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sean(at)stephensville.com
Guest

Posted: Tue Nov 21, 2006 10:06 am Post subject: Homebrew AHRS?

I've been scouring Google trying to find literature, schematics, etc. on 

building an AHRS/ADAHRS.  I've been unable to find anything that would 

get me jump-started on a homebrew project.



If anyone has links that would help I'd appreciate it.



-Sean

ainut(at)hiwaay.net
Guest

Posted: Tue Nov 21, 2006 2:42 pm Post subject: Homebrew AHRS?

check out 3 axis accelerometers and 3 axis magnetometers.



David M.

still trying to get a handle on it myself.



Sean Stephens wrote:



 	  Quote: 	
		   

 <sean(at)stephensville.com>



 I've been scouring Google trying to find literature, schematics, etc. 

 on building an AHRS/ADAHRS.  I've been unable to find anything that 

 would get me jump-started on a homebrew project.



 If anyone has links that would help I'd appreciate it.



 -Sean

Ed Anderson

Joined: 10 Jan 2006
Posts: 475

Posted: Tue Nov 21, 2006 6:08 pm Post subject: Homebrew AHRS?

Hi Sean,



Try out this URL  http://www.aerospectra.com/efis/svis.htm



Dr Jim Hauser has a book worth getting on the basics as well as the 

components to get started.



Ed



Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson(at)carolina.rr.com

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.dmack.net/mazda/index.html

---

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

sales(at)6440autoparts.co
Guest

Posted: Wed Nov 22, 2006 8:05 am Post subject: Homebrew AHRS?

I personally don't see the sense in spending $2000-$5000 

building your own AHRS according to that website when a Dynon or GRT etc. 

can be bought ready to go. And they are tried and true.

            Unless of course one wanted to market one or just does'nt have 

anything better to do.

           But of course time permitting one could be built cheap 

well........



Randy



---

Ed Anderson

Joined: 10 Jan 2006
Posts: 475

Posted: Wed Nov 22, 2006 9:08 am Post subject: Homebrew AHRS?

[quote] Your correct, Randy, assuming that the only objective/goal  is to have an 

 AHRS in your panel.



 But, some simply want to continue the "educational" goal of Amateur build 

 aircraft by expanding into other associated areas.  I designed and built 

 my own EFI Fuel Monitoring System which uses no fuel flow transducer - 

 yes, the parts were certainly cheaper than a purchased one - but, if I 

 included even a modest value for my time - then the commercial one would 

 have been cheaper {:>).  But, the goal was not just to build my own, but 

 to learn to design,build and program using microchips.



 I've just completed a design and prototype for an AOA indicator - again, 

 not because one could not be purchased at a reasonable price - but simply 

 because I enjoy learning new things and building.



 Different strokes for different folks.



 Ed

 Ed Anderson

 Rv-6A N494BW Rotary Powered

 Matthews, NC

 eanderson(at)carolina.rr.com

 http://members.cox.net/rogersda/rotary/configs.htm#N494BW

 http://www.dmack.net/mazda/index.html



 ---

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

nuckollsr(at)cox.net
Guest

Posted: Wed Nov 22, 2006 11:16 am Post subject: Homebrew AHRS?

At 10:03 AM 11/22/2006 -0600, you wrote:



 	  Quote: 	
		  

<sales(at)6440autoparts.com>



              I personally don't see the sense in spending $2000-$5000 

 building your own AHRS according to that website when a Dynon or GRT etc. 

 can be bought ready to go. And they are tried and true.

            Unless of course one wanted to market one or just does'nt have 

 anything better to do.

           But of course time permitting one could be built cheap well........


	


    Depends on the goal. I'm presently trying to sell

    some MBA types on the value of IR&D with an emphasis

    on the "I".



    Should you wish to understand and make utility of

    the ingredients needed to accomplish a task, you need

    to start with the simple-ideas. The task is to explore

    how they perform and the elegant ways they may be

    assembled into useful products.



    If someone expresses a desire to "build" something,

    it's not uncommon for folk to counsel against the

    activity for a variety of reasons not the least of

    which is a perceived re-invention of some wheel.



    Randy has suggested that he might build one "cheap".

    I CAN advise that for the majority of cases, tasks

    of this nature may be emulated but unless your time

    has zero value, it's never cheap. While the hardware

    IS readily available and inexpensive, an AHRS system

    designed around rate sensors is exceedingly software

    intensive. Launching a new project of this type without

    the support of a cadre' of smart people (knowledgeable

    and experienced) is risky . . . especially if you

    plan to poke your airplane into clouds.



