About screws and screwheads

I just found this interesting posting about different types of screw-head and -drivers in Google+.
"When a Phillips is not a Phillips!"



After doing some initial ECG experiments with a simple Arduino shield,
I got my OpenBCI from Kickstarter just in time for 31C3.
For the time being, I'll use this blog posting to collect some links and notes until I get things sorted out.
Much of the OpenBCI documentation on the official site and source code repository is still unwritten,
so I need to do a lot of hunting, gathering, guessing and experimenting.

Results so far:
  • I see clear signals with lots of SNR for muscle movements and eye movement
  • The OpenBCI_GUI app has way too little in the ways of signal analysis.
  • I'm having trouble using my Olimex EEG designs in BrainBay with the OpenBCI

Getting started





ECG/EOG/EEG experiments

I'm a backer of OpenBCI  but they still haven't delivered.
(Other people have, 3 days ago)
So I just ordered myself a "Shield-EKG-EMG" from Watterott.

I managed to get my heatbeat.
(That's the easiest you can do.)
Next step shall be tests of Electro Oculography (electric eye tracking).

Just some notes for myself:


Signal is in the range of 1mV peak to peak .
Eye-blinking artifact is very strong.
50Hz line noise must be removed (of cause). (notch fiter)
low-frequency cutoff to 0.02 Hz
high-frequency cutoff 50Hz


Accuracy tesing 3D scanner

I want to know how well the Sense 3D scanner together with the Skanect software (since the Sense software only works on one computer per scanner and is pretty much crap without CUDA) captures mechanical dimensions.
Both in terms of absolute dimensions in millimeters (scaling of the entire part) and in terms of relative sizes of components to each other.

As a first test I scanned my camera. It's a small object and I had an error of about 10mm for a 130x70mm part in all 3 dimensions. Not very good.

Then I scanned my face.
Cleaned up that scan in Skanect, then NetFabb, then Meshlab (because the free NetFabb version doesn't allow you to fix some errors unless you buy the pro version).
Then imported that mesh into Geometric Design (my CAD program with 3D scanner and -printer integration).
Designed a mask with no allowance (not even under the nose or in the eyes).
Printed that mask on my Ultimaker II using default settings.
result?  It fits my face perfectly!

I'm currently waiting for a FabScan Cube to also scan small objects, where the Sense failes and am waiting for Skanect to support my higher resolution Kinect V2 for Windows. (I'll try the libfreenect2 software on MacOS/Linux next week.)


Im Labyrinth der Telekom

Ich habe einen Business-Tarif. 3 SIM-Karten, nutzt viele Daten (>2GB), nutze ausgiebig die Telekom-Hotspots in den DB Zügen/Bahnhöfen/Mc Donalds, LTE ist mir egal, iPhones auch, telephoniere kaum 5 Minuten im Monat und verschicke keine SMS.
So weit so einfach.
....bis man mal auf der Website von T-Mobile seinen Tarif vergleichen und ändern will.

Ok, ich kann nicht mehr.
nach Wochen kann ich in diesem verd****** Labyrinth von Website bei T-Mobile mich weder einfach mal als Kunde einloggen,
noch meinen Tarif ändern
noch die Hälfte der Tarife ohne "nur für Neukunden",
weder mit "Mit Surfstick", noch "Mit Tablet zum Basic-Tarif"  noch "Mit Tablet zum Premium-Tarif"
 überhaupt sehen.
Geschweige denn mal sinnvoll vergleichen.
Man wird mit seitenweisen PDF Formularen zum ausdrucken ,ausfüllen und per Brief schicken belästigt um sich im Business-Bereich einzuloggen obwohl man schon 3 Logins hat.
Ich will keinen Lieferstatus für ein verd***** iPhone, LTE interessiert mich nicht die Bohne,
es interessiert mich nicht was ihr für bunte Preise gewonnen haben wollt,
ich will nicht noch ein neues Handy,
ich will keine @t-mobile oder @t-online Addresse,
kein Adressbuch, kein Spotify und keinen Kalender!
Ich will einfach nur meinen Tarif für meine Nutzung mit den aktuellen Angeboten vergleichen und bequem ändern können, wenn mir das Vorteile bringt.
Und zwar ohne mich erst zu Arbeitszeiten in's Auto setzen zu müssen, zu irgend einem Laden zu fahren wo ich stundenlang warten muss und dann nur einzelne Details von Tarifen an den Kopf geworfen zu bekommen ohne übersichtlich die Kosten mit allen für mich nötigen Optionen gegenüberstellen zu können.
Das kann doch nicht so schwer sein das Kerngeschäft eines Mobilfunkanbieters zu betreiben.
Jeder schmierige Versicherungsvertreter kriegt das besser hin!


Micro Mesh Pad Holder

I'm using Micro Mesh mini sanding pads (regular and MX) extensively.
So I designed myself a pad-holder that would
  • keep them sorted
  • allow them to dry (wet sanding)
  • tell me the coarseness
  • have symbols to roughly compare the coarsness of regular and MX pads
  • interlock to extens this sorting system
  • add a module for bottles of Mr Surfacer while I'm at it anyway

I printed these on an Ultimaker II. Every module needs about 7 hours using the Cura medium quality default settings.


Adventures with a Sense 3D scanner

I have a problem.
I got a used 3D Systems "Sense" 3D scanner as an Amazon warehouse deal.
(Same manufacturer as my CAD Software, so they integrate perfectly.)

The package did not include the activation code.
Some former user has already activated the software, so I can't activate it.
Amazon has no information about the former owner, so they can't contact him/her.
3D Systems does not answer the phone on their German hotline.
So I just sent them an email about the issue....maybe they can reset it or give me an activation code.

Update: Wow! After 17 minutes I git an email with an activation code asking for my user-name, so it can be associated with my account. That's damn fast customer service!


  • I'm using 3D Systems Geomagic Design as my CAD software. Since they don't have a MacOS version, it runs in a VM with Windows XP.
  • The Sense software installs on XP but crashes on start. Only Windows 7, 8 and 8.1 are supported. :(
  • The Sense scanner registers with Windows as a Carmine Primesense and works with Skanect just like a Kinect but has MUCH BETTER RESULTS then an XBox 360 Kinect V1 sensor. (My Kinect V2 for Windows is not supported yet.) Also more ergonomic to handle.
  • The MacOS Sense software is not signed by a registred developer, so at first MacOS refuses to execute it unless you enter the system settings and add an exception for this program. 
  • On MacOS the Sense software FREEZES MY MACBOOK during entry of the activation code. No mouse or keyboard anymore. Not so on my desktop iMac.
  • The Sense software looses track every 2 seconds where Skanect works just fine, display a white page instead of the scan result and offers only ".ply" as an output format, no STL.
  • Displays a static image on the iMac. The movement commands for touchpad and 3-button wheel-mouse don't work (with a 1-button mouse).