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.