TESORO GOLDEN SABRE

[ivconic]

How do you get such high voltage from 8V supply? Must be very resonant, but then would not be square wave, would be quite sine wave.

Something is not clear about this.

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I tried simulating the oscillator with LTSpice -- cannot get oscillation so far. Strangely, if I disconnect base of BC547, I get small oscillation, under 1 volt. Are the values correct?
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Correction: I had wrong inductance. It oscillates, very jagged as you said. Very strange, will require some analysis.

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I think it is working like ignition spark coil with those values....

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Regards,

-SB

Yes strange and interesting. Signal shape is almost a sinus, but not exact sinus. I will take a shot and post here later.

More i think, more assured i am; that problem is in unapropriate relation at LC tank. Some parasitic sideffects occurs there. Is not that theoretically this can not work, but in practice it can not work good due tolerances and quality of material used. To void problems in future it is better to redesign it and adjust optimal values which will work in a "middle" of range, calm and without sideffects, even if components are not 100% right. Should rise C and lower L. But it will need me to make another coil. I used one already finished and adapted for TGSL. Wouldnt be a problem to make another coil.

Damn i never analyzed circuitry of some newer Tesoro. Is there any chance somebody to post here just TX part of some new Tesoro? Cibola, Vaquero,Tejon or simillar? Just TX part...
(Dang!!!)

[ivconic]

But you need to remember that a doubling in depth requires a 64x increase in TX power. So even doubling TX power doesn't give a good return for your investment.

Nooooo! I am not trying to double the depth. I just want to rise power a bit. TGSL as it is, is already pretty descent on coins. I am doing this experiments to see if there is any closer TX power influence on rest of detector, esspecially on audio behavior.

[ivconic]

Sorry...


made a mistake in last post: if run osc at 24V you'll get around 48V at output tx... the double.

So ...an easy solution is adding a new regulator LDO to the 8V one: this last will produce 12V from e.g. unregulated gel battery output (12.7 at full charge as explained).

The LDO must be 0.3V kind or less.

Then the 12V rail you'll use with oscillator only.

The battery will last several hours if e.g. 2Ah cause TGSL need few current, till reach the LDO minimal operating voltage and so some signaling of battery "discharge" will be employed...

Kind regards,
Max

Actually i use DC 10v ps to run it.
LC tank 10nF+5.8mH. Transistors are BC327 and BC547.

[simonbaker]

No i didnt wanted 45Vpp, i just mentioned that range is 10-45Vpp when turning trimmer from one end to another.
20-25Vpp is real goal at TGSL. Need to be checked.

How do you get such high voltage from 8V supply? Must be very resonant, but then would not be square wave, would be quite sine wave.

Something is not clear about this.

-----------------------------------------

I tried simulating the oscillator with LTSpice -- cannot get oscillation so far. Strangely, if I disconnect base of BC547, I get small oscillation, under 1 volt. Are the values correct?
----------------------------------------------------------------

Correction: I had wrong inductance. It oscillates, very jagged as you said. Very strange, will require some analysis.

--------------------------------------------------------------

I think it is working like ignition spark coil with those values....

--------------------------------------------------------------------------



Regards,

-SB

[metaldetector107]

TGSL

Dear Ivconic
could you please tell me how do i connect Mono mode for yourTGSL1265 last.zip
actually i am happy with the resault but i need more depth.
i have searched all posts but i couldn't find it
please help

best regards

[Qiaozhi]

But you need to remember that a doubling in depth requires a 64x increase in TX power. So even doubling TX power doesn't give a good return for your investment.

[Max]

Sorry...


made a mistake in last post: if run osc at 24V you'll get around 48V at output tx... the double.

So ...an easy solution is adding a new regulator LDO to the 8V one: this last will produce 12V from e.g. unregulated gel battery output (12.7 at full charge as explained).

The LDO must be 0.3V kind or less.

Then the 12V rail you'll use with oscillator only.

The battery will last several hours if e.g. 2Ah cause TGSL need few current, till reach the LDO minimal operating voltage and so some signaling of battery "discharge" will be employed...

Kind regards,
Max

[Max]

No i didnt wanted 45Vpp, i just mentioned that range is 10-45Vpp when turning trimmer from one end to another.
20-25Vpp is real goal at TGSL. Need to be checked.

Hi,
if that's the goal it's simple I think.
Need extra voltage at supply rail for oscillator... in the 20-25V range.

We have alreay 8v regulated... but also (usually) a 12v battery or more...

