Really sensitive pinpointer for grain size objects

[Detectorist#1]

Hi DIY enthusiasts,

This project is started as pinpointer's solution for grain size objects but no problem to be modified to simple PI MD for new people in this area. Increasing of the diameter of search coil to 8 inch (20cm) and changing the values of the damping resistors (the values depends from the type of the wire and the type of the isolation) will be enough to made simple PI MD as start point in this exited hobby!

[Detectorist#1]

Hi Carl,

For the clamp diodes, I have been surprised from your statement that the low power schottky diodes are slower than 1N4148.
Today, I soldered simple tester ( schematic is attached). The results are very clear. You are right!
Thank you - you pay attention for this phenomena for me. In popular books, the authors claim that NO diffusion capacitance in forward biased schottky diode.
I just found scientific paper with explanation of diffusion capacitance in forward biased schottky diodes. (Abstract of the paper is attached)

[pito]

1.5mm ball update
https://www.youtube.com/shorts/o0Ogg_Sb0Q4

[Detectorist#1]

This is the file of PCB ASSEMBLY (Layout) of rev.D of schematic

[Detectorist#1]

Yes, these projects are pointed for DIY peoples, but I think, most of metal detecting enthusiasts haven't deep knowledge and this information will be useful for them

[Detectorist#1]

As I know, Surf PI starts as pinpointer project.
My project uses similar ideas. Also Barracuda project is very similar.
Let's with our common efforts, we make real successor of these two great and widely used projects!

[Detectorist#1]

Also, I use one small round board with soldered "Delay" potentiometer used for very heavy soils, ON-OFF switch and piezo sounder.
It's more convenient when these parts are soldered on additional PCB instead to be fixed only on the upper PVC cap of the pinpointer.

[Detectorist#1]

I agree with you completely.
I will try to make short video - this will be my first attempt in this area.
I will agree with you that will be nice if other participants will be involved with some suggestions for improvements.
Carl gives to me suggestion to change input safety resistor from 200 oHm to 10K and to change repetition rate from 50ppm to 2500ppm and to use "direct sampling" but I don't know what is this.

[ivconic]

Hi Ivconic,
Thank you for your serious help!
My force is in hardware, not in software.
But the aim of this forum is - with our common efforts to achieve results in this good hobby!

I agree.
Would be nice if you can record a short video demonstration of the working device.
And also would be nice if other participants on topic give concrete suggestions about some improvements.

[Detectorist#1]

Hi Ivconic,
Thank you for your serious help!
My force is in hardware, not in software.
But the aim of this forum is - with our common efforts to achieve results in this good hobby!

[ivconic]

So much complication over nothing.
The software and methods you use are impractical.
"Thousands" of files with incomplete information.
Unprecedented boredom to put it all together in some logical whole.
I suggest you start using Sprint Layout to avoid all this boredom.

[ivconic]

[Detectorist#1]

Hi Pito,
According this video, remarkable change in the picture happens appr. at 1/2 inch distance.
My pinpointer also reacts on 0.5 grain target at 1/2 inch distance. The same result.
Thank you for the video.

[pito]

And here is a 1.5 mm steel ball
https://www.youtube.com/shorts/vUPJmrlSTlg

[Detectorist#1]

This is the file for PCB assembly of rev.C of schematic