OpenTX - Application Note 03
Throttle Disable with ‘Sticky’ Throttle Option
Use switch SF in the up position to hold the throttle off, down to enable the throttle.
Add audio files to announce when the throttle is disabled and enabled.
To hold the throttle off, the throttle channel output must be held at –100%. This is done in the mixer with a line added to the throttle channel. The audio files are then created, transferred to the SD card and two special functions are created to announce ‘throttle disabled’ and ‘throttle enabled’. A ‘sticky’ throttle feature is an option to prevent the engine running when the throttle is enabled with the throttle stick above zero until the throttle stick is lowered to zero.
Throttle Disable (No Sticky Throttle)
On the Mixer screen, the two lines are as follows.
Pass the IThr signal through to the throttle output CH1 except when switch SF is up, then replace the throttle output CH1 with –100%.
The first throttle line, if it was set up by the model wizard, may look like this.
This first line passes the IThr signal through to CH1.
Add a second line which is configured as follows.
This second line, when switch SF is up, replaces the throttle output CH1 with –100%.
Audio File Set Up
There are no standard audio tracks on the SD card that say ‘Throttle Disabled’ or “Throttle Enabled’ so you have to create them, transfer them from your PC to the SD card and then use a special function to play them.
Create the Audio Tracks.
The audio tracks can be created using a PC that has a microphone and recording / editing software like NCH Wavepad. The audio file must be a wav type file, mono 32000Hz. Make one track for ‘throttle disabled’ named thrdsbld.wav and a second one for ‘throttle enabled’ called threnbld.wav.
Transfer the Audio Tracks to the SD Card
With the radio power off, remove the SD card from the battery compartment of the radio and plug it into the PC. Transfer the wav files to the SD card folder SOUNDS / en. Reinstall the SD card in the radio.
Alternatively, start the radio in BootLoader mode, connect a USB cable from the PC and radio and transfer the files using Windows Explorer (on Windows PCs) or OpenTX Companion.
Create Special Functions That Play The Audio Tracks
Create the following two special function lines. In this example, SF6 and SF7 are used.
Confirm It Works
Display the channel monitor screen.
When switch SF is switched to the up position, the channel should be –100.0, regardless of the throttle stick position.
When switch SF is switched to the down position, the channel value should reflect the throttle stick position.
When switch SF is switched to the up position, audio file ‘thrdsbld.wav’ is played once. (throttle disabled)
When switch SF is switched to the down position, audio file ‘threnbld.wav’ is played once. (throttle enabled)
WARNING If the throttle stick is not at zero when the throttle is enabled, the throttle will suddenly start at the speed set by the throttle stick. To ensure the throttle only starts from zero when enabled, the ‘sticky throttle’ feature is used.
Throttle Disable with Sticky Throttle
(This application was contributed by Danny.)
This feature requires the throttle stick to be at zero before the throttle is enabled after being disabled. If the throttle is enabled with the throttle stick above zero, the throttle will not be enabled until the stick is lowered to zero first.
SF↑ disables the throttle. SF↓ enables the throttle.
Logic switch LS1 is used to detect when the throttle stick is fully lowered (i.e. less than –99).
Channel 8 is used as a supplementary channel to prevent SF↓ enabling the throttle until the throttle stick is fully lowered (i.e. LS1 is TRUE). Channel 8 is toggled between –100 and +100.
The mixer line for channel 8 is as follows.
When channel 8 is +100, the throttle is enabled. When channel 8 is -100, the throttle is disabled.
Logic switch LS2 is used to detect when channel 8 disables the throttle.
When LS2 is OFF, the throttle is enabled. When LS2 is ON, the throttle is disabled.
LS2 is then used to switch on the ‘Dsbl’ line in the throttle channel (CH 1). The throttle mixer line now becomes as follows.
Audio File Set Up
The audio tracks now use logic switch LS2 as a source as follows.
Data Flow Diagram
The Sticky Throttle Data Flow Diagram is here.
Confirm It Works
Display the Channel Monitor screen.
Set switch SF up to disable the throttle. Check that CH8 is +100. Move the throttle stick up and check that CH1 remains at –100. Leave the throttle stick above minimum.
Set switch SF down to enable the throttle. Check that CH8 is still +100 and CH1 is still –100. Move the throttle stick down to minimum. CH8 will change to –100. This indicates the throttle is enabled. Move the throttle stick up and confirm CH1 also increases.
Confirm that track ‘throttle held’ is played when switch SF is switched up.
Confirm that track ‘throttle enabled’ is played when both switch SF is down AND the throttle stick is fully down.