Go Back  RCU Forums > RC Airplanes > RC Jets
Reload this Page >

15 PWM channels + telemetry out of a single R7008SB Futaba receiver

RC Jets Discuss RC jets in this forum plus rc turbines and ducted fan power systems

15 PWM channels + telemetry out of a single R7008SB Futaba receiver

Reply

Old 12-10-2016, 03:00 AM
  #1  
i3dm
Thread Starter
My Feedback: (51)
 
Join Date: Jun 2004
Location: Reut,Israel
Posts: 4,117
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default 15 PWM channels + telemetry out of a single R7008SB Futaba receiver

Hello guys,

Lately i have been looking for a solution to convert my jets with 14 channels Futaba receivers to telemetry. these models often have 12-14 PWM channels plugged directly to the receiver.
Converting to telemetry is a problem, as the trusty Futaba R7008SB telemetry receiver is only 8 channels.

Solution #1:
To use a dual R7008SB receiver installation - one for channels 1-8 and other for 9-16. this is a viable solution, but is expensive (300$ for 2 receivers) and space / weight consuming in a small jet.

Solution #2:
Use some form of Sbus power box - again expensive and space / weight consuming for a small jet.

Solution #3:
Use a Futaba 18 channel telemetry receiver - this is a viable solution, also expensive, and it seems from the forums that this receivers suffers from a large than usual amount of failures - not an option for me.

Solution #4:
This comes from the FPV world - but proved to be quite useful for our use!
Since the R7008SB has a S-Bus port on Channel 8, which has all 16 channels data, its possible to use an expansion board such as:
https://hobbyking.com/en_us/signal-c...-pwm-s2pw.html
for 9$ and 10 grams you get 8 PWM channels (either CH1-8 or CH9-16).

This board coupled with the R7008SB would provide the following support:
- CH1-7 PWM on receiver.
- CH9-16 PWM on board.
- Telemetry support on receiver.

So total 15 PWM chanenls + telemetry from a single R7008SB receiver - not bad!
So i ordered this board and tested it - really seems to work fine. here is a test video showing a hitec deigital servo on CH9 via the expansion board:
https://www.youtube.com/watch?v=L_tt3Vy9SQk NOTE:
one important factor to take into consideration with any dual installation is power source.
since this board conencts to the receiver using only one signal wire, while its possible to use that single line to power feed the board with its consumers, i would strongly advise against it if you are going to connect power hungry (digital) servos.
if you are using just valves, controllers or any other low current consumption devices - single wire to power the board should work fine.
if you are using more high current consumers on the board, please remove the RED wire from the wire connecting the Rx and board, and splice ("Y" connect) your power to the Rx, feeding power to the board directly. this would share the same power source between your receiver and your expansion board.

Im hoping this helps anyone that wants a similar setup.
thanks for reading.
Attached Thumbnails Click image for larger version

Name:	20161210_123824.jpg
Views:	502
Size:	634.9 KB
ID:	2192917  

Last edited by i3dm; 12-10-2016 at 03:07 AM.
i3dm is offline  
Reply With Quote
Old 12-10-2016, 04:45 AM
  #2  
DelGatoGrande
My Feedback: (23)
 
DelGatoGrande's Avatar
 
Join Date: Mar 2004
Location: ATHENS, , GREECE
Posts: 2,918
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

So instead you buying a second R7008SB FUTABA receiver (140$),
you choose to trust seven functions of your 4,000$ model jet ,
to an unknown made 9$ devise.

..no comment

Last edited by DelGatoGrande; 12-11-2016 at 03:40 AM. Reason: typo ( one zero been removed )
DelGatoGrande is offline  
Reply With Quote
Old 12-10-2016, 04:52 AM
  #3  
i3dm
Thread Starter
My Feedback: (51)
 
Join Date: Jun 2004
Location: Reut,Israel
Posts: 4,117
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by DelGatoGrande View Post
So instead you buying a second R7008SB FUTABA receiver (140$),
you choose to trust seven functions of your 40000$ model jet ,
to an unknown made 9$ devise.

..no comment
From an electrical engineering perspecive (i develop many RC jet electronic systems myself) - the answer is a definite YES. your Futaba receiver is not better nor is its BOM more expensive than this board.
All this board does is simple protocol conversion from SBUS to PWM - every 1$ arduino can do that these days. this board does not handle power (besides to its own processor) so there really nothing to it.

PS - who's flying 40,000$ jets?

