Home automation

1. 4-Jul-22 1
KPR Institute of Engineering and Technology, Coimbatore, Tamil Nadu, India

2. What are the temperature sensors?
• A temperature sensor is a device, typically, a thermocouple or
resistance temperature detector, that provides temperature
measurement in a readable form through an electrical signal.
• A thermometer is the most basic form of a temperature meter that is
used to measure the degree of hotness and coolness.
• Temperature meters are used in the geotechnical field to monitor
concrete, structures, soil, water, bridges etc. for structural changes in
them due to seasonal variations.
• A thermocouple (T/C) is made from two dissimilar metals that
generate an electrical voltage in direct proportion with the change in
temperature.
• An RTD (Resistance Temperature Detector) is a variable resistor that
changes its electrical resistance in direct proportion with the change in
the temperature in a precise, repeatable and nearly linear manner.
TEMPERATURE SENSOR

3. What are the different types of temperature sensors?
• Temperature sensors are available of various types, shapes, and sizes.
The two main types of temperature sensors are:
• Contact Type Temperature Sensors: There are a few temperature
meters that measure the degree of hotness or coolness in an object by
being in direct contact with it. They can be used to detect solids, liquids
or gases over a wide range of temperatures.
• Non-Contact Type Temperature Sensors: These types of temperature
meters are not in direct contact of the object rather, they measure the
degree of hotness or coolness through the radiation emitted by the
heat source.
TEMPERATURE SENSOR

4. Thermostat
• Thermostat is a contact type electro-mechanical temperature sensor or switch,
that basically consists of two different metals such as nickel, copper, tungsten or
aluminium etc, that are bonded together to form a Bi-metallic strip.
• The different linear expansion rates of the two dissimilar metals produces a
mechanical bending movement when the strip is subjected to heat.
• The bi-metallic strip can be used itself as an electrical switch or as a mechanical
way of operating an electrical switch in thermostatic controls.
• They are used extensively to control hot water heating elements in boilers,
furnaces, hot water storage tanks as well as in vehicle radiator cooling systems.
TEMPERATURE SENSOR

5. Thermistors
• Thermistor is type of temperature sensor, THERM-ally sensitive res-ISTOR.
• A thermistor is a special type of resistor which changes its physical resistance
when exposed to changes in temperature.
• These are made of ceramic materials such as oxides of nickel, manganese or
cobalt coated in glass. The main advantages are speed of response to any
changes in temperature, accuracy and repeatability.
• Most types of thermistor’s have a Negative Temperature Coefficient of resistance
or (NTC), that is their resistance value goes DOWN with an increase in the
temperature.
TEMPERATURE SENSOR

6. Resistive Temperature Detectors (RTD)
• RTD’s are precision temperature sensors made from high-purity conducting
metals such as platinum, copper or nickel wound into a coil and whose electrical
resistance changes as a function of temperature, similar to that of the
thermistor.
• Also available are thin-film RTD’s. These devices have a thin film of platinum
paste is deposited onto a white ceramic substrate.
• Resistive temperature detectors have positive temperature coefficients (PTC)
but unlike the thermistor their output is extremely linear producing very accurate
measurements of temperature.
TEMPERATURE SENSOR

7. Resistive Temperature Detectors (RTD)
• However, they have very poor thermal sensitivity, that is a change in temperature
only produces a very small output change for example, 1Ω/oC.
• Any variation in resistance due to self heat of the resistive wires as the current
flows through it, I2R , (Ohms Law) causes an error in the readings.
• To avoid this, the RTD is usually connected into a Wheatstone Bridge network
which has additional connecting wires for lead-compensation and/or connection
to a constant current source
TEMPERATURE SENSOR

8. Resistive Temperature Detectors (RTD)
TEMPERATURE SENSOR

9. • Thermocouples
• Thermocouples are popular due to its simplicity, ease of use and their speed of
response to changes in temperature, due mainly to their small size.
• Thermocouples also have the widest temperature range of all the temperature
sensors from below -200oC to well over 2000oC.
• Thermocouples are thermoelectric sensors that basically consists of two junctions
of dissimilar metals, such as copper and constantan that are welded or crimped
together.
• One junction is kept at a constant temperature called the reference (Cold) junction,
while the other the measuring (Hot) junction.
TEMPERATURE SENSOR

