ESP32 - RFID/NFC - Relay
In this tutorial, we are going to learn how to use RFID/NFC tag to activate relay using ESP32. You can extend this tutorial by using the relay to control motor, actuator...
| 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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If you do not have knowledge of RFID/NFC RC522 Module and relay (pinout, how they work, how to connect them to ESP32, how to program for them...), learn about them in the following tutorials:
The UIDs of some RFID/NFC tags are preset in ESP32 code
User taps an RFID/NFC tag on RFID/NFC reader
The reader reads UID from the tag.
ESP32 gets the UID from the reader
ESP32 compares the read UID with the predefined UIDs
If the UID is matched with one of the predefined UIDs, ESP32 activates the relay.
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#include <SPI.h>
#include <MFRC522.h>
#define SS_PIN 5
#define RST_PIN 27
#define RELAY_PIN 22
MFRC522 rfid(SS_PIN, RST_PIN);
byte authorizedUID[4] = {0xFF, 0xFF, 0xFF, 0xFF};
void setup() {
Serial.begin(9600);
SPI.begin();
rfid.PCD_Init();
pinMode(RELAY_PIN, OUTPUT);
digitalWrite(RELAY_PIN, LOW);
Serial.println("Tap RFID/NFC Tag on reader");
}
void loop() {
if (rfid.PICC_IsNewCardPresent()) {
if (rfid.PICC_ReadCardSerial()) {
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);
delay(2000);
digitalWrite(RELAY_PIN, LOW);
}
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();
rfid.PCD_StopCrypto1();
}
}
}
Because UID is usually not printed on RFID/NFC tag, The first step we need to do is to find out the tag's UID. This can be done by:
Copy the above code and paste it to Arduino IDE
Click Upload button on Arduino IDE to compile and upload code to ESP32 board
Open Serial Monitor on Arduino IDE
Tap an RFID/NFC tag on RFID-RC522 module
Get UID on Serial Monitor
Tap RFID/NFC tag on reader
Unauthorized Tag with UID: 3A C9 6A CB
After having UID:
Update UID in the line 18 of the above code. For example, change byte authorizedUID[4] = {0xFF, 0xFF, 0xFF, 0xFF}; TO byte authorizedUID[4] = {0x3A, 0xC9, 0x6A, 0xCB};
Upload the code to ESP32 again
Tap an RFID/NFC tag on RFID-RC522 module
See output on Serial Monitor
Tap RFID/NFC tag on reader
Authorized Tag
Tap another RFID/NFC tag on RFID-RC522 module
See output on Serial Monitor
Tap RFID/NFC tag on reader
Authorized Tag
Unauthorized Tag with UID: BD 1E 1D 00
We can allow multiple RFID/NFC tags to activate the relay. The below code uses two tags as an example.
#include <SPI.h>
#include <MFRC522.h>
#define SS_PIN 5
#define RST_PIN 27
#define RELAY_PIN 22
MFRC522 rfid(SS_PIN, RST_PIN);
byte authorizedUID1[4] = {0x3A, 0xC9, 0x6A, 0xCB};
byte authorizedUID2[4] = {0x30, 0x01, 0x8B, 0x15};
void setup() {
Serial.begin(9600);
SPI.begin();
rfid.PCD_Init();
pinMode(RELAY_PIN, OUTPUT);
digitalWrite(RELAY_PIN, LOW);
Serial.println("Tap RFID/NFC Tag on reader");
}
void loop() {
if (rfid.PICC_IsNewCardPresent()) {
if (rfid.PICC_ReadCardSerial()) {
MFRC522::PICC_Type piccType = rfid.PICC_GetType(rfid.uid.sak);
if (rfid.uid.uidByte[0] == authorizedUID1[0] &&
rfid.uid.uidByte[1] == authorizedUID1[1] &&
rfid.uid.uidByte[2] == authorizedUID1[2] &&
rfid.uid.uidByte[3] == authorizedUID1[3] ) {
Serial.println("Authorized Tag 1");
digitalWrite(RELAY_PIN, HIGH);
delay(2000);
digitalWrite(RELAY_PIN, LOW);
}
else
if (rfid.uid.uidByte[0] == authorizedUID2[0] &&
rfid.uid.uidByte[1] == authorizedUID2[1] &&
rfid.uid.uidByte[2] == authorizedUID2[2] &&
rfid.uid.uidByte[3] == authorizedUID2[3] ) {
Serial.println("Authorized Tag 2");
digitalWrite(RELAY_PIN, HIGH);
delay(2000);
digitalWrite(RELAY_PIN, LOW);
}
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();
rfid.PCD_StopCrypto1();
}
}
}
Do the similar steps as the above, and then tap one by one tag on RFID-RC522 module. The result on Serial Monitor looks like below:
Tap RFID/NFC tag on reader
Authorized Tag 2
Authorized Tag 1
You can extend the above code for three, four, or more tags.
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