Supply and Ground Side Switching

A significant part of the simulator is in the process of being rewired – there was an assumption avionics equipment would function correctly with ground side switching. Unfortunately with this setup the avionics equipment decided to display an erratic behaviour, even in an unpowered state.

Why Ground Side Switching?

The main instrument panel korry annunciators are wired up to switch in this manner because of the use of LEDs; polarity is important when using this source of illumination. Incandescent bulb on the other hand, allows you to supply from either poles, albeit at a much higher amperage output.

The Solution

Simulator Solution SimStacks, a versatile logic interface board, can logically switch outputs with either ground side, or supply switching. All it requires is a change in the jumpers on the board to enable this function. The main instrument panel outputs continue to be configured to run in ground side switching, but the pedestal avionics have now been configured to run in supply side switching. With these changes the avionics equipment and backlight have the correct bus power logic and behaviour of the real aircraft.

Nota Bene

It is important to tie all your grounds – multiple power supply units are used to power the simulator and a floating ground can wreck havoc to equipment and operations.

A phidgets USB isolator has been installed – not only does this protect the Cockpit Concept AIRINC boards from a floating ground, but also from electrical surges. AIRINC signals are extremely sensitive. Ferrite cores will also be installed to each USB cable to reduce electrical interference.

The main chassis of the simulator should be earthed to allow for an outlet (electrical conduit) in the consequence of a live wire touching the Main Instrument Panel (MIP). Point of contacts from the MIP chassis have been wired to the power supply unit earth point.

On the OEM MIP chassis there are embedded points which can be used for Earthing

A big special thank you to Rodney from Simulator Solutions, Christoph from Cockpit Concept and Mick Cliffe for the support

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