Building a metal detector

[pgill]

Hi everyone,

I have been searching the web for a circuit diagram to build a metal detector, as the ones in this country (South Africa) are very expensive.
I have diagrams for the BFO type and 1 for a impulse type detector. What way are the professional ones made?

Can anybody help me with a diagram for a good detector that works?

I have a kit made detector (TR 330 Cscope, British made) I buried a couple of coins about 50mm deep, and this machine never made a noise, put the coin on the ground and lift the detector above the coin and it reads at about 100mm. So I have figured out that I am waisting my time with this machine.

I need help badly.

Regards,
Peter Gill (South Africa)

 

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[pgill]

Hi Vito,
Thanks for the reply, this Cscope has a plastic sealed head on it. The machine has a off / Vol knob and a knob for sensitivity, and a reset button. I think it is a BFO type but not sure. It is a very clumsy machine in regards to setting it. I will open it up and see what I can see as far as electrics goes. I have done electronics a while back, but a bit rusty now.

Thanks again,
Peter.

 

[Bigcypresshunter]

You must have a BFO type... I think 100mm is 4 inches...The inexpensive detectors will not go very deep. You can still use it. Make sure you always have fresh batteries. A weak battery will loose depth. Learn to use your unit..I set mine with a barely audible constant tone, and I have to keep checking it... Use headphones...The deep coins will be hard to hear...And you will have to put the coil on the ground in the dirt. If you try to search with the coil above the ground, you will loose valuable inches (or mms).... I think I also need a new unit. I am using an old White,s that on land will only pick up 5" deep...

 

[pgill]

Hi Bigcypresshunter,

Thanks for your mail,,,, and yes I totally agree with you on the type of machine I have. I have been searching the net, and Vito has given me an address for some diagrams to maybe look into making a decent machine. Still not 100% sure what type is the best type to build... But I will carry on studying the subject till I get it right.

God bless and thanks again for the tips.
Peter

 

[Carl-NC]

Can anybody help me with a diagram for a good detector that works?

Peter,

Check out my Geotech site at www.thunting.com/geotech. It mainly focuses on detector designs & projects. Also a tech forum for getting help.

- Carl

 

[capela]

This is the one i?ve built from Carl?s PI design, but with some mods comparing to the original design, man.....this is a deep machine for beach hunting and is tuned for yellow goodies (specially rings) !

http://forum.treasurenet.com/index.php/topic,14330.0.html

Capela

 

[Carl-NC]

Hi Carl!

Have U tried the link in my post above??

Duhhh... completely missed it! :P

 

[pgill]

Hi Guys,

Thank you all for the replies and the site and schematics info.... I have downloaded a fair amount of circuits now and must no look at the availability of the components as well as cost.
I can get a "Musketeer 10" detector for R2587 which is a lot of money in this country.... Does anyone have any info on this machine? is it worthwhile getting?

Thanks again for all the help,
God Bless
Peter

 

[Darren in NC]

Peter - there's always ebay

 

[pgill]

Thanks Darren,
Great idea, never been on e-bay before

Peter

 

[Darren in NC]

Peter, maybe I shouldn't have assumed you knew what ebay was. It's like a giant online yard sale. You can find inexpensive metal detectors there...and expensive ones, too. Ebay is easy to register for. You can type in "metal detector" in the search box and look all day at different ones. I recommend checking out the Bounty Hunter brand to start out with. For about $50-100, you can get a decent metal detector. Perhaps I should ask why you want one, before I recommend any detector. What do you plan to do? Coin huinting? Relics? Deep caches?

On ebay, each page will have a seller's user ID with a number in parenthesis next to it. That number is their feedback score. It's kinda like a credit rating. If you click on it, you can find out if they have mostly positive feedback or negative. Obviously, you want to buy a detector from someone you can trust to ship it to you, so you'll want someone with high positive feedback.

It costs nothing to look, so spend some time checking it out. Of course, if you were looking forward to building your own, ignore everything I just said

 

[pgill]

Hi Darren,

Thank you once again I went onto ebay.... wow quite daunting.....

I am wanting to look for anything but will be mostly coins, jewlery and maybe Boer war finds. I am new to this hobby, and it looks like it is not popular here as I cannot find any clubs etc. There was a treasure hunters club once, but seems to have vanished as all the contact addresses and numbers no longer work.
I got some diagrams of detectors, but must go and look for the parts to build one.... I did not realise they were so complex
Funny I have also been looking around for software for the treasure hunter and have found very little, so am now putting together a database program for finds etc....

It is very frustrating living in a country where it is difficult to get anything from another country due to exchange rates etc. The bug has bitten me, but I cannot do anything except read your guys mail Anyway, I must just keep on working on it.

Thanks again,
Peter

 

[JakePhelps]

Sorry to hear about the lack of interest in this hobby where you are But hey, look on the bright side, less hunted-out places
I would think you are better off buying one than building a detector, especially with some of the great technologies at offordable prices Ebay has some decent used and also new detectors but i would have someone who knows ebay real good take a look before you buy it, maybe one of us here could find you a deal I bet alot of people here would be interested in your software for treasure hunting, your right there isnt many programs available who knows, maybe you could make enough money for a detector by selling your software

 

[pgill]

Hi Jake,

Thanks for the great words.... I will get the help when I go to buy, especially if I get on ebay. Umm well I am about 1/2 way in putting together the database I was talking about. I have put in the fields I think will be of help, including a place for a picture for each item added to the database. I have also added a address book for your MD buddies info, and a place to note future sites. I still have to add the reports side of the program, but I think it is looking pretty good. To sell the program that could be one way to get the detector, but hey doing the database is another way of sharing knowledge not that I have any when it comes to detecting.
I have a couple of great places to search when I do get a detector though. We have some knocked down houses that belonged to the railways which are about 60 years old. There is a place which was a stage coach stop. And an old Fort from the Boer war, that held Ghandi prisoner. Umm cannot wait to get that machine.

