Activity 1: Exploring IoT Sensors with Arduino

Temperature, Light, and Moisture Detection

Topic: Internet of Things
Time: 1 Hour

Description

In this activity, you’ll learn how to use common IoT sensors with an Arduino to collect environmental data. You’ll work with a digital temperature sensor, a light-dependent resistor (LDR) sensor, and a soil moisture sensor. You’ll also control an LED based on sensor readings, reinforcing the connection between sensing and action, a core concept in IoT applications.

Materials Required

  • Arduino Uno (or compatible board)
  • USB cable
  • Breadboard and jumper wires
  • Gikfun DS18B20 Waterproof Digital Temperature Sensor with Adapter
  • Teyleten Robot 5MM LDR Photosensitive Sensor Module
  • Soil Moisture Sensor
  • LED
  • 220Ω resistor
  • Computer with Arduino IDE installed (Note: The newest version is preferred)

Extra Sources

Steps to Conduct the Activity

Step 1: Topic Explanation

  • Introduce the Internet of Things (IoT) as the network of devices embedded with sensors, software, and other technologies to collect and exchange data.
  • Explain how sensors collect physical world data, while actuators (like LEDs or motors) perform actions based on that data.
  • Sensors we’ll use:
    • DS18B20 Temperature Sensor: Measures temperature in °C and °F.
    • LDR Light Sensor: Detects light levels.
    • Soil Moisture Sensor: Measures the amount of moisture in the soil.

Step 2: Explain the Problem

  • IoT devices often monitor environmental conditions and take action automatically.
  • In this activity:
    • We’ll read sensor data.
    • We’ll make an LED turn on or off based on temperature or light levels.
    • We’ll monitor soil moisture for potential smart agriculture applications.

Step 3: Interactive Time

Part 1: Temperature Sensor with DS18B20

Setup:
  1. Connect DS18B20:
    • GND to GND
    • DAT to Digital Pin 2
    • VCC to 5V (Note: Some DS18B20 sensors require a 4.7kΩ resistor between DAT and VCC, but many breakout boards include it already.)
  2. Install the DallasTemperature and OneWire libraries in Arduino IDE (via Library Manager).

DallasTemperature
  1. Make sure the right baud rate is Selected : 9600
Code to Read Temperature:
#include <OneWire.h>
#include <DallasTemperature.h>

#define ONE_WIRE_BUS 2
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);

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

void loop() {
  sensors.requestTemperatures();
  Serial.print("Temperature: ");
  Serial.print(sensors.getTempCByIndex(0));
  Serial.print("°C | ");
  Serial.print((sensors.getTempCByIndex(0) * 9.0) / 5.0 + 32.0);
  Serial.println("°F");
  delay(500);
}

DallasTemperature Readings
Extend: Control an LED Based on Temperature

  • Add an LED to Pin 13 with a 220Ω resistor to GND.

  • LED turns ON if temperature ≤ 85°F.

#include <OneWire.h>
#include <DallasTemperature.h>

#define ONE_WIRE_BUS 2
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);

void setup() {
  pinMode(13, OUTPUT);
  Serial.begin(9600);
  sensors.begin();
}

void loop() {
  sensors.requestTemperatures();
  float tempF = (sensors.getTempCByIndex(0) * 9.0) / 5.0 + 32.0;
  
  Serial.print("Temperature: ");
  Serial.print(tempF);
  Serial.println("°F");

  if (tempF <= 85) {
    digitalWrite(13, HIGH);
    Serial.println("Light On!");
  } else {
    digitalWrite(13, LOW);
    Serial.println("Light Off!");
  }
  delay(500);
}

Part 2: Light Detection with LDR Sensor

Setup:

  1. Connect LDR sensor:

    • VCC to 5V
    • GND to GND
    • OUT to Analog Pin A0

LDR Sensor Wiring
Code to Read Light Level:
void setup() {
  Serial.begin(9600);
}

void loop() {
  unsigned int AnalogValue = analogRead(A0);
  Serial.println(AnalogValue);
  delay(250);
}
Extend: Turn LED On/Off Based on Light Level
  • LED turns ON if light value is below threshold (e.g., < 60).
void setup() {
  pinMode(13, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  unsigned int AnalogValue = analogRead(A0);
  Serial.println(AnalogValue);

  if (AnalogValue <= 60) {
    digitalWrite(13, HIGH);
    Serial.println("Light On!");
  } else {
    digitalWrite(13, LOW);
    Serial.println("Light Off!");
  }
  delay(250);
}

Part 3: Soil Moisture Sensor

Setup:
  1. Connect moisture sensor:
    • VCC to 5V
    • GND to GND
    • Signal to Analog Pin A0
    • Code to Read Moisture Level:
void setup() {
  Serial.begin(9600);
  Serial.println("Simple Data Reading Program - send data over serial");
}

void loop() {
  int soilMoistureValue = analogRead(A0);
  Serial.print("Moisture reading: ");
  Serial.println(soilMoistureValue);
  delay(5000);
}
  • Interpret the readings: Higher values mean dry soil, lower values mean wet soil.

Reflection

  • What are some real-world applications of these sensors?
  • How could combining multiple sensors improve automation or decision-making?
  • What challenges did you face in setting up or reading the sensors?

Learning Outcomes

  • Understand the role of sensors in IoT systems.
  • Interface multiple types of sensors with Arduino.
  • Translate sensor data into actionable outputs (like controlling LEDs).
  • Gain experience troubleshooting wiring, code, and sensor behavior.
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