Feature: Emergency Override

Complexity: 🟢 Low Hardware Required: 🔧 Minor (Physical button or none) User Value: ⭐⭐⭐ Essential

Overview

Implement emergency override mechanisms for situations where normal access methods fail or emergency responders need immediate entry. This includes physical buttons, special emergency cards, or remote triggers.

Benefits

• Life safety compliance
• Emergency responder access
• Failsafe during system failures
• Panic button functionality
• Compliance with fire codes

Override Methods

1. Physical Button - Direct relay activation
2. Emergency Card - Special RFID card with override
3. Break Glass - Traditional emergency release
4. Remote Trigger - Network/phone activation
5. Power Failure - Fail-safe or fail-secure options

Implementation Checklist

Phase 1: Physical Button Override

• Hardware setup:

  class EmergencyOverride {
  private:
      uint8_t buttonPin;
      uint8_t glassBreakPin;
      bool overrideActive;
      unsigned long overrideTime;
  public:
      void begin();
      bool checkOverride();
      void activateOverride(uint8_t source);
      void resetOverride();
  };
  

• Button types:
  • Momentary push button
  • Key switch
  • Mushroom emergency stop
  • Recessed button (prevent accidental activation)

Phase 2: Emergency Card System

• Special card designation:

  struct EmergencyCard {
      uint8_t uid[7];
      uint8_t uidLength;
      uint8_t overrideLevel;  // Fire, Police, Medical, Master
      bool logOnly;           // For audit without unlock
      uint32_t validUntil;    // Expiration date
  };
  

• Override behaviors:
  • Instant all-relay activation
  • Extended unlock duration
  • Disable normal access temporarily
  • Trigger alarms/notifications

Phase 3: Override Logic

• Activation Triggers:
  • Physical button press
  • Emergency card scan
  • Glass break sensor
  • Remote command
  • Power failure (configurable)
• System Response:

  void handleEmergencyOverride() {
      // 1. Activate all door relays
      relays.setAllRelays(true);
  
      // 2. Disable normal card reading
      emergencyMode = true;
  
      // 3. Log emergency event
      logger.logEmergency(source, timestamp);
  
      // 4. Sound alarm (if configured)
      audio.playTrack(SOUND_EMERGENCY);
  
      // 5. Send notifications
      remote.sendAlert("EMERGENCY OVERRIDE ACTIVATED");
  }
  

Phase 4: Safety Features

• Fail-Safe vs Fail-Secure:

  enum PowerFailureMode {
      FAIL_SAFE,    // Doors unlock on power loss
      FAIL_SECURE,  // Doors remain locked
      BATTERY_BACKUP // Maintain normal operation
  };
  

• Capacitor backup for relay activation
• Battery monitoring and alerts
• Graceful degradation

Phase 5: Button Installation

• Indoor Emergency Release:
  • Green button near exit
  • “Push to Exit” signage
  • LED illumination
  • ADA compliant height
• Outdoor Emergency Access:
  • Knox box integration
  • Weatherproof enclosure
  • Tamper detection
  • Key or code protection

Phase 6: Notification System

• Local Alerts:
  • Loud alarm/siren
  • Strobe light activation
  • LED status indicators
  • Voice announcement
• Remote Alerts:
  • SMS/Email notifications
  • Security system integration
  • Building management alert
  • Emergency services notification

Phase 7: Reset and Recovery

• Manual Reset:

  void resetEmergencyMode() {
      // 1. Verify authorized reset
      if (!checkResetAuthorization()) return;
  
      // 2. Return to normal operation
      emergencyMode = false;
  
      // 3. Re-lock doors (with delay)
      delay(EXIT_DELAY);
      relays.setAllRelays(false);
  
      // 4. Log reset event
      logger.logReset(resetUser, timestamp);
  
      // 5. System check
      performSystemCheck();
  }
  

• Reset authorization methods
• Automatic timeout options
• Post-emergency audit

Wiring Examples

Emergency Button Circuit

Arduino Pin 2 ----+---- 10K Resistor ---- 3.3V
                  |
                  +---- Emergency Button ---- GND

Break Glass Sensor

Arduino Pin 3 ----+---- 10K Resistor ---- 3.3V
                  |
                  +---- Glass Break NC Contact ---- GND

Compliance Considerations

• Fire Code Requirements:
  • Clearly marked emergency exit
  • Illuminated exit signs
  • Panic hardware on doors
  • Regular testing requirements
• ADA Compliance:
  • Button height 48” max
  • 5 lbs max activation force
  • Clear floor space
  • Visual and audible indicators

Testing Checklist

• Test all override methods
• Verify immediate relay response
• Test notification systems
• Verify logging accuracy
• Test reset procedures
• Power failure testing
• Integration with fire alarm
• Monthly test schedule

Configuration Options

// Emergency configuration
#define EMERGENCY_UNLOCK_ALL true      // Unlock all relays
#define EMERGENCY_DURATION 300000      // 5 minutes
#define REQUIRE_RESET true             // Manual reset needed
#define ALERT_VOLUME 30                // Maximum volume
#define POWER_FAIL_MODE FAIL_SAFE      // Fire code compliance
#define LOG_EMERGENCY_CARDS true       // Track responder access

Future Enhancements

• Integration with fire alarm system
• Smartphone emergency unlock
• Biometric override (first responder fingerprints)
• GPS-based emergency unlock
• Voice-activated emergency release
• Automatic emergency services dispatch