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Quorten Blog 1

First blog for all Quorten's blog-like writings

Want to get a flux disk imager on the cheap? Check out FluxEngine, a design that takes an existing development board and programs it to connect directly to IBM PC floppy disk drives. These are then controlled so that you can capture flux disk images. How is that for inexpensive?

20200826/http://cowlark.com/fluxengine/
20200826/https://github.com/davidgiven/fluxengine

Sure, the newer designs are essential if you expect to manufacture with all new hardware.

UPDATE 2020-10-26: Want to do flux disk imaging with a STM32 instead? Check out the GreaseWeazle project.

20201026/https://github.com/keirf/Greaseweazle/wiki

Wow, now this is really interesting, and indeed resonates with my personal experience. Amid an economy that is doing very poorly, many Americans are doing better on their personal finances: saving more, paying down debt faster, spending less. Consequentially, most Americans have been spared from the worst in this economic downturn.

20200825/https://www.pbs.org/newshour/economy/many-americans-shoring-up-finances-amid-downturn-poll-says

Cooling with electricity? Yes, it’s possible, Peltier module is the name of the game. Thermoelectric cooler in other words. The big gotcha: the function is based off of a long electrical series circuit, and mechanical stress can cause this to break. So, be careful in how you mount your Peltier module.

20200824/https://www.digikey.com/en/articles/important-factors-for-improved-peltier-module-reliability

Get the inner scoop of the theory behind Peltier modules here, I still feel like the whole idea is running circles around my head. Oh, I see, so this is really interesting. Basically, the invention stems from an observation of what happens if you pass an electric current through the circuit of a thermocouple, normally a thermocouple generates electricity from heat, but if you pass an electric current through it, you force the heat flow a specific direction in the thermocouple.

20200824/https://en.wikipedia.org/wiki/Thermoelectric_cooling
20200824/https://en.wikipedia.org/wiki/Thermoelectric_effect#Peltier_effect

Read on →

So, I’m maintaining a GitHub repository for a KiCad project. I’ve seen other projects use manual generation of PDF schematics to include in the repository, but I’m interested in using a CI/CD pipeline. to build these derived artifacts non-interactively. So, what are my options?

Unlike Inkscape, KiCad does not have a direct command-line means to run exports to your favorite file formats. Instead, for Pcbnew, this can be achieved through scripts, and for Eeschema, this can be achieved through an external program, called eeshow.

20200823/DuckDuckGo kicad plot command line
20200823/https://docs.kicad-pcb.org/5.1/en/pcbnew/pcbnew.html
20200823/https://kicad-pcb.org/external-tools/

Another note, right there on the external tools page is altium2kicad, that should greatly ease collaboration with Altium projects.

Oh, interesting. Bootcode that was ROM in previous Raspberry Pi models is now moved to EEPROM in the Raspberry Pi 4. This has the potential, most importantly, to introduce boot from USB after shipping, and eventually network boot, I would be led to believe. Also important is mention of how to recover from a corrupted bootloader, and the fact that boot settings are no longer One Time Programmable (OTP), it’s all in rewritable memory.

20200821/DuckDuckGo rpi-eeprom
20200821/https://www.raspberrypi.org/documentation/hardware/raspberrypi/booteeprom.md

And the really good news about this? Finally, PXE boot is available in beta for Raspberry Pi 4!

20200821/DuckDuckGo raspberry pi 4 pxe boot
20200821/https://hackaday.com/2019/11/11/network-booting-the-pi-4/

Oh, okay, I see how the ID EEPROM works. It contains a device tree fragment that allows Linux to automagically load the required drivers. So then, it just comes down to making sure you have the drivers installed into the Linux system drivers directory, no need to include them in your /etc/modules startup file.

Read on →

Oh wow, now this is really interesting. Citibank made a financial error that wired 100 times more money to a hedge fund Brigade Capital, and in the wrong direction too? This was part of supporting a loan on behalf of Revlon, the cosmetics company in financial trouble when people aren’t going out and buying as much makeup as they once did.

20200820/https://edition.cnn.com/2020/08/18/investing/citibank-sues-brigade-capital/index.html

After reading about an xkcd comic that joked about the problem of undermaintained software dependencies that hold up the entirety of the Internet, I found some other interesting stories about past cases. The proposition was that failure in ImageMagick will cause the entire Internet to come topling down.

Post Heartbleed crisis, more funding for OpenSSL.

