[sdiy] Aaron's first PCB layout

[Aaron Lanterman]

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?