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Bec inside ESC and BEC integrated flight controller compatibility…

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  • Bec inside ESC and BEC integrated flight controller compatibility…

    Hey, I’m new to the rc world. I’m attempting to build a twin 70mm EDF jet for FPV. I plan on using the R9|RXSR Pilot flight controller from FrSky. From what I’ve learned, the FC has an internal integrated BEC. Now knowing this, does that mean I need to get 2 ESC’s without a BEC? Instead of my original plan of getting one ESC with and one ESC w/o internal BEC? (I plan on ordering some custom MGM TMM ESC’s)

    In simple terms, does the BEC in the flight controller “replace” the BEC in my ESC? From what I’ve heard, I don’t want two BEC’s, so I’m making sure my FC and ESC don’t “fight”.

    please keep in mind that I may be completely missing the concept, so if my question doesn’t make sense my bad lol

    pls help :)
    Last edited by KreachurR; Jul 23, 2022, 09:40 AM. Reason: Typo in title

  • #2
    If you need links to the components or more detail just lmk.

    thanks in advance


    • #3
      I'm not familiar with that FC but if it does have its own power circuit and it seems you plug your flight battery and ESC into the FC, then you can put any kind of ESC to it. If the ESC you choose has an internal BEC, it's a simple matter of disconnecting the middle red wire from the throttle lead. It's easy enough to try. Remove the red wire from your ESCs that have an internal BEC and if it all works, done. If the FC doesn't power up, then put the red wire back on one of the ESCs. The only point of confusion for me with that FC, is that I don't understand how the throttle leads are hooked up.


      • #4
        No. The BEC in your FC is designed to power your VTX and camera not your receiver and servos. On a quad, there are no servos, the FC's BEC can power the receiver too. These BECs typically do not have a lot of power, 1/2 amp, maybe a full amp, looks like yours is good for an amp.

        That said your motor ESCs may have an internal BEC (probably a SBEC and not linear). A lot of twins do not use ESCs with internal BECs, these are called OPTO. In that case they need an external dedicated BEC, make sure it has the power to supply your expected servo load.

        I assume you want a FC to have a OSD or GPS?


        • #5
          This is all new to me but here's the product page, which he could have linked easily for all to see .............
          As far as I can tell, it does have an integrated BEC that can put out 5V (to a max of 8V) and 6A to servos. It can use anything from 3s to 12s, with dual ESC taps. Additionally, I see now that it has up to 12 servo/motor outputs but I can't see how you actually plug those in. It also seems to use serial RXs.


          • #6
            Looks like it may be designed to power the servos too... Amazing some of the stuff that's coming out.


            • #7
              Indeed. I tried my hand at FPV when things were still fairly primitive by today's standards. I couldn't progress with it due to me never getting used to flying through goggles. Gave me severe vertigo. Gave it a go for a couple years and that was it.
              With that FC product, I can only guess that to hook up stuff like servos, you have to solder, unless the pins are on the underside and we can't see them. It also surprises me that having stated he's new to RC, that he's jumping in at the deep end of the pool right away.


              • #8
                Many come with header pins to solder in if people want to connect external servos... I have seven airplanes that are FPV with head tracking including two EDFs, the 80mm F-86 and 70mm Yak130. I really like it. None have a FC and I don't think I'd want the extra complication. Just adding the video transmitter, camera, a separate BEC and a fan for cooling the VTX is enough. But things are getting better and better, also more PnP.

                My quads do all FC's and as such enable OSDs. I have had, previously, a Vector FC in one of my planes that gave me OSD with altitude, direction to home, return to home, ground speed, battery current used etc. I removed it from that plane as too much of a distraction and eventually removed the FPV system all together. But that was years ago and analogue.