Wikipedia:Reference desk/Archives/Computing/2015 August 31

= August 31 =

KiCAD
I am considering switching from DipTrace to KiCAD, based mostly on the good things I keep hearing about what CERN is doing with KiCad. I plan on using it on Slackare Linux 14.1 and Windows 7. Some of the customers I consult for are windows-only so I am going to try Windows first.

My problem is that the only choices I seem to have are a 2013 "Old Stable" version that is not recommended for new designs and a recent build that keeps changing every day or so So which version should I download?

Related: --Guy Macon (talk) 07:05, 31 August 2015 (UTC)


 * WP:OR - Isn't conventional wisdom to only use trunk/developer builds if you don't mind taking considerable risk? I don't even use trunk builds for my video games, and I'd be loathe to use them for services I was being paid to provide to a client. I don't have any experience with KiCAD, but I wouldn't risk a client relationship by using an old stable version not recommended for new work, and certainly wouldn't risk using trunk builds for paid work. Either could result in essentially lost work, money, and value. Your relative degree of risk aversion may vary :) SemanticMantis (talk) 14:05, 31 August 2015 (UTC)


 * That is indeed the conventional wisdom, and for good reason. Of course the fact that I am using Windows 7 (in addition to my favorite, Slackware) means that I accept constant upgrades/bugfixes cycle in my OS. :( My degree of risk aversion is very high when it comes to tools that I use to design boards for paying customers. My problem in this case is that the developers say that the stable version that is not recommended for new designs. And it doesn't have all the improvements from CERN, which is my reason to consider switching. --Guy Macon (talk) 14:56, 31 August 2015 (UTC)
 * Looking around a bit further, it seems that *all* OS have an "old stable, not recommended for new projects" version, and then "nightly builds, for testing" - e.g. also not recommended for new commercial ventures. So, regardless of what OS you use, it seems the software is currently in a bit of limbo, and the official party line is to basically not use it for new commercial ventures until a stable version is released. Unless you get lucky and get a response here from someone very familiar with the development cycle, it might be better to check in on the IRC/ community fora listed at the KiCAD website. One potential compromise- abandon the nightly builds and the old stable. See if you can find through the CERN docs some specific version they have used (and preferably published with) that does have the new features, and might benefit from having a small number of known bugs, rather than an unknown number of unknown bugs. SemanticMantis (talk) 15:10, 31 August 2015 (UTC)
 * That's a good idea. Thanks! --Guy Macon (talk) 17:11, 31 August 2015 (UTC)
 * Presumably, you wish to manufacture the items you design using your CAD tool... you should talk to your contract manufacturer's sales representative to see which tools, software, and file formats they can ingest. The software might be stable, but incompatible with your downstream processes and teams.  Nimur (talk) 15:43, 31 August 2015 (UTC)
 * Not a problem with any modern PC board layout tool. They all generate standard Gerber files to send to the board house and if it turns out that there is some sort of incompatibility, I am able to edit gerber files directly. Of course I have to follow the board house's design rules (how close together can they have traces, do they support blind tented vias -- that sort of thing) but that is all old hat to me. --Guy Macon (talk) 17:09, 31 August 2015 (UTC)


 * Y'know, our Via (electronics) article doesn't have anything about either tenting or plugging, or about vias with active (plated) caps. I'd add something myself, but my PCB knowledge is a decade out of date. -- Finlay McWalterᚠTalk 17:19, 31 August 2015 (UTC)

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This is just to attract your attention. Please, answer there. Thank you.--Lüboslóv Yęzýkin (talk) 14:09, 31 August 2015 (UTC)

#! /usr/bin/env python not picking the last version of python
When I run scripts with the


 * 1) ! /usr/bin/env python

shebang, it does not run with the last version of python.

I checked it with,

import sys print(sys.version)

and yes, it's the 2.x version, not the installed 3.x version, that's being picked.

