Motor jitter at low throttle.

[nilsen]

Hello Gents,

Has anyone come across an issue like the following before?

I flashed my ESC's with BLHeli so that I could get damped light and one-shot on the standard N-Fet Lumenier ESC's but one of the motors jumps at low throttle unless you very quickly push it, then it spins up ok.

Video:

I left the props on so that it's easy to see the motors spinning.

The ship flies ok but I have no faith in it as I wonder if at any point it will just fall out of the sky

 

[ExperimentalRC]

The same thing happens to me on DYS bl20a ESCs. It has never fallen out of the sky. If it flys OK than I wouldn't be worried.

 

[razor02097]

Hello Gents,

Has anyone come across an issue like the following before?

I flashed my ESC's with BLHeli so that I could get damped light and one-shot on the standard N-Fet Lumenier ESC's but one of the motors jumps at low throttle unless you very quickly push it, then it spins up ok.

Video:
*snip*

I left the props on so that it's easy to see the motors spinning.

The ship flies ok but I have no faith in it as I wonder if at any point it will just fall out of the sky

Yes I have. You need to recalibrate your ESCs.

 

[narcolepticltd]

I'd say recalibrate, but if you're running with motor_stop unchecked (motors spin up when you arm... had the video muted as I'm in the office so can't be sure), you also want to make sure your min_throttle setting is above where the motors actually start to spin up (just above).

 

[nilsen]

Thanks for the recommendations, I'll try a calibration.

Thanks for the suggestion narco, although I think the ESC is somehow a little iffy, I mean, the other 3 are working fine.

Maybe when I reflashed them I somehow didn't seat the heatsink properly and after using 4s it got magionally damaged.

The reason I posted is the strange way that if you blip the throttle it will spin up, but if you slowly raise the throttle it'll just stutter and jerk.

I'll keep you upadted.

 

[razor02097]

My 250 did the exact same thing. It would fly fine but when I first start the left back motor wouldn't start with the others. Also when I was flying and blipped the throttle it would pitch back and to the right. Calibration fixed both issues.

 

[nilsen]

Thanks for the suggestions everyone! I tried the calibration and still the same issue so I replaced the ESC with a spare I had on hand.
Reflashed with BLHeli and exchanged it, now it is perfect.

I will strip back the shrinkwrap from the dodgy one and see if anything stands out, it's odd that it happened but it's ok now.

 

[BanditJacksRC]

did you cut down the motor wires? I did just that, and the enamel coating that is on the wires was not properly sanded or burned off. I soldered it to the ESC and it was doing exactly the same.

I recommend un soldering the escs, trim wires again and give them a GOOD sanding to make sure any enamel coating is gone, then re solder

 

[cranialrectosis]

I'm with BanditJacksRC on this one. I think you have a not-so-hot solder connection between the motor and the ESC.

 

[nilsen]

Thanks Guys,

I didn shortened the motor wires but there was no enamel, also it was working ok until I flew a while.

I have subsequently replaced the ESC with a spare and it's perfect, somthing dodgy must have happened on the last flight, I most probably didn't seat the heatsink properly when I flashed the ESC's and re-heatshrunk them.

Thanks for all of the suggestions.

Cheers

 

[narcolepticltd]

Thanks Guys,

I didn shortened the motor wires but there was no enamel, also it was working ok until I flew a while.

I have subsequently replaced the ESC with a spare and it's perfect, somthing dodgy must have happened on the last flight, I most probably didn't seat the heatsink properly when I flashed the ESC's and re-heatshrunk them.

Thanks for all of the suggestions.

Cheers

The important thing is it's back in the air and working properly who knows, maybe a solder joint was fractured on the old ESC to one of the motor wires... I've had that happen once before (just reflowing solder sorted it)

 

[HatfieldCW]

I had a similar issue with my most recent build. I fixed it by calibrating my ESCs to a range of 2000-1050 on my throttle. At 0% there's no jitter, and I moved my idle speed up to accommodate the difference. Works great, since I never use less than 25% throttle unless I'm at 0%.

Seems to me that OneShot is so particular that any variance in signal is seen as a command. Just moving the walls away can give it room to absorb those anomalies.