Label Your Shtuff!

Joshua Vasquez wrote a piece a couple of weeks ago about how his open source machine benefits greatly from having part numbers integrated into all of the 3D printed parts. It lets people talk exactly about which widget, and which revision of that widget, they have in front of them.

Along the way, he mentions that it’s also a good idea to have labels as an integrated part of the machine anywhere you have signals or connectors. That way, you never have to ask yourself which side is positive, or how many volts this port is specced for. It’s the “knowledge in the head” versus “knowledge in the world” distinction — if you have to remember it, you’ll forget it, but if it’s printed on the very item, you’ll just read it.

I mention this because I was beaten twice in the last week by this phenomenon, once by my own hand costing an hour’s extra work, and once by the hand of others, releasing the magic smoke and sending me crawling back to eBay.

The first case is a 3D-printed data and power port, mounted on the underside of a converted hoverboard-transporter thing that I put together for last year’s Chaos Communication Congress. I was actually pretty proud of the design, until I wanted to reflash the firmware a year later.

I knew that I had broken out not just the serial lines and power rails (labelled!) but also the STM32 SWD programming headers and I2C. I vaguely remember having a mnemonic that explained how TX and RX were related to SCK and SDA, but I can’t remember it for the life of me. And the wires snake up under a heatsink where I can’t even trace them out to the chip. “Knowledge in the world”? I failed that, so I spent an hour looking for my build notes. (At least I had them.)

Then the smoke came out of an Arduino Mega that I was using with a RAMPS 1.4 board to drive a hot-wire cutting CNC machine. I’ve been playing around with this for a month now, and it was gratifying to see it all up and running, until something smelled funny, and took out a wall-wart power supply in addition to the Mega.

All of the parts on the RAMPS board are good to 36 V or so, so it shouldn’t have been a problem, and the power input is only labelled “5 A” and “GND”, so you’d figure it wasn’t voltage-sensitive and 18 V would be just fine. Of course, you can read online the tales of woe as people smoke their Mega boards, which have a voltage regulator that’s only good to 12 V and is powered for some reason through the RAMPS board even though it’s connected via USB to a computer. To be honest, if the power input were labelled 12 V, I still might have chanced it with 18 V, but at least I would have only myself to blame.

Part numbers are a great idea, and I’ll put that on my list of New Year’s resolutions for 2021. But better labels, on the device in question, for any connections, isn’t even going to wait the couple weeks until January. I’m changing that right now.

A Turing-Complete CPU From RAM

Building a general-purpose computer means that you’ll have to take a lot of use cases into consideration, and while the end product might be useful for a lot of situations, it will inherently contain a lot of inefficiencies. On the other hand, if you want your computer to do one thing and do it very well, you can optimize to extremes and still get results. This computer, built from RAM, is just such an example.

The single task in this case was to build a computer that can compute the Fibonacci sequence.  Since it only does one thing, another part of the computer that can be simplified (besides the parts list) is the instruction set. In this case, the computer uses a single instruction: byte-byte-jump. Essentially all this computer does is copy one byte to another, and then perform an unconditional jump. Doing this single task properly is enough to build every other operation from, so this was chosen for simplicity even though the science behind why this works is a little less intuitive.

Of course, a single instruction set requires a lot of clock cycles to work (around 200 for a single operation). The hardware used in this build is also interesting and although it uses a Raspberry Pi to handle some of the minutiae, it’s still mostly done entirely in RAM chips, only cost around $15, and is a fascinating illustration of some of the more interesting fundamentals of computer science. If you’re interested, you can build similar computers out of 74-series chips as well.

Theremin In Detail

[Keystone Science] recently posted a video about building a theremin — you know, the instrument that makes those strange whistles when you move your hands around it. The circuit is pretty simple (and borrowed) but we liked the way the video explains the theory and even dives into some of the math behind resonant frequencies.

The circuit uses two FETs for the oscillators. An LM386 amplifier (a Hackaday favorite) drives a speaker so you can use the instrument without external equipment. The initial build is on a breadboard, but the final build is on a PCB and has a case.

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Furuta Style Inverted Pendulum Is King Of Geek Desk Ornaments

Newton’s Cradle is thought of as the most elegant of executive desk toys. But that 20th-century dinosaur just got run off the road as [Ben Katz]’s Furuta pendulum streaks past in the fast lane, flipping the bird and heralding a new king of desk adornments.

This Furata pendulum has wonderfully smooth movement. You can watch it go through its dance in the video after the break. Obviously you agree that this is the desk objet d’art for the modern titan of industry (geek). Just don’t stop at watching it in action. The best part is the build log that [Ben] put together — this project has a little bit of everything!

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Understanding Op-amps From Simple To Hard

[Tim] wanted to help out a ECE student struggling with some Op-Amp problems. He put together a video which does a good job of explaining what an Op-Amp does, then tackles each of the questions one at a time.

His analogy is illustrated in this image. There’s an operator using a crane to lift a crate. He is watching a ‘radio man’ in a window of the building to know how high it should be lifted. These roles are translated to the function of an Op-Amp in a way that makes understanding the common parts quite easy. The crane is the Op-Amp and the floor to which it is trying to lift the crate is the input pin. The current height of the crate is the output signal. The radio man is the feedback resistor which is trying to get the desired height and current height to equal each other. Watch the video after the break and all becomes clear.

After this analogy is explained [Tim] tackles the actual homework problems. He’s going through everything pretty quickly, and doesn’t actually give the answers. What he does is show how this — like most circuit solving problems — depends on how you group the components in order to simplify the questions. Grab a pen and paper and put on your electron theory hats to see if you can solve the questions for yourselves.

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Let Paper Dolls Teach You Science

Remember how fun it was studying chemistry and physics in high school? Well we guess your recollection depends on the person who taught the class. Why not have another go at it by learning the A-to-Z of electronics from one of our favorite teachers, [Jeri Ellsworth].

You know, the person who whips up chemistry experiments and makes her own semiconductors? The first link in this post will send you to her video playlist. So far she’s posted A is for Ampere and B is for Battery, both of which you’ll find embedded after the break. Her combination of no-nonsense technical explanation, and all-nonsense paper-doll history reenactment make for a fun viewing whether you retain any of the information or not.

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