Wizard X220 issue: Spektrum Rx intermittently losing connection with DX6e

Discussion in 'Mini Quads & Racing' started by Moon Dude, Dec 16, 2017.

  1. Moon Dude

    Moon Dude New Member

    Hello! I got a Wizard X220 ARF recently and I've run into a problem with getting it ready to fly, and have looked everywhere on the Internet to find a solution, so I've come here for some advice/help.

    So, I got a Spektrum Quad Race Satellite Receiver to use as my Rx. To connect it to the included SP-F3 Flight Controller, I soldered it to the -,+, and Rx ports of UART3.

    From there, I connected it to Betaflight and set it up. Sharing every setting might be difficult, but one setting that may be pertinent to this issue is that, yes, I did enable UART3 Serial Rx on the Ports tab. If there are other settings that may be pertinent to my problem, let me know. I also correctly bound my receiver to my Spektrum DX6e and also calibrated my ESC's.

    Anyways, here's the problem:
    I turn on the remote, plug in the battery, arm it, get it hovering, and then it drops out of the air for a fraction of a second, hitting the ground (I keep it in a hover less than 20 cm high because I know this will happen), and then it regains power and bounces back into the air. As long as I keep doing this, it keeps happening, and it seems to increase in frequency as I continue to fly. Hopefully this flight video demonstrating my issue will help with diagnosis.

    How do I fix this? Any suggestions? I've looked all over and haven't found anything that has fixed it. I am currently suspecting the receiver is intermittently losing connection, causing the flight controller to go into failsafe mode, but I don't know what would be causing this... Thanks in advance for any help you can give!
    Last edited: Dec 21, 2017
  2. Jackson

    Jackson USA member at large

    That's why the introduction forum is important, you can get all your needed posts there.

    Try reorienting your antennas, keep them away from any CF.
  3. Gyro Doctor

    Gyro Doctor Electronics Tech for over 45 years

    Looks to me like it's just stalling out because you're trying to hover way too close to the ground.
    There are pitfalls to staying that low in a hover like negative "ground effect" conditions where the prop wash is creating a vortex, or "loop"
    and is returning into the top of the props and causing loss of lift (not to be confused with Vortex Ring State although the effect IS similar).
    Hovering over a smooth hard surface (such as that floor) increases the likelihood of such effects more than doing the same thing over something like
    grass, where the airstream becomes more diffused and more of the vortex is dispersed before it can be reintroduced into the prop's airflow.
    When you get a chance take the quad outside over some tall grass and increase the height to about two feet, THEN see if it still does the same thing.
    Note: Translational lift (the increase in lift due to forward motion) helps to offset the negative ground effects (and vortex ring state too) for two
    reasons: the forward motion not only increases the natural lift of the props at the same rpm, but also (since you're moving) the returning vortex doesn't re-enter the inductive flow of the prop. In other words, scooting along forward at the same height, over the same floor, you may find that the quad does not
    intermittently drop back to the ground like it does in your video. ;)
  4. Moon Dude

    Moon Dude New Member

    Thanks for the replies!

    To clear up the comment on 'negative ground effect', here's some footage of me flying it outside:

    Notice when it cuts the throttle and goes into failsafe mode—it seems to happen at random times. Like I haven't found any patterns for when it decides to cut out. As you watch the video, just know that anytime it does flies oddly, that probably means the connection just dropped. One thing I thought was interesting however was that it seemed to fly better today than in the past, which might be because of the slightly warmer weather today...

    So, does anyone have any advice on how to fix it? Like I said before, the flight controller seems to keep going into failsafe mode, which most likely because the receiver keeps losing connection, which is most likely because the receiver loses power. But I did resolder my connections on the receiver (connecting it to the ground, positive, and Rx spots on the FC) and the connections appear to be solid, so I don't know what to do to fix this bad boy. Any help would be appreciated. Thanks!

    Also, here's a screenshot of the blackbox flight log during a flight. Notice how all signs point towards it being a brown-out—the rxSignalReceived goes null, then the rcCommand[throttle] cuts off after the failsafe grace period, and then the accelerometer goes to null showing it's falling.

    Does this help? If you need more information to better diagnose this problem, just ask. I'm at a loss for how to fix this. Thanks!
    Last edited: Dec 21, 2017
  5. Moon Dude

    Moon Dude New Member

    Also, if my batteries are 1500mAh and 40C, is that enough? That would make sense except I haven't found any correlation between the receiver losing connection and increasing the throttle...
  6. RENOV8R

    RENOV8R Well-Known Member

    Spektrum RX requires a 3.3 volt power supply, pretty sure the + and - on Uart 3 are 5 volt. This would explain your problem
    Gyro Doctor and mozquito1 like this.
  7. mozquito1

    mozquito1 Well-Known Member

    That's what I was just gonna say as, but would have thought it either would or would not work. For 3v you have to use the IO 2 or ther is one on the back next to led pad.
  8. Moon Dude

    Moon Dude New Member

    Hey, hey, hey! Thanks for your help! Turns out that you can't always assume something is 3.3V when it's actually 5V! :p

    I was able to take it into the shop and solder the positive wire onto the 3.3V pad on the underside, and I've done a test flight, and all seems to be working like a charm.

    Thanks everyone for your help! Can't wait to get flying with this thing. I'll make sure to come to this forum more often. Thanks!
  9. mozquito1

    mozquito1 Well-Known Member

    It ain't YouTube but the likes make it worth it. ;) good luck.
    Moon Dude likes this.

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