[sdiy] Schematic/PCB layout best practices

[Neil Johnson]

Aaron,

> 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.

A final pass I run on the schematic before moving to PCB is to run  
the schematic renumber macro on the schematic, the defaults are  
usually fine.  I also do the same as the PCB is nearing completion,  
as I've usually made various changes on the way (gate swaps,  
component changes, etc). Basically, the schematic is the master  
reference document and should be in the most readable format.

I also find that, in many cases, the PCB layout kind of matches the  
schematic layout too - the general signal flow, etc.

> 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 standardize on 12mil for signals and 24mil for power.  Once the  
layout is nearing completion I review all track widths and widen  
power tracks if sanely possible to, say 32mil.  Any high current  
tracks are dimensioned as per track width guidelines, although most  
synth circuits don't handle that many amps.

> 3) Buchla quite often has separate "Quiet" and "Noisy" grounds.

This is starting to head back into circuit design - getting the power  
architecture right (and that includes grounds) is vital to a  
successful design.  Everything from input decoupling and filtering,  
regulation, ground routes, high current paths, low current blocks,  
partitioning, is all part of the process.  Skip this and you're  
storing up problems.

Even ground/power planes need proper designing (not just splat them  
down and forget about it).

Cheers,
Neil
--
http://www.njohnson.co.uk