What components do I need for the IR Motion Door Alarm project?

For the IR Motion Door Alarm project, you need: 1x Arduino Uno R3 (5V), 1x PIR Sensor (HC-SR501) (5???20V, adjustable), 1x Piezo Buzzer (Passive 5V), 1x Red LED (5mm), 1x Resistor (220 Ohm), 1x Breadboard + Wires (Standard).

How do I build an IR Motion Door Alarm with Arduino?

A PIR sensor watches your door. The moment someone walks in, a loud buzzer triggers — your first home security system. Follow these 5 steps: Step 1: Connect the PIR. Step 2: Add Buzzer and LED. Step 3: Calibration Wait. Step 4: Test the Alarm. Step 5: Adjust Sensitivity.

How long does the IR Motion Door Alarm project take?

The IR Motion Door Alarm Arduino project typically takes 30–60 minutes to complete, including wiring and uploading the code. It is rated as a Basic-level project, suitable for beginners with no prior electronics experience.

Is the IR Motion Door Alarm Arduino code free to use?

Yes. All Arduino code on Volt X, including the IR Motion Door Alarm sketch, is completely free to use, copy, and modify for personal or educational projects.

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Basic . Project #10

🚪 IR Motion Door Alarm

A PIR sensor watches your door. The moment someone walks in, a loud buzzer triggers — your first home security system.

📋 Overview

PIR (Passive Infrared) sensors detect changes in infrared radiation caused by warm bodies moving through their field of view. They output a simple HIGH/LOW digital signal — easy to wire and read.

What you'll learn: PIR sensor usage, digital input reading, buzzer alarm, and LED warning indicators.

Estimated time: 25–35 minutes. Difficulty: ⭐ Beginner-friendly.

🧩 Components Needed

Component	Specification	Qty	Notes
Arduino Uno R3	5V	1
PIR Sensor (HC-SR501)	5???20V, adjustable	1	Most common PIR sensor
Piezo Buzzer	Passive 5V	1
Red LED	5mm	1	Alarm indicator
Resistor	220 Ohm	1	For LED
Breadboard + Wires	Standard	1

📖 Step-by-Step Tutorial

Connect the PIR

PIR has 3 pins: VCC -> 5V, GND -> GND, OUT -> Arduino pin 2.

Add Buzzer and LED

Buzzer+ -> pin 8, LED (with 220 Ohm) -> pin 9, both negatives to GND.

Calibration Wait

The HC-SR501 needs 30???60 seconds to calibrate when first powered. Don't move during this time!

Test the Alarm

Walk past the sensor from 3???5m away. Buzzer and LED should trigger for a few seconds.

Adjust Sensitivity

The PIR has two potentiometers: one for sensitivity (range), one for delay (how long it stays triggered). Adjust with a screwdriver.

💡

Mount the PIR at 2–2.5m height, angled slightly downward. This gives the widest detection zone and minimizes false triggers from pets on the floor.

💻 Arduino Code

motion_alarm.ino

INO

// Motion Door Alarm — Volt X
const int PIR = 2;
const int BUZZER = 8;
const int LED = 9;

void setup() {
  pinMode(PIR, INPUT);
  pinMode(BUZZER, OUTPUT);
  pinMode(LED, OUTPUT);
  Serial.begin(9600);
  Serial.println("Calibrating PIR... wait 30s");
  delay(30000);
  Serial.println("Ready! Watching for motion...");
}

void loop() {
  if (digitalRead(PIR) == HIGH) {
    Serial.println("MOTION DETECTED!");
    digitalWrite(LED, HIGH);
    tone(BUZZER, 2000, 200);
    delay(300);
    tone(BUZZER, 1500, 200);
    delay(300);
    tone(BUZZER, 2000, 200);
    delay(300);

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