CARTOOINO Projects Book

Transcription

1 1 CARTOOINO Projects Book

2 Acknowledgement Acknowledgement This Cartooino Projects Book is a cartoon based adaptation of the Arduino Projects Book. The Cartooino Project Book was developed by the GreenLab Microfactory for use for her One Student One Arduino project. The essence of which is to create a more relatable learning approach for the participants of the One Student One Arduino project. Therefore, the GreenLab Microfactory would like to acknowledge Arduino LLC for their selflessness and contribution to the body of knowledge by fortifying the open source community with their products and projects. In addition, the cartoon characters used in this project book were developed using the online animation platform ToonDoo ( Finally, GreenLab Microfactory will also like to acknowledge that some of the content of this book were derived and adapted from the online platform Tutorials point ( Disclaimer This book was not created for commercial purposes, and the contents of the Cartooino Projects Book are licensed under a Creative Commons Attribution-NonCommercial- ShareAlike 3.0 License 2012 by GreenLab Microfactory. This means that you can copy, reuse, adapt and build upon the text of this book non-commercially while attributing the original work (but not in any way that suggests that we endorse you or your use of the work) and only if the results are transmitted under the same Creative Commons license. Full license terms: creativecommons.org/licenses/by-nc-sa/3.0/ 2

3 Introduction 3

4 Introduction 4

5 Introduction Below you will find the brief explanation of all the components in the project kit for this project This picture shows the Arduino Uno - microcontroller development board that will be at the heart of your projects. It s a simple computer, which you will use to build circuits and interfaces for interaction, and to tell the microcontroller how to interface with other components. This picture shows the Breadboard Though the name sound comical, but this kind of bread cannot be chewed with the teeth. A board on which you can build electronic circuits. It s like a patch panel, with rows of holes that allow you to connect wires and components together. Capacitors - These components store and release electrical energy in a circuit. When the circuit s voltage is higher than what is stored in the capacitor, it allows current to flow in, giving the capacitor a charge. When the circuit s voltage is lower, the stored charge is released. DC motor - Converts electrical energy into mechanical energy when electricity is applied to its leads. Coils of wire inside the motor become magnetized when current flows through them. Liquid Crystal Display (LCD) - A type of alpha-numeric or graphic display based on liquid crystals. LCDs are available in a many sizes, shapes, and styles. Yours has 2 rows with 16 characters each. Battery Snap - Used to connect a 9V battery to power leads that can be easily plugged into a breadboard or your Arduino. 5

6 Introduction USB Cable - This allows you to connect your Arduino Uno to your personal computer for programming. It also provides Jumper wires Are used to connect components to each other on the breadboard, and to the Arduino. Diode - Ensures electricity only flows in one direction. Useful when you have a motor or other high current/voltage load in your circuit. Light Emitting Diodes (LEDs) - A type of diode that illuminates when electricity passes through it. Resistors - Resist the flow of electrical energy in a circuit, changing the voltage and current as a result. Resistor values are measured in ohms (represented by the Greek omega character: Ω). The coloured stripes on the sides of resistors indicate their value (see resistor colour code table). Servo motor - A type of geared motor that can only rotate 180 degrees. It is controlled by sending electrical pulses from your Arduino. These pulses tell the motor what position it should move to power to the Arduino for most of the projects in the kit. Male header pins - These pins fit into female sockets, like those on a breadboard. They help make connecting things much easier. Temperature sensor - Changes its voltage out-put depending on the temperature of the component. The outside legs connect to power and ground. The voltage on the centre pin changes as it gets warmer or cooler. Optocoupler - This allows you to connect two circuits that do not share a common power supply. Internally there is a small LED that, when illuminated, causes a photoreceptor in-side to close an internal switch. When you apply voltage to the + pin, the LED lights and the internal switch closes. The two outputs replace a switch in the second circuit. 6

7 Introduction Pushbuttons - Momentary switches that close a circuit when pressed. They snap into bread-boards easily. These are good for detecting on/off signals. Piezo - An electrical component that can be used to detect vibrations and create noises. H-bridge - A circuit that allows you to control the polarity of the voltage applied to a load, usually a motor. The H-bridge in the kit is an integrated circuit, but it could also be constructed with a number of discrete components. Potentiometer - A variable resistor with three pins. Two of the pins are connected to the ends of a fixed resistor. The middle pin, or wiper, moves across the resistor, dividing it into two halves. When the external sides of the potentiometer are connected to voltage and ground, the middle leg will give the difference in voltage as you turn the knob. Transistor - A three-legged device that can operate as an electronic switch. Useful for controlling high current/high voltage components like motors. One pin connects to ground, another to the component being controlled, and the third connects to the Arduino. When the component receives voltage on the pin connected to an Arduino, it closes the circuit between the ground and the other component. Photoresistor - (also called a photocell, or light-dependent resistor). A variable resistor that changes its resistance based on the amount of light that falls on its face. Tilt sensor - A type of switch that will open or close depending on its orientation. Typically, they are hollow cylinders with a metal ball in-side that will make a connection across two leads when tilted in the proper direction. Capacitor - A components store and release electrical energy in a circuit. When the circuit s voltage is higher than what is stored in the capacitor, it allows current to flow in, giving the capacitor a charge. When the circuit s voltage is lower, the stored charge is released. Often placed across power and ground close to a sensor or motor to help smooth fluctuations in voltage. That is just about everything you need to know about the components for now. With this knowledge we can start developing our projects 7

8 Introduction Before we proceed further, it is worthwhile to know how to read a resistor. Hope you still remember what a resistor is? Below, an explanation on how to read a resistor will be given. Resistors are measured in Ohms (Ω). The values of resistors are represented by colour codes. As represented below, each colour codes represents a specific number. There are three types of resistors, these are 4-band (colour), 5-band, or 6- band. In the 4-band resistor, the first two colours indicate the first two values, while the third band indicate the numbers of zeroes (it represents the power of ten, that is, 10 n ). The last band represents tolerance. In the picture here, Gold has a value of 5% which means that the resistor can tolerate a load of plus or minus 5%. Therefore, this particular 4-band resistor has a value of 10,000 or 10kΩ ± 5% For your first assignment, go through your Arduino project kit and perform the following: 1. What types of resistors are in your kit? 2. Calculate the values of each type. Source: 8

9 Getting to know your tool Understanding the Arduino UNO electronic Board I know you are eager to start building your toys. But there are few information you need to know about the Arduino in your kit. Source: , 17 6, 7, 8, 9 Power USB - Arduino board can be powered by using the USB cable from your computer. All you need to do is connect the USB cable to the USB connection (1). Power (Barrel Jack) Arduino boards can be powered directly from the AC mains power supply by connecting it to the Barrel Jack (2). Voltage Regulator The function of the voltage regulator is to control the voltage given to the Arduino board and stabilize the DC voltages used by the processor and other elements. Crystal Oscillator The crystal oscillator helps Arduino in dealing with time issues. How does Arduino calculate time? The answer is, by using the crystal oscillator. The number printed on top of the Arduino crystal is H9H. It tells us that the frequency is 16,000,000 Hertz or 16 MHz. Arduino Reset You can reset your Arduino board, i.e., start your program from the beginning. You can reset the UNO board in two ways. First, by using the reset button (17) on the board. Second, you can connect an external reset button to the Arduino pin labelled RESET (5). Pins (3.3, 5, GND, Vin) 3.3V (6) Supply 3.3 output volt 5V (7) Supply 5 output volt Most of the components used with Arduino board works fine with 3.3 volt and 5 volt. 9

10 Getting to know your tool Understanding the Arduino UNO electronic Board GND (8)(Ground) There are several GND pins on the Arduino, any of which can be used to ground your circuit. Vin (9) This pin also can be used to power the Arduino board from an external power source, like AC mains power supply. Analog pins The Arduino UNO board has five analog input pins A0 through A5. These pins can read the signal from an analog sensor like the humidity sensor or temperature sensor and convert it into a digital value that can be read by the microprocessor. Main microcontroller Each Arduino board has its own microcontroller (11). You can assume it as the brain of your board. The main IC (integrated circuit) on the Arduino is slightly different from board to board. The microcontrollers are usually of the ATMEL Company. You must know what IC your board has before loading up a new program from the Arduino IDE. This information is available on the top of the IC. For more details about the IC construction and functions, you can refer to the data sheet. ICSP pin Mostly, ICSP (12) is an AVR, a tiny programming header for the Arduino consisting of MOSI, MISO, SCK, RESET, VCC, and GND. It is often referred to as an SPI (Serial Peripheral Interface), which could be considered as an "expansion" of the output. Actually, you are slaving the output device to the master of the SPI bus. Power LED indicator This LED should light up when you plug your Arduino into a power source to indicate that your board is powered up correctly. If this light does not turn on, then there is something wrong with the connection. TX and RX LEDs On your board, you will find two labels: TX (transmit) and RX (receive). They appear in two places on the Arduino UNO board. First, at the digital pins 0 and 1, to indicate the pins responsible for serial communication. Second, the TX and RX led (13). The TX led flashes with different speed while sending the serial data. The speed of flashing depends on the baud rate used by the board. RX flashes during the receiving process. Digital I/O The Arduino UNO board has 14 digital I/O pins (15) (of which 6 provide PWM (Pulse Width Modulation) output. These pins can be configured to work as input digital pins to read logic values (0 or 1) or as digital output pins to drive different modules like LEDs, relays, etc. The pins labeled ~ can be used to generate PWM. AREF AREF stands for Analog Reference. It is sometimes, used to set an external reference voltage (between 0 and 5 Volts) as the upper limit for the analog input pins. 10

11 Getting to know your tool How to Download, Install, and Setup the Arduino IDE software We are one step closer to the real fun. In order to build your toy, you first need to download, install, and setup the Arduino IDE. IDE! But Uncle! What is an IDE? Good question Ope! IDE means Integrated Development Environment, and it is a software that tells the Arduino board what you want to do. As a developer you will be writing and testing software. So the IDE allows you to write and test your code. An IDE contains a code editor, a compiler or interpreter and a debugger that the developer accesses through a single graphical user interface (GUI). I know you also would like to know what I meant by code. A source code is any collection of computer instructions, possibly with comments, written using a humanreadable programming language Code! Oh! I now Understand! Thank you Uncle! 11

