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2016-03-23 00:23 <wolfspraul> wpwrak: hmm. is it possible that that is just this greylisting stuff?
2016-03-23 00:24 <wolfspraul> where does this error msg come from - did you get a final "cannot be delivered" back into your mail client?
2016-03-23 00:25 <wpwrak> so far it's just trying to connect. is it MTA running ? on turandot, telnet localhost 25 -> telnet: Unable to connect to remote host: Connection refused
2016-03-23 00:26 <wpwrak> and the mail hasn't timed out yet on my side. don't remember what timeout i set. probably something relatively large
2016-03-23 00:26 <wpwrak> yeah, 5 days :)
2016-03-23 00:26 <wpwrak> but it'll start complaining after 4 hours
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2016-03-23 00:52 <DocScrutinizer05> seems there's really stormy weather in the internets, eh?
2016-03-23 00:53 <wpwrak> looks more like some system upgrade at qi-hw, and the usual fallout such things produce
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2016-03-23 01:15 <wpwrak> hmm, i wonder if AAA + diode + polyfuse would work for battery reversal protection
2016-03-23 01:16 <wpwrak> (as alternative to an "ideal diode")
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2016-03-23 01:21 <wpwrak> the sub-question there is what the damage mechanism is for battery reversal. i.e., what sort of current has to flow through the reversed AAA battery to actually do damage to the circuit
2016-03-23 01:22 <wpwrak> but i suspect that relatively little may be sufficient, i.e., a few hundred mA
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2016-03-23 01:52 <wpwrak> wolfspraul: thanks ! :)
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2016-03-23 02:52 <whitequark> wpwrak: there are ideal diodes.
2016-03-23 02:52 <whitequark> well, "diodes" with zero drop. they're available. it's actually a fet in a diode package
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2016-03-23 03:08 <wpwrak> got an example ?
2016-03-23 03:09 <wpwrak> looking for "ideal diodes" i found some parts, but usually stuff that's far out of the range we'd need here
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2016-03-23 03:33 <whitequark> wpwrak: hm
2016-03-23 03:33 <whitequark> so there's this 55mV Schottky https://www.digikey.com/product-detail/en/fairchild-semiconductor/SS14FP/SS14FPCT-ND/5892130
2016-03-23 03:34 <whitequark> I can't find the exact device I was looking for yet, but does it even matter for your application?
2016-03-23 03:39 <wpwrak> you mean the 0.55 V = 55 mV type ? :)
2016-03-23 03:39 <wpwrak> the golden rule still applies: if it's too goo to be true then it probably isn't ;-)
2016-03-23 03:39 <wpwrak> or, in the case of digi-key: then it's probably a typo :)
2016-03-23 03:40 <whitequark> ah right, it's a typo
2016-03-23 03:40 <whitequark> anyway, this is what I was talking about: https://www.maximintegrated.com/en/app-notes/index.mvp/id/636
2016-03-23 03:48 <wpwrak> here is a "smart diode". alas, expensive (and designed for higher-current applications): https://www.digikey.com/product-detail/en/texas-instruments/SM74611KTTR/296-35688-1-ND/3911155
2016-03-23 03:49 <wpwrak> ti's data sheet is from 2012. so maybe around 2030, when the patents expire, we'll see more such smart diodes ...
2016-03-23 03:50 <wpwrak> the maxim circuit with boost converter is interesting. haven't thought of that.
2016-03-23 03:51 <wpwrak> the FET circuits all have the problem of low voltage. it's hard to find FETs that are happy to admit ~ 1 A with a low drop and Vgs <= 1 V
2016-03-23 03:52 <wpwrak> a radically different approach would be to block this mechanically
2016-03-23 03:54 <wpwrak> not sure how well that would work, though. the "nipple" of an AAA cell is supposed to stick out by >= 0.8 mm. so an obstacle of about 0.5 mm around the contact should work. however, i don't remember ever seeing such an arrangement in real life. there may be a reason for it.
2016-03-23 04:18 <whitequark> yeah, the voltage is troubling
2016-03-23 04:22 <whitequark> oh, I remember now the proper name for the device I was looking for
2016-03-23 04:22 <whitequark> "MOS Rectifier"
2016-03-23 04:23 <whitequark> they do have lower Vf than regular Schottky diodes but I think not lower enough
2016-03-23 04:24 <whitequark> http://www.ttiinc.com/object/Vishay-45V-Trench-MOS-Barrier-Schottky-Rectifier
2016-03-23 04:24 <whitequark> 0.28V@5A apparently
2016-03-23 04:26 <whitequark> but those are unavailable... and I've definitely seen those in production
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2016-03-23 04:30 <whitequark> AHA! found it.
