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ORA-2 accessory decoder


ORA-2 = Open Rocrail Accessory decoder for use with many systems including ORD-1


ORA-2 is a multi purpose accessory decoder, code compatible with ORA-1 and Opendecoder. It is designed to be small, but yet built with through-hole components.

ORA-2 is a based on and code compatible with Opendecoder (OpenDecoder Hardware 1). Many thanks to Wolfgang Kufer and his OpenDCC project.

Main features

  • Full Rocrail support
  • Compatible with ORD-1
  • 8 outputs ( 4 turnouts )
  • 68x50mm PCB
  • NMRA-DCC compatible
  • Use combined power+data (track voltage) or separate power (AC) + data (low voltage DCC or track voltage DCC)
  • For solenoids and LED/lamps
  • 0,5A or 1,0A current for solenoid drivers


All documentation:
Last version is 1.2

Schematics and PCB artwork was created with KiCad, an Open Source (GPL) PCB Suite.

Component notes

  • Resistors: For best result, use 1%, 1/4W, metal film resistors.
  • Multifuse: This is a safety device, a self resetting fuse, a PTC resistor, to protect your equipment. Preferred type is a 0,9A hold current type, like BOURNS MF-R090.
  • Smoothing capacitors: 470uF is not critical. 220uF-1000uF 50V-63V 5mm leg spacing will do fine. 4,7uF is not critical, any value 1-10uF >16V 2,5mm leg spacing will do fine
  • Rectifier bridge: The bridge must sustain minimum 1,5A.
  • Crystal: 10MHz for parallel capacitance. Can optionally be fixated/grounded with a spare component leg soldered to case.

Programming and Usage

Please see ORA-1 and Opendecoder for detailed descriptions of programming and usage.


K1-K4 Turnouts
P1 AVR-Programmer
JP1 Save state, see OpenDecoder for description
SW_PUSH used to set decoder in learning mode
When JP2+JP3 is bridged
→ K5 and/or K6 combined power+data (track power)
When JP2+JP3 is not bridged
→ K5 data (either track power or low voltage DCC data)
→ K6 power (12-18VAC)


3D Picture from Kicad



ora2-en.txt · Last modified: 2020/07/09 02:23 by rainerk