alasdair

I read somewhere recently about servos that are S.Bus compatible.
Seemed to indicate that several could be plugged into one Rx output to operate different functions, each on its own Tx channel.
Sounds like a neat idea. Tell each servo to listen for its own coded signal.

I read my DX18 manual and found no mention though.

Is this S.Bus thing purely a Futaba thing then?

Do any other makes of Tx use S-Bus?

Does the Transmitter even matter, or is it a Receiver function only?

Is the Spektrum X-Plus expander another trademark for the same thing as S.Bus?

Should I just forget the whole thing, put it down as a bad dream?

FenderBean

SBus is futaba xbus is Jr's version. It allows all signal to be ran through a single line. You basically just program a servo with a channel assignment then when it's plugged in it will act as that channel. So for me I sometimes assign multiple servos to the same channel to save channels. Like my f-14 I have four slat servos and I assigned them all to channel 8 do all the end point matching and servo reversing in the servo itself. The servos are programmable and then you can still do the normal radio settings as well. If you 12 servo on a project u can have all them plugged into a small terminal box that has one lead to the receiver and because the servo is tell the radio I'm channel 1 or 2 or what ever u can plug it in anywhere and it will on operate as the assigned channel. Great system and really cleans up a build. I lost two pounds of wire weight by switching

David Gladwin

If you lost 2 pounds of wiring you must have been using 240 volts (or greater!) cabling. My entire installations weighs far less (1/2 ) of that !!

Alisdair, there will be full description of JR X -Bus in the next RCJI, it works very well ! Not sure it saves much cabling after connecting centre hubs etc.,

it does,however, mean that control of upto 112 servos is possible from a 28x .

David G.

alasdair

112 servos??? Sounds crazy!!

Am I right in thinking that S/X bus starts from the Receiver (not the Tx)?? It is a Rx output coding alternative to the usual PWM. Is that right?

So it needs a special servo that understands the coding, or an inline decoder if using standard servos?

"u can have all them plugged into a small terminal box that has one lead to the receiver"
FenderBean, does that mean that all the amps to all the servos has to pass through a single servo wire? Is that asking a lot, even if it is heavy duty?

David Gladwin

The X-bus protocol starts in the Tx. On the JR you have X-bus and another for third party protocols or X-bus can be inhibited. You then need X-Bus compatible receiver(s). The newer JR receivers such as 712 and 612 (9 grams!) also have PWM outputs perfect for low load demands such as ECU and sequencers etc. However if you feed x-bus signals to standard servos you need PWM converter harnesses and they then work normally. The conversion is done and stored in the harness. If using x-bus servos, the XN series, the X-bus address (ID and sub ID) is recognized by and stored in the servo. XNs are clever servos, they can tell if the input is X-bus or PWM ! Servo action on X-bus is beautifully smooth and accurate because of higher update speeds.

The 112 servos are a result of each channel having an ID, 28 on the 28X , and each channel has 4 sub IDs, all of which can be fully programmed wirelessly via the tx, brilliant !

There are three types of heavy duty center hubs, all of which have dual battery inputs and 1, 3 or 5 HD power outputs for high current demands, one has 14 pwm outputs plus 2 X-bus , another has 4 X-bus outputs, 3 with HD power, and another has 5 X-Bus outputs all with HD power outlets.

There is an excellent JR Propo video on X-bus, just enter JR X-Bus on Youtube and Barron Guss will explain the basics.

I am currently working on an article for the next RCJI explaining X-bus, using a 28x and the various x-bus accessories so it will also be in print there .

Hope this helps !

David.

Malcolm H

Hi Alasdair, hope you are well! My last the F3a models have all used Futaba SBus and my latest turbine model a large Skymaster Hawk also had SBus along with a Robbe Futaba power management system. If we ever get back onto Leuchars your more than welcome to have a rummage around in it!

Malcolm

DrScoles

My Feedback: (18)

Futaba, power box and Robbe make up for some cool combinations. I have several s-bus planes, half with the robe 2018, others with just futaba rx or power box. I think you could save two pounds of weight with a big complex model like Keith's F-14.

You don't need special servos, everyone (I'm assuming JR wouldn't be stupid enough to only let people use newer s-bus servos) makes PWM adaptors so you can run your old servos on s-bus. On medium sized planes, the s-bus servos would be ideal because you wouldn't have to use PWM hubs, that adds cost and weight. On my CARF warbirds, I'm using either the Robbe 2018 or a power box that can take s-bus and use their hubs. Spendy, but much cleaner and bulletproof.

Tech type peeps, correct me if I'm wrong. JR's use of the word "x-bus" is solely marketing and the proper terminology is s-bus. Took JR a while to make it to the party... ;-)

FenderBean

yes you sure can servo wire adds up when you have long leads like my f-14. I thought the same thing that I would never use 18 channels but I can easily use those now flying jets. A normal scale jet has 2 flaps, 2 ailerons, 2 stabs, 2 rudders, 1 nose wheel. That's 11 channels right there so throw in a gear channel, canopy, gear doors, smoke. It adds up, my f14 has 8 servos just in the wings so if I didn't assign them to the same channel I would have ran out

Jgwright

I thought Robbe went under recently and products no longer available. Emcotech make the 2018 and it is available from them. They also make other Sbus items.

http://shop.rc-electronic.com/DPSI-S...=A12101&p=3059


John

FenderBean

Jg your correct Emcotech sells them now, such a great product

Malcolm H

The only problem with going all serial data to the servos is that gyro use becomes problematic. Demon Cortex and other units don't do serial in and serial out and even if they did you would have problems using two receivers into the Emcotec unit. The only workable unit that overcomes this is the iGyro which does allow two SBus receivers to be connected to it. Ideally Emcotec should make a modified unit which allows the data stream it selects from the two receivers to be outputed to a gyro and then inputed back to the servo bus. Then we would also need Demon to produce a unit that allowed serial in and out. I doubt these two conditions are going to be met anytime soon!