What's wrong? I though the env python bit would guarantee that the last version of python was used.--YX-1000A (talk) 20:27, 31 August 2015 (UTC)


 * "python" probably will be /usr/bin/python, which is almost always a symbolic link. On most Debian and derivative systems it seems that it points to the current python2 binary. You'll probably also have /usr/bin/python2 and /usr/bin/python3, which point to the relevant binaries. It's a decision that the people who packaged python for your OS made. -- Finlay McWalterᚠTalk 20:41, 31 August 2015 (UTC)


 * I run Ubuntu, so, this makes sense. --YX-1000A (talk) 20:50, 31 August 2015 (UTC)


 * While you could, in theory, manually change /usr/bin/python to point to python3, you'll surely find lots of scripts have been written with the assumption that "python" is python2, and will break when that isn't the case. When writing your own scripts it may be a good idea to say /usr/bin/env python2 and /usr/bin/env python3 explicitly, so they're somewhat protected for cases when the default value of that symlink is (or, in some future OS release, will become) different. -- Finlay McWalterᚠTalk 20:59, 31 August 2015 (UTC)


 * Not only is it convention to have the "python" command point to a Python 2.X installation, it's part of the official Python recommendations. See PEP 394: "for the time being, all distributions should ensure that python refers to the same target as python2" (Though it explicitly notes this may change in the future.) -- 160.129.138.186 (talk) 17:33, 2 September 2015 (UTC)

How do I connect laptops with female ports to vintage speakers?
I have two Fisher STV 420M (12" woofers, 3" tweeters, and 4" midrange 100 watt 8 ohm) speakers that take a bare copper pair connection from 1987 that I would like to connect to my two Windows 7 laptops (2009 and 2013) which have a single female output. What would tell me how to go about this as cheaply as possible?  Thanks. μηδείς (talk) 20:39, 31 August 2015 (UTC)


 * The line out ports on your laptops have very different impedance levels (see Line level) and delivers a very low level of power (less than 1 Watt). You will need to buy an external amplifier which will drive the speakers, and you'd connect those line out ports to it (probably with a 3.5mm-stereo <-> RCA Y-connector). -- Finlay McWalterᚠTalk 20:49, 31 August 2015 (UTC)


 * You really need an amplifier to drive those speakers, using the Phone_connector_(audio) headphone output if there is no lime green "line out" from your laptops as inputs (1v line input would be OK despite the slight mis-match in impedance) and connecting the amplifier speaker outputs to your screw terminals. You will get some sound if you connect directly without an amplifier, but I wouldn't recommend this because most laptop outputs are not designed to drive large low-impedance speakers.    D b f i r s   21:01, 31 August 2015 (UTC)


 * My bad. I should have made it clear I have a heavy duty SONY amplifier with plenty of RCA ports.  *I can make three storeys of a building bounce rather a lot with my CD input, as well as from the FM antenna.)  The issue is not the lack of an amplifier, but how do I connect a single output from a 2009-2013 computer to an amplifier expecting red and white input?  Is it just a matter of buying the right adapter?  Thanks. μηδείς (talk) 02:35, 1 September 2015 (UTC)


 * Yes, I recommend one of the following as being very high quality: --Guy Macon (talk) 02:56, 1 September 2015 (UTC)


 * When you plug the RCA connectors in, make sure not to plug into the amplifier's RCA_connector socket (if it's old enough to have one). You'll probably have a port on the amp labelled AUX and you'll probably have one or more that are intended for devices (tape, DAT) that you no longer have - use one of those. -- Finlay McWalterᚠTalk 08:56, 1 September 2015 (UTC)
 * For analog output, things haven't really changed that much for a long time. I was doing similar things with my 1995 computers. The only difference was that computers then may have had both a speaker output and a lineout output with different impendences. The real chance was the expansion of digital options, Since sometime 2000-2005, computers started to support SPDIF out as standard (normal coax as optical SPDIF never really gained that much traction with computers) which would be commonly be supports by amplifiers of that generation. Even that probably hasn't really changed much, Intel HD Audio has meant even on laptops you can probably still use a 3.5mm port for SPDIF output with the right drivers. I think most amps will probably still have at least one such input as well. (There was probably a time in the early days were you'd often get amps with only optical.) Since sometime 2008-2010 or so, computers started to have HDMI with audio out, which amplifiers of that generation would usually support. Again this hasn't changed much. However I don't think HDMI is really designed for audio only output, so using it in that fashion can be problematic. Nil Einne (talk) 11:41, 1 September 2015 (UTC)


 * Very interesting, thanks, guys. My amp does indeed have a phono input.  I had assumed all the inputs were the same, but I do have an aux input as well. μηδείς (talk) 22:58, 1 September 2015 (UTC)