Design Requirements

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Specifications for Open Access 3.0 Hardware

General

  • Based on Arduino Mega 2560 Microcontroller
  • Control at least 4 doors
    • 4 Form C relays for doors (5A rating)
    • 2-4 Form C relays for alarm, other functions (5A rating)
  • Real-time clock accurate to +/- 20ppm
    • Consider temperature stability of quartz crystal (AT cut vs tuning fork)
    • Battery backup for date/time
  • Allow for 4 Wiegand Readers
    • 6-pin format to allow control of LED/Beeper
      • PWR,GND,1,0,LED,BEEP
    • Allow for wide range of pulse widths
      • 20-400uS pulses from logic high to GND
  • 8+ Supervised alarm zones
    • 4-state supervision
      • Detect faults such as zone cut/broken, short
      • Detect closed and open states
    • 2-terminal design
    • Include current limiting and ESD protection
  • On-board RS-485 support

Expansion Capability

  • Provision for Ethernet (4xSPI pins)
  • Additional SPI select pins available
  • Provision for SD card support
  • Provision for external host-mode USB support
  • Break-out of all pins, including ICSP

Power

  • 12-14VDC operation
  • Voltage-divided analog inputs for monitoring input voltage
  • Optional analog or digital input for monitoring external PSU voltage
    • Adaptable to 24V with component changes
  • On-board switching PSU for 5V or 3.3V needs
  • Input power protection
    • Reverse polarity protection
    • Surge and ESD protection
    • Fused input rail
  • External power rails
    • Polyfuses or fuses for additional power outputs
    • Can be on-board or on separate power distribution board

Physical

  • 4x6" form-factor
  • 4 #6 mounting screws
  • Arduino mounting screws
  • Double-sided, SMT design
  • 3.5mm screw terminals (~60 count)
    • 24 terminals for 4x6-pin Wiegand inputs
    • 16 terminals for 8x2-pin alarm inputs
    • 18 terminals for 6x3-in relay outputs
    • 2 pins for power input
    • 8 pins for power distribution (optional)

Environmental

  • Working temperature range from -25 to 55C
  • Design towards FCC Class B
    • Only when used with metal case
  • Immunity
    • 2500V standard