[HN Gopher] Spintronics: Build Mechanical Circuits
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Spintronics: Build Mechanical Circuits
Author : mcp_
Score : 457 points
Date : 2021-05-20 15:31 UTC (1 days ago)
(HTM) web link (www.kickstarter.com)
(TXT) w3m dump (www.kickstarter.com)
| nemo1618 wrote:
| I've always been curious how far we could push "mechanical
| computation." Seems like even an operation as simple as
| multiplication requires tons of metal. If I wanted to compute,
| say, a SHA2 hash or an Ed25519 signature with zero electricity,
| would I need a room-sized machine?
| carapace wrote:
| Mechanical multiplication is easy:
| https://en.wikipedia.org/wiki/Sliderule
|
| See more generally: https://en.wikipedia.org/wiki/Nomogram
| Laremere wrote:
| You can hold a mechanical calculator in your hand, so I imagine
| if an industry of effort on perfecting mechanical computation,
| it could get quite small: https://en.wikipedia.org/wiki/Curta
| RandallBrown wrote:
| You should read Neal Stephenson's Diamond Age. It's in an
| alternate future where they use mechanical computers.
| mcp_ wrote:
| The Difference Engine by Bruce Sterling and William Gibson
| would be a good read on that topic too.
| pgboswell wrote:
| For sure - at least with the parts in their current form. A
| simple flip-flop takes up a minimum space of about 30 cm x 30
| cm. But I wonder how small these parts could get. Like, what if
| spintronics was invented in the 19th century instead of the
| 21st century? Would Moore's law have applied to mechanical
| transistors?
| dekhn wrote:
| See https://en.wikipedia.org/wiki/There%27s_Plenty_of_Room_at
| _th... and https://en.wikipedia.org/wiki/Engines_of_Creation
|
| TL;DR we're nowhere close to exploiting the full potential of
| nanoscale mechanical systems.
| mdaniel wrote:
| For those who don't click on the Engines of Creation link,
| be aware that at the bottom of that page is a PDF link to
| the gratis version of Engines of Creation 2.0 from 2007: ht
| tps://web.archive.org/web/20140810022659/http://www1.appst.
| ..
|
| Since I just now learned about that link, I haven't read
| the book to know, but I have always been interested in
| finding out if the ability to create smaller and smaller
| machines is possible by having an outer machine which
| manufactures an inner, smaller, copy of itself, apply the
| process of induction, define the termination criteria, ...,
| profit!
|
| Or, maybe I'm thinking about the problem all wrong -- it's
| not the actual construction machinery that's the problem,
| it's providing the input materials to each step (gears,
| levers, fasteners, wiring(?), etc)
|
| There's a Factorio-clone hiding in this problem ...
| AriedK wrote:
| Thanks for the recommendation. That cover though, is that
| topology specific to a coronavirus or do more viruses
| share it? Especially since the Pfizer/Biontech and
| Moderna vaccines deploy nano-particles for delivering
| their payload.
| lazide wrote:
| The issue is that scaling does not produce linear effects
| as you go down (or up) for a number of reasons. What
| works at the meter scale doesn't work at the millimeter
| scale, which doesn't work at the micrometer scale, etc.
|
| So you end up having to learn an experiment at a more and
| more difficult to access scale to figure out how to make
| something actually work.
|
| That's real life anyway.
| rusticpenn wrote:
| MEMS started out to cater to this dream, unfortunately
| problems like stiction (https://www.sciencedirect.com/top
| ics/engineering/stiction) have been blockers until now.
| tlb wrote:
| Mechanical Turing machines can be small, such as:
| https://hackaday.com/2018/03/08/mechanical-wooden-turing-mac...
|
| They will take a long time to compute something like SHA2
| nynx wrote:
| If you could build mechanisms atom-by-atom, you could make
| reversible mechanical computers that are orders of magnitude
| faster than what we have today.
| gene-h wrote:
| Rod logic will not be faster than electronic computers.
| According to Drexler's thesis, it's reasonable to expect
| "that RISC machines implemented with this technology base can
| achieve clock speeds of ~ 1 GHz, executing instructions at ~
| 1000 MIPS."
