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Arduino - RFID/NFC Door Lock System

In this tutorial, we are going to learn how to make Arduino RFID/NFC Door Lock System using Arduino, RFID/NFC RC522 Kit, and electromagnetic lock or solenoid lock.

※ NOTE THAT:

We also have others Arduino - Door lock system using keypad tutorials.

Hardware Required

1	×	Arduino UNO or Genuino UNO
1	×	USB 2.0 cable type A/B
1	×	RFID/NFC RC522 Kit (reader + tags)
1	×	RFID Key Fob
1	×	RFID Card
1	×	Solenoid Lock
1	×	(Alternative) Electromagnetic Lock
1	×	Relay
1	×	12V Power Adapter
1	×	DC Power Jack
1	×	Jumper Wires
1	×	(Recommended) Screw Terminal Block Shield for Arduino Uno
1	×	(Recommended) Breadboard Shield For Arduino Uno
1	×	(Recommended) Enclosure For Arduino Uno

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

Please note: These are Amazon affiliate links. If you buy the components through these links, We will get a commission at no extra cost to you. We appreciate it.

About RFID/NFC RC522 Module and Electromagnetic Lock

If you do not know about RFID/NFC RC522 Module, Electromagnetic Lock and Solenoid Lock (pinout, how it works, how to program ...), learn about them in the following tutorials:

System Components

The door lock system includes two main parts:

Door Lock: Arduino + RFID/NFC reader + Electromagnetic lock
Door Key: RFID/NFC tags

Arduino arduino rfid door lock component

There are some types of RFID/NFC readers that can work with Arduino. This tutorial uses RFID-RC522 as an RFID/NFC reader because it is cheap.

How RFID/NFC Door Lock Works

Some tags that have UIDs set in Arduino code acts as the authorized keys
User taps an RFID/NFC tag on RFID/NFC reader
The reader reads UID from the tag.
Arduino gets the UID from the reader
Arduino compares the read UID with the predefined UIDs
If the UID is matched with one of the predefined UIDs, Arduino deactivates the electromagnetic lock to unlock the door.

Wiring Diagram

RFID RC522 Door Lock with Solenoid Lock

Arduino RFID RC522 Door Lock System wiring diagram

This image is created using Fritzing. Click to enlarge image

RFID RC522 Door Lock with Electromagnetic Lock

Arduino RFID RC522 Door Lock System wiring diagram

This image is created using Fritzing. Click to enlarge image

To make it simple, the RC522 module's pins are directly connected to the Arduino's pins. However, this may cause the Arduino to stop functioning properly in certain cases since the output pins of the Arduino produce 5V, whereas the pins of the RC522 module function normally at 3.3V. Therefore, it is recommended to regulate the voltage between the Arduino pins and the RC522 module's pins. For more detailed instructions, please refer to the Arduino - RFID RC522 tutorial. The diagram below illustrates how to regulate 5V to 3.3V using resistors:

Arduino RFID RC522 with voltage regulated wiring diagram

This image is created using Fritzing. Click to enlarge image

※ NOTE THAT:

The order of pins can vary according to manufacturers. ALWAYS use the labels printed on the module. The above image shows the pinout of the modules from DIYables manufacturer.

Arduino Code - Single Key

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-rfid-nfc-door-lock-system */ #include <SPI.h> #include <MFRC522.h> #define SS_PIN 10 #define RST_PIN 5 #define RELAY_PIN A5 // the Arduino pin connects to relay MFRC522 rfid(SS_PIN, RST_PIN); byte keyTagUID[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, HIGH); // lock the door Serial.println("Tap RFID/NFC Tag on 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] == keyTagUID[0] && rfid.uid.uidByte[1] == keyTagUID[1] && rfid.uid.uidByte[2] == keyTagUID[2] && rfid.uid.uidByte[3] == keyTagUID[3] ) { Serial.println("Access is granted"); digitalWrite(RELAY_PIN, LOW); // unlock the door for 2 seconds delay(2000); digitalWrite(RELAY_PIN, HIGH); // lock the door } else { Serial.print("Access denied for user 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 Steps

