Low-cost and precise rotary encoder with magnetic spheres

You know what they say that constraints drive creativity, I think this post is just another little example of that.

Usually I do not put time constraints to my hobby projects, but I make sure to have some other kind of constraints, like keeping the cost low and trying to reuse stuff that I already have.

In this case I needed a way to measure the angle and speed of a rotating object for some of my projects, and I wanted a rotary encoder that was inexpensive, but precise enough to work at very low speeds.


Little hacks for a GoPro Hero 3 White

Someone came to me with a broken GoPro Hero 3 White which wasn't turning on anymore, asking if there was a cheap way to fix it.

After tearing it down, a quick inspection revealed that the two flat-flex cables (the Shutter button one and the Power/Mode+LCD one) were both damaged, so neither the buttons or the LCD were working.

However, making contacts on the PCB traces of the Power button resulted in some reaction from the camera, so I knew there was still a chance.


Launching the Windows Recovery Environment

A friend of mine had a problem with his Windows 10 installation: the system booted but it was unresponsive, so it was not possible to enter the Windows Recovery Environment from Windows.


Experimenting with Gtk+ theme variants: Adwaita red

Most Gtk+ themes offer a “light” and a “dark” variant, however I found out that these names are just conventional: a Gtk+ theme can define variants with arbitrary names, so maybe this can be used for some fun stuff.


Remove images from PDF files

Some times ago I ran into some Service Manuals with unusual background images:


SaveMySugar: exchange messages using only phone rings

From “The Lord of the Phone-Rings”, about SaveMySugar:

One RING after them all, one RING to end them,
One RING to get the... messages, and from Morse code decode 'em.


Teclast X98 Air 3G: unbricking a Bay Trail tablet

While I was trying to boot a vanilla linux kernel on the Teclast X98 Air 3G I messed up a bit with the UEFI firmware settings: the battery was not recognized anymore, the tablet was rebooting right after showing the UEFI firmware boot screen, and USB-host was not working either; so no keyboard for accessing the firmware menu to restore the default settings, and no ADB for running flashrom or the Intel FPT to reflash the firmware with.

Teclast X98 Air 3G, internals
Teclast X98 Air 3G, mainboard
ISP with a logic level converter, top
ISP with a logic level converter, angle


Teclast X98 Air 3G: cheap Intel Bay Trail tablet, getting acquainted

I got a Teclast X98 Air 3G tablet from Aliexpress, it costed 168 € ( with free shipping) and has a high-definition screen and it's an Intel Bay Trail device; so Android, x86 architecture, 2GiB of RAM and 32 GiB of storage on EMMC.

boot logo 1
boot logo 2
Attached files: 


JMP-rope, the hardware

The hardware of the first JMP-rope prototype is very simple:

JMP-rope internals overview
JMP-rope handle detail
JMP-rope LED strip tied to the rope
JMP-rope programming socket
JMP-rope lit up