Building an electronic Angle of Attack indicator

RST Engineering - JIm wrote:
Yes. It was made by National Semiconductor and you could get it linear or
logarithmic. It was obsoleted by National about fifteen years ago, but
there are still a few of them in the pipeline at a pretty hefty price.

Jim



wrote in message
...

Isn't there a voltage-to-LED-bar-graph IC? I seem to
remember such a thing. That would make the circuit simple.


Nope. It's still very much available in the surface mount package.

By God, you are correct. When my supplier told me in 1999 that the LM3914
was no longer available, they failed to tell me that the LM3914-1 was a
direct replacement and very much still in the pipeline, even as the larger
18 pin through-hole DIP package. Thanks for correcting me.

Jim


"Rip" wrote in message
...
RST Engineering - JIm wrote:
Yes. It was made by National Semiconductor and you could get it linear
or logarithmic. It was obsoleted by National about fifteen years ago,
but there are still a few of them in the pipeline at a pretty hefty
price.

Jim



wrote in message
...

Isn't there a voltage-to-LED-bar-graph IC? I seem to
remember such a thing. That would make the circuit simple.


Nope. It's still very much available in the surface mount package.

RST Engineering - JIm wrote:
By God, you are correct. When my supplier told me in 1999 that the LM3914
was no longer available, they failed to tell me that the LM3914-1 was a
direct replacement and very much still in the pipeline, even as the larger
18 pin through-hole DIP package. Thanks for correcting me.

Jim


"Rip" wrote in message
...
RST Engineering - JIm wrote:
Yes. It was made by National Semiconductor and you could get it linear
or logarithmic. It was obsoleted by National about fifteen years ago,
but there are still a few of them in the pipeline at a pretty hefty
price.

Jim



wrote in message
...

Isn't there a voltage-to-LED-bar-graph IC? I seem to
remember such a thing. That would make the circuit simple.

Nope. It's still very much available in the surface mount package.


My pleasure. This topic is timely, since I recently built myself a
"Lift Reserve Indicator" based on the LM3914 and a Honeywell sensor.
Now I'm doing a "true" angle of attack indicator based on the Maxim
4210 multiplier (and an op amp) to correct for airspeed ram pressure.

A terrific treatise on the subject (with one inconsequential math error)
can be found he
http://users.cablemo.net/~jjshultz/sonex/aoa.html

Rip

Mike wrote:
Has anyone built an electronic angle of attack meter kit. It seems to
be something that would be easy to design but beyond my feeble
electronics background.

I have seen the products that are out there and they are simple
differential pressure gauges and are expensive. I don't like the
round differential pressure gauges that many of the companies offer
for this kind of system. I was wondering if there would be a way to
put something together that would light up different color LED's for
the different levels of lift that we could build at home without
having to pay out hundreds of dollars for a prebuilt one.

Something like
http://www.barkeraircraft.com/AOA_kit.html

EAA web site says June 07 Sport Aviation Magazine, but I thought it was
more recent than that.

Charlie

Charlie wrote:
Mike wrote:
Has anyone built an electronic angle of attack meter kit. It seems to
be something that would be easy to design but beyond my feeble
electronics background.

I have seen the products that are out there and they are simple
differential pressure gauges and are expensive. I don't like the
round differential pressure gauges that many of the companies offer
for this kind of system. I was wondering if there would be a way to
put something together that would light up different color LED's for
the different levels of lift that we could build at home without
having to pay out hundreds of dollars for a prebuilt one.

Something like
http://www.barkeraircraft.com/AOA_kit.html

EAA web site says June 07 Sport Aviation Magazine, but I thought it was
more recent than that.

Charlie

That's a nice set up. It shouldn't be too hard to add an audio alarm
or shaker. I just hope the pitot tube isn't heated.

Dan, U.S. Air Force, retired

Dan wrote:
Charlie wrote:
Mike wrote:
Has anyone built an electronic angle of attack meter kit. It seems to
be something that would be easy to design but beyond my feeble
electronics background.

I have seen the products that are out there and they are simple
differential pressure gauges and are expensive. I don't like the
round differential pressure gauges that many of the companies offer
for this kind of system. I was wondering if there would be a way to
put something together that would light up different color LED's for
the different levels of lift that we could build at home without
having to pay out hundreds of dollars for a prebuilt one.

Something like
http://www.barkeraircraft.com/AOA_kit.html

EAA web site says June 07 Sport Aviation Magazine, but I thought it
was more recent than that.

Charlie

That's a nice set up. It shouldn't be too hard to add an audio alarm
or shaker. I just hope the pitot tube isn't heated.

Dan, U.S. Air Force, retired


Speaking of which, I have a heated pitot tube head
If anyone is in need of one, drop me a note.

I've worked this problem for a number of years. Let me offer a few
simple points.

