Wikipedia:Reference desk/Archives/Computing/2017 April 28

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April 28

How do I get Gmail to stop using captchas ?

It used to just let me log in with my username and password, and remembered both on my home PC, but now they started adding captchas randomly, without even asking if I wanted them, which I find intensely annoying. How do I turn them off ? StuRat (talk) 04:38, 28 April 2017 (UTC)

I assume you're not doing anything that would cause google to think you're using a brand new computer each time. (Cookie cleaners, incognito mode, overly-aggressive browser privacy plugins, etc.)

It's possible that Google's mysterious hacking detection systems have decided your account is under attack or at risk. Do you have an email app running on a phone or PC that is constantly checking your email with an out of date password? That's a common cause of this.

Allegedly some causes of this problem can be cleared by going to https://accounts.google.com/b/0/DisplayUnlockCaptcha

ApLundell (talk) 14:34, 28 April 2017 (UTC)

Not doing any of that, no. Maybe it's the IP range they don't trust. I'll check out that site, thanks. StuRat (talk) 14:39, 28 April 2017 (UTC)

Uh, I suppose we should at least pay lip service to the idea that it might not be a false alarm, and that Google really might have good reason to keep checking your humanity. If there's a risk that someone really is trying to dictionary-attack your gmail account, switching your account over to two-factor security would be a good idea.

I believe that would stop them from offering captcha checks, but of course two-factor can be just as irritating as captchas. ApLundell (talk) 14:58, 28 April 2017 (UTC)

(edit conflict) It might have decided your IP range was suspicious or something. If you stay on the same address for a while it might settle down. For all sorts of reasons I prefer Fastmail to Gmail, though it isn't free (but there's no ads, it doesn't spy on you, etc). That would be another way to fix it. 173.228.123.121 (talk) 14:35, 28 April 2017 (UTC)

• Regardless of whether you're actively being hacked or not, ApLundell's suggestion is a very good one. Two-factor authentication is really something you should enable whenever possible. ᛗᛁᛟᛚᚾᛁᚱPants Tell me all about it. 18:00, 28 April 2017 (UTC)

I should point out that the login panel has changed, so this new security feature may just come with the new login screen. StuRat (talk) 19:30, 28 April 2017 (UTC)

Is somebody brute-force attacking the account? --Hans Haase (有问题吗) 23:37, 28 April 2017 (UTC)

I have no reason to think so. StuRat (talk) 00:47, 29 April 2017 (UTC)

test a page interacting with cam on Chrome

I have to test a page interacting with cam on Chrome. So I'm trying to launch Chrome with option '--user-data-dir=/test/only/profile/dir', yet I get the error 'Chrome cannot read and write to its data directory', although I set custom permissions to AppData Chrome folders.. Could you please help me?

Cheers --12:09, 28 April 2017 (UTC)~~ — Preceding unsigned comment added by Luga lambrusco (talk • contribs)

Cron expressions

What do these two cron expressions mean?

Start time:

0 0/1 * 1/1 * ? *

Stop time:

0 0 2 ? * * *

Thanks, †dismas†|^(talk) 14:37, 28 April 2017 (UTC)

As far as I know, cron expressions have only 5 fields (minute, hour, day of month, month, day of week), so those examples are ill-formed.

According to man 5 crontab on the NETBSD UNIX system I have access to, "?" means "a single value randomly selected when the crontab file is read". For example, if it's in the hour field for an action to be performed daily, that action might be performed at 03:00 every day and then change to 23:00 when the system is rebooted or the crontab file is changed. And / means "every nth". For example, in the hour field */2 means hours 0,2,4,...,22 of the day, or 0-10/2 means 0,2,4,6,8,10. So as far as I can see it makes no sense to write /1 or to use / with a single number on the left.

--76.71.6.254 (talk) 21:37, 28 April 2017 (UTC)

The cron replacement nncron extends the cron syntax to allow a sixth field, to specify the year. [1] I'm not aware of any cron replacement that uses seven fields but there might be one. "?" is not standard cron syntax, but nncron uses it to mean "the time that the daemon started". I'm also unsure what the OP means by "start time" and "stop time". Each cron specification specifies the time that a command is to be started. There's no such concept as a "stop time" in standard cron (what would it do, kill the process if it's still running at that time?) CodeTalker (talk) 21:50, 28 April 2017 (UTC)

They are start and stop times for a subscription. Thanks for the responses! †dismas†|^(talk) 20:25, 1 May 2017 (UTC)

iphone 5S with no battery

I can get an iphone 5S cheap that has a bad battery. Rather than replacing the battery I'm thinking of removing it completely, and using an external power pack like a Mophie. Does anyone know if the 5S works ok with no internal battery? Yes I know it's easy to replace, but I don't like the iphone feature that it's impossible to know that it's completely powered off. Unplugging the external battery would fix that. Thanks. (Also: how long does it take to cold boot a 5S from powerup? Same question for Ipod Touch 6th gen I guess). 173.228.123.121 (talk) 14:38, 28 April 2017 (UTC)

This is a pretty bad idea and will absolutely void your warranty. It might "work" - the phone might turn on - but you probably can't even begin to imagine the vast number of ways this will change the device's behavior. It might also turn your phone into a devastating fire-hazard!

