Posts by ilmari 255 publicly visible posts • joined 18 Oct 2012
Roughly first half of the noughties, Nokia did the opposite with the battery meter: full bars until 50%, and then vaguely linear dropoff from there to 1 bar, which was whatever threshold their engineers felt the algorithm could reliably predict there'd be enough power left for orderly shutdown.
This "show full until half" was a neat trick, in a day when users' metric was "check out my new phone, got it 5 days ago, on my first charge, and it still has 5 of 5 battery bars!"
Linux fanboy checking in here
The problem with real world is that conditions are random. The problem with background apps is that they perform random crap, through the random quality network environment, and everyone has different set of crapware installed.
Real world example: At home, on my desk, where even IRDA to celltower would work, standby life without background apps would be on the order of weeks.
Out at sea on an island, with closest tower being a solar/windpowered byuoy, standby time is on the order of hours.
There's already massive power use within the fairly wide "full signal" indicated range, let alone when operating with less than perfect signal indicated...
The only purpose of the batttery life ratings is to compare with other ratings. (and hope they use same methodology across models).
As a sidenote, and as someone who doesnt use apple, I have to say I'm rather envious that iphone brightness goes as low as it goes, and that the volume can go low too. Most devices these day feel like getting stabbed in the eye at lowest brightness, and bleeding eardrums at one step above muted..
Then again, I see other people discussîng max screen brightness and volume, as if they actually want even more , to me, ludicrously high levels... Again, shows that one person's real world can be quite different from another's.
Mostly, li-ion fires can be divided into 2 causes: impurities introduced during manufacturing, and bad battery management systems.
Unfortunately, batteries seem to be poorly understood by most electrical engineers, so the amount of flawed battery management systems out there is rather huge.
Still, the 'rules' are pretty simple: Don't go below 2.80V, don't go above 4.20V. Ever. Not even for a millisecond.
Our clever cost-aware EE will then think "I've got 3 in series, so that means I need to stay between 9V and 12.6V. This is wrong, he needs to monitor all 3 cells individually. There will never be cells matched exactly enough, and stay matched throughout their service life.
So, each cell must be monitored individually. On discharging, the device must shut off when the weakest cell reaches the minimum allowable voltage, or sooner. On charging, the charging current must be reduced when the fullest cell reaches maximum permissible voltage. Preferably you have a circuit that can bleed off some charge from the fullest cells, so that all cells can be charged full.
The EE that reads the datasheet closely enough, will notice that samples if cells are put through overdischarge and overcharge testing, wherd they are taken outside of the permissible voltage range, and demonstratedly don't explode, smoke, or emit excessive heat. He will then make the assumption that the limits are more of a guideline for best cycle life, and the worst that will happen is that the battery dies a bit sooner, and the customer needs to buy a new battery or device sooner.
While it's true thay li-ion cells must withstand such tests without failure, they only need to do it once. That is, one test is performed once, and the specific cell in question is never used again.
The reason for this is that every deviation outside the safe range inflicts accumulating damage to the cell. Accumulating meaning that while a 'small' deviation from the safe range might not cause problems the first time, it could cause issues the 10th time or the 200th time it happens.
At one extreme voltage, the copper inside the cell starts dissolving. If this process reverses, you get conductive copper in random places, potentially causing short circuits, or a string of thin copper might carry current, cause heating, and ignite the cell.
At the other end, the battery evolves metallic lithiun, which is the equivalent of the petrol in your car turning into nitroglycerine. Ungood.
On the face of it, rpi loojs like a hard sell. Severely aged SoC, where the cpu is more of a companion thing rather than the main phrpose of the chip, etc etc..
However, what rpi has got is volume and community. While allwinner chips might be 10 times faster, you'll spend a lifetime getting software support up to the same level as on the pi.
For this reason, rpi boards continue to outsell allwinner-based boards, and will probably do so until sunxi has the same level of maturity and ease of use as raspberry pi.
8.2V shutdown threshold is very wasteful, the battery will have delivered far less than half its stored energy at 8.2. At 5.4V, that woukd be closer to 95%.
