Wikipedia:Reference desk/Archives/Computing/2011 September 17

= September 17 =

Signature tracing
many Wikipedia articles contain good, clear examples of signatures that have been somehow traced out of historic documents. What method/program is used to do this? Rmhermen (talk) 03:52, 17 September 2011 (UTC)


 * You would use a image scanner, which creates a pic in a raster format and sends it to the PC, then upload that to Wikipedia. StuRat (talk) 05:32, 17 September 2011 (UTC)


 * Not sure exactly what you're looking for, but there are programs that can convert bitmaps into vector graphics. After conversion, shapes in the picture will be described geometrically by smooth outlines (rather than as a matrix of black/white pixels), and can be scaled up or down without losing quality. Here's an example of an outline tracing program. --71.185.179.84 (talk) 15:17, 17 September 2011 (UTC)

Lithium-ion battery charger
I lost the charger for the Lithium-ion battery of my Digital SLR camera. A friend of mine offered his camera's Lithium-ion battery charger. But its battery output is 7.4v and mine is 7.2v. Can I use this charge if it fits ( the slots, etc) with my battery? 14.139.128.14 (talk) 08:55, 17 September 2011 (UTC)


 * The output of a battery has very little to do with the charging voltage. What you should really be looking up is the output voltage of the charger for your camera, you'll find that 5 volts DC is usually the standard for chargers for most devices (cell phones, MP3 players, etc.) but you should double check.  If the output voltage is the same you should be fine.  HominidMachinae (talk) 21:32, 17 September 2011 (UTC)


 * If I understand this note, a charger with an output of 5 volts can charge a battery up to 7.2 (or 7.4) volts. Can this really happen?  Wanderer57 (talk) 04:15, 18 September 2011 (UTC)
 * No. If the battery is seriously discharged below 5v, then it might partially charge, but only up to 5v.  These chargers are designed for 3.6v and 4.8v batteries, and are current-limited.    D b f i r s   08:32, 21 September 2011 (UTC)
 * that's correct, when you apply reverse voltage to a battery you are reversing the chemical reaction that occurred to produce the voltage in the first place. The voltage this is done at must be over a certain amount but need not be the same as the output voltage, it can be lower, though as Best Dog Ever notes below, if it is higher than the battery's capacity you will damage the battery and indeed with a Li-ion battery could cause a fire or explosion.    — Preceding unsigned comment added by HominidMachinae (talk • contribs) 20:40, 19 September 2011 (UTC)


 * You can try, although make sure your friend's charger doesn't output a voltage higher than your old charger. You can go lower, but if it outputs more volts than your camera can handle, you will terminally damage the device. You can go higher with the amps, though.--Best Dog Ever (talk) 04:40, 19 September 2011 (UTC)


 * These replies would be shot down on the Science desk. A charger with a maximum output of 5v can charge a battery only up to 5v which is probably insufficient to run the camera.  You can try your friend's charger at your own risk, because the voltage is close (7.4 v and 7.2v batteries both have the same number of internal cells), but Li-on batteries normally require a variable charging voltage specially designed for that particular battery.  It is the charging current, not voltage, that is critical.  I have partially charged a Li-on battery using a 12v car battery, but it would be very dangerous to make a direct connection.  I monitored the current carefully, and controlled it using a variable resistance, trying to match the recommended charging currents.  Li-on batteries can explode if wrongly charged.  You have been warned!    D b f i r s   00:07, 21 September 2011 (UTC)

Win7 Behaving Oddly
I got a new Win7 laptop a few weeks back, and I have noticed that it is using my computer name for some products, rather than the name that I specify when I register the product. A notable example is MS Word - it says all my documents were created by [computer name] rather than by [my name]. Is there something I should be doing? It's happening with a lot of applications, so it's not a problem with MS Word. -- KägeTorä - (影虎) (TALK) 13:20, 17 September 2011 (UTC)
 * Um.. there's a pretty obscure system setting that influences this, which used to be sorta possible to get to in 2000/XP, but it appears to have been disappeared in later Windows versions to 'make life easier'. Start->Run, regedit, navigate to 'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion' in the tree and change the 'RegisteredOwner' value. Nevard (talk) 00:43, 18 September 2011 (UTC)

