This project implements a smart room automation system using an Arduino Uno, featuring predefined password-protected secure door access, automatic lighting based on occupancy, and automatic smoke detection with an alarm. The system prioritizes smoke detection over unauthorized access for safety.

• Purpose: Automate room functions (secure door, occupancy-based lighting, smoke detection) with sensor-based control.
• Platform: Designed and simulated in Tinkercad.

https://www.tinkercad.com/things/3gTcExSN1LN-smart-room

• Arduino Uno: Microcontroller (central unit).
• Servo Motor: Pin 3 (controls door lock, 0° = locked, 90° = unlocked).
• LEDs:
  • Red LED (Pin 5): Indicates incorrect password.
  • Green LED (Pin 6): Indicates access granted.
• Buzzer: Pin 4 (audible alarm for smoke detection).
• Gas Sensor (MQ-2): Analog pin A0 (detects smoke, threshold >600 for unsafe level).
• PIR Sensors:
  • PIR1 (Pin A3): Detects entry (outside).
  • PIR2 (Pin A2): Detects exit/inside movement.
• Light: Pin A1 (turns on/off based on occupancy).
• DC Motor (Exhaust Fan): Pin 4 (via 2N2222 (npn) transistor with 1kΩ resistor, activates with smoke).
• Keypad (4x4): Pins 7-13 and 2 (for password entry).
• LCD (16x2 with I2C) (Type [PCF8574], [39 (0X27)]): Default SDA/SCL (A4/A5) (displays status, occupancy, and messages).

1. Servo Motor: Connect signal to Pin 3, VCC to 5V, GND to GND.
2. LEDs: Connect anodes to Pins 5 and 6, cathodes to GND via 220Ω resistors.
3. Buzzer: Connect positive to Pin 4, negative to GND.
4. Gas Sensor: Connect VCC to 5V, GND to GND, AOUT to A0.
5. PIR Sensors: Connect VCC to 5V, GND to GND, OUT to A3 (PIR1) and A2 (PIR2).
6. Light: Connect anode to A1, cathode to GND via 220Ω resistor.
7. DC Motor (Exhaust Fan): Connect positive to transistor collector, negative to GND; transistor base to Pin 4 via 1kΩ resistor, emitter to GND; add a diode across motor terminals (cathode to positive) to protect against back EMF.
8. Keypad: Connect rows to Pins 7-10, columns to Pins 11-13 and 2.
9. LCD: Connect via I2C module to A4 (SDA) and A5 (SCL), VCC to 5V, GND to GND.

• 1.1 Success Prompt if Password is Correct:
  • Enter the default password "0000" (or a new password set via master password "1234") using the keypad.
  • On correct entry (confirmed with 'C'), the LCD displays "Access Granted," the green LED flashes 5 times, and the servo unlocks the door (moves to 90°).
• 1.2 Implement Door Opening Feature:
  • The unlockDoor() function sets the servo to 90° for 10 seconds. Press 'D' on the keypad to lock it manually, or it auto-locks after the timer.
• 1.3 Warning Message if Password is Wrong:
  • On incorrect password entry, the LCD shows "CODE INCORRECT," and the red LED lights up. After 3 failed attempts, a 30-second wait is enforced; otherwise, a 3-second delay applies. Warnings are deferred if smoke is detected.

• 2.1 Detect People Entering/Exiting a Room:
  • PIR1 (A3) detects entry when triggered first, followed by PIR2 (A2) within 15 seconds, indicating movement inward.
  • PIR2 triggered first, then PIR1 within 15 seconds (with exit sequence flag), indicates movement outward.
• 2.2 Keep Count of People Occupied:
  • The loop() function updates the occupancy variable based on PIR sequences, incrementing for entry and decrementing for exit, with a 2-second debounce.
• 2.3 Turn On/Off Light Based on Count:
  • The light (A1) turns on if occupancy > 0 and off if occupancy = 0, managed in loop().

• 3.1 Turn On Alarm if Smoke Detected:
  • The gas sensor (A0) monitors smoke levels. If >600, the exhaust fan (Pin 1) activates via a transistor, and the buzzer (Pin 4) beeps (500ms) as an alarm. This has the highest priority.
• 3.2 Turn Off Alarm When Smoke Level is Below Unsafe Level:
  • When the gas sensor value drops to <=600, the exhaust fan and buzzer turn off, resuming deferred unauthorized access warnings if any.

• Initializes serial communication (9600 baud) for debugging.
• Configures pin modes (OUTPUT for LEDs, buzzer, fan, light; INPUT for sensors).
• Initializes LCD, sets servo to locked (0°), and displays "Smart Room Ready".

• Smoke Detection: Prioritizes checking A0; if >600, activates fan and buzzer, defers unauthorized warnings. If <=600, turns off fan/buzzer and processes pending warnings.
• Door Unlock Countdown: Manages a 10-second unlock timer.
• Keypad Input: Handles password entry, master check, or setup.
• Occupancy Counting: Processes PIR sequences for entry/exit.
• Light Control: Adjusts light based on occupancy.
• Uses a 50ms delay for responsiveness.

• Updates LCD with occupancy count (second line) if not in password/unlock mode.
• Logs to Serial Monitor.

• Clears LCD, shows "Enter Password:" with occupancy.

• Locks door (servo to 0°), updates LCD, resets exit flag.

• Unlocks door (servo to 90°), flashes green LED, sets 10-second timer.

• Sets new password (0-9, 'B' backspace, 'C' confirm).

• Verifies master password ("1234") for setup.

• Processes password input; defers incorrect warning if smoke detected.

• Displays warning, lights red LED, enforces delays after failures.

• Resets PIR flags and timers.

• Smoke Detection Priority: If smoke is detected, the system activates the exhaust fan and buzzer immediately, deferring unauthorized access warnings until smoke levels drop below 600.

• Circuit Overview

• Smoke Detection Active (fan and buzzer on)

• Door Unlocked (servo at 90°, green led blinking)

• Occupancy Display (LCD showing people count, count > 0 turn on blue led)

1. Open the Tinkercad link and start the simulation.
2. Enter "0000" to unlock the door (green LED flashes).
3. Use PIR sensors to simulate entry/exit and watch occupancy/light changes.
4. Set gas sensor >600 to trigger smoke alarm and fan.
5. Test wrong password during smoke to see deferred warning.

• Developed by Fahith K.R.M. on Monday, October 02, 2025.
• Shared on GitHub for portfolio and resume enhancement.