November 4, 2014

Tri-copter fixes

I finally got around to do some of the adjustments I've been planning for such a long time on the tri-copter. I've had numerous issues with this machine like vibrations, video jello, video interference, bad flight characteristics. Those issues was dealt with today. First off, an image before the remake.

The cable mess

I made three major adjustments today (and a handful small ones):

  • Replace the KK board with a CC3D
  • Improved wiring and mounting of the Mobius
  • Replaced a motor shaft

First off the most invasive one, the controller board. I never had any success with the KK board. I know many come a long way with the board and love it because of its price and the LCD display. But not me, and the CC3D has never let me down before. Everything started with ripping out a lot of connectors and removing the KK.

While replacing the flight controller I also installed a power distribution board for the 5V system. I need to source the LEDs, receiver, flight controller and mobius from the 5V BEC and I want to avoid using the flight controller connectors for power distribution.

LV power distribution
Mini power distribution for 5V
I cut all the ESC and servo wires and soldered them directly. Since I sources ground and 5V from the power distribution to the receiver I only needed one wire for the S-BUS to the flight controller. I made a "special cable" for that.

CC3D mounted
Single wire CC3D connection

I made a new "pad" for the mobius to sit on. Place in a better connection with respect to the video cable, I had a lot of trouble keeping it in place before. I used some left over semi rigid foam and stacked a few pieces to build up the platform.

Mobius mounted
Mobius foamy platform

Then I took a look at the bad motor. I had noticed before that there was probably an issue with the motor, mount or prop. Forums had told me that the prop mounts for the NTM Prop drive motors can be of lesser quality. And it was true. Once I spun it up without the propeller on you could clearly see that the shaft/mount was crocked. I replaced it with a new mount (I ordered three extra just in case) and the issue was resolved.

I tested spinning it up and giving it a short flight indoors and everything worked as it should. The CC3D is still on "factory" defaults but it flew anyway, I did not dare take it out of the ground effect as the space was kind of tight.

I had issues with interference in the FPV gear before and I made an LC filter to counter that. It helped somewhat but apparently not completely. I'm unsure if my filter is insufficient or if I need to add another one to the 5V powering the mobius to prevent the mobius from bridging the interference to the transmitter. I caught the interference issue on video, skip to about 50 seconds to see the liftoff and the black lines it comes with.

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