SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Jan 05, 2013, 10:19 PM
wjs
William
United States, MI, Brighton
Joined Oct 2012
1,966 Posts
Quote:
Originally Posted by akschu View Post
When something requires digital servos it's almost always because the PWM signal rate to the servos is over 50hz which is standard for analog servos. If you hook up analog servos to this it will eventually cook them.
It is still 22ms operation. So analog should work, just not as well. Unless I am missing something, which is likely.
wjs is offline Find More Posts by wjs
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 06, 2013, 04:24 AM
DX18QQ #1489/2000
United Kingdom, England, Plymouth
Joined Apr 2009
3 Posts
Quote:
Originally Posted by wjs View Post
It is still 22ms operation. So analog should work, just not as well. Unless I am missing something, which is likely.
@wjs; 22ms is the RF frame rate of the receiver from the transmitter, i.e. data is sent from your Spektrum Transmitter to your Spektrum Receiver approximately 45 times per second or every 22ms (Spektrum Hi-Speed 11ms receivers receive sent data aproximately 90 times a second, 90Hz)
This 22ms (frame) rate contains the data for ALL servo positions, and it is important to remember that this is the RF or Radio Frequency frame rate and not the servo frame rate.
(Technote: Spektrum systems with more than 7 channels spread the servo/channel data across 2 consecutive RF frames, increasing latency of non critical channels to 44ms with a 22ms receiver or 22ms with an 11ms receiver)
Most times the 22ms or 11ms RF frame rate will also be the same frame rate that your servos see, except... when there is a gyro (or other gadget) between the receiver and the servos ;-)

Quote:
Originally Posted by akschu;
Originally Posted by akschu
When something requires digital servos it's almost always because the PWM signal rate to the servos is over 50hz which is standard for analog servos. If you hook up analog servos to this it will eventually cook them.
akschu's post as above is correct ;-)

After receiving updates from your transmitter at 22ms (approx 45Hz or 45 times per second) which determines where you the flyer want your model to fly, the AR635 receiver then also reads the gyros (multiple times) and updates the servo positions to try to make the model Fly where you want it to fly,

The gyro updates to the servos could occur at a much faster individual servo frame rate (refresh rate) than just the 22ms / 45Hz RF receiver frame rate. (It remains to be seen how fast the servos are updated, as the receiver is not yet available ;-)

Have Fun !

Mark S.
Squanto is offline Find More Posts by Squanto
Last edited by Squanto; Jan 06, 2013 at 07:08 AM.
Reply With Quote
Old Jan 06, 2013, 12:28 PM
wjs
William
United States, MI, Brighton
Joined Oct 2012
1,966 Posts
Quote:
Originally Posted by Squanto View Post
@wjs; 22ms is the RF frame rate of the receiver from the transmitter, i.e. data is sent from your Spektrum Transmitter to your Spektrum Receiver approximately 45 times per second or every 22ms (Spektrum Hi-Speed 11ms receivers receive sent data aproximately 90 times a second, 90Hz)
This 22ms (frame) rate contains the data for ALL servo positions, and it is important to remember that this is the RF or Radio Frequency frame rate and not the servo frame rate.
(Technote: Spektrum systems with more than 7 channels spread the servo/channel data across 2 consecutive RF frames, increasing latency of non critical channels to 44ms with a 22ms receiver or 22ms with an 11ms receiver)
Most times the 22ms or 11ms RF frame rate will also be the same frame rate that your servos see, except... when there is a gyro (or other gadget) between the receiver and the servos ;-)
Mark S.
They could update faster, but I doubt it. I would think they would document that as that is kinda big deal. Also I see no other rx that takes 22ms frame rate and outputs faster. The Orange RX3 for example, will take a 11ms from the rx, but always output 22ms. So it can work fast to slow. I don't have one to test, but I would bet 22ms output. But we back to the same question. It should work on analog servos unless some other reason I don't see at the moment. The RX3 works with analog, for example, but they do jitter a bit because of minor PWM differences (on servos with low dead band) injected by the gyro processing overhead and implementation.
wjs is offline Find More Posts by wjs
Reply With Quote
Old Jan 06, 2013, 01:44 PM
Registered User
Mugen4Lfe's Avatar
Joined Sep 2011
668 Posts
Quote:
Originally Posted by wjs View Post
The RX3 works with analog, for example, but they do jitter a bit because of minor PWM differences (on servos with low dead band)
So if analog servos are jittering, wouldn't that mean it's not a good idea to use them? The last thing needed is unwanted servo movement...
Mugen4Lfe is offline Find More Posts by Mugen4Lfe
Last edited by Mugen4Lfe; Jan 06, 2013 at 01:57 PM.
Reply With Quote
Old Jan 06, 2013, 02:02 PM
Canadian Bacon
flypaper 2's Avatar
Kingston, Canada
Joined Jun 2004
12,911 Posts
I use the HXT 900 with the RX3 gyro and it doesn't jitter when it's sitting still. If the trans is off, it will jitter without the signal from the trans.

