Page 249 - Make Your Own PCBs with EAGLE from Schematic Designs to Finished Boards

FIGURE 11-12 Changing a pin.

The various directions allowed for a pin are used by the electrical result checker (ERC). Thus,
for example, it will flag outputs being connected together on a logic gate. In this case, we are
specifying that the pin is electrically speaking passive (pass). This isn’t really true, but selecting

this option will prevent any false warnings from the ERC. Repeat this process for the GRID and
CATHODE pins.

You will have noticed an area at the bottom of the parts window suggesting that you Use the
DESCRIPTION command to enter a description of this object. To do this,
click on the “Description” hyperlink immediately above that message. This will enter a new window
into which you can enter a description of the symbol.
In addition to the two triodes, the tube also has three connections used to provide power to the
heater element, one of the connections being a center tap. We therefore need to bring the three

“power” pins that we can collect together into a third symbol. Even though there are two triodes in
the glass tube, they have shared connections for the heater power.
Create a new symbol, and call it HEATER_SUPPLY. Place three pins on the design, and change

their names to “HA,” “HC,” and “HB” (heater A, B, and common). Pick a pin style with a bit of a tail
on it. The end result of this is shown in Figure 11-13.