12 Getting to know your tool How to Download, Install, and Setup the Arduino IDE software In this section you will be put through on how to download, install, and setup the Arduino IDE after which the real fun begins. To download the IDE, go to this link - Please follow the steps and pictures below to install and setup your IDE. Then we will be ready to start building our prototypes. Step 1: After your file download is complete, unzip the file. 12

13 Getting to know your tool How to Download, Install, and Setup the Arduino IDE software Step 2: After the download the next step is to power up your Arduino board. The Arduino Uno automatically draw power from either, the USB connection to the computer or an external power supply. To power up your Arduino, connect the Arduino board to your computer using the USB cable. The green power LED (labelled PWR) should glow. Step 3: Now launch the Arduino IDE After your Arduino IDE software is downloaded, you need to unzip the folder. Inside the folder, you can find the application icon with an infinity ( ) label (application.exe). Double-click the icon to start the IDE. As shown in the diagram below. Now it is time to open your first project. Once the software starts, you have two options (1) Create a new project, or (2) Open an existing project example. The next pictures explains how to do these. But before you can create your project, you need to do step 5 and 6. So do those first then create your project. 13

14 Getting to know your tool How to Download, Install, and Setup the Arduino IDE software Step 4.1: To create a new project, select File New. As shown in the picture below. Step 4.2: To open an existing project example, select File Example Basics Blink. Here, you are selecting just one of the examples with the name Blink. Blink turns the LED on and off with some time delay. If you like, you can select any other example from the list. 14

15 Step 5: Select your Arduino board. Getting to know your tool How to Download, Install, and Setup the Arduino IDE software To avoid any error while uploading your program to the board, you must select the correct Arduino board name, which matches with the board connected to your computer. Go to Tools Board and select your board. In the picture below, we have selected Arduino Uno board according to our tutorial, but if you are using another Arduino board you must select the name that matches the board you are using. Step 6: Select your serial port. Select the serial device of the Arduino board. Go to Tools Serial Port menu. This is likely to be COM3 or higher (COM1 and COM2 are usually reserved for hardware serial ports). To find out, you can disconnect your Arduino board and re-open the menu, the entry that disappears should be of the Arduino board. Reconnect the board and select that serial port. 15

16 Getting to know your tool How to Download, Install, and Setup the Arduino IDE software Step 7: Finally, upload the code/program to your board. Before explaining how we can upload our program to the board, we must demonstrate the function of each symbol appearing in the Arduino IDE toolbar. A Used to check if there is any compilation error. B Used to upload a program to the Arduino board. C Shortcut used to create a new sketch. D Used to directly open one of the example sketch. E Used to save your sketch. F Serial monitor used to receive serial data from the board and send the serial data to the board. Now, simply click the "Upload" button in the environment. Wait a few seconds; you will see the RX and TX LEDs on the board, flashing. If the upload is successful, the message "Done uploading" will appear in the status bar. Congratulations! You have successfully installed your Arduino IDE. You are now ready to embark on a memorable adventure. 16

17 Project 01 Build a Simple Circuit Hello class, I am glad that you have made it this far. To officially welcome you on the One Student One Arduino project, you will be given an opportunity to build a simple circuit. To complete this project, you will need some switches, a LED, and a 220Ω resistor. Lastly, you will need at least 30 minutes to complete the project. During this project, you will discover some basic electrical theory, and how to connect components in series and parallel. So if you are ready let s start. The Basic Electrical Theory Electricity is a type of energy, much like heat, gravity, or light. Electrical energy flows through conductors, like wire. You can convert electrical energy into other forms of energy to do something interesting, like turn on a light or make some noise out of a speaker. The components you might use to do this, like speakers or light bulbs, are electrical transducers. Transducers change other types of energy into electrical energy and vice versa. Things that convert other forms of energy into electrical energy are often called sensors, and things that convert electrical energy into other forms of energy are sometimes called actuators. You will be building circuits to move electricity through different components. Circuits are closed loops of wire with a power source (like a battery) and something to do something useful with the energy, called a load. In a circuit, electricity flows from a point of higher potential energy (usually referred to as power or +) to a point of lower potential energy. Ground (often represented with a - or GND) is generally the point of least potential energy in a circuit. In the circuits you are building, electricity only flows in one direction. This type of circuit is called direct current, or DC. In alternating current (AC) circuits electricity changes its direction 50 or 60 times a second (depending on where you live). This is the type of electricity that comes from a wall socket. There are a few terms you should be familiar with when working with electrical circuits. Current (measured in amperes, or amps; with the A symbol) is the amount of electrical charge flowing past a specific point in your circuit. Voltage (measured in volts; with the V symbol) is the difference in energy between one point in a circuit and another. And finally, resistance (measured in ohms; with the Ω symbol) is how much a component resists the flow of electrical energy. 17

18 Project 01 Build a Simple Circuit There are few things you need to know about a circuit. These points will be presented in the box below. There needs to be a complete path from the energy source (power) to the point of least energy (ground) to make a circuit. If there s no path for the energy to travel, the circuit won t work. All the electrical energy gets used up in a circuit by the components in it. Each component converts some of the energy into another form of energy. In any circuit, all of the voltage is converted to another form of energy (light, heat, sound, etc.). The flow of current at a specific point in a circuit will always be the same coming in and going out. Electrical current will seek the path of least resistance to ground. Given two possible paths, more of the electrical current will go down the path with less resistance. If you have a connection that connects power and ground together with no resistance, you will cause a short circuit, and the current will try to follow that path. In a short circuit, the power source and wires convert the electrical energy into light and heat, usually as sparks or an explosion. If you ve ever shorted a battery and seen sparks, you know how dangerous a short circuit can be. The diagram below shows a simple circuit made from three jumper cables, a 220Ω resistor, and a LED. Please go to the introduction section to get more information about each of these components. Don t forget that the long leg of the LED is the positive side (+) called anode, while the short leg is the negative (-) side called cathode. 18

19 Project 01 Build a Simple Circuit One major warning for you to note. Always unplug your Arduino from the power source before building the circuit. Connect the jumper cables, push button, resistor, and LED (with a jumper wire connect the long leg of the LED to the anode, and the short leg of the LED to ground) from the Arduino board to the breadboard as shown in this picture. Once you are done connecting them, now connect your Arduino to the computer using the USB cable. Now press the pushbutton to switch on the LED. If the LED lights up then you have successfully built your first circuit. Congratulations! 19

20 Project 01 Build a Simple Circuit After successfully building your first circuit. Now you will learn the differences between the two types of circuit you can build. Which are series circuit and a parallel circuit. Once again do not forget to unplug the Arduino board from the computer before making any changes to the breadboard. Series circuit Components in SERIES come one after another To build this remove your power source, add a switch next to the one already on your breadboard. Wire them together in series as shown in the diagram on the right hand side. Connect the anode (long leg) up the LED to the second switch. Connect the LED cathode to ground. Power up the Arduino again: now to turn on the LED, you need to press both switches. Since these are in series, they both need to be closed for the circuit to be completed. 20

21 Project 01 Build a Simple Circuit Parallel circuit Components in PARALLEL run side by side To wire up switches in parallel, keep the switches and LED where they are, but remove the connection between the two switches. Wire both switches to the resistor. Attach the other end of both switches to the LED, as shown in the diagram on the right hand side. Now when you press any of the buttons, the circuit is completed and the light turns on. We have now gotten to the end of our first project. During this project, you have learned about the basic electrical theory, that is, properties of voltage, current, and resistance while building a very simple circuit on a breadboard. With basic components like LED, resistor and switches, you have created the simplest interactive system where the user presses the button in order to switch on the light. These fundamental knowledge of working with electronics will be built upon in the following projects. In the next project, you will be building a spaceship interface so you can explore and discover the galaxy. See you then. 21

22 Project 02 Spaceship Interface Uncle! At the end of the last class you said we will build a spaceship interface today. But what is a spaceship? A spaceship is a craft, vehicle, vessel or machine designed to take humans or things deep into the sky. Just like the one here. So in today s class, you will learn how to build an interface to send signals deep into the galaxy. The connection diagram here shows how you will build and connect the circuit from the Arduino board to the Breadboard. 22

23 Project 02 Spaceship Interface In this class, you will learn about digital input and output, write your first code, and also about variables. To complete this project, you will need one switch, two red LEDs and one green LED, with three 220Ω and one 10kΩ resistor. Lastly, you will need at least 45 minutes to complete the project. How it Works In this project, you will learn how to control things with your Arduino. You will be making a cool control panel with a switch and lights that turn on when you press the switch. With this interface, a green LED will be on until you press a button. When the Arduino gets a signal from the button, the green light will turn off and 2 other lights will start blinking. The Arduino s digital pins can read only two states: when there is voltage on an input pin, and when there s not. This kind of input is normally called digital (or sometimes binary, for two-states). These states are commonly referred to as HIGH and LOW. HIGH is the same as saying there s voltage here! and LOW means there s no voltage on this pin!. When you turn an OUTPUT pin HIGH using a command called digitalwrite(), you re turning it on. Measure the voltage between the pin and ground, you ll get 5 volts. When you turn an OUTPUT pin LOW, you re turning it off. The Arduino s digital pins can act as both inputs and outputs. In your code, you ll configure them depending on what you want their function to be. When the pins are outputs, you can turn on components like LEDs. If you configure the pins as inputs, you can check if a switch is being pressed or not. Since pins 0 and 1 are used for communicating with the computer, it s best to start with pin 2. To proceed, follow the connection diagram above, wire up your breadboard to the Arduino s 5V and ground (GND) connections, just like the previous project. Place the two red LEDs and one green LED on the breadboard. Attach the cathode (short leg) of each LED to ground through a 220-ohm resistor. Connect the anode (long leg) of the green LED to pin 3. Connect the red LEDs anodes to pins 4 and 5, respectively. Place the switch on the breadboard just as you did in the previous project. Attach one side to power, and the other side to digital pin 2 on the Arduino. You ll also need to add a 10k-ohm resistor from ground to the switch pin that connects to the Arduino. That pull-down resistor connects the pin to ground when the switch is open, so it reads LOW when there is no voltage coming in through the switch. 23

