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.

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.)

I Repeat, Good Soldering is a Must!

However, If you build this 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 and Possibly subject to replacement parts cost. (No parts charges
will be made, without prior confirmation from that person, and most I haven't even
charged for the parts.)

NOTE: It is Important to use a Good Soldering Iron, Rated at 15 to 25 Watts
and having a Small Clean Tip!

Note also the Revision Dates on All My Articles.
Always check for changes, I update most articles quite regularly.



Note: This metal Detector was Not specifically designed
to Detect Gold Nuggets.



Additionally, The only metal that I have found that my metal detector will
NOT DETECT is some Better Qualities of "Stainless Steel". I Didn't know why!

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!

Some Guys Problems
 Click Here to read them


**This project is offered totally Free for those who are interested in it.
I have tried to make this article as complete as possible, but I will Not
assume any liability for any "Errors or Omissions" in this article.

If Needed, I will attempt to help you as much as possible with any problems.
However I have no control of your abilities or skills, so build it totally
at your own risk!

This unit is Extremely Stable, and features three possible configurations
with the coils, as listed below.

I can supply a small Pizo Transducer that works Excellent well on this unit.


The 3 possible coil Configurations are:

1) First configuration is just a single coil. Good 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.
Its Best to use this size coil for 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.


**A Convential Kit of parts Is Available if you want it.

Other than the PCB and coils, most parts are supplied at my Landed Cost.

Click Here for Detector Prices



It would be Greatly Appreciated to recieve Feedback
from ALL persons building this Detector. Reguardless weither you purchase
the Circuit board from me or not! As of May 2003, Well over 200 units have been
built with boards from me, and From Replies recieved none have been
unsatisified with it. I am also aware of a few who have built this
detector using boards they made themselves.

"Want a More Sensitive Meter, Do This"

These values are for a 200 uA Meter, but if you double the two resistor values for a 100 Ua
meter or Quadruple these values for a 50 Ua meter, this should also work fine.



Latest Update: Feb 23 2007




I can Now Supply this Vu Meter
These Meters are Rated at 100 uA at the -3 Db and about 240 uA at the + 3Db.
Reasonably Priced at $8.00 each.




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

Facts about Gold and its detection.





I now have some Coils for sale!
 


A Very Detailed Picture Overlay of the Assembled PCB.
This should print OK, horizontally on a 8.5 x 14 paper.
NOTE: On the Newest Circuit Board, R32 is above the IC, Not beside it as shown here.


A Large Printable Schematic.
Corrections & Re-Drawn Dec 2009, Clearer and with considerable more Info.

Printed Circuit Board

Calibration and Setup Procedures (Revised July 01 2003

Parts List (Revised Mar 6 2006)

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 unit is:
The one I made for myself does detect a Canadian Quarter (made of
Nickel) and also an American Quarter at a distance of 12 inches in free air
and at a good 10 inches in the soil in my yard.

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

However there are too many Variables in Coil Construction, as well as
materials, shapes, sizes and soil conditions to try to predict exactially
what other units 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 & 2009*