UmbralRaptor changed the topic of #kspacademia to: https://gist.github.com/pdn4kd/164b9b85435d87afbec0c3a7e69d3e6d | Dogs are cats. Spiders are cat interferometers. | Космизм сегодня! | Document well, for tomorrow you may get mauled by a ネコバス. | <UmbralRaptor> … one of the other grad students just compared me to nomal O_o | <ferram4> I shall beat my problems to death with an engineer.
<bofh> SnoopJeDi: ooh, neat! I have not seen this yet, thanks :3
<bofh> https://i.redd.it/a2djibfbu0uz.jpg completely unrelated, but have a Cthurkey.
<egg> bofh: Ꙩ_ꙩ
<egg> !choose sleep|don't
<Qboid> egg: Your options are: sleep, don't. My choice: sleep
<egg> ;choose sleep|don't
<kmath> egg: don't
<egg> hmm
<egg> but what should I do instead
<bofh> don't :P
<UmbralRaptor> Opus Magnum, presumably.
e_14159 has quit [Ping timeout: 186 seconds]
e_14159 has joined #kspacademia
<egg> !wpn котя
* Qboid gives котя a radon tadpole which vaguely resembles an axiom
egg is now known as egg|zzz|egg
<bofh> !wpn egg
* Qboid gives egg a nu field extension
<bofh> oops, wrong window
icefire has quit [Read error: Connection reset by peer]
egg|cell|egg has quit [Ping timeout: 200 seconds]
egg|zzz|egg has quit [Ping timeout: 204 seconds]
egg has joined #kspacademia
<bofh> https://mobile.twitter.com/realscientists/status/923343236927717376 world's tiniest violin, courtesy atomic force microscopy
<kmath> https://twitter.com/realscientists/status/923343236927717376 <realscientists> For example, here's a "nanoviolin" made by one of my REU students by biased AFM nanolithography. The features are <… https://t.co/rcLF5kgTVt
<rqou> egg: something for the "plz 2 teach me later" queue: lagrangian dynamics
<rqou> egg: you should go to 34c3 and i can bribe you to teach me things :P
<UmbralRaptor> Looks like le grand K will exit service after 130 years? https://scienmag.com/scientists-update-four-key-fundamental-constants/
<SnoopJeDi> \o/
<bofh> Nice.
<rqou> aw, they didn't end up using that fancy shiny silicon sphere?
<SnoopJeDi> It's still relevant I think, but the Watt balance is preferred for a definition?
<SnoopJeDi> rqou, I believe that's what they're referring to when the article says Avogadro method
<rqou> ah, i see
<SnoopJeDi> and/or the distance between silicon atoms (which is averaged by measuring the diameter of the polished sphere, as I recall)
<SnoopJeDi> if the lattice is pure, the lattice is regular, so at that point it becomes how well you can polish a sphere (reaaaaally well) and the analytical lattice
<kmath> <diodelass> Can we have one of those contrived action movie scenes with computer hacking that's the same exact thing except it's realistic
<Ellied> "Alright, I'm gonna try to crack the encryption on this .RAR file, it might have info on where the bomb is." "how long will that take?" "Oh, uh... I dunno, they probably used a decently long key. Maybe, uh, thirty or forty?" "hours?" "days."
<SnoopJeDi> "Okay, let's brute force the password." "Fuck, locked out after 3 attempts."
<SnoopJeDi> with something in the middle about "it's only [small large number] combinations"
<SnoopJeDi> 4-key entry pad for a safe vault maybe
<rqou> but realistic = "there's a post-it somewhere with the password"
<SnoopJeDi> "Great, we'll search this entire building...wait..."
<rqou> tries 1234 - nope; tries 1111 - ah there we go
<rqou> :P
<rqou> alternately:
<rqou> tries 1234 - nope; tries 1111 - nope; tries 1235 - ah, they avoided the obvious 1234 this time
<SnoopJeDi> it's clearly 0451
<SnoopJeDi> god, I forgot about the 0451 trope, what a great easter egg
<rqou> btw, since these codes are no longer in use, i have some fun pin codes for you guys: 21546, 32546 :P
<rqou> these were the codes for an actual legit building here on campus, and they hadn't been changed for at least a decade
<SnoopJeDi> I don't recognize either one
<rqou> unfortunately a few years back the university got a new security policy that dictated that pins were no longer allowed on exterior doors
<rqou> so they tried to disable these, but apparently nobody knew how to actually disable codes on this lock
<rqou> so they eventually did this by removing the mechanism that unlocks the door from the keypad
<rqou> so if you tried one of these codes after that, there would still be motor noises but the door wouldn't unlock
<rqou> brilliant :P
<Ellied> my uni has a bad habit of using memes for lock combinations
<SnoopJeDi> a former employer had a 4-digit door lock on their (admittedly 24/7 operational) warehouse door...the digits had VERY noticeable button wear
<Ellied> everything in physics is 3141
<SnoopJeDi> comp sci is 1337?
