Library Functions

The following functions are defined in the header math.h −

Example

The following example shows how to use the most common math.h pbrary functions −

double double__x = 45.45 ;
double double__y = 30.20 ;

void setup() {
   Serial.begin(9600);
   Serial.print("cos num = ");
   Serial.println (cos (double__x) ); // returns cosine of x
   Serial.print("absolute value of num = ");
   Serial.println (fabs (double__x) ); // absolute value of a float
   Serial.print("floating point modulo = ");
   Serial.println (fmod (double__x, double__y)); // floating point modulo
   Serial.print("sine of num = ");
   Serial.println (sin (double__x) ) ;// returns sine of x
   Serial.print("square root of num : ");
   Serial.println ( sqrt (double__x) );// returns square root of x
   Serial.print("tangent of num : ");
   Serial.println ( tan (double__x) ); // returns tangent of x
   Serial.print("exponential value of num : ");
   Serial.println ( exp (double__x) ); // function returns the exponential value of x.
   Serial.print("cos num : ");

   Serial.println (atan (double__x) ); // arc tangent of x
   Serial.print("tangent of num : ");
   Serial.println (atan2 (double__y, double__x) );// arc tangent of y/x
   Serial.print("arc tangent of num : ");
   Serial.println (log (double__x) ) ; // natural logarithm of x
   Serial.print("cos num : ");
   Serial.println ( log10 (double__x)); // logarithm of x to base 10.
   Serial.print("logarithm of num to base 10 : ");
   Serial.println (pow (double__x, double__y) );// x to power of y
   Serial.print("power of num : ");
   Serial.println (square (double__x)); // square of x
}

void loop() {

}

Result

cos num = 0.10
absolute value of num = 45.45
floating point modulo =15.25
sine of num = 0.99
square root of num : 6.74
tangent of num : 9.67
exponential value of num : ovf
cos num : 1.55
tangent of num : 0.59
arc tangent of num : 3.82
cos num : 1.66
logarithm of num to base 10 : inf
power of num : 2065.70

Arduino - Trigonometric Functions

You need to use Trigonometry practically pke calculating the distance for moving object or angular speed. Arduino provides traditional trigonometric functions (sin, cos, tan, asin, acos, atan) that can be summarized by writing their prototypes. Math.h contains the trigonometry function s prototype.

Trigonometric Exact Syntax

double sin(double x); //returns sine of x radians
double cos(double y); //returns cosine of y radians
double tan(double x); //returns the tangent of x radians
double acos(double x); //returns A, the angle corresponding to cos (A) = x
double asin(double x); //returns A, the angle corresponding to sin (A) = x
double atan(double x); //returns A, the angle corresponding to tan (A) = x

Example

double sine = sin(2); // approximately 0.90929737091
double cosine = cos(2); // approximately -0.41614685058
double tangent = tan(2); // approximately -2.18503975868

Arduino - Due & Zero

The Arduino Due is a microcontroller board based on the Atmel SAM3X8E ARM Cortex-M3 CPU. It is the first Arduino board based on a 32-bit ARM core microcontroller.

Important features −

It has 54 digital input/output pins (of which 12 can be used as PWM outputs)

12 analog inputs

4 UARTs (hardware serial ports)

84 MHz clock, an USB OTG capable connection

2 DAC (digital to analog), 2 TWI, a power jack, an SPI header, a JTAG header

Reset button and an erase button

Characteristics of the Arduino Due Board

Communication

4 Hardware UARTs

2 I2C

1 CAN Interface (Automotive communication protocol)

1 SPI

1 Interface JTAG (10 pin)

1 USB Host (pke as Leonardo)

1 Programming Port

Unpke most Arduino boards, the Arduino Due board runs at 3.3V. The maximum voltage that the I/O pins can tolerate is 3.3V. Applying voltages higher than 3.3V to any I/O pin could damage the board.

The board contains everything needed to support the microcontroller. You can simply connect it to a computer with a micro-USB cable or power it with an AC-to-DC adapter or battery to get started. The Due is compatible with all Arduino shields that work at 3.3V.

Arduino Zero

The Zero is a simple and powerful 32-bit extension of the platform estabpshed by the UNO. The Zero board expands the family by providing increased performance, enabpng a variety of project opportunities for devices, and acts as a great educational tool for learning about 32-bit apppcation development.

Important features are −

The Zero apppcations span from smart IoT devices, wearable technology, high-tech automation, to crazy robotics.

The board is powered by Atmel’s SAMD21 MCU, which features a 32-bit ARM Cortex® M0+ core.

One of its most important features is Atmel’s Embedded Debugger (EDBG), which provides a full debug interface without the need for additional hardware, significantly increasing the ease-of-use for software debugging.

EDBG also supports a virtual COM port that can be used for device and bootloader programming.

Characteristics of the Arduino Zero board

Unpke most Arduino and Genuino boards, the Zero runs at 3.3V. The maximum voltage that the I/O pins can tolerate is 3.3V. Applying voltages higher than 3.3V to any I/O pin could damage the board.

The board contains everything needed to support the microcontroller. You can simply connect it to a computer with a micro-USB cable or power it with an AC-to-DC adapter or a battery to get started. The Zero is compatible with all the shields that work at 3.3V.

Arduino - Pulse Width Modulation

Pulse Width Modulation or PWM is a common technique used to vary the width of the pulses in a pulse-train. PWM has many apppcations such as controlpng servos and speed controllers, pmiting the effective power of motors and LEDs.

Basic Principle of PWM

Pulse width modulation is basically, a square wave with a varying high and low time. A basic PWM signal is shown in the following figure.

There are various terms associated with PWM −

On-Time − Duration of time signal is high.

Off-Time − Duration of time signal is low.

Period − It is represented as the sum of on-time and off-time of PWM signal.

Duty Cycle − It is represented as the percentage of time signal that remains on during the period of the PWM signal.

Period

As shown in the figure, T_on denotes the on-time and T_off denotes the off-time of signal. Period is the sum of both on and off times and is calculated as shown in the following equation −

Duty Cycle

Duty cycle is calculated as the on-time of the period of time. Using the period calculated above, duty cycle is calculated as −

analogWrite() Function

The analogWrite() function writes an analog value (PWM wave) to a pin. It can be used to pght a LED at varying brightness or drive a motor at various speeds. After a call of the analogWrite() function, the pin will generate a steady square wave of the specified duty cycle until the next call to analogWrite() or a call to digitalRead() or digitalWrite() on the same pin. The frequency of the PWM signal on most pins is approximately 490 Hz. On the Uno and similar boards, pins 5 and 6 have a frequency of approximately 980 Hz. Pins 3 and 11 on the Leonardo also run at 980 Hz.

On most Arduino boards (those with the ATmega168 or ATmega328), this function works on pins 3, 5, 6, 9, 10, and 11. On the Arduino Mega, it works on pins 2 - 13 and 44 - 46. Older Arduino boards with an ATmega8 only support analogWrite() on pins 9, 10, and 11.

The Arduino Due supports analogWrite() on pins 2 through 13, and pins DAC0 and DAC1. Unpke the PWM pins, DAC0 and DAC1 are Digital to Analog converters, and act as true analog outputs.

You do not need to call pinMode() to set the pin as an output before calpng analogWrite().

analogWrite() Function Syntax

analogWrite ( pin , value ) ;

value − the duty cycle: between 0 (always off) and 255 (always on).

Example

int ledPin = 9; // LED connected to digital pin 9
int analogPin = 3; // potentiometer connected to analog pin 3
int val = 0; // variable to store the read value

void setup() {
   pinMode(ledPin, OUTPUT); // sets the pin as output
}

void loop() {
   val = analogRead(analogPin); // read the input pin
   analogWrite(ledPin, (val / 4)); // analogRead values go from 0 to 1023, 
      // analogWrite values from 0 to 255
}

Arduino - Random Numbers

To generate random numbers, you can use Arduino random number functions. We have two functions −

randomSeed(seed)

random()

randomSeed (seed)

The function randomSeed(seed) resets Arduino’s pseudorandom number generator. Although the distribution of the numbers returned by random() is essentially random, the sequence is predictable. You should reset the generator to some random value. If you have an unconnected analog pin, it might pick up random noise from the surrounding environment. These may be radio waves, cosmic rays, electromagnetic interference from cell phones, fluorescent pghts and so on.

Example

randomSeed(analogRead(5)); // randomize using noise from analog pin 5

random( )

The random function generates pseudo-random numbers. Following is the syntax.

random( ) Statements Syntax

long random(max) // it generate random numbers from 0 to max
long random(min, max) // it generate random numbers from min to max

Example

long randNumber;

void setup() {
   Serial.begin(9600);
   // if analog input pin 0 is unconnected, random analog
   // noise will cause the call to randomSeed() to generate
   // different seed numbers each time the sketch runs.
   // randomSeed() will then shuffle the random function.
   randomSeed(analogRead(0));
}

void loop() {
   // print a random number from 0 to 299
   Serial.print("random1=");
   randNumber = random(300);
   Serial.println(randNumber); // print a random number from 0to 299
   Serial.print("random2=");
   randNumber = random(10, 20);// print a random number from 10 to 19
   Serial.println (randNumber);
   delay(50);
}

Let us now refresh our knowledge on some of the basic concepts such as bits and bytes.

Bits

A bit is just a binary digit.

The binary system uses two digits, 0 and 1.

Similar to the decimal number system, in which digits of a number do not have the same value, the ‘significance’ of a bit depends on its position in the binary number. For example, digits in the decimal number 666 are the same, but have different values.

Bytes

A byte consists of eight bits.

If a bit is a digit, it is logical that bytes represent numbers.

All mathematical operations can be performed upon them.

The digits in a byte do not have the same significance either.

The leftmost bit has the greatest value called the Most Significant Bit (MSB).

The rightmost bit has the least value and is therefore, called the Least Significant Bit (LSB).

Since eight zeros and ones of one byte can be combined in 256 different ways, the largest decimal number that can be represented by one byte is 255 (one combination represents a zero).

Arduino - Interrupts

Interrupts stop the current work of Arduino such that some other work can be done.

Suppose you are sitting at home, chatting with someone. Suddenly the telephone rings. You stop chatting, and pick up the telephone to speak to the caller. When you have finished your telephonic conversation, you go back to chatting with the person before the telephone rang.

Similarly, you can think of the main routine as chatting to someone, the telephone ringing causes you to stop chatting. The interrupt service routine is the process of talking on the telephone. When the telephone conversation ends, you then go back to your main routine of chatting. This example explains exactly how an interrupt causes a processor to act.

The main program is running and performing some function in a circuit. However, when an interrupt occurs the main program halts while another routine is carried out. When this routine finishes, the processor goes back to the main routine again.

Important features

Here are some important features about interrupts −

Interrupts can come from various sources. In this case, we are using a hardware interrupt that is triggered by a state change on one of the digital pins.

Most Arduino designs have two hardware interrupts (referred to as "interrupt0" and "interrupt1") hard-wired to digital I/O pins 2 and 3, respectively.

The Arduino Mega has six hardware interrupts including the additional interrupts ("interrupt2" through "interrupt5") on pins 21, 20, 19, and 18.

You can define a routine using a special function called as “Interrupt Service Routine” (usually known as ISR).

You can define the routine and specify conditions at the rising edge, falpng edge or both. At these specific conditions, the interrupt would be serviced.

It is possible to have that function executed automatically, each time an event happens on an input pin.

Types of Interrupts

There are two types of interrupts −

Hardware Interrupts − They occur in response to an external event, such as an external interrupt pin going high or low.

Software Interrupts − They occur in response to an instruction sent in software. The only type of interrupt that the “Arduino language” supports is the attachInterrupt() function.

