eagle schematic module pcb layout editor autorouter module

EAGLE

• Schematic Module

• PCB Layout Editor

• Autorouter Module

EAGLE Freeware

• Maximum printed circuit board area is

– 4 x 3.2 inches

• Only 2 signal layers

• Single sheet schematic

File Types

Type

Schematic

Board

Library

Window

Schematic Editor

Layout Editor

Library Editor

Name

*.SCH*.BRD*.LBR

Drawing windowfor schematics

Schematic Drawing

Grid

• The standard grid for schematics is 0.1 inches.

• Symbols should be placed on this grid or a multiple of it.

• Otherwise, it can happen that nets cannot be connected to the pins.

Commands

ADD - place components

MOVE - move components

NET - make logical connections

BUS - place buses, drawing element only

DELETE - erase individual segments

NAME - allocate names. B$ for buses, P$

for pins and N$ for nets

Commands

LABEL - place bus/net names in any

location

SHOW - show names & details of elements

and objects

JUNCTION - connecting node at the

intersection of nets which are to

be connected to each other

Net, Junction

Bus, Power, Gnd, Label

Commands

SMASH - allow you to change & rotate

the names and values of symbols

VALUE - change the value of resistors,

capacitors, ICs, etc.

Name & Value of Parts

Selecting objects

The cursor takes on the form of an arrow when you want to select an object whose origin is very close to the origin of another object. In this sort of case, the solution is:

Click the left mouse button to select the highlighted object. Click the right mouse button if you want to go on to the next possible object.

PCB Design Procedure

1. Create the board file (.brd)

2. Define measurement units

3. Define board size and shape

- use WIRE command to draw/modify the board outline in the Dimension layer

4. Set up the grid for component placement

PCB Design Procedure (Con’t)

5. Placing Components with the help of the Ratsnest

6. Perform automatic routing or manual routing

Component Placement

• Use Ratsnest to show connection airwires

• Place components to make airwires short

• Try to make airwires uncrossed and no twisted buses

• Try to place components in matrix form and with same orientation

Ratsnest

PCB Drawing

Top Layer (Component layer)

Bottom Layer (Solder layer)

Auto-routing

• Automatic placement of copper tracks and vias for pin connections on the board

• Single layer, double-layer and multi-layer routing

• Use the command RIPUP to change certain unsatisfactory routed tracks into airwires and subsequently route them manually

Auto-routing (Con’t)

• Power supply and ground tracks are usually routed manually before the autorouter is used

• Critical signals (high frequency, high impedance or time-critical signals) are usually routed manually with care

Commands

DISPLAY - get a good overview if some information s not shown

MOVE - move wires, vias or components

GROUP - allow you to select several objects

SPLIT - add a bend in a wire

Commands

CHANGE WIDTH - alter the width of a wire segment

CHANGE LAYER - to move a wire segment to another layer

Commands

DELETE - change a wire segment into an airwire

ROUTE - change an airwire into a wire

RIPUP - turn routed signal tracks into airwires

(turn specified signal OR all signals except specified ones)

Commands

SHOW - to highlight airwires, wires or components

UNDO/REDO - to reverse an action

- to redo a reversed action

Forward Annotation

• Changes made on the schematic drawing will reflect on the PCB drawing

– e.g. choose another NAND gate from the same 7400 IC (Quad 2-input NAND)

– e.g. choose the other OPAMP from the same LM324 IC (Quad OPAMP)

Back Annotation

• Changes made on a PCB drawing will reflect back on its source schematic

– e.g. Rename components, nets

• Note: Some changes are only possible to be carried out from the schematic, no back annotation is allowed.

Using Forward & Back Annotation

Rule 1

Use same name but different file extensions in the same directory for both schematic and PCB drawings. E.g. circuit.sch, circuit.brd

Rule 2

When working on a board, never close the schematic window and vice versa.