litchralee @ litchralee @sh.itjust.works

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2 yr. ago

You might have a house at the end of the mortgage. You'll definitely have the land, but the house and its paint only grow older, its plumbing and utilities more dated, and its interior design antiquated. Upkeep of an owner-occupied home comes with a lot of "weekend projects" that would otherwise be the responsibility of the landlord when renting. For those able and willing, that's fine. But it's not for everyone, and all should enter homeownership fully informed.

To be clear, I do think homeowner should be a realistic prospect for most people, but the notion that paying rent is equivalent to throwing it down the drain requires falsely assuming that one's time is low-value, that homes aren't depreciating assets, and that all land becomes more desirable and thus appreciates over time. Many communities in the Rust Belt, USA demonstrate the latter point.

I think I understand what you're trying to do, but I'm having trouble parsing this sentence:

The big issue is that the interface on the bridge the virtual node is connected to is created on the fly when you connect the node to the external connector

I am obliged to mention The Three Body Problem and the rest of the trilogy, by Liu Cixin. It's an excellent work of 21st Century sci-fi; I haven't watched the TV adaptation though.

Does a webcomic count as a franchise? https://satwcomic.com/

And here are all of France's appearances: https://satwcomic.com/the-world/france

No, I want a decentralized go-to place that I can check many points of view over a subject, just like the Fediverse works today.

I disagree with the premise that multiple POVs on every topic will yield better understandings or discussion. It is the same flaw that Ground News or other services have, which purport to curate POVs from different news media outlets, with the implicit assumption that all the outlets have something useful to offer. This assumption is absolutely balderdash.

The Fediverse is no more -- or less -- immune from disinformation and other ails, but has better user- and instance-level protections: bans and defederation are effective, because if they weren't, people here wouldn't log back on. For Mastodon and Lemmy and other forms of social media, the decentralization has clear and obvious benefits.

A decentralized knowledge-store does not.

There is nothing to fear.

There is everything to fear when knowledge is spread out into small libraries across the land. The historical analog is book-burning incidents that dotted human history, whether to suppress paganism, Mayan culture, or the spread of communism. The modern-day analogy is when Vine went defunct and the content was almost wholly lost to the world. The Fediverse example is when an instance unexpectedly disappears, stranding all its users.

But focusing on a knowledge-store, technology has given us the ability to copy data at rates that outpace all of history's ecclesiastical scribes put together. We can -- and do -- preserve the largest datasets (see !datahoarder@lemmy.ml) because it is a matter of resilience. Yet that endeavor has become more difficult precisely because of technology. The Internet Archive faces this issue, because they cannot save what they don't even know exist or cannot see it.

The Fediverse inhabits a very special Goldilocks zone right now, not unlike Wikipedia, where the availability of interest, capabilities, and materiel allow for the existence of this internet experiment. But fragile it is, and instances are no further from risk than by a DMCA notice, a UK age restriction law, a frivolous but expensive SLAPP suit, or just plain ol running out of money.

If I had spare time and energy and were presented with the options to either: 1) set up a decentralized knowledge store of nebulous benefit, or 2) support the online compendium which I've personally used for over two decades now and has helped untold numbers of students and researchers with starting the research into a new-to-them topic, and could do so by using my servers to seed the all-Wikipedia torrents... well, I think the choice is clear.

As a website or service, sure. But the Wikipedia has been available to download for offline use since basically its inception. This is how users in places with poor internet connections can still benefit from the Wikipedia. Certainly, the idea of distributing Wikipedia on disc is a bit odd.

But whether it be smuggling books across the Iron Curtain, downloading swaths of paywalled scientific papers from an MIT computer, or accessing information about abortion, the pursuit of knowledge is a chiefly human trait and one not easily suppressed. But if all those, the Wikipedia has the best track record for being openly available and free (as in speech, and as in beer).

Anyone -- not just the Wikimedia Foundation -- can protest a proposed age restriction against Wikipedia by sending out enough Wikipedia CDs that would rival AOL's 1990s campaigns. So too could one print a physical volume, just to prove the point that anti-proliferation of information is a lost-cause.

I think we need to start with what Wikipedia is meant to be, before even considering whether it would be aided through federation. By their own words:

Wikipedia's purpose is to benefit readers by acting as a widely accessible and free encyclopedia; a comprehensive written compendium that contains information on all branches of knowledge.

