UNIT – 2: IoT HARDWARE AND SOFTWARE

SENSORS AND ACTUATORS

Sensors and actuators are critical components of embedded systems. These are utilized in various real-
world applications, including flight control systems in aircraft, process control systems in nuclear
reactors, and power plants that require automated control.

Sensors and actuators differ primarily in their purpose; the sensor is utilized to track environmental
changes using measurands, whereas the actuator is utilized when monitoring is combined with control,
such as controlling physical changes.

Sensors: A sensor is a device that detects changes and events in a physical environment. It may
convert physical parameters like humidity, pressure, temperature, heat, motion, etc., into electrical
signals. This signal can be converted into a human-readable display and sent across a network for
additional processing.

Active sensors and passive sensors are the two primary types of sensors. Active sensors necessitate a
power supply, whereas passive sensors don't require a power supply. Some important sensors are as
follows:
1. Biosensors: These biosensors utilize electrochemical technology. These sensors are used in
medical, food, and water testing devices. These biosensors also aid in analyzing proteins, cells, nucleic
acid, etc.

2. Accelerometers: These sensors utilize the Micro Electro Mechanical Sensor Technology. These
sensors utilize in patient monitoring, vehicle systems, etc.

3. Image Sensors: These sensors utilize the Complementary Metal Oxide Sensor mechanism. They
detect and transfer data that is utilized to make an image. These image sensors are very useful in
consumer surveillance and electronic systems.

4. Chemical Sensors: These sensors use ultrasonic, microwave, and radar technology, and they are
used in security systems, video games, and other applications.
Features of Sensors: There are various features of Sensors. Some main features of Sensors are as
follows:
➢ A sensor could be either active or passive. Active sensors necessitate a power source, but
passive doesn't necessitate a power source.
➢ It is a device that monitors and measures changes in the environment.
➢ It is responsible for converting physical quantities into electrical signals.
➢ It is connected to a system's input.
➢ It generates an electrical signal as its output.

Actuators: A device that changes electrical signals into mechanical work is known as an actuator. It is
used to cause movement or a change in the surroundings. For instance, a fan is utilized to lower the
temperature, and a servo motor is utilized to change position, among other things.

Actuators are connected to a system's output. It receives an electrical signal as input and produces
mechanical movement as output. It receives input or instruction from a system or a signal conditioning
device and outputs it to the environment.

Types of Actuators: There are various types of actuators. Some of these are as follows:
1. Manual Actuator: This type of actuator is manually operated via gears, levers, and wheels, among
other things. They do not need a power source because they are powered by human action.

2. Spring Actuator: It has a loaded spring that is triggered and released to generate mechanical work.
It may be triggered in several ways.

3. Hydraulic Actuator: Hydraulic actuators generate pressure by compressing fluid in a cylinder,

allowing mechanical movement.

4. Electric Actuators: These actuators require power to function. It utilizes an electric motor to
produce movement. They are quick and effective.

Features of Actuators: There are various features of Actuators. Some main features of Actuators are
as follows:
➢ The actuator assists in managing the environment based on sensor readings.
➢ A device that converts electrical signals into mechanical movement is known as an actuator.
➢ It requires an additional power source to function.
➢ It receives an electrical signal as input.
➢ It is connected to a system's output.
➢ It produces mechanical work.
Difference between Sensors and Actuators
Features Sensors Actuators
Definition It is a device that detects changes or It is a machine component that moves and
events in the environment and transmits controls mechanisms.
that data to another electronic system.
Basic It converts the physical properties of It converts the system's electrical signals
their environment into electrical signals into various physical characteristics for
for the system. their environments.
Type of Output Electrical signals are generated via It generates energy in the form of heat or
sensors. motion.
Source of It receives input from the environment. It receives input from the system's output
Input conditioning unit.
Placement These are placed at a system's input These are placed at a system's output port.
port.
Output It produces output for the input It produces output for their environment.
Generation conditioning unit of a system.
Examples Sensors include biosensors, motion Actuators include electric motors, comb
sensors, image sensors, and chemical drives, stepper motors, and hydraulic
sensors. cylinders.