Gord.
flypaper 2 is online now Find More Posts by flypaper 2
Reply With Quote
Old Jan 06, 2013, 03:07 PM
wjs
William
United States, MI, Brighton
Joined Oct 2012
1,966 Posts
Quote:
Originally Posted by Mugen4Lfe View Post
So if analog servos are jittering, wouldn't that mean it's not a good idea to use them? The last thing needed is unwanted servo movement...
Digitals would probably jitter more as less dead band. It is not the servos, it is the variance in pwm pulses that cause the "jitter". Which is not really jitter, but just the servo doing what it is told. Digitals have a good feature that you can adjust dead band for a sweet spot.
wjs is offline Find More Posts by wjs
Reply With Quote
Old Jan 06, 2013, 03:09 PM
Registered User
West of California Speedway, East of LaLa, North of Disneyland
Joined May 2001
2,308 Posts
Quote:
Originally Posted by manual
CAUTION: The AR635 is not compatible with Delta, V-tail, or Flaperon
mixing. If using dual ailerons, elevator or rudder, a Y harness must be used


Well, that really sucks!!! Any plane I fly will almost always require either dual ailerons, Delta, flaperons, V-tail or spoilerons - and in some of my sailplanes, combinations of the above.

For those, I'll stick to my non-AS3X or go back to my trusty 72 MHz radios - that segment of the spectrum keeps getting quieter there............................chirp, chirp, chirp.....
356Jim is offline Find More Posts by 356Jim
Last edited by 356Jim; Jan 07, 2013 at 10:49 AM.
Reply With Quote
Old Jan 06, 2013, 03:27 PM
wjs
William
United States, MI, Brighton
Joined Oct 2012
1,966 Posts
Quote:
Originally Posted by flypaper 2 View Post
I use the HXT 900 with the RX3 gyro and it doesn't jitter when it's sitting still. If the trans is off, it will jitter without the signal from the trans.

Gord.
Hi Gord. The dead-band on your HXT900s is probably a bit higher (i.e. less senstive to minor cmd changes). Interesting fact about jitter when trans is off.
wjs is offline Find More Posts by wjs
Reply With Quote
Old Jan 06, 2013, 07:37 PM
Registered User
Mugen4Lfe's Avatar
Joined Sep 2011
668 Posts
Quote:
Originally Posted by wjs View Post
Digitals would probably jitter more as less dead band. It is not the servos, it is the variance in pwm pulses that cause the "jitter". Which is not really jitter, but just the servo doing what it is told. Digitals have a good feature that you can adjust dead band for a sweet spot.
Ok, I see. I guess I misunderstood what you meant by "jitter". It's clear to me now.
Mugen4Lfe is offline Find More Posts by Mugen4Lfe
Reply With Quote
Old Jan 06, 2013, 07:46 PM
wjs
William
United States, MI, Brighton
Joined Oct 2012
1,966 Posts
Quote:
Originally Posted by 356Jim View Post
Quote:
Originally Posted by manual
CAUTION: The AR635 is not compatible with Delta, V-tail, or Flaperon
mixing. If using dual ailerons, elevator or rudder, a Y harness must be used


Well, that really sucks!!! Any plane I fly will almost always require either dual ailerons, Delta, flaperons, V-tail or spoilerons - and in some of my sailplanes, combinations of the above.