Last edited by i3dm; 12-10-2016 at 05:07 AM.
i3dm is offline  
Reply With Quote
Old 12-10-2016, 05:43 AM
  #4  
ww2birds
My Feedback: (14)
 
ww2birds's Avatar
 
Join Date: Feb 2003
Location: Katonah, NY
Posts: 1,312
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Very elegant!

On some planes that I've converted from 6014 to 7008, I had an iGyro or Cortex. Both of them can take Sbus in, and put out standard servo signals, so in effect you get 5 channels (2xAIL, 2xELE,1xRUD) of Sbus to regular servo for "free" from the gyro. Add that to the servos direct from the RX. In some cases that is enough, if not one or two of the Sbus to 3 servo decoders can be added.

I would not have considered anything from that vendor assuming it was low quality/unreliable, but your argument is logical .. it's a very simple function and if implemented with standard chips should work just fine.

Of course the bill of materials is not the only factor to consider with a good vendor. One would hope that Futaba would do a good job on functional, environmental and stress testing (but we don't really know that), and this knock-off stuff probably does none of that... but again we don't really know that either. So in a sense it comes down to faith in the vendor since hobby products don't have that sort of info made available to the buyers as it would be in a more professional environment.


Dave

Last edited by ww2birds; 12-10-2016 at 05:48 AM.
ww2birds is offline  
Reply With Quote
Old 12-10-2016, 08:32 AM
  #5  
Eddie P
My Feedback: (4)
 
Eddie P's Avatar
 
Join Date: Feb 2003
Location: Reno, NV
Posts: 1,913
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I could see this being a viable solution for some of the more complex EDF foamies with high channel counts but not so much $ invested - you get the telemetry data and the high count channel control for a reasonable cost.

Are you using this method on any actively flying aircraft yet? I'd love to see what your longer term experience is with it.

For a turbine powered jet I'd throw the extra $140 and the additional receiver to have redundant power supply wants met.
Eddie P is offline  
Reply With Quote
Old 12-10-2016, 08:36 AM
  #6  
i3dm
Thread Starter
My Feedback: (51)
 
Join Date: Jun 2004
Location: Reut,Israel
Posts: 4,117
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by Eddie P View Post
For a turbine powered jet I'd throw the extra $140 and the additional receiver to have redundant power supply wants met.
Using two Rxs in CH1-8 and CH9-16 configuration does not offer any redundancy, neither in control or in power supply. they are logically independant systems.
i3dm is offline  
Reply With Quote
Old 12-10-2016, 12:13 PM
  #7  
Levels87
 
Join Date: Aug 2005
Location: Hailsham, , UNITED KINGDOM
Posts: 31
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Whilst I have not tried this exact device I have tried a non licensed s-bus to PWM board made by someone for Hobby King. My experience was initially very good in that it all worked absolutely fine on the bench and in the air. I had it fitted to an EDF Taft Viperjet with the gear and throttle on the receiver PWM channels and the flying controls on two s-bus devices. On reflection this was a leap of faith and I later regretted it. On the fifth flight during a low pass I pulled up and nothing happened. The flying controls were all suddenly dead with only the throttle and gear working. There was nothing I could do to get the controls back so I eased off the power and let the model fly into the ground. The model was a right off. Initially I thought one of the devices had failed but when I connected it all together it all worked perfectly again. I bought two more of the S-bus to PWM converters and used them only on the gear and doors (the sequencing was done in my 18MZ transmitter). This time with a new airframe the controls were all on the PWM outputs of another different 7008 receiver. It flew fine for several flights and then low and behold when I selected gear down nothing happened. The same failure but this time non critical using all new components. I discussed this with someone from Futaba and they told me that there are some manufactures that have the license for the s-bus code but not the cheap Chinese ones. They have reverse engineered the code and may well have compatibility issues that manifest in this intermittent way. I would urge caution with this and make sure it is only used for non critical functions until proven over a long period of time. I would be very interested to hear how you get along with it and wish you every success.
Levels87 is offline  
Reply With Quote
Old 12-10-2016, 12:28 PM
  #8  
i3dm
Thread Starter
My Feedback: (51)
 
Join Date: Jun 2004
Location: Reut,Israel
Posts: 4,117
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Interesting find.
I gurss running it on the bench in servo test mode for a long time could prove beneficial.

