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Old 13th September 2006, 05:54 PM   #1
elaar is offline elaar  United Kingdom
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Default Track layout design

Hi all,

This is not in the appropriate section of the forum, sorry i'm not sure where exactly it belongs.
I was wondering if anyone knows of a program that can take a black and white track layout graphic and expand the tracks so there is less no-copper areas? Sure, I could do this myself, but the layout is quite large and there's a tendency for me to expand certain tracks and not others to make my life easier.

Thanks,
Alex
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Old 13th September 2006, 06:15 PM   #2
roger-k is offline roger-k  Norway
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Is it track layout graphic been designed with any program?
And if, du you have the file?
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Old 13th September 2006, 09:01 PM   #3
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Seems like as good a forum segment as any from my POV...

Why not do them piecewise as you suggest, and only expand the higher-current/lower-impedance segments? With high impedance input stages, there's no real requirement for wide tracks, and you may just increase stray/parasitic capacitance... I favor the approach of handling trace widths individually and increasing the size of low-impedance tracks and not otherwise (perhaps even decreasing high-impedance routes). I certainly don't pretend to be any sort of expert, but this has worked well for me, both in digital and analog arenas...

I sort of tend toward a rule-of-thumb per PCB layout/design, which could probably be approximated as:
trace width ~ amps / sqrt(frequency), though I don't mean to say I'm all that rigorous.

Of course, there are NO absolutes. If this were an incorrect statement, this forum might as well cease to exist (which I hope does NOT happen).

Happy listening!
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Old 13th September 2006, 09:55 PM   #4
elaar is offline elaar  United Kingdom
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Hi, thanks for the replies.

The problem I have is that although I like to build amplifiers from the ground up and compare the differences in sound, I am not yet very knowledgeable about how they work, hence i find it quite difficult to work out how wide certain tracks should be compared to others (unless they are power rails).

I have attached the current amplifier layout I am building. It's taken from "High End Audio Equipment" Elektor Electronics book, it's almost identical to this:
http://users.otenet.gr/~athsam/power...hexfet_eng.htm

though i decided to stick with the layout the book provides.

Anyone built this amplifier design before? any comments?

I think the book probably shows the most efficient layout they could come up with, so perhaps i'll just "fill in" the gaps with areas of copper that are not connected to any part of the circuit just so that my boards won't take days to etch.

Thanks,
Alex
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File Type: gif layout-minimised.gif (55.9 KB, 694 views)
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Old 13th September 2006, 10:21 PM   #5
CBS240 is offline CBS240  United States
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Hi elaar,

Just keep in mind that copper trace has resistance, be it small, it will have an effect in certain places, particularly those with lots of current. Douglas Self has explained quite well about the need to have the trace of equal distance and resistance from each output device to the negative feedback point of the circuit or you may (or may not) encounter stability issues. It is a good and helpful design tip made by Mr. Self.
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Old 14th September 2006, 01:15 PM   #6
kvholio is offline kvholio  Netherlands
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Hi Elaar,

the layout from the elektor-book looks very familiar to me, i think i built that one about 18 years ago.
I'm not sure about the amp in the link you provided, cannot check for consistency but the pcb looks like something i could come up with.
If i recall correctly the elektor (elektuur) amp used a c-r-c powersupply with 2x 10.000 uf on the pcb.
The amp ran fine in my system for over two years driving a pair of kef cs-7's.
The only hurdle i encountered after i built it was intermittent shorting of the hexfets to the heatsinks, caused by overtightening of the mounting-screws
using silpads.It's also a good idea to deburr the edges of the to0220s to get rid of the sharp edges.
I ended up using aluminum-oxide isolators to get rid of the problem.
With respect to knowledge, i think we're more or less on the same boat, so i'm not sure if i can offer more help.
The elektor-layout worked fine for me, so my suggestion would be to stick to that.
Hope this helps.

With kind regards,

Klaas
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Old 14th September 2006, 03:06 PM   #7
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Quote:
Originally posted by elaar
I am not yet very knowledgeable about how they work, hence i find it quite difficult to work out how wide certain tracks should be compared to others (unless they are power rails).

Thanks,
Alex
Alex - Understood. If you post a schematic, you'll definitely get a lot of mileage from this particular forum, especially in terms of gaining this kind of expertise. One of my favorite parts of amp design is [what I call] quiescent analysis; where you apply the laws of Ohm and Kirchoff, to determine expected bias currents and node voltages, based in great part upon resistor values. Learning to do that was part of what allowed me to begin to create my own designs, as well as to be able to make strategic modifications, including the sort you wish to engage...

Like I said, I'm not the end-all expert, but I for one would be happy to make my best effort to help you analyze a schematic to this end, and I'm sure I'm not alone in that statement. If you're building amps in the first place, and know how to test them and get them working correctly, you're nearly there already! Even ground-up building of existing designs requires some analysis & troubleshooting ability in most cases.

-Jonathan
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Old 14th September 2006, 03:15 PM   #8
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Default re: your board

Personally, I would just expand the copper area (black) near the left & right edges ... up to but not including your mount holes in the corners.

If that area is to be your "ground plane", then no problem with the added "stray capacitance" ... if not, then not.

I would do this "by hand" with any of the built in paint programs (Apple > Apple Works > Paint, etc.)
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Old 14th September 2006, 04:00 PM   #9
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Quote:
Originally posted by acoustixman

If you post a schematic,
OK, Duh on me. I just realized you had posted this link. I'm looking at it now...
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Old 14th September 2006, 04:54 PM   #10
bscally is offline bscally  United States
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Default Layout Manipulation

Alex

There are a couple of layout programs that can be used to maipulate the layout once it has been scanned.

There are more that will allow the manipulation of gerbers.

Most of the tools are linked to an layout package.


The question is what package are you using for the layout? Then someone may have a tool that will allow manipulation.


Brian
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