TESORO GOLDEN SABRE

[Max]

I hope you try it so we can learn how you do it.

Maybe I would try this: I think I would first make RX coil and fasten it down.

Then get a long piece of wire for the TX coil, bucking coil and another 20% extra wire and wind all the wire on special spools back and forth (not in coil) so the spooled wire has approx zero inductance. When you pull the wire off the spool, each "loop" has zero inductance and will not change inductance of spool (zero).

Pull off about 10% of wire off spool and wind on another "extra spool" which also has zero inductance. This is for adjusting the TX coil later.

From the main spool, start taking wire and winding the TX coil.

If you have a calculation for the bare TX coil inductance (without the bucking coil, should be greater than 5.8 mH because you will subtract bucking coil later), do your best to wind it, checking inductance with meter as you go (connect meter to ends of the spooled wire).

After you finish preliminary TX coil, hook up a signal generator to the spooled wire ends and an oscilloscope to the RX coil.

Now continue taking wire off the main spool and winding the bucking coil. Wind the bucking coil until the RX signal on the oscilloscope hits a minimum (nulled).

Now remove the signal generator from the spooled wire and check the total inductance of the TX and bucking coil with a meter. If the inductance is too low, you need to start adding windings to the TX coil. You do this from the "extra spool". Of course you will spoil the null of the RX coil, so you will need to add some windings to the bucking coil too (from the main spool). You'll have to go back and forth until you get the correct TX + bucking coil inductance (about 5.8 mH), and also the RX signal is nulled.

Then you can cut the wire off the spool, but leave about 2 to 3 meters on each end for final adjustments in case the spools were not zero inductance.

Whew, a lot of work!

Maybe there is a better way, that's my thought.

Cheers,

-SB

Hi,
I didn't know you're an artist!

Anyway... in these cases is better having an hand drawing than nothing... to understand what's going on...

Kind regards,
Max

[simonbaker]

Hi,
I didn't know you're an artist!

Anyway... in these cases is better having an hand drawing than nothing... to understand what's going on...

Kind regards,
Max

Ha ha ha! You noticed! (The diagram can also be used to show how protozoa mate...)

In fact, you shamed me so much that I now have an excuse to post some photos of paintings I did years ago to show the fledgling origins of my unique style...!

P.S. I have not actually tried the "zero inductance spool" idea yet, but I'm intrigued by the idea.

Cheers!

-SB

[Qiaozhi]

I hope you try it so we can learn how you do it.

Maybe I would try this: I think I would first make RX coil and fasten it down.

Then get a long piece of wire for the TX coil, bucking coil and another 20% extra wire and wind all the wire on special spools back and forth (not in coil) so the spooled wire has approx zero inductance. When you pull the wire off the spool, each "loop" has zero inductance and will not change inductance of spool (zero).

Pull off about 10% of wire off spool and wind on another "extra spool" which also has zero inductance. This is for adjusting the TX coil later.

From the main spool, start taking wire and winding the TX coil.

If you have a calculation for the bare TX coil inductance (without the bucking coil, should be greater than 5.8 mH because you will subtract bucking coil later), do your best to wind it, checking inductance with meter as you go (connect meter to ends of the spooled wire).

After you finish preliminary TX coil, hook up a signal generator to the spooled wire ends and an oscilloscope to the RX coil.

Now continue taking wire off the main spool and winding the bucking coil. Wind the bucking coil until the RX signal on the oscilloscope hits a minimum (nulled).

Now remove the signal generator from the spooled wire and check the total inductance of the TX and bucking coil with a meter. If the inductance is too low, you need to start adding windings to the TX coil. You do this from the "extra spool". Of course you will spoil the null of the RX coil, so you will need to add some windings to the bucking coil too (from the main spool). You'll have to go back and forth until you get the correct TX + bucking coil inductance (about 5.8 mH), and also the RX signal is nulled.

Then you can cut the wire off the spool, but leave about 2 to 3 meters on each end for final adjustments in case the spools were not zero inductance.

Whew, a lot of work!

Maybe there is a better way, that's my thought.

