In general, the circuit board design should go through the following steps to complete the schematic design in the SCH design environment.

First, set the size of the drawings used in schematic;

It is best to determine the size of drawings in the design of the beginning. Although the size and attributes of the drawings can be changed during the design process, good habits will benefit future design processes.

Second, the schematic symbols are not available in the production component library;

Because many of the components are not included in the Protel99, then the user needs to draw their own schematic symbols of the components, and eventually applied to the circuit schematic drawing process.

Third, think about the idea of components in the circuit diagram;

Before placing the components, you need to roughly estimate the location and distribution of components. If you ignore this step, sometimes unexpected difficulties will be caused to the back of the work!

Fourth, consider the component layout;

This is the most critical step in drawing the schematic. Although in a simple circuit diagram, even if you are not too concerned about the layout of the components, and ultimately can be successfully automated or manual wiring, in the design of more complex circuit diagram, the rationality of the component layout will directly affect the schematic drawing efficiency and the appearance of the schematic.

Fifth, the electrical connection of schematic diagram;

The lines mentioned here may be wires, contacts, or buses and their branch lines. Of course, in large-scale system design, the schematic line is not much; the network label is used wider to replace the direct line connection. This can ensure the electrical connection of circuit and avoid chaotic schematic.

Six, place the note.

This can make the circuit diagram clear and enhance readability. At the same time, it is also one of the necessary qualities that a qualified PCB circuit design staff must have.