IGSL

[ivconic]

Thank you.
I have a problem with the head. If you touch a blade of grass, sometimes from as indicated.
What is happening? Electrostatic charging and discharging?
Regards!

!?
Shouldn't act like that!?
Seems like it is coil shield related problem?
You made shield on coil, right?

[ivconic]

On the contrary, you can. It is necessary to adjust GEB properly, and the best method is pre-adjusting the GEB(s) using a piece of ferrite, mark that position, and fine tune on real soil by bobbing the coil up and down some ~20cm on some spot that you first check for absence of metal - pre-adjusted GEB is good enough for that purpose.

[mateatek]

!?
Shouldn't act like that!?
Seems like it is coil shield related problem?
You made shield on coil, right?

Yes, they are shielded from the coils.
The unit works well, but a lot of false signals grass.

[Davor]

What build you have, what kind of coil do you use, and what is exactly your Rx input configuration?

[mateatek]

What build you have, what kind of coil do you use, and what is exactly your Rx input configuration?

Tx: Push-pull oscillator, 13.5 KHz, 40 V P-P, 80 turn, 0.4 millimeter. Rx: IGSL original amplifier, 135 turn, 0.25 millimeter. Amplifier and oscillator the head is installed. The head polyester resin and fiberglass material.

[Davor]

Could you post the schematic of the head?

[mateatek]

Could you post the schematic of the head?

I'm sorry, I drew by hand.

[Davor]

There is a configuration of this oscillator that may perfectly fit a pinpointer due to it's instability. Please in the future when you post drawings save them in gif or png format. jpg-s are full of artifacts that spoil them

I made a LTspice sim of the oscillator as per your drawing. Please confirm what op amp you have and what are the exact values of C4, C5, and C6. Especially C4! That makes a big difference.

Actually, please check my schematic for all components.

[mateatek]

There is a configuration of this oscillator that may perfectly fit a pinpointer due to it's instability. Please in the future when you post drawings save them in gif or png format. jpg-s are full of artifacts that spoil them I made a LTspice sim of the oscillator as per your drawing. Please confirm what op amp you have and what are the exact values of C4, C5, and C6. Especially C4! That makes a big difference. Actually, please check my schematic for all components.

The circuit diagram is correct, but three mistakes.
R1=100k
R7 none
U1=TL081
Oscillator signal phase shifters load without: 80-100 volt PP

[Davor]

I corrected the schematic, and you'll see a TL084 model, which is the same thing as TL081. R7 is a lumped representation of coil resistance - I think it is about just right for your coil. Only thing I don't understand is:

Oscillator signal phase shifters load without: 80-100 volt PP

So, are my capacitors correct??? Please clarify.

In case of a different capacitor configuration you can obtain quite high voltage across a coil, but in all such cases you lose stability.

If your oscillator performs as per the attached simulation, I'd exclude it as a problem here.

I'd say it is shielding problem after all. My coil is without shield, but it has a centre tap on the Rx coil.

Here is a latest picture and a LTspice model for everyone's convenience.

[bernte_one]

hello friends

last igsl i build has a confusing problem
U9 7808 gets very hot and from com to out i measure 2,8V how can this be
i replaced the regulator with a second same problem

broken elkos nearby ?

no idea whats the reason for that problem part is place right written side to pcb outer side

if anyone has an idea

regards

[Davor]

Could be elco. On my boards the largest elco was drawn in reverse on the silk screen, and I did not check. By pure chance it did not short, but was bloated and I had to replace it.

[bernte_one]

ok detector works now

i also cutted off c12 and c13 i think they are not needed when detector is battey powered

works fine all parts cold

regards

[ivconic]

Keep C13.

[bernte_one]

hello ivica

Keep C13.

as protection for 7808? ok thanks

was able to indroduce project to german forum with good resonance

i am curious about the improovements which came up here

your little seed from a two channel gsl grows up to storm in diy metal detecting world

regards bernd