"Gary's Pulse Induction Metal Detector"

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Origonally Created: Mar 16 2002
Latest Revision, Nov 7, 2011

EFFECTIVE AUG 1, 2010:
I NO LONGER will give Any help to persons that did Not Buy at least the Basic Kit of parts from me.
As Too many persons make Substitutions or Errors, than expect me to solve there mistakes.

**A Kit of parts Is Available from me.
And other than the PCB and coils, most parts are supplied at my Landed Cost.

When Purchasing this detector Kit from me,
I will also send you a 8.5" X 14" Printed Schematic,
as well as a 4" x 6" color Overlay Picture.
Email Me for the Current Prices.


This detector Features Either a Single Coil Metal Detector,
Or 2 possible Dual Coil Configurations! You Choose which you want.


*Click Here,   Pictures of My Metal Detector Project, Built by Others


*Click Here,    Some Comparison Test Results, by Dave in Australia

Warning: I Do Not Recommend this project for the "Beginner",
It definately Requires Good Soldering Skills and at least a basic working knowledge of electronics is Needed.

NOTE:  Before Testing the Completed Unit
Wash the board to Remove All Flux Residue.
IT WILL NOT WORK CORRECTLY IF YOU DON'T!
It is Also Recommended to use a Current Regulated Power Supply when first testing this unit.
(Less than 300 Ma. is quite satisfactory)

Excessive Current, generating heat, will Distroy the REG1117A.
Failing a Regulated Supply, a 60 Watt/110 volt
standard light bulb can be placed in series with the positive battery lead.
This should limit current to a reasonable level, preventing any damage to parts.

(Where only 220 volt bulbs are available, use a 150 watt bulb or two 75 watts in parallel works well.)

Good Soldering is a Must!

NOTE: It is Important to use a Good Soldering Iron, Rated at about 25 Watts and having a Small Clean Tip!

NOTE:  However, If you build this PI project and have problems, I will offer you as much assistance as possible in e-mails, Even to the extent of Free Repairs, Not Including Postage Charges, Assuming the actual Circuit board has Not been Damaged beyond Repair.


Note:
This metal Detector was Not designed to Detect Gold Nuggets.
It Will detect larger Gold Nuggets with a suitable coil. But if your expecting to detect Tiny Nuggets or Flakes of Gold, FORGET IT!


Additionally, The only metal that I have found that my metal detector will NOT DETECT is some Better Qualities of "Stainless Steel".

Here is a Much Appreciated explaination from one of my readers: Well the reason why you can't detect it is because the conductivity of Stainless is very low. This is true for all pulse induction metal detectors. Because of the low conductivity, the eddy currents have disipated by the time the pulse delay has ended and you begin to sample the signal. The lower the conductivity of the metal, the faster the eddy currents disipate. If I remember right the conductivity of copper is 100, the conductivity of stainless steel is about 1.3 or so. The conductivity of silver is 108 so its the best on range. Gold is in the 60 to 80 range depending on the alloy. The longer the pulse delay on your detector is, the less likely you will be able to pick up lower conductive metals. Hope this helps. Good luck, Charles A Note from me: Well I was aware of the Delay times, I didn't realize that stainless was so low in conductivity. Thanks Charles!


If You Have PROBLEMS when you build this Unit?
Don't Overlook Anything!

Here are Some Persons Problems
Click Here to read them

I will try to help you solve any problems, But its not always possible doing that with emails.


This unit is Extremely Stable, and features: Three possible Coil configurations, as listed here.

1)  First configuration is just a single coil. Best for most applications!

2)  Second is a dual coil, with noise and ground effects cancellation.

3)  Third is a dual coil, one for transmit and one for recieve.


Here is A Very Simple Coil that Will Work,
At least for testing purposes.

Here is a Pretty Good Coil,
and reasonably easy to make.
Decades ago this style of coil was used for AM Antennas in some Old Tube Type Radios.

My Recommended: "Optium Flat Coil Sizes". Depending on my current Stock, I may use a 20, 21 or 22 AWG Wire. And I can Supply these Flat Coils, Up to about 13 Inches OD:

For Really Small Objects: ID = 2.62 inches & OD = 6 inches with 52 turns. Coils wound on Ferrite Rods are also good.

For Medium Objects: ID = 5.8 inches & OD = 8 inches with 34 turns. The Best size coil for General Detecting & finding Coins.

For Larger Objects: ID = 8.2 inches & OD = 10 inches with 28 turns                ID = 10.4 inches & OD = 12 inches with 25 turns.

Or "YOU" can make even Larger Coils:                ID = 13.6 inches & OD = 15 inches with 21 turns.                ID = 39.2 inches & OD = 40 inches with 12 turns.

For Really Large Objects: A 48 inch Square Coil = 8 to 10 turns.

It would be Greatly Appreciated to recieve Feedback from ALL persons building this Detector. As of May 2010, Well over 2000 of this detector have been built, and From Replies recieved no one has been unsatisified with it.

I can supply this "Pizo Transducer" that works Excellent on this unit.

I can also Supply this 3.5mm, Stereo Headphone Jack.
It has a Built in Switch to turn off the Piezo, When the headset is plugged in.


I can Now Supply this "GOOD" Vu Meter

"If you Want a More Sensitive Meter, Make these Changes"


The Pots I supply have Aluminum Shafts. So they can be easily cut to a suitable length with a Hack Saw to fit these "New Knobs" I have acquired at a GOOD PRICE."


"Click on the Titles below to open them"
***********************************************************************

Facts about Gold and its detection.



I have some Coils for sale!

Calibration and Setup Procedures (Revised Mar 15 2010

Updated Coil Winding Info

"UPDATED"Some technical Info and coil pics, Revised April 5 2004

Additional Pictures and More Info
on my Pulse Induction Metal Detector.


A HELP File, if you have problems.

IMPORTANT NOTE

The only claims I will make as to the sensitivity of this Detector is: The one I made for myself does detect a Canadian Quarter (made of Nickel) at 10 Inches in Air and at 10 inches in the soil in my yard. Also an American Quarter (Zinc I Believe) at a distance of 10 inches in Air

Additionally, If built correctly: This Metal detector should detect a "Pop Can" at an "Absolute Minimum Distance" of 15 Inches. AND it could get to 25 Inches or More, depending on the Coil & Meter you use.

However there are too many Variables in Coil Construction, as well as materials, shapes, sizes and soil conditions to try to predict exactially what your detector will do under vaious conditions.

ADDITIONALLY, Remember This:

THE MOST IMPORTANT THING WITH ANY METAL DETECTOR, IS THE OPERATORS "ABILITIES", "SKILLS" AND "PATIENTS" in using it PROPERLY!

All Imformation in this Article is "Copyright protected".

Chemelec

*Copyright © 2002 & 2011*