Cheers,

-SB

Now you can see what I meant when I said "Good Luck!".
Even after all that you still need to make physical adjustments to get the correct initial phase-shift between TX and RX.

[ivconic]

I never tried to make c.c. coil for TGS, mostly due faraday shield issues. Since i am using Al foil only, it would be very difficult to apply it and than after to adjust balance. If i had conditions to use graphite spray instead Al foil, than c.c. would be easier to make. This also requires quite different coil enclosures, suitable for this kind of setup.
Yet, once i made omega coil, just for experiment. It is easy to be made and it is working just fine. Can't beat DD coil on depths, but remained with pretty good performances and much better for pinpointing than DD.
Usual method to null C.C. coil is to leave some extra 50-60cm wire loop at the end of canceling coil and than to null by reducing it size and moving loop to find best spot.
I think; making c.c. coil for TGS must be a bit easier than making c.c. coil for ...let's say Classic. Why? Because of step up relation mostly.
At TGS coils there is no any step up, coils are almost identical and proper off resonance relation is achieved mainly with capacitors. So i presume; must be easier to adjust and null that kind of c.c. coil. Maybe i am wrong, i am not sure.
One thing i am sure; handmade DD coil works much better than original c.c. coil. Of course there are size differences, among other things.

Simonbaker...those are really nice paintings!

[simonbaker]

Thanks for your kind tolerance...

[Mullihaka]

Unwanted oscillation

I have now powered my TGS first time. It screams me welcome, so it works partially. The negative voltage is present at -5.9V.

The half of a LM358 indicated with an red arrow was hot and the device took 130mA. The amp oscillates at 700kHz, 400mVpp, present at pins 1 and 2. The other half is quiet. The transmitter oscilaltor runs on 14.3 kHz.

I have checked all components inside the thin red line and they seem to be OK. Then I desoldered the IC socket of the LM358, cleaned the resin remains and soldered the IC back without the socket. Funny: the current consumption was halved to 60mA, but the oscillation stays. The IC is still a bit warm, but not hot.

The copper side of the PWB has been cleaned from the resin, but the component side has it to some extent; between the components and the surface of the PWB.

Does this phenomenon ring a bell with some of you ie how to continue? The simplest solution would be to desolder everything and clean the PWB, but I'd like to avoid that.

I have never before had any problems with the resin, so I don't believe it could be a problem here. The gains in the device are not so big that it would play any role. Objections?

All hints appreciated,

Andy

[Max]

Ha ha ha! You noticed! (The diagram can also be used to show how protozoa mate...)

In fact, you shamed me so much that I now have an excuse to post some photos of paintings I did years ago to show the fledgling origins of my unique style...!

P.S. I have not actually tried the "zero inductance spool" idea yet, but I'm intrigued by the idea.

Cheers!

-SB

Hi,
so I wasn't mistaken there... good things I see !

BTW the CC coil setup is really critical to adj even on tgs... as you noticed too. The fact is, though there's no step-up or harmonic tuning to find, the phasing and nulling are complicated by such fixed design... where coils don't move but you have to use trick to find the good tuning.

I the best s trying untill a correct method will be elaborated... so far I never saw any detailed description around about that... just simple works that describe e.g. the turns ratio for nulling... but phase issue is much more complicate than a simple calculation of turns... all we know that I think.

The fact is... that I think e.g. Tesoro will actually move internal coil a bit... e.g. in spider coils cause that way is easier than having the troubles described... then it's just a little movement so don't compromise the e.g. detection "bubble" they say...

Kind regards,
Max

[simonbaker]

I have now powered my TGS first time. It screams me welcome, so it works partially. The negative voltage is present at -5.9V.

The half of a LM358 indicated with an red arrow was hot and the device took 130mA. The amp oscillates at 700kHz, 400mVpp, present at pins 1 and 2. The other half is quiet. The transmitter oscilaltor runs on 14.3 kHz.

I have checked all components inside the thin red line and they seem to be OK. Then I desoldered the IC socket of the LM358, cleaned the resin remains and soldered the IC back without the socket. Funny: the current consumption was halved to 60mA, but the oscillation stays. The IC is still a bit warm, but not hot.

