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"I had a good bind and all of a sudden the servos stopped working, still green light on receiver."

Landru

Landru

Strong User
Yesterday, on RCG I came across a report of odd behaviour in a QX7 ACCST transmitter:

It all started when i was setting up a new plane, I had a good bind and all of a sudden the sevos stoped working, still green light on reciever. Took the batt out and plugged it in, nothing. tried to rebind without any luck, figured i needed to upgrade something, but no luck yet. Im running out of idees.
Click to expand...

The various measures tried to fix the problem were posted to RCG.

What really grabbed my interest was that I too have encountered several instances when the control link was lost but the receiver failed to enter failsafe. And so have others. The problem has been dubbed No failsafe Lockout or NFL for short.

The NFL problem has been discussed before and investigated at length, all without result. What I wonder now is if the latest problem reported on RCG might be related to NFL. And more importantly, if it might shed some light.
 
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This is always the fun part of these sorts of issues is trying to get them to repeat. What set of conditions might be the trigger for the issue??
 
Yes, that's the big question. The only answer so far is that nobody knows.

@choochoo22 captured one incident very clearly on video. As I recall, he posted the video in the Uni beta testers forum. Like the recent incident reported on RCG, Rick's occurrence simply happened in bench testing one day. But unlike that recently reported incident, Rick's failure was resolved by rebooting the equipment. Rick also lost a model to another suspected incident.

Last year, I ran a continuous bench test for several weeks and managed to record one possible short occurrence. But again, the cause was a complete mystery.

The range of equipment and conditions in suspected incidents is diverse. There's a spreadsheet in the RCG thread linked in my previous post. Mind you, I haven't updated it in a while.

FrSky has offered to investigate -- but only if there's a known means to reproduce the issue. I figure that the green LED staying on and the lack of failsafe might be a big clue for anyone who had the ability, knowledge, and patience to dig through source code. I suppose that limits the field to FrSky employees. @MikeB investigated but was possibly hampered by not having access to source code.

Someone working in the industry also suggested that FrSky would be in a position to discuss the matter with Semtech. By contrast, I suspect a guy 'off the street' such as myself wouldn't get much attention, especially without intimate knowledge of FrSky's implementation. That's all waaaay out of my league anyway.
 
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Landru said:
Yesterday, on RCG I came across a report of odd behaviour in a QX7 ACCST transmitter:



The various measures tried to fix the problem were posted to RCG.

What really grabbed my interest was that I too have encountered several instances when the control link was lost but the receiver failed to enter failsafe. And so have others. The problem has been dubbed No failsafe Lockout or NFL for short.

The NFL problem has been discussed before and investigated at length, all without result. What I wonder now is if the latest problem reported on RCG might be related to NFL. And more importantly, if it might shed some light.
Click to expand...
I had something similar happen when I was fortunately also setting up a plane. I was using an older 5 cell nicad that hadn't been charged in a while but was still about half charged. When i would move a couple of the sticks repeatedly the servos would stop working but green lite still on. Wait a couple seconds and would return to working again. I think the voltage was dropping low and stopping the rcvr from processing the signal through to the servo outputs even though the recever was still bound and accepting the signal. I read somewhere a while ago that even though the FrSky RX8R receivers and maybe others say 3.5-10 volts they don't like it when they get down below about 4.5. I don't know where I read that but it was probably on either RC Universe or RC Groups forums. I have my low rcvr voltage warning set to announce low voltage at 5.4 volts and the Xmitter was saying that always before it happened so I don't know how low it actually dropped when my servos stopped working. I topped off my nicad and the problem no longer happened. It seems that a 700 mah half charged Nicad doesn't have the current output capacity that is needed. I fly with a 2100 mah 20C LiFe battery so I was setting up under poor conditions for a high load. Maybe that is some insight to look at for you.
 
I have been testing some older servos to see what voltage they will reliably run at. Using a variable power supply it is quick to see that often times a "normal" servo will stop working at around 3 to 3.5 volts, but often times the FrSky receivers are still working to below 3 volts.

I think your battery was simply dipping under load to a point that the servos no longer functioned.

The RX8R-Pro does not like lower voltages, we have a warning on our site about this single FrSky receiver that has this issue. I am not aware of any others with this issue.

(I like to use old NiHM packs when setting up a new plane just in case I screw up and over drive a servo. Less current to do damage.)
 
Yesterday, another somewhat similar report popped up on RCG.

In this new report, a fellow ran into trouble with a brand new RX6R. He bound it to his Taranis X9D (ACCST D16v1), confirmed that the receiver drove a servo, then powered it down. When he powered the receiver up again later, he found that the bind had been lost and could not be reestablished, even after reflashing with the appropriate FrSky firmware.

He then flashed the receiver with Uni firmware and bound and tested it successfully. After power cycling the transmitter and receiver, the bind persisted but the receiver again would not drive a servo.

The report starts at post no. 9 in this thread:

Frsky RX6R not binding to open TX - RC Groups

Discussion Frsky RX6R not binding to open TX Radios
www.rcgroups.com www.rcgroups.com

A few of us have suggested possible causes and fixes, all with no success so far.
 
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Did he enter the code for UNI-RX? If UNI is not activated it will bind but will not drive servos.
 
Yep, he did. He got his Uni setup working with servos. Then, after a power cycle of the Tx and Rx, the servos wouldn't respond.

His experience with the same Rx on FrSky firmware was very similar, except in that case, the bind was also lost and could not be restored, even after reflashing.

I've been wracking my brains for any scenario that could cause such behaviour, some sort of inadvertent mistake or misconfiguration, for example. No useful thoughts so far.
 
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