IoT-based Home Security System

This IoT-based home security system combines 4 sensors and 4 actuators to detect motion, verify access through a keypad, and automate door control. Real-time monitoring with low-latency and remote control are provided through a web interface that displays sensor data, controls actuators, manages system settings and logs security events. Automated actions of fan cooling and door lock control, overall enhance safety and comfort.

Link for the web application hosted on the cloud (Works on Chrome, Edge, Opera): https://iot-security.netlify.app

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Prerequisities

Sensors (in total 4):

• Ultrasonic distance sensor (HC-SR04)
• Temperature & Humidity sensor (DHT11)
• IR sensor
• 4×4 Membrane Keypad

Actuators (in total 4):

• Servo motor (SG90)
• LED
• Buzzer (activate)
• Small Fan

Sensor pins:

• Ultrasonic (HC-SR04) → TRIG, ECHO
• DHT11 → digital pin
• IR sensor → digital pin
• Keypad → 8 pins (rows & columns)

Atuator pins:

• Servo → PWM pin
• LED → digital pin
• Buzzer → digital pin
• Fan → digital pin

Libraries:

• DHT.h for DHT11
• Keypad.h for 4×4 keypad
• Servo.h for servo motor
• NewPing for Ultrasonic
• ArduinoJson.h for sending data

Pin modes:

• Sensors: INPUT
• Actuators: OUTPUT

Default states:

• Servo → 0° (door closed)
• LED → Off
• RGB → Off
• Buzzer → Off
• Fan → Off

Communications:

• USB serial cabel

Main Loop

Monitor the area using ultrasonic + IR sensors:

• Ultrasonic distance sensor: Detects if someone is approaching.
  • If distance < “approaching threshold” → trigger voice/text alert: "Someone is approaching the door"
• IR sensor: Detects if someone is very close to the door.
  • If IR triggered OR ultrasonic distance < “at-door threshold” → trigger voice/text alert: "Someone is at the door. Please enter the code on keypad"

Keypad input:

• If correct code entered:

  • RGB LED → Green
  • Servo → Rotate to “door open” (simulates door opening)
  • Voice/Text → "Door is unlocked"
  • Wait 3–4 seconds
  • Servo → Rotate back to 0° (door closes)
  • Turn RGB LED off

• If wrong code entered:

  • Buzzer → On for 1–2 seconds
  • RGB LED → Red for 1–2 seconds
  • Then turn Buzzer and RGB LED off

No limit on number of attempts; repeat until correct code

Post-door-close action:

• Monitor temperature using DHT11:
  • If temperature > threshold → Turn fan ON
  • Else → Fan OFF

Loop continues: Monitor sensors → Door logic → Fan logic

Main Loop flow-diagram

Circuit Diagram

To see where each wire and pin connects, click here:

Components were connected in the order provided below.

Ultrasonic Sensor (HC-SR04):

• VCC → 5V
• GND → GND
• TRIG → Pin 12
• ECHO → Pin 11

DHT11 Temperature Sensor:

• VCC → 5V (in the middle if not defined)
• GND → GND (or written as "-")
• DATA → Pin 2 (or written as "S")

IR Sensor:

• VCC → 5V
• GND → GND
• OUT → Pin 3

4×4 Keypad:

• Row 1 → A0
• Row 2 → A1
• Row 3 → A2
• Row 4 → A3
• Column 1 → Pin 10
• Column 2 → A4
• Column 3 → A5
• Column 4 → Pin 13

Servo Motor (SG90):

• Red (VCC) → 5V
• Brown (GND) → GND
• Orange (Signal) → Pin 9

RGB LED (Common VCC)

• Common Cathode → GND
• Red pin → Pin 5 (with 220Ω resistor)
• Blue pin → Pin 7 (with 220Ω resistor)

Buzzer:

• Positive (+) → Pin 8
• Negative (-) → GND

Simple Fan (2-wire with NPN Transistor): Required Components:

• 1x NPN Transistor (PN2222A)
• 1x 1kΩ Resistor
• 1x Diode 1N4007 (for protection)

Arduino Pin 4 → 1kΩ Resistor → Transistor Base (middle pin)
Transistor Emitter (left/right pin) → Arduino GND
Transistor Collector (left/right pin) → Fan GND (-)
Fan VCC (+) → Arduino 5V
Diode (1N4007): Cathode to Arduino 5V, Anode to Fan GND

Network Diagram

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Web Interface

System Backlog

The web interface allows a user to:

• Monitor all sensors in real time (door status, temperature sensor, IR sensor)
• Control actuators (door, fan, buzzer, LED)
• Manage system settings (change keypad password, set ultrasonic/temperature threshold, reset settings)
• View sensor history, alerts, and statistics.

