Cadsoft Eagle Tutorial

Objectives Recognise the difference between Through Hole Parts (THP) and Surface Mount Devices (SMD) able to create a new project folder create a new schematic file add and remove library files from Eagle search for and add parts to a schematic set part names and set values Use Electrical Rule Check (ERC) to search for and correct errors in schematic Translate schematic to board layout Create a ground plane Manually route airwires to tracks

Running Eagle for the first time Upon running Eagle, you will see a screen very similar to the one below.

Creating a new project Where it says "Projects“ Click the triangle to the left. Left-click on the "eagle" folder, then right-click to bring up a menu. Choose "New Project". Name your project whatever you'd like.

Creating a new schematic Eagle projects are made of two main files, a schematic file (.sch file extension) and a board file (.brd file extension. Right click on your project folder and select "New Schematic". It will automatically open a blank schematic window.

Creating a new schematic

You can then save this blank schematic. This will create a schematic file for your project. Click on the blue diskette icon to the top left corner and name your file.

Creating a new schematic For this project we will design a circuit and board based around 555 timer chip. We will begin begin by collecting the parts. On the left side of your window click the Add button. This button is below the paste tool and to the right of the big black X or delete button. Clicking the Add button will open a pop up window

Creating a new schematic

There are two ways to find a part you are looking for. – The first is by typing text in the search form towards the bottom left of the window and pressing ENTER. This will narrow down the number of libraries in the left pane. If for some reason it yielded no results or not the results you were looking for, clear the text box and hit ENTER again. It will then display your full library list again. – The second approach is to sift through the libraries in the left window pane. Double-clicking or click on the grey triangle will expand the library as well as open up devices that contain multiple packages. – Searching for simply “555" will probably yield no results, but "*555*" with the asterisk as a wild card will give you exactly what you need. The search function is very literal and so using the wild cards will be extremely helpful.

Creating a new schematic Once you select a part, it will populate the two panes to the right. The one on the left will show you a preview of it as a schematic and the one on the right will show you a preview of it on a board. We're looking for a DIP/DIL (dual inline package) version DIP is a package type with long metal legs. They are easiest to work with but larger than most other packages. Select it and click OK. You'll now be returned to your blank schematic, except this time you'll see a red chip moving wherever you move your cursor. Click on the screen where you'd like to put it.

Creating a new schematic

After clicking once you'll notice that the 555 chip is still stuck to your cursor. Press the ‘Esc’ key on your keyboard once to get rid of it, and to bring you back to the ADD part window. We’ll add the rest of the parts before continuing – Search for and add 1 each of the following to the schematic 1N4004 R-EU_0207/10 (Resistor) CPOL-EUE2.5-6 (capacitor) C-EU X075 (capacitor) VCC GND WIREPAD 2,54/1,0

Creating a new schematic Before we start wiring, we will briefly go over some really helpful tools. – These tools are located on the top toolbar towards the center. They are for zooming in and out of your schematic. The button on the far left is a "Fit" zoom. It will zoom into your schematic so that all the components fit in your window. The second one over is a basic "Zoom In" tool. The third over is a basic "Zoom Out" tool. The second from the right is a "Redraw" tool which is essentially used to refresh the window and redraw the schematic. Use this if the schematic appears to be showing strange artifacts or broken pieces of the schematic. The tool on the far right is a "Select Zoom" tool. Click and drag to create a box in which the window will zoom to.

Creating a new schematic This is the "Move" tool. It is located near the top of the left toolbar. Click the button, click on a part, and it will then allow you to drag the part around your schematic. This is called the "Rotate" tool and is located one button down and to the right from the "Move" tool. This tool lets you rotate a part in your schematic. Click on a part and it will rotate it 90 degrees. The "Delete" tool. Located towards the middle of your toolbar. When activated, it will delete any part or electrical connection in your schematic that you click on. The "Name" tool and the "Value" tool. The "Name" tool will allow you to rename any part in your schematic. So, for example if you have a resistor named "R1" you can change its name to "R10". The "Value" tool lets you annotate the value of a particular part. For example, we placed a couple resistors into our schematic before. This will let us assign a resistor value to them in the form of text. Click on a resistor with the "Value" tool and then type the value you'd like to assign, for example: 220 or 1k.

Creating a new schematic Arrange your parts to look like the diagram shown below.