HUMIDITY SENSOR
A humidity sensor (or hygrometer) senses, measures,
and reports both moisture and air temperature. The
ratio of moisture in the air to the highest amount of
moisture at a particular air temperature is called
relative humidity. Relative humidity becomes an
important factor when looking for comfort.
Humidity sensors work by detecting changes that
alter electrical currents or temperature in the air.
There are three basic types of humidity sensors:
➢ Capacitive
➢ Resistive
➢ Thermal
1. Capacitive: A capacitive humidity sensor measures relative humidity by placing a thin strip of
metal oxide between two electrodes. The metal oxide’s electrical capacity changes with the
atmosphere’s relative humidity. Weather, commercial and industries are the major application areas.

2. Resistive: Resistive humidity sensors utilize ions in salts to measure the electrical impedance of
atoms. As humidity changes, so do the resistance of the electrodes on either side of the salt medium.

3. Thermal: Two thermal sensors conduct electricity based upon the humidity of the surrounding air.
One sensor is encased in dry nitrogen while the other measures ambient air. The difference between
the two measures the humidity.
Features of Humidity sensor
1. Accuracy: Every sensor has its own calibration curve, based on a 9 point system. It basically
pitches the pros against the cons of the particular sensor.

2. Linearity: It indicates the voltage deviation from the BFSL value and the measured output voltage
value, converted to relative humidity.

3. Reliability: The measurements often cause the sensor to fall out of sync. However for a sensor to be
useful, it has to provide reliable measurements.

4. Repeatability: The measurements from a sensor, have to be so that they don’t drift apart.
Repeatability is the measurement of drift among measurements of a single quantity.

5. Response Time: Typically, the time is taken by a sensor to rise to 66% (rise time) or fall to 33%
(fall time) of maximum output voltage, is known as the response time.

ULTRASONIC SENSOR
The ultrasonic sensor is an electronic device used
to measure distances. Because, measuring distance
is an essential factor in many applications such as
robotic control, vehicle detection etc. Sensors such
as optical and sound are the most helpful.

Ultrasonic sensors are used as proximity sensors.

They can be found in parking technology and anti-
collision safety systems. Ultrasonic sensors are
also used in robotic obstacle detection systems and
manufacturing engineering.

Principle of Ultrasonic Sensor: The principle of ultrasonic rangefinders is to measure the time it
takes the signal sent by a transmitter and propagated back to the receiver. As the name implies
ultrasonic sensor operates on ultrasonic frequencies. Frequencies beyond our hearing range are known
as ultrasonic frequencies. Those frequencies are above 20k Hertz.
Working of Ultrasonic Sensor: An ultrasonic sensor is an electronic device that measures the
distance to an object by emitting ultrasonic waves and converting the reflected sound into electrical
signals. Ultrasound travels faster than audible sound (that is, sound that humans can hear). An
ultrasonic sensor consists of two main components: a transmitter (which uses a piezoelectric crystal to
emit sound) and a receiver. The distance is determined by measuring the travel time of ultrasonic
sound and its speed.
Distance = Time x Speed of sound / 2

Reflection of the sensing sound varies with configuration, for example

(A) Flat objects: liquid, box, plastic sheet,
(B) Columnar objects: can, bottle, the human body,
(C) Granular objects: ores, rock, coal, coke, plastic pellet,

To prevent mutual interference between Ultrasonic Sensors, the synchronous operation can be used by
emitting the ultrasonic waves from each Sensor simultaneously.

Specifications:
➢ Supply voltage +5 V;
➢ Consumption in silent mode 2 mA;
➢ Consumption at work of 15 mA;
➢ Measurement range - 2 to 400 cm;
➢ Effective measuring angle 15°;
➢ The dimensions are 45×20×15 mm.

TEMPERATURE SENSORS
Temperature sensors are devices that detect and measure coldness and heat and convert it into an
electrical signal. Temperature sensors are utilized in our daily lives, be it in the form of domestic water
heaters, thermometers, refrigerators, or microwaves. There is a wide range of applications of
temperature sensors, including the geotechnical monitoring field.
A temperature sensor can also be defined as a
simple instrument that measures the degree of
coldness or hotness and then converts it into a
readable unit. There are specialized temperature
sensors used to measure the temperature of the
boreholes, soil, huge concrete dams, or
buildings.

What do temperature sensors do? A temperature sensor is a device that is designed to measure the
degree of hotness or coolness in an object. The working of a temperature meter depends upon the
voltage across the diode. The temperature change is directly proportional to the diode’s resistance. The
cooler the temperature, the lesser will be the resistance, and vice-versa.

