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Drawing schematics

Creating a new schematic

To create a schematic within your project, right click the project in the Eagle main window, choose "New", "Schematic", as shown below.

The schematic drawing tool opens, now click "File", "Save as..." and name your schematic (e.g. "main.sch"). Your schematic is now saved and included in the project.

Drawing a schematic

The schematic software has various tools in order to organize and draw your schematics. An overview of the tools is provided in the following subsections.

Defining the drawing area

To start, one defines if the paper size of the schematic. This is done by adding a part (to add a part, see next subsection) named "FRAME", use the DIN**_L parts, where ** represents A4, A3, etc, depending on the desired size. Add the frame to the schematic and draw everything inside the frame.

Placing parts

To place a component, select the "add" symbol on the left bar. This opens the part library. Note that all parts have a red cross at their "gripping point". Any tool you want to apply to the part must be applied at location of the red cross.

Rotating and mirroring

When placing or moving parts, use the right mouse button to rotate. Mirroring can be done using the "mirror" tool.

Connecting parts

To connect pins of components, nets are used (do not use the "wire" tool). You can start connecting by clicking the "nets"  symbol.

Hint: ANY operation in Eagle is cancelled by pressing [ESC] on the keyboard.

Hint: Place enough ceramic decoupling capacitors as close as possible to all semiconductor power supply nets (100 nF for signal, up to > 1 uF for power) to prevent voltage dips/ringing caused by the trace inductance.

Net naming

When routing your PCB, it is very handy if your nets are named correctly. Naming a net can be done using the "name" tool. For instance, name the signal line for a switch to reset a microcontroller "UC_RESET". To show the name of the net on the schematic, use the "label"  tool.

You can connect nets together just by using identical names as shown in the figure below. Select "yes" if asked to conncet the nets. Connections using net names can make the schematic clean, but be careful not to make it unreadable.

Be warned: if you have double net names, the nets will be connected together on the PCB even if there is no physical net between them.

Supply nets

Most of your parts will require some power. You could connect all power pins using nets, but Eagle offers more a convenient manner, comparable to net names. Using the parts from "supply symbol" (search for it in the add parts tool) you can easily create ground nets (GND) and supply nets (e.g. +5V, +12V). The example schematic above uses these symbols for its supply nets.

Deleting parts

To delete a part, select the "delete" symbol and click on the item you want to delete.

Changing part values and names

Parts are automatically named and numbered, it is recommended to stick with this automatic numbering. If neccessary, you can change its name (e.g. R21 or C5) using the "name" tool. More importantly, the value (e.g. 1k or 10 uF) can be changed by using the "value"  tool.

Group operations

To apply operations to a group of parts, use the "group"   tool to select the group of parts you want to edit. Next, select the tool you want to use (e.g. moving ) and right-click on the schematic. Then select "Move: group" to apply the operation to the group.

Drawing (other)

Things that do not have any physical meaning (e.g. structuring your schematic) can be done using the "wire", "text", "circle" and "arc" tools.

Part libraries

The schematic tool uses part libraries for your component list. If more parts are needed (e.g. your part is not in the list), you can include a library which include this part. This can be done using the Library menu on the top of the window. Select "Use..." to include an additional part library in your component list. Select "update all" if you have made changes in your (already included) library files.

If you find your part list is too long, you can drop libraries. This is done using the "add component" tool. Select the library you want to drop and click the "Drop" button.