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Common Problems and Solutions with Mini Quads
#1
We often see the same problem over and over, to save time repeating the same answer, here is a compilation of issues, with cause and solution. Please let me know if there is a common problem you see people ask all the time, so we can add it to the list.

#1 - Motor twitching when not armed

Caused: When your quad is not armed, your FC would still send a signal to the ESC's, i.e. Min_command. Even at 1000 (the default value), it might still trigger the motors to run at extremely low RPM. This signal isn't high enough though (at 1000), so the motors only twitch, but do no spin.

Solution: Lower Min_Command by step of 10 until the motor stop twitching, Min_Command is at 1000 by default, and you would probably end up somewhere around 990-950.


#2 - Why does one of my motors get really really hot?

Solution: Check if your motor screws are too long and touching motor winding.

#3 - My quadcopter is acting odd (vibration, twitch, rpm raising, etc.) when it's armed, but still sitting on a level surface without propellers

Cause: Arming the quad in any mode - rate, level, etc. will engage the PID controller. The PID controller will attempt to stabilize but without propellers the behavior will be unpredictable - exhibiting many of the reported symptoms, most likely twitching, jerking, apparent increasing of throttle.

Diagnose: Check motor direction and order first. Make sure your quad arms and disarms correctly. Test that failsafe is configured (best failsafe is a quick disarm). Put some propellers on the craft (again check orientation) and try hovering in an open and safe area. Chances are the craft will fly fine, if so tuning and fun are next.

Solution: If craft still jerks or twitches, check for obvious mechanical problems - bent shafts or bells, motor mounts, esc solders. Next most likely cause is the gyro - some are very sensitive to vibrations (MPU6500), in these case soft mounting might help, or a better FC altogether. Many retailers sell rubber mounting screws now that are almost direct replacement to the plastic FC mounts. (http://www.getfpv.com/m3-anti-vibration-...-of-6.html) Anything beyond that I would not consider a common problem and best is to provide detailed description and ask for expert help.

* Credit to Jordan Marinov

#4 - My quad flips on take off

Diagnose and Solution:
  • Check if your board is rotated around yaw axis, and if so please set the correct yaw offset in the software
  • Check if the rotation of propellers are correctly
  • Check if the ESC signal leads are connected in the correct motor pins on the flight controller, and you didn't connect them the wrong order
A better FPV'er than LOS'er :) -- My Fleet
[-] The following 3 users Like Oscar's post:
  • Jordan Marinov, BigglesFPV, juha_j
#2
A variation of this one is asked almost daily now around the forums and FB:

"My quadcopter is acting odd (vibration, twitch, rpm raising, etc.) when sitting on a desk, without propellers, armed"

Cause: Arming the quad in any mode - rate, level, etc. will engage the PID controller. The PID controller will attempt to stabilize but without propellers the behavior will be unpredictable - exhibiting many of the reported symptoms, most likely twitching, jerking, apparent increasing of throttle.

Diagnose: Check motor direction and order first. Make sure your quad arms and disarms correctly. Test that failsafe is configured (best failsafe is a quick disarm). Put some propellers on the craft (again check orientation) and try hovering in an open and safe area. Chances are the craft will fly fine, if so tuning and fun are next.

Solution: If craft still jerks or twitches, check for obvious mechanical problems - bent shafts or bells, motor mounts, esc solders. Next most likely cause is the gyro - some are very sensitive to vibrations (MPU6500), in these case soft mounting might help, or a better FC altogether. Many retailers sell rubber mounting screws now that are almost direct replacement to the plastic FC mounts. (http://www.getfpv.com/m3-anti-vibration-...-of-6.html) Anything beyond that I would not consider a common problem and best is to provide detailed description and ask for expert help.
The next build will be perfect! | Fleet and build info | YouTube Channel |
[-] The following 1 user Likes Jordan Marinov's post:
  • Oscar
Reply
#3
Also every variant of Flight controller numbers the motor locations differently, so sometimes the best intentioned "advice" can completely lead you astray because someone's assumed you've got the same FC.

Everyone says "your PIDs are wrong", not one person can explain why they think they're wrong Smile
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