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Old Aug 23, 2012, 12:06 PM
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Originally Posted by Brandigan View Post
An electric gyro, is a bit different then a mechanical gyroscope
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Old Aug 23, 2012, 12:08 PM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
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Gents,
The more normal and way for the last 10 years to state multicopter sizes is measuring motor center to motor center as diameter on the same axis. For some reason the Chinese started measuring on the outside of their "micro quads" from motor to motor or "box method" as stated in the graphic above which is meaningless for size comparisons. I suppose they did this to get smaller measurements Also in the graphic posted above labeled in Chinglish as "top diameter" should be prop tip-to-tip diameter, or tip diameter. Symantics across languages FWIW...
See this link for yet another mini/micro comparisons: http://www.rcgroups.com/forums/showp...0&postcount=51
Cheers,
Jim
Quadrocopter and Tricopter Info Mega Link Index


.
Quote:
Originally Posted by dave1993 View Post
shaft to shaft is the most common term for "real" quads which is shown in that 1st pic. for a tri its hub to shaft (radius). because prop diameter can vary depending on desired pitch and current draw.
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Old Aug 23, 2012, 12:14 PM
The flightless bird
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Quote:
Originally Posted by jesolins View Post
Gents,
The more normal and way for the last 10 years to state multicopter sizes is measuring motor center to motor center as diameter on the same axis. For some reason the Chinese started measuring on the outside of their "micro quads" from motor to motor or "box method" as stated in the graphic above which is meaningless for size comparisons. I suppose they did this to get smaller measurements Also in the graphic posted above labeled in Chinglish as "top diameter" should be prop tip-to-tip diameter, or tip diameter. Symantics across languages FWIW...
See this link for yet another mini/micro comparisons: http://www.rcgroups.com/forums/showp...0&postcount=51
Cheers,
Jim
Quadrocopter and Tricopter Info Mega Link Index


.
Tis' a problem indeed, unfortunately my only source of such measurements comes from the manufacturers... since I don't own each and every one of these micro quads... if any of you would like to provide updated, corrected measurements for any of the quadcopters mentioned in this thread, I would be more than happy to update it on page one.
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Old Aug 23, 2012, 12:57 PM
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I don't think the V929 has them either. On my hybrid (V929/U816 frame/LB booms), when I center right stick it keeps flying in same direction with same tilt as before I center it.

With the U816, the little I was able to fly it because the throttle control was all over the place, when centering right stick it would attempt to auto level. Sometimes over corrected, but that could be due to it always throttling itself up or down. Literally the thing would ramp to ceiling or fall to floor with no change on my part. Maybe I had a dud.

I'm torn on the two control methods. When you get wildly out of control a good autolevel program is nice. The V911 heli for example has a fairly good self leveling, seems more so than the 9958 helis. But on the other hand I could see where more advanced pilots don't want any pre-programmed leveling getting in the way of their flying.


Quote:
Originally Posted by dave1993 View Post
since v939 controller board is so much cheaper than v929 one we can assume no accel. in fact you can get a v939 pcb for less than an accel chip from digikey. anyway "we doe neeeed no steeenkin' accelerometer".
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Old Aug 23, 2012, 01:01 PM
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Quote:
Originally Posted by e_lm_70 View Post

An accelerometer is accurate for ever
How sure are you about that? Do you have an accelerometer to use? If so turn it on sitting still in your car while pulling values to a PC. Leave it sitting in your car for a few days while you do any normal travelling and let me know what all three axis are measuring when stopped in the same location after a few days and compare them to the start values. According to your theory that there is 0 error in an accelerometer you will read 0,0,1 (in Gs). Now take an accelerometer and drop it out of a plane while taking note of the readings. Try to use these readings to determine the orientation of the board while in free fall, and report back your results.

Also, if you could, explain why this Kalman guy is so smart and why his filters are used extensively in not only gyro applications but also in accelerometer applications when accelerometers are supposed to be error free forever.

Admittedly you could probably use Google to find out how error free accelerometers are, but you can't beat physical proof.

The best option is, of course, using both and then using some sort of filter (low pass, kalman, etc) to minimize errors in both sensors. It just so happens that the errors in these two sensors compliment themselves very well, which is why in professional applications they are always used together.
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Old Aug 23, 2012, 01:40 PM
Flying mostly micro's
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Originally Posted by erdnuckel2 View Post
Well, in a few days you will be able to see it in pictures on my blog ...
The package is listed as being in KEARNY NJ right now, so it can only be a few more days before I get it delivered (if the USPS doesnt mess anything up, which they are unfortunately incredibly talented for ...)

To be honest, the only "real" reason I ordered it, was because I wanted to try the TX as it looks like it may for once not be the POS kind of TX all the other toy clones have ... (even though I am trying to fly most of my crafts with either my 9X or the Devo10 now, if I HAVE to absolutely get a new TX because they use a proprietary protocol just so you are forced to buy their daing TX, then I want it at least to be one that gets as close to FULL SIZE as possible ... I hate this childsize toy tx crap!!! .)
I have small hands so I actually prefer the small tx's. Unfortunately they don't work as well the larger programable tx's. I love my turnigy 9x tx but it is so large I have difficulty with the controls but I make do. But I love the better control with it I wish they would make a smal tx with the big tx features and I would be set!
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Old Aug 23, 2012, 01:46 PM
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Originally Posted by jpconard View Post
I don't think the V929 has them either.
yes. that was my point. if the more expensive v929 dont have one then cheaper v939 certainly wouldnt.

