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Old Sep 28, 2014, 11:41 AM
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One motor sometimes stops for splitsecond

Hi,

I built a wood/GFK quadcopter similar to the RCExplorer Tricopter design. It has the DT-750 motors and Afro 20A ESC's. I now had three flights. I am all in all very happy how well it flys for my first selfbuilt quadcopter, but there is one problem:

The front right motor sometimes stops for a splitsecond during flight and then continues to work. In the first flight it happend one time, in the second one 2 times and in the third flight I had 3 quick stops. The quad always flips about 20 degree to the front right due to the power loss, then the motor spins again and it autolevels again.

Here is a short video from the problem recorded with the onboard camera. (I know that there are heavy vibrations, looks like I have to balance the props again):
Quadcopter Motor Problem (0 min 10 sec)

The FC is a Crius AIO clone with MultiWii 2.3
I read that bad cable connections could cause similar problems, but I let the motor spin and moved every single cable connection randomly arround. The motor did not stop a single time.
At the moment I don't want to fly this thing, I am afraid that it will happen again and that the motor does not run again quick enough.

Does anyone have an idea what could cause this problem? I am very new to this kind of R/C multirotors, so I cannot solve this and I also could not find any further information about this problem.

Thank you for your help, and please forgive me for my bad english.
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Old Sep 28, 2014, 12:59 PM
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Start from the simple stuff, see if you can reproduce it on the ground and do not fly it at that altitude until you solve the issue.


Start by checking the wiring - remove the props and run the motors at low speed (25% or so). If it is a loose connection, you can usually trigger it by playing with the wires. Gently tug and twist to see if the motor does that. Chances are, it could be a bad solder joint.

My next test would be to swap the bad with a good motor and try to reproduce it. If the cutting out happens on the same arm, it is the FC or ESC most likely. If it occurs on the arm with the bad motor, it is the motor.

This should get you started. I am not familiar with that set up but if you can't find a mechanical issue, then make sure you set everything up correctly software wise such as ESC calibration, same setting for all ESCs and so on
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Old Sep 28, 2014, 01:06 PM
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Are you using bullet connectors to the motor or ESCs? If so, bad contact there could not show up until there's a certain amperage flowing through them. Try removing the bullets on that motor and ESC and solder the wires directly together.. if it still happens, get rid of the bullets all around, since the others may fail too, and with worse results.
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Old Sep 28, 2014, 01:28 PM
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Thank you for your helpfull answers!

I already did the first think (wire checking), but yes, there are bullet connenctors (between Lipo and ESC, there is a XT60 plug). The connection between motor and esc is done via this regular soldering and a 'socket'-thing. I think I will re-solder all the connections from the lipo to this ESC and motor. If it still happens I will simply switch front left and front right arms to make sure the FC is working fine.
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Old Sep 28, 2014, 02:33 PM
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If the issue was between the LIPO and the ESC, I'd wager that you would know really quick if that was the problem! It usually takes a second for the ESC to rearm when it looses power and they won't rearm unless of the throttle is at idle.

It almost sounds like there could be a loose wire inside the motor. Just switch two motors to see if the issue is the motor or not.
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Old Oct 01, 2014, 02:07 PM
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Hi,

I now re-soldered the connection between motor and ESC for the front right arm. Then I did a 10min testflight, where everything was fine. Except for one little sound like a high spinning motor for a really short time, maybe it a motor stop again or just a heavy correction. The quadcopter did not made the jerk that he did in the flights before.

I almost thought the problem is solved, but now I made another flight a few hours ago on a field. I had 3 motor failures, 2 of them on the front right, but also one on the back left arm. Maybe both motors are defect, but maybe it it something else.

Has someone an idea what it is?
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Old Oct 01, 2014, 02:48 PM
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How did they fail?
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Old Oct 01, 2014, 04:00 PM
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Just the splitsecond stop. Maybe it is not a real stop, but the quad always rotates quickly over the front-left/back/right axis. In both cases it was the same axis when it happened, one time to the front right, the other time to the back left. The quad always recovers quickly as you can see in the video.
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Old Oct 10, 2014, 09:32 AM
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Hi,

it looks like this is a more or less common problem with the SimonK firmware and high pole count motors like the DT750: http://diydrones.com/forum/topics/si...h-low-kv-motor

Motor and ESC will have difficultys to sync, and this will result in the short interruptions. As someone wrote in the link, this can be solved by changing the motor timing. But at first I will have to learn how to do that and what it does. And I have to replace two props, the quad made some scary ticking noises during flight, so I decieded to decent really fast instead of loosing a motor and falling of the sky. The foldable front left arm folded back and then the quad flipped and the front left and back left props killed each other.

At least I know the problem of the cout outs now.
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Old Oct 10, 2014, 09:53 AM
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They're 12 or 14 poles, that's not exactly high pole count. I read someone saying that he had that issue with afro ESCs and those motors, but the latest simonK fixed it. Aside from that, you can look at the BLHeli firmware.
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Old Oct 10, 2014, 10:01 AM
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Well, as you may have seen, I have no plan about motors, but the problem is exactly the same, and now that I know the problem I find many videos showing the same thing.
In a thread of 2012 the problem was solved by a newer firmware, but shouldn't my 2014 ESC have this new firmware?

Looks like I have to buy a programming cable...
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