Apple's official information page says: "Don’t attempt to replace the iPhone battery yourself—you may damage the battery, which could cause overheating, fire, and injury. The lithium-ion battery in your iPhone should be serviced or recycled by Apple or an authorized service provider...", and points you to the Battery Service webpage.

Do you enjoy unpredictable software and hardware behaviors? Do you enjoy debugging them without access to documentation? Do you think you know enough about lithium batteries to prevent lithium fires? I'm sure you've carefully reviewed the chemical cell safety data sheet, the power controller ASIC documentation, and the software design specification for the battery controller, because you magically got access to all of these documents and could afford the time and engineering-talent to review them? You're very sure that what you're about to do is safe and will not cause over-current or short-circuits or any other electrical or chemical hazard? Because that's a risk that Apple specifically points out when it warns you not to try to replace or modify the battery yourself.

Nimur (talk) 20:09, 28 April 2017 (UTC)

This advice is questionable. Whatever crap Apple may say, unless you screw up when you remove or dispose of the battery and it catches fire, there would have to be something incredibly wrong the iPhone for it to catch fire just because the battery is removed. Software design specification for the battery controller etc are red herring since the OP specifically said they aren't planning to replace the battery. They're simply going to use it without a battery but without an external power plug. The iPhone may not be designed to be used without a battery (as I said below, it most likely simply won't work) but it should be sufficiently designed such that it won't catch fire when someone does try to use it without a battery unless Apple designers are complete idiots. And hopefully you Nimur can attest that they're not. The battery pack the OP is using, if it's a decent one, will have it's own built in safety, such that even if the iPhone does try to do something stupid like draw 10A, it will prevent this and definitely prevent the lithium ion battery inside the battery pack from catching fire. If it doesn't then it's a piece of junk and having access to a wealth of Apple technical document doesn't help. (In other words, protecting the battery in the power pack is largely the responsibility of the power pack designers, not Apple.)

Now removing a non removable lithium ion battery isn't without risks, and yes you could cause a fire if you majorly screw up. Definitely you should have knowledge of the risks involved, and how to deal with them before trying it. But you do not need, and we can be fairly sure not even all Apple certified repairers know all that info about the software controller etc. It's not germane to what they're doing, which is solely to open the iPhone and remove the battery. Even if they have access to the documentation, it's largely a moot point. If you accidentally poke a hole in the battery, you need to know what to do right now, not read up on crap about the software controller. (Of course you should be sufficiently competent that this never happens.) Disposing of the battery safely is another minor concern, hopefully your jurisdiction has some sort of hazardous waste scheme to deal with. But anyway, even if you do something incredibly stupid like throw the battery out with the regular trash, maybe you'll cause a fire in the rubbish truck or dump (in reality probably not), but it's not going to affect your iPhone and battery pack. Well unless the fire spreads to your house or something.

Definitely the people who install the battery in the China in the first place do not know any of that stuff, although it's obviously a lot harder to safely remove a battery than it is to safely install it in the factory. A middle ground would be those who are helping in the recycling of the iPhone. Apple doesn't have the capability (nor I'm thinking the policy even in a number of places where they official sell the iPhone) to be the ones collecting all iPhones for recycling. [2] This means it's down to other ewaste experts to deal with. And we can be fairly sure these people do not have, and it would be ridiculous to expect them to have, all that info before they remove the iPhone battery. They just need the technical expertise on how to safely remove the battery (including what to do if something goes wrong), and what to do with it after.

Nil Einne (talk) 02:15, 29 April 2017 (UTC)

USB chargers just limit the output voltage an the output current. This are not power supplies, they are still chargers. If a computer or similar logic device needs more power in a peak, the voltage drops and causes a brownout of the CPUs. A battery filters the peak. If there's no battery, the device still might not startup. Wen playing with old mobile phones for scrap, carefully have an experienced person remove the battery, even when lithium batteries are blown up of got thick, be careful, it is already damaged! Opening or hurting the lithium battery might cause immediate fire and explosion.[3] --Hans Haase (有问题吗) 23:35, 28 April 2017 (UTC)

It's unlikely this will work. Pretty much all Android phones I've ever owned with removable batteries do not work without the battery. There is no reason an iPhone which does not even have a removable battery is likely to be any different. And it's not impossible the peak power draw of the phone is actually higher than that supplied by the charger even if it's a 2.4A one. Unlike some of many laptops, phones simply aren't generally designed to be used without the battery. Nil Einne (talk) 01:40, 29 April 2017 (UTC)

Thanks all. Nil's info seems particularly relevant, that Android phones don't work without batteries. I'd never tried it with any kind of phone so didn't know. So yeah, I'd expect the iphone to be the same way and therefore my scheme is unlikely to work and I guess I won't pursue it. Absent that approach, if I have to get an iphone at all, it will probably be an SE.

