Good Engineering Practices

[R.G. Keen]

>Some of what I've accumulated is:
>
>1.  Put a large electrolytic 100 uF or larger on all supply lines to
>stabilize     the power distribution.
>
>2.  Put .1 uF bypass (spelled ceramic disc) capacitors at various locations
>(near power connections to op amps and digital ICs) to control noise.
A conservative rule is one per chip per power supply line.
>
>3.  Have board input and output lines well separated to control crosstalk
>and     S/N ratios.
>
>4.  Design "guard" circuits around the inputs to high quality opamps and other
>    "special" components.
>
>What are some of the other practices that one should follow when designing
>PC boards?

Unless FORCED by other considerations, orient all capacitor (+) 
terminals in the same direction; likewise orient all integrated circuits
and transistors in the same direction. This will save enormous amounts 
of time when you populate or repair the board.

Put all the electronic components on the PC board, don't hang ANY onto
controls, switches, etc. for the sake of reliability and ease of
build/repairs.

Standardize the size of all similar components, especially resistors
and jumpers. That way you can make/use a lead bending guide for easy
population. 

Use jumpers! The cost of going to double sided is worth populating 
100 jumpers.

Use the pc board to scramble wires to switches, pots, etc so they are 
simple to run. Don't use off-board wires to make the PC board easier.
Again, this makes building and repairing easier and less confusing.
If it can be done easily, use the PC board to replce wires run between
off-board controls, jacks, etc, so there is a simple, non-interlaced
wire group that runs to each control, switch, etc.

I like to run ground lines between stages even in simplistic audio
boards wherever I have a ground handy and there is room. This is really
and extension of #4. You need to watch the capacitive loading this 
introduces whenever you have high impedance signal lines, though.

Maybe the best guide to pcboard layout is to design the box first, or 
at least know how the board will fit into the box. This lets you 
decide the rough size of your board, how the wires will be routed,
where the controls are located, whether you can use the pc board to
mount the controls, thus eliminating lots of hand wiring, etc. 

Ifyou have trouble visualizing in 3-space, use a 
drafting program to draw up the outside of the box on paper, then
rubber-cement the drawing to cardboard and cut and scotch-tape the 
box  mock-up together to get a good prevue of the actual box and
controls. You can use this to prevue control mounting interference
and mounting of the board. This is pretty much mandatory if you are 
using the pcboard to mount all the controls so you can check locations
on the actual box and at the same time make yourself a cutting and
drilling guide.

Use a program like Easytrax to do your layouts unless you have access
to one of the fancier layout programs. Easytrax is -*free*-.

I'll undoubtedly come up with more. By the way, -*none*- of these, 
including your starter set are taught in EE curricula. 

R.G.