2016-03-23 04:30 <whitequark> wpwrak: http://www.ti.com/lit/ds/symlink/sm74611.pdf
2016-03-23 04:30 <whitequark> 26 mV at 8 A
2016-03-23 04:30 <whitequark> and that's not a typo.
2016-03-23 04:30 <wpwrak> see above :)
2016-03-23 04:30 <whitequark> nope
2016-03-23 04:30 <whitequark> read the datasheet.
2016-03-23 04:31 <whitequark> oh
2016-03-23 04:31 <wpwrak> ;-)
2016-03-23 04:31 <whitequark> oh, you found that device
2016-03-23 04:31 <whitequark> yeah
2016-03-23 04:31 <whitequark> I was under impression that there were more of them
2016-03-23 04:31 <whitequark> but this is exactly the thing I had in mind.
2016-03-23 04:34 <whitequark> the maxim circuit is basically the same thing as that diode, except discrete
2016-03-23 04:55 <whitequark> wpwrak: how about this? https://www.fairchildsemi.com/datasheets/FD/FDN327N.pdf
2016-03-23 04:55 <whitequark> Vgs=1.8
2016-03-23 04:56 <whitequark> Rds(on)=120m, meaning Vf=120mV
2016-03-23 04:56 <whitequark> at your target 1A
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2016-03-23 05:29 <wpwrak> needs boosting. Vgs(th) is too high
2016-03-23 05:30 <wpwrak> after all, that little battery can only cough out 1.5 V when fresh, and with use, it gets worse
2016-03-23 05:31 <wpwrak> these are the results of the little search i did: https://defuse.ca/b/pYH84uqSKqz33KLH2YnlPT
2016-03-23 05:31 <wpwrak> i found no p-FET that looked truly convincing
2016-03-23 05:32 <wpwrak> i found two n-FETs that may be okay
2016-03-23 05:34 <whitequark> oh right, you have an AAA battery, not li-ion
2016-03-23 05:34 <wpwrak> but i wonder if there may be an easier solution. that variant with providing the gate voltage from the boost converter looks interesting. not quite sure if it would actually work, though. the path of components that are borderline operational gets fairly long.
2016-03-23 05:34 <wpwrak> yup. if i had 3.7+ V to burn, there would be no worry at all ;-)
2016-03-23 05:41 <wpwrak> the big concern is to avoid choking the battery too early. e.g., when current demand is high, battery voltage drops in the battery and then again at the FET. the resulting lower boost Vin makes it draw even more current. worse, since that reduced voltage is also Vgs, the FET becomes more resistive, further increasing drop and current demand
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2016-03-23 06:53 <eintopf> mhh, I like smartphones which getting hot when I turn on GPS. Then I have something to heat me up at the bus station when its winter
2016-03-23 07:00 <kyak> it get hot because of GR effects. You phone travels in time and space, and it is quite hot there
2016-03-23 07:01 <kyak> while waiting for a bus, don't forget what's your phone is going through
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2016-03-23 07:21 <xiangfu> wpwrak: Hi
2016-03-23 07:23 <xiangfu> wpwrak: we got 15 N900. one of them is very bad. the others looks like ok. but all used devices. vc.cheng@can.... should be send one email to you. with pictures.
2016-03-23 07:23 <xiangfu> wpwrak: let me know what should I do next?
2016-03-23 07:23 <xiangfu> but it is not easy to get 200 of them. I buy them slowly...
2016-03-23 08:47 <wpwrak> are all 15 from the same source ? and have they been cleaned properly, i.e., are they of similar quality as the refurbished we looked at some months ago ? or are they worse ?
2016-03-23 08:48 <wpwrak> (not easy) the messier the sourcing, the greater the glory ;-)
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2016-03-23 10:06 <whitequark> wpwrak: the boost circuit really shouldn't draw any current
2016-03-23 10:06 <whitequark> maybe microamps. it has to run the charge pump once, and afterwards its job is done
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2016-03-23 12:04 <eintopf> it's not a good idea to glue your usb hubs on your table with a velcro fastener powerband...
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2016-03-23 14:32 <wpwrak> eintopf: why not ?