The resistance across the diode is measured and converted into readable units of temperature
(Fahrenheit, Celsius, Centigrade, etc.) and, displayed in numeric form over readout units. In the
geotechnical monitoring field, these temperature sensors are used to measure the internal temperature
of structures like bridges, dams, buildings, power plants, etc.

Functions of a temperature sensor: Contact sensors include thermocouples and thermistors because
they are in direct contact with the object they are to measure. Whereas, the non-contact temperature
sensors measure the thermal radiation released by the heat source. Such temperature meters are often
used in hazardous environments like nuclear power plants or thermal power plants.

In geotechnical monitoring, temperature sensors measure the heat of hydration in mass concrete
structures. They can also be used to monitor the migration of groundwater or seepage. One of the most
common areas where they are used is while curing the concrete because it has to be relatively warm in
order to set and cure properly. The seasonal variations cause structural expansion or contraction
thereby, changing its overall volume.

Working of temperature sensor: The basic principle of working the temperature sensors is the
voltage across the diode terminals. If the voltage increases, the temperature also rises, followed by a
voltage drop between the transistor terminals of the base and emitter in a diode.

It primarily consists of a magnetic, high tensile strength stretched wire, the two ends of which are fixed
to any dissimilar metal in a manner that any change in temperature directly affects the tension in the
wire and, thus, its natural frequency of vibration.

The dissimilar metal, in the case of the Encardio Rite temperature meter, is aluminum (Aluminum has
a larger coefficient of thermal expansion than steel.) As the temperature signal is converted into
frequency, the same read-out unit which is used for other vibrating wire sensors can also be used for
monitoring temperature also.
The frequency, which is proportional to the temperature and in turn to the tension ‘σ’ in the wire, can
be determined as follows:

f = 1/2 [σg/ρ] / 2l Hz

Where:
σ = tension of the wire
g = acceleration due to gravity
ρ = density of the wire
l = length of wire

Types of temperature sensors: Temperature sensors are available in various types, shapes, and sizes.
The two main types of temperature sensors are:
1. 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. Such temperature sensors fall
under the category of contact type. They can be used to detect solids, liquids, or gases over a wide
range of temperatures.

2. Non-Contact Type Temperature Sensors: These types of temperature meters are not in direct
contact with the object rather, they measure the degree of hotness or coolness through the radiation
emitted by the heat source.

ARDUINO
Arduino is a software as well as hardware platform that helps in making electronic projects. It is an
open-source platform and has a variety of controllers and microprocessors. There are various types of
Arduino boards used for various purposes.

The Arduino is a single circuit board, which consists of different interfaces or parts. The board consists
of the set of digital and analog pins that are used to connect various devices and components, which
we want to use for the functioning of the electronic devices. Most of the Arduino consists of 14 digital
I/O pins.

The analog pins in Arduino are mostly useful for fine-grained control. The pins in the Arduino board
are arranged in a specific pattern. The other devices on the Arduino board are USB port, small
components (voltage regulator or oscillator), microcontroller, power connector, etc.

Features of Arduino
➢ Arduino programming is a simplified version of C++, which makes the learning process easy.
➢ The Arduino IDE is used to control the functions of boards. It further sends the set of
specifications to the microcontroller.
➢ Arduino does not need an extra board or piece to load new code.
➢ Arduino can read analog and digital input signals.
➢ The hardware and software platform is easy to use and implement.
1. Microcontroller: The most essential part of the Arduino is the
Microcontroller, which has following features:
➢ Microcontroller is small and low power computer. Most of
the microcontrollers have a RAM (Random Access
Memory), CPU (Central Processing Unit), and a memory
storage like other computer systems.
➢ It has very small memory of 2KB (two Kilobytes). Due to
less memory, some microcontrollers are capable of running
only one program at a time.
➢ It is a single chip that includes memory, Input/Output (I/O) peripherals, and a processor.
➢ The GPIO (General Purpose Input Output) pins present on the chip help us to control other
electronics or circuitry from the program.

2. Electronic devices: We have many electronic devices around us. Most of the appliance consists of
the microcontroller for its functioning. Microcontroller present in Microwave Oven accepts the user
input and controls the magnet run that generate microwave rays to cook the food and displays the
output timer.

Modern cars also contain dozens of microcontrollers working in tandem (one after another) to control
functions like lighting, radio interface, etc.

