Cheap, Cross-Platform Electronic Circuit Simulation Software?

dv82 writes "I teach circuits and electronics at the undergraduate level, and have been using the free student demo version of OrCad for schematic capture and simulation because (a) it comes with the textbook and (b) it's powerful enough for the job. Unfortunately OrCad runs only under Windows, and students increasingly are switching to Mac (and some Linux netbooks). Wine and its variants will not run OrCad, and I don't wish to require students to purchase Windows and run with a VM. The only production-quality cross-platform CAD tool I have found so far is McCad, but its demo version is so limited in total allowed nets that it can't even run a basic opamp circuit with a realistic 741 opamp model. gEDA is friendly to everything BUT Windows, and is nowhere near as refined as OrCad. I would like students to be able to run the software on their laptops without a network connection, which eliminates more options. Any suggestions?"

Comments

Is a live DVD OK?

[Anonymous Coward]

If booting off a live DVD is OK then you may want to look at https://fedoraproject.org/wiki/ElectronicLab_Spin .

Re:Is a live DVD OK?

[Anonymous Coward]

You sir, are an idiot, or at least the company you work for is.

The last thing you should care about is what brand of software someone
used to learn engineering. This is tantamount to a building contractor
only hiring framers who use "Stanley model 13 hammers".

You should be trying to determine if a candidate actually knows how to
design and solve problems; not worry about what tools they used.

Of course I realize this is how industry operates. The depths of human
stupidity never cease to amaze and amuse, and sadden too, sigh.

CAD

[Klivian]

For simulation, you can get Spice versions for all platforms.

For the CAD part, there is the EAGLE Light Edition from CadSoft http://www.cadsoftusa.com/freeware.htm It runs on Linux, Windows and Mac.

Re:CAD

[Grishnakh]

I use KiCAD and it works quite well for designing PCBs, though it has some rough edges.

However, the discussion is about circuit simulation in college, which has nothing to do with PCB design. KiCAD doesn't currently integrate with Spice unfortunately, though that would be really nice. I don't actually know of any open-source stuff that does Spice well. The SPICE engines themselves are open-source (such as ng-spice), but they have no front-end at all, so you have to do everything at the command line, which is really rather clunky when you want to, say, look at graphs of simulation results.

When I want to simulate a simple circuit (not often), I start up a Windows computer and run an old version of Pspice (9.something) which is freely downloadable. The state of circuit simulation on Linux is very, very bad right now.

Partner with IT dept and get it hosted via RDP

[attemptedgoalie]

We had finance apps that students had to use in their coursework. Trying to get them to work on a Win/Linux/Mac system would have been painful and time consuming.

So we created a terminal server environment that let anybody RDP in to use the course apps. That way nobody had to pay for a real version, we paid for the terminal license.

That might work well for you rather than finding an app to support in 3 environments.

Good luck!

Re:simple solution

[notreez]

The law is never plain and simple.

Eagle is no simulator

[Anonymous Coward]

Electronics CAD != Circuit Simulation.

Re:Netbooks?

[JesseL]

Whether running Linux or Windows - aren't you going to run into some serious horsepower issues if you try to accommodate students who own netbooks?

I don't see why. Most student level electronics simulation just shouldn't be all that CPU intensive. When I was an EE student 10 years ago, people did just fine with 150MHz machines running SPICE.

LTSpice and SolveElec

[Vario]

LTSpice is free as in beer and works nicely even with more complicated problems. There is only a windows version available, but Linux support with wine should not be a problem. http://www.linear.com/designtools/software/

For simple circuits SolveElec runs on windows and mac, has a very nice user interface and is a good tool for teaching. http://www.physicsbox.com/indexsolveelec2en.html

Not a fan of (P/NG/LT/Berkeley)SPICE

[TerranFury]

I've had to use a handful of circuit simulators, and I've always found SPICE brittle. Perfectly reasonable circuits just refuse to simulate, even when good initial conditions are set. Now it's possible I've been doing something wrong. But on the whole I find SPICE deeply frustrating.

The most robust simulator I've used so far has been a demo version of SiMetrix. HSPICE also does a bang-up job... when it doesn't segfault. Unfortunately, HSPICE is very un-free (and buggy-as-hell), and although SiMetrix does have a demo, it's artificially limited in the size of circuits it can simulate.

Thoughts?