<Ellied> probably
<rqou> meanwhile, a while back it was widely circulated that "oh, you need after-hours access to <ee building>? one of the doors has a latch issue and doesn't latch reliably. just yank on it really hard"
<SnoopJeDi> math is 2718
<Ellied> stuff not associated with one particular department (e.g. library) uses the birth year of Vincent DePaul, har har
<rqou> apparently this got circulated enough that the administration noticed
<SnoopJeDi> oh jeez
<rqou> also, for extra bonus points, those two codes i mentioned?
<rqou> don't you think it's weird how i knew _two_ codes? :P
<rqou> yeah, the security was _that bad_
<bofh> 21546 is weirdly common in my experience.
<rqou> what
<rqou> really?
<SnoopJeDi> you can type it with just your left hand on a keyboard, I'd believe it
<Ellied> I have a password I can type with only my left hand, but it's not just numbers and it's different than my encryption passphrase.
<bofh> https://youtube.com/watch?v=sn_aTpZEreo&fmt=18 ahh, psy trance (not to be confused w/psytrance)
<kmath> YouTube - Gangnam Style - Party Trance Remix
<FluffyFoxeh> }WpO{EbH\%`Yh+R;
<FluffyFoxeh> ^free password
<rqou> wow, i have the exact same password on my luggage :P
<rqou> hey, anybody with a not-shit CAS want to help me take the derivative of (l*cos(q_1)*r_1+a*cos(q_2)*r_2)^2 with respect to r_1?
* rqou sucks at basic calculus
<SnoopJeDi> bofh, I rediscovered AMVs tonight and _oh no_ there's so much good music
<FluffyFoxeh> this will create more free passwords for you http://kitsune.fastquake.com/files/randomstring
<FluffyFoxeh> free password generator 2017
<FluffyFoxeh> password generator free
<FluffyFoxeh> Been there many times. Never had a bad meal or bad service. We have brought friends and family here and no one has come away with any complaints. Great spot... Just the name says it all...
<FluffyFoxeh> please click here to unsubscribe
<rqou> huh, lagrangian dynamics are pretty neat; why wasn't i taught it this way?
<egg> !wpn rqou
* Qboid gives rqou an obvious hull
egg is now known as egg|afk|egg
<egg|afk|egg> rqou: for classical mechanics ask UmbralRaptor or bofh
<egg|afk|egg> *maybe* ask me for the Hamiltonian approach but I've basically never touched a Lagrangian
<egg|afk|egg> !wpn rqou
* Qboid gives rqou a dip pen with a gluon attachment
<egg|afk|egg> !wpn whitequark
* Qboid gives whitequark a central yxala
<egg|afk|egg> !wpn Fiora
* Qboid gives Fiora an omicron sum
egg|phone|egg has joined #kspacademia
egg|cell|egg has joined #kspacademia
egg|phone|egg has quit [Read error: -0x1: UNKNOWN ERROR CODE (0001)]
egg|mobile|egg has joined #kspacademia
egg|cell|egg has quit [Ping timeout: 186 seconds]
egg|mobile|egg has quit [Ping timeout: 383 seconds]
ferram4_ has quit [Read error: Connection reset by peer]
ferram4_ has joined #kspacademia
<UmbralRaptor> AIUI, Lagrangian is nicer than Hamiltonian in some details (you just have q and \dot q, no messing with momentum outside maybe of the derivation), but you always get 2nd order differential equations for motion.
<UmbralRaptor> Or was rqou always stuck with Newtonian?
<egg|work|egg> UmbralRaptor: but you get a Poisson bracket
* UmbralRaptor Legendre transforms the bracket.
<bofh> appropriate
<bofh> And yeah, what UmbralRaptor said.
<egg|work|egg> bofh: but Poisson brackets!
<egg|work|egg> {?, ?}
<UmbralRaptor> {?, ?, ?: ?}
<egg|work|egg> !u ??
<Qboid> U+1F421 BLOWFISH (?)
<Qboid> U+1F988 SHARK (?)
APlayer has joined #kspacademia
<UmbralRaptor> !wpn APlayer
* Qboid gives APlayer a vanadium bird-like divergence
<APlayer> !wpn UmbralRaptor
* Qboid gives UmbralRaptor an adiabatic trombone
<APlayer> How are you?
<UmbralRaptor> ∇x?
<UmbralRaptor> Doomed?
<APlayer> !u ?
<Qboid> U+1F426 BIRD (?)
<APlayer> Huh?
<UmbralRaptor> Uneasy about a QM test in, uh, 6 hours.
* APlayer is sorry for UmbralRaptor
<APlayer> Your cold got better?
<UmbralRaptor> Yeah. Mostly better now.
<APlayer> Well, I wish you luck then
<UmbralRaptor> thanks
<APlayer> May the wave function be in your favour :P
<UmbralRaptor> If a wave function collapses on you, does it hurt?