2016-03-23 14:41 <wpwrak> whitequark: yes, it all should work. but i imagine that there could be little quirks like the boost regulator trying to pull significant current in startup or such, and cycling back if it can't (because the FET isn't fully open yet)
2016-03-23 14:42 <wpwrak> so such a circuit would need careful testing, to check that there aren't such quirks while in borderline conditions
2016-03-23 14:43 <wpwrak> but i still very much like the idea to increase the gate voltage this way. that solves a LOT of problems ;-)
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2016-03-23 16:06 <eintopf> wpwrak: it's too strong
2016-03-23 16:06 <eintopf> I tried to remove it again and the whole case creaks in two pieces
2016-03-23 16:07 <eintopf> s/creaks/breaks/
2016-03-23 16:07 <qi-bot> eintopf meant: "I tried to remove it again and the whole case breaks in two pieces"
2016-03-23 16:07 <eintopf> but I have it now
2016-03-23 16:07 <eintopf> I need some knife to remove it :-)
2016-03-23 16:07 <wpwrak> ah, the idea is to make this permanent :)
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2016-03-23 16:20 <DocScrutinizer05> hmmm  >> At t2: When the voltage on the capacitor C1 reaches its predetermined lower level, the FET driver shuts off the FET. The bypass current will then begin to flow through the body diode of the FET, causing the FET body diode voltage drop of approximately 0.6V to appear across ANODE and CATHODE. The charge pump circuitry is re-activated and begins charging the capacitor C1. This cycle repeats until the shade on the panel is
2016-03-23 16:20 <DocScrutinizer05> removed and the string current begins to flow through the PV cells instead of the body diode of the FET.<<
2016-03-23 16:21 <DocScrutinizer05> wpwrak: why the heck you need 1A?
2016-03-23 16:21 <wpwrak> i need a bit less, something like 800 mA
2016-03-23 16:22 <DocScrutinizer05> ugh, that's much
2016-03-23 16:22 <wpwrak> Ibat(max) = 120 mA / Vbat * 3.3 V / efficiency / duty_cycle
2016-03-23 16:22 <DocScrutinizer05> which duty cycle?
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2016-03-23 16:23 <wpwrak> the "charging" part of the inductor
2016-03-23 16:23 <DocScrutinizer05> there's capacitors for that
2016-03-23 16:24 <wpwrak> ah yes, that was the formula for inductor / switch current
2016-03-23 16:24 <wpwrak> so for the battery it's a bit less ...
2016-03-23 16:24 <DocScrutinizer05> I hope so, you won't find a AAA that behav4es under such conditions
2016-03-23 16:24 <wpwrak> ~550 mA (assuming 80% efficiency)
2016-03-23 16:25 <wpwrak> check the AAA short-circuit curve ;-)
2016-03-23 16:26 <DocScrutinizer05> you need to check _all_ those curves, unless you specify an approved battery brand and type for your device
2016-03-23 16:26 <DocScrutinizer05> iirc a 500mA are about max to draw from a AAA
2016-03-23 16:28 <wpwrak> i mean this one: http://www.varta-microbattery.com/applications/mb_data/DOCUMENTS/GRAPHS/04103/G_04103_O_S01_en.pdf
2016-03-23 16:28 <wpwrak> (see my post to he qi-hw list)
2016-03-23 16:33 <DocScrutinizer05> that diagram only mentions Ampere but no voltage
2016-03-23 16:34 <DocScrutinizer05> and it's Varta, a known semi-devcent cell manuf
2016-03-23 16:37 <DocScrutinizer05> actually you can read the diagram as "initial internal Z of cell: 100mOhm, after ~4 minutes 1 Ohm"
2016-03-23 16:39 <DocScrutinizer05> cells of slightly lower quality might already start with 1 Ohm out of the blister
2016-03-23 16:40 <DocScrutinizer05> particularly zink carbon cells
2016-03-23 16:40 <DocScrutinizer05> not every battery is alkaline even today
2016-03-23 16:41 <DocScrutinizer05> sorry I'm not on qi-hw ML
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2016-03-23 16:44 <DocScrutinizer05> I still wonder what draws such huge amount of power in your device
2016-03-23 16:45 <DocScrutinizer05> you must have a power hog you should disable by default and only power up on user request
2016-03-23 16:46 <DocScrutinizer05> if it's backlight, it's prolly a good measure to only enable it when ambient light is low, and definitely keep it disabled during device ramp-up and when battery voltage is low
2016-03-23 16:49 <DocScrutinizer05> ever pondered http://www.batteryjunction.com/10440.html ?
