Created: "May 4 2009" Update: "July 24, 2012"
Here is a Simple Pin Pointing Metal Detector. This is simular to some other Pin Pointing detectors. However. The Meter and other small circuit differences, gives better performance. On the Schematic, I show Two Possible Coils. 1) The Ferrite Rod, creates an Accurate Pin Point. But it also has a Very Narrow Detection Field. 2) The Dual Wound "Tesla Coil" Creates a Wide Field of Detection. With Maximum Sensitivity at the Center of the coil.
Detection of metal is with a Meter and LED. The Meter Gives a Much Better Sensitivity. On My Prototype, I can detect a 1/8 Gram Gold Nugget at One Inch, With Either the Tesla Coil or the Larger Ferrite rod coil. But Only about 1/2 inch with the Tiny Ferrite rod one.
Changes to capacitor "CX" will change the Operating Frequency. It may also Improve Sensitivity. I Recommend Expermenting with Different "CX" Caps and also Various types of coils.
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Picture of a Tesla Coil and a Simple Ferrite Rod Coil. The Tesla Coil has an ID of 1" and an OD of 4 3/8". And Each Coil has an Inductance of 150uH. Using this coil In my Test Circuit, CX is .01uF. On This Ferrite Rod, Coil "A" is 600uH. And Coil "B" is 100uH. Here I used a Ferrite Rod, Made by "FairRite", Part Number "4077312911"
Picture of another Ferrite Rod Coil. I had to Increase the Coarse trimpot to 10K to get it to Oscillate. But it than worked OK. Here I used a Tiny 3/16 dia Ferrite Rod, I bought on-line. Specifications Unknown.
PCB Picture Overlay.
Complete Picture Overlay.
This Coil Worked Very good.
It uses a "Fair Rite" Core, Part Number 4077312911.
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