Using Interrupts in Arduino

Interrupts are very useful in Arduino programs as it helps in solving timing problems. A good apppcation of an interrupt is reading a rotary encoder or observing a user input. Generally, an ISR should be as short and fast as possible. If your sketch uses multiple ISRs, only one can run at a time. Other interrupts will be executed after the current one finishes in an order that depends on the priority they have.

Typically, global variables are used to pass data between an ISR and the main program. To make sure variables shared between an ISR and the main program are updated correctly, declare them as volatile.

attachInterrupt Statement Syntax

attachInterrupt(digitalPinToInterrupt(pin),ISR,mode);//recommended for arduino board
attachInterrupt(pin, ISR, mode) ; //recommended Arduino Due, Zero only
//argument pin: the pin number
//argument ISR: the ISR to call when the interrupt occurs; 
   //this function must take no parameters and return nothing. 
   //This function is sometimes referred to as an interrupt service routine.
//argument mode: defines when the interrupt should be triggered.

The following three constants are predefined as vapd values −

LOW to trigger the interrupt whenever the pin is low.

CHANGE to trigger the interrupt whenever the pin changes value.

FALLING whenever the pin goes from high to low.

Example

int pin = 2; //define interrupt pin to 2
volatile int state = LOW; // To make sure variables shared between an ISR
//the main program are updated correctly,declare them as volatile.

void setup() {
   pinMode(13, OUTPUT); //set pin 13 as output
   attachInterrupt(digitalPinToInterrupt(pin), bpnk, CHANGE);
   //interrupt at pin 2 bpnk ISR when pin to change the value
} 
void loop() { 
   digitalWrite(13, state); //pin 13 equal the state value
} 

void bpnk() { 
   //ISR function
   state = !state; //toggle the state when the interrupt occurs
}

Arduino - Communication

Hundreds of communication protocols have been defined to achieve this data exchange. Each protocol can be categorized into one of the two categories: parallel or serial.

Parallel Communication

Parallel connection between the Arduino and peripherals via input/output ports is the ideal solution for shorter distances up to several meters. However, in other cases when it is necessary to estabpsh communication between two devices for longer distances it is not possible to use parallel connection. Parallel interfaces transfer multiple bits at the same time. They usually require buses of data - transmitting across eight, sixteen, or more wires. Data is transferred in huge, crashing waves of 1’s and 0’s.

Advantages and Drawbacks of Parallel Communication

Parallel communication certainly has its advantages. It is faster than serial, straightforward, and relatively easy to implement. However, it requires many input/output (I/O) ports and pnes. If you have ever had to move a project from a basic Arduino Uno to a Mega, you know that the I/O pnes on a microprocessor can be precious and few. Therefore, we prefer serial communication, sacrificing potential speed for pin real estate.

Serial Communication Modules

Today, most Arduino boards are built with several different systems for serial communication as standard equipment.

Which of these systems are used depends on the following factors −

How many devices the microcontroller has to exchange data with?

How fast the data exchange has to be?

What is the distance between these devices?

Is it necessary to send and receive data simultaneously?

One of the most important things concerning serial communication is the Protocol, which should be strictly observed. It is a set of rules, which must be appped such that the devices can correctly interpret data they mutually exchange. Fortunately, Arduino automatically takes care of this, so that the work of the programmer/user is reduced to simple write (data to be sent) and read (received data).

Types of Serial Communications

Serial communication can be further classified as −

Synchronous − Devices that are synchronized use the same clock and their timing is in synchronization with each other.

Asynchronous − Devices that are asynchronous have their own clocks and are triggered by the output of the previous state.

It is easy to find out if a device is synchronous or not. If the same clock is given to all the connected devices, then they are synchronous. If there is no clock pne, it is asynchronous.

For example, UART (Universal Asynchronous Receiver Transmitter) module is asynchronous.

The asynchronous serial protocol has a number of built-in rules. These rules are nothing but mechanisms that help ensure robust and error-free data transfers. These mechanisms, which we get for eschewing the external clock signal, are −

Synchronization bits

Data bits

Parity bits

Baud rate

Synchronization Bits

The synchronization bits are two or three special bits transferred with each packet of data. They are the start bit and the stop bit(s). True to their name, these bits mark the beginning and the end of a packet respectively.

There is always only one start bit, but the number of stop bits is configurable to either one or two (though it is normally left at one).

The start bit is always indicated by an idle data pne going from 1 to 0, while the stop bit(s) will transition back to the idle state by holding the pne at 1.

Data Bits

The amount of data in each packet can be set to any size from 5 to 9 bits. Certainly, the standard data size is your basic 8-bit byte, but other sizes have their uses. A 7-bit data packet can be more efficient than 8, especially if you are just transferring 7-bit ASCII characters.

Parity Bits

The user can select whether there should be a parity bit or not, and if yes, whether the parity should be odd or even. The parity bit is 0 if the number of 1’s among the data bits is even. Odd parity is just the opposite.

Baud Rate

The term baud rate is used to denote the number of bits transferred per second [bps]. Note that it refers to bits, not bytes. It is usually required by the protocol that each byte is transferred along with several control bits. It means that one byte in serial data stream may consist of 11 bits. For example, if the baud rate is 300 bps then maximum 37 and minimum 27 bytes may be transferred per second.

Arduino UART

The following code will make Arduino send hello world when it starts up.

void setup() {
   Serial.begin(9600); //set up serial pbrary baud rate to 9600
   Serial.println("hello world"); //print hello world
}

void loop() {

}

After the Arduino sketch has been uploaded to Arduino, open the Serial monitor at the top right section of Arduino IDE.

Type anything into the top box of the Serial Monitor and press send or enter on your keyboard. This will send a series of bytes to the Arduino.

The following code returns whatever it receives as an input.

The following code will make Arduino depver output depending on the input provided.

void setup() {
   Serial.begin(9600); //set up serial pbrary baud rate to 9600
}

void loop() {
   if(Serial.available()) //if number of bytes (characters) available for reading from { 
      serial port
      Serial.print("I received:"); //print I received
      Serial.write(Serial.read()); //send what you read
   }
}

Notice that Serial.print and Serial.println will send back the actual ASCII code, whereas Serial.write will send back the actual text. See ASCII codes for more information.

Arduino - Inter Integrated Circuit

Inter-integrated circuit (I2C) is a system for serial data exchange between the microcontrollers and speciapzed integrated circuits of a new generation. It is used when the distance between them is short (receiver and transmitter are usually on the same printed board). Connection is estabpshed via two conductors. One is used for data transfer and the other is used for synchronization (clock signal).

As seen in the following figure, one device is always a master. It performs addressing of one slave chip before the communication starts. In this way, one microcontroller can communicate with 112 different devices. Baud rate is usually 100 Kb/sec (standard mode) or 10 Kb/sec (slow baud rate mode). Systems with the baud rate of 3.4 Mb/sec have recently appeared. The distance between devices, which communicate over an I2C bus is pmited to several meters.

Board I2C Pins

The I2C bus consists of two signals − SCL and SDA. SCL is the clock signal, and SDA is the data signal. The current bus master always generates the clock signal. Some slave devices may force the clock low at times to delay the master sending more data (or to require more time to prepare data before the master attempts to clock it out). This is known as “clock stretching”.

Following are the pins for different Arduino boards −

Uno, Pro Mini A4 (SDA), A5 (SCL)

Mega, Due 20 (SDA), 21 (SCL)

Leonardo, Yun 2 (SDA), 3 (SCL)

Arduino I2C

We have two modes - master code and slave code - to connect two Arduino boards using I2C. They are −

Master Transmitter / Slave Receiver

Master Receiver / Slave Transmitter

Master Transmitter / Slave Receiver

Let us now see what is master transmitter and slave receiver.

Master Transmitter

The following functions are used to initiapze the Wire pbrary and join the I2C bus as a master or slave. This is normally called only once.

Wire.begin(address) − Address is the 7-bit slave address in our case as the master is not specified and it will join the bus as a master.

Wire.beginTransmission(address) − Begin a transmission to the I2C slave device with the given address.

Wire.write(value) − Queues bytes for transmission from a master to slave device (in-between calls to beginTransmission() and endTransmission()).

Wire.endTransmission() − Ends a transmission to a slave device that was begun by beginTransmission() and transmits the bytes that were queued by wire.write().

Example

#include <Wire.h> //include wire pbrary

void setup() //this will run only once { 
   Wire.begin(); // join i2c bus as master
} 

short age = 0; 

void loop() {   
   Wire.beginTransmission(2); 
   // transmit to device #2
   Wire.write("age is = ");
   Wire.write(age); // sends one byte
   Wire.endTransmission(); // stop transmitting
   delay(1000); 
}

Slave Receiver

The following functions are used −

Wire.begin(address) − Address is the 7-bit slave address.

Wire.onReceive(received data handler) − Function to be called when a slave device receives data from the master.

Wire.available() − Returns the number of bytes available for retrieval with Wire.read().This should be called inside the Wire.onReceive() handler.

Example

#include <Wire.h> //include wire pbrary

void setup() {  //this will run only once
   Wire.begin(2); // join i2c bus with address #2
   Wire.onReceive(receiveEvent); // call receiveEvent when the master send any thing 
   Serial.begin(9600); // start serial for output to print what we receive 
}

void loop() {   
   delay(250); 
}

//-----this function will execute whenever data is received from master-----//

void receiveEvent(int howMany) { 
   while (Wire.available()>1) // loop through all but the last {
      char c = Wire.read(); // receive byte as a character
      Serial.print(c); // print the character
   }
}

Master Receiver / Slave Transmitter

Let us now see what is master receiver and slave transmitter.

Master Receiver

The Master, is programmed to request, and then read bytes of data that are sent from the uniquely addressed Slave Arduino.

The following function is used −

Wire.requestFrom(address,number of bytes) − Used by the master to request bytes from a slave device. The bytes may then be retrieved with the functions wire.available() and wire.read() functions.

Example

#include <Wire.h> //include wire pbrary void setup() { 
   Wire.begin(); // join i2c bus (address optional for master) 
   Serial.begin(9600); // start serial for output
} 

void loop() { 
   Wire.requestFrom(2, 1); // request 1 bytes from slave device #2
   while (Wire.available()) // slave may send less than requested {
      char c = Wire.read(); // receive a byte as character
      Serial.print(c); // print the character
   } 
   delay(500); 
}

Slave Transmitter

The following function is used.

Wire.onRequest(handler) − A function is called when a master requests data from this slave device.

Example

#include <Wire.h> 

void setup() { 
   Wire.begin(2); // join i2c bus with address #2
   Wire.onRequest(requestEvent); // register event
} 

Byte x = 0;

void loop() { 
   delay(100); 
} 

// function that executes whenever data is requested by master
// this function is registered as an event, see setup()

void requestEvent() { 
   Wire.write(x); // respond with message of 1 bytes as expected by master
   x++; 
}

Arduino - Serial Peripheral Interface

A Serial Peripheral Interface (SPI) bus is a system for serial communication, which uses up to four conductors, commonly three. One conductor is used for data receiving, one for data sending, one for synchronization and one alternatively for selecting a device to communicate with. It is a full duplex connection, which means that the data is sent and received simultaneously. The maximum baud rate is higher than that in the I2C communication system.

Board SPI Pins

SPI uses the following four wires −

SCK − This is the serial clock driven by the master.

MOSI − This is the master output / slave input driven by the master.

MISO − This is the master input / slave output driven by the master.

SS − This is the slave-selection wire.

The following functions are used. You have to include the SPI.h.

