Using the Breadboard
Use a solderless breadboard to construct simple circuits.
Site:
iCODE
Course: Machine Science Guides (Arduino Version)
Book:
Using the Breadboard
Printed by: Ivan Rudnicki
Date:
Wednesday, July 30, 2014, 03:17 PM
Contents
About the Breadboard
Internal Connections
Preparing the Breadboard
About Power and Ground
About Jump Wires
Connecting the Battery Pack
About LEDs
About Resistors
Building the LED Circuit
About the Breadboard
A solderless breadboard (Figure 1) is a tool that allows you to construct simple circuits without
making permanent solder connections. To make connections among components, you simply plug
them into the holes in the breadboard. If you need to change a connection, you can easily extract and
reconfigure the components.
Figure 1. Breadboard. The breadboard's name dates from the early days of electrical engineering, when engineers would
create circuits by driving nails into wooden boards and then wrapping conductive wire around the
nails.
Internal Connections
The breadboard has hundreds of tiny holes that hold wires and electronic components. Figure 2
shows a close­up view of one end of the breadboard. Notice that each row of holes is assigned a
number, and each column is assigned a letter. This way, the exact position of any hole on the
breadboard can be specified by a combination of a letter and a number. For example, in Figure 2, the
hole in the upper­left corner is hole A1.
Figure 2. Close­up view of breadboard.
Metal clips inside the breadboard make electrical connections between the wires and components
that you plug into certain holes. Look closely at the long edges of the breadboard. On each side,
there are two columns: one marked with a red line, and the other marked with a blue line. All of the
red line holes on a side are connected to one another, and all of the blue line holes on a side are
connected to one another.
Now, look at the breadboard's numbered rows of holes. Notice that each row has 10 holes­­five in
columns A to E, and five in columns F to J­­separated down the middle by a shallow groove. Within
each row, the five holes in columns A to E are connected, and the five holes in columns F through J
are connected. However, the breadboard has no built­in connections across the central groove. The
internal connections at one end of the breadboard are marked with green lines in Figure 3.
Figure 3. The breadboard's internal connections, highlighted in green.
Preparing the Breadboard
Before you begin building circuits on your
breadboard, a metal plate should be affixed to
the bottom of the board. The metal plate will
help all of your components function more
consistently. NOTE: If your board already has
a metal plate on the bottom, you can skip this
step.
1. Peel the backing from the breadboard,
leaving the sticky foam layer in place, as
shown in the video on in Figure 4.
2. Apply the metal plate to the bottom of the
breadboard, as shown in the video and in
Figure 4.
Figure 4. Applying the metal plate.
About Power and Ground
The holes marked with red and blue lines along the edges of the breadboard (Figure 5) are called
power holes and ground holes, respectively. These holes have a special purpose: making it easy to
supply electricity to the components in your circuit. No matter where you put a component, there's
always a power hole and a ground hole nearby. Think of the power and ground holes as a "power
strip" for your breadboard.
Figure 5. Power holes and ground holes. Later, you will set up this "power strip" by establishing a 5­volt difference between the power holes
and the ground holes. About Jump Wires
A jump wire is a length of insulated wire specifically designed to work with the solderless
breadboard. Each jump wire has a short uninsulated section at either end. Inserting these sections into
any two breadboard holes creates an electrical connection between the two holes. The kit contains
two types of jump wires: 1) pre­bent jump wires, which come in various, color­coded lengths; and 2)
flexible jump wires, which are all the same length. Figure 6 shows these two types of jump wires.
Figure 6. Pre­bent (left) and flexible (right) jump wires.
Although the two types of wires can be used interchangeably, a pre­bent jump wire is typically used
to make a semi­permanent connection between two holes in the same row or column on the
breadboard, whereas a flexible jump wire is typically used to make a more temporary connection
between two holes that are not in the same row or column.
Connecting the Battery Pack
The battery pack included with your kit holds four AA batteries, which together supply power to the
board. The battery pack has a red (power) lead and a black (ground) lead, terminating in a three­way
wire harness. The following instructions show how to connect the harness to the breadboard to
reduce the risk of accidentally reversing power and ground. 1. Insert three pre­bent jump wires into the breadboard, making two connections to ground
and one to power, as shown in Figure 7. Figure 7. Inserting jump wires.
2. Using pliers or scissors, break off a three­segment piece of the 36­prong bent connector
included in the kit, making a three­prong connector, as shown in Figure 8. Figure 8. Breaking off a three­prong connector. 3. Insert the three­prong bent connector into the board, aligning it with the three jump wires,
as shown in Figure 9.
Figure 9. Inserting three­prong connector.
4. Connect the battery pack wire harness to the three­prong connector, taking care to align
the red (power) wire with the center prong, as shown in Figure 10. Notice that, even if the
harness is inverted, the proper power and ground connections will be maintained, as long as
you line up the harness correctly with the three­prong connector.
Figure 10. Connecting the wire harness.
5. Connect the red line holes and the blue line holes on each side of the board by inserting two
red pre­bent wires, as shown in Figure 11. NOTE: You will need to bend the wires slightly to
get them to fit.
Figure 11. Connecting power and ground from one side of the breadboard to the other.
About LEDs
Light emitting diodes (LED) are electronic components that emit light when electricity passes
through them. Figure 12 shows yellow, red, and green LEDs. Figure 12. LEDs.
Because LEDs generate lots of light, use very little electricity, and last for thousands of hours, they
are becoming ubiquitous in modern electronic devices. Your computer keyboard probably has a few
LEDs to indicate when the Caps Lock or Num Lock keys have been pressed. Grouped together,
LEDs can produce enough light to be used as a source of household illumination, as in the lamp
shown in Figure 13.
Figure 13. LED lamp.
Every LED has a specific polarity, meaning one of its two pins must connect to the power side of the
circuit and the other pin must connect to the ground side. A tiny flat segment on the round rim of the
LED's circular base marks the ground pin. The power pin is typically longer than the ground pin, but
this is an unreliable indicator, since the pins may be trimmed during installation. Figure 14 shows
these distinguishing features.
Figure 14. LED polarity.
About Resistors
A resistor is a component that limits the flow of electricity in an electronic circuit. In some cases,
resistors are needed to protect other components, which may be unable to operate at the full voltage
supplied by the batteries in a circuit. Resistors vary widely in terms of their resistance, a property measured in Ohms, which determines
how much current passes through them. The resistors included in your kit have colored bands to
indicate their resistance. (To learn how to interpret these colored bands, see the Resistors Quick
Reference document.) For the activity in the next section, you need to use a 1.0K Ohm (1,000 Ohm)
resistor. Figure 15 shows two ways to identify this resistor.
Figure 15. Two ways to identify a 1.0K Ohm resistor.
Building the LED Circuit
Using one resistor, one jump wire, and one LED, create the circuit shown in Figure 16. Be sure to
orient the LED so that its longer (power) pin aligns with the jump wire connected to power, and its
shorter (ground) pin aligns with the resistor connected to ground. Before turning on the power,
double check all your connections to ensure that you do not create a short circuit. The LED should
light when power is supplied!
Figure 16. LED circuit.