Sensors Coding Practice (Arduino)

This file contains simple sensor examples I learn with clear line-by-line explanations. It needs more read, then explain each marked line in once own words.

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1. PIR Sensor (Motion)

int pirPin = 2;            // pin connected to PIR sensor
int ledPin = 13;          // pin connected to LED
int pirState = 0;         // variable to store sensor value (HIGH or LOW)

void setup() {
  pinMode(pirPin, INPUT);     // PIR sends signal to Arduino
  pinMode(ledPin, OUTPUT);    // Arduino controls LED
  Serial.begin(9600);         // start communication with computer
}

void loop() {
  pirState = digitalRead(pirPin);   // read sensor: HIGH = motion, LOW = no motion

  if (pirState == HIGH) {           // check if motion exists
    digitalWrite(ledPin, HIGH);     // turn LED ON
    Serial.println("Motion");      // print message
  } else {                          // if no motion
    digitalWrite(ledPin, LOW);      // turn LED OFF
    Serial.println("No motion");   // print message
  }

  delay(500);                       // wait before next read
}

Practice: Explain this line: pirState = digitalRead(pirPin);

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2. Capacitive Touch Sensor

int touchPin = 2;          // touch sensor pin
int ledPin = 13;           // LED pin
int touchState = 0;        // store touch value

void setup() {
  pinMode(touchPin, INPUT);    // read touch input
  pinMode(ledPin, OUTPUT);     // control LED
}

void loop() {
  touchState = digitalRead(touchPin);   // HIGH = touched, LOW = not touched

  if (touchState == HIGH) {             // if finger touches sensor
    digitalWrite(ledPin, HIGH);         // LED ON
  } else {                              // no touch
    digitalWrite(ledPin, LOW);          // LED OFF
  }
}

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3. Step Response Sensor (Analog Read)

int sensorPin = A0;        // analog input pin
int value = 0;             // store sensor value

void setup() {
  Serial.begin(9600);      // start serial monitor
}

void loop() {
  value = analogRead(sensorPin);   // read value from 0 to 1023

  Serial.println(value);           // show value on screen

  delay(200);                      // small delay
}

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4. Ultrasonic Sensor (Distance)

int trigPin = 9;          // send signal
int echoPin = 10;         // receive signal
long duration;            // time of signal travel
int distance;             // calculated distance

void setup() {
  pinMode(trigPin, OUTPUT);   // trigger output
  pinMode(echoPin, INPUT);    // echo input
  Serial.begin(9600);
}

void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);

  digitalWrite(trigPin, HIGH);   // send pulse
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);   // measure return time

  distance = duration * 0.034 / 2;     // convert to cm

  Serial.println(distance);

  delay(500);
}

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5. LDR (Light Sensor)

int ldrPin = A0;        // light sensor pin
int ledPin = 13;        // LED pin
int lightValue = 0;     // store light value

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

void loop() {
  lightValue = analogRead(ldrPin);   // read light level

  if (lightValue < 500) {            // if dark
    digitalWrite(ledPin, HIGH);      // LED ON
  } else {
    digitalWrite(ledPin, LOW);       // LED OFF
  }

  Serial.println(lightValue);
  delay(300);
}

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6. Temperature Sensor (LM35)

int tempPin = A0;        // temperature sensor pin
float temperature;       // store temperature value

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

void loop() {
  int value = analogRead(tempPin);    // read sensor value

  temperature = value * (5.0 / 1023.0) * 100;  // convert to Celsius

  Serial.print("Temp: ");
  Serial.println(temperature);

  delay(500);
}

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How to Practice

1. Read one sensor at a time
2. Explain one line in simple words
3. If not clear, rewrite simpler
4. Repeat until confident

You can come back and we continue step by step.

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Mini Dictionary (Core Arduino Concepts)

Commands (Functions you call)

pinMode()

pinMode(13, OUTPUT); // set pin 13 as OUTPUT

• Definition: tells Arduino if a pin is INPUT or OUTPUT
• Purpose: prepare a pin before using it
• Arguments: (pin number, mode)

Serial.begin()

Serial.begin(9600); // start serial communication

• Definition: starts communication with computer
• Purpose: send/receive data via Serial Monitor
• Argument: speed (baud rate)

digitalWrite()

digitalWrite(13, HIGH); // turn LED ON

• Definition: write HIGH or LOW to a digital pin
• Purpose: control devices (LED, relay)
• Arguments: (pin, value)

analogRead()

int v = analogRead(A0); // read analog value

• Definition: reads analog value (0–1023)
• Purpose: get sensor levels (light, temp)
• Argument: analog pin

Serial.println()

Serial.println(v); // print value with new line

• Definition: prints data to Serial Monitor
• Purpose: debugging and observing values
• Argument: data to print

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Core Concepts

function

void setup() { }

• Definition: a block of code that does a task
• Use: organize code (setup runs once, loop repeats)

command

digitalWrite(13, HIGH);

• Definition: an instruction you give to Arduino
• Use: performs an action immediately

arguments

pinMode(13, OUTPUT);

• Definition: values passed into a function
• Use: tell the function what to work with

variable

int x = 5;

• Definition: named storage for a value
• Use: save and reuse data

datatype

int a = 1;        // integer (whole number)
float b = 2.5;    // decimal number
String s = "Hi"; // text
bool f = true;    // true/false

• Definition: type of data a variable holds
• Use: choose based on needed value

conditional

if (a == 1) { }

• Definition: decision making (if/else)
• Use: run code based on a condition

math operators

int c = a + 2; // + - * /

• Definition: arithmetic operations
• Use: calculations

comparison operators

if (a == 1) { }
if (a != 2) { }

• Definition: compare values
• Use: conditions (true/false)

library

#include <Servo.h>

• Definition: pre-written code you can use
• Use: add features (servo, sensors)

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Small Combined Example

int led = 13;                 // variable (int)
int sensor = A0;              // variable (int)

void setup() {                // function
  pinMode(led, OUTPUT);       // command with arguments
  Serial.begin(9600);         // command
}

void loop() {                 // function
  int value = analogRead(sensor);   // read sensor

  if (value > 500) {          // conditional + comparison
    digitalWrite(led, HIGH);  // command
  } else {
    digitalWrite(led, LOW);   // command
  }

  int doubled = value * 2;    // math operator
  Serial.println(doubled);    // print result
}

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