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.
<egg|zzz|egg>
!wpn UmbralRaptor
* Qboid
gives UmbralRaptor a hydromatic чертовщина
<egg|zzz|egg>
!wpn bofh
* Qboid
gives bofh a prompt-critical magma
<UmbralRaptor>
uh
<UmbralRaptor>
Did Qboid just make corium detonate?
<UmbralRaptor>
!wpn egg|zzz|egg
* Qboid
gives egg|zzz|egg a kappa hull
<UmbralRaptor>
Is it normal for an office to run ~68-70 F?
<egg|zzz|egg>
that's a big capacitor of an office
<UmbralRaptor>
It's useful for the railguns.
<bofh>
yeah that's a decent ultracap
<UmbralRaptor>
293-294 K
<egg|zzz|egg>
bofh: right, so the reason why the logs of this channel are the only result for "ネコノミコヌ" is that it's properly spelled "ネコノミコン" :-p
<bofh>
oops
<UmbralRaptor>
Does that reduce the likelihood of being consumed by an Elder Thing?
<kmath>
<ElecnorDeimos> #HelloOSIRISREx from #DeimosSkySurvey! First images of @OSIRISREx, 2 million km away, as we prepare #DeSS to captur… https://t.co/XbLz86WoQK
<kmath>
<SpaceflightNow> Tonight's Atlas 5 launch of #NROL42 spy satellite is being postponed by a technical issue. Now targeting Saturday.… https://t.co/JlFZQ3clX1
<kmath>
<Pharniel> Soon my twitter feed is just going 2 be cosplayers posting anime jokes requiring intimate knowledge of the x86 arch& 3 editions of Shadowrun
<UmbralRaptor>
Aside maybe from shadowrun, it's her?
<Fiora>
is that my fault
<UmbralRaptor>
I'm not sure it was a complaint.
<bofh>
it wasn't a complaint at all
<Fiora>
i mean shadowrun is also good
<bofh>
it is. man, I haven't had an oppprtunity to play it in so long
<Iskierka>
I have only really played the recent shadowrun games
<kmath>
<dril_ln> QUÆSTIO: utrum avis viae cursor esset filius wile e coyote OBJ: videtur quod observent aliquantum inter se SED CONT… https://t.co/tVnqmeh9I0
<kmath>
<sondy> @nadiamdrake Ángel Vasquez and Joe Taylor have made contact with staff at Arecibo Observatory. They're all safe. Ro… https://t.co/BuyqCsj4w1
<Iskierka>
sooo wizards of the coast think you should only be finishing the first part of hoard of the dragon queen at about 300 xp and only just levelling, and end it with a meant-to-lose fight
<Iskierka>
we finished with 1320 and won the meant-to-lose-fight
<SnoopJeDi>
nice
<SnoopJeDi>
we literally stumbled into the green dragon we were looking for at the end of our last session
<SnoopJeDi>
things, uh, might not go great.
<UmbralRaptor>
DnD?
<Iskierka>
the blame appears to be on the paladins (who I am one of) who refused to abandon anyone so we fought *everyone*
<Iskierka>
and with three front-liners who charged straight in, saved everyone bar like one woman at the very start
<SnoopJeDi>
anti murder-hobo, heh
<Iskierka>
I mean we murdered plenty of poeple. Just only people already trying to murder
<Iskierka>
and yes, DnD
<Iskierka>
found a group on a discord so went with that
<kmath>
<JanelleCShane> For science! I'm collecting D&D character backstories for training neural networks. Submit as many as you like. https://t.co/phclLHHfR3
<Iskierka>
postgame coverage: "He also tells you to kill the elf, but he always says that, even when there isn't an elf around. You suspect your diety may be racist."
<SnoopJeDi>
Is the diety a dwarven deity? In the wise words of my DM: "All dwarves are a little racist."
<Iskierka>
orc. so probably the same
<Iskierka>
we're now discussing next episode and, without clear spoilers, noting that there's a crowd of enemies that should kill us by sheer numbers but DM says using terrain & double thunderwave we can probably win that too
<Iskierka>
so hopefully at least a solid level 4 when we should probably be barely looking at 3
<Iskierka>
also the barbarian got a half-dragon's head turned into a helmet. half-dragon is probably also the grandson of what's likely to become a boss later on
<Iskierka>
boss is also from the dragon half of the family and is an adult. This is gonna become interesting
<rqou>
egg|zzz|egg or anybody else, what's your favorite lowest-learning-curve computer algebra system that isn't wolfram alpha?