be aware "self leveling" of those micro helis has nothing to do with accels or gyro which is only for yaw stabilization.
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Old Aug 23, 2012, 01:49 PM
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Originally Posted by BlueHavoc View Post
I have small hands so I actually prefer the small tx's. Unfortunately they don't work as well the larger programable tx's. I love my turnigy 9x tx but it is so large I have difficulty with the controls but I make do. But I love the better control with it I wish they would make a smal tx with the big tx features and I would be set!
your wish has been granted. v911 radio upgraded to er9x:

http://www.rcgroups.com/forums/showthread.php?t=1631369
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Old Aug 23, 2012, 01:59 PM
Flying mostly micro's
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Originally Posted by dave1993 View Post
your wish has been granted. v911 radio upgraded to er9x:

http://www.rcgroups.com/forums/showthread.php?t=1631369
That is soooo freakin' awesome! wish I had the skills to make one!
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Old Aug 23, 2012, 02:01 PM
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Quote:
Originally Posted by e_lm_70 View Post
Using Accelerometer on X and Y

Actually I think it is even more accurate then not using gyro.

Tchuss

e_lm_70
Yes

But i'm still refering to real one, existing V929 board that have in front of me.

If you look at the PDF specs of ITG-3205 gyro used on this board you have this:

Quote:
5.3 Three-Axis MEMS Gyroscope with 16-bit ADCs and Signal Conditioning
The ITG-3205 consists of three independent vibratory MEMS gyroscopes, which detect rotational rate about the X
(roll), Y (pitch), and Z (yaw) axes. When the gyros are rotated about any of the sense axes, the Coriolis Effect causes a
deflection that is detected by a capacitive pickoff. The resulting signal is amplified, demodulated, and filtered to
produce a voltage that is proportional to the angular rate
So there are in fact three gyro's for every axis (X,Y,Z)
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Old Aug 23, 2012, 03:01 PM
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Quote:
Originally Posted by skitchen8 View Post
How sure are you about that? Do you have an accelerometer to use? If so turn it on sitting still in your car while pulling values to a PC. Leave it sitting in your car for a few days while you do any normal travelling and let me know what all three axis are measuring when stopped in the same location after a few days and compare them to the start values. According to your theory that there is 0 error in an accelerometer you will read 0,0,1 (in Gs). Now take an accelerometer and drop it out of a plane while taking note of the readings. Try to use these readings to determine the orientation of the board while in free fall, and report back your results.

Also, if you could, explain why this Kalman guy is so smart and why his filters are used extensively in not only gyro applications but also in accelerometer applications when accelerometers are supposed to be error free forever.

Admittedly you could probably use Google to find out how error free accelerometers are, but you can't beat physical proof.

The best option is, of course, using both and then using some sort of filter (low pass, kalman, etc) to minimize errors in both sensors. It just so happens that the errors in these two sensors compliment themselves very well, which is why in professional applications they are always used together.
I will make a short reply ... so maybe you will get it

For stabilize, for avoid any rotation, the best are he gyros , since the goal is to make the gyro reading equal to zero

For autolevel, the best and possibly only solution is accelerometers

Don't speak about kalman or other forces like centrifugal, free fall case, etc etc ... you will not follow me anymore

One issue about using accelerometer only, it is that it will be needed a very sensible accelerometer, otherwise little angle of +/- 5 deg it will not be detected properly ... a gyro measuring radial speed is more accurate on keep under control variation of little degrees ... at the cost of drifting error

Tchuss

E_lm_70
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Old Aug 23, 2012, 03:04 PM
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Anyhow ... v929 is already a big quad ... v939 is a real micro, like the sh 6043, miniPet, etc ... I'm would be surprised if 6 axis are not used in all these micro ... autolevel in this size I believe it is a must

Tchuss

E_lm_70
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Old Aug 23, 2012, 03:05 PM
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I had no skills and I made one.It needs determination.When I look back....... I asked Dave a lot of silly question on that thread.Now because of that it's easy to make one by a newbie.However, one has to read all posts.


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That is soooo freakin' awesome! wish I had the skills to make one!
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Old Aug 23, 2012, 03:11 PM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
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S,
The ITG 3205 MEMs contains one gyro for each x, y, z axis.

Note that all gyros have drift that is affected by temperature changes. That is one of the reasons why you will find you have to trim if you go from indoors to outdoors if you don't allow for the fcb to acclimate to the temperature. Also to some extent this happens as the devices on the flight control board warm up too. The better flight controllers have temperature compensation to mitigate this drifting with temperature changes. Accelerometers do not drift, but must be calibrated for the level of the multicopter props plane or the code corrections will cause oscillations and poor performance. Maintaining an accurate reference voltage for the gyros and accelerometers (IMU) is also important to minimize requiring trim corrections.
Future IMUs will also be capable of automatic temperature and EMF calibrations to further enhance precision. It will only keep getting better as it has been over the last 10 years of flying multicopters...
Cheers,
Jim
Quadrocopter and Tricopter Info Mega Link Index

Quote:
Originally Posted by shafter View Post
Yes

But i'm still refering to real one, existing V929 board that have in front of me.

If you look at the PDF specs of ITG-3205 gyro used on this board you have this:



So there are in fact three gyro's for every axis (X,Y,Z)
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Old Aug 23, 2012, 03:15 PM
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@BlueHavoc,
Walkera's Devo 6 is small with all the programmable feature. Too bad it's Walkera Devo protocol only.
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