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It shows us clearly how important the gain manipulation is. Only today I was flying in 50kmh wind & was disapponted with the stabiliser. It was very turbulent close to ground. Even the Ibis birds were getting rocked from side to side Of course I didn't think to increase the gain. ![]() Your demo has taught me something. Thanks for your time & effort Kev |
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South East, MN
Joined Mar 2007
1,241 Posts
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Next year, just watch, Spektrum, maybe futaba, and probably orange will all come out with 3axis accelerometer / gyro / receiver all in one units.
It's the obvious progression. Spektrum already has one for helicopters, and it's built into the micros. |
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Joined Jan 2011
3 Posts
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Regarding Melnic's reply in post #543.
I have read through 555 posts in this thread. It must have taken the best part of three hours. Yet, after all that time we still do not have a definitive description of what this device can do. Worse still, the very guy that wrote what seems to have been adopted by HobbyKing as THE manual for this appears to be getting angry because someone asks a simple question that may, or may not, have been answered on one or more of the other 541 pages up to that particular time. I don't want to appear rude or arrogant but there is, as far as I can tell: THERE IS ONLY ONE LOGICAL WAY TO MOUNT THIS DEVICE WITH RESPECT TO THE AIRFRAME. If you have an aircraft that is already built and set-up to fly correctly then it is imperative that the addition of this device into the control system is done by connecting like for like inputs and outputs, i.e. elevator to elevator, rudder to rudder and aileron to aileron (L) - yes, I know that this is not so obvious until you try it as there is only one aileron input but two outputs (without any obvious reason)! The next step orient the device so that the arrow on the printed circuit board points to the front of the fusilage, i.e. in the direction of the thrust, and with the connector pins on top. Whatever else happens, ignore any other psuedo arrow markings on the outer case as they are NOT arrows just some young graphics guy’s doodles. Now, ANY rotation about an axis ROTATES the other TWO GYRO AXES through 180 degrees. This means that for those two axes the SENSE of the GYROS will be REVERSED and the aircraft will become totally unstable as regards those two axes. To understand this if you are not sure: spin a wheel on an axle then rotate the axle so it points in exactly the other direction – which way is the wheel now rotating with respect to its initial rotation? I fully understand that all this turning of the orientation of the unit this can be overcome if you have a fancy transmitter, reversing leads w.h.y. with the facility to reverse the outputs and all that other complicating mumbo jumbo. BUT, WHY BOTHER TO MAKE IT SO COMPLICATED IN THE FIRST PLACE? In an engineering environment you would be laughed out of the room if you came up scheme like this. Remember the Hubble Mirror? They had to spend a great deal of effort (money) to fix a situation that they spent a great deal of effort (money) in creating, all of which need not have arisen in the first place. If you are building an RC aircraft you should build it so that it works with a “STANDARD” transmitter/servo setup that is logical and without fixes such as reversing of inputs etc. UNLESS THERE IS A VERY GOOD REASON TO. You know what the acronym "KISS" stands for so make it a principle to work by. Another point, what is wrong with simple wiring diagrams to describe how to connect the various elements of the system together. Circuit diagrams have been developed over a period of around two centuries to a point where they are beautifully elegant and accepted as the most succinct, most accurate and the easiest way to describe such interconnections - why on Earth are we using of words to do this? Following on: I noticed that RCPowers have supplied some diagrams as well. They also state that one must use a certain control sytem power schema but without saying why or giving a meaningful explanation. I have a feeling that they have been having trouble with electrical noise from servos and ESC's corrupting the gyro data. As this device was (this is not a guess) designed to work in this environment any noise susceptability should have been addressed by the circuit designer and accounted for. In Europe, any electrical or electronic item should not be susceptible to noise emanating from other sources and no item, except transmitters, should be radiating electromagnetic interference that could affect the operation of other devices - where does that leave HobbyKing and the manufacturers of this device? For, if this is the case, then these devices cannot have been CE approved and should not, therefore be sold in Europe. In the USA there are similar laws in place and they would certainly be in breach of regulations. This noise, if it exists, can be reduced by the use of electrical filters and by sensible routing of signal and power wiring, i.e. seperating them to reduce cross-talk. What does seem odd, is that this device consists of a microprocessor which is inherently a very noisy device and the gyros use digital signals (II2C or I squared C) to communicate with the processor so should be fairly noise tolerant if adequate, on board, precautions were taken. In conclusion, this lack of documentaion is due solely to cost cutting by the manufacturers and sellers of these item made in the Far East. About 25 years ago in the States, there was an engineer who designed and kitted the parts for a homebuilt biplane that was absolutely first class - I can't remeber his or the aircraft's names. They even made a documentary for the Open University over here in the UK about the design, manufacture and documentation processes that were involved - I think it cost around half the total budget to document the kit. I know from peronal experience how much work has to go into documentation, development, compliance etc. when designing and building equipment here in the UK and it seems to me that almost none of this occurs with so much of the stuff that comes out of the Far East. Just look how much trouble it causes when you buy what might be a nice, simple and useful piece of kit but are frightened to use it in case it falls out of the sky and kills someone because the manufacturer and retailler are only interested in one thing - Profit _ and not about customer care. So here we are, we spend three hours trying to find a definitive description of how to use one small device and still cannot be certain we have! Sincerely, John |
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Australia, WA, Perth
Joined May 2007
3,129 Posts
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John,
With respect to saying the gyros needs to be mounted in a particular direction, I don't quite follow your example. Rotate a wheel 180* and which way are the other axis pointing? Yes, they'll be rotated. but. That's based on the Newtonian (stationary) frame. The gyros are mounted to the aircraft, the accelerated frame, and the controls are all acting reference the aircraft. Same as a heli flybarless controller - doesn't matter if you're right way up, inverted, knifeedge - they don't know where the horizon is, they just damp movement along their respective axis (reference the aircraft) If people have mounted them transverse, and it works, you can't really say it's wrong, no? |
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The only interesting thing I got from the bartonwood post was the possible cause, and maybe cure, of the servo glitching. I haven't really had any problems with this in flight, but it's a bit irritating on the ground. I think I'll try a ferrite core around the male-male leads between the Rx and ORx, and also some Al foil wrapped around the ORx and grounded to the battery negative "ground" to see if this makes any difference, though I've got a feeling that the glitching is entirely self-generated by the ORx itself.
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Bill, my only advice is to be able to physically move the ORx itself (not the plane) in the 3 axes while everything is connected up and gains set fairly high, to check that the control surfaces correct against these movements, as it all happens pretty fast. Lower the gains after this. Expect so see servo glitching even when the ORx is totally stationary.
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