Welcome to NL5

This blog is an "informal" part of NL5 Circuit Simulator website. I'm going to explain what NL5 is, how is it different from popular (Spice-based) simulation tools, and why it worth trying.

It turned out that in Spice-dominating world many people undervalue, or simply are not aware of apparent benefits of simulation with "ideal" components. Some people strongly oppose the whole idea of "ideal" simulation, some people love it. I believe, both "real" and "ideal" simulation approaches make sense, as long as you understand what you are doing: "use right tool for right task".

Thanks.

NL5: step into a real world

What? "Ideal" simulator finally simulates "real" circuits? Not yet...

Components are still ideal. What you can do now is import real scope data, and:
- apply it to you circuit (use it as a "stimulus": voltage or current source signal);
- compare real data with simulation results of an ideal circuit;
- simply use unique NL5 tools and graphical capabilities to explore real data.

NL5: simulate circuits that do not exist

The question I've got from the visitor at ECCE-2011 Exposition: "Simulator with ideal components? Why would anybody need components that do not exist?".

The answer is simple and obvious: "To simulate circuits that do not exist".

With standard SPICE-based simulators, a result of the simulation is considered correct if it matches a known real circuit's behavior. What if real circuit does not exist yet? When you design a new principle, a new topology: how can you make sure the idea is feasible? That's what ideal components are used for.

Making everything as simple as possible, you eliminate problems caused by complex models, methods, and algorithms. Starting with ideal components gives you much more confidence that simulation results you see on the screen is true behavior of your circuit - even if the circuit does not exist.

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Is there any other Simulator with ideal components?

Recently I tested PLECS: the last non-SPICE type simulator for switching circuits I'm aware of. As I expected, it could not simulate none of my test circuits: voltage multiplier, charge pump, circuits with discontinuous inductor current.

I was surprised, since they do have true "ideal" components: switches and diodes with zero/infinite impedance. However, in almost all circuits you have to add either small resistor in series, or large resistor in parallel to those components, so that I don't understand what is the use of those components at all. You cannot, for example, instantaneously connect voltage source and capacitor charged to different voltage: it has to be done through non-zero resistor or limited current source. Same for interrupting current through the inductor. For "ideal" diodes there is special parameter "turn-on threshold", which could be different than diode forward voltage. Some circuits simply stuck in the middle of simulation: same "old good SPICE" convergence problem? This is very confusing.

Originally PLECS was designed to work with MATLAB as Simulink toolbox; stand-alone simulator is kind of a new product. This probably explains very poor interface and lack of many useful and, in fact, required features. For instance, you have to define initial conditions for all capacitors and inductors. I don't think this is acceptable for real engineering tool.

Anyway... so far, I don't know any simulator offering "ideal" component (or even close to "ideal"), and what is more important, providing reliable and fast simulation with those components. I tend to state that NL5 is the only one capable to do that. I'm not aware of any (reasonable) circuits that can not be simulated with NL5: it passed all the tests I designed, and I do not hear any complains from users. They are either happy or shy...

Dear NL5 users, please report problems you have: it would help further improving NL5 and make it more robust and useful for you and for thousands of other users! And please don't forget to download latest builds and revisions: you will definitely find something new and exiting.

NL5 - "Concept Proving" Tool

The main idea of NL and any other tool used for what I call "concept proving" is ability to

1) simulate schematic with true ideal components;
2) simulate schematic with arbitrary, even non-realistic, topology and component values;
3) have a minimal number (if any) of simulation parameters.

For instance, LTSpice gave a wrong solution for simple switching capacitors circuit, where I just tried to understand the principle, so I used ideal switches, floating capacitors with C=1F, and switching interval 1s. When I asked for explanation on one of LTSpice forums, I was literally accused of simulating "silly" circuits, "intentionally selecting difficult component values", and suggested to use "more reasonable" component values and parameters (TrTol, RelTol, etc.)

I don't think simulating silly circuits with unreasonable component values is a bad thing to do: this must be the only way to invent something really new or at least understand how things work. Of course it would be advantageous to have an easy to use and fast simulation tool as well, but this is another story...

Using circuit simulator in other disciplines

Here is an example of using NL5 for simulation in other disciplines using electrical analogy principle. If you know differential equations for the process - mechanical, heat transfer, fluid flow, whatever - and you know at least basics of electricity, it's not going to be much of a problem to find a correlation between two. Having simple ideal components, where none of parameters are hidden "under the hood" and component behaviour is clear and predicted - is absolutely required. And that's why NL5 is good for this type of analysis.