Wow, so when getting ready to get started on Digi-Key for making my
first purchase from there, I found an interesting blog article and the
maker.io site that is sponsored by Digi-Key. Digi-Key is definitely
a growing company. Surprise surprise, Digi-Key even sells a 14 pound
brass sledgehammer!
20191124/https://www.digikey.com/en/blog/tech-talk-volume-1
20191124/https://www.digikey.com/en/maker
I have previously seen inside the Raspberry Pi device tree (DT) overlay information on how to wire up a power button for a Raspberry Pi. Now that I am about to use a Raspberry Pi as a desktop PC replacement, I have a more immediate need for an actual power button. So I thought I better do some additional web searching and write an actual blog article with the information on how to do this.
A cursory search brings up an article about how to create a Raspberry
Pi power button without the use of the device tree (DT) overlay.
After a little bit more searching, it looks like this is the “old
technique” as the necessary device tree overlay, gpio-shutdown, did
not exist in earlier versions of Raspbian before Debian Stretch.
20191123/DuckDuckGo raspberry pi power button
20191123/https://howchoo.com/g/mwnlytk3zmm/how-to-add-a-power-button-to-your-raspberry-pi
That being said, it is my preference to use the device tree (DT) overlay version instead because I think it is simply a cleaner way to solve the same problem.
Intuitively possible but mind-boggling as it is, I took another look at single-wire earth return and nown I understand the operating principles. Intuitively, this would work better with AC than with DC current, and indeed AC is quite practical for this for a number of reasons I will explain.
First of all, single-wire earth return uses an isolation transformer to keep the grid voltage loop out of the single-wire earth return voltage loop. There is also another such isolation transformer on the customer premises to keep their local power out of the single-wire earth return distribution current loop. So, right off the bat, we can say that isolation of current loops is important.
Some more intuition would lead you to believe that AC at a sufficiently high frequency is needed to be able to pump the charge out of the ground without having the signal want to short striaght to ground. Because if it did, you would have virtually no current flow through your distribution wire, and thus your electricity would travel nowhere.
Mask ROM? Mask ROM is the type of ROM that requires sending a custom mask to the manufacturer to make. It is the most expensive type, but also has the highest storage density and is highly durable, aspired for the possibility of high-density durable archiving but out of reach simply due to the costs.
20191122/https://en.wikipedia.org/wiki/Mask_ROM
PROM is the much more practical alternative for conventional use, if you need true read-only memory. Writing out a PROM is quite easy, use a 6 V pulse to burn away a gate to convert the default “1” to a “0”. Not much different than programming EPROM at 12 V.
20191122/https://en.wikipedia.org/wiki/Programmable_read-only_memory
20191122/https://en.wikipedia.org/wiki/EPROM
Note that some EPROM chips can run off of a lower voltage when programming. See my old blog post for an example of such a chip.
Oh, interesting. I found out that the Raspberry Pi audio plug on all Raspberry Pis except the original also includes another “ring” connection for the composite video connection. All you need is the proper adapter cable to split this out to use it with a composite video television.
20191122/DuckDuckGo raspberry pi 4 composite video
20191122/https://www.raspberrypi-spy.co.uk/2014/07/raspberry-pi-model-b-3-5mm-audiovideo-jack/
Wow, interesting. Can a leaf blower fly. Well, almost, but no, not quite.
20191122/https://hackaday.com/2018/11/12/fail-of-the-week-leaf-blowers-cant-fly/
Okay, okay, so the whole thing about driving DC motors at low speed. Surely, the brushes limit the lowest speed you can reliably drive such motors at? So, brushless DC motors could be driven at lower speeds, could they? Well, looks like they can. However, they do so at the expense of less torque than stepper motors. So, what it comes down to is that stepper motors are the most effective way to get very small movement from a motor, but if you want to cut costs, yeah you can use a brushless DC motor or a brushed DC motor with a gear reduction box.
So, the critical question is how much cost can you cut before your compromise on accuracy is too great to be usable for your application? Only you can answer this question for your specific application.
20191122/DuckDuckGo low speed brushless dc motor
20191122/https://www.quora.com/Why-cant-we-use-a-BLDC-motor-for-low-speed-applications?share=1
20191122/https://www.amazon.com/Makermotor-Variable-Brushless-Electric-Gearmotor/dp/B005LY2LDO
20191122/https://hackaday.com/2015/04/20/driving-a-brushless-dc-motor-sloooooooowly/
Wow, so the news of WeWork not doing well financially was looming long, and now it finally happened, a sweeping layoff. WeWork cut its non-core businesses, WeLive and hte WeWork inspired private school, and is focusing in its primary area, office real estate leasing. Yes, just as I anticipated, WeLive did end up to be a failure in the marketplace, and I was surprised that they did pursue their idea of a WeWork inspired school at all. Cleaning and facilities maintenance jobs were all kept by transferring them to an external real estate services contracting company.
20191122/https://www.nytimes.com/2019/11/21/business/wework-layoffs.html
WeWork thought of a whole lot of great ideas, it’s just that the ongoing problem must hold, that it is very difficult to innovate in real estate, especially “consumer” real estate, due to customer lack of willingness for change. But in the business world, where change is inevitable, obviously people are forced to move at a faster pace.
Wow, this is interesting. The idea of boot from USB and USB gadgets? That has been expanded to create a Raspberry Pi Zero that can be used as a USB attached GPIO expander for the Raspberry Pi Debian x86 PC distribution. How do they do this? With power of udev… ugh, that sounds like a very ephemeral and brittle solution that is going to break at the earliest moment that a incompatible change allows it to. Yeah, it’s an interesting demo short-term, and useful at that in so far as the price points of Raspberry Pi Zero (and the amount of money saved) are so low.
Also, note that the Raspberry Pi Zero uses BCM2708, not BCM2835. Only the Raspberry Pi Compute Modules have the newer BCM chip revisions in them.
20191120/https://www.raspberrypi.org/blog/gpio-expander/
20191120/https://www.raspberrypi.org/documentation/hardware/computemodule/cm-emmc-flashing.md
Also, I found this otther interesting article announcing the expansion of Raspberry Pi Zero W distributors. Gosh, I thought the Raspberry Pi Zero was hard to come by inside the United States, but I’ve been told, outside the United States, it is heck to get hold of a Raspberry Pi Zero W!
20191120/https://www.raspberrypi.org/blog/pi-zero-distributors-annoucement/
Here are two useful articles I’ve read from IEEE Spectrum that are useful for organizing with the rest of my electronics blog information. You can construct small, low-power DC motors via a printed circuit board: the motor windings are trace patterns printed onto your circuit board.
20191119/https://spectrum.ieee.org/geek-life/hands-on/how-to-print-an-electric-motor
The second one, the “dead bug” approach to constructing prototype high-speed circuits. You can’t construct high-speed circuits on a conventional perfboard because you don’t have a large grounding plane. So instead, you can use an unprinted circuit board as your large ground plane, and wire together your IC chips directly, with them upside-down like “deada bugs.”
20191119/https://spectrum.ieee.org/geek-life/hands-on/with-the-dead-bug-method-hobbyists-can-break-through-the-highfrequency-barrier