could anyone tell me a simple open source pcb design software?
-
There are not "simple" PCB packages. Every package I've ever heard of has been berated for being "non-intuitive" and hard to learn. That's because drawing a circuit is a lot more complicated than drawing a picture. Really.
-
open source wise, people are using "kicad" and "geda." kicad is getting a reasonable reputation. For very simple things, there is fritzing.
-
Free-wise, there is Cadsoft's EAGLE. Not open-source, but... relatively enlightened distribution terms, IMO. All the Arduino PCBs are in EAGLE, for instance.
EagleCAD is a popular standard in the community. They have a limited function free version that you might find adequate, depending on what you plan to design with it.
- There are not "simple" PCB packages. Every package I've ever heard of has been berated for being "non-intuitive" and hard to learn. That's because drawing a circuit is a lot more complicated than drawing a picture. Really.
I could not agree more.
Except for very simple designs all EDA tools have a learning curve. You need
to learn the nomenclature and the quirks of each tool.
Since all of these tools have quirks my preference is a for a tool that is easy
to augment with scripts. I switched to gEDA from Eagle about six years ago.
The file formats are open enabling a scripting in Python, Perl, etc. The file
formats are ASCII making design automation tasks easy. I have not
used Kicad.
My gEDA stuff is at Loading...
(* jcl *)
--
You can't create open hardware with closed EDA tools.
Since all of these tools have quirks my preference is a for a tool that is easy
to augment with scripts. I switched to gEDA from Eagle
Huh. One of the reasons that I like EAGLE is because of it's "user programming" capabilities! (It has a C-like extension language that can do quite a lot...) It would be nicer if the file formats were documented enough to use third party languages for manipulating the files as well.
I like kicad http://www.lis.inpg.fr/realise_au_lis/kicad/.
It's open-source and cross-platform (linux and windows). Also it doesn't have the 8 by 10cm PCB size restriction Eagle does (as I understand it). I have never used Eagle (nor gEDA for that matter). I have needed bigger PCB than 8 by 10cm once 
I doubt I will need that often though.
But kicad is no exception to having its quirks to learn, it might not be as "intuitive" as other software. In particular the mouse control are a bit odd. But it is really an excellent piece of software, and you cant beat the price!
This helped me a lot using kicad: http://www.curiousinventor.com/guides/kicad
And this: Kicad/FAQ - Wikibooks, open books for an open world
Here's a lot of additional parts for kicad, in case you are interested: http://www.kicadlib.org/
And here's a lot of converted Eagle libs for kicad: http://library.oshec.org/
You can also design your own parts, even in 3D (with wings3D http://www.wings3d.com/), for better visualization of the finished product. Not important maybe, but I find it helpful. And cool
Huh. One of the reasons that I like EAGLE is because of it's "user programming" capabilities! (It has a C-like extension language that can do quite a lot...) It would be nicer if the file formats were documented enough to use third party languages for manipulating the files as well.
Scripting wasn't the main reason I switched 
I like the user interface of gEDA much
better. Having undocumented file formats is a major negative. Pseudo-C
seems like a negative as well. With gEDA most people use Python. I prefer Perl.
Others use scheme.
The library management seemed strange but I could be wrong on that since I
didn't spend much time with it. I have heard that you can't do hierarchical design.
I could be wrong on that one too or maybe it was an older version.
My gschem/PCB setup integrates my Postgres materials management database
to generate boms, kit lists, etc. I also have an rule-based attribute assignment
script that assigns attributes based on approved parts status, cost, inventory
or a preferred parts table. Very easy to do when the file formats are open.
Although the OP doesn't need any of these features I would still consider
extensibility of the tool when making a decision.
All of these complex software tools (including gEDA) have limitations which
you usually don't find for many months. I am tending to use simpler less
integrated tools that I can augment with Perl scripts, shell scripts, Makefiles
and TeX.
(* jcl *)
--
You can't create open hardware with closed EDA tools.
I have not yet taken the time to play with Eagle, but I have played with Fritzing.
