This is a wide coil of heavy wire placed around the bottom of
the secondary coil. This sets up a rapidly oscillating electromagnetic field,
which is absorbed by the secondary coil.
For this section, you will need the following items:
1. 40 feet of 10 gauge, solid, insulated wire.
2. A 4-inch high section of 6-inch diameter cardboard tube.
3. A tube or roll of something that measures about 5 inches in diameter. I used a roll of duct tape.
Since you will be using solid wire for this, I recommend wrapping the wire around something about 5 inches wide first. The wire can then be 'transferred' from the small tube to the 6-inch wide tube. This can be done one turn at a time. This method keeps the wire wrapped relatively tight against the outer wall of the 6" diameter cardboard tube.
Make sure that the primary coil is wound in the SAME direction as the secondary coil.
Once this coil is wound, secure it with hot glue at several places. This will keep the wire from loosening or coming off.
This is what the finished primary coil should look like.
Cost of the Primary Coil
1. I bought the 10 gauge wire for $0.05 a foot at Sears Hardware.
2. This 6-inch cardboard tube also came from a trash can at a machine shop. You might be able to get Sonotube in this diameter. Sonotube is a large cardboard tube that is used for making concrete cylinders, and is available at hardware stores. Unfortunately, it is sold in much longer lengths than is needed here, so I advise checking out shipping stores - they might use large cardboard tubes either to ship things in, or else shipping supplies themselves may be shipped wrapped around such tubes.
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