Taranis Signal Interference With Bluetooth Audio?

[JBWingnut]

I had an unexplained loss of aircraft last week. It was during a pylon race, and after turning a pylon, I completely lost control of the aircraft. It appeared that the controls just went to neutral, but the throttle stayed wide open. Since I had just leveling out after the turn, the airplane was almost in knife-edge with full throttle, and descended smoothly into the ground at that attitude. This is the only time I've ever lost control response with my X9D Plus. The only thing that had changed in the radio configuration, was that I had added a Bluetooth audio transmitter to the back of the case, so that I could hear audio from the transmitter in my Bluetooth earpiece during a race. I had flown about a dozen successful flights on this airplane with my Bluetooth audio setup prior to the incident. Long pre-amble to get to the question: Is it possible that this Bluetooth setup could interfere with the transmitter signal to cause loss of control?

[Kilrah]

It runs on the same frequency so it is possible, but since it is close to the radio's transmitter what would be more likely to be interfered with is the telemetry downlink (you'd have "telemetry lost" messages), not the uplink to the aircraft.

Did the aircraft obey the failsafe settings you configured?

[jhsa]

As far as I understand from his post, he didn't have failsafe programmed. It seems the receiver assumed the last position received. Not a very good idea with a fast IC powered aircraft..

João

EDIT: something just came to my mind. Perhaps a receiver brownout? Itf the receiver battery voltage gets too low, the receiver can just stop responding.. I think it's worth checking, specially if the receiver and servos are powered by a NiCad or NiMh battery pack..

[Kilrah]

That's why I asked about failsafe. If he had set one and it didn't take those positions then the issue is very likely a power problem onboard. If he didn't set one then firstly it's very bad practice, and secondly nobody will ever know the true cause.

[JBWingnut]

Nope. Failsafe was set. The reason I don't think failsafe kicked in is because the power stayed at full throttle. Failsafe would have killed the power. I didn't get a Low Not sure how it could have been a brown-out either. No Low RSSI or Telemetry Lost messages (at least not until the battery seperated from the airplane at the point of the crash). I've been racing for a couple of years with the identical set-up, and never had a problem. Since the only new twist to the configuration in this case was the Bluetooth transmitter, I was wondering if maybe the transmitter happened to hop over to the same frequency as the Bluetooth long enough to get interfered with, especially with the Bluetooth so close to the transmitter antenna.

[JBWingnut]

Forgot to note that this was an EF-1 racer, so it's all-electric. The motor was obviously pulling a lot of amps, but aside from the motor, there's not much else to pull juice from the battery. It was using one of my newer racing batteries that I had checked internal resistance on the evening before with no indication of problems. Good question, though. I haven't checked the battery since the crash. I'll have to pull it and put it on the tester.

[Kilrah]

A cable or component can be failing in your setup, doesn't matter that it's worked for ages. Both Bluetooth and the FrSky system change frequency dozens of times per second, it's almost impossible for it to be the cause of a loss of control. And since your failsafe was set then it would have kicked in after 1 second of signal loss.

[jhsa]

I have Bluetooth modules installed INSIDE all my radios, along side with frsky or multiprotocol modules. never had a loss of control..

If your model is electric than I think the ESC would have stopped the motor if the PWM from the receiver had stopped. That makes me possibly exclude an eventual brownout or cable failure.
Most ESCs have some safety protections and stop the motor if signal from the receiver is lost.
That means, it could be loss of RF link with the failsafe not set, or set incorrectly.. Please check the failsafe is working correctly with the receiver on the bench.
Is your model made of carbon fiber, or has carbon fiber parts?
Also, please range test your setup, with Bluetooth ON and again with Bluetooth OFF.

João

[JBWingnut]

That is the info I was looking for... If anyone else using Bluetooth with their radio had ever had a problem. I'm pretty confident that failsafe is set correctly, but good advice to check that again, and to do a Bluetooth On/Off check. Haven't done that yet. I've been meaning to check to see if RSSI has any fluctuation with Bluetooth on/off, but I've been sulking all week, and haven't set foot in my shop. Just now coming out of my emotional funk...

[jhsa]

You can also log your flights..


João

[Kilrah]

Note that audio bluetooth would transmit a LOT more than the modules that are used for telemetry, difficult to compare.

Would recommend to at least put the audio BT module as far as psossible to the radio's module and antenna.

[jhsa]

Completely forgot that it is an audio module..
Still, a range test with it ON and OFF might help finding the problem.
About interference, I don't know how many models are racing at the same time, but if many, the RF band could become quite crowded. Add Bluetooth and possibly wifi devices, and we could start seeing a potential problem here??
All this needs to be tested..
João

[budavaril]

The possible solution is using R9M 868MHz or 915MHz. Different frequency bands, no interference. Finally can using bluetooth or WiFi without that limits before..(Example controlling remotely my GoPro using by it's own bult in hotspot or using ESP8266 WiFi telemetry on pixhawk or pixracer etc.) I think with this R9M system we got a big opportunity and freedome..
Also I know it's cost us, but now with this £30 bundles I don't believe is unavailable for most of us who spending hundreds of pounds for our hobby anyway and also this added value is definitely worth for a money.
(Not as ~£80-£100 spending for 4 new motors for 0.2sec better LAP time.. but is my point of view of course..)