Welcome to the training module on Drawing a Schematic. This training module explains how to draw a schematic using EAGLE Schematic Editor. .
Before creating a PCB, we must first draw a circuit schematic. This can be done using the Schematic Editor Window. The Schematic Editor window opens when you load an existing schematic or create a new one. Here shows the user interface of the window. On top of the window is the title bar, which contains the file name and path, and then the menu bar and the toolbar. Below the toolbar is the parameter toolbar, which contains different icons for different commands. EAGLE accepts commands in different ways; mouse clicks, text via command line, or from script files. On the left of the work space is the command toolbar, which contains most of the Schematic Editor's commands. Above the working area is the coordinate display on the left, with the command line, where commands can be entered in text format, to the right of it.
After you create a new project, right click on the project and select “New->Schematic”; or you can select “file->New->Schematic” in control panel. Both will bring up the Schematics Editor Window. After you create an empty schematic, the first thing that should be done is to save it. This is done to let EAGLE know the name of the schematic and extra files that will be created along the way.
It is helpful to first place a frame in the empty schematic. Click the Add button or type “add” in the command line and the “ADD” dialog opens. The ADD command is used to select devices from active libraries. We use this command to load a frame since frames are in libraries. You can use the search-box at the bottom to search all libraries for frame you want. In the search-box, the wildcard character * can be used. Find the frame you want and click OK. The selected frame will be attached to the mouse cursor and you can place it wherever you want on the schematic by clicking the left mouse button. We will normally place the frame at coordinates (0,0) which is indicated by a black cross in the schematic editor. If you don’t want to use the supplied frames, you can also draw a frame by selecting “Draw->Frame” in schematic window.
After you place a frame, now you can start to draw a circuit diagram. First you need to add components to a schematic from ADD dialog by means of the mechanism described previously. If you have place a component with ADD, and then want to return to the ADD dialog in order to choose a new component, press the ESC key or click the ADD icon again. If the position, the name or the value of a component is not what you want, you can right click the component and then pop up a command bar to re-edit it.
You might think that you'd use the &quot;wire&quot; command to make connections in your circuit. However, a wire in EAGLE is just a line; to properly make actual electrical connections, you need to use the &quot;net&quot; command. Nets will automatically form junctions when terminated on pins or other nets. Once you've clicked the NET button, your mouse pointer become your drawing tool. Click on a pin (or anywhere, actually), move your mouse somewhere else and you'll see a line. The actual route that the line takes is controlled by the &quot;wire bend&quot; setting for the line, which you can control with your right mouse button. Schematic designers tend to like nice straight lines with right angles. Net with same name are connected to one another, regardless of whether or not they appear continuous on the drawing. This is very useful when they appear on different schematic sheets.
Buses receive names which determine which signals they include. A bus is a drawing object. It does not create any electrical connections. Connections are always created by means of the nets and their names. The associated menu function is a special feature of a bus. A menu opens if you click onto the bus with NET. The contents of the menu are determined by the bus name. Clicking on the bus line while the NET command is active, opens the menu as shown. The name of the net that is to be placed is selected from here. If no bus name is used, a name of the form B$1 is automatically allocated. This name can be changed with the NAME command at any time.
A final thing that should be done before creating the PCB-layout is running the Electrical Rule Check (ERC). This is done by the ERC-command from the toolbar. will check whether the pins designated outputs are connected to inputs, whether there are obvious missing junctions, and so on. It also warns if you are connecting the supply voltage inappropriately or if you forget to connect it. You should, however, know that an ERC can not guarantee that no errors exist, but only help pinpointing some of the more obvious ones. If the ERC comes up with any warnings, you should try to pinpoint and solve the problem before moving on. Sometimes an error message or warning can be tolerated. In this case you can click “Approve” to ignore them. Once all ERC errors and warnings have been eliminated, you can go on to routing the circuit board.
EAGLE can output drawings, for example for documentation purposes, using the PRINT command which can be found in the File menus. The PRINT command allows generating PDF files, too. You also can use the EXPORT command to provide ASCII text files which can be used e.g. to transfer data from EAGLE to other programs, or to generate an image file from the current drawing. Here we list some output files.
Many documentation items can be generated with the aid of User Language programs. The parts list can be created by bom.ulp. Start it from the Schematic Editor, using the RUN command. The Bill Of Material window with the parts summary opens first. It is possible to import additional information from a database file into the parts list ( Load ), or to create a new database with its own properties such as manufacturer, stores number, material number or price.
