Admit your Brain lock - Page 1
Forum section: electronics / general

author: mkiijam
author_rank: Regular Contributor
timestamp: March 28, 2024, 06:52:32 pm
content: We all have them. Areas that we just can't seem to get our head around. I've been repairing electronics for almost 30 years, but transistors still baffle me. It's not because I don't get or can't get the concept. And not because I haven't read up on them, which I have about 100 times. For some reason, the info just doesn't seem to stick. I find myself having to re-read the basic function articles AGAIN.Put it this way, I have junior techs that I show the ropes and answers questions from, and I wince at the day or times where they ask me how a transistor works beyond what the answer of "amps signals" or "switches" will satisfy them.Anybody else? Brain locks?

author: coppercone2
author_rank: Super Contributor
timestamp: March 28, 2024, 06:57:59 pm
content: the PFC. Suddenly your taxes turned into multinational government affiliated enterprise levelI am supposed to do this why, for the sake of the power company???you think I can figure out if its going to work well in japan???

author: Halcyon
author_rank: Unknown
timestamp: March 28, 2024, 11:44:16 pm
content: Regular expressions.

author: coppercone2
author_rank: Super Contributor
timestamp: March 28, 2024, 11:54:29 pm
content: also IEC connectors. I wired probobly at least 100 of them in various things with solder and crimps and I never remember which pin is what.Transistors are not easy either. My first projects were with diodes. Easier, until you have alot in feedback loops, then they are awful

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 28, 2024, 11:58:28 pm
content: Taxes, and a large part of quantum physics.

author: joeqsmith
author_rank: Super Contributor
timestamp: March 29, 2024, 12:41:56 am
content: Ladies.

author: xrunner
author_rank: Super Contributor
timestamp: March 29, 2024, 12:46:33 am
content: Saved me typing -Quote from: joeqsmith on March 29, 2024, 12:41:56 amQuote from: SiliconWizard on March 28, 2024, 11:58:28 pm

author: Smokey
author_rank: Super Contributor
timestamp: March 29, 2024, 01:07:01 am
content: I have a mental model for this... (... I'm not a neuroscientist.. so don't listen to me...)Think of your brain as a big filing cabinet full of organized file folders (or a relational database, or something of that nature). Every new bit of information gets put in some folder, but it's significantly easier to put information INTO a folder than it is to move it to another folder afterwards.There is unfortunately one big folder labeled "I don't understand this", which links to nothing else. Once you put something in the "I don't understand this" folder it's sort of stuck there until you exert a huge amount of effort to move it.With that in mind, I try to make a conscious effort if it seems like something might be important or useful not to just initially toss it into the "I don't understand this" folder. The "mental purgatory" folder is better than the "I don't understand this" folder... and there are still some things that I feel will forever be stuck in the "I don't understand this" folder... like regular expressions...

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 29, 2024, 01:36:27 am
content: That will be okhttps://www.freecodecamp.org/news/practical-regex-guide-with-real-life-examples/

author: Halcyon
author_rank: Unknown
timestamp: March 29, 2024, 02:58:36 am
content: Quote from: SiliconWizard on March 29, 2024, 01:36:27 amThe most frustrating thing about regex is that there are so many different "flavours" of it. Then of course you have Microsoft who implement regex in their mail flow rules entirely differently to everything else.

author: pcprogrammer
author_rank: Super Contributor
timestamp: March 29, 2024, 07:38:31 am
content: Quote from: xrunner on March 29, 2024, 12:46:33 amOnly with some slight differences.Not just Ladies, humans in general.I understand why taxes are needed, but some are just plain theft. Like inheritance tax, why does the government feel that they are entitled to take a slice from money that people have carefully saved and already paid taxes for. Same as with donations. I someone gives me money the government has nothing to do with that.And why all the complex rules that make it so hard to fill in your tax forms. Must be to keep employment up. Otherwise no need for the accountants.

author: switchabl
author_rank: Frequent Contributor
timestamp: March 29, 2024, 12:47:08 pm
content: Quote from: pcprogrammer on March 29, 2024, 07:38:31 amUnless you have actually failed to understand/retain relevant theories of distributive justice (like Rawls'), rather than just disagreed with them, this seems like a bad example.For me, I'm having a hard time with music theory, the finer points of harmony in particular.On the topic of transistors, on a behavioural level, IMHO the key is not just read about but 1) analyze circuits yourself, lots of them, starting with the basic ones, on paper; small/large-signal, input/output impedances, gains, distortion, diff/common mode... 2) design some transistor circuits, again starting with simple ones (again on paper, then verify with SPICE). On a fundamental level, beyond simple drift-diffusion models, frankly the first step is to get a graduate degree in semiconductor physics. Most people don't need that.

author: Andy Chee
author_rank: Super Contributor
timestamp: March 29, 2024, 01:03:35 pm
content: For me, Karnaugh maps and Smith charts.

author: tszaboo
author_rank: Super Contributor
timestamp: March 29, 2024, 01:27:11 pm
content: Object oriented code. Not using it, writing it. And callbacks.If any of those come up, I just say: "Screw this, someone else will write that code."Quote from: Halcyon on March 28, 2024, 11:44:16 pmI won't even attempt that. My time is better spent on literally anything else.

author: Bud
author_rank: Super Contributor
timestamp: March 29, 2024, 01:55:47 pm
content: McDonald's burger ads. No matter how many are pushed on me they do not stick.

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: March 29, 2024, 03:02:11 pm
content: Why there's something rather than nothing.

author: temperance
author_rank: Super Contributor
timestamp: March 29, 2024, 03:52:22 pm
content: QuoteI think it is the way they are being explained together with mostly useless bad examples and how good or bad you are at reading function pointers. If the latter is not your language (that's becoming good at reading backwards), try to experiment with them and you will probably start to write callback functions without realizing to solve some problems.

author: tggzzz
author_rank: Super Contributor
timestamp: March 29, 2024, 04:39:07 pm
content: Quote from: Halcyon on March 29, 2024, 02:58:36 amYes, just like logic families, types of opamp, resistor, ....Digital hardware people always hanker after creating a better microprocessor. Few actually do, fortunately.Software people always hanker after creating a programming language. Too many end up creating scrotty little Domain Scripting Languages (DSLs), of which regexp languages are a subset. At least regexp languages are useful for command-line arguments, but 99% of things written in a DSLanguagewould be better written in a DSLibraryin a traditional language.My brain lock: electromagnetic theory.

author: nctnico
author_rank: Super Contributor
timestamp: March 29, 2024, 04:47:36 pm
content: My brainlock is not about technical stuff but why people do bad things to others and/or themselves.

author: mkiijam
author_rank: Regular Contributor
timestamp: March 29, 2024, 05:14:03 pm
content: On my Transistor issue:Here it is cause it just happened again with an NPN. Does the transistor "START" to conduct with the .7v on its base or is it fully on with .7? I think my brain lock is the voltage range at which it amplifies and isn't just a switch?

author: switchabl
author_rank: Frequent Contributor
timestamp: March 29, 2024, 05:15:52 pm
content: Quote from: tggzzz on March 29, 2024, 04:39:07 pmThere are alternative formulations like VerbalExpressions (https://github.com/VerbalExpressions/PythonVerbalExpressions), although I would argue that this is still a kind of DSL, just a more verbose one. Which one is clearer will vary depending on the complexity of the expression, as well as personal preference/familiarity.Can you give an example of a pattern-matching library with flexibility comparable to regular expressions with a different approach?

author: fourfathom
author_rank: Super Contributor
timestamp: March 29, 2024, 05:38:02 pm
content: Quote from: switchabl on March 29, 2024, 12:47:08 pmMe, it's philosophy like the above. Or most philosophy, once it get's much beyond "Do unto others as you would have them do unto you", and even with that there are outliers. Actual people are way too complicated.But that's my personal Brain Lock.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: March 29, 2024, 07:00:45 pm
content: For me it is 'DECIBELS'.

author: IanB
author_rank: Super Contributor
timestamp: March 29, 2024, 07:17:59 pm
content: I don't think I have ever failed to learn about something that I have tried to learn about. But often the learning doesn't work without lots of practice in applying it. Which means learning things successfully takes significant effort.On the other hand, there are things like general relativity or quantum physics that I have not tried very hard to learn, and have not dedicated the time or effort required. So they remain somewhat as mysteries to me.As I get older, I feel I have a limited capacity to learn new things, and have to be selective. It's like my brain is filling up. I feel that if I try to learn too much new stuff, my brain is probably going to erase old stuff to make room.

author: pcprogrammer
author_rank: Super Contributor
timestamp: March 29, 2024, 07:26:25 pm
content: Quote from: switchabl on March 29, 2024, 12:47:08 pmThere is a difference between fair sharing based on income and wealth while paying taxes during your life, and taking a, sometimes big, slice of the pie that is often intended to make the life of loved ones better.How is it fair that frugal people are penalized to cater for the willy nilly behavior of people that can't balance their checkbook, the government included for that matter.And just like fourfathom, though I can wrap my brain around it somewhat dislike philosophy.Quote from: fourfathom on March 29, 2024, 05:38:02 pmI always thought it was the negated saying that is used. Boils down to the same though. "Don't do upon others that what you don't want done to you". The Dutch phrase is "Wat gij niet wilt dat u geschiedt, doet gij dat ook een ander niet".Recently a lot of dash cam shorts pop up in my youtube feed showing idiot who break check trucks. Most of them get rear ended and then scream hell about it.Can't wrap my brain around that. How stupid can you be?

author: tggzzz
author_rank: Super Contributor
timestamp: March 29, 2024, 07:36:17 pm
content: Ooooh! Politics!10, 9, 8, ...

author: pcprogrammer
author_rank: Super Contributor
timestamp: March 29, 2024, 07:37:51 pm
content: Quote from: tggzzz on March 29, 2024, 07:36:17 pmNah Philosophy.

author: tggzzz
author_rank: Super Contributor
timestamp: March 29, 2024, 07:38:49 pm
content: Quote from: pcprogrammer on March 29, 2024, 07:37:51 pm7, ...

author: Smokey
author_rank: Super Contributor
timestamp: March 29, 2024, 07:59:52 pm
content: Quote from: nctnico on March 29, 2024, 04:47:36 pmhttps://www.amazon.com/Thinking-Fast-Slow-Daniel-Kahneman/dp/0374533555/https://www.amazon.com/Righteous-Mind-Divided-Politics-Religion/dp/0307455777/

author: temperance
author_rank: Super Contributor
timestamp: March 29, 2024, 08:57:42 pm
content: QuoteIf a transistor has 0.7 V across it's base emitter junction indicates that the BE diode is forward biased if the base more positif than the emitter in an NPN transistor. That's often enough to know if a circuit works or not. But it doesn't say anything about the state the transistor is in. If a transistor is biased into the linear region or saturated depends on the collector emitter voltage.Why doesn't the BE voltage doesn't mean anything? To understand that you must understand a concept called dynamic resistance. For a forward biased diode, the dynamic resistance is the variation in forward voltage / variation in forward current. In a textbook ideal diode this resistance is zero. For a real diode it can be something 10...70 Ohm.Although the BE voltage varies with changing base current it is the base current which translates onto a collector current. The collector current is Hfe x base current. The base emitter voltage depends on the circuit configuration and is simply calculated with ohm's law.A second concept to you have to understand is current sources and current sinks. If that concept is not understood, you will have a very hard time understanding transistors.I found this for you:Dave explaining voltage and current sourcesw2aew explaining transistor biasingIf you understand the current sink concept explained here you will be good to go. (that is, the collector current doesn't change when changing the collector resistor within the limits of the circuit)

author: temperance
author_rank: Super Contributor
timestamp: March 29, 2024, 09:02:04 pm
content: QuoteThink about the mathematical concept called average and now translate what that means to a populations IQ.Edit: break checking someone is stupid but taking advantage of that fact that you have a webcam to prove that someone was break checking you is equally stupid in many ways.

