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Two motors spin at the same time when motortest

Just finished my tarot 680pro with pixhawk onboard.
When everything was finished i did a motortest and discovered that motor A and D started at the same time when I tested motor A. The same thing happened when I tested motor D, motor A also started. I can see that motor D not running smoothly, it’s hacking a bit.
Looked at my wiring and can’t find a thing that’s wrong.
Is it my esc that’s going crazy?!

Thanks for all the help I can get!

Do you find that if you start A that D just kicks over (ie does a turn then stops) but A continues as per the time specified in the motor test? It happens to me to but I’ve never really looked into it as it stops straight away and doesn’t cause any flight issues.

My thinking here is that a PWM pulse is being set to these ESC’s to make them turn and because your ESC’s are not calibrated yet they don’t spin at the same rate. But this is a problem as they should not do that. If you unplug one of the ESCs from the Flight Controller does it still spin? This would indicate some kind of short or cross talk going on.

Mike

[quote=“iseries”]My thinking here is that a PWM pulse is being set to these ESC’s to make them turn and because your ESC’s are not calibrated yet they don’t spin at the same rate. But this is a problem as they should not do that. If you unplug one of the ESCs from the Flight Controller does it still spin? This would indicate some kind of short or cross talk going on.

Mike[/quote]

Hi Mike,

Not in my case, my ESC’s had already been calibrated - used the all at once method. This has happened on 2 of my pixhawks, my APM2.6 it didn’t happen (different ESC’s and Motors too unfortunately). As I say the non selected motor only does one revolution if I’m lucky and then stops, the selected motor follows the time and power setting. One day I’ll turn on full logging (log when disarmed) and see what’s happening. Not a major issue for me, just noticed it was similar to Steffan’s issue.

Staffan, were your ESC’s calibrated?

Chris

Great inputs!
The thing is have calibrated the esc, one at a time but maybe I should try all at once as well.
When I start motor A motor D starts to spin and continue to spin as long as motor A spins. Not with the same speed and like I said before it also hacks a bit, don’t spin smoothly.
The ESCs are Hobbywing and they haven’t been a problem with them before.
Thanks a lot for your help!

[quote=“staffan_w”]Great inputs!
The thing is have calibrated the esc, one at a time but maybe I should try all at once as well.
When I start motor A motor D starts to spin and continue to spin as long as motor A spins. Not with the same speed and like I said before it also hacks a bit, don’t spin smoothly.
The ESCs are Hobbywing and they haven’t been a problem with them before.
Thanks a lot for your help![/quote]

Hi Staffan,

Sounds like a slightly different issue to mine.

More questions:
[] If you change motors to test - does the same thing happen to the same additional motor or another one?
[
] The motors spin smoothly otherwise? The hacking you describe is purely an electrical issue, like it ‘stutters’?

I’d also try the all at once method of calibrating the ESC’s, it may resolve your issue. Having said that I’d be worried that a PWM signal is getting to a motor not being tested.

Can you turn on logging while disarmed and try again and post up the results. It might have some information that leads us to find the issue.

Regards,

Chris

[quote=“cbrk1”][quote=“staffan_w”]Great inputs!
The thing is have calibrated the esc, one at a time but maybe I should try all at once as well.
When I start motor A motor D starts to spin and continue to spin as long as motor A spins. Not with the same speed and like I said before it also hacks a bit, don’t spin smoothly.
The ESCs are Hobbywing and they haven’t been a problem with them before.
Thanks a lot for your help![/quote]

Hi Staffan,

Sounds like a slightly different issue to mine.

More questions:
[] If you change motors to test - does the same thing happen to the same additional motor or another one?
[
] The motors spin smoothly otherwise? The hacking you describe is purely an electrical issue, like it ‘stutters’?

I’d also try the all at once method of calibrating the ESC’s, it may resolve your issue. Having said that I’d be worried that a PWM signal is getting to a motor not being tested.

Can you turn on logging while disarmed and try again and post up the results. It might have some information that leads us to find the issue.

Regards,

Chris[/quote]

The only motors that spin at the same time are motor A and D. The other motors behave normal when doing the motor test.
I’m away at the moment but tomorrow I’ll try to do another test and make a log file and post it here.

Regards,
Staffan

Has anyone solved this problem? When I do motortest 3 & 6 spins together whether I test 3 or 6. Other motors testing as expected.

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