Multiple OctoPrint Instances using systemd

This is a “work in progress”, which I have only tested for a few days. It workes fine, but there could be issues not yet found. This article is based on my other article about setting up OctoPrint on a regular (x86_64) computer system running Ubuntu (Server) Linux. Recently, I got a second 3D printer…

Pixhawk Clones – Selecting ArduPilot Copter Firmware

Backstory There are different (flight) controllers available that are named “Pixhawk”, but in this article, I want to concentrate on the mostly Chinese “clones”. Although “clone” is the wrong term here, since the whole Pixhawk platform is an open hardware project. So building and selling hardware of this design is perfectly legal (which doesn’t mean…

Simple MOSFET LED Switch for Pixhawk

The Pixhawk flight controller, using the ArduPilot Copter firmware, allows for switching one or more AUX pins as GPIO pins from low to high (or vice versa) using the provided “Relay” function. Unfortunately the STM32 MCU of the Pixhawk uses a 3.3 V logic voltage on the white/yellow signal wire, which means that most regular…

Building wooden cases for the Ruideng DPS power supplies.

The “DPS” series of power supplies from the Chinese manufacturer Ruideng is popular among hobbyists. It allows to set voltage and current, but still needs a source power supply – so basically it’s a DC buck converter. It also doesn’t come with a case. I built three cases, using some scraps of plywood. Two cases…

Calculate LED current limiting resistor

To power an LED, the current that flows through it needs to be limited. For simple LEDs like the ones for signalling purposes, the cheapest and easiest way is to use a resistor in series with the LED, to limit the current. The question that normally remains is: Which value should the resistor have?

Fan-controller for the APS 3005D bench power supply

Like for the Lavolta power supply, I wanted to build a simple fan-controller circuit. Actually, I built this one first, and unlike the other one, which used the ATtiny85, I decided to build this one with a ATtiny13a. Because of this, the library for the DS18b20 digital sensor was too big to fit into the…

Fan-controller for the Lavolta BPS305 bench power supply

The Lavolta BPS305 is a cheap bench power supply of Chinese origin. The device comes with a 24 V DC fan, but without any means to control it in any way. The fan will just run the whole time, which is pretty annoying. Because of that, I decided very build a fan-controller using a microcontroller…

Wooden Raspberry Pi case

A few years ago, I decided to build a case for the Raspberry Pi out of oak wood. Since I wanted to power the Pi from a 12 V source, I included a switch mode voltage regulator. Here are some pictures of the project. 🙂

Self-signed SSL certificates

This article describes, how to use OpenSSL to create a self-signed certificate authority and sign certificates with it.

avr-gcc/avr-libc Tutorial

avr-libc is the standard library for AVR micro-controllers. It already contains many functions and header files that are optimised for the target platform.