author: switchabl
author_rank: Frequent Contributor
timestamp: March 29, 2024, 09:06:42 pm
content: Quote from: pcprogrammer on March 29, 2024, 07:26:25 pmI really don't want to argue one side or the other here. Just that "I can't get how taxes are fair" doesn't seem to be in the same category as "I can't get how transistors work". At least assuming that the first one is mainly an expression of opinion rather than saying you repeatedly tried to study the concept of fairness and couldn't make sense of it.Actually, the latter has definitely happened to me with some philosophy texts. Sometimes because I really couldn't figure out what they were trying to say (mostly 19th century stuff) and sometimes because they were very complicated and abstract and I didn't have the motivation to really dig in (mostly analytic philosophy). But others have really helped me structure my thoughts better. As well as provide some perspective and humility because usually the best arguments I can come up with have already been made (and criticised) a long time ago, in a much clearer and more detailed way.

author: unseenninja
author_rank: Regular Contributor
timestamp: March 29, 2024, 09:07:41 pm
content: Quote from: IanB on March 29, 2024, 07:17:59 pmIt does, trust me. For every new thing I learn, something gets forgotten.My block is that I just can't get my head around joins (plain, inner and outer) in SQL.

author: TimFox
author_rank: Super Contributor
timestamp: March 30, 2024, 12:10:26 am
content: Quote from: mkiijam on March 29, 2024, 05:14:03 pmStart with a NPN transistor with, say, +5V connected from the emitter to the collector through a current meter.If youcarefullyandslowlyincrease the BE voltage from 0 to roughly 0.7 V, the collector current increasesexponentially, reaching a “typical” current value for Vbe approximately 0.7 V.The current increases rapidly, but not discontinuously.

author: pcprogrammer
author_rank: Super Contributor
timestamp: March 30, 2024, 07:45:41 am
content: Quote from: temperance on March 29, 2024, 09:02:04 pmEveryone, despite it's level of intelligence can do stupid things for sure. But based on your average you would expect more people to act "normal" but it seems like people are getting more and more stupid every day. Can be biased of course on one sided input of information, and being on the higher end of the scale based on several tests in the past it is sometimes hard to grasp that "normal" is not more normal across the population. Maybe it is that "normal" is just on a sliding scale.This is inline with nctnico and not understanding why the human race acts like it acts. For instance a while back on the news it was about AI and robots and the question was if in the future one AI should be allowed to marry another AI.Who comes up with such, in my eyes, nonsense.Quote from: temperance on March 29, 2024, 09:02:04 pmAnd I agree that if you have a web cam and then purposely rear end someone who break checks you is, well not really stupid but, criminal. Taking physics into account some just won't have enough time and space to avoid it. And that might also be possible to extract from the footage. Calculating if indeed it could not have been avoided.

author: tggzzz
author_rank: Super Contributor
timestamp: March 30, 2024, 09:44:23 am
content: Quote from: mkiijam on March 29, 2024, 05:14:03 pmBJTs are current devices, not voltage devices. There is no simple easy relationship between a BJT's "input" and "output" voltage, so if you start there you areboundto be perplexed.There is a single simple relationship between "input" current and "output" current; IC=hFEIBSo, start by working out the input (base) current, that will give you the output (collector) current. That current flowing through the load will determine the output voltage.

author: Zero999
author_rank: Super Contributor
timestamp: March 30, 2024, 03:25:18 pm
content: Quote from: tggzzz on March 30, 2024, 09:44:23 amLet's not start that.In applications where the BJT is being used as a linear amplifier, it's always right to consider it to be a voltage controlled device, with ICbeing dependant on VBE.Current control only makes sense when dealing with a saturated switch, but even then, in order to ensure a fast turn-off time, it's necessary to take the base voltage below the normal 0.6V diode drop, preferably even negative.

author: tggzzz
author_rank: Super Contributor
timestamp: March 30, 2024, 04:07:20 pm
content: Quote from: Zero999 on March 30, 2024, 03:25:18 pmAh, let's get back to basics: does the current through a resistor causes the voltage across it, or the voltage across a resistor causes the current through it. Answer: mu.Realise that the OP is not considering BJTs on their own, he is trying to understand how they work (i.e. design equations) for typical simple amplifiers.If you look at most simple amplifiers, linear or saturated, the input voltages is much more than VBE. That enables design patterns which more-or-less remove the variation in VBEfrom that equations defining the amplifier's operation. The current relationships, however, remain.For common collector amplifier, consult TAoE section 2.2.2-2.2.5; for common emitter, 2.2.8-2.2.9. Any other introductory textbook ought to be similar.For more comprehensive analysis, consult TAoE chapter 2x, but the OP won't be interested in that.

author: nctnico
author_rank: Super Contributor
timestamp: March 30, 2024, 04:10:03 pm
content: Quote from: Zero999 on March 30, 2024, 03:25:18 pmNo. Absolutely not. You are writing about a common-emitter amplifier with a resistor in the emitter to turn a transistor into a voltage to current converter. But this is a circuit, not the basic operating mode of the transistor itself.

author: Siwastaja
author_rank: Super Contributor
timestamp: March 30, 2024, 04:38:39 pm
content: Ah, the good old "bipolar transistor is current controlled" "no it's voltage controlled" "no it's current controlled". This is a variation of "it's current that kills" "no it's the voltage" "no it's the current". In reality, both are correct: in say NPN bipolar transistor, Vbe and Ib are interlocked. You control current, and measured voltage changes. You control voltage, and measured current changes. There is a simple relationship between each other, a simple function, which you can plot on a 2D plane. Now because this function happens to be quite exponential (or logarithmic, depends on which way you look at it), applying a voltage e.g. from a lab supply, and hoping to get a transistor to a specific level of conduction is quite finicky, even small changes of voltage make a big difference. This is why it's tempting - and useful - to say that a BJT is current controlled, but saying it's voltage controlled isn'twrongper se.

author: tggzzz
author_rank: Super Contributor
timestamp: March 30, 2024, 05:10:55 pm
content: Quote from: Siwastaja on March 30, 2024, 04:38:39 pmPrecisely.IMHO for simple introductory purposes, the current version is easier to understand and analyse. OTOH, the more complex linearisations and translinearisations are fascinating.

author: nctnico
author_rank: Super Contributor
timestamp: March 30, 2024, 05:41:39 pm
content: Quote from: tggzzz on March 30, 2024, 05:10:55 pmBut those are only somewhat usefull when the transistors are next to eachother on the same die. Otherwise process and temperature variations will introduce errors quickly. IC designers have to use quite a few tricks to match transistors used to build a good opamp. And even then the opamps on the same die don't behave exactly the same. Just look at the metalisation pictures in datasheets for some of the older opamps to see how complex some structures are to achieve good as possible symmetry.

author: tggzzz
author_rank: Super Contributor
timestamp: March 30, 2024, 05:52:51 pm
content: Quote from: nctnico on March 30, 2024, 05:41:39 pmI'm not sure what you mean by "those".There are many circuits where is is not necessary to have semiconductors on the same substrate.There are many circuits where it is necessary to haveresistorson the same substrate.There are many circuits where it is sufficient to thermally couple semiconductors that weren't made on the same die.The issue is of adequacy and fitness for purpose.All models are false, but some are useful.And all those are irrelevant to someone struggling to understand basic BJT circuit behaviour.

author: nctnico
author_rank: Super Contributor
timestamp: March 30, 2024, 06:02:08 pm
content: You missed the point that where transistor voltage control is actually useful (like current mirrors and other translinear circuits like multipliers), the transistors need to be matched closely where it comes to temperature and process to a point where that is only possible with the transistors being on the same die. So not really applicable to common transistor circuits where you'll need some form of feedback to cancel process and temperature variations in order to make a circuit behave. And in those circuits, using Hfe or Beta (current gain ) is a much more sensible approach.

author: Zero999
author_rank: Super Contributor
timestamp: March 30, 2024, 06:17:47 pm
content: Quote from: tggzzz on March 30, 2024, 05:10:55 pmThe voltage controlled version is more applicable to linear amplifiers.How do your explain a current mirror only considering the current model?Now consider a current mirror with transistors of different hFEs, yet everything else being equal.Lets be lazy and put it in SPICE.How do you explain the current mirror still working, if the BJTs are current controlled?Current mirror hFE.ascEDIT: Wrong quote.The answer is the hFEis irrelevant to most BJT linear amplifier designs. ICvs VBEis what's important.

author: tggzzz
author_rank: Super Contributor
timestamp: March 30, 2024, 07:18:56 pm
content: Quote from: nctnico on March 30, 2024, 06:02:08 pmI hadn't missed it; I developed my first translinear circuit in 1979!Obviously there are some circuits that depend on VBE- but most strive to avoid dependence on that, or on hFE/beta for that matter.Since the context is someone who is having difficulties with understanding basic transistor operation, I think it is inappropriate and unhelpfui to introduce "advanced" topics.That leads to your final sentence, which think is more likely to help this beginner. There we are in full agreement.

author: soldar
author_rank: Super Contributor
timestamp: March 30, 2024, 08:48:44 pm
content: Perhaps because I learnt bipolar transistors at a very young age for me they are absolutely intuitive and obvious.On the other hand magnetics and electro-mechanical motors are something I never learned deeply and so I am like a permanent beginner.

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 30, 2024, 10:18:48 pm
content: Quote from: tggzzz on March 30, 2024, 05:10:55 pmYes. And this is why even active engineers (not students), apart from a few, also usually find BJTs much easier to work with than MOSFETs (except for basic switching purposes).That's always a matter of models. Like, what is DC?

author: Red Squirrel
author_rank: Super Contributor
timestamp: March 30, 2024, 11:26:03 pm
content: Math, especially once the big formulas come out. I understand the concept, but I just don't know how to start when it comes to applying it. I tend to get hung up on what each variable represents, and what unit to use as often it's not really specified. Ex: if looking at a data sheet.

author: Zero999
author_rank: Super Contributor
timestamp: March 31, 2024, 10:57:56 am
content: Quote from: Red Squirrel on March 30, 2024, 11:26:03 pmI have a similar problem. Especially when there are formulae with variables in lower and upper case, and Greek characters, which look similar to Latin ones. My hand wring is hard to read and slow, which doesn't help. I just about scraped through mathematics at college.

author: nctnico
author_rank: Super Contributor
timestamp: March 31, 2024, 11:09:12 am
content: Quote from: Zero999 on March 30, 2024, 06:17:47 pmYou use a more complex model to solve these kind of circuits. Namely the diode equation where you solve the current through each leg by making Vbe equal. So Vbe is constant but only in a relative fashion, not absolute. But from the formula it becomes clear immediately that any temperature or process difference between the transistors, is going to mess this circuit up when it is build from random, seperate transistors.QuoteNope. If you look at amplifier designs closely, you'll always see voltage to current conversion stages using resistors and other parts (like red LEDs) to cancel the temperature and process dependent Vbe changes / differences.

author: Zero999
author_rank: Super Contributor
timestamp: March 31, 2024, 11:12:48 am
content: Quote from: nctnico on March 31, 2024, 11:09:12 amSorry, I have no idea what you're talking about.The fact is, you can calculate the change in IC, purely using VBEand changing hFEmakes no difference.

author: nctnico
author_rank: Super Contributor
timestamp: March 31, 2024, 11:18:28 am
content: https://en.wikipedia.org/wiki/Shockley_diode_equationhttps://en.wikipedia.org/wiki/Translinear_circuitBut keep in mind that the diode equation still is a very crude estimation of how a transistor will actually behave.

author: tggzzz
author_rank: Super Contributor
timestamp: March 31, 2024, 11:22:19 am
content: Quote from: Red Squirrel on March 30, 2024, 11:26:03 pmSI units, except for some dimensions. The data sheet must make dimensions clear, somewhere!Alternatively, sometimes dimensional analysis is useful for checking you've done algebraic manipulations correctly.

author: tggzzz
author_rank: Super Contributor
timestamp: March 31, 2024, 11:27:53 am
content: Quote from: nctnico on March 31, 2024, 11:18:28 amIt is a model. All models are wrong, but some are useful.The models for MOSFETs are notoriously poor, especially in the subthreshold range.FFI see TAoE chapter 3x.5.5 and 3x.5.6, which show the extraordinary lengths required to get some SPICE models to behave as the actual devices.

author: Zero999
author_rank: Super Contributor
timestamp: March 31, 2024, 11:47:02 am
content: Quote from: nctnico on March 31, 2024, 11:18:28 amMy point was is it's a heck of a lot easier to use the voltage model, rather than the current for things like current mirrors.It also doesn't explain why a BJT will always turn off faster, when the base voltage is driven negative, compared to simply stopping the base current.