24 Project 02 Spaceship Interface For you to be able to control things with your Arduino you will need to write some codes to instruct the Arduino. Below, we will be talking about how to write the Codes. Understanding Arduino Code The source code in Arduino is called Sketch. Arduino programs can be divided in three main parts: Structure, Values (variables and constants), and Functions. In this tutorial, we will learn about the Arduino software program, step by step, and how we can write the program without any syntax or compilation error. Let us start with the Structure. Software structure consist of two main functions Setup( ) function Loop( ) function { Curly brackets Any code you write inside the curly brackets will be executed when the function is called. The setup() function is called when a sketch starts. Use it to initialize the variables, pin modes, start using libraries, etc. The setup function will only run once, after each power up or reset of the Arduino board. This is where you configure the digital pins to be either inputs or outputs using a function named pinmode(). The pins connected to LEDs will be OUTPUTs and the switch pin will be an INPUT. The loop() function does precisely what its name suggests, and loops continuously, allowing your program to change and respond. Use it to actively control the Arduino board. The loop() is where you ll check for voltage on the inputs, and turn outputs on and off. To check the voltage level on a digital input, you use the function digitalread() that checks the chosen pin for voltage. To know what pin to check, digitalread() expects an argument. Arguments are information that you pass to functions, telling them how they should do their job. For example, digitalread() needs one argument: what pin to check. In your program, digitalread() is going to check the state of pin 2 and store the value in the switchstate variable. If there s voltage on the pin when digitalread() is called, the switchstate variable will get the value HIGH (or 1). If there is no voltage on the pin, switchstate 24 will get the value LOW (or 0).

25 Project 02 Spaceship Interface S Enter the Code below on your Arduino IDE to build and control the spaceship interface int switchstate = 0; // this is a comment. Comments are used to explain a code void setup() { // put your setup code here, to run once: pinmode(3,output); pinmode(4,output); pinmode(5,output); pinmode(2,input); Case sensitivity Pay attention to the case sensitivity in your code. For example, pinmode is the name of a command, but pinmode will produce an error. void loop() { // put your main code here, to run repeatedly: switchstate = digitalread(2); if (switchstate == LOW) { // the button is not pressed digitalwrite(3, HIGH); // green light digitalwrite(4, LOW); // red light digitalwrite(5, LOW); // red light Comments If you ever want to include natural language in your program, you can leave a comment. Comments are notes you leave for yourself that the computer ignores. To write a comment, add two slashes // The computer will ignore anything on the line after those slashes. else { // the button is pressed digitalwrite(3, LOW); digitalwrite(4, LOW); digitalwrite(5, HIGH); delay(250); // waits for a quarter second digitalwrite(4, HIGH); digitalwrite(5, LOW); delay(250); 25

26 Project 02 Spaceship Interface If Statement In the code above, you used the word if to check the state of something (namely, the switch position). An if() statement in programming compares two things, and determines whether the comparison is true or false. Then it performs actions you tell it to do. When comparing two things in programming, you use two equal signs ==. If you use only one sign, you will be setting a value instead of comparing it. Spaceship Interface Code digitalwrite() is the command that allows you to send 5V or 0V to an output pin. digitalwrite() takes two arguments: what pin to control, and what value to set that pin, HIGH or LOW. If you want to turn the red LEDs on and the green LED off inside your if() statement, your code would look like this. You ve told the Arduino what to do when the switch is open. Now define what happens when the switch is closed. The if() statement has an optional else component that allows for something to happen if the original condition is not met. In this case, since you checked to see if the switch was LOW, write code for the HIGH condition after the else statement. To get the red LEDs to blink when the button is pressed, you ll need to turn the lights off and on in the else statement you just wrote. To do this, change the code to look like this. After setting the LEDs to a certain state, you ll want the Arduino to pause for a moment before changing them back. If you don t wait, the lights will go back and forth so fast that it will appear as if they are just a little dim, not on and off. This is because the Arduino goes through its loop() thousands of times each second, and the LED will be turned on and off quicker than we can perceive. The delay() function lets you stop the Arduino from executing anything for a period of time. delay() takes an argument that determines the number of milliseconds before it executes the next set of code. There are 1000 milliseconds in one second. delay(250) will pause for a quarter second. Once your Arduino is programmed, you should see the green light turn on. When you press the switch, the red lights will start flashing, and the green light will turn off. Try changing the time of the two delay() functions; notice what happens to the lights and how the response of the system changes depending on the speed of the flashing. When you call a delay() in your program, it stops all other functionality. No sensor readings will happen until that time period has passed. While delays are often useful, when designing your own projects make sure they are not unnecessarily interfering with your interface. 26

27 Project 02 Spaceship Interface We have now gotten to the end of our second project. In this project, you created your first Arduino program to control the behaviour of some LEDs based on a switch. You have used variables, an if()...else statement, and functions to read the state of an input and control outputs. Good question! In the next class I will explain everything better to you. What is a Function! Uncle! What is a function? What is int, and I also need more information about variables. 27

28 Project 03 Understanding the Program Structure Hello Everyone! Welcome back to our Arduino class. In today s class, you will learn more about functions, variables, if-statements, loops, and other concepts used in Arduino. Again, you will use the analogwrite() function to make a LED fade. To complete this simple project, you will need one LED, one 220Ω resistor, and some jumper wires. Lastly, you will need at least 60 minutes to complete the project. Uncle! Why do we need to know all these? You see Ope, without all these information you will not be able to build your toys and other prototypes properly. 28

29 Project 03 Understanding the Program Structure Without further ado, let s carry on with our explanation. Please be informed that only brief information with regards to the structure will be provided. Data types Data types are used for declaring variables or functions of different types. It determines how much space it occupies in the storage and how the bit pattern stored is interpreted. The following are all the data types that you will use during Arduino programming. 1). void 2). Boolean 3). char 4). Unsigned char 5). Byte 6). int 7). word 8). Unsigned int 9). long 10). Unsigned long 11). String-object 12). short 13). float 14). double 15). array 16). String-char array void The void keyword is used only in function declarations. It indicates that the function is expected to return no information to the function from which it was called. Example Void Loop ( ) { // rest of the code Boolean A Boolean holds one of two values, true or false. Each Boolean variable occupies one byte of memory. Example boolean val = false ; // declaration of variable with type boolean and initialize it with false boolean state = true ; // declaration of variable with type boolean and initialize it with true 29

30 Project 03 Understanding the Program Structure Char A data type that takes up one byte of memory that stores a character value. Character literals are written in single quotes like this: 'A' and for multiple characters, strings use double quotes: "ABC". However, characters are stored as numbers. You can see the specific encoding in the ASCII chart. This means that it is possible to do arithmetic operations on characters, in which the ASCII value of the character is used. For example, 'A' + 1 has the value 66, since the ASCII value of the capital letter A is 65. Example Char chr_a = a ;//declaration of variable with type char and initialize it with character a Char chr_c = 97 ;//declaration of variable with type char and initialize it with character Unsigned char Unsigned char is an unsigned data type that occupies one byte of memory. The unsigned char data type encodes numbers from 0 to 255. Example Unsigned Char chr_y = 121 ; // declaration of variable with type Unsigned char and initialize it with character y byte A byte stores an 8-bit unsigned number, from 0 to 255. Example byte m = 25 ;//declaration of variable with type byte and initialize it with 25 int Integers are the primary data-type for number storage. int stores a 16-bit (2-byte) value. This yields a range of -32,768 to 32,767 (minimum value of -2^15 and a maximum value of (2^15) - 1). The int size varies from board to board. On the Arduino Due, for example, an int stores a 32-bit (4- byte) value. This yields a range of -2,147,483,648 to 2,147,483,647 (minimum value of -2^31 and a maximum value of (2^31) - 1). Example int counter = 32 ;// declaration of variable with type int and initialize it with 32 30

31 Project 03 Understanding the Program Structure Unsigned int Unsigned ints (unsigned integers) are the same as int in the way that they store a 2 byte value. Instead of storing negative numbers, however, they only store positive values, yielding a useful range of 0 to 65,535 (2^16) - 1). The Due stores a 4 byte (32-bit) value, ranging from 0 to 4,294,967,295 (2^32-1). Example Unsigned int counter = 60 ; // declaration of variable with type unsigned int and initialize it with 60 Word On the Uno and other ATMEGA based boards, a word stores a 16-bit unsigned number. On the Due and Zero, it stores a 32-bit unsigned number. Example word w = 1000 ;//declaration of variable with type word and initialize it with 1000 Long Long variables are extended size variables for number storage, and store 32 bits (4 bytes), from - 2,147,483,648 to 2,147,483,647. Example Long velocity = ;//declaration of variable with type Long and initialize it with Unsigned long Unsigned long variables are extended size variables for number storage and store 32 bits (4 bytes). Unlike standard longs, unsigned longs will not store negative numbers, making their range from 0 to 4,294,967,295 (2^32-1). Example Unsigned Long velocity = ;// declaration of variable with type Unsigned Long and initialize it with short A short is a 16-bit data-type. On all Arduinos (ATMega and ARM based), a short stores a 16-bit (2- byte) value. This yields a range of -32,768 to 32,767 (minimum value of -2^15 and a maximum value of (2^15) - 1). Example short val = 13 ;//declaration of variable with type short and initialize it with 13 31

