ECE101 – Basic Electrical and Computer Engineering

EAGLE (Easily Applicable Graphical Layout Editor) is a PCB design tool with a freely available Light version. While there are restrictions on the use and limitations on the capabilities of the freeware version, it provides students and hobbyists with a great tool at no cost. In the coming weeks and months, articles posted here will explain how to use this tool to the best of our knowledge and ability. With the free version of EAGLE, support is limited to email and what can be found online. There are certain quirks and nuances that can be frustrating, such as merging two boards (schematics, layouts, or both). Before getting into this, we need to cover the basics.

After installation is complete, you’ll see a screen similar to the one below. We’ll start by covering the “Libraries” and “Projects” trees, as they are the two you’ll need to get started.

Under the “Projects” tree, you’ll find a few example projects to begin. Expand the examples section and find one of the example projects; it will have at least one .sch file and one .brd file.  A .sch file is a schematic file; it’s a block diagram representation of the board you’re designing.  The .brd file is a board file and it shows the physical layout of the board. Double-click either file to open it and Eagle should open the matching board or schematic. I opened the singlesided example, as shown below. In this example you’ll see various components, and a lot of yellow lines between the components on the board. These yellow lines, or air wires, represent signals from the schematic that need to be routed.  We’ll go into more detail about how to use these in the next post.

These signals can be routed using EAGLE’s autorouter, by manually routing each signal, or a combination of both. Depending on your needs, any one of the three can be a good choice. To see how the autorouter works, click on the autorouter button , located towards the bottom of the left sidebar. The autoroute dialog appears.

Select the asterisk in the drop-down menus labeled “1 Top” and “16 Bottom” to allow the autorouter to route in any direction. Selecting N/A disables the layer, and selecting any of the other options sets the preferred routing direction for that layer. Press OK and watch as EAGLE routes all of the signals for you. EAGLE won’t always be able to route all of your signals, but it can at least get you started.

In the next post, we’ll cover how to make your own schematic and board from scratch.  Until then, play around in the software to get used to the interface and some of the terminology that EAGLE uses.