other (a few mm), it is unlikely that there is an extreme deviation in the magnetic field between them not affecting the neighboring points. So – can we use an algorithm to do educated guesses for sup-pixels of our analysis? Or in other words: Can we cheat nicely with math?

In the simplest case, the intermediate values could be found by means of a linear function, that is to say the values would be connected to a straight line. More complex ways would be to find a curve that fits the data to estimate the “in-between” values not measured.

In MATLAB there is a function that mathematically calculates approximate values between individual measurement results: The spline function. Starting from the neighboring points (for example, in a 3×3 or 5×5 grid), it reconstructs a graphical course on which these measured values lie by different methods – linearly or by curve trajectory. Have a look:


This is a zoom into a surface plot – on the left is the original data, middle shows linear interpolation and right image shows the spline function. The noise is preserved, but we already have a solution for it…

This function can be used to measure fields faster or with higher resolution. If, for example, a measurement is carried out only once every 5 steps in a 100×100 field, instead of measuring every single step, the measurement process can be 25 times faster. From the upper graph, however, it can also be seen that the measured values still show noise point despite the mean value formation. Just interpolating the data carries on these inaccuracies so that it can be useful to perform a smoothing of the data:


This comparison shows that the same magnetic field. In the upper left you see a zoom into a surface plot of a 20×20 field. The downer left shows the exact same magnetic field scanned with a 25times higher physical resolution of 100×100 samples.

The images on the right side show the mathematical approximations: The upper right image is interpolated from 20×20 to 100×100, increasing the physical resolution to a virtual one by factor 25 as well as an applied vector median filter. It still shows some of the noise, but it is very smooth and accurate now. The image on the down right side is a median filter on the pure 100×100 physical resolution – no noise, no artifacts.

As our aim was to keep the project as open as possible, so we looked for alternatives to visualize the data. We still work with MATLAB, but have an alternative version with the Raspberry Pi – there is Wolfram Alfa (which is for free on the Raspberry) as well as powerful tools like Matplotlib..

We submitted this project this year to Jugend Forscht in Berlin and won first prize on Berlin’s regional level. Keep your fingers crossed for the next competition level, please 😉


Medication that cant be ingested through the gastrointenstinal tract has to be injected intravenous – usually by a doctor but in chronic diseases it can also be
carried out by yourself  (“home treatment”, for example, venous puncture with
medication 3 times per week).

A chronic disease which requires frequent venous puncture is hemophilia.
In the blood clotting chain, one or more essential enzymes are missing or build in a non-working way due to DNA corruption. This can cause severe bleeding into joints, muscles or inner organs and is potentially live threatening if the rest activity of the clotting factors is below a few percent. Today, most of the clotting factors can be artificially synthesized through biomedical engineering (cell cultures with a changed DNA  produce them), but they still have to be 
administered externally – injected into the blood stream by venous puncture. Children and families often face great difficulties here.
Venous blood vessels used for medication are not always easy to recognize and if the needle is not secure in the vein, it must be punctured again at another point.

Here our project comes into play
: Using NIR (near infrared) Illumination and real-time image processing, we can make the veins more visible!


Screenshot: upper left original camera, upper right automatic image adjustment, manual adjustment, colormap

We (my brother Elias, Lucie [a friend of mine] and me) submitted this project to Jugend Forscht and won first prize on Berlin’s regional level. Please keep your fingers crossed for the next level on the 21st and 22nd of March…

Our aim was to develop an assistive technology for venous puncture for diagnostic purposes (blood sampling) or for medical drug administration.
Easy reproduction and low costs are important criteria for development.

In addition to the research and review of specialist literature on methods of venous localization and optical characteristics of human skin, we carry out our own experiments: 

Illumination of skin with different wavelengths, cooling the arm and using thermography to watch the surface veins warming the skin again as well as a spektrometrical analysis of arterious and venous blood samples were among them.

With the results and findings, we developed two prototypes for computer-assisted venous localizationThey differ regarding to the camera system used – one works with the PiCAM, the other with a modified webcam. Both have their own pros and cons…


Frame for Webcam

Usually, cameras have an infrared blocking filter, which only allows the visible range of the electromagnetic spectrum to pass, because otherwise the image representation deviates strongly from our viewing habits. For the Raspberry Pi, there is a camera, where such a filter was not build in. It can be used without further modifications. However, this camera offers only a fixed focus and cannot focus the image scene automatically.


Modding Webcam – remove IR-Blocking Filter

Another possibility is the modification of a webcam. The housing has to be opened, the blocking filter removed and as an additional lighting, 1mm small infrared LEDs need to be soldered in; along with some pieces of old analog developed film (blocking visible light, passing NIR). We have been able to use such a camera from my previous research project (“eye control wheelchair”).

