A PCB for your project -- part 2

In a previous article I wrote about designing your own PCB for a project using Eagle.  In this space I planned to write about using the schematic and layout editor, but I’m far from an expert and there are lots of well written tutorials out there.

For starters you can look at SparkFun, which has a tutorial on schematic entry, a tutorial on PCB layout, a tutorial on design rules and techniques for making your board more manufacturable, and a tutorial  on creating a new library part.  Actually, there are lots of tutorials on lots of different things over at SparkFun, and they’re all good.

In the schematic entry tutorial they give the secret to copying and pasting, which is not intuitive, or at least not like other GUI environments do it.  The layout tutorial, in particular, is very good.  Schematic capture, being a virtual implementation of a circuit, is pretty straightforward.  PCBs, however, live in the physical world and there are plenty of ways that a perfectly functional schematic can result in an unusable PCB.  There can be problems such as connectors that physically overlap other components, parts with footprints that are hard or impossible to obtain, etc.

Towards the end of the SparkFun tutorial they talk about board bringup, and doing everything possible to get your board working even if it has errors.  This is good advice, because you’ll certainly want to find and fix all of the errors before spinning a new board, not just n-1 errors.  You’ll also want to come up with some sort of revision control so you’ll know exactly what schematic and layout go with a particular board.  Put some text on the board with a revision number, and copy the design files that created the board into a directory labeled with that revision number.  Or you can use proper revision control such as Subversion.  You’ll also want to keep notes of the changes and bug fixes you make from one revision to the next.  I put these notes right on the schematic in a numbered list.

There is also an Instructable on making your own library components, which is a skill you’re going to have to develop if you’re going to use Eagle.  Learn how to do it, and then place your new components into a library of your own creation.  Also, copy commonly used components from the Eagle library to your own library.  It’ll save you a lot of time to have commonly used connectors, passives, and other parts in their own small library.

Next time:  how to solder those small pitch surface mount parts.

Send in your gadget!

Design News is always looking for new gadets to feature in the print edition of the magazine.  Mechanical, electrical, pneumatic, whatever.  Believe me, if they’ll run my hot rodded Billy Bass they’ll run anything.  If you’ve creating something clever and would like to see it in print, submit it to the Design News editors:

http://www.designnews.com/file/25333-Submit_Your_Gadget_Freak_Design.pdf

You’ll get the thrill of seeing your product show up in a print magazine right in your mailbox, and you’ll get a check for $500 as well.

Steve Ravet

Design News Gadgeteer