METAL DETECTOR HELP easytreasure

[RECEIVER7]

I HAVE MINIMAL KNOWLEDGE HEARS THE SITE I GOT IT FROM
http://www.easytreasure.co.uk/bfo.htm

I CANT GET THIS TO WORK ANY ONE HAVE ANY HELP
NOTES OR POINTERS ASK ME WHAT YOU NEED TO KNOW

IT IS ALL ON A PROTO BREAD BORD I CHECK ALL THE PARTS ARE RIGHT ASK ME WHAT YOU NEED TO SHOW WERE I FAILED I MADE TWO COILS THE SAME TO TEST IT BUT NO CHEEPING IT WILL MAKE NOIES WHEN I PULG IN THE COILS BUT THEN STOPS

 

[DerStrom8]

I CANT GET THIS TO WORK ANY ONE HAVE ANY HELP
NOTES OR POINTERS ASK ME WHAT YOU NEED TO KNOW

You can start by not typing in all capital letters. It sounds like you're yelling and it gets very annoying. Please fix your capitalization.

 

[JimB]

I am sorry, but there is not much that I can say about that circuit which will be very encouraging to you.

The correct operation requires two oscillators to be running at (nearly) the same frequency.
There are no adjustments built in to the design to allow this to happen.
The frequency of the oscillators will depend very much on the actual values of the components, and the normal tolerance of the components will be about 5 to 10 percent, enough to set the oscillators so far apart in frequency that you will not hear them beating together.

The audio stages which feed the loudspeaker are a very good example of how NOT to design audio amplifiers.
The results you get will be very dependant on the exact characteristics of the transistors and the ambient temperature.

I visited the website which you give the link for, and saw how he was slagging off others for copying his design.
If I had designed this circuit, I would keep very quiet about it. Really!

JimB

 

[tvtech]

I also visited http://www.easytreasure.co.uk/bfo.htm today..

I agree that if I designed that....I would rather not talk about it...I learned stuff there though about how not to build a Metal Detector.

I have always wanted to build one though....a proper one...since I was a kid. I have had this thing in my head for years now when taking a walk along the beach with the dogs leashed to one hand and the light, sensitive MD in the other hand....

The MD starts screaming.....I stop. Show the dogs where to start digging....they dig and expose a Treasure Chest. Just a little dream, but a good one.

If you cannot dream if you have nothing to live for

I am going to build a proper Metal Detector at last. Based on a solid published design....if I can find it on the Web. I know Elektor from way back had some nice designs....years ago though.

To dream is good

Regards,
tvtech

 

[Nigel Goodwin]

I visited the website which you give the link for, and saw how he was slagging off others for copying his design.
If I had designed this circuit, I would keep very quiet about it. Really!

I agree, it's so bad as to not be a 'design' at all

 

[RECEIVER7]

i feel better and worse now its not all my fault thank you all for your comments

 

[chemelec]

Yes it is a CRAPPY CIRCUIT.

But you can TUNE the Frequency by Starting with Two Round Coils.
Than FLATTEN One or the Other Coil as needed. (NOT BOTH.)
Flattening a Round Coil to an OVAL SHAPE will change its Inductance and Frequency of Oscillation.

 

[tvtech]

Hi Gary

You are clued up on these matters. Care to give me pointers where I can find diagrams/built units that are up to the precision standards that are at the cutting edge today?

Like smart stuff that is worth building/buying? Not a learning tool. Proper up to date stuff

Regards,
tvtech

 

[Nigel Goodwin]

Proper up to date stuff

Buy one!!

 

[chemelec]

Hi Gary

You are clued up on these matters. Care to give me pointers where I can find diagrams/built units that are up to the precision standards that are at the cutting edge today?

Like smart stuff that is worth building/buying? Not a learning tool. Proper up to date stuff

Regards,
tvtech

Most CUTTING EDGE are Digital based VLF Detectors with Discrimination of varous Metals.
VERY Unlikely You Will find PLANS for those Units.

Discrimination can be useful, But Definatey not usually important.
Just because something is NOT GOLD or SILVER, Does Not mean it isn't VALUABLE.

But there are some Descent Pulse Induction Detectors, that are Quite Good.

I have some on my site!

 

[tvtech]

Buy one!!

LOL

Where???

Nigel....South Africa here.

Picture this...tvtech walks into store......

• Hello, I would like to buy a Metal Detector
• What sort of Metal Deflector Sir
• I said a METAL DETECTOR.
• What sort of Metal does it reflect Sir.....
• Metal..anything of Value..
• And so it goes on....

LOL. Ah well, it can only get better as the Years pass.

Stay well Guys,
tvtech

 

[4pyros]

I HAVE MINIMAL KNOWLEDGE HEARS THE SITE I GOT IT FROM
http://www.easytreasure.co.uk/bfo.htm

I CANT GET THIS TO WORK ANY ONE HAVE ANY HELP
NOTES OR POINTERS ASK ME WHAT YOU NEED TO KNOW

IT IS ALL ON A PROTO BREAD BORD I CHECK ALL THE PARTS ARE RIGHT ASK ME WHAT YOU NEED TO SHOW WERE I FAILED I MADE TWO COILS THE SAME TO TEST IT BUT NO CHEEPING IT WILL MAKE NOIES WHEN I PULG IN THE COILS BUT THEN STOPS

Unless you have a lot of time on your hands and free parts you would be better off buying one from the toy isle at Walmart.

 

[RECEIVER7]

were with a frequency, conter would i take measurements

 

[alec_t]

Measure at the transistor bases.

 

[chemelec]

were with a frequency, conter would i take measurements

I Don't think that circuit will work.
It does not look like Q1 and Q2 are properly Biased.

What Transistors are you using for Q1 and Q2?
I'll Prototype it up later today and see if it works.

 

[audioguru]

When a common-emitter transistor (like the two transistors with the coils) has its base DC shorted to its collector (by the coil) then the transistor does almost nothing.

 

[chemelec]

When a common-emitter transistor (like the two transistors with the coils) has its base DC shorted to its collector (by the coil) then the transistor does almost nothing.

Yes I think the Coil should go between Supply and Collector.
And one of those .1 Caps should be .01.

 

[alec_t]

I Don't think that circuit will work.

LTspice thinks it will (assuming ~ 100uH coils), but it would be interesting if you could confirm with a breadboarded version.

When a common-emitter transistor (like the two transistors with the coils) has its base DC shorted to its collector (by the coil) then the transistor does almost nothing.

LTspice agrees. Oscillation does occur in the sim, but amplitude is only ~0.7V.

 

[chemelec]

Just because LTspice shows it works, Does NOT mean that it does.

I gave upon Simulation programs years ago.

I found too many circuits simulate as working but don't.
And some circuit that do work, but won't simulate as working.

 

[chemelec]

This Circuit WILL WORK.
Tested in real Life.