Hacker Public Radio

Episódios

• 
  HPR4708: Programmable Logic Controls - Episode 1 19.08.2026

  Introduction 01 This is the first episode in an 8 part series. 02 This series is on programmable logic controllers, or PLCs as they are commonly known. What is a PLC you ask? In short, it is a general purpose programmable industrial control device. They are used all through industry in factories, utilities, and anywhere industrial machines need to be controlled. 03 They are a fully integrated system of hardware, software, and development environment tailored specifically for automatic industrial equipment. It is probably easiest to describe them by first giving a bit of historical background as to what preceded them. 04 The Early Days of Automation You have probably heard of the Jacquard loom of the early 19th century and its use of punch cards with respect to it being one of the technologies which eventually lead to computing. However, for our purposes here, its significance is that it was an early form of industrial automation control system, since it was after all controlling a machine in a factory. 05 For other types of machines, a common purely mechanical means of having the various parts of a complex machine move in a coordinated manner was through the use of shafts and cams. A series of cams located on a shaft or set of shafts connected by gears, could move parts of a machine, turn valves on or off, and generally coordinate the parts of a machine. With the spread of the use of electricity in factories in the early 20th century, it was now possible to use the new electrical technology to perform control and automation functions. 06 The Background of Relay Logic I will need to explain some electromechanical terminology here as it is necessary to understand these terms and the concepts behind them in order to understand PLCs, as the latter is an evolution of its predecessors and uses the same terms. What preceded PLCs was what was commonly known as "relay logic". 07 What is a Relay A relay is an electromechanical device that responds to and controls the flow of electric current. A relay has a "coil" which as the name implies is a coil of conductive wire. When you energize the coil, that is you apply electric current to it, it forms an electromagnet. 08 This electromagnet draws in an armature. The armature is a moving piece of metal which is attracted to the coil when the latter is energized. The relay being activated is referred to as closing. Deactivating is referred to as opening. Alternative names for these states are "pulls in" and "drops out" respectively. 09 The armature in turn is attached to one or more contacts. You can think of a contact as being like a switch. When the switch is turned one way, the electrical path is closed and current can flow. When it is turned the other way, the electrical path is broken and current flow is interrupted. 10 Contacts can be normally open, in which case the path is closed and current can flow when the relay turns on. Alternatively, they can be normally closed, in which case the path is closed and current can flow when the relay turns off. A relay can, and typically does, have multiple contacts, including both normally open and normally closed. Remember these terms, coil, contact, normally open, and normally closed. 11 What is a Latching Relay There is a special type of relay known as a
• 
  HPR4707: UNIX Curio #12 - expr 18.08.2026

  This series is dedicated to exploring little-known—and occasionally useful—trinkets lurking in the dusty corners of UNIX-like operating systems. Arithmetic is something that one would normally expect computers to be able to do. With UNIX, one could of course always write a program to perform a calculation, but for people like me who are bad at programming, it would be nice to have a tool that makes things a bit easier. First Edition UNIX in 1971 included such a tool, called dc , which stands for "desk calculator" 1 . This utility performed integer arithmetic (though later versions can handle real numbers) using reverse Polish notation. To divide 11 by 4 with this method, instead of entering "11 ÷ 4 =", you would key in "11 ENTER 4 ENTER ÷". The very first calculator I ever used, one made by Hewlett-Packard that my father brought home from work a few times, employed reverse Polish notation but I have never gotten used to it. All the calculators I have made significant use of and bought for myself used the more common infix notation "11 ÷ 4"—I also prefer computer utilities following that pattern, so I almost never use dc . For reasons explained in the rationale for the bc utility 2 , dc has not been standardized in POSIX despite its long tenure. However, while it doesn't seem to get a lot of attention, I still would not consider dc to be a UNIX Curio. Today, it is possible to do integer arithmetic in a standard POSIX shell without any outside utilities. This is called "arithmetic expansion" and is described in references or manual pages for many shells. It wasn't always this way, however. Before a shell was available that supported arithmetic expansion, you needed to call another utility for your calculations, and expr was one of those 3 . That program is the UNIX Curio for this episode. Some people might pronounce this name, but I find it awkward to say, so I just spell out expr the same as I would do with dc . Its name is an abbreviation of "expression", and it takes arguments representing an expression. An expression is formed by combining integers or strings with zero or more operator symbols. There is quite a variety of operators—some are mathematical, some perform comparisons, one matches a regular expression, and others are used for grouping or logical tests. Since we started this episode talking about arithmetic, let's tackle those first. The "+", "-", "*", and "/" symbols are for performing addition, subtraction, multiplication, and division respectively, as is common in many programming and scripting languages. The "%" produces the remainder of integer division. So, expr 11 / 4 would output 2 ; it only does integer calculations. The command expr 11 % 4 would output 3 —in this case, the remainder left after "4" is removed from "11" twice. Take note that
• 
  HPR4706: Quirks and Customisations 17.08.2026

