3D printed drones

I just found some old prototypes of drones I printed out and want to share my experience with them in a small post.

The first design was downloaded from thingiverse. I printed it out but it never worked out that great because in my opinion the design had some serious flaws e.g. the arms did not fit in the socket because my printer had some inaccuracies.

After that I made my own design and I strengthen it for better durability. Also I thought a hexacopter would be cool. It was flying great, but unfortunately the 3d printed parts were too fragile.

The last design I made was a kind of hybrid design of 3d printed parts and copper rods. It was super light weight and also quite durable because of the rods. However, the feeds broke easily at faster landing approaches as one can see on the photo.

All the drones I printed with PLA and this was the main issue with them - they break so easily, it just doesn't make any sense! Well, back in the days I could really only print PLA with my first printer. After the 3. prototype I decided to just buy a 15 Euro carbon frame from Aliexpress which was way easier. Nowadays, I am thinking about giving it another shot with TPU. I saw some Videos where people print RC parts with TPU (a bit thicker, but weight is not a very huge problem for me). With TPU, durability doesn't seem to be an issue anymore (I already did some field tests and it was really sturdy).

3D prints for a loving home

As I walked through my apartment recently, I noticed how many 3D-printed stuff I have printed over the last 3-4 years. So I decided to create a larger post here, with some useful projects I printed for a loving home. May it can inspire someone for future projects.

Kitchen Utilities


To be honest, this angels could also be bought but using printed ones just feels so much better. kitchen shelves Then I have printed this things. I never saw them in a hardware store. kitchen shelves Screw them on some planks ... kitchen shelves ... and voila, shelves for spices are built! kitchen shelves I said spices! kitchen shelves More spices!! kitchen shelves

Coffee utilities

There are some cool things to print for a porta filter machine. First, here is the most obvious device: a tamper for pressing in the coffee into the porta filter. The tamper works extremely well, because the bottom is very flat because of a flat print surface and a bit over extrusion. porta filter utilities

This thing belongs to a... porta filter utilities small table trash can to remove the wet coffee ground from the porta filter after extracting a coffee. porta filter utilities

Lightning tools

Light Box

I always wanted to have a softlight for filming videos on my desk. But instead of using a single bulb with a shade, I thought about soldering a long led strip (this one was one of the cheapest I could find) to a grid and building a box for it.

soft light box soft light box

As a ground plate, I took some milk glass to soften the light. The milk glass is hold by some printed accessories and below the box there is a printed camera holder for a go pro (unfortunately the top part can not be seen in the picture). Because the lamp is 0.5 meters long and wide, the image of the go pro is lightened out perfectly.

soft light box


Here is a lamp with moving joints, I designed pretty early. Unfortunately, the joints are not so durable, so I ended up reprinting them and just glued them together with hot glue.

lamp lamp

For Animals and Pets

The prints I enjoyed using most are those for animals and pets.

Bird swing

The bird swing was well appreciated by my budgies. I designed it with OpenSCAD and strengthen out the edges with a triangle structure. bird swing bird swing

Bird feeder

This was just a prototype, where I tested out if a print in combination with an RC servo can make a feeding machine for small grains. It really worked out but did not make it to a final product yet. bird feeder

Bird shower

Also a prototype where I connected a small water pump to a printed shower head. This worked out perfectly but I could not get the damn budgies under that thing :( bird shower

For outside

Bird house / Food dispenser

Without a doubt, this thing was the best print to look at. Enjoying breakfast while viewing happy birds using this print for a living? - Just awesome!

bird house or food dispenser bird house or food dispenser


Key hooks

Just a key holder for hooking up keys and smaller things next to the apartment door.

key hooks

Fixing furniture

I bought a small drawer from IKEA some years ago and they have this very thin rails that broke super easy as you can see on the left. fixing ikea drawers

So I decided to redesign them in a more stable way.

fixing ikea drawers

There you can see three iterations of it. The solid ones where much stronger - as expected.

fixing ikea drawers

Final result:

fixing ikea drawers

Curtain rod holders

I could not get these double rod holders for hanging up curtains infront of a big window/door in the living room, so I outsourced the design of those things and printed it out myself.

curtain holder

They are not solid but printed with a higher infill percentage. However, next time I would rather design them with two screws than with only one, to make sure it sticks to the wall even with pulling on the curtains.

curtain holder

Hope you enjoyed this post. If so, please leave a comment and share ;)

Determining the total revenue of a blackmailer: Bitcoin is offering new possiblities

reading harsh spam emails

Last weekend I was kind of bored and every time I am bored I take a look into my spam folder to amuse myself. As I scrolled through the list I suddenly was shocked for half of a second because the subject of this one email was my email address and my default password, which I used for several services.

Since I was aware of the fact, that this password was leaked several times in the past, this shocking moment disappeared quite fast. To check if your passwords got leaked, visit this page. My credentials were leaked 7 times.

However, I was excited to read the content of the email. Not surprisingly, it was a very harsh blackmail where the sender accused me of watching porn. Further on, he had hacked my webcam and now has some videos of me watching porn. He also kindly mentioned that I have a good taste, which I think was nice.

