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<DocScrutinizer05>
watch out for capacitor ESR
<wpwrak>
i guess they rarely indicate that on the package. so he couldn't check that anyway. no need to worry :)
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<DocScrutinizer05>
they sort of indicate it on the package, and you also can conclude about needed low ESR from position in circuit
<DocScrutinizer05>
replacing a capacitor that needs low ESR by a standard type usually results in a great working fix - for max 1 week
<DocScrutinizer05>
depending on circuit it also can go poof after just 10 seconds
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<DocScrutinizer05>
and funny enough it's usually exactly those capacitors that need low ESR that pop in any appliance like TV, or computer PSU or whatever
<DocScrutinizer05>
there was an industry wide issue with capacitors a few years ago
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<DocScrutinizer05>
billions of capacitors were faulty and had a way too short lifespan
<DocScrutinizer05>
whitequark: audiophile capacitors are one of the very few things that are not scam
<DocScrutinizer05>
IOW you actually can prove the effect with a meter
<DocScrutinizer05>
or scope or whatever
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<DocScrutinizer05>
it's not like "audiophile caps" are the only brand/type of capacitor that yields decent audio results, but there are many non-audiophile caps that actually spoil it
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<DocScrutinizer05>
whitequark: ((variation of capacitance with voltage)) yes, a known effect, and particularly nasty since it turns the capacitor into a non-linear component that introduces distortions
<DocScrutinizer05>
ideally when you need capacitors and there is no alternative to ceramic, you should use a capacitance *and* voltage way larger than what a conservative design would suggest
<DocScrutinizer05>
at least for signal paths
<DocScrutinizer05>
analog signal paths
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<DocScrutinizer05>
whitequark: the capacitance can half when C is charged to nominal voltage. You know what happens to voltage of a (e.g. air+plates) capacitor when you decrease the capacitance (increase plate distance). When the capaictor is charged to Q at V/2, and the voltage rises to V, the capacity halves and Q stays constant
<whitequark>
yeah
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<wpwrak>
whitequark: just use NP0 and you'll be fine ;-)
<eintopf>
i didn't check the esr
<wpwrak>
eintopf: it's a parameter you probably can't control without more preparation anyway, even if you can find out the design value (which is unlikely, given that the actual component you find may have an ESR that differs from the design)
<wpwrak>
oh, and "better" is almost always "lower", but there are exceptions
<eintopf>
ah,ok.
<eintopf>
i bought the parts twice
<eintopf>
so i am prepared for a next fix
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<eintopf>
I have the feeling that the background light is better than before
<DocScrutinizer05>
eintopf: when you actually need to do the fix again, I'd for sure not use the same capacitors, even when you got them twice. Rather get low-ESR types, they cost twice as much but possibly last 1000 times as long
<DocScrutinizer05>
they seem to not state ESR, only max allowable ripple current which creates heat inside the component according to P=U^2*R (where R == ESR)
<DocScrutinizer05>
err sorry
<DocScrutinizer05>
they seem to not state ESR, only max allowable ripple current which creates heat inside the component according to P=I^2*R (where R == ESR)
<DocScrutinizer05>
and I=Ripplecurrent
<DocScrutinizer05>
watch out, they state ripple current as RMS and @ 120Hz
<DocScrutinizer05>
those are usually no low-ESR type, far from it
<DocScrutinizer05>
what's closest to ESR rating is their "Dissipation Factor" I guess
<DocScrutinizer05>
a switched power supply will charge and discharge the capacitor (over the "virtual resistor" ESR) a 500 to 20000 times more often per second than what they are rating their "max ripple current" for (120Hz)
<eintopf>
ah, you mean I should buy parts which are marked as "low-ESR" only?
<DocScrutinizer05>
yes, they should be explicitly marked "Low ESR (x.xx Ohm)"
<DocScrutinizer05>
at least in datasheet
<eintopf>
ok.
<eintopf>
but now it works somehow
<DocScrutinizer05>
sure, it works for a few seconds to a few weeks always
<eintopf>
you believe it will break in ~ few weeks?
<eintopf>
but there is also a chance it will work ~years
<DocScrutinizer05>
first approach you could check if the new capacitors get hot - beware, remove mains voltage before you touch them, and keep your left hand in pocket!
