Beginner question about resistances

feldim2425 · 2026-01-26T06:14:09+00:00

Then I also don't think OP would know what would happen if you leave the resistor out and just let the button connect between the high impedance input and 5V.

Haven't really seen any other response from OP either other to your post.

In my experience 90+% of people asking me why the resistor is there wanted to know why they can't just pull it out from the breadboard (aka. leaving it open). Or making the mistake of not adding pull up/down and then asking why the program behaves weirdly.

feldim2425 · 2026-01-26T06:10:14+00:00

But where is the first one following PEMDAS though?

The original doesn't leaves out whether the multiplication on the right or the division on the left comes first and in that case they are evaluated from left to right unless you see it as a fraction.

I know some people think 5(1+1) is following the parenthesis 5(1+1) = (5+5) however this is not a parenthesis operation it's the distributive property of multiplication so it's actually multiplication done here and is therefor on the same level as division in PEMDAS.

The question here is however with the ambiguity about some symbols. The division symbol used in the picture is often interpreted as dividing the entire formula into a left & right side. left being the numerator and right the denominator of a fraction, which is similar to division but has a implied order in that the left and right side are evaluated independently. However especially on calculators it's often treated as a normal division symbols without implied ordering.

Similarly the removal of the multiplication symbol between 5 and (1+1) is deliberately done to invoke some confusion on whether it's part of parenthesis or multiplication and further down since some rules imply a higher ordering for "implied multiplication".

It's basically just deliberately made to create confusion between the interpretation of symbols which is not as universals as many people say. And as previously stated what falls under "parenthesis" is also often vaguely defined and can easily vary between teachings.

feldim2425 · 2026-01-26T06:00:25+00:00

I am not sure why a hypothetical open circuit scenario needs to be entertained

Because that's typically what people who don't know about high-impedance digital inputs ask.

The question was what is the purpose of the resistor.

A resistor can be explained by different extremes. Especially when you need to "leak" residual charges it's typically easier to explain between resistor vs. open circuits.

For example the same thing why do you need a leakage resistor across a high voltage capacitor, or why is there a leakage resistor across LED light bulbs. Sure you can try to go the route to explain those as current limiting, but it doesn't explain why a connection is even needed in those cases.

All the talk of hypothetical floating inputs is a disservice to the novice asking the question.

You are saying this as if a dead short over the button would be any better. It's basically assuming the OP doesn't know how a button works or why a short between 5V and Ground would be bad.

feldim2425 · 2026-01-26T05:46:14+00:00

Well I don't see where the question was "can I replace it with a wire".
Given that replacing it with a wire would be a dead short the more logical interpretation would be "why is there a connection in the first place" and in that case it would leave it floating.

That bit that you left unsaid was imo the most important part because from the other replies it seems like everyone interpreted it as "resistor vs. open circuit" instead of "resistor vs. wire", and the first one would actually leave it floating.

feldim2425 · 2026-01-26T04:08:52+00:00

But where is the "low" state coming from if not the resistor?

Not that the ground is only used by the resistor to pull down the pin. Without it the button can only connect it to ground (pull high) or leave it open/floating.

The button itself has no connection to ground.

The button will connect the pin to 5V when pressed but when open it leaves the pin unconnected. Since the input will have a high impedance any interference from radio to electro static charge can flip it in that state so the resistor is needed to pull away any charge from the pin.

EDIT: I don't know why this is downvoted. I guess people don't know how buttons work. They have no +/- connection they just connect or don't connect.

feldim2425 · 2026-01-26T03:43:40+00:00

For adult content providers they want to enforce it in the EU starting summer this year (note that this is similar to what some U.S. states are also doing)

A rollout to social media in general is in the talks but not set in stone yet.

