Recovering 18650 Lithium Cells from Damaged Battery Packs
Salvaging lithium-ion cells from old battery packs can be a practical way to repurpose valuable components for hobby electronics, robotics, or backup power projects. This article walks through the careful and methodical process of identifying, testing, and recovering 18650 cells from discarded equipment like laptops and garden tools—highlighting key voltage thresholds, safety procedures, and the tools required to do so responsibly. But make no mistake—working with lithium cells is not without serious risks. Improper handling can lead to fires, explosions, and long-term instability. This project log focuses on safety-first recovery strategies, how to spot dangerous cells, and when to dispose rather than reuse. If you're an experienced DIYer with the right equipment and an eye for caution, this deep dive into battery salvage may be just what you're looking for.
GPU size estimation for LLMs
Ever wondered how much VRAM you actually need to run a 13B, 65B, or even 500B language model? This compact, no-fluff guide - mostly a personal reference - breaks down GPU memory needs by model size, quantization, and task complexity. Includes real-world GPU examples with affiliate links for anyone thinking of building or upgrading their own AI rig. Great for hobbyists, tinkerers, and anyone asking, 'Can I run that locally?'
Simple laser cutting and engraving capabilities for a 3D printer with a 450nm diode laser
This article summarizes some experiments using a simple 450nm laser diode on a 3D printer for some basic laser cutting and engraving in paper, plywood and other simple to cut materials.
A simple digitally controlled small current source
Simple project that provides a digitally controllable linear current source up to 500 mA powered from a rectified 230V to 12V transformer. The whole current source is bias-able to high voltage (-2 kV in this case) by opto isolating it's serial communication path
Controlling the Korad KA3005P using Python
A short summary on how to control the Korad KA3005P power supply using Python as well as some simple samples on how to use my own control library
Logarithm and exponential function with OpAmps
A summary how to implement the logarithmic and exponential function using operational amplifiers - and how to use this to build simple mixers when combining with a simple summation amplifier
Gold plating on copper surfaces
A summary on a procedure on how to use a galvanic process to plate copper (and other metallic surfaces) with gold using a galvanic bath
A short story of the migration process for The-Things-Network v2 to v3
This article is a mini summary of the steps that have been required to migrate from the v2 to the v3 stack of the things network, a community driven LoRA-WAN backend solution.
Building a simple 6 kV DC power supply
Short summary on how to build a small 6 kV power supply using an 2.1 kV microwave oven transformer, two of the accompanying capacitors and a bunch of diodes that is capable of delivering a little bit more than half a kilowatt of power
A simple OpAmp photodiode readout circuit
A short summary on the workings of photodiodes, how one can interface them to simple electronics and a simple amplifier circuit
The AD7705 dual channel analog digital converter with AVRs
Mini summary on how to use the AD7705 with Atmel AVRs
Adding Grafana annotations using HTTP API
Sometimes it's convenient to add annotations to Grafana dashboards and panels using Grafanas flexible HTTP API instead of writing them into a database and fetching them from there using Annotation queries. Since I lacked a complete example and it took me some minutes to find out how this works this blog post summarizes the process.
Electroplating / Galvanic deposition of copper on 3D printed PLA objects
A summary on a procedure on how to use a galvanic process to plate 3D printed objects made out of PLA or PET-G with copper and possibly also other metals
Mini note on robust serial communication with microcontrollers (basically: use checksums and synchronization patterns)
Some notes on robust serial communication
Matching impedance using NanoVNA v2, NanoVNASaver and SimSmith
A mini summary on how to perform impedance matching for antennas or other devices using the NanoVNA v2 together with the NanoVNASaver and SimSmith applications based on the impedance matching of an electron deflection system
Building a simple improvised electron gun from common of the shelf components
Mini blog article that summarizes the build of a simple 2 mA beam current electron gun from common of the shelf components gathered from the hardware store as well as some 3D printed components.
Cutting glass vacuum tubes using hot wire
Something easy and simple. How to cut glass tubes and other glass parts using electrically heated hot wire.
How to extrude polygons in OpenJSCAD
Since I always have to lookup how this works in some examples or hidden deep in the manual I decided to write a short summary about linear extrude, rectangular extrude and rotate extrude
3D printed parts using PLA and standard FDM process in vacuum?
