25.5.5 Push Button
There are many types of buttons used in electronic circuits. Among them, Push-Button is a very simple input device. Pressing the button will connect the circuit, and if the switch is released, the connection is cut off immediately, so it is also called a momentary contact switch.
25.5.4 Resistor
25.5.4.1 Meaning of Resistor
A resistor is an electronic component that has the effect of dropping voltage by interrupting the flow of current so that the current does not flow well in the electric circuit. It is often used in most electronic circuits. The unit of resistance is ohm (ohm), which is denoted by Ω.
25.5.3 Jumper Wire
Jump wires are used to connect components and circuits when constructing a circuit. With a breadboard, you can connect electronic components to Raspberry Pi to a certain extent without using wires, but you still need wires to connect rows and rows on the breadboard.
25.5.2 Breadboard
25.5.2.1 Structure of Breadboard
The breadboard is a device where the 2.54mm spaced holes to allow wires to be inserted are placed in a lattice pattern on the front so that electronic components can be easily inserted and removed again.
The device below is a typical breadboard. The part where two red and blue lines are drawn vertically on the left and right is called a Bus area. It is usually used by connecting the power source. Connect the (+) power source to the red color and the negative (-) power source to the blue color. In the center, the part where is separated into two parts horizontally and consists of each 5 holes is called an IC (Integrated circuits) area. It is a place where various parts can be arranged. Both sides have small holes, so you can construct the circuit by inserting the legs of various parts.
25.5 Preparations and Usages for Interface
25.5.1 GPIO Extension Board
Raspberry Pi’s GPIO pin is attached to the body of the system board, so it is difficult to connect to the external circuit when you put the board itself in the protective box. Also, as the name of each pin is not marked, you have to check each pin one by one when you are work with it. Also, it is very inconvenient to connect electronic parts or circuits directly to the GPIO pins due to the shape of individual pin or the space constraint between the pins.
25.4.6 Direct Current Power
The power of electricity is called electric power. The electric power is equal to the value of multiplying a voltage by a current. Electric power means the amount of energy consumed when a current goes through a resistance. The electric power is expressed in W (Watt).
The electric power at direct current is calculated as follows.
Electric Power = Voltage × Current ( P = VI )
25.4.5 Pull-up Resistor and Pull-down Resistor
In many electronic circuits, it is the pull-up resistor and pull-down resistor that are used as one of the methods to safely protect the circuit from being broken down from various electrical shocks and to ensure that it can operates correctly according to the originally designed intention under any circumstances. Basically, the pull-up resistor and pull-down resistor are a term defined by where to equip the resistor between power supply and ground, and allow a small current to flow by using a resistor of appropriate size for each resistor. Next, we will explain this.
25.4.4 Kirchhoff’s Laws
Kirchhoff’s law has a first law of current and a second law of voltage.
25.4.4.1 First Law – The Law of Current
The first rule is that on a certain path of current, the sum of incoming currents and the sum of outgoing currents is the same. That is, the sum of the current flowing into one point of the circuit and the current flowing out of the point is the same.
25.4.3 Series and Parallel of Power
There are three ways of connecting the power supply: series connection, parallel connection and series/parallel connection.
25.4.3.1 Series Connection
The way to connect a (+) pole of one cell to a (-) pole of another is series connection. At this time, the total electromotive force is the sum of the electromotive force of all the batteries.
25.4.2 Series and Parallel of Resistance
Basic resistance connections include a series connection where the combined resistance increases and a parallel connection where the combined resistance is reduced.There are three ways of connecting resistance: series connection, parallel connection and series/parallel connection.
25.4.2.1 Series Connection of Resistance
● Combined resistance of series connection