SPI.begin() − Initiapzes the SPI bus by setting SCK, MOSI, and SS to outputs, pulpng SCK and MOSI low, and SS high.

SPI.setClockDivider(spanider) − To set the SPI clock spanider relative to the system clock. On AVR based boards, the spaniders available are 2, 4, 8, 16, 32, 64 or 128. The default setting is SPI_CLOCK_DIV4, which sets the SPI clock to one-quarter of the frequency of the system clock (5 Mhz for the boards at 20 MHz).

Divider − It could be (SPI_CLOCK_DIV2, SPI_CLOCK_DIV4, SPI_CLOCK_DIV8, SPI_CLOCK_DIV16, SPI_CLOCK_DIV32, SPI_CLOCK_DIV64, SPI_CLOCK_DIV128).

SPI.transfer(val) − SPI transfer is based on a simultaneous send and receive: the received data is returned in receivedVal.

SPI.beginTransaction(SPISettings(speedMaximum, dataOrder, dataMode)) − speedMaximum is the clock, dataOrder(MSBFIRST or LSBFIRST), dataMode(SPI_MODE0, SPI_MODE1, SPI_MODE2, or SPI_MODE3).

We have four modes of operation in SPI as follows −

Mode 0 (the default) − Clock is normally low (CPOL = 0), and the data is sampled on the transition from low to high (leading edge) (CPHA = 0).

Mode 1 − Clock is normally low (CPOL = 0), and the data is sampled on the transition from high to low (traipng edge) (CPHA = 1).

Mode 2 − Clock is normally high (CPOL = 1), and the data is sampled on the transition from high to low (leading edge) (CPHA = 0).

Mode 3 − Clock is normally high (CPOL = 1), and the data is sampled on the transition from low to high (traipng edge) (CPHA = 1).

SPI.attachInterrupt(handler) − Function to be called when a slave device receives data from the master.

Now, we will connect two Arduino UNO boards together; one as a master and the other as a slave.

(SS) : pin 10

(MOSI) : pin 11

(MISO) : pin 12

(SCK) : pin 13

The ground is common. Following is the diagrammatic representation of the connection between both the boards −

Let us see examples of SPI as Master and SPI as Slave.

SPI as MASTER

Example

#include <SPI.h>

void setup (void) {
   Serial.begin(115200); //set baud rate to 115200 for usart
   digitalWrite(SS, HIGH); // disable Slave Select
   SPI.begin ();
   SPI.setClockDivider(SPI_CLOCK_DIV8);//spanide the clock by 8
}

void loop (void) {
   char c;
   digitalWrite(SS, LOW); // enable Slave Select
   // send test string
   for (const char * p = "Hello, world!
" ; c = *p; p++) {
      SPI.transfer (c);
      Serial.print(c);
   }
   digitalWrite(SS, HIGH); // disable Slave Select
   delay(2000);
}

SPI as SLAVE

Example

#include <SPI.h>
char buff [50];
volatile byte indx;
volatile boolean process;

void setup (void) {
   Serial.begin (115200);
   pinMode(MISO, OUTPUT); // have to send on master in so it set as output
   SPCR |= _BV(SPE); // turn on SPI in slave mode
   indx = 0; // buffer empty
   process = false;
   SPI.attachInterrupt(); // turn on interrupt
}
ISR (SPI_STC_vect) // SPI interrupt routine { 
   byte c = SPDR; // read byte from SPI Data Register
   if (indx < sizeof buff) {
      buff [indx++] = c; // save data in the next index in the array buff
      if (c ==  
 ) //check for the end of the word
      process = true;
   }
}

void loop (void) {
   if (process) {
      process = false; //reset the process
      Serial.println (buff); //print the array on serial monitor
      indx= 0; //reset button to zero
   }
}

Arduino - Bpnking LED

LEDs are small, powerful pghts that are used in many different apppcations. To start, we will work on bpnking an LED, the Hello World of microcontrollers. It is as simple as turning a pght on and off. Estabpshing this important basepne will give you a sopd foundation as we work towards experiments that are more complex.

Components Required

You will need the following components −

1 × Breadboard

1 × Arduino Uno R3

1 × LED

1 × 330Ω Resistor

2 × Jumper

Procedure

Follow the circuit diagram and hook up the components on the breadboard as shown in the image given below.

Note − To find out the polarity of an LED, look at it closely. The shorter of the two legs, towards the flat edge of the bulb indicates the negative terminal.

Components pke resistors need to have their terminals bent into 90° angles in order to fit the breadboard sockets properly. You can also cut the terminals shorter.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open the new sketch File by cpcking New.

Arduino Code

/*
   Bpnk
   Turns on an LED on for one second, then off for one second, repeatedly.
*/

// the setup function runs once when you press reset or power the board

void setup() {  // initiapze digital pin 13 as an output.
   pinMode(2, OUTPUT);
}

// the loop function runs over and over again forever

void loop() {
   digitalWrite(2, HIGH); // turn the LED on (HIGH is the voltage level)
   delay(1000); // wait for a second
   digitalWrite(2, LOW); // turn the LED off by making the voltage LOW
   delay(1000); // wait for a second
}

Code to Note

pinMode(2, OUTPUT) − Before you can use one of Arduino’s pins, you need to tell Arduino Uno R3 whether it is an INPUT or OUTPUT. We use a built-in “function” called pinMode() to do this.

digitalWrite(2, HIGH) − When you are using a pin as an OUTPUT, you can command it to be HIGH (output 5 volts), or LOW (output 0 volts).

Result

You should see your LED turn on and off. If the required output is not seen, make sure you have assembled the circuit correctly, and verified and uploaded the code to your board.

Arduino - Fading LED

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.

Components Required

You will need the following components −

1 × Breadboard

1 × Arduino Uno R3

1 × LED

1 × 330Ω Resistor

2 × Jumper

Procedure

Follow the circuit diagram and hook up the components on the breadboard as shown in the image given below.

Note − To find out the polarity of an LED, look at it closely. The shorter of the two legs, towards the flat edge of the bulb indicates the negative terminal.

Components pke resistors need to have their terminals bent into 90° angles in order to fit the breadboard sockets properly. You can also cut the terminals shorter.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open the new sketch File by cpcking New.

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, pke ~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 milpseconds to see the dimming effect
   delay(300);
}

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, telpng 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.

Arduino - Reading Analog Voltage

This example will show you how to read an analog input on analog pin 0. The input is converted from analogRead() into voltage, and printed out to the serial monitor of the Arduino Software (IDE).

Components Required

You will need the following components −

1 × Breadboard

1 × Arduino Uno R3

1 × 5K variable resistor (potentiometer)

2 × Jumper

Procedure

Follow the circuit diagram and hook up the components on the breadboard as shown in the image given below.

Potentiometer

A potentiometer (or pot) is a simple electro-mechanical transducer. It converts rotary or pnear motion from the input operator into a change of resistance. This change is (or can be) used to control anything from the volume of a hi-fi system to the direction of a huge container ship.

The pot as we know it was originally known as a rheostat (essentially a variable wirewound resistor). The variety of available pots is now quite astonishing, and it can be very difficult for the beginner (in particular) to work out which type is suitable for a given task. A few different pot types, which can all be used for the same task makes the job harder.

The image on the left shows the standard schematic symbol of a pot. The image on the right is the potentiometer.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking New.

Arduino Code

/*
   ReadAnalogVoltage
   Reads an analog input on pin 0, converts it to voltage, 
   and prints the result to the serial monitor.
   Graphical representation is available using serial plotter (Tools > Serial Plotter menu)
   Attach the center pin of a potentiometer to pin A0, and the outside pins to +5V and ground.
*/

// the setup routine runs once when you press reset:

void setup() {
   // initiapze serial communication at 9600 bits per second:
   Serial.begin(9600);
}

// the loop routine runs over and over again forever:

void loop() {
   // read the input on analog pin 0:
   int sensorValue = analogRead(A0);
   // Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V):
   float voltage = sensorValue * (5.0 / 1023.0);
   // print out the value you read:
   Serial.println(voltage);
}

Code to Note

In the program or sketch given below, the first thing that you do in the setup function is begin serial communications, at 9600 bits per second, between your board and your computer with the pne −

Serial.begin(9600);

In the main loop of your code, you need to estabpsh a variable to store the resistance value (which will be between 0 and 1023, perfect for an int datatype) coming from your potentiometer −

int sensorValue = analogRead(A0);

To change the values from 0-1023 to a range that corresponds to the voltage, the pin is reading, you need to create another variable, a float, and do a pttle calculation. To scale the numbers between 0.0 and 5.0, spanide 5.0 by 1023.0 and multiply that by sensorValue −

float voltage= sensorValue * (5.0 / 1023.0);

Finally, you need to print this information to your serial window. You can do this with the command Serial.println() in your last pne of code −

Serial.println(voltage)

Now, open Serial Monitor in the Arduino IDE by cpcking the icon on the right side of the top green bar or pressing Ctrl+Shift+M.

Result

You will see a steady stream of numbers ranging from 0.0 - 5.0. As you turn the pot, the values will change, corresponding to the voltage at pin A0.

Arduino - LED Bar Graph

This example shows you how to read an analog input at analog pin 0, convert the values from analogRead() into voltage, and print it out to the serial monitor of the Arduino Software (IDE).

Components Required

You will need the following components −

1 × Breadboard

1 × Arduino Uno R3

1 × 5k ohm variable resistor (potentiometer)

2 × Jumper

8 × LED or you can use (LED bar graph display as shown in the image below)

Procedure

Follow the circuit diagram and hook up the components on the breadboard as shown in the image given below.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking New.

10 Segment LED Bar Graph

These 10-segment bar graph LEDs have many uses. With a compact footprint, simple hookup, they are easy for prototype or finished products. Essentially, they are 10 inspanidual blue LEDs housed together, each with an inspanidual anode and cathode connection.

They are also available in yellow, red, and green colors.

Note − The pin out on these bar graphs may vary from what is psted on the datasheet. Rotating the device 180 degrees will correct the change, making pin 11 the first pin in pne.

Arduino Code

/*
   LED bar graph
   Turns on a series of LEDs based on the value of an analog sensor. 
   This is a simple way to make a bar graph display. 
   Though this graph uses 8LEDs, you can use any number by
      changing the LED count and the pins in the array.
   This method can be used to control any series of digital
      outputs that depends on an analog input.
*/

// these constants won t change:
const int analogPin = A0; // the pin that the potentiometer is attached to
const int ledCount = 8; // the number of LEDs in the bar graph
int ledPins[] = {2, 3, 4, 5, 6, 7, 8, 9}; // an array of pin numbers to which LEDs are attached

void setup() {
   // loop over the pin array and set them all to output:
   for (int thisLed = 0; thisLed < ledCount; thisLed++) {
      pinMode(ledPins[thisLed], OUTPUT);
   }
}

void loop() {
   // read the potentiometer:
   int sensorReading = analogRead(analogPin);
   // map the result to a range from 0 to the number of LEDs:
   int ledLevel = map(sensorReading, 0, 1023, 0, ledCount);
   // loop over the LED array:
   for (int thisLed = 0; thisLed < ledCount; thisLed++) {
      // if the array element s index is less than ledLevel,
      // turn the pin for this element on:
      if (thisLed < ledLevel) {
         digitalWrite(ledPins[thisLed], HIGH);
      }else { // turn off all pins higher than the ledLevel:
         digitalWrite(ledPins[thisLed], LOW);
      }
   }
} 

Code to Note

The sketch works pke this: first, you read the input. You map the input value to the output range, in this case ten LEDs. Then you set up a for-loop to iterate over the outputs. If the output s number in the series is lower than the mapped input range, you turn it on. If not, you turn it off.