Just a short description of what I've tried (and didn't expect to work) about the usage of 3D printed parts made out of PLA in the typical desktop FDM 3D printing process, i.e. a method to build really low cost parts at home.
A simple colinear coaxial 1090 MHz antenna for ADS-B
A really simple colinear coaxial 1090 MHz antenna for ADS-B, one of the most simple antenna constructions that can be used to receive automatic dependent surveillance squitters using low cost software defined receivers such as DVB-T sticks.
Basic operational amplifier (OpAmp) circuits
Summary of the most basic OpAmp circuits that are usually built as well as their basic properties
A simple home-built epoxy counter-top
Short blog post about the casting of a simple epoxy countertop with embedded sink.
How stuff works - Line power distribution and protective measures in Europe (consumer side)
Since it seems to be a huge mystery to many people this blog post tries to summarize some of the parts relevant to the consumer side of power grid systems.
Automatic plant watering and illumination (smallest version)
In this blog article I'm describing a small automated plant watering solution that's used indoor to grow basil, capsicum and chili pepper indoor.
Capacitance measurement with AVR (simple, fast)
Mini article about the measurement of capacitance with AVRs with a minimum of external components (in it's most extreme form none external components exploiting the gate capacitance of the micro-controllers input)
3D printing NACA airfoil profiles
Mini Blog-Post that describes modelling 4 digit NACA airfoil profiles in OpenJSCAD
Using Sonoff T4EU1C non-neutral switches with own firmware
A short review about the T4EU1C Sonoff Switch as well as an example how to flash Sonoff basic switches with custom firmware
Using piezo disks for automatic bed leveling on 3D printers
Description of an easy way of using piezo disks as touch sensors to perform bed leveling with 3D printers or other CNC machines. This blog entry describes the most basic possible way without much external circuits (only an ATtiny13A and two resistors are used)
Authenticating and signing using Austrias citizen card
A short summary on how to embed authentication and generally signing with the Austrian citizien card
Building an I2C controllable stepper driver board with DRV8825 breakout boards and ATMega328p
This is the description of a small carrier board for two DRV8825 breakout boards (or compatible) that are controlled by an AVR (ATMega328p) which runs a small (linear) motion processor that gets it's commands via I2C.
I2C communication between RaspberryPi and an AVR based I2C slave
This article explains how to use an AVR as I2C slave device (basically how to set registers for the TWI controller) and how to interface that to an RaspberryPi running FreeBSD
Building a simple 3D printer (and what turned out to be not so simple)
This article describes some of the ideas and thoughts during building my first FDM printer and which lessions have been learned from that project.
Linear stepper motor control - A summary
A short summary of the algorithms required for linear accelerated and decelerated stepper motor control on microcontrolers.
Getting started with STM32F401RE Nucleo starter board on FreeBSD
How to get started with the STM32F401RE nucelo development board on FreeBSD with gcc and openocd
Using Sonoff basic switches with own firmware
Example how to flash Sonoff basic switches with custom firmware (using cli tools or the Arduino IDE)
Building a LoRA WAN gateway (and supplying data for the things network)
The following article leads the reader through building an LoRA-WAN gateway from an iMST ic880a concentrator board and an RaspberryPi. Optionally is shows the reader how to add GPS, enable remote configuration via the tinc VPN daemon and via a TOR stealth hidden service.
Merchants and manufacturers
A (short) list of manufacturers and merchants for various stuff used for hobby projects that also ship to private individuals near Austria / in Europe.
Selected screw and nut dimensions
This page is a personal reference I put together to keep track of dimensions and specs for standard screws, nuts, and similar fasteners. I use it as a quick lookup during design work, prototyping, or when I'm in the workshop and just need the right numbers without digging through datasheets. It's not meant to be complete or official-just something that helps me stay organized. Keep in mind there might be occasional gaps or small mistakes.
Cable crosssections
Just a short summary of the most important data about cable cross sections and current carrying capabilities. Please note that this article is not a substitute of looking up in your local regulations - I just keep these values here to have a quick guess at hand when thinking about such stuff.
