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The home made AoA indicator from BarkerAircraft.com
has a 5V regulator. With that running the electronics and a 2.2V typical forward
V @ 10ma on the LED's, that leaves 2.8V at 100ma total dissipated by the chip
with all LED's illuminated. The total dissipation of the chip comes out to about
0.28W. I don't see that raising the chip temperature to any where neat a 100C
limit.
Wolfgang
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It is an interesting product with some clever
ideas, but a very poor implementation. It is unlikely that it will keep
working reliably for long in the real-world/real-aircraft
environment.
The system does not take into account flap deployment.
Anyone here use flaps?
The "normal" position of the probe is with
the Hall sensor at the zero point of the magnet. Anyone concerned about
the fact that the system could report "normal" output if the probe or the
magnet falls off?
Even the most rudimentary analysis of the Hall
sensor's output as its temperature varies from -20C to +50C would reveal a
potential for some worrisome inaccuracies. You could stall several LEDs
before you expect to, or you could be several LEDs away from a stall when
the system says you should be stalling. Would you be more or less likely
to actually stall in these situations?
The design does not take
into account the fact that each LED that is on will cause the main IC's
temperature to rise by about 15C. A little slow flight practice with a 6
LEDs on and the IC is well past its 100C limit, generating a burning smell
and possibly smoke. Same would happen after an engine out as you glide
down at best glide speed. Can you think of a worse time to find smoke in
the cockpit?
This is just a partial list of issues, but I think it
gets the picture across. The only thing worse than not having something is
having something that is not
reliable.
Regards,
Hamid
Gary Fitzgerald wrote:
He has an article on this project in the Dec. 2008
edition of Sport
Aviation. Interesting use of a Hall Effect
sensor. |
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