Dienstag, 11. November 2014

Electric longboard

A large RC car brushless motor + huge Lipo batteries + a rather smooth to ride longboard = a lot of fun :)

Pictures and comments of the construction progress here:

The whole design is based on the experience from the endless-spheres forum:

Dienstag, 29. Juli 2014

Fireflys in a jar

New! Webinterface

A toy webinterface for a similar jar can be found here:
Note that it is the real deal and the jar, standing next to my window, will actually start flashing if you click any of the buttons


  • A large jam jar (Ikea)
  • Mini USB Nano V3.0 ATmega328 5V Microcontroller Board (eBay)
  • FTDI serial cable for flashing (eBay)
  • Solar cell, 5.5 V, 50 mA or larger (eBay)
  • Lipo - battery cell, 100 mAh - 600 mAh (eBay / old laptop / old cellphone, etc.)
  • 12 x tiny LEDs, different colors, the smaller the better, with ~80 - 200 Ohm series resistors, depending on how bright you want it (kit from eBay)
  • Very thin magnet wire from the coil of a miniature relais
  • SMD resistors with 1 % tolerance: 2 x 560 kOhm,  2 x 160 kOhm. For two voltage dividers to sample the solar cell and battery voltage
  • SMD ceramic capacitors, 2 x 100 nF, to stabilize the analog inputs of the AVR
  • Some circuit board, glue, prototyping wires, sticky tape 
The making-of after the click ...

Montag, 17. März 2014

The "Foculus Rift" part 3: Spoofing the EDID

The libOVR SDK recognizes if an Oculus Rift is attached to the PC by checking two particular things:
  1. The USB tracker with the right VendorID, ProductID must be present (this has been solved in Part 2)
  2. The Head Mounted Display (HMD) must be attached, which is nothing more than an ordinary monitor connected over HDMI. The HMD is identified by its so called Extended display identification data (EDID).

Dienstag, 4. März 2014

The "Foculus Rift" part 2: Reverse engineering the motion tracker

The function of the motion tracker is to estimate the current roll, pitch and yaw angles of the head mounted display (HMD), which allows the 3D game to know what you are looking at and render the scene accordingly.

The original Rift uses the following configuration (as nicely shown by ifixIt):
  • Invensense MPU-6000, gyroscope and accelerometer sensor
  • Honeywell HMC5983, magnetic field sensor / compass
  • ST  32F103C8, ARM 32 bit microcontroller (with USB connection)

Montag, 3. März 2014

The "Foculus Rift" part 1: Building a Head Mounted Display

Some time ago I read BitCortex's manual on building a homemade "head mounted display" (HMD), just like the Oculus Rift:

The concept is surprisingly simple and low tech. A LCD panel presents seperate pictures to the left and right eye, lenses are used to place the panel close to the eyes and hence produce a wide field of view (FOV). What I read about these very simple homemade glasses made me curios. The people on the mtbs3d forums (the birth-place of the rift) claimed that the 3D effect is fantastic and the head tracker allows the games to become extremely immersive.

It was clear, I had to try to build some of these fancy 3D goggles.
These posts will document the progress I have made, the problem I encountered and the improvements I came up with along the way.

Samstag, 13. April 2013

Microwave filters for dummies

For a recent project I needed a bandpass filter in the microwave range, made from non-magnetic materials. Remembering this very nice article from Paul Wade, I decided to give it a shot and roll my own. As the results turned out to be spectacular, I had to share this experience.