SimStack – A Versatile Simulator Interface Board

Interfacing original aircraft equipment for use into a Flight Simulator was always going to be a challenge. As you progress through the integration of the many components, you soon begin to realise there are other many other features you would like to accurately simulate. Some of these functions include:

  • Backlighting logic and power – only supplied to the Aircraft when the correct Bus is powered (Aircraft external power, APU on, or engines started)
  • Avionics Power On/Off – instruments and other avionics should only function when the correct Bus is powered
  • Driving incandescent bulbs found in the original Korry Push Button Switches (5 VDC at 0.115 amps per bulb in an Airbus flightdeck)
  • Dimming of the incandescent bulbs with the overhead switch
  • Integration with the Simulator Software (ProSimA320 in our scenario) variables

Other interfacing boards available in the market did not meet these requirements. They were incomplete solutions requiring extensive complicated wiring to implement the correct aircraft function. A Phidgets interface board for example, might be able to supply the output to a korry output, but is unable to integrate with the overhead dimming switch. This leads to compromise (don’t simulate the function), or an additional layer of complexity required to add the function. The traditional way to dim the korry outputs would be to use a relay to switch the voltage when the dimming switch is enable. But what if you didn’t require a relay to perform the function? What if theres an interface solution smart enough to perform these features in an integrated fashion?

SimStack Foundation Board

Enter SimStack by Simulator Solutions. Founded and based in Sydney, Australia by Rodney Redwin and John Golin in 2014, Simulator Solutions have successfully interfaced professional simulators around the world. Their clients use a variety of avionics software including Aerowinx PSX, ProSim737 and ProSimA320. Simulator Solutions also offer an MCDU Conversion Kit; replacement parts for the OEM unit are provided allowing you to bypass AIRINC429 and 115VAC requirements. SimStack makes all of this possible, an Ethernet enabled interface board which can be ‘stacked’ with other boards based on the simulator configurations and needs.

The hardware is flexible, allowing you to use low side (common cathode) or high side switching (common anode), and sink a variety of voltage and up to 3 amps per output. With this feature outputs can be used to drive incandescent bulbs found in aircraft OEM korry switches, backlighting in panels and power avionics (on an Airbus, usually with 28VDC). The board also has inputs for switches and analog inputs. The magic happens when SimStack is able to integrate seamlessly with the avionics software variables. The logic of the hardware then follows exactly what the software tells it to do. For example, backlighting is controlled by the integral lighting knob found in the pedestal, but if the aircraft is in an unpowered state, then the panels shouldn’t illuminate. The avionics software updates the backlighting variable which SimStack reads and as a result disables the backlighting output for the panel(s). By linking into the variables, the panel hardware interfaces directly into the logic of the aircraft systems, simulating the hardware realistically – As-Real-As-It-Gets.

SimStack – Foundation, Output, and Input Board stacked on top of each other; Photo by Simulator Solutions

SimStack is extremely versatile and can be used in a variety of simulator configurations; the only downside is the programming required to perform its function. If you are not familiar with basic Arduino sketch programming (I wasn’t), you may initially struggle. But after reviewing the official support forum and receiving an example sketch from Rodney I was able to implement and run the hardware as intended. John has written some clever  programming to allow the incandescent bulbs to dim with pulse width modulation (PWM). He has also written a specific function to exclude korry bulbs which are not suppose to dim with the switch. The outputs possibilities are limitless with the flexible programming, with SimStack even able to directly power avionics equipment, gates, and solenoids.  

In this test bench the SimStack board is connected to the integral light knob, Terrain on ND panel, and the Overhead Lighting panel; The power state of the aircraft is initially off; after external power is supplied backlighting is applied to the panels, the korry is turned on and output dimmed

Conclusion

There are a multitude of other interface boards available in the market but none provide an all-encompassing solution which can drive a variety of outputs and inputs without any additional complex wiring or relays. SimStack is software smart allowing it use logic sourced from the avionics software. It has a steep learning curve and implementing functions requires some knowledge of the Arduino programming language.  There is no graphical user interface (all configuration is done by script), as this allows the hardware to be adaptable and work with a variety of OEM parts. SimStack was designed from the ground up to be used with professional simulators and has impressive scalability and function. It has been successfully integrated in many B747 aircraft simulator builds and I can’t wait to start to integrate OEM A320 equipment with SimStacks.

SimStack is available at Simulator Solutions.

Advantages 

  • Outputs are able to drive original korry incandescent bulbs
  • Each output is rated up to 3 amps and individually fused
  • Dimming function without any additional relays or wiring
  • Able to power avionics and backlighting panels with correct logic
  • Integrates directly with avionics software (Aerowinx/ProSimA320/ProSim737/FSUIPC/X-Plane) variables
  • Ethernet ready allowing for execution anywhere over the local network
  • Additional output/input/distribution boards can be stacked on top of one another
  • DIN rail mounts provided for easy mounting

Disadvantages 

  • Steep programming learning curve if unfamiliar with Arduino sketch language (C/C++) 
  • Output fuses are surface mounted and can be a challenge to replace

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