Well thanks again and God bless you all.
Peter

 

[JakePhelps]

Wish you luck in your quest to get a detector and make some great software or freeware

 

[Deepseeker 1]

A BFO metal detector circuit kit that looks promising

I thought I would post this information as I am progressively building this kit as we speak. The diagram can be found in the Encyclopedia of Electronic Circuits Volume One. Page 408. It's called "Micropower metal detector". The reason I am building it is that the circuit looks like it can function well and have respectable depth. Why I feel it will give you good depth and perform well is ;the coil has 140 turns of 18 AWG magnet wire, that it will operate from 3 to 18 volts, and the heart of and most of the electronics is in one 4030 I.C. chip. I feel that this may be one of the better BFO circuits that you can build and with an operating range from 3 to 18 volts gives you an incredible power range! It is wired to be basically a dual oscillator circuit all from one chip. As an electronic tech myself... I would suggest to wind the coil and pott it, or encapsulate it as so the coil windings don't wiggle at all.(I'm dipping mine multiple times in polyurethane to do this). The only part that is odd to find is the 10 mH tunable coil...this you can possibly get(which I DON'T have yet!!) is from a vintage radio, or website that sells vintage radio parts. The chip can be very cheaply purchased on-line from Mouser, or Digikey catalog(which is free). I believe the chip is about $.25 ...my suggestion when building this device...it can be very repairable if you put a socket under the chip...in case of a burnout...pop it out and put a new one in!!! For the cable to connect the electronics to the coil you could experiment...try using thrown out video, or cable TV wire(for the shielding) or even RCA type video connection cable. The diagram has no patents,... so it's free domain...the book tells you to build it with no copyright names attached to it! The comments on the circuit toward the end kinda' tells me of it's performance as it states "The sensitivity of this device is good enough to detect coin type objects typically about a foot away". This tells me that with voltages up to 18V the coil must have a significantly large magnetic field...this should give good depth! I can't see why this kit would cost more than 20 or 30 dollars for parts...the most expensive would be buying (new) 18 AWG wire (140 turns) and the tunable (most likely air fin plate) capacitor from a radio parts outlet. My calculations on how much length of wire you will need(continuous) would be; 6 inch diameter coil times pi, equals the length of one wrap(or turn) equaling 18.849 inches, times 140 wraps(or Turns) equaling 2638.9378 inches....which boils down to exactly 219.114 feet total ...which you want to allow for a little extra for the diameter building up on the other windings as your coil is being wrapped. Sooo if you are electronically inclined, give this little kit a try...I love building stuff like this , please let me know how your circuit comes out,and if you have any suggestions; I'm "Deepseeker 1" ...I'm new to Treasurenet but have been a metal detector buff for several years. Love to hear your comments! ...HAPPY DIRTFISHIN' !

 

[pgill]

Deepseeker 1, thanks for the reply to this topic..... wow I never thought I would get any more replies on this one as it was posted in October 2005
I do have a "TR 330 Cscope, British made" which is basically what you have explained, but find that as soon as an item is beneath the ground, it battles to pick up. While on top of the ground, it picks up fantastic. As you know, the type you are talking about is a BFO circuit, and with experimants of these circuits I have found that any obsticle that gets in the way of the signal, i.e. ground..... shifts the phase of the circuit and out tunes it. If you are using this type of circuit above ground for some sort of detector in a shop etc, it would work great....... a person who walks through a entrance and gets scanned by the detector to see if he has any sort of metal on him, it would pick up fantastically because there is no interference in the BFO phases of the coil, it would also pick up a big distance.
I do believe that you will find similar sort of results with your when when you have built it. Am I saying do not build it No, because it is a great lesson to learn on the basics of detector building and how they operate. In fact it would be great to build and then keep modifying it till you have built something great.....
I do have a number of these circuits diagrams for the BFO, but just did not bother with it due to that reason...... In my earlier days, I built tons of similar stuff when I was heavily in electronics.

Since my post of this topic, I now have gotten a Tesoro Silver Sabre II which is a very nice detector, and am enjoying the hobby very much. If you look at the topics on this site, you will see the stuff that I have been finding, including a Kruger gold pound coin

I wish you all the luck on your building of a great detecor and would love to see the pictures of the finished product. Please keep me informed on what you find also I would love to be the first one to congratulate you on you first find with a homemade detector

Thanks again for replying, and God bless you.
Peter

 

[goldencoin]

I built one for a school project once, it only went about 2 inches deep for coins. http://forum.treasurenet.com/index.php/topic,161298.0.html

Good luck building you own!

HH
-GC

 

[pgill]

Thanks guys for the input....... mts, I am not sure about that size coil on a bfo detector, that does seem pretty large, but what about an array of coils? that would be more accurate and more sensitive, so you will not miss a thing...... I am not sure how you would go about joining them into the circuit though, that you would need to try and find out by making a detector. The other factor is which coil picked up the object? You would need a way of telling which coil set the detector off. You could place a LED on each coil circuit that will latch in and glow when set off, then you will just need to reset that LED again ready for the search to carry on.
I also do not think you can have discrimination on a bfo detector, in fact definately not as the the way the bfo's work just would not allow this.
I must admit, I do like your suggestion though, with a detector like that you could just go around concerts the next day etc finding all the goodies before anyone else can. I think you could maybe if done properley make a small living out of it

Get building and keep us informed, would love to see a picture of the final product..... sounds like fun.

God bless
Peter

 

[pgill]

Thanks mts, wow this all sounds like great fun to me

You can post here as much as you like as you are not stealing this post at all, in fract you are just adding a better agle to it.

God bless
Peter