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Old Mar 25, 2012, 08:02 AM
No bounce, No play.
davidmc36's Avatar
Canada, ON, Ottawa
Joined Oct 2010
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Question
Would two recievers have any use?

I was playing around testing two Rx's that I bought and wondered if you bind them both to the same model memory, will they both work at the same time.

Sure enough they will.

Is there any use for doing this that you could not achieve with "Y' cables. I can't think of any.
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Old Mar 25, 2012, 08:34 AM
Registered User
USA, CA, Santee
Joined Jul 2002
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A lot of the Giant Scale guys run 2 Rx's. You run the right ail, right elev and rudder on one and the left ail, left elev and throttle on another. Gives you redundancy if one fails, you still (may) have enough control to get the airplane back, and, if you're running multiple servos on control surfaces, such as 3 servos on rudder and 2 servos on ail, running 2 Rx's allows you to run the servo's direct and reduces the power through the Rx's internal power buss.
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Old Mar 25, 2012, 10:52 AM
No bounce, No play.
davidmc36's Avatar
Canada, ON, Ottawa
Joined Oct 2010
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OK Iv'e never got into anything huge like that so it never occured to me.

So it could be an alternate way to using one of the big power modules.
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Old Mar 25, 2012, 10:59 AM
59 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,127 Posts
Also, some people use a second receiver for ground or water steering. In the first case, they have a takeoff dolly with its own steering receiver that gets left on the ground when the model lifts off. In the other case, the water rudder on a float plane is controlled by a separate receiver, thus eliminating the need for either mechanical linkages from the air rudder or a servo cable to the float.

In another application, you can set up a wireless buddy box system by using two receivers (and two transmitters) with a switch in the model. The master radio (instructor) uses an additional channel to determines which radio is in control. I have just set up such a system using the HobbyKing Assan switch. I haven't flown it yet, but it works perfectly on the bench.
EDIT: Flew it this afternoon and it worked exactly as expected.

If either radio loses signal, the switch goes automatically to the other, meaning that you could also use the switch as a redundant setup with one transmitter driving two receivers.

Where to get them:
This is the so-called 8-channel switch (since one channel is needed to operate the switch, only seven are switched between the two receivers);
http://www.hobbyking.com/hobbyking/s...dProduct=18703
Here's the four-channel (which really does have four switched channels):
http://www.hobbyking.com/hobbyking/s...dProduct=20002
Note that you need a package of 10 male-to-male leads like this (or you'll go nuts making your own).
http://www.hobbyking.com/hobbyking/s...0pcs_set_.html OR
http://www.hobbyking.com/hobbyking/s...0pcs_set_.html
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Last edited by Daedalus66; Mar 25, 2012 at 03:32 PM.
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Old Mar 25, 2012, 11:18 AM
No bounce, No play.
davidmc36's Avatar
Canada, ON, Ottawa
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Quote:
Originally Posted by Daedalus66 View Post
Also, some people use a second receiver for ground or water steering. In the first case, they have a takeoff dolly with its own steering receiver that gets left on the ground when the model lifts off. In the other case, the water rudder on a float plane is controlled by a separate receiver, thus eliminating the need for either mechanical linkages from the air rudder or a servo cable to the float....
I like that idea. It could make switching from floats to wheels much simpler. It would not add much weight if you were running a six foot or so airplane since the float battery would not need to be all that large.
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Old Mar 25, 2012, 11:42 AM
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dickw's Avatar
Luton, UK
Joined May 2006
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I sometimes fly in competitions for electric gliders where we have to provide a second receiver to be plugged into the scoring system so the scoring system knows if our motor is on or off.
I even have a third receiver that starts a pair of "talking stopwatches" that help me second guess the scoring system!.

I believe some people operating robots use more than one receiver so they don't have to get wiring through 360 degree rotating joints.

The possibilities are endless.

Dick
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Old Mar 25, 2012, 12:22 PM
TigreJohn
United States, CA, Corona
Joined Aug 2008
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Among other things, you may need two receivers when you need a channel mix that is not pre-programmed into your transmitter. I ran into a problem where I had a dual servo situation where I had to use a manual mix. Dual elevator servos where I had to reverse one servo because of the plane construction. Found I had no trim function available on one servo. Solution was to install second receiver which was less expensive than a radio with more channels and functions.
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Old Mar 25, 2012, 01:39 PM
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davidmc36's Avatar
Canada, ON, Ottawa
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Quote:
Originally Posted by dickw View Post
....I believe some people operating robots use more than one receiver so they don't have to get wiring through 360 degree rotating joints....
I sort of thought robot applications because I imagined
folks wanting a lot of servos. The rotating joint solution would sure help make construction easier in a lot of cases. I saw the video of the guy who has been excavating his basement for the last fifteen years or so with RC backhoes and the like. It could allow you to make the platform of a High-Hoe go full circles without reversing.
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Old Mar 25, 2012, 01:41 PM
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davidmc36's Avatar
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Quote:
Originally Posted by jjkupinski View Post
....Dual elevator servos where I had to reverse one servo because of the plane construction. Found I had no trim function available on one servo. Solution was to install second receiver which was less expensive than a radio with more channels and functions.
How did you make that work?
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Old Mar 25, 2012, 02:07 PM
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solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
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Not only the redundnacy aspect and safety - but having multiple Rx's can get rid of servo lead extenders that can in fact detract from signal strength ... inductance and all that jazz ..
By having the extra Rx - you can mount it close to location needed.

It used to be a req't of LMA in UK - I assume it's still the case ?

They also req'd back up Rx power systems either in dual active or main with auto switched back-up. I still have an auto switcher called a Battery Backer from my LMA days in UK.

(LMA = Large Model Association)
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Old Mar 26, 2012, 11:14 AM
TigreJohn
United States, CA, Corona
Joined Aug 2008
993 Posts
Quote:
Originally Posted by davidmc36 View Post
How did you make that work?
Hate to admit it, I really don't know, I'll have to ask. The guy who sold me the second receiver and servo set it up.

In retrospect, I may been suckered into buying that second receiver. I have since found out you can reverse a servo by switching wires on the pot. I can't see reversing polarity on either second item as the electronics wont work. If so, I should have been able to use just a Y-connector on the two servos with one modified.
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Old Mar 26, 2012, 01:47 PM
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Quote:
Originally Posted by davidmc36 View Post
How did you make that work?
Inquiring minds would sure like to know
Pete
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Old Mar 26, 2012, 02:46 PM
k2k
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The wires on the pot AND the motor have to be swapped.
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Old Mar 26, 2012, 03:31 PM
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The Northeast Kingdom, Vermont
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Yes, that's how you can reverse a servo if need be.
The question was in regard to how on earth using another receiver would be of help, since in this case it would amount to no more than an expensive Y harness for all channels
Pete
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Old Mar 26, 2012, 04:33 PM
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Evan D's Avatar
Charlotte, NC
Joined Jan 2004
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I have two orange 6ch with satellite receivers in this airplane. It is much easier to do that than run all the extensions and stuff.

It's about 11 years old and flew on two Hitec 555 receivers for years.
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