TESORO GOLDEN SABRE

[Molzar]

Rx Phase shift

This is not because your RX coil leads are reversed. It is because your coil is under-nulled, rather than over-nulled. During the nulling procedure, as you move the two coils together (I assume it's a DD configuration) the residual RX voltage will be reduced. You need to pass through this minimum and null your coils on the other side of this zero-voltage point. In other words - on one side of the null, all metal targets gives a phase-shift to the right, and on the other they give a phase-shift to the left. Although you can get both configurations to work, the left phase-shift position gives the most sensitivity and better discrimination.

Hello,

Recently completed TGS and am now trying to tune it properly.

I also get Rx phase shift to the right when triggering on the Tx. I tried Qiaozhi suggestion of under / over nulled coil. This changes the amplitude charateristic (goes higher only (over nulled?), goes lower than higher (undernulled?) but the Rx always moves to the right vs the Tx.

The above happens when metal is in the overlapped area of the DD.

When the metal is in the other area of the coils it does shift somewhat to the left.

What am I doing wrong?

Molzar

[scevlik]

Hi!
I fineshed my TGS.Now I need only good coil.Please what is the best coil type and how meny turns i must made.

Thanks and sorry for my English

[sonar]

Theories is only good start and all of them sounds like good story from fables.

Good test is only way to true - but in practice life is very brutal for metal detector designes

We have no hope - but we can still try to start a new experiments...

[Max]

Hi Max,

if you need more power from LC-osc, look at some maxwell-bridges. A very simple LC osc with maxwell-bridge + fast OPamp + driving transistors can deliver much more power.
I measured a ca. 650 Vpp with such an high power LC-osc on the coil!!! So, the amplifier stage can be neglected. You need a good attenuator on the RX-coil!
;-)
Regards,
Aziz

Hi,
thanks I will keep in mind.

Don't know how much voltage put there without making a big mess....
but I will make some test and see what happens on TGSlight.

Kind regards,
Max

[Aziz]

Hi Max,

if you need more power from LC-osc, look at some maxwell-bridges. A very simple LC osc with maxwell-bridge + fast OPamp + driving transistors can deliver much more power.
I measured a ca. 650 Vpp with such an high power LC-osc on the coil!!! So, the amplifier stage can be neglected. You need a good attenuator on the RX-coil!
;-)
Regards,
Aziz

[Max]

sorry. i make test on 5m like on your circuit

on 5m - BZX84C15L work great too

all clear now

but on 50 its not look soo good

thanks for solution Max...

Hi,
you are welcome... now that I dug that files I can start thinking at it again...

I was thinking some months ago of putting more power there but then something happened and I switched to other projects... nice to see there are still people interested in the topic.

The big problem is that the colpitts osc there is not a great solution about power delivered. Also I'm worried that trying to put 30 or more Vpp on coil will make device unstable on soil... cause one need really perfect GEB to deal with that stuff on little hot soil ...with fragments and magnetic compounds.

Anyway, I will test a bit on it with my TGSlight board (I never totally tuned/completed so far!).

Kind regards,
Max

[sonar]

sorry. i make test on 5m like on your circuit

on 5m - BZX84C15L work great too

all clear now

but on 50 its not look soo good

thanks for solution Max...

[Max]

hmmm. no problem




its was test only remember
nothing sure... frequency and others...

Hi,
the 5ms transient an. time limit is wrong: use 20ms or better 50ms.

At 5ms you could see amplitude before stabilization... so a sharp and tall peak of voltage that then drop after to real values.

Now see my simulation using a custom (MAX20 ) 20v zener diode (not in shops unfortunately ) and 24V positive supply.

Big wave, but too distorted for my taste and also one need 24v there... not good stuff to test on real circuit.

Kind regards,
Max

[sonar]

i send the file on Your PM Max... have fun or delete it

[Max]

Hi,
this is one with coil params showed...

as you can see the voltage is well under 16Vpp.

But maybe you meant some other params there ?

Kind regards,
Max

[sonar]

hmmm. no problem




its was test only remember
nothing sure... frequency and others...

[Max]

Yes i know Max

I just make some test on Your circuit only.

Coil is the same 5m8 - like in Your test generator...

Hi,
yes, but I don't remember now the values (was some months ago ?)... I think I've modified values from original schematic, right ?

Let me take a look at backups...

I will find answers somewhere (digging the long-time buried pile of dvds).

Kind regards,
Max

[sonar]

Yes i know Max

I just make some test on Your circuit only.

Coil is the same 5m8 - like in Your test generator...

[Max]

Ivconic, Max

take a look this...

Hi,
yes I see, but in practice is less, something 16Vpp: I've tested also with Tesoro original 9x8'' coil and measured always something around 16Vpp. What's your model definition (params) for coil ?

Kind regards,
Max

[sonar]

Ivconic, Max

take a look this...