Naze32 Mini-Quad suddenly falls out of the sky

[daneel]

Hi all,

I have a curious problem with one of my mini-quads, which I cannot pinpoint. Since the Baseflight/Cleanflight experts live here, I hoped that you could maybe point me into the right direction based on your experience.

The mini quad will fly great for a long time. Often there are whole flight-days without any issues. But then - suddenly - it will fall out of the sky.

Here is a video:
http://youtu.be/6_GMn8O9-Ig

The problem does not come from low voltage. Also the motors and the ESCs are not hot after flying (not even warm). It will happen suddenly, often when hovering (without any special load on motors or ESCs), even when I raced it before. When I pick it up, everything looks great and the quad also has power - I can continue flying without issues.

The quad is a ZMR250 with team legit PDB. It uses Multistar 6A Opto ESCs (http://hobbyking.com/hobbyking/store/__65983__Turnigy_Multistar_6A_V2_ESC_With_BLHeli_and_OPTO_2_3S.html) and Multistar 1704-1900Kv motors (http://hobbyking.com/hobbyking/store/__66414__Turnigy_Multistar_1704_1900Kv_12_Pole_Multi_Rotor_Outrunner_V2.html?strSearch=1704) with 5" Gemfan props. I measured the setup with my ampere meter and the 6A ESCs are more than enough for this setup (as I said above, neither the ESCs nor the motors even get warm). As FC I use a Naze32 (http://hobbyking.com/hobbyking/store/__55819__AfroFlight_Naze32_Acro_AbuseMark_FunFly_Controller.html) which is mounted on dampening screws (https://www.hobbyking.com/hobbyking/store/__40604__M3_Shock_Absorbing_Screws_8Pcs_Bag_.html).

My props are balanced. I tried with both Baseflight and Cleanflight.

Another hint: A friend of mine has another quad, but with the same FC, ESCs and motors and has similar issues.

I'd appreciate any hints / tips what the cause of this could be.

Many thanks for any inputs,
Michael

[Noctaro]

Hi!
Sounds like a brownout.
You may try to add an capacitor to the 5V pins where you also connect + and - of the BEC to your board.
What kind of BEC do you use?


Greetz

[daneel]

Hi Noctaro,

many thanks for your reply. I use the Team Legit PDB Board (http://team-legit.com/product/nucleus-p ... or-zmr250/) which provides a BEC:
"ON board (clean)filtered 5v 1A LM2940 regulator to power 5v FpV hardware with pads at each FPV component locations and FC if using non bec esc’s"

The curious thing is that this happens while hovering (not while racing), so there is no particular load on the system when this happens. And it happens really rarely, maybe 1 out of 5 flights.

All the best,
Michael

[Deet]

sounds like brown out, add the cap as mentioned above

[daneel]

Hi all,

awesome. Many thanks. Will do!

All the best,
Michael

[daneel]

Hi all!

I have only connected the (+) of the BEC to the board. Could this be the reason for my brown outs? I've connected all (-) and (signal) of all ESCs. The receiver is connected through ppm (-)(+)(signal). Should I also connect the (-) of the BEC to the board - can this be the reason for my infrequent brown outs?

Many thanks and all the best,
Michael

[Deet]

yes

[daneel]

Hi all!

Short update:
Connecting the (-) of the BEC did not help - fell out of the sky after about 3-4 lipos. I also tried the capacitor, with the same results.

I also tried an external uBEC and that did not resolve the issue either - again fell out of the sky (this time after about 2 lipos of flying).

This leaves either the ESCs or the FC board itself as a point of failure. I do not think it is the ESCs, since that would probably look different (see my video in my initial post). So I'm starting to suspect the board itself. I will have another board available in about one week to test this.

All the best,
Michael

[scrat]

Maybe ESC lost sync?