[Elecraft] Angle of attack - PIC Question - WAY off topic!

[Dan Barker]

I know this is the wrong forum, but there's so much brain-power here, I just
had to ask.

Answers could include:

 a) the <right> forum, or

 b) a part number<g>.

I <think> I need a PIC controller for my new gizmo. It will most likely turn
into a Finite State Automaton, with states and events to control:

Land sequence:

 Switch goes to "Land" position.
 ADC voltage goes over x0 volts for over 20 seconds = Armed
 If Armed:
   voltages between x1 and x2 volts sound a beep once a second.
   voltages between x2 and x3 volts sound a beep once a half second.
   voltages below x3 sound a solid tone (FLARE!)


Tow Sequence:
 Similar logic for when to drop the cart, but the other way around. I'll
most likely also want an "Off" position to avoid noise in rowdy thermals.

Input will be a voltage from a differential pressure transducer. Output will
be noise.

Actually, I want to carefully monitor the angle of attack (relative wind to
wing) in the range from about 10 to over 15 degrees. The best idea
(mechanical vanes aren't very stable) I've got so far is two dynamic
pressure ports (pitots) 90 degrees apart.

It's a trivial implementation on an airplane, due to the high speeds (0.5 in
H2O Delta Dynamic Pressure = stall, 2.0 = gobs-o-lift), but my application
is on a hang glider, and the pressures are far lower. With only a 10 m/s
airflow, the differences between these two ports will probably be around .10
to .12 (ish) inch H2O at near-stall.

The electronics will likely be a PIC uController which arms if the pressure
goes over .15 (wild guess - I need some test time) for 20 seconds and beeps
once a second as it goes under .12 and sounds solid as it hits .10 in h2o
(or whereever).

The beep is "Get Ready" and the tone is "Flare Now!". Sould make landing
timing a piece of cake!

FYI, in landing a hang glider, you push out hard and firmly, and simply step
onto the ground. It is absolutely graceful when done with the correct
timing.

The problem is that an early flare balloons you up and you plop down ($75 of
bent aluminum). If you flare late there's not enough energy left to stop the
kite (Can you run 15 m/s with 40 Kg on your back?) and you plop down and
whack (Nose of the kite goes over hard - $75 of bent aluminum).

I guess I gotta build a small, low-velocity wind tunnel and figure out some
voltages, angles and etc, but it ought to be far more reliable than some
mechanical doo-dad with optical sensing of the position of a vane flopping
about in the turbulence!

Alternate Use: Slide the switch from "Landing" mode to "Towing" mode, and
the tone indicates you are going fast enough to drop the cart (wheeled dolly
that supports you while the tow-plane gets up to speed. Let go too soon, and
you might mush back into the ground or the cart itself). Same logic,
different sense to the algorithm.

References:

 Aircraft installation: http://home.hiwaay.net/~sbuc/journal/liftreserve.htm

 Homebuilt version: http://www.snyder.on.ca/pages/lri.htm

 Probe details: http://www.snyder.on.ca/pages/angle%20of%20attack.jpg

Dan Barker / WG4S / Comm-ASEL-IA-H4 / K2 #2456