And as others have said earlier, 6xAA battery holder, or even 6xAAA, would be far more cost effective.
Carbon-zinc, zinc chloride (Super) Heavy Duty batteries are only useful in the case where the wage cost of replacing them is near zero. Or in the case where the batteries last years anyway, though you run an increased risk of leakage.. Which again you'd want free workers for the cleanup.
I wonder if their computer system had redundancy...
You woukd think they would, as even the amateur high altitude balloon people have used , well essentially triply redundant arduino arrays, and have been able to detect and report back the number of times their cpus have been affected by radiation.. iirc around half dozen 'events' at balloon altitudes..
You would think the amsat community designed their previous sats sanely too, as some of them are still up there and working..
But then, are thess people just some random dudes that threw together a kickstarter and ignored the experiences of amateur satellite operators that came before them, or did they indeed have best practice design and got hit by too much radiation for their redundancy to cope with?
Brightness doesn't go low enough on most devices. Turning them on in a dark place is still similar to looking into the end of a lightsabre when switching it on...
Also, I feel the ambient light sensors dont quite work as intended when they're on fhe front of the devices. Either I myself place the sensor in shadow, or they pick up something bright behind me, or pick up dark behind me, and completely ignore what is, from my point of view, the background against which the display's brightness should match.
Considering 30 minutes from clicking and receiving goods, I assumed they'd all be electric rather than internal combustion engine.
Although, on another note, the challenges involved in making a ICE powered multicopter are kinda interesting, and as a side-effect you'd probably end up with a more aerodynamically efficient, and a more aerobatically capable vehicle :-) Sort of like a multirotored helicopter, instead of multipropellered flattened airplane standing on its tail.
I thought the top vs bottom fermenting stuff was mostly related to so called "top fermenting" varieties fermenting vigorously enough that the Co2 produced stirs the liquid enough to toss the little critters around and form foam at the top..
As for flocculation, perhaps a German HefeWeizen or Belgian Wit will taste better in space, because the yeast will NOT accumulate at the bottom, so you don't have to shake the bottle in order to knock the yeast loose (and lose some carbonation while doing so).
I bought one, mostly because I wondered how the hell any browser in the year 2013 can run usably on less than a gigabyte or two of ram and dual cores. Well, the answer was that it doesn't.
My 2009 Nokia N900 with its 2010 gecko-based browser and 600MHz cpu loads websites (those that still work on 3 year old browsers) faster than the Zte Open..
Try load theregister in landscape mode on ZTE Open. You get notice about cookies splattered on the bottom half of the screen, and attempts to tap "I agree" just opens whatever link is underneath the "I agree" button. Usually some ad.
I couldn't agree more about the keyboard. Comparing it with the N900 again (it might be unfair to compare with 2009 $600 phone), its unpredictive onscreen keyboard on 3.5" RESISTIVE screen is more usable than the ZTE Open keyboard... that's quite an achievement..
I wanted a simple device just for web browsing in bed after laptop and tablet become too heavy to hold up over my head, and thought that even if firefox os has no apps, atleast it has a browser that should be good.. Too many websites don't work in it, and there's no way to disable the broken "mobile" websites, atleast firefox for android has such an option, and even an extension that makes it default..
As for apps, most of them are garbage. Ignoring games, Filter out all the "website as an app" (including youtube, netflix and everything else that only exists because the browser and/or website sucks too much), reference/book/cityguide/wallpaper crud, soundboards and other gimmicks, and you're left with a pretty small number of apps on any app store.
As for my own "killer apps", it would be openvpn, a scientific/graphing calculator (or gnuplot), some spreadsheet thing.
Both "Microsoft" and "Windows" brands are burdens.
Despite the majority of the world's PCs running windows doesn't mean people love windows, or microsoft. They put up with it. When they've got non-microsoft-windows choices in tablet area, they'll go for something they don't yet hate.
I wonder what would've happened if Microsoft had called xbox "Microsoft Windows Vista Game machine"...
With SSL you're at the mercy of the certificate authorities, who are slaves to their governments and to money. The only app that doublechecks stuff is the Chrome browser, which has hardcoded the expected certificate chain for google services.Not that that helps, as google is subject to government spying anyways.
