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Motor jittering intermittantly at start up and wont spin

Posted by Adam Rivera on August 25, 2011 at 7:29pm

Has anyone ever experienced a motor not being able to spin up? It just sort of jitters back and forth like its trying to start, but wont spin up. The weird thing is that if I disconnect and reconnect power, the problem goes away. It is only about 1 in 4 times this happens. I am running AXI motors with exceed rc ESCs.

 

Thanks!

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Tags: axi, motor jittering
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Replies

  • Ben Schwehn August 26, 2011 at 10:37am

    Hi, I've had  a similar problem: occasionally motor 2 would not start up properly (jittering only), sometimes the motor 2 esc would reboot randomly (I was lucky that this never happened during flight but only during ground testing).

     

    The problem persisted even after I'd re-soldered all ECS connections and put better and bigger connectors on.

     

    I've just now replaced the ESC in question with a Hobbywing Pentium 30A and so far (litterally just put the soldering iron away and only did a few start up tests) the problems seems to be gone.

     

    I'm thinking about replacing the other ESCs as well, but until then I'm wondering if it's save to fly with a heterogeneous ESC setup? 

    The other 3 ESC are still the jDrones 20A stock ESCs. 

    You guys think it's save to fly for now?

  • specpro30 August 26, 2011 at 8:28am

    I've been having the same problem.  So do most people agree that if the problem is intermittent than it is most likely a bad connection versus an ESC or motor problem?

  • Jeff E August 26, 2011 at 5:15am

    I have AXI motors on one of my frame, and found 2 things that they mentioned causes this

    - Bad ESC

    - poor connection on motor wires, I soldered mine directly to ESC

     

    after I solder I normally would hook it to received and try it alone by doing a throttle exercise..go 0-50% fast ans see if no jerky/jitter/stutter

  • Developer
    Olivier ADLER August 26, 2011 at 4:34am

     

    I did see this if the ESC timing setting is too agressive or start sequence to fast. Try to set the timing setting and start sequence at low or medium (soft or very soft for start sequence) to see if it helps.

     

    Could be a defectuous ESC, bad wire or connector soldering problem. Last, can be a defectuous motor, but AXI have rigourous quality checks so this is less probable except if you did burn out a motor phase perhaps because of bad previous starts.

     

    First check wire and connectors soldering. Then try to swap with another motor and see if you still get the problem. Then you'll know for sure if it is an ESC or a motor problem.

     

     

  • 100KM
    u4eake August 26, 2011 at 3:05am
    Agree with Toby. A motor jittering back and forth, sometimes spinning a turn and then half a turn backwards is typical when only 2 of the 3 motorwires are connected. So either you've burnt out 1 coil, or more likely you have a bad solderjoint or connector in 1 of the motorwires. This last would explain why it only happens sometimes. When you have moved the copter (by reconnecting power) the bad connection has slightly moved and makes contact again.

    Anyway, if the motorwireconnection fails in flight, your copter will flip and crash.
  • Toby Mills August 25, 2011 at 9:45pm

    or you have blown one or more coils in your motor. If it tries to start against one of these coils it will just jitter back and forward. if you give it a little push, it will spark into life.

    This can be cause by overloading your motor with too large a prop or letting the motor get too hot.

    If it does the same thing with a different ESC, replace the motor as its probably only a matter of time before it fails catestrophically.

  • 3D Robotics
    Chris Anderson August 25, 2011 at 8:11pm

    Sounds like a bad ESC. Try swapping in another one.,

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