Time of flight sounds good, but you need to make sure you're hearing the air-wave and not the wave propogated through the aircraft structure.
Thermal will likely get confused by humidity
Is there a way to detect an imminent stall and just goose the motor a bit if that triggers?
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since it's mass flow that gives lift that's probably not a big problem. humiidity is going to mess it up though.
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That's an easy way to enter a spin.
On a sunny day (24 Nov 2013 04:47:04 GMT) it happened Jasen Betts wrote in :
Yes, that is one thing that needs to be tested, and also motor noise (motor plus propeller) may interfere with things.
Perhaps, again I will need to test things, at least thermal, with enough power, will not have the icing problem..
It is not s simple as increasing motor power, plane attitude, altitude (air pressure), wind, all play a role.
All this is why I have not 'decided' on a solution yet as I do not have perfect one.
Long time ago I did some experiments with old piezo transducers from acoustic remote controls, and made a Doppler radar with it. I still keep wondering if, instead of time of flight I could just use the Doppler interference frequency. Man that thing was sensitive, in a room it would detect if you blinked your eye. Pretty simple circuit too, just mixer difference frequency -> audio lowpass -> amplifier.
-- Larkin's post, to which I was responding, has nothing to do with lift.
--
Since
L dI
E = ------,
dt
and - to a first approximation - L stays fixed, we have:
L dI 82e-6H * 5e-1A
dt = ------ = ---------------- = 8.2e-7s
E 5e1V
that's about 820ns from space to mark as the tooth edge traverses
the magnetic field when it's spinning at the right speed.
That doesn't seem like such a big deal to me.
I make lots of mistakes, including stupid ones. No big deal. I'm not at all persuaded that this is one of them--if the required measurement is as narrowband as you suggest, it seems perverse to generate a signal so inconveniently large.
Cheers
Phil Hobbs
-- This is all conjecture, of course, but if one were interested in the period of the signal driving the tank, then the highish Q would enhance the slew rate around resonance and allow more accurate zero-crossing to zero-crossing measurements to be made.
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