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Magnetic Door Lock Implementation Guide

caution

Our magnetic lock system operates using an electromagnet that secures the door to its wall-mounted frame. This requires a continuous electrical current to maintain the locked state.

Overview​

This guide provides step-by-step instructions for building a functional magnetic door lock system with authentication, remote monitoring, and fail-safe mechanisms. The implementation covers both hardware and software aspects, ensuring a secure and efficient solution.

System Design & Implementation​

Hardware Components​

Required Materials​

  1. Electromagnet (12V/24V DC) – Provides the locking mechanism.
  2. Microcontroller (Arduino, ESP32, or Raspberry Pi) – Controls the lock operation.
  3. Relay Module – Interfaces between the microcontroller and the electromagnet.
  4. Power Supply (12V or 24V) – Supplies power to the electromagnet.
  5. Uninterruptible Power Supply (UPS) or Battery Backup – Ensures operation during power failures.
  6. Authentication Module – Options include:
    • RFID reader (e.g., MFRC522)
    • Keypad (4x4 matrix keypad)
    • Biometric scanner (fingerprint sensor)
  7. Door Sensor – Detects door open/closed status.
  8. Buzzer & LED Indicators – Provides status feedback.
  9. Emergency Override System – A manual release button or battery-powered alternative.

Circuit Connections​

  1. Electromagnet: Connect the positive wire to the relay's normally open (NO) terminal, and the negative wire to ground.
  2. Relay Module: Connect the relay's common (COM) terminal to the power supply positive, and control pin to the microcontroller.
  3. Microcontroller:
    • Connect the relay control pin to a digital output.
    • Interface authentication modules (RFID, keypad, or biometric) via GPIO pins.
    • Connect status LEDs and buzzer to digital output pins.
  4. Power Backup:
    • UPS or battery backup should be wired in parallel to provide continuous power.
    • A voltage regulator may be required depending on power requirements.

Software & Control Logic​

Programming the Microcontroller​

The firmware (written in C/C++ for Arduino or MicroPython for ESP32) should handle:

  1. Authentication Process

    • Read user input from the RFID reader, keypad, or fingerprint scanner.
    • Validate credentials against a stored database.
    • Grant access if credentials match; otherwise, trigger an alert.

  2. Lock Control

    • Activate the relay to energize the electromagnet upon authentication.
    • Deactivate the relay to release the door after a timeout.

  3. Remote Monitoring & Logging

    • Log every access attempt (valid or invalid) with timestamps.
    • Store data locally or send logs to a remote server.

  4. Fail-Safe & Emergency Handling

    • Configure fail-safe mode (unlock during power failure) or fail-secure mode (stay locked unless power is restored).
    • Implement an emergency override mechanism (manual release or battery-powered alternative).

Example Arduino Code​

#include <SPI.h>
#include <MFRC522.h>
#define RST_PIN 9
#define SS_PIN 10
#define RELAY_PIN 7

MFRC522 mfrc522(SS_PIN, RST_PIN);
void setup() {
    Serial.begin(9600);
    SPI.begin();
    mfrc522.PCD_Init();
    pinMode(RELAY_PIN, OUTPUT);
    digitalWrite(RELAY_PIN, LOW);  // Lock engaged by default
}
void loop() {
    if (mfrc522.PICC_IsNewCardPresent() && mfrc522.PICC_ReadCardSerial()) {
        Serial.println("Access Granted");
        digitalWrite(RELAY_PIN, HIGH);  // Unlock the door
        delay(5000);
        digitalWrite(RELAY_PIN, LOW);   // Re-lock the door
    }
}

Security & Compliance Considerations​

  1. Encryption & Authentication

    • Store credentials securely, using hashed/encrypted formats.
    • Use multi-factor authentication for higher security.

  2. Tamper Detection

    • Install sensors to detect forced entry attempts.
    • Trigger alarms and send notifications when tampering is detected.

  3. Compliance with Fire Safety Regulations

    • Ensure an emergency exit mechanism complies with local regulations.
    • Implement an automatic unlock function in case of fire alarm activation.

Testing & Deployment​

  1. Power the System – Verify proper operation under normal and backup power.
  2. Authenticate Access – Test various authentication methods.
  3. Fail-Safe Mode – Simulate a power outage and ensure correct behavior.
  4. Tamper & Alarm Testing – Simulate break-in attempts to verify response mechanisms.

Conclusion​

This guide provides a detailed roadmap for implementing a custom magnetic door lock system with authentication and security features. Future improvements may include network-based access control, mobile app integration, and AI-powered threat detection.