TESORO GOLDEN SABRE

[eclipse]

Err problems with the coil. Seems like I have the big chance for failure there.
Need to make few more tryies to get the picture clearly. I must be missing something there.

[eclipse]

simonbaker,
I have drawn the schematic using eagle layout 5, if you want I can give it to you (is that what you want??)
Also my main problem with the coil is that using scope I just can't get lower than 30-40mV. How do you guys achieve even 1mV? Around 30mV-40mV the recieved signal just changes its phase and the amplitude remains the same.
With this adjustment - coin at 10cm, not good.
The bigger one is Tx 16V the smaller one is Rx with leads of scope connected to Rx coil with 15nF + 1K and it is ~30mV
If i try to get it lower it just jumps around with the phase, no amplitude change. Argh damn

[simonbaker]

simonbaker,
I have drawn the schematic using eagle layout 5, if you want I can give it to you (is that what you want??)
Also my main problem with the coil is that using scope I just can't get lower than 30-40mV. How do you guys achieve even 1mV? Around 30mV-40mV the recieved signal just changes its phase and the amplitude remains the same.
With this adjustment - coin at 10cm, not good.

File would be appreciated, yes. And image so people make sure what circuit you use. I don't have eagle, trying to draw with ExpressPCB, but maybe get eagle.

It would help if you take photos of your coil and cables. I think capacitance between coils can cause high null voltage -- If you separate them (with cardboard or something), can you get a better null?

I'm not sure null is problem with coin depth. Is sensitivity and threshold at lowest setting?

Put switch in Discrimination mode and use scope and look at outputs of U104, U105 simultaneously. They should both move in same direction for coin, opposite direction for iron. You can affect amplitudes with discrimination and ground balance pots.

The ground balance pot only affects signal at U105. The signal just needs to go above sensitivity threshold whenever U104 signal goes up for coin. It must be OK because you get some depth.

You can see effect of discrimination pot on U104 output -- set it for max signal for now just to see best you can get.

If you are indoors, maybe too much emi is preventing you from setting sensitivity and threshold pots low enough.

I made a 28 cm coil, not so sensitive on smaller coins. Right now I can beep a quarter at about 15 cm, but my sensitivity and threshold quite high due to noise.

Interested in what you find.

-SB

[simonbaker]

simonbaker,
I have drawn the schematic using eagle layout 5, if you want I can give it to you (is that what you want??)
Also my main problem with the coil is that using scope I just can't get lower than 30-40mV. How do you guys achieve even 1mV? Around 30mV-40mV the recieved signal just changes its phase and the amplitude remains the same.
With this adjustment - coin at 10cm, not good.
The bigger one is Tx 16V the smaller one is Rx with leads of scope connected to Rx coil with 15nF + 1K and it is ~30mV
If i try to get it lower it just jumps around with the phase, no amplitude change. Argh damn

BTW - is RX coil connected or disconnected to circuit when measure? Voltages mentioned here for disconnected I think.

-SB

[Max]

simonbaker,
I have drawn the schematic using eagle layout 5, if you want I can give it to you (is that what you want??)
Also my main problem with the coil is that using scope I just can't get lower than 30-40mV. How do you guys achieve even 1mV? Around 30mV-40mV the recieved signal just changes its phase and the amplitude remains the same.
With this adjustment - coin at 10cm, not good.
The bigger one is Tx 16V the smaller one is Rx with leads of scope connected to Rx coil with 15nF + 1K and it is ~30mV
If i try to get it lower it just jumps around with the phase, no amplitude change. Argh damn

Hi,
in CC coils you leave one turn off the boudle and use that to find null : this way it's hard but possible getting also 1mV null (even less if needed). Usually phase is another issue... sometimes you get 1mV null with too far phase shift, so the coil will disc bad way... better having larger null voltage and right phase.

In DD coil the nulling is more easy at 10-15mV level... just move the loops till get it, then glue them down. Problem is that you haven't the tweaking loop and so all is just by movements: the tickness of boundles is an important failure factor in that process... you get lateral coupling and so it's extremely hard go down to few mV voltage there.

A solution, like in RH coil, is using a small round loop to compensate lateral coupling and getting right nulling, of few mV and right phase same time.

But in Tesoro's coils this doesn't happen: they just use DD config, and null is around (usually) 15mV at that original coils. You don't need so 1mV to get it work good... but sure the less the better, also less false signals from coil.

If the null is high there's more chance that superimposed noise will trigger an audio response cause the amplifiers will give a big voltage at end of chain... triggering comparators more easy.

So, if you get 10-15mV stay with that for now... you could made better coils in the future with less nulling voltage... but now you can focus on detector with good discrimination.

Also, 30-40mV is no good... try using the output of preamp then divide by gain of the stage to know which voltage you have at rx coil.

Kind regards,
Max

[Max]

File would be appreciated, yes. And image so people make sure what circuit you use. I don't have eagle, trying to draw with ExpressPCB, but maybe get eagle.

It would help if you take photos of your coil and cables. I think capacitance between coils can cause high null voltage -- If you separate them (with cardboard or something), can you get a better null?

I'm not sure null is problem with coin depth. Is sensitivity and threshold at lowest setting?

Put switch in Discrimination mode and use scope and look at outputs of U104, U105 simultaneously. They should both move in same direction for coin, opposite direction for iron. You can affect amplitudes with discrimination and ground balance pots.

