The solderless breadboard (generally a large, white, plastic component with rows
and columns of holes) provides a working space where temporary circuits can
easily be built1. Leads of electrical components (e.g. resistors) can
easily be pushed into the breadboard holes.
A typical breadboard has a large number of holes which are organized in rows of
five or six. The holes in any single row are electrically connected to one
another. Any two rows of holes are isolated electrically from one another. A
central groove or channel generally separates two banks of these holes. The
overall situation is illustrated in Fig. 1. The holes on either side of this
channel are also not electrically connected. The channel is not
important to us now, but will become useful in later lab assignments when we
create circuits containing integrated circuit (IC) chips packaged as DIPS (Dual
Holes in a breadboard which are electrically connected are said to be at the
same node in a circuit. A node is a point in a circuit where two or
more components are interconnected by a short circuit. No energy is
required to transfer current through a short circuit, so the short circuit
does not restrict the flow of current—it has zero resistance. This
means that there can be (theoretically) no voltage difference between two
holes in any single row in a breadboard.
No current will flow from one hole to another on a breadboard if the holes
are not electrically connected. Different physical points in a circuit which
are not electrically connected are sometimes said to be connected by an
open circuit. No current can flow through an open circuit. There is no
limit to the possible voltage difference across an open
Some breadboards have, in addition to the hole layout shown in Fig. 1,
supplementary rows of holes running the entire length of the breadboard. These
rows are called bus strips, and are indicated in Fig. 2. Bus strips are
mostly useful when connecting the same voltage level at multiple locations in
larger-scale circuits. Ground and fixed voltage supplies, for example, may be
used in multiple stages in an overall circuit. Bus strips are often marked with
a red or blue line running next to them.
A number of additional variants on this basic setup are relatively common. For
example, larger breadboards may contain multiple breadboards like those shown in
Fig. 2 placed side-by-side. Other breadboards may have terminal strips which
provide banana-plug type connectors on the breadboard; these types of connectors
can facilitate connection of certain types of equipment to the breadboard. None
of the variations, however, affect the basic breadboard functionality shown in
Most breadboards have holes which are organized in rows of five.
The holes in each row are connected electrically. That is, if you insert
terminals of electrical components in two holes in the same row, you have
“connected” those two terminals to one another.
The holes in different rows are isolated electrically. That is, if you
insert terminals of electrical components in two holes which are in different
rows, those terminals are not connected to one another.
Breadboards will generally have one or more channels or grooves in them. The
channels are for inserting integrated circuits (ICs) in the breadboard. The
ICs are inserted such that they straddle the channel. Holes on either side
of the channel are isolated from one another.
Test Your Knowledge!
Several holes are indicated on the breadboard below. Indicate whether the
following pairs of holes are connected or not.
a and b.
b and c.
a and c.
a and d.
e and f.
d and f.
Several holes are indicated on the breadboard below. Which holes are
connected to one another?
Holes d, e, and f are connected to one another. Holes b and c are also
connected to one another. No other highlighted holes are connected to
1Breadboards are also called protoboards, since they
are used to build prototype circuits.