Unit 3 Sensors and Actuators.pdf

© Kalasalingam academy of research and education
IoT – Sensors and
Devices

Course Outline
IOT – SENSORS AND DEVICES
CO2: Analyze the optimal usage of
microcontroller.
CO3: Demonstrate the usage of sensors and
actuators for specific requirements
CO4: Analyze the communication protocols for
different devices and its applications.
CO5: Inspect the various cloud services in alignment
with the corresponding IoT devices.
CO6: Work effectively in as team and individual in doing the
experiments following the safety procedures and ethics and
document effectively the experiments carried out in the
laboratory.
CO1: : Distinguish between the different concepts of
IoT for its applications.
Course description:
To expose the students to the fundamental
concepts of Microcontrollers and its interfacing,
that will help them put a strong foundation for the
implementation of Internet of things in real time.

Unit-2: Sensors & Actuators
Syllabus – Lecture contents
❖ Introduction to Sensors and Actuators and their
types
❖ Overview of Sensors and Actuators working
❖ Specifications
❖ Temperature - Humidity
❖ Touch – Flex
❖ Pressure - Accelerometer / Gyroscope - proximity
- IR - PIR
❖ Ultrasonic sensors - Relays - Solenoids - LCD
❖ Motor Drivers.
Unit 3
Sensors & Actuators
© Kalasalingam academy of research and education COURSENAME: IOT: SENSORS AND DEVICES

Sensors
❖Sensor as an input device which provides an output (signal) with respect to a specific physical quantity
(input).
❖The term “input device” in the definition of a Sensor means that it is part of a bigger system which
provides input to a main control system (like a Processor or a Microcontroller).
❖Another unique definition : It is a device that converts signals from one energy domain to electrical
domain. The definition of the Sensor can be better understood if we take an example into
consideration.

© Kalasalingam academy of research and education IOT – SENSORS AND DEVICES
Sensor : Example
❖The simplest example of a sensor is an LDR or a Light Dependent Resistor. It is a device, whose
resistance varies according to intensity of light it is subjected to. When the light falling on an LDR is
more, its resistance becomes very less and when the light is less, well, the resistance of the LDR
becomes very high.
❖When a light level of 1000 lux (bright light) is directed towards it, the resistance is 400R (ohms).
❖When a light level of 10 lux (very low light level) is directed towards it, the resistance has risen
dramatically to 10.43M(10430000ohms).

Sensor : Example
Source : https://technologystudent.com/

Actuators
❖An actuator is a device that produces a motion by converting energy and signals going into the
system. The motion it produces can be either rotary or linear.
❖Electric linear actuators, as the name implies, produce linear motion.
❖This means that linear actuators can move forward or backwards on a set linear plane – a set distance
they can travel in either direction before they must stop.
❖Rotary actuators on the other hand produce rotary motion, meaning that the actuator revolves on a
circular plane.

Actuator : Examples
❖electric motors
❖stepper motors
❖Jackscrews
❖electric muscular stimulators in robots, etc.

Difference between Sensor & Actuator

Active and Passive Sensors

Sensors Classifications
❖In the first classification of the sensors, they are divided in to Active and Passive.
❖Active Sensors, on the other hand, do not require any external power signal and directly generates output
response.
❖Passive Sensors are those which require an external excitation signal or a power signal.

Examples for Active and passive sensors
Source : https://realpars.com/

Sensor classifications

❖The other type of classification is based on the means of detection used in the sensor.
❖Some of the means of detection are Electric, Biological, Chemical, Radioactive etc.
❖The next classification is based on conversion phenomenon i.e., the input and the output.
❖Some of the common conversion phenomena are
✓Photoelectric,
✓Thermoelectric,
✓Electrochemical,
✓Electromagnetic,
✓Thermo-optic etc.

❖The final classification of the sensors are Analog and Digital Sensors.
❖Analog Sensors produce an analog output i.e., a continuous output signal (usually voltage but sometimes
other quantities like Resistance etc.) with respect to the quantity being measured.
❖Digital Sensors, in contrast to Analog Sensors, work with discrete or digital data.
❖The data in digital sensors, which is used for conversion and transmission, is digital in nature.

Different Types of Sensors
❖The following is a list of different types of sensors that are commonly used in various applications. All these
sensors are used for measuring one of the physical properties like Temperature, Resistance, Capacitance,
Conduction, Heat Transfer etc.
Source: https://www.electronicshub.org/

Temperature / Humidity Sensors

Humidity - Sensor
❖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.

