As previously stated many times in this book, the true value of Raspberry Pi comes from its flexibility. This stands true for the electronics, where the General Purpose input/output (GPIO) pins allow Raspberry Pi to connect to different sensors and electronic components. In plain English, this means that the GPIO pins connect Raspberry Pi to the real world.
In this chapter, you will learn the basic laws of electronics, which is of absolute importance for creating electronics projects with your Raspberry Pi. Along with this, you will be introduced to various electronics components that will be used in the later part of this chapter to make an e-mail notifier and alarm clock. In this chapter, we will cover the following topics:
- Basic laws of electronics
- Introduction to different electronic components
- Introduction to Raspberry Pi electronics
- Developing a digital clock
- Developing an e-mail notifier
- Developing an alarm clock
Electronics is the study of how electrons flow across different materials or space when subject to a variety of conditions.
These various materials can be classified into three categories based on their conductivity, which means the degree to which a specified material conducts or transfers electricity:
- Conductors have a large number of free electrons that can flow freely in the materials in one or the other direction. As a result, they have the highest conductivity amongst all three types. Some examples of conductors are copper and aluminum. Most of the electrical cables that you see are made of copper because they can carry electricity along its length without much loss.
- Nonconductors or insulators are the materials whose internal electrons do not flow freely because of the arrangement of the electrons and protons inside the material structure. Some examples are glass, paper, Teflon, rubber-like polymer, and most plastics. Such materials are used for insulating electrical cables for safety purposes as well as to avoid unnecessary loss. Please note that a perfect conductor or a perfect insulator does not exist in reality, and can only be used for the purposes of modeling (an ideal conductor or insulator).
- Semiconductor materials have conductivity that lies between a conductor and insulator but which is mainly dependent on the temperature, on a macroscopic level. The important point to note is that as the temperature increases, the conductivity of the semiconductor increases. This is different in the case of the conductor, where the conductivity will decrease due to the increase in resistance (covered in the next section).
Semiconductors are the foundation of the modern electronics, including transistors, analog and digital integrated circuits, and light-emitting diodes (LED). Transistors, LEDs, and other modern electronics components will be introduced in a later part of this chapter.
Charge, voltage, and current are the three important terms that you should know. Like mass, charge is a fundamental property or label for an atom, but no one really knows what this is. As a label, charge can be represented and measured in the real world. Just like gravity is the name of the force between masses that can be felt and measured, the electrostatic force was observed by scientists (and all manner of people); that bodies under certain electrical conditions also exerted forces on each another. As this can also be measured, a label called charge was invented to explain the observation, in the same way that mass was used to explain gravity.
Charge can be positive or negative, where the electron has a negative charge while the proton has a positive charge. This is measured in units of Coulombs, abbreviated as C, with the unit named to honor Charles Augustin Coulomb (1736-1806). He was the French aristocrat and engineer who first measured the force between charged objects using a sensitive torsion balance he invented. The important point to remember is that opposite charges attract each other while similar charges repel, meaning it requires some force to keep two opposite charges separated or two similar charges together. This is similar to gravity in the sense that it requires some force to keep an apple falling on the ground and to raise a big mass against gravity.
The potential that separates two points/charges is called voltage. In technical terms, voltage is the electrical potential difference between two points. It is measured in units of volts, abbreviated as V. The unit was named to honor Volta, an Italian scientist.
A flow of electric charge is called a current. The current flows in the direction from a higher voltage to lower voltage.
Note
The conventional current represents the flow from positive to negative; following the direction that independent, positively charged particles would travel. Nonconventional current represents the flow in the opposite direction (from negative to positive) and is the direction in which electrons would flow.
There is the potential for some confusion here because electrons (the charge carriers in a circuit) flow from a lower voltage to higher voltage. So, the direction of the current is represented as opposite to the flow of electrons.
Current is measured in amperes (a), amps for short, and was named after André-Marie Ampère, another French scientist who worked mostly with magnetic effects. An ampere is defined as a flow of one Coulomb of charge in one second after some point.
Electrical current is of two types: direct current (DC) and alternating current (AC). In DC, the direction of charge does not change, so in other words, this is unidirectional flow of charge. In AC however, the movement of charges periodically reverses direction.
Another important term that you should know is resistance. It is the inverse quantity of conductance, so in simple terms, resistance is the degree to which a specified material resists electricity.
The conventional symbol for resistance is R. To honor the German physicist, Georg Ohm, it is measured in Ohms.