10. Interfacing of Temperature Sensor to Arduio
• LM35 is a temperature sensor introduced by Texas Instruments. It
works by producing an analog signal with respect to the temperature
at the rate of 10mV/°C.
• LM35 series are precision integrated-circuit temperature devices with
an output voltage linearly proportional to the Centigrade temperature.
• It is a small, in-budget component that is calibrated in Centigrade,
unlike other sensors that are calibrated in Kelvin.
• Its key features like low impedance, linear analog output, and accurate
centigrade calibration make its interfacing quite simple with the
microcontroller units.
TEMPERATURE SENSOR

11. Interfacing of Temperature Sensor to Arduino
TEMPERATURE SENSOR

12. Components Required
• 1 × Breadboard
• 1 × Arduino Uno R3
• 1 × LM35 sensor
TEMPERATURE SENSOR

13. TEMPERATURE SENSOR

14. TEMPERATURE SENSOR
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
• }

15. TEMPERATURE SENSOR
Application of Temperature sensor
• There are Temperature Sensor applications in many industries including
medical, motorsport, HVAC, agriculture, industrial, aerospace and
automotive. Here are some of the specific temperature sensor applications
which we have come across.
• Motors– there are many different aspects of motors and most of these
require temperature measurement to ensure the motor itself does not
overheat.
• Home appliances – kettles, toasters, washing machines, dishwashers and
coffee machines will all contain temperature sensors.
• Computers– within computers there are temperature sensors to ensure
the system does not overheat
• Industrial equipment – temperature sensors used within these
applications will need to be robust as the environment can be very
demanding.
• Warming Electrical Radiators – NTC thermistors are used to control the
heat on electric radiators.

16. TEMPERATURE SENSOR
Application of Temperature sensor
• Exhaust Gas Monitoring on Motorsport Vehicles – Motorsport
temperature sensors need to be highly reliable and durable to ensure
performance is not compromised in this harsh environment.
• Food Production; 3D printed chocolates – temperature sensors are used
to monitor the temperature of the melted chocolate for 3D printing.
• Alcohol breathalyser – thermistors are used within alcohol breathalysers
to measure the temperature of the subject's breath.
• Other Applications Include:
• HVAC, Power and Utilities, Calibration and Instrumentation
• Heat Exchangers, Industrial Processes, Drilling, Heating/cooling systems,
Laboratory and Energy.

17. GAS/SMOKE SENSOR
What is gas sensor
• A gas sensor is a device which detects the presence or concentration of
gases in the atmosphere. Based on the concentration of the gas the sensor
produces a corresponding potential difference by changing the resistance
of the material inside the sensor, which can be measured as output voltage.
Based on this voltage value the type and concentration of the gas can be
estimated.
• Different Types of Gas sensors
• Classification of the various types of gas sensors based on the sensing
element that are generally used in various applications:
• Metal Oxide based gas Sensor.
• Optical gas Sensor.
• Electrochemical gas Sensor.
• Capacitance-based gas Sensor.
• Calorimetric gas Sensor.
• Acoustic based gas Sensor.

18. GAS/SMOKE SENSOR
MQ-2 Gas Sensor
• The MQ-2 smoke sensor is sensitive to smoke and to the following
flammable gases: LPG, Butane, Propane, Methane, Alcohol, Hydrogen.
• The resistance of the sensor is different depending on the type of the gas.
• The smoke sensor has a built-in potentiometer that allows you to adjust
the sensor digital output (D0) threshold. This threshold sets the value
above which the digital pin will output a HIGH signal.

19. GAS/SMOKE SENSOR
Working
• The voltage that the sensor outputs changes accordingly to the smoke/gas
level that exists in the atmosphere. The sensor outputs a voltage that is
proportional to the concentration of smoke/gas.
• In other words, the relationship between voltage and gas concentration is
the following:
• The greater the gas concentration, the greater the output voltage
• The lower the gas concentration, the lower the output voltage

20. GAS/SMOKE SENSOR
Construction of the Gas Sensor
• The MQ2 module of the gas sensor is useful for gas leakage detection in the
home as well as in the industries. It observes the level of gases present in
the atmosphere. The gas sensor operates on 5V and 800mW.
• Depending on the level of concentration, the sensor observes the potential
difference and this changes the resistance of the material inside the sensor.
The output voltage value gives us the type of gas.
• Normally these sensors are available as a comparator. These comparators
are able to set up a threshold value for gas concentration. The digital pin
will go high only when the concentration of the gas is above the threshold
value. The sensor will work in analog mode to detect the concentration of
the gas.