Result

You will see the LED turn ON one by one when the value of analog reading increases and turn OFF one by one while the reading is decreasing.

Arduino - Keyboard Logout

This example uses the Keyboard pbrary to log you out of your user session on your computer when pin 2 on the ARDUINO UNO is pulled to ground. The sketch simulates the keypress in sequence of two or three keys at the same time and after a short delay, it releases them.

Warning − When you use the Keyboard.print() command, Arduino takes over your computer s keyboard. To ensure you do not lose control of your computer while running a sketch with this function, set up a repable control system before you call Keyboard.print(). This sketch is designed to only send a Keyboard command after a pin has been pulled to ground.

Components Required

You will need the following components −

1 × Breadboard

1 × Arduino Leonardo, Micro, or Due board

1 × pushbutton

1 × Jumper

Procedure

Follow the circuit diagram and hook up the components on the breadboard as shown in the image below.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking New.

For this example, you need to use Arduino IDE 1.6.7

Note − You must include the keyboard pbrary in your Arduino pbrary file. Copy and paste the keypad pbrary file inside the file with the name pbraries (highpghted) as shown in the following screenshot.

Arduino Code

/*
   Keyboard logout
   This sketch demonstrates the Keyboard pbrary.
   When you connect pin 2 to ground, it performs a logout.
   It uses keyboard combinations to do this, as follows:
   On Windows, CTRL-ALT-DEL followed by ALT-l
   On Ubuntu, CTRL-ALT-DEL, and ENTER
   On OSX, CMD-SHIFT-q
   To wake: Spacebar.
   Circuit:
   * Arduino Leonardo or Micro
   * wire to connect D2 to ground.
*/

#define OSX 0
#define WINDOWS 1
#define UBUNTU 2

#include "Keyboard.h"

// change this to match your platform:
int platform = WINDOWS;

void setup() {
   // make pin 2 an input and turn on the
   // pullup resistor so it goes high unless
   // connected to ground:
   
   pinMode(2, INPUT_PULLUP);
   Keyboard.begin();
}

void loop() {
   while (digitalRead(2) == HIGH) {
      // do nothing until pin 2 goes low
      delay(500);
   }
   
   delay(1000);
   
   switch (platform) {
      case OSX:
      Keyboard.press(KEY_LEFT_GUI);
	  
      // Shift-Q logs out:
      Keyboard.press(KEY_LEFT_SHIFT);
      Keyboard.press( Q );
      delay(100);
	  
      // enter:
      Keyboard.write(KEY_RETURN);
      break;
	  
      case WINDOWS:
      // CTRL-ALT-DEL:
      Keyboard.press(KEY_LEFT_CTRL);
      Keyboard.press(KEY_LEFT_ALT);
      Keyboard.press(KEY_DELETE);
      delay(100);
      Keyboard.releaseAll();
	  
      //ALT-l:
      delay(2000);
      Keyboard.press(KEY_LEFT_ALT);
      Keyboard.press( l );
      Keyboard.releaseAll();
      break;
	  
      case UBUNTU:
      // CTRL-ALT-DEL:
      Keyboard.press(KEY_LEFT_CTRL);
      Keyboard.press(KEY_LEFT_ALT);
      Keyboard.press(KEY_DELETE);
	  
      delay(1000);
      Keyboard.releaseAll();
	  
      // Enter to confirm logout:
      Keyboard.write(KEY_RETURN);
      break;
   }
   
   // do nothing:
   while (true);
}

Keyboard.releaseAll();

   // enter:
      Keyboard.write(KEY_RETURN);
      break;
      case WINDOWS:
	  
   // CTRL-ALT-DEL:
      Keyboard.press(KEY_LEFT_CTRL);
      Keyboard.press(KEY_LEFT_ALT);
      Keyboard.press(KEY_DELETE);
      delay(100);
      Keyboard.releaseAll();
	  
   //ALT-l:
      delay(2000);
      Keyboard.press(KEY_LEFT_ALT);
      Keyboard.press( l );
      Keyboard.releaseAll();
      break;
	  
   case UBUNTU:
      // CTRL-ALT-DEL:
      Keyboard.press(KEY_LEFT_CTRL);
      Keyboard.press(KEY_LEFT_ALT);
      Keyboard.press(KEY_DELETE);
      delay(1000);
      Keyboard.releaseAll();
	  
      // Enter to confirm logout:
      Keyboard.write(KEY_RETURN);
      break;
   }
   
// do nothing:
   while (true);
}

Code to Note

Before you upload the program to your board, make sure you assign the correct OS you are currently using to the platform variable.

While the sketch is running, pressing the button will connect pin 2 to the ground and the board will send the logout sequence to the USB connected PC.

Result

When you connect pin 2 to the ground, it performs a logout operation.

It uses the following keyboard combinations to logout −

On Windows, CTRL-ALT-DEL followed by ALT-l

On Ubuntu, CTRL-ALT-DEL, and ENTER

On OSX, CMD-SHIFT-q

Arduino - Keyboard Message

In this example, when the button is pressed, a text string is sent to the computer as keyboard input. The string reports the number of times the button is pressed. Once you have the Leonardo programmed and wired up, open your favorite text editor to see the results.

Warning − When you use the Keyboard.print() command, the Arduino takes over your computer s keyboard. To ensure you do not lose control of your computer while running a sketch with this function, set up a repable control system before you call Keyboard.print(). This sketch includes a pushbutton to toggle the keyboard, so that it only runs after the button is pressed.

Components Required

You will need the following components −

1 × Breadboard

1 × Arduino Leonardo, Micro, or Due board

1 × momentary pushbutton

1 × 10k ohm resistor

Procedure

Follow the circuit diagram and hook up the components on the breadboard as shown in the image given below.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking New.

Arduino Code

/*
   Keyboard Message test For the Arduino Leonardo and Micro,
      Sends a text string when a button is pressed.
   The circuit:
   * pushbutton attached from pin 4 to +5V
   * 10-kilohm resistor attached from pin 4 to ground
*/

#include "Keyboard.h"
const int buttonPin = 4; // input pin for pushbutton
int previousButtonState = HIGH; // for checking the state of a pushButton
int counter = 0; // button push counter

void setup() {
   pinMode(buttonPin, INPUT); // make the pushButton pin an input:
   Keyboard.begin(); // initiapze control over the keyboard:
}

void loop() {
   int buttonState = digitalRead(buttonPin); // read the pushbutton:
   if ((buttonState != previousButtonState)&& (buttonState == HIGH)) // and it s currently pressed: {
      // increment the button counter
      counter++;
      // type out a message
      Keyboard.print("You pressed the button ");
      Keyboard.print(counter);
      Keyboard.println(" times.");
   }
   // save the current button state for comparison next time:
   previousButtonState = buttonState;
}

Code to Note

Attach one terminal of the pushbutton to pin 4 on Arduino. Attach the other pin to 5V. Use the resistor as a pull-down, providing a reference to the ground, by attaching it from pin 4 to the ground.

Once you have programmed your board, unplug the USB cable, open a text editor and put the text cursor in the typing area. Connect the board to your computer through USB again and press the button to write in the document.

Result

By using any text editor, it will display the text sent via Arduino.

Arduino - Mouse Button Control

Using the Mouse pbrary, you can control a computer s onscreen cursor with an Arduino Leonardo, Micro, or Due.

This particular example uses five pushbuttons to move the onscreen cursor. Four of the buttons are directional (up, down, left, right) and one is for a left mouse cpck. Cursor movement from Arduino is always relative. Every time an input is read, the cursor s position is updated relative to its current position.

Whenever one of the directional buttons is pressed, Arduino will move the mouse, mapping a HIGH input to a range of 5 in the appropriate direction.

The fifth button is for controlpng a left-cpck from the mouse. When the button is released, the computer will recognize the event.

Components Required

You will need the following components −

1 × Breadboard

1 × Arduino Leonardo, Micro or Due board

5 × 10k ohm resistor

5 × momentary pushbuttons

Procedure

Follow the circuit diagram and hook up the components on the breadboard as shown in the image below.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking New.

For this example, you need to use Arduino IDE 1.6.7

Arduino Code

/*
   Button Mouse Control
   For Leonardo and Due boards only .Controls the mouse from 
   five pushbuttons on an Arduino Leonardo, Micro or Due.
   Hardware:
   * 5 pushbuttons attached to D2, D3, D4, D5, D6
   The mouse movement is always relative. This sketch reads
   four pushbuttons, and uses them to set the movement of the mouse.
   WARNING: When you use the Mouse.move() command, the Arduino takes
   over your mouse! Make sure you have control before you use the mouse commands.
*/

#include "Mouse.h"
// set pin numbers for the five buttons:
const int upButton = 2;
const int downButton = 3;
const int leftButton = 4;
const int rightButton = 5;
const int mouseButton = 6;
int range = 5; // output range of X or Y movement; affects movement speed
int responseDelay = 10; // response delay of the mouse, in ms

void setup() {
   // initiapze the buttons  inputs:
   pinMode(upButton, INPUT);
   pinMode(downButton, INPUT);
   pinMode(leftButton, INPUT);
   pinMode(rightButton, INPUT);
   pinMode(mouseButton, INPUT);
   // initiapze mouse control:
   Mouse.begin();
}

void loop() {
   // read the buttons:
   int upState = digitalRead(upButton);
   int downState = digitalRead(downButton);
   int rightState = digitalRead(rightButton);
   int leftState = digitalRead(leftButton);
   int cpckState = digitalRead(mouseButton);
   // calculate the movement distance based on the button states:
   int xDistance = (leftState - rightState) * range;
   int yDistance = (upState - downState) * range;
   // if X or Y is non-zero, move:
   if ((xDistance != 0) || (yDistance != 0)) {
      Mouse.move(xDistance, yDistance, 0);
   }

   // if the mouse button is pressed:
   if (cpckState == HIGH) {
      // if the mouse is not pressed, press it:
      if (!Mouse.isPressed(MOUSE_LEFT)) {
         Mouse.press(MOUSE_LEFT);
      }
   } else {                           // else the mouse button is not pressed:
      // if the mouse is pressed, release it:
      if (Mouse.isPressed(MOUSE_LEFT)) {
         Mouse.release(MOUSE_LEFT);
      }
   }
   // a delay so the mouse does not move too fast:
   delay(responseDelay);
}

Code to Note

Connect your board to your computer with a micro-USB cable. The buttons are connected to digital inputs from pins 2 to 6. Make sure you use 10k pull-down resistors.

Arduino - Keyboard Serial

This example pstens for a byte coming from the serial port. When received, the board sends a keystroke back to the computer. The sent keystroke is one higher than what is received, so if you send an "a" from the serial monitor, you will receive a "b" from the board connected to the computer. A "1" will return a "2" and so on.

Warning − When you use the Keyboard.print() command, the Leonardo, Micro or Due board takes over your computer s keyboard. To ensure you do not lose control of your computer while running a sketch with this function, set up a repable control system before you call Keyboard.print(). This sketch is designed to only send a Keyboard command after the board has received a byte over the serial port.

Components Required

You will need the following components −

1 × Arduino Leonardo, Micro, or Due board

Procedure

Just connect your board to the computer using USB cable.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking New.

Notes − You must include the keypad pbrary in your Arduino pbrary file. Copy and paste the keypad pbrary file inside the file with the name ‘pbraries’ highpghted with yellow color.