|
| This is because the speed of sound, which limits how fast
| mechanical signals can propagate, is much lower than the
| speed of light.
|
| The main advantages of rod logic is that its compact and
| power efficient. The aforementioned CPU would consume ~100
| nW.
|
| Really the reason why Drexler analyzed rod logic in the first
| place is that it was easy to analyze and something that his
| proposed assemblers could plausibly construct, better
| alternatives for fast computing may exist.
|
| [0]https://dspace.mit.edu/handle/1721.1/27999
| nynx wrote:
| This is true, but it's important to consider that you could
| squeeze several billion of these processors into the space
| taken up by current CPUs.
| pgboswell wrote:
| This is very interesting. Why would they be faster?
| MayeulC wrote:
| seeing that nynx hinted at reversible computing, they would
| just be smaller and more energy efficient. The idea being
| that you can cram more of these in a given volume.
|
| Reversible computing tries not to destroy information,
| allowing to go under Laundauer's limit [1].
|
| When you discard the previous value held by your flip-flop,
| you clear the output bit, returning electrons (or a chain
| displacement) to the power supply. If you can instead
| repurpose that energy, you'll have to supply a lot less
| energy since you'll dissipate less. That would be
| reversible or adiabatic computing [2]. I have to note that
| processors these days are mostly power-limited, trying not
| to melt themselves as the energy flux inside a chip
| approaches that of a nuclear reactor. Just look at modern
| sockets and count the pins dedicated to power supply![3]
|
| [1]: https://en.wikipedia.org/wiki/Landauer's_principle
|
| [2]: https://en.wikipedia.org/wiki/Reversible_computing#Rev
| ersibi...
|
| [3]: https://arstechnica.com/gadgets/2015/11/5d-electronic-
| blood-...
| dang wrote:
| Sorry that HN's software rate limited your account! New
| accounts are subject to a few extra restrictions, and it
| always makes me sad when a project creator shows up and
| gets hit by those (I'm a mod here). That's not at all a
| case that we're trying to restrict!
|
| I've marked your account legit so this will not happen to
| you again, and I've approved your comments that got
| throttled, so they're up now. Welcome to HN and
| congratulations on this exceedingly cool work.
| zardo wrote:
| Building at the molecular scale you can achieve extremely
| low friction coefficients in the moving parts. Inertia also
| gets extremely low, and material strengths tend toward
| their theoretical values.
|
| Of course electronics aren't standing still, but resistance
| tends to get harder to deal with as feature sizes decrease.
| PeterisP wrote:
| What I've always wondered is that wouldn't very tiny
| molecular mechanisms get problems with "accidental
| welding" since a part could be permanently destroyed by a
| few molecular bonds forming or breaking and (IMHO - this
| is my guess/assumption) such events would be likely at
| e.g. room temperature.
| db48x wrote:
| Unless designed well, yes. Parts that move relative to
| each other need to be designed so that unwanted bonds are
| unlikely to form. This generally means designing them so
| that unwanted bonds are less energetically favorable than
| the bonds they start out with. Of course, as temperature
| rises, the chance of breaking existing bonds rises, as
| does the chance of forming new unwanted bonds.
| nxpnsv wrote:
| I guess you can do it with pen and paper and patience...
| AriedK wrote:
| I was blown away (no pun intended) by the mechanical analog
| computers used fire control systems on battle ships:
| https://arstechnica.com/information-technology/2020/05/gears...
| This was 3000 pounds for calculating a shell trajectory (with a
| good number of parameters).
| hypertele-Xii wrote:
| Here's a video detailing some of the math and mechanisms
| used.
|
| https://www.youtube.com/watch?v=s1i-dnAH9Y4
| gene-h wrote:
| I wonder if you could make a torque amplifier[0] with the
| transistors? A torque amplifier is a mechanical device which
| takes in a shaft rotation and power outputting the same rotation
| angle except with higher torque.
|
| This was an important component in mechanical computers to
| amplify outputs disc integrators which outputted shaft rotations
| at low torque.
|
| It might be a fun device to make because you could use this to
| make part of a steampunk exoskeleton where the user can turn a
| small arm to move a much large arm. Because torque is amplified
| it will be easier to move the heavier arm.
