BEMF Decoders and slow speed operation.

Discussion in 'DCC & Electronics' started by billwv, Jan 23, 2005.

  1. billwv

    billwv Member

    Comments appreciated.

    What is your experience with decoders using BEMF? Do they really help with slow speed operation?

    What slow speed operation (i.e. SMPH) are your able to obtain with HO Atlas and P2K Diesels?

  2. moria

    moria Member

    Greetings :)

    Good question, not so simple answer :) Let me explain.

    Back EMF does not, in my humble opinion, help slow speed running at all. BEMF is designed to compensate for load on the loco, so that when running uphill or downhill the power to the motor is adjusted and the speed remains constant. Now.. having said that, if you are running slow speed and then go up a hill, the BEMF decoder will continue and a non-BEMF one may well slow enough to stall the loco.

    Generally, to improve slow speed you need some sort of dither or pulse control to keep kicking the motor into going forward, especially if the track is not spotless.

    Having said that, if you are using speed tables (and hopefully something like decoder pro to program the little critters so you can get it done in less than 3 weeks) then you should be able to program any loco on DCC to run in the order of 2 or 3 SMPH at notch 1 on the controller.

    My decoder of choice is the TCS M1 as it has a wonderful dither feature and Back EMF equivalency so the locos just pur along the track.

    The new Lenz Gold decoders with the USP module may be very good as well.. am awaiting a couple to try.

    One cautionary word though.. If you run Digitrax and one day expect to run transponding, then only use Dither or High Frequency decoders made by digitrax.. all other makes are incompatible with transponding and the dither/pulse needs to be turned off to allow transponding to work.

    Hope this helps some.
  3. billwv

    billwv Member


    Have you tried, or do you have an opinion on Digitrax Series 3 decoders for slow speed operation?

  4. moria

    moria Member


    Yep, in the past I have used series 3 decoders, especially when I used to use Plug and Pray (not a mispelling) ones. However, I always found them rather expensive, and now, even if a Plug and Pray is available, I tend to rip out the circuit board and hardwire in something like an M1 from TCS as they are a lot cheaper (generally I only use a couple of functions) and to me have a better performance.

    Your mileage may vary, this is all a very subjective personal thing :)

  5. billwv

    billwv Member


    Thanks for the info. Decoder expense is not a great issue with me since I only have a few Locos. I am planning a small shelf layout.

    I will look into TCS along with Digitrax series 3.

    Thanks again.

  6. kchronister

    kchronister Member

    FWIW, I have both BEMF and non-BEMF decoders... Will never buy another one without it.

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