Humidity - Sensor
The ranges and accuracy of the DHT11 are:
❖ Humidity Range: 20-90% RH
❖ Humidity Accuracy: ±5% RH
❖ Temperature Range: 0-50 °C
❖ Temperature Accuracy: ±2% °C
❖ Operating Voltage: 3V to 5.5V
Source: https://www.circuitbasics.com///

Humidity Sensor
❖All humidity sensors measure relative humidity (a ratio
of water content in air to maximum potential of air to
hold water). Since relative humidity is dependent on
temperature of air, almost all Humidity Sensors can also
measure Temperature.
❖Humidity Sensors are classified into Capacitive Type,
Resistive Type and Thermal Conductive Type. DHT11 and
DHT22 are two of the frequently used Humidity Sensors
in DIY Community (the former is a resistive type while the
latter is capacitive type).

Humidity - Sensor
Source: https://create.arduino.cc/

Humidity - Sensor
Technical Details:
❖Power − 3-5V
❖Max Current − 2.5mA
❖Humidity − 0-100%, 2-5% accuracy
❖Temperature − 40 to 80°C, ±0.5°C accuracy
Source: https://www.tutorialspoint.com//

Humidity – Sensor connection with Arduino

Humidity Sensor

Humidity Sensor
HOW TO SET UP THE DHT11 ON AN ARDUINO?
❖Wiring the DHT11 to the Arduino is really easy, but the connections are different depending on which type you
have.
Source: https://www.circuitbasics.com///

Humidity
DISPLAY HUMIDITY ON THE SERIAL MONITOR:
❖Before you can use the DHT11 on the Arduino, you’ll need to install the DHTLib library.
❖It has all the functions needed to get the humidity and temperature readings from the sensor.
❖It’s easy to install, just download the DHTLib.zip file below and open up the Arduino IDE.
❖Then go to Sketch>Include Library>Add .ZIP Library and select the DHTLib.zip file.

Touch Sensor
❖Touch Sensors, as the name
suggests, detect touch of a finger or a
stylus.
❖Often touch sensors are classified
into Resistive and Capacitive type.
❖ Almost all modern touch sensors
are of Capacitive Types as they are
more accurate and have better signal
to noise ratio.
Source: http://www.touchsemi.com/

© Kalasalingam academy of research and education COURSE NAME
Flex Sensor
❖A flex sensor, also known as a bend
sensor, is a low-cost, simple-to-use sensor
used to measure the amount of deflection
or bending.
❖It is used to measure joint movement, a
door sensor, a bumper switch to detect
walls, and a pressure sensor on robotic
grippers.
https://lastminuteengineers.com/flex-sensor

Flex Sensor
❖A flex sensor is basically a variable resistor,
whose resistance varies when bent. Because the
resistance is directly proportional to the amount
of bending, it is often referred to as a Flexible
Potentiometer.
❖Flex sensors are typically available in two sizes:
2.2′′ (5.588cm) long and 4.5′′ (11.43cm) long.
❖A conductive ink based flex sensor is made of a
phenolic resin substrate onto which conductive
ink is applied. A segmented conductor is then
placed on top to create a flexible potentiometer.

How Do Flex Sensors Work?
❖The conductive ink on the sensor serves as a
resistor. When the sensor is straight, this
resistance is around 25k.
❖When the sensor is bent, the conductive
layer is stretched, resulting in a reduced cross
section (imagine stretching a rubber band)
and increased resistance. At a 90° angle, this
resistance is approximately 100K.
❖When the sensor is straightened out again,
the resistance returns to its original value. By
measuring the resistance, you can determine
how much the sensor is bent.

Light Sensor
❖Sometimes also known as Photo Sensors, Light Sensors are one of
the important sensors. A simple Light Sensor available today is the
Light Dependent Resistor or LDR.
❖The property of LDR is that its resistance is inversely proportional
to the intensity of the ambient light i.e., when the intensity of light
increases, its resistance decreases and vise-versa.
❖By using LDR is a circuit, we can calibrate the changes in its
resistance to measure the intensity of Light.
❖There are two other Light Sensors (or Photo Sensors) which are
often used in complex electronic system design. They are Photo
Diode and Photo Transistor. All these are Analog Sensors.

Light Sensor
❖There are also Digital Light Sensors like BH1750, TSL2561, etc., which can calculate intensity of light and
provide a digital equivalent value.
Source :http://electronicsgurukulam.blogspot.com/

Accelerometer

Accelerometer
❖An accelerometer is an electronic sensor that
measures the acceleration forces acting on an
object, in order to determine the object’s
position in space and monitor the object’s
movement.
❖Acceleration, which is a vector quantity, is
the rate of change of an object’s velocity.
❖(velocity being the displacement of the
object divided by the change in time.
❖There are two types of acceleration forces:
static forces and dynamic forces.

