IRC log for #qi-hardware on 20160312

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02:02.17DocScrutinizer05watch out for capacitor ESR
02:26.30wpwraki guess they rarely indicate that on the package. so he couldn't check that anyway. no need to worry :)
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02:45.52DocScrutinizer05they sort of indicate it on the package, and you also can conclude about needed low ESR from position in circuit
02:46.44DocScrutinizer05replacing a capacitor that needs low ESR by a standard type usually results in a great working fix - for max 1 week
02:47.23DocScrutinizer05depending on circuit it also can go poof after just 10 seconds
02:49.25DocScrutinizer05and funny enough it's usually exactly those capacitors that need low ESR that pop in any appliance like TV, or computer PSU or whatever
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02:53.57DocScrutinizer05http://www.low-esr.com/  http://www.illinoiscapacitor.com/pdf/Papers/low_ESR_fact_or_fiction.pdf etc
02:54.09whitequarkceramic capacitors are such a lie
02:55.15whitequarknot only massive variation of capacitance with temperature, but also voltage
02:55.32DocScrutinizer05very interesting: http://www.satcure.co.uk/accs/low_ESR_capacitors.htm#heating
02:57.50whitequarklol suggesting audiophile caps
02:58.05DocScrutinizer05there was an industry wide issue with capacitors a few years ago
03:02.30DocScrutinizer05billions of capacitors were faulty and had a way too short lifespan
03:03.17DocScrutinizer05whitequark: audiophile capacitors are one of the very few things that are not scam
03:03.54DocScrutinizer05IOW you actually can prove the effect with a meter
03:04.07DocScrutinizer05or scope or whatever
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03:06.15DocScrutinizer05it'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
03:23.11DocScrutinizer05whitequark: ((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
03:24.22DocScrutinizer05ideally 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
03:24.52DocScrutinizer05at least for signal paths
03:25.21DocScrutinizer05analog signal paths
03:55.09DocScrutinizer05whitequark: 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
03:55.40whitequarkyeah
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07:26.39wpwrakwhitequark: just use NP0 and you'll be fine ;-)
07:26.42eintopfi didn't check the esr
07:38.13wpwrakeintopf: 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)
07:38.35wpwrakoh, and "better" is almost always "lower", but there are exceptions
07:42.50eintopfah,ok.
07:43.20eintopfi bought the parts twice
07:43.34eintopfso i am prepared for a next fix
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09:09.34eintopfI have the feeling that the background light is better than before
09:09.50eintopfmaybe this was broken a long time ago
09:11.18eintopfhttp://copy.sh/v86/?profile=windows98
09:34.44DocScrutinizer05eintopf: 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
09:38.11eintopfok.
09:40.36DocScrutinizer05<PROTECTED>
09:42.59eintopfhttp://www.produktinfo.conrad.com/datenblaetter/425000-449999/445112-da-01-en-ELKO_RAD_105_C_1000uF_25V_10X19RM5G.pdf
09:43.04eintopfwhere is the ESR value?
09:43.07eintopftolerance?
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09:58.38DocScrutinizer05they 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)
09:58.50DocScrutinizer05err sorry
09:58.58DocScrutinizer05they 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)
09:59.16DocScrutinizer05and I=Ripplecurrent
10:00.48DocScrutinizer05watch out, they state ripple current as RMS and @ 120Hz
10:01.06DocScrutinizer05those are usually no low-ESR type, far from it
10:02.32DocScrutinizer05what's closest to ESR rating is their "Dissipation Factor" I guess
10:07.05DocScrutinizer05a 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)
10:07.24eintopfah, you mean I should buy parts which are marked as "low-ESR" only?
10:08.09DocScrutinizer05yes, they should be explicitly marked "Low ESR (x.xx Ohm)"
10:08.31DocScrutinizer05at least in datasheet
10:09.10eintopfok.
10:09.17eintopfbut now it works somehow
10:09.41DocScrutinizer05sure, it works for a few seconds to a few weeks always
10:10.22eintopfyou believe it will break in ~ few weeks?
10:10.38eintopfbut there is also a chance it will work ~years
10:10.40DocScrutinizer05first 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!
10:11.10DocScrutinizer05actually remove all cables
10:11.11eintopfthen I need to disassemble everything again :(
10:11.16eintopfyes, sure
10:11.47DocScrutinizer05well, you can just wait and see how long it works until next failure, maybe you're lucky
10:12.12eintopfok
10:12.24eintopfI will be back when it's broken again :-)
10:12.35DocScrutinizer05I fixed a PC PSU of a client when I wasn't aware of ESR yet. It worked great... for 2 weeks
10:12.36eintopfbut why they don't selling low-ESR only?
