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-   -   LT Spice ASC into PCB layout ? (http://www.diyaudio.com/forums/software-tools/211280-lt-spice-asc-pcb-layout.html)

Mark.Clappers 23rd April 2012 03:06 PM

Forget about auto routing, there's only 1 good way to do it, manually. You can ofcourse add layout design rules, such as spacing, track with, PCB stackup, transmission lines, differential pairs, ...

PCB layouting is a real art, especially when designing high speed digital or sensitive analogue circuits. High speed in this context means "fast edges".

Professionally I use Altium, not as expensive as for example Cadance but still not cheap.

Whatever layout tool you use, start with finalising the schematic first, second is component placement, third are the most sensitive traces + any guard traces, 4th power / ground planes and last the remaining traces.

guitar89 23rd April 2012 03:24 PM

yeah, I agree we can't rely on auto-routing, since there are many placement which has detrimental effect on the sound quality of an amplifier.
Well... what I mean is something like auto routing of wiring simple. (Previously I was drawing manually, and it takes me like many days to only design, then draw, and finally not suitable and redo. drawing using pencils really a headache regarding wirings.)

Simon B 23rd April 2012 03:27 PM

Quote:

Originally Posted by marce (http://www.diyaudio.com/forums/software-tools/211280-lt-spice-asc-pcb-layout-post2995917.html#post2995917)
Spice is simulation, any routing will be done in the PCB design package.
Forget autorouting, there is no such thing, there is interactive routing, but no autorouting.
The best way to lay out a board is concentrate on placeing, this should take between 60-40% of the time for a layout for analogue and digital with small devices.
The most important part of a CAD system set up is the libraries, these are critical and setting them up is a good way to learn the CAD system, as well as controlling your designs.


Very good advice. Marce is working at the opposite end of the spectrum to me wrt circuit complexity and density, but what he says holds regardless.

I've had access to and tried out a couple of CAD suites over the years, but now, working by myself, on the comparatively simple stuff I do (no motherboards, thank god!) I stick with LTSpice and FreePCB.

The 'project management' features of packages like Orcad drive me crazy (well, even crazier), but for big projects they're probably vital. Horses for courses and all that.

I've learnt, the slow way, by watching and taking notes as I go along just what these programs do. Where they put things, where they look for things. An important thing is your libraries. Your libraries. Of spice models, footprints and pinouts. I've put a deal of work into mine, but in return I know what's in them and more-or-less what's happening as I work. I store and use them carefully.

As with any computer program GIGO applies. Routing for me, in FreePCB consists of importing the netlist, with models that include correct pinouts and footprints - electrolytics and discrete transistors need checking. The outlines appear on screen, connected with ratsnest wiring, then I place the parts and route the tracks.

If you're doing stuff like amplifiers and you've been drawing layouts manually, do try FreePCB.

guitar89 23rd April 2012 03:42 PM

m... will try out freePCB later, seems very good ^^

Simon B 23rd April 2012 03:54 PM

Quote:

Originally Posted by guitar89 (http://www.diyaudio.com/forums/software-tools/211280-lt-spice-asc-pcb-layout-post2997494.html#post2997494)
m... will try out freePCB later, seems very good ^^


Start off with a very simple circuit, eg a trivial r-c filter. You'll need to specify package footprints not in dimensions/hole spacing as you're probably used to if you've been hand drawing, but in terms of package names that contain that information. Most of what you need will be available in the FreePCB libraries, but if you need to create or edit one, that's quite do-able. You also need to associate this device information with the netlist you're importing, which can be done in various ways, see the tutorial and help file, they're not bad. Incidentally, if you work systematically, you can create netlists in a text editor if you really need to.

Keep looking inside files with wordpad or suchlike, a lot of them are readable text and you'll learn from that.

You will almost certainly find it frustrating at first, but well worth the effort if you stick with it.

marce 23rd April 2012 08:25 PM

Yes, that is one use of the autoroter, it gives you a metric on placement.
I am sure there has been a thread on DIYAudio regarding eagle parts.

geraldfryjr 8th May 2012 05:39 PM

This is the reason I like Circuitmaker 2000 so much as it comes with Traxmaker PCB program built in to it and I can go from schematic netlist directly to laying out the board.

Jer :)

jmillerdoc 19th May 2012 04:29 AM

Is there anyone here willing to turn a schematic (fairly simple done in Spice) into a PCB format for a noob like me? I have a fairly simple linestage design done up in Spice and was going to point to point the build...now I am thinking of having some PCBs made but have no idea how to create a PCB file from a schematic....honestly, i really wouldnt want to spend the time learning...i would rather pay someone if possible. Please shoot me an email if you are willing to assist....
Thanks,
Jeff

guitar89 19th May 2012 07:42 AM

Hm.... before this I was trying to do as you, but it doesn't work quite easy. you need to do from scratches to put the layout. Depends on the complexity of the layout, someone could help out. (at least know the parts count) and depends what is your usage.

Simon B 19th May 2012 12:43 PM

I've only ever done layouts for pcbs I etch myself (long time since anyone else was daft enough to employ me for this stuff!), so mostly single-sided stuff. marce on the other hand, I think, lays out boards that are more complex than most medium size cities.....

If you're having someone else make them for you, it might be a good idea to get them to tell you what they like to work from.

Also, show us yer schematic!


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