As for everything else, a compromised, rogue or court controlled certificate authority can issue certs that appear (and technically are) entirely legit, but enable man in the middle eavesdropping. If the data at any point flows through a node on the internet located in a hostile country (hostile towards free speech and privacy that is), it will be compromised. Considering the majority of traffic on the internet at some point goes through the US, UK and EU, basically everything you send can be intercepted.
The big problem with encryption is in the key exchange.
PGP where you physically exchange keys with eachother is a little bit better, but you can't trust the software and operating system, and you can't trust the hardware, they've all been exposed to hostile governments at some point in the supply chain.
For all the bad rap China gets for it's great firewall and censorship, they're starting to look benigner and refreshingly honest, because atleast they let people know there indeed exist such policies.
(Disclaimer: I don't live in UK)
Yeah, biggest fun with getting a smart meter for me was that it has a blinking led, which is easy to interface with an arduino to log and plot power use. It was much harder to read the old spinning disc type meter.
As a result, when the inhabitants can see how much power the dish washer, washing machine and tumble dryer use, we've been much better at running them at night when the electricity is cheaper. The old myths about fridge and freezer being energy bandits have also been proven wrong.
As for the other issues, people here are mostly concerned about the smart meters' alarming tendency to spontaneously explode and charr the wallpaper. On the other hand, people are enthusiastic hoping they get a meter that just silently fails. It typically takes 2 or 3 months before the distribution company notices the meter is dead, so you get 2-3 months free power :)
It doubles as thunderstorm comfort, if you forget to unplug your computer when leaving the house, and you get a lightning strike somewhere within 3km of the 10km long aerial wire feeding your house, when weeeping over the charred remains of your computer, you can comfort yourself with that the meter probably also died, and you can enjoy free power for a few weeks :)
I would think the amount of power generated indoors is too little to even power a notification led, which means it would make no difference if you keep it screen up or screen down on a desk. Unless your desk is outdoors, that is.
Also makes me wonder why you'd point the screen at the sun, will just make the screen contents invisible and fingerprints+scratches very visible..
The idea of ISPs charging us for various value added services was tried before, and the walled garden systems thankfully died with MSN and Compuserve.
In general though, a working micropayments system would be nice. Paypal and CCs don't work well for micropayments. Cellphone operators tried to do it, and we ended up with a million random companies accepting a grunt or a "no" on the phone, or a "please stop sending me this crap!" in an sms as signing a contract to pay them 10p per day for nothing.
Today most ISPs are too incompetent to send out correct bills for the simple fixed monthly fees they charge, or then they mess i up intentionally, so they can motivate hiring more people to answer phones, people who click a button to "fix the bill" quickly, to dilute the number of real unresolved issues people call to complain about, and thus their statistics look nicer.
I'm told bitcoins aren't that useful for microtransactions either..
It's somewhat amusing that it's 2013 and still no successful microtransaction system. Is it because there's no demand, difficult to do, or a chicken and the egg problem?
I didnn't attempt to read the paper, the quoted bits were enough to put me off.
Speaking of bits, I do remember some sysadmin stating a couple of years ago, that rebuilding a degraded raid5 error is essentially poinless, and the best course of action is to restore from your backup onto a fresh array.
The argument was, that if you look at the expected bit error rates of a harddrive, and compare it to the size of your array, you'll discover you're statistically likely to encounter atleast one flipped bit during raid rebuild, and end up with corrupted data, in one file, somewhere.
As I'm a mere caveman studying the entrails of a wooly mammoth, I must admit I'm just speculating when I propose the theory, as told to me by the mammoth's internals, that perhaps these researchers are presenting error correction codes, and placement strategies for these codes, that would push the probability of single bit errors up into the realm of "wont happen" for another decade or so?
Current comercially available technology is roughly on the order of a D sized lithium-ion battery being able to start a petrol car engine. That's not capacity or energy though, it's power. The Energy in a Li-ion like that is about the same as in the much smaller (by dimensions and weight) battery in your phone.
