[sdiy] Aaron's first PCB layout

[David Moylan]

What's the circuit for on this board?

Aaron Lanterman 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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