We use the single board computer Raspberry Pi (will work from from version 2 on), which is available at low cost worldwide and has proven itself in many projects as sufficient for image analysis and image processing. Using 3D printing, all required housings for the Raspberry Pi, the cameras the infrared illumination and the display could be designed and changed easily 🙂 And you can build your own version by just downloading the code and the cad-files from my github…


Discussing the Project


Dr. Klamroth testing our Prototype

We presented our project to Dr. Klamroth, head of department of internal medicine at Vivantes Berlin Friedrichshain, who was impressed and gave us some tipps to improve the usability.

A possible future development would be the use of smartphones with an external camera that can record infrared light – but until now I haven’t had success in installing Android Studio and working with openCV yet…

You can download the full report here (in German): Veindetection_German_Report



In the autumn holidays Finja and I were invited to the Fraunhofer Institut IIS in Erlangen. They have developed the HallinSight, a sensor similar to our magnet field scanner, but they use a sensor array instead, which means they don’t have to move the sensor. And the most amazing thing about their sensor is that they can receive the measurements in real-time (up to 200 Hz) – so it is a true magnetic field camera! It uses a sensor array of 16×16 sensors that measure the magnetic flux as a 3d vector field – but instantly. And with some very sophisticated math they can interpolate the readings to sub-pixel precision! Unfortunately, this sensor is not used in schools so far – just imagine visualizing the magnetic flux of a motor on action!

Our Visit started with an overview of the institute and the applications they develop sensors for. It was very interesting to hear about the different working places. They have a lot of amazing projects starting from facial expressions detections to an intelligent toothbrush! This is so cool!

Then we presented our project in front of the entire team that developed the HallinSight and did a few measurements – they were very interested in our development and the decisions in design and software architecture we did during the development. And we got a lot of tips and ideas as well!


After that we had a very delicious lunch in their canteen, followed by a tour through the Institute. At first we got to know about the audio technology, because the Fraunhofer Institute is known for inventing the mp3 compression.

We were at their home cinema and it was in 3d! That was so cool to watch short films. Unfortunately the cinema is only for research 😉

At the end of the tour they told us that they have a surprise for us and we were super nervous and excited!

It was like Christmas – or even better: Dr. Hohe und Dr. Peters gave us two of their magnetic field cameras as a loan (respectively our schools in Duisburg and Berlin, since we are not attending the same school anymore because my family and I moved to Berlin). We were shocked, because we never would have expected that and it is such an honor to us!

I will post some measurements from our MAG3D and the HallinSight here in the future so you can compare both.


Maker Faire Berlin 2016

Posted: 4. October 2016 in Allgemein

A m2016-10-03-photo-00000034onth ago my family and me moved to Berlin. It is so cool to be back here but of course I miss my friends 😦

From Friday till Sunday Finja and
I were at the Maker Faire in Berlin with our Magnetic Field Scanner. It was such a cool experience! Meeting interested people, getting feedback and getting to know new people … and of course a lot of other amazing electronic projects. But standing for 8 hours a day was exhausting too.  🙂





Posted: 15. June 2016 in Allgemein

I was invited to give a TedxTalk! The topic was “Everyday Breakthroughs” and I must admit I had fear of speaking in English for 18 minutes in front of many people! But as I got there and listened to the other speakers, it wasn’t that bad J. They were so fascinating and I really enjoyed being there! My talk was about my breakthroughs I had before and during my projects and about different kinds of breakthroughs in general.

Because break-through is a huge word, and it implies that all the mysteries or problems have been solved at once (… far from it in reality…) and sometimes these changes are just the starting point of new developments.

There also was a magician who performed two of his tricks! The others had a lot of cool ideas and rousing talks! It was so interesting and I am really glad to had the chance to speak there and to get to know the other talkers!!


You can download the paper from my talk here (thanks to Phill Sears for proofreading) and I will link a video of the talk as soon as it’s available.


Intel ISEF 2016

Posted: 15. June 2016 in Allgemein

When I got the invitation for the Intel ISEF 2016 I wIMG_7676as so excited and was very happy to be able to participate in this competition with my eye-controlled wheelchair.

After a few months and a lot of paper work we packed our stuff together and flew to America!

Our flight was going from Düsseldorf to London (where we had to wait 6 hours because the flight was too late) and from London to Pheonix, Arizona. The safety control was easier than we first thought… They just waved us through with all our electronics in our bags (we had to take the wheelchair, 1 extra big bag for the electronics, 2 smaller ones for the electronics too and 2 big ones for our clothes)!

Our hotel had a great view and all the people were so nice! Wherever we went the people were so excited that we came from Germany!  The whole first day was time to make your project ready and fit the posters etc.  Firstly we had some difficulties with the space but till the end of the day we solved them.

The next day, Monday, we made a trip to a recommended river, which at least was in the blazing sun so that we decided to eat ice cream. 😉

IMG_7770IMG_7825On Tuesday we also made a trip but this time it was so awesome! That was the moment I realized we really were in the desert. There was nothing except cactus families, sand and rocks. It was really hot and your water was warm after a few seconds only…

On the next day the most exciting thing started: the judging day!

