Wikipedia:Reference desk/Archives/Computing/2014 August 18

= August 18 =

Priming/initial charging a lithium-ion battery?
Is it even necessary? Some claim that I should give them an initial charge for like six hours to even a day, while others don't. In the case of a just-purchased tablet with a Lithium iron phosphate cell, do I really need to initialise it? Blake Gripling (talk) 01:21, 18 August 2014 (UTC)
 * I've never heard of this and I've been using LiPo batteries with remote controlled helicopters and airplanes for years. Did your device come with instructions? That's usually covered in the manual. As far as I know, Lithium batteries do not suffer from memory effect, but that might not be the only reason to charge a battery for that long. Also, lithium batteries are very sensitive to OVER voltage, so any device that's designed to charge them should STOP charging them when they hit full charge, so I can't see how leaving it plugged in for 6 or 24 hours would make any difference. But, like I said, I'd read what it says in the manual and stick to that. Vespine (talk) 03:35, 18 August 2014 (UTC)
 * It did come with some documentation, but there's nothing in the manual that suggests leaving the device charged for hours to prep a battery for first use. Also, during the time when I bought a Lenovo smartphone, the only advice the saleslady told me (at another store) was not to drain the battery at too low a voltage to curb any damage. Blake Gripling (talk) 04:47, 18 August 2014 (UTC)
 * As Vespine has said, you cannot prime a lithium ion battery by charging it for six hours or a day. Unless there is something seriously wrong with charger, it will completely stop charging once the battery reaches capacity. There is no trickle charging or anything like that for lithium ion batteries, if you keeping trying, there's a good chance you could cause sufficient damage to your batteries to cause the infamous "venting with flames".
 * The good news is that unless you're charging a raw 18650 with a dumb charger or something, it's fairly unlikely you will ever do so. However there is still a good reason not to leave your device plugged in. Because people generally expect their devices to be at fully charge, many will try to keep the battery at full charge when plugged in which has a negative effect on the capacity of the battery over time.
 * There is sometimes a suggestion you should let your battery charge fully without using it first. AFAIK, the only reason to actually do so for a lithium ion battery is that it may help the device more accurately understand charge state faster. In other words, failing to do so doesn't affect the battery negatively, it just means your device may not be very accurate at reporting battery capacity for longer. (Of course many of these warnings are simply an ancient legacy of nickel based rechargable batteries.)
 * Nil Einne (talk) 14:13, 21 August 2014 (UTC)

Bitmap Header Field - Importance?
A while back I made my own image enhancement software (just to tinker with), I was going over it and decided to change the header it uses to the standard windows one (it's just for tinkering, so it assumes a certain structure). At any rate, what actually uses the biXPelsPerMeter and biYPelsPerMeter fields? As in, if I left them 0, would the image display differently anywhere? I understand what the values mean, but I can't find anything indicating if they need be correct - and I know that not all bmp headers have them. Just curious. Thank you:-)Phoenixia1177 (talk) 06:30, 18 August 2014 (UTC)


 * My own, rather limited experience, with generating bitmap (BMP or otherwise) headers from scratch is that physical specifications (DPI, DPM, PPI, etc.) are ignored for all but a few print-ready formats (TIFF, PS, EPS, PDF) and even than any actual print job being done, a designer or operator will still check (print-preview, essentially) what's to be printed before starting a job, to avoid nasty surprises - caused by mad suggested-size values in vector media (like SVG) or page size variances in page-aware formats (A4/letter/legal). Back when BMP had some currency as an interchange format, pretty much "what Windows does" was the nearest you'd get to compliance with its rather hazy specification (given that's it's just an old OS/2 "barf your internals into a file" type format). A corollary of your question is surely "if you don't know the physical dimensions of your bitmap, what values should bi[XY]PelsPerMeter have?". If you can, it's surely better to be silent (to not have the entry at all) than to lie. If you have to lie, it's better to lie with a sensible-ish guess than a definitely wrong value like 0 or NaN or -1 - because if some code somewhere does honour it, it'll surely do something like width_in_metres = width_in_pixels/biXPelsPerMeter - and your 0 value will either make the decode fail silently or with an error. Better, surely, to have a default that shows the image (at a wrong but recognisable size) than have the image not appear at all. These days I'd only add "what does libbmp do" and "what does libmagick do" to "what does windows do".  Personally, if I were writing my own graphics software now and I wasn't going to use standard formats like JPEG or PNG, I'd probably use Netpbm format (with any of my own info in comments) as a path-of-least-makework. If I needed fancier features like alpha, gamma, compression, or progressive rendering I'd probably use libpng (with my custom data in PNG custom chunks). -- Finlay McWalterᚠTalk 12:21, 18 August 2014 (UTC)


 * I'm a strong advocate of following standards in every possible respect, regardless of whether you know why they are written that way. I've never worked with that particular file format, but you can find documentation for the header structure at http://www.herdsoft.com/ti/davincie/davp3xo2.htm, where it states: "biXPelsPerMeter 	DWORD 	Specifies the horizontal resolution of the target device in pixels per metre. Applications often use this value to select the resource bitmap that best matches the characteristics of the current device.".  In other words, you should specify the device resolution that makes your bitmap look best -- neither too large nor too small. Looie496 (talk) 13:11, 18 August 2014 (UTC)

Preventing Spam
Apparently that advice about ignoring internet trolls and cyber-bullies doesn't always work, since mine is now threatening to send a flood of spam against my twitter account, emails and most likely anywhere else he can find. I am wondering if anyone can recommend some way of blocking him from doing this, pre-emptively protecting myself in case he comes through with his threats?