Regarding replacing the iphone 5s battery: 1) I'm not worried about the warranty since the phone is presumably out of warranty; 2) I didn't want to replace the battery, but rather, to remove it completely and operate the phone on external power without it; 3) I'm not too worried about replacing the battery either, it's not brain surgery. Yeah there's that Apple info page, but there was also a tag on my mattress that said "do not remove this tag under penalty of law". I cut it off while no one was looking and the police never came after me, so now I take those sorts of warnings with a grain of salt. 173.228.123.121 (talk) 03:37, 29 April 2017 (UTC)

It might help to replace the battery with a large capacitor. --Hans Haase (有问题吗) 12:31, 29 April 2017 (UTC)

... but that might be a problem if the voltage floats significantly above what the circuitry is designed for. This might not happen if the charger is well-regulated. Check it's maximum voltage. Dbfirs 17:01, 29 April 2017 (UTC)

Yes, per Dbfirs I'd expect the charger to expect a load that behaves like a lipo cell and that could get confused by a capacitor. But my current thought is to use an external lipo cell connected to the internal battery terminals (drill hole in back of phone to run wires through), instead of a Mophy-like power pack that connects to the phone's charge port with that special Apple connector. Actually I might be able to get an iphone 3GS for free (vs a 5S for cheap) for this purpose, so I just have to find out if it can run the app that I need (it's something they want me to use at work). Thanks again. 173.228.123.121 (talk) 01:52, 30 April 2017 (UTC)

Connecting a different cell not designed for use with the iPhone and which the iPhone isn't designed to use is something that probably isn't going to work, and may very well get into Nimur's advice territory. Note in particular it isn't uncommon that mobile phone batteries have 4 pins. Other than the positive and negative, one may be for a thermistor and one for some sort of dataport. See e.g. [4]. At least some iPhones indeed use batteries with 4 connectors, and one is a thermistor, the other for HDQ a TI data protocol [5] [6] [7]. There's a very good chance the phone will refuse to work if it doesn't receive or doesn't understand or does understand but the values are not as expected from either of these connections. If you do want to do this, it would IMO make a lot more sense to look for a reliable supplier of iPhone batteries. A third party battery from a reliable supplier actually designed for the phone is likely to be a lot safer than using some other cell not designed for the iPhone and vice versa. Even if your cell is a high quality original from LG or someone reputable. At the very least, you'd need to investigate maximum charging and discharging current, and end voltage for both, and also maximum discharge state. Nil Einne (talk) 09:45, 1 May 2017 (UTC)

Headphone jack vs USB

The headphone socket on my Toshiba laptop is going. I have to hold the jack in place or I lose some of the audio. Will a headset connected to a USB port give me the equivalent audio quality? I assume buying one of those will be cheaper than getting the socket repaired or replaced. Rojomoke (talk) 22:27, 28 April 2017 (UTC)

Short answer: Yup.

Long answer: You can actually drastically increase your audio quality with an external sound card (and keep your favorite headphones). I recently picked up this one for one of my home computers. I do not recommend getting a gaming headset, as the audio quality is utter crap, even with the expensive ones. However, if you're not on the same level of snobbish audiophile/geekiness that I'm at, you may not notice a difference. ᛗᛁᛟᛚᚾᛁᚱPants Tell me all about it. 22:41, 28 April 2017 (UTC)

Are you sure it's the socket that's going bad and not the jack on the headphone cord? In my experience the latter is more likely to fail, due to a broken/frayed wire or similar failure. You can check by testing with a different set of headphones. If you have expensive headphones and the jack is bad, you can replace it for about US$5. CodeTalker (talk) 22:47, 28 April 2017 (UTC)

Maybe the phone connector (audio) jack needs just to be cleaned or resoldered.[8] Some were assembled in Surface-mount technology in portable devices,[9] but not on desktop mainboards. Some basic knowledge of metallurgy and electronic might be useful. While computer audio jacks close an switch on the back end when a connector is plugged, analog hifi jacks open the line(s) trough and disable the internal microphones(s) or speaker(s). Audio adapters for USB are USB sound cards. Sound cards have an analog and a digital part. For the analog circuit, separate power input pins are on the device. A better filtered operating voltage should be avail for this. Today, the costs of such separate voltage regulators are the differences in cheap and decent sound cards. It still might be possible to achieve something acceptable due USB devices are 5 volts tolerant 3.3 volts devices. Just a low-pass filter for each part of the audio device causes the first huge reduction of noise. An constant voltage delivered from a linear voltage regulator is even better, but not achievable without an boost converter inside an USB device an the boost converter is sill a source of noise. On mainboards the AC'97 an its successor, the Intel High Definition Audio codec devices are still analog/digital converter devices. The bus interface and other logical circuit has been moved into the chipset. --Hans Haase (有问题吗) 23:10, 28 April 2017 (UTC)

I use a Musical Fidelity V90-HPA and it is very flexible - I use it for more than I intended. It is a D/A converter, has a USB input and RCA inputs and outputs. It has a switch to switch between inputs. I have the USB going to the computer, of course. I also have a stereo system next to my desk and I have the RCA inputs and outputs going to it. With this arrangement, I can play either the computer or the stereo through the headphones or play the computer sound through the stereo. And it sounds a lot better than plugging headphones into the computer. Bubba73 ^{You talkin' to me?} 02:41, 29 April 2017 (UTC)