A simple switching SMPS can convert the 12V in 24V very easy... but will introduce some noise also. But you can shield whole SMPS section in a metallic box... then filter output rail to catch residues of hi-frequency commutations... and have a short parassite turn on transformer... that will absorb much magnetic energy from there.

I think is possible this way getting 24-25V but also more, if needed.

A 78s40 will do that simply.

Then simply change some oscillator component and you'll run at higher voltage but pure sinus.

PS... if don't wanna mess with SMPS use two batteries 12v in series... and get 24V then... use also a low dropout stuff and you'll run easy at around 24V with just 24.3 or more at input from batteries...

A charged gel battery gives usually 12.7v at full charge and just 11.95 at full discarge... so... you'll run at start with 25.4V to get 24V, not bad. Then could run good till 50% of charge... and considering consumption is low , e.g. 2Ah can last hours and hours.

Kind regards,
Max

[ivconic]

No i didnt wanted 45Vpp, i just mentioned that range is 10-45Vpp when turning trimmer from one end to another.
20-25Vpp is real goal at TGSL. Need to be checked.

[Max]

Ok, i was looking the way to gain more power. TGSL's oscillator as it is, is weak. So i made small experiment on perfborad. I took oscillator from Classic III (or Caesar - "Serbian most wanted") and connected TGSL 5.8mH TX coil to it. Not good, frequency was about 4.6kHz.
Than original 0.22 capacitor reduced to 0.01 and than gained frequency is approx. 15kHz. Scoping that signal and adjusting R1 (200ohms) i noticed that amplitude goes up to 45Vpp !!! From 10Vpp to 45Vpp!!! Wow! Aint that a power!?
But...signal shape is not good sinus. It looks more square than sinus. Not good.
So...
I would like to hear opinions on this;
in LC tank which combination is more desirable; small capacitance and larger inductance or oposite? Are there any major drawbacks if capacitance is small and inductance large? Oposite?
Other words; are there any major sideffects to be expected?

I presume TX coil would have to be made different than it is now. Smaller inductance and for C6 to use larger capacitance.
Also, since amplitude is now much higher, are there any possbile problems than, at coupling to phase circuitry stage?
I will experiment this anyway and find out proper solution, just want to hear other opinions...

Hi,
if the signal is not sinusoidal I see it very hard use it on device.

The 45Vpp could have a meaning if sinus stuff... but getting sinus wave with that amplitude at 14Khz is not so trivial if use common e.g. low power transistor stages.

The best will be resonant stuff... but we know... resonant coil/tank/oscillator is not easy solution.

The best tank is the one that have max Q ... in most cases inductor and capacitor are balanced to achieve higher Q from that thing... thus resulting in a narrow peak and higher...

But the problem is at oscillator: if look e.g. at relichawk you know very well... there's a trick in that oscillator and coil/cap params are really strict... not a case... it's resonant stuff too.

I think the idea is good but don't see easy method for pushing in 50Vpp range tx without redesign everything at there...

Kind regards,
Max

[simonbaker]

Ok, i was looking the way to gain more power. TGSL's oscillator as it is, is weak. So i made small experiment on perfborad. I took oscillator from Classic III (or Caesar - "Serbian most wanted") and connected TGSL 5.8mH TX coil to it. Not good, frequency was about 4.6kHz.
Than original 0.22 capacitor reduced to 0.01 and than gained frequency is approx. 15kHz. Scoping that signal and adjusting R1 (200ohms) i noticed that amplitude goes up to 45Vpp !!! From 10Vpp to 45Vpp!!! Wow! Aint that a power!?
But...signal shape is not good sinus. It looks more square than sinus. Not good.
So...
I would like to hear opinions on this;
in LC tank which combination is more desirable; small capacitance and larger inductance or oposite? Are there any major drawbacks if capacitance is small and inductance large? Oposite?
Other words; are there any major sideffects to be expected?

I presume TX coil would have to be made different than it is now. Smaller inductance and for C6 to use larger capacitance.
Also, since amplitude is now much higher, are there any possbile problems than, at coupling to phase circuitry stage?
I will experiment this anyway and find out proper solution, just want to hear other opinions...

Good question -- and very interesting such high voltage.

My premature opinion -- we want maximum "ampere-turns" in our coil for max magnetic field. (That assumes that more is better...)

So if we experiment with LTSpice (or equations!), we can try different values and graph current in coil for different arrangements (don't forget to increase resistance of coil with inductance).

Then we use Qiaozhi's coil calculator to estimate the number of turns.

