Mostly Free Engineering Software, Part 2

In Part 1, we covered CAD, simulation, and instrument control. Let's continue with:

EM simulation

• The light version of the well known Sonnet EM software still looks pretty capable, whether you're working with PCB transmission lines, filters, vias, or many other structures.
• EM3DS is another impressive looking EM package. It appears to be even more 3D-oriented than Sonnet.
• The Mayo Clinic is not a name I'd associate with EM tools, but live and learn.

Man, I've gotta start playing with some of this cool software!

By the way, if you just need some quick geometry for a controlled impedance trace, there are plenty of online calculators. Search for something like "microstrip calculator," and you'll get a bunch of good hits right away. Remember though to always work with your board shop if you need accurate trace impedance. They have their own tools to optimize accuracy and yield. And get them to add an impedance test coupon so there are no doubts they got it right.

Math
Although I haven't used it as frequently as I'd like, I'm a longtime fan of Mathcad. Think of Mathcad as a word processor, backed with a powerful math and symbolic engine. It provides a great way to document as you're designing. I remember using this program on my PC-XT under MSDOS! For better or worse, it has largely maintained the same look and feel in its latest Windows incarnation, but with vastly increased power, and unfortunately, price. This latter fact sent me looking for more economical alternatives.

• The closest free alternative I've found is CompPad, which is not a standalone program, but an Open Office plugin. I've used it a bit, and while Mathcad's breadth and depth may not be here, it's good enough for many applications.
• With Xcas, we enter the realm of computer algebra systems (CAS), which include the commercial Maple and Mathematica products. Xcas bills itself as the "Swiss knife for mathematics." It looks quite powerful.
• The name Sage connotes something old and massive to me, and this eponymous program appears to deliver. I think you could do some serious mathematical damage with this package.
• Maxima is another CAS with old roots, and wxMaxima gives it a more modern face. If I understand correctly though, the entire package is contained within Sage. So, take your pick.
• Axiom is another CAS that looks better suited to mathematicians than engineers. Take a look if you dare.
• I know a lot of engineers use MATLAB however, especially those working with DSP. I also know this program is very expensive, and it's very difficult just figuring out which options you need! Fortunately, there are alternatives. Scilab is the one I've heard most about.
• Isn't it great having choices? Octave is another free MATLAB workalike. I'm afraid I've used neither. I haven't even used MATLAB, so I'd love to read some comments about how you've used any of them in conjunction with scopes and EE in general.

Many OS X users probably aren't even aware of the powerful Grapher program sitting in their applications directory. Want to push your processor's cooling system? Open a few 3D examples, and set them all spinning.

Office and more
I'll mention OpenOffice here because it's a great alternative to that other office suite, and also because you'll need it to use CompPad, mentioned above. And of course, the spreadsheet app is often used for data analysis. OS X users also have the NeoOffice variant available.

I'm happy to say that faxes, like databooks, seem headed for extinction. But if you must fax, at least you can do it virtually. And free, if you don't need many:

• FaxZero
• GotFreeFax
• BestFreeFax

I'm glad to see that many of the programs discussed in this article are multiplatform, helped along by the existence of generic GUI toolkits, I assume. And to the developers out there who plan to stick with Windows, please at least make sure that the software you write runs under Wine (the Windows API replacement for Linux and OS X). Surely that's not too hard. But better yet, make it multiplatform from the get-go.

Many programs here have active user communities -- a mailing list or Yahoo group perhaps. LTC's Spice group is particularly well known. So don't forget to check these resources when picking up a new piece of software.

I hope this survey will get you interested enough to try some of the programs discussed, and comment about them here.