[sdiy] Schematic/PCB layout best practices

[Aaron Lanterman]

Greeting schematicians and PCBeings,

1) Is there a Best Practice for numbering components? I'm putting in  
schematics into Eagles in a semirandom fashion, and am hence getting  
them numbered in a semirandom fashion.

I was thinking:

A) It might be best to renumber them based on how they appear on the  
final PCB, maybe number with increasing numbers left to right or  
something, to make things easier to find there, or

B) It might be best to number based on the schematic, where say parts  
near one another in the circuit have similar numbers; or maybe if  
there are multiple similar subcircuits, or...

C) Number based on the schematic, but instead have the equivalent  
parts in the different subcircuits have similar numbers (i.e. input  
resistors R1 through R5, feedback resistors R6 through R10, resistors  
to ground R11 or R25), or

C) I'm totally overthinking this and should let randomness rule.

2) What's the Best Practice for choice of trace width for (A) typical  
signals and (B) power and ground for typical synth module operation? I  
realize I've been using Eagle's default, which is 0.016 for default,  
for signals, and 0.024 for ground and power since it was the next step  
bigger from 0.016 from the drop down menu, but then I figured I should  
have better reasons for picking values than they happen to be some  
Eagle defaults.

3) Buchla quite often has separate "Quiet" and "Noisy" grounds. He  
uses the Noisy grounds in digital circuitry, but he also seems to use  
the noisy grounds sometimes in circuitry related to control signals,  
in places where it seems hooking things to a "Quiet" grounds would do  
no harm. If a circuit I'm working on is pretty much all analog, is the  
a compelling reason to keep separate "signal" and "control" grounds,  
or can I just lump them all together? Is it related to Buchla using  
1/8" for signal but bananas for control?

- Aaron