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Electronics: Design

This collects various technical (i.e. physical and CAD-related) information from circuit design to PCB production based on what I am actually doing and found useful.

EAGLE: CAD Tool for Schematics and Board Layouts

For circuit and PCB design I am using CadSoft's EAGLE (easily applicable graphics layout editor and btw it means the same in German: einfach anwendbarer grafischer Layout-Editor). It is available for Linux and Windows and you may download and use a light version for free as long as you do not earn money. As for circuit design, the light version limits you to one sheet per circuit, the PCB is limited to 8x10cm and two signal layers.
Thanks to CadSoft for making available such a great tool!

All circuit schematics which can be seen on this homepage were drawn with EAGLE and all of my PCB layouts were done with it. EAGLE has a quite large library for standard elements (from resistors and connectors to logic chips etc.) and it is quite easy to create your own parts yourself. Further features include design rule check (make sure routed signal do not make short citcuits and the like) and electrical rule check as well as an auto-router (but better keep your hands off that one!). For a beginner, the GUI may be somewhat anti-intuitive and there would probably be some room for increased productivity by changing the way the mouse is used but after some time, you'll get by...

gerbv: Simple and easy-to-use Gerber File Viewer

When not making boards oneself, it is often necessary to produce Gerber files in order to have the boards manufactured. Therefore, one usually wants to visually check the Gerber file before submitting them.

gerbv is a free Gerber file viewer available natively for Linux (and other Unices; there is also a Windows version). Although the program does not support all Gerber types and contents, it works fine for Gerbers created by EAGLE.

Printing Layout Slides

In order to actually produce a printed circuit board (PCB) using the standard hobbyist method (photoactive board and corrosion), the first action is to print the board layout (e.g. done with EAGLE) onto a transparent slide. I recommend to use a laser printer for that since their black color normally absorbs UV light very well (in contrast to several black ink variants used by ink jets). However, laser printers tend to have the disadvantage of not filling black areas to 100%...

My procedure is to produce two top-side layouts and two bottom-side layouts (see below why) of the standard 8x10cm board using EAGLE's CAM processor (download single CAM job printer.cam [8kb] which does it all) and merge them onto a single DIN-A4 transparent slide for printing using a self-written conversion script. This is a simple perl script (download layout.pl [1kb]) which processes the files created by the above CAM job and merges them onto a single A4 file called layout.ps which can then be printed onto a slide. The printer.cam job will also produce a place.ps file to be printed on paper which displays what parts need to be soldered where on the board and hence aids when driling/soldering.

The reason for using two copies of each side is that I'm normally using two stacked slide layers (on top of each other) for better UV absorbtion at the black regions, so that those transparent spots which should actually be black on one of the slides will normally not produce holes in the board's copper layer.

Making a board: Creating two-sided PCBs

PCBs (printed circuit boards) are the "natural" way to actually implement electronic circuits when using CAD and/or SMD parts. For most non-trivial circuits, (at least) two signal layers are rquired. Fortunately, creating two-sided PCBs is nearly as easy as making single-layered ones. Read more...


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