R8Pro + R4 redundancy configuration

[stephen66]

Situation: Biplane using all 8 channels for flight control. I am short one channel to handle the ignition opto kill switch. Yes, I can use an R10 but want to use what I have--and gain the advantage of redundancy. I think I understand but nothing is ever clear cut with FrSky products...so check my sanity.

Plug R4 S.port/F.port SBUS-In --->> R8Pro SBus-Out

Does the TX simply continue Channel counting UP from the Master? Meaning R8 CHs 1-8 adds R4 running 9-12 ? Can I just "y" out of the switch and run both RX on a single battery? Yes, the battery becomes a single point of failure...but it already is in every other single RX plane. I believe this gives me RF redundncancy but not battery redundancy.

Am I correct? What am I missing?

Oh, is it just me or does the plug for the S.F.port on the Archer seem much less secure than a standard servo plug? If so, is anyone doing anything to increase confidence in that connection? Hot glue? Nails and duct tape?

Stephen

 

[stephen66]

Ok, my brain was making this harder than necessary. I would still like an answer to "how-to" redundancy correctly. In my cause, the battery was in Ch8 so I "y"ed out the kill switch...ez-pz.

 

[gnichola]

For your extra channel needs, you could always use one of the SBUS converters, like https://alofthobbies.com/frsky-sd1-sbus-converter.html or https://alofthobbies.com/frsky-sbus-decoder.html

 

[Wayne]

@stephen66 - Think you are jumbling things here..

First off - the R10 is also capable of redundant receiver connections.

You have an R8 Pro and would like more channels out of it, no problem, as mentioned above you can use an S-Bus decoder to add more PWM outputs. Keep in mind that ANY ACCESS receiver is able to output up to 24 channels, you just need a way to access them, and that is what the decoder does, it converts the Sbus feed into normal PWM outputs that normal servos understand.

Another option is to use an Sbus servo. We sell the cheap Corona brand as well as the new FrSky units. And the decoders some in 1 channel and 4 channel versions.

Now onto redundancy, we are not adding any channels with redundancy, simply adding a second RF reception point to the existing receiver. What does this do? If the main receiver should have receptions issues, it will switch over to the backup receiver if it is able to hear the transmitter better. It is a good idea for the second receiver to be installed some distance from the main receiver to gain the maximum benefit a new location can offer.

If you decide to use an S Bus decoder, it is a good idea to also get a channel changer. This is used to set what channels will be output by the decoder. Each PWM output can be anywhere from channel 1 to 24. You can set them all to the same channel if you like, but the default I think is channels 1,2,3 & 4. Probably not super useful like that.

Hope this helps..

 

[stephen66]

@Wayne Thanks a lot. You threw a lot at me so I will bounce it back to make sure I understand. FYI, I was flying FM when I dropped out of the hobby so 2.4 and S.bus is a new world.

1) the S.Bus Decoder allows me to use the R8/10 Pro S.bus Out ... into the Decoder ... and then out to 4 PWM servos. Right ? And a Channel Changer is needed to assign channel #s. Yes ?
2) Corona s.bus servos. A single servo plugs directly into the S.bus Out and I would use the Channel Changer to assign a PWM channel to the servo. Right?
3) Redundancy. I would get RF redundancy by running R8/10 Pro S.Bus Out to the F/S.Port of the other RX (say, R4). ? Would I have access to the use the 4 channels on the second RX ? Or, do I ONLY get RF redundancy and nothing more ? No matter the answers on redundancy an R4 is cheap insurance on an expensive model.

4) It is my understanding you can use a R8/10 Pro in conjunction with an SRx series RX and get stabilization as well as redundancy. ?? Yes, I am aware of the SR8/10 Pro...looking into stabilization for the R8 Pros I already own.

 

[Wayne]

1) the S.Bus Decoder allows me to use the R8/10 Pro S.bus Out ... into the Decoder ... and then out to 4 PWM servos. Right ? And a Channel Changer is needed to assign channel #s. Yes ?
2) Corona s.bus servos. A single servo plugs directly into the S.bus Out and I would use the Channel Changer to assign a PWM channel to the servo. Right?
3) Redundancy. I would get RF redundancy by running R8/10 Pro S.Bus Out to the F/S.Port of the other RX (say, R4). ? Would I have access to the use the 4 channels on the second RX ? Or, do I ONLY get RF redundancy and nothing more ? No matter the answers on redundancy an R4 is cheap insurance on an expensive model.

