HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Dec 26, 2003, 08:06 PM
David Cairns
dcairns's Avatar
Orange, CA
Joined Apr 2002
1,095 Posts
Dual receiver wiring

I am going to be using two receivers and two batteries on my 11 foot B-52. First reason is safety. The second reason is to handle the load of 10 servos. There will be three servos per wing working as flaperons. There will be two servos for the elevators. One servo for the bomb-bay doors and one servo for the bomb drop mechanism.
Any opinions on how to split the servo assignments between the two receivers? I have an idea how to do it, but I want to harness other brains out there to imagine failure modes that I have not considered.
dcairns is offline Find More Posts by dcairns
Reply With Quote
Sign up now
to remove ads between posts
Old Dec 27, 2003, 04:04 PM
Super Member
davensocal's Avatar
United States, NY, Mechanicville
Joined Mar 2003
1,203 Posts
never heard of trying to split the work load...

I don't know if it can be easily done, if for no other reason that the fact that all FM radios are limited to 9 or 10 channels. I think PCM may be able to hit 12 channels, but I'm not sure..

I think what you may want to do instead is run a lot of the servos in parallel, and provide a seperate power source just for the servos. I think you can just make Y cables for the servos, and then attach another battery to one of the Y's to provide the extra power needed.

I think JR makes some equipment for this purpose, to time several servos for one control surface. You can probably find more info in the scale or 3d forums, I think both use mutliple servos on one surface for extra strength..

Good luck!
davensocal is offline Find More Posts by davensocal
Reply With Quote
Old Dec 27, 2003, 04:54 PM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
20,841 Posts
If you split each aileron into the same # of sections as you had servos, you wouldn't have to "time" them, and if one failed, it probably would be better than if they were "ganged" together on one single larger surface...

I think I remember hearing in the giant scale circles that you can split the plane into right and left halves for the two Rx's.
target is offline Find More Posts by target
Last edited by target; Dec 27, 2003 at 04:57 PM.
Reply With Quote
Old Dec 27, 2003, 05:04 PM
Registered User
USA, WA, Bellevue
Joined Apr 2000
198 Posts
The back-up battery is the way to go I would think. I kind of remember a battery backup system available from someone, maybe a search would turn it up. I don't know what good a "spare" receiver would do. If one is hit so would the other, no?

But then all you may want is more servo outlets, in which case I would think "y"s with a big battery would better serve you.

If I missed the point, I am as interested as anyone to know what you are after.

Bruce
bruce ryan is offline Find More Posts by bruce ryan
Reply With Quote
Old Dec 27, 2003, 05:58 PM
David Cairns
dcairns's Avatar
Orange, CA
Joined Apr 2002
1,095 Posts
Perhaps this will help:


Each wing has three control surfaces. Only two channels are needed to drive them, using flaperon mixing and allowing for crow. So the servos are hooked up with Y connectors. The reason there are three surfaces per side is due to the way the wing constructed and the way it comes apart for transport. It also allows for spreading the load around to more servos.
The elevator halves are mechanically independent, but only commanded by one channel.

If any one servo fails, the plane can still be flown. By using two receivers, I hope to still maintain some degree of control if one receiver were to fail. I realize this won’t offer much in terms of glitch control or bad piloting, but what I am trying to protect against are some of the most common equipment related crash causes, such as a failed servo, battery failure or receiver failure (such as when the crystal goes bad). I know these are rare events, but I have lost a power plane to a tooth breaking off the elevator servo, so I know they do happen. Considering the size and weight of this plane, not to mention the time and money invested, I think it wise to add what redundancy I can.
Splitting the servo assignments to right and left halves is one way of doing this. It could also be done by having the outer aileron servos assigned to receiver A and the middle servos assigned to receiver B, etc.
dcairns is offline Find More Posts by dcairns
Reply With Quote
Old Dec 27, 2003, 06:44 PM
Registered User
Keitha's Avatar
USA, CA, Costa Mesa
Joined Mar 2002
648 Posts
Check out this product, it is a servo syncronizer from Futaba:
'Futaba Servo Sync

Good Luck,
Keith
Keitha is offline Find More Posts by Keitha
Reply With Quote
Old Dec 27, 2003, 08:03 PM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
20,841 Posts
It'll be pretty cool to "crow" with the inner flaps down, middle up, and still have the outers for aileron control when landing, if you can do all that.
target is offline Find More Posts by target
Reply With Quote
Old Dec 28, 2003, 12:44 AM
Super Member
davensocal's Avatar
United States, NY, Mechanicville
Joined Mar 2003
1,203 Posts
Going backwards a little, back to the Y cables.. I believe the issue of having multiple servos in parallel is that the power consumption may be more than the receiver is designed to handle. Of course voltage sags under load, etc.. may come into play as well.

I guess if you really wanted to have the redundant servos, there are tow potential ways of doing it. The first is to split the load, but I wouldn't go right and left with it, it would be very hard to fly if one receiver was doing whatever it want on the left side, and all you can control is the right side. I would think your chances would be better if one receiver was inboard controls, the other was outboard controls. This way, you may have a chance to override the failed receiver.

