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I-Phone Inclinometer

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rparigor(at)SUFFOLK.LIB.N
Guest

Posted: Fri Aug 08, 2008 7:21 pm Post subject: I-Phone Inclinometer

My partner just showed me the 2 axis Inclinometer on his I-Phone.



Curious if one can use it as emergency attitude indicator? Degree wheel

for roll, pitch you would use the less definitive widening line?



Anyone want to give it a try?



Ron P.

mprather(at)spro.net
Guest

Posted: Fri Aug 08, 2008 9:08 pm Post subject: I-Phone Inclinometer

Would you suppose it uses force or acceleration sensors for this data.  I

did a minor amount of googling to try to learn that..  If force, I doubt

it would provide reliable pitch and roll data - just like the 'ball'

doesn't provide bank angle while in coordinated flight.  Even if it's a

mems gyro I suspect for that application, very little effort would have

been made to cancel out drift rates.  I'd be happy to be wrong, however...

Matt-



 	  Quote: 	
		   



 My partner just showed me the 2 axis Inclinometer on his I-Phone.



 Curious if one can use it as emergency attitude indicator? Degree wheel

 for roll, pitch you would use the less definitive widening line?



 Anyone want to give it a try?



 Ron P.

rgf(at)dcn.davis.ca.us
Guest

Posted: Fri Aug 08, 2008 9:32 pm Post subject: I-Phone Inclinometer

Won't work because it doesn't have a gyro.  Would get fooled just like a

weight on a string.



RF



--

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Sat Aug 09, 2008 5:22 pm Post subject: Re: I-Phone Inclinometer

 	  Quote: 	
		  Won't work because it doesn't have a gyro. Would get fooled just like a weight on a string. RF 	




Or that Saint Christopher medal on a chain you hang from your compass now.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

rampil

Joined: 04 May 2007
Posts: 870

Posted: Sun Aug 10, 2008 4:25 pm Post subject: Re: I-Phone Inclinometer

Actually Ron has a reasonable question.



All of the modern inertial platforms use MEMS-based accelerometers

not gyros as sensors. The problem with MEMS chips is that they drift

and require correction or compensation.  Often the drift correction

can be done with a GPS ala BlueMountain, etc.



So... some enterprising programmer could, with the new GPS

capabilities in the development software now in beta, create an

emergent AI, better in theory that the GPS only system like in the

Garmin 496.



I'm not an engineer, but I played one in grad school for 4 years

_________________
Ira N224XS

etienne.phillips(at)gmail
Guest

Posted: Sun Aug 10, 2008 9:40 pm Post subject: I-Phone Inclinometer

On 11 Aug 2008, at 2:25 AM, rampil wrote:

 	  Quote: 	
		  



All of the modern inertial platforms use MEMS-based accelerometers

not gyros as sensors. The problem with MEMS chips is that they drift

and require correction or compensation.  Often the drift correction

can be done with a GPS ala BlueMountain, etc.

	


All the electronic systems I've come across (MGL and Dynon in particular) use both accelerometers and "solid-state" gyros, and some even use an electronic compass and airspeed. The SS gyros only output the rate of change of direction whereas the accelerometers, compass and airspeed measurements give an absolute value at any time. If the gyros have even a very slight offset error, this will be integrated over time to be a constant change in direction, which is compared 

Etienne

 [quote][b]

rampil

Joined: 04 May 2007
Posts: 870

Posted: Mon Aug 11, 2008 5:20 am Post subject: Re: I-Phone Inclinometer

Etienne,

SS Gyros are in fact MEMS accelerometers.

Actually SS Gyro is an oxymoron since a gyro implies gyroscopic

which implies spinning parts (hard to be solid state at the same time).



See: http://en.wikipedia.org/wiki/MEMS_gyroscope

http://www.sensorsmag.com/articles/0203/14/

http://www.analog.com/en/mems-and-sensors/imems-gyroscopes/adxrs610/products/product.html



etc., etc.



To my knowledge, the inertial platforms of BMA, Dynon, Avidyne (entegra), and Garmin (G1000) are all MEMS-based.  No Gyro components at all.