Accelerometer
❖Static forces are forces that are constantly being applied to the object (such as friction or gravity).
❖Dynamic forces are “moving” forces applied to the object at various rates (such as vibration, or the force
exerted on a cue ball in a game of pool).
❖This is why accelerometers are used in automobile collision safety systems, for example:
❖When a car is acted on by a powerful dynamic force, the accelerometer (sensing a rapid deceleration) sends an
electronic signal to an embedded computer, which in turn deploys the airbags.

© Kalasalingam academy of research and education COURSE NAME : INTRODUCTION TO IOT
Accelerometer
❑There are three different types of accelerometers, and they are each designed to efficiently function in their
intended environments. The three types are:
❖A Piezoelectric accelerometer utilizes the piezoelectric effect (piezoelectric materials produce electricity
when put under physical stress) to sense change in acceleration. Piezoelectric accelerometers are most
commonly used in vibration and shock measurement.
❖Piezoresistance accelerometers are much less sensitive than piezoelectric accelerometers, and they are
better suited to vehicle crash testing. A piezoresistance accelerometer increases its resistance in proportion to
the amount of pressure applied to it.
❖Capacitive accelerometers use change in electrical capacitance to determine an object’s acceleration. When
the sensor undergoes acceleration, the distance between its capacitor plates changes as the diaphragm of the
sensor moves.

Accelerometer – Example- ADXL335
Source : https://www.javatpoint.com/arduino-accelerometer

Accelerometer : ADXL335 Connection Diagram to Arduino
Source : https://www.javatpoint.com/arduino-accelerometer

Accelerometer : ADXL335 Connection to Arduino
Connections:
❖ Accelerometer X to Pin A3 of Arduino
❖ Accelerometer y to Pin A2 of Arduino
❖ Accelerometer Z to Pin A1 of Arduino
❖ Accelerometer VCC to Pin A5 of Arduino
❖ Accelerometer GND to Pin A4 of Arduino
❖ Accelerometer ST to Pin A0 of Arduino

Accelerometer : ADXL335 Connection to Arduino
Source : https://circuitdigest.com/

Accelerometer - Applications
Applications:
❖Detection of Earthquake.
❖For the protection of hard drive of the laptop.
❖Uphill movement of the object.
❖Any customized project.

Gyroscope

Gyroscope - Sensor
What is a gyroscope sensor?
❖The gyroscope measures rotational velocity or rate of change of the angular position over time, along the X, Y
and Z axis.
❖The outputs of the gyroscope are in degrees per second, so in order to get the angular position, we just need
to integrate the angular velocity.
❖Briefly, it can measure gravitational acceleration along the 3 axes and using some trigonometry math we can
calculate the angle at which the sensor is positioned

Gyroscope - Sensor
How does an Arduino gyroscope sensor work?
❖The accelerometer measures the acceleration along one direction, while the gyroscope measures the angular
acceleration on one axis.
❖The analogic pins are not set on INPUT because it's their default setting.
❖The values read by the analogic pins will be sent to the serial port.
❖Open the Serial Monitor, move the sensor and try to see how the values change.
❖Accelerometers can be used for fun projects, for example, to realize a game controller.

Gyroscope - Sensor
How to use an Arduino Gyroscope sensor?
❖To operate with a gyroscope sensor, you need to connect four wires to your Arduino.
❖You need wires to be connected to the ground (Gnd) from the gyroscope's Gnd pin and a second wire from the
VCC pin of the gyroscope to the 5v pin of the Arduino.
❖Then, you need another two wires to be connected to two analog inputs of the Arduino.
❖The first one of these wires goes from the SCL pin of the gyroscope, and the second wire goes from the
gyroscope's SDA pin.

Gyroscope – Arduino Connection
Source : https://www.circuitstoday.com/

Gyroscope – GY521 Module
❖ It is a 3- axis gyroscope and accelerometer module .
❖ It has six built in 16- bit ADC channels, 3 for the gyroscope outputs and 3 for the accelerometer outputs.
❖ It communicates using the I2C protocol.
❖ Operating voltage is from 2.37v to 3.46V.
❖ A low drop out regulator is provided with the GY521 board for providing this voltage.