<kmath> <sjs917> @abhirajan "Don't believe anything that's published... unless you published it yourself. And even then, sometimes..." #bdexocon
<egg|work|egg> !wpn UmbralRaptor
* Qboid gives UmbralRaptor an extensional line
<egg|work|egg> !wpn bofh
* Qboid gives bofh an Oxford scale
<UmbralRaptor> A long line?
<APlayer> Uh, Ellied: First round of obtaining the MOSFETs was a partial success. I think I got a fitting n-channel one (only checked the datasheet, did not try if it works), but the p-channel one is an "NPN darlington transistor", whatever that might be.
<APlayer> !wpn egg|work|egg
* Qboid gives egg|work|egg a moral supremum
<APlayer> Wikipedia says it is a brute force transistor combination to increase the rated voltage, apparently
<APlayer> Anyway, I got it. Still, the question remains - will it work?
<APlayer> Also, if the datasheet has a minimum and a maximum value for the V_GS threshold, which one should I use?
<APlayer> If I want to simulate the MOSFET in falstad, let's say
<bofh> so an NPN darlington transistor is very very far from a P-channel MOSFET. Maybe Ellied knows how to recreate the circuit appropriately to use one instead but I can't see it myself.
<bofh> !wpn UmbralRaptor
* Qboid gives UmbralRaptor an enriched bolt
<APlayer> I am instead modifying the current circuit to be able to use a transistor
<APlayer> The main difference I see id that in conducts from gate to emitter?
<APlayer> s/gate/base/
<Qboid> APlayer meant to say: The main difference I see id that in conducts from base to emitter?
<APlayer> And falstad does not seem to provide any parameters I may edit regarding the darlington transistor?
<APlayer> You know what? Let me just build the circuit for real. I mean, won't kill anyone. A transistor, at most
<bofh> Yeah.
<kmath> https://twitter.com/bofh453/status/923576326073798657 <bofh453> Today I learned why autoconf/m4 comments are "dnl" - it stands for "delete until newline". It literally is *accidentally* used for comments.
<SnoopJeDi> w..what is the other use-case
<UmbralRaptor> Storage so limited you delete comments?
<UmbralRaptor> Really bad interpreted language, where comments substantially reduce performance?
* UmbralRaptor stares at JavaScript.
<SnoopJeDi> I like to think of JS as the scrappy kid out of the hood among programming languages. Came from a rough beginning but made good
<UmbralRaptor> AIUI, that is an actual problem. Or was as of 2016.
<SnoopJeDi> Comments in JS?
<UmbralRaptor> Comments in JS causing nontrivial performance loss, yes.
<SnoopJeDi> ...huh, apparently V8's in-lining is indeed sensitive to whitespace/comments.
<UmbralRaptor> Granted, it doesn't help that websites run 10s of megabytes of style and tracking scripts to display kilobytes of text. >_>;;
<SnoopJeDi> that one pixel at a time code execution flaw in an ad network from last year continually blows my mind
<kmath> https://twitter.com/wellerstein/status/923316964734402562 <wellerstein> @ColdWarScience On *my* laptop? Nothing that should make anyone *too* uncomfortable... https://t.co/It4o1ZydMl
<SnoopJeDi> LOL
* egg|work|egg gives Fiora a moth
<SnoopJeDi> man, that blast radius schematic is one of the most attractive maps I've seen in ages
<Fiora> wah
<egg|work|egg> Fiora: well, котя and whitequark eat moths, so maybe you also do, being a cat,
<UmbralRaptor> bofh: oh, good. If Capitol Hill gets nuked, I'm safe for anything under a megaton.
<UmbralRaptor> egg|work|egg is eggsploring greener protein sources.
APlayer has quit [Ping timeout: 383 seconds]
<kmath> <jasonkastner> A sign above the trash can in the men's room on the @NASAEuropa floor applies some appropriate pressure. https://t.co/74WdkpHauZ
APlayer has joined #kspacademia
* egg|work|egg screams incoherently at CJKV unification
* Iskierka wonders why
* bofh also wonders why
<APlayer> Uh, nope. Either I messed up creating the circuit, or something does not work, or something is broken, or it's my testing no-soldering board
<APlayer> Anyway something is wrong, although it certainly conducts
<APlayer> Not much, though
<Iskierka> multimeter time
<APlayer> Used it
<APlayer> Only in one spot, but whatever
<APlayer> It was enough to determine that something is not behaving as expected
<Iskierka> so ... ?
<Iskierka> keep poking it. debug it.
<APlayer> Now testing if the transistors even work
<APlayer> I guess that's the only thing that could actually be broken
<APlayer> Meanwhile, anyone could double check this? http://tinyurl.com/ybfjyfjv And how do I "customize" the darlington transistor there?
