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Old Aug 23, 2012, 04:18 PM
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Originally Posted by e_lm_70 View Post
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
i predict you are wrong. just based on cost it is impossible. as i said in the other post v939 is cheaper than v929 which DEFINITELY has no accel. in fact one 3x accel chip costs more than whole v939 board.
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Old Aug 23, 2012, 04:22 PM
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Originally Posted by e_lm_70 View Post
An electric gyro, is a bit different then a mechanical gyroscope
I sure hope not, else what would be the point?

Nothing anyone is saying is going to affect what's in the actual models and all we really need is for people to fly, compare and report what they all do so we can make a choice.

It's like arguing whether brown- or white-shelled eggs taste better when you've not actually tasted either of them.
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Last edited by Brandigan; Aug 23, 2012 at 04:28 PM.
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Old Aug 23, 2012, 04:31 PM
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Originally Posted by dave1993 View Post
i predict you are wrong. just based on cost it is impossible. as i said in the other post v939 is cheaper than v929 which DEFINITELY has no accel. in fact one 3x accel chip costs more than whole v939 board.
Sh 6043 cost like the v939, and it has 6 axis sensors
An accelerometer cost less the 1$ ... I'm sure soon on the market for 1$ there will be a 9 sensor in a little chip ... these chip are common on mobile phone, with millions of unit produces per day ... price is sinking at light speed

Tchuss

E_lm_70
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Old Aug 23, 2012, 04:33 PM
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even though i have never eaten an egg i predict white tastes better simply because it dont have that yuccchy brown flavor.
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Old Aug 23, 2012, 04:35 PM
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Originally Posted by e_lm_70 View Post
Sh 6043 cost like the v939, and it has 6 axis sensors
im referring to the controller board. v939 is $8, v929 is $13 and im sure 6043 is much more. btw do you have link to $1 accel?
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Old Aug 23, 2012, 04:39 PM
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Originally Posted by Brandigan View Post
I sure hope not, else what would be the point?

Nothing anyone is saying is going to affect what's in the actual models and all we really need is for people to fly, compare and report what they all do so we can make a choice.

It's like arguing whether brown- or white-shelled eggs taste better when you've not actually tasted either of them.
I fly my 250 micro quad with kk2.0 board, with and without autolevel

So I know the difference on having or not the accelerometer for help the flight level

Yes, you can fly without autolevel ... but then all is much more complicated in the little size

My sh6043 even if it is far from me and if I cant see it well ... I can still control due to the autolevel, and fix flying angle based on stick position

All make more relaxing the flight, and allow to make more extreme maneuver

For me a micro quad with gyro only is a bad toy

And don't forget ... these are toy, not hobby level quad ... people that buy these expect something easy to fly ...

Tchuss

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Old Aug 23, 2012, 04:43 PM
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Originally Posted by dave1993 View Post
im referring to the controller board. v939 is $8, v929 is $13 and im sure 6043 is much more. btw do you have link to $1 accel?
I post an ebay link of a 4.2$ accelerometer board ...shipping included

How much can cost the chip only ... if in 4.2$ there is shipping, ebay cost, seller profit, pcb, capacitor, etc etc ... and a single quantity ... for 1000 unit chip only I'm sure these chips can't cost more then 1$
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Old Aug 23, 2012, 04:47 PM
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Originally Posted by e_lm_70 View Post
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
So you're refusing to answer any of the questions I posed proving that the statements you made are false? Is it maybe because you don't understand the things I was talking about? I'll be happy to explain further if that is the case. I'm not trying to be a jerk but it irks me a little when people say I am wrong and back it up with false information. I have been wrong plenty of times and have had a lot of very smart people on this forum correct me and I appreciate all the knowledge I've gained, but you seem to be pretty misinformed about this particular topic, and I don't know if it is just the language barrier or not.

Nobody mentioned centrifugal force, and Kalman isn't a force, it is a mathematical filter used to help correct for error in gyros and accelerometers. The free fall example was proving that not only are accelerometers not error free forever, as you stated, but that in some circumstances they are in fact totally useless. In most situations they are superior, but in a quad you need something that works all the time, which gyros do. When I fly straight at the ground I want to know that when I say stop the quad will listen
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Old Aug 23, 2012, 04:56 PM
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Originally Posted by e_lm_70 View Post
I post an ebay link of a 4.2$ accelerometer board ...shipping included

