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Nov 27, 2018, 12:25 PM
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FrSky Taranis adjustable throttle curve


I have my throttle set up on a couple of curves and use a switch to change in flight, but I would like to set up a curve on one of the knobs (S1) so that I can adjust the center of the curve in flight. Any suggestions on how to do this? I know that it is possible, as my Futaba 9Z has this on the throttle curve in the heli program.
Thanks, Sam
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Nov 27, 2018, 01:44 PM
Regexistentialist
ridgerunr's Avatar

Pot adjustable throttle center point


Yes, this is easily done. There's probably many ways to accomplish this but here's how I do it:

This solution requires one POT, one INPUT, one MIXER line, one GLOBAL VARIABLE and one SPECIAL FUNCTION. The description below is a bare-bones model which uses GV1 and S1.

First create a new INPUT line and name it something like "ThrM". The SOURCE is the throttle stick, the WEIGHT is -GV1, the OFFSET is +GV1 and the CURVE is FUNC |x|:



Once you complete all the following steps, the graph on the INPUT edit screen has a "V" shaped curve that goes up and down as the S1 is moved through its range. The horizontal position on the curve follows the throttle stick position. The following image is what it looks like with a throttle stick position of -37.7 and a GV1/S1 value of +51:



Next add one mixer line to the throttle channel which simply adds the newly created iThrM INPUT to the throttle channel:



Be sure to turn OFF the trims for this mix line:



The GV1 GLOBAL VARIABLE is used to contain the parameter needed by the "V" curve INPUT we just created:



The last step is to create a SPECIAL FUNCTION that causes the GV1 value to follow the S1 value:



And thats all there is to it.

Hope this helps!

p.s. I use this mix on all my powered planks and with a sprung throttle stick, it gives me an easily adjustable cruise speed at center stick.
Nov 27, 2018, 02:10 PM
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Thread OP
Where does the number 51 come from in the GV1 GLOBAL VARIABLE
Never mind, I see it
Nov 27, 2018, 03:39 PM
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Thread OP
I only get the inverted curve by putting numerical values in the Weight and Offset boxes.
Nov 27, 2018, 08:17 PM
Registered User
Possibly you did not enable the Special Function that adjusts GV1. It's the check at the end of the line.

One thing I note is that when S1 is in the 0 to +100 range the throttle channel value maxes out. I don't think that is the intent. Possibly something is missing.
Nov 27, 2018, 10:07 PM
Regexistentialist
ridgerunr's Avatar
Quote:
Originally Posted by pressalltheknobs
... One thing I note is that when S1 is in the 0 to +100 range the throttle channel value maxes out. I don't think that is the intent. Possibly something is missing.
Can you elaborate? I've tested this technique extensively...

As the throttle stick is moved from the center to the top/fwd limit, the throttle channel output value should linearly move from the chosen center point to +100. If the S1 pot is fully clockwise (S1==GV1=+100), then the output value remains constant at +100 throughout the upper range of stick travel. A similar effect happens when S1 is at its minimum value (-100).

Once correctly setup, as S1 is varied from 0 to +50 to -50 and back to 0, the effective throttle channel output curve should vary like so :
Last edited by ridgerunr; Nov 27, 2018 at 10:25 PM.
Nov 27, 2018, 10:21 PM
Regexistentialist
ridgerunr's Avatar

Entering a GLOBAL VAR into a numeric field


Quote:
Originally Posted by esl1885
I only get the inverted curve by putting numerical values in the Weight and Offset boxes.
Normally, when you edit a WEIGHT or OFFSET field, it is a numeric value that is changed using the PLUS and MINUS buttons. To change this from a simple number to GV1, press and hold the ENTER key. Then you can select any of the GLOBAL VARs (both plus and minus versions can be selected). If you press and hold the ENTER key again, the field reverts back to a simple numeric value. (i.e. When editing a field, a long press of ENTER toggles between the two entry modes.)
Last edited by ridgerunr; Nov 27, 2018 at 10:41 PM.
Nov 28, 2018, 07:25 AM
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I am sure it probably is me. Will work with it some more today and get it working.
Nov 28, 2018, 12:42 PM
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OK, works just as you say. How I would set it so that the knob only controls 25% +or- instead of 100%?
Nov 28, 2018, 01:10 PM
Registered User
Quote:
Originally Posted by ridgerunr
Can you elaborate? I've tested this technique extensively...

As the throttle stick is moved from the center to the top/fwd limit, the throttle channel output value should linearly move from the chosen center point to +100. If the S1 pot is fully clockwise (S1==GV1=+100), then the output value remains constant at +100 throughout the upper range of stick travel. A similar effect happens when S1 is at its minimum value (-100).

Once correctly setup, as S1 is varied from 0 to +50 to -50 and back to 0, the effective throttle channel output curve should vary like so :
I think you forgot to scale S1 to limit it to -50,+50 in the above settings, maybe?

EDIT: Yeah adding an INPUT S1 weight 50 and using that to adjust GV1 seems to improve things.
Last edited by pressalltheknobs; Nov 28, 2018 at 01:16 PM.
Nov 28, 2018, 01:12 PM
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Thread OP
I see no place to scale the rotation of the S1 knob.
Nov 28, 2018, 01:20 PM
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Quote:
Originally Posted by esl1885
I see no place to scale the rotation of the S1 knob.
Create an INPUT
Set the Source to S1
Adjust the weight and offset to get the range you want.
Then use the INPUT instead of S1

100 weight 0 offset gets -100 <-> +100

50 : 50 gets 0 <-> 100

etc.

In this case I think we want 50 weight 0 offset
Nov 28, 2018, 01:34 PM
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Thread OP
Could you explain a little more fully what I do with this new input. Please remember that I am new to this radio.
Nov 28, 2018, 01:39 PM
Regexistentialist
ridgerunr's Avatar
Quote:
Originally Posted by esl1885
I see no place to scale the rotation of the S1 knob.
On the MIXER page edit the mix we added (the one using iThrM as SOURCE) and change its WEIGHT from 100 to, say, 50% (or 25% or whatever value you like).
Nov 28, 2018, 01:44 PM
Regexistentialist
ridgerunr's Avatar
Quote:
Originally Posted by pressalltheknobs
Create an INPUT
Set the Source to S1
Adjust the weight and offset to get the range you want.
Then use the INPUT instead of S1

100 weight 0 offset gets -100 <-> +100

50 : 50 gets 0 <-> 100

etc.

In this case I think we want 50 weight 0 offset
Not necessary!
Quote:
Originally Posted by pressalltheknobs
I think you forgot to scale S1 to limit it to -50,+50 in the above settings, maybe?

EDIT: Yeah adding an INPUT S1 weight 50 and using that to adjust GV1 seems to improve things.
The easiest way to scale the effect of S1 is to simply change the WEIGHT of the added MIX from 100% to some lower value. No need to add/change any INPUTs.


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