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OpenTX - Application Note 20

Altitude Limiter Using a Vario

 

Create an altitude limiter for electric powered gliders which re-enables power at a lower altitude.

 

(This application was contributed by Danny)

 

The limiter cuts the motor off when the glider reaches the target altitude and enables the motor again when the altitude drops below a lower preset altitude. This enables multiple ascents to the target altitude without having to land.

This limiter simulates some of the features of altitude limiters used for altitude limited electric soaring (ALES) competition. (The 30 second motor run limit is not implemented here.) The target altitude and resumption altitude may be set as required but this example uses 100m and 15m respectively.

Switch SB↑ turns altitude limiting OFF.

Switch SB- and SB↓ turn altitude limiting ON.

 

Logical Switch

Number

 

 

Function

 

 

V1

 

 

V2

 

 

Switch

 

 

Duration

 

 

Delay

LS11

a>x

Alt

100

---

0.0

0.0

LS12

a<x

Alt

15

---

0.0

0.0

LS13

OR

L12

!SB↑

---

0.0

0.0

LS14

OR

L11

L14

!L13

0.0

0.0

 

The ladder diagrams that represent these lines are as follows.

 

 

 

L11 is ON when the altitude > 100m.

 

 

 

 

L12 is ON when the altitude < 15m

 

 

 

 

When L13 is ON, the throttle is enabled..

If the altitude < 15m or switch SB is up, the throttle is enabled.

 

 

 

 

L14 latches on to disable the throttle above 100m.

L14 is unlatched by L13, disabling altitude limiting.

 

L14 is now used to disable the throttle.

Throttle Disable without Sticky Throttle Option.

Add the following line as the last line in the Mixer screen throttle channel.

 

Channel Number

 

Weight

 

Source

 

Curve

 

Trim

 

Switch

Delay /

Slow

Mix Name

 

 

:=  (replace)

-100

MAX

 

 

L14

 

Alt Lim

Throttle Disable with Sticky Throttle Option

Add the following line as the last line in the Mixer screen supplementary ‘Sticky’ channel.

 

Channel Number

 

Weight

 

Source

 

Curve

 

Trim

 

Switch

Delay /

Slow

Mix Name

 

 

:=  (replace)

-100

MAX

 

 

!L14

 

Alt Lim

 

Refer to Application Note 3 for further details.

Audio Files

Create the following audio files and transfer them to the [SOUNDS]/[en] folder of the SD card

 

Announcement

File name

‘Altitude Limiting On’

altlimon.wav

‘Altitude Limiting Off

altlimof.wav

 

Create the following two special function lines. In this example, SF8 and SF9 are used.

 

Function Number

Source

Function

Parameter 1

Parameter 2

Check Box

SF8

SB↑

Play Track

altlimof

 

1x

SF9

!SB↑

Play Track

altlinon

 

1x

Confirm It Works

With switch SB up (altitude limiting OFF), check that switch SF enables and disables the throttle as described in Application Note 9.

With switch SB down (altitude limiting ON), at ground level, check that the throttle is enabled. Ascend and confirm the throttle is disabled at 100m. Descend below 15m and confirm that the throttle becomes enabled.

Again ascend until the throttle disables at 100m. Before descending below 15m, set switch SB up (turning OFF altitude limiting) and confirm that the throttle is enabled. Confirm that the aircraft can ascend above 100m.

References

Refer to Application Note 9 for information about the Vario.

Refer to Application Note 3 for throttle disabling control and sticky throttle control.

AMA ALES regulations http://www.modelaircraft.org/files/RCE13-2-2Kallevang.pdf

 

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