IMHO, Fritzing is a piece of software that has a chance to grow with and like the community that has sprung up around the Arduino. It has its problems, certainly (lack of parts, mainly; though the auto-route function needs work too - but then again, I have heard that Eagle's isn't all that great, either) - but here's the thing:
Fritzing is open-source, and based on open-source standards. Sound familiar?
If we want more parts for Fritzing (personally, I want a TO-3 NPN transistor for an h-bridge layout), then all we have to do is make them ourselves; people have made tons of parts libraries for Eagle, so why not Fritzing? The thing has a built-in part editor, anyhow, and anything extra is just some SVG and tweaking away...
Fritzing also offers something that Eagle doesn't: Virtual breadboarding.
You can design your circuit or lay it out on virtual breadboards using "parts" with graphics, connecting the pins, etc - putting it together just like you would (or in the case of an existing design, already have) in real-life. The wire nets are automatically built, which means in the schematic editor and pcb editor, any change you make in any of them are reflected in all of them (same as Eagle). That doesn't mean you won't have some tweaking/editing to do to shift things around (once again, from what I understand, like Eagle), but it does seem like it would make for an interesting "prototype to final design" experience.
If the thing only had a fule SPICE simulator or something to simulate electronic designs it would be perfect - but nothing says that couldn't be done in the future; once again, it is open-source.
In the near-future (likely within 3-6 months), I plan on playing with Fritzing more; I want to transfer the h-bridge schematic (part of the controller for a high-power steering servo-mechanism) I made in gEDA (or was it gschem?) and breadboarded, over to it, and hopefully make a homemade PCB using it (or if I can find the money, have some professionally made through a boardhouse). To do that, though, I will have to (at minimum) design that TO-3 case transistor (which should be interesting, considering that the TO-3, while it fits on a breadboard, doesn't exactly lend itself to the graphical manner of Fritzing's breadboard layout system, given the connections needed with the pins on the bottom and the case acting as the collector).
So I expect to become more familiar with it, and I will probably form a better opinion on its usefullness and ability to deal with complex real-world circuitry. But my first impression of it was a solid "Wow!"; the ability to seemingly easily go from breadboard prototype on-screen to a routed schematic to a routed PCB really struck me as something wonderful.
I sincerely wish the community would embrace it for the wonderful tool I think (currently) it is; it being open-source, in theory, only means it can get better with community input and resources. If it is missing a component or feature, it only needs to be added by someone with the skills to do so. Those with Eagle experience could certainly help with this; it has stubs on the menu for Eagle import/export, but I don't think either work yet - so someone with that experience could be a plus to expansion (supposedly, though I haven't tried it, it does output Gerber files).
With the Arduino, Fritzing, and two other projects; RepRap and Contraptor - the DIY and open-source crowd has an interesting oppourtunity to embrace and extend open-sourced hardware and software in a manner unseen before. But only if we take an interest in doing so.
could anyone tell me a simple open source pcb design software?
These other folks are talking about some pretty complex system - I've played with Eagle some - POWERFUL program there. "Powerful" and "simple" usually do not go together.
"IF" and I do mean "IF" you are talking "simple" as in easy to use and you're only wanting to draw up 1 or 2 sided boards, then PCB Express might be something you'd like to look at. Again, depends if you are planning to etch your own PCB - or send out for commerical.
Diptrace is another system you might wish to look at - both DipTrace and PCB Express are free for non-commerical users.
If you are just starting to etch PCB - you might wish to check the yahoo group for homebrew_PCB.
Have fun!
If you are a student, you can pick up National Instruments' MultiSIM Design Suite 11 for like $40 USD.
If you are not a student, it will cost more.
It is a schematic capture software with PSPICE simulation. So, you draw your schematic in the schematic capture portion, simulate it to be sure it does what you want, then you export it to its built in UltiBoard software which basically lays the PCB out for you based on your schematic.
I've used MultiSim for years, and the only complaint I have is that they are not made for Mac, and there is no indication that they will ever make a Mac version.