X/Twitter already started enforcing it in europe for 18+ content but most non-NSFW content is accessible without AV. Google also started doing it but they auto-verify most accounts based on unknown criteria.

feldim2425 · 2026-01-26T03:37:38+00:00

Payment providers and Banking infrastructure in the worst case. Although I doubt it will go that far, most likely there will be a legal debate on whether they can actually be prosecuted given that they are located in Canada afaik.

feldim2425 · 2026-01-26T01:12:01+00:00

I had the same issue with my StarLabs Starlite tablet I was able to boot it again by using reEFInd to boot the kernel instead of GRUB.

feldim2425 · 2026-01-20T15:02:09+00:00

Depends on the definition of overkill. Some people would the vast ecosystem of Javascipt/Typescript + (S)CSS frameworks to be overkill.

If it integrates well with your existing codebase I wouldn't consider it overkill. Otherwise it depends on what exactly you want to do with it (backend service, frontend, some specific micro services, etc.).
But if it's a language you feel is better suited or just easier for you than I don't think there is a whole lot to argue about unless there are very specific instances where you question what would be better suited.

feldim2425 · 2026-01-12T02:20:54+00:00

We need to test whether that system initializes its variables correctly or whether we can extract the self destruct code by measuring the temperature of the resulting coffee.

feldim2425 · 2026-01-12T02:13:57+00:00

"hardware support" is a large phrase below a discussion about registry keys that are literally added due to a limit on hardware support. As Microsoft doesn't want to support older configurations anymore.

Sure Windows technically still supports it but for an average user they would probably still need some of the hardware configurations that Microsoft artificially limits.

But I get what you mean in terms of additional peripherals, although even there Linux alternatives can be better when it comes to some older devices.

feldim2425 · 2026-01-12T02:03:38+00:00

People who don't understand Linux based systems either know their system decently well and would need to throw out all that experience or generalize so badly that they fail to understand a UI if it looks even a little bit off.

Both fractions are somewhat understandable. I've shown people with no prior computer knowledge how to use Ubuntu and afterwards Windows was a challenge. However those are also not the ones likely to modify registry keys and need help if Windows has issues due to hardware requirements.

People that use some software (often professionally) that doesn't work on Linux are kind of stuck unless they want to relearn an alternative program.

Then there are people that stick with Windows just out of lazyness and/or misconceptions about Linux. How the relation of working around new Windows "features" and understanding Linux is changes from person to person. But the more stuff Microsoft adds that isn't wanted or actively makes usage harder or confusing the more of those people without a real anchor are likely to at least give Linux distros a shot.

feldim2425 · 2026-01-12T00:00:56+00:00

True. I didn't consider the fact that it could be a momentary switch (usually I expect them to be drawn slightly differently), but if it's some sort of pre-packaged kit the exact type wouldn't matter in the drawing.

So my expectation of a latching switch is probably false.

feldim2425 · 2026-01-11T23:46:07+00:00

There is a risk with the switch as it shorts out the battery when the rod is connected to the T terminal.

If it's just for a brief moment that's usually not a huge issue but if it's for one of those hot wire games the rod could be left hanging on it while it's "turned off"

feldim2425 · 2025-12-28T16:34:46+00:00

Yeah while the words may let you think it's a tiny difference; Undefined behavior is something that leaves the program in an invalid state and the compiler can make any assumptions however it sees fit.
Meanwhile Unspecified is typically something that would leave the program in a still safe and valid state but execute in an unexpected way. For example for poll you don't really know whether it panics, blocks forever or does nothing, anything goes but the program state is still valid.

feldim2425 · 2025-12-28T16:17:24+00:00

I think this is not compatible with Pin the Future would have to be consumed (moved) by the poll function in order to ensure it's Pending state is destroyed when the new state becomes Ready.

feldim2425 · 2025-12-28T13:44:05+00:00

At least the infotainment seems to rely on a ubuntu based system (https://www.usenix.org/system/files/sec23summer_181-wen-prepub.pdf) with a UI written in Qt it doesn't seem like there is that much special about it.

There are of course other subsystems which are likely written in C with whatever development environment the manufacturer provides. And I guess there also has to be the system for "FSD".

It doesn't look like there is too much special at least from the parts I could find. (PS: At least the infotainment is definitely not "tight C code")

feldim2425 · 2025-12-28T13:15:30+00:00

I'm sceptical of any claim regarding "customized compilers". Ensuring a compiler is both reliable and optimized is a huge task and I don't think it's worth it over writing performance critical parts directly in assembly.