Malcolm

David Gladwin

The new JR "Axis" gyro works perfectly with Futaba S bus as well as JR X-Bus !

Malcolm H

Dave, although the Axis allows the use of Xbus or Sbus in and out, if you want to use a redundant receiver you have to use the JR XB2-CHB Xbus redundant hub to combine the data streams from the two receivers before feeding this into the Axis and this only works with Xbus not Sbus. Good try though!

Malcolm

Turbotronic

There is no logic in that. When using S-bus you clearly have to use an S-BUS redundant system.
The two data streams are never "combined", X or Sbus. The redundant system uses one or the other.
Dave is correct.

Malcolm H

Turbotronic, you sir are engaging in semantics!

Of course you don't combine serial data streams. The point is the JR system uses a separate device to poll the two data streams before deciding on what data to pass onto the Axis unit and the polling device doesn't work with Sbus only Xbus. So Dave is not correct in that the JR Axis system isn't useable with redundant Sbus receiver systems and indeed the JR literature makes that point clear.

Malcolm

Jgwright

Malcom I hope you are not correct here!

I have a power box Cockpit SRS. It allows 2 small cheap Futaba 3 channel S bus receivers to be connected to it and to have the 12 amplified servo channels out to a max of 21 servos as normal servos not S Bus ones plus the connections for the built in sequencer. I will be using a Gyro and the gyro will be on the line from the Cockpit SRS to the elevon normal servos. I used a similar system in the past with a Powerbox RRS (Before S Bus) and a gyro in the elevon channels coming out to the normal servos. I have used ACT Fuzzy gyros for years and see no need to change now. I am unlikely to switch to S bus wiring and servos at any stage as I see not real advantage for me. I use Futaba 12Fg transmitter.

All this new technology is getting a bit confusing and that is before you add telemetry into the mix!

John

Turbotronic

I think we are talking about different devices. If you are saying the "separate" device from JR does not work with SBUS that could be correct.
The point is that if you want to use an SBUS based system any other than this specific JR device will have to be used to select any which rx you want.
This is not a limitation of the Gyro. Unless you for some reason want the upstream JR devices to use SBUS (why would you?) then you are correct.
Remember that any redundant type system that can output S or Xbus can use this gyro.
The point of SBUS compatibility is to use the Gyro with Futaba devices.
Clearly JR wants a broader appeal for the Gyro than just JR.
How I know is that I have engineered such a device that can output either or both protocols, PPM as well and can take input from DSM, DSMX, DSMJ, Xbus, JR "satellites" ,SBUS RX's, "Spektrum satellites", anything.

dirtybird

My Feedback: (5)

You can also use the FR-SKY Taranis with s-buss. Then you will have the power of the opentx operating system

FenderBean

simple solution to the Battery backer power system is to just use the Igryo. I get it folks like demon but if you love the robbe battery backer like I do having to use the igyro isnt that big of a deal. Its a nice gyro.

on that note if you have an older Igyro you have to update to the latest software. I had gyro glitches before updating, they changed some stuff to support the robber type setup

George

My Feedback: (57)

I have two s-bus set-ups and really like it. I have already attempted to use serial in only gyros in these set-ups to no avail. In order to do it, you basically need to split your system up and that defeats the purpose of the exercise. I may look at the Axis as an alternative to the iGyro for future use, but have had zero issues with the iGyro.

On another note, the video in this thread http://www.rcuniverse.com/forum/rc-j...bbe-s-bus.html is no longer available (Bart, please repost), but it showed 6 servos in different arrangements being cycled continuously under sustained heavy loads. It was a pretty convincing video, but he did not actually "stall" any of the servos to see the result. I have been told that a "stalled" servo will wipe out the system, but I have no proof other than what was said. And although a "hard-over" or sustained stalled servo is rare, it does occur and it concerns me. Does anyone have any concrete information/data (video) showing a stalled condition in an s-bus system?

Bart,
Maybe you could do another torture test stalling a servo in your test rig?

jetmaven

If you go to the back inside cover of this months Model Aviation magazine ( yuuuuck ) and scan the QR code in the Futaba ad,
a nice man will come up on the screen and 'splain it .

BarracudaHockey

My Feedback: (11)

The Fly RC at the printer now has an article explaining how it works here's some key points though.
S.bus servos can be used as normal servos. Normal servos can be made to work with S.bus
You connect a servo to (in my case) a 14FG and pull its address by pressing RECALL and then program it and write it to the servo.
You can also use a terminal program and a laptop to program the servo.

You can more or less think of it as USB for your servos, though not completely plug and play like USB, it doesn't matter where your servo is physically plugged in, once its programmed for aileron it will act via the aileron stick as long as its plugged into the bus.

dribbe

Aura will do S.bus in so you can have all 18 or so channels of data available in the 'gyro'. It has 8 servo output ports... No s.bus out at this time...

www.flexinnovations.com/aura

David

alasdair

Thanks, all of you. You have thoroughly confused a 20th century modeller with 21st century electrickery.

I think that the answer to my question is that my old DX18 does not have single wire coded servo output (neither S.bus nor X.bus nor ?? that other one?)
Not in the Tx, nor in the Rx, and I don't have S.bus servos anyway so I stick with 3 wires per servo.

BarracudaHockey

My Feedback: (11)

Thats correct, Spektrum doesn't do X or S bus. Though I wouldn't be surprised to see them come out with some version of it sooner rather than later.