21. GAS/SMOKE SENSOR
Construction of the Gas Sensor

22. GAS/SMOKE SENSOR
How Does Gas Sensor Work
• The sensor has a sensing element in order to sense the smoke or any
gaseous material. In this sensor, the sensing material is a stainless steel
mesh. This mesh contains aluminium-oxide-based ceramic, coated with tin
dioxide.
• There are mainly 6 leads in the sensing element. Two are used for heating
of sensing elements, the remaining four are used for the output signal.
• Let's consider that we want to identify the Oxygen gas, the oxygen atoms
get absorbed on the sensing element when it will be heated at a higher
temperature.

23. GAS/SMOKE SENSOR
How Does Gas Sensor Work
• Tin oxide has donor electrons present in it, which are attracted towards
oxygen. So by identifying the donor electrons, we can detect the amount of
oxygen that gets absorbed as well as we can oppose the flow of current to
give the signal.
• When reducing gases are present on the sensor, oxygen atoms try to
interact with reducing gases and reduce the absorbed surface density of
the oxygen atom. Hence current can flow through the sensor to generate
an analog output signal.
• This output signal generates the voltage values by which we will get an
idea about the concentration of gases. When the concentration of gas is
high voltage will be high.

24. GAS/SMOKE SENSOR
How Does Gas Sensor Work

25. GAS/SMOKE SENSOR
How Does Gas Sensor Work
• The tubular sensing element is made up of Aluminum Oxide (AL2O3)
based ceramic and has a coating of Tin Dioxide (SnO2). The Tin Dioxide is
the most important material being sensitive towards combustible gases.
• However, the ceramic substrate merely increases heating efficiency and
ensures the sensor area is heated to a working temperature constantly.
Working Principle
• When tin dioxide (semiconductor particles) is heated in air at high
temperature, oxygen is adsorbed on the surface.
• In clean air, donor electrons in tin dioxide are attracted toward oxygen which
is adsorbed on the surface of the sensing material. This prevents electric
current flow.
• In the presence of reducing gases, the surface density of adsorbed oxygen
decreases as it reacts with the reducing gases.
• Electrons are then released into the tin dioxide, allowing current to flow freely
through the sensor.

26. GAS/SMOKE SENSOR
• A smoke detector is an electronic fire-protection device that automatically
senses the presence of smoke, as a key indication of fire, and sounds a
warning to building occupants.
• Household smoke detectors, or smoke alarms, issue an audible and/or visual
alarm locally from the detector itself. They can be battery-powered single
units or several interlinked hardwired (mains-powered) devices backed up by
batteries.
• Smoke detector types
• There are two basic types of passive smoke detectors:
• photoelectric (optical) and ionisation (physical process).
• A combination of the two types of alarm (dual sensor smoke alarm) is
recommended for maximum protection from both fast flaming and slow
smouldering fires.
• Combined optical smoke and heat alarms and combined smoke and carbon
monoxide alarms are also available.
• A photoelectric detector senses sudden scattering of light when smoke enters
the detector chamber, triggering the alarm.

27. GAS/SMOKE SENSOR
• Photoelectric smoke detectors respond an average of 15 to 50 minutes faster
to fire in its early, smouldering stage, before it breaks into flame, than
ionisation alarms. They can be installed near kitchens. Some dual optical
models are available.
• Ionisation smoke alarms are highly sensitive to small smoke particles and
typically respond about 30 to 9 seconds faster to fast flaming fires than
photoelectric smoke alarms, but not to smouldering fires. They may be too
easily set off if they are installed too close to kitchens, or garages.

28. GAS/SMOKE SENSOR
Interfacing Gas Sensor with Arduino
• In this example, you will read the sensor analog output voltage and when
the smoke reaches a certain level, it will make sound a buzzer and a red
LED will turn on.
• When the output voltage is below that level, a green LED will be on.
• The voltage that the sensor outputs changes accordingly to the smoke/gas
level that exists in the atmosphere. The sensor outputs a voltage that is
proportional to the concentration of smoke/gas.
• In other words, the relationship between voltage and gas concentration is
the following:
• The greater the gas concentration, the greater the output voltage
• The lower the gas concentration, the lower the output voltage