Log Alerts:

• Door Access: Time of unlock, method (web or keypad).
• Failed Password Attempts: Keypad wrong entry, number of attempts.
• Motion Alerts: "Someone approaching", "Someone at the door".
• Temperature Alerts: “Fan ON due to high temp”.
• Features: Filter by date/event type and export logs to CSV/JSON.

| Timestamp | Event           | Source  | Extra      |
| --------- | --------------- | ------- | ---------- |
| 14:33     | Door unlocked   | Keypad  | Code: 1234 |
| 09:50     | Wrong attempt   | Keypad  | 3 tries    |
| 08:11     | Someone at door | Sensors | IR Trigger |

Control of actuators:

• Servo (Door Lock): Open / Close
• Fan: Turn ON/OFF override
• RGB LED: Choose (Red, Blue)
• Buzzer: Turn ON/OFF (for alarm test)

Password Management:

• Change the door unlock password (Arduino keypad code).
• Require confirmation before saving.
• Minimum 4 digits.
• Must push new password to Arduino.

Data Visualization:

• Temperature trend (line chart, last 30 seconds).
• Number of door unlock attempts (bar chart).

Data Analysis:

• Average Temperature: 23.5°C
• Total Visitors Today: 12
• Failed Attempts Today: 3
• Maximum Temperature Today: 29°C
• Number of times Fan Activated: 5

Device Settings:

• Set temperature threshold for fan.
• Set ultrasonic thresholds (someone approaching the door).
• Set a new door unlock password.
• Reset settings to the default state.

Folder Tree structure

iot-security/
├──── LICENSE
├──── README.md
│
├──── paper/               
│     └── IoT_Report_00015775.pdf         # project's detailed description
│
├──── arduino
│    ├── arduino-webapp-controller.ino.   # main project logic
│    └── index.html                       # web interface 
│
├──── components-testing
│    ├── actuators/                        # unit testing code actuators only
│    ├── sensor-actuator-testing/          # unit testing code using both actuators and sensors
│    └── sensors/                          # unit testing code sensors only
│
└──── diagrams
     ├── circuit-diagrams/                  # circuit diagram for all individual components
     │    ├── *.png
     │    └── cirkit-designer/              # contains .ckt editable files of circuit diagram
     │
     ├── network-diagrams/                  # network diagram of hardwares .pkt file
     └── uml-diagrams/                      # auxiliray system design diagrams

References:

to see Reference List, click here:

Reference List:

• Servo: https://lastminuteengineers.com/servo-motor-arduino-tutorial/
• DHT11: https://lastminuteengineers.com/dht11-module-arduino-tutorial/
• IR: https://lastminuteengineers.com/pir-sensor-arduino-tutorial/
• Keypad: https://lastminuteengineers.com/arduino-keypad-tutorial/
• Ultrasonic: https://lastminuteengineers.com/arduino-sr04-ultrasonic-sensor-tutorial/
• ArduinoJson: https://arduinojson.org/
• Code adapted from https://www.electronicsforu.com/electronics-projects/sensor-data-sending-over-web-serial
• Code adapted from https://forum.arduino.cc/t/servo-motor-with-a-ultrasonic-sensor/921109
• Code adapted from https://www.scribd.com/document/829854684/CODE-FOR-THE-PROJECT
• Code adapted from https://yedianyang.medium.com/how-to-send-data-to-a-web-page-from-arduino-serial-port-7aef849ccdd6
• The circuit design is adapted from https://www.youtube.com/watch?v=uwe-IMqm7GA
• The circuit design is adapted from https://www.youtube.com/watch?v=01ycWiAeKpA
• The circuit design is adapted from https://www.youtube.com/watch?v=qF75ZS3YjNE
• Code adapted from https://github.com/funnierinspanish/web-serial-example
• Code adapted from https://github.com/kjj6198/web-serial-api?tab=readme-ov-file
• Code adapted from https://www.makerspace-online.com/controlling-microcontrollers-over-usb-with-the-web-serial-api
• Code adapted from https://github.com/svendahlstrand/web-serial-api
• Information learned from https://foostack.ru/web-serial-api-arduino/
• Code adapted from https://www.youtube.com/watch?v=a8UhkWDP-dI
• Code adapted from https://www.youtube.com/watch?v=rkiDjfTt4T0