A bit more done... but tough to photograph it. Some blurry shots coming soon..... sorry..... camera is still an issue on close ups.
Tonight I "attacked" wiring up one more of the overhead panels .... did some very minor work on some others already.
The one I selected tonight was the "Bleed Air / Packs" panel. This panel will control a number of "real world" important functions in the pit.... such as all of the real air circulation blowers for my "creature comfort" while flying

. Unfortunately in the FS2004 basic sim, there is little FSUIPC data supported for the bleed air and the packs. So I will have to "fake it" to a degree. And I will add some "in sim" functions also as I go later.
The panel I made allows the APU and engine #2 and engine #3 to generate bleed air. There is an isolation valve to separate the right air from the left air systems..... with the APU able to run either side. For these bleed air switches to be "active" they will be "fed" from the panels that control the engine starts and the APU start. No appropriate engine(s) or APU...... and the switches on this panel will do nothing. (There are APU and Air and Packs annunciators located elsewhere.)
Once the bleed air is established and the switch lights up "green" , then the left and right packs can be selected and turn "green". Once the packs are running, they will allow the two recirculation valves to be switched open (light "green") and warm/cold air to be directed to the flight deck, the structural anti-ice system, and the passenger cabin (non-existant).
What I am really controlling here is simply a supply of +12 VDC. To get keypresses (eventually) into the sim itself.... I will use a couple of relays connected to the keyboard emulator or the Phidget inputs. That will be addressed later.
If this 12V switching just involved a series of single switches.... it would be very easy wiring. Feed the plus side of the 12V through one switch to the next switch...to the next switch... to the next switch. Unless the whole "chain" of switches is "closed", no current flows in the circuit. Simple... and that kind of thing will show up in a couple of places in the pit.
The "problem" with THIS panel comes when you want multiple possible switches carrying the 12V to be a "source" for something downstream.... and don't want ALL the indicator lights to light up no matter WHAT switch is thrown... and to not feed 12V power "backwards" down the interconnected wires. That gets you results that are often "unexpected" as far as the "logic" goes :o.
The "trick" to deal with this potential issue is to use a diode in the 12V + supply line.
A diode can act as a "one way valve" for electrons. The flow of current goes from the anode side to the cathode side of the diode with a slight voltage drop across the diode (about 1 - 1.5 volts). In the reverse direction....... until you get to a pretty high voltage (breakdown voltage)........ no current flows through it at all. So putting these diodes in strategic locations... you can feed electricity down a "one way street".
I'll put up a picture and a schematic to explain this a little better later.
So the Bleed Air / Packs panel is now basically finished and all the lighted rocker and toggle switches function with the logic I desired.......... a bunch of hook-up wire amd solder and six 1N4001 silicon diodes later
best,
..................john
PS: The diodes will handle 1 Amp forward current and the brekdown voltage is 50V... way above my 12V DC. My blowers on a single circuit will not exceed 1 Amp draw each (there are two circuits to utilize).