29. GAS/SMOKE SENSOR
Interfacing Gas Sensor with Arduino

30. GAS/SMOKE SENSOR
Arduino Coding
#define MQ2pin (0)
float sensorValue; //variable to store sensor value
void setup()
{
Serial.begin(9600); // sets the serial port to 9600
Serial.println("Gas sensor warming up!");
delay(20000); // allow the MQ-2 to warm up
}
void loop()
{
sensorValue = analogRead(MQ2pin); // read analog input pin 0
Serial.print("Sensor Value: ");
Serial.print(sensorValue);
if(sensorValue > 200)
{
Serial.print(" Smoke detected!");
}
Serial.println("");
delay(2000); // wait 2s for next reading
}

31. GAS/SMOKE SENSOR
Arduino Coding
int redLed = 12;
int greenLed = 11;
int buzzer = 10;
int smokeA0 = A5;
// Your threshold value
int sensorThres = 400;
void setup() {
pinMode(redLed, OUTPUT);
pinMode(greenLed, OUTPUT);
pinMode(buzzer, OUTPUT);
pinMode(smokeA0, INPUT);
Serial.begin(9600);
}
void loop() {
int analogSensor = analogRead(smokeA0);
Serial.print("Pin A0: ");
Serial.println(analogSensor);
// Checks if it has reached the threshold value
if (analogSensor > sensorThres)
{
digitalWrite(redLed, HIGH);
digitalWrite(greenLed, LOW);
tone(buzzer, 1000, 200);
}
else
{
digitalWrite(redLed, LOW);
digitalWrite(greenLed, HIGH);
noTone(buzzer);
}
delay(100);
}

32. MOTION SENSOR
• A motion sensor is a device that notices moving objects, mainly people.
• These sensors form a very important component of security, home control, energy
efficiency, automated lighting control, and other helpful systems.
• The main principle of motion sensor is to sense a burglar and send an alert to your
control panel, which gives an alert to your monitoring center.
• Motion sensors react to different situations like movement in your living room,
doors, windows being unbolt or closed.
Types of Motion Detectors Principle
• Motion detectors are classified based on how they detect motion of a body.
Active Detectors
• Active detectors are also known as Radar-based motion sensors.
• The active detector sensors emit the radio waves/ microwaves across a room or
other place, which strike on nearby objects and reflect it back to the sensor
detector.

33. MOTION SENSOR

34. MOTION SENSOR
• When an object moves in motion sensor controlled area at this time, the sensor
looks for a Doppler (frequency) shift in the wave when it returns to the sensor
detector, which would indicate that the wave has hit a moving object.
• The motion sensor can understand these changes and send an electrical signal to
the alarm system, light or other types of device that is connected to the motion
sensor.
Passive Detectors
• Passive Motion Sensors are opposite to active sensors, they do not send out
anything, but it simply detects the infrared energy.
• Infrared (heat) energy levels are sensed by passive detectors.
• Passive sensors scan the room or area, it is installed for infrared heat that is
radiated from living beings.
• Heat is radiated from any object with a temperature above absolute zero.

35. MOTION SENSOR
• When an object walks into the detection area of a passive sensor, it detects
heat emitted from that object and activates the alarm or turns on the light
or any application.
• These sensors would not be effective if they could get activated by a small
animal or insect that moves in the detection range, however, most passive
sensors can be adjusted to pick up the motion of an object with a certain
level of emitted heat, for example adjusting the sensor to pick up
movement only by humans.

36. MOTION SENSOR
Types of Motion Sensors
Ultrasonic Sensor
• It can be active (or) passive, where passive ones pay attention for particular
sounds like metal on metal, glass breaking.
• These sensors are very sensitive, but they are frequently expensive and prone to
fake alarms.
• Active ones generate ultrasonic wave (sound wave) pulses and then determine the
reflection of these waves off a moving object.
Microwave Sensor
• These sensors generate microwave pulses and then calculate their reflection off of
objects, in order to know whether objects are moving or not.
• Microwave sensors are very sensitive, but sometimes these can be seen in
nonmetallic objects which can be detected moving objects on the outside of the
target range.

37. MOTION SENSOR
Combined types of Motion Sensors
• Some types of motion detectors mix some sensors in order to decrease
fake alarms.
• But, dual sensors are only activated when both kinds sense motion.
• For instance, a dual microwave or PIR sensor will start out on the passive
infrared sensor setting, because that consumes less energy.