3. Projects: Let's consider a simple project of LED blink. We need a software to install our sketch or
code to the Arduino board. The LED will blink after the successful uploading of code. The software is
called as Arduino IDE (Integrated Development Environment). There are various projects created with
the help of the Arduino. Some of the projects are listed below:
➢ Home Automation System using IOT (Internet of Things).
➢ Solar Power water trash collector.
➢ Fire Detector, etc.

4. Arduino Kits: We can easily start with our electronics projects using the complete kit. It also helps
us to create hand-on and engaging projects. Some of the popular Arduino kits are listed below:
➢ Arduino Starter kit
➢ Robot Linking UNO kit for learning
➢ Arduino UNO 3 Ultimate starter kit
➢ UNO Super starter kit
➢ Mega 2560 Starter Kit

5. Arduino IDE: The IDE makes the traditional projects even easier and simpler. The USB cable is
used to load the program or sketch on the specific Arduino board. The IDE application is suitable for
Windows, Mac OS X, and Linux. It supports the programming language C and C++. We need to
connect the Genuino and Arduino board with the IDE to upload the sketch written in the Arduino IDE
software.
6. Arduino Boards: There are variety of Arduino board used for different purposes. The board varies
in I/O pins, size, etc. The various components present on the Arduino boards are Microcontroller,
Digital Input/Output pins, USB Interface and Connector, Analog Pins, Reset Button, Power button,
LED's, Crystal Oscillator, and Voltage Regulator. Some components may differ depending on the type
of board.
➢ Arduino UNO
➢ Arduino Nano
➢ Arduino Mega
➢ Arduino Due
➢ Arduino Bluetooth

RASPBERRY PI
It is a cheap, credit-card-sized device that uses a daily keyboard and mouse and joins to a TV or
computer monitor. It is a thin weighable computer that let every person of all ages to discover
programming and gain how to programmed in variant languages like Python and Scratch. From
exploring the internet and watching high-definition video, word-processing, to creating spreadsheets,
and it can do every possible thing we'd expect a desktop computer to do and playing sports.

Earlier, the Raspberry Pi device stress on supporting basic computer science instructing in schools and
in progressing countries. The real type later became much more popular than targeted, selling for
works such as robotics the target outside market.

1. SD card: We recommend a class 4 or class 10 microSD card of at least 8 GB. People can get a card
which is pre-existed with NOOBS or Raspberry Pi OS to save the time but it's easy to establish self-
card.

2. Display and connectivity cable: Any HDMI/DVI monitor or TV can work as a display for the Pi.
Use a monitor with an HDMI input for the best results; other link types are also available for older
devices.
3. Keyboard and mouse: Any regular USB keyboard and mouse will work with Raspberry Pi. If
already paired, wireless keyboards and mice can run. For configuration options for keyboard
configurations, see raspi-config.

4. Power supply: Pi is represented by a USB Micro or USB Type-C for power supply. Like Model
4B, 2A at 5V for 3B and 3B+, or 700mA at 5V for the earlier, low-powered Pi versions, we require
good-quality power connection that can facilitate legit 3A at 5V.

Low-current power supplies can work for normal, but if it gets too much supply, it might cause the Pi
to restart. For work with the Pi 3 or 4, they are not comfortable.

5. Optional Peripheral: [Model B/B+/2B/3B/3B+/4B only] Ethernet (network) cable for linking our
Pi to an area network or to the internet, an Ethernet cable will be required.

6. Wireless USB dongle: Required only if we require wireless connectivity and operating an older
model without wireless qualities pre-installed.

7. Audio lead: It can be played by speakers or headphones working with a standard 3.5mm jack. An
audio lead is required without an HDMI cable to produce sound.

Lite OS
It is lightweight, with a kernel size of under 10 KB, and consumes very little power — it can run on an
AA battery for up to five years! It also allows for fast startup and connectivity and is very secure.