    The task is much more than buying some parts and

    wiring them together. You need a working knowledge

    of crafting flight stabilization software. You also

    need a means for testing it without risking life, limb

    or airplane. We used to do a lot of this work at RAC

    Missiles and had hardware-in-the-loop simulation for

    testing.



    So before we can advise Randy well, we need to

    know what his plan is. The starting point is today

    and the end point is (????). What is it you wish

    to achieve Randy? Be aware too that the successful

    ventures of this type are never "cheap."



    Bob . . .

sportav8r(at)gmail.com
Guest

Posted: Wed Nov 22, 2006 11:29 am Post subject: Homebrew AHRS?

Okay, Ed.  Want to tell us how you did it without a transducer?



Minds that need examining want to know...



-Stormy



On 11/22/06, Ed Anderson <eanderson(at)carolina.rr.com> wrote:

[quote] 





 > Your correct, Randy, assuming that the only objective/goal  is to have an

 > AHRS in your panel.

 >

 > But, some simply want to continue the "educational" goal of Amateur build

 > aircraft by expanding into other associated areas.  I designed and built

 > my own EFI Fuel Monitoring System which uses no fuel flow transducer -

 > yes, the parts were certainly cheaper than a purchased one - but, if I

 > included even a modest value for my time - then the commercial one would

 > have been cheaper {:>).  But, the goal was not just to build my own, but

 > to learn to design,build and program using microchips.

 >

 > I've just completed a design and prototype for an AOA indicator - again,

 > not because one could not be purchased at a reasonable price - but simply

 > because I enjoy learning new things and building.

 >

 > Different strokes for different folks.

 >

 > Ed

 > Ed Anderson

 > Rv-6A N494BW Rotary Powered

 > Matthews, NC

 > eanderson(at)carolina.rr.com

 > http://members.cox.net/rogersda/rotary/configs.htm#N494BW

 > http://www.dmack.net/mazda/index.html

 >

 > ---

ceengland(at)bellsouth.ne
Guest

Posted: Wed Nov 22, 2006 12:20 pm Post subject: Homebrew AHRS?

You're out of luck, Bill. It takes a fuel delivery system designed post 

stone age.



Charlie

(reluctantly contemplating a stone age engine to save build time)



Bill Boyd wrote:



 	  Quote: 	
		   

 <sportav8r(at)gmail.com>



 Okay, Ed.  Want to tell us how you did it without a transducer?



 Minds that need examining want to know...



 -Stormy



 On 11/22/06, Ed Anderson <eanderson(at)carolina.rr.com> wrote:



> 

> <eanderson(at)carolina.rr.com>

>

>

> > Your correct, Randy, assuming that the only objective/goal  is to 

> have an

> > AHRS in your panel.

> >

> > But, some simply want to continue the "educational" goal of Amateur 

> build

> > aircraft by expanding into other associated areas.  I designed and 

> built

> > my own EFI Fuel Monitoring System which uses no fuel flow transducer -

> > yes, the parts were certainly cheaper than a purchased one - but, if I

> > included even a modest value for my time - then the commercial one 

> would

> > have been cheaper {:>).  But, the goal was not just to build my 

> own, but

> > to learn to design,build and program using microchips.

> >

> > I've just completed a design and prototype for an AOA indicator - 

> again,

> > not because one could not be purchased at a reasonable price - but 

> simply

> > because I enjoy learning new things and building.

> >

> > Different strokes for different folks.

> >

> > Ed

> > Ed Anderson

> > Rv-6A N494BW Rotary Powered

> > Matthews, NC

> > eanderson(at)carolina.rr.com

> > http://members.cox.net/rogersda/rotary/configs.htm#N494BW

> > http://www.dmack.net/mazda/index.html

Ed Anderson

Joined: 10 Jan 2006
Posts: 475

Posted: Wed Nov 22, 2006 12:35 pm Post subject: Homebrew AHRS?

[quote] Ok Stormy, you asked for it {:>).



 The "secret" is that my fuel system is Electronic Fuel Injection - The 

 short of it is - I measure the pulse width of the signal sent to the fuel 

 injectors. Skip the rest of the explanation which follows  if that is 

 sufficient enough answer {:>).