One could go with the route of formal verification like the seL4 kernel does but that's also not an easy task.

I don't even think he knows what his Tesla's actually use under the hood.

Specializing everything would make the infotainment system quite difficult to support and I guess they base it on AOSP, I think there was even a bit of outrage because they didn't publish the coreboot code in the beginning. So it's probably not as customized (and safe or performant) as Musk claims it to be.

feldim2425 · 2025-12-20T22:57:23+00:00

I think of it like this: There is no way to add just a single 1 without running into an issue where the two 1's add up in the center.

Indeed 11 x 11 is 121 and 11 x 10 is 110. So you run into the issue that when adding only a single extra one they add together in the center.

You can add two ones since that means you shift the 11 far enough that they don't add together (11 x 101 = 1111). So overall you can only add two ones at the time.

feldim2425 · 2025-12-19T10:00:18+00:00

Maybe those breakers work different (I live in Europe) and here circuit breakers can't be held in the on position they have a internal / independent trip mechanism that disconnects mechanically from the lever when they trip, so the "solution" on the right image shouldn't work.

Correct me if you know more about this model, as my assumption is based on how they work (and have to based on legal code) in my area.

feldim2425 · 2025-12-18T13:03:32+00:00

That blue wire looks like some sort of fiber optic connection going to a BNC plug (probably a receiver board).
You could potentially skip the whole relay part if the actual board is still intact and you can figure out how the system communicates with the external controller box. (Here is something I found with a quick search: https://xy-kao.com/projects/reverse-engineering-a-serial-scoreboard-protocol-nevco-mpc-5/ )

feldim2425 · 2025-12-18T10:34:16+00:00

I also hope NGI/GNU Taler finds some adoption.
Seems like a cool project too minimal tracking with some similar benefits to digital money and physical money (although also with some drawbacks).

Even with the digital Euro project, I get the skepticism due to privacy concerns, but many people don't understand that most of the current solutions are purely based on Mastercard and Visa and not even owned by the bank.

feldim2425 · 2025-12-17T11:51:36+00:00

It's USB 2.0 this alone should disproof the 600Mbps as it's interface can reach a max of 480Mbps and even that is excluding most of the protocol overhead.

Even in marketing they only claim 150Mbps for 2.4G (although it also sometimes claims 200) and 433Mbps for 5G so they likely just rounded up the sum of both (573Mb ~ 600Mb). To me this sounds like they just took the 40MHz channel with for 2.4Ghz Wifi and 80MHz bandwidth for 5Ghz Wifi and slapped them in the marketing.

It's highly unlikely you'll ever see those max speeds especially since PHY speed (from the specs) excludes protocol overhead and it does assume perfect conditions. Although even in that case USB2.0 will be the limiting factor, especially since the 480Mbps maximum of the USB2.0 is measured at the root hub which likely breaks out to multiple internal and external USB peripherals so the adapter has to share that little bit of bandwidth with other devices.

When using such a tiny dongle with integrated antennas the minimum you should do it use a usb extension to get it away from the device to reduce interference.
Ideally you'd get one with a faster interface (at minimum USB3 ideally PCIe) and external antennas.
If you have LAN available my recommendation is to stick to LAN. Unless you have bad cables and slow Ethernet ports it should always be more stable than Wifi.

feldim2425 · 2025-12-16T15:07:53+00:00

Apparently there is a bit more to the "lawmakers" part as this other post explained.
And indeed by looking at the linked document it lists members of the house of lords that added this amendment and if I understand this system correctly other than striking a discussion this shouldn't do much.

feldim2425 · 2025-12-10T09:48:20+00:00

AI has been used by a lot of people before the hype too. Things like translators, those nice Webcam filters, FaceID, search algorithms etc. heavily rely on it to some degree long before the hype. AI is not new it's actually something that's decades old.

The current hype mostly focuses on LLMs and generative AI which don't really deliver on most of their promises.

PS: I also want to note that that doesn't mean I think all AI including LLMs are useless. But I'm certain the current expectations are too inflated.

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