Never heard about a problem of that sort though..
i3dm is offline  
Reply With Quote
Old 12-10-2016, 12:38 PM
  #9  
Levels87
 
Join Date: Aug 2005
Location: Hailsham, , UNITED KINGDOM
Posts: 31
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I did eventually get it to happen on the bench but it took a lot of time. The trouble is you won't know if you have given it long enough. I think the best answer is to use two 7008 receivers which is what I now do in a few of my models. At that price it is certainly not a licensed product and the reverse engineering of the code is clearly not perfect in every case. The price of a jet makes this a risky business.
Levels87 is offline  
Reply With Quote
Old 12-10-2016, 01:05 PM
  #10  
i3dm
Thread Starter
My Feedback: (51)
 
Join Date: Jun 2004
Location: Reut,Israel
Posts: 4,117
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

You make a valid point about testing.
Communication protocols dont just stop working one day, and 99% of sbus boards are not authorized.

Do you have a link to the product that caused you trouble?
i3dm is offline  
Reply With Quote
Old 12-10-2016, 02:22 PM
  #11  
Halcyon66
 
Join Date: Aug 2016
Location: Sydney
Posts: 96
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

9 bucks is an awful big risk for the value of a jet.

IN finance it is called the risk reward ratio, seems like a pretty big risk for a potentially very small reward.

Regards,
Halcyon66 is offline  
Reply With Quote
Old 12-10-2016, 02:25 PM
  #12  
i3dm
Thread Starter
My Feedback: (51)
 
Join Date: Jun 2004
Location: Reut,Israel
Posts: 4,117
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

In our hobby, anything for a fair price is considered low quality.
This is why companies like Futaba sell a 5$ receiver for 200$ and its ok
i3dm is offline  
Reply With Quote
Old 12-10-2016, 03:03 PM
  #13  
Levels87
 
Join Date: Aug 2005
Location: Hailsham, , UNITED KINGDOM
Posts: 31
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by i3dm View Post
You make a valid point about testing.
Communication protocols dont just stop working one day, and 99% of sbus boards are not authorized.

Do you have a link to the product that caused you trouble?
https://hobbyking.com/en_us/sbd4-4-c...ard-combo.html

I was so pleased with it to start with I left a good review. (Scoobydoo).

I fully take your point but the fact is that it happened. Cheap doesn't always mean poor quality. FRsky make some great quality things at an amazing price and show just how much the big manufacturers make on receivers and accessories. I don't think the problem was the quality of the hardware as that seemed very good. The problem was that they didn't have the code from Futaba, they worked it out for themselves and a something like a specific combination of signal requests, that takes a long time to fall into place, cause it to fall over. If they had the proper code it would be as good as an original Futaba product. I am led to believe they won't release the code to manufacturers that may not respect their intellectual property rights which is understandable, would you??
Levels87 is offline  
Reply With Quote
Old 12-10-2016, 03:04 PM
  #14  
Halcyon66
 
Join Date: Aug 2016
Location: Sydney
Posts: 96
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

36 yrs in the hobby and lived in a lot of countries doing it and have always built to a specification and not a price. The problem is that everyone is just going lower and lower on price for everything RC related. People bit**in that they should be able to get 50 kg thrust turbines for $500 as they deserve to have them. Used to be questions yrs ago about "Is it OK to use 8$ orange servos" on these forums and I left yrs ago because it was doing my head in.

I always stayed away from clubs and fields and flew in my own area's and as time goes on i am happy to go further and further away just so i don't end up flying next to someone with a hobby king TX/RX combo next to me. The top end systems have a name they built over yrs not over a weekend and that is where the cost come in.

Everyone wants to pay nothing and then are the first to complain when everything goes wrong. Truly wonder there this hobby will be in another 5 yrs?

Regards,
Halcyon66 is offline  
Reply With Quote
Old 12-10-2016, 03:06 PM
  #15  
mr_matt
My Feedback: (10)
 
mr_matt's Avatar
 
Join Date: Dec 2001
Location: Oak Park, CA,
Posts: 10,293
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by Levels87 View Post
https://hobbyking.com/en_us/sbd4-4-c...ard-combo.html

I was so pleased with it to start with I left a good review. (Scoobydoo).

