Schematic Drawing & PCB Design

Schematic Drawing & PCB Design James Bonnyman University of Nottingham , Elec Eng Dept.

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

Introduction (2) • Tools Available here in EEE • EasyPC • Protel • Good Practice • Assessments and things to come

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

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 1950’s ) NO! YES YES

Schematic Diagrams • Rules • Four wires must not connect at at point; ie Wires must not cross & connect NO YES

Schematic Diagrams • Rules • Always use the same symbol for the same device ( eg Resistors as boxes & zig-zag’s ) YES NO

Schematic Diagrams • Rules • Wires & components go horizontally or vertically unless there is a good reason to do otherwise YES NO

Schematic Diagrams • Rules • Label pin numbers on the outside of a symbol, signal names on the inside 3 7 + 6 2 - 4

IC 748 3 Schematic Diagrams • Rules • All parts should have values or types indicated; it’s best to give all parts a label too, eg R or IC 7 3 3 7 + 6 2 - 4

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 /U1a[74LS04] 1[A=N0004] 2[Y=N0000] _DESTPACK:DIL # /U1b[74LS04] 3[A=N0000] 4[Y=N0006] _DESTPACK:DIL #

Netlist -> 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

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 )

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.

The milling process

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

A zoomed in version

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

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.

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

Schematic Drawing & PCB Design