Re:Not a fan of (P/NG/LT/Berkeley)SPICE

[Andrew Sterian]

It's quite likely you've been doing something wrong :-) I was at the same place, getting frustrated because perfectly reasonable circuits refuse to simulate. 99.9% of the time it was my fault, and it was a great learning opportunity. "Reasonable circuits" are not necessarily practical circuits. For example, you can put in an ideal switch into SPICE and cause brittleness, because practical circuit voltages and currents don't change instantaneously like ideal switches do. "But wait!", you say, "Inductor voltages can change instantaneously! That's what it says in my textbook!". No, they can't :-) There's a reason SPICE lets you specify an inductor's parasitic parallel capacitance.

Also, another source of brittleness/bugginess is poor third-party circuit models. I've downloaded some MOSFET models that just plain stunk.

BTW, LTSpice is my favorite simulator, hands down.

Re:Not a fan of (P/NG/LT/Berkeley)SPICE

[bitrex]

Real men don't need no stinkin' simulators! We just write down the equivalent circuit models, use Kirchoff's current law and apply Cramer's rule! Nothing's more exciting than spending a leisurely weekend computing the determinant of a 258 element matrix in the s-plane by hand. Frequency response sometimes takes a bit longer....:)

I don't know...

[thatskinnyguy]

I don't know if it's been mentioned already or not, but Multisim from National Instruments is a very good software. It's been used by the professors at the school where I work for as long as I can remember.

Qucs !

[Ruie]

Qucs is very capable.

Re:Linux?

[bemasher]

I've used Oregano on Ubuntu with not very many problems. My original reason for trying it out was that the academic demo for OrCAD wouldn't simulate circuits large enough for my projects at school. I've found that it duplicates most of the features we used in courses on OrCAD. Oregano

Re:simple solution

[KillerBob]

He's not exactly wrong, he's just deliberately misinterpreting the law to further his own agenda.

In this case, he's deliberately ignoring the part that says that such circumvention is legitimate for classroom purposes iff it's no longer readily available to acquire through legitimate channels, or only a small exerpt is actually required. In other words, you can photocopy a page from a textbook to use as a handout as an alternative to students forking over $150 for just that one page, or you can provide photocopies of books that are no longer in print, but you cannot hand out copies of software that people are still selling.

For pro software, the OS is secondary

[fermion]

I deal with the issue as well. Here is my opinion, take it or leave it. For certain pro software, you buy the machine that runs the software, no the other way round. So, in many cases, the Mac is not an option without a VM. I use my mac to run these tools, but I use a VM. For cad work, there is simply no substitute for Solidworks or Autodesk. For circuit and control work, it is National Instruments. There is a push to get these ported to the Mac, but so far to no avail. Autodesk does not run so well under the VM, so I often run it on a dedicated machine or boot into Windows.

I would say that it these students are in an engineering or science program, they must know how to use these tools, just like someone in a science/math program must know how to use Mathematica. That said, if the course in question is just a survey course, the specific tools may be less important than the exposure. For this there may be alternatives. For instance, an only breadboard simulator is available. Google circuit simulators and there may be more available. I am not sure what is available for CAD.

Here is another issue. If the class teaches the design techniques and not the application, the maybe students can use whatever they want. What distresses me is that we are no longer teaching the high level concepts, but the mouse based menu selection. Instead of teaching the concept of cut and paste, we are teaching the menu commands. The problem is when the menu changes, the students are SOL. For career training, this is fine, but I think we should be teaching at a higher level for college. For instance, in my college, we were just told to write a program to solve the problem or create a simulation. How we did it using the available tools were up to us.

Re:Use LTSpice

[Animats]

LTSpice is quite good if you want to design power supplies with Linear Technology components. The component library has just about everything Linear makes, and not much else. So you need some additional libraries for other purposes. You'll probably have to put together a model library for your students, from various downloaded models.

I've had fun with LTSpice. As an exercise, I've been designing hardware to run a Model 15 Teletype (1930s technology) from a USB port. The usual power supply for the 60mA current loop required is a 120VDC supply through a 2K 10W resistor, to get enough punch to energize the 4H 55 ohm selector magnet of the Teletype fast enough. Most of the energy is wasted heating up the big resistor. But I've designed something that up-converts 4.5VDC to 120VDC using an IC intended for photoflash applications, charges up a capacitor when the input is low, and when the input transitions to high (MARK), dumps the energy into the magnet. The 120VDC is only needed for the first 1ms or so of each bit time, to push current through the big inductance. A 3.3V linear regulator then provides the sustain current to keep the magnet pulled in after the cap dumps. The whole thing needs 250mA at 4.5V, which can be taken from a USB port. Separately, a small CPU is needed to do the serial port stuff for the signal.