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

kmcsjr Jun 9, 2017

  1. kmcsjr

    kmcsjr TrainBoard Member

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    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?


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  2. RBrodzinsky

    RBrodzinsky Staff Member TrainBoard Supporter

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    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

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    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.

    Greg
     
  4. gatrhumpy

    gatrhumpy TrainBoard Member

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    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

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    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

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    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.

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    kmcsjr likes this.
  7. lexon

    lexon TrainBoard Member

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    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.

    http://home.cogeco.ca/~rpaisley4/DCCvolts.html

    This guy has proven circuits.

    Rich
     
    Last edited: Jun 24, 2017

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