Protecting BIOS flash against modification
Let's say you want to make sure that the BIOS of your computer is not modified without user intervention. How can you tell if your motherboard has a jumper or switch for enabling/disabling BIOS reflash? If you don't care about warranty and are willing to risk bricking the motherboard, is it easy to modify a typical motherboard to add a switch that must be set before the BIOS can be reflashed? — Preceding unsigned comment added by 96.227.49.58 (talk) 14:11, 17 September 2011 (UTC)
 * The easiest way will be to find the manual for the motherboard. If you cannot find the exact board a similar one by the same manufacturer may have the same features.  Even more tricky will be to identify the kind of chip that the BIOS is stored in and then find the data sheet for that chip, which will explain how to program it.  If you trace out the connections from the relevant pins you may be able to find a jumper.  Cutting a PCB track to prevent modification will probably void any guarantee. Don't expect there to be enough space in there to solder in a switch as 1 it may be a multilayer board with the track you want embedded inside the board, and 2 the track may be very close to others and not have enough space for a hole for a lead, or a blob of solder. Graeme Bartlett (talk) 09:56, 19 September 2011 (UTC)

HTML and Java Plug-ins
I'm using a PBworks wiki to create a mock website. When I edit, I get a window with an options bar along the top that allows me to make basic formatting changes, like alignment and text highlighting. I can also add tables and insert HTML and other plug-ins. I've added an image, but I don't like the way the text is in relation to it. As it stands, I just cut-and-paste the image and it appears in its own line. I can add text to the end of the line, but then the next line starts under the image. I would like to have the image on the top left and then have several lines of the text running down the right edge of the image. Just like you get in newspapers, or you get on Wikipedia. I've added an image to this post so you can see what I mean. I can just type and the text fits nicely at the side of the image. Does anyone have any idea how to get this effect in PBworks? Is there some HTML code I can use, or some other plug-in? — Fly by Night  ( talk )  14:49, 17 September 2011 (UTC)


 * The CSS for that is float:left
 * To get that for an image you'd say    or something like that. If you want the image to have a caption, like the wikipedia one, you'd wrap it in a DIV and put the IMG and caption text in there, and you'd float the DIV rather than the IMG. -- Finlay McWalterჷTalk 15:10, 17 September 2011 (UTC)


 * That's great, thanks! — Fly by Night  ( talk )  17:40, 17 September 2011 (UTC)

One other thing that I would like to do is have collapsible sections. So I'd have a list of section titles and if I clicked a title or an icon then the section would open, a bit like when you access Wikipedia from an iPhone or an Android phone. It has the Expand buttons next to the sections. You click it and the information appears and the Expand button changes to a Hide button. — Fly by Night  ( talk )  17:58, 17 September 2011 (UTC)


 * You'd use Javascript for that. Clicking the expand button calls a little piece of code that sets the "display" CSS property of a given section's DIV between block and none -- Finlay McWalterჷTalk 18:11, 17 September 2011 (UTC)


 * A super-simple example (built using jquery) is here. -- Finlay McWalterჷTalk 19:17, 17 September 2011 (UTC)


 * I have no idea how to do that. Could you supply some code, or link to some? — Fly by Night  ( talk )  19:52, 17 September 2011 (UTC)


 * "view source" for the page I linked to above. -- Finlay McWalterჷTalk 19:53, 17 September 2011 (UTC)

Magnet in floppy disk drive


As seen in the accompanying picture, the spinning hub, which is folded back at the right, has a magnetic tip that mates with the metallic part of the floppy disk. The magnet is strong enough to hold onto and move the disk, so it's not incredibly weak. The body of the disk passes right over this magnetic tip as it's being inserted and removed. The shutter cover is not metallic with this particular disk, so it would not provide any magnetic shielding. How does the passing of this magnet so close to the disk not mess it up? Peter Michner (talk) 15:55, 17 September 2011 (UTC)


