Let's discuss current draw for DCC. N and other scales

kmcsjr Jun 9, 2017

  1. kmcsjr

    kmcsjr TrainBoard Member

    In another thread a modeler considering DCC in N, is concerned about the 2A limit of the standard DCC++ system.
    I've been using a PowerCab for a while now. It has the stock wall wart, with less than 2A output. I've had 5 to 7 or 8 engines moving at once, some sound, some double headed, 2 lighted passenger trains, always lit, on sidings, throwing multiple switches. I use Unitrack, 16gauge bus. 18 to 22 gauge feeders. Some of my decoders are drop in, or stock. Some, I've soldered (and I don't consider myself to be great, with an iron). Unless I short out (usually because I forgot to throw a switch), I have yet to draw more than 1A. I really don't remember seeing 0.9.

    So, in your experience, when do you need more than 2A? How much current do you draw, doing what?

    Sent from my iPhone using Tapatalk
  2. RBrodzinsky

    RBrodzinsky Staff Member TrainBoard Supporter

    I have a RRampMeter permanently installed in-line directly after my command station (DCS-100) on the JACALAR. I have had upwards of 25-30 locos on the tracks at any given time, many (now most) sound installed. Typically never have more than 5-6 locos moving at once (never more than 3 trains, but with consists), and I have never seen my current draw exceed 1.75 amps. That was with all running locos sound installed, and even then only momentarily. Tends to fall back down to near 1.2-1.3 amps once everything is moving.

    Note - none of my switches or lighting are powered from track. All of those come from auxiliary power.
  3. Greg Elmassian

    Greg Elmassian TrainBoard Member

    I replaced the non-regulated wall wart with something more substantial and regulated. Then I used a RRamp meter also. The current draw indicator in the PowerCab itself is not very accurate.

    Yes, once everything is started up, power draw is a lot lower than most people are led to believe. It's startup current and transients that can give you erratic operation.

  4. gatrhumpy

    gatrhumpy TrainBoard Member

    I've never had a problem with 2A. I've had 3 sound engines running with lit passenger cars.
  5. CSX Robert

    CSX Robert TrainBoard Member

    I have the original Digitgrax Zephyr, which is 2.5 amps. I have tried to see if I could reach its limits , and so far I haven't. The most I have had running at the same time so far is 7 trains with a total of 9 engines. This included an Athearn Challenger with sound and a dual motored Bachmann DD40AX. The engines were not running light either, they had trains of varying lengths. The shortest was 3 cars - an Athearn Bombardier commuter train - and the longest was 25 Micro-Trains boxcars. I also had some lighted cars, 3 Kato Superliners(with the original incandescent lighting kits, not the newer LED kits) and an Aerotrain with one 3-car add-on set.
  6. Karl Masoner

    Karl Masoner New Member

    I'm new to this forum. I don't currently have a layout, but I operate on several layouts in different scales. I also am involved or have been involved in construction of layouts. In my experience there should be less concern about the current capacity of the primary command station/booster and more attention paid to proper design of the layout for operations. This will minimize overkill and cost as well as labor. Even on a small layout things like inrush current at start up can easily be minimized by isolating idle locomotives. Proper sizing and use of boosters and power districts will make a 2 amp limit on a command station moot. We all hate it when derailment of one train disables all trains on a layout, but good power district design will prevent that and keep current requirements low enough to prevent instantaneous meltdown when accidents occur. I worked on a large automated layout at Union Station in Kansas City for several years. It was over powered and under protected. I still have a melted Burlington Zephyr and a lump that used to be an SD26 as reminders.

    Sent from my SM-T330NU using Tapatalk
    kmcsjr likes this.
  7. lexon

    lexon TrainBoard Member

    I built two DCC amp meters some years ago. One for my NCE Power Cab at home and one for the clubs five amp NCE Power Pro.
    I clipped a high amperage rheostat across the rails. I lower the resistance and my Power Cab trips at about 1.98 amps.
    The clubs Power Pro at about 4.97 amps.
    I bought the converting device online. PC board and components. Less than ten dollars as I recall.
    It uses a Harbor Freight multi-meter that cost me about two dollars each. I set it on the 20ma current scale.
    These forums have a forum that shows interesting projects that users post and the administrator put the discussion there.
    The club version, I used the voltmeter option and bought a large LED display so the club can see the current readings easily.
    The ZXCT does the converting.
    The one at home, I used the current option with HF meter.
    The HF meters read about 13.6 VAC I have four of these meters. My digital Scope shows the results for voltage and no spiking.
    Yes I know about RMS meters but not needed in my case.


    This guy has proven circuits.

    Last edited: Jun 24, 2017

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