The copper side of the PWB has been cleaned from the resin, but the component side has it to some extent; between the components and the surface of the PWB.

Does this phenomenon ring a bell with some of you ie how to continue? The simplest solution would be to desolder everything and clean the PWB, but I'd like to avoid that.

I have never before had any problems with the resin, so I don't believe it could be a problem here. The gains in the device are not so big that it would play any role. Objections?

All hints appreciated,

Andy

As a quick check I would replace the op amp and see if same behavior. If so, we can focus on circuit. I have not seen anyone report similar problem.

What are you using for the bipolar 4.7 uF capacitor? Maybe that is problem if defective or not bipolar.

Cheers,

-SB

[Max]

I have now powered my TGS first time. It screams me welcome, so it works partially. The negative voltage is present at -5.9V.

The half of a LM358 indicated with an red arrow was hot and the device took 130mA. The amp oscillates at 700kHz, 400mVpp, present at pins 1 and 2. The other half is quiet. The transmitter oscilaltor runs on 14.3 kHz.

I have checked all components inside the thin red line and they seem to be OK. Then I desoldered the IC socket of the LM358, cleaned the resin remains and soldered the IC back without the socket. Funny: the current consumption was halved to 60mA, but the oscillation stays. The IC is still a bit warm, but not hot.

The copper side of the PWB has been cleaned from the resin, but the component side has it to some extent; between the components and the surface of the PWB.

Does this phenomenon ring a bell with some of you ie how to continue? The simplest solution would be to desolder everything and clean the PWB, but I'd like to avoid that.

I have never before had any problems with the resin, so I don't believe it could be a problem here. The gains in the device are not so big that it would play any role. Objections?

All hints appreciated,

Andy

Hi Andy,
seems you have a little problem there : the 700Khz you read are probably from self oscillations at that op amp.

The fact you read 130mA consumption is not so good... I think you've it damaged already.

My suggestion is , apart cleaning very well pcb as you can, desolder it... then remount the socket; try to add 100nF caps just under the ic socket at power rails and other lead to gnd.

That way you'll probably solve that, but have to use a brand new ic.

Other things that could be involved are pcb tracks... too near can be a problem and sometimes op amps use special ring guards for that at inputs (yes, the amplification factor plays a major role in that but not only)... but if you used any of the pcb designs here you'll probably need just that filtering at power rails.

Kind regards,
Max

[metaldetector107]

crack

Sir Max Ivco Quzi and all
please help my device works ok TX freq is 14.7.
RX6.5mh TX6mh after sheilding which is exactly what Ivconic
said so the only problem now i have
just very very little movement the device gives signal
i have tried many many ways like nulling from 0mv to 40mv
nothing happned the stand is plastic tube the coil very stiff
and what else
please help..........
Max by the way when i read your responce to Simon about his drwing
10minutes laughing
thanks all

[simonbaker]

Sir Max Ivco Quzi and all
please help my device works ok TX freq is 14.7.
RX6.5mh TX6mh after sheilding which is exactly what Ivconic
said so the only problem now i have
just very very little movement the device gives signal
i have tried many many ways like nulling from 0mv to 40mv
nothing happned the stand is plastic tube the coil very stiff
and what else
please help..........
Max by the way when i read your responce to Simon about his drwing
10minutes laughing
thanks all

Hi 107 - I try to entertain...

If you turn the sensitivity control to decrease the sensitivity, is there a point where the movement does not give a signal?

Can you take some photos of your metal detector and show us what each part looks like?

Cheers,

-SB

[Max]

Sir Max Ivco Quzi and all
please help my device works ok TX freq is 14.7.
RX6.5mh TX6mh after sheilding which is exactly what Ivconic
said so the only problem now i have
just very very little movement the device gives signal
i have tried many many ways like nulling from 0mv to 40mv
nothing happned the stand is plastic tube the coil very stiff
and what else
please help..........
Max by the way when i read your responce to Simon about his drwing
10minutes laughing
thanks all

Hi,
nice that you enjoy little humor there... just was lloking at that mess of wires... and had the illumination... that simon is an artist...

