Annunciator

[Bigdog]

I've got an annunciator panel and had it set up for to show Alt Hold On with an Altrac. I've upgraded to a VSGV and don't see anything obvious in th pinouts to drive an annunciator to show that either pitch or roll is engaged. I'm still building so I have some flexibility and can drive the annunciator either with power or ground. Has anyone done anything like this or have suggestions.

Thanks,
Greg

[TrutrakTech]

What is the voltage input for your annunciator? The easiest way for some autonomy there is to drive it off the torque signal to the pitch servo. The only thing you have to watch for is make sure it's not a big voltage drop or your torque will be reduced. This is a 5V signal though.

[Bigdog]

It's 12 volts that's dropped by a resistor to drive the LED. Could I use the line to trigger a 5v relay that would drive the annunciator? Is the torque signal continuous so the light would not flicker?

[TrutrakTech]

The torque signal is continuous.

[lcbowen]

This thread is a little old, but is the above approach still the way to go? Can the same be done using the roll servo instead of pitch? The pitch servo is not necessarily engaged all the time, right?

[TrutrakTech]

It's the only thing that changes between engaging the servo and not, unless you had some sort of current driven circuit that could be wired into the servo power line and activate when a predetermined current threshold is reached, ~1A. The servos draw no power until they're activated by the controller but then continuous current draw is over 1A. That would actually be ideal.

[lcbowen]

So there is potential for an external annunciator light to give a false negative if driven by the pitch torque signal. Isn't there? Roll servo engaged, but pitch not yet engaged or disengaged.


"Altitude Hold Mode -- When the autopilot is engaged it will be in the basic lateral track mode, and will synchronize to the direction being flown at the time. The pitch servo will not be engaged at this time. To engage the altitude hold the aircraft must be at the desired altitude and be trimmed for level flight. After trimming the aircraft, to enter the altitude hold mode, simply press and release the ALT button."

[TrutrakTech]

If you have a Digiflight II (no letters after that) then yes, the pitch torque signal is not what you should use. The roll servo will always be engaged though.

If your Digiflight II has VS capability then the pitch servo is engaged at the same time as the roll.