  System Quirks & Tweaks System Info:- CPU: 16-core AMD Ryzen 9 3950X (-MT MCP-) speed/min/max: 2433/2200/4761 MHz Kernel: 6.8.0-134-generic x86_64 Up: 18h 28m Mem: 17.58/62.73 GiB (28.0%) Storage: 3.64 TiB (81.9% used) Procs: 616 Shell: Bash inxi: 3.3.34 Some of the hacks:- Shell & Terminal Setup Visual Host Identifiers: I use custom terminal prompt colors and styles on different boxes so I can immediately see which machine I am logged into. Command Line Overrides: Standard tools are aliased to modern alternatives ( cat to batcat , df to duf , du to dust , ls to eza ). Word-Break Tweak: My shell config strips - and . from word-break rules so tab-completion handles hyphenated or dotted filenames as single words. History Search: I mapped Ctrl+F (instead of Ctrl+R ) to run a custom, colorized, interactive fuzzy history search using fzf . Local AI Tooling: I use AI coding interfaces, with ollama aliased to run Qwen Coder by default. Complex Toolchains: My system runs multiple co-existing environments, including conflicting Java runtimes (8 and 17), Android SDK, Rust, Go, and local Perl/Python libraries. Autostart & Background Services Audio & RGB Tweaks: Custom services handle Bluetooth switching for my Bose QC35 headphones, and cycled my keyboard lighting profiles based on the time of day. Passive Time Tracker: A custom background system tracks files via inotifywait and polls network connections to log my work hours into a 15-minute rounded log file. Typo Alert Keylogger: A root-owned background script buffered my keystrokes globally to run a spellcheck, firing a desktop alert when I made a typo. Work/Life Balance: Discord is configured to launch only on weekends or after 17:30 on weekdays. Custom Applications & Launchers Local LLM Voice Assistant: A desktop launcher opened "Marvin," a private local voice-chat assistant. Custom Remote Control: A custom script used ADB and Monkeyrunner to mirror and control an Android tablet screen in a local window. KWin Layout Fixes: Joplin
• 
  HPR4705: Free Software Is Wasted On You Teens 14.08.2026

  Freedom 0–3 (verbatim reference) The four freedoms, GNU/FSF: https://www.gnu.org/philosophy/free-sw.html Richard Stallman: https://www.stallman.org/ Named FOSS figures (freedom 3 list) Linus Torvalds (Linux): https://en.wikipedia.org/wiki/Linus_Torvalds Dries Buytaert (Drupal): https://dri.es Guido van Rossum (Python): https://gvanrossum.github.io Ian Murdock (Debian): https://en.wikipedia.org/wiki/Ian_Murdock Brian Behlendorf (Apache): https://en.wikipedia.org/wiki/Brian_Behlendorf Miguel de Icaza (GNOME/Mono): https://en.wikipedia.org/wiki/Miguel_de_Icaza Infrastructure block (post beer 1) curl / Daniel Stenberg: https://curl.se and https://daniel.haxx.se xkcd 2347 (dependency comic): https://xkcd.com/2347/ xz backdoor, CVE-2024-3094: https://en.wikipedia.org/wiki/XZ_Utils_backdoor Andres Freund's original disclosure: https://www.openwall.com/lists/oss-security/2024/03/29/4 Licensing block (beer 2–3) GPL: https://www.gnu.org/licenses/gpl-3.0.html MIT License: https://opensource.org/license/mit FreeBSD: https://www.freebsd.org macOS/Darwin BSD lineage: https://en.wikipedia.org/wiki/Darwin_(operating_system) PlayStation using FreeBSD (Orbis OS): https://en.wikipedia.org/wiki/Orbis_OS Industry acquisitions (beer 4) Microsoft acquires GitHub, 2018, $7.5B: https://news.microsoft.com/2018/06/04/microsoft-to-acquire-github-for-7-5-billion/ FOSDEM field report (beer 4–5) FOSDEM: https://fosdem.org Ladybird browser / Andreas Kling:
• 
  HPR4704: HPR Beer Garden 17 - Double DDH IPAs 13.08.2026