4) It is my understanding you can use a R8/10 Pro in conjunction with an SRx series RX and get stabilization as well as redundancy. ?? Yes, I am aware of the SR8/10 Pro...looking into stabilization for the R8 Pros I already own.

1) You are CORRECT.
2) You are almost CORRECT. The Corona servos use their own programmer to change the channel. Nothing in the hobby is ever straight forward..
3) WRONG, but close.. The R8/10PRo would be the main receiver, so the R4 SBus OUT will connect to the Sbus IN on the R8/10 Pro. Yes, you will still control all of the channels. Everything will plug into the main receiver, all sensors, all servos, etc.
4) Tricky question.. Last I knew FrSky does not recommend using a stabilized receiver for redundancy. Why? Basically, there is a lot of special stuff the stabilized units require, and also because it would be out of sync at the time of a redundancy switch over. So, no, don't do it. There are probably some other reasons I have not thought of..

 

[Droptanks]

Can’t you use trio control and have Rx1 doing ch1-8 and Rx2 doing 9-16?

 

[Wayne]

Can’t you use trio control and have Rx1 doing ch1-8 and Rx2 doing 9-16?

That is an option, but need to be clear here, that is not redundant. Loose connection to a receiver and you loose those channels in your plane.

We have seen a few people with large planes that simply set up multiple receivers and power systems through out the plane. Thus no wires going from one section of the plane to another. For example, the left wing is its own stand alone system, the right wing is another stand alone, etc. Should the radio loose one section, the others can still be working. There is a level of redundancy here.. but loose that elevator and you are in a world of hurt. It is not a horrible approach to a very large airframe.

One of our customers actually uses fiber optic setup in his large scale airframes. This gets rid of the huge wire lengths that tend to pick up RF noise. He is a bit of a rocket scientist and makes this all himself.

 

[Keith Kimes]

1) You are CORRECT.
2) You are almost CORRECT. The Corona servos use their own programmer to change the channel. Nothing in the hobby is ever straight forward..
3) WRONG, but close.. The R8/10PRo would be the main receiver, so the R4 SBus OUT will connect to the Sbus IN on the R8/10 Pro. Yes, you will still control all of the channels. Everything will plug into the main receiver, all sensors, all servos, etc.
4) Tricky question.. Last I knew FrSky does not recommend using a stabilized receiver for redundancy. Why? Basically, there is a lot of special stuff the stabilized units require, and also because it would be out of sync at the time of a redundancy switch over. So, no, don't do it. There are probably some other reasons I have not thought of..

About your answer to question#2. Does this mean that to program the Corona, FrSky, or Futaba sbus servo or decoder you must use the coresponding manufactorers servo programmer and they will only work with that manufactorers servos and decoders? That's a bummer if true.

 

[gnichola]

About your answer to question#2. Does this mean that to program the Corona, FrSky, or Futaba sbus servo or decoder you must use the coresponding manufactorers servo programmer and they will only work with that manufactorers servos and decoders? That's a bummer if true.

Yep, that is generally the case. However, the decoders pointed out earlier have plugs and thus are independent of the servo used. So if you went with the FrSky SBus converters you need to buy the $18 programmer https://alofthobbies.com/frsky-servo-channel-changer-sbus-cppm.html but then you can use the converters with any servo you want.

 

[Keith Kimes]

This may have been explained earlier but to clarify one more time as there does not seem to me to be many people using sbus.

1. Even though FrSky sbus signals are inverted from Futaba sbus all sbus servos will work on both systems but require their corresponding manufacturers servo programmer to program the servo of a corresponding manufacturer to the desired channel. Is this correct? In other words you can use a Corona servo programmed only with a Corona servo programmer with either FrSky sbus or Futaba sbus even though the signals are inverted from each other?