|
| [0]https://en.wikipedia.org/wiki/Torque_amplifier
| Doxin wrote:
| I'd imagine that would have to be possible, seeing as the
| junctions function as differentials. It might be as simple as
| adding negative feedback to the input of the transistor, though
| we'll probably need to wait for spintronics to be shipped to
| find out for sure.
| mcphage wrote:
| That seems to be where physical computing (pulleys, etc) always
| falls down--no amplifier. So the system needs to be input with
| more and more energy, the more gates there are.
| quanto wrote:
| This reminds me of when I was taking an advanced circuit design
| class. The analog circuit in question had many moving parts, and
| I just didn't have the intuition. The teaching fellow at the time
| thought it would help to visualize a mechanical analog (ha!) of
| the circuit and drew for me a complex mechanical diagram. It was
| so complex that I found it more intuitive to just study the
| electrical circuit directly.
|
| After years of working with electrical circuits, I now often find
| it easier to translate a mechanical system in question to an
| analogous electrical system and analyze it. In fact this is where
| the phrase "analog electronics" comes from: It is an analogue of
| a real world (often mechanical) system. At the end of the day,
| these are all (mostly second order) differential equations.
| hintymad wrote:
| This is amazing and looks fun! I immediately paid to support the
| project, so I can play the toy later.
|
| That said, I wonder if it will really make learning circuit
| easier. I have a hard time imagining that kids would give up
| learning circuit just because they couldn't get the abstractions.
| The biggest obstacle to learning, per my limited observation of
| course, is always lack of innate curiosity or sometimes talent.
| Those who get discouraged by the so-called difficult abstraction
| probably do not need to learn circuitry in the first place.
|
| By the way, I find the promotional video interesting. There are a
| few frames that talk about how a kid had to resort to maths and
| what not to understand circuits, and videos showed kids checking
| out oscilloscopes, square waves, some complex circuits that
| looked like Y-delta transforms, and voltage-ampere curves (or
| something like that). I mean, if a kid would look into those
| things, why would we worry that the kid can't learn circuit? And
| since when looking into math is a bad thing?
|
| Boswell's idea seems aligned with the movement of progressive
| math education in the US, which advocates that there's gotta be
| an easy and intuitive way to motivate and enable _every_ kid to
| discover and grasp math concepts. I think it 's a noble goal. I'm
| just not sure if everyone is born with the drive or aptitude.
| krastanov wrote:
| I teach and from my experience drive and aptitude is not the
| problem. "Math" and "abstraction" are not the problem either,
| except that for many educators they are synonymous with rote
| memorization which leads to ridiculous amounts of math phobia
| in the US that I have not seen in Europe.
|
| When you hear people avoiding math in teaching, they usually
| mean avoiding the rote "non beautiful" perversion of math
| frequently presented by educators with limited math experience.
| ofou wrote:
| Where is the memristor?
| jerf wrote:
| I am positively agog. This is amazing.
|
| I would suggest to pgboswell that it may be interesting to reach
| out to a few local professors who teach introductory circuits at
| some nearby universit(y/ies) and do an in-person demo of the
| components. You may find you have a significant educational
| market you could tap into. I could well believe there's a lot of
| people who just never quite make it over the abstraction gap to
| understand circuits who would be able to follow them if they
| could physically interact with a mechanical circuit running at
| human orders of magnitude.
| ocdtrekkie wrote:
| This reminds me of something I read about the other day (probably
| also from HN), a mechanical exploratory rover:
| https://www.jpl.nasa.gov/news/a-clockwork-rover-for-venus
|
| This really helps visualize how one might make "computation" with
| mechanical parts possible!
| scott-smith_us wrote:
| In high school I took electronics and learned enough about
| capacitors, inductors and transistors to design and test simple
| circuits. I'd gotten a Radio Shack "100-in-1" kit when I was in
| fifth grade, but the projects within were all opaque recipes to
| me. Most circuits had illustrations with cartoons components
| saying things like "I'm the capacitor, and I give a little 'kick'
| to the transistor!". I remember being kind of surprised at just
| how un-enlightening these cartoons were. If I followed the wiring
| steps for a project and then it didn't work, I'd double-check my
| wiring. If it still didn't work, there was nothing further to do;
| I just gave up. I had no idea how it 'ought' to work, so there
| was nothing I could measure or verify that would mean anything to
| me.