 Knowing the flow rate of the injectors and the duration of each revolution 

 of the engine in which they are "turned on".  This is used to form a ratio 

 of Injector-On_time/Period-of-revolution which is multiplied by the total 

 fuel flow capacity of the 4 injectors which gives the instantaneous flow 

 rate.  Then  I (rather the chip) calculates the instantaneous rate of flow 

 (adjusts the value for a 1 hour period) and displays it as "Gallons/Hour" 

 fuel burn.



 To totalize the amount of fuel use, I set a variable with a value of time 

 (microseconds) that equals 1/100 of a gallon (you could set it any 

 quantity).  When the "on-time" of the injectors has equaled that amount of 

 time the Fuel totalizer increments by .01 gallon. and the "on-time" resets 

 to zero waiting for the injector-on duration to again build up to that 

 amount of time that equals 0.01 gallon again which then ticks over the 

 display to 0.02 gallons, etc.



  These values are stored in memory so when you shut down, when you restart 

 the engine, it picks up where it left off.   Pilot set  "Switch tank" and 

 "low fuel" alarms are incorporated as well as an Air/Fuel indictor for 

 mixture control. Fuel used, fuel remaining, time remaining at current burn 

 rate, RPM and calculated HP (just because the info was there to do it) are 

 also calculated and displayed on user selectable screens.  It all fits in 

 a 2 1/4" instrument hole.



 So the only thing the unit needs is a single wire to one of the Fuel 

 injectors to get the pulse data (also needs one wire to the O2 sensor, if 

 using the Air/Fuel indication function) , this saves the $200 or so for a 

 fuel flow transducer.  But, of course, it only works for electronic fuel 

 injectors.  Another nice feature is you don't need to even consider the 

 unused fuel returned to the tank (some systems require two transducers to 

 handle this ) because this unit only measure fuel actually injected and 

 consumed and therefore doesn't worry about the fuel flowing in the lines 

 or being diverted back to the tank.



 The parts cost considerably less than the fuel transducer- but, the amount 

 of time it took me to learn to design with and program these microchips - 

 would have amounted to thousands of dollars even at the minimum wage rate 

 {:>)



 Now, aren't you sorry you asked {:>)?



 Ed

 Ed Anderson

 Rv-6A N494BW Rotary Powered

 Matthews, NC

 eanderson(at)carolina.rr.com

 http://members.cox.net/rogersda/rotary/configs.htm#N494BW

 http://www.dmack.net/mazda/index.html

 ---

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

sean(at)stephensville.com
Guest

Posted: Wed Nov 22, 2006 1:01 pm Post subject: Homebrew AHRS?

Sorry to stir up a debate.



This is purely for an educational experience on my part.  I am in the 

middle of down time from building the airframe due to a relocation, so 

merely wanted to do some "experimenting" just to feed my brain.



I was just looking for some literature and maybe a less $$ option than 

buying a commercial grade ADAHRS such as the xbow NAV420.



Thanks all,



-Sean (RV-10 40303 buildus interuptus)



Bill Boyd wrote:

[quote] 

 <sportav8r(at)gmail.com>



 Okay, Ed.  Want to tell us how you did it without a transducer?



 Minds that need examining want to know...



 -Stormy



 On 11/22/06, Ed Anderson <eanderson(at)carolina.rr.com> wrote:

> 

> <eanderson(at)carolina.rr.com>

>

>

> > Your correct, Randy, assuming that the only objective/goal  is to 

> have an

> > AHRS in your panel.

> >

> > But, some simply want to continue the "educational" goal of Amateur 

> build

> > aircraft by expanding into other associated areas.  I designed and 

> built

> > my own EFI Fuel Monitoring System which uses no fuel flow transducer -

> > yes, the parts were certainly cheaper than a purchased one - but, if I

> > included even a modest value for my time - then the commercial one 

> would

> > have been cheaper {:>).  But, the goal was not just to build my 

> own, but

> > to learn to design,build and program using microchips.

> >

> > I've just completed a design and prototype for an AOA indicator - 

> again,

> > not because one could not be purchased at a reasonable price - but 

> simply

> > because I enjoy learning new things and building.

> >

> > Different strokes for different folks.

> >

> > Ed

> > Ed Anderson

> > Rv-6A N494BW Rotary Powered

> > Matthews, NC

> > eanderson(at)carolina.rr.com

> > http://members.cox.net/rogersda/rotary/configs.htm#N494BW

> > http://www.dmack.net/mazda/index.html

> >

> > ---

Terry Watson

Joined: 09 Jan 2006
Posts: 290
Location: Seattle, WA USA

Posted: Wed Nov 22, 2006 1:48 pm Post subject: Homebrew AHRS?