Gyroscope – GY521 Module
Source : https://www.circuitstoday.com/

Gyroscope – Sensor- Interfacing with Arduino
Source: https://www.ozeki.hu/

Proximity Sensor (IR Sensor)
❖A Proximity Sensor is a non-contact type sensor that detects the presence of an object. Proximity Sensors
can be implemented using different techniques like Optical (like Infrared or Laser), Sound (Ultrasonic),
Magnetic (Hall Effect), Capacitive, etc.
❖Some of the applications of Proximity Sensors are
❖Mobile Phones, Cars (Parking Sensors),
❖ industries (object alignment),
❖Ground Proximity in Aircrafts, etc.

• A Proximity Sensor is a non-contact type
sensor that detects the presence of an
object. Proximity Sensors can be
implemented using different techniques
like Optical (like Infrared or Laser), Sound
(Ultrasonic), Magnetic (Hall Effect),
Capacitive, etc.
• Some of the applications of Proximity
Sensors are Mobile Phones, Cars
(Parking Sensors), industries (object
alignment), Ground Proximity in
Aircrafts, etc.

Proximity Sensor

Source: https://www.smlease.com/

Infrared Sensor (IR Sensor)
❖There are two types of Infrared or IR Sensors:
Transmissive Type and Reflective Type.
❖In Transmissive Type IR Sensor, the IR
Transmitter (usually an IR LED) and the IR
Detector (usually a Photo Diode) are positioned
facing each other so that when an object passes
between them, the sensor detects the object.
Source: https://instrumentationtools.com/

❖The other type of IR Sensor is a Reflective Type IR Sensor.
In this, the transmitter and the detector are positioned
adjacent to each other facing the object.
❖When an object comes in front of the sensor, the infrared
light from the IR Transmitter is reflected from the object
and is detected by the IR Receiver and thus the sensor
detects the object.

Source: https://www.keyence.com/

Ultrasonic sensor

Ultrasonic Sensor
❖An Ultrasonic Sensor is a non-contact type device that
can be used to measure distance as well as velocity of an
object.
❖An Ultrasonic Sensor works based on the properties of
the sound waves with frequency greater than that of the
human audible range.
❖Using the time of flight of the sound wave, an Ultrasonic
Sensor can measure the distance of the object (similar to
SONAR).
❖The Doppler Shift property of the sound wave is used to
measure the velocity of an object.

Ultrasonic Sensor : Example

Relays
COURSE NAME : IOT – SENSORS AND DEVICES

Relay
❖ Whenever we need to connect any AC Appliance in our embedded circuits, we use a Relay.
❖ Here we are not using any Relay Driver IC like ULN2003 and will only use an NPN transistor to control relay.
❖ Relay is an electromagnetic switch, which is controlled by small current, and used to switch ON and OFF relatively
much larger current.
❖ Means by applying small current we can switch ON the relay which allows much larger current to flow.
❖ A relay is a good example of controlling the AC (alternate current) devices, using a much smaller DC current.

Interfacing of Relay
Commonly used Relay is Single Pole Double Throw (SPDT) Relay, it has five terminals as below:

❖ When there is no voltage applied to the coil, COM (common) is connected to NC (normally closed contact).
❖ When there is some voltage applied to the coil, the electromagnetic field produced, which attracts the Armature
(lever connected to spring), and COM and NO (normally open contact) gets connected, which allow a larger
current to flow.
❖ Relays are available in many ratings, here we used 6V operating voltage relay, which allows 7A-250VAC current to
flow.
❖ The relay is always configured by using a small Driver circuit which consists a Transistor, Diode and a resistor.
❖ Transistor is used to amplify the current so that full current (from the DC source – 9v battery) can flow through a
coil to fully energies it.
❖ The resistor is used to provide biasing to the transistor.
❖ And Diode is used to prevent reverse current flow, when the transistor is switched OFF.

❖ Every Inductor coil produces equal and opposite EMF when switched OFF suddenly, this may cause permanent
damage to components, so Diode must be used to prevent reverse current.
❖ A Relay module is easily available in the market with all its Driver circuit on the board or you can create it on perf
board or PCB like below.
❖ Here we have used 6V Relay module.

❖ Here to turn on the Relay with Arduino we just need to make that Arduino Pin High (A0 in our case) where Relay
module is connected.
❖ Below given is Relay Driver Circuit to build your own Relay module:

Arduino Relay Control Code
#define relay A0
#define interval 1000
void setup() {
pinMode(relay, OUTPUT);
}
void loop()
{
digitalWrite(relay, HIGH);
delay(interval);
digitalWrite(relay, LOW);
delay(interval);
}

❖ Controlling a relay module with the Arduino is as simple as controlling
any other output.
❖ This relay module has two channels (those blue cubes).
❖ There are other models with one, four and eight channels.
❖ This module should be powered with 5V, which is appropriate to use
with an Arduino.
❖ There are other relay modules that are powered using 3.3V, which is
ideal for ESP32, ESP8266, and other microcontrollers.

