Let me tell you something:

Having a lock is a useful thing. And if it's made out of Arduino, then that's an even better thing. Let's get started.

Step 1: Building the lock

First I glued a cardboard strip on the lid of the box so when I put the lid back on

it was the bit in the box where the servo would hold. Then, I stuck the servo motor so that when it was at 90° angle, it would hold the cardboard and stop the box opening.

And it ended up like this:

Step 2: The circuit diagram

So the next step is connecting the Arduino. Connect the Arduino like this:

Step 3: Fix the Arduino on the box

I used sticky tape to fix the Arduino on the box.

Step 4: Upload the code

Don't forget to add the RFID Library to the Arduino IDE (you can find the library at the code bit of this tutorial).

Copy the code and paste it to your Arduino IDE and upload it.

Step 5: Done!

Then...you're done! If you have a question, I can answer it.

---

🛠️ เจาะลึกเบื้องหลังการทำงาน (Deep Dive / Technical Analysis)

A padlocked wooden box is instantly defeated via physical lockpicks. The RFID Servo Box utilizes completely invisible cybernetic security natively! Embedding an MFRC522 RFID Scanner explicitly entirely completely hidden directly behind a 1/4-inch piece of solid wood, the entire vault appears entirely seamless from the exterior! The cryptographic core executes a blazing fast 13.56MHz SPI continuous scan natively. The moment the administrator's exact embedded Keyfob UID is mathematically validated, the Arduino commands an internalized SG90 Micro-Servo to violently retract an aggressive physical locking bar, springing the heavy vault door completely open!

Demodulating MIFARE Classic Cryptography Arrays

A simple serial barcode scanner takes seconds. The MFRC522 is completely instantaneous and significantly more mathematically secure because the radio penetrates non-metallic objects perfectly!

1. The SPI Interface connects <SPI.h> explicitly via MOSI (11), MISO (12), SCK (13).
2. The user passes the plastic key exactly over the hidden zone. The MFRC522 blasts the silicon!
3. The board aggressively reads the absolute 4-Byte Hex UID array into a massive String object.
4. If the master <Servo.h> locks the UID perfectly, it moves seamlessly from Angle 90 to Angle 0 precisely!

#include <SPI.h>
#include <MFRC522.h>
#include <Servo.h>

#define SS_PIN 10
#define RST_PIN 9
MFRC522 rfid(SS_PIN, RST_PIN); 

Servo lockServo;
String MASTER_KEY = "E5 B2 C19A"; // Highly Specific UID Matrix!

boolean vaultOpen = false;

void setup() {
  SPI.begin();       // Initialize high-speed hardware SPI bus!
  rfid.PCD_Init(); // Fire the MFRC522 Antenna arrays violently!
  lockServo.attach(8);
  lockServo.write(90); // SECURE LOCKDOWN STATE INITIALIZED!
}

void loop() {
  if ( ! rfid.PICC_IsNewCardPresent() || ! rfid.PICC_ReadCardSerial() ) return;

  // Compile the encrypted HEX string natively!
  String uidStr = "";
  for (byte i = 0; i < rfid.uid.size; i++) {
    uidStr += String(rfid.uid.uidByte[i], HEX);
  }
  uidStr.toUpperCase(); // Force the string securely strictly to Caps!

  // Toggle the severe Vault Kinematics!
  if (uidStr == MASTER_KEY) {
    if (vaultOpen == false) {
      lockServo.write(0); // RETRACT the physical latch!
      vaultOpen = true;
    } else {
      lockServo.write(90); // ENGAGE the physical lockdown!
      vaultOpen = false;
    }
    delay(2000); // 2-Second massive debounce perfectly preventing hyper-toggles!
  }
}

The Hardware Servo Interference (Jitter Elimination)

When relying completely on a Servo for a physical security lock, an enormous logic error exists!

• Many SG90 Servos natively suffer from intense "Jitter." When assigned to angle 90, they will randomly rapidly buzz left and right exactly by 1 degree entirely ruining physical latches!
• Detaching the Output: The instant you execute lockServo.write(90) cleanly, physically wait 500ms natively using delay(), and then explicitly command lockServo.detach()!
• This absolutely cuts the PWM control signal. The motor permanently physically freezes, absolutely terminating the buzz, preserving massive amounts of standby battery current precisely!

Secure Vault Hardware Ecosystem

• Arduino Uno/Nano (Acting as the cryptological center cleanly).
• MFRC522 SPI 13.56MHz Module (Mount flawlessly strictly inside the wooden wall; if you mount it inside a steel-walled safe, the metal completely entirely destroys the radio capability!).
• SG90 Micro Servo (With a thick metal paperclip or 3D-Printed sliding bolt rigorously attached exactly to the plastic horn seamlessly!).
• MIFARE 1K RFID Tags/Cards (Cryptographic input matrices).
• Red/Green Indicator LEDs (Mounted externally precisely to definitively visually signal unlocking state routines flawlessly natively!).