2. When using decoders, the decoded outputs of the decoders are programmed by the servo programmer to the desired channel. The decoded output is PWM or digital and any PWM or digital servo can be connected to them (What about analog serovs, are they PWM?). In other words servos plugged into the decoders do not need to be sbus servos. This makes it possible to use an sbus single 3 wire cable into a wing and then decode to drive multiple servos through one or more decoders. The channel programmer for FrSky is https://alofthobbies.com/frsky-servo-channel-changer-sbus-cppm.html. The 4 channel sbus decoder for FrSky is https://alofthobbies.com/frsky-sbus-decoder.html. The FrSky single channel sbus decoder is https://alofthobbies.com/frsky-sd1-sbus-converter.html . Is this correct?

3. If you wish to use pure sbus, directly driving servos, you use multiple y cables to directly drive a programmed sbus servo on a branch and cascade down to the next servo or servos on the other branch. Each servo must be programmed to the desired channel with a programmer. You can do the same thing with sbus and standard none sbus servos in this type of daisy chain if you use the single servo decoder between the sbus and standard servo such as the FrSky https://alofthobbies.com/frsky-sd1-sbus-converter.html if you are using FrSky. Is this True?

Seems odd to me that this type of wiring is not more common for FrSky setups if it is all true. Especially since the use of the single channel decoders in a daisy chain setup does not require a y cable as it has two sbus connections, one for sbus in and one for sbus out to the next servo. Is there some major downside to this type of setup that I do not see causing it's minimal use?

Final question: does the sbus and decoded signals work at 9 ms or should the transmitter be set to 18 ms in binding?

 

[gnichola]

The one downside I have found is the range issue I mentioned https://forum.alofthobbies.com/inde...coder-sd1-doesnt-support-extended-range.2138/

 

[Wayne]

1. Even though FrSky sbus signals are inverted from Futaba sbus all sbus servos will work on both systems but require their corresponding manufacturers servo programmer to program the servo of a corresponding manufacturer to the desired channel. Is this correct? In other words you can use a Corona servo programmed only with a Corona servo programmer with either FrSky sbus or Futaba sbus even though the signals are inverted from each other?

As far as I know Futaba and FrSky are the same, not inverted. Later on Futaba went to Sbus-2 or whatever they call it, and now FrSky has come out with F-Port, these 2 are different. But Sbus is Sbus but we have found some issues with compatibility with third party Sbus hubs not working with FrSky. I have nit researched it much other than to ask the manufacturers to address the issue.
There are not many Sbus servos out there. Futaba, FrSky and Corona are the main ones I am aware of, but imagine there may be others. Corona are by far the cheapest way to play with Sbus, but they do require their own programmer. I understand the FrSky channel changer will program Futaba servos as well as FrSky servos and decoders.

2. When using decoders, the decoded outputs of the decoders are programmed by the servo programmer to the desired channel. The decoded output is PWM or digital and any PWM or digital servo can be connected to them (What about analog serovs, are they PWM?). In other words servos plugged into the decoders do not need to be sbus servos. This makes it possible to use an sbus single 3 wire cable into a wing and then decode to drive multiple servos through one or more decoders. The channel programmer for FrSky is https://alofthobbies.com/frsky-servo-channel-changer-sbus-cppm.html. The 4 channel sbus decoder for FrSky is https://alofthobbies.com/frsky-sbus-decoder.html. The FrSky single channel sbus decoder is https://alofthobbies.com/frsky-sd1-sbus-converter.html . Is this correct?

The channel changer simply sets what channel you would like to output on the decoder, or the servo. For example we want it to decode channel 12. The output is PWM (Pulse Width Modulation) this is what all servos use, digital or analog, but the frame rate is 9ms, this is too fast for most analog servos, while they may work for a while, they will usually burn up within 45 minutes at this faster rate of data.

Yes, with a decoder in the wings you can pass just 3 wires from the fuselage into the wings and drive a bunch of servos. But there is a catch when doing this, it is power delivery. You need to be aware that that little servo connector is only able to pass about 7 amps, maybe as high as 10, but not for long. So keep in mind how work you are asking these little servo plugs to do. If using the little corona servos, you should be fine with 4 servos out there, but if using FrSky or Futaba, some of those can really suck some amps when the servo is working hard. This is ALWAYS a concern for larger aircraft regardless of sbus or not.