As for 3D electrodes, Edison invented a similar thing for the Edison battery. If I've understood (and remembered) correctly, he made thin sheets of material, which he then shredded coated onto thin sheets, which were shredded and coated onto sheets, repeated until he arrived at a sheet with a total surface area several orders of magnitude larger than the dimensions as measured by a ruler :)
Now everyone will be blaming memory effect for everything
... "I installed 50 background apps, but only 49 of them use gps and 3g, and I'm not sure about the 50th, what's a bitcoin miner do? Anyway, now my battery doesn't last anymore??? Can't be the apps, must be memory effect!!"
... "I left my phone empty in a drawer for a month after I droppped phone in beer, and now battery life sucks. I opened up the phone and attached the battery to a car battery charger for a week, but that didn't help, so I borrowed a medical defibrillator and gave the battery repeated shocks, but memory effect is just getting worse and worse, halp!"
In all seriousness though, if you take someone very familiar with typical Li-Ion batteries such as LiCoO2 and similar, which we have in phones and computers, and tell them LiFePo4 is "just like" LiCoO2 but explosion-proof and lower voltage. it takes just one charge cycle for them to discover that LiFePo4 behaves nothing like traditional LiCoO2. When I first got a LiFePo4 batterypack I immediately noticed that charge behaviour was quite different. I couldn't find much litterature on the subject, except vague nonsense about "forming charge", and a somewhat competent looking research paper that used xray microscopy to compare slowcharged batteries to fastcharged batteries (where fast was on the order of 10 minutes), the findings being that fast charge caused less wear and tear.
Anyway, the point being that there's only one laptop ever (OLPC), and no phones at all, that have used a LiFePo4 battery. Considering how different LiFePo4 is from what's actually used in laptops and phones, this memory effect is entirely irrelevant for the normal user, even if the discovered effect wa s bigger than 1/1000th..
1/1000th is ldudicrously small anyways, considering battery meters in phones andsuch often are off by 20 percent or more... That also means it's nearly impossible for regular users to draw any meaningful conclusions from how they charge and use their devices, as there's no accurate measurement of drain and charge level, and the zero-point often jumps around from cycle to cycle.. Zero-point being the charge level at which the phone considers itself empty..
How do you implement these kinds of rules? You need to get them far enough upstream so that your links don't get saturated, but the further up you go the more reluctant the admins become of doing any filtering.
As for spamhaus itself using dns this or that, it's wholly irrelevant to whether they'd be vulnerable to this attack or not. They'd be just as vulnerable to this attack if they had 0 computers, 0 servers and 0 services on offer on their line.. their line would still get saturated by the traffic.
It's odd how nobody complains about increased cancer levels near coal fired powerplants, when they emit more radiation than nuclear powerplants. :)
The difference, I guess, is that everybody knows radiation is produced in large amounts in nuclear powerplants (and contained within), whereas fewer people are aware of the continous emission of low level radiation from coal powerplants. :)
Individual voltage monitors per cell is an absolute must!! Without that capability, the cells WILL drift apart over time, and one cell will get overdischarged or overcharged.
NiMH, NiCd and Pb batteries tolerate overcharge (within reason), so those packs ae always slightly overcharged, to ensure that the individual cells stay balanced. LiIon has zero tolerance for both overcharge and overdischarge. When charging, individual cells must all be monitored, if a cell reaches max voltage beforr others, the battery management system must tell the charger to slow down, and also start draining power away from that cell.
Without this, the batterypack is a ticking timebomb.
DRAM cache is what the OS does. Throw in the preload utility, and the kernel will get hints to use idle I/O time to preread in disk contents. I wish it could go further than just reading in executables and libraries though, if it senses you've got ludicrous amounts of ram.
As for execute-in-place (XIP), due to the block nature of nand flash, xip only works on NOR flash, which is horribly expensive and doesn't exist in anything with a faster cpu than your fancy wristwatch.
