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01-19-2009 02:53 AM  9 years agoPost 41
Goose(is dead...)

rrApprentice

UK

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Done !
Hi again Onquick,
So I agree that the ATV INDIRECTLY controls how much general throw the tail will move due to a higher piro rate will require more tail pitch. But the ATV will not affect the holding power or resolution.
I agree with your statement 100%. This one has been a little tricky to get to the bottom of, but that's a good explanation of - I guess -what I was trying to get across.

Next !

cheers

- g

Vibe 90 & 50 WITH flybars (old skool), CY Rave, flying for many years, talent rating, absolute zero

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01-19-2009 02:56 AM  9 years agoPost 42
DWS6

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Newark,DE

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Quick,
Resolution is the steps in which a servo output moves in relation to the input. The higher the resolution the finer the control output of the servo. Kinda like resolution on your tv, the higher the resolution the finer the pixels and the sharper the image output.
You agree that the atv controls the output of the servo/ pirouette rate. Correct?
The higher the ATV the higher the servos available resolution. The higher the resolution the finer the output control. The finer the control the better the gyro can control the tail and better it can hold.

Dave Williams
Team Align

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01-19-2009 03:40 AM  9 years agoPost 43
AaronJohnson

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mason,MI

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DWS6,

I see what you mean about the servo's resolution by "it steps in relation to input", that is why when you move the ball in on the servo arm, you are decreasing the speed and increasing the resolution. By your previously stated definition,
Resolution is the steps in which a servo output moves in relation to the input
This must be true because when we move the ball in on the servo arm, the servo must move futher to get the same pitch which gives us a better resolution because we have to use more servo travel to get the same effect.

While I think now we are getting close to being on the same page but our words make it sound like we arent. The thing to think about in regards to the actual servos throw is that gyro is not ever going to use the whole movement of the tail to hold. Some of my buddies tested this awhile back by using pieces of fuel tubing on the tail linkage, we found that it came nowhere near the max travel. Also, I agree that the ATV tells the gyro we want a higher or lower piro rate, but it is purely the gyro that determines how far it will have to move the servo to achieve this piro rate. Hence my terms "indirectly" Remember, no matter what your ATV's are, the gyro knows how far it can move the servo by where we set the end point limiter pot at. So it will move the servo as far as it needs to hold the tail no matter what the ATV is set to. Next time you go fly, reduce your ATV and fly, it will not have any effect on the holding power of the tail. Only things like gain, tail linkage mechanical setup, tail blades, and headspeed will alter the holding behavior.

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01-19-2009 03:43 AM  9 years agoPost 44
AaronJohnson

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mason,MI

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Done !

Hi again Onquick,
So I agree that the ATV INDIRECTLY controls how much general throw the tail will move due to a higher piro rate will require more tail pitch. But the ATV will not affect the holding power or resolution.
I agree with your statement 100%. This one has been a little tricky to get to the bottom of, but that's a good explanation of - I guess -what I was trying to get across.

Next !

cheers

- g
Im am glad we figured it out. Talking in depth about gyros is VERY difficult in writing. It is very hard to word things properly. If we were all together with a heli in front of us and a transmiter it would be very easy to explain.

Aaron

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01-19-2009 04:00 AM  9 years agoPost 45
DWS6

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Next time you go fly, reduce your ATV and fly, it will not have any effect on the holding power of the tail. Only things like gain, tail linkage mechanical setup, tail blades, and headspeed will alter the holding behavior
I respectfully disagree with this statement. It may not be something you or I can feel under normal flight charicteristics but I believe the higher servo resolution by having a higher ATV gives the servo the ability to make more precise movevments and under hard 3D manuevers makes a difference. There is a reason why the manufacture (JR)recommends the setup this way.

Dave Williams
Team Align

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01-19-2009 05:16 AM  9 years agoPost 46
AaronJohnson

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mason,MI

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The funny thing about that is that the vibe 50's manual tells you to set your ATV to 105% if you are using the 770 gyro, but the gyro manual tells you to use 150%. I think in time you will find otherwise but I have to stop our respectfull disagreement at this time. Maybe to be continued someday....

BTW, I actually like to have these discussions about these very technical things however some aspects of the r/c helis we fly are very hard to type about. I do not have any problems with being wrong however I have been down this "gyro road" before. If you really want to test my theory then next time you take your heli out, do some long death slides (with the heli falling on its side) Use different ATV's and compare the holding behavior. Say try 150% and 100% ATV. You will find that the tail holds just the same no matter where the ATV is set. I really cant think of a more demanding manuever on the gyro then a death slide. Happy flying to you!!

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01-19-2009 06:37 AM  9 years agoPost 47
Goose(is dead...)

rrApprentice

UK

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Frame rates and Pulse widths on gyro amps & servos
This memo is actually a kind of 'preceeding' chapter of where this thread is at. I've posted it many times so apologies to those who have seen already. If you haven't it's worthwhile understanding what's going on.

