PowerBUS setup advise needed

  • Good evening everyone,

    I'm setting up a big jet and I'm using the PowerBUS for the first time together with a Champion SRS. Transmitter is Spektrum DX18.

    My intention was to split the plane in half and assign each aileron, flap, rudder and elevator to a dedicated BUS to PWM converter, one connected at the B output and the other connected to the A output.

    A will be RED and it will power the left side of the airplane. B will be BLUE and it will power the right side of the plane.

    Super basic setup at the DX18, being:
    AILERON on 2
    ELEVATOR on 3
    RUDDER on 4
    FLAPS on 6 (AUX1)

    Output mapping at the Champion:
    BLUE bus:
    A=2=DIRECT 2
    B=3=DIRECT 3
    C=4=DIRECT 4
    D=6=DIRECT 6

    RED bus:
    S=6=DIRECT 6
    V=2=DIRECT 2
    W=3=DIRECT 3
    X=4=DIRECT 4

    Chosen for symmetry, not any other particular reason.

    P.BUS channel assignment (and this is where I loose it):
    CH1, output D, function DIRECT 6, on servo socket 1, press once to assign CH1 to servo socket 1
    CH2, output A, function DIRECT 2, on servo socket 2, press twice to assign CH2 to servo socket 2
    CH3, output B, function DIRECT 3, on servo socket 3, press 3x to assign CH3 to servo socket 3
    CH4, output C, function DIRECT 4, on servo socket 4, press 4x to assign CH4 to servo socket 4

    It is pretty clear to me and before I got started I thought I got it. I now got the rudder on the RED bus operating right but it appears that the other channels are not working or not right (I'll re-program the PWM adapter).

    The BLUE bus I cannot get it to work but there is something I'm missing for sure.

    Am I doing this right or am I asking for something that cannot be done?

    Any advise would be highly appreciated.

    Thank you,



  • Hello,

    for me it looks that you got it. Also your setup should work. The only thing I can imagine is that the PWM adapter adress is not correct.

    How I do it:

    I make the PWM adapters like that:



    The I put them into the plane. The mapping is done completely in the P-BUS mapping of the PowerBox. For the Rudder: Make two outputs direct 4- then you can servo match them.

  • Hi Richard,

    thank you for your reply. I figured out one of the issues and I was able to setup the left side completely (the RED BUS).

    It was my mistake: when you program the servo socket, what matters is to get the light flash rather than feeling the button being pressed in. Sometimes you press it in and you feel it clicking but the light does not flash and therefore your count is not aligned with that of the unit.

    2 issues remaining.

    1. After setting up the RED BUS, I tried the BLUE one to which I assigned the same inputs but with your numbering (5-6-7-8) as to avoid address conflicts.

    CH5, output D, function DIRECT 6, on servo socket 1, press 5x to assign CH5 to servo socket 1
    CH6, output A, function DIRECT 2, on servo socket 2, press 6x to assign CH6 to servo socket 2
    CH7, output B, function DIRECT 3, on servo socket 3, press 7x to assign CH7 to servo socket 3
    CH8, output C, function DIRECT 4, on servo socket 4, press 8x to assign CH8 to servo socket 4

    The BUS ADAPTER does not even light up when I connect the lead while keeping the SET button pressed in. No signs of life. It works because I was able to program it a while back while trying to figure it out.

    Maybe I have yet not understood what discriminates between BUS A and B in the powerbox, I assume the outputs, A to F being assigned to BUS B (BLUE) and G to X being assigned to BUS A (RED). It seemed pretty clear and intuitive to me.
    I also tried to disconnect RED BUS while attempting to program BUS BLUE but it didn't matter.

    2. On the BUS that works, if I plug the FLAP servo to the Powerbox socket everything is fine. If I then plug the servo into the BUS ADAPTER socket to which it belongs, the flap will move down by a tiny yet non negligible bit that throws the setup off. It only happens with the flap, not with the aileron and not with the rudder (elevator yet to be setup). This is strange.

    At the time being, I saw a lot of advantages with the BUS system and I'm usually very open to new systems and very willing to experiment with them but I think I'll drop this one because I don't have a clear understanding of what is going on and I don't want to risk my biggest model.

    Thank you for any advise,


  • Hello,

    Bus A and BUS B - the difference is only: Bus A is powered by regulator pair 1 and Bus B is powered by regulator pair 2. You can run Bus A with 5.9V and Bus B with 7.4V if you want.
    The signal is the same on all two bus systems. So Bus A and and B can be programmed to the output from A to X.

    Once the Bus system is correctly installed, this system runs really good and reliable.
    If your BUS to PWM adapter has no lights when pressing the button at the Power Up there is something wrong.