Repair the Syma X12S quadcopter by replacing the motors and rotor blades (and what to do if it does not lift off afterwards)

Syma X12S quadcopter with new motorsMy friend owns a Syma X12S quadcopter that was cheaply imported from China. It really is an amazing piece of hardware and the perfect entertainment when you spend an evening with friends. Piloting this miniature aircraft is quite easy – it only takes a few flying sessions until you acquired enough skills to handle it. However, I still managed to crash the quadcopter in a way that damaged two of its four motors. The beauty of this toy is its modular design: Even though it is a cheap product, most of the parts are LRUs, so you can simply order a replacement for the defect part and replace it yourself.
This short post shows how to replace the motors of a Syma X12S quadcopter and highlights some difficulties to look out for.

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Low-Latency Live Streaming your Desktop using ffmpeg

I recently bought myself a projector, which I installed in one corner of the room. Unfortunately I didn’t buy a long enough HDMI cable with it, so I could not connect it to my desktop computer and instead used my loyal ThinkPad T60 for playback. But I also wanted to be able to play some games using the projector, for which my laptop wasn’t beefy enough. So I thought, why not just stream the games from my desktop computer to the laptop?

In this post I will explore how to stream 720p (or any quality for that matter) from one computer to another using ffmpeg and netcat, with a latency below 100ms, which is good enough for many games. TL;DR; If you don’t care about the technical details, just jump to the end of the post to try it out yourself.

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Fixing Full-HD VGA support for the Epson EH-TW5200 Projector

If you happen to own an Epson EH-TW5200 projector, you might have experienced problems setting Full-HD (1920×1080) resolution using a VGA connection under linux. When I set the resolution to Full-HD, the whole screen would stay completely black. This is just a quick fix for the other 4 people that might have this problem.

The difference between the original modeline and the new one is the vertical refresh rate: The projector proposed 60.02 Hz via EDID, and the new modeline is just a tad slower, using 59.94 Hz. I was connecting a ThinkPad T60 to the projector, so the problem might also be the RAMDAC of the laptop, something about blank phases, who knows.


Homeserver Upgrade: Odroid XU3-Lite Setup on a SD-Card

I recently bought a new home server, the Odroid XU3-Lite to replace my poor man’s home server I called the thin-server, to run CherryMusic and the like.


That little ARM machine is a beast in the size of a cigarette pack, featuring a total of eight CPU cores, an ethernet port and most importantly an USB 3.0 port to connect an external hard drive. It also comes with a plastic case, with a small fan inside and a PSU that is strong enough to power external hard drives connected to the USB ports. I ordered the smaller “Lite” version, which has a slightly lower CPU clock rate, but costs a lot less than its bigger brother.

In this post I’ll guide you quickly through the installation process of the ubuntu image on a micro SD-Card, how to make use of all the space on the microSD card and how to secure this little fellow a little after the installation of the image.

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How to add USB Gamepad support for your Android phone or tablet


I was almost at the point to buy a playstation or xbox controller to use with my tablet, since they seem to be supported out-of-the-box. But actually I still have an old USB controller lying around, which would be more than good enough for playing some games. Interestingly my gamepad did in fact work partly, but only the left analog stick and one or two buttons, and the rest did not. My hacker spirit told me that this must be fixable somehow.

So I started hacking around and added support for my old USB gamepad for my android tablet. In this post, I’ll show you how I did it and how you can to add support for any gamepad to your phone or tablet as well!

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DIY: Black Rolls/Trigger Point-like foam rollers for myofascial release

Black RollsFinished DIY version

I am a big fan of using foam rollers for myofascial release, especially after workout.

There are a lot of foam roller products for myofascial trigger point treatment out there, but I am too cheap to buy a piece of recycled plastic pressed into a cylindrical form for 20 EUR or higher. This is one of the easiest DIY projects possible, so make your own! Continue reading

Samsung Galaxy S3 repair – Glass screen/digitizer replacement and why it is not recommended

Glass screen replacedA friend asked me to repair her friends Samsung Galaxy S3 mobile phone, that had a broken glass screen/digitizer, so I had a closer look at it. The process of replacing the glass screen/digitizer on a Samsung Galaxy S3 is straight forward and not many tools are needed. However, what you really need is patience… a lot of it.

This post shows how it is done and why I still would not recommend it anyway.

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DIY: “barefoot”/natural running shoes

Finished sole

At the end of last year I went to a sports and health fair, where I wanted to have a closer look at the available natural running shoes, especially the ones from Vibram (FiveFingers) and Leguano. Both type of shoes were comfortable and seemed to be of good quality. However, with an above the 70 EUR price range, they are quite expensive for a shoe that aims to be like no shoe at all. In fact, they are more like a pair of high quality socks with a special thin rubber layer glued to the sole (whereas the Vibram FiveFingers also seem to have some supportive structure integrated, which is kind of a contradiction to the barefoot philosophy). Making a custom fitted version should not be that hard, so I decided to make my own.

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QCAD – Symbols, special characters and font styles in dimension labels

Cover - QCAD with Alpha and l_ABz dimensions

QCAD is a great free and open source CAD software. Although limited to 2D design, it is my favorite tool for drafting, construction and simple sketches. It is well documented overall, but one issue I could not find a solution for, was how to label dimensions with symbols, special characters or certain font styles (bold, italic, super-/subscript).

This blog post provides a simple trick to get it done.

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Maxima (software) and gnuplot – plot functions using lines with symbols on it (workaround)


I am recently working on some scientific papers for which I have to visualize a lot of mathematical functions. In a good scientific paper the graphs (and visualizations in general) should be colorless and utilize dotted/dashed lines or lines with symbols on it instead of colors. This has several advantages: A colorless plot is more neutral to the reader, he/she does not get distracted by the different colors. A reader may also have a (subliminal) preference in color, so he/she pays more attention to e.g. the red curve than the yellow one, that is hardly readable on the white background anyway. This also helps to distinguish functions, if they are plotted in one diagram and printed in gray scale mode or read by color blind people. Also, if two identical functions are plotted in one diagram, using just colors will probably only show one of the functions and hide the other.

I am using the CAS software Maxima to do the calculations, which in turn uses gnuplot to plot the functions. Gnuplot alone does the job perfectly. However, when plotting functions (and not discrete data points) using lines with symbols on it from within Maxima (which also uses gnuplot to plot the graphs), the results are quite ugly. There seems to be no proper solution to this problem.

This blog post suggests a workaround that is rather ugly, but which produces very nice graphics, that meet the above-mentioned requirements.

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