[CRITICAL] MultiWii jam condition

Post Reply
artis
Posts: 21
Joined: Sun Jul 20, 2014 10:41 pm

[CRITICAL] MultiWii jam condition

Post by artis »

Hello everyone. Today I lost my second quad under same circumstances. Random disarm during flight and crash on a tree with 0 throttle.

Luckily most of the stuff survived. After a few hours of testing while connected to MultiwiiConf I discovered (horrified if I may) that there is a certain condition when this happens.

While armed and on 30% throttle I started twisting cables to see if there is any loose connection or anything like that. I got to the receiver when I shaked it I noticed the red status led on it turned off (the quad went into failsafe).
Still that doesnt explain the crash because my failsafe is tunned to land it pretty softly (tried that multiple times). I shaked it again and the red light came back (the power cable was internally damaged, causing loss of power).
The moment the receiver's light turned on all motors stopped at the same time. (exactly what happened 2 hours earlier in flight). Repeated the test several times. When I unplug the throttle cable (which also has 2 power cables) the quad goes into failsafe.
When I plug it back in the motors stop working immediately. Happens every single time with no exceptions. The MultiWii conf shows something interesting. The MultiWii board is not exactly rebooted as it seems but rather seems to be jammed or something.
All readings (gyro, acc, mag, baro, gps) stop immediately, but the connection to the PC remains. The cycle time becomes roughly twice as high (~7 000) and it starts spamming I2C errors like no tomorrow (overflows the integer in about 1-2 secs).

Board: MultiWii SE 2.5
ESC: Q-Brain 25A (if matters)
Battery: 3S LiPo (not sure that matters)

Be ware of loose power connection between the receiver and the MultiWii - it will be deadly. At least with that particular board.

Haven't tested with any other board.

I hope this message would save someone's drone from the same faith.

artis
Posts: 21
Joined: Sun Jul 20, 2014 10:41 pm

Re: [CRITICAL] MultiWii jam condition

Post by artis »

Interesting thing that only I find this disturbing...

PatrikE
Posts: 1976
Joined: Tue Apr 12, 2011 6:35 pm
Location: Sweden
Contact:

Re: [CRITICAL] MultiWii jam condition

Post by PatrikE »

Sending power peaks or shortcut the Arduino will with almost 100% guarantee kill the processor.
I guess your FC reboots or get blocked for a while.
Only way to protect against that is to use a separate bec for FC and run the rest from the esc BEC's
And keep the cables under control!

kilby
Posts: 76
Joined: Wed May 28, 2014 10:17 am

Post by kilby »

As Patrick says

As your rx is powered by the throttle connector (usually) almost anything could be happening (including shorting the power taken from the flight controller, which would be a very bad thing for the multiwii)

Problems like that could easily toast rather than crash/reboot the flight controller. The average rx boots in less than a second but if the multiwii is also rebooting or is having issues then you have yourself a crash.

Secondly it depends on what failsafe you have set.

There is rx failsafe where losing radio connectivity will cause the rx to use its failsafe settings.

However this seems to show a complete loss of power to the rx, so the rx can't put out any failsafe values.

However if you are losing your rx entirely then you are depending on the multiwii failsafe value, and to be honest I haven't a clue how to test that while in flight, as I don't know how to disconnect the rx while it's flying?

artis
Posts: 21
Joined: Sun Jul 20, 2014 10:41 pm

Re: [CRITICAL] MultiWii jam condition

Post by artis »

Its not short circuit. When I unplug the throttle cable (which includes the power as well) the quad goes into failsafe as it should. When I plug the throttle/power back in it jams. It is not even rebooting. I examined it on MultiWii Conf. It is not rebooted. Rather the sensors are freezed, the cycle time jumps twice and the I2C errors are all over the place. It will not reboot whatever you do unles you unplug main power and plug it back in. Failsafe is useless in this case as the board/software is jammed and the motors are turned off.

kilby
Posts: 76
Joined: Wed May 28, 2014 10:17 am

Post by kilby »

Nobody say it had shorted (though I gave it as one possibility)

You are disconnecting a load from the FC and then reconnecting that is never a good thing, adding into that any 'bounce' then you have even more potential for problems with the flight controller getting upset.

Easiest thing to do is to power your rx from a BEC

artis
Posts: 21
Joined: Sun Jul 20, 2014 10:41 pm

Re:

Post by artis »

kilby wrote:Easiest thing to do is to power your rx from a BEC


Which is exactly what I was planning to do. Generally I found the problem on my own, I already thought about possible solutions. I just thought this is something not to be expected. At least not something you will think about when you connect a receiver. I just wanted to warn the community as I didn't find any similar topic and potentially save someone from loosing his machine and potentially be dangerous for surrounding people.

