EAGLE CAD - Libraries

A library is a file that contains electronic devices. Every device is made out of the symbol (used in the schematic) and the package (used in the board).

EAGLE CAD has libraries for each family of devices like passive components (rcl.lbr), diodes (diode.lbr), transistors (transistor.lbr), power supplies (supply.lbr) and so on.

To use a certain library in a project you should first say tot the program to use that library. This is accomplished in the schematic editor by selecting the Use option from the Library menu. A selection window appear, that allows you to chose the libraries you want to include/use in the project.

EAGLE CAD - How to add a library to the project

EAGLE CAD - Use Library Window

Once included, the library can be accessed with the tool Add from the tool panel. Using this tool opens a window that contains all the libraries that are in use.

EAGLE CAD - Add window

If you want to place a resistor on your schematic you should go to the rcl.lbr library and select the appropriate type for your project:

EAGLE CAD - Adding a resistor to the schematic

On the left side of the Add window I selected the rcl.lbr library which expanded. From the expanded list I selected the R-EU option which expanded as well, allowing me to see all available types of resistors.

The left column contains the resistors names and the right column contains the name of the package (footprint). The selected resistor is named R-EU_0207/7 and it's package is a 0207/7 (THT resistor).

The right side of the Add window contains images of the symbol and package, as well as additional data about the selected component.

To use the selected device into schematic simply press the OK button (right side, bottom) and you will be allowed to place the device wherever you want on the workspace by left-clicking. You can place how many components you like, until you press the ESC button.

EAGLE CAD - Adding a resistor to the schematic

Commonly used libraries:

• Power Supply - supply1.lbr, supply2.lbr
• Pin Headers - con-lsta.lbr, con-lstb.lbr
• Screw Connectors - con-ptr500.lbr
• Resistors (european symbol) - rcl.lbr > R-EU_ (for US symbols replace EU with US)
• Capacitors (european symbol) - rcl.lbr > C-EU
• Polarized Capacitors (european symbol) - rcl.lbr > CPOL-EU
• Inductors (european symbol) - rcl.lbr > L-EU
• Diodes - diode.lbr
• NPN Transistors - transistor-npn.lbr
• PNP Transistors - transistor-pnp.lbr
• Field Effect Transistor - transistor-fet.lbr
• LED's - led.lbr > led
• Voltage Regulators - v-reg.lbr

Free downloadable libraries are to be found on CADSOFT's website.

Another valuable libraries resource can be found on Element14's website (one library for each manufacturer).
To create your own libraries check out this tutorial.