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2016-03-23 16:50 <DocScrutinizer05> http://www.batteryjunction.com/10440-category.html
2016-03-23 16:55 <wpwrak> the power hog is the memory card. it can draw up to 75 mA for up to 250 ms (per operation)
2016-03-23 16:55 <wpwrak> otherwise, anelok uses a lot less, of course
2016-03-23 16:56 <wpwrak> and there's no stinkin' backlight. in OLED we trust :)
2016-03-23 16:56 <wpwrak> (besides, OLED looks much better)
2016-03-23 16:58 <wpwrak> (zinc carbon) naw, i expect people to use alkaline of halfway decent quality. it's not as if they were difficult to find.
2016-03-23 16:58 <DocScrutinizer05> good, then don't power up the memory card until the device is fully up to provide proper bias for Vgs
2016-03-23 17:00 <DocScrutinizer05> besides that, a fuse plus reversal diode is the means of choice to protect from battery reversal
2016-03-23 17:00 <DocScrutinizer05> use a schottky
2016-03-23 17:00 <wpwrak> (10440-category.html) -> "UltraFire" how appropriate ;-))  http://avherald.com/h?article=495aeb31
2016-03-23 17:00 <DocScrutinizer05> yeah funny
2016-03-23 17:01 <DocScrutinizer05> the right one there is nice
2016-03-23 17:01 <DocScrutinizer05> only 350mA but seemingly safe chemistry
2016-03-23 17:01 <wpwrak> (fet charged) yes, anelok can ramp up "nicely". but "setting up" the FET is actually something that happens even earlier, long before the MCU even begins to reset
2016-03-23 17:03 <DocScrutinizer05> toldya, use a pushbuttom to power up, it can even generate 2*Vbatt on gate
2016-03-23 17:03 <wpwrak> it's kinda funny that all three refer to fire, either directly in the name or in the logo ;-)
2016-03-23 17:04 <DocScrutinizer05> ...for long enough to boot the MCU
2016-03-23 17:05 <wpwrak> pushbutton wouldn't really help. this is between battery, fet, and boost converter. there is no change in the configuration of the boost converter.
2016-03-23 17:05 <DocScrutinizer05> hm?
2016-03-23 17:05 <wpwrak> the boost converter starts enabled (unless there is usb power)
2016-03-23 17:06 <wpwrak> and only the presence of USB power can turn it off
2016-03-23 17:06 <DocScrutinizer05> so?
2016-03-23 17:06 <DocScrutinizer05> I don't get it
2016-03-23 17:07 <wpwrak> so such a hypothetical button wouldn't affect what happens at this early system bringup
2016-03-23 17:07 <DocScrutinizer05> errr
2016-03-23 17:07 <DocScrutinizer05> what for is tha FET then?
2016-03-23 17:07 <wpwrak> to protect against battery polarity reversal
2016-03-23 17:07 <DocScrutinizer05> ohmy
2016-03-23 17:08 <wpwrak> i was thinking of also using it to disconnect the battery, but it seems that this would get too complicated. in any case, even if i do this, it would be controlled by the presence of a good USB voltage.
2016-03-23 17:08 <DocScrutinizer05> you know each decent device doesn't allow to reverse AAA batteries since the button on plus is the only thing that can touch the battery contact?
2016-03-23 17:09 <wpwrak> i use a reset generator for detecting USB voltage. that way, i won't get funny things happening on connect / disconnect, when USB ramps through Vgs(th). had issues there in the CR2032 design, and it would only get worse in the AAA design
2016-03-23 17:10 <DocScrutinizer05> [2016-03-23 Wed 18:00:12] <DocScrutinizer05> besides that, a fuse plus reversal diode is the means of choice to protect from battery reversal
2016-03-23 17:12 <wpwrak> i'm not so sure about diode + fuse. it would seem that a partially spent battery may end up just producing enough reverse current to do damage, yet wouldn't trip the fuse
2016-03-23 17:12 <DocScrutinizer05> I think my last comment on all this was to recommend battery change only when attached to USB, to keep RTC running. When a user doesn't follow that recommendation, they will have to adjust date and time anew after battery inserted
2016-03-23 17:13 <wpwrak> (mechanical prevention) i wonder about that. i don't recall ever seeing that done in practice, though the mechanical design of the AAA (et al.) cells clearly suggests such a design
2016-03-23 17:13 <wpwrak> no, i don't want to require USB power
2016-03-23 17:13 <DocScrutinizer05> a schottky is supposed to be <0V5 which is well within allowable voltage range in every chip I know
2016-03-23 17:14 <wpwrak> you should be able to change batteries in the field, without preparation
2016-03-23 17:14 <DocScrutinizer05> well, you can do this
2016-03-23 17:15 <DocScrutinizer05> I honestly don't see how you want to keep RTC running without a decent power source
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2016-03-23 17:15 <wpwrak> (schottky) yes, but i also want to make sure the fuse trips. wouldn't be so nice if the battery merely fast-discharges through the schottky.