It's great to see we have a good level of respect for each other. No-one like to be shot down. You'll get more respect by discussing and explaining why what has been posted is not quite accurate.

Have fun.

Tail servo's and all the mystery...

This is a very abridged memo on this topic. It is far more complex and out of my depth to write a 100% tight article, but the following will potentially save you blowing tail servos up. I've blown 2 in my time because I was litterally stupid.

1. Forget other servos and focus on tail servos as they are unique.

On the spec sheet of any tail servo, there are two critical line items:

a) The Pulse width/duration (uSec)
b) The Frame Rate per Second (FPS) or Hz rating

What is the difference between these two?

The servo's position is determined by an electrical pulse referred to as a pulse width input sent by the gyro to the servo. This pulse width is constantly repeated and the cyclic repetition per second is referred to as the Frame Rate per Second (FPS). The Old school also refer to this number a Hertz (HZ).

As the electronics of helis started to improve over time (20 years ago perhaps??) The standard Pulse width / duration to tell the servo to go to its CENTRE position was 1520uSec (of course, these nominal figures can change per Brand). When the Pulse width changes (longer or shorter) the position of the servo horn will change accordingly to a new position; If the Pulse width becomes shorter the servo moves clock-wise & visa versa. As time went by there was a clear demand for gyros to react more quickly to lock the tail in.

Naturally, the first movers' were the kind folk from JR & Futaba. Futaba went from a frame rate of 50 FPS up 333 FPS (or 333Hz) and JR to 250 FPS.

But this, right here is where some confusion arises. To this point the Pulse Width (or duration) had not changed..

Then Futaba had a theory that if they reduced the Pulse Width by exactly half from 1520uSec to 760uSec the servo would know its 'new desired' position in half the time. But we're getting into Nano-seconds and the latency of motors', gear's, friction, etc; I'd rather take the Pepsi challenge.

I ripped these specs off another post (just so you know I didn’t make them up…)

Specs

Servo's with a Pulse Width of 1520uSec or 333Hz/sec or 333FPS are:

Futaba S9253 / S9254 / S9257 / S9650 / S3153 / S3154
JR 8900G / 3400G, Sanwa ERG-WRX, Airtronics 94758 / 94761, Hitec 5925MG / 6965HB, Robbe FS61BB, LogicTech 2100G

760uSec / 333Hz servos
Futaba S9251 / S9256 / BLS251, LogicTech 6100G

1520uSec / 250Hz Servos
JR 2700G / 8700G / 810G, Sky HDS-577 / HDS-877

Okay, that's the theory out of the way.

The very simple problem between gyro's and compatible servo's is the FPS and the Pulse width. If you have a gyro amp that is delivering 333FPS at 760uSec's it can overload the IC Board of a servo designed to receive only, say, 250 FPS or a longer Pulse width. Most of the time the servo if it's going to pop, it will do so in about 5 flights. But some higher quality servo's will handle the mis-match of info.

Two main problems:

1. Running a servo on 6 volts that has a rating of 4.8 volts.

Even if the Pulse width and FPS are equal, there is the very real potential of the servo oscillating so fast because of the higher voltage it will pop. Think about it, 333 input's every second to lock your tail in; that's hard work.

However, you only have to read a few forums and many people don’t generally bother to drop the voltage. The Solid G is rated for 7 volts and I have (the old) 8700G on 6 volts and it’s fine. But then again, is it Align? that has a drop volt regulator built into another component which is a really good idea. Sorry, someone will have to answer that for me.

2. Gyro / Servo mis-match

Putting together a gyro and servo that have different specs is basically asking the servo to pop at some stage. It's going to happen sooner or later ( I should point out that it's NOT a problem if you input 250FPS to a 333FPS servo. The other way is the killer). That's why the 611 & 9256 are so good as they are native to each other. And earlier in this thread when comparing the 2 gyro’s, the JR does have the ability to change frame rate (I read from someone else’s post) can it change pulse width also?

The Solid G is crazy programmable. After mechanical limit programming, you can go down one of two paths:

1. Easy, just pick a heli and a servo or;
2. A little more involved going through the 4 menu’s with about 8 – 10 settings in each.

If you put the now out-dated JR- 8700G which accepts 250 FPS & 1520uSec with a 611 gyro delivering 333fps at 760uSec. It will pop. It’s too much info and it’s asking the servo to move more quickly than the – electronic elements – are designed for.

So, when you programme a Solid G or Spartan or the 770, check the specs on your servo and make sure they are the same specs the gyro will be sending to your servo.


