[sdiy] Aaron's first PCB layout

[Naoki Iwakami]

Hello Aaron,

I'd recommend to short two ground planes on the circuit board.
I think splitting the ground plane by a signal line might bring
problem of picking up noise and/or unstability.
Also, I found that the wire from 33k on the right bottom makes a large
loop.  Since the wire ends at the pin 7 of right-hand NE5532, the wire
can be shorter if you place the 33k at the above of 10k
(horizontally).  And this would easily short the two ground planes.
How about the idea?

I prefer printing part numbers rather than values.  This is because I
sometimes discuss board design over network/telephone.  Using part
number would make it easier to specify the part on the subject.  (But
this is a matter of preference anyway)

Thank you,
-- gan

On Sat, Jun 7, 2008 at 4:55 PM, Aaron Lanterman <lanterma at ece.gatech.edu> wrote:
> After much cussing and fussing, I think I finally have come to an
> understanding with Eagle. Wow, what an unintuitive program! But I think I
> have the hang of it.
>
> Anyway, I've put together my very first PCB layout, and wanted to show a
> picture of it the group so that people could tell me if something that looks
> really wrong jumps out at them. I'm probably making all sorts of neophyte
> PCB layout mistakes:
>
> http://users.ece.gatech.edu/~lanterma/aarons_first_board.png
>
> The board is 3.4" x 2.8".
>
> I did one that was smaller where I just plunked down the parts and used the
> autorouter to make a two-sided board. But then I got obsessed with doing a
> one-sided board, so I made one where I placed the parts down a few at a time
> and hand routed as I went. I was all proud of myself that I was able to do
> it without using any jumpers.
>
> I found I really like the style of Ken Stone's boards, where resistors and
> caps are just given by their value, and you can just plug parts in without
> having to look up "OK, what is R32 again?" So I made a modified version of
> the capacitor symbol that doesn't include the schematic-looking symbol on
> the PCB, and that puts the value inside the box.
>
> One thing I need to go back and think about is the sizes of the capacitors.
> I used all the same size in my initial layout; I need to actually go look at
> some real caps and see what's realistic and tweak accordingly.
>
> A few specific things I'm wondering about:
>
> 1) To avoid using jumpers, I run a signal line between the MOTM style ground
> pins. So this requires that the user be sure to apply ground to both pins.
> I'm not sure if that's good practice or not.
>
> 2) There's one big ground plane (well, two really, one coming out of each
> ground pin). I also have a +15V plane (running along the top half of the
> 5532 chips) and a -15V plane (running along the bottom half of the 5532
> chips). Is it a good idea to power things with a "plane" like that? Or does
> that do something weird, so I should just be using wide traces?
>
> 3) When I do the design rule check, eagle complains about clearance at a
> specific spot on the board, but I can't figure out what it is complaining
> about. You can see Eagle's complaint here:
>
> http://users.ece.gatech.edu/~lanterma/eagle_complaining.png
>
> If you look closely you can see hatch marks in the middle.
>
> I find I really enjoy the puzzle of laying out PCBs - it's like a game of
> Tetris.
>
> If I get this working I'll make extra copies of the board available, kind of
> like Ken and JH do, but at a more informal level, if people are interested.
>
> - Aaron
>
> P.S. When people are hand routing in Eagle and want to put in a jumper - is
> it a good idea to go back to the schematic and put it in as a part somehow?
> Or maybe use a second layer to decide where you want jumpers, but not send
> that to the PCB house? How do people handle that?
>
> P.P.S. Any recommendations for places that make small-run single-layer PCBs?
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