Digital technologies/Arduino/Arduino- Beginner
Understanding of the Arduino Board
What is a micro-controller?
A mico-controller is a compact integrated circuit that receives input from the environment, processes the input and can produce an output. It receives input from its I/O pins and processes the signals received using the CPU onboard the chip. Micro-controllers are usually embedded in larger systems and are utilized in many areas of life including vehicles, medical devices, home appliances, and more.
Arduino is an open source electronics platform that provides an easy and accessible way to make robotics projects. The boards are able to receive input signals from sensors and can produce outputs through the I/O pins that will be discussed next in this section. Arduinos boards are used by a diverse subset of people, including students,hobbyists, engineers, researchers, and more due to the simple layout and programmability of the arduino boards.
Arduino board sections
There are 5 important board sections that the user must have a solid understanding of to complete the project. These sections are outlined below:
| Section | Description |
|---|---|
| USB connector | The arduino can be powered through a type A/B USB connector from the user’s laptop/computer to the board. This port is also used to upload programs onto the board. |
| Power port | The arduino board can be powered through an AC-DC adapter or a battery. The power jack of the board can be connected to a 2.1 mm center-positive plug. |
| Power pins | To power external circuitry, 3 standard voltages (0 V or GND, 3.3V, 5V) are provided in the ‘Power Pins’ section of the board. |
| Digital pins | Digital pins on the arduino board can be configured as an input or an output. When the pins are configured as an input, the pins will send a binary signal into the board, which enables the board to read the sensed logic voltage levels (ie. either 0/low or 1/high). If the digital pins are configured as an output, then the arduino will send a binary signal to the pin. There is a built-in LED pre-connected to digital pin 13. When the value of the pin is driven HIGH by the processor, the LED on the board is illuminated, when the pin is LOW, it's turned off. This can be used as a status indicator when programs are running. |
| Analog pins | The analog pins allow the arduino board to receive or send an analog signal. These signals need to be converted into digital representations which can be used inside the software-executing portion of the Arduino processor (which only uses binary digital signals). Analog signal inputs can be accepted for conversion into digital via the Analog Pins header. The Analog to Digital (A/D or “A to D”) conversion is done inside the processor with specialized circuitry. |
Analog VS Digital signals
A signal is an electromagnetic or electric current that transfers information from one source to another. There are two main types of signals used in electronics: analog or digital signals.
Analog signals
This is a time-varying and continuous type of signal that is often used to measure changes in light, sound, position, temperature, or other physical phenomena. When plotted in a voltage-time graph, the result is often a continuous and smooth curve.
Digital signals
A digital signal is a signal that represents information as a series of discrete binary values. Digital signals are used in all modern electronic applications, including communication and network devices. When plotted in a voltage-time graph, the signal is discrete, and ranges from 0 V to VCC (usually 1.8V, 3.3 V, or 5V).
Basic Understanding of Programming
Introduction to coding
The process of programming includes designing and executing code in an integrated development environment, otherwise known as an IDE. Many different IDEs exist and are adopted for different usages, and allow programs to edit, debug, and execute (or compile) their code. In order to program an arduino, one must have the Arduino IDE downloaded, which can be accessed from here: https://www.arduino.cc/en/software. The arduino IDE provides users with a programming editor as well as a way to easily upload and compile programs onto the arduino board. Programmes in the arduino IDE are called sketches, and are normally saved with the .ino extension. The language used to programme the arduino board is based on the C++ language, which is a general use Object Oriented language. Like any common language, in order to start coding, one must be aware of the grammar rules and vocabulary that is used. An important word that will be often encountered is a “function”, which is a block of code that takes in an input, processes the input, then returns an output.
Some other basic considerations:
| Symbol | Description | |
|---|---|---|
| Brackets | {....} | Starts and ends a function or is used to group different statements together |
| Comment bars | /* ….*/ or // | Allows coders to add comments to their code to make it more readable to other humans. Important to note that all comments do not get executed by the program and therefore do not alter the program! |
| Semicolon | ...; | This character ends a program statement and lets the compiler know ‘the end of the current line/statement’ |
It is also important to be aware that the arduino editor is case sensitive, meaning that the words “DOOR” and “Door” are not understood to be the same word by the compiler. Furthermore, to make writing and editing code more friendly, the arduino IDE will color code important functions, comments, etc. This will be seen later in this section.
Variables
Variables allow information in programmes to be stored or changed within the code. In order to create a variable within your program, it must be declared. To declare a variable, the coder has to write the type of variable to be declared first. Different types exist, most commonly used are:
| Type | Syntax |
|---|---|
| Integers | int |
| non-integers (rational and non-rational) | dpuble or float |
| charecters | char |
After declaring the variable type, the coder must then name the variable. The variable name should clearly reflect the purpose of the value, so that the coder and the reader can easily identify which value is associated with what variable. Additionally, variables cannot have spaces imbedded within the name. For example, "My deposit" is not a valid variable name, but "MyDeposit" is. Note that capitalizations can be useful for readability. Furthermore, variables should not start with digits, or with an underscore "_".
