For induction balancing of this flat spiral coil, same copy of the coil (as RX-Coil) is positioned at a distance of 85.8 mm from the center point of TX-Coil. The RX-Coil has also a distance of 1.5 mm height from the copper layer of TX-Coil. Standard PCB boards have a thickness of 1.5 mm. So, if you want to balance this coils together, just put them together and move the RX-coil 85.8 mm from the center point of TX-coil.
Attached picture shows both coils in overlapping display:
PDF-File showing in a better resolution.
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Flat Spiral Coil Analysis
Hello,
I found very interesting, to analyse the flat spiral coil. Especially the effects on the flattening and the weakening the magnetic fields.
The spiral coil has a starting radius (20 mm in this example) and an ending radius (80 mm in this example) with 50 windings.
Figure below shows the magnetic fields strength and directions on a half cross section of the coil. Red elements are the coil wire elements with showing the current direction. Black vectors are magnetic fields (H-Field).
By reducing the complexity of the coil for a better view (reducing the number of windings), you can see, why flat spiral coils are not effective. Between each two windings there occur canceling regions. The generated magnetic field from the outer winding will be slightly cancelled by the next inner winding. Also, this causes the flattening of the magnetic fields above the coil. See below picture for more details.
The detailed result is shown on the next picture:
The next picture shows two flat sprial coils with different diameters (same winding direction). The inner coil is driven with 0.4 A and the outer with 0.1 A current to show the canceling field better.
to be continued..
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