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Feb 06, 2018, 11:59 AM
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scottand1000's Avatar
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Aileron Diff with Expo in OpenTx


I'm trying to figure out a good way to establish Aileron Differential and Expo on an airplane with 2 aileron servos on separate channels.

I'm fairly new to OpenTx, I have been using a year and have successfully set up and flown several models (including the FrSky SxR Rx's), but this is the first time I tried to set up aileron diff. I have reviewed/searched OpenTXU, Youtube, Google, etc. but haven't found a great explanation on how to do this, at least one that I can follow. This is probably a learning experience best done by actual practice. I have a working solution now on the Companion simulator, but I was wondering if ppl well-versed in OpenTx could comment on what's good or bad about this solution.

Taranis X9D+, OpenTx 2.2.1

With the current model I'm working with, I decided to add two more temporary channels just to see how they simulate; channels 15 and 16 for R Ail and L Ail. These will eventually be eliminated when I find what I need to set up Aileron Diff and Expo on channels 1 & 5...

Mixes is where I usually set up Expo. I see there is a Diff option too, but if I use it, then I would have to establish Expo somehow else. I chose keep Expo as the selection for each channel under Mixes.

I decided to establish differential on the Inputs screen using two curves to define the motion. Curves 10 & 11. After playing around with the curve values, I got the results I was hoping for. I have now established Aileron Diff, and my normal 3-position Rates/Expo swt controls the output as I would expect.

Some of the things I notice about this solution are:
-If I want to change/edit the amount of Diff (currently 100/70), I have to edit two separate curves
-I can continue to edit Expo/Rates as I'm used to in the Mixes screen

But I'm not sure if what I've done is good practice for establishing Aileron Diff in regards to how things like weights, offset, trims will effect the overall result. Also, it would be nice to be able to change just one thing to adjust the Aileron Diff (my solution currently requires adjusting two curves). It's fine now while it's fresh in my mind, but a year from now, I hope I can remember there are *two* curves to adjust.

Thanks
Last edited by scottand1000; Feb 06, 2018 at 12:47 PM.
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Feb 06, 2018, 12:57 PM
Sagitta Fanboy
You've basically got it backwards from best practice in this case.

Set expo on your stick (Inputs). Stick conditioning like Expo/DR is best set there (this is the main reason there is an Inputs page).

Do your differential at the mixer.

That will result in 2 less lines (because you only need a single Aileron Input, with Expo) and trims, offsets, etc will work.

If you want a master class in differential (and advanced mixing in general), take a look at Mike Shellim's E-Soar Plus or F3J templates, which implement on-the-fly adjustable aileron differential on a per-flight mode basis, using GVAR's for calibration.
Feb 06, 2018, 01:30 PM
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scottand1000's Avatar
Quote:
Originally Posted by mawz
You've basically got it backwards from best practice in this case.

Set expo on your stick (Inputs). Stick conditioning like Expo/DR is best set there (this is the main reason there is an Inputs page).

Do your differential at the mixer.

That will result in 2 less lines (because you only need a single Aileron Input, with Expo) and trims, offsets, etc will work.

If you want a master class in differential (and advanced mixing in general), take a look at Mike Shellim's E-Soar Plus or F3J templates, which implement on-the-fly adjustable aileron differential on a per-flight mode basis, using GVAR's for calibration.

Thanks so much Mawz. Of course right after I post this, I stumble onto a couple of posts by Mike Shellim on aileron diff and calibration of servos. rc-soar.com/opentx/setups/(etc). It's fascinating, but a lot to digest.

I'm going to try your suggestions (which are easier for a newer OpenTx guy like me to understand).

I find it curious... With my Futaba radios, it seems so easy and innocent setting up aileron diff and expo/DR (triple rates, whatever) When doing so in OpenTx, you are forced to think about so many situations and how one setting affects another. And then circling back, I begin to wonder just how does the programming in say a Futaba radio actually work when combining functions like aileron diff, expo/RD, EPA and trims. I have a Popsicle headache now LOL.
Last edited by scottand1000; Feb 06, 2018 at 01:54 PM.
Feb 06, 2018, 01:37 PM
Registered User
scottand1000's Avatar
Quote:
Originally Posted by mawz
You've basically got it backwards from best practice in this case.

Set expo on your stick (Inputs). Stick conditioning like Expo/DR is best set there (this is the main reason there is an Inputs page).

Do your differential at the mixer.

That will result in 2 less lines (because you only need a single Aileron Input, with Expo) and trims, offsets, etc will work.

If you want a master class in differential (and advanced mixing in general), take a look at Mike Shellim's E-Soar Plus or F3J templates, which implement on-the-fly adjustable aileron differential on a per-flight mode basis, using GVAR's for calibration.

And just to clarify, this is a simple HK Tundra I'm setting up. I chose to ditch the Y-cables on the aileron and flap servos so I could learn more about adjusting end points as well as setting up aileron diff. Who knows if aileron diff will even make a noticeable improvement on a plane like a Tundra; I'm using this as a learning exercise to explore more capabilities with OpenTx. As always, these forums and help from people like you is much appreciated.
Feb 06, 2018, 04:57 PM
Sagitta Fanboy
Quote:
Originally Posted by scottand1000
Thanks so much Mawz. Of course right after I post this, I stumble onto a couple of posts by Mike Shellim on aileron diff and calibration of servos. rc-soar.com/opentx/setups/(etc). It's fascinating, but a lot to digest.

I'm going to try your suggestions (which are easier for a newer OpenTx guy like me to understand).

I find it curious... With my Futaba radios, it seems so easy and innocent setting up aileron diff and expo/DR (triple rates, whatever) When doing so in OpenTx, you are forced to think about so many situations and how one setting affects another. And then circling back, I begin to wonder just how does the programming in say a Futaba radio actually work when combining functions like aileron diff, expo/RD, EPA and trims. I have a Popsicle headache now LOL.
The Futaba (or Spektrum, Jeti, JR or other radio) does all of that behind the curtain. They largely work in the same progression as OpenTX, Input->Input conditioning-> Mixing->output conditioning->output

Expo and DR are input conditioning, EPA and Trims can be mixing or output conditioning depending on implementation. Diff is always a mixer level operation.
Feb 08, 2018, 11:55 AM
Registered User
scottand1000's Avatar
Quote:
Originally Posted by mawz
The Futaba (or Spektrum, Jeti, JR or other radio) does all of that behind the curtain. They largely work in the same progression as OpenTX, Input->Input conditioning-> Mixing->output conditioning->output

Expo and DR are input conditioning, EPA and Trims can be mixing or output conditioning depending on implementation. Diff is always a mixer level operation.
Been reading and digesting the Open Tx Clinic on www.rc-soar.com . Starting to become clearer and make better sense. Really good stuff on this site.


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