Beginner would like to build Sandbanks PI Metal Detector

Al , it could be two wires which are shielded  . If you have two wires individually shielded  , that should work too . Don't worry about this  . Remember that there are two wires going to ( and from ) the coil  . These wires should be shielded  ( with the shield going to ground ) . Wether both wires are shielded  individually is of no importance  .  Cornelius

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		Quote:			Posted by aliman
	Thanks again Cornelius ! Another question, how many ohms approx. should the completed 200mm x 20 turns of 26 gauge wire coil, read?

Resistance makes no difference at all. Impedance is what counts. Wrap as per directions and don't fret over the resistance.

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		Quote:			Posted by treasuremomo
	Hi Cornelius, I've a question to ask you...Would a basic tech/trade school course in electronics be enough schooling in electronics to enable a person to build metal detectors? Or would a person need to be an electronics engineering grad to know his/her stuff well enough to design and build VLF or other type units?  I'm interested in building a VLF or TR unit with good depth and a good discriminator...maybe an ID meter.

If you can solder, read and understand a schematic, you can build a metal detector.

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Here is some coil info to give you some Idea's!

Common pulse induction search coils with their physical properties Size Shape Turns Wire size Inductance Resistance

SIZE                     TURNS        WIRE SIZE                INDUCT    RESISTANCE

? 120 mm Round      36 ?     0.40 mm / 0.14 mm2     405 ?H     1.9 Ohm
? 150 mm Round      31 ?     0.40 mm / 0.14 mm2     394 ?H     2.0 Ohm
? 175 mm Round      28 ?     0.40 mm / 0.14 mm2     387 ?H     2.1 Ohm
? 200 mm Round      26 ?     0.40 mm / 0.14 mm2     406 ?H     2.2 Ohm
? 250 mm Round      22 ?     0.40 mm / 0.14 mm2     380 ?H     2.3 Ohm
? 300 mm Round      20 ?     0.50 mm / 0.20 mm2     390 ?H     1.6 Ohm
? 400 mm Round      17 ?     0.50 mm / 0.20 mm2     396 ?H     1.8 Ohm
? 500 mm Round      15 ?     0.50 mm / 0.20 mm2     400 ?H     2.0 Ohm
1.0 x 1.0 m Square    10 ?     0.66 mm / 0.34 mm2     406 ?H     2.0 Ohm
1.4 x 1.4 m Square      8 ?     0.66 mm / 0.34 mm2     387 ?H     2.2 Ohm
1.8 x 1.8 m Square      7 ?     0.80 mm / 0.50 mm2     398 ?H     1.7 Ohm


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Ali , that was fast .  Use the two 12V batteries for the besr result .Be careful with the polarities though !!!!!!!! . Have fun with the detector  . Do not consider this a toy , it is NOT .     Cornelius

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