<rqou>
need it urgently
* UmbralRaptor
embarassedly stares at his TI-89.
<SnoopJeDi>
There are SymPy and Sage, depending on precisely what it is you need?
<SnoopJeDi>
(and assuming you ssssssspeak Python)
<bofh>
SymPy ain't half bad if you do indeed speak Python.
<kmath>
<whitequark> #catcognition update: I've observed our cat use no less than THREE separate methods for opening our front door
<egg|zzz|egg>
!wpn bofh, Fiora, Iskierka, rqou, UmbralRaptor, and whitequark
* Qboid
gives bofh, Fiora, Iskierka, rqou, UmbralRaptor, and whitequark an Ada nonagon
<rqou>
hello egg|zzz|egg
<egg|zzz|egg>
!acr -add:adj equinoctial
<Qboid>
egg|zzz|egg: I added the explanation for this acronym.
<egg|zzz|egg>
um
<egg|zzz|egg>
!wpn -add:adj equinoctial
<Qboid>
egg|zzz|egg: Adjective added!
<egg|zzz|egg>
!acr -remove:adj
<Qboid>
egg|zzz|egg: I removed the explanation for adj
<rqou>
egg|zzz|egg: now that i finished my problem set, what is your favorite not-necessarily-lowest-learning-curve computer algebra system?
<rqou>
i should probably move off of wolfram alpha which is slow, dumb, inconsistent, and proprietary
<egg|zzz|egg>
rqou: well that won't help for the last bit, but I've been quite satisfied on the computer algebra system & plotting side by Mathematica (got it for free at ETHZ)
<rqou>
i do have access to mathematica
<rqou>
but i've never learned to use it
<rqou>
i've also tried sage math and found it really annoying
<egg|zzz|egg>
well if you have questions about mathematica I can try answering them
<rqou>
i've never actually used it
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<egg|zzz|egg>
also, happy equinox
* egg|zzz|egg
pokes the ascending node with a stick
<kmath>
<twoscooters> If I were the kind of person what ever changed their display name I'd be Princess Monster Truck RIGHT NOW https://t.co/6s4hmDhCY4
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<soundnfury>
bofh: but I don't _want_ to be visited by comforting darkness. Rage, rage against the dying of the light.
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<Ellied>
SnoopJeDi: same
<UmbralRaptor>
SnoopJeDi, Ellied: same.
<SnoopJeDi>
Data's mini-speech on "I don't know" being the most important scientific statement is probably my favorite part of Star Trek as a whole. https://www.youtube.com/watch?v=8eDYVtPwWiM
<kmath>
YouTube - Data's Wisdom: "The beginning of wisdom is: I do not know." from Star Trek: TNG
<bofh>
SnoopJeDi: as far as speeches go, it's both pretty accurate & pretty important.
<SnoopJeDi>
I bring it up often in discussions of impostor syndrome
<kmath>
<bofh453> Just when you think *nothing* about the 2017 hurricane season will surprise you anymore, a tropical storm randomly… https://t.co/quSwwO1GTN
<bofh>
SnoopJeDi: it's very fitting there, imo
<SnoopJeDi>
twss
<SnoopJeDi>
couldn't help myself >_>
<bofh>
rofl I had to google what that acronym decomposed into, then immediately facepalmed :P
<APlayer>
Ellied: In case you have time now, I do.
* egg|zzz|egg
pokes bofh with UmbralRaptor and tensors
APlayer has quit [Ping timeout: 383 seconds]
<bofh>
egg|zzz|egg: what was your horrible pun again btw? I lost it in backlog
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<SnoopJeDi>
WOO vertically confined beam \o/
<bofh>
wait what? nice.
<UmbralRaptor>
bofh: (traditional Chinese cat) = (simplified Chinese cat) ⊗ C
<Qboid>
7d 0h 0m 0s left to event #8: Intelsat 37e & BSAT 4a/Ariane 5 ECA VA239 [at 2017-09-29 21:47:00]. Say '!kountdown 8' for details
<bofh>
right, that one. :P
<Ellied>
tzh, I need to reinstall this machine and check the 'use encrypted LVM' box this time.
