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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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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Samsung SSD 840 EVO 2.5 Zoll SATA – Firmware update under GNU/Linux

I recently bought a Samsung SSD to replace my HDD in my Arch Linux notebook. It is a “Samsung SSD 840 EVO 2.5 Zoll SATA”. One of the first things I do when I get new hardware is to make sure the latest firmware is installed. Mine did not have the latest firmware update and – as it was to expect – Samsung SSD firmware updates under GNU/Linux are not (officially) supported. Samsung ships only Microsoft Windows software, called “Magician”, which can directly update the firmware or create a live USB-Stick to do the update. Additionally, they provide *.iso image files (one for Microsoft Windows systems and one for Apple computer, respectively) to update the firmware from a live CD. The *.iso image file intended for Microsoft Windows would also work under GNU/Linux, only that my notebook does not have a CD Drive anymore. Obvioulsy, the only option left was to create my own live USB-Stick under GNU/Linux – without using Microsoft Windows and that crappy Samsung “Magician” software. A simple “dd” comand to “burn” the *.iso file on an USB-Stick did not do the trick, as the Isolinux version Samsung uses is over 10 years (!) old.

This article shows how to update the firmware of a “Samsung SSD 840 EVO 2.5 Zoll SATA” under GNU/Linux using a bootable live USB-Stick.

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UEFI, GNU/Linux and HP notebooks – problems and how to get it working

There is a lot of confusion and wrong information in the internet about the Unified Extensible Firmware Interface (UEFI) and how to set it up correctly – especially under GNU/Linux. What makes things worse and also confused me a lot is that all vendors tend to implement this “standard” differently. So although UEFI is defined as a new industry standard replacing the BIOS, it can hardly be called “standard” at this time. Yet another problem of understanding UEFI is, that people seem to mix up words that have a special meaning.

My old notebook still uses the old BIOS-MBR setup, not capable of any UEFI fancy-ness. But it is dying, so I recently bought a new one. It is an “HP EliteBook 840 G1”. I used that opportunity to familiarize myself with UEFI and GNU/Linux.

This article explains two things (only taking GPT setups into account):

  • How is UEFI implemented in practice and set up with GNU/Linux?
  • How to set up UEFI and GNU/Linux on HP notebooks?

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Create a GNU/Linux multiboot USB-Stick (Live USB) with Syslinux chainloading

Since USB-Sticks, that are fast and have a high capacity, are finally affordable, I decided to buy a new one. I usually install a GNU/Linux live CD (more precisely live USB) distribution on my USB-Sticks: either SystemRescueCd or Kali Linux (former Backtrack). The left over space is used for the classical purpose of an USB-Stick – data exchange. Todays USB-Sticks have enough capacity to easily fit several GNU/Linux live distributions on them, while still leaving enough space for other data. So my plan was to create a multiboot USB-Stick, that would boot my favourite GNU/Linux live distributions mentioned above. Unfortunately, searching the internet for implementing this did not give me any satisfactory results. There are a ton of guides that explain how to create an USB-Stick that boots GNU/Linux, but there are almost no multiboot solutions. The few howto’s about multiboot USB-Sticks are either about booting *.iso files (which only works with some GNU/Linux distributions) with GRUB 2 (which is designed for static boot setups anyway) or require further customized modifications of the GNU/Linux live distributions. I wanted a simpler solution that – once created – allows for easy updating of the installed GNU/Linux live distributions.

This guide will explain how to create a multiboot USB-Stick that can boot several GNU/Linux live dirstibutions via Syslinux chainloading. It will have several partitions (one for each OS and one for the main Syslinux bootloader) and a separate data partition, that can be formated independently in any way you like, so that your data is seperated from the operation system data. This guide installs SystemRescueCD and Kali Linux on your multiboot USB-Stick, but any other GNU/Linux live distribution should work as well. Adding more than two OS should also be no problem.

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How to install and configure CherryMusic on a Debian Wheezy (headless) server


This guide explains how to correctly — and more importantly cleanly — install CherryMusic on a (headless) server running Debian Wheezy — without polluting the operating system in any way. For Arch Linux or a more generic installation see the CherryMusic Arch Linux wiki page and CherryMusic’s own wiki on GitHub.

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