 * The strength of a magnetic field drops off exponentially with distance. The magnets you are referring to do not have to be strong because they are making physical contact with the disk case. The read/write head is almost making contact with the disk itself. The disk isn't designed to completely fail in the presence of a magnetic field. Electricity flow causes magnetic fields and, after all, a floppy drive is an electronic device. Care is taken to ensure that the magnetic field that is near the disk itself is not strong enough to alter the data. -- k a i n a w &trade; 18:00, 17 September 2011 (UTC)


 * Are you sure that you mean "&hellip;drops off exponentially&hellip;"&thinsp;? In gravitation, electrostatics and electromagnetism (or more generally most forces that propagate in three dimensional space) the inverse square law plays a staring role. — Fly by Night  ( talk )  20:11, 17 September 2011 (UTC)
 * If something is reduced by a squared quantity it is indeed exponential, because the numbers will follow a multiplicative curve (IE 64, 32, 16...) HominidMachinae (talk) 21:35, 17 September 2011 (UTC)
 * No a power law is not the same as an exponential decay. For example, there is no exponential function, $$y = A\,e^{-b\,x}$$ that is equivalent to $$y = {1 \over x^2}$$, e.g. (1, 1), (2, 1/4), (3, 1/9), (4, 1/16), (5, 1/25).  Dragons flight (talk) 22:10, 17 September 2011 (UTC)


 * Because there are no known magnetic monopoles, static magnetic fields will always fall off by at least the inverse cube power of distance once you are far from the magnetic source. Some magnets, such as many fridge magnets, often contain alternating magnetic domains with the intent that the field should decay even faster than the cube law.  Of course if you are right next to the magnet, then the shape and intensity of the field will depend of the details of the spatial configuration of the magnetic sources.  Dragons flight (talk) 22:20, 17 September 2011 (UTC)


 * That's very interesting. Is there any geometrical justification for this? I can see why the ISL holds because the force is "spread out" over the surface of a sphere and as the radius of the sphere increases, the surface area increases as a function of the square of the radius. I'm a mathematician and work in differential geometry so a geometrical explanation would be great, although I realise that one might not exist! — Fly by Night  ( talk )  22:31, 17 September 2011 (UTC)


 * For electric charges we imagine lines of forces flying out as straight lines in all directions, e.g. File:Inverse square law.svg. At greater distances, the same lines are spaced more sparsely over the surface of the surface.  That explains the inverse square law.  However, as far as we know there are no comparable sources of magnetic field lines, i.e. magnetic monopoles.  Instead the fundamental field configuration in magnetism is not a straight line, but rather a closed loop resulting from a dipole field.  All known magnetic fields can be described as a combination as dipoles.  As one increases in distance from a dipole, two things happen.  First, the area per field line increases in the same way as one would expect by considering the inverse square law.  However, there is an important second effect.  Since each field loop has a limited extent, the number of field loops present also decreases with distance.  Qualitatively, these two effects combine to give an inverse cube law.  Dragons flight (talk) 05:29, 18 September 2011 (UTC)

Free 3D CAD program
I am looking for a free 3D CAD program. It doesn't have to be to advanced. I just want to put my smartphone designs down on "paper". --Melab±1 &#9742; 21:21, 17 September 2011 (UTC)


 * You could try SketchUp - I've not tried it myself, but it looks capable of being used for basic CAD work. Most proper CAD software (as opposed to simple 3D modelling software) seems to be proprietary, and expensive (see Comparison of 3D computer graphics software) AndyTheGrump (talk) 21:32, 17 September 2011 (UTC)


 * Try DAZ 3D. This is free (mostly). Or Blender (software) -- <font face="Freestyle Script" color="blue">KägeTorä - (影虎) (TALK) 22:24, 17 September 2011 (UTC)


 * I've used Blender; it has a considerable learning curve (its interface is highly unintuitive if you haven't used these kinds of programs before). I've also tried SketchUp — honestly, I preferred Blender. SketchUp is more immediately intuitive, but I found it very hard to do the kind of careful creation that I was accustomed to in Blender, once I had learned how to use Blender. But they're both free, so give them a shot. I preferred Blender, but it took working through a "how to make things" tutorial until I felt comfortable enough with it to really do very much. --Mr.98 (talk) 22:49, 17 September 2011 (UTC)
 * Wings 3D may be a good choice. It's not as powerful as Blender, but it's easier to get used to, and in my opinion, it's slightly better for precision work (which is a big plus for CAD work). -- Link <sup style="font-size: x-small;">(t&bull;c&bull;m) 11:11, 18 September 2011 (UTC)