<APlayer> I.e. input threshold voltage for starters
<APlayer> Well, there we go
<APlayer> Either I was too stupid to interpret the datasheet, or it lied on what the pin layout is
<APlayer> Wut
<APlayer> When I connect the base, the Collector-emitter resistance seems to oscillate between 12 and 22 kOhm
egg|phone|egg has joined #kspacademia
<APlayer> Heh, EE is more fun than expected :P
<APlayer> Okay, what the actual hell, I am not getting any closer to finding out how that thing works
<APlayer> Am I reading this correctly? http://cdn-reichelt.de/documents/datenblatt/A100/TIP120_TIP121_TIP122_TIP125_TIP126_TIP127%23STM.pdf the pins should be, from left to right, base, collector, emitter?
<Ellied> APlayer: an NPN darlington pair is analogous to an N-channel MOSFET, not p-channel
<APlayer> Let me first get straight how it works by itself
<Ellied> TIP120 is a common part, I have a few lying around. It's just a bipolar transistor with a DC current gain of 1000.
<egg|phone|egg> !Wpn Ellied, Fiora, whitequark, et al.
* Qboid gives Ellied, Fiora, whitequark, et al. a trampoline impenetrability condition
<Ellied> (e.g. if you put 1 mA into the base terminal, it allows 1 A to flow collector to emitter)
<APlayer> Well, then I have 2 similar working parts
<APlayer> Can't do much about that
<APlayer> Will return one of them tomorrow, if not both
<Ellied> a PNP darlington pair would do the job in place of the P-channel MOSFET if it had a high enough current tolerance
<kmath> <DeliaDDay> Thank you @computermuseum for a top day of #DeliaDerbyshire inspired activities! And thank u to #Cambridge audience… https://t.co/DE6F5s8q1S
<Ellied> er, current rating, "tolerance" is not the right word but I keep using it :P
<SnoopJeDi> it's a fair enough word to use
<Ellied> sure, it just has a specific meaning in EE that's not really that, no?
<APlayer> Anyway, I still don't understand what pins to connect where :P
<Iskierka> I think its meaning is contextual on what you attach it to anyway. Given current isn't exactly a fixed property of a device that it was made to, default definition doesn't match
<SnoopJeDi> I don't know enough EE-fu to really say
<SnoopJeDi> I guess it's perhaps more commonly used for performance values than "this is what it can take"?
<APlayer> Also, Ellied, I wanted to remind you that I have already saved the image of the circuit diagram you made me a while back. May take it down from your server if it is annoying or anything
<Ellied> noted, but I have no pressing need to take it down at the moment
<APlayer> Okay then
* Iskierka tends to leave stuff where it is until there is some reason to alter
<Ellied> 'tolerance' usually means 'manufacturing variance' IME, e.g. resistors with a gold band meaning that they'll be within 5% of the specified resistance.
<APlayer> Iskierka: Same. Usually my mother is the reason, though :P
<Ellied> also yes, you're reading that correctly, the base is usually not in the middle for TO-220 packages for whatever reason
<SnoopJeDi> that's the one I really like bofh
<Ellied> the metal tab is probably the collector, which IMO is even weirder
<SnoopJeDi> I'm really glad I quarantined news away from my Twitter feed, stuff that fits my particular brain damage showing up more often makes the experience delightful
<kmath> <FemmesofStem> Our next Historical Femme will be Sofya Kovalevskaya, a 19th century Russian mathematician! ??‍? Who loves her alre… https://t.co/wgTHqabLqd
<SnoopJeDi> so...is PanSTARRS being maybe interstellar all hype, or is there something to it?
<APlayer> Ellied: In that case, I am too dumb to operate it
<Ellied> no way
<Ellied> you have demonstrated that that isn't true
<APlayer> I have proof :P
<APlayer> So, I connect the base to +3.3 V and the emitter to ground
<APlayer> And then I measure collector-emitter resistance
<Ellied> okay, so there are two immediate problems here
<Ellied> One, this is a current-operated device, unlike a MOSFET which is voltage-operated, so you need a resistor between the power rail and the base or you'll end up with too much current flowing
* APlayer mumbles something indistinct about being or not being dumb ;-)
<Ellied> two, it's not ohmic, so measuring the resistance is going to give you the wrong idea
<APlayer> Okay, let me see
<APlayer> So that's why falstad has no parameters for those?
<Ellied> you can think of the base as being internally connected to the emitter by a magic diode that measures how much current flows through it. Connecting emitter straight to ground and base straight to 3.3V is going to make a lot of current flow
<Ellied> yeah
<APlayer> And what about thresholds?
<Ellied> BJTs just have the forward barrier potential of a diode from B to E, so the threshold is about 0.7V for silicon
<APlayer> Ah
<Ellied> when they're switched on you end up with that same barrier from C to E, so there will always be a small voltage drop there too
<APlayer> Very well, let me use one of those 100 kOhm gems
<Ellied> Unlike a MOSFET where it's actually ohmic between D and S while on
<APlayer> And what does it do when switched on/off if it is not ohmic?