Any system of measuring AOA will need to be calibrated. It doesn't
really need to be linear since the major interest is in the region
near stall and Cl max. It just needs to give a variable output that
is related to AOA - and be very repeatable.

If the cockpit is in clean free air flow as with a pusher or
sailplane, an effective AOA indicator can be made with a simple string
taped to the side of the canopy. On sailplanes, these 'pitch strings'
tends to 'over-indicate' by about 2:1 which is fine as it increases
the resolution of the indicator. Stall, Cl max and L/D max can be
marked on the inside of the canopy with grease pencil. It helps to
put one on each side of the canopy as they tend to validate each
other.

If you like the pressure differential AOA probes, this is a good one.
http://www.cgmasi.com/aviation/index.html

If you want NASA quality data, the gold standard is the pitch vane
mounted on an air-data nose boom. There are a number of vendors who
sell these for UAV's which are about the right size for homebuilt
airplanes.
Here's an example: http://www.spaceagecontrol.com/Adpmain

Bill D


On May 9, 6:30*am, Mike wrote:
Has anyone built an electronic angle of attack meter kit. *It seems to
be something that would be easy to design but beyond my feeble
electronics background.

I have seen the products that are out there and they are simple
differential pressure gauges and are expensive. *I don't like the
round differential pressure gauges that many of the companies offer
for this kind of system. *I was wondering if there would be a way to
put something together that would light up different color LED's for
the different levels of lift that we could build at home without
having to pay out hundreds of dollars for a prebuilt one.

In addition to Bill's comments the calibrations process must consider the position of the flaps. Remember you are measuring the AOA of the airfoil, not just the airflow relative to the fuselage.

Wayne
http://www.soaridaho.com/Schreder
..
"bildan" wrote in message ...
I've worked this problem for a number of years. Let me offer a few
simple points.

Any system of measuring AOA will need to be calibrated. It doesn't
really need to be linear since the major interest is in the region
near stall and Cl max. It just needs to give a variable output that
is related to AOA - and be very repeatable.

If the cockpit is in clean free air flow as with a pusher or
sailplane, an effective AOA indicator can be made with a simple string
taped to the side of the canopy. On sailplanes, these 'pitch strings'
tends to 'over-indicate' by about 2:1 which is fine as it increases
the resolution of the indicator. Stall, Cl max and L/D max can be
marked on the inside of the canopy with grease pencil. It helps to
put one on each side of the canopy as they tend to validate each
other.

If you like the pressure differential AOA probes, this is a good one.
http://www.cgmasi.com/aviation/index.html

If you want NASA quality data, the gold standard is the pitch vane
mounted on an air-data nose boom. There are a number of vendors who
sell these for UAV's which are about the right size for homebuilt
airplanes.
Here's an example: http://www.spaceagecontrol.com/Adpmain

Bill D

bildan wrote:
I've worked this problem for a number of years. Let me offer a few
simple points.

Any system of measuring AOA will need to be calibrated. It doesn't
really need to be linear since the major interest is in the region
near stall and Cl max. It just needs to give a variable output that
is related to AOA - and be very repeatable.

If the cockpit is in clean free air flow as with a pusher or
sailplane, an effective AOA indicator can be made with a simple string
taped to the side of the canopy. On sailplanes, these 'pitch strings'
tends to 'over-indicate' by about 2:1 which is fine as it increases
the resolution of the indicator. Stall, Cl max and L/D max can be
marked on the inside of the canopy with grease pencil. It helps to
put one on each side of the canopy as they tend to validate each
other.

If you like the pressure differential AOA probes, this is a good one.
http://www.cgmasi.com/aviation/index.html

It occurs to me that a differential system should be fairly simple to
build. Solid state pressure sensors have been around a long time. Since
AOA would be the ratio between the two sensors it should be simple to
make a comparator to voltage converter since actual pressures are
irrelevant as long as they are sufficient to be read. Airspeed would
also not be a factor. I suppose a purely mechanical system could also be
built by a mechanically inclined type. Pressure from each port would be
sent to opposing bellows in an indicator which would position a needle.

Dan, U.S. Air Force, retired

On Sat, 9 May 2009 05:30:37 -0700 (PDT), Mike
wrote:

Has anyone built an electronic angle of attack meter kit. It seems to
be something that would be easy to design but beyond my feeble
electronics background.

I have seen the products that are out there and they are simple
differential pressure gauges and are expensive. I don't like the
round differential pressure gauges that many of the companies offer
for this kind of system. I was wondering if there would be a way to
put something together that would light up different color LED's for
the different levels of lift that we could build at home without
having to pay out hundreds of dollars for a prebuilt one.
Buy an electronic differential pressureindicator and put a bar graph
on it.

Not cheap - new Setras are about $400 but they are available surplus
occaisionally at good prices. You want 0-5 volt, not 20ma outputs.