32 Project 03 Understanding the Program Structure float Data type for floating-point number is a number that has a decimal point. Floating-point numbers are often used to approximate the analog and continuous values because they have greater resolution than integers. Floating-point numbers can be as large as E+38 and as low as E+38. They are stored as 32 bits (4 bytes) of information. Example float num = 1.352;//declaration of variable with type float and initialize it with double On the Uno and other ATMEGA based boards, Double precision floating-point number occupies four bytes. That is, the double implementation is exactly the same as the float, with no gain in precision. On the Arduino Due, doubles have 8-byte (64 bit) precision. Example double num = ;// declaration of variable with type double and initialize it with 45. Now that you have learnt about the different types of data types, next you will be learning about variables. But before you proceed further, make sure you spend more time learning the data type by heart. That will eventually make you a real Arduino genius you aspire to be. 32

33 Project 03 Understanding the Program Structure What is Variable Scope? Variables in Arduino has a property called scope. A scope is a region of the program and there are three places where variables can be declared. They are Inside a function or a block, which is called local variables. In the definition of function parameters, which is called formal parameters. Outside of all functions, which is called global variables. Local Variables Variables that are declared inside a function or block are local variables. They can be used only by the statements that are inside that function or block of code. Local variables are not known to function outside their own. Following is the example using local variables Void setup () { Void loop () { int x, y ; int z ; Local variable declaration x = 0; y = 0; actual initialization z = 10; Global Variables Global variables are defined outside of all the functions, usually at the top of the program. The global variables will hold their value throughout the life-time of your program. A global variable can be accessed by any function. That is, a global variable is available for use throughout your entire program after its declaration. The following example uses global and local variables int T, S ; float c = 0 ; Global variable declaration Void setup () { Void loop () { int x, y ; int z ; Local variable declaration x = 0; y = 0; actual initialization z = 10; 33

34 Project 03 Understanding the Program Structure Operators An operator is a symbol that tells the compiler to perform specific mathematical or logical functions. The following are the types of operators: Arithmetic Operators Assume variable A holds 10 and variable B holds 20 then Example void loop () { int a = 9,b = 4,c; c = a + b; c = a - b; c = a * b; c = a / b; c = a % b; Result a + b = 13 a - b = 5 a * b = 36 a / b = 2 Remainder when a divided by b = 1 Operator name Operator simple Description Example assignment operator = Stores the value to the right of the equal sign in the variable to the left of the equal sign. A = B addition + Adds two operands A + B will give 30 subtraction - Subtracts second operand from the first A - B will give -10 multiplication * Multiply both operands A * B will give 200 division / Divide numerator by denominator B / A will give 2 modulo % Comparison Operators Modulus Operator and remainder of after an integer division 34 B % A will give 0

35 Project 03 Understanding the Program Structure Comparison Operators Assume variable A holds 10 and variable B holds 20 then Example void loop () { int a = 9,b = 4 bool c = false; if(a == b) c = true; else c = false; if(a!= b) c = true; else c = false; if(a < b) c = true; else c = false; if(a > b) c = true; else c = false; if(a <= b) c = true; else c = false; if(a >= b) c = true; else c = false; Result c = false c = true c = false c = true c = false c = false Operator name Operator simple Description 35 Example equal to == Checks if the value of two operands is equal or not, if yes then condition becomes true. (A == B) is not true

36 Project 03 Understanding the Program Structure Comparison Operators - continued Operator name Operator simple Description Example equal to == Checks if the value of two operands is equal or not, if yes then condition becomes true. (A == B) is not true not equal to!= Checks if the value of two operands is equal or not, if values are not equal then condition becomes true. (A!= B) is true less than < Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true. (A < B) is true greater than > Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true. (A > B) is not true less than or equal to <= Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true. (A <= B) is true greater than or equal to >= Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true. (A >= B) is not true Please try as much as possible to try out all the examples in your Arduino IDE. 36

37 Project 03 Understanding the Program Structure Boolean Operators Assume variable A holds 10 and variable B holds 20 then Operator name Operator simple Description Example and && Called Logical AND operator. If both the operands are non-zero then then condition becomes true. (A && B) is true or Called Logical OR Operator. If any of the two operands is non-zero then then condition becomes true. (A B) is true not! Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true then Logical NOT operator will make false.!(a && B) is false Example void loop () { int a = 9,b = 4 bool c = false; if((a > b)&& (b < a)) c = true; else c = false; if((a == b) (b < a)) c = true; else c = false; if(!(a == b)&& (b < a)) c = true; else c = false; Result c = true c = true c = true 37

38 Project 03 Understanding the Program Structure Bitwise Operators Assume variable A holds 60 and variable B holds 13 then Operator name Operator simple Description Example and & Binary AND Operator copies a bit to the result if it exists in both operands. (A & B) will give 12 which is or Binary OR Operator copies a bit if it exists in either operand (A B) will give 61 which is xor ^ Binary XOR Operator copies the bit if it is set in one operand but not both. (A ^ B) will give 49 which is not ~ Binary Ones Complement Operator is unary and has the effect of 'flipping' bits. (~A ) will give -60 which is shift left << Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand. A << 2 will give 240 which is shift right >> Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand. A >> 2 will give 15 which is Example void loop () { int a = 10,b = 20 int c = 0; c = a & b ; c = a b ; c = a ^ b ; c = a ~ b ; c = a << b ; c = a >> b ; 38 Result c = 12 c = 61 c = 49 c = -60 c = 240 c = 15

39 Project 03 Understanding the Program Structure Compound Operators Assume variable A holds 10 and variable B holds 20 then Operator name Operator simple Description Example increment ++ Increment operator, increases integer value by one A++ will give 11 decrement -- Decrement operator, decreases integer value by one A-- will give 9 compound addition += Add AND assignment operator. It adds right operand to the left operand and assign the result to left operand B += A is equivalent to B = B+ A compound subtraction -= Subtract AND assignment operator. It subtracts right operand from the left operand and assign the result to left operand B -= A is equivalent to B = B - A compound multiplication *= Multiply AND assignment operator. It multiplies right operand with the left operand and assign the result to left operand B*= A is equivalent to B = B* A compound division /= Divide AND assignment operator. It divides left operand with the right operand and assign the result to left operand B /= A is equivalent to B = B / A compound modulo %= Modulus AND assignment operator. It takes modulus using two operands and assign the result to left operand B %= A is equivalent to B = B % A compound bitwise or = bitwise inclusive OR and assignment operator A = 2 is same as A = A 2 compound bitwise and &= Bitwise AND assignment operator A &= 2 is same as A = A & 2 39

40 Project 03 Understanding the Program Structure Example void loop () { int a = 10,b = 20 int c = 0; a++; a--; b += a; b -= a; b *= a; b /= a; a %= b; a = b; a &= b; Result a = 11 a = 9 b = 30 b = 10 b = 200 b = 2 a = 0 a = 61 a = 12 Next, you will be learning more about the control statements which are if-else and switch case statements. As shown in the picture here, if the condition is true then the conditional code is executed, else it is not executed. 40

41 Project 03 Understanding the Program Structure Control Statements are elements in Source Code that control the flow of program execution. They are S.NO. Control Statement & Description 1 If statement It takes an expression in parenthesis and a statement or block of statements. If the expression is true then the statement or block of statements gets executed otherwise these statements are skipped. 2 If else statement An if statement can be followed by an optional else statement, which executes when the expression is false. 3 If else if else statement The if statement can be followed by an optional else if...elsestatement, which is very useful to test various conditions using single if...else if statement. 4 5 switch case statement Similar to the if statements, switch...case controls the flow of programs by allowing the programmers to specify different codes that should be executed in various conditions. Conditional Operator? : The conditional operator? : is the only ternary operator in C. Next, you will be learning about the loop statement. A loop statement will allow you to execute a statement or group of statements multiple times 41

42 Project 03 Understanding the Program Structure the following types of loops to handle looping requirements. S.NO. Loop & Description 1 while loop while loops will loop continuously, and infinitely, until the expression inside the parenthesis, () becomes false. Something must change the tested variable, or the while loop will never exit. 2 do while loop The do while loop is similar to the while loop. In the while loop, the loop-continuation condition is tested at the beginning of the loop before performed the body of the loop. 3 for loop A for loop executes statements a predetermined number of times. The control expression for the loop is initialized, tested and manipulated entirely within the for loop parentheses. 4 5 Nested Loop C language allows you to use one loop inside another loop. The following example illustrates the concept. Infinite loop It is the loop having no terminating condition, so the loop becomes infinite. Functions 42

43 Project 03 Understanding the Program Structure Functions allow structuring the programs in segments of code to perform individual tasks. The typical case for creating a function is when one needs to perform the same action multiple times in a program. Standardizing code fragments into functions has several advantages Functions help the programmer stay organized. Often this helps to conceptualize the program. Functions codify one action in one place so that the function only has to be thought about and debugged once. This also reduces chances for errors in modification, if the code needs to be changed. Functions make the whole sketch smaller and more compact because sections of code are reused many times. They make it easier to reuse code in other programs by making it modular, and using functions often makes the code more readable. There are two required functions in an Arduino sketch or a program i.e. setup () and loop(). Other functions must be created outside the brackets of these two functions. The most common syntax to define a function is Return type function name (argument1, argument2, ) { Statements; Function Declaration A function is declared outside any other functions, above or below the loop function. We can declare the function in two different ways The first way is just writing the part of the function called a function prototype above the loop function, which consists of Function return type Function name Function argument type, no need to write the argument name Function prototype must be followed by a semicolon ( ; ). The following example shows the demonstration of the function declaration using the first method. Example int sum_func (int x, int y) // function declaration { 43

44 Project 03 Understanding the Program Structure Example int sum_func (int x, int y) // function declaration { int z = 0; z = x+y ; return z; // return the value void setup () { Statements // group of statements Void loop () { int result = 0 ; result = Sum_func (5,6) ; // function call The second part, which is called the function definition or declaration, must be declared below the loop function, which consists of Function return type Function name Function argument type, here you must add the argument name The function body (statements inside the function executing when the function is called) The following example demonstrates the declaration of function using the second method. Example int sum_func (int, int ) ; // function prototype void setup () { Statements // group of statements Void loop () { int result = 0 ; result = Sum_func (5,6) ; // function call int sum_func (int x, int y) // function declaration { int z = 0; z = x+y ; return z; // return the value The second method just declares the function above the loop function. 44