author: tggzzz
author_rank: Super Contributor
timestamp: March 31, 2024, 01:51:49 pm
content: Quote from: Zero999 on March 31, 2024, 11:47:02 amTrue, but for someone who is having difficulty understanding basic BJT operation, those are "advanced" topics that should be deferred.

author: nctnico
author_rank: Super Contributor
timestamp: March 31, 2024, 07:01:04 pm
content: Quote from: Zero999 on March 31, 2024, 11:47:02 amFor that you'll need a more complete model. Like described here:https://en.wikipedia.org/wiki/Hybrid-pi_modelthis shows a capacitor between base and emitter to model the extra energy needed to pull a BJT out of saturation. But using a model like this gets cumbersome with pen, paper and a calculator.In the end the simplified models are good to get the DC biasing in order. After that a simplified AC model can be used to get an idea whether the circuit may have the desired frequency response. But the final proof of whether a circuit is viable, is simulation using even more complicated models.

author: Zero999
author_rank: Super Contributor
timestamp: March 31, 2024, 07:23:16 pm
content: Quote from: tggzzz on March 31, 2024, 01:51:49 pmIf you're teaching an average 12 year old, then may be, but the Ebers–Moll model is about the level of advanced GCSE, or simple AS level mathematics. The problem with telling students that a simple model is the truth is it can trip them up later. I much prefer to say, it can be approximated as, rather than saying it is.Quote from: nctnico on March 31, 2024, 07:01:04 pmIt is the charge in said capacitor, which determines the collector current, rather than the base current. As the Wikipedia article correctly states, the BJT is similar to a FET.

author: tggzzz
author_rank: Super Contributor
timestamp: March 31, 2024, 07:24:06 pm
content: Quote from: nctnico on March 31, 2024, 07:01:04 pmHybrid-pi model is a small-signal linear model => suitable for linear amplifiers, not suitable for non-linear switches.For non-linear behaviour you'll need an Ebers-Moll or Gummell-Poon model. Even that is, of course, only an approximation - and manufacturer's values for its components can be, awful.TAoEx notes a case where an amplifier circuit had a simulated gain of 200, rather that the calculated and measured 400. Horowitz and Hill traced that to an improbably large value inonemanufacturer's transistor model. Subsituting another manufacturer's model lead solved the discrepancy.In the early 80s I was approached by salesmen to implement models of many 74 series devices for their HiLo digital simulator. I asked the obvious questions about acceptance criteria, and they really didn't care. Clearly all the potential client wanted was to be able for their clients to be able to tick the "74xxx models available" box. I didn't want my name (and my company's) on such crap, so I recommended a no-bid

author: tggzzz
author_rank: Super Contributor
timestamp: March 31, 2024, 07:30:14 pm
content: Quote from: Zero999 on March 31, 2024, 07:23:16 pmFor much back-of-the-envelope analysis, the Ebers-Moll model is overkill. Evidence: the existence and usefulness of the hybrid-pi model, plus see TAoE.Doyou have and have you read TAoE and TAoE x-chapters?Much engineering intuition is based on understanding the consequences of very simple models, plus the limits due to the simplicity.That simplicity can enable beginners to get a toe-hold in the subject.Understanding the limits can enable improved designs that mitigate the limits.

author: Zero999
author_rank: Super Contributor
timestamp: March 31, 2024, 07:56:58 pm
content: Quote from: tggzzz on March 31, 2024, 07:30:14 pmI've read the Art of Electronics, but don't have the x-chapters.I agree about Ebers Moll being overkill. Heck, for basic calculations, I don't even use the hFE. I just assume VBE= 0.7V, set IBto between 5 and 500 of IC, depending on the type of transistor and whether it's being driven into saturation or not and that's it.

author: tggzzz
author_rank: Super Contributor
timestamp: March 31, 2024, 08:05:11 pm
content: I like the x-chapters.They are simultaneously more detailed, practical, and have a lighter tone as you might find in a good university lecture.

author: temperance
author_rank: Super Contributor
timestamp: April 01, 2024, 02:10:09 am
content: It is somehow funny how the OP not understanding transistors ends in a debate about which transistor model to use. From my understanding the OP has problems with basic circuit theory. The transistor model doesn't matter if that is true. In such case I would start with a very simple transistor amplifier in which the BE voltage isn't of much concern and Ohm law is enough to understand what is happening. That's how I started and learned about voltage and current sources very long ago. The more advanced models you will need to understand current mirrors, early effect, high frequency models,... will only look confusing and intimidating.

author: tggzzz
author_rank: Super Contributor
timestamp: April 01, 2024, 07:08:15 am
content: Quote from: temperance on April 01, 2024, 02:10:09 amPrecisely.The single most important parameter in a BJT is the current gain, hFE. That plus Ohms law enables a lot of understanding of how simple amplifiers operate. Bonus points for stating VBE=0.6V.That is not sufficient, however, to understand simple amplifier's deficiencies - but that is something to considerafterbasic operation is understood.

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 01, 2024, 07:46:14 am
content: The hybrid-pi model is useful for small-signal analysis, and is relatively straightforward to understand:https://en.wikipedia.org/wiki/Hybrid-pi_model

author: Circlotron
author_rank: Super Contributor
timestamp: April 01, 2024, 08:26:16 am
content: Getting back on track, I can never remember someone's name if their name is Dominic. Total blank spot in my brain. And yes, I had to sit and think for about a minute before I could actually post this.

author: temperance
author_rank: Super Contributor
timestamp: April 01, 2024, 12:21:06 pm
content: QuoteEnough laughing. I remember phone numbers instead of peoples names and I often dial the number directly because the phone book is too slow. Not remembering names is very embarrassing at times. But I do remember IC and transistor type numbers and their most important parameters and pin layout. Practical because TO92 packages came with different pin-outs.In mathematics I somehow I have problems subtracting numbers. It is almost as if my brain hates subtracting and goes blank. I really have to push my brain to work it out or write it down. All other operations work fine.Edit:QuoteNot if you are 10 years old and concepts like current and voltage sources are very abstract to you.

author: audiotubes
author_rank: Regular Contributor
timestamp: April 01, 2024, 01:24:55 pm
content: Quote from: Halcyon on March 28, 2024, 11:44:16 pmJust use SNOBOL4 and you'll never use regexp again

author: Sredni
author_rank: Frequent Contributor
timestamp: April 01, 2024, 02:19:54 pm
content: Quote from: mkiijam on March 29, 2024, 05:14:03 pmIt is understandable because even diodes are taught to be on-off devices that switch state at the infamous 0.7 V threshold.But in reality that threshold is not there at all, as one could easily see by plotting the exponential characteristic on a log scale (it's a frigging straight line!)So why we say there is a knee and a 'sharp' transition at 0.7? Because at the scale of the current we use ordinary diode, there appears to be a knee. Even if it's not there and only depends on the scale.https://electronics.stackexchange.com/questions/655076/forward-bias-voltage-of-diode/655157#655157It's just a side effect of the self-similarity property of the exponential function.

author: fourfathom
author_rank: Super Contributor
timestamp: April 01, 2024, 03:10:32 pm
content: Quote from: Circlotron on April 01, 2024, 08:26:16 amOk, here's mine: I can't remember numbers, names, or faces without a lot of effort. I often can't recall the names of people whom I have known for years, it takes a lot of exposure to make a name stick.But sounds -- I have an good ability to remember sounds. If I want to remember a number I generally say it out loud and listen to myself saying it. Then I have a chance, at least for a short while.But hearing someone say their name, or even when I listen to myself repeating it back, I usually forget it within thirty seconds.I can also recognize a giant catalog of music from just a fraction of a second of the beginning. Even the particular tone of a single snare drum hit can be enough. Of course then I still can't remember the name of the song. I also recognize voices, say on a radio commercial or a voice-over in a film. Again, the actor's names elude me.However I can remember schematics from stuff I designed 50 years ago. This isn't an Alzheimer's thing, I've been this way all my life.

author: mkiijam
author_rank: Regular Contributor
timestamp: April 01, 2024, 03:25:40 pm
content: Here is a good example of what I think I do not know or understand. I was working on a QSC amp that I believe was staying in some sort of speaker protection mode. I had a healthy amp to A-B with.Q4 B seemed to be around .6V on both ampsOn the healthy amp I remember measuring Q5 as, C=14V E = -14, and B = -14-ish.The sick amp C =1.5V E =-4V I can't remember for sure what B was, but I'm not sure it matters for getting help with transistor function so I will continue with what I "assumed" as this may illuminate where my brain lock is.1. I thought the connection between the emitter and collector on the healthy amp was being held off by the large amount of negative voltage on its base.2. Q4 B would be driven NEGATIVE somehow (by the unseen circuitry to the left) and then connect its C and E3. This would then pull the B of Q5 less negative than its E causing it to connect E and C and that would shut down the +/-15V rails?How does Q4 turn on?

author: BILLPOD
author_rank: Frequent Contributor
timestamp: April 01, 2024, 06:34:02 pm
content: I'm TOTALLY confused; is this a thread about transistor theory, or about Brain Locks

author: fourfathom
author_rank: Super Contributor
timestamp: April 01, 2024, 06:47:31 pm
content: Quote from: BILLPOD on April 01, 2024, 06:34:02 pmYes, logical OR.

author: m k
author_rank: Super Contributor
timestamp: April 01, 2024, 06:58:00 pm
content: Quote from: fourfathom on April 01, 2024, 03:10:32 pmThat's a general advice here.When you're leaving say things out loud.Stove is off, coffee maker is off, etc.

author: TimNJ
author_rank: Super Contributor
timestamp: April 01, 2024, 06:59:07 pm
content: After about 15 years, I've finally remembered which side of the diode symbol is "cathode" and which is "anode".It will be another 15 years to remember whether the long lead of an LED is the cathode or anode.

author: IanB
author_rank: Super Contributor
timestamp: April 01, 2024, 07:05:27 pm
content: Quote from: TimNJ on April 01, 2024, 06:59:07 pmIt's honestly best not to use the words anode and cathode, since depending on context an anode can be either positive or negative, and a cathode can be either negative or positive. Those two words should be stricken from the dictionary as being meaningless without context.Anyone who wants to communicate accurately should say "positive electrode" and "negative electrode" instead.

author: coppercone2
author_rank: Super Contributor
timestamp: April 01, 2024, 09:42:37 pm
content: oh yeah those terms suck

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 01, 2024, 09:46:33 pm
content: This puts my brain into deadlock (and also tends to trigger some anger, which is a paradox):https://www.europarl.europa.eu/doceo/document/E-9-2023-002312_EN.html

author: TimNJ
author_rank: Super Contributor
timestamp: April 01, 2024, 10:14:55 pm
content: Quote from: SiliconWizard on April 01, 2024, 09:46:33 pmWas in Ireland last summer. An absolute immense number of cows. Wow! On the other hand, I saw no evidence of mass factory farming and the ecological disaster that follows (see: Texas). It seems like, if you are going to have a ton of cows, Ireland does it the best way possible. Cows free grazing, tons of room per animal. They looked happy. .So, yes let's kill 200,000 cows and then what happens? Increase the supply in some factory farm hellhole in the UK to meet the supply again?

author: nctnico
author_rank: Super Contributor
timestamp: April 01, 2024, 11:11:32 pm
content: Quote from: SiliconWizard on April 01, 2024, 09:46:33 pmOfftopic: It is a very sensible question and drastic action is needed. If you take into account how small the Netherlands is versus the immense agricultural output (second largest exporter of agricultural products after the US), you can only come to the conclusion that a huge reduction of farming activities is required. In some places the soil is more acidious compared to Coca-Cola due to nitrogen deposits which kills nearly all plant life. Yes, we have the very super best of the best farmers of the world in the NL. Please make them stop doing such a good job!

author: Sredni
author_rank: Frequent Contributor
timestamp: April 01, 2024, 11:48:27 pm
content: Quote from: IanB on April 01, 2024, 07:05:27 pmNah, just remember that (conventional) current always* goes into the anode and you're good.Try it connecting a chemical cell to an electrolytic bath: the current exits from the positive pole of the battery (hence not an anode) and enters the positive pole of the electrolytic bath (now it's an anode). Exits the bath from its cathode and enters the battery from its anode.The swapping of the names happens because of the different convention adopted for sources and sinks: current exits the positive terminal of a battery and enters the positive terminal of a resistor.*Zener diodes are an exception because we use them backwards.

