Circuit Documentation

Summary of the Circuit

This circuit integrates an ESP32 microcontroller with an RFID-RC522 reader and a 12V single-channel relay. The ESP32 is responsible for controlling the RFID reader to scan for RFID tags and, upon successful detection of a valid tag, activating the relay. The relay can be used to control a higher power device, such as turning on a light or triggering a motor. The circuit is powered by the ESP32, which also communicates with the RFID reader via SPI protocol.

Component List

ESP32 (30 pin)

• Description: A microcontroller with WiFi and Bluetooth capabilities, featuring a wide range of GPIO pins.
• Purpose: Acts as the central processing unit of the circuit, reads RFID tags, and controls the relay.

RFID-RC522

• Description: An RFID reader/writer module that operates at 13.56 MHz.
• Purpose: To read RFID tags and communicate the tag information to the ESP32.

12V SINGLE CHANNEL RELAY

• Description: An electromechanical switch that allows the ESP32 to control high power devices.
• Purpose: To switch on/off devices in response to RFID tag detection.

Wiring Details

ESP32 (30 pin)

• D26: Connected to the relay module's IN pin to control the relay.
• D27: Connected to the RFID-RC522's RST pin.
• GND: Common ground with RFID-RC522 and the relay module.
• D23: Connected to the RFID-RC522's MOSI pin.
• D19: Connected to the RFID-RC522's MISO pin.
• D18: Connected to the RFID-RC522's SCK pin.
• D5: Connected to the RFID-RC522's SDA pin.
• 3V3: Powers the RFID-RC522 and the relay module.

RFID-RC522

• RST: Connected to the ESP32's D27 pin.
• GND: Common ground with ESP32 and the relay module.
• MOSI: Connected to the ESP32's D23 pin.
• MISO: Connected to the ESP32's D19 pin.
• SCK: Connected to the ESP32's D18 pin.
• SDA: Connected to the ESP32's D5 pin.
• VCC (3.3V): Powered by the ESP32's 3V3 pin.

12V SINGLE CHANNEL RELAY

• IN: Controlled by the ESP32's D26 pin.
• GND: Common ground with ESP32 and the RFID-RC522.
• VCC: Powered by the ESP32's 3V3 pin.

Documented Code

/*
 * ESP32 with Relay and RFID-RC522
 * This code initializes the RFID-RC522 module and reads RFID tags.
 * When a valid RFID tag is detected, it activates a relay connected to the ESP32.
 */

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

#define RST_PIN 27 // ESP32 pin connected to RFID RST
#define SS_PIN 5   // ESP32 pin connected to RFID SDA
#define RELAY_PIN 26 // ESP32 pin connected to Relay IN

MFRC522 rfid(SS_PIN, RST_PIN); // Create MFRC522 instance

void setup() {
  Serial.begin(115200);
  SPI.begin(); // Init SPI bus
  rfid.PCD_Init(); // Init MFRC522
  pinMode(RELAY_PIN, OUTPUT);
  digitalWrite(RELAY_PIN, LOW); // Ensure relay is off
  Serial.println("RFID Reader and Relay Initialized");
}

void loop() {
  // Look for new cards
  if (!rfid.PICC_IsNewCardPresent() || !rfid.PICC_ReadCardSerial()) {
    delay(50);
    return;
  }

  Serial.print("Card UID:");
  for (byte i = 0; i < rfid.uid.size; i++) {
    Serial.print(rfid.uid.uidByte[i] < 0x10 ? " 0" : " ");
    Serial.print(rfid.uid.uidByte[i], HEX);
  }
  Serial.println();

  // Activate relay for 5 seconds
  digitalWrite(RELAY_PIN, HIGH);
  delay(5000);
  digitalWrite(RELAY_PIN, LOW);

  // Halt PICC
  rfid.PICC_HaltA();
  // Stop encryption on PCD
  rfid.PCD_StopCrypto1();
}

This code is designed to be uploaded to the ESP32 microcontroller. It initializes the RFID-RC522 module and sets up the relay pin as an output. In the main loop, it continuously checks for new RFID cards. When a card is detected, it prints the card's UID to the serial monitor and activates the relay for 5 seconds.