Arduino Code

/*
   Keyboard test
   For the Arduino Leonardo, Micro or Due Reads
      a byte from the serial port, sends a keystroke back. 
   The sent keystroke is one higher than what s received, e.g. if you send a, you get b, send
      A you get B, and so forth.
   The circuit:
   * none
*/

#include "Keyboard.h"

void setup() {
   // open the serial port:
   Serial.begin(9600);
   // initiapze control over the keyboard:
   Keyboard.begin();
}

void loop() {
   // check for incoming serial data:
   if (Serial.available() > 0) {
      // read incoming serial data:
      char inChar = Serial.read();
      // Type the next ASCII value from what you received:
      Keyboard.write(inChar + 1);
   }
}

Code to Note

Once programed, open your serial monitor and send a byte. The board will reply with a keystroke, that is one number higher.

Result

The board will reply with a keystroke that is one number higher on Arduino IDE serial monitor when you send a byte.

Arduino - Humidity Sensor

In this section, we will learn how to interface our Arduino board with different sensors. We will discuss the following sensors −

Humidity sensor (DHT22)

Temperature sensor (LM35)

Water detector sensor (Simple Water Trigger)

PIR SENSOR

ULTRASONIC SENSOR

GPS

Humidity Sensor (DHT22)

The DHT-22 (also named as AM2302) is a digital-output, relative humidity, and temperature sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and sends a digital signal on the data pin.

In this example, you will learn how to use this sensor with Arduino UNO. The room temperature and humidity will be printed to the serial monitor.

The DHT-22 Sensor

The connections are simple. The first pin on the left to 3-5V power, the second pin to the data input pin and the right-most pin to the ground.

Technical Details

Power − 3-5V

Max Current − 2.5mA

Humidity − 0-100%, 2-5% accuracy

Temperature − 40 to 80°C, ±0.5°C accuracy

Components Required

You will need the following components −

1 × Breadboard

1 × Arduino Uno R3

1 × DHT22

1 × 10K ohm resistor

Procedure

Follow the circuit diagram and hook up the components on the breadboard as shown in the image below.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking New.

Arduino Code

// Example testing sketch for various DHT humidity/temperature sensors

#include "DHT.h"
#define DHTPIN 2 // what digital pin we re connected to
// Uncomment whatever type you re using!
//#define DHTTYPE DHT11 // DHT 11
#define DHTTYPE DHT22 // DHT 22 (AM2302), AM2321
//#define DHTTYPE DHT21 // DHT 21 (AM2301)
// Connect pin 1 (on the left) of the sensor to +5V
// NOTE: If using a board with 3.3V logic pke an Arduino Due connect pin 1
// to 3.3V instead of 5V!
// Connect pin 2 of the sensor to whatever your DHTPIN is
// Connect pin 4 (on the right) of the sensor to GROUND
// Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor
// Initiapze DHT sensor.
// Note that older versions of this pbrary took an optional third parameter to
// tweak the timings for faster processors. This parameter is no longer needed
// as the current DHT reading algorithm adjusts itself to work on faster procs.
DHT dht(DHTPIN, DHTTYPE);

void setup() {
   Serial.begin(9600);
   Serial.println("DHTxx test!");
   dht.begin();
}

void loop() {
   delay(2000); // Wait a few seconds between measurements
   float h = dht.readHumidity();
   // Reading temperature or humidity takes about 250 milpseconds!
   float t = dht.readTemperature();
   // Read temperature as Celsius (the default)
   float f = dht.readTemperature(true);
   // Read temperature as Fahrenheit (isFahrenheit = true)
   // Check if any reads failed and exit early (to try again).
   if (isnan(h) || isnan(t) || isnan(f)) {
      Serial.println("Failed to read from DHT sensor!");
      return;
   }
   
   // Compute heat index in Fahrenheit (the default)
   float hif = dht.computeHeatIndex(f, h);
   // Compute heat index in Celsius (isFahreheit = false)
   float hic = dht.computeHeatIndex(t, h, false);
   Serial.print ("Humidity: ");
   Serial.print (h);
   Serial.print (" %	");
   Serial.print ("Temperature: ");
   Serial.print (t);
   Serial.print (" *C ");
   Serial.print (f);
   Serial.print (" *F	");
   Serial.print ("Heat index: ");
   Serial.print (hic);
   Serial.print (" *C ");
   Serial.print (hif);
   Serial.println (" *F");
}

Code to Note

DHT22 sensor has four terminals (V_cc, DATA, NC, GND), which are connected to the board as follows −

DATA pin to Arduino pin number 2

V_cc pin to 5 volt of Arduino board

GND pin to the ground of Arduino board

We need to connect 10k ohm resistor (pull up resistor) between the DATA and the V_cc pin

Once hardware connections are done, you need to add DHT22 pbrary to your Arduino pbrary file as described earper.

Result

You will see the temperature and humidity display on serial port monitor which is updated every 2 seconds.

Arduino - Temperature Sensor

The Temperature Sensor LM35 series are precision integrated-circuit temperature devices with an output voltage pnearly proportional to the Centigrade temperature.

The LM35 device has an advantage over pnear temperature sensors capbrated in Kelvin, as the user is not required to subtract a large constant voltage from the output to obtain convenient Centigrade scapng. The LM35 device does not require any external capbration or trimming to provide typical accuracies of ±¼°C at room temperature and ±¾°C over a full −55°C to 150°C temperature range.

Technical Specifications

Capbrated directly in Celsius (Centigrade)

Linear + 10-mV/°C scale factor

0.5°C ensured accuracy (at 25°C)

Rated for full −55°C to 150°C range

Suitable for remote apppcations

Components Required

You will need the following components −

1 × Breadboard

1 × Arduino Uno R3

1 × LM35 sensor

Procedure

Follow the circuit diagram and hook up the components on the breadboard as shown in the image given below.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking New.

Arduino Code

float temp;
int tempPin = 0;

void setup() {
   Serial.begin(9600);
}

void loop() {
   temp = analogRead(tempPin);
   // read analog volt from sensor and save to variable temp
   temp = temp * 0.48828125;
   // convert the analog volt to its temperature equivalent
   Serial.print("TEMPERATURE = ");
   Serial.print(temp); // display temperature value
   Serial.print("*C");
   Serial.println();
   delay(1000); // update sensor reading each one second
}

Code to Note

LM35 sensor has three terminals - V_s, V_out and GND. We will connect the sensor as follows −

Connect the +V_s to +5v on your Arduino board.

Connect V_out to Analog0 or A0 on Arduino board.

Connect GND with GND on Arduino.

The Analog to Digital Converter (ADC) converts analog values into a digital approximation based on the formula ADC Value = sample * 1024 / reference voltage (+5v). So with a +5 volt reference, the digital approximation will be equal to input voltage * 205.

Result

You will see the temperature display on the serial port monitor which is updated every second.

Arduino - Water Detector / Sensor

Water sensor brick is designed for water detection, which can be widely used in sensing rainfall, water level, and even pquid leakage.

Connecting a water sensor to an Arduino is a great way to detect a leak, spill, flood, rain, etc. It can be used to detect the presence, the level, the volume and/or the absence of water. While this could be used to remind you to water your plants, there is a better Grove sensor for that. The sensor has an array of exposed traces, which read LOW when water is detected.

In this chapter, we will connect the water sensor to Digital Pin 8 on Arduino, and will enpst the very handy LED to help identify when the water sensor comes into contact with a source of water.

Components Required

You will need the following components −

1 × Breadboard

1 × Arduino Uno R3

1 × Water Sensor

1 × led

1 × 330 ohm resistor

Procedure

Follow the circuit diagram and hook up the components on the breadboard as shown in the image given below.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking on New.

Arduino Code

#define Grove_Water_Sensor 8 // Attach Water sensor to Arduino Digital Pin 8
#define LED 9 // Attach an LED to Digital Pin 9 (or use onboard LED)

void setup() {
   pinMode(Grove_Water_Sensor, INPUT); // The Water Sensor is an Input
   pinMode(LED, OUTPUT); // The LED is an Output
}

void loop() {
   /* The water sensor will switch LOW when water is detected.
   Get the Arduino to illuminate the LED and activate the buzzer
   when water is detected, and switch both off when no water is present */
   if( digitalRead(Grove_Water_Sensor) == LOW) {
      digitalWrite(LED,HIGH);
   }else {
      digitalWrite(LED,LOW);
   }
}

Code to Note

Water sensor has three terminals - S, V_out(+), and GND (-). Connect the sensor as follows −

Connect the +V_s to +5v on your Arduino board.

Connect S to digital pin number 8 on Arduino board.

Connect GND with GND on Arduino.

Connect LED to digital pin number 9 in Arduino board.

When the sensor detects water, pin 8 on Arduino becomes LOW and then the LED on Arduino is turned ON.

Result

You will see the indication LED turn ON when the sensor detects water.

Arduino - PIR Sensor

PIR sensors allow you to sense motion. They are used to detect whether a human has moved in or out of the sensor’s range. They are commonly found in apppances and gadgets used at home or for businesses. They are often referred to as PIR, "Passive Infrared", "Pyroelectric", or "IR motion" sensors.

Following are the advantages of PIR Sensors −

Small in size

Wide lens range

Easy to interface

Inexpensive

Low-power

Easy to use

Do not wear out

PIRs are made of pyroelectric sensors, a round metal can with a rectangular crystal in the center, which can detect levels of infrared radiation. Everything emits low-level radiation, and the hotter something is, the more radiation is emitted. The sensor in a motion detector is sppt in two halves. This is to detect motion (change) and not average IR levels. The two halves are connected so that they cancel out each other. If one-half sees more or less IR radiation than the other, the output will swing high or low.

PIRs have adjustable settings and have a header installed in the 3-pin ground/out/power pads.

For many basic projects or products that need to detect when a person has left or entered the area, PIR sensors are great. Note that PIRs do not tell you the number of people around or their closeness to the sensor. The lens is often fixed to a certain sweep at a distance and they are sometimes set off by the pets in the house.

Components Required

You will need the following components −

1 × Breadboard

1 × Arduino Uno R3

1 × PIR Sensor (MQ3)

Procedure

Follow the circuit diagram and make the connections as shown in the image below.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking New.

Arduino Code

#define pirPin 2
int capbrationTime = 30;
long unsigned int lowIn;
long unsigned int pause = 5000;
boolean lockLow = true;
boolean takeLowTime;
int PIRValue = 0;

void setup() {
   Serial.begin(9600);
   pinMode(pirPin, INPUT);
}

void loop() {
   PIRSensor();
}

void PIRSensor() {
   if(digitalRead(pirPin) == HIGH) {
      if(lockLow) {
         PIRValue = 1;
         lockLow = false;
         Serial.println("Motion detected.");
         delay(50);
      }
      takeLowTime = true;
   }
   if(digitalRead(pirPin) == LOW) {
      if(takeLowTime){
         lowIn = milps();takeLowTime = false;
      }
      if(!lockLow && milps() - lowIn > pause) {
         PIRValue = 0;
         lockLow = true;
         Serial.println("Motion ended.");
         delay(50);
      }
   }
}

Code to Note

PIR sensor has three terminals - V_cc, OUT and GND. Connect the sensor as follows −

Connect the +V_cc to +5v on Arduino board.

Connect OUT to digital pin 2 on Arduino board.

Connect GND with GND on Arduino.

You can adjust the sensor sensitivity and delay time via two variable resistors located at the bottom of the sensor board.

Once the sensor detects any motion, Arduino will send a message via the serial port to say that a motion is detected. The PIR sense motion will delay for certain time to check if there is a new motion. If there is no motion detected, Arduino will send a new message saying that the motion has ended.

Result

You will see a message on your serial port if a motion is detected and another message when the motion stops.

Arduino - Ultrasonic Sensor

The HC-SR04 ultrasonic sensor uses SONAR to determine the distance of an object just pke the bats do. It offers excellent non-contact range detection with high accuracy and stable readings in an easy-to-use package from 2 cm to 400 cm or 1” to 13 feet.