|
| This is what I wish I'd had at the time. I'd have understood
| intuitively what each of the components did. The time-scale is
| slowed down enough that I could see what was going on. I could
| build and test in stages and see how each new change affects the
| outcome. Endless experimentation and possibilities...
|
| This is just terrific!
| amelius wrote:
| Another approach would be to have capacitors with little leds
| on them which show charge, leads with little leds which show
| current, etc.
| dpeck wrote:
| This is from the same person (team?) that made Turing Tumble,
| which has been great fun to do with my 8 year old. The puzzles
| are a lot of fun and gives a nice intuitive feel for "circuits"
| and basic mechanical logic ( ands, ors, counters, etc)
| computation.
|
| Highly recommended if you've got a kid in your life who likes
| figuring out and building things. https://www.turingtumble.com/
| scott-smith_us wrote:
| Every time I see stuff like this, it reminds me of Neal
| Stephenson's "The Diamond Age: Or, a Young Lady's Illustrated
| Primer".
|
| If/when technology switches over to the micro-mechanical, we'll
| suddenly all be scrambling to re-introduce a generation to this
| 1800s-era mechanical design stuff...
| rcxdude wrote:
| > If/when technology switches over to the micro-mechanical,
| we'll suddenly all be scrambling to re-introduce a generation
| to this 1800s-era mechanical design stuff...
|
| Probably not. Micromechanics is completely different from
| larger scale mechanics, the kinds of problems you have to
| solve and the tools you have to solve them are often
| completely turned on their head.
| selfsimilar wrote:
| Given the recent work to design a 'clockwork' rover for Venus
| exploration[0] I could see some utility for mechanical
| circuits in harsh environments like Venus, or helping in the
| event of a nuclear meltdown like Fukashima Daishi, or other
| environments particularly antagonistic to electronics.
|
| 0 - https://news.ycombinator.com/item?id=27164195
| MayeulC wrote:
| I'm not sure it will, though, except in specific cases.
|
| For now, it looks like the progress has mostly been:
| mechanical -> electrical -> optical (/RF)
|
| For good reason too: reliability, integration, and energy
| efficiency. We're a bit stuck on electrical for now as
| integration is slightly better, electrons being smaller than
| photons, and it seems to be more suited for power
| transmission and conversion, at least for now.
|
| Basic principles haven't changed much though, and it's always
| interesting to understand those. There is just the "field"
| concept that can be tough to understand.
| krasin wrote:
| Yes, this is from the same person. Turing Tumble is almost
| amazing. Unfortunately, gears and balls used there are not
| reliable enough and more complex circuits have abysmal
| reproducibility (~50%).
|
| I tried it with my kids and they were _very_ excited up until
| this unreliability killed all the fun. I wish Turing Tumble had
| a premium version with a better determinism.
| coupdejarnac wrote:
| Sounds like a pretty authentic engineering experience then.
| krasin wrote:
| Yes. But kids like to be exposed to the joy of engineering
| first. It's otherwise hard for them to justify the pain
| that's required to get to the joy of success.
| jacobolus wrote:
| Did you try putting the little "high-friction washers" on
| the gear pieces?
| krasin wrote:
| Sadly, by the time I discovered the community
| improvements / hacks, my kids lost all the interest.
|
| Hopefully, Spintronics would be more reliable, given that
| the author is well aware of the unreliability issue with
| Turing Tumble.
| spoonjim wrote:
| Where can I find the community hacks?
| krasin wrote:
| https://community.turingtumble.com/
|
| Specific thread that I had read at the time is
| https://community.turingtumble.com/t/crossovers-dont-
| work-or...
|
| While my memory is fuzzy, it was indeed crossovers which
| caused majority of undeterminism, at least in the set I
| had. There are some alternative 3d-printable
| implementations if you walk by the links there. I didn't
| try.
| jacobolus wrote:
| They shipped the little washers in the box, with the
| recommendation to use them when connecting 2 gear bits,
| but leave them off when connecting 3 gear bits.
