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  1. #1
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    External BEC...How to?

    Can anyone help me understand how to wire a servo directly to power (Castle 10A BEC) an pull signal from my receiver (Traxxas 2218X)? For the life of me I an a friend cannot figure it out. We have tried two different castle BECs and 3 different servo brands with no luck. Does te Traxxas rx not support this kind of setup or am I missing somthing?

    I am replacing the stock dual 2075 setup with one large high current draw servo and adding rear steer to my Summit powered by the same servo.

    This is the diagram I am using

    My rear steer.

    Any help would be apriciated!


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  2. #2
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    You also may need a ground between the Rx and the BEC.
    Last edited by JimmyNeutron; 09-01-2012 at 06:43 PM.
    Whatever it is I just typed... could be wrong.

  3. #3
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    Quote Originally Posted by Jimmie Neutron View Post


    You also may need a ground between the Rx and the BEC.
    Connect black to black? Or Brown on the bec to black on the rx?


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  4. #4
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    Positive to positive, negative to negative, signal to signal.

    If your wire colors are different, you are going to have to figure out which is which.
    Whatever it is I just typed... could be wrong.

  5. #5
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    Sweet, thanks Jimmie. The help is much appriciated.


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  6. #6
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    Sorry I couldn't be more help on which is which... I have to figure it out for myself each time I mess with any other color set other than black/red/white. lol

    Let us know if that works out...
    Whatever it is I just typed... could be wrong.

  7. #7
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    So I cut the red out of this y connector and plugged it into an old am receiver in the steering channel. Plugged the servo in one side, the bec in the other. hooked it up to a battery and it worked great.



    Unplugged it from the old am receiver and into my summit and it melted the insulation of the black neg wire going to the esc and filled the room with smoke.
    I unplugged it as fast as I could and it still seems to work, although I undoubtedly shortened it's life.

    Why did it work fine on the am but not my summit?




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  8. #8
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    You have got me.
    Whatever it is I just typed... could be wrong.

  9. #9
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    Thanks Jimmie, I'll do some more lookin around I realize this is hard to teach online and not in person. Wish me luck!


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  10. #10
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    Funny thing is... if it was in front of me I might know exactly what is wrong. lol

    I have PM'd Krall about this thread... maybe he can help.
    Whatever it is I just typed... could be wrong.

  11. #11
    RC Turnbuckle Jr. jamann's Avatar
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    I believe it's how the evx is wired internally. Have to get the power from the bec side.not sure why though.


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  12. #12
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    Thanks Jimmie I'll take all the help I can get!

    That makes sense Jamann cause I am trying to pull power from the other battery in effort to drain them more evenly like I said above...maybe I can try it on the other side.

    Gonna finish my burger and give it a whirl I already need to split the esc to solder on a new futaba plug anyway.

    Thanks guys.


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    Last edited by happymachinist; 09-01-2012 at 10:44 PM.

  13. #13
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    Here is how I have mine:

    It is not a high voltage BEC... just 6.1v so I have it running through the Rx.
    Whatever it is I just typed... could be wrong.

  14. #14
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    I can do that also, these are 6v servos, do it would work quite well. But can the rx take the demand as well?

    Of coarse the manf doesn't list amp draw of the servos I may try to get ahold of them.


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  15. #15
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    I am not sure what the stock Rx can handle... I am not running a stock Rx.
    I have an 8channel FS Rx.... ran by my hacked "3" channel FSGT3B.


    I have not really ran her hard yet... hopefully I will find time soon.
    Even if I fry the Rx I am only out $15 for a new one.
    Whatever it is I just typed... could be wrong.

  16. #16
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    So I switched the ext bec around quick to the int bec side and everything seems to be functioning normally...without the smell of burning insulation!

    I am using a power tab (6541 used with telemetry I guess) so it is easy to undo anything if I need to.

    I greatly appriciate the help gentlemen. I most definatly wouldn't have figured it out alone. Hopefully others can learn from this fiasco I started...lol

    Thanks again.



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  17. #17
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    Sorry for the late reply, but as far as I can tell you figured it out at the end! That last picture seems pretty simple to me: BEC getting power direct from the battery.

    Those little CC bec's are my fav, I am using two of them in my build!

  18. #18
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    Quote Originally Posted by krallopian View Post
    Sorry for the late reply, but as far as I can tell you figured it out at the end! That last picture seems pretty simple to me: BEC getting power direct from the battery.

    Those little CC bec's are my fav, I am using two of them in my build!
    Hey no biggie! Installation is easy now, all you need is a y connector with the red (+) wire snipped on the male end that plugs into your receiver. Then plug your bec into one female, plug the servo into the other.

    JUST MAKE SURE YOU HOOK YOUR EXT BEC TO THE SAME SIDE AS THE INT BEC!!! Or you will fry your esc.

    Hey krall...or anyone for that matter where are you putting the bec? I have a couple waterproof rx boxes that come stock on the summit on order but I'm worried about heat. I'm more worried about a random water splash, though, this thing looks vulnerable.


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  19. #19
    RC Turnbuckle Jr. jamann's Avatar
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    When I ran one,I liquid taped the ends of the shrink to keep water/moisture out


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  20. #20
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    Thought about that...might have to give that a go...it will be a lot easier to find a place to put vs a box.


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  21. #21
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    I'm not worried about waterproofing, I'm going to have so much non-waterproofable stuff on my car I've given up on the water worries heh. But heat isn't a big issue with those guys unless you're driving a lot constantly! =)

  22. #22
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    Another question though, are you still powering your ESC with two batteries? If you disconnect the power from the ESC to the RX, that second battery is now useless isn't it? I am looking to do this very setup:

    One battery to power the motor through the ESC, and another to power everything else. But because I need the ESC to still get info from the RX, I would wire just the ground and the signal wire from the ESC to the RX, and the RX would receive power from my CC BEC via another battery.

  23. #23
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    Yeah I'm still running two batteries to my esc. My rx is still receiving power from the esc's int bec.

    I might get another cc bec to power the rx (this includes the front steering servo) and take the internal bec out of the equation all together...from what I've read all I would need to do is cut the red wire from the esc.

    Its a few more wires but might hold up better than the int bec. Just because the int bec will do it doesn't mean it's the best way...I dunno.

    This is all new to me. With my 3.3 revo it was all about what can I take off to lighten it up. This Summit I just keep piling stuff on. She's gettin chubby to say the least.



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  24. #24
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    You wouldn't need to cut the wire...

    Take a sharp knife and carefully lift up on the little tangs of plastic where you see the metal from the pins. Once this tang is lifted up, you should be able to pull the pin(s) out. Just don't lift too much or they will snap off.
    Whatever it is I just typed... could be wrong.

  25. #25
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    Yeah I prefer pulling the female pin also...makes it easily reversed. But should work correct?


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  26. #26
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    ...should work as in eliminate the + and I can used an ext bec to eliminate the int bec


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  27. #27
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    Yes... eliminating the positive servo wire from the ESC will effectively stop the ESC's BEC from working.
    Whatever it is I just typed... could be wrong.

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