||Dual Brightness Annunciators
On the forward overhead there nine (blue) annunciators that have two levels of brightness. The bright state indicates that the commanded state has not been reached yet.
I am using the FDS-SYS1 interface board from Flight Deck Solutions to connect up all the switches and annunciators of the forward overhead panel. I could not get their recommended way for the dual brightness annunciators to work satisfactorily. They suggest to use two outputs, one output connects to the annunciator via a diode and the other via a diode and resistor. Since my implementation of the pressurization panel uses a Phidgets LED-64 card and I had 18 outputs left, I added some code to the panel software to drive the 9 annunciators. The software checks for each output the brightness state and sets the output level accordingly.Connection diagram
The table below shows how they are connected to the Phidgets board.