❖ The six pins on the left side of the relay module connect high voltage,
and the pins on the right side connect the component that requires low
voltage—the Arduino pins.

❖ The high-voltage side has two connectors, each with three sockets: common
(COM), normally closed (NC), and normally open (NO).
❖ COM: common pin
❖ NC (Normally Closed): the normally closed configuration is used when you
want the relay to be closed by default, meaning the current is flowing unless
you send a signal from the Arduino to the relay module to open the circuit
and stop the current.
❖ NO (Normally Open): the normally open configuration works the other way
around: the relay is always open, so the circuit is broken unless you send a
signal from the Arduino to close the circuit.
❖ If you just want to light up a lamp occasionally, it is better to use a normally-
open circuit configuration.

Solenoids
❖It uses electromagnetism to convert electrical
energy into mechanical motion.
❖The pulling and pushing strength is
determined by the number of turns on the coil.

LCD (Liquid Crystal Display)
❖It is a thin display device that offers support for large
resolutions and better picture quality.
❖An LCD contains a backlight rather than the firing electrons
at a glass screen, which offers light to individual pixels
arranged in a rectangular grid.
❖As compared to CRT technology, LCD consumes much less
power and allows displays to be much thinner that also
makes them very less heavy.
❖Instead of emitting light, LCDs work on the principle of
blocking light.

LCD (Liquid Crystal Display)
Advantages of LCD
❖Takes less Space
❖Low Power Consumption
❖Sufficient Brightness in low lit areas
❖Low Screen Flickering rate
Disadvantages of LCD
❖Expensive for their size
❖Inconsistent Interfacing
❖Small viewing Angle
❖Limited brightness
❖Poor reproduction of blacks
https://www.javatpoint.com/what-is-lcd

Motor Drivers (L298N)
We can only have full control over a DC motor if we can control its speed and spinning direction.
This is possible by combining these two techniques.
➢PWM – to control speed
➢H-Bridge – to control the spinning direction

Motor Drivers (L298N)
H-Bridge – to control the spinning direction
❖The spinning direction of a DC motor can
be controlled by changing the polarity of its
input voltage.
❖An H-bridge circuit is made up of four
switches arranged in a H shape, with the
motor in the center.
❖Closing two specific switches at the same
time reverses the polarity of the voltage
applied to the motor. This causes a change in
the spinning direction of the motor.

L298N Motor Driver Module
https://lastminuteengineers.com/l298n-dc-stepper-driver-arduino-tutorial/

Other Sensors
COURSE NAME : IOT – SENSORS AND DEVICES

Smoke and Gas Sensors
❖One of the very useful sensors in safety related
applications are Smoke and Gas Sensors. Almost all offices
and industries are equipped with several smoke detectors,
which detect any smoke (due to fire) and sound an alarm.
❖Gas Sensors are more common in laboratories, large scale
kitchens and industries. They can detect different gases like
LPG, Propane, Butane, Methane (CH4), etc.
❖Now-a-days, smoke sensors (which often can detect
smoke as well as gas) are also installed in most homes as a
safety measure.
❖The “MQ” series of sensors are a bunch of cheap sensors
for detecting CO, CO2, CH4, Alcohol, Propane, Butane, LPG
etc. You can use these sensors to build your own Smoke
Sensor Application.

Smoke and Gas Sensors

Alcohol Sensor
❖As the name suggests, an Alcohol Sensor detects alcohol.
Usually, alcohol sensors are used in breathalyzer devices, which
determine whether a person is drunk or not.
❖Law enforcement personnel uses breathalyzers to catch drunk-
and-drive culprits.
Source : https://lastminuteengineers.com/

Color Sensor
❖A Color Sensor is an useful device in building color
sensing applications in the field of image processing,
color identification, industrial object tracking etc.
❖ The TCS3200 is a simple Color Sensor, which can detect
any color and output a square wave proportional to the
wavelength of the detected color.

Tilt Sensor
❖Often used to detect inclination or orientation, Tilt Sensors are one of the simplest and inexpensive
sensors out there.
❖Previously, tilt sensors are made up of Mercury (and hence they are sometimes called as Mercury
Switches) but most modern tilt sensors contain a roller ball.
IOT – SENSORS AND DEVICES Source: https://instrumentationtools.com/

Thank You!
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Unit 3 Sensors and Actuators.pdf

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