Solving equations on notepad

Discussion in 'Math' started by victorhugo289, Apr 20, 2011.

  1. victorhugo289

    Thread Starter Member

    Aug 24, 2010
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    Does anybody know about a method to solve a circuit without writing anything on paper?

    -----If I have to apply Branch Current Method on a circuit with 5 unknowns I usually do it on paper: by drawing assumed current directions and assigning unknowns like I1, I2, etc, then tallying voltages around the loops. OK.

    But how do I do that without paper?

    I have issues with straining my eyes by looking up to the monitor and then to my notebook, especially because I study at night and the light of the light bulb reflects on the notebook causing me to blink constantly. Especially when I have to submit long equations to Octave, it gets really eye intensive.

    I want to keep my focus on the computer, please tell me about a method to do all of this without using paper.
    I have an idea that it could be on notepad.


    Thanks.

    Victor.
     
  2. Georacer

    Moderator

    Nov 25, 2009
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    I use scrap paper all the time and even use a pencil instead of a pen. If it's so much trouble for you, maybe you should consider buying a digital tablet. In my opinion, only freehand drawing/writing is suited for solving non-repeated mathematical problems.
     
  3. victorhugo289

    Thread Starter Member

    Aug 24, 2010
    49
    3
    Thanks Georacer.
    The tablet seems like a very good idea.
    To write netlists on Spice I've been dictating them on a Sound recorder first, yeah, and I do the same for Octave when long equations have to be solved.
    Moving my eyes off and on the screen does put a tremendous strain on my eyes.
    I figured with a little bit of imagination I could do everything on the computer, and I'm also gonna try the tablet. Definitely.
     
  4. steveb

    Senior Member

    Jul 3, 2008
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    I hate to make a recommendation for a Microsoft product, but I'll mention something I've been doing for 3 years now. As much as I hate Microsoft Word as a word-processor, I've found it makes a good tool a an engineering notebook, and problem solving worksheet. One can quickly make diagrams, equations and text, with practice. The drawing tools can be used to draw a schematic and label all components, voltage polarities and current directions. Then the equations can be entered relatively quickly, and cut and paste can be used to do derivations with the equations. The process is a little longer than using paper, but I find I make fewer mistakes doing it this way.

    Note that when I do formal writing for papers/reports etc, I prefer TeX/LaTex for text and equations and I use more sophisticated drawing tools for figures. However, for some reason Word makes a good general tool for less formal tasks.

    As a side-note, I'll mention that I almost always use paper (pure white with no lines) and pencil to sketch out the general approach I will use to solve a problem. For some reason a clean white sheet of paper gets my mind in a problem solving mood. For this reason, I'm guessing that a tablet may be useful for you to help be creative in problem solving. Still, you may want to consider using Word if you plan to do a lot of work and want to have a high quality record of the work you do. It may take you a month or two to get proficient at using the drawing and equation tools, but long term it's worth the effort. I only stumbled on this approach because my job forces me to use Word, which I used to hate with a passion.

    I'll also mention that I've been trying to find a free tool similar to Word (such as open office etc.) but I have yet to find one that I like as much as Word for integrating text, equations and drawings all in one file with one tool.
     
  5. someonesdad

    Senior Member

    Jul 7, 2009
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    I concur with steveb's recommendation; however, I use Open Office for my documentation tool. I used MS Word for 20 years because I was forced to by the work environment (although it was a pretty good tool in 1985 on the touchscreen HP150). About 9 years ago I started using Open Office and have come to prefer it. Now, that said, please don't let's have any arguments over which one is better. They are both powerful tools. I used to hate Word's method of entering equations because it was so painfully slow -- it's possible they might have improved it. I liked OO's method because it is so TeX/LaTeX-like. The other thing I like about Open Office is that I can write my macros in python. So far I've only done this for some spreadsheet stuff, but that's exactly where you typically need some good language tools -- not the horrid Basic languages that come with either MS or OO tools.

    Regardless of which tool you use, you'll find that, yes, it takes substantially more time than writing in a lab notebook. However, the beauty is that you can include drawing objects, spreadsheets, etc. (in fact, any OLE-aware tool). You can also fix your mistakes. :p For me, the ultimate kickers are a) I put it into my revision control system and b) it gets backed up.
     
  6. soundman

    New Member

    Dec 27, 2010
    13
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    One of the engineers that I work with is a big fan of MS Excel for doing certain types of calcs. There is set up time involved but it can be very handy for repetitive situations where you need to make numerous plug-ins. There's no Greek Alphabet on my version so it definitely has its limitations.
     
  7. steveb

    Senior Member

    Jul 3, 2008
    2,433
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    Excel is like a set of Lego pieces. The capabilities are limited only by the imagination of the user. Years ago I ran across someone who used Excel to solve Laplace's equation in 2D for field problems. He used each cell as a grid point and entered the boundary conditions and finite-elements equations into the appropriate cells.

    The only thing I don't like about Excel is the plotting features. The plotting tools seem to be better suited for business, rather than science/engineering.
     
  8. steveb

    Senior Member

    Jul 3, 2008
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    I think Open Office is good. I have it installed and played around with it. It's free and seems to have all the capabilities as Word. The reason I haven't switched is because I'm forced to use Word at work and although importing is possible, the translations back and forth are not good for anything but text only documents. So, I think one needs to use one or the other. If one is not concerned with compatibility and translatabiltiy, the free program should be preferred - especially since someonesdad has already successfully used the program without any issues.
     
