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AOA circuitry

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Mike Welch

Joined: 13 Feb 2011
Posts: 272

Posted: Fri Feb 25, 2011 11:46 am Post subject: AOA circuitry

Guys,

  

   Just for fun, I am going to build that AOA circuit recently referred to on this list.

 It's the one that uses a Hall Effect sensor, and airstream probe that has a

 tiny magnet that swings past the sensor, depending on AOA (airspeed controlled).

 (see enclosed attachment)

  

   The author refers to the Hall Effect sensor as the Allegro N503 (as well as it also 

 being N305, but I suspect this is a typo).  In either case, it appears that this particular

 sensor may be out of production, and replaced with the A1302, and the more sensitive

 A1301.  (This is just a guess on my part, because I can't seem to find out anything about

 a N503, but I did find an Allegro N3503, which they say is replaced by the A1302/A1301.)

  

   In analyzing this circuit, can anyone identify if the Hall Effect sensor A1302, would work?

 Why I be better off with the more sensitive A1301?  Are these not even the correct ones,

 and there is a better choice?

  

   What about a magnet suggestion.  The author suggests the .374" long x.1mm x .1mm

 samaruim cobalt magnet, and then lists a neomydium magnet in his list of parts.  ???

  

 Thanks for your help,

  

 Mike Welch

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jimw_btg(at)earthlink.net
Guest

Posted: Fri Feb 25, 2011 12:54 pm Post subject: AOA circuitry

Mike,

The Neodymium and Samarium Cobalt magnets are both rare-earth magnets.  They are both used in Servo motor and stepper motor technology.  I would believe either would work just basic supply availability.

 

I looked at the article as well and felt that was a typo as well.  I did not compare the specs of the N35o3 to the new replacements.  Take care happy building.

 

Jim Wickert

Tel 920-467-0219

Cell 920-912-1014



 

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Mike Welch

Sent: Friday, February 25, 2011 1:42 PM

To: aeroelectric-list(at)matronics.com

Subject: AOA circuitry

 

Guys,

 

  Just for fun, I am going to build that AOA circuit recently referred to on this list.

It's the one that uses a Hall Effect sensor, and airstream probe that has a

tiny magnet that swings past the sensor, depending on AOA (airspeed controlled).

(see enclosed attachment)

 

  The author refers to the Hall Effect sensor as the Allegro N503 (as well as it also 

being N305, but I suspect this is a typo).  In either case, it appears that this particular

sensor may be out of production, and replaced with the A1302, and the more sensitive

A1301.  (This is just a guess on my part, because I can't seem to find out anything about

a N503, but I did find an Allegro N3503, which they say is replaced by the A1302/A1301.)

 

  In analyzing this circuit, can anyone identify if the Hall Effect sensor A1302, would work?

Why I be better off with the more sensitive A1301?  Are these not even the correct ones,

and there is a better choice?

 

  What about a magnet suggestion.  The author suggests the .374" long x.1mm x .1mm

samaruim cobalt magnet, and then lists a neomydium magnet in his list of parts.  ???

 

Thanks for your help,

 

Mike Welch

 

  [quote][b]

retasker(at)optonline.net
Guest

Posted: Fri Feb 25, 2011 1:41 pm Post subject: AOA circuitry

If you look at his web site, there is a new PDF for download there, which I have included.  There is also a different one on the web that was presented to an EAA chapter meeting as well.

 

 These new descriptions say to use a Honeywell SS49 for the sensor.  See http://www.mouser.com/search/ProductDetail.aspx?qs=%2Ffq2y7sSKcICtUFaib78cA%3D%3D

 

 How that compares to the one you are suggesting, I do not know.  The circuit is pretty simple.  It just connects the output of the hall sensor to the input of the display IC with provisions for gain and offset settings.

 

 Dick Tasker

 

 Mike Welch wrote:  	  Quote: 	
		     Guys,

  

   Just for fun, I am going to build that AOA circuit recently referred to on this list.

 It's the one that uses a Hall Effect sensor, and airstream probe that has a

 tiny magnet that swings past the sensor, depending on AOA (airspeed controlled).

 (see enclosed attachment)

  

   The author refers to the Hall Effect sensor as the Allegro N503 (as well as it also 

 being N305, but I suspect this is a typo).  In either case, it appears that this particular

 sensor may be out of production, and replaced with the A1302, and the more sensitive

 A1301.  (This is just a guess on my part, because I can't seem to find out anything about

 a N503, but I did find an Allegro N3503, which they say is replaced by the A1302/A1301.)