2016-03-23 17:16 <DocScrutinizer05> maybe get a Dallas chip ;-)
2016-03-23 17:16 <wpwrak> i have caps to hold power for a litte while
2016-03-23 17:16 <DocScrutinizer05> I don't want to have to cope with such worries you seem to have
2016-03-23 17:16 <wpwrak> and a FET before them, to isolate the MCU from the rest of the system
2016-03-23 17:17 <wpwrak> we'll get to this when debugging neo900 power ;-)
2016-03-23 17:18 <DocScrutinizer05> IF a battery has a button on minus (instead of flat plate) so it could make contact from minus pole to plus battery contact mechanically, AND the battery is already empty enough so it doesn't trip fuse, then you don't want that battery to get discharged
2016-03-23 17:18 <DocScrutinizer05> no, we won't get to this with Neo900 power
2016-03-23 17:18 <DocScrutinizer05> been there, done that
2016-03-23 17:21 <DocScrutinizer05> I'd be more worried about somebody inserting a 9V AAA than about discharging a weird mechanical nonstandard half-empty secondary 1.5V AAA
2016-03-23 17:24 <DocScrutinizer05> odds are the user completely depleted the battery anyway before even noticing she needs a new battery, so RTC is void in either case
2016-03-23 17:25 <wpwrak> (trip) let's see ... battery: Vinternal = 1.5 V, Rinternal = 1 Ohm; fuse: Ihold > 600 mA; diode: Vf@Ireversed = 0.5 V. so the short-circuit current through the diode would be (1.5 - 0.5 V) / Rinternal = 1 A.
2016-03-23 17:26 <wpwrak> so the difference between Itrip and Ihold would be only 400 mA. difficult to find a fuse that's that selective.
2016-03-23 17:26 <DocScrutinizer05> and when you want user to take care about not losing the date and time while battery swapping, provide a "swap battery" function user needs to activate before removing battery, which will store the current date and time to non volatile storage and recovers it from there during power-up after new battery inserted. will be off a minute maybe
2016-03-23 17:27 <DocScrutinizer05> the fuse is only to avoid damage to the device, not to protect a half-dead battery
2016-03-23 17:28 <DocScrutinizer05> keep in mind that with proper mechanical design it's virtually impossible to reverse battery
2016-03-23 17:29 <DocScrutinizer05> only needs a 10mm^3 of plastic to form a stopper that keeps minus plate of battery from touching the plus battery contact of device
2016-03-23 17:30 <DocScrutinizer05> unless you do extremely weird things, you _cannot_ reversa a AAA cell in device
2016-03-23 17:30 <wpwrak> one minute would be very long. e.g., TOTP has a default time increment of 30 s.
2016-03-23 17:31 <DocScrutinizer05> ohmy, then add a adjustable offset, let user guess
2016-03-23 17:31 <DocScrutinizer05> measure discharge of a capacitor and calculate the battery off time, simple as that
2016-03-23 17:32 <wpwrak> (mechanical prevention of battery polarity reversal) have you seen anything like this in real life ? even high-end equipment seems to have very reversal-friendly contacts. i wonder why
2016-03-23 17:33 <DocScrutinizer05> because they are fools? I've seen it in ~80% of my devices
2016-03-23 17:33 <DocScrutinizer05> you usually don't even notice it
2016-03-23 17:33 <wpwrak> (cap) hmm ! now that's an interesting idea ! i like that :)
2016-03-23 17:36 <DocScrutinizer05> yeah, a funny simple concept I just invented in a fraction of a second
2016-03-23 17:37 <DocScrutinizer05> actually best part of (18:31:57 - 18:31:31 ) taken by typing
2016-03-23 17:40 <DocScrutinizer05> you can start discharge at very moment you take the timestamp, before you write said timestamp to storage
2016-03-23 17:40 <wpwrak> something like 47 uF vs. 1 MOhm should do the trick for times in the order of 1 minute
2016-03-23 17:40 <DocScrutinizer05> I guess you could even use 10M
2016-03-23 17:41 <DocScrutinizer05> AD-inputs are high impedance, no?