Huawei LiteOS enabling IoT terminals to quickly access the network. It will make intelligent hardware
development easier. Thereby accelerating the realization of the interconnection of all things. It
provides a unified open-source API that can be used in IoT domains as diverse as smart homes,
wearables, Internet of Vehicles (IoV), and intelligent manufacturing. It enables an open IoT ecosystem,
helping partners to quickly develop IoT products and accelerate IoT development.
Features of Lite OS
➢ Lightweight Kernels: Smaller Kernel Size, Lower Power Consumption, and Faster Response
➢ Sensor Frameworks: Lower Delay, Higher Precision, and Intelligent sensing
➢ Connectivity Engine: More Protocols, Wider Connectivity, Intelligent Connection (Support
NB-IoT, Wifi, Ethernet, BLE, Zigbee and other different IoT protocols)
➢ Operating Engine: Lighter Frameworks, Better Performance, and Intelligent Applications
➢ Optimizes performance and reduces power consumption by coordinating JS frameworks, JS
VMs, and OS
➢ Small-sized ROM with low memory usage;
➢ Provides independent user space and application separation to ensure application security

RIOT OS
It is a free, open-source IoT OS that is backed by a supportive development community. It is designed
to provide IoT services and is released under an unclonable GNU Lesser General Public License. The
community, which is commonly known as the Linux of the IoT world, is made up of academics,
programmers, and enthusiasts. RIOT is a low-power operating system based on microkernel
architecture and the C and C++ programming languages.

It supports full multithreading and SSL/TLS libraries, including wolfSSL, and runs on 8-bit, 16-bit,
and 32-bit processors. RIOT is provided with a port that enables it to execute as Linux or macOS
processes and support single board computers and IoT devices. Other characteristics include partial
POSIX compliance, TCP, content-centric networking, UDP, and CoAp network protocols. It provides
IoT devices and microcontroller designs with security, connectivity, privacy, and durability.

Features of RIOT: There are various features of RIOT. Some features of RIOT OS are as follows:
➢ It supports the 8, 16, 32-bit microcontroller platforms.
➢ It maintains energy efficiency.
➢ There aren't any new programming environments. C or C++ programming languages may be
used directly with existing tools, such as gdb, gcc, etc.
➢ There is less hardware-dependent code.
➢ It allows multithreading.
➢ It supports the complete network stack of the Internet of Things.
➢ Because all output can be seen in the terminal if the hardware is not accessible, a visualization
tool called RIOT-TV is supplied.

CONTIKI OS
Contiki is a free and open-source operating system for connecting low-power, low-cost
microcontrollers to the internet and a toolbox for creating complicated wireless systems.

Contiki is designed to adhere to the highest Internet standards, such as full support for IPv4 and IPv6.
It's written in C language to provide a rapid programming environment in a single download, and it
includes an active community to make any user feel at ease.
Advantages
➢ It offers powerful low-power Internet communication.
➢ It supports completely standard IPv6 and IPv4.
➢ It can be used with a variety of low-power wireless devices, some of which are readily
available online.
➢ It is free and open-source software that can be used in commercial and noncommercial
systems, with the source code available.

Disadvantages
➢ Contiki is an event-driven operating system; therefore, no advanced scheduling algorithms are
used.
➢ As events come, they are dispatched to the destination application.
➢ Contiki doesn't facilitate the deployment of real-time applications, so no real-time process
scheduling algorithms are included in this operating system.

TINY OS
Tiny OS is a component-based open-source OS. Tiny OS's fundamental language is nesC, a version of
the C programming language. It is designed for wireless sensor networks. TinyOS is very popular
among developers because to its memory optimization capabilities. TinyOS includes a component that
neutralizes some IoT system abstractions, such as sensing, packet transmission, routing, etc.

Advantages
➢ TinyOS is an event-driven operating system, which means it depends on the events it receives
from its surrounding environment.
➢ TinyOS is an embedded operating system that runs on all devices. TinyOS requires less
memory to execute. If you wish to run this OS, you don't require buying more memory devices.
➢ TinyOS' source code is relatively minimal. The code may be optimized to help run for any
particular system. Devices run faster due to their reduced code, and the OS doesn't overload the
device.
➢ TinyOS is a portable OS that may be used on several devices. If the devices are of the same
nature, the coding doesn't need to be altered.
➢ TinyOS is made up of various modules. The modules have various functions, including tasks,
microcontrollers, commands, hardware, events, and software. Each module performs its own
function.

Disadvantages
➢ Some modifications are required to allow communication among hardware and software. It is
due to the low voltage constraint.
➢ TinyOS programming is tough due to constraints such as memory limits, asynchronous
behavior, and low voltage. The main downside of this operating system is the NesC
programming language.
➢ Because network sensor devices must refresh their data from their surroundings every second,
programmers must keep this in mind to ensure that the code works in all circumstances.