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 open with Arduino IDE
Click Upload button on Arduino IDE to upload code to Arduino
Open Serial Monitor
Tap an RFID/NFC tag on RFID-RC522 module
Get UID on Serial Monitor

COM6

Send

Tap RFID/NFC tag on reader Access denied for user with UID: 3A C9 6A CB

Autoscroll Show timestamp

Clear output

9600 baud

Newline

After having UID:

Update UID in the line 18 of the above code. For example, change byte keytagUID[4] = {0xFF, 0xFF, 0xFF, 0xFF}; TO byte keytagUID[4] = {0x3A, 0xC9, 0x6A, 0xCB};
Upload the code to Arduino again
Tap an RFID/NFC tag on RFID-RC522 module
See output on Serial Monitor

COM6

Send

Tap RFID/NFC tag on reader Access is granted

Autoscroll Show timestamp

Clear output

9600 baud

Newline

Check the electromagnetic lock, it should be unlocked
Tap another RFID/NFC tag on RFID-RC522 module
See output on Serial Monitor

COM6

Send

Tap RFID/NFC tag on reader Access is granted Access denied for user with UID: BD 1E 1D 00

Autoscroll Show timestamp

Clear output

9600 baud

Newline

※ NOTE THAT:

To make it easy to test, the unlocked time is set to 2 seconds, it should be increased in practical use/demonstration
It need to install MFRC522 library. See Arduino - RFID/NFC RC522 tutorial

Arduino Code - Multiple Keys

Let's imagine that a room allows the manager and secretary to unlock the door only.

In this case, we need to use two RFID/NFC tag: one for the manager and the other for the secretary. We have to specify the UIDs of two tags in the code

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-rfid-nfc-door-lock-system */ #include <SPI.h> #include <MFRC522.h> #define SS_PIN 10 #define RST_PIN 5 #define RELAY_PIN A5 // the Arduino pin connects to relay MFRC522 rfid(SS_PIN, RST_PIN); byte managerKeyUID[4] = {0x3A, 0xC9, 0x6A, 0xCB}; byte secretaryKeyUID[4] = {0x30, 0x01, 0x8B, 0x15}; 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, HIGH); // lock the door Serial.println("Tap RFID/NFC Tag on 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] == managerKeyUID[0] && rfid.uid.uidByte[1] == managerKeyUID[1] && rfid.uid.uidByte[2] == managerKeyUID[2] && rfid.uid.uidByte[3] == managerKeyUID[3] ) { Serial.println("Access is granted for manager"); digitalWrite(RELAY_PIN, LOW); // unlock the door for 2 seconds delay(2000); digitalWrite(RELAY_PIN, HIGH); // lock the door } else if (rfid.uid.uidByte[0] == secretaryKeyUID[0] && rfid.uid.uidByte[1] == secretaryKeyUID[1] && rfid.uid.uidByte[2] == secretaryKeyUID[2] && rfid.uid.uidByte[3] == secretaryKeyUID[3] ) { Serial.println("Access is granted for secretary"); digitalWrite(RELAY_PIN, LOW); // unlock the door for 2 seconds delay(2000); digitalWrite(RELAY_PIN, HIGH); // lock the door } else { Serial.print("Access denied for user 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 } } }

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:

COM6

Send

Tap RFID/NFC tag on reader Access is granted for secretary Access is granted for manager

Autoscroll Show timestamp

Clear output

9600 baud

Newline

You can extend the above code for three, four, or more tags.

※ NOTE THAT:

In the above code, the keys are hard-coded. In the practice, it should be able to add/delete keys dynamically via a special mode. If so, the keys should be saved on EEPROM memory. The number of keys can be saved depends on the EEPROM's size. The code will become complicated. If you want to build such system, we provide a coding service. Please feel free to contact us.

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