2016-03-23 17:42 <wpwrak> i should probably only activate ADC briefly. lemme check ...
2016-03-23 17:43 <wpwrak> without ADC, input leakage is 1 uA or maybe 25 nA (25 C).
2016-03-23 17:43 <DocScrutinizer05> charge, measure voltage and stop charging, wait 2s and measure voltage again [1], then charge again, take timestamp from RTC [2] and stop charging, write [1] and [2] to storage
2016-03-23 17:45 <DocScrutinizer05> hmm, no, [1] needs to be a derived value from both voltage measurements
2016-03-23 17:45 <DocScrutinizer05> representing the percentage of discharge during 2s
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2016-03-23 17:46 <DocScrutinizer05> and actually you need the absolute voltage too, in storage, to know a reference later on
2016-03-23 17:46 <wpwrak> spec also applies to ADC, so real-life leakage should not be much higher than 0.1 uA. so yes, maybe 2 or 3 MOhm should work fine.
2016-03-23 17:47 <DocScrutinizer05> so store both voltage at t0 and voltage at t2s as well as timstamp to storage
2016-03-23 17:47 <wpwrak> yes, the critter needs to recalibrate every once in a while. not a big deal, though.
2016-03-23 17:48 <wpwrak> the trickiest bit is avoiding messing up that cap when the system ramps up/down
2016-03-23 17:49 <DocScrutinizer05> hmm yes
2016-03-23 17:49 <wpwrak> but even if we don't take precautions, having a calibration happen while the rail changes dramatically should have a pretty low probability. prolly better than 1e-5
2016-03-23 17:50 <wpwrak> (all that assuming nothing nasty happens for too long when the MCU is below safe operating voltage)
2016-03-23 17:50 <DocScrutinizer05> you should spend a 2 GPIO, one for "power" and one for "gate", where the switch (FET) charges on power != gate
2016-03-23 17:52 <wpwrak> yes, that could be an option
2016-03-23 17:53 <wpwrak> in any case, a sufficiently large cap would also be immune to very brief GPIO upsets, given that Ron of the GPIOs is around 100 Ohm.
2016-03-23 17:54 <DocScrutinizer05> well, or you simply connect the AD/GPIO to capacitor via 3M and have a small capaicor (for glitches) and a 47kR from AD/GPIO to GND
2016-03-23 17:54 <wpwrak> but having an extra fet would also help to keep the "high" cap voltage from a powered-down MCU. it has no upper clamp diodes, but you never know what else may happen
2016-03-23 17:55 <DocScrutinizer05> err uh, that idea of mine would spoil the AD probing :-/
2016-03-23 17:55 <wpwrak> and it would make charging a lot of work :)
2016-03-23 17:56 <DocScrutinizer05> so use a GPIO with all that birdseed for charging/discharging and a separate AD input to capacitor via 10M for measuring
2016-03-23 17:56 <DocScrutinizer05> aah yes, chatging takes a while then, but then, who cares
2016-03-23 17:57 <DocScrutinizer05> keep capacitor charged all the time
2016-03-23 17:57 <wpwrak> seems easier and safer with one measure/charge pin and one to switch a FET
2016-03-23 17:57 <wpwrak> also, i'm pretty limited when it comes to IO pins
2016-03-23 17:57 <DocScrutinizer05> maybe not
2016-03-23 17:58 <DocScrutinizer05> you need two pins for both concepts
2016-03-23 17:58 <wpwrak> if i have a direct charging pin, then i could use that as well for measuring
2016-03-23 17:58 <DocScrutinizer05> that's the initial idea
2016-03-23 17:58 <wpwrak> so if separating the two, that's ADC + charge + switch(FET). not so nice
2016-03-23 17:59 <DocScrutinizer05> you don't need a FET when charging takes "ages"
2016-03-23 17:59 <DocScrutinizer05> short glitches will be irrelevant then
2016-03-23 17:59 <wpwrak> ah, i see what you mean
2016-03-23 18:00 <DocScrutinizer05> 3 resistors (the 47k from charging GPIO to GND for proper discharging during MCU down) and 2 pins is all you need
2016-03-23 18:01 <DocScrutinizer05> add a small capacitor in parallel to the 47k for even better glitch immunity
2016-03-23 18:02 <DocScrutinizer05> hmm maybe that's a bad idea, it will buffer any glitch and extend its duration
2016-03-23 18:03 <DocScrutinizer05> so no small capacitor in parallel to 47k
2016-03-23 18:04 <DocScrutinizer05> if you could make sure the GPIO is tied to GND via a strong pulldown in all MCU glitch resp reset situations, you can even leave out that 47k
2016-03-23 18:05 <DocScrutinizer05> and use one pin only
2016-03-23 18:07 <wpwrak> after reset, gpios are high-Z. so, no
2016-03-23 18:07 <wpwrak> but yes, the rest should work
2016-03-23 18:09 <wpwrak> on power loss, the MCU needs to save the whole data set to a pre-erased flash page. takes some 70 us per longword on average. the usual optimizations apply.
