Thread: Mini-HowTo VTOL-Trainer Build Thread
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Old Feb 05, 2013, 09:15 PM
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United States, CA, Sunnyvale
Joined Dec 2006
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I rewired the plane to have the KK2 drive the servo's, it didn't work, and now I have put it back to where it was.

It turns out that the KK2 board has a fatal flaw when it comes to driving servo's on any aircraft that might glide. When you go to full idle the servo's go dead. They still have power, but no PWM input. I can understand why and ESC should go dead, and I can understand why the servo's might go dead when the board is not armed, but to have them go dead at full idle is just odd.

Now that I think about it, I better be careful about applying full left rudder when gliding as well. Likewise, gliding for more than 30 seconds could also be a problem. Fortunately, none of these scenarios has ever come up, and at least with this plane they probably never will. Full right rudder while gliding might be an interesting maneuver, though it is unlikely that I would have time to pull it off if I needed to.

I am assuming that everyone here knows that full right rudder at full idle arms the motors, and full left ruddder at idle disarms the motors. Full idle for more than about 30 seconds also disarms the motors, but at least that is an option you can select in the menu. I rather like it as a safety feature actually.

I also noted that even at the maximum value for the respective aileron, elevator, and rudder mix, the servo's only traveled about 2/3 as far as they do with the straight output from the TX. I would not consider that to be a fatal flaw necessarily, but a fairly bad one.

Overall I have been very positively impressed by the KK2. It has done an amazingly good job of what I needed, especially considering that it was never intended for this application. It is, however, not a universal flight controller. It doesn't seem to handle servo's very well.

Fortunately, I still have an entirely acceptable solution. I had just hoped to make it a tad better.
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