|
| My impression is that the main design flaw with Turing
| Tumble is the steep board angle, and it would have worked
| a bit better if designed for a 45deg (or something)
| board. That and using heavier rotating parts with a bit
| higher moment of inertia. But I think it's still great
| despite the occasional malfunctioning part.
|
| As for frustrated kids: I think interaction with an adult
| who could notice parts sometimes malfunctioning (and
| correct them on the spot) would probably help forestall
| some frustration. But my kid is only 4.5 so we have to do
| the puzzles together.
| krasin wrote:
| They didn't ship with mine! :)
|
| Probably, an update to a later version. I don't know?
| icedata wrote:
| Same thing happened to me with Digi-comp II, although I was
| the kid and I thought that I had screwed up the assembly. The
| model printed on the cover had wooden bars and looked a lot
| more reliable, but the production model was plastic and not
| reliable at all.
| spoonjim wrote:
| I love Turing Tumble but I've had to create a list of which
| specific parts can't be placed on which specific pegs, and
| thus when we use it have to carefully keep track of
| everything like a bomb defusal squad. Still love it.
| Animats wrote:
| Oh, that's precious. I hope they ship this, and that the
| components aren't too expensive. They look expensive.
| kizer wrote:
| You'd think the water analogy would be easier to build and sell.
| Regardless, the more "analogies" the better, as the abstract
| concept reveals itself more readily.
|
| When I was taking physics, the water analogy of circuitry helped
| me out a lot, especially with regards to capacitors and
| inductors. Inductors being like a water wheel, taking time to
| ramp up to speed then reinforcing flow of current (as I
| remember?). And capacitors being like a rubber sheet separating
| water. A strong current provokes a respective force against the
| water on the other side and slowly stretches the rubber until
| current stops; the key thing is it requires constant voltage to
| keep the rubber stretched; the elastic energy of the rubber is
| analogous to the stored electric field in a capacitor (?).
|
| Physics was hardest for me... I preferred the more structural and
| compositional nature of computer science. Things changing
| continuously is hard for my brain :(
| sumthinprofound wrote:
| Wish I had this as a kid but still excited to own it once it's
| released!
| [deleted]
| lxe wrote:
| Mechanical inductors, capacitors, and even transistors? That's
| and incredible feat. Developing intuition about how to put the
| components together to build something like an oscillator or a
| flip flop is a must for electronics enthusiasts.
| spoonjim wrote:
| To the founder's point about math not being necessary for
| developing intuition about electronics: Michael Faraday's three
| volume treatise on electromagnetism, which essentially created
| the entire scientific field, has essentially zero math in it.
| syoc wrote:
| This looks really cool. Would be interested myself even if I am
| probably outside the intended age bracket. I can't help think
| that the parts look really flimsy based on the videos. They look
| kind of 3d printed and the plastic seems cheap. Hope that's not
| the case.
| adeledeweylopez wrote:
| That's probably because they are 3D printed prototypes. He says
| in the link that they're working on creating the molds for
| injection molding.
| lapetitejort wrote:
| I'm amazed at all the ways we can simulate circuits. The classic
| is pipes and water, however you can also use car traffic, heat
| transfer, and now gears!
|
| My question is can you simulate how resistors behave in series
| versus parallel? How about capacitors?
| pgboswell wrote:
| Yup. I actually tried making an analog of electronics with
| water and air first. Water didn't work very well because of the
| high resistance. Air didn't work very well because of it's
| compressibility - each time it compresses and decompresses,
| there's serious hysteresis and you lose a ton of energy.The
| trickiest part to make in a mechanical version is the simplest
| part in electronics - the junction: Where one wire splits into
| two wires. I spent a lot of time trying to figure out how to do
| that with anything besides a fluid or a gas. Fortunately,
| planetary gear systems do the trick. Once I got that working,
| everything fell into place. Using a junction, you can easily
| make parallel circuits. Capacitors are just torsion springs in
| the spintronics model.
| [deleted]
| pontusrehula wrote:
| The heading seemed contradictory to me with both "spintronics"
| and "mechanical" in it until I realised that it is not the other
| sprintronics (https://en.wikipedia.org/wiki/Spintronics).
