Understanding mixer offset

ersky9xr is the port of the er9x firmware to the 9XRPRO radio.
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rsilk49
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Joined: Wed Oct 26, 2016 10:33 am
Country: United Kingdom

Understanding mixer offset

Post by rsilk49 » Sun Jul 12, 2020 12:37 pm

I want to add a small amount of up elevator on launch using the ELE switch.

This mix produces a result by lowering the pwm from 1500 (mid point) except the max pwm is much lower than the required 2000.

CH2 100 Ele
+ -30 sELE Ofst -30

I had to decrease both the weight AND Offset otherwise the mid position was not at 1500 when the switch was off.
Is there a better way to achieve the same result, or should I control this in iNav?
S500 + Pixhawk 1 clone + Mauch PM + C&T Telemetry adapter + 9XR-Pro (Taranis gimbals)/XJT/X8R


rsilk49
Posts: 137
Joined: Wed Oct 26, 2016 10:33 am
Country: United Kingdom

Re: Understanding mixer offset

Post by rsilk49 » Sun Jul 12, 2020 4:43 pm

Second attempt:

CH2 100 Ele
+ -30 HALF
Sw ELE, Ofst 0

This seems to work better. Only minor issue is the max down elevator PWM is less than 2000 (1850).

I also restricted it to work only with the flight MODES I might use for launching.
S500 + Pixhawk 1 clone + Mauch PM + C&T Telemetry adapter + 9XR-Pro (Taranis gimbals)/XJT/X8R

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MikeB
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Re: Understanding mixer offset

Post by MikeB » Sun Jul 12, 2020 7:36 pm

This works:
CH2 +100% Ele
R +130% Ele Switch(ELE) Offset(-30%) Curve(x>0) [Replace mix]
+ 70% Ele Switch(ELE) Curve(x<0)

With ELE off, you have normal +/- 100% from the stick.
With ELE on, you have an offset of -30%. In one direction the stick then gives 130% to go from -30 to +100. In the other direction the stick gives 70% to go from -30 to -100.

If you use sELE as the source, then the output (2-position switch) is either -100% or +100%, which is why you needed to change the weight as well.

I've also got a couple of ideas where you could use a pot to set the offset amount!

Mike
erskyTx/er9x developer
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jhsa
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Re: Understanding mixer offset

Post by jhsa » Mon Jul 13, 2020 10:15 am

Mike, can't it be done using a GVAR?

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MikeB
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Re: Understanding mixer offset

Post by MikeB » Mon Jul 13, 2020 11:04 am

Probably not with a single GVAR that both moves the offset AND changes the throw to get to 100% in the opposite direction to the offset and only 100% in the same direction.

Mike
erskyTx/er9x developer
The difficult we do immediately,
The impossible takes a little longer!


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