Eagle use in Prototyping

In the development of any product it is necessary to develop prototypes to test key ideas and concepts. The design for team 12 is no different requiring several iterations of prototypes to ensure the design is on track to work properly. The team decided to use CADSoft Eagle software to develop breakout boards for parts because the components are surface mount devices. This makes working with components easier because the leads do not Objective This application notes is written as a way to help students develop their prototypes using CADSoft Eagle. Eagle is a powerful tool that allows students to quickly and economically develop their prototypes. Additionally, Eagle is the software that is recommended by the Electrical and Computer Engineering Shop to develop prototypes. There are a number of sources for students to use but this aims to consolidate some of those sources into a more compact document. Getting a Version of EAGLE Eagle is a commercial product sold by CADSoft Eagle. However, students can acquire a light version of the software for educational purposes. The light version has some limitations that include only being able to develop boards that are 100 mm by 80 mm or 4 by 3.2 inches [1]. Additionally only two signal layers can be used a top and a bottom, and the schematic editor can only create one sheet. Selecting components in Eagle The student version of Eagle comes with a pre-determined library. However, this library is not an exhaustive list of all known parts. Sometimes the desired components are not in the default library and a student can either make their own library file or can find their necessary library file on the internet. In particular element 14 offers extensive libraries for different companies ranging from Texas Instruments, Microchip, Freescale and many more. In order to begin choosing parts the user needs to click on the “ADD” button on the left sidebar. This will bring up the menu shown in figure 1. Parts are listed in alphabetical order but also allow users to type and search for a specific part. Figure1: ADD Menu Once the correct parts have been chosen the devices can be wired using the “Wire” command on the left hand menu bar. With all the parts selected and wired the user now wants to go to the “switch to board” option in the left hand corner of the screen. This takes the user to the board layout and allows the board to be arranged and routed as necessary. Inserting ground planes in EAGLE Open Eagle and start a new schematic, select the parts and then switch over to the board. Click on the ‘polygon’ icon located toward the bottom of the toolbar. It is possible to choose what layer the ground plane is placed on by clicking on the toolbar in the left hand side called ‘Layer Settings’. Route the polygon in the desired shape. Make sure to close the polygon at the starting point or there may be problems generating gerber files later in the process [2]. At this point a polygon with a dashed line will appear. Once you have drawn the desired polygon click on the “Ratsnest’ icon and the polygon will fill with copper [2]. This process is shown in figure 2. In order to ensure that the placed polygon connects the proper pins of the components to the ground plane it is necessary to name the polygon the same name given to the ground plane in the schematic. This is done either by typing in ‘name’ on the eagle toolbar or right clicking on the polygon and clicking on name. This brings up a small menu and allows the user to change the name. This menu is shown in the figure 3. Figure 2: Polygon Construction Process