45 Project 03 Understanding the Program Structure Now, it is time to use the analogwrite() function to make a LED fade. Don t forget that you will need one LED, one 220Ω resistor, and some jumper wires. Lastly, you will need at least 45 minutes to complete the project. To build the project, follow the circuit diagram and hook up the components on the breadboard as shown in the image given here. 45

46 Project 03 Understanding the Program Structure This example demonstrates the use of the analogwrite() function in fading an LED off. AnalogWrite uses pulse width modulation (PWM), turning a digital pin on and off very quickly with different ratios between on and off, to create a fading effect. Arduino Code /* Fade This example shows how to fade an LED on pin 9 using the analogwrite() function. The analogwrite() function uses PWM, so if you want to change the pin you're using, be sure to use another PWM capable pin. On most Arduino, the PWM pins are identified with a "~" sign, like ~3, ~5, ~6, ~9, ~10 and ~11. */ int led = 9; // the PWM pin the LED is attached to int brightness = 0; // how bright the LED is int fadeamount = 5; // how many points to fade the LED by // the setup routine runs once when you press reset: void setup() { // declare pin 9 to be an output: pinmode(led, OUTPUT); // the loop routine runs over and over again forever: void loop() { // set the brightness of pin 9: analogwrite(led, brightness); // change the brightness for next time through the loop: brightness = brightness + fadeamount; // reverse the direction of the fading at the ends of the fade: if (brightness == 0 brightness == 255) { fadeamount = -fadeamount ; // wait for 30 milliseconds to see the dimming effect delay(300); 46

47 Project 03 Understanding the Program Structure Code to Note After declaring pin 9 as your LED pin, there is nothing to do in the setup() function of your code. The analogwrite() function that you will be using in the main loop of your code requires two arguments: One, telling the function which pin to write to and the other indicating what PWM value to write. In order to fade the LED off and on, gradually increase the PWM values from 0 (all the way off) to 255 (all the way on), and then back to 0, to complete the cycle. In the sketch given above, the PWM value is set using a variable called brightness. Each time through the loop, it increases by the value of the variable fadeamount. If brightness is at either extreme of its value (either 0 or 255), then fadeamount is changed to its negative. In other words, if fadeamount is 5, then it is set to -5. If it is -5, then it is set to 5. The next time through the loop, this change causes brightness to change direction as well. analogwrite() can change the PWM value very fast, so the delay at the end of the sketch controls the speed of the fade. Try changing the value of the delay and see how it changes the fading effect. Result You should see your LED brightness change gradually. We have now gotten to the end of this long project. In this project you learnt about the loop statements, if-else statements, the operators, data types, variables, and functions. Thank you for sticking around. See you in the next class. 47

48 Project 04 Next Einstein (Know how Hot you are) Hello Everyone! Welcome back to our fourth Arduino class. In today s class, you will be building a device to measure how hot you truly are. To complete this project, you will need three LED, three 220Ω resistors, a temperature sensor, and some jumper wires. Once again, you will need at least 45 minutes to complete the project. The temperature sensor is the tiny black component in your kit with three legs labelled TMP. With this sensor will be measuring how warm your skin is. Once you are ready, look through your kit and connect the components as shown in the image here. 48

49 Project 04 Next Einstein (Know how Hot you are) Please Note the following How to connect the components 1. Attach the cathode (short leg) of each of the LEDs you re using to ground through a 220-ohm resistor. Connect the anodes of the LEDs to pins 2 through 4. These will be the indicators for the project. 2. Place the TMP36 on the breadboard with the rounded part facing away from the Arduino (the order of the pins is important!) as shown in Fig. 2. Connect the left pin of the flat facing side to power, and the right pin to ground. Connect the center pin to pin A0 on your Arduino. This is analog input pin 0. The temperature sensor is a component that outputs a changing voltage depending on the temperature it senses. It has three pins: one that connects to ground (GND), another that connects to power, and a third that outputs a variable voltage to your Arduino. In the sketch for this project, you ll read the sensor s output and use it to turn LEDs on and off, indicating how warm you are. There are several different models of temperature sensor. The model in your kit is the TMP36. TMP36 is convenient because it outputs a voltage that changes directly proportional to the temperature in degrees Celsius. Moreover, the Arduino IDE comes with a tool called the serial monitor that enables you to report back results from the microcontroller. Using the serial monitor, you can get information about the status of sensors, and get an idea about what is happening in your circuit and code as it runs. The image depicts how the Arduino IDE will output the outcome of this project. 49

50 Project 04 Next Einstein (Know how Hot you are) To build the code for this project, you will need to know few new things about the code. These information are presented below. Constants Constants are similar to variables in that they allow you to uniquely name things in the program, but unlike variables they cannot change. Name the analog input for easy reference, and create another named constant to hold the baseline temperature. For every 2 degrees above this baseline, an LED will turn on. You ve already seen the int datatype, used here to identify which pin the sensor is on. The temperature is being stored as a float, or floating-point number. This type of number has a decimal point, and is used for numbers that can be expressed as fractions. Serial.begin() In the setup you re going to use a new command, Serial. begin(). This opens up a connection between the Arduino and the computer, so you can see the values from the analog input on your computer screen. The argument 9600 is the speed at which the Arduino will communicate, 9600 bits per second. You will use the Arduino IDE s serial monitor to view the information you choose to send from your microcontroller. When you open the IDE s serial monitor verify that the baud rate is For() loop Next up is a for() loop to set some pins as outputs. These are the pins that you attached LEDs to earlier. Instead of giving them unique names and typing out the pinmode() function for each one, you can use a for() loop to go through them all quickly. This is a handy trick if you have a large number of similar things you wish to iterate through in a program. Tell the for() loop to run through pins 2 to 4 sequentially. In the loop(), you ll use a local variable named sensorval to store the reading from your sensor. To get the value from the sensor, you call analogread() that takes one argument: what pin it should take a voltage reading on. The value, which is between 0 and 1023, is a representation of the voltage on the pin. Serial.print() The function Serial.print() sends information from the Arduino to a connected computer. You can see this information in your serial monitor. If you give Serial.print() an argument in quotation marks, it will print out the text you typed. If you give it a variable as an argument, it will print out the value of that variable. 50

51 Project 04 Next Einstein (Know how Hot you are) Serial.begin() In the setup you re going to use a new command, Serial. begin(). This opens up a connection between the Arduino and the computer, so you can see the values from the analog input on your computer screen. The argument 9600 is the speed at which the Arduino will communicate, 9600 bits per second. You will use the Arduino IDE s serial monitor to view the information you choose to send from your microcontroller. When you open the IDE s serial monitor verify that the baud rate is For() loop Next up is a for() loop to set some pins as outputs. These are the pins that you attached LEDs to earlier. Instead of giving them unique names and typing out the pinmode() function for each one, you can use a for() loop to go through them all quickly. This is a handy trick if you have a large number of similar things you wish to iterate through in a program. Tell the for() loop to run through pins 2 to 4 sequentially. In the loop(), you ll use a local variable named sensorval to store the reading from your sensor. To get the value from the sensor, you call analogread() that takes one argument: what pin it should take a voltage reading on. The value, which is between 0 and 1023, is a representation of the voltage on the pin. Serial.print() The function Serial.print() sends information from the Arduino to a connected computer. You can see this information in your serial monitor. If you give Serial.print() an argument in quotation marks, it will print out the text you typed. If you give it a variable as an argument, it will print out the value of that variable. Uncle! Why are there so many codes to learn? Hmmm! Ope! I am afraid without knowing these information you will not be able to build use your Arduino well. 51

52 Project 04 Next Einstein (Know how Hot you are) The Code const int sensorpin = A0; // room temperature in Celsius const float baselinetemp = 20.0; void setup(){ // open a serial connection to display values Serial.begin(9600); // set the LED pins as outputs // the for() loop saves some extra coding for(int pinnumber = 2; pinnumber<5; pinnumber++){ pinmode(pinnumber,output); digitalwrite(pinnumber, LOW); void loop(){ // read the value on AnalogIn pin 0 // and store it in a variable int sensorval = analogread(sensorpin); // send the 10-bit sensor value out the serial port Serial.println("sensor Value: "); Serial.println(sensorVal); // convert the ADC reading to voltage float voltage = (sensorval/1024.0) * 5.0; // Send the voltage level out the Serial port Serial.println(", Volts: "); Serial.println(voltage); // convert the voltage to temperature in degrees C // the sensor changes 10 mv per degree // the datasheet says there's a 500 mv offset // ((voltage - 500mV) times 100) Serial.println(", degrees C: "); float temperature = (voltage -.5) * 100; Serial.println(temperature); // if the current temperature is lower than the baseline // turn off all LEDs if(temperature < baselinetemp){ digitalwrite(2, LOW); digitalwrite(3, LOW); digitalwrite(4, LOW); 52

53 Project 04 Next Einstein (Know how Hot you are) // if the temperature rises 2-4 degrees, turn an LED on else if(temperature >= baselinetemp+2 && temperature < baselinetemp+4){ digitalwrite(2, HIGH); digitalwrite(3, LOW); digitalwrite(4, LOW); // if the temperature rises 4-6 degrees, turn a second LED on else if(temperature >= baselinetemp+4 && temperature < baselinetemp+6){ digitalwrite(2, HIGH); digitalwrite(3, HIGH); digitalwrite(4, LOW); // if the temperature rises more than 6 degrees, turn all LEDs on else if(temperature >= baselinetemp+6){ digitalwrite(2, HIGH); digitalwrite(3, HIGH); digitalwrite(4, HIGH); delay(100); After typing these codes on the Arduino IDE, you can now upload the code on the IDE. With the code uploaded to the Arduino, click the serial monitor icon just as shown in the picture above. You should see a stream of values coming out, formatted like this: Sensor: 200, Volts:.70, degrees C: 17 Try putting your fingers around the sensor while it is plugged into the breadboard and see what happens to the values in the serial monitor. Make a note of what the temperature is when the sensor is left in the open air. Close the serial monitor and change the baselinetemp constant in your program to the value you observed the temperature to be. Upload your code again, and try holding the sensor in your fingers. As the temperature rises, you should see the LEDs turn on one by one. Congratulations Einstein! We have now gotten to the end of this class. In this project you have successfully built a sensor to check how warm you are. 53