After naming the variable, the coder can choose to initialize the variable, which is choosing an initial value to be assosiated with the variable (which can change throughout the program). Be careful to stay consistent with the type of the variable. For example, you cannot initialize the variable int Age with a value of "k", as "k" is not an integer. The code segments below illustrate the process of initialization:
int a;// not initialized, which is ok!
double b=1.23;/* Note that the 1.23 value matches with the “double” type which is a rational number*/
char MyVariable = “h”; //note the semicolons!
The following will produce an error, which will disable the compiler from compiling your code:
char YourVariable= 1.23; // 1.23 is not a character!
Variables can be classified into either global or local variables. The main difference is the scope at which they can be accessed. A global variable can be accessed by all functions that exist within a program, whereas a local variable can be accessed through only the function where it is declared. The example below illustrates this well [https://www.arduino.cc/reference/en/language/variables/variable-scope-qualifiers/scope/]:
/* There are two functions in this program: setup() and loop(), and three variables: "k", "i", "f".*/
int k; // any function will see this variable, thus called a global variable.
void setup() {
// ... }
void loop() {
int i; // "i" is only "visible" inside of "loop"
float f; } // "f" is only "visible" inside of "loop"
.....// some lines of code}
Arduino IDE
After getting introduced to some of the basic structures of coding, its important to get to know the integrated development enviroment, or IDE that the coder will use to edit and compile the written programmes. For all arduino boards, the IDE used is the Arduino IDE, available online at: https://www.arduino.cc/en/software. The following figure guides the users to the basic on the basic options available on the IDE.
Blink program
The Arduino IDE provides creators with a plethora of written programs that are fully ready to run on an arduino board. They are located in the Files>Examples folder. Amongst the most basic is the "Blink" program, which can be used to not only get to know the basic features in the software and the hardware, but are also a great way to test the connectivity between the arduino board and the user's computer. This program is located in Files>Examples>01.Basics>Blink.
The following provides an overview of the different functions used in this program:
| Function | Description |
|---|---|
| Setup() | Performs any actions that are initially required to run the rest of the program, such as initializing any peripheral components and setting the communication frequency between the Arduino and the PC. |
| Loop() | The loop function acts as the program's driver, it runs on a continuous loop and specifies the order of operation the microcontroller will perform. Execution starts at the top, goes through the contents of the loop and then starts executing from the top again. This procedure is repeated forever. |
| pinMode (pin number, INPUT or Output) | Configures the pin to behave as either an INPUT or an OUTPUT. |
| digitalWrite (pin number, HIGH or LOW) | Writes a HIGH or LOW value to a digital pin. If the pin has been configured as an OUTPUT, then the signal sent over (ie the voltage) will be set as 5 V (HIGH), or 0 V (LOW). For 3.3 V output boards, the high value will be set to 3.3 V, whereas the low is the same as the 5V board, which is 0V. |
| Delay (time in milliseconds) | Pauses the program for the amount of time specified in the parameter. |
Basic Understanding of Sensors
Introduction to Sensors
Sensors enable the microcontroller to sense the surrounding environment. Many sensors exist on the marker, including but not limited to buttons, temperature sensors, pressure sensors, photoresistors, humidity and moisture, and many more. The output of the sensor (a voltage) changes based on the measured environment properties, and sends that signal over to the arduino board.
Introduction to basic electronic components
LED
A Light Emitting Diode, or LED, is a semiconductor device that lights up when an electric current passes through it. They come in many different colors and shapes, and are very versatile. LEDs are diodes, which means that current flows through the element in only one way, from the positive to the negative end. On an LED, the cathode end can be identified by either a flat edge on the body, or as the shorter leg. As such, the anode is the other end (the longer leg on the LED).
Pushbutton
A pushbutton is an electronic switch component that completes the circuit only when pressed. In an electric circuit, electricity needs to flow continuously through the circuit in order for all parts to function. The pushbutton interrupts this circuit and forms a gap, so that electricity doesn't flow to the other side of the pushbutton. When the pushbutton is pressed. a small spring is activated that is made of conducting material so that electricity flows through the spring to the other side of the pushbutton.
Resistor
A resistor is an electrical component which creates electrical impedance, or resistance to current flow. The amount of resistance a resistor provides can be read from the bands of color on the resistor, which are read left to right. For four bands resistors, the first and second bands represent digits, while the third band represents a multiplier to multiply the digits of the first and second band by. The fourth band is the tolerance, it represents how much the resistor may deviate from the value indicated by the bands. The value of the resistor can also be determined using the ohmic function of a multimeter. Resistors are often used in series with components to reduce the amount of current flowing through a circuit, often to protect components rated for lower current amounts. Pull-up and pull-down resistors are used to bias an input on the Arduino to be either HIGH or LOW respectively. This needs to be done as the resting level of the input isn’t necessarily 0. This is especially useful when working with sensors that have an analog output.
Breadboard
A breadboard is used to prototype a temporary circuit. The user can build, test and analyze a circuit without any permanent connections. It is made up of terminal strips and power rails. The terminal strips are used to hold any number of components in place and make electrical connections in a horizontal row. The power rails are the long vertical strips and are used to facilitate power (+) and ground (-) connections by placing them all in one column.