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Bench Test: Motors don't slow down when reducing throttle
#1
So I recently did some rewiring of my receiver on the bumblebee (X4RSB to Omnibus F4 Clone). I had a handfull of troubles with it and ultimately I think I placed it in a spot where something was interfering or shorting... I needed to put the reciever away from the FC basically and problem solved. 

Problem is, while testing on the bench spinning up the motors to make sure that I had fixed the issue (failsafe was kicking in before) I noticed that sometimes the motors didn't slow back down when throttle was reduced until I disarmed... 

Now... my quad always has airmode enabled when its armed... so I don't exactly expect the thing to know how to behave without the props on.. but this behavior makes me concerned about flying it without checking with my fine friends Smile

Is this just my quad freaking out to air mode or should I figure out the problem before putting it back in the air? 

I am about to go on a trip and I'd like to bring the bumblebee along with me but if it's not going to fly I'd rather bring the diatone as a backup quad.

Edit: forgot to note. Receivers tab shows throttle reducing correctly
carl.vegas
Current Quads: Operational: Diatone GT2 200 In need of repair: Bumble Bee, tehStein,  Slightly modified Vortex 250 
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#2
The best way to test if the 5" craft behaves properly in the air I found is to mount... 3" props on it and arm under a tree, rooof or whatever will make it fail miserably and crash Smile. Even if it starts running away it won't do major damage... Hopefully Smile
Find me on Youtube and Instagram. I currently fly: DRC Aura, NOX5R, Minimalist 112 and drive a scrap RC car
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#3
that would be fun to see what happens... but I don't have any 3 inch props...

Also I do know at a minimum that if I start of have a flyaway I can just disarm (which would probably be just as damaging as a tree impact above)
carl.vegas
Current Quads: Operational: Diatone GT2 200 In need of repair: Bumble Bee, tehStein,  Slightly modified Vortex 250 
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#4
Update and additional information.

So something I didn't consider adding but might be relevant. One of the behaviors that seem to happen when I lose signal is the motors beep.

I put some props on and took it to a small patch of grass to do some LOS testing. I figured if it flies away I can just kill the arm switch hopefully.

For the most part it flew OK except it dropped out of the sky again... (with the beeps mentioned above at least one of the two times that it did it)... When it drops it seems to be falling back and to the left (motor 3 drops first).

I came back and looked at the blackbox logs... I confirmed that the FC recognizes throttle as low with motor #2 at full thrust (see screenshot)
[Image: YRLGo15l.png]

Is it possible that I have a FC or ESC issue here? Originally I thought it was a receiver probem which still might be the case. I just modified the X4RSB, depinning it which could have led to some sort of damage or shorts because I was a little rough with it a couple of times... but I think it might be more than just the reciever.
carl.vegas
Current Quads: Operational: Diatone GT2 200 In need of repair: Bumble Bee, tehStein,  Slightly modified Vortex 250 
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#5
Interesting,

Without Blheli_32 our ESCs are not returning any info to our FC, so I would GUESS that the problem would be in the FC? Unless a bad ESC could be asking the FC for more power somehow...
Flying: Talon 6S 6" 2407s 381g no bat, Martian 3, 5" 2205s sooo heavy + gopro session 5 573g AUW, Aurora 5" 2205s 280g no bat, Druckbaer 3" 1404s 172g AUW 3S 550, BQE Megapixel 2.5" 1107s 139g AUW 3S 550, BabyHawk R 2.5" 164g AUW 3S 550 (stock except microeagle, CRSF, 2.5" arms) and maybe 3 more, for now...
 




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#6
Bench testing by arming the quad with no props will only serve to confuse you. Don't do it!

If you're having problems with the quad falling out of the sky, post the entire black box log.
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#7
(16-Oct-2017, 08:00 AM)unseen Wrote: Bench testing by arming the quad with no props will only serve to confuse you. Don't do it!

If you're having problems with the quad falling out of the sky, post the entire black box log.