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 02, 2024, 12:08:36 am
content: When it comes to diodes, they can be used in a number of ways that would make naming the pins + and - very confusing. Anode and Cathode are much more preferable to avoid any possible confusion: it's just a convention that has become unambiguous.You might argue that it was initially a bad choice, but I'm not sure + and - would have been much better, and obviously changing now a well-established convention would be way worse.

author: Circlotron
author_rank: Super Contributor
timestamp: April 02, 2024, 12:12:46 am
content: Quote from: Sredni on April 01, 2024, 11:48:27 pmFor the sake of upping the ante on the confusion index, with a vacuum tube, when looking from the inside we could say electrons enter the anode, but when looking from the outside the electrons exit the anode connection.

author: Sredni
author_rank: Frequent Contributor
timestamp: April 02, 2024, 12:30:25 am
content: Quote from: Circlotron on April 02, 2024, 12:12:46 amWell, I guess that happens with batteries and resistors, as well.But if you look at components from a circuital perspective, the rule 'current into anode' always hold (apart from those pesky zener diodes, that is).In general, looking inside components can shake one's beliefs about reality: look inside an inductor and you will discover KVL is no longer working; look inside a capacitor and it's KCL that stops functioning.

author: IanB
author_rank: Super Contributor
timestamp: April 02, 2024, 12:32:00 am
content: Quote from: Sredni on April 01, 2024, 11:48:27 pmThis is a useful and helpful aid to understanding, but it does mean that the positive terminal of a secondary cell is its cathode when it is discharging, and is its anode when it is charging. (And logically, has no name when the cell is open circuit, neither charging nor discharging.)QuoteThis description therefore defines anode and cathode operationally according to the sourcing or sinking behavior of the device and not according to the physical nature of the device itself.QuoteAccording to the above arguments, Zener diodes should not be an exception. Like secondary cells, the assignation of anode and cathode should depend on the direction of operating current flow. And should change depending on whether the Zener is being operated in rectifying mode or breakdown mode.

author: Sredni
author_rank: Frequent Contributor
timestamp: April 02, 2024, 12:39:40 am
content: Quote from: IanB on April 02, 2024, 12:32:00 amThe same applies to capacitors and inductors: when you are charging them, positive conventional current enters the positive terminal; when you discharge them on the attached circuit (a resistor, for example), positive conventional current exits the positive terminal.Regarding the physical (or chemical) nature of the process, rememeber that "OXANa has a RED CAT". I.e. OXidation happens at the ANode, and REDuction at the CAThode.

author: Halcyon
author_rank: Unknown
timestamp: April 02, 2024, 01:22:37 am
content: Quote from: IanB on April 01, 2024, 07:05:27 pmThanks for un-doing what high school electronics taught me.

author: pcprogrammer
author_rank: Super Contributor
timestamp: April 02, 2024, 05:19:49 am
content: Quote from: m k on April 01, 2024, 06:58:00 pmFor this you need Google control.Quote from: fourfathom on April 01, 2024, 03:10:32 pmFaces, images or written texts stick rather easily, but names need lots of repetitions before they stick. Sometimes indeed a bit embarrassing when you meet someone and have to guess their name.

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 02, 2024, 05:55:55 am
content: It seems everyone's memory has its own ways. As for me, I used to have a hard time remembering complicated paths that I had been exposed to only once or twice when driving, and it took really a number of times for paths to stick. That was before the GPS of course, but even before using this, I got better over time. So, I guess for me that was visual cues that were not as effective as they should be, but that's always something you can work on.

author: c64
author_rank: Frequent Contributor
timestamp: April 02, 2024, 06:30:35 am
content: Quantum computing.

author: Zero999
author_rank: Super Contributor
timestamp: April 02, 2024, 07:11:11 am
content: Quote from: nctnico on March 31, 2024, 11:09:12 amWhat I mean by changes in ICvs VBEisn't process dependent variation, but ∆VBEvs ∆IC. Take the common emitter amplifier for example. Note the AVhas nothing to do with hFE.

author: tggzzz
author_rank: Super Contributor
timestamp: April 02, 2024, 07:47:21 am
content: Quote from: Sredni on April 02, 2024, 12:30:25 amThe only thing that exists are the electromagnetic fields, potential difference, and charge. Everything else is a simplified model of the consequences of those, useful in some circumstances, wrong in others.That's not much of an exaggeration.Unfortunately EM fields are my brain lock.

author: nctnico
author_rank: Super Contributor
timestamp: April 02, 2024, 09:24:14 am
content: Quote from: c64 on April 02, 2024, 06:30:35 amThat is largely mistified. A while ago I had a talk with somebody involved in quantum computing and the programming is pretty similar to what you'd do on a normal microprocessor. The only problem is that quantum computers don't have much logic to work with at this moment. There are simulated environments available like this one though:https://www.quantum-inspire.com/

author: nctnico
author_rank: Super Contributor
timestamp: April 02, 2024, 09:31:13 am
content: Quote from: pcprogrammer on April 02, 2024, 05:19:49 amSame here

author: tggzzz
author_rank: Super Contributor
timestamp: April 02, 2024, 10:40:18 am
content: Quote from: Zero999 on April 02, 2024, 07:11:11 am(1) que?(2) you aremissing the point: very few circuitsmake useof that dependence, whereas most circuits try tominimise its consequencesQuoteSo what?

author: Siwastaja
author_rank: Super Contributor
timestamp: April 02, 2024, 11:01:22 am
content: Quote from: Zero999 on March 31, 2024, 10:57:56 amI couldn't agree more, and being the self-righteous asshole I am, I refuse to call this a brain lock of mine; I blame the math folks, they are just wrong. Mathematical notations, theory, and typical teaching material used would never pass modern day code review process. It's total obfuscation from day one, and especially difficult for people who "think aloud in their heads" like me, when we try to understand a new concept. You can't read out obfuscated formulae where a single letter which is pronounced exactly the same is stylized in three-four different visual ways, to denote completely different things, when all they had to do is to give variables descriptive names.The tendency to not explain the variables at all (and not give a reference to page where they can be found) is totally inexcusable. It's sadism.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 02, 2024, 11:20:48 am
content: Quote from: TimNJ on April 01, 2024, 06:59:07 pmWhile I quite often, on this forum and elsewhere, give expert-ish advice on lithium ion batteries, I have to Googleevery timewhich of the electrodes is anode and which cathode. It does not help the convention is reversed* compared to electrolytic or ultra capacitors. I just can't come up with a rule of thumb, I have to Google every time.*) or is is? Or is my brain just too locked so that I think it is?Diodes, somehow I don't have any trouble with. Maybe because I learned about them at age 9-10 or something like that. I guess it was early enough to stick. Batteries and electrolytic capacitors used (and still use) + and - in practical engineering, so the arbitrary "anode" and "cathode" naming only hinders the "look we are scientists!" LARP.

author: IanB
author_rank: Super Contributor
timestamp: April 02, 2024, 01:20:48 pm
content: Quote from: Siwastaja on April 02, 2024, 11:20:48 amThat's because, as mentioned earlier in this thread, anode and cathode swap positions in a lithium ion cell depending on whether it is being charged or being discharged. When being charged the anode is the positive terminal, and when being discharged the anode is the negative terminal.The rule of thumb was helpfully provided by Sredni. Conventional current in a circuit enters the anode and leaves the cathode.

author: mkiijam
author_rank: Regular Contributor
timestamp: April 02, 2024, 02:28:46 pm
content: To me the ANODE looks more like an "A" on the schematic. That's still my trick.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 02, 2024, 03:29:06 pm
content: Quote from: IanB on April 02, 2024, 01:20:48 pmBut no one - not the scientific community, not the battery industry - uses such alternating naming; they are not temporary role names; earlier comments on this thread were speculation or opinion how it "could" or "should" be, not a description how it really is. Terms "lithium ion cathode" and "anode" are widely used, well definedfixednames for the two electrodes. The choice which is which is, as far as I know, completely arbitrary. I prefer to call them positive and negative electrode instead, and I know I'm not the only one; even many in the industry do the same. The advantage of calling them positive or negative is that the potential difference (voltage) never changes its sign, even if the current direction reverses.

author: coppice
author_rank: Super Contributor
timestamp: April 02, 2024, 03:35:48 pm
content: Viterbi decoding gets me every time. Its far from the most complex thing I've ever dealt with, and its not hard to understand how it works and takes you closer to the Shannon limit. Still I go around in circles implementing it every time I come back to dealing with it.

author: nctnico
author_rank: Super Contributor
timestamp: April 02, 2024, 03:41:08 pm
content: Quote from: Siwastaja on April 02, 2024, 11:01:22 amThat reminds me... last week I was in a building names after this guy:https://nl.wikipedia.org/wiki/Hans_FreudenthalAccording to you he should have done a better job.IMHO math is like a language you need to learn & understand. Just like trying to make sense of the ever more abstract paintings by Picasso.

author: tggzzz
author_rank: Super Contributor
timestamp: April 02, 2024, 04:08:31 pm
content: Quote from: IanB on April 02, 2024, 01:20:48 pmEr, no.The anode has the more positive voltage, the cathode the more negative. That doesn't change between charging and discharging.QuoteYes, but it is not a rule of thumb, it is a convention. Other things follow from that convention, e.g. power dissipation.The power dissipated in a circuit element is I*V, where I is the (conventional) current goingintothe more +ve terminal, and P=VI where V is the voltage across the element.For a cell, the more positive terminal is the anode, and thus current flowingintothe cell's anode causes apositivepower dissipation in the cell.For a cell, the more positive terminal is the anode, and thus current flowingout ofthe cell's anode causes anegativepower dissipation in the cell.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 02, 2024, 04:27:32 pm
content: Quote from: nctnico on April 02, 2024, 03:41:08 pmYou are right. As such, it's also open to discussion, and one can have opinions about it. In my opinion, it sucks. Also, in my opinion, it doesn't need to be permanently fixed because of some great man made decisions 300 years ago. Even the wheel has improved.In the end, mathematics is used as atoolall over in the scientific community and engineering. But sometimes I can't avoid the feeling that the tool becomes a master, instead of servant; or some kind of secret club of those who really grok it, and the others who try to cope with it. I feel confident that some modernization of notations and conventions (e.g., multi-character descriptive variable names, and explanations of variables used i.e.comments) would significantly increase the social scope, and decrease the number of engineers who are intelligent per se, but still struggle to use math as their tool to the fullest extent.

author: IanB
author_rank: Super Contributor
timestamp: April 02, 2024, 05:49:48 pm
content: Quote from: Siwastaja on April 02, 2024, 03:29:06 pmIt seems we are of like mind. Which is why I wrote something similar above:Quote from: IanB on April 01, 2024, 07:05:27 pmAs for a lithium ion cell, I think the industry designation of anode and cathode follows the convention of the cell being treated as a source (the reason it exists), rather than as a sink. You don't construct lithium ion batteries to consume electricity, you construct them to supply electricity--hence the positive terminal becomes the cathode.

author: coppice
author_rank: Super Contributor
timestamp: April 02, 2024, 05:54:26 pm
content: Quote from: Siwastaja on April 02, 2024, 04:27:32 pmYou seem to be confusing mathematics, and the commonly accepted notations we use for mathematics. The notation is open to discussion. The only discussion about maths itself is whether our understanding is complete and accurate.