Sean,



There used to be an experimental avionics list somewhere. You might check

the archives on Matt's Matronics Avionics list and see if there is still any

discussion of what you are interested in, or maybe a reference to a list

that does have it.



Terry

This is purely for an educational experience on my part.  I am in the 

middle of down time from building the airframe due to a relocation, so 

merely wanted to do some "experimenting" just to feed my brain.



I was just looking for some literature and maybe a less $$ option than 

buying a commercial grade ADAHRS such as the xbow NAV420.



Thanks all,



-Sean (RV-10 40303 buildus interuptus)

ainut(at)hiwaay.net
Guest

Posted: Wed Nov 22, 2006 2:34 pm Post subject: Homebrew AHRS?

Great things are being done now with MEMS, and at just a few dollars per 

function.



David M.

Ed Anderson wrote:



[quote] 

 <eanderson(at)carolina.rr.com>





> Your correct, Randy, assuming that the only objective/goal  is to 

> have an AHRS in your panel.

>

> But, some simply want to continue the "educational" goal of Amateur 

> build aircraft by expanding into other associated areas.  I designed 

> and built my own EFI Fuel Monitoring System which uses no fuel flow 

> transducer - yes, the parts were certainly cheaper than a purchased 

> one - but, if I included even a modest value for my time - then the 

> commercial one would have been cheaper {:>).  But, the goal was not 

> just to build my own, but to learn to design,build and program using 

> microchips.

>

> I've just completed a design and prototype for an AOA indicator - 

> again, not because one could not be purchased at a reasonable price - 

> but simply because I enjoy learning new things and building.

>

> Different strokes for different folks.

>

> Ed

> Ed Anderson

> Rv-6A N494BW Rotary Powered

> Matthews, NC

> eanderson(at)carolina.rr.com

> http://members.cox.net/rogersda/rotary/configs.htm#N494BW

> http://www.dmack.net/mazda/index.html

>

> ---

Ed Anderson

Joined: 10 Jan 2006
Posts: 475

Posted: Wed Nov 22, 2006 2:52 pm Post subject: Homebrew AHRS?

I agree David,



The MEMS accelerometers and gyros certain are making very capable autopilots 

possible at very reasonable prices.  Hummm.



Ed

---

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

mthomson(at)showmeproduct
Guest

Posted: Thu Nov 23, 2006 6:13 am Post subject: Homebrew AHRS?

I was the President of Blue Mountain Avionics for about 15 months and I can

confirm the h/w parts of an AHRS system are not very extensive.  However,

the required software engineering skills and experience with this type of

technology are considerable if you want the AHRS to work well under the

conditions we might encounter in flight.  I have two Crossbow AHRS 425's

which still do not work correctly. Crossbow claims the latest update fixes

things others have told me not so. They have been fixing problems with the

425 for over a year!



What kind would you build - basic AHRS - a GPS aided AHRS - a GPS and Air

Data aided AHRS?



I know BMA and others continue to make refinements to their AHRS software -

rarely do they need to change or update the hardware. I would not advise a

home built approach to this critical part of your aircraft.



Malcolm.



--

Mike@Crossbow

Joined: 28 Nov 2006
Posts: 8

Posted: Tue Nov 28, 2006 12:36 pm Post subject: Re: Homebrew AHRS?

Malcolm,



If you are having trouble with your Crossbow NAV425EX, please contact us directly.  Crossbow is committed to our customers and we will do everything in our power to ensure that you are receiving proper operation from your AHRS.  Since we started the upgrade program, we have had dozens of these units completed and have not had any further problems with the NAV425.

_________________
Michael Smith
Application Engineer Inertial Systems
Crossbow Technology
msmith@xbow.com

mthomson(at)showmeproduct
Guest

Posted: Tue Nov 28, 2006 7:13 pm Post subject: Homebrew AHRS?

Will you confirm that your test sites are now trouble free?  I would really

like to get these units working properly.

Malcolm. 



--

Mike@Crossbow

Joined: 28 Nov 2006
Posts: 8

Posted: Wed Nov 29, 2006 7:43 am Post subject: Re: Homebrew AHRS?