20200820/https://arstechnica.com/information-technology/2014/04/tech-giants-chastened-by-heartbleed-finally-agree-to-fund-openssl/

This other issue, when a developer, upset by a legal request to rename a package called kik. It was forcibly removed from NPM by the CEO, that angered the author who promptly unpublished all his packages, thereby causing most major Node.js projects to break because they depended on one called left-pad.

20200820/DuckDuckGo leftpad broke the internet
20200820/https://www.theregister.com/2016/03/23/npm_left_pad_chaos/

And this other interesting one, a typematic error in OpenStreetMap that was later corrected, but not before Microsoft Flight Simulator pulled in the data, resulted in a 212-story tall obelisk in the middle of an otherwise quiet Melbourne suburb.

20200820/DuckDuckGo microsoft flight simulator melbourne tower
20200820/https://www.engadget.com/flight-simulator-open-street-map-building-205545509.html

I was looking for info on setting up standoffs for reflow solder, but I didn’t really find anything. One interesting thing that I found, you can solder surface-mount standoffs directly to your board, and there is high-temperature tape that you can use for securing components during reflow soldering, called Kapton tape.

20200817/DuckDuckGo pcb reflow standoffs
20200817/https://www.digikey.com/en/product-highlight/k/keystone/surface-mount-threaded-standoffs
20200817/DuckDuckGo Kapton tape
20200817/https://www.uline.com/Product/Detail/S-11730/High-Temperature-Tape/Kapton-Tape-1-Mil-1-x-36-yds

ANother interesting and informative article I’ve found, common causes of reflow soldering defects. Good thing I haven’t yet seen any of these issues in my experience of reflow soldering, but my solder paste is still pretty fresh.

20200817/https://resources.altium.com/p/common-smt-process-defects-to-avoid-during-soldering

Okay, I was having quite a bit of trouble figuring out how to hand-apply solder paste to SSOP pads without stencils, but I got some very good insight here. One method of soldering fine pitch pads is the “pool of solder” method, whereby you flood the pads and pins with solder, then you use solder wick to remove the excess. You’ll have nice, cleanly separated pads.

So, that’s really great to hear! The technique can be extended to using solder paste too. You apply the solder paste such that the pads are bridged together, but then you can use solder wick to remove the excess. But, the good things don’t stop there. Thanks to surface tension magic, most bridges across pads will break apart on their own because the molten, liquid solder wants to stick to the metal pad surfaces more so than the insulative solder mask surface. That leaves less work for solder wick cleanup, not to mention less likelihood of failure to properly clean up the overflow.

That being said, this technique of course doesn’t work with Quad-Flat-No-Leads (QFNL) or Ball Grid Array (BGA) components due to the lack of exposed leads where you can do cleanup with solder wick.

20200815/DuckDuckGo hand apply solder paste tssop pads
20200815/http://skywired.net/blog/tutorials/how-to-solder-qfp-tssop-soic-surface-mount/

20200815/https://electronics.stackexchange.com/questions/145271/whats-the-easiest-way-to-solder-tssop-parts

Read on →

Can you retrobright a yellowed with only hydrogren peroxide? I’d really like to do retrobrighting with less chemicals.

Well, the answer to that question is quite interesting. It turns out that you can retrobright with no chemicals at all, just bright sunlight and exposure to the oxygen from open air. This is a much gentler process than the chemical-based ones.

20200815/DuckDuckGo hydrogen peroxide retrobrite
20200815/https://en.wikipedia.org/wiki/Retr0bright
20200815/https://www.instructables.com/id/DIY-Retrobright-Whitening-solution/
20200815/http://retr0bright.com/
20200815/DuckDuckGo retrobright only hydrogen peroxide
https://dfarq.homeip.net/retrobright-with-sunlight-and-no-chemicals/

That being said, it still leaves me with a lot of questions. I have some white plastic items that are covered by cardboard or stored in boxes outside of the sunlight, but they are still in hot places. Over the years, they have curiously become yellow. Is there possibly an anti-retrobrightening process going on? Retrobrighting can be done with exposure to only infrared light, so its possible the infrared light as radiated heat is doing something chemical that has an undesirable effect in the absence of oxygen, which would come from open air exposure.

Another note, the “active oxygen” part, i.e. Oxyclean, is only added in a small quantity. Purportedly if you used a thin layer of hydrogen peroxide or some other method to ensure access to oxygen, this would also work well?