Circuit Documentation

Summary of the Circuit

This circuit is designed to interface an Arduino UNO with an RFID-RC522 module, a 20x4 LCD display with I2C interface, and a Servomotor SG90. The Arduino UNO acts as the central processing unit, controlling the RFID reader for scanning tags, displaying information on the LCD, and driving the servomotor based on the RFID tags detected. The RFID-RC522 module is used for reading RFID tags, the LCD display shows the scanned tag's UID, and the servomotor is potentially used for a physical response, such as unlocking a mechanism.

Component List

Arduino UNO

• Microcontroller board based on the ATmega328P
• Provides digital I/O pins, analog inputs, and various power outputs
• Interfaces with other components via SPI and I2C protocols

LCD Display 20x4 I2C

• Alphanumeric liquid crystal display
• 20 characters by 4 lines display area
• I2C interface for communication, reducing the number of pins required for interfacing

RFID-RC522

• RFID reader/writer module
• Operates at 13.56 MHz for Near Field Communication (NFC)
• Interfaces with the Arduino UNO via SPI

Servomotor SG90

• Small and lightweight servo motor
• Provides precise control of angular position
• Powered directly from the Arduino UNO

Wiring Details

Arduino UNO

• D10 connected to RFID-RC522 SDA
• D13 connected to RFID-RC522 SCK
• D11 connected to RFID-RC522 MOSI
• D12 connected to RFID-RC522 MISO
• GND connected to GND of all components
• D9 connected to RFID-RC522 RST
• 3.3V connected to RFID-RC522 3.3V
• 5V connected to Servomotor SG90 VCC and LCD Display VCC
• A4 connected to LCD Display SDA
• A5 connected to LCD Display SCL
• D3 connected to Servomotor SG90 SIG

LCD Display 20x4 I2C

• SDA connected to Arduino UNO A4
• SCL connected to Arduino UNO A5
• VCC connected to Arduino UNO 5V
• GND connected to Arduino UNO GND

RFID-RC522

• SDA connected to Arduino UNO D10
• SCK connected to Arduino UNO D13
• MOSI connected to Arduino UNO D11
• MISO connected to Arduino UNO D12
• IRQ not connected
• GND connected to Arduino UNO GND
• RST connected to Arduino UNO D9
• 3.3V connected to Arduino UNO 3.3V

Servomotor SG90

• SIG connected to Arduino UNO D3
• VCC connected to Arduino UNO 5V
• GND connected to Arduino UNO GND

Documented Code

/*RFID tag scan code
 * https://srituhobby.com
 */
 
#include <LiquidCrystal_I2C.h>
#include <SPI.h>
#include <MFRC522.h>

#define RST_PIN 9
#define SS_PIN  10
byte readCard[4];
byte a = 0;

LiquidCrystal_I2C lcd(0x27, 16, 2);
MFRC522 mfrc522(SS_PIN, RST_PIN);

void setup() {
  Serial.begin(9600);
  lcd.init();
  lcd.backlight();
  while (!Serial);
  SPI.begin();
  mfrc522.PCD_Init();
  delay(4);
  mfrc522.PCD_DumpVersionToSerial();
  lcd.setCursor(2, 0);
  lcd.print("Put your card");
}

void loop() {
  if ( ! mfrc522.PICC_IsNewCardPresent()) {
    return 0;
  }
  if ( ! mfrc522.PICC_ReadCardSerial()) {
    return 0;
  }

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Scanned UID");
  a = 0;
  Serial.println(F("Scanned PICC's UID:"));
  for ( uint8_t i = 0; i < 4; i++) {  //
    readCard[i] = mfrc522.uid.uidByte[i];
    Serial.print(readCard[i], HEX);
    Serial.print(" ");
    lcd.setCursor(a, 1);
    lcd.print(readCard[i], HEX);
    lcd.print(" ");
    delay(500);
    a += 3;
  }
  Serial.println("");
  mfrc522.PICC_HaltA();
  return 1;
}

The code provided is for the Arduino UNO and is responsible for initializing the RFID-RC522 module and the LCD display. It continuously checks for new RFID tags. When a tag is detected, it reads the UID and displays it on the LCD. The code also sends the UID to the serial monitor for debugging purposes.