<Ellied> it sort of acts like a current regulator. B-E is a magic diode that measures current; C-E is another kind of magic diode that looks at the B-E diode's current and allows a proportionally larger (by the DC current gain) current to flow through it.
<APlayer> Okay, I guess I'd better use the MOSFET then
<APlayer> (Man, I have a better understanding of those than of a normal transistor by now)
<Ellied> having *less* current than that flow through is fine (that's called "saturation" which is where you want it when it's turned on) but if the transistor is the only thing in the circuit limiting current, it'll have a higher voltage across it than just the barrier potential of the diode.
<Ellied> yeah MOSFETs are straightforward IMO, they should cover those first in schools
<APlayer> Thank you, multimeter
<APlayer> Went into standby mid-measurement
UmbralRaptor is now known as DoomedRaptor
<FluffyFoxeh> a long time ago I spent a lot of time trying to make simple amplifiers with transistors. I couldn't stop it from clipping the signal one way or another :|
<Ellied> clipping means either a) you're giving it too much of an input signal, b) too much gain, or or c) if you really want to amplify that signal at that gain, not enough supply voltage
<FluffyFoxeh> is it possible the base bias was wrong?
<DoomedRaptor> SnoopJeDi: partial hype. Hoping we can get decent orbital parameters before it's too faint.
<Ellied> I mean yeah, if your bias network was trying to produce too much gain
<SnoopJeDi> DoomedRaptor, gotcha, thanks
* APlayer needs a big chunk of metal to discharge things more easily
<DoomedRaptor> Iskierka: I want to say that that's an actual outreach strategy. >_>
<FluffyFoxeh> well I'm thinking for an amp to work, the input has to have a DC offset at the midpoint between cutoff and saturation so the input signal doesn't turn it completely on or off (which would cause clipping)
<FluffyFoxeh> does that sound right?
<DoomedRaptor> APlayer: like a coke can, or…?
<APlayer> Like an iron 25 kg weight :P
<APlayer> Okay, thank god the MOSFET is not acting weird
<APlayer> Good boy :D
<FluffyFoxeh> though I think something I often failed to realize was that the base voltage relative to ground was not the same as the base voltage reletive to... whatever it was supposed to be measured relative to (I don't recall)
<DoomedRaptor> SnoopJeDi: hopefully we'll see more here http://www.minorplanetcenter.net/mpec/K17/K17UI3.html
<DoomedRaptor> (C→A because it has stopped showing cometary activity.)
<APlayer> But things are impossible to test as a whole like this, I am getting resistances on the order of up to 5 MOhm from a plug connection
<FluffyFoxeh> The emitter, I think. In a common-emitter configuration where the emitter is connected to gnd
<SnoopJeDi> I saw something on Twitter about dropping an outlier bringing the eccentricity below 1.0, but I don't grok it all well enough to do my own examination of the data without investing a little chunk of time
<SnoopJeDi> I'm happy to just be patient and let astro sort it :P
egg|cell|egg has joined #kspacademia
egg|phone|egg has quit [Read error: Connection reset by peer]
<DoomedRaptor> I suspect egg knows the method for getting orbital elements out of RA/Dec/time measurements.
<DoomedRaptor> I'd have to look it up, but more or less a regression equation.
<SnoopJeDi> oh yea, I know I could crack open Fitzpatrick's book and figure it out, I just don't wanna :P
<APlayer> Probably straightforward brute force euclidean vector stuff?
<APlayer> Anyway, thanks Ellied
<DoomedRaptor> I think so?
* DoomedRaptor pokes Halley's ghost.
<APlayer> Will just bring the parts back, they are much over-rated, the threshold voltage of the MOSFET is not quite in the range I need (might get ugly if the voltage is not exactly as expected), and they are overrated and too large for the job
<APlayer> Woops, I named "overrated" twice
<APlayer> I meant to say that I have two n-channel-like parts instead of one of those
<egg|afk|egg> DoomedRaptor: wah?
egg|afk|egg is now known as egg
<egg> STARRS?
<egg> PAN-STARRS?
<egg> PANSTARRS?
<egg> hmm
<APlayer> Fork-STARRS
<egg> !acr -list
<Qboid> egg: I will send you a list of my acronyms!
<egg> ah,
<Iskierka> PanSTARRS?
<Qboid> Iskierka: [PanSTARRS] => Panoramic Survey Telescope and Rapid Response System
<egg> yup
* Iskierka saw formatting in official
<Ellied> FluffyFoxeh: re: biasing; yes, you want it to be already partially turned on with no signal so that the absolute maximum input oscillates between just barely fully off and just barely fully on
<Ellied> so yeah that could easily have been the problem
<APlayer> egg? Could you help me a bit with vector stuff?
