We are currently developing a VTOL UAV powered by a gasoline engine and would like to ask for your assistance regarding the ICE parameters.
Our goal is to connect a kill switch, which is linked to the ignition, to the flight controller (FC), so that the FC can control the kill switch ON/OFF. Ultimately, we aim to have the kill switch turn OFF automatically just before landing during autonomous flight.
The issue we are facing is that the kill switch does not turn ON when it is connected to the FC, even though we have set the parameters according to the manual. However, when we connect the kill switch directly to the RC receiver, it does turn ON, so it seems the problem is not with the kill switch itself.
We would sincerely appreciate it if you could take a moment to review the following product and parameter details and provide any guidance you can.
Parameter Information:
ICE_ENABLE: 1
ICE_START_CHAN: 6 (Channel 6 is also used on the transmitter.)
ICE_STARTCHN_MIN: 0
SERVO6_FUNCTION: 56[RCIN6] (Kill switch is connected to the FC’s Servo 6.)
ICE_PWM_IGN_OFF: 1100
ICE_PWM_IGN_ON: 1800
(The reason for modifying ICE_PWM_IGN is that my transmitter’s PWM range is only from 1066 to 1933.)
ICE_PWM_STRT_OFF: 1000
ICE_PWM_STRT_ON: 2000
As you suggested, I upgraded to version 4.6 and tested it, but unfortunately, the ignition kill switch still does not activate.
I have one question I’d like to ask. Should the ignition kill switch be connected to the flight controller (FC), or to the RC receiver?
I’m wondering if the DO_ENGINE_CONTROL mission command would work even when the ignition kill switch is connected to the receiver instead of the FC.
For reference, I’m using the CubePilot Cube Orange FC and a FUTABA T14SG transmitter.
Currently, both the RC receiver and the ignition kill switch are connected to the FC.
Hi everyone,
It’s been quite a while since my last question on this topic, but I finally discovered the root cause and a working solution. I’m posting this so others don’t have to go through the same frustration.
My setup and the problem
Kill switch: RCEXL Opto Gas Kill Engine Switch v2.0
Flight controller: CubePilot OrangeCube
Receiver: Futaba R7308SB
I first tried connecting the RCEXL kill switch directly to the OrangeCube’s output. Unfortunately, there was no response at all—the RCEXL’s status LED stayed OFF regardless of my transmitter switch position.
As a workaround, I powered and controlled the RCEXL from the receiver. That did work, but then the kill switch was manual-only (transmitter-driven). I couldn’t use the FC’s logic or mission-based control to turn it ON/OFF automatically.
The wiring change that solved it
I wondered if the issue was a missing common reference, so I tried splitting the ground wire (“Y” connection):
Power (+5V/red) + Ground (black) to the receiver
Signal (white/yellow) to the FC output, and share the same Ground (black) from the “Y” split to the FC as well
In other words, the RCEXL is powered by the receiver, but the signal comes from the FC—and both devices share the same ground through the Y-split.
Result: it worked perfectly. The FC can now reliably command the RCEXL kill switch, and the status LED reflects the correct state.
How I automate it in missions
Instead of the ICE parameters suggested elsewhere, I use a DO_SET_SERVO mission command inserted just before the landing sequence to toggle the kill switch OFF/ON automatically. This has been reliable in my tests.
I’d like to express my sincere thanks to @LupusTheCanine for earlier guidance. Your pointers helped me think in the right direction.
Out of curiosity, how are you powering the servos? In your full set-up I would expect the servo rail to be powered by the same BEC that powers the servos, unless you are using higher voltage servos.
Hi @LupusTheCanine — long time no see. I’ll share my understanding first; if I’ve misread anything, please let me know and I’ll correct it right away.
Going straight to your question: we’re using higher-voltage servos (they need about 6–7 V or more). As far as I know, the FC only provides 5 V, which isn’t sufficient for these servos, so we power them with a Matek Systems dual-output 4 A BEC (photo below).
OUT-1 is configured to output 7.2 V and feeds the servos, and
OUT-2 provides a fixed 5 V (not adjustable) and powers the gas kill switch.
Side note: I believe this particular BEC model might be discontinued now.
And a follow-up question from my side: does the FC’s servo rail normally provide 5 V to the servos(servo motors), or is it generally expected that an external BEC powers the servos(servo motors)? I haven’t used 5 V servos on this airframe, so I’m not fully sure how that’s typically handled.
On most open-source FCs the servo rail does not generate 5 V for the servos. The PWM1–PWM16 “VCC” pins are simply tied together as a common power bus. You’re expected to power the servos with an external BEC (set to whatever your servos need, e.g., 5–8.4 V).
Connect the BEC’s VCC and GND to any spare PWM header (only those two pins). Because the rail is commoned, this will power all servos on the rail.
Note: The SBUS/RC header on the same row often provides a regulated 5 V for the receiver, but its current is small—it’s not intended to drive servos.
I’m sorry I couldn’t reply earlier. Thank you very much for the great information.
I’m trying to build a small VTOL and asked the question because I wanted to reduce the build cost, but as far as I understand from your answer, it means I definitely need to buy a BEC.
Once again, I would like to express my sincere gratitude for your support.
