This tutorial instructs you how to use an RFID/NFC tag to trigger a relay with the help of ESP8266. You can further expand upon this tutorial by using the relay to control motors, actuators, and more.
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Overview of RFID/NFC RC522 Module and Relay
If you are not familiar with the RFID/NFC RC522 Module and relay (including pinout, functionality, and programming), then check out the following tutorials:
The sequence of pins may differ depending on the manufacturer. ALWAYS use the labels printed on the module. The image above displays the pinout of modules from DIYables producer.
ESP8266 Code - Single RFID/NFC Tag
/* * This ESP8266 NodeMCU code was developed by newbiely.com * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp8266/esp8266-rfid-relay */#include <SPI.h>#include <MFRC522.h>#define SS_PIN D8 // The ESP8266 pin D8#define RST_PIN D2 // The ESP8266 pin D2#define RELAY_PIN D1 // The ESP8266 pin connects to relayMFRC522 rfid(SS_PIN, RST_PIN);byte authorizedUID[4] = {0xFF, 0xFF, 0xFF, 0xFF};voidsetup() {Serial.begin(9600);SPI.begin(); // init SPI bus rfid.PCD_Init(); // init MFRC522pinMode(RELAY_PIN, OUTPUT); // initialize pin as an output.digitalWrite(RELAY_PIN, LOW); // deactivate the relaySerial.println("Tap an RFID/NFC tag on the RFID-RC522 reader");}voidloop() {if (rfid.PICC_IsNewCardPresent()) { // new tag is availableif (rfid.PICC_ReadCardSerial()) { // NUID has been readedMFRC522::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 secondsdelay(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 } }}
Detailed Instructions
To get started with ESP8266 on Arduino IDE, follow these steps:
Connect the ESP8266 board to your computer using a USB cable.
Open Arduino IDE on your computer.
Choose the correct ESP8266 board, such as (e.g. NodeMCU 1.0 (ESP-12E Module)), and its respective COM port.
In order to discover the UID of an RFID/NFC tag, the first step is to copy the code and open it with Arduino IDE. After that, click the Upload button on the Arduino IDE to upload the code to the ESP8266. Then, open the Serial Monitor and tap the RFID/NFC tag on the RFID-RC522 module. Finally, the UID will be displayed on the Serial Monitor.
Newbiely | Arduino IDE 2.3.8
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File
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Nodemcu 1.0 (ESP-12E Module)
Newbiely.ino
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8Serial.println("Hello World!");
Output
Serial Monitor
Message (Enter to send message to 'Nodemcu 1.0 (ESP-12E Module)' on 'COM15')
New Line
9600 baud
Tap RFID/NFC tag on reader
Unauthorized Tag with UID: 3A C9 6A CB
Ln 11, Col 1
Nodemcu 1.0 (ESP-12E Module) on COM15
2
After obtaining the UID:
Replace the value of byte authorizedUID[4] = {0xFF, 0xFF, 0xFF, 0xFF}; with the UID in line 18 of the code. For example, byte authorizedUID[4] = {0x3A, 0xC9, 0x6A, 0xCB};
Upload the code to ESP8266 again
Tap an RFID/NFC tag on the RFID-RC522 module
Check out the output on the Serial Monitor
Newbiely | Arduino IDE 2.3.8
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File
Edit
Sketch
Tools
Help
Nodemcu 1.0 (ESP-12E Module)
Newbiely.ino
···
8Serial.println("Hello World!");
Output
Serial Monitor
Message (Enter to send message to 'Nodemcu 1.0 (ESP-12E Module)' on 'COM15')
New Line
9600 baud
Tap RFID/NFC tag on reader
Authorized Tag
Ln 11, Col 1
Nodemcu 1.0 (ESP-12E Module) on COM15
2
Tap a different RFID/NFC tag on the RFID-RC522 module.
Check the output on the Serial Monitor.
Newbiely | Arduino IDE 2.3.8
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File
Edit
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Tools
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Nodemcu 1.0 (ESP-12E Module)
Newbiely.ino
···
8Serial.println("Hello World!");
Output
Serial Monitor
Message (Enter to send message to 'Nodemcu 1.0 (ESP-12E Module)' on 'COM15')
New Line
9600 baud
Tap RFID/NFC tag on reader
Authorized Tag
Unauthorized Tag with UID: BD 1E 1D 00
Ln 11, Col 1
Nodemcu 1.0 (ESP-12E Module) on COM15
2
※ NOTE THAT:
To facilitate testing, the active time is set to two seconds, however it should be increased for practical use/demonstration.
We can enable the relay to be activated by multiple RFID/NFC tags. As an illustration, the code below uses two tags.
/* * This ESP8266 NodeMCU code was developed by newbiely.com * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp8266/esp8266-rfid-relay */#include <SPI.h>#include <MFRC522.h>#define SS_PIN D8 // The ESP8266 pin D8#define RST_PIN D2 // The ESP8266 pin D2#define RELAY_PIN D1 // The ESP8266 pin connects to relayMFRC522 rfid(SS_PIN, RST_PIN);byte authorizedUID1[4] = {0x3A, 0xC9, 0x6A, 0xCB};byte authorizedUID2[4] = {0x30, 0x01, 0x8B, 0x15}; voidsetup() {Serial.begin(9600);SPI.begin(); // init SPI bus rfid.PCD_Init(); // init MFRC522pinMode(RELAY_PIN, OUTPUT); // initialize pin as an output.digitalWrite(RELAY_PIN, LOW); // deactivate the relaySerial.println("Tap an RFID/NFC tag on the RFID-RC522 reader");}voidloop() {if (rfid.PICC_IsNewCardPresent()) { // new tag is availableif (rfid.PICC_ReadCardSerial()) { // NUID has been readedMFRC522::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); // activate the relay for 2 secondsdelay(2000);digitalWrite(RELAY_PIN, LOW); // deactivate the relay }elseif (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); // activate the relay for 2 secondsdelay(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 } }}
Repeat the same steps as before, and then press each tag on the RFID-RC522 module. The output on the Serial Monitor will be similar to the following:
Newbiely | Arduino IDE 2.3.8
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☐
✕
File
Edit
Sketch
Tools
Help
Nodemcu 1.0 (ESP-12E Module)
Newbiely.ino
···
8Serial.println("Hello World!");
Output
Serial Monitor
Message (Enter to send message to 'Nodemcu 1.0 (ESP-12E Module)' on 'COM15')
New Line
9600 baud
Tap RFID/NFC tag on reader
Authorized Tag 2
Authorized Tag 1
Ln 11, Col 1
Nodemcu 1.0 (ESP-12E Module) on COM15
2
You can expand the code mentioned above for three, four, or more tags.
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