X8 Octo Quad with E1200 DJI system

I am using a RCtimer Pixhawk with RCtimer power module (6S compatible) along with a 750mm X8 frame and DJI E1200 standard propulsion system running on a 6S 10,000 multistar pack.

Running 3.3.3 latest firmware.

Futaba 8FG controller with 6303 SBUS receiver.

Using 915mhz telemetry also.

Fairly new to Pixhawk in multirotors but have used them in fixed wing.

The multi's I have used the Pixhawk in did not have DJI motors/esc's.

I went through the wizard and setup all parameters.

Everything checks out OK and initializes fine.

Tested motor directions and they are good. Had a bit of trouble decoding the ABCDEFGH motor test but ended up finding the required information.

Held down the unit to triple check rotation and inputs.

While in stabilize mode with me holding it down so I could test input directions and only raising throttle maybe 10%, the motors rapidly start to increase speed, enough to make me lower throttle not knowing if it is just going to rocket off while I am trying to hold it down. Did not feel safe at all.

Makes me worried that I will have very sensitive throttle control.

Tried taking off in ALT Hold mode and as soon as I get above 50% throttle the 2-5 motors starts to slow down and the whole unit starts to shudder so I cut the throttle.

Log files attached, hoping someone could shed light on what is happening.

2016-08-20 16-21-49.log

2016-08-20 16-21-49.bin

2016-08-20 16-12-05.log

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  • Still running 3.2.1.

    We had a successful mission with the Octa but I was unable to do an AutoTune because it would put 14.25 values in the Roll/Pitch boxes and when I would try to take off the next flight it would oscillate like mad. I had to perform a "reset to default", go through ALL the setup procedures and just fly on those values.

    It actually performed quite well but it would lose about 3 meters altitude when executing a turn in auto mode and it was constantly pitching fore and aft while flying straight lines. We were flying at 9m/s.

    One other thing we ran into was the 724 limit on way points. We had a total flight time of 24 minutes with payload but with the Digicam control in the mix we only really had about 350 waypoints. We were flying a 9 meter spaced grid and trying to cover about 300 acres.

    It required a lot of flights but we did complete the project.

    I am aware of the distance trigger method but we had irregular shaped areas were were treating and the vaccine pellets are expensive so we did not want to drop them unless it was in a required area.

    Next step is to implement fixed wing or traditional helicopter and drop 3 pellets at a time. Payload will be right at 16 pounds and we need flight times of 1 hour.

    With that amount of flight time and needing to control the relay trigger we need a solution for expanding the waypoints.

    Is anyone familiar with code that could be used to store the points on SD card rather that the EEPROM?

  • Well that didn't change anything.

    It does still supply 5.3 to board, just no amp detection obviously.

    I decided to simplify the ship and removed the lower four motors from the equation by unplugging them and removing props. Motors were still attached to the craft.

    Loaded 3.3.3 quad copter firmware, verified motor directions with motor test. I had to swap C and D.

    Same thing happened. Motors would almost stop above half throttle and it would tip back when in Stabilize.

    Beginning to think the FC is bad.

    Loaded rover firmware and then loaded 3.2.1

    Went through wizard, verified settings for basic and extended tuning and found RC Feel Roll/Pitch and Climb Sensitivity were both maxed out full right????

    Did the overhead test and it was fighting me when I would tilt and roll it.

    Took it outside and it popped straight up in stabilize mode. Hovered it for a minute, tested roll pitch and then flew it around a bit. Flew great.

    Not sure if the maxed out settings were the problem all along.

    One thing I never did when Octa-quad configuration is the overhead test, but I verified motor rotation about fifty times.

    I have noticed that even though I loaded new firmware, settings seem to remain.

    What should I be doing different to make sure it is a clean install each time?

  • I am going to solder a jumper on the power module today so power goes straight through and see if that makes a difference. Just need to verify the 5.3vdc will still be supplied by it.
  • Hey Kurt,

    I have built a Hex using E800 setup. I had several such issues and finally I seem to have solved most of them. The maiden however is still left as I am waiting for the 6S battery to arrive. I will post if I have any similar issues.

    I am waiting for others to revert here.


  • Here is the amp and throttle position graph.

    Doesn't look like the amps dropped until I lowered the throttle.

    I wonder if the power module is causing it? is it possible to jumper across it and still have 5.3vdc supplied to Pixhawk?

    3702286134?profile=original3702285939?profile=original I removed the lower 4 motors and loaded quad firmware and tried again. Same results as in no lift off and motors slowing down but the motors were pulsing apparently. It didn't sound like it.

    Attempt as a quad log attached.

    I was in stabilize again and the motors surged rapidly so i switched to alt hold as shown in graph.

    What the heck is causing this?

    2016-08-20 18-28-41.log

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