Arduino Project
RFID Access4.0
Course Introduction
In this lesson, we’ll build a 4.0 access-control system using the MFRC522 module, leds, a digital servo motor, and gas sensor module.
Note
If this is your first time working with an Arduino project, we recommend downloading and reviewing the basic materials first.
1.1 Install Arduino IDE(Important)
1.2 Introduction of Arduino IDE
Required Components
In this project, we need the following components:
Wiring
Common Connections:
MFRC522 Module
IRQ: Connect to 7 on the Arduino.
SDA: Connect to 6 on the Arduino.
SCK: Connect to 5 on the Arduino.
MOSI: Connect to 4 on the Arduino.
MISO: Connect to 3 on the Arduino.
GND: Connect to breadboard’s negative power bus.
RST: Connect to 2 on the Arduino.
3.3V: Connect to breadboard’s passive power bus.
MQ-2 Gas Sensor Module
A0: Connect to A0 on the Arduino.
GND: Connect to breadboard’s negative power bus.
VCC: Connect to breadboard’s red power bus.
LED
Connect the LEDs cathode to the negative power bus on the breadboard, and the LEDs anode to 1kΩ resistor then to 11 on the Arduino.
Digital Servo Motor
Connect to breadboard’s positive power bus.
Connect to breadboard’s negative power bus.
Connect to 9 on the Arduino.
Writing the Code
Note
You can copy this code into Arduino IDE.
The RFID1 library is used here. You can click here RFID1.zip to download it.
Don’t forget to select the board(Arduino UNO R4 WIFI) and the correct port before clicking the Upload button.
#include // Library for RFID reader
#include // Library for servo motor
#define ID_LEN 4
RFID1 rfid;
Servo myServo;
// Pin setup
const int servoPin = 9;
const int ledPin = 11;
const int smokePin = A0;
// Your RFID card UID
uchar userId[ID_LEN] = {0x36, 0xE2, 0xC4, 0xF7};
uchar userIdRead[ID_LEN];
// Smoke threshold (>200 = danger)
const int smokeThreshold = 200;
// State flags
bool smokeAlert = false;
bool smokeRecovering = false;
unsigned long smokeRecoverStart = 0;
bool cardAction = false; // Door opened by valid card
unsigned long cardTimer = 0;
int targetPos = 0; // Target position for servo
int currentPos = 0; // Current position for servo
// Set target angle for servo
void setServoAngle(int angle) {
targetPos = constrain(angle, 0, 90);
}
// Move servo smoothly (non-blocking)
void servoSmoothRun() {
static unsigned long lastStep = 0;
if (millis() - lastStep >= 15) {
lastStep = millis();
if (currentPos < targetPos) currentPos++;
else if (currentPos > targetPos) currentPos--;
myServo.write(currentPos);
}
}
// Blink LED without delay()
void ledBlinkNonBlock() {
static unsigned long lastBlink = 0;
static bool ledState = false;
if (millis() - lastBlink >= 120) {
lastBlink = millis();
ledState = !ledState;
digitalWrite(ledPin, ledState);
}
}
// Read UID from RFID card
void getId() {
uchar status, str[MAX_LEN];
status = rfid.anticoll(str);
if (status == MI_OK) {
for (int i = 0; i < ID_LEN; i++) userIdRead[i] = str[i];
rfid.halt();
}
}
// Compare UID with stored valid UID
bool idVerify() {
for (int i = 0; i < ID_LEN; i++)
if (userIdRead[i] != userId[i]) return false;
return true;
}
// Clear UID buffer
void clearBuffer() {
for (int i = 0; i < ID_LEN; i++) userIdRead[i] = 0;
}
// LED blink for invalid card
void denyAccessBlink() {
for (int i = 0; i < 4; i++) {
digitalWrite(ledPin, HIGH); delay(200);
digitalWrite(ledPin, LOW); delay(200);
}
digitalWrite(ledPin, HIGH);
}
// Setup runs once
void setup() {
rfid.begin(7, 5, 4, 3, 6, 2);
rfid.init();
pinMode(ledPin, OUTPUT);
myServo.attach(servoPin);
myServo.write(0);
currentPos = 0;
targetPos = 0;
digitalWrite(ledPin, HIGH);
}
// Main loop runs repeatedly
void loop() {
// Valid card opening (smooth + wait 1s)
if (cardAction) {
if (currentPos < 90) {
servoSmoothRun();
return;
}
if (cardTimer == 0) {
cardTimer = millis();
}
if (millis() - cardTimer >= 1000) {
setServoAngle(0);
cardAction = false;
cardTimer = 0;
digitalWrite(ledPin, HIGH);
}
servoSmoothRun();
return;
}
// Smoke detection logic
int smokeVal = analogRead(smokePin);
bool allowRFID = false;
if (smokeVal > smokeThreshold) { // Danger smoke
smokeAlert = true;
smokeRecovering = false;
setServoAngle(90);
ledBlinkNonBlock();
allowRFID = false;
}
else if (smokeVal > 50) { // Light smoke
ledBlinkNonBlock();
allowRFID = false;
}
else { // No smoke
if (smokeAlert) {
if (!smokeRecovering) {
smokeRecovering = true;
smokeRecoverStart = millis();
}
if (millis() - smokeRecoverStart < 1000) {
ledBlinkNonBlock();
allowRFID = false;
} else {
smokeAlert = false;
smokeRecovering = false;
setServoAngle(0);
digitalWrite(ledPin, HIGH);
allowRFID = true;
}
} else {
digitalWrite(ledPin, HIGH);
allowRFID = true;
}
}
// RFID scanning if safe
if (allowRFID) {
uchar status, str[MAX_LEN];
status = rfid.request(PICC_REQIDL, str);
if (status == MI_OK) {
getId();
if (idVerify()) {
setServoAngle(90);
cardAction = true;
cardTimer = 0;
digitalWrite(ledPin, LOW);
} else {
denyAccessBlink();
}
clearBuffer();
}
}
// Keep servo moving
servoSmoothRun();
}