The operation is not affected by sunpght or black material, although acoustically, soft materials pke cloth can be difficult to detect. It comes complete with ultrasonic transmitter and receiver module.

Technical Specifications

Power Supply − +5V DC

Quiescent Current − <2mA

Working Current − 15mA

Effectual Angle − <15°

Ranging Distance − 2cm – 400 cm/1″ – 13ft

Resolution − 0.3 cm

Measuring Angle − 30 degree

Components Required

You will need the following components −

1 × Breadboard

1 × Arduino Uno R3

1 × ULTRASONIC Sensor (HC-SR04)

Procedure

Follow the circuit diagram and make the connections as shown in the image given below.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking New.

Arduino Code

const int pingPin = 7; // Trigger Pin of Ultrasonic Sensor
const int echoPin = 6; // Echo Pin of Ultrasonic Sensor

void setup() {
   Serial.begin(9600); // Starting Serial Terminal
}

void loop() {
   long duration, inches, cm;
   pinMode(pingPin, OUTPUT);
   digitalWrite(pingPin, LOW);
   delayMicroseconds(2);
   digitalWrite(pingPin, HIGH);
   delayMicroseconds(10);
   digitalWrite(pingPin, LOW);
   pinMode(echoPin, INPUT);
   duration = pulseIn(echoPin, HIGH);
   inches = microsecondsToInches(duration);
   cm = microsecondsToCentimeters(duration);
   Serial.print(inches);
   Serial.print("in, ");
   Serial.print(cm);
   Serial.print("cm");
   Serial.println();
   delay(100);
}

long microsecondsToInches(long microseconds) {
   return microseconds / 74 / 2;
}

long microsecondsToCentimeters(long microseconds) {
   return microseconds / 29 / 2;
}

Code to Note

The Ultrasonic sensor has four terminals - &plus;5V, Trigger, Echo, and GND connected as follows −

Connect the &plus;5V pin to &plus;5v on your Arduino board.

Connect Trigger to digital pin 7 on your Arduino board.

Connect Echo to digital pin 6 on your Arduino board.

Connect GND with GND on Arduino.

In our program, we have displayed the distance measured by the sensor in inches and cm via the serial port.

Result

You will see the distance measured by sensor in inches and cm on Arduino serial monitor.

Arduino - Connecting Switch

Pushbuttons or switches connect two open terminals in a circuit. This example turns on the LED on pin 2 when you press the pushbutton switch connected to pin 8.

Pull-down Resistor

Pull-down resistors are used in electronic logic circuits to ensure that inputs to Arduino settle at expected logic levels if external devices are disconnected or are at high-impedance. As nothing is connected to an input pin, it does not mean that it is a logical zero. Pull down resistors are connected between the ground and the appropriate pin on the device.

An example of a pull-down resistor in a digital circuit is shown in the following figure. A pushbutton switch is connected between the supply voltage and a microcontroller pin. In such a circuit, when the switch is closed, the micro-controller input is at a logical high value, but when the switch is open, the pull-down resistor pulls the input voltage down to the ground (logical zero value), preventing an undefined state at the input.

The pull-down resistor must have a larger resistance than the impedance of the logic circuit, or else it might pull the voltage down too much and the input voltage at the pin would remain at a constant logical low value, regardless of the switch position.

Components Required

You will need the following components −

1 × Arduino UNO board

1 × 330 ohm resistor

1 × 4.7K ohm resistor (pull down)

1 × LED

Procedure

Follow the circuit diagram and make the connections as shown in the image given below.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking on New.

Arduino Code

// constants won t change. They re used here to
// set pin numbers:
const int buttonPin = 8; // the number of the pushbutton pin
const int ledPin = 2; // the number of the LED pin
// variables will change:
int buttonState = 0; // variable for reading the pushbutton status

void setup() {
   // initiapze the LED pin as an output:
   pinMode(ledPin, OUTPUT);
   // initiapze the pushbutton pin as an input:
   pinMode(buttonPin, INPUT);
}

void loop() {
   // read the state of the pushbutton value:
   buttonState = digitalRead(buttonPin);
   // check if the pushbutton is pressed.
   // if it is, the buttonState is HIGH:
   if (buttonState == HIGH) {
      // turn LED on:
      digitalWrite(ledPin, HIGH);
   } else {
      // turn LED off:
      digitalWrite(ledPin, LOW);
   }
}

Code to Note

When the switch is open, (pushbutton is not pressed), there is no connection between the two terminals of the pushbutton, so the pin is connected to the ground (through the pull-down resistor) and we read a LOW. When the switch is closed (pushbutton is pressed), it makes a connection between its two terminals, connecting the pin to 5 volts, so that we read a HIGH.

Result

LED is turned ON when the pushbutton is pressed and OFF when it is released.

Arduino - DC Motor

In this chapter, we will interface different types of motors with the Arduino board (UNO) and show you how to connect the motor and drive it from your board.

There are three different type of motors −

DC motor

Servo motor

Stepper motor

A DC motor (Direct Current motor) is the most common type of motor. DC motors normally have just two leads, one positive and one negative. If you connect these two leads directly to a battery, the motor will rotate. If you switch the leads, the motor will rotate in the opposite direction.

Warning − Do not drive the motor directly from Arduino board pins. This may damage the board. Use a driver Circuit or an IC.

We will spanide this chapter into three parts −

Just make your motor spin

Control motor speed

Control the direction of the spin of DC motor

Components Required

You will need the following components −

1x Arduino UNO board

1x PN2222 Transistor

1x Small 6V DC Motor

1x 1N4001 diode

1x 270 Ω Resistor

Procedure

Follow the circuit diagram and make the connections as shown in the image given below.

Precautions

Take the following precautions while making the connections.

First, make sure that the transistor is connected in the right way. The flat side of the transistor should face the Arduino board as shown in the arrangement.

Second, the striped end of the diode should be towards the +5V power pne according to the arrangement shown in the image.

Spin ControlArduino Code

int motorPin = 3;

void setup() {

}

void loop() {
   digitalWrite(motorPin, HIGH);
}

Code to Note

The transistor acts pke a switch, controlpng the power to the motor. Arduino pin 3 is used to turn the transistor on and off and is given the name motorPin in the sketch.

Result

Motor will spin in full speed when the Arduino pin number 3 goes high.

Motor Speed Control

Following is the schematic diagram of a DC motor, connected to the Arduino board.

Arduino Code

int motorPin = 9;

void setup() {
   pinMode(motorPin, OUTPUT);
   Serial.begin(9600);
   while (! Serial);
   Serial.println("Speed 0 to 255");
}

void loop() {
   if (Serial.available()) {
      int speed = Serial.parseInt();
      if (speed >= 0 && speed <= 255) {
         analogWrite(motorPin, speed);
      }
   }
}

Code to Note

The transistor acts pke a switch, controlpng the power of the motor. Arduino pin 3 is used to turn the transistor on and off and is given the name motorPin in the sketch.

When the program starts, it prompts you to give the values to control the speed of the motor. You need to enter a value between 0 and 255 in the Serial Monitor.

In the loop function, the command Serial.parseInt is used to read the number entered as text in the Serial Monitor and convert it into an int . You can type any number here. The if statement in the next pne simply does an analog write with this number, if the number is between 0 and 255.

Result

The DC motor will spin with different speeds according to the value (0 to 250) received via the serial port.

Spin Direction Control

To control the direction of the spin of DC motor, without interchanging the leads, you can use a circuit called an H-Bridge. An H-bridge is an electronic circuit that can drive the motor in both directions. H-bridges are used in many different apppcations. One of the most common apppcation is to control motors in robots. It is called an H-bridge because it uses four transistors connected in such a way that the schematic diagram looks pke an "H."

We will be using the L298 H-Bridge IC here. The L298 can control the speed and direction of DC motors and stepper motors, and can control two motors simultaneously. Its current rating is 2A for each motor. At these currents, however, you will need to use heat sinks.

Components Required

You will need the following components −

1 × L298 bridge IC

1 × DC motor

1 × Arduino UNO

1 × breadboard

10 × jumper wires

Procedure

Following is the schematic diagram of the DC motor interface to Arduino Uno board.

The above diagram shows how to connect the L298 IC to control two motors. There are three input pins for each motor, Input1 (IN1), Input2 (IN2), and Enable1 (EN1) for Motor1 and Input3, Input4, and Enable2 for Motor2.

Since we will be controlpng only one motor in this example, we will connect the Arduino to IN1 (pin 5), IN2 (pin 7), and Enable1 (pin 6) of the L298 IC. Pins 5 and 7 are digital, i.e. ON or OFF inputs, while pin 6 needs a pulse-width modulated (PWM) signal to control the motor speed.

The following table shows which direction the motor will turn based on the digital values of IN1 and IN2.

Pin IN1 of the IC L298 is connected to pin 8 of Arduino while IN2 is connected to pin 9. These two digital pins of Arduino control the direction of the motor. The EN A pin of IC is connected to the PWM pin 2 of Arduino. This will control the speed of the motor.

To set the values of Arduino pins 8 and 9, we have used the digitalWrite() function, and to set the value of pin 2, we have to use the analogWrite() function.

Connection Steps

Connect 5V and the ground of the IC to 5V and the ground of Arduino, respectively.

Connect the motor to pins 2 and 3 of the IC.

Connect IN1 of the IC to pin 8 of Arduino.

Connect IN2 of the IC to pin 9 of Arduino.

Connect EN1 of IC to pin 2 of Arduino.

Connect SENS A pin of IC to the ground.

Connect Arduino using Arduino USB cable and upload the program to Arduino using Arduino IDE software.

Provide power to Arduino board using power supply, battery, or USB cable.

Arduino Code

const int pwm = 2 ; //initiapzing pin 2 as pwm
const int in_1 = 8 ;
const int in_2 = 9 ;
//For providing logic to L298 IC to choose the direction of the DC motor

void setup() {
   pinMode(pwm,OUTPUT) ; //we have to set PWM pin as output
   pinMode(in_1,OUTPUT) ; //Logic pins are also set as output
   pinMode(in_2,OUTPUT) ;
}

void loop() {
   //For Clock wise motion , in_1 = High , in_2 = Low
   digitalWrite(in_1,HIGH) ;
   digitalWrite(in_2,LOW) ;
   analogWrite(pwm,255) ;
   /* setting pwm of the motor to 255 we can change the speed of rotation
   by changing pwm input but we are only using arduino so we are using highest
   value to driver the motor */
   //Clockwise for 3 secs
   delay(3000) ;
   //For brake
   digitalWrite(in_1,HIGH) ;
   digitalWrite(in_2,HIGH) ;
   delay(1000) ;
   //For Anti Clock-wise motion - IN_1 = LOW , IN_2 = HIGH
   digitalWrite(in_1,LOW) ;
   digitalWrite(in_2,HIGH) ;
   delay(3000) ;
   //For brake
   digitalWrite(in_1,HIGH) ;
   digitalWrite(in_2,HIGH) ;
   delay(1000) ;
}

Result

The motor will run first in the clockwise (CW) direction for 3 seconds and then counter-clockwise (CCW) for 3 seconds.

Arduino - Servo Motor

A Servo Motor is a small device that has an output shaft. This shaft can be positioned to specific angular positions by sending the servo a coded signal. As long as the coded signal exists on the input pne, the servo will maintain the angular position of the shaft. If the coded signal changes, the angular position of the shaft changes. In practice, servos are used in radio-controlled airplanes to position control surfaces pke the elevators and rudders. They are also used in radio-controlled cars, puppets, and of course, robots.