| Pet_Ant wrote:
| Yes I and pedantically bothered by the fact that it isn't
| really about spintronics nor electronics, but rather mechanical
| engineering and merely co-opting a more marketable term... that
| said I'll still buy a copy for my kids. Already playing
| LaserMaze with them. Even if they don't end up in stem I hope
| it helps in their A levels one day.
| https://www.thinkfun.com/products/laser-maze/
| oceanghost wrote:
| Amazing. I have a friend whose building a logic system for marble
| runs-- think and/or/xor/nor gates made with marbles. I love stuff
| like this.
| gugagore wrote:
| I am glad to see that they are using LEGO Technic chains
| (https://www.bricklink.com/v2/catalog/catalogitem.page?P=3711) ,
| and therefore the gear pitches are LEGO compatible (at least with
| the non-bevel gears, but the traditional spur gears). I am
| excited about the potential of interacting with existing Technic
| parts!
| scott-smith_us wrote:
| Ah. I wondered about their choice of chain type vs a ball/bead
| chain. Now it makes sense.
| Xunxi wrote:
| I personally find it quite refreshing to see accessible hardware
| projects showing up once again. The ensuing discussions are full
| of nuggets and somewhat esoteric recommendations that always
| draws me down the rabbit hole where I end up discovering a lot of
| things I wish I could visualize when I was much younger.
|
| Is a pleasurable learning experience.
|
| NB:This post and OpenFlexure
| ajarmst wrote:
| I was a backer for their previous project: Turing Tumble. It was
| a very positive experience, with timely informative updates and
| ultimately a high quality product.
| spoonjim wrote:
| Turing Tumble is so great.
| spoonjim wrote:
| I was going to say "this better be as good as Turing Tumble!" Now
| I see it's by the same guy. BUY
| pgboswell wrote:
| Hey cool! I made this. It's fun to see it here on Hacker News!
| jkingsman wrote:
| I took four years of engineering in university and work in
| software now, and one gif on your page made inductors click
| intuitively for me in a way that so many courses did not --
| thank you!
| elliekelly wrote:
| Is there a word or a phrase for this learning phenomenon?
| When someone is suddenly able to fully understand a concept
| that has been explained to them before but, for whatever
| reason, they just didn't quite "get" it?
| anjel wrote:
| Epiphany
| pgboswell wrote:
| Ha ha! Thanks so much!
| GistNoesis wrote:
| I'm eager to see what a memristor would look like.
| aj7 wrote:
| In my fifties, I finally figured out that the INTEGRAL
| constuitive relations for inductors and capacitors were much
| more fundamental than the differential ones. Solved virtually
| all understanding problems for me.
| jbotz wrote:
| You have a link to that gif?
| mcp_ wrote:
| I loved playing your last project Turing Tumble with my
| daughter. So I am really looking forward to your new project.
| pgboswell wrote:
| Thanks so much for the kind words.
| rkagerer wrote:
| Quick question: I noticed a Form 3 in the video. How much of
| the prototyping did you do on it?
|
| Also, I wish there were a pledge level where I'd buy one kit
| for me, and anonymously gift one to any random kid in another
| part of the world who wants one but can't afford it (kind of
| like OLPC did).
| [deleted]
| Judgmentality wrote:
| I'm only just hearing about this now but I love the idea and
| wish you great success.
| garrettgarcia wrote:
| I just pledged! My 67 year old mother got me Turing Tumble for
| Christmas and we worked through the first half of the puzzle
| book together. It was so nice to be able to explain to her what
| I do for a living with actual physical switches and marbles. I
| recommend it to everyone and anyone who will listen.
| devgoldm wrote:
| Really amazing work, well done! Having something like this when
| growing up would've made electronics so much more accessible.
|
| I can't think of anyone I know close to me that would really
| appreciate this gift, so I'm with another comment on here that
| gifting it online somehow would be something I'm interested in.
| I'd feel happy knowing I'm supporting a great product and
| helping the less fortunate of the younger generation get better
| access to fun educational tools.