38. MOTION SENSOR
• Applications of Motion Sensors
• Some of the key applications of motion detectors include:
• Intruder alarms
• Automatic ticket gates
• Entryway lighting
• Security lighting
• Hand dryers
• Automatic doors
• Ultrasonic sensors are used for triggering the security camera at home and for
wildlife photography.
• Active infrared sensors used To indicate the presence of products on conveyor
belts

39. MOTION SENSOR
• Interfacing of Motion Sensors to Arduino

40. MOTION SENSOR
Interfacing of Motion Sensors to Arduino
const int led = 9; // Led positive terminal to the digital pin 9.
const int sensor = 5; //signal pin of sensor to digital pin 5.
const int state = LOW;
const int val = 0;
void setup() { // Void setup is ran only once after each powerup or reset of the
Arduino board.
pinMode(led, OUTPUT); // Led is determined as an output here.
pinMode(sensor, INPUT); // PIR motion sensor is determined is an input here.
Serial.begin(9600);
}

41. MOTION SENSOR
Interfacing of Motion Sensors to Arduino
void loop(){ // Void loop is ran over and over and consists of the main program.
val = digitalRead(sensor);
if (val == HIGH) {
digitalWrite(led, HIGH);
delay(500); // Delay of led is 500
if (state == LOW) {
Serial.println(" Motion detected");
state = HIGH;
}}
else {
digitalWrite(led, LOW);
delay(500);
if (state == HIGH){
Serial.println("The action/ motion has stopped");
state = LOW;
}}}

42. LIGHT SENSOR
What is a Light Sensor?
• A light sensor is a photoelectric instrument that converts light energy or photons
(that can range from the infra-red to ultraviolet spectrum) into an electrical
(electrons) signal. The light sensor generates an electrical output signal having an
energy corresponding to the input light energy. Light Sensors are also termed as
photo sensors or photoelectric sensors.
Principle of light sensors
• The working principle of the light sensor is based on internal photoelectric effect,
which states that when light energy or photons are bombarded on a metal surface
than it can cause the free electrons from the metal to excite and jump out resulting
in electron flow or electric current.
• The amount of current produced depends on the energy of the photon (i.e.
wavelength of light). The emission of electrons from the metal surface occurs only
after the light reaches a certain threshold frequency that corresponds with the
minimum energy required by the electrons to break the metal bonds

43. LIGHT SENSOR
Types of light sensors
• Light sensors can be of several types. These sensors can either generate energy in
presence of light or various other electrical properties. The most common types of
light sensors are photovoltaic cells, photodiodes, photo-resistors, and photo-
transistors.
Photovoltaic cells:
• Photovoltaic cells, like the name suggests, follows the principle of the photovoltaic
effect for converting light energy directly into electrical energy. These cells produce
an electromotive force proportional to the radiant energy received.
• The most popular single-junction silicon cells generate a maximum open-circuit
voltage of about 0.5 to 0.6 Volts. Solar cells use selenium as a photovoltaic material.
• Apart from generating and storing electrical energy, photovoltaic cells also act as
photodetectors. Photo-conductive cells and photo-emissive cells also provide a
similar function.

44. LIGHT SENSOR
Types of light sensors
Photodiodes:
• Photodiode light sensors are diodes that change light energy into a flow of
electrons. Photodiodes are comparable to the common P-N junction diodes, but
instead of an opaque casing, these diodes have a transparent lens for focusing light
on the P-N junction.
• These diodes are more sensitive towards the light with longer wavelengths i.e. light
belonging to the red and infra-red spectrum than the visible or ultraviolet
spectrum. Silicon and germanium are the most commonly used materials in such
diodes. Since photodiodes are sensitive to infrared light, they offer a lot of
applications in medicine.

45. LIGHT SENSOR
Types of light sensors
Photo-resistors:
• Photo-resistors are also known as light-dependent resistors or LDR. Photo-
resistors are devices that vary its resistance based on the amount of light energy it
receives. The lower the intensity of light, the higher is the resistance. This is
because more light (intensity) ensures more flow of electrons and hence, less is the
resistance.
• Cadmium sulfide cells (a high resistance semiconductor material) that is sensitive
towards infrared light, are mostly used in photo-resistors. Sometimes, materials
like indium antimonide (InSb), lead selenide (PbSe), and lead sulfide (PbS) are also
used. Photo-resistors take a considerably longer time (of about a few seconds) to
respond to the exposed light.

