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Schematics help you understand how a particular electronics project works

as well as how to build it. You can build the circuit on a breadboard (more on

that in the upcoming section, “Breadboarding”) by inserting the components

and making the connections on the board that are indicated by the schematic.

Perusing a simple schematic ..............................................................

An example of a very simple schematic shows a battery, one electronic com-

ponent, and the wires connecting them. Figure 4-1 shows a schematic that

contains a 1.5 volt battery, a wire from the positive side of the battery (+V)

connecting it to one of the leads on an LED, and a wire connecting the other

lead of the LED to the negative side of the battery. With both wires connected,

current flows from one terminal of the battery through the LED, making it light

up, and back to the other terminal of the battery. (If the LED is connected to

only one battery terminal, no current flows, and the LED will not light up.)

Some circuits use too many components for the schematic to show the wire

connecting every component to the battery. In those cases, we use a conven-

ient symbol for a voltage source to represent the positive side of the battery

and a ground symbol to represent the negative side of the battery, as shown

in Figure 4-2. This is same circuit as the preceding figure with a voltage source

symbol and ground symbol representing connections to the battery. These

symbols are also used in applications where a metal chassis is used as ground

and a power supply is used to supply voltage.

You can read more about connecting to +V and ground in the later section,

“The anatomy of a breadboard.”

+

1.5V LED1

Figure 4-1:

A simple

circuit with

a battery.

60 Part I: Project Prep