Circuit design/simulation software?

[Gopher]

I've been researching what software exists for designing and simulating electronic circuits. I'm currious, what (if any) software people use for this, or have used before.

[JesseWelling]

I'm just scratching the surface with Eagle but it's becomeing the opensource (free speech and free beer) standard for Layout and design

[Gopher]

Looks interesting; I've been researching the subject because I'm concidering writing a circuit design/simulation package (as a first step towards a larger project). Eagle, like most other packages I've seen, seems to largely be a tool for preparing formal circuit boards. Is ordering or machine-fabricating custom boards more common than I think? I tend to imagine hobbyists doing this kind of work by hand...

The tool I'm planning is much simpler, and will be designed more for quickly and easily experimenting with circuits; it won't let you refine a design to the point that it can be machine-made, but it will let you put together a simple circuit and simulate it in action; if you have sensors, you'll be able to control or script their inputs to verify that your circuit behaves as it's supposed to. I'm really more interested in what software is out there with this kind of simulation, and I haven't really found much in my searches...

[JesseWelling]

I don't really know what eagle has available....alas i am no ee.....just cs......

[Gopher]

Well, I went through their "guided tour" and didn't see anything about simulating the circuit, just some basic automated validity checks. I used to have a program for my old Apple][GS, when I was very young, which is the closest thing I've seen to what I'm envisioning. I know such simulation software must exist, but from what I've seen it seems to be mostly targeted at professional applications and massive projects, which is fine but would likely be overwhelming to many novices starting out and just plain overkill for many small robot projects.

Basically I'm wondering if there's an untapped market here (however small). My simple circuit simulator would be able to stand alone, but it's greater purpose is to support a 3d robot simulator I would develop later. Again, this would be designed to target hobbyists, people designing BEAM robots and other simple autonomous bots rather than professionals developing more complex commercial or industrial robots. Basically it'd be a way to rapidly prototype chassis ideas and allow easier testing of software by eliminating the need to reprogram the bot to test every minor change.

[Charlie1138]

That sounds like an awsome idea, Gopher. You should do it. Definitely.

[Gopher]

Thanks; I've got a way to go before I decide whether to implement any of this or not. I've got lots of grand, impractical visions of what it ultimately could be that would take me 10 years working full time to implement, but I'm forcing myself to reduce it to a minimum useful feature set; the idea of doing a stand-alone circuit testing app came out of this process. It is a subset of the core code for the final application which might be independently useful. If there's even a small market, I could make some money selling it as shareware, so I may pursue it even if I ultimately reject the 3d simulator idea. I'm working on a detailed design document now, so I can do a thorough task breakdown and estimate the total man-hours it would require. I'm also researching the existing market, which may be overcrowded already but seems to be relatively empty.

[sdk32285]

I primarily use multisim for basic designs. I use Xilinx which has a free ISE development for digital design and testing. you can also download modelsim which lets you simulate your design with test waveforms. Xilinx also can do VHDL design and synthesis.

[Admin]

SPICE I believe is the most popular circuit simulator software out there. There are many many versions, most listed on that link.

As for Eagle, yea its too overcomplicated for hobbyists . . . good only if you want to manufacture a board. I wasnt happy with its components library so I stopped using it the same day I started . . .

Anyone know good circuit drawing software? Just one level above paint, I mean . . . 

[Gopher]

Thanks for all the links; I'll have to research all of those. SPICE in particurlar, because it's core is open-source; it seems to be far more high-end than I had intended to implement myself, but if building my tools around it's core simulation is easier than developing a simpler one from scratch then it's logically what I should do. Whether it's easier or not depends on how SPICE is implemented.

Admin: Not that I know of, but it might actually be a nice way for me to break the circuit simulator down into two phases, make just a drag-and-drop circuit layout system first, so I'm glad you asked Taken by itself, it's a nice, manageable project. 

[sdk32285]

theres a program called Tina which is decent for circuit drawing (step above paint). however it is also based from the spice engine and allows for some simulation.
there is a free version but it limits your components
http://focus.ti.com/docs/toolsw/folders/print/tina-ti.html