46. LIGHT SENSOR
Types of light sensors
Photo-transistors:
• Photo-transistors can be referred to as photodiodes with amplification. Photo-
transistors have a reverse biased collector-base P-N junction that is exposed to the
radiant light energy source. Photo-transistors are much more (about 50 to 100
times) sensitive compared to photo-diodes because of amplification. Photo-
transistors have bipolar NPN transistors with the base region electrically
unconnected. Here, the radiant light energy is focused on the base junction by a
transparent lens. Photo-transistors are widely used in mobile phones and
automobiles.

47. LIGHT SENSOR
Applications of light sensors
• Solar cells - Photovoltaic cells are commonly used as solar cells for generating
electricity.
• Consumer Electronics - Smartphones and tablets. The motion sensors and auto-
brightness sensors present in smartphones use light detectors like photo-
transistors. Remote control devices that operate in infrared light also use
photodiodes for conducting its functions.
• Automobiles - Light sensors or light detectors are used in automobiles for
detecting the surrounding ambient light. These detectors automatically switch on
the automobile lights when it gets dark. Nowadays, light detectors are also used for
ensuring safe driving and parking in several car models.
• Security devices - Light sensors are commonly used for processing shipment
cargos in order to ensure whether the boxes are properly sealed or not. Several
types of movement sensors also use light detectors that sense the variation in the
exposure of light. Photodiodes are also used in smoke detectors present in offices,
airports, trains, etc.
• Agricultural devices - These sensors detect the amount of surrounding ambient
light to activate the sprinkler irrigation system. Light sensors activate the
sprinklers only when the intensity of sunlight is less for ensuring adequate
hydration of crops.

48. LIGHT SENSOR
Interfacing light sensors to Arduino

49. LIGHT SENSOR
Arduino Coding
// Interfacing Arduino uno with LDR sensor
const int ledPin = 5; // digital pin 5
const int ldrPin = A0; // analog pin 0
void setup() { // The setup() function will only run once, after each powerup Serial.begin(9600);
pinMode(ledPin, OUTPUT); // Here LED is determined as an output or an indicator.
pinMode(ldrPin, INPUT); // Here LDR sensor is determined as input.
}
void loop() { // Void loop is ran again and again and contains main code.
int ldrStatus = analogRead(ldrPin);
if (ldrStatus <= 200) {digitalWrite(ledPin, HIGH); // If LDR senses darkness led pin high
Serial.print("Darkness over here,turn on the LED :");
Serial.println(ldrStatus);
} else {
digitalWrite(ledPin, LOW); // If LDR senses light led pin low that means led will stop glowing.
Serial.print("There is sufficient light , turn off the LED : ");
Serial.println(ldrStatus);
}
}

50. RGB LED
What is RGB LED
• A white light produce by mixing 3 different colors like RGB- Red, Green, and Blue is
an RGB LED. The main purpose of this RGB model is for sensing, representation,
and displaying images in the electronic system.
• A LED (Light Emitting Diode) is a semiconductor device that works on the
principle of electro luminous. The main advantage of LEDs is that they are small in
size, longer lifetime, good switching speed, etc. Hence by using different
semiconductor elements and changing their intensity property we can obtain
single color LED in different color LEDs, like Blue and ultraviolent LED, White LED,
OLED’s (Organic Light Emitting Diodes), Other white LEDs.
• The color of the light can be determined based on the energy gap of the
semiconductor.
• RGB LED Structure
• White light can be generated by combining 3 different colors like green, red, blue,
or by using phosphor material. This LED consist of 3 terminals (RGB in color)
which are present internally and a long lead which is present is either a cathode or
an anode as shown below

51. RGB LED
RGB LED Structure
• White light can be generated by combining 3 different colors like green, red, blue,
or by using phosphor material. This LED consist of 3 terminals (RGB in color)
which are present internally and a long lead which is present is either a cathode or
an anode as shown below.
• These 3 LED’s on combining they produce a single color output light, and by
changing the intensity of the internal individual LED’s we can obtain any desired
output color light. There are 2 types of LED’s, they are common cathode or
common anode which are similar to a 7 segment LED.

52. RGB LED
Structure of Common Anode and Common Cathode LED
• The structure of Common Anode and Common Cathode LED consists of 4
terminals, where the first terminal is “R” the second terminal is “Anode +” or
“Cathode –“, the third terminal is “G” and the fourth terminal is “B” as shown below.
• In a common anode configuration, the colors can be controlled by applying a low
power signal or by grounding the RGB pins and connecting the internal anode to a
positive lead of the supply.
• In common Cathode configuration, the colors can be controlled by applying a high
power input to the RGB pins and connecting the internal cathode to a negative lead
of the supply.