author: tggzzz
author_rank: Super Contributor
timestamp: April 02, 2024, 06:19:46 pm
content: Quote from: coppice on April 02, 2024, 05:54:26 pmDidn't Kurt Godel have something to say about that?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 02, 2024, 06:29:52 pm
content: Quote from: Siwastaja on April 02, 2024, 04:27:32 pmI am not ready to pooh-pooh this comment without seeing a complete development of your ideas. It certainly runs counter to my instincts. Replacing dt with Differential_Time_Increment and like substitutions elsewhere would make almost all equations multi-line and many multi-page, with little or no improvement in understanding. The usage of comments for definitions is fine, and is already widely used, albeit with two major styles, and omissions just as there are in the software environment. Your approved software environment uses compact symbols with complex meanings. They are usually called operators, and cause little confusion to anyone when they overlap with widely used conventions. Examples being + and -. * for multiplication already violates the grade school convention of X, and things get really confusing for non-experts when casting and piping operators come into play.In one sense you are right. The math notation is a domain specific language designed to convey concepts quickly and compactly to those who understand the language and what it represents (grok it). Perhaps your ire should be reserved for your math teachers that failed to convey those concepts to you, rather than those who codified the language used. Teaching is always a difficult job, and one size does not fit all. Some teachers do not recognize this, or do not use alternate teaching paths. Sometimes due to incapacity, sometimes laziness, and sometimes due to constraints placed on them by the school administration.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 02, 2024, 06:38:47 pm
content: Quote from: tggzzz on April 02, 2024, 06:19:46 pmAll Godel said was that no mathematics could be complete without some unproveable axioms.A sublety of almost no relevance when applying math to science and engineering. In engineering the only concern is if the mathematics correlates to some physical problem. The same is often true in science, though one corner of science concerns itself with whether the math is exactly representative of the universe, or just a damn good approximation. The question is important because in some cases the math has preceded the observations and then subsequently phenomena (particles, reactions and the like) discovered which matched the mathematics. But in other cases observations the math has been proved wrong. Leading to the question: Have we found the one true mathematics, or is it yet to be discovered, or is there no such thing. it is not clear to me whether Godel's proof has any relevance to this question.

author: IanB
author_rank: Super Contributor
timestamp: April 02, 2024, 07:14:55 pm
content: Quote from: coppice on April 02, 2024, 05:54:26 pmMathematics happens to be a favorite subject of mine, and I found from childhood that I had a natural aptitude for it. For instance, I could score 100% on a GCSE mock paper without effort when I was 14, and got a grade A in the Further Mathematics A-Level when I was 17.One thing I have observed is that when I see people struggling with mathematics, I see them trying to manipulate symbols and notation, and applying rules to rearrange symbols to get a desired result.I find this is not how I comprehend mathematics. For me, my comprehension consists of concepts and visualizations in my mind of abstract ideas, like painting with thought. In fact, people like Einstein and Feynman would invent their own notations to make writing things down easier.I know this is not necessarily going to help others, but I do think the way mathematics is taught has a lot to blame for this. It's like the analogy of learning music. Do you learn music first by learning musical notation and theory on paper, or do you learn first how to pick up an instrument and make music? Mathematics is like music. If you don't learn as a child how to hear and play the music of mathematics, it will be always harder than it ought to be.

author: tggzzz
author_rank: Super Contributor
timestamp: April 02, 2024, 07:53:04 pm
content: Quote from: IanB on April 02, 2024, 07:14:55 pmMine too.Everybody in my local state school passed maths O-level (Inc calculus) one year early, many went on to do further maths O-level the next year. In the next two years, I and several others passed 3 maths A-levelsQuoteYes, but so did Newton and Leibnitz - and many othersMaths progresses by introducing new notations, e.g. "0", "=" , etc.It helps if the new notations obeys the arithmetic conventions for addition, subtraction, multiplication, and preferably divisionQuoteMy school had two 6th form maths teachers. One had created a new method of generating Pythagorean triads; his lessons were almost (but not quite) incomprehensible. The other had got his maths degree and realised he wasn't going any further; his lessons were superb.By superb, I mean teaching differentiation from first principles in 3 hours. Later repeated with integration. Younger maths teachers don't believe it, but I have one of the textbooks to wave under their nose(Limited to polynomials except 1/x; that was an A-level topic!)

author: IanB
author_rank: Super Contributor
timestamp: April 02, 2024, 08:15:22 pm
content: Quote from: tggzzz on April 02, 2024, 07:53:04 pmI remember once at school, finding a stack of old O-level mathematics textbooks buried at the back of a store cupboard. I was surprised to find that they contained an introduction to calculus, and that at one time calculus was on the O-level syllabus. By the time I was doing GCE mathematics after O-levels had been replaced, they had dumbed everything down so much that they didn't even show the derivation of the quadratic formula. It was just, "Here is the formula, trust us, it works, you don't need to know how to derive it, just use it."How can you properly understand it if you don't know where it came from?

author: tggzzz
author_rank: Super Contributor
timestamp: April 02, 2024, 08:18:44 pm
content: Quote from: IanB on April 02, 2024, 08:15:22 pmWe used to go through old exam questions, from papers dating back to ~1953. They werehard.But back then... "We choose to go to the Moon in this decade and do the other things, not because they are easy, but because they are hard; ..."

author: coppice
author_rank: Super Contributor
timestamp: April 02, 2024, 09:00:24 pm
content: Quote from: tggzzz on April 02, 2024, 08:18:44 pmAt least for the London papers we took, the only real difference between the O-level and A-level maths paper from the late 40s until I took mine in the early 70s was that the O-level had been split into traditional maths and modern maths. The additional maths O-level and A-level syllabus and papers could have been from any year. By the time I took my A-levels in 1973 I had answered every A-level question from 1948 to 1972, and found very little variation in their difficulty. I did quite a few additional maths O-level past papers before my O-levels in 1971, and they were similar. The traditional maths O-level had some basic differentiation and integration. The modern maths O-level had lots of statistics, matrix algebra and other things instead. The additional maths o-level had quite a lot of calculus. When I was at university, mixing with people who had taken various board's papers, people told me London was hard, so if you took other papers things may have varied.Everything we learned in maths was taught by deriving it from first principles. We were never spoon fed any formulae. Even things like Gaussian distributions were taught from basic principles, although the central limit theorem missed the complexity that distributions without a stable mean can't be munged together to arrive at a Gaussian distribution (e.g. Pareto).

author: tggzzz
author_rank: Super Contributor
timestamp: April 02, 2024, 09:26:17 pm
content: Quote from: coppice on April 02, 2024, 09:00:24 pm<goes and looks at the 2" high line printer output> University of London "363 Maths syll D". June '72, so I was 15.I remember being told by the maths teacher that they chose to do this in preference to another syllabus, but I have no recollection of what might have been in those.Somewhere I have an SMP maths textbook that I bought in Hay-on-Wye, which states "integration and differentiation of polynomials except 1/x".QuoteI missed stats, and thermodynamics for that matter. I do remember we had to point out to the teacher that, with about a month to go, we hadn't been taught complex numbers. Quickly rectifiedThey did bring in a guest teacher for a few lessons, and he introduced us to aleph-null (ℵ0) and transfinite numbers, even though it wasn't on the syllabus.I also remember my junior school teacher introducing me to very simple algebra.

author: coppice
author_rank: Super Contributor
timestamp: April 02, 2024, 09:35:47 pm
content: Quote from: tggzzz on April 02, 2024, 09:26:17 pmSMP was the School Mathematics Project, the basis for the London board's modern maths O-level. I think London may have had another modern maths options, but I know other exam boards around the UK did. It was a weird time. Some schools found the modern maths syllabus to be hard for the less able, so only the most able streams took it. Other schools felt the modern maths stuff was easier, so only used it for the less able streams. So, the top kids from one school were competing against the less able from others in weird ways. If you were the sort that wanted to cover the greatest ground the SMP O-level plus the additional maths O-level covered a lot of ground. If you did traditional + additional you covered quite a bit of ground twice, just answering harder questions about similar material in the additional course.

author: IanB
author_rank: Super Contributor
timestamp: April 02, 2024, 09:39:48 pm
content: Quote from: coppice on April 02, 2024, 09:00:24 pmI remember being told that at my school. They picked London for every subject except mathematics, where they picked Cambridge instead.

author: IanB
author_rank: Super Contributor
timestamp: April 02, 2024, 09:48:58 pm
content: Hmm. I found a Further Mathematics exam from 1981 similar to the one I sat in 1979 (same exam board).On glancing through it, it would certainly give me a headache now. I would for sure have to review a lot of the material before attempting it.https://www.slideshare.net/telescoper/a-level-further-mathematics-1981

author: pcprogrammer
author_rank: Super Contributor
timestamp: April 03, 2024, 06:20:04 am
content: Quote from: IanB on April 02, 2024, 09:48:58 pmSame here. At school I was very good at it and scored nines and tens on tests, but not having used more than basic calculus in my working days it got lost. With the brain fog I now often have it is hard to concentrate on learning again. Even working on my projects is cumbersome and takes way longer than it used to. When I work on a project I get tired and need to walk away from it or take a nap.Guess it is both my illness and getting older.

author: BradC
author_rank: Super Contributor
timestamp: April 03, 2024, 10:40:22 am
content: Perl. Always has looked more like line noise to me.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 03, 2024, 11:50:23 am
content: Quote from: IanB on April 02, 2024, 07:14:55 pmYeah. And when I complained above about using the same letter in three or four different styles within a formula, from which CatalinaWOW made a straw man, I was not exaggerating, I was dead serious. I have no issue withdt, especially if it's explained somewhere. But Ididhave major issues with a formula which contained letter "r" in four and letter "e" in three different meanings, all in different shapes and forms. It just... makes my brain lock. Distinguishing between r, R,r,r, r with ^ on top, R stylized as cursive, all within the same formula, simply wastes time and mental effort. Maybe somebody else just looks at the text and the symbols intuitively enter their brain. When I see such formula for the first time and not understand it, I try to read it out loud in my mind. If it reads out [r r r e x r e r], the things only get worse, and I'm stuck.I was straight-A full scores in mathematics in high school and until about half of the first year in uni. At some point my motivation started drooping as the pace increased, while the disconnect between engineering-minded courses and math courses widened at the same time. It was clear that to truly understand the math courses, I would have had to investa lotmore time to the matter, finding secondary sources apart from the lectures, official lecture notes, and maybe indeed invent my own notation. It did not happen.

author: Zero999
author_rank: Super Contributor
timestamp: April 03, 2024, 12:38:09 pm
content: Quote from: Siwastaja on April 03, 2024, 11:50:23 amA simple example:VC(t) = ϵ(1−e−t/τ)

author: IanB
author_rank: Super Contributor
timestamp: April 03, 2024, 02:36:22 pm
content: Quote from: Zero999 on April 03, 2024, 12:38:09 pmThere may be a kind of analogy here with natural language. When I read and write, I don't see words as a group of letters, I seem them as pictures. Hence I quickly sense if a word is spelled incorrectly because when I see it the picture looks wrong.When I look at the equation above, I also don't see a formula, I see pictures. I see voltage as a function of time, and I see that being a small number scaling a first order rise with a given time constant.(If ϵ does not actually represent a small number, then that would be a poor choice of symbol in the equation.)

author: coppice
author_rank: Super Contributor
timestamp: April 03, 2024, 02:44:02 pm
content: Quote from: Siwastaja on April 03, 2024, 11:50:23 amI find it amusing when younger people say this. When I was at school I never got above 93% in maths. All answers correct. All workings shown. That got me 93% consistently. 70% would get you an A, as the questions were tough enough that this restricted those As to less than 10% of students. I find the expectation that anyone but a genius on a good day would get 100% on an exam an indictment of that exam. A well formed exam should be able to separate even the top 1% of student's performances in that exam.

author: IanB
author_rank: Super Contributor
timestamp: April 03, 2024, 02:53:04 pm
content: Quote from: coppice on April 03, 2024, 02:44:02 pmI think this shows how many people have a brain lock with mathematics, and how mathematics is "hard". For example, in the O-level test paper where I was able to answer all the questions correctly, most of my classmates were marked below 70% and only one or two above that. So, statistically, it was not an easy test for the population as a whole.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 03, 2024, 03:11:41 pm
content: Quote from: coppice on April 03, 2024, 02:44:02 pmI think this just represents small implementation differences between countries. Here, the scoring system usually required around 40-50% score to pass, then linearly the best grade for 100% correct answers, without such weird 7% deadzone on the top. With finite resolution and usual rounding rules, the best possible exam score could be had even with one or two small mistakes.Maybe it was easier for us here.