  In the seventeenth episode of the HPR Beer Garden, the guys look at a beer style (or label) that has recently appeared from across the pond: DDH IPA. Kevie tries out Smug DDH IPA by Northern Monk , Paul samples Hazy Jaipur by the Thornbrige Brewery and Dave enjoys Pinball by Brewdog . Connect with the guys on Untappd : Dave Paul Kevie The intro sounds for the show are used from: https://freesound.org/people/mixtus/sounds/329806/ https://freesound.org/people/j1987/sounds/123003/ https://freesound.org/people/greatsoundstube/sounds/628437/ The next 3 beer styles to be reviewed: Amber Ale Lager Mild
• 
  HPR4703: Ebooks and Audiobooks 12.08.2026

  I tend to prefer Ebook and Audiobooks to physical books, and these are some of the apps I use, and some of the sources I go to to find Ebooks or Audiobooks. These can be inexpensive, or in the case of Public Domain, free. Ebooks and Audiobooks I no longer wish to devote space to accumulating and storing physical books. As a former college professor I had more of them than most people, and tended to fill the house with bookcases and shelves. That made a certain sense in the pre-Internet years since I would often want to go back to them to look up things. But now I have more information at my fingertips than I ever had in those days, and I find it more convenient to just look up anything I need to know. And with Ebooks I can take my library with me anywhere I go. This means if I am sitting in a waiting room for a Doctor’s appointment (and at my age that happens often enough) I can just pull out my phone and open up a book. I always have at least one. Right now on my phone I have apps for Kindle , Google Play , Barnes & Noble Nook , Kobo Cantook (successor to Aldiko), Bookshop.org , and Calibre . As for devices other than my phone, I own a kindle, I once owned a Nook, and I will buy a Kobo reader when Trump is gone. Kobo is Canadian, and last time I looked Trump had put on a tariff that was twice what the device costs. And finally I have the Bookshop.org app and Calibre. I started collecting Ebooks some years back, and at first the only option seemed to be buying them from large corporations. That has changed now, but I still have collections On Kindle, Google Play, Nook, and Kobo. I have all four because it seemed prudent to not put all my eggs in one basket. But now there are other options. One I like to use when possible is Bookshop.org. It is group of independent bookstores and I would rather support them than some giant corporation. And they seem to have all of the popular titles. Another similar site is Books-a-Million , which lets you order online and pick up at a local store if you need a physical book. Cantook and Calibre are both good for holding any miscellaneous Ebooks you have, and you can give them your Ebooks from the other sellers, though I have found that the native apps tend to work better. These days I rarely purchase books on Kindle, etc. But sometimes they have a special deals. If you want to build your library, there are some good places to try. One is BookBub which will send you emails with deals on books. On any one e-mail you may not see anything you want, but I found that once or twice a month I did see books I wanted and at good prices. And Books-a-Million has 99 cent deals to check out. But if you want to get free books, you have several options. If you want a chance to read a popular Ebook but don’t need to own it, see what your local Library offers. Mine offers Hoopla which is good for Ebooks, Audiobooks, and streaming music. What you can find depends on what your library has in its collect
• 
  HPR4702: MakeACopy is an open-source document scanner app for Android 11.08.2026

  MakeACopy MakeACopy is an open-source document scanner app for Android that allows you to digitize paper documents with OCR functionality. The app is designed to be privacy-friendly, working completely offline without any cloud connection or tracking. Features Camera Scanning : Capture documents using the device camera Edge Detection : Automatic document edge detection using OpenCV, enhanced with an ONNX model (DocAligner) Perspective Correction : Adjust and crop documents with manual or automatic perspective correction Image Enhancement : Apply filters (grayscale, contrast, sharpening) OCR : Offline text recognition with Tesseract OCR Review : Interactive review and correction of OCR results with word-level editing, dictionary-based suggestions, confidence highlighting, and re-OCR for individual words PDF Export : Save as searchable PDF with recognized text JPEG Export : Export scans as high-quality JPEG images (configurable quality, color/BW) Multi-page Scanning : Combine multiple pages into one document; reorder and manage pages before export Last Scans : Quickly access and reuse your most recent scans Share & Save : Export locally or share with other apps Dark Mode : Material 3 theme with day/night support Privacy-Focused : 100% offline functionality, no internet connection required
• 
  HPR4701: Elsbeth muses with Lee on her experiences and opinions on AI 10.08.2026