I fully take your point but the fact is that it happened. Cheap doesn't always mean poor quality. FRsky make some great quality things at an amazing price and show just how much the big manufacturers make on receivers and accessories. I don't think the problem was the quality of the hardware as that seemed very good. The problem was that they didn't have the code from Futaba, they worked it out for themselves and a something like a specific combination of signal requests, that takes a long time to fall into place, cause it to fall over. If they had the proper code it would be as good as an original Futaba product. I am led to believe they won't release the code to manufacturers that may not respect their intellectual property rights which is understandable, would you??
Same one died on me after 20 or 30 flights in a test plane. Same exact circumstances.
mr_matt is offline  
Reply With Quote
Old 12-10-2016, 04:41 PM
  #16  
dbsonic
My Feedback: (3)
 
dbsonic's Avatar
 
Join Date: Oct 2005
Location: san jose, CA
Posts: 855
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

With any electronics, it is hard to know how much QA by the manufacturer goes into the released product. They should be running a set of vectors to verify there are no faults - to weed out the manufacturing defects and meet a signoff spec. This does cost something and involves time and tester time is not cheap. My expectation is that companies like Futaba and JR have something like this in place as they have a name to protect, besides the fact it is probably required by their industrial business. When buying a device with no name, hard to know, so to be safe you probably need to do that testing yourself ...but you'll not be able to exhaustively test.
dbsonic is offline  
Reply With Quote
Old 12-10-2016, 07:43 PM
  #17  
Viper1GJ
My Feedback: (19)
 
Viper1GJ's Avatar
 
Join Date: Oct 2003
Location: Saint George , SC
Posts: 1,057
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Quote from Levels87 . This time with a new airframe the controls were all on the PWM outputs of another different 7008 receiver. It flew fine for several flights and then low and behold when I selected gear down nothing happened. The same failure but this time non critical using all new components....


This is exactly what happened to me in my 1/5 F-16 using a 7008 with flight controls on ch 1-7 PWM and three non Futaba Sbus decoders for aux systems, including landing gear. In first 20 flights I had three gear extend failures that eventually did come down prior to landing but not before lots of tense moments and multiple tries. I could not duplicate on the ground. I just guessed something was amiss in the Sbus system that was intermittently affecting the gear.

After the third time the jet was grounded and will be refitted with a PowerBox Royal SRS with dual 7008 inputs and PowerBus outputs for flight controls. I hope this will fix the intermittent problems with the non Futaba Sbus decoders.

I think you hit the problem on the head with the non Futaba code issues that sometimes does and sometimes doesn't ..

Thanks

Gary
Viper1GJ is offline  
Reply With Quote
Old 12-10-2016, 11:51 PM
  #18  
Levels87
 
Join Date: Aug 2005
Location: Hailsham, , UNITED KINGDOM
Posts: 31
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by dbsonic View Post
With any electronics, it is hard to know how much QA by the manufacturer goes into the released product. They should be running a set of vectors to verify there are no faults - to weed out the manufacturing defects and meet a signoff spec. This does cost something and involves time and tester time is not cheap. My expectation is that companies like Futaba and JR have something like this in place as they have a name to protect, besides the fact it is probably required by their industrial business. When buying a device with no name, hard to know, so to be safe you probably need to do that testing yourself ...but you'll not be able to exhaustively test.
I absolutely agree with this comment. When you go out flying it is important to have confidence in your radio, without it the fun is lost as you anticipate the next failure. For this reason I now only use genuine branded or licensed equipment. Confidence takes a long time to grow but can be lost in an instant be that personal or product related.
Levels87 is offline  
Reply With Quote
Old 12-11-2016, 08:38 AM
  #19  
i3dm
Thread Starter
My Feedback: (51)
 
Join Date: Jun 2004
Location: Reut,Israel
Posts: 4,117
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Everybody is making valid points, and im glad i managed to create an interesting discussion.

Futaba, being a top name in radio industry, still has bugs here and there, even when they develop and test in house.
same goes for big names like Powerbox etc - remember the PB SRS Igyro problems?

nothing is fault free, and i am personally skeptical that Futaba does better screen testing than most. i dont think thats the reason for their high pricing.

I have had very good experience with these protocol conversion boards in many hours of FPV flying - i guess thats why i trust them more than most.

i have not tested this specific board extensively. i will admit to that. the ones i flew were different.

it is still possible to use non flight critical controls on these boards, especially if you have many AUX channels (smoke, lights, air brakes etc).

Last edited by i3dm; 12-11-2016 at 08:41 AM.
i3dm is offline  
Reply With Quote
Old 12-12-2016, 02:24 AM
  #20  
mauryr
 
Join Date: Dec 2010
Location: , ITALY
Posts: 456
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by i3dm View Post
Everybody is making valid points, and im glad i managed to create an interesting discussion.

