3.8. Drawing Electronic Schematics

Learning to draw accurate schematic diagrams is an essential skill for communicating your electronic design, and a required element for project reports.

Traditionally schematics were simply drawn on paper using drafting tools, and it is still feasible to draw schematic in ordinary graphics tools such as Illustrator, but specialized CAD software makes it easier to follow conventions and edit diagrams without damaging them.

Please note that a schematic is an abstract connection diagram and shows circuit topology without necessarily reflecting the physical shape. The breadboard diagrams are not acceptable for our documentation purposes.

The schematic diagrams in the course materials were mostly produced using Fritzing with a few produced using EAGLE. Fritzing is a relatively new DIY-friendly system which is quick to learn but limited. EAGLE is the de-facto standard for hobby electronics since they offer a feature-limited free edition, but has a quirky user interface and takes a long time to learn. EAGLE is quite capable of producing sophisticated designs, but can be very time-consuming.

We recommend learning to use Fritzing first. The course repository contains several folders of Fritzing parts resources which may help: see the Fritzing parts folder for our locally-defined parts, and the Fritzing images folder for source images useful in creating new parts.

We also have a few EAGLE resources for those you wish to try that route.

Some students have had success with the commercial browser-based CircuitLab.

3.8.1. PCB Design

Printed circuit board design is not included in this course. But please note that for many electronic CAD programs, drawing the schematic is the first step in the physical design of the circuit in the form of a PCB board. It is for this reason that these programs include part footprints in the specification of a part. If the mechanical description in the footprint precisely corresponds to the abstract symbolic description in the schematic symbol, then a correctly drawn schematic can be translated into a correct copper design for circuit board traces and drill pattern using these tools.