<DocScrutinizer05>
actually remove all cables
<eintopf>
then I need to disassemble everything again :(
<eintopf>
yes, sure
<DocScrutinizer05>
well, you can just wait and see how long it works until next failure, maybe you're lucky
<eintopf>
ok
<eintopf>
I will be back when it's broken again :-)
<DocScrutinizer05>
I fixed a PC PSU of a client when I wasn't aware of ESR yet. It worked great... for 2 weeks
<eintopf>
but why they don't selling low-ESR only?
<eintopf>
expensive?
<DocScrutinizer05>
low ESR are way more expensive, 2 to 5 times
<eintopf>
ah, ok.
<eintopf>
this stupid cost-factor makes everything more breakable
<DocScrutinizer05>
yes
<DocScrutinizer05>
nowadays almost everything appliance is not working longer than 3 years, due to poor component quality
<DocScrutinizer05>
manufs are happy with it
<DocScrutinizer05>
cheaper products, sold more often
<eintopf>
but then you could buy broken ones at ebay
<eintopf>
repair it
<eintopf>
then sell it again
<DocScrutinizer05>
that's what a lot of repair shops do, commercially
<eintopf>
but this makes you not lucky and rich
<eintopf>
win-win situation for repair shops and manufactors
<DocScrutinizer05>
I once bought a refurbished washing machine. Of the two heating rods one was broken and they "fixed" it by simply cutting the wires for power supply to that rod.
<eintopf>
ah, ok.
<eintopf>
I know some heating issues at coffee machines
<eintopf>
they have two heating pipes
<DocScrutinizer05>
I literally can hear the service dummy: "this is beyond economic repair, we deliver the new machine and fetch the old one for free"
<whitequark>
reminds me I want to make a tea machine that's like...
<eintopf>
I had two of them and repaired one
<whitequark>
produces tea instantly at a drinkable temperature
<whitequark>
nice exercise in mechanical design too
<eintopf>
sounds like a good kickstarter project
<eintopf>
I want such teamachine
<eintopf>
"produces tea instantly at a drinkable temperature"
<whitequark>
i'm not going to spend my time and mental health on that treadmill
<whitequark>
in fact, if this goes viral on hackaday and some chinese company makes a clone, i would be very happy
<eintopf>
things on hackaday will be cloned from chinese companies?
<whitequark>
I mean, hypothetically
<eintopf>
ok.
<whitequark>
if I made a kickstarter, it will obviously get cloned at some point if it's successful
<eintopf>
indeed
<whitequark>
since i'm not going to get more out of a kickstarter campaign than i put in, then how about cutting out the middle step?
<whitequark>
in qty 1 this thing is a breeze
<eintopf>
you need to announce it on kickstarter when the product is already done, but this is not how kickstarter works
<whitequark>
in qty 1000 already it's a complete nightmare
<whitequark>
no, I'm not saying this is what will happen. I'm saying this is what I wish would happen because I sure as hell am not going to manufacture that
<whitequark>
most likely nothing happens at all and i'm ok with that too.
<DocScrutinizer05>
this is a really great design. Only one "downside": water is always boiling hot when it gets on the tea leafs
<whitequark>
right, so it needs to have *two* mixing taps
<whitequark>
I also wonder if you could make it automatically swap the leaves
<DocScrutinizer05>
it needs another electronic valve on top tank which heats the water, it now only has a inverted U pipe that makes water go down to tea when it boils
<DocScrutinizer05>
(auto swap leafs) hardly
<whitequark>
why not?
<whitequark>
you could make a piston with two O-ring seals that can take three positions in a horizontally placed cylinder
<whitequark>
left: open from top, can add leaves
<whitequark>
center: connected to hot water inlet and tea outlet
<whitequark>
right: open from bottom, ditches content
<whitequark>
and a servo or something to move it
<DocScrutinizer05>
hmm, maybe it's actually simpler to just pull out the middle container, turn it top down and spray some small amount of water in to remove the tea leafs sticking to walls, the turn top up and fill with new tea leafs by whatever means you like (you don't want to drink same tea all week long, do you?), then shove the thing in again
<whitequark>
you mean manually?
<whitequark>
that's exactly what i suggest to do automatically
<DocScrutinizer05>
no, you can do that by any servo
<DocScrutinizer05>
actually iirc you *need* to remove the middle container to disengage the electromagnetic valve at bottom
<DocScrutinizer05>
aaah, for the temperature of water: you can add a pressurizer air hose with valve (or a small air pump) to press the water out of top container. Instead of using steam pressure of boiling water
<whitequark>
or just a pump
<whitequark>
like peristaltic
<whitequark>
or even piston pump
<DocScrutinizer05>
nasty
<whitequark>
how so?