<FluffyFoxeh> I also recall it got weird to try and reason about the base-emitter voltage because by some definition it was always 0.7 or something?
<FluffyFoxeh> there wasn't supposed to be a question mark there
<APlayer> s/something?/something/
<Qboid> APlayer meant to say: /me mumbles something indistinct about being or not being dumb ;-)
<APlayer> No, not really
<Ellied> if you take [egg]v = λv, does v refer to the eggenvectors?
<APlayer> aee-eggenvectors
<FluffyFoxeh> APlayer: \
<APlayer> ?
<FluffyFoxeh> the question mark is a regex metacharacter and needs escaping
<FluffyFoxeh> with a backslash
<FluffyFoxeh> :p
<APlayer> Ah
* APlayer sucks at regex
<APlayer> That is, /me has no idea about regex
<SnoopJeDi> in certain flavors*
<FluffyFoxeh> yeah. certain flavours. regular expressions are actually pretty irregular
<Ellied> FluffyFoxeh: yes, it's 0.7 because that's the barrier potential of a silicon junction
<Ellied> really it varies by a tiny amount with the input, which corresponds to a much larger change in current.
<Ellied> the I-V curve is very steep once you clear the barrier, so a tiny change in voltage corresponds to a large change in current.
<FluffyFoxeh> Hm. So I don't understand how you're supposed to define base-emitter voltage since they are connected in a way that keeps it constant
<Ellied> it ideally is constant. I think generally you talk about input bias current, right?
<kmath> https://twitter.com/jadankety/status/923547486131773440 <jadankety> aside from tweeting more, May has embraced a " t h e r e s a m a y p o r w a v e " a… https://t.co/Tffdn5CQJh
<FluffyFoxeh> Ellied: well for an amplifier, or even a simple switch, you want to set the base voltage in order to turn it (partially) on or off (right?). I'm confused about what this voltage is measured relative to
<Ellied> Emitter, it's just that it's *nearly* constant
<Ellied> you want to bias it so that it's operating halfway between saturation and cutoff, which holistically does mean a specific base voltage, but practically is easier to define as a certain base current
<FluffyFoxeh> yeah so how can you set the base-emitter voltage to 3V or whatever if the behaviour of the transistor won't allow it to move that far from 0.7V?
<Ellied> you can't set it to 3V, at least not realistically. it would be, like, 0.703 or something
<Ellied> what you might do instead is connect some value resistor from 3V to base so that you get the bias current you want
<FluffyFoxeh> so when people talk about saturation voltage, they're referring to the voltage that would be present *if* the base-emitter current were fixed at 0?
<FluffyFoxeh> i.e. not connected
<Ellied> er, if the b-e voltage is less than the barrier potential then you're in cutoff, not saturation
<egg> whitequark: how is котя doing?
<DoomedRaptor> Majiir: what are you doing?! https://twitter.com/7News/status/923195976814383105
<kmath> <7News> Kia recalls more than 300,000 Souls in US for second time https://t.co/UKzrYFQt9C
<SnoopJeDi> LOL
<kmath> <TheTXI> @7News I have to say I am less than impressed with this Rapture
<FluffyFoxeh> trying to find a datasheet for a "typical" NPN transistor to see what specs they give you but apparently the 2N2222(A) is obsolete now?
<FluffyFoxeh> oh well the datasheet still exists so that's fine
<whitequark> egg: pretty well, actually
<egg> yay :-)
<whitequark> we set up https://www.feliway.com/us
<whitequark> i think that's working very well
<egg> what's that?
<whitequark> cat pheromones
<egg> huh, fun
<Ellied> Biasing might look like this: your transistor has a hFE of 1000, you have a power rail voltage of 10V, and and output pull-up resistor of 100Ω. Your saturation C-E current is (10V-0.7V)/(100Ω), or 93 mA, so you need to introduce 0.093*0.5/1000 mA of bias current into the base; that means you need a resistor from 10V to the base of (10V-0.7V)/(1000*46.5mA) = 200kΩ
<Ellied> I think I did that right
<Ellied> FluffyFoxeh: I think the metal can 2N2222 is obsolete, but the PN2222A is in common use still?
<egg> whitequark: Ꙩ_ꙩ when I don't do /us that site redirects me to /fr
<FluffyFoxeh> Ellied: I have like, a shit ton of the cans
<FluffyFoxeh> :p
<egg> *must refrain from diagnosing bad i18n*
<Ellied> I suppose that means the input bias resistor is just 0.5*hFE*output resistor
<egg> !wpn whitequark
* Qboid gives whitequark a benzene cube
<Ellied> oh, looks like it's Fucked O'clock for the wifi here again
egg is now known as egg|sandwichmaking|egg
<FluffyFoxeh> Ellied: sorry, where di the 0.5 come from?