Futaba, being a top name in radio industry, still has bugs here and there, even when they develop and test in house.
same goes for big names like Powerbox etc - remember the PB SRS Igyro problems?

nothing is fault free, and i am personally skeptical that Futaba does better screen testing than most. i dont think thats the reason for their high pricing.

I have had very good experience with these protocol conversion boards in many hours of FPV flying - i guess thats why i trust them more than most.

i have not tested this specific board extensively. i will admit to that. the ones i flew were different.

it is still possible to use non flight critical controls on these boards, especially if you have many AUX channels (smoke, lights, air brakes etc).
Futaba makes it's own SBUS decoder, why don't you consider that instead? I've had the same problem you had and considered this solution, but then I just used sbus servos so didn't actually put it in practice.
While I am pro-hobbyking stuff (been using power turnigy supplies for years in all of my airplanes with great success), I wouldn't trust a non-branded sbus decoder, because as it was said before, sbus is a proprietary technology and, while it can be reverse engineered, it cannot be reproduced up to spec unless these specs are actually in hand when you design your device.
mauryr is online now  
Reply With Quote
Old 12-12-2016, 12:31 PM
  #21  
i3dm
Thread Starter
My Feedback: (51)
 
Join Date: Jun 2004
Location: Reut,Israel
Posts: 4,117
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by mauryr View Post
I wouldn't trust a non-branded sbus decoder, because as it was said before, sbus is a proprietary technology and, while it can be reverse engineered, it cannot be reproduced up to spec unless these specs are actually in hand when you design your device.
From an engineering stand point, i have to completely disagree with that statement.
can you provide a link to the Futaba decoder?
i3dm is offline  
Reply With Quote
Old 12-12-2016, 03:17 PM
  #22  
stevekott
 
stevekott's Avatar
 
Join Date: Nov 2006
Location: yorba linda, CA
Posts: 593
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

http://www.xtremepowersystems.net/pr...rod=XPS-X10%2B

This is an Xtreme Power systems X10 pwm port expander. I have used this before as well as the Futaba SBD-1 3-port and the Robbe 4-port expander.

I still prefer to put all of the critical flight surfaces on the R7008 native ports.

The XPS is nice in that you can provide pretty high current to it. It appears to be built to a high quality. It will also decode SBUS.2 so you can use the bottom port on the RX rather than giving up channel 8 for SBUS 1. On the Demon Cortex Gyro SBUS.2 will not work so you have to configure channel 8 as SBUS 1.

Last edited by stevekott; 12-12-2016 at 03:24 PM.
stevekott is offline  
Reply With Quote
Old 12-12-2016, 10:20 PM
  #23  
i3dm
Thread Starter
My Feedback: (51)
 
Join Date: Jun 2004
Location: Reut,Israel
Posts: 4,117
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

The XPS board seems to do the same job as the HK board i linked, but with better specs, more channels and more features. For 30$ it sounds like a good deal!
i3dm is offline  
Reply With Quote
Old 12-13-2016, 02:04 AM
  #24  
mauryr
 
Join Date: Dec 2010
Location: , ITALY
Posts: 456
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by i3dm View Post
From an engineering stand point, i have to completely disagree with that statement.
can you provide a link to the Futaba decoder?
http://www3.towerhobbies.com/cgi-bin/wti0001p?I=LXZKA6

Why do you disagree? I look at it from a software point of view and I believe not knowing the exact specs the system was implemented with you cannot possibly produce a 100% reliable and compatible system.
The problem is this is a proprietary protocol and it does not need to follow any public specification or standard.
What if futaba decided to implement some sort of dumb booby trap, such as 'if you don't receive packet xyz on the 1st of april, kill the airplane' in the receiver?
Just saying, it might be perfectly fine, or it might not, so I don't know if the non-official product could be trustworthy or not.
mauryr is online now  
Reply With Quote
Old 12-14-2016, 11:04 AM
  #25  
i3dm
Thread Starter
My Feedback: (51)
 
Join Date: Jun 2004
Location: Reut,Israel
Posts: 4,117
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

i agree its hard to tell, but these protocols usually are easy to reverse engineer, and if done right - work fine.
you see a variety of these boards for a reason, and mass wisdom is taking case - lots of people decoded these protocols with arduino and published their codes.

the chinese manufacturers just made the boards
i3dm is offline  
Reply With Quote

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service