See for ref:http://www.flyingmag.com/article.asp?section_id=12&article_id=869



or look up the tech specs on the individual systems



PS: The iPhone would need a 3axis sensor to do an inertial platform.

I dont know if thats what's inside.

_________________
Ira N224XS

rampil

Joined: 04 May 2007
Posts: 870

Posted: Mon Aug 11, 2008 8:36 am Post subject: Re: I-Phone Inclinometer

As it turns out, the iPhone uses a monolithic 3 axis sensor, digitally

sampled 8 bit outputs scaled to +/- 2 g or 8 g with 400Hz serial output.



Sounds like the makings of an inertial platform to me!

_________________
Ira N224XS

david.glauser(at)xpsystem
Guest

Posted: Mon Aug 11, 2008 9:18 am Post subject: I-Phone Inclinometer

Several folks are experimenting already:



http://blog.medallia.com/2007/08/fun_with_the_iphone_accelerome.html



"As it turns out, the iPhone has a built-in LIS302DL, a tiny 3-axis

accelerometer. While some have attempted to use it from within the

Safari browser (the Tilt game detects changes to the width of the

browser page; it is basically used as a 1-bit input device), its

potential is still somewhat untapped. After a rather lengthy bout of

reverse-engineering (I had barely touched ARM assembly before this), I

finally figured out how to access the raw data from the accelerometer

itself, as can be seen in the video above. Source code is posted here.

(update: yes, it is possible to access the accelerometer directly

through UIKit without this hack -- however, you'll be locked to the

default sample rate, which is too slow for some of the fun stuff)"



http://www.tuaw.com/2007/09/10/iphone-coding-using-the-accelerometer/

dg 



--

ainut(at)hiwaay.net
Guest

Posted: Mon Aug 11, 2008 10:34 am Post subject: I-Phone Inclinometer

Freescale (used to be Motorola) makes a ton of these MEMS accelerometers.  I 

have one on one of their sample boards that also has several other goodies 

for experimentation.  It was like $99 or so, including the class for the 

cpu.  However, CodeWarrior is the only software they use for demo'ing and it 

is SO arcane it's practically like pulling teeth every time I want to use 

it.  Also, the laptop that has all their routines has crashed, of course. 

Dang laptops.  Anyway, ...



If there is anything I can do to help, let me know.



I plan to use the accelerometer, or one similar, for wing leveling and etc 

for a Mustang II.



David

---

etienne.phillips(at)gmail
Guest

Posted: Mon Aug 11, 2008 12:11 pm Post subject: I-Phone Inclinometer

 	  Quote: 	
		   On 11 Aug 2008, at 3:20 PM, rampil wrote:

> 

> <ira.rampil(at)gmail.com>

>

> Etienne,

> SS Gyros are in fact MEMS accelerometers.

> Actually SS Gyro is an oxymoron since a gyro implies gyroscopic

> which implies spinning parts (hard to be solid state at the same  

> time).

>

> See: http://en.wikipedia.org/wiki/MEMS_gyroscope

> http://www.sensorsmag.com/articles/0203/14/

> http://www.analog.com/en/mems-and-sensors/imems-gyroscopes/ 

> adxrs610/products/product.html

>

> etc., etc.

>


	


and



On 11 Aug 2008, at 8:28 PM, David M wrote:

 	  Quote: 	
		  

 I plan to use the accelerometer, or one similar, for wing leveling  

 and etc for a Mustang II.



 David




	


How does an accelerometer know which way is up in a co-ordinated turn?



My understanding of a "solid-state gyro" (please correct me if I'm  

wrong), is that it contains a sprung vibrating weight which, like a  

pendulum, is adverse to changing the axis of it's motion. The sensor  

part of the device measures the deviation of the weights axis of  

vibration against the casing of the unit, and from that can calculate  

the rate of change in direction of the casing...



An accelerometer (again, according to my understanding) has a similar  

sensor between a non-vibrating sprung weight, and the deviation of  

the weight from the centre of the casing can then be used to  

determine the acceleration of the casing.