**Remember at the very start of this memo, I said to forget about the other servos? This is because for a typical PCM 1024 set up, all other servo’s ran at 50 FPS. Never been able to find the Pulse with on non-tail servo’s but it doesn’t really matter in comparison. I have not researched 2.4. I know it’s up to 2048 but I’m still on PCM. So if someone could write a good article on 2.4 around the same points of reference in this post, that would be cool as I’m too, curious to know what’s going on.

Vibe 90 & 50 WITH flybars (old skool), CY Rave, flying for many years, talent rating, absolute zero

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01-19-2009 04:07 PM  9 years agoPost 48
TmMugen

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Tiny Little Red Dot aka Singapore

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Actually 17% on the Gyro Menu of the 12X on the Tail Lock mode is equal to 67%?

Anyone can advise?

Actually the tail holds. But when I switch it to "Normal" mode, the tail is in rate mode.

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01-19-2009 04:22 PM  9 years agoPost 49
DS 8717

rrProfessor

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Quick,
Resolution is the steps in which a servo output moves in relation to the input. The higher the resolution the finer the control output of the servo. Kinda like resolution on your tv, the higher the resolution the finer the pixels and the sharper the image output.
You agree that the atv controls the output of the servo/ pirouette rate. Correct?
The higher the ATV the higher the servos available resolution. The higher the resolution the finer the output control. The finer the control the better the gyro can control the tail and better it can hold.

Dave
I dont think this is correct,by lowering the ATV you only decrease the amount of steps but not the amount of each step.The resolution is 2048 for 60 degrees of servo resolution,if you decrease the atv or use dual rate you only take away the total amount of steps but the step resoultion is still 2048 you are just not using all the steps. Beside you have no choice to lower the ATV if you want to slow the piro rate down.
Now on a control surface like an airplane or on the cyclic or collective of a heli you would want to use all the travel by setting up the mechanical linkage.

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01-19-2009 04:25 PM  9 years agoPost 50
DWS6

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Newark,DE

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the numbers I gave you are what the gyro menu says.

Dave Williams
Team Align

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01-19-2009 05:11 PM  9 years agoPost 51
DWS6

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Newark,DE

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I dont think this is correct,by lowering the ATV you only decrease the amount of steps but not the amount of each step.The resolution is 2048 for 60 degrees of servo resolution,if you decrease the atv or use dual rate you only take away the total amount of steps but the step resoultion is still 2048 you are just not using all the steps. Beside you have no choice to lower the ATV if you want to slow the piro rate down.
Maybe someone on the radio manufacture side of things can verify this.

My understanding is that if the radio can send or transmit at 2048 resolution then that system is CAPABLE of running that high. But reducing the servo ATV endpoints, servo arm lengths, ect... will impact that end result.

Dave Williams
Team Align

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01-19-2009 05:32 PM  9 years agoPost 52
AaronJohnson

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mason,MI

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Goose, that is some great info to go along with our discussion. Thanks.

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01-19-2009 06:03 PM  9 years agoPost 53
DS 8717

rrProfessor

Here wishing i was somewhere else

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My understanding is that if the radio can send or transmit at 2048 resolution then that system is CAPABLE of running that high. But reducing the servo ATV endpoints, servo arm lengths, ect... will impact that end result.
If you lowered the ATV and it kept full 2048 steps of resolution for a smaller travel then you would have a finer resolution but i dont think this is the case.

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01-21-2009 04:28 AM  9 years agoPost 54
Goose(is dead...)

rrApprentice

UK

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I couldn't sleep so I went for for manufactuer evidence
This post is not another hypothetical. It's the truth. Well, it's the truth for the Futaba GY-611 / 9256 Combo anyway as it's all in the manual. Further, I had a chat over a fine Whiskey with an RC electronics 'know it all' - those guys are bloody scary. It's like there is another dark world we have no idea about... just when we thought we became a little smarter.

The link below is the manual for the 611 combo and read slowly as manuals sometimes suck but this one is actually pretty good. I have a 611 but have never a Futaba radio. And please don’t start a JR vs Futaba thing. That’s two kids in a sandpit.

I would read the manual first.

http://manuals.hobbico.com/fut/gy611-manual.pdf

To surmise where this thread is at;

1.A normal servo can be told to go to any spot and there are 2048 spots

2. Normal servos run at 50FPS, I don't know their pulse width and don't really care. At a guess for PCM's its 1520uSec. For analogue there is no such thing as a pulse width but still an FPS of 50

3. We all had out theories on what happens when you change your ATV's.

But now that you read the manual you will see that reducing you ATV’s reduces the resolution ( putting this another way, you no longer have 2048 points, you will have 2048 x gamma = number of points where gamma is a percentage of the maximum ATV).

