Breadboard Basics
A breadboard
is a rectangular plastic box filled with holes,
which have contacts in which you can insert electronic components and
wires. A breadboard is what you use to string together a temporary
version of your circuit. You don’t have to solder wires or anything
else; instead, you poke your components and wires into the little
contact holes arranged in rows and connected by lines of metal; then you
can connect your components together with wires to form your circuit.
The nice thing about
breadboards is that you can change your mind and replace or rearrange
components as you like. You typically create an electronics project on a
breadboard to make sure that everything works. If it’s a project you
wish to save, you can create a more permanent version. We use
breadboarded versions of circuits exclusively in this part of the web
site.
If you want to create a permanent version of your
circuit, you need to create a soldered or printed circuit board; see the
sidebar, “Printed circuit boards,” to find out how to go about that.
There are a few different sizes of breadboards, some of which are shown
in Figure 3-10. You can link breadboards to make a larger circuit, like
the one shown in Figure 3-11. See "Discovering schematics" for more about how to build
a breadboard.
Printed circuit boards
If you create a circuit on a breadboard and decide
that it’s worthy of immortality, you can make it permanent by soldering
components in place on a printed circuit board. To do this, you have to
get your hands on a universal printed circuit board. This is much like a
breadboard except that you can solder all the connections you’ve made to
keep them around. A universal printed circuit board has rows of
individual holes throughout the board with copper pads around each hole
and metal lines connecting the holes in each row, like in a breadboard.
You mount parts on the face of the board and then pass leads through
holes to the components. You can solder the leads to the copper pads on
the bottom of the board.
Universal printed circuit boards are available in a
variety of patterns of contact holes and metal lines. The figure here
shows one we like because there are rows on either side that accommodate
discrete components handily. This circuit board is made by One Pass,
Inc. (
www.onepassinc.com).
You can get custom printed circuit boards made for
your circuit; this is typically done by submitting a drawing of your
circuit to a printed circuit board company. These boards eliminate the
need to solder jumper wires between components.
Wires pull it all together
When you place components in a
breadboard, you don’t get much action until you connect those components
with wire. Wire used in electronics is copper
You can get custom printed circuit boards made for your circuit; this is
typically done by submitting a drawing of your circuit to a printed
circuit board company. These boards eliminate the need to solder jumper
wires between components.
surrounded by a plastic insulator, usually called
hookup wire.
Hookup wire comes in various diameters referred to
as a
gauge.
The standard gauge measurement used in the U.S. is
American Wire Gauge, also referred to as
AWG.
We generally use 22 gauge or 20 gauge wire. Someone
decided at some point that the smaller the gauge, the larger the
diameter of wire. For example, 20 gauge wire is 0.032" in diameter, and
22 gauge wire is 0.025" in diameter. Don’t ask us why — just memorize
this fact! We use 22 gauge solid wire for most of the projects in this
book. (Okay, in two chapters, we use 20 gauge; and in one, we use 26
gauge, but you’ll find out why when you get to those projects.)
Use solid wire — never stranded wire — between
components within a breadboard because stranded tends to separate when
you try to insert it into the holes of a breadboard. You can buy hookup
wire in spools; we generally get spools containing 100 feet of wire. If
you are starting with only a few projects, you can get smaller spools
containing as little as 30 feet of wire.
The insulating plastic that surrounds wire is made in
different colors. Pick up a spool of red and a spool of black. Using
different colors helps you to identify the purpose of different wires in
your project. You might also consider buying an assortment of different
lengths of prestripped and prebent 22 gauge wire jumpers.
Jumper wires
— which
are used to connect components in a breadboard — save you a lot of time
you might otherwise spend cutting small wires to length, stripping them,
and bending the stripped wire when you’re building a breadboard.
Insulating those naked wires
You will also use various
materials to insulate bare wires. You can use electrical tape, for
example, to insulate solder joints that might touch each other and cause
a short. Heat shrink tubing is a tidy way to insulate the point where
wires connect in a solder joint. Heat shrink tubing is simply a plastic
tube. When you slip a short length of this tubing over a solder joint
and apply heat, the plastic tube shrinks, providing an insulating layer
around the wire. When working with 22 gauge wire, we use 3⁄32
"
heat shrink tubing.
Liquid electrical tape is also handy to insulate bare
wire in situations where heat shrink tubing or conventional electrical
tape doesn’t work very well. We use liquid electrical tape in Chapters 5
and 10, for example.
Connectors
Finally, terminal blocks are
used to connect wires from components such as speakers, motors, and
microphones to the breadboard. A
terminal block
is a
small block of plastic that you mount on a breadboard. You insert the
wires into the terminal block through a hole in the block and then
tighten screws to hold the wire securely. When choosing terminal blocks,
the diameter of the pin that inserts into the breadboard or circuit
board is important. Some terminal blocks that work fine in circuit
boards where the components are soldered in do not stay in place on
breadboards. We have had the most success with RadioShack part
#276-1388.