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Old May 22, 2015, 03:32 AM
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q {bld(); fly(); brk(); q();}
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Cleanflight reminder - Set fail safe on your Receiver AND flight controller

I learned a valuable lesson today. On my 250mm quad, I only had fail safe setup on my D4R-II receiver (set to cut throttle) since I was planning on doing the flight controller (clean flight) after I got basic flight working. I never did. I've always relied on my receiver fail safe, so I wasn't too concerned.

After a crash today I blew off some dirt, replaced 2 props, did a hand thrust test of the quad, and took off again in FPV. Little did I know the crash almost completely severed my FC connection to my receiver. About 10 seconds into the flight I started to roll up, and lost control (the connection finally severed), rendering the aircraft out of control with my last inputs being present. I was extremely lucky in that I was slowly pitching up at the time, so I slowly saw the sky, then the ground. Once it crashed the motors remained spinning until I skillfully disconnected the battery while grabbing and flipping over the quad with the motors spinning full speed.

If I was in angle mode or flying directly forward|up, I cringe at the thought of what might have happened.

Lesson learned. Hopefully for you too.

Quote:
feature failsafe
set failsafe_delay = 10
set failsafe_throttle = 1000
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Last edited by The Recursion; May 22, 2015 at 03:47 AM.
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Old May 22, 2015, 04:13 AM
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The Ground is the Limit
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Good advice. Recent user of Naze32 and Cleanflight.

Remembering to set failsafe on Flight Controller. CHECK
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Old May 22, 2015, 08:11 AM
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Yep, I keep posting that reminder and this is the exact reason to Always enable the FS in the FC.
If the RX to FC disconnects it can be bye, bye copter.

Good your copter crashed instead of flying away.
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Old May 22, 2015, 09:36 AM
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As a new flier, this is very helpful advice, thank you.

Time for the "new guy" question.
I see a few potential problem areas:
1. TX stops transmitting/working (TX battery dies, for example)
2. RX loses it's lock with TX (craft flies too far away, for example) or
3. RX stops sending TX input to the FC (RX breaks for whatever reason)
(any others?)

It seems to me that setting the failsafe in CleanFlight (or any FC) would help with #3 only (RX stops sending signals to FC), right?
In what scenario does the TX failsafe come in? And is there any protection against scenario #2?
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Old May 22, 2015, 10:25 AM
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For #2 to activate the FC's FS you must ensure the RX outputs NO PULSEs (or pulses that are outside the FS pulse threshold limits) on loss of the TX signal.
You must refer to your Radio RX's manual to learn how to set it up to do this. and then TEST to ensure to actually works as you expect.

#4- The power to the RX drops out.
#5- A wire or wires between the RX and FC break or disconnect.
For these the FC must have FS enabled.

If the FS is not enabled in the FC and the RX is disconnected/powered off, then the FC HOLDs the last good values from the RX. If this is full throttle then it holds full throttle until the battery dies even it it crashes or hits something/someone.
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Old May 22, 2015, 10:42 AM
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My method is that the Receiver should handle the fail safe if the transmitter loses connection. With the D4R-II you put the sticks/switches into the spots you want them (in this case, zero throttle and centred), then push the FS button to set. Others may differ but the concept should be the same. You can test this by turning off the receiver with the motors spinning (without props). This was all I had setup, and would really be 99% of the situations you'll likely run into (1-2).

For the cleanflight configuration, the full details including testing can be found here: https://github.com/cleanflight/clean...cs/Failsafe.md

Basically the concept is that if pulses are not sent from the receiver to the flight controller, it'll trigger fail safe. In the configuration I posted above if the FC doesn't see pulses for a second it'll shut the motors off.
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