Another option, which would be tough, but workable..... Dedicate one channel per receiver for a gang of switches. Basically, you would try to allow either receiver to override complete control of the other reciever. So, for example, you could have the outputs from each receiver go into a set of switches (let's say receiver A and B). Then, Ch8 from rcvr A directs the switch, and Ch9 from rcvr B directs the switch.

Now you fly rcvr A as a primary. If there is a problem, you turn Ch9 high to force all the servos to switch over to the output from rcvr B.

I think this could be done with a bank of switches in a chip, as you would only be dealing with the signals. You could then add a small SSR to also flip power to a reserve batt.

The next level would be to rape the circuitry from a Lost Model Alarm, and tie it's audio output into the switch, you coudl then theoritacally have the LMA monitor the frames from the primary rcvr (rcvrA), and if a dropped frame is detected, have it force the switch automatically.

You could also create an automatic switch if you are using PCM radios, you could have one reciever default on LOS to push one channel high and activate the switch. I guess you would then want to add a flip-flop to make sure it didn't default back.. I guess this wouldn't work though, because the PCM is only going to Lockout if it losses the tx signal, and in that case you are kinda hosed anyway..


Of course, now you have to ask yourself if you trust your transmitter. Should you keep a backup Tx on hand as well?


Anyway, just thinking outloud..

lemme know if you are going to want to tackle the switching method. I might be interested in trying to design something to do that..
davensocal is offline Find More Posts by davensocal
Reply With Quote
Old Dec 28, 2003, 01:45 PM
Registered User
Tucson, AZ, USA
Joined Sep 2000
794 Posts
In full size commercail planes the redundecy is split so that you would still have symmetrical control after a failure......ie rudder on one system ailerons on the other (And/or inbd ailerons and otbd on seperate systems) spoilers split so that any failure still leaves some on each wing working and so on.....With 4 or 5 hydraulic systems...you end up with 5 different ways to turn the airplane. (as long as you don't lose all your hydraulic fluid that is can any one say "Sioux City"..ouch!)

anyway that sort of philosophy of redundecy may be what your looking for??

JIM
me11owman is offline Find More Posts by me11owman
Reply With Quote
Old Dec 28, 2003, 01:45 PM
Registered User
Tucson, AZ, USA
Joined Sep 2000
794 Posts
In full size commercail planes the redundecy is split so that you would still have symmetrical control after a failure......ie rudder on one system ailerons on the other (And/or inbd ailerons and otbd on seperate systems) spoilers split so that any failure still leaves some on each wing working and so on.....With 4 or 5 hydraulic systems...you end up with 5 different ways to turn the airplane. (as long as you don't lose all your hydraulic fluid that is can any one say "Sioux City"..ouch!)

anyway that sort of philosophy of redundency may be what your looking for??

JIM
me11owman is offline Find More Posts by me11owman
Reply With Quote
Old Dec 28, 2003, 02:46 PM
Super Member
davensocal's Avatar
United States, NY, Mechanicville
Joined Mar 2003
1,203 Posts
HEY-
No fair trying to up your post numbers with double posts...

cheater
davensocal is offline Find More Posts by davensocal
Reply With Quote
Old Dec 28, 2003, 02:48 PM
David Cairns
dcairns's Avatar
Orange, CA
Joined Apr 2002
1,095 Posts
Yes, those are the kind of thoughts I am looking for. How to split the functions between the receivers for best redundancy in case of failure.
dcairns is offline Find More Posts by dcairns
Reply With Quote
Old Dec 28, 2003, 05:06 PM
Registered User
Lincolnshire, UK
Joined Sep 2002
653 Posts
Try here http://www.smservices.net/

Loads of solutions for large models. Opto Isolation and a unit for dual RX use that looks perfect for your needs.

SM46 RX Buddy

Mark
Cones is offline Find More Posts by Cones
Reply With Quote
Old Dec 28, 2003, 05:09 PM
Registered User
Lincolnshire, UK
Joined Sep 2002
653 Posts
Here's the data sheet link

http://smservicesuk.co.uk/acatalog/sm46rxbuddy.html

This may help with some wiring ideas as well.

Mark
Cones is offline Find More Posts by Cones
Reply With Quote
Old Dec 28, 2003, 08:19 PM
Feeling FrSky
surfimp's Avatar
United States, CA, Santa Barbara
Joined Feb 2003
19,912 Posts
Looks like there have been some good suggestions so far, but have you considered poking around in Scale Sailplanes or some of the giant scale forums? This has got to have been totally sussed by this point, I would like to think.

Not much help but just a thought...

Steve
surfimp is offline Find More Posts by surfimp
RCG Plus Member
Latest blog entry: Buzz Evo RTF acro glider review
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Help! Butterfly Receiver Wiring ifxmnfly Scratchbuilt Indoor and Micro Models 6 Dec 31, 2005 02:37 PM
Receiver wiring catfight Micro Helis 2 Oct 29, 2005 06:43 PM
Were Can I Find Out, How To Set Up A Dual Receiver, Battery, For 33% falcon41176 Sport Planes 0 Oct 19, 2005 11:44 PM
How-To Implement Dual Receiver? humberto Radios 13 Sep 21, 2005 12:54 PM
esc to receiver wiring connersw Beginner Training Area (Aircraft-Electric) 2 Feb 28, 2005 07:37 PM