burning wires in COMPASS_MOT calibration !

Hi,

during the COMPASS_MOT calibration I burned the wires with the DF13 plugs from the PM to the Pixhawk.

I'm lost because it is the second time this happened with two different FC on the copter.

I'm using 6S Lipo and a PM that reads DC in 2S - 7S - 5.4V, 3A

It looks (pic) the two ground wires smoked most.

Please- I could use a hint on whats my error is. The copter formerly flies, it is a rebuild.

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Permalink Reply by Mossbackfarm on July 22, 2016 at 11:37am

Many power modules don't support 6S...is it an attopilot, or (maybe) the HK module?

Permalink Reply by Andre K. on July 22, 2016 at 3:30pm
You have a huge gnd resistance causing village drop between PM and at least one ESC.
Then the negative is traveling thru PM and ESC wire.

Fix the poor gnd connection, and\or remove ground loop by disconnecting pwm Ground and +5v
Permalink Reply by Andre K. on July 22, 2016 at 3:31pm
Village=voltage (the crappy mobile version does not allow edit)
Permalink Reply by Bernardo on July 23, 2016 at 1:49am

It is the PM that is delivered with the Pixhawk or the CUAV FC.

So they're too weak for 6S.

@Andre = I don't understand the ESC thing. I have (hexacopter) ESC with two wires (gnd and signal). How that could fry the ground wires between the PM and the DF13 power plug to the Pixhawk?

Permalink Reply by Bernardo on July 23, 2016 at 1:49am



Mossbackfarm said:

Many power modules don't support 6S...is it an attopilot, or (maybe) the HK module?

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Permalink Reply by Bernardo on July 23, 2016 at 1:52am



Bernardo said:Can I make a derivation and feed one of the the + and - over a 5V BEC (2S - 8S)??



Mossbackfarm said:

Many power modules don't support 6S...is it an attopilot, or (maybe) the HK module?

Permalink Reply by Bernardo on July 25, 2016 at 1:31am

ok, found the cause of the problem:

the hint with the "poor ground connection" is right, It was even worse. Due to a crash into an apple tree one or more motors continued spinning for a while (perhaps  RTL).

That burned the main conductor track on the PDB.! It acted like a fuse. (See pic)

So ALL the current flows over the two 26AWG wires between the PM and the power connector to the Pixhawk. wow!

I found it because after Andre mentioned the ground thing I test all the ground wiring with a multimeter und suddenly found no continuity from the negative Lipo plug (in) to the negative connector of a motor at the end of the arm. :o

So I opened the shell of the PDB an saw the burned track!

Now solved, ready to take off again.  Thank you very much for writing Andre and Mossbackfarm !!! :)

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Permalink Reply by Ravi on July 25, 2016 at 6:36pm

remove the Vcc and GND wire form the compass JST connector. looks like your Vcc and GND wires are reversed on compass. I assume that you are using a Compass amd GPS combo.

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