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71871Re: [softrock40] Re: Quick question about winding Transformers

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  • R. R. (Robby) Robson
    Jan 22, 2013
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      I have modified the build instructions such that, in each step calling for the installation of an inductor, I print out an expanded winding instruction.  For example, in the step calling for the installation of the T5 transformer in the RXTX Ensemble, the instruction is:
      XFRMR: 0.6uH: 14T/2x7T bifilar #30 on T25-6 (yellow) 8"
      Primary: Using approximately 9 inches of #30 wire, wind 14 turns on a T25-6 (yellow) ferrite.
      Secondary: Using a total of 9 inches of #30 wire, wind 7 turns , bifilar, on the ferrite in the same direction as the primary winding. Inductance of the single winding (usually the primary) is 0.60 uH."

      The instructions are computer-generated and may have rounding errors in the computed wire lengths (e.g., in the above the shorthand version says 8"; the generated version says 9").  I conservatively round up.

      If you are not seing this in the build instructions, please refresh the page in your browser (F5) to remove any cached older pages.

      I am open to suggestions as to how I should re-program the instruction generation algorithms for more clarity.  

      Since I maintain this website and its associated infrastructure at no cost to the consumer of its instructions and receive no compensation for any of my labors or outlays, I am somewhat limited by my other commitments in my ability to respond as promptly as some might otherwise wish.

      On Mon, Jan 21, 2013 at 12:54 PM, Alan <alan4alan@...> wrote:

      ----- Original Message -----
      Subject: [softrock40] Re: Quick question about winding Transformers

      > I read that page several times before sending my first email, but it does not deal with how to interpret this very cryptic
      > statement:
      > 0.69uH: 16T/2x8T bifilar #30 on T25-6 (yellow) 9" (top)


      As I've never followed Robby's instructions I'm not familiar with following them But on the page I linked is:-

      "Specification Format
      Winding specs will generally resemble the following:

      5.0 uH 17T bifilar/34T #30 on T30-2 (red) (19").

      This can be interpreted as:

      a.. Use a T30-2 toroid (color is red and O.D. is 0.3")
      b.. You will need two 19" lengths of #30 wire.
      c.. For toroids, one turn is a single pass through the center hole.
      d.. For binocular cores, one turn is a pass in which the wire goes in the bottom, comes out the top, goes back in the other hole
      at the top, and comes out the other hole at the bottom.
      e.. The transformer will have a single, 34 turn, secondary winding of 19" of #30 wire. Usually the single winiding is wound onto
      the core first. Winding should be evenly spaced and ideally cover all but a 15 degree "wedge" of the toroid. Sometimes, it may be
      necessary to wind over the top of existing turns where there is more wire than there is bare core left.
      f.. The transformer will have two primary windings each of 17 turns of #30 wire. The term "bifilar" means to take one of the two
      lengths of wire, bend it at the half-point so the resultant "hairpin" is composed of the two 9.5" long halves, and then twist the
      two strands together to make a "bifilar" strand with approximately 3 twists to the inch. The bifilar windings are usually wound
      AFTER (and over) the single strand winding. You should wait until you have wound it correctly before cutting the "hairpin" end of
      the bifilar strand.
      g.. The inductance value is provided primarily to help validate the number of turns. It is the inductance of the single-strand
      Which to me seems to give a reasonable idea. And the other links on that page must give more information.
      Once you have done one then it seems uneccessary to repeat the instructions. It is a one-time learning procedure.
      Many others have made the coils before with only a few asking about them.
      However, if you feel Robby should make things clearer then I'm sure he will be glad to discuss it with you.

      73 Alan G4ZFQ


      Richard R. (Robby) Robson
      LTC USA (RET)
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