Drawings

The Drawing Set

Design Drawings System Block Diagram Circuit Design Sketch Packaging Plan

Working SchematicBreadboard DrawingPC Board Design LayoutPC Board Artwork

Electronic Project Design and Fabrication 4th edition, Ronald Reis ( page 76)

The Drawing Set (Continued)

PC Board Fabrication DrawingPC Assembly DrawingSheet Metal DrawingWiring DiagramFinal Packaging Drawing

Electronic Project Design and Fabrication 4th edition, Ronald Reis ( page 76)

The Design Drawings

System Block Diagram

Electronic Project Design and Fabrication 4th edition, Ronald Reis ( page 60)

Circuit Design Sketch

Electronic Project Design and Fabrication 4th edition, Ronald Reis ( page 61)

Packing Plan

Electronic Project Design and Fabrication 4th edition, Ronald Reis ( page 61)

Introduction to Schematics

ANSI and IEEE

Define accepted practices and symbols for schematic and electrical diagrams.Most CAD program conform to these standards.

Schematic symbols are covered by (ANSI Y32.2)

Standard Symbols

Designators

Resistor - RSwitch - STransformer – TTransistor - QIC – UCrystal – Y

Capacitor – CDiode – DFuse – FRelay – KCoil/Inductor – LMicrophone – MK

Protel places the proper designator on all parts for you.

Layout Considerations

If a schematic is large, split the schematic into functional sections, each on a separate page, making sure to properly label connection ports.

Layout should be arrange to develop from the top to bottom and from left to right as the signal flows

Layout Considerations (continued)

Voltages should be clearly marked.

Ground symbols should always be drawn below the line.

Proper Signal Flow Example

INPUTS Outputs

Higher Potential

Lower Potential

Layout Considerations (continued)

All connecting lines are either vertical or horizontal. There are a few exceptions:

Bus connections Flip flops Bridge Rectifiers

Layout Considerations (continued)

Similar circuits should be drawn uniformly.

Common circuits should be drawn according to accepted conventions.

ExampleNon-Standard Schematic

ExampleNon-Standard Schematic

Standard Schematic

Layout Considerations (continued)

When identifying values of resistors, capacitors or inductors: Use proper unit prefixes

p for Pico u for Micro m for milli K for Kilo M for Mega

For resistors, ohms is implied and should not be used.

Layout Considerations (continued)

Parts should be numbered starting from the upper left hand side of the schematic to the lower right hand side.

This method makes it very easy to locate parts on the schematic.

Part Numbering Example

Layout Considerations (continued)

Short dashed lines indicate mechanical interconnects.

Each schematic should have a filled in title block.

Layout Considerations (continued)

Lines should be drawn with the minimum of crossovers and joggles.

Junctions of 3 or more wires should be marked with a dot to indicate a connection. No dot, no connection.

Lines between components should take the shortest path.

Example of Crossover and Joggles

Connections and Dots

What’s Wrong With This Picture?

Improved Schematic