📘 Home Security Code 

🎯 Objective of This Lesson

Students will learn:

• How to read digital input from PIR

• How to detect motion

• How to print status on Serial Monitor

• How basic intrusion detection logic works

🔌 Hardware Reminder

🧾 Complete ESP32 Code (Copy–Paste Ready)

#define PIR_PIN 27 // PIR OUT connected to GPIO 27

int motionState = 0;
int lastState = 0;

void setup() {

Serial.begin(115200);
pinMode(PIR_PIN, INPUT);

Serial.println("Home Security System Started...");
Serial.println("Warming up PIR Sensor...");
delay(30000); // 30 seconds warm-up
Serial.println("System Ready!");
}

void loop() {

motionState = digitalRead(PIR_PIN);

if (motionState == HIGH && lastState == LOW) {
Serial.println("⚠ MOTION DETECTED! Intruder Alert!");
lastState = HIGH;
}

else if (motionState == LOW && lastState == HIGH) {
Serial.println("Area Clear - No Motion");
lastState = LOW;
}

delay(200);
}

🧠 Code Explanation (Step-by-Step)

1️⃣ Define PIR Pin

This tells ESP32 that PIR OUT is connected to GPIO 27.

2️⃣ Motion Variables

• motionState → Current PIR reading

• lastState → Previous PIR reading

Why we use this?

To avoid repeated printing of same message.

3️⃣ Serial Communication

Used to display output in Serial Monitor.

4️⃣ Warm-Up Time

PIR needs 30 seconds to stabilize.

Without this:

• False triggers may occur.

5️⃣ Reading PIR Output

Returns:

HIGH → Motion detected
LOW → No motion

6️⃣ Motion Detection Logic

This means:

Motion just started.

Print:

⚠ MOTION DETECTED! Intruder Alert!

Then update lastState.

7️⃣ Motion End Detection

This means:

Motion stopped.

Print:

Area Clear – No Motion

8️⃣ Why Use lastState?

Without it:

Serial Monitor would continuously print:

MOTION DETECTED
MOTION DETECTED
MOTION DETECTED

Using state comparison makes system professional.

📊 Example Serial Monitor Output

System start:

Home Security System Started
Warming up PIR Sensor…
System Ready!

When someone walks:

⚠ MOTION DETECTED! Intruder Alert!

When movement stops:

Area Clear – No Motion

🎓 Learning Outcomes

After this lesson, students understand:

• Digital sensor reading

• HIGH vs LOW logic

• State change detection

• Intrusion detection programming

• Basic security system design