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$Path hijacked by PacletManager? I'm trying to wire up 6 RGB LEDs in parallel, all controlled from a single source (well, three sources, one for each colour). The LEDs came supplied with resistors to limit the current of 270 Ohm for a 5v supply.  The problem is, 6 LEDs x 3 colours = 18 resistors, which is a lot, and means I need a much bigger board and a lot more soldering.  So, can I instead wire the LEDs in parallel with each other, with a single resistor protecting all six? (3 resistors in total, one for each colour). How do I calculate the value of that resistor?  More details:  The LEDs are being driven from a  to supply a bit of current, which is in turn controlled by a Netduino providing a PWM signal on the three channels.  . If I've correctly understood the data sheet they want 20mA of current, and forward voltages of 2, 3, 3 volts (for R,G and B respectively?). The supplied resistors were all 270 Ohm, so the channels may not be balanced quite right.  For extra credit: I'm only using 3 of the transistors in my driver chip, which has 8 in total. could I wire the PWM from the netduino to a second trio of transistors, and split the LEDs into two groups of three? Is it worth the effort?  PS I don't have any diagramming tools to hand, but I can provide a diagram (drawn in paint) if it would help clarify my question. (see also ) It is being surprisingly hard to achieve. I've tried so far:   Download file manager apps from Google Play. Unfortunately, "share" shares the files, not the file names. None of them had a option like copy file names Download backup apps. Unfortunately, none of them backup the file names of a folder.   Any idea to copy to the clipboard or share the file names of all the files of a folder? Number of triangles formed by $m$ lines Problem:    How many triangles do $m$ lines form if   a) Every two lines intersect and no three lines intersect at one point.  b) There are $n$ lines among $m$ lines that are parallel to each other. No other line is parallel to these $n$ lines, and no other two lines are parallel to each other. Again no three lines intersect at one point.  Thank you. Configure up-arrow to browse through commands with same initial characters rather than all previous commands On the bash command-line, ↑ gives me the previous command. On the command-lines in ipython or matlab, when I type a few characters, ↑ gives me the previously entered command starting with those characters. How can I enable exactly this behaviour in bash? I am aware of more advanced ways of searching through the command-line history, but sometimes a simple way is more convenient. I have an ASUS N550JK laptop (BIOS version 204) running Ubuntu 14.04 (3.13.0-43-generic kernel).  My issue is that the battery indicator ALWAYS shows that it's using battery power - even when plugged in and fully charged. So even though I have selected to show the battery status in the menu bar only when charging or in use (in power settings), it is ALWAYS displayed. When it reaches a full charge, the indicator icon will either show just the percentage (usually 99% or 100%), or sometimes a very big number for time (like 22:14) along with the percentage. If I go to the power settings menu, it always says "Using battery power", with something like 40 hours remaining. This is all while plugged in and fully charged.  Are there any fixes less drastic than trying to update BIOS, or is a BIOS update necessary to fix this? The latest BIOS version is 208 according to the ASUS website, but the (very brief) descriptions of the updates don't mention anything about battery issues. If at all possible I'd like to avoid updating BIOS because of the risk involved.  I've already tried letting the battery drain all the way and then charging to full, with no luck.  Thanks in advance! bash if -a vs -e option Both about -a and -e options in  is said:  -a file     True if file exists. -e file     True if file exists.    Trying to get what the difference is I ran the following script:  resin_dir=/Test/Resin_wheleph/Results  if [ -e ${resin_dir} ] ; then     echo "-e "; fi  if [ ! -e ${resin_dir} ] ; then     echo "! -e"; fi  if [ -a ${resin_dir} ] ; then     echo "-a"; fi  if [ ! -a ${resin_dir} ] ; then     echo "! -a"; fi   /Test/Resin_wheleph/Results exists and is a directory. And this is what I get:  -e -a ! -a   which seems to be a little strange (notice -a and  ! -a). But when I use double brackets (e. g. if [[ -e ${resin_dir} ]]) in the similar script it gives reasonable output:  -e -a   So:    What is a difference between -a and -e options? Why -a produces a strange result when used inside single brackets? Disallow downvoting other answers if I've posted my own Possible Duplicates:        As Dan Dyer mentioned in his comment on , there is a conflict of interest when you have posted your own answer and are allowed to downvote other answers.  Despite the vote editing window being drastically reduced, the fundamental problem remains: I can downvote the other answers permanently and still benefit - my answer gets upvoted ONCE and wham, I have just made up the rep loss for my 10 other downvotes. The vote editing window fixes part of the problem, but there is a more complete fix that has the extra benefit of not preventing legitimate vote changes: to disallow downvotes on competing answers when you have posted one yourself.  The temptation to wrongfully downvote competing answers is huge. The rep loss is tiny in comparison. It has to be in order for people to continue to legitimately downvote.  Details:   If I have previously voted and then post my own answers, delete my downvotes. Continue to allow me to remove the upvotes - I think this is fully legitimate. If I delete my answer it's probably best to continue to deny downvotes (perhaps even including the question), but I don't have a strong opinion either way. Where should I go to ask a question about guns? Which is faster/best? SELECT * or SELECT column1, colum2, column3, etc Weighted choice short and simple Prefer composition over inheritance? What is the proof that the total number of subsets of a set is $2^n$? Whenever I create a document in Microsoft Word, it complains about a lot of my sentences being in passive voice. But, when I read that sentence aloud, it sounds fine to me. I am not sure if it is just me and will a statement in passive voice sound strange to a native speaker?  So, my question is, is it considered bad form to use passive voice generally? Or in some specific cases like written communications only?  Edit: If it is ok to use passive voice, then why does MS-Word complain? How to add a dot after the section number? I wonder is there any way to change the format of section numbering from 1.1 to 1.1. ? I know this is trivial, but I really need to add one more dot after the section number. Does anybody know how to do that?  Thanks a lot Why directory with large amounts of entries does not shrink in size after entries are removed? Can "what kind" be plural? Is it correct to say, "What kind of patents are being issued in these sophisticated times?" It seems like it should be What kind of patents is being issued..., but that sounds wrong.  What kind of patent is being issued... is correct and sounds right, but loses a little bit of the original meaning.  Is there something magic about what kind that allows it to be plural, or do people just misuse it a lot? I am using find -type f command to recursively find all files from a certain starting directory. However, I would like to have some directories prevented from entering and extracting names of files inside. So basically I am looking for something like:  find . -type f ! -name "avoid_this_directory_please"   Is there a functioning alternative to this? Is there a symmetry associated to the conservation of information? Conservation of information seems to be a deep physical principle. For instance, Unitarity is a key concept in Quantum Mechanics and Quantum Field Theory.  We may wonder if there is an underlying symmetry, in some space, which may explain this conservation of information. SQL command based on PHP strstr or LIKE