Encyclopedias are designed to introduce readers to a topic, not to be the final point of reference. Wikipedia, like other encyclopedias, is a tertiary source and provides overviews of a topic.

Content is governed by three principal core content policies – neutral point of view, verifiability, and no original research.

That describes the content intended to go into the Wikipedia, but we need to also mention the distinction between the Wikipedia itself, the MediaWiki software package which powers Wikipedia, and the Wikimedia Foundation.

With MediaWiki, which is FOSS (GPLv2), anyone can set up their own encyclopedia-style volume of articles to host on the web. And that's exactly what many fandom websites or technical documentation websites do, because that level of detail would not be accepted into the general-knowledge Wikipedia. And you can hardly blame the Wikipedia for wanting to avoid scope-creep.

Likewise, if someone disagrees with how a topic is discussed in a Wikipedia article, they can go in and make the change, provided that they follow the same rules and procedures as everyone else. Yes there are moderators, but even moderators can be moderated. In a way, Wikipedia is a collective effort that somehow democratized editorship and it's shocking that it hasn't devolved into major terf wars.

And that's where the Wikipedia Foundation comes in. They are both the charitable foundation that keeps the Wikipedia servers running, as well as administering the collection, much like how a museum protects cultural treasures. Dissatisfaction with the limited role that the Foundation plays can be solved by forking the Wikipedia; they don't assert a monopoly on the collective knowledge, and indeed the entire thing can be downloaded for offline use or to host a mirror under separate administration.

With all that said, Wikipedia as a concept hews very closely to the print version of an encyclopedia. It is functionally a really big book, painstakingly edited by untold numbers of people. The fact that it's not just a bunch of random blog posts is its strength. Wikipedia is not social media; it is distributed editorship.

But supposing you do want a distributed knowledge base, where there might exist multiple versions of an article, please explain why the World Wide Web doesn't already accomplish that. People have been writing their own thoughts since the 1990s. If the WWW is too general-purpose for your liking for knowledge articles, then perhaps something like the DICT protocol is more palatable?

Despite ostensibly dealing with dictionaries, DICT has been used to offer the CIA World Factbook and the Jargon File, which are more like subject-matter specific encyclopedias. As a standardized protocol -- even CURL can fetch DICT entries -- the Fediverse doesn't need another protocol to do the same thing.

I personally think there is value -- a lot of value -- in the Wikipedia, precisely because of what it's not. Wikipedia is not a place to express opinions, it is not a popularity contest of ideas, and it is not a space untethered from facts and logic.

Battery electric trains can resolve a lot of the technical conflicts, since a battery averages out power demanded from the electric network. But then you need to figure out the logistics of where trains would charge (eg layover in some towns with good electricity connections) and what the battery capacities might be for your story. If we say batteries are now 10x more efficient in 100 years, then that basically solves most of the difficulties.

But we don't even need the batteries on the train. With such efficient battery technology, it would be entirely feasible to connect to a neighborhood distribution circuit, with a track-side battery that slow-charges from the grid. Then when the train whizzes by, the track-side battery dumps power onto the overhead line, which powers the train.

This latter idea is entirely feasible today but the sheer number of batteries is what makes it impractical or financially impossible. Hence why if batteries became 10x more efficient, then the idea can be implemented.

Phrased another way, to build a trackside battery in 2025 would likely take a lot of skilled engineers to build a structure about the size of one or two houses, then fill it with batteries that hopefully don't explode or catch fire. But in 100 years, the advanced battery tech for a trackside battery could conceivably fit the same capacity into the space of one of those roadside green utility boxes. And that would be a lot easier to install in a fictional future where the country is rebuilding at a grass-roots level, when large-scale coordinated engineering might not be possible.

The two major factors for vehicle energy consumption -- rail or otherwise -- are rolling resistance and air resistance. For rolling resistance, this primarily means the weight of the vehicle, because the rolling resistance is proportional to the force on the wheel bearings. And that goes up with weight.