54 Project 05 Welcome to YouNiversity Hello Class! Welcome to YouNiversity! At the YouNiversity, you have to do the following: Go to YouTube Find an Arduino project Follow how it was built and build it Then, present your project to your friends explaining to them why you selected the project, what you have learnt, and how others can learn from the project. 54

55 Project 06 Colour Mixing Lamp Hello Class! Welcome back from YouNiversity! Hope you learnt one or two vital lessons. Now we carry on with our remaining projects. In this project, you will create a lamp that changes its color depending on the room's lighting conditions. Shine red and blue light on a set of three light sensors, and the LED will turn purple! This project uses three analog inputs and you will watch data from the sensor in the "serial monitor." You will need the following electrical components for this project: one RGB LED, three 220Ω resistors, three 10 kω resistors, three photoresistors, and at least 45 Minutes. Using a tri-colour LED and three photoresistors, you will be creating a lamp that smoothly changes colours depending on external lighting conditions. So if you are ready, connect your components as shown in the image here. 55

56 Project 06 Colour Mixing Lamp Please note that the RGB LED you will use for this project has four pins instead of the two pin LED you have used thus far. In this project, the photoresistors (sensors that change their resistance depending on the amount of light that hits them, also known as photocells or light-dependent resistors) will be used as inputs. If you connect one end of the resistor to your Arduino, you can measure the change in resistance by checking the voltage on the pin. How to connect 1. Place the three photoresistors on the breadboard so they cross the center divide from one side to the other, as shown in Fig. 1. Attach one end of each photoresistor to power. On the other side, attach a 10-kilohm resistor to ground. This resistor is in series with the photoresistor, and together they form a voltage divider. The voltage at the point where they meet is proportional to the ratio of their resistances, according to Ohm s Law (see Project 1 for more on Ohm s Law). As the resistance of the photoresistor changes when light hits it, the voltage at this junction changes as well. On the same side as the resistor, connect the photoresistors to Analog In pins 0, 1, and 2 with hookup wire. 2. Take the three colored gels and place one over each of the photoresistors. Place the red gel over the photoresistor connected to A0, the green over the one connected to A1, and the blue over the one connected to A2. Each of these filters lets only light of a specific wavelength through to the sensor it s covering. The red filter passes only red light, the green filter passes only green light, and the blue filter passes only blue light. This allows you to detect the relative colour levels in the light that hits your sensors. 3. The LED with 4 legs is a common cathode RGB LED. The LED has separate red, green, and blue elements inside, and one common ground (the cathode). By creating a voltage difference between the cathode and the voltage coming out of the Arduino s PWM pins (which are connected to the anodes through 220-ohm resistors), you ll cause the LED to fade between its three colours. Make note of what the longest pin is on the LED, place it in your breadboard, and connect that pin to ground. Connect the other three pins to digital pins 9, 10 and 11 in series with 220-ohm resistors. Be sure to connect each LED lead to the correct PWM pin, according to the figure on the left. 56

57 Project 06 Colour Mixing Lamp The Code const int greenledpin=9; const int blueledpin=10; const int redledpin=11; const int redsensorpin=a0; const int greensensorpin=a1; const int bluesensorpin=a2; int redvalue=0; int greenvalue=0; int bluevalue=0; int redsensorvalue=0; int greensensorvalue=0; int bluesensorvalue=0; void setup() { Serial.begin(9600); pinmode(greenledpin,output); pinmode(blueledpin,output); pinmode(redledpin,output); void loop() { redsensorvalue=analogread(redsensorpin); delay(5); greensensorvalue=analogread(greensensorpin); delay(5); bluesensorvalue=analogread(bluesensorpin); Serial.print( Raw Sensor Value \t red: ); Serial.print(redSensorValue); Serial.print( \t green: ); Serial.print(greenSensorValue); Serial.print( \t blue: ); Serial.println(blueSensorValue); 57

58 Project 06 Colour Mixing Lamp The Code - continued //report the calculated LED light levels redvalue=redsensorvalue/4; greenvalue=greensensorvalue/4; bluevalue=bluesensorvalue/4; Serial.print( Maped Sensor Value \t red: ); Serial.print(redValue); Serial.print( \t green: ); Serial.print(greenValue); Serial.print( \t blue: ); Serial.println(blueValue); analogwrite(redledpin,redvalue); analogwrite(greenledpin,greenvalue); analogwrite(blueledpin,bluevalue); Use it Once you have your Arduino programmed and wired up, open the serial monitor. The LED will probably be an off-white colour, depending on the predominant colour of the light in your room. Look at the values coming from the sensors in the serial monitor, if you re in an environment with stable lighting, the number should probably be fairly consistent. Turn off the light in the room you re in and see what happens to the values of the sensors. With a flashlight, illuminate each of the sensors individually and notice how the values change in the serial monitor, and notice how the LED s colour changes. When the photoresistors are covered with a gel, they only re-act to light of a certain wavelength. This will give you the opportunity to change each of the colours independently. We have now gotten to the end of this project. Hope to see you in our next class. 58

59 Project 07 Mood Cue Welcome back to our Arduino class! Arriving to this project means not only that you are starting to familiarize with Arduino, but also that you are determined to be able to create amazing things with it. So first of all, we would like to congratulate you. The knowledge you have gained so far is really important, but we really have to step things up by learning how to make things move. For this purpose, a servomotor is going to be used. So let us begin. In today s class, you will be making use of the following, one potentiometer, one Servomotor, two 100UF Capacitors, three male header pins, and as usual some jumper wires. Lastly, this project will require at least 60 minutes of your time. But before we proceed further, we will be giving a short explanation of the servomotor below. 59

60 Project 07 Mood Cue The picture here shows what the Servo motor looks like. Servo motors are a special type of motor that don t spin around in a circle, but move to a specific position and stay there until you tell them to move again. Servos usually only rotate 180 degrees (one half of a circle). Similar to the way you used pulses to PWM an LED in the Colour Mixing Lamp Project, servo motors expect a number of pulses that tell them what angle to move to. The pulses always come at the same time intervals, but the width varies between 1000 and 2000 microseconds. While it s possible to write code to generate these pulses, the Arduino software comes with a library that allows you to easily control the motor. Because the servo only rotates 180 degrees, and your analog input goes from , you ll need to use a function called map() to change the scale of the values coming from the potentiometer. One of the great things about the Arduino community are the talented people who extend its functionality through additional software. It s possible for anyone to write libraries to extend the Arduino s functionality. There are libraries for a wide variety of sensors and actuators and other devices that users have contributed to the community. A software library expands the functionality of a programming environment. The Arduino software comes with a number of libraries that are useful for working with hardware or data. One of the included libraries is designed to use with servo motors. In your code, you ll import the library, and all of its functionality will be available to you. Before reading the code, note that a servomotor library is being used. After importing it, you can use all the functions that contains making the code much easier. As it is shown in the picture below, the potentiometer must be connected to an analog input as long as to the 5V entry and to the ground (GND). Otherwise, the servo must be to a digital input as well as to the 5V and the GND. Make sure you connect the capacitors properly as they have polarity. 60

61 Project 07 Mood Cue Once you are ready, connect the components on your Arduino board and breadboard as shown in the picture here. After this you have to enter the codes on the Arduino IDE. How to connect 1. Attach 5V and ground to one side of your breadboard from the Arduino. 2. Place a potentiometer on the breadboard, and connect one side to 5V, and the other to ground. A potentiometer is a type of volt-age divider. As you turn the knob, you change the ratio of the voltage between the middle pin and power. You can read this change on an analog input. Connect the middle pin to analog pin 0. This will control the position of your servo motor. 3. The servo has three wires coming out of it. One is power (red), one is ground (black), and the third (white) is the control line that will receive information from the Arduino. Plug three male headers into the female ends of the servo wires (see Fig. 3). Connect the headers to your breadboard so that each pin is in a different row. Connect 5V to the red wire, ground to the black wire, and the white wire to pin When a servo motor starts to move, it draws more current than if it were already in motion. This will cause a dip in the voltage on your board. By placing a 100uf capacitor across power and ground right next to the male headers as shown in Fig. 1, you can smooth out any voltage changes that may occur. You can also place a capacitor across the power and ground going into your potentiometer. These are called decoupling capacitors because they reduce, or decouple, changes caused by the components from the rest of the circuit. Be very careful to make sure you are connecting the cathode to ground (that s the side with a black stripe down the side) and the anode to power. If you put the capacitors in backwards, they can explode. Your servo motor should come with female connectors, so you ll need to add header pins to connect it to the breadboard as shown in this picture 61