When you can’t find the component in the included libraries, you have to draw it yourself. First we create a new library. In Control Panel choose “File -> New -> Library”. This opens the library editor with a new empty library. Click “symbol” button in the toolbar to create a new symbol based on the manufacturer’s specification. If there is an existing package you can use, you can easily copy it to your new library file. Otherwise, you have to draw a new one based on manufacturer’s package dimensions in Package Editor. In Device Editor, you need to connect the symbol and footptint. The final thing to do before saving the library is to set the prefix to IC. This is the prefix used for naming the component when it is added to the schematics.
Now you may notice that to finish a schematic is based on different commands. For instance, to add a component, you need ADD command. EAGLE designs to use multiple ways to enter a command, listed in the page.
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1. Build Your Own PCB with EAGLE II – Drawing a Schematic <ul><li>Source: CadSoft </li></ul>
2. Introduction <ul><li>Purpose </li></ul><ul><ul><li>To explain how to draw a schematic using EAGLE Schematic Editor. </li></ul></ul><ul><li>Outline </li></ul><ul><ul><li>EAGLE Schematic Editor User Interface </li></ul></ul><ul><ul><li>Key steps for drawing a schematic </li></ul></ul><ul><ul><li>Schematic output </li></ul></ul><ul><ul><li>Component design </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>14 pages </li></ul></ul>
3. Schematic Editor User Interface Title Bar Toolbar Menu Bar Parameter toolbar Command Line Command Toolbar Working Area Coordinate Display Status Bar
4. Creating a New Schematic <ul><li>If your right click on the project and select “New -> Schematic”, it will bring up the Schematics Editor Window; or </li></ul><ul><li>You can select “File -> New -> Schematic to start the Schematics Editor. </li></ul>
5. Adding a Frame <ul><li>Click “Add” button ( ) in command toolbar or type “add” in command line to open “ADD” dialog. </li></ul><ul><li>Select a suitable frame from the frames-library (frames.lbr) . </li></ul><ul><li>After add a frame, click the stop icon or press ESC to Terminate the ADD command. </li></ul>ADD Command : Add elements into a drawing. Library List Search Box Symbol Preview Package Preview Description Area
6. Adding Components <ul><li>If you have place a component with ADD, and then want to return to the ADD dialog in order to choose a new component, press the ESC key or click the ADD icon again. </li></ul>Definition of attributes for devices Cope devices Delete devices Swap equivalent gates on a schematic Call a specific symbol from a device Mirror devices Move devices Display and change the name of a device Define a package variant for a device Replace a device Rotate a device Highlight a device Separate text variables and attributes from devices Display and change values Define the possible technology parts of a device name
7. Wiring the Schematic <ul><li>Use the NET command ( ), not WIRE to draw net connections. </li></ul><ul><li>Nets with the same name are affiliated with each other. </li></ul>NET Command : Draw nets on a schematic. Nets with same name
8. Drawing a Bus <ul><li>A bus has to be drawn with the BUS command ( ). </li></ul><ul><li>A bus does not create any electrical connections. </li></ul>BUS Command : Draw buses in a schematic. Bus Name List of Net name
9. Electrical Rule Check (ERC) <ul><li>The ERC command ( ) is used to test schematics for electrical errors. </li></ul><ul><li>The results are warnings and error messages listed in the ERC window. </li></ul><ul><li>The ERC can only discover possible error sources. </li></ul>ERC Command : Electrical rule check. A line points to the corresponding location in a schematic for the selected errors or warnings.
10. Schematic Output <ul><li>For documentation purposes, the drawing can be output using the PRINT command. </li></ul><ul><li>The PRINT command allows generating PDF files. </li></ul><ul><li>The EXPORT command is used to provide you with ASCII text files which can be used to transfer data from EAGLE to other programs. </li></ul><ul><ul><li>Netlist: generates a netlist for the loaded schematic. </li></ul></ul><ul><ul><li>Partlist: generates a component list for schematics. </li></ul></ul><ul><ul><li>Pinlist: generates a list with pins, containing the pin directions and the names of the nets connected to the pins. </li></ul></ul><ul><ul><li>Image: exports an image file (*.bmp, *.png, *.pbm, *.tif, etc.) </li></ul></ul>
11. Generating Bill of Material <ul><li>Select “File -> Run…”, a dialog pops up for selecting the User Language Programs. </li></ul>Select “bom.ulp” to generate the BOM
12. Component Design Symbol Editor Package Editor Device Editor Package Button Symbol Button Device Button
13. Some Hints <ul><li>Many EAGLE commands can be entered three ways </li></ul><ul><ul><li>via the buttons on the left-hand vertical toolbar </li></ul></ul><ul><ul><li>via the text menus on the top of the window </li></ul></ul><ul><ul><li>via the text command input area </li></ul></ul>Don't get confused...
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