author: tggzzz
author_rank: Super Contributor
timestamp: April 03, 2024, 03:25:01 pm
content: Quote from: coppice on April 03, 2024, 02:44:02 pmMy father was once given 96% on an exam (probably maths) on the principal that nobody should be able to get 100%My second year undergraduate elwctronics degree was given by someone from the maths faculty. We showed our notes to a friend doing that course, and he was flabberghasted - saying that the content was most ofhiscourse. The end-of-year exam rubric memorably stated "full marks may be obtained for answers toabout6 questions". One other person on this forum might remember that

author: IanB
author_rank: Super Contributor
timestamp: April 03, 2024, 03:27:18 pm
content: It's odd (what coppice said). Mathematics does not have fuzzy marking like, say, a language exam. If you get all answers correct, you would get 100%. There is a marking scheme with marks allocated to each question according to each part of the answer that needs to be provided to obtain the marks. For someone to get 93% that means that marks were dropped somewhere, probably due to not providing some expected element of some answers, or maybe by being incorrect in some answers that were given.

author: coppice
author_rank: Super Contributor
timestamp: April 03, 2024, 04:07:22 pm
content: Quote from: tggzzz on April 03, 2024, 03:25:01 pmOur maths teachers said 100% was unreasonable, as if they gave someone 100% and the next paper in the pile used some great insight the previous paper had taken a longer way around, they would have no room to complement that insight. Why 93% seemed to be that cap below 100% I don't really know. They were awfully vague about that.

author: coppice
author_rank: Super Contributor
timestamp: April 03, 2024, 04:09:00 pm
content: Quote from: IanB on April 03, 2024, 03:27:18 pmWhen I was at school if you wrote all the correct answers in a maths paper without any workings you wouldn't get more than maybe 60%.

author: Zero999
author_rank: Super Contributor
timestamp: April 03, 2024, 09:19:55 pm
content: Quote from: IanB on April 03, 2024, 02:36:22 pmI just see letter and numbers. I read ϵ and e and t and τ the same. Then there's the nonsense of having lower and upper case in the same formula. It's even worse when I write it down because my handwriting is very slow and scruffy. My hand doesn't do as it's told and sometimes I just randomly write the wrong letter for no reason. I was diagnosed with dyslexia, but probably have dyspraxia, as my reading is fine.Mathematics is great in that it's either right or wrong, which isn't the case with other softer subjects, but that means there's less room for error. I can misspell words and the sentence still makes sense, but miswriting a symbol or number would lose me more marks.

author: Circlotron
author_rank: Super Contributor
timestamp: April 03, 2024, 10:59:24 pm
content: Quote from: IanB on April 03, 2024, 03:27:18 pmUnfortunately, mathematics is not what is used to be in the minds of some people. Get a load of this nonsense.

author: tggzzz
author_rank: Super Contributor
timestamp: April 03, 2024, 11:06:09 pm
content: Quote from: Zero999 on April 03, 2024, 09:19:55 pmOK, so you literally can't comprehend the formula. Shame, but that the "fault" lies with you, not with maths or the notation.Frequently lower/upper case is used to convey information, by conventions. For example, in my first week at university my "Senturia and Wedlock" textbook section 2.3.4 is "Notation Conventions" indicates these conventions are in widespread use...General network variable: vA, iCDC component of a waveform: VCC, IBPeak amplitude of a sinusoid: Va, IcIncremental component of a waveform: va, icQuoteMy handwriting is becoming appallingAge and keyboard use are the main points, but a traumatic biceps injury didn't help.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 04, 2024, 02:31:36 am
content: Quote from: Circlotron on April 03, 2024, 10:59:24 pmWOW. In these four pages there is a small amount of truth and potential added value. Buried among a lot of trash, and wit much opportunity to misunderstand the little that is useful.

author: Zero999
author_rank: Super Contributor
timestamp: April 04, 2024, 07:06:21 am
content: Quote from: CatalinaWOW on April 04, 2024, 02:31:36 amUnfortunately this thread has become full of boastfulness and overinflated egos, rather than attempts at providing useful information.Quote from: tggzzz on April 03, 2024, 11:06:09 pmOh course I understand the formula. I just read it as numbers and letters. The notation is at fault because it would be easier to learn, if it didn't use similar letters.

author: elektryk
author_rank: Regular Contributor
timestamp: April 04, 2024, 08:04:52 am
content: Maths... How abouthttps://en.wikipedia.org/wiki/Classical_field_theory?

author: m k
author_rank: Super Contributor
timestamp: April 04, 2024, 08:16:18 am
content: Quote from: coppice on April 03, 2024, 02:44:02 pmHere completion of 12 years, the second level, theoretical side, has a final exam where each subject has two hours.(pre requirement for university, from that route)All results are gaussian, or at least used to be.If memory serves 5% will fail.Second level of practical side, maybe a career college, had 5 to 9 scoring.Full scale was 4 to 10, but school was paid by graduates, so nobody was perfect and practically all graduated.Employers had also plenty of levels to choose.Now it's three levels.3 is for those who know what they should.2 is for those who at least tried hard.1 is for do not hire.Practical side is also reformed from earlier decades.Old career college time was stretched so that it got a higher EU level status.Level of education practically remained.New career college was also created and its level was lowered.Now all reformed old career college graduates get a title engineer.The problem is that current graduates are still using the old title scale.Practical result is that construction foremen are no more, everybody are construction engineers.For some reason construction foreman education is restarting.

author: tggzzz
author_rank: Super Contributor
timestamp: April 04, 2024, 08:27:05 am
content: Quote from: Zero999 on April 04, 2024, 07:06:21 amWell, that is a clearer statement. Becauseyouhave difficulty distinguishing between different letters, the notationeverybodyuses is wrong.Provided the semantics of the equation and variables is adequately described/understood, I don't see any strong cause for complaint.

author: IanB
author_rank: Super Contributor
timestamp: April 04, 2024, 01:24:19 pm
content: This thread has been a bit of a revelation to me.Previously, I would not have imagined that there are people who might have trouble seeing the difference between \$t\$ and \$\tau\$ in a formula. Or who might not make the immediate mental association that \$t\$ = "time" and that \$\tau\$ = "time constant".Or that it is natural that both symbols are different forms of "t", since both symbols represent time and correspondingly have the same dimensions. It is thus a deliberate choice to have things this way, and the association of "t" with time would be lost if different symbols were used.

author: nctnico
author_rank: Super Contributor
timestamp: April 04, 2024, 01:48:50 pm
content: Quote from: coppice on April 03, 2024, 02:44:02 pmI find this an odd reasoning. If you have all the answers correct, you should get a 100% score. I'm not opposed to including more complicated questions to get from 70% to 100% though.Then again I have had my fair share of inconsistent teachers. Like one who taught digital logic design and made tests where you could score 110%. And at one point I fail a math test while having all answers correct. I missed a few classes due to illness so my father (who is rather math savvy) helped me to catch up with math but made me use me the wrong (according to the teacher) method to get to the right answer

author: Zero999
author_rank: Super Contributor
timestamp: April 04, 2024, 01:53:39 pm
content: Quote from: tggzzz on April 04, 2024, 08:27:05 amIt isn't just me who has this issue.There are 26 letters in the alphabet, which should be more than enough.Not using weird symbols and upper lower case v and V would greatly improve the accessibility of mathematics.Quote from: IanB on April 04, 2024, 01:24:19 pmIt's a bit confusing, when printed, although I can normally handle it, but I don't stand a chance of being able to write it down, without making an error.Quote from: nctnico on April 04, 2024, 01:48:50 pmIf a maths teacher only gives 93% or over 100%, when all the answers are correct, complete with working, then he or she doesn't deserve their job, because they clearly don't understand percentages.If you showed your method and arrived at the answer using logic, not just guesswork, then your method is the right one. The exception being the exam question specified which method to use, i.e. use mesh analysis to calculated the voltages in a resistor network and you used a different one.

author: IanB
author_rank: Super Contributor
timestamp: April 04, 2024, 02:31:17 pm
content: Quote from: Zero999 on April 04, 2024, 01:53:39 pmAs I observed above, there is typically, in fairness to all candidates, a defined marking scheme for exams. For each question, there are certain elements that have to be provided to get the marks. If you correctly provide all the elements required for a question, you get all the marks. If you do this for all questions, you should get full marks.

author: tggzzz
author_rank: Super Contributor
timestamp: April 04, 2024, 02:38:33 pm
content: Quote from: IanB on April 04, 2024, 01:24:19 pmAgreed.It would not, however, be wrong to use a different symbol for time and \$t\$ for something else - provided it was clearly stated. Nonetheless, that would be bad taste since avoiding following a "design pattern" would violate "the principle of least surprise".Unfortunately too many schematics ignore design patterns

author: tggzzz
author_rank: Super Contributor
timestamp: April 04, 2024, 02:44:12 pm
content: Quote from: nctnico on April 04, 2024, 01:48:50 pmIn the UK I was impressed about how teaching arithmetic to 7-11 year olds had improved.In my day it was "follow the algorithm" - which was admittedly useful when I've had to implement floating point arithmetic! Nowadays they are taught that you can get the right answer by several different "successive approximations", e.g. 99y is easily calculated as 100y-y. That encourages a much better "feel" for the "shape" of numbers and arithmetic.

author: IanB
author_rank: Super Contributor
timestamp: April 04, 2024, 03:04:46 pm
content: Quote from: tggzzz on April 04, 2024, 02:44:12 pmOn a related note, when I watch (the UK quiz show) Countdown, I am always impressed at how adept Rachel Riley is with her mental arithmetic. She can, in the moment, multiply say 47 by 83 and write down the answer while speaking to camera. I think she must dream numbers in her sleep.

author: nctnico
author_rank: Super Contributor
timestamp: April 04, 2024, 03:21:26 pm
content: Quote from: Zero999 on April 04, 2024, 01:53:39 pmBut who says the alphabet you are using isTHEalphabet to use for math? There are so many different sets of symbols in use across the globe. Think about Arabic, Cyrillic, Greek to name only a few. Unicode defines about 150000 different characters for a good reason. In math and science quite a few Greek characters have a special meaning like lowercase tau, upper case delta and last but not least, lower case pi. You really have to consider math a language in itself.

author: Zero999
author_rank: Super Contributor
timestamp: April 04, 2024, 03:30:52 pm
content: Quote from: nctnico on April 04, 2024, 03:21:26 pmThe Latin alphabet is used over much of the globe, for the purposes of information exchange. Until fairly recently, virtually all text was ASCII. A good number of those Unicode symbols look virtually identical, which is also a security vulnerability: look up homoglyph attack. There's no need for that crap in the field of mathematics. It's pure obfuscation.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 04, 2024, 05:01:12 pm
content: Absolutely not intentional obfuscation. There are more than 26 unique concepts/entities in math and physics. The people who started the use of these "special" characters did it to provide shorthand and avoid confusion with other entities. The usage was productive and therefore adopted by others, eventually becoming widespread, used by people whose written language did not involve those characters.In today's world of ubiquitous data processors there is an argument that multi-character identifiers could be used, and commonly is for some symbols like pi. But this all started when you had to write your ideas on paper with a pencil or pen and a terse notation is a benefit to avoid getting bogged down in the mechanics of writing equations. Having a different notation for notebooks/scratch pads and publication made (and makes) no sense so it stuck.I am unconvinced that long variable names would be an improvement.Area_of_Circle Is_Identically_Equal_To Distance_Around_The_Rim Times The_Square_Of(Distance_From_Rim_To_Center) Times The_Ratio_Of_Circumference_To_DiameterThis expression still requires prior knowledge of terms like Equal, Identially, Rim, Square, Center, Ratio, Circumference and Diameter and is horribly unwieldy. Imagine the fun for a truly complex expression.Finally, as a native speaker of English, I will point out the 26 characters is not enough even to encode the languages common in Europe. Even leaving the Greeks and Slavs out there are enough umlauts and tildes and diacritical marks to exhaust that limited set. Unicode may go too far, but was done in a time when it had been found that even the expanded 255 characters in a byte weren't really enough and the obvious idea is to dedicate two bytes.

author: coppice
author_rank: Super Contributor
timestamp: April 04, 2024, 05:45:27 pm
content: Quote from: Zero999 on April 04, 2024, 01:53:39 pmThere can ALWAYS be greater clarity in the workings. There is ALWAYS the possibility of an insightful way to speed up the derivation of an answer that would deserve an extra mark or two. 100% says nothing could be better. I award you 0%, must try harder.

author: coppice
author_rank: Super Contributor
timestamp: April 04, 2024, 05:49:13 pm
content: Quote from: Zero999 on April 04, 2024, 03:30:52 pmUnicode is certainly a security nightmare. Between all the bugs in the character set (e.g. Chinese characters split into 2 separate ones that aren't actually different), the ability to express the same string in multiple ways, and other complexities, its nearly impossible to do a simple comparison between two pieces of text in Unicode. IBM produced a massive normalisation library in the late 90s, to try to make strings comparable, but its far from a complete answer, and isn't that widely used anyway.

