Hi guys,

I'm new to the hobby and I've a diy drone that i'm working on, using the APM 2.6 on 3.2.1 Firmware.I've calibrated my ESCs,and all the manual calibrations that have to be done (radio,accelerometer,comapss,etc), and am able to arm my quad.

However, whenever i rev the throttle, i only get 3 motors spinning, and am not able to get all 4 motors spinning.Although the "dead" motor does not spin when i rev the throttle, when i increase the yaw and/or pitch on my transmitter, the "dead" motor starts spinning, however, there will be another motor that stops spinning, so that at any one time, i only have 3 motors spinning on my quad.Furthermore, when i pick up my quad (props off) in stabilize mode and tilt it manually, the "dead" motor starts spinning to correct the quad, as i assume it is meant to do.( There will be another motor that shuts down, with only a total of 3 motors spinning at any one time).

I've looked on google for people with only 3 motors spinning and only came across ESC calibration issues , where 3 motors slowly start up together while the 4 one does not. I do not think that this is my problem as i've calibrated my ESCs (all together) , and the 3 working motors spin immediately instead of slowling starting up 1 by 1. I'm not sure if the people with the esc calibration issues on google have the same issue as me where the "dead" motor is able to spin when they apply yaw and/or pitch as they do not make any mention of it.

I would appreciate any help rendered, opinions given to help me get my quad up into the air.

Thanks!

P.S I'm trying to get my logs up but can't seem to figure out how to do it, if someone could kindly direct me to a page with instructions, or tell me how to extract and upload my log giles, and how to analysis it, that would be great!.

EDIT: I uploaded the firmware using the mission planner's wizard, and did all the calibrations, with arming and takeoff attempt in the stabilize flight mode.

Build:

- APM 2.6 with external compass & GPS

- 2800maH Battery,

- 4 EMAX motors

- F450 frame

- Castle Creations 25A ESC Quad pack.

EDIT 2: Uploaded log files, and auto analysis results as follows :-

Log File C:/Program Files (x86)/Mission Planner/logs/QUADROTOR/1/2015-02-21 21-08-11.log
Size (kb) 1541.7314453125
No of lines 22051
Duration -1 day, 20:35:15
Vehicletype ArduCopter
Firmware Version V3.2.1
Firmware Hash 36b405fb
Hardware Type 
Free Mem 0
Skipped Lines 0

Test: Autotune = UNKNOWN - No ATUN log data
Test: Balance/Twist = GOOD - 
Test: Brownout = GOOD - 
Test: Compass = GOOD - mag_field interference within limits (21.90%)

Test: Dupe Log Data = GOOD - 
Test: Empty = FAIL - Empty log? Throttle never above 20%
Test: Event/Failsafe = GOOD - 
Test: GPS = FAIL - Min satellites: 4, Max HDop: 9.82
Test: IMU Mismatch = NA - 
Test: Parameters = GOOD - 
Test: PM = GOOD - 
Test: Pitch/Roll = GOOD - 
Test: Thrust = GOOD - 
Test: VCC = GOOD -

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Have you actually tried to get off the ground yet? While on the ground, unless it's perfectly level, it will attempt to level the quad and can not, since you are still on the ground. This is only an issue if it also happens while in a hover.

HI Sascha,

Thanks for taking the tie to reply,i've tried attaching the props and having it try to take off, but it is unable to do so.Upon arming, when i rev throttle to max, 3 motors start spinning while 1 motor doesn't even twitch at all, and the quad is unable to take off. However, when i apply yaw/pitch/roll, the "dead" motor reacts accordingly, and my quad is able to limp around on the ground.It manages to pitch forward and back, with 2 out of the 4 legs off the ground, but it never manages to clear the ground totally. During the rolling/yawing/pitching, the "dead" motor switch around accordingly( the "dead" motor switches between motors 1 ~ 4,) while rolling/pitching/yawing accordingly.

The quad is working perfectly(the motors react with all TX input) EXCEPT for the fact that i only have 3 motors working at any one time, and one falsely "dead" motor.

EDIT: The throttle is not working fine as i thought, an auto analysis of the log gave me the following,

Test: Autotune = UNKNOWN - No ATUN log data
Test: Balance/Twist = GOOD - 
Test: Brownout = GOOD - 
Test: Compass = GOOD - mag_field interference within limits (21.90%)

Test: Dupe Log Data = GOOD - 
Test: Empty = FAIL - Empty log? Throttle never above 20%
Test: Event/Failsafe = GOOD - 
Test: GPS = FAIL - Min satellites: 4, Max HDop: 9.82
Test: IMU Mismatch = NA - 
Test: Parameters = GOOD - 
Test: PM = GOOD - 
Test: Pitch/Roll = GOOD - 
Test: Thrust = GOOD - 
Test: VCC = GOOD -

I'm getting an error with the throttle not going over 20%?

Attachments:

Hi Kenneth. Perhaps you should try calibrating the motors seperately, using a battery and the receiver, Then that will take one issue out of the equation, if they all work properly when powered and connected to your throttle channel on your receiver...?

Good luck. DP

I have had the same problem.  Two steps to correct were calibrate ESC's carefully.  Second the motor spin on arm has a setting for minimum rotation speed.  If it is too low some motors will spin some will not.  Raise the minimum setting until all motors spin but not enough to lift off.

Check if your THR_MAX value is set to 1000, not 80. There's a bug that sometimes sets it to 80.

I had a similar motor problem and found that there is a parameter called" minimum voltage to keep motors spinning"

I increased this value and found the problem cured.

I do not remember the value I ended up with but just try some different ones.

Let us know how you make out.

I had the same issue for quite a while, and my problem definitely had to do with ESC calibrating. Full throttle at startup puts hobbyking ESCs on programming mode, which caused me some problems. I just skipped ESC calibrating all together and my quad's been flying fine since then. Obviously ESC tuning is important but if you just want to get off the ground, you can probably skip it.

I've did what you said and set the THR_MAX value to 1000, and now my quad is working like a charm; it just flew up in the air like a rocket.

Hi Guys,

I changed the THR_MAX to 1000, instead of the 80 it was on, and it solved my problem with the dead motor. 

Thanks for all your help, your input has been invaluable!

Had the same problem with only 3 motors spinning at the same time. It turned out that the accelerometer calibration was only partly done... Redoing the calib fixed the problem for me.

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