Then multiply current X turns and find maximum magnetic field.

Maybe that is best??? If interested in depth over everything else, maybe. Maybe compromise for least battery drain, or other...

As for high voltage -- you know my story with TGSL, I feel some cases need voltage divider from oscillator if too high for discrim circuit -- maybe same here.

Regards,

-SB

[simonbaker]

Speaker was cause of some strange behavior in the past, at first pcbs. Than many things changed. On latest pcbs speaker is not a problem. Use 8ohms, or even better 16 ohms.
"CZ5" was a hell of a pcb for me. My very best (deepest and calmest) handmade was on that pcb. Only drawback is - it is large. Last pcb is also very good, but smaller.
I am not that conversant and cant explain what's going on with those handmades. I experienced same thing at some handmades: chatters, instabillity, faint audio, low sense etc...etc..
It is not about pcb anymore. Mostly it is about coil, 99%.
I had chance to see original Silver Sabre, Eldorado and now Bandido II. Except Bandido II which is on excellent ceramic pcb, the others two were made on ordinary "pertinax" and those pcbs are more than funny! Designed in a way i would never do. Wires everywhere, mixing, crossing.....mess!
Yet those worked pretty good and rock stabille. Also those were with 16 ohms speakers and earphone sockets.
Quality of used material in those - average. Nothing special. So...????
Coil, coil and nothing but the coil!
Dont torture yourself thinking to much about other things - focus on coil.
Regards!

P.S.
One more thing; Eldorado, SS and Bandido II were with smaller coils, 8". 1e detecting at 22-24cm in air. Rock stabille, sharp audio and loud.
All the "problems" are tied to new DD coils, larger dimensions and with air depths over 25cm! Is this a clue? I think so.
From newer Tesoros i tested Vaquero and Tejon. Both were tested with newer and larger DD coils. When adjusted to run "hot", both chatters and acting instabille. Another clue? I think so.
We are trying here to push those machines over their limits, that's why we get chatters and other sideffects. No wonder.

Thanks for that perspective. It sounds very correct.

I am putting more effort now into coils.

I notice that most "noise" comes from coil -- if I disconnect coil, electronics very quiet -- so not spending too much effort on super-low noise parts, designs, etc. But I remember people say some Op amps not work well, others do -- that seems a little strange, so important.

I agree early Tesoro models designed more for smaller coils and fast recovery, fast response. I think that is why audio on TGS is quite "sharp" and quick. Probably we should mod the filters slightly for slower response when using deeper coils; I intend to experiment with that after I first make a satisfactory TGSL using the standard circuits here.

I just want to know why some coils, even when nulled correctly, are no good? Why can't we adjust circuit to make those coils work fine? How do we find that out? Do you keep the "bad" coils for investigating?

One last question about shielding material. Your (Ivconic) video shows aluminum tape for shielding. Does that tape have insulating layer on it, or is it bare aluminum and makes electrical contact with itself on each turn? Is it same as aluminum foil, or better in some way? Have you tried other shieldings and have idea on what is best for TGSL coils?

Regards,

-SB

[ivconic]

More power on TGSL

Ok, i was looking the way to gain more power. TGSL's oscillator as it is, is weak. So i made small experiment on perfborad. I took oscillator from Classic III (or Caesar - "Serbian most wanted") and connected TGSL 5.8mH TX coil to it. Not good, frequency was about 4.6kHz.
Than original 0.22 capacitor reduced to 0.01 and than gained frequency is approx. 15kHz. Scoping that signal and adjusting R1 (200ohms) i noticed that amplitude goes up to 45Vpp !!! From 10Vpp to 45Vpp!!! Wow! Aint that a power!?
But...signal shape is not good sinus. It looks more square than sinus. Not good.
So...
I would like to hear opinions on this;
in LC tank which combination is more desirable; small capacitance and larger inductance or oposite? Are there any major drawbacks if capacitance is small and inductance large? Oposite?
Other words; are there any major sideffects to be expected?

I presume TX coil would have to be made different than it is now. Smaller inductance and for C6 to use larger capacitance.
Also, since amplitude is now much higher, are there any possbile problems than, at coupling to phase circuitry stage?
I will experiment this anyway and find out proper solution, just want to hear other opinions...

[Darko]

BD140 audio is taken from Cscope (BC636 originally) also!

Then, you must try this! Much better and stronger audio.
Cheers!

[ivconic]

BD140 audio is taken from Cscope (BC636 originally) also!