Chapter 2: IoT Components & Arduino

1. Introduction to IoT Components

An IoT system is a complex integration of various physical and digital components that work together to sense, communicate, analyze, and act upon data.

A. Sensing Components (The "Senses" of IoT)

These are hardware devices that detect and measure physical properties from the environment and convert them into electrical signals (data).

Sensors:

• Temperature Sensor (e.g., LM35, DHT11): Measures ambient temperature.
• Humidity Sensor (e.g., DHT11, DHT22): Measures the amount of moisture in the air.
• Light Dependent Resistor (LDR): Measures light intensity; resistance decreases with increasing light.
• PIR Motion Sensor: Detects movement of humans or animals by measuring infrared radiation.
• Gas Sensor (e.g., MQ-2, MQ-135): Detects the presence of various gases like LPG, smoke, CO2.
• Ultrasonic Sensor (e.g., HC-SR04): Measures distance using sound waves.

Actuators (The "Muscles" of IoT):

• Relays: Electrically operated switches used to control high-voltage appliances.
• Servo Motors: Motors that can be controlled to rotate to a specific angular position.
• DC Motors: Convert electrical energy into mechanical rotation.
• Solenoids: Convert electrical energy into linear motion (a push or pull).

B. Communication Components (The "Nervous System" of IoT)

These components are responsible for transmitting data between devices (Things) and to the cloud/network.

Wired Communication:

• Ethernet (LAN): Provides reliable, high-speed wired network connectivity.

Wireless Communication:

• Wi-Fi (IEEE 802.11): Most common for local area, high-data-rate applications.
• Bluetooth (IEEE 802.15.1): For short-range, low-power communication.
• Zigbee (IEEE 802.15.4): Low-power, low-data-rate wireless mesh network.
• Radio Frequency (RF) modules (e.g., 433MHz): Simple, low-cost modules for one-way wireless communication.
• Cellular (4G/LTE, 5G, NB-IoT): Uses cellular networks for long-range communication.

C. Computing & Control Components (The "Brain" of IoT)

This is the core processing unit that reads sensor data, processes it, makes decisions, and sends commands to actuators.

• Microcontrollers (MCUs): Small, low-cost computers on a single integrated circuit.
• Microprocessors (MPUs): More powerful than MCUs, typically requiring external components.

D. Structural Components

The physical hardware that forms the platform for the electronic components.

• Boards: The main PCB that hosts the microcontroller.
• Shields: Add-on boards that plug directly into the main board.
• Modules: Stand-alone components that can be connected via wires.
• Breadboard: A reusable platform for prototyping circuits.
• Jumper Wires: Used to make temporary connections on a breadboard.

2. Introduction to Arduino

Arduino is an open-source electronics platform based on easy-to-use hardware and software.

A. Why Arduino?

• Inexpensive
• Cross-platform
• Simple, clear programming environment
• Open-source and extensible software & hardware
• Large community support

B. Arduino Uno Board Anatomy (Key Components)

• Microcontroller: ATmega328P
• Digital I/O Pins: 14 (Pins 0-13)
• Analog Input Pins: 6 (Pins A0-A5)
• Power Pins: 3.3V, 5V, GND, Vin
• USB Port: For connecting to a computer
• DC Barrel Jack: For external power supply
• Reset Button: Resets the microcontroller
• On-board LED (Pin 13): Connected to digital pin 13

C. Arduino IDE (Integrated Development Environment)

The software used to write, compile, and upload code (called a sketch) to the Arduino board.

Basic Structure of a Sketch:

// 1. Variable Declarations & Pre-processor Directives
int sensorPin = A0; // Assign analog pin A0 to variable 'sensorPin'

// 2. setup() function - Runs only once when the sketch starts
void setup() {
  pinMode(13, OUTPUT); // Initialize digital pin 13 as an output
  Serial.begin(9600); // Initialize serial communication at 9600 baud rate
}

// 3. loop() function - Runs repeatedly forever after setup()
void loop() {
  digitalWrite(13, HIGH); // Turn the LED on (HIGH is the voltage level)
  delay(1000); // Wait for a second (1000 milliseconds)
  digitalWrite(13, LOW); // Turn the LED off by making the voltage LOW
  delay(1000); // Wait for a second
}
        

D. Basic Arduino Commands/Functions

3. Interfacing Components with Arduino

A. Interfacing a Digital Sensor (e.g., PIR Sensor)

• Connection:
  • VCC → 5V
  • GND → GND
  • OUT → Digital Pin (e.g., 2)
• Code Logic:
  • pinMode(2, INPUT); in setup()
  • int motion = digitalRead(2); in loop()

B. Interfacing an Analog Sensor (e.g., LDR)

• Connection:
  • One leg → 5V
  • Other leg → Analog Pin (e.g., A0) and to one leg of a resistor (e.g., 10kΩ)
  • Other leg of the resistor → GND
• Code Logic:
  • int lightValue = analogRead(A0); in loop()

C. Interfacing an Actuator (e.g., LED)

• Connection:
  • Anode (Long leg) → Digital Pin (e.g., 13) through a resistor (e.g., 220Ω)
  • Cathode (Short leg) → GND
• Code Logic:
  • pinMode(13, OUTPUT); in setup()
  • digitalWrite(13, HIGH); or digitalWrite(13, LOW); in loop()

D. Interfacing an Actuator (e.g., Relay Module)

• Connection:
  • VCC → 5V
  • GND → GND
  • IN → Digital Pin (e.g., 7)
• Code Logic: Treat it like an LED
  • digitalWrite(7, HIGH) activates the relay
  • digitalWrite(7, LOW) deactivates it
• CAUTION: The relay's high-voltage terminals are used to control AC appliances. Extreme care must be taken to avoid electric shock.

4. Key Concepts for Practicals

• Voltage Divider Circuit: Crucial for understanding how many analog sensors work.
• Pull-up/Pull-down Resistors: Used with digital inputs to ensure the pin is in a known state.
• PWM (Pulse Width Modulation): A technique to get analog-like results with a digital signal.
• Serial Monitor: An essential tool for debugging.

Summary: This chapter forms the foundation of practical IoT development. Understanding the role of each component and mastering their interfacing with an Arduino using the basic functions is the primary goal.