| d--b wrote:
| This is great! I didnt even know there were mechanical analogs to
| electronic parts. This is going to make electronic teaching an
| awful lot mote intuitive!
| hellbannedguy wrote:
| The USA should start teaching electronics in third grade, and
| through high school. Don't even grade the kids. I think it's
| more important ever for kids to know.
|
| I pick third grade only because I was thinking about kids
| safety. I don't know when kids stop swallows stuff these days.
|
| I wonder why they don't start teaching kids important stuff
| early on, like; mechanics, finance, starting a business
| (profitable lemonade stand, and how ridiculous a permit is
| technically needed to operate, building residences. I for one
| colored to many maps, and memorized who Ecuador produces.
|
| I think in the USA electronics couldn't be taught in grade
| school is the shortage of teachers who barely understand
| electricity, and math now, but that would change eventually?
|
| I just pictured a dad from the future telling 13 year old Opie
| to fix the Tesla in Dan Akroyd voice. "Opie, but you learned
| how to properly dischge a capacitor in Miss Orliey's class?"
|
| Maybe just reading, writing, and arithmetic after all that?
| c-smile wrote:
| There are also such things as "pneumonics" and "fluidics" :
| https://en.wikipedia.org/wiki/Fluidics
|
| These are used, for example, in avia and rocket engines - in
| first or independent contours of their control systems. Such
| logic devices are very reliable, relatively simple and can work
| at extreme temperatures.
| gugagore wrote:
| There are two possible mechanical analogies to electrical
| circuits (https://en.wikipedia.org/wiki/Mechanical%E2%80%93electr
| ical_...). In domains (electrical, acoustic, thermal, mechanical,
| ...) there are two kinds of quantities, sometimes called "across"
| (voltage, temperature difference, ...) and "through" (current,
| heat, ...).
|
| My first guess was that the analogy here appears to be velocity
| is voltage and force is current, but I think I have that
| backwards. The battery, which I was taking to be a ideally a
| voltage source without internal resistance, appears to be a
| constant-torque mechanical device. Connecting it in series to
| different resistances means it spins at different speeds
| (different current is drawn).
|
| But the battery will also spin if it's not connected to
| anything... so I'm struggling to keep the analogy straight while
| thinking about how these parts behave ideally and non-ideally.
|
| Looking at the ammeter, it's definitely velocity = current.
|
| Edit: and finally direct evidence
|
| > But the most practical place for [ground] to be is anywhere
| there is zero force (i.e., voltage) on the chain.
| avhon1 wrote:
| If you scroll way far down on the campaign page, there's
| actually a table of Spintronics Physical Units:
|
| Spin Volt = 0.1 newtons
|
| Spin Coulomb = 10 meters of chain
|
| Spin Ampere = 10 meters of chain per second
|
| Spin Ohm = 0.1 newton-seconds per meter
|
| Spin Farad = 100 meters per newton
|
| Spin Henry = 0.01 newton-second-seconds per meter
|
| Spin Watt = 1 newton-meter per second
| colanderman wrote:
| Interesting, I'm curious why this analogy was chosen, and not
| the other way around. Current as torque and voltage as
| (rotational) velocity would seem to allow the junctions to be
| much simpler -- just a gang of gears on a single axle, rather
| than the differential mechanism used here -- since torques
| (like current) add at an axle/junction, while rotational
| velocity (like voltage) transmits through an axle/junction.
|
| Edit: I suppose a/the major reason is to get the resistance =
| friction analogy down. With current as torque, friction acts as
| conductance. E.g., a constant-torque/"current" motor would need
| to be held still (high friction) to prevent its speed/"voltage"
| from growing, whereas with the equivalent electrical circuit,
| you need to short the terminals (low resistance) of a current
| source to do the same.
|
| I suppose the reason for this seeming discrepancy is that, in
| an electric circuit, wires are separated by high resistance.
| But in a physical circuit, "wires" are separated by low
| friction (= not touching). Flipping around the natural behavior
| of a junction allows you to take the dual of the entire
| circuit, thus causing the behavior of resistance and friction
| to line up.
| mdiesel wrote:
| All natural systems are spring+damper. That means they're
| effected in the same way by a difference in potential
| (spring) and also resistance to rate (damper).