<UmbralRaptor>
SnoopJeDi: yay?
<SnoopJeDi>
very yay
* UmbralRaptor
wonders if resurrecting a Dell Optiplex 755 for work porpoises is a good idea.
<SnoopJeDi>
I'd been doing only "nice" beams in this cyclotron for recent memory, and as we pick up steam on the tooling I started simulating beams with much more variation in 6D phase space...only to find that *any* vertical spread would shear the beam apart almost immediately
<SnoopJeDi>
(these aren't self-interacting beams either, so it's a huge problem with the machine itself, not a collective/plasma effect)
<Ellied>
UmbralRaptor: what sort of CPU?
<SnoopJeDi>
anyway turns out my supervising researcher (who generated the input fieldmap) zigged when he should have zagged, and there was a sign error. I think all the quadrupoles were effectively swapped, so a focusing quad were a defocusing one should be and vice versa
<Ellied>
heh
<SnoopJeDi>
Optiplex 755 is C2D I think?
<UmbralRaptor>
Ellied: ambiguous C2D
<Ellied>
could do worse
<UmbralRaptor>
RAM could be anywhere from 2 to 8 GiB.
<SnoopJeDi>
I like optiplexes for general office prod
<SnoopJeDi>
...mostly because they were *very* plentiful off-lease when I worked in IT, heh.
* UmbralRaptor
can dig up a DVI cable and USB mouse easily enough, but a keyboard will be harder.
<Ellied>
we have a yuge stack of extra keyboards here... I'd try to mail you one, but I bet someone would get mad.
<UmbralRaptor>
!wpn -add:wpn gasket
<Qboid>
UmbralRaptor: Weapon added!
<SnoopJeDi>
The discrete lines in the log-log figs give me a lot of frission
<UmbralRaptor>
Ellied: quick, steal one with buckling springs!
<Ellied>
they're all the same garden-variety Dell keyboard
<UmbralRaptor>
Bah
<APlayer>
Ah, hi Ellied!
<Ellied>
hi
<UmbralRaptor>
lo
<APlayer>
So, I was about to understand that circuit yesterday
<APlayer>
(If you have the time and will today)
<SnoopJeDi>
UmbralRaptor, I made a Slack reminder for myself, that paper will be my stand-by for next week's happy hour email.
<SnoopJeDi>
Speaking of happy hour, it is ?:30!
<UmbralRaptor>
Hah
<APlayer>
But it is :04
<UmbralRaptor>
Local sidereal (or solar) time?
<APlayer>
It may vary by increments other than 60 min?
<UmbralRaptor>
Hence local!
<UmbralRaptor>
Also note timezones like UT+5.5
<UmbralRaptor>
(about 1e9 people live there)
<APlayer>
Welp
<Ellied>
sorry yeah I'm here
<Ellied>
but give me like 30 seconds while I bug out to the basement, the main part of the house is too hot to think in
<Ellied>
okay there we go
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<APlayer>
Woops, sorry
<APlayer>
So, that capacitor which is connected to the battery and the N-Ch MOSFET... How does that work? How can it discharge?
<soundnfury>
!wpn -add:adj Sierpiński
<Qboid>
soundnfury: Adjective added!
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<APlayer>
I'm sorry, I've got to go for today. Let's continue tomorrow, though. Just highlight me whenever you have time, I shall receive that fairly quickly.
<Ellied>
"A stop job is running for session C2 of user ellie [15s/01:30]" ## fucking love systemd
* soundnfury
? systemd
<Ellied>
APlayer: the capacitor's two poles have the same voltage when it's discharged, yes?
<APlayer>
I think so, yes
<Ellied>
APlayer: so if one end is initially at 0V (when the battery is off), and then jumps up to 5V as the battery turns on, so does the other pole.
<Ellied>
APlayer: But then the one end is held at +5V, and the other end is discharging through a resistor that wants to pull it down to 0V
<APlayer>
Yes
<Ellied>
And the diode prevents it from discharging through the low UART pin, so it has to discharge through that resistor
<APlayer>
What about the MOSFET?
