Schematic Drawing

1
Schematic Drawing PCB Design

• James Bonnyman

University of Nottingham , Elec Eng Dept.
2
Introduction (1)

• Producing a PCB from scratch in EEE
• Schematic Layout
• PCB Layout ( via a netlist )
• Production of required file
• Milling of the final board

3
Introduction (2)

• Tools Available here in EEE
• EasyPC
• Protel
• Good Practice
• Assessments and things to come

4
Schematic Diagrams

• Layout of a circuit in terms of individual
  components ( not devices, eg 74ALS04)
• Regardless of drawn by hand or on a PC it should
  be
• Clearly labeled
• Unambiguous

5
Schematic Diagrams

• Rules
• Wires connecting are indicated by a heavy black
  dot wired crossing but not connecting, have no
  dot ( do not use a little jog they went out in
  the 1950s )

NO!
YES
YES
6
Schematic Diagrams

• Rules
• Four wires must not connect at at point ie Wires
  must not cross connect

YES
NO
7
Schematic Diagrams

• Rules
• Always use the same symbol for the same device (
  eg Resistors as boxes zig-zags )

YES
NO
8
Schematic Diagrams

• Rules
• Wires components go horizontally or vertically
  unless there is a good reason to do otherwise

YES
NO
9
Schematic Diagrams

• Rules
• Label pin numbers on the outside of a symbol,
  signal names on the inside

3
7

6
2
-
4
10
Schematic Diagrams

• Rules
• All parts should have values or types indicated
  its best to give all parts a label too, eg R or
  IC

7
3
3
7

6
2
-
4
11
Netlist

• When producing a netlist the system
• Takes the schematic diagram and produces a file
  that contains information on the components used.
• Details the connections between components.

Written by EPCWIN 3.0.4 /U1a74LS04 1AN0004
2YN0000 _DESTPACKDIL /U1b74LS04 3AN000
0 4YN0006 _DESTPACKDIL
12
Netlist -gt PCB

• The netlist file is then read, the system
• Replacing the schematic components with physical
  components.
• showing the connections, often as a rats-nest
• We then
• Route the board ( add tracks ), either manually
  or with the aid of an auto-router
• Produce files suitable for production of the
  final PCB, the standard type being Gerber files

13
Final Stage

• The Gerber files are used to produce the final
  PCB.
• Gerber files include details of
• Drilling Holes
• Board outlines
• Track Paths
• Techniques using them for production include
• Etching
• Routing ( as here in EEE )

14
Tools Available

• We have two PCB production packages available (
  both on NAL )
• Easy-PC
• Basic, easy to use windows PCB design tool
• Protel
• Comprehensive, but very time-consuming to learn
  to use.

15
The milling process
16
Demo Time

• We will now take a quick look at Easy PC.

17
A zoomed in version
18
Good Practice

• There are a number of pointers on the separate
  sheet, taken from

The Art of Electronics, Horrowitz, Paul Hill,
Winfield. Pub. Cambridge University Press 1998
19
Assessment

• Draw using Easy-PC ( or protel if you wish ) a
  schematic for the circuit provided
• From this produce a PCB for this circuit.
• Printouts of BOTH are to be submitted along with
  your review paper.

20
Next Week

• Careers Lecture
• Given by Peter Kay Debra Cass of the Careers
  service.
• Topics covered include
• CV Interview techiques (provisional)
• Attendance is MANDATORY