Creating a new schematic To connect all your parts together in your schematic you will be using the "Net" tool. You can also select the Net tool by going to the "Draw" drop-down menu at the top of your screen and selecting "Net". DO NOT use the "Wire" tool which you may think is what you need.

Creating a new schematic

Simply click the "Net" tool, then click on the tip of the pin you'd like to start a connection at and then click on the tip of the pin where you'd like to complete the connection. The electrical connection will be bright green at first and will turn darker green when a connection has been successfully made.

PCB Design & Board Layout

Designing the circuit board With your schematic complete, to create a circuit board from this, begin by clicking the 'Board' button on the top toolbar. It is located between the CAM tool, and the sheet selector. The 'Board' button contains a logic gate above an IC or chip drawing.

Designing the circuit board Upon clicking the button it will ask if you'd like to create a board file from your schematic, you will click YES and then a black window will open displaying all your electronic components and a big rectangle denoting the outline of your board dimensions.

Designing the circuit board First begin by moving all your components over to the board and orienting everything the way you'd like them. This can be done by a combination of the 'Move' tool and the 'Rotate' tool. You may have noticed that a lot of the same tools you used in the Schematic file are the same in the Board file. So, go ahead and put everything where you'd like them to be. It may be a good idea to keep in mind the usability of your board. Also try to keep components that will be working together close, e.g. placing components that form the power supply adjacent to each other.

Designing the circuit board If you'd like to move everything over at once, click the 'Select' tool then click and drag a selection box over all your components. Once you release the mouse, it will automatically choose the 'Move' tool for you. Now press CTRL and right-click on one of the components in the group and you will now notice all the components you selected are available to be moved at once.

Designing the circuit board If you notice that there is a lot of empty space. The board is probably too large for the small amount of components you'd like to put on it. Select the 'Move' tool and click on either a side of the board dimension (the grey box) or a corner of the board dimension and you'll be able to adjust it.

Designing the circuit board You may notice there are alot of dark yellow lines connecting everything. These are the electrical connections you need to make. Eagle is nice enough to keep track of all connections from your schematic. Before we start running connections, lets use the 'Ratsnest' tool to have Eagle untangle everything and compute the shortest connection to be made with your new configuration. The 'Ratsnest' tool looks like this

Designing the circuit board Time to route our traces and complete the electrical connections. There are two tools that are very useful when routing traces. The tool on the left is the 'Route' tool that allows you to begin laying traces and the tool on the right is the 'Ripup' tool which lets you delete traces you've already made.

Routing Traces The two options for routing traces for your board are the automatic way and the manual way. In almost every situation, I recommend the manual way. The reason is that the automatic routing in Eagle does a decent job, but a messy one at that. And, on occasion the automatic route is unable to route everything for you and will leave the work unfinished. If you want a beautiful board, do it yourself. If you plan to use chemical etching and don't care how messy things look, consider the automatic routing. However if you plan to use the mechanical PCB etching machine, only PCB’s that have been neatly routed will be manufactured. Take note though, designing a circuit board with not much time to spare can be a risky undertaking. Take your time, double-check your work, and don't rush things.

Adding a Ground Plane To add a ground plane to your circuit, click on the ‘Polygon’ tool. Draw a closed rectangle around the outline of your board. Select the ‘Name’ tool and click on the outline of the rectangle. Rename the polygon to ‘GND’ and select the radio button beside ‘the Entire Signal‘

Adding a Ground Plane

Jumping Over Traces At some point you may be faced with an airwire that you cant successfully route without it crossing over another trace. This can be overcome by following the steps below:

Autorouting The 'Autoroute' tool is located towards the bottom of your side toolbar and looks like this... If you click on this tool a window will open.

Autorouting This window is giving you the option of configuring how your Autorouter works. You may ignore most of this unless you are more experienced and wish to customize things to your liking. On the left side of the window there are two drop-downs for Top and Bottom. These drop-downs let you configure the direction of the traces on the top and bottom layers. If you only wish to do a single layer of traces, for example if you are designing a board that you'd like to chemically etch, then turn off one of the layers by setting it to N/A. If you're etching a single-sided board, turn off the top layer so your traces will only be on the bottom. When done, click OK, watch it work, and cross your fingers it finishes successfully. At the bottom left of your screen you will see a percentage complete.