<Ellied>
so the transistor switches off after however long it takes for the voltage to drop below its threshold
<Ellied>
s/transistor/MOSFET/ for that last
<APlayer>
Yes
<Ellied>
assuming the Pi wakes up and the UART pin goes high before that happens, it stays on
<APlayer>
Now what happens when I shut down and UART goes low?
<Ellied>
when the uart goes low, the capacitor (still held at the +5V on one end) discharges like normal and the transistor turns off after the set time
<APlayer>
(The pin goes high nearly instantly)
<Ellied>
perfect
<Ellied>
at some point after the transistor shuts down, presumably the battery then registers that no significant current is being drawn and shuts down
<APlayer>
Uh, when the N-Ch MOSFET is powered, so is the RPi
<Ellied>
yes
<APlayer>
So while the capacitor discharges, the RPi is powered, and so is the battery
<Ellied>
yes
<APlayer>
But how can it fully discharge when it's receiving current directly from the battery?
<Ellied>
I suppose it's possible that the capacitor won't discharge back to the same voltage at both terminals very fast with the battery off (I don't know enough about the battery's circuitry) so if it isn't waking up properly after the first successful run, try attaching a big resistor (like 1M) from +5V to 0V on the battery supply just to make sure the two rails equalize after it shuts down
<APlayer>
I mean, except the UART pin goin low, nothing changes
<Ellied>
It's important that the capacitor starts with no charge (both legs at 0V) when you go to turn it on, so that means when the battery is off you should be able to expect it to conduct at least slightly from positive to negative. It probably does, or at least the Pi does. I don't know for sure, though.
<APlayer>
Also, what does the resistor between the 5V attachment and the P-Ch MOSFET do?
<Ellied>
that makes sure the P-channel MOSFET's gate goes high again (off) after the N-channel one stops pulling it low (on)
<Ellied>
If you don't put that there, then in theory the P-channel MOSFET will never turn off. In practice it will, very slowly, as charge bleeds from the gate through the other MOSFET and into the air and stuff, but you don't want that because it will make the transition time much too long and risk damaging the MOSFET with excessive heat production
<Ellied>
and maybe even the Pi by shutting it off too slowly, not sure about that
<APlayer>
Okay
<Ellied>
I don't really know what happens if you ramp down the current supplied to the Pi really slowly. I don't know why that would cause trouble, but I also don't expect the manufacturers planned for such a case.
<APlayer>
As for the capacitor not fully discharging... I think you misunderstood my question.
<Ellied>
perhaps
<APlayer>
I mean that, while everything is turned on and UART is high, the capacitor is fully charged
<APlayer>
Now the RPi shuts down, but all that changes for the circuit is UART going low
<APlayer>
How does that affect the capacitor?
<Ellied>
ah, I was using inconsistent nomenclature there. "Discharged" from the MOSFET's perspective means "the terminal I'm looking at is at 0 volts" but that's actually still charged from the capacitor's perspective in this arrangement because the other leg is attached to +5V
<Ellied>
the UART going low allows the transistor-facing leg of the capacitor to continue to discharge towards 0 volts. If the UART pin is high, it can't do that and the MOSFET says on.
<APlayer>
Why is the terminal at 0V if the other one is at a constant 5V?
<soundnfury>
APlayer: it's a capacitor, current doesn't flow through it
<Ellied>
because current is draining through the resistor attached to 0V
<soundnfury>
or rather, *DC* doesn't flow through it
<soundnfury>
each terminal only cares about _changes_ to the other terminal's voltage
<Ellied>
remember that + and - is completely arbitrary. If you reverse the polarities of every supply and semiconductor layer (diodes reversed, NPN replaced with PNP and vice versa, N-channel with P-channel etc), you should get a circuit that behaves exactly the same way.
<APlayer>
Uh, okay. As I was fearing, I did not quite understand capacitors. I think I get it now
<Ellied>
having a capacitor with one lead in ground and being charged by a positive voltage at the other lead is not fundamentally different from a capacitor with one lead in a positive voltage and the other gaining charge from ground.
<soundnfury>
APlayer: capacitors are defined by I = C * d(V₁-V₀)/dt
<Ellied>
now, some capacitors do care which direction you charge them, but not all; that's just about design.
<APlayer>
So the capacitor should discharge for as long as I need between UART going low and the Pi fully shutting down? After it discharges, the circuit cuts the power supply.