  Overview: Elroy sits down with Elsbeth to unpack her perspective on AI ethics — where the technology helps, where it risks harm, and what responsible use actually looks like in practice. Topics covered (In no particular order, as the rabid squirrels of Elsbeth's AuDHD brain don't do "order"): Elsbeth's path into AI evaluation and content moderation, and how that shaped her thinking on ethics in practice What "ethical use" of AI means day-to-day, not just in the abstract Respecting intellectual property — the case for protecting artists and creators as AI tools become more capable and widespread Finding the balance: supporting AI's genuine benefits without letting them come at creators' expense AI as an accessibility tool — its particular promise for neurodivergent people, and where it can lower barriers others don't face Where the conversation is heading next, and what listeners should watch for Closing thoughts: Elsbeth's take is one of cautious optimism — a call to hold both truths at once: AI can do real good, and that good has to be built on respect for the people whose work made it possible. Further Reading & Resources On AI, Ethics, and Intellectual Property AI and Intellectual Property in 2026: why transparency and court rulings will define the next phase of governance — The AI Journal https://aijourn.com/ai-and-intellectual-property-in-2026-why-transparency-and-court-rulings-will-define-the-next-phase-of-governance/ Global laws governing intellectual property rights for AI-generated works — Discover Artificial Intelligence, Springer Nature Link https://link.springer.com/article/10.1007/s44163-026-01165-8 AI and IP laws 2026: Understanding Authorship and Ownership legalities — AnalystIP https://analystip.com/ai-and-ip-laws-2026-authorship-ownership-explained/ AI Art in 2026: The Ethics, Law, and What Artists Should Know — UrduPure https://www.urdupure.com/blog/ai-art-in-2026-the-ethics-law-and-what-artists-should-know On AI and Neurodivergent Accessibility Navigating Neurodivergence with AI Chatbots: Benefits, Tensions, and Implications for HCI — CHI 2026 Conference Proceedings https://dl.acm.org/doi/10.1145/3772318.3791334 Is AI making work more accessible for neurodiverse people? — Everway https://www.everway.com/en-gb/blog/is-ai-making-work-more-accessible-for-neurodiverse-people/ Autoethnographic Insights from Neurodivergent GAI "Power Users" — NCBI/PMC https://www.ncbi.nlm.nih.gov/pmc/articles/PMC
• 
  HPR4700: Robert A. Heinlein: The Juveniles 07.08.2026

  Heinlein wrote a series of books under contract to Scribners that were aumed at younger readers, pre-teen and teen. Today we would call them Young Adult, but back then they were called Juveniles. But even an adult reader can enjoy many of these books. Because they were aimed at younger readers, he could not always be as explicit as he might have liked, but if you pay attention you just might noticed he slipped in something subversive. Heinlein: The Juveniles As a boy I read voraciously. I remember my mother organizing weekly trips to the town library, where I would load up on books, and I quickly became focused on Science Fiction, along with the usual stuff kids read, like the Hardy Boys, Tom Swift, and the Walter Farley horse books. But the idea of going into space grabbed me very early. And one of the first authors I read was Heinlein. He had taken a leave from publishing during World War II, when he was doing research at the Philadelphia Navy Yard. But when the war was over, he set out to move beyond the “pulps” and expand the market for his stories. And one big market for him was what were called “juveniles” at the time, and would today be called “Young Adult”. I was reading adult fiction by the time I was 11 or 12, but before that (and even after that, in fact) I read these Heinlein novels with great relish. Heinlein’s target audience for these novels was teenage boys. He did a few stories aimed at girls, but mostly he wrote for boys. And these were mostly “coming of age” stories where the teenage protagonist has adventures, and as a result grows and develops. They are very loosely related via some internal references, but should really be thought of as stand-alone stories. They also in some cases have references to his other stories, including the Future history stories. He wrote 13 of these novels, one per year, from 1947 to 1959. The series was published by Scribners until the last one was rejected by them. Heinlein then published it with a different publisher, and stopped writing these novels altogether in favor of more adult fiction. The novels roughly form a progression telling the story of space exploration. It starts with a trip to the Moon, then Venus, Mars, Jupiter’s moon, and so on until we reach the Lesser Magellanic Cloud. Rocket Ship Galileo (1947) – While readable, this initial effort was not up to Heinlein’s later standards. The plot concerns three teenagers who assist an uncle to build a rocket ship and go to the Moon. When they get there they discover Nazis have already arrived. The Nazis try to kill the group, but they succeed in turning the tables, stealing the Nazi ship, and returning to Earth as heroes. This novel became the basis (loosely) for the movie Destination Moon (1950), and I personally would consider the movie to be superior to the novel. It is also worth noting that the theory brought up in Blowups Happen reappears in this novel. They find evidence of an ancient Lunar civilization that was destroyed, and theorize that the craters on the moon were caused by the explosion of nuclear reactors that caused the extinction of the civilization. Space Cadet (1948) – This was in part the inspiration for the
• 
  HPR4699: Sunshine, Moonlight, Playnite !? 06.08.2026