53. RGB LED
Advantages of RGB LED
• It occupies less area
• Small in size
• Less weight
• Greater efficiency
• Toxicity is less
• Contract and brightness of the light is better compared to other LED
• Good maintenance of Lumen.
Disadvantages of RGB LED
• Cost of manufacturing is high
• Dispersion of color
• The shift in color.
Applications of RGB LED
• LCD, CRT, Indoor and Outdoor lighting, Automotive industries
• They are used in mobile applications.

54. RGB LED
Interfacing of RGB LED to Arduino

55. RGB LED
Interfacing of RGB LED to Arduino
//Defining variable and the GPIO pin on Arduino
int redPin= 5;
int greenPin = 6;
int bluePin = 7;
void setup() {
//Defining the pins as OUTPUT
pinMode(redPin, OUTPUT);
pinMode(greenPin, OUTPUT);
pinMode(bluePin, OUTPUT);
}
void loop() {
setColor(255, 0, 0); // Red Color
delay(1000);
setColor(0, 255, 0); // Green Color
delay(1000);
setColor(0, 0, 255); // Blue Color
delay(1000);
setColor(255, 255, 255); // White Color
delay(1000);
setColor(170, 0, 255); // Purple Color
delay(1000);
setColor(127, 127, 127); // Light Blue
delay(1000);
}
void setColor(int redValue, int greenValue,
int blueValue) {
analogWrite(redPin, redValue);
analogWrite(greenPin, greenValue);
analogWrite(bluePin, blueValue);
}

56. LCD DISPLAY
What is LCD
• Liquid Crystal Display (LCD) is a flat, electronic device generally used as a screen in
televisions, computers, smartphones and display signs for producing still and
movable images.
• LCD is composed of liquid crystal particles. Liquid crystals generally do not emit
light on their own rather they are illuminated by a fluorescent backlight.
Working Principle
• An LCD panel is made of many layers. These consist of a polariser, polarised glass,
LCD fluid, conductive connections etc.
• Polarisation is a process in which the vibration of light waves is restricted to a
single plane, resulting in the formation of light waves known as polarised light.
• Since liquid crystals do not produce light of their own, they need an external light
source to work. An LCD panel has sets of polarised glass consisting of liquid crystal
materials in between them.
• When the external light passes through one of the polarised glasses and electric
current is applied on the liquid crystal molecules, they align themselves in such a
way that polarised light travels from the first layer to the second polarised glass,
causing an image to appear on the screen.

57. LCD DISPLAY
What is LCD

58. LCD DISPLAY
Types of LCD
Reflective
• This type of LCD has a mirror layer. When a light ray within an LCD is reflected by
the mirror layer, then visible patterns are produced on the LCD.
Transmissive
• The LCD has a backlight, which passes through the LCD polarised glass to produce
visible pattern. But because it uses backlight for working, the images displayed in
such LCD types appear very dim when used under bright sunlight.
Transflective
• This LCD type has a reflective mirror layer and a backlight. It uses both outside
light and backlight, making it suitable for indoor and outdoor conditions.

59. LCD DISPLAY
Types of LCD

60. LCD DISPLAY
Advantages
• LCD’s consumes less amount of power compared to CRT and LED
• LCD’s are consist of some microwatts for display in comparison to some mill watts
for LED’s
• LCDs are of low cost
• Provides excellent contrast
• LCD’s are thinner and lighter when compared to cathode-ray tube and LED
Disadvantages
• Require additional light sources
• Range of temperature is limited for operation
• Low reliability
• Speed is very low
• LCD’s need an AC drive
Applications of LCDs
• Test and measurement devices to display sensor readings
• Clocks and wrist watches.
• Digital cameras and smartphones to display images.
• Televisions and promotional banners

61. LCD DISPLAY
Interfacing LDC to Arduino

62. LCD DISPLAY
Interfacing LDC to Arduino
#include<LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2); // sets the interfacing pins
void setup()
{
lcd.begin(16, 2); // initializes the 16x2 LCD
}
void loop()
{
lcd.setCursor(0,0); //sets the cursor at row 0 column 0
lcd.print("16x2 LCD MODULE"); // prints 16x2 LCD MODULE
lcd.setCursor(2,1); //sets the cursor at row 1 column 2
lcd.print("HELLO WORLD"); // prints HELLO WORLD
}