<Ellied>
yes
<Ellied>
where "discharged" means "there is no longer current flowing in the resistor connecting the N-channel MOSFET's gate to ground"
<APlayer>
And the circuit is initiated again once the battery starts delivering current to the capacitor and it feeds the current again?
<APlayer>
The circuit again*
<soundnfury>
APlayer: (between that and the inductor V = L * dI/dt, you can derive essentially all of passive linear circuit theory)
<Ellied>
it's initiated again once the positive rail of the battery falls to 0 volts, and the capacitor (which will now have 0 volts on the lead attached to the battery + and -5V on the lead attached to the MOSFET gate) discharges back to 0V at both terminals, and THEN you turn the battery on and bring the + back up to +5V.
<APlayer>
Wait, where do the -5V come from? I'm sorry, as I said I am kind of stupid about those things...
<Ellied>
when the capacitor is at +5 from the battery side and 0 on the transistor side, you can think of it as "holding" a difference of 5V. the capacitor doesn't care what the absolute voltages are, just that one side is 5 volts higher than the other, so if you force the side holding the higher voltage to 0 volts, the other side holds a voltage 5 volts lower, so it goes to -5V.
<Ellied>
this is where you hope that you have some non-infinite resistance across the battery while it's off, so that the capacitor's negative voltage can drain back to 0 before you go to turn it on again.
<APlayer>
The -5V terminal is connected to the MOSFET, which should not (?) deliver any current, and to the resistor, which is grounded
<Ellied>
yes
<Ellied>
so the resistor allows current to flow from the negative side to ground
<APlayer>
Would the MOSFET not be enough to drain the capacitor?
<Ellied>
which it will, but only if there's some conduction from + to ground on the battery, so that the ground rail doesn't just move down to negative 5 volts (or if you like, the + rail held up at +5V, same thing)
<Ellied>
the MOSFET won't draw any current so it won't drain the capacitor
<APlayer>
So the MOSFETs gate only cares about there being an absolute voltage, but does not actually drain it as transistors (?) do?
<Ellied>
Here, I have a test for you to do: If you take a multimeter and probe the + and - terminals of the battery while it's off, what voltage do you get?
<Ellied>
APlayer: a relative voltage from gate to source, yes
<Ellied>
that's what makes them Field Effect Transistors (FETs) - they just care about the voltage, no current drawn at the gate
<APlayer>
That'd require me to rip apart a USB cable. I'll do that eventually, just not right now, as I don't even have the necessary cable
<APlayer>
Ah, now that starts making sense!
<Ellied>
Worst case scenario, you'll have to put a 1M across the battery to make sure the capacitor discharges, and wait for however long it takes before turning it back on after each time you turn it off.
<APlayer>
I expect zero voltage across the battery, actually. I mean, it should shut down, shouldn't it?
<Ellied>
my advice for actually setting the time is to just test it with a lamp or LED instead of the Pi and a switch instead of the UART pin until you get a time you like (if too short, bigger resistor/cap, if too long, smaller of either)
<Ellied>
it's possible for it to just shut down by effectively opening a switch on one end or other, without allowing any current to flow once it's off.
<Ellied>
then you'd need an external resistor for your capactor to discharge and the circuit to reset for the next switch-on
<Ellied>
it might have the equivalent of a resistor inside it already though, so you might not need that. I don't know
<Ellied>
...I'm curious, though. let me go probe my own battery bank and see.
<APlayer>
Just one more thing I am unsure about still
<APlayer>
That resistor which is connected to the P-Ch MOSFET, you said it keeps it off after the N-Ch one stops pulling it down
<APlayer>
How do you mean that? Pulling down in what sense?
<APlayer>
I think I'd better understand if I knew during what part of the circuit's cycle it is needed...
<Ellied>
a very small current can flow through the resistor connecting the +5V rail to the gate of the P-channel MOSFET, which is enough to charge (or discharge, depending on where you look) the very small capacitance of the gate back up to the same voltage as the power rail. If it isn't there, there's no way for the voltage on the gate to get back to the off-state (same as source, so +5V)
<Ellied>
hmm. okay, my cheap power bank I got in Hangzhou actually does stay powered at +5V when off. But mine works where you can just plug something in and it comes on, I don't have to actually push the button.