  

   In analyzing this circuit, can anyone identify if the Hall Effect sensor A1302, would work?

 Why I be better off with the more sensitive A1301?  Are these not even the correct ones,

 and there is a better choice?

  

   What about a magnet suggestion.  The author suggests the .374" long x.1mm x .1mm

   samaruim cobalt magnet, and then lists a neomydium magnet in his list of parts.  ???

  

 Thanks for your help,

  

 Mike Welch

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Ed Anderson

Joined: 10 Jan 2006
Posts: 475

Posted: Fri Feb 25, 2011 2:49 pm Post subject: AOA circuitry

Sounds like an interesting project,  Mike

  

 I had not seen a magnet mounted in that orientation  to a Hall effect sensor previously (but, then my experience with their use is  quite limited), however, it became clear (based on the graph below) that that  specific orientation provides a way to determine which side of the  pitot center line (air flow vector) the van is pointing based on voltage  magnitude.

  

   If VCC is 5 volts, then it looks like 2.5  volts would be VOQ - in which case, a voltage above 2.5 volts would indicate the  vane was pointing in one direction (say Up relative to orientation of pitot  tube)) and if voltage is below 2.5 volts the vane would be pointing to the  opposite direction (say Down relative to the pitot tube).  The magnitude of  the voltage would then indicate the degree of variation from the reference  point.

  

  

 The sensitivity of both of the subtitute sensor you  mentioned are in millivolt/gauss  mv/g.  The old sensor apparently was  around 1.3 mv/g with the A1301 being more sensitive at 2.5 mv/g than the A1302  at 1.3 mv/g 

  

 The effect of substituting the more sensitive A1301  would in effect increase the voltage swing by 2.5 / 1.3 = 1.92 or almost twice  the voltage swing for the same gauss strength over the less sensitive Hall  sensor.  This would undoubtedly call for a different calibration  point in the processing circuit - but should reduce the effects of  electrical noise with a higher voltage input. (See Spreadsheet graph of  this effect below) 

  

 If you did not change the circuit calibration then  I suspect the what you would get (without having analyzed the circuit) is that  your LEDs would in effect indicate approx 1/2 the degree variation of the less  sensitive sensor.  In other words, you would hit the voltage limit  excursion of your LED (due to the 2 times higher voltage per gauss) in about 1/2  of the angular variation of the less sensitive sensor.  

  

                   [img]cid:3A5913E9902A4428A8177526CFE55E75(at)EdPC[/img]

               

                   [img]cid:963D45B0691544578B9A1BE836D56304(at)EdPC[/img]

               

    In plotting their comparative sensitivities to  magnetic field strength change I derived the above chart - so as you can see for  the same magnetic field strength the A1301 gives you approx twice the voltage  swing of the less sensitive 1302 sensor

 So for example, at approx 2000 on the gauss scale  that would give you around 2.5 volts vs almost 5 volts for the 1301.  So  your LED (at 5 volts output)  would be maxed out at 1/2 the gauss  (degree divergence?) strength of the less sensitive sensor - but, I would assume  you could compensate for that in the calibration or an resistor of twice the  called for value someplace in the circuit - otherwise, just go with the drop in  replacement the 1302.

  

 In any case, looks like a fun and interesting  project

  

 Good Luck with it, be interested in hear the  results once you are flying with it.

  

 Ed

  

 Edward L. Anderson

Anderson Electronic  Enterprises LLC

305 Reefton Road

Weddington, NC 28104

http://www.andersonee.com

http://www.eicommander.com



  



  



  



  From: Mike  Welch (mdnanwelch7(at)hotmail.com) 

 Sent: Friday, February 25, 2011 2:41 PM

 To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)  

 Subject: AOA circuitry

 



Guys,

 

  Just for fun, I am going to build that  AOA circuit recently referred to on this list.

It's the one that uses a Hall  Effect sensor, and airstream probe that has a

tiny magnet that swings past  the sensor, depending on AOA (airspeed controlled).

(see enclosed  attachment)

 

  The author refers to the Hall Effect sensor as  the Allegro N503 (as well as it also 

being N305, but I suspect this is a  typo).  In either case, it appears that this particular

sensor may be  out of production, and replaced with the A1302, and the more  sensitive

A1301.  (This is just a guess on my part, because I can't seem  to find out anything about

a N503, but I did find an Allegro N3503, which  they say is replaced by the A1302/A1301.)

 

  In analyzing this  circuit, can anyone identify if the Hall Effect sensor A1302, would  work?

Why I be better off with the more sensitive A1301?  Are these not  even the correct ones,

and there is a better choice?