Thank you

82.132.212.22 (talk) 12:04, 18 August 2014 (UTC)


 * As previously advised...ignore trolls. They crave attention - they delight in causing you grief.  So, don't react.  Don't acknowledge that there is a problem. "Dont Feed the Trolls" is excellent advice. SteveBaker (talk) 02:28, 19 August 2014 (UTC)


 * yes, random trolls feed on attention, but this concrete case seems much more like stalking by someone the OP knows in real life. Maybe this is a case to be reported to the police, if it gets to far.OsmanRF34 (talk) 16:04, 19 August 2014 (UTC)


 * I'd say it's time to change your accounts. Only give the new names to people you trust not to pass them along. StuRat (talk) 16:41, 19 August 2014 (UTC)


 * ISTM that the term "Troll" has changed or extended in popular meaning since the advice of "Do not feed the Trolls" was formulated. Back then it was applied merely to those who tried to provoke arguments – preferably between others rather than with themselves – by subtly provocative comments, and of course derived from the angling term "trolling" (often for "newbies"). For such provocateurs, the advice frequently worked.
 * Latterly the term seems to have been misunderstood as deriving from to the ugly mythological monsters, and is misapplied particularly by the mainstream media to people directing often crude or obscene attacks or continued harassments against other individuals. This sort of behavior is significantly different and the advice will often not work.
 * This has resulted in people who are suffering the latter type of attacks being additionally seriously distressed by the inapplicability of the advice, not realizing that it refers to a different sort of troll.
 * It might be desirable to establish consensus for a different term for the latter behavior – "Cyber-bully" is one possible example – and convince the media to use it appropriately. How this could be achieved, however, is beyond me.
 * Apologies for side-tracking rather than addressing the OP's problem {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 13:51, 20 August 2014 (UTC)

Label printers
I'm in need of printing a bunch of shipping labels for my wife's business (http://renm.us) - and it's clear that using our inkjet printer isn't a good option because you have to print an entire sheet of labels at one time.

I see that there are a bunch of devices by different manufacturers that take a roll of stickers - so (presumably) I can print to them one at a time.

My question is how those devices interface to the PC. Are they (in effect) just tiny inkjet printers as far as the operating system is concerned...or do I have to use some horrible (probably!) software that comes with the printer itself?

We use an SQL customer database, with custom web interface software - and I'd like to use our standard query software with a "PRINT ADDRESS LABEL" button. I can write the code to do that if the interface to the label printer isn't something exotic.

Does anyone have any experience with these machines? (Also, if you can recommend a good one, that would be nice).

TIA SteveBaker (talk) 20:06, 18 August 2014 (UTC)
 * Brother, Seiko and Dymo make affordable thermal label printers but they use special software. Zebra makes higher end printers with a higher price that you can create a print file in ZPL language. --  Gadget850talk 01:30, 19 August 2014 (UTC)


 * Are there significant problems with the thermal-printed labels fading in strong sunlight and 100 degree Texas days? They won't experience any of those things when they're in our control - but we ship packages around the world. SteveBaker (talk) 02:32, 19 August 2014 (UTC)


 * For the lengths of time that your packages would see those temps, I don't think you should have an issue. Dismas |(talk) 06:05, 19 August 2014 (UTC)


 * There are basically two types of thermal printing: direct and indirect. Direct thermal uses a print head to essentially burn the label in a controlled way to print. Cash register receipts are often printed this way. They tend to have low operating costs because there's no ribbon or ink, but they do tend to be thermally sensitive. I would definitely request samples and/or specs if you're thinking of going that way. Indirect thermal printing uses a wax/resin ribbon that gets burned onto the label by the print head. They tend to have higher operating costs (but the amount of ribbon you'd need would be negligible) and, IIRC, are somewhat pricier off the shelf as well. In my experience, they do not fade with heat, but you may experience cracking if you print to poly labels (the plastic expands in the heat and cracks the printing). I don't think that would happen if you printed to paper labels. I use a Datamax indirect thermal printer which has done yeoman's work for many years. The software is ridiculously priced, but it can marry up with standard DBF files and so forth. Matt Deres (talk) 17:15, 19 August 2014 (UTC)
 * I have never seen the term "indirect thermal" used— this is thermal transfer (TT) as opposed to direct thermal (DT). If you need durable labels, then you need thermal transfer with coated paper, vinyl or poly labels and a resin ribbon. The more popular label applications are Neat Label, LabelView and BarTender. --  Gadget850talk 22:39, 19 August 2014 (UTC)