TESORO GOLDEN SABRE

[taliesin]

just built tgsl .got constant tone

i have a constant tone i've nulled the coils at the lowest volume? it happens in the garden as well.when i lift the jumper circled (signal from 4024 ) in edwardo's pcb it stops and i have nothing at all. any ideas ?

[habitbraker]

tgsl discrimination

Long time i thought that i understand how discrimination on tgsl works, but something doest match with my waveforms and my theory. Before I play with modifications I must understand it.

So what i know (at least I think I know) that geb sample is taken at zerocrossing so if changes only amplitude - Vout of SD is zero. Only metals make phase shift so for all metals Vout is positive. Ok in real life ground makes phi too (As Dfbowers describes)

But now disc. Something I dont get. I can sample it at zerocross too and at same time disc out iron.
For example Alu foil makes both positive and negative Vout of SD depending of where disc sample is taken...
What makes it(Vout of disc SD) go negative , positive? How phase shift of metals affect it ? Is it amplitude changes as well?
Maby some examples? Its hard to see exactly it on scope.

[simonbaker]

Long time i thought that i understand how discrimination on tgsl works, but something doest match with my waveforms and my theory. Before I play with modifications I must understand it.

So what i know (at least I think I know) that geb sample is taken at zerocrossing so if changes only amplitude - Vout of SD is zero. Only metals make phase shift so for all metals Vout is positive. Ok in real life ground makes phi too (As Dfbowers describes)

But now disc. Something I dont get. I can sample it at zerocross too and at same time disc out iron.
For example Alu foil makes both positive and negative Vout of SD depending of where disc sample is taken...
What makes it(Vout of disc SD) go negative , positive? How phase shift of metals affect it ? Is it amplitude changes as well?
Maby some examples? Its hard to see exactly it on scope.

Hi habitbraker -

Normally you don't center DISC sync pulse on zero crossing of null signal.

DISC sync pulse is typically centered on zero crossing of target signal you want to reject. However, we normally never see the target signals, they are too small! We just trust they are there and that they have a certain phase relative to the TX signal. The phase of the target signals is completely independent of the null signal phase. You can change your null signal phase by balancing your coils, but it does not affect the target signal phases.

So if iron has phase1 and aluminum has phase2, we use DISC pot to center the sync pulse over the iron signal zero crossing. Then iron will have zero response and other metals with greater phase shift will make positive pulse.

If we use DISC pot to center the sync pulse over the aluminum signal zero crossing, then metals with phase less than aluminum will make a negative response, and metals with phase greater than aluminum will make a positive response.

In the GB channel, it should work out that all metals make a positive response if you set it correctly.

As you know, only if both channels make a positive response will we hear audio beep.

In the ground channel, we set the pot so the null signal makes a zero response ideally if it is modulated by the ground. Then we don't care too much if the null signal makes a positive response or not in the DISC channel. However, I believe the ground can still modulate the DISC channel response in some cases, which is worth thinking about.

That's my basic take on it. There are some subtle questions on how much you can control the "true" null signal phase during your nulling to optimize your MD.

Regards,

-SB

[habitbraker]

Thanks for the answer!
Yes I understand further signal processing (filters, opamp-AND etc)

But why received signal changes phase and A when I move metal objects near the coil?
Isnt those target signals which I can see?
So more conductive metal - more phase shift. If i disc out foil, i just center disc sample on al foil signal zerro crossing? So in that case al foil will have zero response and iron negative?

Is there some proof what i can see on scope?

[habitbraker]

Actually i think I finally get it. It is like that, I checked. At exact point where foil is disced out Vout of SD doesnt change when i wave foil over the coil- explines zero cross.

If disc is increased, Vout starts to decrease when I wave it and when decreased below al zero cross point, Vout starts to go up.

And because of AC coupled amplifiers only changes are detecded...

[simonbaker]

Actually i think I finally get it. It is like that, I checked. At exact point where foil is disced out Vout of SD doesnt change when i wave foil over the coil- explines zero cross.

If disc is increased, Vout starts to decrease when I wave it and when decreased below al zero cross point, Vout starts to go up.

And because of AC coupled amplifiers only changes are detecded...

Yes!

-SB

[habitbraker]

Thanks SB!

[taliesin]

can someone help please?

i've just built tgsl v 3.on most of the tesoro designs (that i've anyhow) have the MR pin 2 on 4024 tied down to ground.on the v3 there's a 1k resistor from pin 2 via one of the fet's .is this paramount to the design or am i able to just lift the 1k.?

[Dennis the Mennis]

Dicrimination made visible

Hi habitbraker -

Normally you don't center DISC sync pulse on zero crossing of null signal.

DISC sync pulse is typically centered on zero crossing of target signal you want to reject. However, we normally never see the target signals, they are too small! We just trust they are there and that they have a certain phase relative to the TX signal.

Yes, they are very , very small .
This graph is made on C12 direct output of the FET vs the TX signal, but I had to drag the coin over the coils to see this respons :



I think it is (almost) impossible to see phase relative to the Tx , can't see which one triggers the target signal .

Someone any idea for this : I can ad a mathimatical channel to the scope ( for example A + sqr B ) ?

This next graphs show the results on the outputs of the LM308's
( Green = U105 GB channel and Red = U104 DISC channel)

The phase of the target signals is completely independent of the null signal phase. You can change your null signal phase by balancing your coils, but it does not affect the target signal phases.

So if iron has phase1 and aluminum has phase2, we use DISC pot to center the sync pulse over the iron signal zero crossing. Then iron will have zero response and other metals with greater phase shift will make positive pulse.

Detection on piece of Al foil in AM mode :

If we use DISC pot to center the sync pulse over the aluminum signal zero crossing, then metals with phase less than aluminum will make a negative response, and metals with phase greater than aluminum will make a positive response.

A nickel Disced out / rejected or 'nulled'





Same nickel at the point to be rejected :





Steel Bottle Cap rejected (as replacement 2 steel washers ) :





Iron discriminated out :

In the GB channel, it should work out that all metals make a positive response if you set it correctly.
As you know, only if both channels make a positive response will we hear audio beep.

Detection of an 1 Eurocoin in AM mode :

In the ground channel, we set the pot so the null signal makes a zero response ideally if it is modulated by the ground. Then we don't care too much if the null signal makes a positive response or not in the DISC channel. However, I believe the ground can still modulate the DISC channel response in some cases, which is worth thinking about.

Ferrite slug / bar 10 cm with GB pot set correctly in am mode

That's my basic take on it. There are some subtle questions on how much you can control the "true" null signal phase during your nulling to optimize your MD.

Regards,

-SB

Just a small graphical support for anyone's interrest

kind regards ,

Danny

Dennis the Mennis

[eduardo1979]

TGSL-EDU

Hey guys! I leave here some pictures and a video of my TGSL. The tests are made at home and had some interference. In the field detector is going well. Greetings! Eduardo
http://imageshack.us/g/638/imagen0064o.jpg/

[bernte_one]

hello eduardo
video link doesn´t work pics are good thx for sharing with us

[eduardo1979]

http://www.youtube.com/watch?v=KE2REksFOX8

[ivconic]

http://www.youtube.com/watch?v=KE2REksFOX8

That's right! That's how TGSL supposed to work! Bravo!

[eduardo1979]

Hvala IVCA.

[satdaveuk]

Hi
Hope mine works like that
My PCB is assembled, not tryed it yet , need to double check everything first, on my second set of coils so i can play around, took all readings etc as i assembled, so all should be ok.
I will post soon
Dave