Page 205 - Make Your Own PCBs with EAGLE from Schematic Designs to Finished Boards

FIGURE 8-5 Adding a netclass.

This is by no means essential, but given that if all the segements of one digit are lit, there could be
over 100 mA flowing through the collector-emitter path of the transistors. Thus, to change the net
class of the four nets that connect the collector of the transistor to DIG1 through DIG4 on the display,

you also should set any GND net path to be of class “Power” too. The easy way to change these
netclasses is to use the Change command, select “Class” and then “1 Power,” and then click on the
nets you need to change.
Having drawn the schematic, it’s time to run the electric rule checker (ERC). The result of this is
shown in Figure 8-6.

FIGURE 8-6 ERC results.

At first sight, it seems like there are some things to worry about. But actually there aren’t. The
errors referring to power supplies all spring from unmade connections to power on the Arduino.
Because the Arduino is providing power to the shield, not the other way around, we can safely ignore
these. None of the warnings are relevant either.

PCB Layout

When you first select the menu option “Switch to Board,” the board layout that is subsequently
generated will look something like Figure 8-7.