<Ellied> you want it halfway to saturation
<FluffyFoxeh> ah yeah
<Ellied> you could game that as you like for various input signal characteristics but if you're using capacitive coupling and a signal with an average duty cycle of 50% you'll want 0.5
<FluffyFoxeh> oddly I've either never read about transistor biasing in terms of current rather than voltage or never understood it
<FluffyFoxeh> it does seem more intuitive though
<APlayer> sudo make egg a sandwich
<DoomedRaptor> sudo make sandwich -egG
<DoomedRaptor> sudo make sandwich --egg
<DoomedRaptor> <_< >_>
<SnoopJeDi> mv egg sandwich
<FluffyFoxeh> well thanks for the info, Ellied. it's given me something new to think about
egg|sandwichmaking|egg is now known as egg
<Ellied> sure thing
<egg> !wpn DoomedRaptor
* Qboid gives DoomedRaptor an encrypted array
<DoomedRaptor> !wpn egg
* Qboid gives egg a cetacean vertex
<Ellied> I keep remembering and being shocked by the fact that before the end of my sophomore year here, I didn't even *know* that electronics was my thing
<Ellied> like I was interested in it but I thought I wanted to go into mech eng
<FluffyFoxeh> Ellied: heh I switched from software engineering to comp sci 3 days before my first day
<FluffyFoxeh> I saw the insane (and immutable) first year engineering schedule and said "nope"
<Ellied> lol yeah majoring in engineering in undergrad seems crazy honestly
<SnoopJeDi> it's been a cool arc to watch from afar Ellied
<FluffyFoxeh> I was talking to my then-boss on my last day of my summer job and he said if I like coding, don't go into soft eng
<FluffyFoxeh> and so I considered alternatives and now I'm in fourth year of comp sci :p
<Ellied> it's almost like the curricula are designed less around actually learning engineering and more around getting a preordained fraction of first-years to drop out so that accredited paper-pusher engineers can justify their huge salaries
<FluffyFoxeh> hah\
<Iskierka> that wouldn't surprise me
<SnoopJeDi> the gatekeeping evil is even less romantic than that
<SnoopJeDi> the university makes more money off of students who bounce off gating and then have to switch courses
<FluffyFoxeh> it's amusing to think about but I feel like it's an unlikely conspiracy
<SnoopJeDi> the engineer-society one is, agreed
<SnoopJeDi> universities being for-profit businesses is just a fact of academic life though :/
* SnoopJeDi glances at $700K fees applied to his department this year
<Ellied> conspiracies rarely actually exist as conspiracies, usually they're just vicious cycles that everyone acknowledges but the few people who can change them don't want to
<Qboid> 4d 0h 0m 0s left to event #12: 무궁화 5A호/Falcon 9 v1.2 [at 2017-10-30 19:34:00]. Say '!kountdown 12' for details
<SnoopJeDi> yep, there are way fewer mustachioed villains in the world than people would like to believe
<FluffyFoxeh> Ellied: well I can't visualize a flow of incentives that would cause universities to bolster engineer salaries
<SnoopJeDi> a truly evil person who is at least in control of events is more comforting than people with the best of intentions fucking it up anyway
<FluffyFoxeh> maaaaybe attracting more people into engineering to pay the high tuition fees? but if they're turning away so many of them it doesn't quite work out
<SnoopJeDi> classclickers.txt
<FluffyFoxeh> and there's a lot of indirection between those outcomes besides
<Iskierka> not convinced best intentions are that common
<SnoopJeDi> even if they are, they're not a sufficient condition, was my point
<SnoopJeDi> (or that malice is not a necessary one, if you like)
<FluffyFoxeh> the root of hanlon's razor
<SnoopJeDi> yep
<Ellied> I don't think there's literally a direct conspiracy or incentive flow going on that leads universities to actively try to increase engineers' salaries; however, I do think there's a "if too many people are succeeding you're doing it wrong" culture in STEM departments that isn't just a direct result of scheming administration anymore
<SnoopJeDi> to be sure
<FluffyFoxeh> that's possible. but on the other hand some level of standards are a good thing
<SnoopJeDi> only if they're helpful standards
<SnoopJeDi> which by and large they are not imo (hence why certifications exist at all: the degree indicates nothing of real value)
<FluffyFoxeh> certifications?
<Ellied> putting undergrads through 3 years of AC network analysis just to try to burn them out isn't high standards, I would say
<SnoopJeDi> a lot of mech/civil engineering is certificate-driven AIUI
<FluffyFoxeh> ah
<SnoopJeDi> not sure about AE, and EE is probably not
<SnoopJeDi> but like, making it through a program does not really indicate you are competent
<Ellied> the way my prof framed it is that certifications are necessary if you're keen on becoming a high-paid desk jockey but much less so if you actually want to spend your time building things
<FluffyFoxeh> SnoopJeDi: yeah, that's where work experience matters
<FluffyFoxeh> co-op is good
<Ellied> I mean lots of specific ones still are, just not whatever thing that big-boss engineers get is
<Ellied> AFAIK EE is very cert-driven, although the degree is certainly worth something on its own
<SnoopJeDi> yea I'm being fairly flippant about the competency thing
<SnoopJeDi> there are certain skills you expect to have been mastered or at least familiar, a common language, etc.