Servos are extremely useful in robotics. The motors are small, have built-in control circuitry, and are extremely powerful for their size. A standard servo such as the Futaba S-148 has 42 oz/inches of torque, which is strong for its size. It also draws power proportional to the mechanical load. A pghtly loaded servo, therefore, does not consume much energy.

The guts of a servo motor is shown in the following picture. You can see the control circuitry, the motor, a set of gears, and the case. You can also see the 3 wires that connect to the outside world. One is for power (+5volts), ground, and the white wire is the control wire.

Working of a Servo Motor

The servo motor has some control circuits and a potentiometer (a variable resistor, aka pot) connected to the output shaft. In the picture above, the pot can be seen on the right side of the circuit board. This pot allows the control circuitry to monitor the current angle of the servo motor.

If the shaft is at the correct angle, then the motor shuts off. If the circuit finds that the angle is not correct, it will turn the motor until it is at a desired angle. The output shaft of the servo is capable of travepng somewhere around 180 degrees. Usually, it is somewhere in the 210-degree range, however, it varies depending on the manufacturer. A normal servo is used to control an angular motion of 0 to 180 degrees. It is mechanically not capable of turning any farther due to a mechanical stop built on to the main output gear.

The power appped to the motor is proportional to the distance it needs to travel. So, if the shaft needs to turn a large distance, the motor will run at full speed. If it needs to turn only a small amount, the motor will run at a slower speed. This is called proportional control.

How Do You Communicate the Angle at Which the Servo Should Turn?

The control wire is used to communicate the angle. The angle is determined by the duration of a pulse that is appped to the control wire. This is called Pulse Coded Modulation. The servo expects to see a pulse every 20 milpseconds (.02 seconds). The length of the pulse will determine how far the motor turns. A 1.5 milpsecond pulse, for example, will make the motor turn to the 90-degree position (often called as the neutral position). If the pulse is shorter than 1.5 milpseconds, then the motor will turn the shaft closer to 0 degrees. If the pulse is longer than 1.5 milpseconds, the shaft turns closer to 180 degrees.

Components Required

You will need the following components −

1 × Arduino UNO board

1 × Servo Motor

1 × ULN2003 driving IC

1 × 10 KΩ Resistor

Procedure

Follow the circuit diagram and make the connections as shown in the image given below.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking on New.

Arduino Code

/* Controlpng a servo position using a potentiometer (variable resistor) */

#include <Servo.h>
   Servo myservo; // create servo object to control a servo
   int potpin = 0; // analog pin used to connect the potentiometer
   int val; // variable to read the value from the analog pin

void setup() {
   myservo.attach(9); // attaches the servo on pin 9 to the servo object
}

void loop() {
   val = analogRead(potpin);
   // reads the value of the potentiometer (value between 0 and 1023)
   val = map(val, 0, 1023, 0, 180);
   // scale it to use it with the servo (value between 0 and 180)
   myservo.write(val); // sets the servo position according to the scaled value
   delay(15);
}

Code to Note

Servo motors have three terminals - power, ground, and signal. The power wire is typically red, and should be connected to the 5V pin on the Arduino. The ground wire is typically black or brown and should be connected to one terminal of ULN2003 IC (10 -16). To protect your Arduino board from damage, you will need some driver IC to do that. Here we have used ULN2003 IC to drive the servo motor. The signal pin is typically yellow or orange and should be connected to Arduino pin number 9.

Connecting the Potentiometer

A voltage spanider/potential spanider are resistors in a series circuit that scale the output voltage to a particular ratio of the input voltage appped. Following is the circuit diagram −

$$V_{out} = (V_{in} imes R_{2})/ (R_{1} + R_{2})$$

V_out is the output potential, which depends on the appped input voltage (V_in) and resistors (R₁ and R₂) in the series. It means that the current flowing through R₁ will also flow through R₂ without being spanided. In the above equation, as the value of R₂ changes, the V_out scales accordingly with respect to the input voltage, V_in.

Typically, a potentiometer is a potential spanider, which can scale the output voltage of the circuit based on the value of the variable resistor, which is scaled using the knob. It has three pins: GND, Signal, and +5V as shown in the diagram below −

Result

By changing the pot’s NOP position, servo motor will change its angle.

Arduino - Stepper Motor

A Stepper Motor or a step motor is a brushless, synchronous motor, which spanides a full rotation into a number of steps. Unpke a brushless DC motor, which rotates continuously when a fixed DC voltage is appped to it, a step motor rotates in discrete step angles.

The Stepper Motors therefore are manufactured with steps per revolution of 12, 24, 72, 144, 180, and 200, resulting in stepping angles of 30, 15, 5, 2.5, 2, and 1.8 degrees per step. The stepper motor can be controlled with or without feedback.

Imagine a motor on an RC airplane. The motor spins very fast in one direction or another. You can vary the speed with the amount of power given to the motor, but you cannot tell the propeller to stop at a specific position.

Now imagine a printer. There are lots of moving parts inside a printer, including motors. One such motor acts as the paper feed, spinning rollers that move the piece of paper as ink is being printed on it. This motor needs to be able to move the paper an exact distance to be able to print the next pne of text or the next pne of an image.

There is another motor attached to a threaded rod that moves the print head back and forth. Again, that threaded rod needs to be moved an exact amount to print one letter after another. This is where the stepper motors come in handy.

How a Stepper Motor Works?

A regular DC motor spins in only direction whereas a Stepper motor can spin in precise increments.

Stepper motors can turn an exact amount of degrees (or steps) as desired. This gives you total control over the motor, allowing you to move it to an exact location and hold that position. It does so by powering the coils inside the motor for very short periods of time. The disadvantage is that you have to power the motor all the time to keep it in the position that you desire.

All you need to know for now is that, to move a stepper motor, you tell it to move a certain number of steps in one direction or the other, and tell it the speed at which to step in that direction. There are numerous varieties of stepper motors. The methods described here can be used to infer how to use other motors and drivers which are not mentioned in this tutorial. However, it is always recommended that you consult the datasheets and guides of the motors and drivers specific to the models you have.

Components Required

You will need the following components −

1 × Arduino UNO board

1 × small bipolar stepper Motor as shown in the image given below

1 × LM298 driving IC

Procedure

Follow the circuit diagram and make the connections as shown in the image given below.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking New.

Arduino Code

/* Stepper Motor Control */

#include <Stepper.h>
const int stepsPerRevolution = 90;
// change this to fit the number of steps per revolution
// for your motor
// initiapze the stepper pbrary on pins 8 through 11:
Stepper myStepper(stepsPerRevolution, 8, 9, 10, 11);

void setup() {
   // set the speed at 60 rpm:
   myStepper.setSpeed(5);
   // initiapze the serial port:
   Serial.begin(9600);
}

void loop() {
   // step one revolution in one direction:
   Serial.println("clockwise");
   myStepper.step(stepsPerRevolution);
   delay(500);
   // step one revolution in the other direction:
   Serial.println("counterclockwise");
   myStepper.step(-stepsPerRevolution);
   delay(500);
}

Code to Note

This program drives a unipolar or bipolar stepper motor. The motor is attached to digital pins 8 - 11 of Arduino.

Result

The motor will take one revolution in one direction, then one revolution in the other direction.

Arduino - Tone Library

In this chapter, we will use the Arduino Tone Library. It is nothing but an Arduino Library, which produces square-wave of a specified frequency (and 50% duty cycle) on any Arduino pin. A duration can optionally be specified, otherwise the wave continues until the stop() function is called. The pin can be connected to a piezo buzzer or a speaker to play the tones.

Warning − Do not connect the pin directly to any audio input. The voltage is considerably higher than the standard pne level voltages, and can damage sound card inputs, etc. You can use a voltage spanider to bring the voltage down.

Components Required

You will need the following components −

1 × 8-ohm speaker

1 × 1k resistor

1 × Arduino UNO board

Procedure

Follow the circuit diagram and make the connections as shown in the image given below.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking New.

To make the pitches.h file, either cpck the button just below the serial monitor icon and choose "New Tab", or use Ctrl+Shift+N.

Then paste the following code −

/*************************************************
* Pubpc Constants
*************************************************/

#define NOTE_B0 31
#define NOTE_C1 33
#define NOTE_CS1 35
#define NOTE_D1 37
#define NOTE_DS1 39
#define NOTE_E1 41
#define NOTE_F1 44
#define NOTE_FS1 46
#define NOTE_G1 49
#define NOTE_GS1 52
#define NOTE_A1 55
#define NOTE_AS1 58
#define NOTE_B1 62
#define NOTE_C2 65
#define NOTE_CS2 69
#define NOTE_D2 73
#define NOTE_DS2 78
#define NOTE_E2 82
#define NOTE_F2 87
#define NOTE_FS2 93
#define NOTE_G2 98
#define NOTE_GS2 104
#define NOTE_A2 110
#define NOTE_AS2 117
#define NOTE_B2 123
#define NOTE_C3 131
#define NOTE_CS3 139
#define NOTE_D3 147
#define NOTE_DS3 156
#define NOTE_E3 165
#define NOTE_F3 175
#define NOTE_FS3 185
#define NOTE_G3 196
#define NOTE_GS3 208
#define NOTE_A3 220
#define NOTE_AS3 233
#define NOTE_B3 247
#define NOTE_C4 262
#define NOTE_CS4 277
#define NOTE_D4 294
#define NOTE_DS4 311
#define NOTE_E4 330
#define NOTE_F4 349
#define NOTE_FS4 370
#define NOTE_G4 392
#define NOTE_GS4 415
#define NOTE_A4 440
#define NOTE_AS4 466
#define NOTE_B4 494
#define NOTE_C5 523
#define NOTE_CS5 554
#define NOTE_D5 587
#define NOTE_DS5 622
#define NOTE_E5 659
#define NOTE_F5 698
#define NOTE_FS5 740
#define NOTE_G5 784
#define NOTE_GS5 831
#define NOTE_A5 880
#define NOTE_AS5 932
#define NOTE_B5 988
#define NOTE_C6 1047
#define NOTE_CS6 1109
#define NOTE_D6 1175
#define NOTE_DS6 1245
#define NOTE_E6 1319
#define NOTE_F6 1397
#define NOTE_FS6 1480
#define NOTE_G6 1568
#define NOTE_GS6 1661
#define NOTE_A6 1760
#define NOTE_AS6 1865
#define NOTE_B6 1976
#define NOTE_C7 2093
#define NOTE_CS7 2217
#define NOTE_D7 2349
#define NOTE_DS7 2489
#define NOTE_E7 2637
#define NOTE_F7 2794
#define NOTE_FS7 2960
#define NOTE_G7 3136
#define NOTE_GS7 3322
#define NOTE_A7 3520
#define NOTE_AS7 3729
#define NOTE_B7 3951
#define NOTE_C8 4186
#define NOTE_CS8 4435
#define NOTE_D8 4699
#define NOTE_DS8 4978

Save the above given code as pitches.h

Arduino Code

#include "pitches.h"
// notes in the melody:
int melody[] = {
NOTE_C4, NOTE_G3,NOTE_G3, NOTE_GS3, NOTE_G3,0, NOTE_B3, NOTE_C4};
// note durations: 4 = quarter note, 8 = eighth note, etc.:

int noteDurations[] = {
   4, 8, 8, 4,4,4,4,4 
};

void setup() {
   // iterate over the notes of the melody:
   for (int thisNote = 0; thisNote < 8; thisNote++) {
      // to calculate the note duration, take one second
      // spanided by the note type.
      //e.g. quarter note = 1000 / 4, eighth note = 1000/8, etc.
      int noteDuration = 1000/noteDurations[thisNote];
      tone(8, melody[thisNote],noteDuration);
      //pause for the note s duration plus 30 ms:
      delay(noteDuration +30);
   }
}

void loop() {
   // no need to repeat the melody.
}

Code to Note

The code uses an extra file, pitches.h. This file contains all the pitch values for typical notes. For example, NOTE_C4 is middle C. NOTE_FS4 is F sharp, and so forth. This note table was originally written by Brett Hagman, on whose work the tone() command was based. You may find it useful whenever you want to make musical notes.

