CHAPTER 23 ■ THE MOTHERBOARD
Looking at the end results, there are a couple of other factors that make printed circuit boards better
than point-to-point-soldered circuits. As illustrated in Figure 23-3, the point-to-point circuit (on the left) is
much messier, takes up more space, and is more likely to fail (due to loose wires) than is the printed circuit
(on the right).
Figure 23-3. Underside of breadboard showing point-to-point wiring (left) and printed circuit board (right)
after soldering
I’ve created the line-following robot both ways: with point-to-point soldering and with a printed circuit
board. Because there aren’t an overwhelming number of connections and because you can build the board
up in modules, any beginner should be able to create the circuit using point-to-point soldering. Point-to-
point instructions follow in the next sections of this chapter.
However, I highly recommend purchasing a printed circuit board with the line-following circuit from
Solarbotics (#SandPCB $12), even if you don’t buy the full kit. This will save you soldering, frustration, and
debugging, so that you can more quickly reach the goal of experimenting with your finished robot. It’s not cheating
to use a PCB since you’ve already built the circuit on a solderless breadboard. It’s an optimization of your time.
Instructions for stuffing the ready-made PCB are posted at http://www.robotroom.com/SandwichPCB.html.
Point-to-Point Soldering the Line-Following Circuit
Soldering the line-following circuit is the most arduous part of building Sandwich. But, the soldering
practice you’ve had with the motors and switches should help a lot. Be patient.
If possible, obtain a second set of parts so that the original parts from the tested circuit can remain on
the solderless breadboard. The line-following circuit components should cost less than $10.
If you’re not buying the PCB, obtain a perforated breadboard (also called perf board, stripboard, or
prototyping board) that is approximately 7 cm (or less) by 10 cm (or less), with 700 or more holes spaced at
0.100 of an inch. Each hole should have copper plating around it. Examples are: All Electronics #PC-4 $2.00
or Adafruit.com #723 $5.95 or #1609 $4.50.
Laying Out the Line-Following Circuit Components
A grid-style solderable breadboard is more freeform than a solderless breadboard. You can change
the positions of components considerably from the rigid 5-position groups imposed by the solderless
breadboard. Since the robot is going to be stuck with whatever arrangement you solder together, take some
time to carefully plan the positions of the components.