So if you had a 40,000 lbs bus versus a (very light) 40,000 LRT car, then the rolling resistance will be similar. That said, the next biggest factor is rubber tires vs steel wheels. But since this is a converted bus for use on rails, that becomes very similar. The third factor is the number of wheels that the weight is spread over. A bus might only need four wheels touching the rails. But an LRT car might have two bogies, so maybe 8 wheels. So there'd be more resistance just because of the number of wheels, even if the LRT car weighed the same as the bus.

For air resistance, it's mostly a matter of frontal cross section and then "skin effect" along the surfaces that the air blows past. Buses and trains are mostly about the same cross section, assuming a single level bus and a single level railcar. For the skin effect, a longer railcar has more "skin" on its sides than a bus.

So overall, yes, a bus on steel wheels will likely need a lot less power than an LRT car, due to being shorter and lighter. But we need not stop with my mere speculation: San Francisco and other places still have trolley buses, which are rubber tire buses powered by overhead line. So you can probably look up the power requirement for these buses and get an idea of the power system required.

And because a converted bus sits on steel wheels and would run on gentler slopes than hilly San Francisco, it would be reasonable that a lot less power than a trolley bus would be fine in your story.

Alternatively, the trains can just run slower, since that reduces the power draw as well. But that could limit your plot, since it means rural trains might be substantially limited in speed, only due to insufficient power. Which could tilt the story into one of rebuilding the electric system, which I suspect isn't what you had in mind.

I like it!

I once endeavored to do something similar, but it would have been for opening the blinds in the morning and closing them after sunset.

But could this comparison not be done with some hysteresis?

It can, but analog design is also not my forte.

The part count is not important as long as the parts aren't terribly expensive, since this is exclusively for my personal use

In that case, the original suggestion of using an ADC and an op-amp would be the most flexible for software. You would, however, need to do some research on wiring an op-amp to amplify the sense voltage to something your microcontroller's ADC is capable of resolving.

One other thing I wanted to mention is the complexity of supplying power to overhead lines. This is based off a thought experiment I had long ago, about whether a municipality could "grow into" an electric rail network, by initially underprovisioning the power system until more trains in service demanded that upgrade. My conclusion was that no, it doesn't quite work like that. These are my observations.

The primary issue is one of raw power. That is, delivering kilowatts over wires that could be very long. We can consider Denver's commute train operation, which specifies mainline speeds (>79 MPH), 25 kV AC power, and an output power of 620 HP (456 kW).

That 456 kW is the focus, since that's generally what's needed at either peak acceleration or at top speed. We should assume that overhead lines should not wreck themselves just because a train is running hard.

If there's only one train on an overhead line segment, then the power requires is the same as one train's draw, which is 456 kW here. The problem is that compared to what's typically provisioned for a home (200 Amp, 240v service; aka 48 kW) or a light commercial business (400 Amp, 120/208Y service, aka 144 kW), this is a massive amount of power.

And even when a power company does supply a neighborhood of homes or a commercial district, they use oil-filled transformers that can be intentionally overloaded by some 30-50% for hours, on the premise that peak electric loads would die down afterwards and the transformer can cool down. Also, not every home or business uses anywhere near full power, so transformers are also undersized accordingly.

But for a single train, the need for that 456 kW is very real, very present, and if the overhead line is even 10 miles, that's 8 minutes if the train passes through at 79 MPH. If only one train passes per hour, the average power is only 60 kW but I don't think any transformer rated for 60 kW could survive an overload of 456 kW for 8 minutes and cool down for the next 52 minutes. That oil will have boiled by then.

So in reality, to provision power for just one train per hour, the transformer has to be rated for something closer to 200 kW. An entire suburban subdivision might total up to 200 kW depending on the time of day, and somehow the power company would need to supply this to wherever the railroad's power conversion equipment is.

So in your story where different communities are working to rebuild tracks and electrify, the latter effort has some gargantuan hurdles. The nature of the electricity network precludes attaching a 200 kW transformer to any random point in the network. A residential neighborhood might be fed with a 7200v 600 Amp ring circuit, which also connects to adjacent neighborhoods. Attaching the transformer to this circuit would work, but it would singlehandedly be 5% of the ring capacity. And the ring has to be nearby the railroad's power equipment. So stringing new high-voltage power lines toward the railroad is highly likely.

