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SBUS Receivers - I'm a little puzzled

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Old 07-19-2018, 10:14 AM
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nheather
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Default SBUS Receivers - I'm a little puzzled

Now this is not a problem, just that I'm a little puzzled, so I would like to understand a little better.

So we have a SBUS receiver, it supports 18 channels, and as physical connections it has 3 normal (Channels 1, 2 and 3) and an SBUS connection.

So I get the SBUS - it is a digital connection that carries all 18 channels and if you plug in compatible servos, or a hub or something like a FBL gyro you can access these.

The most common application I can imagine is for a FBL helicopter plugging into a gyro like the MicroBeast. Simply plugging the SBUS into the MicroBeast will allow me to access 8 channels on it - that's great I understand that.

So what is the point of the physical channels 1,2 and 3 on the receiver. As I understand they can't be reassigned, so will relate to the AIL, ELE and THR controls. I can't imagine how they would be useful on their own (without the SBUS), except maybe for a car or a boat. And if you do use the SBUS then they are already covered. I could understand if you could associate them with channels 9, 10 and 11 but you can't.

What purpose would they ever serve?

Cheers,

Nigel
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Old 07-19-2018, 02:37 PM
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A good use for an S.Bus receiver with Ch 1-3 PWM outputs would be in a full house sailplane.
Assuming you have a transmitter with the ability to reassign any function to any channel, as my Futaba 8FG does. You could have rudder on Ch 1, Elevator on 2 and throttle on 3. The S.Bus output would then be used for the aileron and flap servos in the wing, reducing wiring and the number of connections to the wings.
Another good use is in really large scale models. You could use a pair of the smaller receivers for redundancy, connected to an S.Bus capable power box, such as the XPS X24 for driving the actual servos.
S.Bus is cool!
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Old 07-19-2018, 03:36 PM
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Originally Posted by pilotpete2 View Post
A good use for an S.Bus receiver with Ch 1-3 PWM outputs would be in a full house sailplane.
Assuming you have a transmitter with the ability to reassign any function to any channel, as my Futaba 8FG does. You could have rudder on Ch 1, Elevator on 2 and throttle on 3. The S.Bus output would then be used for the aileron and flap servos in the wing, reducing wiring and the number of connections to the wings.
Another good use is in really large scale models. You could use a pair of the smaller receivers for redundancy, connected to an S.Bus capable power box, such as the XPS X24 for driving the actual servos.
S.Bus is cool!
Pete
Now that makes sense - I had been told that the channels couldn’t be reassigned - so that Ch1 was always AIL and Ch2 always ELE. So I was thinking these would be in the SBUS going to the FBL controller as Ch1 and Ch2.

But I think what you are saying is that I could reassign AIL and ELE to be Ch8 and Ch9 to be picked up by the FBL controller FBL and I could use the physical Ch1 and Ch2 to operate servos to do other things - like controlling a camera.

Cheers,

Nigel
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Old 07-21-2018, 04:15 PM
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Originally Posted by nheather View Post


Now that makes sense - I had been told that the channels couldn’t be reassigned - so that Ch1 was always AIL and Ch2 always ELE. So I was thinking these would be in the SBUS going to the FBL controller as Ch1 and Ch2.

But I think what you are saying is that I could reassign AIL and ELE to be Ch8 and Ch9 to be picked up by the FBL controller FBL and I could use the physical Ch1 and Ch2 to operate servos to do other things - like controlling a camera.

Cheers,

Nigel

What radio are you using? Many Futaba radios allow you to reassign the functions to different channels.
As you say, S.Bus works great for FBL helis. I use it on my gliders. I will put rudder, elevator, and ESC (F5J planes) on channels 1,2,3 and use S.Bus for the wing.
Lots of guys use S.Bus on larger planes. You can use S.Bus for the elevator and rudder servos of a larger plane and only have a single wire coming forward from the tail. Or have multiple wing servos and only a single lead at each wing root.
It is a very flexible tool.
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Old 07-23-2018, 10:36 AM
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Originally Posted by nheather View Post
I had been told that the channels couldn’t be reassigned - so that Ch1 was always AIL and Ch2 always ELE.
Sort of yes, but no. Open house architecture on transmitters means you can assign any function to any channel. But you cannot assign one channel to transmit to another channel, i.e. channel 1 will never transmit to channel 8 on the receiver. That's not how the encoding works.
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Old 07-23-2018, 10:43 AM
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What causes confusion as well is we are used to thinking of "channel" as being the same thing as "function". Newer radios allow functions (aileron, elevator, etc.) to be mapped to any "channel" or port on a RX. Look at the R7008SB RX. When using it in dual RX mode you can have "channels" 1-8 on ports 1-8 on RX#1 and channels 9-16 on ports 1-8 on RX #2. Ans then you can have almost any function you want assigned to one of those channels!!

Last edited by FUTABA-RC; 07-23-2018 at 11:23 AM.
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