 * If all you want is to draw a design, you can use Inkscape, Gimp, or another computer drawing program. Technically, Blender falls into this category: it's a surface modeler, not a CSG CAD program.  If all you want is to draw a 3D shape, Blender is probably a suitable choice.
 * If you want to use CAD for modeling and manufacturing design, you need to use a CAD tool that exports in a standard CAD file format (e.g., a .dwg file) - like OrCAD or SolidWorks, (which are not free). BRL-CAD and FreeCAD are comparable and free; but in my opinion, they are just not as ... good ... as SolidWorks, which really does set the standard.
 * Remember - CAD is not just "drawing with snap-to-grid." It's putting geometry into a format that a computer program can use and understand - for thermal and mechanical simulations; manufacturing analysis, stress simulations, ... these are not "user-friendly" tasks, and they require advanced knowledge of computer programming and engineering concepts.  Do not expect a "fun and easy" user-interface to a CAD program: it is not just a fancy paint-program.  Have a look, for example, at BRL-CAD documentation: particularly the industry overview, which shows the "intended use-cases"; and the Principles of Effective Modeling.  You will quickly see that CAD is much more complicated than just drawing pictures.  Nimur (talk) 19:29, 19 September 2011 (UTC)
 * All I am doing is just making designs for the case/shell. --Melab±1 &#9742; 02:24, 20 September 2011 (UTC)


 * Then Blender is recommended. Don't expect to be making CGI quality stuff on the first day, though. :) Be patient and stick with tutorials first. And while Blender does have a quite difficult interface, you have the advantage of being totally new to 3d modeling. It's substantially more difficult to adapt to its interface if you're used to other programs (even if you know all the concepts of 3d modeling already).


 * Blender also supports the universally accepted format in 3d graphics for exporting/importing to other modeling programs, in case you need to switch for a render or some other reason - .obj. So if you want you can actually do the modeling elsewhere, like in Wings 3D, export it as .obj and import it into Blender for tweaking and rendering. Most professional 3d artists I know use at least two 3d programs - one they're comfortable with, and the rest for necessity with certain workflows not possible in their 'home' program. In addition to being proficient with a host of other programs as well, of course, including Photoshop/GIMP.


 * Sketchup is very basic and I don't actually consider it a 3d modeling software. I would have liked to recommend a commercial software but they're all heinously expensive. Autodesk also seemed to have stopped giving away noncommercial student versions of 3dsMax and Maya. Meh.


 * Anyway some tips: save often, have a lot of backup files. It can save your ass. Like CAD, 3d modeling for graphics isn't exactly as easy as it looks either. It's all about workflows and learning 'tools' that can all be applied in different ways to get the same results. A certain bit of planning ahead is usually required, especially if you're modeling from an actual concept and not just winging it. --  Obsidi ♠ n   Soul   14:33, 22 September 2011 (UTC)

Trying to play or convert .ogg files?
First, sorry Im new the the english language, I'm playing Dungeons a PC game and I go into program files and find the music tracks for the game but theyre .ogg files. Perhaps anyone would know how to play these files? Or convert them? Thanks much CHRISTIANgamer97 (talk) 22:45, 17 September 2011 (UTC)
 * Your files are in Ogg Vorbis, an open source music format. See Vorbis for some of the software that supports it. --Stephan Schulz (talk) 23:03, 17 September 2011 (UTC)
 * The VLC Media Player from http://www.videolan.org/vlc/ will do it. It's free to download. HiLo48 (talk) 23:10, 17 September 2011 (UTC)
 * You should be able to convert them by opening them up with Audacity and saving them as MP3 files. TheGrimme (talk) 19:07, 19 September 2011 (UTC)

No need to convert if you can play them, something any decent playback software can manage. ¦ Reisio (talk) 20:20, 20 September 2011 (UTC)