I can do that but I'll have to get a fresh log and I am out of town for two weeks (and didn't bring that quad because of its problems). I can try getting a log when I get back.
carl.vegas
Current Quads: Operational: Diatone GT2 200 In need of repair: Bumble Bee, tehStein,  Slightly modified Vortex 250 
[-] The following 1 user Likes Carl.Vegas's post:
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#8
(15-Oct-2017, 06:32 PM)McDee Wrote: Interesting,

Without Blheli_32 our ESCs are not returning any info to our FC, so I would GUESS that the problem would be in the FC? Unless a bad ESC could be asking the FC for more power somehow...

my thought was possible issues with the ESC failing and needing to re-initialize and that somehow freaking out the FC but this is a good point. although the FC should at least know if the circuit for the signal is complete right?  Thinking definitely have to learn a few more things on that one either way.
carl.vegas
Current Quads: Operational: Diatone GT2 200 In need of repair: Bumble Bee, tehStein,  Slightly modified Vortex 250 
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#9
The ESC does not ask the flight controller for power!

The ESC is told to run the motor at a level between zero and full power by the flight controller. It draws power from the battery directly.

If an ESC makes the startup beeps, it has re-initialised. The only things that would cause this are a momentary disconnection from power or the power to the ESC dropping under 3.3V.

The flight controller sends data to the ESC. Unless you are using a BLHeli32 ESC with telemetry connected, the flight controller has absolutely no idea if the ESC is connected or not.

The only time there is a two way conversation between the ESC and the flight controller is when the flight controller is acting as a passthrough for ESC programming or flashing. In normal flight, the ESC is a dumb device that only listens.

My suspicion is that you have a bad power connection as this is the only thing that would cause the ESCs to re-initialise. Without the log, this is only a suspicion.

On a hunch, I'll update my guess to say that your XT60 connector is loose.
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#10
(16-Oct-2017, 08:29 PM)unseen Wrote: The ESC does not ask the flight controller for power!

The ESC is told to run the motor at a level between zero and full power by the flight controller. It draws power from the battery directly.

If an ESC makes the startup beeps, it has re-initialised. The only things that would cause this are a momentary disconnection from power or the power to the ESC dropping under 3.3V.

The flight controller sends data to the ESC. Unless you are using a BLHeli32 ESC with telemetry connected, the flight controller has absolutely no idea if the ESC is connected or not.

The only time there is a two way conversation between the ESC and the flight controller is when the flight controller is acting as a passthrough for ESC programming or flashing. In normal flight, the ESC is a dumb device that only listens.

My suspicion is that you have a bad power connection as this is the only thing that would cause the ESCs to re-initialise. Without the log, this is only a suspicion.

On a hunch, I'll update my guess to say that your XT60 connector is loose.
 
So I have a few thoughts between now and getting the blackbox log... 

First on ESC power. While the main power is fet outside of the FC and really has nothing to do with connections to the FC even in an all-in-one PDB/FC combo... there is still a circuit sending the signal from the FC to the ESC. My thought is if this low-amperage signal with the motor protocol was broken that the FC could detect that it has nothing to send a signal to. The idea being these FCs have enough computing power to run windows 95 on them so maybe they can tell when a signal circuit is complete or not. Based on the fact that this isn't something you first jumped to when I mentioned the idea I am going to guess that it doesn't keep track of that circuit to make sure that it's complete. 

Next no telemetry on this quad... it was my first full build... I did bare bones so none of the features. 

My suspicion is the same that it might be a power connection, however not a power connection back at the PDB but at the motor that is having the problem. If it was the XT60 that was an issue I wouldn't continue to get blackbox log after the event because there wouldn't be power to the FC to record it I would think. 

I did just recently solder a new XT60 pigtail onto the FC and it's very secure. The connector is tight on the new pigtail

(oh also, BLHELI_S not 32)
carl.vegas
Current Quads: Operational: Diatone GT2 200 In need of repair: Bumble Bee, tehStein,  Slightly modified Vortex 250 
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#11
The output from the flight controller to the ESC is a general purpose IO pin on the flight controller's MCU that connects to a similar general purpose IO pin on the ESC's MCU. The GPIO pin has no way of knowing if there's something listening, it just outputs a logic level signal and as it's just a single wire with no response back, it can't know if there's something on the other end of the wire.

It's not about the soft(firm)ware, it's about the electrical nature of the connection. There are invariably pull up resistors on the wire and therefore there's no way to detect if there is a load on the wire. The circuitry that would be needed to detect that condition is not part of the MCU design either.
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