|
| This isn't so much analogies, more that the physics of
| natural systems means they're governed by 2nd order
| differential equations, so really do behave the same.
|
| More importantly, they're all forms of energy and
| transferable. Power=IV=Fv=TO=PQ.
| gugagore wrote:
| I don't think I understand the point you are making. Power
| = product of two quantities. You have these two quantities
| in various domains: I and V, F and v, T and O, P and Q, ...
|
| The analogizing comes from saying "I is like P and V is
| like Q", or vice versa.
|
| 2nd order ODEs are very common, and I agree that it is
| unifying to see different systems modeled by the same
| equation. But I think more fundamental than that is the
| understanding of "through" and "across" variables, the
| notion of a "port" [1], and series/parallel toplogies for
| combining two one-port components to form a new one-port
| component.
|
| You could still make an analogy between domains, even if
| you don't have second-order ODEs. This is clear even from
| your comment because, note that a spring+damper is going to
| be a first-order ODE. You would need moving mass to store
| kinetic energy, in addition to the spring to store
| potential energy.
|
| [1] https://en.wikipedia.org/wiki/Port_(circuit_theory)
| steerablesafe wrote:
| > My first guess was that the analogy here appears to be
| velocity is voltage and force is current, but I think I have
| that backwards.
|
| For at least planar circuits there is a dual circuit that is
| equivalent with voltages and currents switched. So maybe both
| analogies are correct.
|
| https://basicelectronicsguide.blogspot.com/2018/08/duality.h...
| gugagore wrote:
| When you choose to call one spintronic component a capacitor
| and another a inductor, you've determined which of the two
| analogies is the correct one. You could swap the names for
| the components, and you would swap which analogy is correct.
| prpl wrote:
| Sort of unfortunate to reuse this term which has been a field of
| study in solid state physics for a very long time:
|
| https://en.m.wikipedia.org/wiki/Spintronics
| lapetitejort wrote:
| The main difference is that spinning gears makes sense, whereas
| spinning electrons do not!
|
| (I kid of course. Spin in physics relates to inherent angular
| momentum. If you wonder why that exists, you may also want to
| wonder why mass exists.)
| whatshisface wrote:
| Intrinsic angular momentum is weirder than intrinsic mass
| because you can take it out and put it back in - although for
| most particles you're not allowed to have zero. But you are
| allowed to take 1 from an electron to go from 1/2 to -1/2. If
| that is not enough, you can go back from -1/2 to 1/2 by
| changing your basis vectors. ;)
| jacobolus wrote:
| I don't know enough physics and haven't put in enough
| effort to understand https://arxiv.org/pdf/1910.10478.pdf
| but it seems intriguing.
| whatshisface wrote:
| I thought complex phase precession was from energy, I
| don't see how it's related to spin.
| jeffwass wrote:
| Further - paired electrons can collectively form the spin-
| zero singlet state, or spin-one triplet state. In either
| case the two electrons, which are fermions independently,
| together act like a boson (eg, Cooper Pairs in a
| Superconductor).
|
| Addition of quantum angular momentum is _really weird_.
| jeffwass wrote:
| Agreed, it's an unfortunate namespace collision. Spintronics is
| a really cool area of physics, with decades of research.
|
| Electrons have spin. Although 'classical semiconductors'
| exploit the electron's spin via the Fermi-Dirac distribution in
| transistors, the actual sign / direction of the 'spin' is
| ignored in everyday electronics. Making use of this available
| spin degree-of-freedom opens up a whole wealth of new
| possibilities.
|
| Spintronics has already revolutionized certain industries (eg,
| GMR in magnetic hard drives), and there are further open areas
| of research (eg, spin as qubit basis states in quantum
| computers).
| spoonjim wrote:
| Would you say that about Apple computer, or Continental
| Airlines?
| mumblemumble wrote:
| But then, all puns are unfortunate. It's kind of their thing.
| pgboswell wrote:
| I think there's space for two spintronics. They are different
| enough that I don't think anyone will get confused.
| hexo wrote:
| Unfortunately, no. I do really think this only pollutes
| namespace. You could have picked better name without
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