Page 451 - Robot Builder's Bonanza

420 MAKING CIRCUIT BOARDS

Whether you use Eagle or some other software, here is the basic process for designing and
making your printed circuit board:
1. Create a schematic of your circuit. The schematic uses symbols for all electronic parts
and lines to indicate how everything is connected together.
2. Create the PCB layout by dragging the outlines of your parts onto a template of the
size of board you want.
3. Convert the schematic and the PCB layout. Finish the PCB design by linking compo-
nents that need to be connected.
4. If you are having a service produce the board, order the board by submitting it. Pay-
ment is collected up front. Most services will prepare two or three boards for the base
price.

PRINTED CIRCUIT BOARD DETAILS

Following are concepts you should know about when making printed circuit boards:
Pads, traces: PCBs are composed of pads and traces. The metal leads of the components
are soldered to pads, and the pads are connected together via traces. The traces are the
interconnecting wires of a PCB.
One or two sides: All printed circuit boards have two sides, but you may elect to have pads
and traces on one side only. It’s a little cheaper that way.
Layers: Each side of the PCB can be separated into individual layers. The layers are insu-
lated from one another by a protective film, so that the pads and traces in one layer
don’t short- circuit into those of another layer. Your quick- turn PCB may have two, four,
six, even eight layers. The more layers, the more expensive it is.
Soldermask: If you choose to order it as an option, a soldermask applies an insulating
lacquer over your board that covers everything except the pads to which components
are to be soldered.
Silkscreening: Another option is the silkscreen legend, which marks where the compo-
nents go. You can include the outline shapes of the components, component values,
part number references, even limericks. It’s completely up to you.

Producing Arduino- Specific Boards

with Fritzing

Fritzing (available at www.fritzing.org) is a nifty, free ECAD program designed for creating
printed circuit boards. What sets it apart is that it is designed from the ground up to support
the open- source Arduino, one of the key microcontrollers used in projects throughout this
book.
By connecting wires on a virtual solderless breadboard, your circuit designs are automati-
cally converted to schematics and printed circuit board layouts. These layouts are meant to be
Arduino shields, circuit boards that attach on top of the Arduino and extend its functionality.
(The Arduino and shields are detailed in Chapter 37, “Using the Arduino.”)
Figure 33- 6 shows one of the example projects that come with the Fritzing software, a step-
per motor experimenter board. Simply by clicking tab buttons inside the Fritzing program, you
can view the circuit as a schematic (see Figure 33- 7) and even as a Arduino shield PCB.

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