Sbus on edf with plug in wings

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joefly

New member
Jan 23, 2018
25
1
#1
I have an edf jet that has retracts, flaps and ailerons. There are 3 servo leads coming out of each wing that needs o be connected to the 6 extensions in the fuselage. Its a rat’s neast. I want to use sbus to simplify the assembly. The receiver is a RX8 and it only has one sbus connector. Since I’ll have two connectors coming from each wing, how do I connect both to the single sbus connector?
 

Konrad

Active member
Jan 23, 2018
705
41
San Francisco
#2
I assume you are using S-Bus servos. Just make an S-Bus "Y" harness (AKA, a normal aileron "Y" harness). The arms will go the the wing roots and the trunk would be plugged into the RX S-Bus port. Assign the appropriate S-Bus identifier to the servos and have fun.

If your retract are not S-Bus compliant you can wire in one of these S-Bus converters to each retract.
https://alofthobbies.com/frsky-sd1-sbus-converter.html
 
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joefly

New member
Jan 23, 2018
25
1
#3
No, I’m not using Sbus servos. I just want to simplify the wiring. I want to have one connector for each wing instead of three. I plan on using a sbus decoder in each wing to achieve this. The only thing I don’t know is: where do I connect the two connectors from the wings into the receiver. The receiver only has one sbus output. I will need two.
 

Konrad

Active member
Jan 23, 2018
705
41
San Francisco
#5
Yes, to a servo Y-connector. Not sure I understand the other part of the question, S-bus is a serial bus no need for a second S-bus output.

Each servo (control) will need its own S-bus decoder (address).
 
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Konrad

Active member
Jan 23, 2018
705
41
San Francisco
#8
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joefly

New member
Jan 23, 2018
25
1
#9
I do not have any sbus servos. The edf is a Habu 32. In the wings, I’m using digital hs- 85 mg. I do plan on using the decorder you mentioned. One for each wing. Each wing has an aileron servo, a flap servo and a main retract. I’m converting it from Spectrum radio to a Frsky radio. I thought I would use Sbus to simplify the wiring. I also plan to use it on gliders. I have managed to convert 2 club members from Spectrum to Frsky that I fly gliders with. I’m constantly expanding my knowledge about Frsky/ Opentx. Sbus was next on the list.
 

Wayne

Administrator
Staff member
Nov 29, 2017
885
107
Novato, CA USA
#10
Should work a treat for you, but one concern, I think the HS85MG is an analog servo, the decoder will output a fast frame rate and we have found this can kill analog servos after a while. Please be aware that we recommend running digital servos with the Sbus feeds for this reason.
They analogs may work for a while, but there is a risk they will fail in flight!
 

joefly

New member
Jan 23, 2018
25
1
#11
The servos that I’m using on thr main control surfaces are hs-5085 mg. I’m using hs-85 on nose gear steering and flaps only.
Before I try it on the jet, I’ll install it on ugly stick that has all digital servos tp test it.
 

Konrad

Active member
Jan 23, 2018
705
41
San Francisco
#12
Should work a treat for you, but one concern, I think the HS85MG is an analog servo, the decoder will output a fast frame rate and we have found this can kill analog servos after a while. Please be aware that we recommend running digital servos with the Sbus feeds for this reason.
They analogs may work for a while, but there is a risk they will fail in flight!
With the digital refresh rate issue I've been thinking of how the Servo amplifier in the retacts will work? As these have effectively huge dead bands (only activate at extreme pulse width) I don't see them burning out. But I really don't know enough about these electric retracts.

Now I do have grave concerns about the HS -85 (flaps), as I can see the output transistors or the motor burning out as a result of the refresh rate. (Note the servo doesn't know if it is set up on a aileron or a flap. It will try to hold its commanded position regardless. If it is asked to do this at 3 to 10 times more often the average power draw will go up almost as much).
 

joefly

New member
Jan 23, 2018
25
1
#14
Here's an update on my SBus project. Today, I received my order from Aloft of a Servo Channel Changer and 4 SBus decoders. Ordered them on Thursday and they arrived today.
Grabbed my 4.8V batterey and connected it to the Channel changer and then connected one decoder to the channel changer. Changed the channel to 2 & 5 (Ailerons) and 6 & 7 (flaps). These corresponded to the test plane that i have on my 12S. The test plane has all digital servos as recommended. Bound a spare 8 channel receiver to the 12S. Plugged in the SBus port and turned the power on. Everything worked great. Weather permitting, I will test fly it to verify everything works.
If that works, the Jet is next. I have to replace 2 of the servos from analog to digital and I also have a S8R to set up.
Our club meeting is on the 1st of November. I plan on a demonstration of the QX7, G-R8R, SBus and telemetry. I've already
turned 2 members from spectrum to FrSky and I have a few more that are interested.
Thanks for all the help setting this up!
 

Wayne

Administrator
Staff member
Nov 29, 2017
885
107
Novato, CA USA
#15
You bet!! Keep up the good work. Maybe you should have someone video your club presentation to share with others. We get asked about this sort of setup all the time.
 

joefly

New member
Jan 23, 2018
25
1
#16
Here is an update of what I have done with SBus:
My Ugly Stick has 4 servos in the wing, 2 for the Ailerons and 2 for the flaps. All digital servos and on 4 different channels.
I programmed the decoder for each on the 4 servos and connected it to the SBus out port on the receiver (RX8R). It worked perfect on the bench.
I then took it out to the field and flew 3 times and again it worked perfect.
The one advantage that I really liked was that I only had to connect one extension from the wing to the plane. I live in Amarillo, TX and the wind blows here all the time. The Ugly Stick has a large wing and it was a challenge trying to mount the wing with the wind blowing and trying to connect 4 extensions at the same time. SBus to the rescue. Now I only have 1 extension to connect that is easily done even with the wind blowing.
Next I plan on using SBus on my HABU 32.