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Re: Tranzformer wires

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  • Jeff Merill
    Since you are running Z scale, wire size is much less than with larger scales. To calculate, lets say that each loco draws 0.05Amps (that s 50 milliamps). Be
    Message 1 of 3 , Sep 25, 2006
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      Since you are running Z scale, wire size is much less than with larger
      scales. To calculate, lets say that each loco draws 0.05Amps (that's
      50 milliamps). Be conservative and figure a worst case 0.1A (100 mA)
      for a single loco. Double this for Consists, grades, long trains,
      multiple locos per track, etc. and you should be likely no more than
      0.5A (500 mA). Add sound to a car or tender and you may need another
      1A !!! (with all the sound problems I have been reading and hearing
      about, I'd either put a second decoder under the layout and feed a
      quality sound system or wait a bit for the porported Soundtrax multi-
      address sound box).

      So back to the wire. Wire has resistance rated in ohms-per-foot. If
      you pass current through wire it causes a voltage drop which you
      calculate as: I (current in Amps) x R (in ohms). So, 1A and 1 ohm =
      1V. Figure the 0.5A max and same 1 ohm and you have only 0.5V. Got
      it?

      Now the size Versus length. U.S. wire is AWG (or "gauge") and Euro is
      in milimeters. Some examples common in the U.S. is Lamp cord and
      Speaker cord (also known as zip-cord as you used to be able to split
      the two by simply pulling it apart) which is 18 AWG (#18 or 18 gauge)
      or ~1mm with 0.0065 ohms-per-foot(OPF). Nada, nothing. Take a really
      worst case 1A and .0065 ohms results in, you guessed correct: .0065V
      or only 6.5mV. After 100', you'll have 0.65V. Not really significant.
      The wheels on the track, wheel pickups and rails joiners will have
      worse resistance.

      Common quality multiconductor cable wire is 22AWG - 26AWG or smaller
      and computer 9, 15 or 25 pin cables are 26 - 30 AWG (0.25mm). By
      comparison, #22 has 0.0165 OPF (1.65V @ 1A @ 100'). #30 is fine for a
      loco wiring, like a DCC decoder. An example is 0.1A max motor, LED
      and lamps. #30 has 0.1 OPF so .1A x 0.1 OPF = 0.01 V or 10mV. Nada.
      And you're going only use a few inches which is proportionally less.

      So wire away with what ever you can get a hold of.

      BTW: common house wire is 14 gauge. @ 15A max rated and 0.00258 OPF
      = 0.0387V per foot. Figure up to 100' with all the bends getting to
      your plugs, that's a 3.87V drop. Now you know why the have short
      extension cords.

      Jeff

      --- In z_scale@yahoogroups.com, "Fred Ladd" <zeagle99@...> wrote:
      >
      > Groupers,
      > I have 7 transformers to run 7 trains in a 12'x10' room with the
      > layouts running on the walls. I'd like to have a Central control
      board.
      > My question-- How long can the wires be from transformer to each
      track?
      > Thanks in advance for input,
      > Fred
      >
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