And this plan isn't even great, because the train passing would cause a lot of issues for the neighborhoods' electricity voltage stability. There's also the problem of supplying 7200v (called "low voltage" in the industry) if the overhead lines are meant to be 25 kV. Converting voltage up at the consumer point is generally not a good idea for efficiency, so a realistic rail power system would need to attach to medium voltage (eg 36 kV) or high voltage wires. So now our transformer needs to be located somewhere near such wires, and also will cost more because of the high voltage rating. High voltage wires are only placed where they are by necessity, because they're awfully dangerous otherwise. Some communities may be miles away from the high voltage lines that eventually power their homes.

In terms of technical requirements, this is rapidly getting out of hand, and I cannot see how a community smaller than say 50k-100k people would have the electricity resources and knowledge to build out an electric rail supply. And it only goes up as this piece of track gets more trains per hour.

If your story does wish to hew towards the almost-insane engineering for electric rail systems, it might be worth examining how Caltrain in the California Bay Area electrified their 50 mile corridor, between Silicon Valley and San Francisco. IIRC, they needed 10 power transforming stations along the route, with special engineering for each one of them.

Overall, this is why rural areas (and even semi-urban) don't tend to have electrified rail, despite having electricity service for streetlights, homes, and retail. Because they really just can't do it.

Out of curiosity, what is this project?

Ah, I entirely missed the sense pin when skimming the datasheet.

That said, using a shunt for an inductive load like a motor may have to contend with the corresponding spikes caused when switching the motor. This just means the thing doing the sensing needs to tolerate the spikes. Or mitigate them, with either a snubber or a flyback diode (is this actually doable with an H bridge?).

As for the op-amp and ADC, if we already accept the additional of the op-amp part, it is also feasible to instead use a comparator with a reference voltage set for the max safe current. The digital output of the comparator can then be fed directly to the microcontroller as an interrupt, providing fast reaction without the sampling time of an ADC. But this would be so quick that the spikes from earlier could get picked up, unless mitigated. It also means software will not know the exact current level, other than that it's higher than the threshold set by the reference voltage.

Still, these solutions are adding to the part count. If that's a concern, then I'd look for a motor driver with this functionality built in.

Sadly, the original source article is: 1) paywalled, and 2) in Dutch, but it wasn't immediately obvious to me if the linked article is using "fatbike" in reference only to electric fatbikes. That would certainly make more sense, since the quotations primarily seem concerned with speed. And as you said, acoustic fatbikes are not fast. It could be a translation issue.

The only mention of size/mass being an issue seems to be for large cargo ebikes, which I imagine is referring to boxy delivery vehicles that crowd out the bike paths. Eg UPS, DHL, Amazon parcel ebikes.

At least that's what I would think is what's happening. Considering how many people in Dutch cities rely on the bike infrastructure, it would make sense to designate more space for bike-adjacent transport by taking space from the road (as in, automobile lanes).

I would hope that if municipalities are empowered to prohibit motor-assisted ebikes from the existing bike network, then they should also have to carry the obligation to build a secondary network of hard infrastructure using space from roads that have traffic speeds above 30 kph.

The demand for electric bikes is clearly there; it is infeasible and illogical to make them disappear by a mere prohibition. The demand for parcel delivery bikes is there, and prohibiting them would only exacerbate automobile traffic. Hence, the Dutch should do what they've always done: build their way out.

In that case, I would suggest looking at a different motor driver. The driver you've specified doesn't seem to have any provisions to detect a motor stall, which is something that other drivers can potentially do. Ideally, the driver would detect the back EMF from the stall and inform the microcontroller, which would then decide to stop movement.

An external current sensor might work, but that's adding to the part count and might not be as capable as built-in functionality within the motor driver. Plus, fancier motor drivers have some neat features that you could take advantage of as well. I think it would be more prudent to consider a different driver before adding additional parts.

With regards to the UK regulatory structure for ebikes and where they blur into other categories, it seems that the UK has a "missing middle" situation: there's nothing legal that is quicker than a 25 kph (15.5 MPH) ebike other than a "S-pedelec", moped or motorbike, all of which require registration, licensure, and insurance. I'm unreliably informed that insurance is a major impediment in the UK, because of the broad criteria that insurers can use to set rates.