author: coppice
author_rank: Super Contributor
timestamp: April 04, 2024, 05:54:29 pm
content: Quote from: tggzzz on April 04, 2024, 02:44:12 pmThe only things we were taught in maths as "follow the algorithm" were the basic arithmetic operations between 5 and about 9 years old. Everything else was derived, explained, and often alternatives were presented. Now the ONLY things taught in a way to develop understanding are the basic arithmetic operations. Everything beyond that is spoon fed. I'm not sure that "follow the algorithm" is a bad thing in primary schools. Until you've started to identify which kids are capable of anything more than following rote procedures, flexibility might be a problem.

author: Zero999
author_rank: Super Contributor
timestamp: April 04, 2024, 06:31:23 pm
content: Quote from: CatalinaWOW on April 04, 2024, 05:01:12 pmI'm not in favour of long variable names or even the complete elimination of non-Latin glyphs, but a happy medium. There's no reason to use lower case v and upper case V and similar looking glyphs ϵ and E in the same formula. Far from making it easier to write down, it introduces more room for error and confusion.

author: IanB
author_rank: Super Contributor
timestamp: April 04, 2024, 07:03:37 pm
content: Quote from: Zero999 on April 04, 2024, 06:31:23 pmI'm sorry, but I think you are alone with this viewpoint.There really is a reason to use different versions of letters in formulas. For example, \$v\$ can represent velocity while \$V\$ can represent volume, and both can appear in the same formula. If you tried to use the same letter \$v\$ for both, it would be hopelessly confusing. Similarly, we would typically have \$\epsilon\$ for an error, or for a small change, while \$E\$ would represent energy. Using symbols in a clear and consistent way like this aids communication and reduces ambiguity.

author: IanB
author_rank: Super Contributor
timestamp: April 04, 2024, 07:05:44 pm
content: Quote from: coppice on April 04, 2024, 05:49:13 pmBear in mind we are talking about text documents and communication. How are there security problems arising from the text in a technical paper or a book?

author: IanB
author_rank: Super Contributor
timestamp: April 04, 2024, 07:10:22 pm
content: Quote from: coppice on April 04, 2024, 05:45:27 pmI think you are simply wrong about this. When we consider public exams like GCSE or A-levels, there is a defined marking scheme, and every examiner is supposed to follow the scheme consistently. There are cross-checks and adjudication procedures to ensure all exam candidates get equal and fair treatment. There is no opportunity for a person marking a paper to allocate extra marks for creativity outside the marking scheme. This would be heavily frowned upon and may get the examiner removed from their job.

author: coppice
author_rank: Super Contributor
timestamp: April 04, 2024, 07:14:20 pm
content: Quote from: IanB on April 04, 2024, 07:05:44 pmThink things like URLs. Two strings are identical as text on the screen. The actual string of bytes isn't. So, you don't know which web site you are actually going to. There have been exploits based on this. Its probably a big part of the reason non-ASCII domain names have not been a huge success.

author: coppice
author_rank: Super Contributor
timestamp: April 04, 2024, 07:18:07 pm
content: Quote from: IanB on April 04, 2024, 07:10:22 pmThese days this is true for most public exams. However, they have been massively dumbed down compared to the past. I had a maths and a physics teacher who marked O-level and A-level papers in the early 70s. They had to attend a training course to try to maximum the consistency of marking between the various people marking the same papers, and the marking was expected to be quite brutal back then.

author: tggzzz
author_rank: Super Contributor
timestamp: April 04, 2024, 09:02:24 pm
content: Quote from: IanB on April 04, 2024, 07:03:37 pmAs I noted earlier, there are other reasons too...Frequently lower/upper case is used to convey information, by conventions. For example, in my first week at university my "Senturia and Wedlock" textbook section 2.3.4 is "Notation Conventions" indicates these conventions are in widespread use...General network variable: vA, iCDC component of a waveform: VCC, IBPeak amplitude of a sinusoid: Va, IcIncremental component of a waveform: va, icYes, those differences can be important, e.g. when discussing how small signal behaviour varies as bias points are changed.

author: Tation
author_rank: Regular Contributor
timestamp: April 04, 2024, 09:43:17 pm
content: For me it is stochastic processes, ergodicity and related topics. Maybe it is that I have never needed them during my career.

author: Zero999
author_rank: Super Contributor
timestamp: April 05, 2024, 04:43:22 pm
content: Quote from: IanB on April 04, 2024, 07:03:37 pmClearly not. Also note there are probably many others who feel the same but haven't posted, either through shame or just not noticing this thread,https://www.eevblog.com/forum/chat/admit-your-brain-lock/msg5428682/#msg5428682QuoteI know why. That doesn't change the fact that I find it confusing and non-intuitive.

author: IanB
author_rank: Super Contributor
timestamp: April 05, 2024, 05:13:57 pm
content: Quote from: Zero999 on April 05, 2024, 04:43:22 pmI can read what you are saying, but I cannot comprehend what you are saying. That is probably my mental block.Maybe there is some general difference in how different minds process information? Some minds may work verbally, and some minds may work visually. With verbal reasoning, there is "vee" and there is "vee", and they are hard to distinguish. With a visual mind, there is \$v\$ and there is \$V\$, and these are two different pictures, with different sizes and shapes. They are as unalike as a cat and a dog.

author: Zero999
author_rank: Super Contributor
timestamp: April 05, 2024, 05:41:24 pm
content: Quote from: IanB on April 05, 2024, 05:13:57 pmExactly people think differently.When I see something which looks vaguely like a letter, I just see the letter. Subtle differences between glyphs such as ω and w are discarded. I can clearly see the difference between T and τ, but I remember them as the same letter. This is even worse when I'm writing it down, since my hand doesn't do as my brain tells it. I often miswrite words I know how to spell. The weird non-English letters are even worse.

author: nctnico
author_rank: Super Contributor
timestamp: April 05, 2024, 05:58:05 pm
content: Sounds like a form of dyslexia to me.

author: IanB
author_rank: Super Contributor
timestamp: April 05, 2024, 06:06:14 pm
content: Quote from: Zero999 on April 05, 2024, 05:41:24 pmBut I do think learning and practice can help. Minds are not fixed, they can change.For instance learning and using the different names for different things, such as \$T\$ "tee" and \$\tau\$ "tau". If you think "tau", it could help to avoid writing a "tee". Similarly for \$\omega\$ "omega" and \$w\$ "double-u". Different names, therefore different things. (Though I admit, in this case, \$\omega\$ and \$w\$ do look very similar. That is unfortunate.)

author: Siwastaja
author_rank: Super Contributor
timestamp: April 05, 2024, 06:11:57 pm
content: Quote from: IanB on April 04, 2024, 07:03:37 pmSaying that, when others such as myself raised the same point, underlines the "secret math cult" arrogancy. You are totally proving our point.Besides, this thread is titled "admit your brain lock". What the fuck are you doing, we are discussing honestly about issues we are having understanding stuff and you come here to ridicule us for that.QuoteNice idea, but this shows how little you have actually worked with. The idea of fixed assignments of <100 symbols is completely dead. v and V can represent a lot of other things besides velocity and volume, and notoriously E can and WILL represent both energy and voltage, both of which often appear within the same formulae (also, W can represent energy (often change in energy, why won't you ever say dE for consistency?), U and V voltage - so much for "volume"). This is a total mess. Improvement starts from accepting this fact and not expecting fixed symbols to work.The only real way to deal with this mess is to choose best suitable symbols for the job,and always explain the symbols used. Come one, if you have a formula with 10 variables, it's ten lines of text to explain them all. There is no excuse not to do this. But no, you guys here come to defend this mess and outright refuse to admit its existence. You think math and its notation is elegant and consistent, in reality this couldn't be further from the truth.This discussion has made me more certain than ever that what we are indeed seeing is 100% deliberate obfuscation.I'm not suggesting of implementing modern-day programming practices into math directly, but it is quite revealing to think how most of mathematical work would never pass any code review process.

author: nctnico
author_rank: Super Contributor
timestamp: April 05, 2024, 06:24:03 pm
content: If you have the same issue as Zero999 (not registering the difference between symbols), then I'm afraid the problem is at your end (even though it isn't your fault). It is similar for a color blind not being able to work in a paint shop. And I'm not trying to make fun here. Somebody I know works at a hardware store but due to color blindness, this person can't work at the paint department. However the person can't tell the world to discard every color a color blind person can't distinguish.

author: IanB
author_rank: Super Contributor
timestamp: April 05, 2024, 06:28:17 pm
content: Quote from: Siwastaja on April 05, 2024, 06:11:57 pmYes, I know. I really meant "in a minority" but didn't manage to write that.QuoteYes, of course, but I didn't say anything about fixed assignments. I said the symbolscanrepresent certain things, as an example, not that they always do. Of course I know on an electrical forum that V can represent voltage, and that E can too. If you want to use E for voltage and also for energy in the same formula, well that would be a mess. What would you do in that situation?QuoteYes, and in every professional text I have ever read, this is what is done. Do you see places where it is not the case?QuoteIt would only be obfuscation if people were choosing unconventional symbols for things, and also not explaining what they are being used for.

author: Zero999
author_rank: Super Contributor
timestamp: April 05, 2024, 06:32:58 pm
content: Quote from: IanB on April 05, 2024, 06:06:14 pmI agree about learning like that and can cope to some degree, especially with print, but stood no chance with handwriting. I still don't see the point in make it more difficult than necessary.

author: tggzzz
author_rank: Super Contributor
timestamp: April 05, 2024, 06:35:25 pm
content: Quote from: nctnico on April 05, 2024, 06:24:03 pmPrecisely.It is a great shame for someone to have their ambitions dashed when they find their chosen career depends on normal colour vision. I've heard of aspiring pilots discovering that rather late in the day. I feel for them - but if they railed against the "colour elite" I would thing they were twats.

author: tggzzz
author_rank: Super Contributor
timestamp: April 05, 2024, 06:37:10 pm
content: Quote from: Zero999 on April 05, 2024, 06:32:58 pmIsn't that true foreverything?The discussion now pivots to the definition of "more difficult" and "necessary"

author: Siwastaja
author_rank: Super Contributor
timestamp: April 05, 2024, 06:43:11 pm
content: Quote from: nctnico on April 05, 2024, 06:24:03 pmYet, somehow, magically, I have zero problem with symbols otherwise, and definitely am not dyslexic. I read and write pretty fast and make very few spelling mistakes.And yet, if course material represents a formula with four different styles of r in it, my brain locks and I have to use much more time to parse it, than the complexity of the formula itself would require. Or if the definitions of symbols are missing, as is quite common, I say "fuck it" and try to invest my precious time in a more fruitful way.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 05, 2024, 06:46:00 pm
content: Quote from: IanB on April 05, 2024, 06:28:17 pmBut exactly this happens on a regular basis. When I point it out, people deny it by explaining that E is "completely usual" notation for voltage and I'm just stupid and wrong for not realizing that it's not energy this time.At least volume and voltage rarely appear on the same formula - but sometimes they do.

author: IanB
author_rank: Super Contributor
timestamp: April 05, 2024, 06:48:03 pm
content: Quote from: Zero999 on April 05, 2024, 06:32:58 pmWell, we have the unfortunate situation that the Roman alphabet does quickly run out of letters if you want them to be intuitive (thus we may use V for voltage, L for length, A for area, C for capacitance, N for number of turns, and so on). And we have the convention in algebra that adjacent symbols are multiplied. So if we tried to use \$ang\$ for angular velocity, it could be confused with \$a \times n \times g\$. We could try to use v or V, but that is already taken for voltage. Maybe A, but that's often area. Hence history settled on Greek letter omega (\$\omega\$). It wasn't done to confuse, it was done to avoid confusion.