62 Project 07 Mood Cue The Code #include <Servo.h> Servo TestServo; int const potpin=a0; int potvalue; int angle; void setup() { TestServo.attach(9); Serial.begin(9600); void loop() { potvalue=analogread(potpin); Serial.print( potvalue: ); Serial.print(potValue); angle=map(potvalue, 0,1023,0,179); Serial.print(,angle: ); Serial.println(angle); TestServo.write(angle); delay(15); How it works To use the servo library, you ll first need to import it. This makes the additions from the library available to your sketch. To refer to the servo, you re going to need to create a named instance of the servo library in a variable. This is called an object. When you do this, you re making a unique name that will have all the functions and capabilities that the servo library offers. From this point on in the program, every time you refer to myservo, you ll be talking to the servo object. Set up a named constant for the pin the potentiometer is attached to, and variables to hold the analog input value and angle you want the servo to move to. In the setup(), you re going to need to tell the Arduino what pin your servo is attached to. Include a serial connection so you can check the values from the potentiometer and see how they map to angles on the servo motor. In the loop(), read the analog input and print out the value to the serial monitor. To create a usable value for the servo motor from your analog input, it s easiest to use the map() function. This handy function scales numbers for you. In this case it will change values between to values between It takes five arguments : the number to be scaled (here it s potval), the minimum value of the input (0), the maximum value of the input (1023), the minimum value of the output (0), and the maximum value of the output (179). Store this new value in the angle variable. Then, print out the mapped value to the serial monitor. Finally, it s time to move the servo. The command servo. write() moves the motor to the angle you specify. At the end of the loop() put a delay so the servo has time to move to its new position. 62

63 Project 07 Mood Cue Once your Arduino has been programmed and powered up, open the serial monitor. You should see a stream of values similar to the one here potval : 1023, angle : 179 potval : 1023, angle : 179 When you turn the potentiometer, you should see the numbers change. More importantly, you should see your servo motor move to a new position. Notice the relationship be-tween the value of potval and angle in the serial monitor and the position of the servo. You should see consistent results as you turn the pot. One nice thing about using potentiometers as analog inputs is that they will give you a full range of values between 0 and This makes them helpful in testing projects that use analog input. Congratulations! You have successfully completed the project. In this project you learnt how t make things move using a servo motor. Now, your dream of making your toy robots is 70% accomplished. See you in the next class. 63

64 Project 08 Little Symphony Welcome back to our Arduino class! Hope you are still in a good mood after the last class. Today we will be doing another spectacular project. In today s project we will be building a little symphony using a theremin. A theremin is an instrument that makes sounds based on the movements of a musician s hands around the instrument. A piezo is a small element that vibrates when it receives electricity. When it moves, it displaces air around it, creating sound waves. To build project, a Piezo element, a Photoresistor, and a 10KΩ resistor. Lastly, you will need 45 minutes to complete the project. Uncle! What is a Theremin and Piezo? 64

65 Project 08 Little Symphony Once you are ready please make the connection as shown on this picture. In case you need more information on the components, please consult the introduction. Take your piezo, and connect one end to ground, and the other to digital pin 8 on the Arduino. Place your photoresistor on the breadboard, connecting one end to 5V. Connect the other end to the Arduino s analogin pin 0, and to ground through a 10-kilohm resistor. The theremin detects where a performer s hands are in relation to two antennas by reading the capacitive change on the antennas. These antennas are connected to analog circuitry that create the sound. One antenna controls the frequency of the sound and the other controls volume. While the Arduino can t exactly replicate the mysterious sounds from this instrument, it is possible to emulate them using the tone() function. Instead of sensing capacitance with the Arduino, you ll be using a photoresistor to detect the amount of light. By moving your hands over the sensor, you ll change the amount of light that falls on the photoresistor s face, as you did in Project 4. The change in the voltage on the analog pin will determine what frequency note to play. You ll connect the photoresistors to the Arduino using a voltage divider circuit like you did in Project 4. You probably noticed in the earlier project that when you read this circuit using analogread(), your readings didn t range all the way from 0 to The fixed resistor connecting to ground limits the low end of the range, and the brightness of your light limits the high end. Instead of settling for a limited range, you ll calibrate the sensor readings getting the high and low values, mapping them to sound frequencies using the map() function to get as much range out of your theremin as possible. This will have the added benefit of adjusting the sensor readings whenever you move your circuit to a new environment, like a room with different light conditions. 65

66 Project 08 Little Symphony About the Code Create a variable to hold the analogread() value from the photoresistor. Next, create variables for the high and low values. You re going to set the initial value in the sensorlow variable to 1023, and set the value of the sensorhigh variable to 0. When you first run the program, you ll compare these numbers to the sensor s readings to find the real maximum and minimum values. Create a constant named ledpin. You ll use this as an indicator that your sensor has finished calibrating. For this project, use the on-board LED connected to pin 13. In the setup(), change the pinmode() of ledpin to OUTPUT, and turn the light on. The next steps will calibrate the sensor s maximum and minimum values. You ll use a while() statement to run a loop for 5 seconds. while() loops run until a certain condition is met. In this case you re going to use the millis() function to check the current time. millis() reports how long the Arduino has been running since it was last powered on or reset. In the loop, you ll read the value of the sensor; if the value is less than sensorlow (initially 1023), you ll update that variable. If it is greater than sensorhigh (initially 0), that gets updated. When 5 seconds have passed, the while() loop will end. Turn off the LED attached to pin 13. You ll use the sensor high and low values just recorded to scale the frequency in the main part of your program. In the loop(), read the value on A0 and store it in sensorvalue. Create a variable named pitch. The value of pitch is going to be mapped from sensorvalue. Use sensorlow and sensorhigh as the bounds for the incoming values. For starting values for output, try 50 to These numbers set the range of frequencies the Arduino will generate. Next, call the tone() function to play a sound. It takes three arguments : what pin to play the sound on (in this case pin 8), what frequency to play (determined by the pitch variable), and how long to play the note (try 20 milliseconds to start). Then, call a delay() for 10 milliseconds to give the sound some time to play. Once you are done, then enter the code on the next page in your Arduino IDE. 66

67 Project 08 Little Symphony The Code int sensorvalue; // variable to calibrate low value int sensorlow = 1023; // variable to calibrate high value int sensorhigh = 0; // LED pin const int ledpin = 13; void setup() { // Make the LED pin an output and turn it on pinmode(ledpin, OUTPUT); digitalwrite(ledpin, HIGH); // calibrate for the first five seconds after program runs while (millis() < 5000) { // save the maximum sensor value sensorvalue = analogread(a0); if (sensorvalue > sensorhigh) { sensorhigh = sensorvalue; // save the minimum sensor value if (sensorvalue < sensorlow) { sensorlow = sensorvalue; //turn the LED off, signaling the end of the calibration digitalwrite(ledpin, LOW); void loop() { //read the input from A0 and store it in a variable sensorvalue=analogread(a0); // map the sensor values to a wide range of pitches int pitch=map(sensorvalue, sensorlow, sensorhigh, 50, 4000); // play the tone for 20 ms on pin 8 tone(8, pitch, 20); // wait for 10ms delay(10); 67

68 Project 08 Little Symphony How it works When you first power the Arduino on, there is a 5 second window for you to calibrate the sensor. To do this, move your hand up and down over the photoresistor, changing the amount of light that reaches it. The closer you replicate the motions you expect to use while playing the instrument, the better the calibration will be. After 5 seconds, the calibration will be complete, and the LED on the Arduino will turn off. When this happens, you should hear some noise coming from the piezo! As the amount of light that falls on the sensor changes, so should the frequency that the piezo plays. Congratulations! It is time for a little jamboree! So let s dance everybody! GBOSA! GBOSA!! GBOSA!!! Three GBOSA for GreenLab! GBOSA! GBOSA!! GBOSA!!! 68

69 Project 09 Welcome back to YouNiversity Hello Class! Welcome back to YouNiversity! Just like you did in the last YouNiversity, once again: Go to YouTube Find an Arduino project Follow how it was built and build it Then, present your project to your friends explaining to them why you selected the project, what you have learnt, and how others can learn from the project. 69

70 Project 10 Piano Hello Class! Welcome back from YouNiversity! Without doubt I know you are learning while having as much fun as you can. To carry on with our Music lessons we will be building a little Piano that has 4 notes. Who knows what those notes are? Uncle! Me! Uncle! Please can I try? Tayo please try. Exactly! Oh Yes! It is Do Re Mi Fa. 70

71 Project 10 Piano To build this project, you will need four switches, your Piezo, one 10KΩ, one 220Ω, and one 1MΩ. Finally, just like the previous projects you will need at least 45 minutes to complete this project. But I encourage you not to rush, take your time and have fun while you learn. As we wanted the instrument to have 4 notes, we put four switches in parallel. In three branches we connected a resistor in series with the switch and in the fourth one a wire connected directly to power. This kind of structure is called a mixed resistor circuit. Each resistor had a different value, so every time we pushed one switch the voltage read by the analogic entrance was different. Then, in function of this value, the piezometer vibrated at a different frequency. 71

72 Project 10 Piano Once you are ready please make the connection as shown in this picture. How to connect 1. Wire up your breadboard with power and ground as in the previous projects. Connect one end of the piezo to ground. Connect the other end to pin 8 on your Arduino. 2. Place your switches on the breadboard as shown in the circuit. The arrangement of resistors and switches feeding into an analog input is called a resistor ladder. Connect the first one directly to power. Connect the second, third and fourth switches to power through a 220-ohm, 10-kilohm and 1-megohm resistor, respectively. Connect all the switches outputs together in one junction. Connect this junction to ground with a 10-kilohm resistor, and also connect it to Analog In 0. Each of these acts as a voltage divider. Understanding the Code In this program, you ll need to keep a list of frequencies you want to play when you press each of your buttons. You can start out with the frequencies for middle C, D, E and F (262Hz, 294Hz, 330Hz, and 349Hz). To do this, you ll need a new kind of variable called an array. An array is a way to store different values that are related to each other, like the frequencies in a musical scale, using only one name. They are a convenient tool for you to quickly and efficiently access information. To declare an array, start as you would with a variable, but follow the name with a pair of square brackets: []. After the equals sign, you ll place your elements in curly brackets. 72

