Inductor Coil Interpretation

[hisoka147]

I need help on how to interpret the illustration below. Do I need to wound 3 wires to obtain 6 1/2, 35, and 165 turns? and how about the 1 turn?

Anyway, I am trying to build the project Deep seeking metal detector by Phil Wait and Roger Harrison.

[porkluvr]

The tapped inductor is one continuous winding, with taps at 6-1/2, 35, and 165 turns, for a total of 206-1/2 turns.

A good way to tap the inductor is to stop at whatever number, make a small flying loop of maybe 5~7mm by twisting a short length of wire back on itself, then continue by winding in the same direction as before, restarting the count from zero. Count to the next tap, make another small loop... . You'll connect the wires going to Q1, -Ve, RV1-C2, C4-CV1 to those loops.

You would probably have the least trouble if you start with the biggest number. Wind the 135 first.

Loosely twist two wires together before making that single turn. It is a separate winding, and it looks like you should wind that single turn in the same direction as the tapped coil. It's easy enough to reverse those two leads if by any chance that direction is wrong.

[hisoka147]

Thank you very much and I would like to add another question. What does the symbol on the illustration where I encircled mean?

[porkluvr]

That indicates that the coil inductance is adjustable. That coil is supposed to be wound on a potcore, having a bobbin adjuster. I have no experience with winding that type coil so you'll need to figure out exactly how the pieces fit together.

The bobbin either slides or screws down into the potcore, I'm not sure which, and that will change the inductance.

[hisoka147]

Okay thank you very much. That information is already good enough. I'll try to post my projects later on some other threads.