How much can cost the chip only ... if in 4.2$ there is shipping, ebay cost, seller profit, pcb, capacitor, etc etc ... and a single quantity ... for 1000 unit chip only I'm sure these chips can't cost more then 1$
now that i think you are probably right that those chips cost pennies in qty. but i will still bet money (not too much ) that the v939 has no accel.

guess why i cant lose. lol!
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Old Aug 23, 2012, 05:01 PM
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So you're refusing to answer any of the questions I posed proving that the statements you made are false? Is it maybe because you don't understand the things I was talking about? I'll be happy to explain further if that is the case. I'm not trying to be a jerk but it irks me a little when people say I am wrong and back it up with false information. I have been wrong plenty of times and have had a lot of very smart people on this forum correct me and I appreciate all the knowledge I've gained, but you seem to be pretty misinformed about this particular topic, and I don't know if it is just the language barrier or not.

Nobody mentioned centrifugal force, and Kalman isn't a force, it is a mathematical filter used to help correct for error in gyros and accelerometers. The free fall example was proving that not only are accelerometers not error free forever, as you stated, but that in some circumstances they are in fact totally useless. In most situations they are superior, but in a quad you need something that works all the time, which gyros do. When I fly straight at the ground I want to know that when I say stop the quad will listen
Trying to keep message short I may given the impression that kalman is a force ... i know it is just formula/algorithm ... I put the centrifugal force and free fall as example how you can get things complicated

Anyhow, somebody else already explain about the error that gyro introduce for reading an angle

Gyro are used for keep stable ... but the algorithm used has no idea, and also doesn't care about angle from level ... that's why autolevel need accelerometer

Gyro are used since ages in the rc world, while accelerometer and magnetometer are new chips just entering in the rc arena ... this should tell you why current board have been born with gyro only

I'm sure it can be made a control board with just a gyro for z, and accelerometer for x y ... or even better ... just a 3 axis magnetometer

Anyhow ... noise level, speed .. vibrations ... etc all play a role in real implementation

Tchuss

E_lm_70
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Old Aug 23, 2012, 05:06 PM
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Originally Posted by dave1993 View Post
now that i think you are probably right that those chips cost pennies in qty. but i will still bet money (not too much ) that the v939 has no accel.

guess why i cant lose. lol!
If the v939 has no accelerometer, then for me it is a huge design mistake

Actually, I'm waiting for next generation with magnetometer ...when the quad is far .. having a fix heading will help a lot ... also this chip cost less then 1$

Add gps ... still cost some money ... still no less then 10$ for cpu and antenna
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Old Aug 23, 2012, 05:11 PM
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if you haunt the walkera ladybird thread youll find most prefer 3 axis mode and turn off 6 axis (accel) mode. and preliminary reviews favor the v939 (no accel) over ladybird.
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Old Aug 23, 2012, 05:21 PM
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Originally Posted by dave1993 View Post
if you haunt the walkera ladybird thread youll find most prefer 3 axis mode and turn off 6 axis (accel) mode. and preliminary reviews favor the v939 (no accel) over ladybird.
Guess is all about looping ... due to quick and dirt autolevel implementation, 6 axis means no loops in most of cases

Anyhow ... my experience with 250 quad, tell me is better 6 then 3, but everybody can have is flying style
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Old Aug 23, 2012, 06:09 PM
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Originally Posted by e_lm_70 View Post
If the v939 has no accelerometer, then for me it is a huge design mistake

Actually, I'm waiting for next generation with magnetometer ...when the quad is far .. having a fix heading will help a lot ... also this chip cost less then 1$

Add gps ... still cost some money ... still no less then 10$ for cpu and antenna
While cost certainly is a concern for these quads so is weight. While GPS and magnetometer would be pretty nice you are not only adding component weight but also upping the micro controller requirements. Personally I am happy with three axis gyro as it let's me be the one flying and not the electronics and the light weight allows me to carry my camera as well. Honestly I don't personally see a need for a magnetometer in most quad applications as the gyro is more than capable of holding heading and for my flying it doesn't really need to know what heading that is. Also magnetometers are, in my experience, grossly inaccurate in many situations. There are simply too many points of magnetic interference, and too many differences in magnetic fields from location to location.

That being said if I do build an fc from the ground up this winter I will be doing it with the goal of full autonomy so in that case I need all of the above. Maybe I should just buy an APM and only do the part I enjoy: coding
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Old Aug 23, 2012, 06:16 PM
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Guys, I think the very technical talk deserves it's own thread as it sometimes gets heated and quite off topic.
Please remember that this is a hobby thread and not an engineering thread.
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