I imagine a "live usb key"-on-ssd approach might work. Squashfs image of the OS, initrd script to preload all of that into ram at startup, in one sequential chunk and not in random order. Optional "persistence" mode, where saved files, changed settings, etc get added to a ext4/btrfs/f2fs partition.. The latter will of course slow you back to traditional ssd level of runtime performance..
I'm more annoyed with applications today than operating systems. On your regular sd card or usb flash, the amount of I/O that, for example, clicking back in firefox causes is about 2 seconds of I/O busy... Why? Because databases. Everything is a database these days, and databases go to great lengths to ensure that data is on disk NOW, RIGHTAWAY, and that data is written so that no corruption or loss occurs if power is lost or drive yanked in the middle of that write. This is the perfect recipie to defeat every I/O reducing, optimizing and make-go-faster algorithms that operating systems have.
Some people might care if a website cookie was lost, or that the visited/not-visited status of a link is comitted to disk within 1ms of you clicking the link.. Personally I'm not that fussy. Sometimes when running from usb live keys, I just copy and symlink the dot-mozilla directory to tmpfs (ramdisk) before starting firefox, and copy it back once I exit firefox. That means I avoid sqlite's disk-abusing tendencies, but with the risk that the entire browser session's history, cookies and saved forms/passwords data is lost to the state it was in before starting firefox.
I have a feeling there should be some middle ground between the default extreme, and my hacked together extreme.
People tell me windows has largely started to ignore requests made by apps wanting to commit data to disk immediately.. I guess they must have a new api for things that /really/ do want/need it.. Soon enough every app catches on to the new way of doing things, and we're back at slow I/O, and have to ignore requests through the new API, and create a new new API for things that really really want it. Sigh.
Standby times are pretty good as is, power consumption is on the order of 5mA in standby, including 3g standby. This gives you a standby battery life of over a week.. Improving that to 2 weeks or 4 weeks with same battery sounds fantastic, but...
The issue is that the amount of time our devices spend in standby is very low. There's stuff constantly updating in the background for no good reason, and the controls available to the user is poor.. Every widget and app seems to think they're special, that they can ignore being a good citizen because the user installed it they must have the right and obligation to constantly update their UI, data and what not, even if user hasn't used or looked at it all day..
Even if standby power use could be reduced to 0, we'd still not get more than the day or two of battery life..
I agree, mostly because I find it hard to believe a japanese company like GS Yuasa would make substandard battery cells.
Li-Ion at too low voltage or too high voltage will start producing metallic lithium (highly volatile), or starts dissolving the copper current collectors into the electrolyte. This dissolved copper then becomes metallic again when battery voltage is restored to safe levels, and the copper might have formed thin strands acting as shunts. Current across those can locally heat up the cell sufficiently to set off thermal runaway (iirc the required temperature is slightly above 100C). Think of it as chemically "growing" an ignition wire into the insides...
When having multiple cells, each cell must be individually monitored to stay within prescribed voltage limits. In order to not get the entire pack limited by the lowest voltage cell and highest voltage cell, you need some sort of system that either adds more charge to the lowest cell, or removes power from the highest cell. Removing from the highest cell is the most common practice. Then you need to design this balancing system so that it fails in a safe way. Many electrical vehicle hobbyists have been bitten by this, their electronics have failed and a single battery cell has been drained totally dead. Trying to either charge or discharge that pack will then most likely cause a fire.
The charging system needs feedback from this balancing system, so that the charging system doesn't charge faster than the balancing system can remove charge from the highest cell(s). Without that feedback, there'll be atleast one cell that gets overvolted for a brief period of time. The damage accumulates (you can't just say "oops, but it didnt blow up this time, so it's ok")
Same applies to discharge portion, must cease discharging when the lowest cell reaches lowest permissible voltage. Using the pack voltage for this purpose will lead to problems.
I've seen a surprising amount of highly skilled electrical and electronics engineers that have absolutely no clue about batteries, they would blow up a Li-Ion pack quite quickly with the battery management they'd design. Alot of EEs seem to treat batteries as some sort of black boxes that work as electronic fuel tanks and manage themselves. I guess it makes sense, they're electronics people not chemistry people.. Wouldn't surprise me if the problem can be traced back to the battery management system...
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