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Quorten Blog 1

First blog for all Quorten's blog-like writings

Nowadays, I don’t get very much in the way of old schoolwork papers to stock up on to use for paper mache projects, so I had to resort to junkmail as an alternative paper source, one that I personally tongue-un-cheek refer to as a “renewable scratch paper source.” Yet, I am still learning new things, despite not being in school. So, let me reflect. What were the sources of old schoolwork papers? Old schoolwork papers can be classified into three big categories:

  • Class handouts
  • Assignments
  • Examination

These large categories can be further broken down as follows.

  • Class handouts
    • Syllabus
    • Slides/notes
  • Assignments
    • In-class assignments
    • Homework assignments
    • Writing assignments
    • Art projects
  • Examination
    • Permitted exam notes
    • In-class exam
    • Take-home test

Read on →

When researching reflow soldering ovens, I happened to find this interesting article about TechShop going bankrupt.

20190102/https://spectrum.ieee.org/tech-talk/geek-life/hands-on/techshop-goes-bankrupt

TechShop was a makerspace started by Jim Newton, “who once served as an advisor to the TV show Mythbusters.” Why did it fail? Basically, they highlighted that most makerspaces are not-for-profit and get large grants, “often bankrolled by government or philanthropic organizations.” For these costs, we’re largely talking hardware tools, the kind of large, specialized tools that most people would not personally own themselves.

For my own side, I’ve had other discussions that made me think. What are the primary costs of some of the research projects I am following progress on or doing myself? How are these being funded? Some of the most interesting research projects I am following, such as the EOMA68 Earth Friendly Computing Devices project, are entirely crowd-funded. The EOMA68 project exceeded its funding goal. Despite delays and slowdowns, interestingly this project seems like it is coming through. Yes, due to the delays, there were later some shortages of money, there were later additional donations, and there were some large anonymous private donors who pitched in more money.

Read on →

So, now that I am getting underway with learning more about electronics and Raspberry Pi, it is clear that I need to not be so hyper-focused on building the final “project” based off of the minimal specifications and requirements of it, but to also have some leeway of some kits that integrate many useful components together that I can experiment with and learn from.

Also, I might just happpen to find a board that does exactly what I want it to do for my 3D scanning project. However, I must re-emphasize that many of the reasons I am going on technically extra Raspberry Pi excursions is simply to learn more about electronics hardware for my own sake. For example, I don’t need a 4-digit, 7-segment LCD screen and 16-key matrix keyboard for a 3D scanner. However, I do need that kind of interface for other interesting and related electronics projects, some of which are related to spatial measurement, although not in a direct 3D scanning sense.

Anyways, the Gertboard is purportedly a good place to start looking if you want an easy way to experiment with different ways to interface external devices with the Raspberry Pi via the GPIO pins. So, let’s take a look at features and functions it provides.

20181230/DuckDuckGo gertboard
20181230/https://www.sparkfun.com/products/retired/11773
20181230/https://projects.drogon.net/raspberry-pi/gertboard/
20181230/http://www.farnell.com/datasheets/1683444.pdf

I’ll summarize the strengths/weaknesses here:

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TSOP, TSSOP, VMFP. All kinds of quite cryptic acronyms that I am told refer to some sort of surface-mount device packaging. So, considering that I am going to need to work with these to do what I want, what does Wikipedia have to say to enlight me on the subject? There is one article on Small Outline Integrated Circuit (SOIC). Unfortunately, that Wikipedia article contains a dearth of information on the full variety of surface-mount device packaging types. For example, VMFP is nowhere to be seen.

20190101/https://en.wikipedia.org/wiki/Small_Outline_Integrated_Circuit
20190101/https://en.wikipedia.org/wiki/File:SEG_DVD_430_-_Hynix_HY29LV800BT-70-4279.jpg

Nevertheless, it still is a useful introduction to the variety of packaging types in the subject, and the difference between narrow SOIC (1.27 mm pin spacing) and small outline package (SOP, 0.65 mm pin spacing). Add a “T” in front for “thin” in TSOP, and an “S” for “shrink” in TSSOP. An Exposed Pad (EP) means that there is a large exposed pad purportedly on the bottom of the IC that acts as a heat sink.

Now, if you want some great background information on the current state of affairs, the 7400 series integrated circuit article is a great one.

20190101/https://en.wikipedia.org/wiki/7400-series_integrated_circuits

Read on →

When I was reviewing the software GPIO interface for Raspberry Pi, on second thought, I realized that if my 8-pin connector doesn’t have the GPIO pins selected so that all bits are continuous, I am going to have a tremendous performance loss by trying to rearrange bits in software, rather than simply being able to copy one byte and shift it around. So, let’s double-check. Where are the holes in my otherwise continuous range of GPIO pins on the 8-pin connector?

8-bit  Pin  07, 13, 15, 16, 18, 22, 29, 31
       GPIO 04, 27, 22, 23, 24, 25, 05, 06

       GPIO 04, 05, 06, 22, 23, 24, 25, 27
                       X               X

Okay, that was a fail in being a continous range. Let’s try again, trying to straighten up the holes in our nearly continuous range as much as possible.

Unfortunately, it appears the verdict is clear. To get ideal software alignment, I would have to forfeit part of either SPI0 or SPI1, in effect rendering it just another collection of GPIO pins. Also, it looks like I might need to forfeit I2S. So, let’s sample a layout that forfeits SPI1 and the I2S DATA pin.

8-bit  Pin  38, 40, 15, 16, 18, 22, 37, 13
       GPIO 20, 21, 22, 23, 24, 25, 26, 27
            SP  IS                  SP

Well, at least the hardware PWM pins are still free.

