I have a low fuel light on my annunciator panel.  the problem I am having, is that it runs off of how many gallons are in the tanks, not percentage.   
   example:  I have it set to on at 20 gals remaining..good for a cessna or mooney, bad for a 737 .

Is there any way I can run it off of percentage remaining?  If so, what is the offset?  I have looked and cant find it.

PS I am running FSX


Thanx in advance.

I know there is a percentage for each tank...I was hoping for a percentage in total. Is that possible?

737 fuel gauges are in LBS or KG's in the real world. 

Matt

gokhotit,

Not that I know of.  But someone more knowledgable in the internals of the FS program itself might know a way.  But that would be some serious hacking into the main code of the program, I think.

There is one main stream of data that Microsoft programmed into the sim and that data stream is what is accessed by FSUIPC.  It contains a LOT iof information, some of which apparently is still not fully explored.  But there is apparently a lot left OUT of that stream too.  Drives us cockpit builders nuts........ and makes money for people like Project Magenta.  

Many of the "tricks" that you see done to get "slick functions" out of the sim that Microsoft never intended are done EXTERNALLY to the sim itself using the FSUIPC data stream (and now SimConnect for FSX).  Software like Project Magenta that accurately emulates such systems as hydraulics (which are WOEFULLY under simulated in the default simulator) do that by creating a set of software code that takes the actions of stuff that the sim DOES provide (like maybe knowing the engine is now running) ... and builds off of that to add the missing functions in as realistic a way as possible, and then feed some of that info back into FSUIPC to be available at some offset so that other things can access it.

In your case all you need to do to solve YOUR problem is write some code that looks at the total fuel that your aircraft can carry in all of the individual tanks as a percent, adds all of them together, looks at some preselected level at which you want to turn on a light (say at 10%) and compares the two values.  If the percent level is equal to or less than that 10% value, the program needs to write a "1" or a "0" to one of FSUIPC's unused offsets that Pete Dowson made available for such uses.  THAT is the "missing piece" of stuff you likely need to do this.

The next step is handled by FS2Phidget.

Then your annunciator lighting software (FS2Phidget ?) needs to be set up to look at that offset and monitor the value.  If the value changes from the "OK" value to the "low fuel" value, it needs to then tell the hardware it is driving (Phidgets LED64 ?) to send voltage to the LED in the annunciator.

Another possible avenue here is to approch it via an XML gauge.  Do what I described above but as an invisible gauge in the aircraft's panel.  How to get the info OUT into an offset is the big question I would have in this.  But I don't know anything about XML gauge programming...so hopefully someone who does will read this and respond.

I really don't know how to do that in another manner.  Again...... maybe wait for the new release of FS2Phidget.... Alan said he is adding some conditional functions that can be stacked up.  Maybe that will allow it.

best,

.....................john