Noctaro
Posts: 280
Joined: Thu Sep 08, 2011 11:15 am
Contact:

Re: [CRITICAL] MultiWii jam condition

Post by Noctaro »

Hi!
As far as i know you may also add an additional capacitor to your board. Just solder it to a servolead + and - and plug it into one of the rc ports of your arduino, where normally the BEC from the ESCs is connected. This could be a way to make things safer without an extra BEC. But i agree that best solution will be to add this additional power source. Wanted just to share that hint, if you want to give it a try. By the way, do not connect all ESC BECs to your board if you use these, only one. Depending on the used ESC BECs this may lead to problems because of voltage differecne or similar things i dont exactly know ;)

Hope this never happens to you again. Good luck for your next flights. :)

Greetz
Noc

nechaus
Posts: 21
Joined: Wed May 14, 2014 12:10 am

Re: [CRITICAL] MultiWii jam condition

Post by nechaus »

sounds like it could be your wiring or something..
try run fc from a good known ps

Id be checking voltages of your becs and running though the whole thing with a magnifying glass.
you really need to diagnose this and not guess and only fly it once you know what went wrong.

I will not fly a quadcopter that's of reasonable size unless i know everything is 100%.. then its down to my pilot skills for a failure or the occasional prop blowing apart.

User avatar
treym
Posts: 258
Joined: Sat Jul 21, 2012 12:28 am

Re: [CRITICAL] MultiWii jam condition

Post by treym »

artis wrote:IWhen I unplug the throttle cable (which includes the power as well) the quad goes into failsafe as it should.
When I plug the throttle/power back in it jams.


make sens to me

brewski
Posts: 483
Joined: Tue Apr 29, 2014 12:04 am
Location: Cleveland Qld Australia

Re: [CRITICAL] MultiWii jam condition

Post by brewski »

artis wrote:Hello everyone. Today I lost my second quad under same circumstances. Random disarm during flight and crash on a tree with 0 throttle.

Luckily most of the stuff survived. After a few hours of testing while connected to MultiwiiConf I discovered (horrified if I may) that there is a certain condition when this happens.

While armed and on 30% throttle I started twisting cables to see if there is any loose connection or anything like that. I got to the receiver when I shaked it I noticed the red status led on it turned off (the quad went into failsafe).
Still that doesnt explain the crash because my failsafe is tunned to land it pretty softly (tried that multiple times). I shaked it again and the red light came back (the power cable was internally damaged, causing loss of power).
The moment the receiver's light turned on all motors stopped at the same time. (exactly what happened 2 hours earlier in flight). Repeated the test several times.
When I unplug the throttle cable (which also has 2 power cables) the quad goes into failsafe.
When I plug it back in the motors stop working immediately. Happens every single time with no exceptions. The MultiWii conf shows something interesting. The MultiWii board is not exactly rebooted as it seems but rather seems to be jammed or something.
All readings (gyro, acc, mag, baro, gps) stop immediately, but the connection to the PC remains. The cycle time becomes roughly twice as high (~7 000) and it starts spamming I2C errors like no tomorrow (overflows the integer in about 1-2 secs).

Board: MultiWii SE 2.5
ESC: Q-Brain 25A (if matters)
Battery: 3S LiPo (not sure that matters)

Be ware of loose power connection between the receiver and the MultiWii - it will be deadly. At least with that particular board.

Haven't tested with any other board.

I hope this message would save someone's drone from the same faith.


If the bind or power light goes out when you move or knock the RX then your receiver is faulty. There could be a component shorting or more likely a bad solder joint.
I recently had some crazy intermittent performance issues with my Lemon 8 ch including total motor stop. I traced it to the 3.3V regulator on RX board.
When cold it was putting out approx. 3V but after it warmed up voltage started jumping erratically from 1-3 to 5V. The poor FC just said enough I guess & reset.
Plugging active loads into your FC (or having an intermittent connection or regulator) while it is running is definitely asking for trouble.

waltr
Posts: 733
Joined: Wed Jan 22, 2014 3:21 pm
Location: Near Philadelphia, Pennsyvania, USA

Re: [CRITICAL] MultiWii jam condition

Post by waltr »

There has been reports of MW doing weird stuff if the pulses from the RX go too far below 1000usec.
Hot plugging the RX can produce glitches, very short pulses, which could also be related to the symptoms the OP is seeing.

Post Reply