10:12.57eintopfexpensive?
10:13.05DocScrutinizer05low ESR are way more expensive, 2 to 5 times
10:13.24eintopfah, ok.
10:13.50eintopfthis stupid cost-factor makes everything more breakable
10:13.55DocScrutinizer05yes
10:14.33DocScrutinizer05nowadays almost everything appliance is not working longer than 3 years, due to poor component quality
10:14.53DocScrutinizer05manufs are happy with it
10:15.05DocScrutinizer05cheaper products, sold more often
10:15.29eintopfbut then you could buy broken ones at ebay
10:15.32eintopfrepair it
10:15.35eintopfthen sell it again
10:16.06DocScrutinizer05that's what a lot of repair shops do, commercially
10:16.09eintopfbut this makes you not lucky and rich
10:18.11eintopfwin-win situation for repair shops and manufactors
10:18.13DocScrutinizer05I 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.
10:18.39eintopfah, ok.
10:18.51eintopfI know some heating issues at coffee machines
10:18.59eintopfthey have two heating pipes
10:19.11DocScrutinizer05I literally can hear the service dummy: "this is beyond economic repair, we deliver the new machine and fetch the old one for free"
10:19.33whitequarkreminds me I want to make a tea machine that's like...
10:19.35eintopfI had two of them and repaired one
10:19.43whitequarkproduces tea instantly  at a drinkable temperature
10:20.03whitequarktank + heater + leaf cartridge + adjustable mixer + PID
10:20.20whitequarkcan't be too hard
10:20.45whitequarknice exercise in mechanical design too
10:21.39eintopfsounds like a good kickstarter project
10:21.46eintopfI want such teamachine
10:21.57eintopf"produces tea instantly  at a drinkable temperature"
10:22.06whitequarki'm not going to spend my time and mental health on that treadmill
10:22.19whitequarkin fact, if this goes viral on hackaday and some chinese company makes a clone, i would be very happy
10:22.56eintopfthings on hackaday will be cloned from chinese companies?
10:23.08whitequarkI mean, hypothetically
10:23.12eintopfok.
10:23.22whitequarkif I made a kickstarter, it will obviously get cloned at some point if it's successful
10:23.34eintopfindeed
10:23.41whitequarksince i'm not going to get more out of a kickstarter campaign than i put in, then how about cutting out the middle step?
10:24.06whitequarkin qty 1 this thing is a breeze
10:24.10eintopfyou need to announce it on kickstarter when the product is already done, but this is not how kickstarter works
10:24.11whitequarkin qty 1000 already it's a complete nightmare
10:25.04whitequarkno, 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
10:25.53whitequarkmost likely nothing happens at all and i'm ok with that too.
10:34.35DocScrutinizer05https://www.galaxus.ch/de/s2/product/cloer-t42-silber-teemaschine-217616?tagIds=496-110
10:35.48whitequarkout of stock...
10:36.00DocScrutinizer05dang
10:36.44whitequark"quite prone to defects" too
10:37.02DocScrutinizer05this is a really great design. Only one "downside": water is always boiling hot when it gets on the tea leafs
10:37.17whitequarkright, so it needs to have *two* mixing taps
10:38.09whitequarkI also wonder if you could make it automatically swap the leaves
10:38.46DocScrutinizer05it 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
10:39.05DocScrutinizer05(auto swap leafs) hardly
10:39.11whitequarkwhy not?
10:39.39whitequarkyou could make a piston with two O-ring seals that can take three positions in a horizontally placed cylinder
10:39.45whitequarkleft: open from top, can add leaves
10:39.51whitequarkcenter: connected to hot water inlet and tea outlet
10:39.59whitequarkright: open from bottom, ditches content
10:40.17whitequarkand a servo or something to move it
10:47.00DocScrutinizer05hmm, 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
10:47.48whitequarkyou mean manually?
10:47.57whitequarkthat's exactly what i suggest to do automatically
10:48.02DocScrutinizer05no, you can do that by any servo
10:50.39DocScrutinizer05actually iirc you *need* to remove the middle container to disengage the electromagnetic valve at bottom
10:52.48DocScrutinizer05aaah, 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
10:53.00whitequarkor just a pump
10:53.03whitequarklike peristaltic
10:53.14whitequarkor even piston pump
10:53.29DocScrutinizer05nasty
10:53.32whitequarkhow so?