The ground balance pot only affects signal at U105. The signal just needs to go above sensitivity threshold whenever U104 signal goes up for coin. It must be OK because you get some depth.

You can see effect of discrimination pot on U104 output -- set it for max signal for now just to see best you can get.

If you are indoors, maybe too much emi is preventing you from setting sensitivity and threshold pots low enough.

I made a 28 cm coil, not so sensitive on smaller coins. Right now I can beep a quarter at about 15 cm, but my sensitivity and threshold quite high due to noise.

Interested in what you find.

-SB

Hi,
don't know why you have such poor results... but 15cm on a quater is really few stuff, device is much more sensitive.

Kind regards,
Max

[ivconic]

"...The bigger one is Tx 16V the smaller one is Rx with leads of scope connected to Rx coil with 15nF + 1K and it is ~30mV..."

Eclipse remove 15nF + 1K and connect plain coil to scope. Of course RX coil keep not connected to detector while nulling.
Other method is to scope LF353's pin 7. while nulling.
Than observe differences and try to null again.
Cheers!

[Max]

"...The bigger one is Tx 16V the smaller one is Rx with leads of scope connected to Rx coil with 15nF + 1K and it is ~30mV..."

Eclipse remove 15nF + 1K and connect plain coil to scope. Of course RX coil keep not connected to detector while nulling.
Other method is to scope LF353's pin 7. while nulling.
Than observe differences and try to null again.
Cheers!

Hi,
the cap + resistor stuff works too but to have an exact idea of residual voltage seen by preamp one must do with preamp output...

For example: yesterday I made a test with a new coil... read easy (by movements) a nulled voltage of 0.22Vpp at pin 7 of LF353 thus I know it's about 5mV nulling at rx coil... that's what preamp see.

Using resistor and cap I read much lower... or, well... cannot read cause 1K resistor dumps everything under particular voltage...

I don't use multimeter cause had unreliable results with some coils... so I'm using just scope , but if one has a good reliable result with multimeter (like you) why not ?

Problem is phase... always...

At very strong null phase variations are often too far from expected value. That's real pain getting 1mV null but missing required phase angle. Have to unglue coil again and null at higher voltage!

It's furstrating...

PS: I'm also experiencing lot of problems due to indoor noise... at now! This last, big coil I made (35cm inner diameter) pick-up so much noise!

I light/unlight a room at 15meters from it and hear detector sound at each commutation ! Seems like an LRL this way!

Must conclude that so big coils are totally unuseful at TGS ???

Kind regards,
Max

[miki73]

How many voltage on lf353 pin 7 equal 1mv on rx coil?

[Max]

How many voltage on lf353 pin 7 equal 1mv on rx coil?

Hi,
it's 43.13mV.
(not considering internal offset...)

Kind regards,
Max

[ivconic]

"...Problem is phase... always...

At very strong null phase variations are often too far from expected value. That's real pain getting 1mV null but missing required phase angle. Have to unglue coil again and null at higher voltage..."

Ha,ha! You got that right Max! I agree 100%.
That's why i finally got scope!
Actually is not an issue to null coil at minimum residual voltage, but problem is to maintain proper phase at RX. Without scope is just illusion or a lot of hard labour, as it was in my case till few days ago...sheesh!
Sooner or later man will face the phase problem, like i did. My coils works fantastic on "coloured" items, but choking to much iron and alloys...all those due unproper phase adjusted with them.
Final question is; what should be the most proper phase shift on TGSL coil?
I dont have a clue; i had never seen or experienced any original TGS so far..!? Shame...

[tiktak]

Hi,

Hi,
I am agree.Thats why I am also trying to get one.But the 2-chanel onece are too expencive for me.What is yours Ivica?
Because the picture is not so good.
Thanks

p.s.I am shore that you will find the source of that noise with that scope.

[Max]

"...Problem is phase... always...

At very strong null phase variations are often too far from expected value. That's real pain getting 1mV null but missing required phase angle. Have to unglue coil again and null at higher voltage..."

Ha,ha! You got that right Max! I agree 100%.
That's why i finally got scope!
Actually is not an issue to null coil at minimum residual voltage, but problem is to maintain proper phase at RX. Without scope is just illusion or a lot of hard labour, as it was in my case till few days ago...sheesh!
Sooner or later man will face the phase problem, like i did. My coils works fantastic on "coloured" items, but choking to much iron and alloys...all those due unproper phase adjusted with them.
Final question is; what should be the most proper phase shift on TGSL coil?
I dont have a clue; i had never seen or experienced any original TGS so far..!? Shame...

Hi Ivconic,
I posted that data: it's about 200° out of phase for original coils.

In the Qiaozhi's picture (of a 9x8'' coil) you see it very clear.

That's the phase, I got the same both on my 9x8'' and an 8'' round.

But still some problem exist on larger coils... expecially DD like.
Iron detection is better avoided in CC than DD... the flux shape is a problem for near iron, I noticed that even at right phase some large coils show that iron detection at overlap area when target is huge or too near the overlap.

Kind regards,
Max

[driscoll]

Hi,

Added corrections from the last IVCONIC schematic (BD140).



TGS last mods.zip
Regards

[simonbaker]

Hi,

Added corrections from the last IVCONIC schematic (BD140).

[ATTACH]6620[/ATTACH]

[ATTACH]6621[/ATTACH]
Regards

Does the battery check work for this PCB? If not, there are more resistors you can remove, everything connected to U107b op amp.

-SB