For those, I'll stick to my non-AS3X or go back to my trusty 72 MHz radios - the spectrum keeps getting quieter there............................chirp, chirp, chirp.....
I saw that too. I wonder if you can have one ail gyro controlled and have second ail in aux like a normal dual ail config. At least get stabilized on one ail. Like the Orange rx3.
wjs is offline Find More Posts by wjs
Reply With Quote
Old Jan 07, 2013, 09:18 AM
Registered User
Blacksburg, VA 24060 USA
Joined Feb 2000
3,204 Posts
In Post #8 Pouncer asked whether the servos need to have metal gears. It was pointed out that the instructions say the servos must be digital, high-speed, and high-resolution. But does that imply that all digital servos have metal gears? It's well-known that metal gear servos are recommended because they will be worked very hard by the autostabilizer.

Jim R.
JRuggiero is offline Find More Posts by JRuggiero
Reply With Quote
Old Jan 07, 2013, 09:24 AM
Kev Waite
Plymouth UK
Joined Nov 2005
355 Posts
Now in stock at Totem Hobbies

http://www.totemhobbies.co.uk/produc...-receiver.aspx
rcpaintfx is offline Find More Posts by rcpaintfx
Reply With Quote
Old Jan 07, 2013, 10:34 AM
Registered User
Ireland, Co. Dublin, Dublin
Joined Feb 2012
316 Posts
Quote:
Originally Posted by wjs View Post
I saw that too. I wonder if you can have one ail gyro controlled and have second ail in aux like a normal dual ail config. At least get stabilized on one ail. Like the Orange rx3.
Interesting point, I also wonder if it will support x plus? Hopefully will have my hands on one later this week so will find out.
Quandry is offline Find More Posts by Quandry
Reply With Quote
Old Jan 07, 2013, 09:28 PM
DX18QQ #1489/2000
United Kingdom, England, Plymouth
Joined Apr 2009
3 Posts
I think these little micro flyers could do with the latest in AS3X technology to help them counteract the wind ...

http://www.youtube.com/watch?NR=1&v=SEBLt6Kd9EY

but hey, maybe they still just need a little trimming out


Back to Analog vs. Digital servos, I think the smaller deadband of a digital servo would be advantageous with the gyro outputs, as every little twitch of the airplane would be output to the servos and they would be more responsive to small movements.

Also, coreless motors for faster servo reaction times, not sure about metal gears as some metal gear servos do wear quite quickly introducing more slop (which would tend to negate a smaller deadband), Hitec carbonite gears seem to wear very little over time so might be a good choice.

Another important consideration I think is the quality of the feedback potentiometer, as there will be a lot of small movements in the servos and the surface of a cheap pot might wear considerably quicker because of this, some high end servos have multiple wiper fingers contacting the 'carbon' of the potentiometer track.

Have Fun !

Mark S.
Squanto is offline Find More Posts by Squanto
Reply With Quote
Old Jan 09, 2013, 04:58 AM
Registered User
Ireland, Co. Dublin, Dublin
Joined Feb 2012
316 Posts
Reading through the manual it seems that the AR635 has two gain modes - sport & 3d. The programming looks a little complicated for field adjustments, also the gain can only be adjusted in increments of 10% which back in my heli days 10% is massive.

Still I've had good experience with my Beast 3D and Hyper Taxi so can't loose faith at this early stage

I wonder will the gain be sufficient to hold a hover hands off? I know the mechanical setup of the plane has to be condusive but just wondering..
Quandry is offline Find More Posts by Quandry
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Wanted Immersion stand alone receiver goldsworthy FPV Equipment (FS/W) 0 Nov 24, 2012 06:20 AM
Wanted Immersion stand alone receiver goldsworthy FPV Equipment (FS/W) 2 Nov 21, 2012 09:47 AM
Idea Stand alone on-board GPS logger for Google Earth iskess DIY Electronics 20 Sep 19, 2012 01:20 AM
Idea DIY - stand alone receiver test module midelic DIY Electronics 0 Sep 15, 2012 08:23 AM
Question Stand alone balancer question kscheck Batteries and Chargers 16 Mar 27, 2012 11:30 PM