Now, coming back to the problem... if pole is stiff... and all very solid contruction... could be some wire also.

When you move the md there are long wires e.g. in the control box that move ?
Sometimes happens that long wires move inside control box and you get a false signal.

Other things I could not imagine... if anything is fixed properly and no vibrations of e.g. metal parts near coils there wouldn't be any false signal due to movements only.

Anyway, if the problem is just when you move it it's probably something mechanically related... the movement make something move and you get the signal.

Otherwise could be electrostatic issue also... but you used a metallic box for circuit right ? Have you connected the metal of control box to gnd (be really careful you don't make short circuits e.g. with sockets connections when try that) ? If you mantain box potential all the same at gnd level your control box will act as a faraday cage for circuit... thus removing any electrostatic related trouble at pcb.

Kind regards,
Max

[simonbaker]

Hi,
so I wasn't mistaken there... good things I see !

BTW the CC coil setup is really critical to adj even on tgs... as you noticed too. The fact is, though there's no step-up or harmonic tuning to find, the phasing and nulling are complicated by such fixed design... where coils don't move but you have to use trick to find the good tuning.

I the best s trying untill a correct method will be elaborated... so far I never saw any detailed description around about that... just simple works that describe e.g. the turns ratio for nulling... but phase issue is much more complicate than a simple calculation of turns... all we know that I think.

The fact is... that I think e.g. Tesoro will actually move internal coil a bit... e.g. in spider coils cause that way is easier than having the troubles described... then it's just a little movement so don't compromise the e.g. detection "bubble" they say...

Kind regards,
Max

Yes, easier for Tesoro, they can afford much wire to play with and get it right finally. Then maybe extra single loop adjustment will do it - we have seen that on xray pictures. Certainly not recommended for first-time builders though.

Cheers!

-SB

[Max]

Hi 107 - I try to entertain...

If you turn the sensitivity control to decrease the sensitivity, is there a point where the movement does not give a signal?

Can you take some photos of your metal detector and show us what each part looks like?

Cheers,

-SB

Hi,
that's not a solution !

Never decrease that sensitivity.... work always at 110% like russian reactors!

Returning serious...

Decreasing sensitivity is good when e.g. on soil... one have too much troubles at max sens then reduce... it.

But if device is quiet then you move it and sounds.... there's something wrong I think.

I think he has a mistake on either mechanical stability of the assembly... or electrostatic related "ghost" (means that pcb reads some static and thus give a false signal... if box is not at a potential like in the circuit... it will not act as faraday cage... but like the plate of a capacitor!)

Kind regards,
Max

[ivconic]

Sir Max Ivco Quzi and all
please help my device works ok TX freq is 14.7.
RX6.5mh TX6mh after sheilding which is exactly what Ivconic
said so the only problem now i have
just very very little movement the device gives signal
i have tried many many ways like nulling from 0mv to 40mv
nothing happned the stand is plastic tube the coil very stiff
and what else
please help..........
Max by the way when i read your responce to Simon about his drwing
10minutes laughing
thanks all

Don't "sir" me! "Sir" on my language means cheese!!!

For example... Cheese Alec Guinness!!! Or...Cheese John Cleese.....Booooahahahahaha!

Ok...let's try to solve your problem, right?
The way you described your problem; looks like you made wrong wirements in coil, at cable ends and possibly at pcb.
Look back at TGS thread, somewhere on some page i posted sketches of one and only proper wirements.
Also pay attention on cable you using to connect coil with device. MUST be proper cable. Also already explained well.
Dont be lazy, search back the pages. You have all already explained very well.
Next; if PROPER cable wired as posted - PROPERLY, than you will be able to adjust phase with GEB trimmer and achieve perfect stabillity on cable movements, choking,twisting etc...etc... same as with search head. Adjust GEB trimmer at the very precise end on ferrite rod rejection (to hear just small cracks on it) and voila; you adjusted all other things also. If you can not achieve this than i am 100% sure you wired up wrongly cable-coil-pcb..
Cheers!