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ESP32 - RFID/NFC - Relay
This tutorial instructs you how to use ESP32, RFID/NFC and relay. In detail, we will learn how to activate a relay when an anthorized RFID/NFC tag is tapped on RFID reader.
This tutorial can be extended by connecting the relay to an electromagnetic lock, actuator...
Hardware Used In This Tutorial
| 1 | × | ESP-WROOM-32 Dev Module | |
| 1 | × | Micro USB Cable | |
| 1 | × | RFID/NFC RC522 Kit (reader + tags) | |
| 1 | × | Relay | |
| 10 | × | Jumper Wires |
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Introduction to RFID/NFC RC522 Module and Relay
We have specific tutorials about RFID/NFC RC522 Module and relay. Each tutorial contains detailed information and step-by-step instructions about hardware pinout, working principle, wiring connection to ESP32, ESP32 code... Learn more about them at the following links:
How RC522 Module Works
- Several authorized UIDs of RFID/NFC tags are predefined in ESP32 code
- When an RFID/NFC tag is tapped on a RFID/NFC reader
- ESP32 read the UID from the RFID/NFC reader
- ESP32 looks for the read UID in the predefined UIDs list
- If the predefined UIDs list contains the read UID, ESP32 activates the relay.
Wiring Diagram
This image is created using Fritzing. Click to enlarge image
ESP32 Code - Single RFID/NFC Tag
/*
* This ESP32 code is created by esp32io.com
*
* This ESP32 code is released in the public domain
*
* For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-rfid-nfc-relay
*/
#include <SPI.h>
#include <MFRC522.h>
#define SS_PIN 5 // ESP32 pin GIOP5
#define RST_PIN 27 // ESP32 pin GIOP27
#define RELAY_PIN 22 // ESP32 pin GIOP22 connects to relay
MFRC522 rfid(SS_PIN, RST_PIN);
byte authorizedUID[4] = {0xFF, 0xFF, 0xFF, 0xFF};
void setup() {
Serial.begin(9600);
SPI.begin(); // init SPI bus
rfid.PCD_Init(); // init MFRC522
pinMode(RELAY_PIN, OUTPUT); // initialize pin as an output.
digitalWrite(RELAY_PIN, LOW); // deactivate the relay
Serial.println("Tap an RFID/NFC tag on the RFID-RC522 reader");
}
void loop() {
if (rfid.PICC_IsNewCardPresent()) { // new tag is available
if (rfid.PICC_ReadCardSerial()) { // NUID has been readed
MFRC522::PICC_Type piccType = rfid.PICC_GetType(rfid.uid.sak);
if (rfid.uid.uidByte[0] == authorizedUID[0] &&
rfid.uid.uidByte[1] == authorizedUID[1] &&
rfid.uid.uidByte[2] == authorizedUID[2] &&
rfid.uid.uidByte[3] == authorizedUID[3] ) {
Serial.println("Authorized Tag");
digitalWrite(RELAY_PIN, HIGH); // activate the relay for 2 seconds
delay(2000);
digitalWrite(RELAY_PIN, LOW); // deactivate the relay
}
else
{
Serial.print("Unauthorized Tag with UID:");
for (int i = 0; i < rfid.uid.size; i++) {
Serial.print(rfid.uid.uidByte[i] < 0x10 ? " 0" : " ");
Serial.print(rfid.uid.uidByte[i], HEX);
}
Serial.println();
}
rfid.PICC_HaltA(); // halt PICC
rfid.PCD_StopCrypto1(); // stop encryption on PCD
}
}
}
Quick Instructions
- If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
- On Arduino IDE, Navigate to Tools Manage Libraries
- Type “MFRC522” on the search box, then look for the library by GithubCommunity
- Install the library by clicking on Install button.
- Find out the tag's UID by doing the following steps:
- Copy the above code and paste it to Arduino IDE.
- Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
- Open Serial Monitor on Arduino IDE
- Tap an RFID/NFC tag that you want to give authorization on RFID-RC522 reader
- Write down the UID printed on Serial Monitor
COM6
Tap an RFID/NFC tag on the RFID-RC522 reader
Unauthorized Tag with UID: 2B B8 59 B1
Autoscroll
Clear output
9600 baud
Newline
- Update the UID in the line 18 of the above code. For example, change byte authorizedUID[4] = {0xFF, 0xFF, 0xFF, 0xFF}; TO byte authorizedUID[4] = {0x2B, 0xB8, 0x59, 0xB1};
- Upload the code to ESP32 again
- Tap the authorized RFID/NFC tag on RFID-RC522 module
- See the result on Serial Monitor
- Tap an unauthorized RFID/NFC tag on RFID-RC522 module
- See the result on Serial Monitor
COM6
Tap an RFID/NFC tag on the RFID-RC522 reader
Authorized Tag
Autoscroll
Clear output
9600 baud
Newline
COM6
Tap an RFID/NFC tag on the RFID-RC522 reader
Authorized Tag
Unauthorized Tag with UID: 1C 2A 52 E3
Autoscroll
Clear output
9600 baud
Newline
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