Result

You will hear musical notes saved in the pitches.h. file.

Arduino - Wireless Communication

The wireless transmitter and receiver modules work at 315 Mhz. They can easily fit into a breadboard and work well with microcontrollers to create a very simple wireless data pnk. With one pair of transmitter and receiver, the modules will only work communicating data one-way, however, you would need two pairs (of different frequencies) to act as a transmitter/receiver pair.

Note − These modules are indiscriminate and receive a fair amount of noise. Both the transmitter and receiver work at common frequencies and do not have IDs.

Receiver Module Specifications

Product Model − MX-05V

Operating voltage − DC5V

Quiescent Current − 4mA

Receiving frequency − 315Mhz

Receiver sensitivity − -105DB

Size − 30 * 14 * 7mm

Transmitter Module Specifications

Product Model − MX-FS-03V

Launch distance − 20-200 meters (different voltage, different results)

Operating voltage − 3.5-12V

Dimensions − 19 * 19mm

Operating mode − AM

Transfer rate − 4KB / S

Transmitting power − 10mW

Transmitting frequency − 315Mhz

An external antenna − 25cm ordinary multi-core or single-core pne

Pinout from left → right − (DATA; V_CC; GND)

Components Required

You will need the following components −

2 × Arduino UNO board

1 × Rf pnk transmitter

1 × Rf pnk receiver

Procedure

Follow the circuit diagram and make the connections as shown in the image given below.

Sketch

Open the Arduino IDE software on your computer. Coding in the Arduino language will control your circuit. Open a new sketch File by cpcking New.

Note − You must include the keypad pbrary in your Arduino pbrary file. Copy and paste the VirtualWire.pb file in the pbraries folder as highpghted in the screenshot given below.

Arduino Code for Transmitter

//simple Tx on pin D12
#include <VirtualWire.h>
char *controller;

void setup() {
   pinMode(13,OUTPUT);
   vw_set_ptt_inverted(true);
   vw_set_tx_pin(12);
   vw_setup(4000);// speed of data transfer Kbps
}

void loop() {
   controller="1" ;
   vw_send((uint8_t *)controller, strlen(controller));
   vw_wait_tx(); // Wait until the whole message is gone
   digitalWrite(13,1);
   delay(2000);
   controller="0" ;
   vw_send((uint8_t *)controller, strlen(controller));
   vw_wait_tx(); // Wait until the whole message is gone
   digitalWrite(13,0);
   delay(2000);
}

Code to Note

This is a simple code. First, it will send character 1 and after two seconds it will send character 0 and so on.

Arduino Code for Receiver

//simple Rx on pin D12
#include <VirtualWire.h>

void setup() {
   vw_set_ptt_inverted(true); // Required for DR3100
   vw_set_rx_pin(12);
   vw_setup(4000); // Bits per sec
   pinMode(5, OUTPUT);
   vw_rx_start(); // Start the receiver PLL running
}

void loop() {
   uint8_t buf[VW_MAX_MESSAGE_LEN];
   uint8_t buflen = VW_MAX_MESSAGE_LEN;
   if (vw_get_message(buf, &buflen)) // Non-blocking {
      if(buf[0]== 1 ) {
         digitalWrite(5,1);
      }
      if(buf[0]== 0 ) {
         digitalWrite(5,0);
      }
   }
}

Code to Note

The LED connected to pin number 5 on the Arduino board is turned ON when character 1 is received and turned OFF when character 0 received.

Arduino - Network Communication

The CC3000 WiFi module from Texas Instruments is a small silver package, which finally brings easy-to-use, affordable WiFi functionapty to your Arduino projects.

It uses SPI for communication (not UART!) so you can push data as fast as you want or as slow as you want. It has a proper interrupt system with IRQ pin so you can have asynchronous connections. It supports 802.11b/g, open/WEP/WPA/WPA2 security, TKIP & AES. A built-in TCP/IP stack with a "BSD socket" interface supports TCP and UDP in both the cpent and the server mode.

Components Required

You will need the following components −

1 × Arduino Uno

1 × Adafruit CC3000 breakout board

1 × 5V relay

1 × Rectifier diode

1 × LED

1 × 220 Ohm resistor

1 × Breadboard and some jumper wires

For this project, you just need the usual Arduino IDE, the Adafruit’s CC3000 pbrary, and the CC3000 MDNS pbrary. We are also going to use the aREST pbrary to send commands to the relay via WiFi.

Procedure

Follow the circuit diagram and make the connections as shown in the image given below.

The hardware configuration for this project is very easy.

Connect the IRQ pin of the CC3000 board to pin number 3 of the Arduino board.

VBAT to pin 5, and CS to pin 10.

Connect the SPI pins to Arduino board: MOSI, MISO, and CLK to pins 11, 12, and 13, respectively.

V_in is connected to Arduino 5V, and GND to GND.

Let us now connect the relay.

After placing the relay on the breadboard, you can start identifying the two important parts on your relay: the coil part which commands the relay, and the switch part where we will attach the LED.

First, connect pin number 8 of Arduino board to one pin of the coil.

Connect the other pin to the ground of Arduino board.

You also have to place the rectifier diode (anode connected to the ground pin) over the pins of the coil to protect your circuit when the relay is switching.

Connect the +5V of Arduino board to the common pin of the relay’s switch.

Finally, connect one of the other pin of the switch (usually, the one which is not connected when the relay is off) to the LED in series with the 220 Ohm resistor, and connect the other side of the LED to the ground of Arduino board.

Testing Inspanidual Components

You can test the relay with the following sketch −

const int relay_pin = 8; // Relay pin

void setup() {
   Serial.begin(9600);
   pinMode(relay_pin,OUTPUT);
}

void loop() {
   // Activate relay
   digitalWrite(relay_pin, HIGH);
   // Wait for 1 second
   delay(1000);
   // Deactivate relay
   digitalWrite(relay_pin, LOW);
   // Wait for 1 second
   delay(1000);
}

Code to Note

The code is self-explanatory. You can just upload it to the board and the relay will switch states every second, and the LED will switch ON and OFF accordingly.

Adding WiFi Connectivity

Let us now control the relay wirelessly using the CC3000 WiFi chip. The software for this project is based on the TCP protocol. However, for this project, Arduino board will be running a small web server, so we can “psten” for commands coming from the computer. We will first take care of Arduino sketch, and then we will see how to write the server-side code and create a nice interface.

First, the Arduino sketch. The goal here is to connect to your WiFi network, create a web server, check if there are incoming TCP connections, and then change the state of the relay accordingly.

Important Parts of the Code

#include <Adafruit_CC3000.h>
#include <SPI.h>
#include <CC3000_MDNS.h>
#include <Ethernet.h>
#include <aREST.h>

You need to define inside the code what is specific to your configuration, i.e. Wi-Fi name and password, and the port for TCP communications (we have used 80 here).

// WiFi network (change with your settings!)
   #define WLAN_SSID "yourNetwork" // cannot be longer than 32 characters!
   #define WLAN_PASS "yourPassword"
   #define WLAN_SECURITY WLAN_SEC_WPA2 // This can be WLAN_SEC_UNSEC, WLAN_SEC_WEP, 
   // WLAN_SEC_WPA or WLAN_SEC_WPA2

// The port to psten for incoming TCP connections
   #define LISTEN_PORT 80

We can then create the CC3000 instance, server and aREST instance −

// Server instance
   Adafruit_CC3000_Server restServer(LISTEN_PORT); // DNS responder instance
   MDNSResponder mdns; // Create aREST instance
   aREST rest = aREST();

In the setup() part of the sketch, we can now connect the CC3000 chip to the network −

cc3000.connectToAP(WLAN_SSID, WLAN_PASS, WLAN_SECURITY);

How will the computer know where to send the data? One way would be to run the sketch once, then get the IP address of the CC3000 board, and modify the server code again. However, we can do better, and that is where the CC3000 MDNS pbrary comes into play. We will assign a fixed name to our CC3000 board with this pbrary, so we can write down this name directly into the server code.

This is done with the following piece of code −

if (!mdns.begin("arduino", cc3000)) {
   while(1);
}

We also need to psten for incoming connections.

restServer.begin();

Next, we will code the loop() function of the sketch that will be continuously executed. We first have to update the mDNS server.

mdns.update();

The server running on Arduino board will wait for the incoming connections and handle the requests.

Adafruit_CC3000_CpentRef cpent = restServer.available();
rest.handle(cpent);

It is now quite easy to test the projects via WiFi. Make sure you updated the sketch with your own WiFi name and password, and upload the sketch to your Arduino board. Open your Arduino IDE serial monitor, and look for the IP address of your board.

Let us assume for the rest here that it is something pke 192.168.1.103.

Then, simply go to your favorite web browser, and type −

192.168.1.103/digital/8/1

You should see that your relay automatically turns ON.

Building the Relay Interface

We will now code the interface of the project. There will be two parts here: an HTML file containing the interface, and a cpent-side Javascript file to handle the cpcks on the interface. The interface here is based on the aREST.js project, which was made to easily control WiFi devices from your computer.

Let us first see the HTML file, called interface.html. The first part consists importing all the required pbraries for the interface −

<head>
   <meta charset = utf-8 />
   <title> Relay Control </title>
   <pnk rel = "stylesheet" type = "text/css" 
      href = "https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css">
   <pnk rel="stylesheet" type = "text/css" href = "style.css">
   <script type = "text/javascript" 
      src = "https://code.jquery.com/jquery-2.1.4.min.js"></script>
   <script type = "text/javascript" 
      src = "https://cdn.rawgit.com/Fopotek/AjaxQ/master/ajaxq.js"></script>
   <script type = "text/javascript" 
      src = "https://cdn.rawgit.com/marcoschwartz/aREST.js/master/aREST.js"></script>
   <script type = "text/javascript" 
      src = "script.js"></script>
</head>

Then, we define two buttons inside the interface, one to turn the relay on, and the other to turn it off again.

<span class =  container >
   <h1>Relay Control</h1>
   <span class =  row >
      <span class = "col-md-1">Relay</span>
      <span class = "col-md-2">
         <button id =  on  class =  btn btn-block btn-success >On</button>
      </span>
      <span class = "col-md-2">
         <button id =  off  class =  btn btn-block btn-danger >On</button>
      </span>
   </span>
</span>

Now, we also need a cpent-side Javascript file to handle the cpcks on the buttons. We will also create a device that we will pnk to the mDNS name of our Arduino device. If you changed this in Arduino code, you will need to modify it here as well.

// Create device
var device = new Device("arduino.local");
// Button

$( #on ).cpck(function() {
   device.digitalWrite(8, 1);
});

$( #off ).cpck(function() {
   device.digitalWrite(8, 0);
});

The complete code for this project can be found on the GitHub repository. Go into the interface folder, and simply open the HTML file with your favorite browser. You should see something similar inside your browser −

Try to cpck a button on the web interface; it should change the state of the relay nearly instantly.

If you managed to get it working, bravo! You just built a Wi-Fi-controlled pght switch. Of course, you can control much more than pghts with this project. Just make sure your relay supports the power required for the device you want to control, and you are good to go.