To that end, I think a regulatory change would be to loosen the burden for "S-pedelecs". For reference, I say "S-pedelec" to mean a 45 kph (28 MPH) pedal-assist ebike, with a 250 W or 500 W power limit, making these almost comparable to American Class 3 ebikes. In the UK, the insurance requirement should be dropped outright, and the registration requirement reduced to a "plate" requirement, kinda like how California requires mopeds to pay a one-time fee to obtain an identification plate. This would directly address the supposed issue of snatch-and-run incidents using ebikes, and while I don't agree with the whole surveillance state thing going on in the UK, they've already set the precedent for this with the rest of the regulatory system.

In terms of rider training, I'm not entirely certain what to suggest. By far, the rest of the world has better road education than here in the USA, so I'm reluctant to suggest a "laisse-faire" approach where UK S-pedelec riders need zero qualifications to ride. In California, we are still coming to grips with whether our Class 2 ebikes can be safely ridden by children, premised on the somewhat shaky assumption that they're as easy to control as an acoustic bike. So with all that said, I could vaguely see changing the requirements so that S pedelec riders need some form of UK license to ride, so at least riders will know the road markings and intersection priorities.

It is fairly well-documented that American youth -- despite being surrounded by unshakable car culture for a thousand miles -- are less interested in a driving license than ever, and I imagine the same is true in the UK where driving an automobile is even more expensive and prohibitive. But I would hope that perhaps UK youth have a higher propensity than American youth at pursuing a motorbike license, and then using that to ride a cheap S-pedelec, if the regulatory changes I've proposed were to take shape.

My main gripe is that without a smooth gradient in personal mobility regulatory requirements, there is no cognizable difference between an S-pedelec, moped, or motorcycle today in the UK. There has to be some sort of distinction, or else people will either: 1) decline all options, or 2) ride illegally.

I harbor no airs that the California regulatory structure is perfect -- it dang well isn't -- but at least I can envision plausible two-wheeler scenarios for a 6-year old, a 16-year old, a 26-year old, and a 66-year old, given the breadth of permissible two-wheelers here and how the skills and training stack up. But in the UK right now, there's a huge chasm between riding an acoustic bike as a child, and then.... nothing for young adult transportation.

Do I understand the inquiry is for how to build a line-powered electric, single railcar by retrofitting? In terms of engineering complexity, starting with an EMU and cutting it down to a single railcar would work.

If not that, then a battery electric railcar would work as a base, since it would only need the line power equipment (eg pantograph, trolley pole) added, and disabling/removing the battery pack.

If not that, then a diesel railcar -- or DMU and cut it down -- and swap the diesel generator for line power equipment. The criteria is that for any self-propelled vehicle -- rail or otherwise -- having to reconstruct the propulsion mechanism is a big ask.

For that reason, the conversion of an unpowered railcar -- like a passenger coach or a freight wagon -- is way down the list, as any existing vehicle with propulsion makes for a better starting candidate.

So well before that, we would look to putting other land vehicles onto the rails. A motorcoach bus is a good candidate, but if hauling unpowered wagons is allowed again, a tractor-trailer cab (aka 18-wheeler) could be electrified and then tasked with pulling a consist of trailers converted with passenger seating.

I wish to reiterate that the effort to add a drivetrain to an unpowered vehicle is very high. Some vehicles might not even make this possible: imagine starting with a wellcar. There wouldn't be any room to put the drive motors near the bogies, without cutting and modifying the frame. And then it would need an operator cab, overhead power equipment, all manner of electric wiring, and so on. And that would still only yield a freight self-propelled railcar. More work would be needed to bring this into passenger service, unless the passengers are fine riding on an open car.

I don't think there's a good way to adapt this circuit to provide current limiting on the 18v rail. Supposing that it was possible, what behavior do you want to happen when reaching the current limit? Should the motor reduce its output torque when at the limit? Should the 18v rail completely shut down? Should the microcontroller be notified of the current limit so that software can deal with it? Would a simple fuse be sufficient?

All of these are possible options, but with various tradeoffs. But depending on your application, I would think the easiest design is to build sufficient capacity on the 18v rail so that the motor and 5v converter inherently never draw more current than can be provided.

Only a hub motor before, and that was just to replace the feeder wires. This was a step up in complexity.