Linear equation solver

Discussion in 'General Electronics Chat' started by tindel, Mar 24, 2014.

  1. tindel

    Thread Starter Well-Known Member

    Sep 16, 2012
    Does anyone know of a free software that has a linear equation solver?

    I use mathcad at work and it has a great linear equation solver that can solve a linear equation with variables... Unfortunately, I don't have the means to purchase mathcad for my home use. My ti89 will do it also but it's a bit cumbersome and I keep it at work too.

    Any ideas?
  2. bertus


    Apr 5, 2008
  3. Little Ghostman


    Jan 1, 2014
  4. Papabravo


    Feb 24, 2006
    MATLAB clone Scilab is free and will solve systems of linear equations.
    R the statistical package is free and will find linear equationss to fit arbitrary data.
  5. #12


    Nov 30, 2010
  6. russ_hensel

    Distinguished Member

    Jan 11, 2009
    Checkout SageMath, you can use a free server or install. Just Google it.
  7. tindel

    Thread Starter Well-Known Member

    Sep 16, 2012
    Thanks for the tips...

    I guess you get what you pay for in this scenario. What I'm trying to do is solve for nominal resistor values in a comparator circuit... I can do it by hand - no problem, but it's error prone. After solving for the resistor values then I want to determine the worst case of my comparator, given offset voltages and stuff like that.

    This is super easy in Mathcad because in a solve block you can put in all of your input equations and it spits out the equations for R1, R2, and Rf without having to solve by hand (which is error prone - at least for me).

    Any other suggestions. The real problem is that there is a 1Million different configurations for a comparator and I get tired of solving the equations for all of the resistors each time.

    Actually, I was able to get pretty close to what I wanted by entering the following into the website pretty quickly... Took me a few minutes to figure out what the hell was going on at that website though, and then the lightbulb turned on.

    1.235=2.5*(R23/(R1+R23)), 1.235=2*(R23/(R1+R23))+0.7*(R12/(R3+R12)), R12=R1*R2/(R1+R2), R23=R2*R3/(R2+R3), R1=100000

    as you can see - this would be pretty time consuming to solve by hand... not impossible, but time consuming.
    [end edit]
    Last edited: Mar 26, 2014
  8. gootee

    Senior Member

    Apr 24, 2007
    If you go to and get the book, "Essential Mathcad", by Brent Maxfield, it comes with a license key for the full Mathcad software, which you can download, including several application add-ons. It's less than $50.
  9. tindel

    Thread Starter Well-Known Member

    Sep 16, 2012
    Oooo... good tip gootee! I'll have to save my pennies! I wonder if you can get the license if you buy the book used... hrmmm.
  10. gootee

    Senior Member

    Apr 24, 2007
    I would buy a new/unused copy. You probably would only be able to use the license from a used copy if the included license key had not ever been used by a previous owner.

    But 40-something dollars for a Mathcad license is a fantastic bargain.

    Also: I remember reading that the license was a full, non-expiring, latest version. But someone else mentioned that it looked like it might be set to expire in one year. I can't tell, because my computer died and I haven't yet attempted to install it on my new computer. But mine would be more than one year old, now.

    I thought that the book was out of print. But I was told that they had new copies on Amazon, again, recently. So you should verify, in the Amazon information, that the version you buy does include a Mathcad license. I haven't looked, lately.