3. If you wish to use pure sbus, directly driving servos, you use multiple y cables to directly drive a programmed sbus servo on a branch and cascade down to the next servo or servos on the other branch. Each servo must be programmed to the desired channel with a programmer. You can do the same thing with sbus and standard none sbus servos in this type of daisy chain if you use the single servo decoder between the sbus and standard servo such as the FrSky https://alofthobbies.com/frsky-sd1-sbus-converter.html if you are using FrSky. Is this True?

Correct!

Seems odd to me that this type of wiring is not more common for FrSky setups if it is all true. Especially since the use of the single channel decoders in a daisy chain setup does not require a y cable as it has two sbus connections, one for sbus in and one for sbus out to the next servo. Is there some major downside to this type of setup that I do not see causing it's minimal use?

If you have a connector issue, then all servos after that point are dead. Also, every time you have a connector in the chain it is adding some resistance (lower voltage) and adding another possible point of failure to the chain.

Final question: does the sbus and decoded signals work at 9 ms or should the transmitter be set to 18 ms in binding?

Regardless of the setting, Sbus is always at 9ms. I personally leave my receivers in 18ms as I do not see an advantage to 9ms. This way should I ever plug in an analog servo to that receiver I'm not going to kill it.

Hope this helps.

 

[gnichola]

Yes, with a decoder in the wings you can pass just 3 wires from the fuselage into the wings and drive a bunch of servos. But there is a catch when doing this, it is power delivery. You need to be aware that that little servo connector is only able to pass about 7 amps, maybe as high as 10, but not for long. So keep in mind how work you are asking these little servo plugs to do.

I was in another forum discussing SBus and one guy mentioned the load of the 4 wing servos running through a single servo plug and my response was that most likely all 6 servos were running through a single servo type plug at the end of the battery, so talking about the 4 wing servos was sort of moot.

 

[Keith Kimes]

I was in another forum discussing SBus and one guy mentioned the load of the 4 wing servos running through a single servo plug and my response was that most likely all 6 servos were running through a single servo type plug at the end of the battery, so talking about the 4 wing servos was sort of moot.

Yes, with a decoder in the wings you can pass just 3 wires from the fuselage into the wings and drive a bunch of servos. But there is a catch when doing this, it is power delivery. You need to be aware that that little servo connector is only able to pass about 7 amps, maybe as high as 10, but not for long. So keep in mind how work you are asking these little servo plugs to do. If using the little corona servos, you should be fine with 4 servos out there, but if using FrSky or Futaba, some of those can really suck some amps when the servo is working hard. This is ALWAYS a concern for larger aircraft regardless of sbus or not.

The power issue is something that I never considered and can see that it is a major problem for setups with a lot of servos. It would be a problem also if you are driving all servos directly from the receiver since all power is through the little servo size power plug powering the receiver as gnichola implies. This seems like a good argument for running a separate power and ground daisy chained to various groups of servos such as large wings and tail independently and then running only the signal wire from the receiver to the individual servos. This would also reduce the wire bundle size though not quite as much as sbus. I am sure some of you experienced members already do something like this.

Thanks Wayne, based on your feed back and the power issue I think I will avoid sbus. I may look into dierctly powering groups of servos seperate from the reciever though. This looks like a good compromise to reduce wire weight and assure current availability when I am trying to save as much weight as possible. Seems that the main down side would be a bad connection could kill multiple servos so soldered connection to the y in the power cable may be best here to minimize that risk.

 

[Cole Hallman]

Ok one more option. If you have a second receiver that has pwm channels you can hook the opto to it. Bind it and select 9 through 16 or whatever. Sbus still passes all 16 or 24 channels depending on if you are using access or accst. Always use redundant pwm channels for stuff that can't krash you if there is a link failure. I have often done this when running out of pwms. This works well, I have noticed that the 4 channel sbus to pwm converters. Cause jitter in fast digital servos