 

  What  about a magnet suggestion.  The author suggests the .374" long x.1mm x  .1mm

samaruim cobalt magnet, and then lists a neomydium magnet  in his list of parts.  ???

 

Thanks for your  help,

 

Mike Welch

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_________________
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com

Mike Welch

Joined: 13 Feb 2011
Posts: 272

Posted: Fri Feb 25, 2011 3:58 pm Post subject: AOA circuitry

Thanks for the information and pointers, Jim, Dick, and Ed!!

  

 That updated article you shared, Dick, is much sharper and has a lot more detail. 

  

 I found some magnets on eBay that I think would be perfect for trying out, Jim.

  

 Ed, I think you are correct about the A1302 being the better sensor (compared to 

 the 1301).  I'm not trying a reinvent the wheel, (completely), so I think I'll get a couple 

 of those 1302's and the Honeywell SS49, and compare the two.

  

   It'll be a couple of weeks before I can round up all the parts, but when I get something

 soldered together, I'll get back to ya'll with some details, and a picture or two.

  

 Thanks again, guys!!

  

 Mike Welch

 

 

 		 	   		    [quote][b]

email(at)jaredyates.com
Guest

Posted: Fri Feb 25, 2011 4:38 pm Post subject: AOA circuitry

I know it isn't exactly on topic for your question, but I am remembering a discussion at Oshkosh 2009 hosted by Corky Fornoff.  He was talking about the Bede jet that he and Burt were trying to get flying for a movie, and said that the feds required them to have an AOA indication.  After much head-scratching, they went with a mechanical AOA that featured a vane and a pointer on a common pivot, with the vane on the outside of the fuse and a pointer on the inside of the fuse.  With one moving part, it was about as simple as it gets.  I know you're looking for an electrical project, but it might be considering if anyone wants a simple AOA instead.

 

On Fri, Feb 25, 2011 at 6:50 PM, Mike Welch <mdnanwelch7(at)hotmail.com (mdnanwelch7(at)hotmail.com)> wrote:

[quote]      Thanks for the information and pointers, Jim, Dick, and Ed!!

  

 That updated article you shared, Dick, is much sharper and has a lot more detail. 

  

 I found some magnets on eBay that I think would be perfect for trying out, Jim.

  

 Ed, I think you are correct about the A1302 being the better sensor (compared to 

 the 1301).  I'm not trying a reinvent the wheel, (completely), so I think I'll get a couple 

 of those 1302's and the Honeywell SS49, and compare the two.

  

   It'll be a couple of weeks before I can round up all the parts, but when I get something

 soldered together, I'll get back to ya'll with some details, and a picture or two.

  

 Thanks again, guys!!

  

 Mike Welch

 

 

 		 	   		     	  Quote: 	
		  



ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

tp://forums.matronics.com

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[b]

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Feb 25, 2011 5:32 pm Post subject: AOA circuitry

At 05:38 PM 2/25/2011, you wrote:

Sounds like an interesting project, Mike



I had not seen a magnet mounted in that orientation to a Hall effect 

sensor previously (but, then my experience with their use is quite 

limited), however, it became clear (based on the graph below) that 

specific orientation provides a way to determine which side of the 

pitot center line (air flow vector) the van is pointing based on 

voltage magnitude.



If VCC is 5 volts, then it looks like 2.5 volts would be VOQ - in 

which case, a voltage above 2.5 volts would indicate the vane was 

pointing in one direction (say Up relative to orientation of pitot 

tube)) and if voltage is below 2.5 volts the vane would be pointing 

to the opposite direction (say Down relative to the pitot tube).  The 

magnitude of the voltage would then indicate the degree of variation 

from the reference point.



   We looked at linear hall effect sensors as potential

   non-contact position feedback for use in actuators.

   This particular technology didn't get off the ground

   due to the limited range of linear output performance

   . . . combined with some temperature drift issues.



   Years later, Microswitch came out with a chip that

   contained a pair of magnetometers oriented 90 degrees

   to each other. The output of these two devices could

   be resolved into a discrete value over the full 360

   degrees of magnet rotation. But these were analog

   outputs that required a lot of external support hardware

   and perhaps software too. A friend of mine did a proof-

   of-concept potentiometer replacement using this technology.

   Never found a good fit for the idea.



   Then came these guys:



http://www.austriamicrosystems.com/eng/Products/Magnetic-Encoders/Rotary-Encoders



   I've proposed several programs that would exploit

   this technology for the purpose of replacing

   rotary variable differential transformers and/or

   potentiometers.