<DocScrutinizer05>
boiling water, moving parts
<whitequark>
the pump acts on cold water exclusively
<whitequark>
i want to use an inline heater
<DocScrutinizer05>
ooh, well
<DocScrutinizer05>
that's not the best idea for tasty tea
<whitequark>
why not?
<DocScrutinizer05>
tea should get boiling water purred over it, in short time
<whitequark>
sure
<whitequark>
4kw inline heater
<DocScrutinizer05>
well, that needs a special outlet
<DocScrutinizer05>
;-)
<whitequark>
does it?
<DocScrutinizer05>
here yes
<DocScrutinizer05>
3kW is abs max
<whitequark>
ahhh right
<whitequark>
I meant 3kw, misremembered what the limit is
<DocScrutinizer05>
230V@16A
<whitequark>
still should be enough
<whitequark>
it's not enough if you wanna take a shower, but to make some tea? sure
<DocScrutinizer05>
3kW will take a minute or more to boil 2L of water
<whitequark>
who said about 2L?
<whitequark>
what I want is a device with a button. press a button, get a teacup. instantly.
<whitequark>
i have the attention span of a ferret on meth
<DocScrutinizer05>
ouch, one cup
<whitequark>
like... you know why i want this device, right?
<DocScrutinizer05>
yeah
<whitequark>
because if i have to leave tea to extract then I forget about it entirely
<whitequark>
same about water in teapot
<whitequark>
actually even better idea, direct line to mouth. take a straw, pull air from it, get some nice warm tea
<whitequark>
since we're already doing *everything* inline that could just work
<whitequark>
I don't think that has the cool down function
<DocScrutinizer05>
((if i have to leave tea to extract then I forget about it entirely. same about water in teapot)) that's the nice thing about the first one. You simply fill in cold water and tea, and a 5 min later you got a complete can of ready made and filtered tea
<DocScrutinizer05>
with extraction time to the second
<whitequark>
besides it uses the capsules, like keurig,which are insanely expensive and probably unavailable here in HK
<DocScrutinizer05>
yes
<whitequark>
(5 min later) see this is the problem
<DocScrutinizer05>
you're in HK now?
<whitequark>
I will forget about it 5 minutes later, 100% certainty,
<whitequark>
yeah, I moved to HK
<DocScrutinizer05>
hmm, congrats?
<whitequark>
ehhh I guess
<whitequark>
there's not much difference frankly
<whitequark>
somewhat faster post, less food that i like
<DocScrutinizer05>
and Mao instead Stalin
<whitequark>
less extreme cold but no heating meaning that 15° is excruciating
<whitequark>
you wouldn't know about Mao if you just lived in HK as a foreigner
<whitequark>
it's a very western place
<DocScrutinizer05>
I know, I think I've been there
<whitequark>
hence: not much difference
<whitequark>
taobao is fairly nice
<whitequark>
although US amazon is still more cnvenient if you live near it
<DocScrutinizer05>
how's internet in HK, particularly on weekends?
<DocScrutinizer05>
in TPE it was abysmal
<whitequark>
extremely shit
<DocScrutinizer05>
well, a 7 years ago
<whitequark>
I have ADSL 8 down 0.5 up
<whitequark>
at home
<whitequark>
and fiber 10 down 10 up in the office
<whitequark>
why do yo ueven bother with fiber if there's no plan over 20mbps??
<DocScrutinizer05>
well, as long as it *works*
<whitequark>
it's stable
<whitequark>
but mind you
<whitequark>
i used to have 200/200
<DocScrutinizer05>
on weekends you always had almost no connection to EU and USA
<whitequark>
not anymore
<DocScrutinizer05>
I could get a max 150 down here, on shared medium (cable), which is not even a guarantee for 10 when your neighbours also use the net. Or I get 'up to' 16 via ADSL
<DocScrutinizer05>
not even VDSL
<DocScrutinizer05>
could you be my "boots on the ground" in HK?
<whitequark>
sure
<whitequark>
whatcha need?
<DocScrutinizer05>
maybe components or devices, e.g. refurbished N900
<whitequark>
possible but keep in mind i dont speak chinese