<Ellied> apparently you have to be able to do AC network analysis while someone sticks pins in your kneecaps, grumble grumble
<DoomedRaptor> Ellied: AC network analysis tested with https://twitter.com/diodelass/status/923624433549561856 ?
<kmath> <diodelass> cursed image https://t.co/R4qeDY0CZc
<Ellied> yes, definitely
<egg> !wpn Ellied
* Qboid gives Ellied a radium ㎭
<Ellied> calculate the impedance between your two index fingers at 50 Hz
<Ellied> ㎭ium
<egg> eggsactly
<FluffyFoxeh> DoomedRaptor: psychology ethics board has been approving some weird things lately
<DoomedRaptor> Ow
<DoomedRaptor> Also, wait. 50 Hz?
<Ellied> presuming you are in a 240V/50Hz country, like most(?) of the world
* DoomedRaptor thought everything in the US was 60 Hz.
<FluffyFoxeh> it is
<Ellied> yeah, I suppose it would be uncharacteristic of most EEs around here to think that globally lol
<FluffyFoxeh> I'm not sure what various places use actually. I know Europe is 50 and NA is 60
<FluffyFoxeh> australia is 50. huh.
<DoomedRaptor> Now look up Japan. >_>
<FluffyFoxeh> lol
<FluffyFoxeh> both
<APlayer> America has always been special
<APlayer> Like the IE of browsers
<bofh> Japan is "fun".
<APlayer> Anyway, got to go. See you!
<bofh> What's awesome is when multinational song production results in both 15.625kHz *and* 15.734kHz flyback hum in the song >_>
<bofh> it's actually almost consonant musically.
<SnoopJeDi> o.O
<FluffyFoxeh> that's a thing?
<DoomedRaptor> APlayer: Arguably more of Safari these days. >_>
<bofh> so TV flyback hum in the release of professionally recorded and mastered songs is so fucking common I could start a tumblr with examples and have like 15 pages to start.
<bofh> most people just don't notice unless it's really loud (which does happen sometimes).
<Ellied> There was a mains hum you could hear really loud from something outside near our apartment in China. I *think* it was three-phase, because it had a few higher harmonics audible as well.
<DoomedRaptor> If whitequark can have a powerlines in anime tumblr…
<SnoopJeDi> I may very well sign up for crunchyroll premium next month to watch Inuyashiki
<SnoopJeDi> caught a delightfully unsettling clip of it last night, and we've finished up with Nichijou
<SnoopJeDi> (Nichijou is a treasure too good for humanity)
<Ellied> I wonder if you get explosions modulated at 10Hz if you connect 60Hz and 50Hz generators in parallel.
APlayer has quit [Ping timeout: 383 seconds]
<Ellied> I bet having the US switch from 120V to 240V would be ridiculously difficult to do without starting widespread housefires at the moment of switch-over. Even if you had a good decade beforehand full of warnings "hey, if you have something that won't take 240V, UNPLUG IT BEFORE $DATE OR ELSE"
<Ellied> plus everyone would start buying step-down transformers built to shoddy specs and getting hurt that way too
<SnoopJeDi> the status quo is already a rolling disaster
<FluffyFoxeh> DoomedRaptor: half of it would be Lain
<DoomedRaptor> FluffyFoxeh: https://powerlinesinanime.tumblr.com/
<FluffyFoxeh> yay
<DoomedRaptor> Houses would have to be rewired, so…
<egg> !wpn DoomedRaptor
* Qboid gives DoomedRaptor a nitrogen optically thick terminal
<egg> !wpn bofh
* Qboid gives bofh a ε-δ haloalkane
<DoomedRaptor> optically thick *nitrogen*?
* SnoopJeDi glances up
<egg> DoomedRaptor: solid maybe?
<soundnfury> !wpn egg
* Qboid gives egg a solvable fuse
* egg wires the fuse in derived series
whitequark has quit [Ping timeout: 183 seconds]
whitequark has joined #kspacademia
icefire has joined #kspacademia
whitequark has quit [Ping timeout: 200 seconds]
whitequark has joined #kspacademia
<egg> !wpn bofh
* Qboid gives bofh a harmfully-considered blaster
egg is now known as egg|zzz|egg
<egg|zzz|egg> !wpn whitequark
* Qboid gives whitequark a banana-like trie
DoomedRaptor is now known as CollapsedRaptor
* CollapsedRaptor has his wavefunction tested.
* egg|zzz|egg observes CollapsedRaptor
* CollapsedRaptor vanishes in a burst of neutrinos.
* egg|zzz|egg tries petting the neutrinos
<CollapsedRaptor> Hypothesis: from egg's point of view, most things are cats.