Can't get ESCs to calibrate - Pixhawk fails pre-arm checks

Hi all,

I looked through the questions already answered, and I can’t find a solution. I have the drone built and have successfully bound the receiver and transmitter. I even updated the Pixhawk firmware successfully with Mission Planner.

My problem is that I unable to calibrate the ESCs and get the motors to respond. I have removed the UBEC lines in three of the motors as instructed in the video. When I plug in the LIPO battery I hear the beeps from the ESCs, and the lights on the Pixhawk come on; however, the big LED right behind the arrow flashes through a lot of colors and then just keeps flashing yellow twice. According to the Ardupilot website, that means ‘Failing pre-arm checks (system refuses to arm)’. Any suggestions on what I might being doing wrong?

It sounds like the ESCs are calibrated and the pre-arm check is failing because there isn’t a GPS lock. What do you see on the Mission Planner HUD? This is a normal issue when doing this indoors. Moving near a window and away from building obstructions might help. Also look at the MP Messages tab.

I took the drone outside well away from buildings and I still get the two flashing yellow lights. Mission Planner tells me “PreArm: 3D Accel calibration needed”. The transmitter is binded with the drone but no matter what, the motors do not respond to the throttle. The transmitter appears to be working fine when I move the gimbels around according to Mission Planner. I will go ahead and complete the 3d Accel calibration, but any suggestions on why no movement from the motors?

The motors won’t engage until you have completed the pre-arm check and pressed the safety switch off. Sounds like you are on the right track by re-calibrating the vehicle. Also, often magnetic anomalies at home might warrant re-calibration of the compass each time you are flying in the field.

Making progress… Completed the 3D Acceleration calibration. Now when I turn on the power up the drone and the R/C controller, and press the safety switch, the Pixhawk main LED turns as flashing blue for few seconds, then it begins flashing green. However, the motors still do not spin up when I increase throttle on the controller.

When it starts flashing green that means you have GPS lock and you then just need to arm the throttle.

Move the left stick to the lower right-hand corner and the motors will engage.

Use all safety precautions and ready to fly.

That worked; however, only two motors (right front, and back left) come on. The motors on the left front and back right do not work.

OK try one more esc calibration. Use the one with Mission Planner. If that doesn’t work then will next need to look at your wiring.

Consider using the MP Motor Test.

That did it. All four motors are now functioning. Only thing I noticed is that even when the throttle is in the lowest position the motors are spinning at a low speed. Is this normal?

Yes it’s normal. Congratulations!

Thank you for all your help and assistance.

I’m having the same issues you had (unable to calibrate ESC, Pixhawk flashing yellow).

How did you manage to calibrate the 3D accelerometers? I cannot see that step in the tutorials (https://dojofordrones.com/courses/how-to-build-a-raspberry-pi-drone/).

thanks!

Start here and then go to each next page. I recommend using the MP esc calibration rather than moving the stick as shown.

https://ardupilot.org/copter/docs/common-accelerometer-calibration.html

Let me know how it goes.

Thanks @jax200 - that’s super helpful. I’ve managed to calibrate the GPS and compass now. The ESCs are still not calibrating, and after a single run of not having the yellow flashing light on the Pixhawk, it’s back to flashing yellow each time again - but it still feels like it is a small step in the right direction, so thank you!

Re getting the ESC to calibrate, it feels like it may be linked with a myriad of other oddities my drone is displaying (at least compared to what I’m seeing in the video tutorials), so I’ll create a new thread in case they all related.

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