Switched mode DC-DC converter basics
40 mins
A short summary of the basic principles behind switched mode DC-DC converters (buck, boost, buck-boost, etc.), maximum power point tracking and impedance matching as well as a short recapitulation of the charging and discharging of reactive elements such as inductors and capacitors.
A simple digitally controlled small current source
11 mins
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
Simple 230V monitoring using PC817 opto coupler
3 mins
A really simple circuit to monitor the presence of a 230V AC line using an PC817 opto coupler and a 5V or 3.3V microcontroller
Simple DHCP failover with ISC-DHCP
6 mins
Mini summary on how to configure DHCP failover or load balancing when using ISC-DHCP for legacy IP networks. This is not a full explanation of all details, just a quick sample on how to get up failover in a few minutes.
How to use fetchmail to collect mail from different mail servers
7 mins
This blog post tackles a common challenge in email service administration where users set up mail forwarding without implementing Sender Rewriting Scheme (SRS), which leads to problems with email authentication methods like DKIM and SPF. The suggested workaround is to reverse the forwarding process by configuring the receiving mail server to periodically fetch mail from external accounts using the `fetchmail` tool, which requires only the target server to be configured. Detailed steps explain how to configure `fetchmail` alongside a local MTA like Postfix to pull emails while bypassing SPF and DKIM checks for localhost deliveries. The author shares his personal experience using this setup during a mail service migration, emphasizing the advantages of the method while also discussing the security consideration that `fetchmail` needs access to plaintext credentials. The post includes comprehensive steps for installing and configuring `fetchmail` on a FreeBSD system, and configuring Postfix to ensure proper mail delivery without authentication checks for fetched mail.
Measuring the speed of light at Wiener Forschungsfest 2022
14 mins
This article allows you to discover how we (a group from TU Vienna and University of Vienna) brought the fascinating world of physics to life at the Wiener Forschungsfest 2022! Using a visible range laser, a bicycle wheel, and modern photodiodes, we demonstrated how to measure the speed of light in an interactive and engaging setup designed mainly for children. This hands-on experiment highlighted the incredible speed of light while also conveying the fact that light is fast but not infinitly fast and allowed visitors to influence the accuracy of the measurement themselves. This article provides a short summary about the historical context, experimental setup, and the exciting outcomes of this educational outreach project.
OpAmp based voltage controllable current source
7 mins
A simple temperature drift compensated voltage controlled current source up to 8A (10A peak) and 30V rail to rail based on OPA549 or other power operational amplifiers
Discrimination of coherent and incoherent cathodoluminescence using temporal photon correlations
1 min
Published in Ultramicroscopy: We present a method to separate coherent and incoherent contributions of cathodoluminescence (CL) by using a time-resolved coincidence detection scheme. For a proof-of-concept experiment, we generate CL by irradiating an optical multimode fiber with relativistic electrons in a transmission electron microscope. A temporal analysis of the CL reveals a large peak in coincidence counts for small time delays, also known as photon bunching. Additional measurements allow us to attribute the bunching peak to the temporal correlations of coherent CL (Cherenkov radiation) created by individual electrons. Thereby, we show that coincidence measurements can be employed to discriminate coherent from incoherent CL and to quantify their contribution to the detected CL signal. This method provides additional information for the correct interpretation of CL, which is essential for material characterization. Furthermore, it might facilitate the study of coherent electron-matter interaction.
SSH command execution and SFTP file transfer using paramiko in Python
6 mins
Recipes to execute remote commands and transfer files using the native Python SSHv2 implementation of paramiko
The ID3 algorithm
87 mins
A short summary on the inner workings of the Iterative Dichotomiser 3 (ID3) decision tree algorithm, a small Python playground implementation and application to one toy and two real world datasets out of the world of biology and medicine
