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Newbie: How to Design PCB?

Posted: Fri Apr 08, 2005 6:50 am
by adamthole
I would like to design a PCB, but I know basically nothing about it and would like some help. I have both a Mac & a PC, and I was wondering what some of the most popular software was. I read in one post that someone mentioned MultiSim. MultiSim can do PCB layouts? I am familiar with MultiSim for simulations, but I was not aware you could make PCB's with it.

I am looking to design a PCB and put it onto the board myself (copper clad). However, after I get a working prototype I may submit it to spark fun.

Any suggestions, links, or anything is appreciated. Thanks!

Posted: Sat Apr 09, 2005 12:05 am
by Caffeine
Go to www.altium.com and get hold of Protel. It's one of the very best PCB design packages around. It's also directly supported by SparkFun's PCB service (just send in the PCBDOC file, no need to worry about all the stuff the eagle users are having trouble with...)

Posted: Sat Apr 09, 2005 4:29 am
by nall
am i reading this right? a single license costs $9,995?

http://www.altium.com/protel/contacts/usa.htm

Posted: Sat Apr 09, 2005 4:34 am
by Caffeine
nall wrote:am i reading this right? a single license costs $9,995?

http://www.altium.com/protel/contacts/usa.htm
Yeah I think so.

Ask them for an evaluation version.

Posted: Sat Apr 09, 2005 7:13 am
by jrcfg
Now you know why we use Eagle... :wink:

Eagle may not be the most intuitive program out there, but it is free for home/hobby use (with some limitiations). Once you play with it for a while and get used to it, it's not too bad at all.

John

Posted: Sat Apr 09, 2005 7:30 am
by nall
yes, i'm using eagle currently and like it pretty well. you're right that it's perfect for hobbyists.

Posted: Sat Apr 09, 2005 8:13 am
by meander
I use Rimu PCB, which works so far and its free. plus its easy to use.

Posted: Sat Apr 09, 2005 1:36 pm
by nall
meander wrote:I use Rimu PCB, which works so far and its free. plus its easy to use.
really? it looks like their demo is fully featured, but doesn't support saving.

also, does it include an autorouter?

Posted: Sat Apr 09, 2005 8:02 pm
by meander
i dont believe that there is an autorouter, but even at the full price of $72, thats a lot better than 10 grand and its a lot easier to use. it only took me about an hour or so going through the included tutorials to be making my own boards. ive submitted them here and its imported just fine.

Posted: Sun Apr 10, 2005 5:58 am
by MGP
Autorouters are highly overrated IMO. Anything a hobbyist is likely to do can be done much better manually routing the board, especially when working with 2 layers.

You have to step up to something like Specctra ($$$) to get a decent autorouter and it's not trivial to setup and use.

I do a couple dozen PCB designs a year and we have never autorouted a board, the results are simply not as good as doing a good manual route.

We use Protel99SE here and the manual routing tools are excellent. The few test boards we've played with autorouting on required as much time to cleanup and re-route bad routes as it would have to manually route the board right the first time.

Most aututorouters are also very sensitive to component placement. You'll spend as much time placing parts, autorouting, checking the board then re-placing, re-routing and cleaning up the board as you would just placing the parts right the first time and manually routing.

No matter how you do it, PCB design is not simply a "throw the netlist at the PCB tool and voila!, finished PCB" kind of exercise. It's an interactive process that takes real work and thought to get a good result. I guess that's why they call it "PCB design"... ;)

Posted: Sun Apr 10, 2005 1:56 pm
by nall
MGP,
your point is well taken. i'm very much a newbie and about to finish my first board (which is little more than a toy). of course the autorouter can handle it with no problems, but i can see how larger designs might cause it to be more trouble than it's worth.

Posted: Mon Apr 11, 2005 9:35 am
by MGP
Well on smaller designs it's a no-brainer. You, as a designer, can see all the things an autorouter can't -- how your analog signal flow needs to lay out (using short, compact routes), your power layout (critical even in a small design) and a lot of other things like maximizing signal traces and minimizing vias.

Autorouters do lots of other bad things but those are the major ones. Personally I'd never use an autorouter unless the design was several thousand nets and maybe 6-8 layers -- and with a design like that you'd really need an "industrial strength" autorouter like Specctra. For anything I'm putting on a 2 or 4 layer board I'd hand route it.

I know a lot of other people will probably disagree with me but I've never seen a board that meets my "hand route" criteria yet that looked better from an autorouter vs. hand routed.

Here's an example board. It's a 4-layer board, about 800 nets and a mixture of analog, digital and power circuits (like a lot of "hobby" projects, only bigger). I doubt many autorouters could have completed this board, let alone done a better job than hand routing.

Here's another example board that's much closer to what a hobbyist might do. It's a 2 layer board and is about 2.75" x 1.25". It also has analog, digital and power components.

These are pretty typical of the board designs I do. I don't believe any autorouter would do a better job or save much (if any) time in the PCB design. They also couldn't handle the mix of analog, digitial and power very well.

I think a lot of people figure that if they have an autorouter they must use it and that it will automatically save them time and produce a better result. This is my perception of the online discussions I see but not the results (in my experience). A lot of people should really consider hand routing their boards unless there's an overriding reason not to. Ask any experienced professional PCB designer and he'll tell you that the hand routed boards are generally a lot better layout.

I'm not "anti-Autorouter", I just think there's a time and place for them and that the vast majority of boards are better off routed by hand than autorouted.

Posted: Mon Apr 11, 2005 1:38 pm
by moorejl
Wow, those are some nice layouts, I think you just sold me on manual routing.

Whats the best way to get things rolling for quality manual routing?

I have to admit "I am a Eagle auto-router (over)user" and need to reform :)

I do spend about 90% of the time moving parts by .005 and changing trace widths etc to get good looking 100% auto routes on really simple layouts with < 50 nets. Now the results actualy look good, but I would rather do it manually and have more control. Getting the router to jump through hoops is a bit like working on microwave circuits.

Jamie

Posted: Thu Apr 21, 2005 12:29 pm
by sparky
Autorouters rule! Of course they are all horrendously bad, but they save incredible time even on simple designs.

We use Protel here. Sure, it will do some really silly things, but as a hobbyist/tinker/SFE Employee, designs change so rapidly it would be a huge time hole to route everything by hand. I end up running the AR a couple times to allow it to do its best. It always manages 100% routing. I then go back and touch up all the silly dog legs or long routes.

Now if we were running 10,000 PCBs a year of a single design, I would most certainly do it by hand. But as designs roll over and components move, routing by hand just doesn't make sense. I guess we are really stuck between the home hobbyist who has plenty of time and the design firm that needs an impeckable layout.

My $0.04
-Nathan

Posted: Thu Apr 21, 2005 11:12 pm
by pittuck
ditto

My PCB designs are done on the fly, like i now know i need to redesign my motor driving circuits to handle low voltages. Do i just rip up all signals, make the schematic changes and click autoroute, DONE.

I do check the analog traces tho, and make sure i position components that are 'connected' close to each other. But i am a hobbyist, cutting $0.05 out of a design by optimizing track lengths is not something i worry about!

hehe