  sunshine / xbox contlers / plex / steam / UWPHook / Bluetoothctl restart / HDMI dongle https://www.youtube.com/watch?v=FM4FbA4-W_c UGREEN USB C Hub 5 in 1 Multiport Adapter Revodok 105 4K HDMI, 100W Power Delivery, 3 USB-A Data Ports, USB C Dongle for MacBook Pro/Air, iPad Pro, iMac, iPhone 16 Pro/Pro Max, XPS, Thinkpad https://www.amazon.com/dp/B0BR3M8XHK Detached Command: @ECHO OFF cd "C:backupgamestream_launchpad" c:windowsSystem32HdrSwitcher.exe disable start /MIN gamestream_launchpad.exe 1920 1080 gamestream_playnite.ini .bindkeys rc cat .xbindkeysrc /bin/bash /home/plex/.local/bin/Plex.sh /bin/bash /home/plex/.local/bin/Steam.sh /home/plex/.local/bin/kasa --host 192.168.1.239 --port 9999 --type dimmer on; /home/plex/.local/bin/kasa --host 192.168.1.239 --port 9999 --type dimmer brightness 100;xgamma -gamma 1.3 /home/plex/.local/bin/kasa --host 192.168.1.239 --port 9999 --type dimmer on; /home/plex/.local/bin/kasa --host 192.168.1.239 --port 9999 --type dimmer brightness 40;xgamma -gamma 1.3 /home/plex/.local/bin/kasa --host 192.168.1.239 --port 9999 --type dimmer on; /home/plex/.local/bin/kasa --host 192.168.1.239 --port 9999 --type dimmer brightness 12;xgamma -gamma 1.3 /home/plex/.local/bin/kasa --host 192.168.1.239 --port 9999 --type dimmer off;xgamma -gamma 1.3" cat /home/plex/.local/bin/Steam.sh # requires wmctrl -l and xbindkeys # # xdotool windowactivate ```xdotool search --name 'window name'``` # 0 StartSteamLink(){ echo "restarting bluetooth" sudo systemctl restart bluetooth echo "Waking Game PC" sudo /usr/sbin/etherwake -i enp1s0 -D "d8:bb:c1:a2:2c:0b" echo "Starting steamlink" killall -9 steamlink killall moonlight sleep 20 # /snap/bin/moonlight /home/plex/.local/bin/Moonlight-6.1.0-x86_64.AppImage } StartSteamLink SUMMARY: Speaker discusses technical challenges with Sun Shine, Moonlight, and Play Night setups. IDEAS: Sun Shine and Moonlight enable remote game streaming. Play Night acts as a multimodal launcher for Steam. Resolution changes cause display issues during gameplay. Proper exit sequence is critical to revert settings. Ultra-wide resolutions are unusable in some configurations. Multiple launchers require separate logins for different games. Environment variables can adjust client dimensions. Background commands improve system stability. Cat named Mojo is mentioned during the discussion. 5G networks support slower-paced gaming. Technical glitches include frame drops and latency. Steam accounts are tied to specific game libraries. Detached commands run in the background without user interaction. GameStream Launchpad manages resolution and launcher paths. Magical system behavior simplifies remote gaming. Star Wars and Baldur’s Gate are cited as example games. 22nd Millie thing refers to network latency. Multiple Steam accounts complicate game access. Task killing reverts system settings automatically. Cross-platform streaming solutions are highlighted. RECOMMENDATIONS: Use environment variables for client resolution adjustments. Exit applications properly to revert settings. Set up detached background commands for stability. Monitor ultra-wide resolution