Electronics Basics - Arduino Sketches: Tools and Techniques for Programming Wizardry - page 47

Voltage is the difference in electronic charge between two points.

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Amperage is the rate at which electrons l ow past a point in a circuit.

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Resistance is the amount a component resists the l ow of electrical energy.

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Voltage

Voltage is dei ned as the amount of potential energy between two points in a
circuit. In all circuits, the direction of the l ow of electrons is determined by a
location with higher potential electronic energy, and a point with lower potential
energy. All available voltage will be used in a circuit.
It is possible to increase the amount of voltage in a circuit by placing power
sources in series. For example, one AA battery typically has 1.5 volts of potential
energy between the two ends. To have a potential energy of three volts, you can
place two AA batteries end to end (so the “+” end of one touches the “-” end of
the other). In this way, you would add the voltage of both batteries to create a
power supply of three volts.
All electrical devices, have a voltage rating. The voltage rating describes the
ideal voltage for that device. It also describes the type of circuit it is designed to
be used with. In most cases, all the AC power sockets in your house provide the
same voltage. Appliances and devices that are designed to plug into the wall are
all rated for this sort of voltage. The power supply for the device will typically
step-down the AC voltage to a DC voltage that is appropriate for the device. For
example, my DVD player plugs into the wall, but the components inside run on
12 V DC. However, if you bought a device in the United States, l ew across the
Atlantic and tried to plug it into a socket in the United Kingdom, you may have
an unpleasant surprise. Household electricity in the United States is 110V AC,
and in Europe it is approximately 230V AC, depending on the country. Because
all available voltage is used in a circuit, a device that is rated for 110 V will be
overloaded trying to use the excess voltage in a 230 V socket and be damaged
as a result. Some devices (like many laptop chargers) can automatically adapt
between voltages, but many electronic devices cannot.
The Atmel ATmega328 microcontroller, found on the Arduino Uno, is an elec-
tronic device that can function between 1.8 V DC and 5.5 V DC. This describes
the component's tolerance ; it can function with a voltage between the two values.
Typically, most devices connected to an Arduino won't work with voltages at
the lower end of the range. To simplify design, the Arduino Uno has a voltage
regulator: a device that accepts a wide range of input voltage from a power
supply and provides a steady output voltage. In the case of the Arduino Uno,
the input voltage can range between 6 V DC and 20 V DV and supplies a steady
5 V DC to the ATmega328 and any external components. Five volts is a common
voltage for hobbyist electronics and some professional electronics. Some sensors