Malcolm,



I can confirm that we have not seen a repeat of any of the items called out in our service bulletin nor have we seen any new failures in the upgraded units.  We have over 30 of these units in the field and have not had any further problems with the NAV425EX.  If you are running the NAV425EX, we offer this update for free and will do everything possible to minimize any down time to your aircraft.

_________________
Michael Smith
Application Engineer Inertial Systems
Crossbow Technology
msmith@xbow.com

Todd.Stovall(at)pentagon.
Guest

Posted: Wed Nov 29, 2006 8:32 am Post subject: Homebrew AHRS?

Michael,

I'm considering purchasing the OP Tech EFIS which uses the NAV420.  Has

it suffered the same problems as the 425? 



Thanks,

Todd



--

Mike@Crossbow

Joined: 28 Nov 2006
Posts: 8

Posted: Wed Nov 29, 2006 8:50 am Post subject: Re: Homebrew AHRS?

First, I would like to apologize for hijacking the thread.  That wasn't my intention.  In reference to the original topic, what Malcolm and others have said is completely correct.  We are approached by customers occasionally that complain that they could build the unit for far less because the parts are relatively inexpensive.  Yes, the parts aren't too expensive but the software is very complicated and you will need to rely upon some sort of aiding (GPS, Kalman filtering, Airspeed, etc..) to improve performance of an AHRS.  MEMS gyro's without this aiding are really not accurate enough for aviation in my opinion.  By the time you are done creating software and testing a fully functional unit you would have saved a significant amount of money by purchasing a completed solution.  Now, if you want to create an AHRS for your personal enjoyment...then yes it's probably worthwhile.



In regards to OP Tech, we have not seen any failures with the NAV420's that we shipped to OP Tech, but a very large percentage of the ones that were shipped to OP Tech were already updated with the latest hardware/firmware so we wouldn't expect to see much.  The early units that were shipped OP Tech have also come back to be updated and we haven't been informed of any problems with those units.  



Crossbow is aware of the delay and inconvenience that we have put our NAV425EX customers through and on behalf of Crossbow I would like to personally apologize for the amount of time that it took to get this fix in place.  We have been updating these units since May of this year and are confident that the fixes we have in place remedy all noted issues that are stated in the service bulletin.

_________________
Michael Smith
Application Engineer Inertial Systems
Crossbow Technology
msmith@xbow.com

nuckollsr(at)cox.net
Guest

Posted: Wed Nov 29, 2006 6:51 pm Post subject: Homebrew AHRS?

At 08:50 AM 11/29/2006 -0800, you wrote:



 	  Quote: 	
		  



First, I would like to apologize for hijacking the thread.


	




    Nobody "hijacks" anything if they have good

    data to share . . .



 	  Quote: 	
		     That wasn't my intention.  In reference to the original topic, what 

 Malcolm and others have said is completely correct.  We are approached by 

 customers occasionally that complain that they could build the unit for 

 far less because the parts are relatively inexpensive.  Yes, the parts 

 aren't too expensive but the software is very complicated and you will 

 need to rely upon some sort of aiding (GPS, Kalman filtering, Airspeed, 

 etc..) to improve performance of an AHRS.  MEMS gyro's without this 

 aiding are really not accurate enough for aviation in my opinion.  By the 

 time you are done creating software and testing a fully functional unit 

 you would have saved a significant amount of money by purchasing a 

 completed solution.  Now, if you want to create an AHRS for your personal 

 enjoyment...then yes it's probably worthwhile.



In regards to OP Tech, we have not seen any failures with the NAV420's 

that we shipped to OP Tech, but a very large percentage of the ones that 

were shipped to OP Tech were already updated with the latest 

hardware/firmware so we wouldn't expect to see much.  The early units that 

were shipped OP Tech have also come back to be updated and we haven't been 

informed of any problems with those units.



Crossbow is aware of the delay and inconvenience that we have put our 

NAV425EX customers through and on behalf of Crossbow I would like to 

personally apologize for the amount of time that it took to get this fix 

in place.  We have been updating these units since May of this year and 

are confident that the fixes we have in place remedy all noted issues that 

are stated in the service bulletin.


	


    Mike, thanks for monitoring the List and for

    joining this conversation. Did we meet at

    Raytheon's Missiles Division when Crossbow

    came out to propose an AHRS for our AQM-37D

    target upgrade?



    I looked for my business cards from those meetings

    but they were now quite some time ago . . . about

    10 years I think.



    bob . . .

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