The bottom line is this: to get the best result out of your servo it’s all about the mechanical set up of the servo horn fulcrum to the centre of the ball joint. If for example this distance is 2cm and when you are programming your gyro and telling it the physical parameters of the throw it has to play with, i.e the distance of the tail pitch slider, if your values are 60% either way and /or your servo horn is only moving 30 degrees essentially you are halving the number of points the gyro can tell the servo where to go. Bad…

The very simple solution as noted throughout the thread is to change the ball joint to fulcrum distance so you get around 60 deg.

And all of a sudden, regardless of which gyro you use, if all you take from this whole thread is

a. leave your ATV’s alone
b. The Piro rate for plug and play gyros that are still excellent quality (such as the 770, 401 /9256, whatever), is controlled buy the dual rates
c. Give your Gyro every chance to do it’s thing by finding the correct distance between horn fulcrum – ball centre, balance with gain. There is a very strong relationship between these two; If that distance is too small so you increase the gain it will hunt. Conversely distance to far and gain low = tardy and no lock in.

That’s a wrap. My Head hurts

For the benefit of all it would be great to hear how everyone has gone.

All the best

- g
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Vibe 90 & 50 WITH flybars (old skool), CY Rave, flying for many years, talent rating, absolute zero

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01-21-2009 04:51 AM  9 years agoPost 55
AaronJohnson

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mason,MI

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Good info Goose, thanks for taking the time to post your findings and yes, gyros are a headache. I have often thought that gyro setup is one of the most overwhelming and confused topics of setting up a heli. I know there is some differences between the different gyros and many of them are very good. I have my 770 working pretty darn good right now. Electronics is no doubt another dark world!

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01-21-2009 02:58 PM  9 years agoPost 56
DWS6

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Newark,DE

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But now that you read the manual you will see that reducing you ATV’s reduces the resolution ( putting this another way, you no longer have 2048 points, you will have 2048 x gamma = number of points where gamma is a percentage of the maximum ATV).
So then I was correct in stating increasing your ATV to 150% gives higher resolution.

Thanks for the info Goose. We appreciate your efforts.

Dave Williams
Team Align

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01-21-2009 03:15 PM  9 years agoPost 57
DS 8717

rrProfessor

Here wishing i was somewhere else

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Isn't this a mute point with the TR channel because you have to reduce the atv to slow the piro rate. I can see where it would be better with the cyclic and collective,but with the TR you have no choice.

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01-21-2009 03:35 PM  9 years agoPost 58
Pinecone

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Maryalnd

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There is NO difference in reducing piro rate by end points or dual rate. Dual rate only gives you the ability to change the endpoints by flicking the switch.

Setting your end points to 50 or dual rate to 50 is the SAME THING.

Digital is the one that doesn't pulse widths. It is digital, bits, 0's and 1's. Analog is actually infinite. Except that from Rx to servo is always a pulse width modulated servo.

For normal servos, the center position relates to a pulse width of abou 1500 us. The range is 1000 - 200 us for full travel (max endpoints and dual rates and maybe een a bit more). There are specialized tail servos that run with a 720 us center pulse width. But making the pulse width smaller, you can increase the frame rate. The Futaba specialized tail servos cqn run something like 500 fps. For a standard 1500 us center pusle widht, you are limited to about 333 fps. A standard Tx -> Rx - > servo conncetion runs at 50 FPS, and is limited to the fact that the Tx has to send the data for all the channels (except for some Tx which only update some channels every other pulse train).

Show me a servo that can actually respond to 2048 steps. I have seen test data of digital servos with only 500 steps. Align 75 amp ESC is only 200 steps.

Terry
Blade CP Trex 450 SE
QJ EP8v2 EX Gaui Hurricane 550
Vibe 50 Bergen Intrepid Gasser

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01-21-2009 05:24 PM  9 years agoPost 59
AaronJohnson

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mason,MI

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So then I was correct in stating increasing your ATV to 150% gives higher resolution.
Nope!! I said before the gyro/servo doesnt know what the max EPA or ATV is. It only knows what the dual rate is telling it. Like pinecone said, It makes no difference wether your D/R is set to 50 or your ATV is set to 50, the gyro will never know the difference. ATV has nothing to do with resolution in HH mode. Only mechanical linkage setup.

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01-21-2009 07:21 PM  9 years agoPost 60
DWS6

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Oh right, I guess when your doing fast sideways flight then, the gyro doesn't give more pitch to continue with the same piro rate as with stationary piros?
Your d/r is not the end all be all adjustment. The gyro will continue to give pitch to the tail blades to maintain piro speed up to the limit adjusted on the pot if need be. As a matter of fact with a 770 gyro if you adjust the gain you will effectively change the piro rate even though you never changed the D/R. It's just an arbitrary number for reference.
I gave you proof of the resolution change via ATV's and so did Goose. We can agree to disagree.

Dave Williams
Team Align

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