Circuit Documentation

Summary

This circuit integrates an Arduino UNO with an RFID-RC522 module, a servo motor, an LCD display, and several LEDs. The purpose of the circuit is to create an access control system that reads RFID tags, displays messages on the LCD, and controls a lock mechanism through a servo motor. The system provides visual feedback using LEDs: a red LED indicates access denied, and a green LED indicates access granted.

Component List

Arduino UNO

• Microcontroller board based on the ATmega328P
• It has 14 digital input/output pins, 6 analog inputs, a 16 MHz quartz crystal, a USB connection, a power jack, an ICSP header, and a reset button.

RFID-RC522

• An RFID reader/writer module that operates at 13.56 MHz
• It is used for contactless communication and can read and write to tags that are compatible with the Near Field Communication (NFC) standard.

LCD Display 16x4 I2C

• A 16-character, 4-line liquid crystal display with an I2C interface
• It is used to display messages to the user, such as "Place card/tag," "Access Granted," or "Access Denied."

LED: Two Pin (green)

• A basic green LED for visual indication
• It lights up to indicate that access has been granted.

LED: Two Pin (red)

• A basic red LED for visual indication
• It lights up to indicate that access has been denied.

Resistor (220 Ohms)

• Two resistors with a resistance of 220 Ohms
• They are used to limit the current through the LEDs to protect them from damage.

Servomotor SG90

• A small and lightweight servo motor
• It is used to actuate the locking mechanism of the access control system.

Buzzer

• A simple piezoelectric buzzer
• It can be used to provide audible feedback, although it is not utilized in the provided code.

Wiring Details

Arduino UNO

• D5 connected to the anode of the red LED
• 3.3V supplies power to the RFID-RC522 module
• 5V supplies power to the servo motor and the LCD display
• GND is a common ground for the servo motor, RFID-RC522, LCD display, and both LEDs
• D6 connected to the anode of the green LED
• D9 connected to the RST pin of the RFID-RC522
• D12 connected to the MISO pin of the RFID-RC522
• D11 connected to the MOSI pin of the RFID-RC522
• D13 connected to the SCK pin of the RFID-RC522
• D10 connected to the SDA pin of the RFID-RC522
• A4 connected to the SDA pin of the LCD display
• A5 connected to the SCL pin of the LCD display
• D7 connected to the buzzer (not used in the code)
• D3 connected to the SIG pin of the servo motor

RFID-RC522

• VCC (3.3V) receives power from the Arduino's 3.3V pin
• RST connected to D9 on the Arduino
• GND connected to the common ground
• IRQ not connected
• MISO connected to D12 on the Arduino
• MOSI connected to D11 on the Arduino
• SCK connected to D13 on the Arduino
• SDA connected to D10 on the Arduino

LCD Display 16x4 I2C

• SCL connected to A5 on the Arduino
• SDA connected to A4 on the Arduino
• VCC receives power from the Arduino's 5V pin
• GND connected to the common ground

LED: Two Pin (green)

• anode connected to D6 on the Arduino
• cathode connected to one of the 220 Ohm resistors

LED: Two Pin (red)

• anode connected to D5 on the Arduino
• cathode connected to the other 220 Ohm resistor

Resistor (220 Ohms)

• One resistor connected between the cathode of the green LED and ground
• Another resistor connected between the cathode of the red LED and ground

Servomotor SG90

• SIG connected to D3 on the Arduino
• VCC receives power from the Arduino's 5V pin
• GND connected to the common ground

Buzzer

• PIN connected to D7 on the Arduino (not used in the code)
• GND connected to the common ground

Documented Code

#include <SPI.h>
#include <RFID.h>
#include <Servo.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

RFID rfid(10, 9);       // D10:pin of tag reader SDA. D9:pin of tag reader RST
unsigned char status;
unsigned char str[MAX_LEN]; // MAX_LEN is 16: size of the array

String accessGranted[2] = {"4121241702", "153310137212"};  // RFID serial numbers to grant access to
int accessGrantedSize = 2;                                // The number of serial numbers

Servo lockServo;                // Servo for locking mechanism
int lockPos = 15;               // Locked position limit
int unlockPos = 75;             // Unlocked position limit
boolean locked = true;

int redLEDPin = 5;
int greenLEDPin = 6;

// Initialize LCD with I2C address 0x27 (or check your display's address)
LiquidCrystal_I2C lcd(0x27, 16, 2);  // 16 characters, 2 lines

void setup() {
  Serial.begin(9600);     // Serial monitor is only required to get tag ID numbers and for troubleshooting
  SPI.begin();            // Start SPI communication with reader
  rfid.init();            // Initialization

  pinMode(redLEDPin, OUTPUT);     // LED startup sequence
  pinMode(greenLEDPin, OUTPUT);
  digitalWrite(redLEDPin, HIGH);
  delay(200);
  digitalWrite(greenLEDPin, HIGH);
  delay(200);
  digitalWrite(redLEDPin, LOW);
  delay(200);
  digitalWrite(greenLEDPin, LOW);
  lockServo.attach(3);
  lockServo.write(lockPos);         // Move servo into locked position

  // Initialize the LCD
  lcd.init();
  lcd.backlight();  // Turn on the backlight
  lcd.setCursor(0, 0);
  lcd.print("Place card/tag");

  Serial.println("Place card/tag near reader...");
}

void loop() {
  if (rfid.findCard(PICC_REQIDL, str) == MI_OK) { // Wait for a tag to be placed near the reader
    Serial.println("Card found");
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Card found");

    String temp = "";                             // Temporary variable to store the read RFID number
    if (rfid.anticoll(str) == MI_OK) {           // Anti-collision detection, read tag serial number
      Serial.print("The card's ID number is : ");
      lcd.setCursor(0, 1);  // Move to the second row
      lcd.print("ID: ");
      for (int i = 0; i < 4; i++) {              // Record and display the tag serial number
        temp = temp + (0x0F & (str[i] >> 4));
        temp = temp + (0x0F & str[i]);
      }
      Serial.println(temp);
      lcd.print(temp);     // Display ID on the LCD
      checkAccess(temp);   // Check if the identified tag is allowed to open
    }
    rfid.selectTag(str); // Lock card to prevent a redundant read
  }
  rfid.halt();
}

void checkAccess(String temp) {  // Function to check if an identified tag is registered to allow access
  boolean granted = false;
  for (int i = 0; i <= (accessGrantedSize - 1); i++) {  // Runs through all tag ID numbers registered in the array
    if (accessGranted[i] == temp) {                      // If a tag is found, then open/close the lock
      Serial.println("Access Granted");
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("Access Granted");

      granted = true;
      if (locked == true) {          // If the lock is closed then open it
        lockServo.write(unlockPos);
        locked = false;
      } else if (locked == false) {  // If the lock is open then close it
        lockServo.write(lockPos);
        locked = true;
      }
      digitalWrite(greenLEDPin, HIGH);    // Green LED sequence
      delay(200);
      digitalWrite(greenLEDPin, LOW);