73 Project 10 Piano To read or change the elements of the array, you reference the individual element using the array name and then the index of the item you want to address. The index refers to the order in which the items appear when the array is created. The first item in the array is item 0, the second is item 1, and so forth. Set up an array of four notes using the frequencies listed above. Make this array a global variable by declaring it before the setup(). In your setup(), start serial communication with the computer. In the loop(), declare a local variable to hold the value read on pin A0. Because each switch has a different resistor value connecting it to power, each will have a different value associated with it. To see the values, add the line Serial. println(keyval) to send to the computer. Using an if()...else statement, you can assign each value to a different tone. The values included in the example program are ballpark figures for these resistor sizes. As all resistors have some tolerance for error, these may not work exactly for you. Use the information from the serial monitor to adjust as necessary. After each if() statement, call the tone() function. The program references the array to determine what frequency to play. If the value of A0 matches one of your if statements, you can tell the Arduino to play a tone. It s possible your circuit is a little noisy and the values may fluctuate a little bit while pressing a switch. To accommodate for this variation, it s a good idea to have a small range of values to check against. If you use the comparison &&, you can check multiple statements to see if they are true. If you press the first button, notes[0] will play. If you press the second, notes[1] will play, and if you press the third, notes[2] will play. This is when arrays become really handy. Only one frequency can play on a pin at any given time, so if you re pressing multiple keys, you ll only hear one sound. To stop playing notes when there is no button being pressed, call the notone() function, providing the pin number to stop playing sound on. If your resistors are close in value to the values in the example program, you should hear some sounds from the piezo when you press the buttons. If not, check the serial monitor to make sure each of the buttons is in a range that corresponds to the notes in the if()...else statement. If you re hearing a sound that seems to stutter, try increasing the range a little bit. Press multiple buttons at the same time, and see what sort of values you get in the serial monitor. Use these new values to trigger even more sounds. Experiment with different frequencies to expand your musical output. You can find frequencies of musical notes on this page: arduino.cc/frequencies 73

74 Project 10 Piano The Code //Create a matrix with the frequencies of the musical notes C4,D4,E4,F4 int notes[ ]={262,294,330,349; void setup() { //To force transmission speed between Arduino and the computer to be 9600 bytes/second Serial.begin(9600); void loop() { int PushedKeyValue=analogRead(A0); Serial.println(PushedKeyValue); //Depending on the value obtained, we make the piezometre vibrate at the correspondant frequence. If PushedKeyValue==1023 it will be a C4, for example. if (PushedKeyValue==1023){ tone(8,notes[0]); else if (PushedKeyValue >=990 && PushedKeyValue<=1010){ tone(8,notes[1]); else if (PushedKeyValue >=505 && PushedKeyValue<=515){ tone(8,notes[2]); else if (PushedKeyValue >=5 && PushedKeyValue<=10){ tone(8,notes[3]); else{ notone(8); If your resistors are close in value to the values in the example program, you should hear some sounds from the piezo when you press the buttons. If not, check the serial monitor to make sure each of the buttons is in a range that corresponds to the notes in the if()...else statement. If you re hearing a sound that seems to stutter, try increasing the range a little bit. Press multiple buttons at the same time, and see what sort of values you get in the serial monitor. Use these new values to trigger even more sounds. Experiment with different frequencies to expand your musical output. You can find frequencies of musical notes on this page: arduino.cc/frequencies 74

75 Project 10 Piano Thank you for your time and attention. Please try if you can build a 5 notes or 6 notes piano. We are now at the end of today s class. 75

76 Project 11 - Digital Hourglass Hello Class! Welcome back to our Arduino class. In today s class we will be digitizing the hour glass. Uncle! Please can I ask a question? What is an hour glass? That s a great question Tayo! This is an Hourglass, and it is a device used to measure time in the olden days. It has two glass compartments from which sand runs from the upper compartment to the lower one. In our project, the sand will be replaced by some LEDs and a tilt switch (also known as mercury switch) will detect when the hourglass turns. Oh yes! I remember seeing it in one of my cartoons. 76

77 Project 11 - Digital Hourglass In today s class, you will be making use of the following, six LEDs, six 220Ω resistor, one 10KΩ, one tilt switch, and as usual some jumper wires. Lastly, this project will require at least 30 minutes of your time. But please spend as much time as required so you can fully understand the project. During this project you will learn about tilt switches and how to use them. In addition, we are using the millis() function, which is going to replace delay(). Long variables are being introduced too. Up to now, when you ve wanted something to happen at a specific time interval with the Arduino, you ve used delay(). This is handy, but a little confining. When the Arduino calls delay(), it freezes its current state for the duration of the delay. That means there can be no other input or output while it s waiting. Delays are also not very helpful for keeping track of time. If you wanted to do something every 10 seconds, having a 10 second delay would be fairly cumbersome. The millis() function helps to solve these problems. It keeps track of the time your Arduino has been running in milliseconds. You used it previously in Project 6 when you created a timer for calibration. So far you ve been declaring variables as int. An int (integer) is a 16-bit number, it holds values between -32,768 and 32,767. Those may be some large numbers, but if the Arduino is counting 1000 times a second with millis(), you d run out of space in less than a minute. The long datatype holds a 32- bit number (between -2,147,483,648 and 2,147,483,647). Since you can t run time backwards to get negative numbers, the variable to store millis() time is called an unsigned long. When a datatype is called unsigned, it is only positive. This allows you to count even higher. An unsigned long can count up to 4,294,967,295. That s enough space for millis() to store time for almost 50 days. By comparing the current millis() to a specific value, you can see if a certain amount of time has passed. When you turn your hourglass over, a tilt switch will change its state, and that will set off another cycle of LEDs turning on. The tilt switch works just like a regular switch in that it is an on/off sensor. You ll use it here as a digital input. What makes tilt switches unique is that they detect orientation. Typically they have a small cavity inside the housing that has a metal ball. When tilted in the proper way, the ball rolls to one side of the cavity and connects the two leads that are in your breadboard, closing the switch. With six LEDs, your hourglass will run for an hour, just as its name implies. 77

78 Project 11 - Digital Hourglass How to connect 1. Connect power and ground to your breadboard. 2. Connect the anode (longer leg) of six LEDs to digital pins 2-7. Connect the LEDs to ground through 220-ohm resistors. 3. Connect one lead of the tilt switch to 5V. Connect the other to a 10-kilohm resistor to ground. Connect the junction where they meet to digital pin 8. You don t need to have your Arduino tethered to the computer for this to work. Try building a stand with some cardboard or styrofoam and power the Arduino with a battery to make a portable version. You can create a cover with some numeric indicators alongside the lights. Understanding the Code 1. You re going to need a number of global variables in your program to get this all working. To start, create a constant named switchpin. This will be the name of the pin your tilt switch is on. 2. Create a variable of type unsigned long, This will hold the time an LED was last changed. 3. Create a variable for the switch state, and another to hold the previous switch state. You ll use these two to compare the switch s position from one loop to the next. 4. Create a variable named led. This will be used to count which LED is the next one to be turned on. Start out with pin The last variable you re creating is going to be the interval between each LED turning on. This will be be a long datatype. In 10 minutes (the time between each LED turning on) 600,000 milliseconds pass. If you want the delay between lights to be longer or shorter, this is the number you change. 6. In your setup(), you need to declare the LED pins 2-7 as outputs. A for() loop declares all six as OUTPUT with just 3 lines of code. You also need to declare switchpin as an INPUT. 7. When the loop() starts, you re going to get the amount of time the Arduino has been running with millis() and store it in a local variable named currenttime. 8. Using an if() statement, you ll check to see if enough time has passed to turn on an LED. Subtract the currenttime from the previoustime and check to see if it is greater than the interval variable. If 600,000 milliseconds have passed (10 minutes), you ll set the variable previoustime to the value of currenttime. 9. previoustime indicates the last time an LED was turned on. Once you ve set previoustime, turn on the LED, and increment the led variable. The next time you pass the time interval, the next LED will light up. 10. Add one more if statement in the program to check if the LED on pin 7 is turned on. Don t do anything with this yet. You ll decide what happens at the end of the hour later. 11. Now that you ve checked the time, you ll want to see if the switch has changed its state. Read the switch value into the switchstate variable. 12. With an if() statement, check to see if the switch is in a different position than it was previously. The!= evaluation checks to see if switchstate does not equal prevswitchstate. If they are different, turn the LEDs off, return the led variable to the first pin, and reset the timer for the LEDs by setting previoustime to currenttime. 13. At the end of the loop(), save the switch state in prevswitchstate, so you can compare it to the value you get for switchstate in the next loop(). 78

79 Project 11 - Digital Hourglass The Code const int switchpin = 8; unsigned long previoustime = 0; int switchstate = 0; int prevswitchstate = 0; int led = 2; long interval = ; void setup() { for(int x = 2;x<8;x++){ pinmode(x, OUTPUT); pinmode(switchpin, INPUT); void loop(){ unsigned long currenttime = millis(); if(currenttime - previoustime > interval) { previoustime = currenttime; digitalwrite(led, HIGH); led++; if(led == 7){ switchstate = digitalread(switchpin); if(switchstate!= prevswitchstate){ for(int x = 2;x<8;x++){ digitalwrite(x, LOW); led = 2; previoustime = currenttime; prevswitchstate = switchstate; We are now at the end of today s class. Please do not hesitate to ask your tutor for help or check online for more information. See you in the next class. 79

80 Project 12 Crystal Ball Hello Class! Welcome back to our Arduino class. In today s class we will be building a crystal ball to predict the future. To complete this project, you will need 220Ω resistor, one 10kΩ resistor, the tilt switch, one potentiometer, one LCD screen, and lots of jumper wires. This project also requires at least 60 minutes of your time. 80

81 Project 12 Crystal Ball Crystal balls can help predict the future. You ask a question to the all-knowing ball, and turn it over to reveal an answer. The answers will be predetermined, but you can write in anything you like. You ll use your Arduino to choose from a total of 8 responses. The tilt switch in your kit will help replicate the motion of shaking the ball for answers. The LCD (Liquid Crystal Display) can be used to display alphanumeric characters. The one in your kit has 16 columns and 2 rows, for a total of 32 characters. There are a large number of connections on the board. These pins are used for power and communication, so it knows what to write on screen, but you won t need to connect all of them. See Fig. 1 for the pins you need to connect. Once you are ready please make the connection as shown in this picture. 81