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
Type Schematic Board Library Window Schematic Editor Layout Editor Library Editor File Types Name *.SCH *.BRD *.LBR
Drawing window for 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.
