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05-31-2012, 02:53 PM
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Join Date: Mar 2006
Location: Newport, TN
Posts: 7,496
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I created a GitHub repository for this project here:
https://github.com/brantel/AOA
I have never used this development tool before so I will have to learn as I go.
Those that are interested in helping with the project can join in the fun....
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06-04-2012, 09:47 AM
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Join Date: Jan 2008
Location: Atlanta, GA
Posts: 240
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"There will be two calibrations to account for flaps and no flaps. I plan to use the Arduino serial port to monitor the G3X's datastream for the flap position in order to not require an additional flap deployed switch. "
Correct me if I'm wrong, but isn't AOA going to be the same regardless of flap position? In other words, if you calibrate it clean, the speeds that will correspond to a particular point on the AOA curve might change with flaps, but the angle will be the same relative to the stall... 1.5x clean stall speed vs 1.5x dirty stall speed ought to report roughly the same angle I'd think.
__________________
Ian
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06-04-2012, 10:02 AM
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Join Date: Mar 2006
Location: Newport, TN
Posts: 7,496
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The flaps do alter the critical AOA. Some systems just simplify it to worse case but others do have two or more configurations.
It also depends on what type of flap you have. The RV6/7's flaps alter the lift for about 20degrees and the rest is just drag.
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06-05-2012, 08:53 AM
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Join Date: May 2012
Location: San Diego
Posts: 5
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Consideration of vibration, temperature and moisture on the hardware is obviously important. Here's some anecdotal info on "potting" electronics which may be useful for this project:
Look up conformal coating ? it isn?t expensive.
If you have a reasonable supply of water, you can produce boards as good as any manufacturer who doesn?t use a clean room.
After you make the board and shield the IO/Power connectors, you need to obtain some saponifier.
These make water wetter and can be bought from many places in small quantities.
It is amazingly close to a certain dish detergent that leaves things ?virtually spotless?, and which works well enough for most purposes if you have access to dishwasher. In either case, run the boards through a dishwasher and dry them.
Then bake them in an oven @200F for a while (think about your solder?s melting point and work backwards) ? or set it to 125 or 150 and leave it for a few hours. The goal is to bake out any residual moisture.
After that, purchase any conformal coating ? it?s sold as such, and comes in a spray can. One or two coats and air dry is adequate. Wait a day or more if you can ? everything out-gasses.
Then ? and only then ? do you pot the product.
For high vibration, you use epoxy, for high chance of corrosion/water/etc, use silicone. For inserting it into a body, medical grade silcone.
You can even do both.
A little foam or rubber around the edges helps with vibration isolation ? much more than simply bolting it down. If you have flexible leads that come from the board, knot them and then mechanically secure them to the board with a screw or bracket or hold-down that doesn?t permit movement. This prevents water from sneaking in.
Finally, you might bake the whole thing at a lower temp for a day or two. After that, if you want to shield for RF, thin copper (You can use steel or brass as well) foil origami with soldered seams will have you ready to take on sky net like a pro.
Need to verify that you?re turning out decent electronic hardware?
Pressure, temp and steam test ? old fashioned pressure cooker. Good for a couple atmospheres.
Vacuum/High altitude is harder, but you can get close with almost any vacuum pump and an old pressure cooker body. Or find a used commercial vacuum chamber. You can make one, and use multiple pumps to overcome your sloppy workmanship.
Vibration: Anything that shakes. Car frames work well, especially if you drive off-road or your city is too poor to care. Sweet talking someone with a paint shaker [really excellent] is easier
if you mount your device securely in a paint bucket and stay away from big chain stores.
Be sure to check at several regimes ? the hitachi giant wand/lawn mower deck/paint shaker trio will uncover almost anything.
Finally, RF ? go find someone with a 2 stroke dirt bike not made in japan and try to run your project board attached to the frame with the gnd lead attached to the frame. That will separate the men from the boys within two minutes.
When your project survives all this, it will be suitable for almost anything from submarines to low earth orbit. A good final test is to let your dog/children play with it for a quick game of fetch/keep away.
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06-05-2012, 07:37 PM
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Join Date: Jan 2005
Posts: 68
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Very cool. I'll be eagerly watching this thread. We really will need a simple probe for those of us without Dynon. Will all the machinists in the group I don't doubt someone can whip one out quickly along with some sort of nice housing for the light display for the top of the panel.
Wow .. I love open source and creative people!
DWS
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06-06-2012, 01:16 PM
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Join Date: Mar 2006
Location: Newport, TN
Posts: 7,496
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My sensors have arrived and I am now awaiting some tubing before I can build a test rig to be able to test this thing by sticking it out the window of the truck while my wife drives me down the interstate.
Here is what it looks like so far:
A bit of sample output while in development mode:
So far the code is pretty simple.
Temperature compensation is built into the sensor so I do not have to worry about that.
I have developed a way to automatically cancel out the zero error that all of these type of sensors have to get both sensors on the same bias. Not sure if I will make this automatic at startup or require some sort of operator action to trigger it.
More to come...
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06-07-2012, 09:09 AM
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Join Date: Oct 2007
Location: Novato, CA
Posts: 319
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Pickup AOA
What's the stall speed of your pickup truck? 
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06-07-2012, 09:14 AM
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Join Date: Mar 2006
Location: Newport, TN
Posts: 7,496
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Quote:
Originally Posted by AllThumbs
What's the stall speed of your pickup truck? 
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250kts  ........
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06-07-2012, 09:42 AM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
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Quote:
Originally Posted by AllThumbs
What's the stall speed of your pickup truck? 
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Quote:
Originally Posted by Brantel
250kts  ........
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Let me guess, the liftoff speed is 251kts??
__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010
Phase 1 done, 2/4/2011 
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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06-12-2012, 02:46 PM
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Join Date: Mar 2006
Location: Newport, TN
Posts: 7,496
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Been working on this a little at a time in the evening and during lunch.....
Here is a video that shows where I am at:
First you see the hardware then you will see me blowing into the Pitot line and the results are shown on the LCD screen. Basically a pure Pitot input results in an IAS increase and a negative AOA %.
Next you will see me switch lines and blow into the AOA line and the results on the LCD and the results are shown on the LCD screen. Basically a pure AOA input results in an increase of the AOA%.
Finally you will see me switch to both lines and blow equally into them and the results are shown on the LCD screen. Basically an equal pressure to both results in a 0% AOA and an increase in IAS. The IAS cancels out the AOA% increase.
So now I am left with the challenge of developing some sort of calibration routine for setting the scaling of the LED's to the % of AOA. They are currently scaled linearly across the range of 0-99%. Any of you expert programmers have any suggestions of how to accomplish this task? Looking for different ideas so we can pick the most efficient one.
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