I have an X8 with Tmotor U8's being controlled by a pixhawk. I originally had tmotor 45A SimonK ESCs on, but the U8's apparently don't like SimonK firmware. I had the copter off the ground with this setup, but decided to switch out the ESCs with Turnigy KForce 70A-HV ESCs for compatibility with the U8s and so I could power the copter with an 8S battery instead of a 6S.

After hooking up the new ESCs, I can't get them to do anything. They won't calibrate, whether I do it all at once or from channel 3 on my receiver. The Pixhawk will arm, but the motors won't spin.

I have the throttle channel on my Futaba 14SG reversed and have tried moving the end points up and down. The motors just beep about once a second.

I'm really at a loss on this one and am wondering if I'll be buying a DJI flight controller this weekend. I'd rather not, but it's starting to look like a compatibility issue with the Pixhawk. Any input would be appreciated.


Posted this on RCGroups too, just trying to get the most response possible.

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  • Thanks for the reply Para. I forgot to add that I tried to operate the esc and motor directly from the receiver again after plugging back in the 5V red wire and the esc calibrated and the motor operated perfectly. After returning the connection to the pixhawk, I still couldn't get it to calibrate or spin.

  • Matt.

    If your ESCs won't calibrate off your receiver throttle channel, then the problem lies not with the Pixhawk. And buying a DJI FC won't solve it.

    I have no experience with the 70AHV, but I've played alot with K-Force 40As and they're rock-solid ESCs.

    I have encountered one ESC - the brand and model eludes my memory now - that had an interesting particularity. It was a HV OPTO unit, where OPTO not only meant it didn't have an onboard BEC, but it had an opto isolator on the signal wire which would only work if one would supply it with +5V on the red wire.

    Good luck,


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