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Thread: Fast Pulses with Sharp Edges

  1. #1
    Join Date
    Jun 2009
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    Default Fast Pulses with Sharp Edges

    Above title should have read "RayMarine ST4000 Ram motor" instead of "test."

    In preparation for RtR, I needed to replace the electric motor of my X5 Ram. It uses a basic Mabuchi RC-555SH hobby motor but with some additional cross wiring near the neg and positive terminals.

    What are the 4 wires? I suspect they may have to do with handling the sudden change in current direction and voltage.

    I have found this on my 2011 model ram and a 2014 model. Crazy Rhythm did not have this on his RAM which is about same circa.

    Name:  AP Mabuchi 555SH motor small pic.JPG
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    Last edited by BobJ; 07-26-2020 at 09:48 AM.

  2. #2
    Join Date
    Dec 2012
    Location
    Alameda CA
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    It appears the 4 wires serve to put 3 capacitors into the mix... one bridging +/- and one each connecting positive and neg to the case ground.
    I can't read the numbers on the capacitors, so the specifics aren't possible, but they are likely there to smooth out the current spikes, as you mention.
    The 2 on the ground wires probably serve the ensure current only moves to the ground, and not back to the other motor pole.

    Full disclaimer, my knowledge about Ray Marine products is limited, there are certainly others who know more.
    paging Dr Boschma...
    DH
    Last edited by DaveH; 07-23-2020 at 10:46 AM.

  3. #3
    Join Date
    Sep 2007
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    Default

    THey are there for noise suppression to pass FCC and EU specs on radio interference. They would have some impact on current flow but they are quite small in value to do much. If you have an SSB aboard, for example, these would lower some of the weird tones you hear when the motor is turning in any direction on some frequencies. VHF likely not quite as sensitive. The signal to the motor is not a pure DC signal, it is a series of fast pulses with sharp edges that create quite a bit of electrical noise.

  4. #4
    Join Date
    Jun 2009
    Posts
    120

    Default

    Thank you very much guys!!

    My hope is renewed that I will be there for Round the Rocks!

    BTW, "..it is a series of fast pulses with sharp edges..." That descriptive phrase takes me immediately back to SHTP 2014. The whirring and grinding noises not only resonated inside the small cabin but tortured and grated my sleep. In time, it became the background rhythm to my dreams like the theme music in "Shaft."

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