Etienne

nuckolls.bob(at)cox.net
Guest

Posted: Mon Aug 11, 2008 2:46 pm Post subject: I-Phone Inclinometer

At 06:20 AM 8/11/2008 -0700, you wrote:

 	  Quote: 	
		  



Etienne,

SS Gyros are in fact MEMS accelerometers.


	


 	  Quote: 	
		  Actually SS Gyro is an oxymoron since a gyro implies gyroscopic

which implies spinning parts (hard to be solid state at the same time).


	


   Correct. The devices are not accelerometers but rotational

   rate sensors. Same sensed stimulus that your turn/bank

   or turn-coordinator responds to.

 	  Quote: 	
		  See: http://en.wikipedia.org/wiki/MEMS_gyroscope

http://www.sensorsmag.com/articles/0203/14/

http://www.analog.com/en/mems-and-sensors/imems-gyroscopes/adxrs610/products/product.html



etc., etc.



To my knowledge, the inertial platforms of BMA, Dynon, Avidyne (entegra), 

and Garmin (G1000) are all MEMS-based.  No Gyro components at all.



See for ref:http://www.flyingmag.com/article.asp?section_id=12&article_id=869



or look up the tech specs on the individual systems.


	




    There are a variety of MEMS sensors responsive to

    apparent gravity vectors which ARE true accelerometers.

    There are a number of "digital inclinometers" on the market

    that utilize two and three axis sensors of this variety.

    Unlike precision accelerometers of yesteryear, these things

    have a frequency response that goes down to DC. Imminently

    suited to inclinometer service.



    The rotational rate sensors are finding their way into

    high-end GPS receivers to resolve vehicular turning

    rate to let the guidance software know that you've

    REALLY turned the corner it suggested. Less expensive

    units need several seconds of new GPS data to resolve a

    new course over the ground to confirm that the turn was

    made.



    Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

Ed Anderson

Joined: 10 Jan 2006
Posts: 475

Posted: Mon Aug 11, 2008 3:51 pm Post subject: I-Phone Inclinometer

Etienne,



I am well underway designing my own Lateral Stabilization System (more

commonly know as a wing leveler) using MEMS Gyros and Accelerometer.



There is a lot of assumptions made and it takes a lot of studying to

understand the use and limitations of such devices.  For one thing, the

capability of the MEMS units vary from cheap toy quality to very expensive

top quality units.  So one can not just lump them all together in terms of

capability (or cost {:<()



For example, a lot of folks believe that in a coordinated, level turn the

accelerometer is useless in defining the attitude of the aircraft.  It

depends on the accelerometer, but a two axis accelerometer of sufficient

sensitvity can indeed tell you that you are in a turn of X deg bank.  The

reason is that, of course, in a coordinated turn the number of G's you pull

is dependent on your bank angle.  The old 60 deg = 2 G example comes to

mind.  So if your accelerometer is measuring 2 Gs then you are not straight

and level and are most likely in a 60 deg bank. But, an accelerometer is not

very good in attitude rapid changes which the gyro excels at. On the other

hand, the gyro has inherent drift which if integrated over time becomes very

large.  So the gyro for rapid sensing and the accelerometer for the steady

state is an approach taken by many.    So the right combination draws on the

strengths of both types to overcome the weakness of the others.



However, not just any accelerometer can do that - its only recently that

some of the MEM accelerometers have been developed with sufficient

sensitivity - measurable in milli gs!! that this has been fairly easy to do.

But, even so, I never really understood how complex the entire area is until

I started on this project and really got into it.  Does Cascade PID with

poles and zeros ring your chimes {:>)?  But, it is interesting and fun

regardless of the outcome.



I have my circuit board designed and components just ordered.  Now working

on the software to try to make it all work.  We, will see.



So jump in and get started - your mind will like you for it {:>)



Ed Anderson



Rv-6A N494BW Rotary Powered



Matthews, NC



eanderson(at)carolina.rr.com



http://www.andersonee.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

livingjw(at)earthlink.net
Guest

Posted: Wed Aug 13, 2008 4:32 pm Post subject: I-Phone Inclinometer

I believe that all of these SS gyros use a vibrating beam and measure the

angular rate by measuring the twist induced by Coriolis force. See

"Vibrating structure gyro" in the Wikipedia.



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