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ML PI coil patent app.

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  • #1

    ML PI coil patent app.

    This looks interesting. Flat wound coil variation. I think, I'll give it a try.

    US20210273335A1 - Antenna of a Metal Detector - Google Patents
    https://patents.google.com/patent/US20210273335A1/en?oq=US20210273335
    An antenna of a handheld metal detector for detecting a target in a soil, the antenna including a housing including a bottom plane for facing the soil; two lateral sides; a front side; and a rear side; wherein the lateral sides, the front side and rear side are with respect to a user of the handheld metal detector holding and operating the handheld metal detector to detect the target in the soil; and at least one winding within the housing. A mean distance of conductors of the at least one winding near at least one of the two lateral sides of the housing is closer to the bottom plane than a mean distance of conductors of the at least one winding near at least one of the front side and rear side of the housing.
    Attached Files
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  • #2
    Hi Altra !
    A flat cable for a computer could be used here ?

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    • #3
      Originally posted by Orbit View Post
      Hi Altra !
      A flat cable for a computer could be used here ?
      That could work, but that wire is usually very fine gauge with high resistance. I have some 18awg (1mm) twin speaker wire to try. Not sure how to form it yet.

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      • #4
        Better just use double sided tape on a cylinder, use the wire that you have best result for pi coils (litz, tinned copper, normal copper wire) put another tape on the outside and after try to bend the wires like in the picture.

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        • #5
          To achieve precise geometry, perhaps a 3D print for the shape to provide the rigid form.

          Then wind a flat spiral coil on adhesive backing (maybe double sided Scotch tape) and stick on to 3D printed form.

          Then seal and harden the coil with some kind of brush on sealant.

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          • #6
            Maybe this cannot work.

            If you were to flatten out the 3D shape, perhaps it is not a concentric circle. It may have some wobbly shape.

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            • #7
              Some gold nuggets and possible test targets. Didn't test gold chain today, it was borrowed and measured awhile back for time constant. I purchased the 1 gram of nuggets (a thru g) awhile back. #9 lead shot harder to detect than any of the nuggets. Nugget e a little less signal than #8 lead shot.
              Nuggets vary a lot. Think, need to pick one of the lead shots for a desired target before defining coil and amplifier specs?

              Need about a 3 times signal increase to increase detection 1 inch from chart for 133mm coil.
              Attached Files
              Last edited by green; 02-26-2022, 10:18 PM. Reason: added sentence

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              • #8
                That's a nice collection of targets Green. That #8 shot is tiny.

                I think you could wind a flat coil to spec, bond the wire with flexible glue. Then make a wooden form to hold the front and rear parts of the coil at 90 degrees. Finish by brushing on a few coats of epoxy resin to lock the windings into that shape. A basket coil could be wound on a preformed plastic jig with slots. Another idea, wind the coil flat glued to a piece of that plastic sheet that can be formed with warm water. Don't remember the name of this plastic, but it's used for making removable arm cast etc.

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