   On my website at:



http://www.aeroelectric.com/Mfgr_Data/Sensors/Austriamicrosystems/



   you'll find a data package on the AS5040, which is

   a 10-bit encoder. There's a video that demonstrates

   a portion of its functionality. I had to shoot the

   video in subdued light so that the LEDs would show

   up so the foreground features are pretty noisy . . .

   but you get the idea.



   The green LED in the center is driven by the chip's

   PWM output. Note that the count goes over the cliff

   at 1024 and drops to zero. The green LED appears to

   go dark and comes back alive as the count increases.

   There's another pair of LEDS in the upper left corner

   that are warning flags for magnet mis-positioning.

   You see these flash around count 910 as a result

   of my clumsiness. When I pull the shaft out of the

   hole to show the magnet, the display goes nuts. The

   lights come on to annunciate bad data.



   This chip internally decodes rotary position and

   outputs it simultaneously as serial data (0001-1024)

   and PWM 5V full scale with 1024 bits of resolution.

   If your range of display interest spreads over say, 6

   degrees. Delta-V in the PWM output is on the order

   of 80 millivolts. It would take very little gain

   to drive a meter movement.



   At the same time, you could consider processing

   serial data with something like a PIC

   microcontroller. That approach could drive an LED

   array directly. The 6 delta-degrees of interest

   would offer a delta-count on the order of 17.

   If more resolution is needed, the AS5045 would

   offer 4096 bits of resolution. This wouldn't help

   the PWM output except to offer finer granularity

   of data. The delta-count in the digital stream

   would go up by a factor of 4 to 85 counts.



   These are modern parts, readily available (samples

   are even free) and a whole lot more predictable

   in performance than the linear hall effect devices.



   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Feb 25, 2011 5:34 pm Post subject: AOA circuitry

P.S.



EmagAir uses the Austriamicrosystems technology as a crankshaft

position sensor to drive their ignition timing routine.



   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Feb 25, 2011 7:32 pm Post subject: AOA circuitry

 	  Quote: 	
		  



   It'll be a couple of weeks before I can round up all the parts, 

 but when I get something

soldered together, I'll get back to ya'll with some details, and a 

picture or two.



Thanks again, guys!!



Mike Welch


	


    I dug around in the skunk-werks inventory

    and found a package of 5 AS5040 chips and some

    "baby aspirin" magnets. If you'd like to

    explore this technology, I can send them to

    you. Also, someplace in the digital archives,

    I'm pretty sure I have a layout for the ECB

    that would mount these puppies and bring

    the relevant leads out to a .1" space c-grid

    header. Unfortunately, these critters only

    come in a not too terribly friendly 16-lead

    surface mount part. But once they're down

    on the board, the rest is pretty straight

    forward.



   Bob . . .

earl_schroeder(at)juno.co
Guest

Posted: Fri Feb 25, 2011 8:28 pm Post subject: AOA circuitry

Hi Bob,

I've built the AOA from the kit that has been under discussion.  However, I could not  get full scale display 

from the vane movement desired with the time I had to spend on the project and put the parts in a drawer.

Perhaps the AS5040 could be retrofitted but it probably would require more connecting wires than the 

three in the original design.



I also have an AOA in the Lancair that has sensing ports in the upper and lower wing skins along with

airspeed, static air, flap and gear position inputs.  This system works great and used in getting that slick

machine shoe horned in a 2200 grass strip it calls home.



If you have surplus parts after supplying the current builders, I would try to find time to experiment a bit..



Thanks, Earl

 

--------

user9253

Joined: 28 Mar 2008
Posts: 1935
Location: Riley TWP Michigan

Posted: Sat Feb 26, 2011 12:27 pm Post subject: Powerful magnets

If you have an old hard drive that you do not want, you can take it apart and remove the powerful magnets.  Do not get your fingers between them!

Joe

_________________
Joe Gores

email(at)jaredyates.com
Guest

Posted: Sat Feb 26, 2011 1:58 pm Post subject: AOA circuitry

If you want an old hard drive to take apart and don't have one, send me an email and I'll fill up a flat-rate envelope for you.



On Sat, Feb 26, 2011 at 3:27 PM, user9253 <fran4sew(at)banyanol.com (fran4sew(at)banyanol.com)> wrote:

 [quote]--> AeroElectric-List message posted by: "user9253" <fran4sew(at)banyanol.com (fran4sew(at)banyanol.com)>

  

 If you have an old hard drive that you do not want, you can take it apart and remove the powerful magnets.  Do not get your fingers between them!

 Joe

 

 --------

 Joe Gores

 

 

 

 

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