  9. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
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    I do occasional consulting and a few days ago a customer sent me a 20+ MB Word document to review. I opened it in Open Office OK and added comments and sent it back. I don't know what version of Word they used, but I'm using Open Office 3.2.1. Basic stuff like adding comments, new text, etc. seem to work OK, but you'll soon run into problems if you want to do more sophisticated stuff. Before you castigate Open Office, remember that the folks who made Open Office work with Word documents did it by reverse engineering Word's document format. This was a significant piece of engineering work, as Microsoft helped (AFAIK) zilch.

    Word used to be horrible for crashing and ruining big engineering documents. I remember one enjoyment of a group I worked in used to be hearing the curses of one of our group's members over the partition walls as he had to work with Word. He was a highly-educated person and his curses were very creative and entertaining. He had a habit of talking to himself and was a tad eccentric -- but we all enjoyed it.

    I suspect Microsoft finally figured out how bad the tool was and probably improved it. Before I quit using Word about 8 years ago, I don't think it was trashing documents much anymore. But I did see an enormous amount of engineering time wasted over Microsoft's bugs. Truthfully, Open Office probably crashes more frequently than Word. However, I've actually only had one occasion where my work was completely lost with Open Office (and I foolishly didn't have the document checked into my version control system yet). After an Open Office crash, the program knows something went wrong and recovers the document.

    Since I've been writing word processing documents with Word or OO for 25+ years, I wondered how many documents I have on my data drive. I was a bit surprised to find the count at 3180. I have no idea what all those are for. My normal /doc directory (where I usually keep my documents) only has around 400 documents, so that makes me feel better. :p Now I'm wondering if I should go figure out what those other 2600 are...
     
  10. victorhugo289

    Thread Starter Member

    Aug 24, 2010
    49
    3
    Boy, I should have named this thread "Paper is a thing of the past".
    I'm gonna use Microsoft Word, I take a lot of notes on it already, with pictures. I want to copy circuits taken from Multisim, paste them in Word and do the circuit analysis right there, not sure how but it would be so convenient.
     
  11. victorhugo289

    Thread Starter Member

    Aug 24, 2010
    49
    3
    I won't deny, it was very awkward, but with some practice I think I can manage!

    Made in MS Word:

    ---Circuit taken from Multisim
    ---Arrows added in Mspaint
    ---Simultaneous equations set up by me.
    ---Solutions copied and pasted from Octave.

    Whew!

    I hope it gets easier!
     
  12. Georacer

    Moderator

    Nov 25, 2009
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    Multisim makes some great-looking circuits but it takes forever to build them. I wish I could find some simpler and faster circuit-making tool...
     
  13. victorhugo289

    Thread Starter Member

    Aug 24, 2010
    49
    3
    What I'm looking for right now is a good software calculator for Windows, so far I've downloaded 3 open source calculators and I have not been very happy, all of them output their result very ugly. I want to copy and paste the values in metric notation, but they are not giving me good outputs, they show a lot of decimals or they show no decimals :S
    On Linux I use "Qalculate" which is the best I have found! Too bad it doesn't work on Windows.
     
  14. Georacer

    Moderator

    Nov 25, 2009
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    I too must confess that I prefer my pocket digital multiline calculator than the Windows virtual version.
     
  15. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    For calculations that I've never done before I use just plain white paper and pencil (which I also use for any kind of notes in my daily work). And I keep an eraser handy.

    Excel comes into play when I start repeating calculations of any kind. That is useful software really!

    Planed to download Octave to start working with digital filters but I am not so sure about learning something new for the moment. No too much spare time left.
     
  16. Wendy

    Moderator

    Mar 24, 2008
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    Agreed. I also keep a scientific calculator on my computer desk.
     
  17. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    YES! I always carry one with me, even in my daily work, just in case I want to check any kind of calculation that comes to mind. Functions I use frequently, are EXP for powers of 10 and the conversions for bin, dec, hex bases.

    Operating in hex/dec allows to see the results, truncated as the micro will get them. Took me time to realize that possibility.

    The other one I use continuously is the one allowing to change exponents of a given quantity (-3, -6, -9, 3, 6 , 9 etc) back and forth. Practical as its best.

    Software calculators? Never found a good reason to use them.
     
    Last edited: Apr 26, 2011
  18. Wendy

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    Mar 24, 2008
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    I'll use a software calculator if there isn't anything else available.

    Sometimes I'm at someone elses computer desk. :D
     
  19. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Excel is an awesome engineering tool. I always have a .xls for any serious (and many trivial) projects also. A recent job had a sheet for component value justifications (things like resistor value & power calculations), a sheet for the derivation of some underlying calculations for some software (doing a piecewise linear interpolation of an exponential function) that would even generate some C code from the results ready to copy & paste into the dot c file, a sheet for breadboard data, and even a sheet for the bill of materials.

    When revising the design (damn customers!) it was simple to copy entire sheets, rename them, and thus have an ongoing history of what changes and why.

    There is a short list of complaints, mostly its inability to TRUST WHAT I TYPE and not only silently changing mA to Ma when typed in CAPS ON mode but also changing the mode to caps off. Also it's calculation of interpolation polonomials goes whack for more then 2 or 3 powers of X.

    However, MS Word is an evil work of the devil himself and should be shunned whenever possible. MS Publisher does much less then Word and thus a much better job.
     
  20. Wendy

    Moderator

    Mar 24, 2008
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