author: nctnico
author_rank: Super Contributor
timestamp: April 05, 2024, 06:51:34 pm
content: There are some different conventions indeed. In the world of physics E can be used for Voltage and Energy. In the world of electricity E and P can be used for power. Typically the units used in a formula give a hint about what is what. I don't recall formulas where people use random symbols if there is a domain specific convention.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 05, 2024, 06:56:48 pm
content: Quote from: IanB on April 05, 2024, 06:48:03 pmAnd just like in programming, you add over the top of the old, until your code becomes mess, and needs to berefactored. But even justsuggestingthis is disgrace.Motor control theory for example is full of what totally looks like obfuscation, even if it's originally unintentional. Think about concept of "electromotive force", which is often shown with ANY of these symbols:EEMF (which could be confused to being E*M*F)UVuvAnd guess what - it isn't a force at all, which is made more confusing by the fact that force is a related concept (e.g. in a linear motor, very directly).But "electromotive force" already has a modern name: all you had to do is to call it voltage and use either U or V, the two most common symbols for voltage. And when you are trying to grasp motor control theory in whole, having such basic concept as fuckingVOLTAGEobfuscated to some magical "new concept" is going to be a huge time sink. Same can be said about stuff like flux linkage. Linkage what? Flux linking something to something..?There is A LOT to be improved in how we COMMUNICATE scientific concepts.

author: IanB
author_rank: Super Contributor
timestamp: April 05, 2024, 07:04:00 pm
content: Quote from: Siwastaja on April 05, 2024, 06:56:48 pmNot gonna disagree.

author: Zero999
author_rank: Super Contributor
timestamp: April 05, 2024, 07:07:18 pm
content: Quote from: tggzzz on April 05, 2024, 06:35:25 pmIt's not quite the same. Fortunately we have computers which can be programmed with plain old ASCII, so lots of this is unnecessary. It's just a shame to have to be subjected to it during education. I see it as a form of hazing.

author: DiodeDipShit
author_rank: Regular Contributor
timestamp: April 05, 2024, 07:33:30 pm
content: Which Witch is which? Which troubled those witches in Salem?Here Yee.... Hear Yea? Yes You, come here, here me !Coke or Pepsi? Pass the Mirror.Where is the ware on your wear? My Underwear. Where?Regional Dialects play havoc with foreign language. eh. Oui oui.Opinions matter, what's it matter? Matter of fact, Dark Matter matters.Pardon me, do you have any Grey Poupon? No, I poop fine. I meant mustard. Sorry, I only speak French.I order you ! Aye Aye Captain. Then an eye for an eye? Alas, Aye sailor. Aye Yai Yai ! ! !This court is out of order ! Orderly, order for takeout. Is that and order?B, B, R, O, Y, G, B, V, G, WYou can't say that ! O I B C'N U ....... next Tuesday

author: Circlotron
author_rank: Super Contributor
timestamp: April 05, 2024, 09:47:48 pm
content: Quote from: nctnico on April 05, 2024, 06:51:34 pmE is for EMF I would expect. But is EMF rigorously defined as the same thing as voltage? If so, why are there two terms for the same thing?Edit - already covered by Siwastaja above.

author: Sredni
author_rank: Frequent Contributor
timestamp: April 05, 2024, 10:09:29 pm
content: In an electromagnetic circuit, the EMF is the line integral of the induced (nonconservative) electric field; voltage on the other hand is the line integral of the total electric field and is the sum of the scalar potential difference (line integral of the conservative part of the electric field) and the EMF contribution along that path.Sorry, I could not help myself.I felt like Roger Rabbit when someone is singing "shave and a haircut"...

author: IanB
author_rank: Super Contributor
timestamp: April 05, 2024, 10:37:44 pm
content: Quote from: Siwastaja on April 05, 2024, 06:56:48 pmQuote from: Sredni on April 05, 2024, 10:09:29 pmNotwithstanding my earlier comment, it is possible to shed some light on the choice of symbol used for EMF.In electrochemical thermodynamics, the following formula may be found for the change in Gibbs free energy:$$\mathrm{d}G=-S\mathrm{d}T+V\mathrm{d}P+\mathcal{E}\mathrm{d}Q$$In which \$G\$ is Gibbs free energy, \$S\$ is entropy, \$T\$ is temperature, \$V\$ is volume, \$P\$ is pressure, \$\mathcal{E}\$ is EMF, and \$Q\$ is charge.We find here a dilemma, since in thermodyamics \$E\$ is already taken for total energy, \$V\$ is taken for volume, and \$U\$ is taken for internal energy. All the regular letters are therefore already accounted for, and using \$\mathcal{E}\$ for EMF becomes a somewhat forced choice.

author: Sredni
author_rank: Frequent Contributor
timestamp: April 05, 2024, 10:51:23 pm
content: I use double struck capital letters for Energy , Power, potential energy (U) and kinetic energy (T), work and a few others. They stick out pretty well.

author: tggzzz
author_rank: Super Contributor
timestamp: April 05, 2024, 10:54:56 pm
content: Quote from: DiodeDipShit on April 05, 2024, 07:33:30 pmFor a more, um,accomplishedexasperated variant of that, I refer you to this old chestnut:http://ncf.idallen.com/english.htmlor the version I posted herehttps://www.eevblog.com/forum/blog/perverse-language/msg607129/#msg607129

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 06, 2024, 12:07:34 am
content: In some sense these last couple of pages have been a variant of "Why can't we all just use the same words for everything." It would be so much easier if everybody just spoke English, or Chinese or Spanish or whatever. Much of the confusion described here comes because many different fields of expertise developed as independent islands. Whether that island consisted of a technology area, a university group, a scientific society or geographical unit doesn't matter. They developed conventions that made sense in the context, and passed those conventions on to their own peers and successors.The term interdisciplinary only became popular in the last 50 years or so. The reality of interdisciplinary work has caused overlap in the conventions. But no one who has spent half their career steeped in one convention enjoys the idea of uprooting for another. The convention they grew up with isn't confusing to them, the new one is, and seems an attempt to upset the applecart.The only way a unified symbology and terminology will take over is if the benefits seem to outweigh the drawbacks (Reprinting textbooks, retraining existing practitioners, time invested in trying to unravel all of the different needs and objectives). I don't object to the process, but don't see how pejoratives such as obfuscation contribute to the solution.

author: fourfathom
author_rank: Super Contributor
timestamp: April 06, 2024, 01:35:19 am
content: Quote from: CatalinaWOW on April 06, 2024, 12:07:34 amEveryoneshould speak West-Coast American English, as God intended.

author: pcprogrammer
author_rank: Super Contributor
timestamp: April 06, 2024, 06:43:19 am
content: Quote from: fourfathom on April 06, 2024, 01:35:19 amAt the risk of being punished, here in lies proof that a god does not exist.If there actually is one and the intent was to have every body speak West-Coast American English, would it not already be the case. You know that when "he" created it all that "he" would have made sure of this.Or do we blame it upon the opening ofPandora's boxthat this is not the case.

author: VinzC
author_rank: Frequent Contributor
timestamp: April 06, 2024, 08:40:22 am
content: Quote from: mkiijam on March 28, 2024, 06:52:32 pmThings I've done more than a few minutes ago.Oh, and things I've done less than a few minutes ago.Quote from: mkiijam on March 28, 2024, 06:52:32 pmIt's not brain locks, I think, it's just brain slips. And it doesn't get better with age. (At least speaking for my own little self.)

author: Siwastaja
author_rank: Super Contributor
timestamp: April 06, 2024, 08:56:47 am
content: Quote from: CatalinaWOW on April 06, 2024, 12:07:34 amNo, it's the exact opposite: I am showing we must admit that we are NOT using the same words for everything, and we should not even try too hard for a totally universal symbol system as it's futile, but instead should try to concentrate on:* Making communication simple and clear* Explain and document the terms usedThere is synergy between these two points: when you simplify, you reduce your own documentation task.For example, a voltage produced by rotating permanent magnet motor does not care about line integral versus other types of integrals. It is just voltage, which you can measure with a multimeter, a simple one-dimensional scalar which changes as function of time. Therefore, a motor-generated voltage can be called voltage, and the term "electromotive force" or "line integral" does not need to appear in motor control theory at all.Therefore, the explanation about what "motor-generated voltage" is, will be much shorter and easier to understand, than historical review of why electromotive force is called electromotive force and... well look at Sredni's reply. To really understand what he is saying I would need ten times more explanation, make myself a few cups of coffee, and look at it carefully. This is completely wasted time if I'm interested about the voltage that appears on the wires of a rotating permanent magnet motor, which is very relevant when I want to control the motor.

author: DiodeDipShit
author_rank: Regular Contributor
timestamp: April 07, 2024, 01:14:27 am
content: Quote from: tggzzz on April 05, 2024, 10:54:56 pmFor a more, um,accomplishedexasperated variant of that, I refer you to this old chestnut:http://ncf.idallen.com/english.htmlor the version I posted herehttps://www.eevblog.com/forum/blog/perverse-language/msg607129/#msg607129Tggzzz, thank You for that link ! !Getting half way through was rough.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 07, 2024, 02:38:05 am
content: Quote from: Siwastaja on April 06, 2024, 08:56:47 amI agree, simple is good. But your example is a good one to start with. Do a thought experiment. Connect an ideal battery (no internal impedance) to an ideal DC motor (no friction, but it does have mass). Assuming the motor is not rotating at the start what happens over time? The motor accelerates until the back EMF (use that term for the moment, we'll get back to that) equals the battery voltage. The acceleration is proportional to the difference between the battery voltage and the back EMF. Where do you attach your voltmeter to measure the back EMF? You can't, it is a virtual voltage which must be kept separate from what your voltmeter measures across the motor terminals. You could infer it by measuring motor speed and using the motor constant you measured in another experiment. But it is a separate and unique voltage that must be identified separately from the supply voltage. You could use a subscript, perhaps B for back, but that could be confusing relative to B for battery. So now we are just quibbling over symbols. EMF has apparently confused you because forces and voltages are not the same thing, but you have not complained about the fact that a stack of electro-chemical cells has nothing to do with an array of cannons.While there probably is a historical reason involving line integrals for the original use of EMF as the symbol for this term, the key is that a specific symbol is needed (just as there is a need for a specific symbol for the voltage at each node of a Kirchhoff loop) and that there will always be arguments about which mnemonic is best. Unless you concede to sentence length subscripts, which might not need to be standardized to improve communication.

author: Smokey
author_rank: Super Contributor
timestamp: April 07, 2024, 02:50:25 am
content: Quote from: fourfathom on April 06, 2024, 01:35:19 amDude!

author: paulca
author_rank: Super Contributor
timestamp: April 07, 2024, 10:35:03 am
content: Quote from: tszaboo on March 29, 2024, 01:27:11 pmIt's better that way. Based on the number of regular expression bugs I find and fix I figure more people need to take the approach of "I don't understand this" and ask for help.Probably the no.1 most common bug is over-greed and un-anchored wild cards..*eevblog.comto match sub-domains, as an example.A better example, but still very, very wrong, would then be:.*.eevblog.comNope!.*\.eevblog.comNope!.*\.eevblog\.com$Now we are getting somewhere.trojan.eevblog.com.h8xzor.xx.ttWhat definitely goes into my pile of "I don't understand this", is anything beyond about middle school mathematics. Once the material comes from Mathematicians and not "normal people" I just stop following. For some reason, maths or particularly the language of maths ended up in the bin. I'm usually okay when the concepts are explained, but when I then get presented with a formula in a datasheet which contains greek, I'm immediately "Nope". Not worth my time.On a more micro level, I have issues processing "inclusions" and "exclusions" on ranges. It's not that I have a problem, it's more that I can't give straight answers to those questions like "How many days between Monday and Wednesday?", without having to stop and think carefully if it's x-y, or if it's x-(y-1) or if it's x-(y+1) or x+1-y. If Monday and Wednesday are included then it's 3. If they are not it's 1. The "commonly interrupted answer" I believe is actually y-(x+1) which is 2 days. I still have to stop and think everytime.I have programmer "out by one" paranoia.

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: April 08, 2024, 09:48:37 pm
content: My brain lock: transitioning from time domain to frequency domain and back. I'm ok with the mechanics (math) of it, but just can visualize what the math is doing.

author: Zero999
author_rank: Super Contributor
timestamp: April 10, 2024, 09:01:30 am
content: Quote from: Ground_Loop on April 08, 2024, 09:48:37 pmThat's odd because I have the opposite problem. I can visualise transitioning from the frequency to the time domain, but I struggle with the calculations, partly due to my difficulty with the notation, as I've mentioned above.