Nica Mioara Raluca - 334CA

The Automatic Parking Gate project simulates a real-world automated parking system with controlled access. It allows vehicles to enter only if they have valid authorization (via an RFID card) and only if parking spots are available. The system uses a servo motor to raise and lower a barrier, ultrasonic sensors to detect vehicle presence, an LCD to display the number of available spots, and colored LEDs to indicate the status of the parking lot.

The purpose of this project is to develop a smart access control system for parking areas, using multiple electronic modules and key concepts learned during laboratory sessions—such as RFID communication, PWM control, sensors, LCD interfacing, and interrupt handling. The goal is to build a functional and interactive prototype that simulates a secure and efficient real-life parking gate.

The idea for the project came from the observation that managing parking lots in crowded urban areas is increasingly difficult without automation. Many institutions and residential areas already use automated gates with card access and visual status indicators. This project aims to replicate such a system at a smaller scale, making use of accessible hardware and the skills acquired in class.

This project is useful as it demonstrates a practical implementation of several microcontroller-based technologies in a single integrated system. For us, it provided valuable experience in system design, hardware-software integration, and real-world problem solving. For others, it can serve as a learning resource or as a base for further development of smart parking or access control systems. It is educational, expandable, and applicable to real-life needs.

The Automatic Parking Gate project is a smart system that manages the entry of vehicles into a parking area based on access authorization (via RFID) and space availability (detected by ultrasonic sensors). The system integrates both hardware and software components that interact with each other in a coordinated manner, managed by the Arduino UNO microcontroller.

Below is the block diagram of the system, showing all modules involved:

• Arduino UNO Acts as the central controller, processing data from sensors and sending commands to output devices.
• RFID Module (RC522) Reads the UID of the scanned card via SPI. The Arduino compares this UID to a list of authorized IDs.
• Ultrasonic Sensors (x2) Detect vehicle presence at the entrance (sensor 1) and exit (sensor 2). This helps update the count of available parking spots.
• Servo Motor Controls the parking barrier, raising it if access is granted and lowering it after the car has passed.
• LCD 16×2 with I2C Module Displays dynamic information such as the number of available spots or access denied messages.
• LEDs (green, orange, red) Provide quick visual feedback:
  1. Green → available
  2. Orange → almost full
  3. Red → full
• Push Button (Override) Connected via interrupt, allows manual barrier control in emergency situations or system fallback.

• The RFID module reads the card → Arduino checks if UID is authorized.
• If valid, ultrasonic sensor 1 checks if a car is present.
• If a vehicle is detected and parking space is available:
  • Servo motor raises the barrier.
  • LCD shows: “Access Granted | Free spots: X”.
  • Green LED turns on.
• If the parking is full or card is unauthorized:
  • Barrier stays closed.
  • LCD displays appropriate message.
  • Red LED turns on.
• After car enters, sensor 2 updates spot count.
• Push button can trigger barrier manually, handled via interrupt.

• IDE: PlatformIO in VS Code
• Tool-chain: avr-gcc + avrdude (bundled with the IDE)
• MCU clock: 16 MHz
• Debug: Serial Monitor @ 9600 baud; optional logic-analyzer capture

• Wire – I2C bus (Arduino core)
• LiquidCrystal_PCF8574 – 16×2 LCD via PCF8574 backpack
• SPI – hardware SPI for MFRC522 (Arduino core)
• MFRC522 – 13.56 MHz RFID reader API (miguelbalboa/MFRC522)
• Servo – PWM control for the barrier arm
• avr/io.h – direct register access for fast LED updates

  1.**State Flow**
  1. *Idle / Scan Card* – LEDs show occupancy, LCD “Scan card…”.
  2. *Entry Granted* – valid UID **and** free spots.
  3. *Raise Barrier (Entry)* – ultrasonic #1 detects a vehicle **and** ≥ 10 s since last raise.
  4. *Count Entry* – ultrasonic #2 sees vehicle, barrier lowers, `carsInside++`.
  5. *Raise Barrier (Exit)* – `carsInside > 0`, ultrasonic #2 sees vehicle **and** cooldown met.
  6. *Count Exit* – vehicle clears sensor, barrier lowers, `carsInside--`.

1. Key Data

```cpp

  const byte authorizedUID[][4];   // whitelist of UIDs
  int  carsInside;                 // vehicles inside
  unsigned long lastRaiseMillis;   // last time barrier was raised
  ```

1. Timing Constants
   • `minRaiseInterval` = 10 000 ms – global cooldown between raises
   • `carClearTime` = 1 500 ms – confirm sensor field is empty before lowering

• `parking_barrier.ino`
  • `setup()` – hardware init, “Welcome” splash
  • `loop()` – full FSM for entry/exit
  • `readDistanceCm()` – HC-SR04 helper
  • `isAuthorized()` – UID whitelist check
  • `updateLEDs()` – green/orange/red status LEDs
  • `showMessage()` – text output on LCD

• Safety photocell to block lowering if an obstacle is detected
• EEPROM-stored whitelist with master-card admin functions
• Web dashboard (ESP8266/ESP32) for live telemetry and OTA updates

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