Design Requirements

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