Can pinpointer detecting thin chain?

[Nupi]

Nupi - If you're a magnet for gold, then why don't you have any money?

I give everything to foundations.
A very good foundation is:"NUPI's foundation" they help all foundations.
Highly recommended.

[Waikiki_Sweep]

Thank you! Frankly I think your invention is much more valuable for that guys who hitting dust trying to find small gold nuggets.
I do not know how to use pinpointer if I stay in water 4ft. deep all the day.
....
Wait a moment!!! Idea!!!
I can fill it with epoxy and put pinpointer inside my diving boot.
So I can find a target with my foot!
That is an improvement.

May be your LONG RANGE pinpointer as attachment for the boot is an interesting idea.
Imagine: If you have a doubts where target is just try it with your foot!!!
Anyway both your hands are busy to hold scoop and detector and you have no tail to hold pinpointer.

[Qiaozhi]

26.6666667 degrees Celsius that be a lot better. I have no money for the trip!! but I can help you find a lot of GOLD
I AM A MAGNET FOR GOLD!!!!! .

Nupi - If you're a magnet for gold, then why don't you have any money?

[Nupi]

Here on Hawaii 80 F air and water all the year. I have dumped air conditioner to the dumpster because never turned it on for last seven years.
I like 80 F may be it is too hot for some people.

Living here is expensive but worth to try.

26.6666667 degrees Celsius that be a lot better. I have no money for the trip!! but I can help you find a lot of GOLD
I AM A MAGNET FOR GOLD!!!!! .

[Waikiki_Sweep]

Here on Hawaii 80 F air and water all the year. I have dumped air conditioner to the dumpster because never turned it on for last seven years.
I like 80 F may be it is too hot for some people.

Living here is expensive but worth to try.

[Thomas]

Outside Phoenix Arizona, and yes many air conditioners.

[Nupi]

No, I want to make sure everything is correct and I'm In the process of getting ready for the summer here 120+ (49)C+ temperatures,
So not much time now, But the summer is when I'm stuck inside with time for projects.

You live in California? Man that's too hot for me. I would not survive. I would also stay home. With many air conditioners.

[Thomas]

Have you already made the pinpointer on your layout?

No, I want to make sure everything is correct and I'm In the process of getting ready for the summer here 120+ (49)C+ temperatures,
So not much time now, But the summer is when I'm stuck inside with time for projects.

[Nupi]

Corrected [ATTACH]29117[/ATTACH]

Have you already made the pinpointer on your layout?

[Thomas]

Corrected

[Thomas]

Don't use the layout I posted, Nupi Maybe Final. The components C5, C6 are wrong size.

[Davor]

Here you go, both versions in LTspice and only slightly edited.

[Davor]

LTspice is a great learning tool, and a great way of improving circuits. It is as good as the models you use, and more often than not the models are simplified in a way that simulations converge faster. Some things are very difficult to simulate, say comparators with positive feedback.
The Colpitts oscillator I suggest here has a few interesting details and I'll most certainly try it in a real circuit. It detects coil loading by excess current flowing through a transistor base during saturation. As such shallow saturation stabilises the oscillator amplitude, I expect some more stability with this design than the strictly linear ones. At the same time the detection voltage change largely exceeds coil amplitude change in target presence.

[Nupi]

It is possible, but it is often more rewarding to do some makeover for the specific purpose of improvement.
I rearranged your detector's front end to a Colpits type, and it is far more interesting to me because it uses a single coil, and in this configuration it operates in near saturation mode. I guess it will have better stability, but I'd have to test it in real life. If you are up to it, please let us know if it works and how it performs.
I only made a few small changes against the original layout, but the mode of operation is quite different.
A single coil is much easier to make, and it would lend itself nicely if you ever wish to make a grown-up detector with a large air coil and a stem out of this project.
Here is the schematic, lower pane is with no target and the upper with a target near by:

I'm not a technician like you and my expertise is limited, but I think with a colpits we will not be able to improve. I've tried it with multiple oscillators, but I did not succeed.
There is another component that played a role, maybe something "with regenerative loops."
I think LTspice not told everything.
Maybe we should LTspice "hacking".

[Davor]

@Thomas, CD4060 might be handy for it's access to the input stages (pins 9,10,11) but because the bias is set in the oscillator, this feature does not seem essential for this kind of detector. Pulse counting approach takes care of the analogue response. BTW, I did not test the Colpitts version in real life, and I'm confident it should work only because I used two inverters simulated with MOSFETs to mimic the real life conditions.

@porkluvr, "K" statements handle coil couplings. In a Hartley version i used a dirty trick and stated only L1 and L3 coupling at .1 ... which is not correct in spice, but works for very weak couplings without triggering any error messages.
In Colpitts version I simply copied the K2 statement and did not go into tidying it.
The "click" parameter's name is inspired by a clicker that some people use to make some professional pinpointers more sensitive. It was an arbitrary choice. It sets coupling value (presented as {click} in the K statement). ".step param" command makes LTspice go for two passes, first with coupling at 0.001 (negligible) and then 0.1. The goal was to find a "potentiometer" value at which the first pass does not trigger beeps on neither of the "pin#" outputs after some initial settling period, while it should beep wildly in a second pass.

Now, I have a model of mine of variably coupled coils that I wish to try here, because I can supply it with a varying coupling and see how the pinpointer copes with it. I'll make all these soon and post the Spice files here.

There is a hidden detail that might prevent you from mimicking the device properly, and that is the coil Q. There is always some resistance of the coil, and I just left it hidden.