Circuit Documentation

Summary

The circuit in question is designed to interface an Arduino Nano with an RFID-RC522 module, a Tower Pro SG90 servo motor, a piezo buzzer, and a green LED. The purpose of the circuit is to detect RFID tags, actuate a servo, and provide audio-visual feedback upon successful tag detection. The Arduino Nano serves as the central processing unit, controlling the RFID reader for tag detection, driving the servo motor to a specific position, and triggering the buzzer and LED to indicate the detection event.

Component List

Arduino Nano

• Microcontroller board based on the ATmega328P
• It has a variety of digital and analog I/O pins
• Capable of serial communication, SPI, and I2C

RFID-RC522

• RFID reader/writer module
• Operates at 13.56 MHz for communication with RFID tags
• Interfaces with the Arduino via SPI

Tower Pro SG90 Servo

• Small and lightweight servo motor
• Capable of precise angular positioning
• Controlled by PWM signal

Piezo Buzzer

• Simple electronic device that produces sound
• Used to provide audio feedback

LED: Two Pin (green)

• Basic green LED
• Used for visual indication

Wiring Details

Arduino Nano

• D7 connected to the cathode of the green LED and pin 1 of the piezo buzzer
• GND connected to the anode of the green LED, GND of the servo, and pin 2 of the piezo buzzer
• D3 connected to the signal pin of the servo
• 5V connected to the +5V of the servo
• 3V3 connected to the 3.3V of the RFID-RC522
• D9 connected to the RST pin of the RFID-RC522
• D10 connected to the SDA pin of the RFID-RC522
• D11/MOSI connected to the MOSI pin of the RFID-RC522
• D12/MISO connected to the MISO pin of the RFID-RC522
• D13/SCK connected to the SCK pin of the RFID-RC522

RFID-RC522

• 3.3V connected to 3V3 of the Arduino Nano
• GND connected to GND of the Arduino Nano
• RST connected to D9 of the Arduino Nano
• SDA connected to D10 of the Arduino Nano
• MOSI connected to D11/MOSI of the Arduino Nano
• MISO connected to D12/MISO of the Arduino Nano
• SCK connected to D13/SCK of the Arduino Nano

Tower Pro SG90 Servo

• Signal connected to D3 of the Arduino Nano
• +5V connected to 5V of the Arduino Nano
• GND connected to GND of the Arduino Nano

Piezo Buzzer

• pin 1 connected to D7 of the Arduino Nano
• pin 2 connected to GND of the Arduino Nano

LED: Two Pin (green)

• cathode connected to D7 of the Arduino Nano
• anode connected to GND of the Arduino Nano

Documented Code

#include <SPI.h>
#include <MFRC522.h>
#include <Servo.h>

#define SS_PIN 10
#define RST_PIN 9
MFRC522 rfid(SS_PIN, RST_PIN);

Servo myServo;
int buzzerPin = 7;

void setup() {
  Serial.begin(9600);
  SPI.begin();
  rfid.PCD_Init();
  
  myServo.attach(3);
  pinMode(buzzerPin, OUTPUT);

  Serial.println("Ready to Scan!");
}

void loop() {
  if (!rfid.PICC_IsNewCardPresent() || !rfid.PICC_ReadCardSerial()) {
    return;
  }

  Serial.println("Card detected!");
  
  String cardUID = "";
  for (byte i = 0; i < rfid.uid.size; i++) {
    cardUID += String(rfid.uid.uidByte[i], HEX);
  }

  Serial.print("DATA,TIME,");
  Serial.print(cardUID);
  Serial.println(",Accepted");

  digitalWrite(buzzerPin, HIGH);
  delay(100);
  digitalWrite(buzzerPin, LOW);

  myServo.write(90);
  delay(2000);
  myServo.write(0);

  rfid.PICC_HaltA();
}

Code Explanation

• The code begins by including the necessary libraries for SPI communication, RFID interaction, and servo control.
• Two constants SS_PIN and RST_PIN are defined for the RFID reader's slave select and reset pins.
• An MFRC522 object and a Servo object are instantiated.
• The buzzerPin is defined and set to digital pin 7 on the Arduino Nano.
• In the setup() function, serial communication is initiated, SPI is begun, and the RFID reader is initialized. The servo is attached to pin 3, and the buzzer pin is set as an output. A ready message is printed to the serial monitor.
• The loop() function continuously checks for new RFID cards. If a card is detected, its UID is read and printed to the serial monitor along with a timestamp and an "Accepted" message.
• The buzzer is briefly turned on to provide audio feedback, and the servo is actuated to move to 90 degrees, then back to 0 degrees after a delay.
• Finally, the RFID card reading is halted to prepare for the next card detection.