📘Home Security System 

🎯 Objective of This Lesson

Students will learn:

• How to connect PIR sensor with ESP32

• How digital output works

• Proper GPIO selection

• Power considerations

• Correct installation position

🧪 Components Required

• ESP32 Development Board

• PIR Motion Sensor (HC-SR501 recommended)

• Breadboard

• Jumper wires

• USB cable

🔌 PIR Sensor Pin Description

Most PIR modules have 3 pins:

🔌 Circuit Connections (ESP32 + PIR)

📍 Connection Table

You can use any digital GPIO, but GPIO 27 is safe and recommended.

🧠 Why We Use GPIO 27?

• Supports digital input

• Safe for sensor signals

• Not used for boot configuration

• Stable and reliable

⚡ Power Considerations

Important points:

1️⃣ PIR works on 5V
2️⃣ ESP32 works on 3.3V logic
3️⃣ PIR output is safe for ESP32 digital input
4️⃣ Do NOT power PIR from 3.3V (may cause unstable detection)

🧠 How the Circuit Works

1️⃣ PIR senses infrared radiation
2️⃣ When motion is detected → OUT becomes HIGH
3️⃣ When no motion → OUT becomes LOW
4️⃣ ESP32 reads HIGH or LOW from GPIO 27
5️⃣ Program decides what to do

So basically:

Motion → HIGH
No Motion → LOW

📏 Physical Installation Guidelines

To get best performance:

• Mount sensor at height of 6–8 feet

• Face toward entrance or movement area

• Avoid pointing directly at windows

• Avoid facing fans or AC

• Keep away from heat sources

⚙ PIR Module Adjustments

Most PIR sensors have two potentiometers:

🔹 Sensitivity Adjustment

• Clockwise → Increase range

• Counterclockwise → Decrease range

🔹 Time Delay Adjustment

• Controls how long output remains HIGH

• Adjustable from few seconds to few minutes

🔁 Trigger Mode Jumper

Two modes available:

H Mode (Retriggerable)

• Output stays HIGH if motion continues

• Recommended for security systems

L Mode (Non-Retriggerable)

• Output goes LOW after delay even if motion continues

For Home Security:

👉 Use H Mode

⏳ Warm-Up Time

After powering ON:

• Wait 30–60 seconds

• Sensor stabilizes

• During warm-up, output may fluctuate

Important to explain this to students.

📊 Signal Behavior Summary

🎓 Learning Outcomes

After this lesson, students understand:

• Digital sensor interfacing

• GPIO input concept

• Motion detection basics

• Practical installation logic

• Sensor calibration basics