#qi-hardware IRC log for Monday, 2015-06-22

--- Mon Jun 22 201500:00
nicksydneywpwrak: http://mcuoneclipse.com/2015/06/17/tinyk20-new-board-with-micro-sd-card/14:21
wpwrakoh dear: http://avherald.com/h?article=48833089&opt=015:48
DocScrutinizer05pilot, how dull could you be to not notice a cat sitting on the wing of your UL16:13
kyakpoor thing16:21
kyakbut what an adventure!16:21
wpwrakmaybe the cat hopped on after he checked. or maybe he was too busy reassuring his girlfriend. she does seem to be a bit tense.16:32
kyakso i've got that phone with 2A charger (out of the box). Would it be bad if i charge it with 1A charger?16:38
DocScrutinizer05depends on the charger signaling17:14
DocScrutinizer05and whether the phone cares about such thing or simply assumes 2A17:15
DocScrutinizer05absolutely worst case your charger will go up in flames17:15
DocScrutinizer05more likely the charger will cut out on OC prot and no charging happens at all17:16
DocScrutinizer05ideally the phone notices and reduces charge current accordingly so charger is happy17:16
DocScrutinizer05simply test it17:18
kyakok, so i better buy another 2A charger :) thanks!17:18
DocScrutinizer05when the charger gets very hot, sth is odd and you should stop the experiment17:18
DocScrutinizer05otherwise just see if it charges to full in acceptable time17:19
kyakif everything's fine, it should charge for approx. two times longer?17:19
DocScrutinizer05it's probably safe to assume that all chargers are short / OC resilient17:20
DocScrutinizer05err not even 2 times17:20
DocScrutinizer05the 2A take effect only during initial maybe 30min17:20
DocScrutinizer05after that the charge current dropped to a level that doesn't matter for 1A vs 2A17:21
kyakoh, i rememeberd i have an usb-in-the-middle kinf of thing that can show current17:21
kyaki'll measure how much it actually consumes17:21
DocScrutinizer05keep in mind that the current depends on discharge level of battery17:22
DocScrutinizer05only from 0% to maybe 15% it will charge with maximum current17:22
kyakok, i got it17:22
DocScrutinizer05after that the charge current drops more or less linearly to 0 when battery full17:23
DocScrutinizer05that's why 2A charger is never twice as fast as 1A17:23
kyakif i don't discharge to less than 20%, i probably won't need those 2A17:24
DocScrutinizer05it is more like 1.2 times17:24
DocScrutinizer05yes, exactly17:24
kyakok, thanks for your advice17:24
DocScrutinizer05the 20% however are a number you need to evaluate by experiment17:24
DocScrutinizer05might be 30% or even 50%17:25
DocScrutinizer05depends on battery and phone circuit17:25
kyakand that's what i'll find out using that usb thing17:26
DocScrutinizer05yes, excellent plan17:26
kyakit looks liek this17:27
DocScrutinizer05:-) thanks!17:27
kyakat 60%, it draws 1.05A, meaning thatit maxes out this charger at this moment17:30
kyaki should measure with the 2A one17:30
DocScrutinizer05it may stay at that level down to 0%, when the phone actually notices that it's the charger's maximum17:31
kyakwhich i don't have at hand at the moment -\17:31
DocScrutinizer05the phone has at least 2 ways to detect this17:31
DocScrutinizer05up to anybody's guess if it actually does any of the both17:31
DocScrutinizer05or up to your tests to prove yay or nay17:32
kyakone way i'm guessing is from software, by measuring how charge is changing. .What's the other?17:32
DocScrutinizer05one way is to detect voltage drop of charger when it maxes out. The other is by signaling which is done via D+/- lines17:33
DocScrutinizer05the latter is the more commonly used method17:33
DocScrutinizer05actually there are two or three different variants of it17:34
DocScrutinizer05~#neo900 bd17:34
infoboti guess #neo900 bd is http://neo900.org/stuff/block-diagrams/neo900/neo900.html the very fine and detailled Block Diagram, or http://talk.maemo.org/showthread.php?p=1445200#post144520017:34
kyakthis usb-in-the-middle thing might affect the D+/- lines though17:34
DocScrutinizer05check the charger chip datasheet17:34
DocScrutinizer05o.O that would be bad17:34
DocScrutinizer05(datasheet) it has a nice sum up of how the signaling works17:35
kyakha, it's up to tests then :) 17:37
DocScrutinizer05the voltage drop method basically works like   do increase-current until delta-voltage>0.4V; decrease current by one step17:37
DocScrutinizer05this method is _not_ safe. some chagers have no voltage drop and still they overheat17:39
DocScrutinizer05rare but possible17:40
DocScrutinizer05some notebooks are like this, they don't have voltage drop on USB port but simply break on overcurrent17:41
kyakit doesn't seem to use this method, the current and voltage are pretty stable17:41
DocScrutinizer05yeah, it's not a commonly used method, as I said above17:42
kyakit heats up, but doesn't burn hand17:42
DocScrutinizer05most common method is D+/- resistor network. Closely followed by D+/- short17:42
kyaki guess when it burns hands, it's too late :P17:42
DocScrutinizer05it's quite possible that your 1A charger has a voltage drop to 4V or even 3.5V on >1A current, and that automatically reduces the current the phone _can_ draw17:44
DocScrutinizer05can you test the voltage?17:44
kyakthe usb device shows 5.1- 5.2 V17:45
DocScrutinizer05it *should* be 5V +/- a few17:45
DocScrutinizer05that's great then17:45
kyakso voltage drop is basically a protection from overcurrent?17:46
DocScrutinizer05rather a natural physical consequence of overcurrent17:46
kyakah yeah, makes sense17:46
DocScrutinizer05not always though. See blowfuse17:47
DocScrutinizer05it blows when you connect too many heaters to your mains outlets, without voltage drop from 230V to 150V or whatever17:48
wpwrakblowfuses drop the voltage, too ... :)17:48
DocScrutinizer05laptops work in a similar way17:48
DocScrutinizer05some at least17:48
DocScrutinizer05http://portablesolarpanels.co/product/abovetek-usb-power-meter-voltage-tester-current-monitor-usb-2-0-3-0-volt-amp-reader-multimeter-led-screen-portable-durable-mv-ma-measurement-solar-panel-voltmeter-battery-power-bank-ampmeter/  is a great gadget17:53
kyaki'm now getting all the phones i have at home and measuring their charge current :)17:53
kyakolder nokia phone, charged it in the morning, now it wouldn't even start charging, "battery full". In your face, android!17:58
DocScrutinizer05wpwrak: the cat was *inside* the wing18:43
wpwrakwhoa. sloppy fabrication process ! :)19:10
wpwrakbut indeed. good spotting ! that also explains why he never saw it coming :)19:41
DocScrutinizer05hmm, another 10h PC nonstop. time for a break20:02
DocScrutinizer05you know sth is wrong with your life when the only two times you leave flat during the week are to buy new milk for coffee20:03
DocScrutinizer05I'm actually grateful we have no delivery service for groceries here20:04
wpwrakin joergtown, there is a city-wide pipe system for water (operates only once per week) and one for milk (non-stop), and coffee is traded by 100 kg bags20:09
DocScrutinizer05I prefer a third pipe system ;-)20:17
whitequarkwpwrak: I've spent quite a few minutes trying to think of a way to safely transfer milk city-wide20:30
whitequarkuntil I realized what "joergtown" means20:30
--- Tue Jun 23 201500:00

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