FxSolver is a Math Notebook for Engineers

If you like to rely on the web to do your electronics and computer math, you’ll want to bookmark FxSolver. It has a wide collection of formulae from disciplines ranging from electronics, computer science, physics, chemistry, and mechanics. There are also the classic math formulations, too.

When you first hit the page you’ll see a message that your solver is currently empty. There’s a sidebar on the left and a search box. To start, try searching for a few things you know you’ll want to use. We did Ohm’s law and a voltage divider, winding up with a custom page of calculators.

The calculators can take values as a table or in a spreadsheet-like format. You can save the worksheet and restore it later. If you provide a list of values, it can plot the results for you. For example, the graph below is what happens when you vary a resistor around 50 ohms across 25V.

The arrow on the left of a graph opens a menu where you can customize the plots. Even though the drop down for units showed mA (milliamps) and MA (megaamps), every time we tried for milliamps, it reverted to mega amps. On the plus side, you can group the calculators together and show or hide groups.

What was really interesting, though, is that you can create your own formula, if you like. We didn’t see one for the resonant frequency of an LC circuit, for example, so we cooked one up.

Once you create the formula, you can have it solve for any of the values. Another thing of interest is you can link the result of one formula to another. However, experimenting with that led to some odd results. Even after disconnecting the formulas there seemed to be something still going on.

We couldn’t see a way, though, to create a formula that would easily create a list, although maybe we just missed it. For example, it would be nice to have a formula to generate frequencies from 100 Hz to 10000 Hz in steps of 100 Hz instead of having to type out the whole list. Then you could ink that formula to another. On the plus side, in spreadsheet mode, you can copy data from a spreadsheet into the calculator.

This isn’t going to compete with Wolfram Alpha, but it is still useful. Of course, if you want to just dump your old TI calculator to the web, there’s a way to do that, too.

12 thoughts on “FxSolver is a Math Notebook for Engineers

  1. I just had a look for resonance stuff myself, and they actually do have a formula labelled as calculating the resonant frequency of an LC circuit, but it actually converts radians per second to Hz…

  2. I’d be interested in a good electronics calculator program, but there are none to be found.

    My best practice so far is to google the situation and find an online calculator specific to the situation. Even though I know the formulas, it’s usually a lot easier to type the numbers into a form. Example, this site: http://www.deephaven.co.uk/lc.html

    (I don’t even do this for Celsius to Fahrenheit conversions – much simpler to type “30 F in C” into google directly – it’ll recognize and do the calculation.)

    For formulas that chain together, such as when physically designing a resonant circuit, starting with capacitor plate distance, I use a spreadsheet. The output from one calculation feeds into the next. Easy to do experimental tweaking, such as “what happens if the capacitor plates are further apart”, see what the savings in coil windings are, and so on.

    Note: I just typed in “0.1uH coil, 13.56 mHz, find resonant capacitor” into Wolfram Alpha, and the answer was $4.74 (four dollars and seventy four cents). I would never have guessed this answer from the formulas… :-)

    1. “Note: I just typed in “0.1uH coil, 13.56 mHz, find resonant capacitor” into Wolfram Alpha, and the answer was $4.74 (four dollars and seventy four cents). I would never have guessed this answer from the formulas… :-)”

      No, it is telling you the amount you need to pay for the answer.

  3. Thanks for this review Al!

    I’m part of the development team of this tool and I wanted to add a few – hopefully helpful – comments.

    As a general note, we really appreciate that you put the effort to evaluate certain features which many users might miss entirely. Especially since nowadays, there’s not much time for most users to read through a help section – although we do have one and it’s reasonably thorough: https://www.fxsolver.com/help/

    To your main points:

    – You can always overwrite any default unit by typing over the one you want to change to, including mixing inch and metric units. The unit drop-down menu issue you encountered however seems to be a glitch with the capitalization of “m” in “mA” and we’re working to fix it soon, as part of a general “overhaul” of the units section. Typing “megaamps” or “milliamps” should work fine in this case though.
    – The stepping between 100 Hz to 10000 Hz or any other desired values for that matter, can be done by using the menu bar at the bottom of the Solver tab/page. There you can find the “Generate values” button which allows you to create arithmetic, geometric and random progressions, Fibonacci sequences, etc
    – The Linking of values between formulas is one of the features which we believe make fxSolver unique and allow the users to solve a problem from start to finish, like in this example : https://www.fxsolver.com/solve/Hx2gerluLSQqVll2PdySMw==/
    So, any issues related to the formula Links are very important for us to know in order to improve their functionality.

    1. Glad to know I didn’t just mess up the mA issue. I missed the bottom menu bar — thanks for the tip. As for the linking, I will try to reproduce and let you know. I think I remember what I was doing.

      1. Great!

        I forgot to mention that after reading your review we added the missing Resonance frequency in LC circuits:

        There will always be important formulas across all fields that we should be adding to the library.

        That’s the main reason why we implemented the formula editor in the first place, for users to create and optionally submit missing formulas to make them public.
        This editor can be also used to modify any existing formula on fxSolver by clicking the little pencil icon on the upper right corner of each formula’s box in the Solver tab/page.

        1. …and a correction: the link I posted in the first comment regarding the Linking formulas example should have been this one:

          There is no registration needed to use the full functionality of fxSolver except for when you want to share a worksheet with another user (who doesn’t need to be registered to open it or to edit it). This is only due to storage limitations otherwise we would have offered this for unregistered users as well.

    2. Thanks for answering some questions.
      One important series of numbers for any electronics engineer is the E series, derived from the Renard-Series. (E6, E12, E24, E48, E96 and E192). Usually we have to buy our components at these specific values, does the fxSolver support these series of numbers? Might be interesting to have a solver that spits out what values in parallel or series you should order to have the smallest deviation from the ideal value your previous function has spit out.

      1. That’s actually a great idea as an addition to the geometric series we currently support!
        We need some time to think about how to implement this but it is now on our to-do list.
        To make sure we understand, you’re asking for a geometric progression generator that provides the E series values and tolerances once you plug in the desired specs, perhaps from a provided data table?
        With out current functionality you have to define the start, multiplier and count value of the geometric progression and in the case of E12(multiplier:1.2115…) you get something like this:

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