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    U-47 Electronics Issues Servo Fluttering


    Posts : 5
    Join date : 2011-09-08
    Age : 75
    Location : Marietta, GA USA

    U-47 Electronics Issues Servo Fluttering Empty U-47 Electronics Issues Servo Fluttering

    Post  2051476 Sat Feb 11, 2012 6:20 pm

    Need a Little advice.
    I'm having fluttering on my rudders and dive planes when I activate the Engel 824EA using the Engel UNI

    Prior to adding the UNI and Piston Tank all three servos and ESC worked perfectly Since this is my first R/C I was patting myself on my back, but alas too soon, I guess?

    Here's what I'm using Rx Futaba R168DF (75mhz in US), Rokraft 120uP, Engal EA825-6 Channels. Rx Cannels 1+2 Rudder and Rear Dive Plane, Channel 3 ESC, Channel 4 Front Dive Plane, Channel 5 the Engal Piston Tank. I disconnected the center lead (White) from the RX to the ESC. During my testing I'm using a battery pack for Rx power but will be using a BEC.

    Does anyone have an idea of what's causing the servos to flutter when the Piston Tank is activated? Per Engel the Motor has built in noise suppression. I have added noise suppression on the two motors

    Thanks John
    david f
    david f
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    Posts : 2143
    Join date : 2010-11-10
    Age : 70
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    U-47 Electronics Issues Servo Fluttering Empty Re: U-47 Electronics Issues Servo Fluttering

    Post  david f Sun Feb 12, 2012 10:43 am

    Hi John,

    You have had a good reply to the same question posted on Model Boat Mayhem. But in addition unplug one item of equipment at a time and see when the problem goes.

    However it is a "black art" sorting it out. Some contributing factors can be:

    - Servo use a high current when they move and this can produce voltage spikes which trigger all the other servos and so produce the "flutter" (Try unplugging some.)
    - I've even found that outside conditions can produce interference e.g fluorescent lighting in your workshop.
    - Try to separate control wiring from high current wiring.
    - BECS can be a problem. Switch mode BECs can be bad for interference (Info from John R)
    - Ferrite rings are often worth trying.
    A good discussion on the topic here:


    Posts : 97
    Join date : 2011-06-10

    U-47 Electronics Issues Servo Fluttering Empty servo fluttering

    Post  johnrobinson Sun Feb 12, 2012 1:52 pm

    HI John
    This sounds like you have a ground loop problem, back emf from piston tank motor from what you said the problem only happens when you plug that part of the circuit in to RX, one thing i would try is the wires coming off motor on piston tank try and make the wires a little longer and twist them together tight put the twisted wires around a ferrite ring about 8 times and then take back to control board. Do the same thing with wires coming from control board for piston tank that plugs in to RX I know that you said you have put sirpression on motor on piston tank trouble is caps needs to be worked out for the frequency you are using to control the sub, you could always put across the motor a bipolar cap that they use in speakers i have seen this work quite well. What somebody said about taking earth wire from metal can of motor back to neg on battery was spot on that is the right thing to do, all neg wires should go back to the same point neg on main battery. Little tip on using BEC a lot of BEC,S regs work by switching high frequency at about 300 KHZ i have seen people loss about half of there range with the radio try and go for a linear reg i have been playing about with one that will give about 5AMPS

    What is a good thing to do is twist all power cables together as what you are doing by doing this is forming capacitance down the wires and will take out high frequency noise
    Hope that helps Sub John

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