gaussmarkov: diy fx

To design my circuit boards, I use the freeware version of the Eagle Layout Editor by CadSoft Computer GmbH. The software is located in the download area of their site. On this site, I describe the software and offer component libraries and circuit examples. The libraries are organized for diy pedal circuit design and the examples are popular pedal circuits.

Below is a summary of how I designed a circuit layout with the Eagle Layout Editor. This is part of a series of posts about Eagle that introduce this software in step-by-step detail.

First, I made a schematic of the circuit using libraries containing symbols of the required components. The components snap to a grid that keeps the schematic neat. I drew in the connections and assigned values to the components with my mouse. This is usually the easiest way to record the relationships among the components correctly.

The circuit above is the “Basic Fuzz Face” found in R.G. Keen’s article The Technology of the Fuzz Face on GEOFEX.com, a classic diy pedal article. If you go to GEOFEX, you can find the entire “The Technology of …” series and much, much more.

Second, I prepared to layout a circuit board by arranging the physical shapes of the components on another grid. “Rubber bands” (the thin yellow lines) show the connections with nearby components so that you can experiment with where the connections will actually run.

The components and their connections come directly from the schematic, preventing omitted components and mistaken or missed connections. You can toggle between the two layouts, the schematic and the board, making changes in either and they remain consistent.

Third, I completed the layout of the board by routing the wires/traces. The software also has an autorouter that will complete the routing mechanically. Typically, placing the components and routing connections is a process with lots of experimentation.

Notice that two of the components, capacitors C1 and C2, have different lead spacing than before. I revised the placement and routing many times to get to this arrangement.

You can use this layout to make the circuit on perfboard or to create a template for etching a circuit board.

Images can be exported in standard graphical formats at a resolution that you choose. Here is an example of a template for etching a pcb produced from the layout above. All of the gm libraries use a drill size of 0.8 mm (approximately 0.03 inches). To make this image, all of the pad sizes were increased, the components were made invisible, and the image was made monochrome. I chose a 300dpi resolution.

Notes: See eagle: drill size for an explanation of how to change the drill sizes in an Eagle library and see eagle: pad size for an explanation of how to change the pad sizes.

For this perfboard layout image, various colors were changed.