Here is the mail:

I am aware <my_default_password> is one of your passwords. Lets get directly to the purpose. Nobody has paid me to check you. You do not know me and you're probably wondering why you are getting this e mail?

actually, i actually installed a software on the 18+ streaming (sexually graphic) web-site and do you know what, you visited this web site to have fun (you know what i mean). While you were watching videos, your web browser started out operating as a Remote Desktop having a keylogger which provided me access to your display as well as webcam. after that, my software gathered all your contacts from your Messenger, Facebook, and e-mail . and then i made a double-screen video. First part shows the video you were watching (you have a good taste rofl), and 2nd part shows the recording of your cam, yea it is u.

You have got two different solutions. Lets take a look at each one of these options in aspects:

Very first alternative is to neglect this email. Then, i will send out your actual video to all of your personal contacts and also think about about the humiliation you can get. and definitely should you be in an intimate relationship, just how it will certainly affect?

other alternative would be to pay me $989. We are going to describe it as a donation. in this scenario, i will straight away discard your video. You could continue on with everyday life like this never took place and you will not hear back again from me.

You will make the payment through Bi‌tco‌in (if you do not know this, search for 'how to buy b‌itcoi‌n' in Google search engine).

B‌T‌C‌ ad‌dre‌ss to send to: 1DG8pnwK9vdevHjB1nfDQRUmyYVJyPQNf9

[CaSe sensitive so copy & paste it]

if you may be thinking about going to the law, surely, this email message can not be traced back to me. I have taken care of my moves. i am also not looking to charge a fee a whole lot, i just want to be paid for. right now if i do not receive the ‌bi‌tco‌in‌, i definitely will send out your video recording to all of your contacts including relatives, co-workers, and so on. Having said that, if i receive the payment, i'll destroy the video right away. If you need proof, reply with Yea! then i will certainly send your video recording to your 15 friends. it is a non:negotiable offer so do not waste my time & yours by responding to this email message. 

However, I hope all of my readers know that this kind of emails are bullshit. And by the way: I do not even have a webcam. Hacking a webcam through the internet is quite hard, but hacking a non-existing webcam is nearly impossible!

Bitcoin offers new possibilities

I remembered, that you can publicly see all activities from a particular web page. This is a big disadvantage in terms of privacy, but in this case it is more an advantage, I guess.

I searched for a service to view bitcoin data, and I have found https://www.blockchain.com. So to check the total revenue of this blackmailer, just open https://www.blockchain.com/en/btc/address/1DG8pnwK9vdevHjB1nfDQRUmyYVJyPQNf9.

At the time of writing this post, the blackmailer has gotten 17 payments and earned 2.77 bitcoins, which is 9277.15 Euro. I think this is not a bad revenue for tapping a leaked data set with user credentials and send a few mails with a nasty text through a hacked email server. If the blackmailer gets lucky, the bitcoin exchange rate even goes up again.

I am not quite sure but i guess the downside for the hacker also is, that he can not easily change the bitcoins to any real currency. Maybe it is easy, I am not so familiar with this shady businesses.

Comparison with the state of the art

I was curious about how other spammers perform and as a scrolled through my spam folder again, I have found another blackmail. That one had a similar text and also a bitcoin address. The only difference I noticed, was the missing leaked password. The bitcoin address had no transactions and was empty.

So my conclusion for this is, that the leaked password approach is way more efficient in terms of profit. However, to prove this hypothesis more evidence in this field of research is needed.

Skyline Frankfurt

Skyline Frankfurt am Main. Skyline Frankfurt am Main. Skyline Frankfurt am Main. Skyline Frankfurt am Main. Skyline Frankfurt am Main. Skyline Frankfurt am Main.

Tiny Core - a very small linux distribution for the Raspberry PI (piCore)

Recently, I searched for a very small linux distribution for my Raspberry PI Zero. I wanted to build a small camera project which demands a very fast boot process. I searched for that in the internet and then I came to Tiny Core, a linux distribution that promised everything I need for that. I tried it out and I was so surprised, that I wanted to write a small how-to here, that describes how easy it is to set up and get things running.

Smith Waterman Distance for feature extraction in NLP

I recently competed in a http://hackerrank.com competition. The task was to classify text with multi-labels. Therefore, I started with a basic bag of words approach, which performed quite good. After analyzing the data a bit, I realized that some keywords came up in slightly different representation - which for bag of words is a bit unfavorable. E.g. the keyword years of experience consist of 3 words which aren't handled with a bag of words approach because BOW don't know that these 3 words belong together. You can use ngrams to compensate that a bit, but my experience showed, that this fails most of the times. Also, this example can also appear without the word of or it can appear with other words in between. Often the words have small typos in them or other signes like - or 's, which would e.g. affect the matching of regular expressions.

OpenSCAD implementation of bezier curves of any degrees

Recently, I saw a Youtube video where someone implemented bezier curves for 3 and 4 degrees, and I thought it would be nice if there would be a version with any degrees. I didn’t find something like that, so I implemented it myself. First, you need a definition of a line (which is surprisingly not a standard datatype in OpenSCAD):

recent posts

2021-10-07 in maker space
3D printed drones
2019-03-10 in maker space
3D prints for a loving home
2019-02-27 in off topic
Determining the total revenue of a blackmailer: Bitcoin is offering new possiblities
2019-02-21 in photography
Skyline Frankfurt
2019-02-15 in maker space
Tiny Core - a very small linux distribution for the Raspberry PI (piCore)

about me

just me

I am a PhD-candidate from Bielefeld, Germany. My research topics are machine learning and human-robot cooperation. More precisely I work on active learning and cooperative intelligence in a human-robot teaching setting. If you are interested in my research, you can check out my publications here.