Read on →

Okay, okay. Despite all the discussion that I have thus set down on the issue of motor control integrated circuits at 3.3 V, I am still determined to search for information. Can I get 3.3 V motor control from through-hole packages?

20181231/DuckDuckGo 3.3 volt through hole h-bridge

So, here is another alternative, one that uses a simple MOSFET and some diodes to source the motor control voltage and gate it by a microcontroller switch.

20181231/https://electronics.stackexchange.com/questions/235845/3-3v-input-to-5v-output-for-motor-control

This is an interesting example that took an surface-mount integrated circuit and put it on a printed circuit board to make connections to it easier.

20181231/https://www.pololu.com/file/0J806/drv8838.pdf

Important! The documentation on the Pololu motor controller notes that the IC has overheat shutdown, but the overheat shutoff is quite high, so the chip can get so hot that it can burn you before the thermal shutoff kicks in. Also, the documentation on this controller notes that the controller heats up more when PWM control at high frequencies is employed. I’ll discuss more on this in my next article on surface-mount techniques in general.

Read on →

These are some random interesting articles I discovered during Raspberry Pi research.

Boeing, why is the company called Boeing? It’s because it was founded by William Boeing. Indeed, the goal of the company early on was to focus on building airplanes. There’s quite an interesting history section on this blog article, and you can clearly see the visual difference between the early, obsolescent not-so-well designed aircraft and the rapid progression to fully modern aviation, not just in terms of technology, but also in terms of style in the practice of running the businesses involved, and the purposes of the technology being used.

20181228/https://en.wikipedia.org/wiki/Boeing

20,000 feet you ask? Why does that number just feature in my head automatically when thinking about the “cool aviation of drones”? “Drone flying high, at 20,000 feet.” Well, let’s see. What does Wikipedia have to say about this specifically. Not much, unfortunately. That being said, I guess the Boeing article reference to the first passenger airplane to fly at 20,000 feet with a pressurized cabin is by far the best source you can come by.

20181228/https://en.wikipedia.org/wiki/Nightmare_at_20,000_Feet

This is a pretty interesting article reflecting on the history of Doom over the past 25 years, and how even the original game engine is still massively popular today. Often times one of the developing software to target miscellaneous computer hardware is “Does it run Doom?” Oh, and there was also an interesting mention of playing Doom on an ATM.

Read on →

So, you want to do an electronics project on the cheap, with minimal tooling. “Do I really need to buy a pair of wire strippers?” Of course not, you can use alternate tools to achieve the same thing. But can you really get the same quality and speed that you can with a dedicated wire stripper tool? Under some circumstances, yes.

I’ll focus on a very specific use case that is pertinent to me: stripping old 6P4C telephone “patch cable” wires. These particular wires are stranded copper wires, as they are meant to be able to bend and flex without breaking. I chose these wires specifically because I wanted to recycle and reuse unused old equipment as much as possible for my electronics projects, of which these were a candidate. However, there is something specific about these wires that makes them perhaps a little bit different from your typical electronics project stranded wires: the strands are not twisted together. This actually creates a particular problem that makes them more difficult to strip using a conventional wire stripping technique: after you have cut the insulation and are pulling off the bit of insulation, the insulation tends to stick to some or all of the individual strands of wire. Thus, when you pull the insulation off, you end up pulling large parts, or even entire strands, out of the remainder of the wire’s insulation. So, how do you mitigate this problem? As it turns out, the easiest methods to mitigate this problem come naturally when you are using a pair of scissors to strip the wire.

Read on →

I’ve been wondering perhaps a bit too much about PWM motor speed control of brushed DC motors. Does it really work? Why should it work? Won’t it not work as well as motor voltage control? After lots of reading and thinking through this carefully, I think I can explain this in a way that is sure to sway skeptics like myself.

Earlier, I’ve already read that the Raspberry Pi uses some sort of PWM control to generate its built-in analog audio output. Yeah, that makes sense, as the original Macintosh did that too. Just earlier today, I’ve read in detail exactly how it works, and I’ve explained why it is better than the original Macintosh’s way of doing so. But, here is the most interesting specific part pertinent to our discussion on motors. A PDM audio signal can be trivially converted to an analog signal via an RC (resistor-capacitor) low-pass filter circuit. Indeed, simply by storing up the pulse charges in a capacitor, you can blur out the waveform by averaging its values over a larger area to get a nice analog signal.

Read on →

Okay, so for additional old Macintosh communications cables, namely for means of serial communication with a Macintosh SE, I went searching around on Digi-Key to see if I could find the parts to build my own cable. Indeed, I could, but it appears the Mini DIN-8 cable is very short-stocked nowadays, and the only source I could find stocked the cables in units of 100. Okay, fine, so one way or another, I’ve got to solder the connections. My final verdict was to go back to Amazon, find a cable with the correct connector ends but incorrect internal wiring, break that open, and wire it up correctly on my own.

This is my pick.

20181230/https://www.amazon.com/C2G-25041-Female-Mini-DIN-Adapter/dp/B001BS8O26

This is what I’ve found on Digi-Key. Unfortunately, the manufacturer’s original site is down as of 2018, so I had to find an old copy of the specifications sheet from the Internet Archive Wayback Machine.

20181230/https://www.digikey.com/product-detail/en/assmann-wsw-components/A-KMD-08AFMM-WP-R/AE10174-ND/1089545
20181230/https://web.archive.org/web/20171216045604/http://www.assmann.us/specs/A-KMD-08AFMM-WP-R_REV00.pdf

F.Y.I., the DB-9 connector ends were plentiful on Digi-Key. Of course they have to be, as they were traditionally much more popular back in their heyday too.