10:53.44DocScrutinizer05boiling water, moving parts
10:53.56whitequarkthe pump acts on cold water exclusively
10:54.00whitequarki want to use an inline heater
10:54.07DocScrutinizer05ooh, well
10:54.37DocScrutinizer05that's not the best idea for tasty tea
10:54.41whitequarkwhy not?
10:55.12DocScrutinizer05tea should get boiling water purred over it, in short time
10:55.20whitequarksure
10:55.23whitequark4kw inline heater
10:55.39DocScrutinizer05well, that needs a special outlet
10:55.42DocScrutinizer05;-)
10:55.46whitequarkdoes it?
10:55.51DocScrutinizer05here yes
10:55.57DocScrutinizer053kW is abs max
10:56.03whitequarkahhh right
10:56.08whitequarkI meant 3kw, misremembered what the limit is
10:56.09DocScrutinizer05230V@16A
10:56.11whitequarkstill should be enough
10:56.33whitequarkit's not enough if you wanna take a shower, but to make some tea? sure
10:57.44DocScrutinizer053kW will take a minute or more to boil 2L of water
10:57.55whitequarkwho said about 2L?
10:58.08whitequarkwhat I want is a device with a button. press a button, get a teacup. instantly.
10:58.18whitequarki have the attention span of a ferret on meth
10:58.22DocScrutinizer05ouch, one cup
10:58.34whitequarklike... you know why i want this device, right?
10:58.41DocScrutinizer05yeah
10:58.57whitequarkbecause if i have to leave tea to extract then I forget about it entirely
10:59.01whitequarksame about water in teapot
10:59.32whitequarkactually even better idea, direct line to mouth. take a straw, pull air from it, get some nice warm tea
10:59.39whitequarksince we're already doing *everything* inline that could just work
10:59.45DocScrutinizer05you're better off with http://www.amazon.de/dp/B00THB4VT4/?tag=glv-21&ascsubtag=4ea4350ada05458b2d468c3f13adaea1
11:00.46whitequarkI don't think that has the cool down function
11:01.01DocScrutinizer05((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
11:01.15DocScrutinizer05with extraction time to the second
11:01.15whitequarkbesides it uses the capsules, like keurig,which are insanely expensive and probably unavailable here in HK
11:01.24DocScrutinizer05yes
11:01.31whitequark(5 min later) see this is the problem
11:01.35DocScrutinizer05you're in HK now?
11:01.40whitequarkI will forget about it 5 minutes later, 100% certainty,
11:01.46whitequarkyeah, I moved to HK
11:02.20DocScrutinizer05hmm, congrats?
11:02.31whitequarkehhh I guess
11:02.36whitequarkthere's not much difference frankly
11:02.56whitequarksomewhat faster post, less food that i like
11:03.16DocScrutinizer05and Mao instead Stalin
11:03.20whitequarkless extreme cold but no heating meaning that 15° is excruciating
11:04.05whitequarkyou wouldn't know about Mao if you just lived in HK as a foreigner
11:04.08whitequarkit's a very western place
11:04.21DocScrutinizer05I know, I think I've been there
11:04.23whitequarkhence: not much difference
11:05.08whitequarktaobao is fairly nice
11:05.26whitequarkalthough US amazon is still more cnvenient if you live near it
11:14.05DocScrutinizer05how's internet in HK, particularly on weekends?
11:14.33DocScrutinizer05in TPE it was abysmal
11:14.51whitequarkextremely shit
11:14.53DocScrutinizer05well, a 7 years ago
11:15.01whitequarkI have ADSL 8 down 0.5 up
11:15.05whitequarkat home
11:15.11whitequarkand fiber 10 down 10 up in the office
11:15.21whitequarkwhy do yo ueven bother with fiber if there's no plan over 20mbps??
11:15.22DocScrutinizer05well, as long as it *works*
11:15.29whitequarkit's stable
11:15.37whitequarkbut mind you
11:15.43whitequarki used to have 200/200
11:15.55DocScrutinizer05on weekends you always had almost no connection to EU and USA
11:16.02whitequarknot anymore
11:18.19DocScrutinizer05I 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
11:19.05DocScrutinizer05not even VDSL
11:20.54DocScrutinizer05could you be my "boots on the ground" in HK?
11:21.18whitequarksure
11:21.23whitequarkwhatcha need?
11:21.49DocScrutinizer05maybe components or devices, e.g. refurbished N900
11:22.07whitequarkpossible but keep in mind i dont speak chinese
11:22.15DocScrutinizer05I see
11:22.16whitequarkthis is a huge problem overall
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17:20.58arossdotmewhitequark, thx
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