One presentation should exactly take 15 minutes. There was a list were judgers could register themselves to listen to the projects. But there could come unheralded judgers too. We had one or two breaks because as one judger went to the next project, another judger came to judge our project. This was really stressful but interesting as well. All judgers were nice and it was very exciting to explain our project to professional people. After the judging day was officially closed, we could then enjoy the rest of the day.

The special award ceremony was on Thursday in the evening. Before that the visitors could listen to the projects. A lot of students got there too. We all were excited and I must admit I really didn’t await to receive any award. But we won three special awards!!! One from Sigma Xi, the scientific research society (“First Place Life Science Award”), one from the Chinese Association for Science and Technology (CAST) for originality and innovation as well as an honorable mention from the Assocation for the Advancement of Artificial Intelligence.IMG_7746

The next day the grand award ceremony took place: And we won a second prize in our category “embedded systems”!! All in all team Germany did a really good job! 😀 After the ceremony we then started our way back home. It was a fantastic week in which we got to know interesting people, and new places and a different culture and I think we all enjoyed these days!!


Magnetic fields are a fascinating subject – they surround us, protect life on earth and allowed orientation, e.g. of migratory birds on far distances and for us humans, long before we relied on smartphones with GPS 😉

We have no sensory organ for magnetic fields, so in physics classes we discuss magnetic fields with the help of their force effects. Iron filings are used to visualize the force field of magnets magnetic, because they form line patterns indicating the magnetic field lines.

This is a very vivid visualisation – but there are several limitations: It is only qualitative (you cannot measure the magnetic flux density by this) and works only on the horizontal plane. Furthermore, what is, for example, “between” the lines that result from the alignment of the iron filings? Should the magnetic field not decrease gradually with distance, instead of significantly staggered?

My friend Finja and I tried several visualization approaches to circumvent these limitations. First, we experimented with ferrofluids (great fun, very messy, still only qualitative) and moved on to use sensors, microcontrollers and some other electronic bits and pieces.

Our first scanner was build from ABS tubes and customized 3d-printed parts we developed on our own. It was supposed to operate with parallel kinematics to have both motors in one place – not to interfere with the measurements taken. We did not get the right bolt drives for it and the strings slipped too much to be precise.

P1010921Since the deadline for the science fair was getting close, we chose another path and started all over again. This time we used an old fischertechnik plotter from the 1980’s that has been laying around in our school ever since (unopened!).

We exchanged the steel tubes for carbon ones and changed the design a little bit as well. Instead of a pencil it now carries a breakout board for an SMD magnetic sensor, commonly used in robotics to orient the robot according to earth’s magnetic field. It measures the magnetic flux density in 3 dimensions and with 8 different ranges – the HMC588L.

We used a motorshield, added an SD-Card-Shield we built from an Micro-SD-Card Adapter our self, an LCD-Display and Bluetooth to make the device controllable via a Smartphone-App.


We can now analyse the magnetic field by measurement of its flux density and visualize it in 3D. For the moment we only scan regions (a plane) and measure the three-dimensional vector (BX | BY | BZ) | of every single measuring point with assigned coordinates (Y X) automatically.

The result is a vector field – a bit uncommon in 9th class math to P1010948work with 😉

But it is quite easy to understand the principle: If you imagine that the invisible magnetic flux can be measured and the direction of a force resulting from interaction with it would be visualized as an arrow, the direction of the arrow gives you the orientation in space and the length the value or “intensity”. In Physics, you use vectors on an incline to determine the forces acting on an object – and is very obvious that the direction and the value are important!

To imagine a vector field you can simply think of a grainfield, with every grain representing a vector. If no external fource acts upon them, the grains grow more or less identical (same orientation) and reach the same height. External forces can now change the orientation of vectors in this particular field, like a wind blowing over it.

Coming back to magnetic fields, we can determine the spatial orientation and intensity of the magnetic flux at any given point on a 2d plane (scanner area).Herz_88uT__4A

As a result, we have a 5D-vector field of the examined magnets, which can be visualized with the aid of mathematics programs such as Matlab and investigated further.

steppermotor-core--magnified-200x200 130µTWe have some nice examples of current loops and magnets. You can also visualize how the earth’ magnetic field is distorted by even small steel items like a keyhole saw blade.

For further development we want to extend the scanning device so that the height of the scans can be changed as well – then we would measure a 6D vector field…


mag_schraubenzieher2We won first prize in Physics on the federal state level of the science fair Jugend forscht (Schüler experientieren) and a special price for nondestructive examination.
A special thanks to Sebastian Groß from Mathworks – he supported us with the licences of Matlab we needed to visualize and analyse the data!


You can download the PDF here, but it’s in German. We might translate the most interesting parts later on…

MAG3D – Analyse von Magnetfeldlinien als 3D-Vektorfeld