2016-03-23 18:10 <wpwrak> so that doesn't look too bad
2016-03-23 18:11 <wpwrak> nice idea, thanks !
2016-03-23 18:11 <DocScrutinizer05> yw
2016-03-23 18:11 <DocScrutinizer05> CC by attribution
2016-03-23 18:12 <DocScrutinizer05> ;-))
2016-03-23 18:19 <wpwrak> in the post where i explain the part ? alas, there's no document explaining the whole system. not enough hours in a night :(
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2016-03-23 18:26 <DocScrutinizer05> wherever you feel it's appropriate
2016-03-23 18:27 <DocScrutinizer05> it's just a ;-) thing
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2016-03-23 18:35 <DocScrutinizer05> do you have a power-good signal which tells you when battery removed, by getting drawn to GND? If yes, you might want to connect the 47k pulldown to that signal instead of GND, so you don't get quiescent currents during normal operation (battery inserted)
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2016-03-23 18:47 <wpwrak> yes, i thought of that, too. the boost converter i'm considering has a "battery good" signal. i think it may be used for something like this, but need to check some more.
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2016-03-23 19:05 <DocScrutinizer05> wpwrak: (mech reversal block) http://maemo.cloud-7.de/share-service/DSCF1916.JPG http://maemo.cloud-7.de/share-service/DSCF1917.JPG AA but the principle is the same
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2016-03-23 19:12 <DocScrutinizer05> http://wstaw.org/m/2016/03/23/DSCF1914.JPG  halfassed implementation, actually a fail
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2016-03-23 19:23 <wpwrak> kewl. so it does exist in real life. no FET or polyfuse needed then :)
2016-03-23 19:24 <wpwrak> the less gunk in the power path, the better
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2016-03-23 20:36 <wpwrak> hmm. too good to be true ? https://www.kickstarter.com/projects/olo3d/olo-the-first-ever-smartphone-3d-printer
2016-03-23 20:52 <mth> the campaign period does include April 1st
2016-03-23 20:52 <mth> if it's a light-sensitive resin, shouldn't it be kept in opaque bottles?
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2016-03-23 20:56 <wpwrak> mth: yes, at heise.de they have a pretty long list of doubts: http://www.heise.de/newsticker/meldung/Olo-3D-Druck-mit-dem-Licht-aus-dem-Smartphone-Display-3149561.html
2016-03-23 20:56 <wpwrak> puzzling
2016-03-23 21:14 <mth> here is a company that claim to use daylight resins as well: http://www.photocentric3d.com/
2016-03-23 21:14 <mth> all their bottles are black though
2016-03-23 21:15 <mth> maybe the tech is real but the video is faked since the kickstarter project has no working product yet?
2016-03-23 21:20 <mth> (which would violate kickstarter rules for hardware projects)
2016-03-23 21:29 <mth> hmm, in their demo video they seem to fill the tank from a black bottle
2016-03-23 21:30 <mth> so the bottles shown in the main video are probably not actual resin
2016-03-23 21:31 <mth> also, if it takes 4 hours to print a small object, is it actually a good idea to use a phone as the screen?
2016-03-23 21:31 <mth> well, if you have an old smartphone around that you no longer use as a phone, I guess
2016-03-23 22:34 <wpwrak> if the thing works, it would still be cheap if you add the cost of a new smartphone :)
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